Is this what a 0.1 layer height should look like?

This may be an effect of the not using a "Magic Number" for your layer height. The Monoprice Select Mini has a z-resolution of 0.04375mm, so layer heights should be multiples of that. (See What are the “magic numbers” on a Monoprice Select Mini?)

If you slice with a layer height of 0.1mm, each layer will be a little smaller (0.0875mm) or bigger (0.13125mm) to get close the the ideal height. The extrusion won't change, causing some layers to be thin and overextruded and others to be thick and underextruded.


The larger the diameter and the higher the voltage the larger the detection distance. You do not need to do much wire modification if you use an optocoupler, see this anwer.


The behaviour of "frozen filament" will entirely depend from the specific formulation of it.

The term "flexible filament" encompasses a variety of different polymers as for example: thermoplastic elastomers like TPE and TPU (e.g.: ninjaflex), copolymers (e.g.: bendlay), copolyesters (e.g.: Ngen Flex), polycaprolactones (e.g.: PCL), etc...

Even in those broad classes of chemicals, the amount, type and quality of additives will affect the physical properties of the filament a lot.  In fact rigid.ink even produces a flexible PLA that proves the point of additives radically affecting the properties of the main material.

In general, all materials lose elasticity at lower temperatures (a Space Shuttle came down because engineers failed to account for this).  Polymers that do not contain water are unlikely to crystallise though, so I would expect it to become stiffer but not to fail catastrophically at 0°C.


Is there such thing as a sealed dual extruder hot end?

It doesn't work that way, or perhaps in some sense it already does.
The "straw effect" you're describing depends on the water not being under any pressure that exceeds the outside atmosphereic pressure. If you squeeze the straw or otherwise apply pressure, it will immediately spill out.
If you're printing at more than a ridiculously slow print speed (slow enough that it would fail for other reasons, like the nozzle melting the already-printed part just by proximity to it), the filament is under very high pressure from the extruder gear. The primary function of retraction is not to move the filament back out of the nozzle orifice, but simply to relieve that pressure. (A little bit more is needed to prevent oozing, however.) When retraction happens, it's exactly like the "straw effect" you're describing. The material pulled back out of the hotend into the heatbreak hardens enough that it makes a nearly air-tight seal, preventing the molten material below from flowing out of the nozzle due to gravity.
If your hotend does not have design problems and if you're using retraction correctly (that means using it everywhere that you're making a move that's not an extrusion one, not skipping it with "Limit Support Retractions" or "Combing"), you should not see oozing, ever. The system already works the way you want it to. But you can't magically get rid of the need for retraction. It's part of how the system you want works.


You have a too thick layer: to get straight lines, the plastic has to be squished together to some degree as it is pushed out of the nozzle. The result is a shape similar to a circle with the top and bottom cut. This works well until your layer thickness is more than 3 quarters of the nozzle diameter - above the "squishing" is practically nonexistent, and if you go above the nozzle diameter, there is almost no way to get the desired thickness out of the nozzle at all.

To aid in depositing the layers, it is also advised to demand a line width that is about 10 % larger than the nozzle diameter. As illustration, this is roughly what 0.4 mm extrusion width with 0.4 mm layer height (blue) and 0.45 mm extrusion width with 0.3 mm extrusion height (yellow) look like:


How to extend Marlin to support additional movement axis?

I found many ways to re-task extruder steppers to
behave like cartesian-like controls:

If your application does not require contemporary movement of
all axes, you can enable multiple extruders setting the EXTRUDERS
define in Marlin's Configuration.h.

Then you can select which extruders will be set as E
variable in G1 commands, by sending T0, T1 and so on.
If your application require contemporary movement of all axes,
you can enable the MIXING_EXTRUDERS option (source).

With that option, you are basically splitting the E argument
between steppers. To set the ratio of your movement, you can give

    M163 S0 P0.6    # Set stepper 0 to ratio 0.6
    M163 S1 P0.4    # Set stepper 1 to ratio 0.4
    M164 S2         # Create a virtual stepper with given settings
    T2              # Select the virtual stepper

If you want to configure additional steppers as proper axis,
check this commit.


Update:

Cura 2.5, and higher, does load and print G-code.

(The support was added April 19, 2017.)


How does slipping Bowden tube affect retraction or does it at all?

The slipping does result in lost retraction distance. It does not result in underextrusion, lost material (except possibly via having insufficient retraction after the reduction), or anything like that.

If your retraction is set to 6 mm, but the bowden pulls 2 mm into the coupler when you retract, those first 2 mm of filament motion do not pull the filament out of the hotend at all. The position of the filament relative to the tube (and thus relative to the nozzle) remains constant. After the tube can be pulled back no further into the coupler, the remaining retraction pulls the filament back through the bowden tube, for 4 mm of retraction at the hotend/nozzle.

When unretracting, the reverse happens. The first 2 mm of extruder motion push the bowden tube out of the coupler, and don't move the filament relative to the tube (or the hotend). After that the next 4 mm push the filament through the tube and back to the nozzle orifice.

The result is the filament ending up back exactly where it started, but having backed out only 4 mm from the nozzle, not the requested 6 mm.

These numbers are just examples but probably about right. If you put the plastic clip on the pneumatic coupler, the slipping should stop, but you can also just increase retraction if the amount after the loss to slipping is not sufficient.


All printers will have some fluctuation and it's not a concern. This is similar to the fluctuation you'll see in your home temperature around the thermostat setting.  There are a couple reasons. One is that the feedback loop (thermistor to control board to heater to extruder block) will always have some lag. Another is that most systems have built-in "hysteresis," i.e. set the "turn off heat" a couple degrees above the "turn on heat" thresholds. This avoids "chatter" from on to off right at the setpoint.
Some thermistors (e.g. my AnetA8 clone) can be held in place with a setscrew. If yours doesn't have a similar capability, use Kapton tape to hold it in. This tape is designed for high temperature operations so it won't age or collapse, and it has good holding strength.


Retraction is the reversal of the direction of the filament and is generally used when moving from one non-contiguous point of the print to another, in order to prevent stringing and oozing of the filament. If retraction is not employed then the filament still coming out of the nozzle, after the last point was printed (and paused), will stretch, thus creating a fine string, as the print head is moved to the next position where printing is to recommence.

The retraction speed is the speed at which the filament is retracted, or pulled back (by the extruder stepper), and the retraction length is the amount that is pulled back.
These settings are dealt with in the XYZware User manual, on page 43, section 11.5 Retraction

11.5 Retraction

11.5.1 Retract Length
In printing object, before large movement of print module, print
filament will be drawn back, such that slight negative  pressure
occurs  in  print  nozzle,  preventing  material  from  adhering  to
the  object  while  moving, improving surface quality of print object
11.5.2 Activate Threshold
Such  setting  will  allow  users  to  set  up  retraction  mechanism
activation  style.  For  setup  mode,  users  usually specify the
minimal print module movement distance for retraction mechanism
activation
11.5.3 Lifting height for extruder withdrawal
After retraction, the print module will be elevated slightly with such
setup value. Such action prevents material from adhering to the
object, and makes a more orderly final print stop point. However, it
should be noted that excessively large elevation will extend print
preparation time for the next print layer, and portions of angles may
results cooling and difficult to bond conditions between layers
11.5.4 Add Extra Filament after Travel < Retraction
Material  compensation  may  be  used  to  improve  upon  holes  or
poor  extrusion  due  to  excessive  extruder withdrawal

Retraction speed isn't dealt with in the above section though. In section 3.3, of the XYZware Pro. User Manual, it is mentioned:

Retract Speed
The speed for pulling filament backwards. Refer to the function introduction in the next chapter for more about retraction.
Hint:
Cooperation of retraction speed and other print speeds will affect feeding stability directly in printing. A print speed slightly faster than the retraction speed would prevent material squeeze from interrupt.

However, the manual doesn't then go on to give any setting. However, the default settings should suffice, unless you are experiencing issues with stringing and/or oozing.
A further explanation can be found here, Stringing and oozing:

Reason 2: Retraction Length
The retraction function includes two setting options. One is
retraction length and the other is retraction speed. The retraction
length determines how much melted filament will be pulled out of the
nozzle. In general, the more plastic that is retracted from the
nozzle, the less likely the nozzle is to ooze while moving. As for the
issue, the default setting in the expert mode is enough for you to
solve the problem. If you encounter stringing with your print job, you
can increase the retraction length slightly to test again to see if
the performance improves.
Reason 3: Retraction Speed
The retraction speed determines how fast the filament is retracted
from the nozzle. If the speed is too low, it will make no difference
to your print job., the melted filament will still drop down through
the nozzle and leave on the model. On the contrary, if the speed is
too fast, the filament will be back to the nozzle and cannot be
extruded out in the next movement of printing. As for the retraction
speed setting, users can reserve the default setting which is perfect
for almost every models.

Testing your settings
As 0scar has reminded me, there are a good number of retraction test prints available (cubes, towers, bridges), which will help you check that your settings are adequate. These prints provide models that have a lot of print breaks (points between which printing is paused and then resumed), which can cause stringing to be exhibited. See RepRap Wiki - Oozebane:

Oozebane
Objective: stop material oozing out of the nozzle during
'non-printing' moves.
Many extruders will emit (ooze) plastic even when the extruder motor
is not turning. To overcome this your slicing software needs to
'retract' the print medium during head movement when not printing. The
retraction creates negative pressure within the hot end heating
chamber which effectively sucks the print medium back up through the
nozzle, stopping it from oozing.
Calibration Object: oozebane-test.stl
The calibration object prints two towers about 30 mm apart. The head
must move between each of the towers at each layer. If your printer is
not set correctly then you will see many fine filaments (or strings)
between the two towers. You can eliminate these filaments by
eliminating ooze.
Calibration Object 2 (Variable sized towers for testing ooze): variable_size_ooze_test_nobase.stl
This is a simple model to help tune reversal parameters for a stepper
extruder (using much less filament before actually testing the
ooziness). It consists of a number of towers with different
thicknesses, with different spacing between each tower. A well-tuned
bot should be able to produce even the smallest towers.

A simple google search, thingiverse retraction, shows up a lot of examples, such as:

10 Minute Mini Calibration Test for Oozing/Retraction at Different Distances
4 Cube Retraction Calibration
Retraction Tower Test or String retraction tower test

Check out the following (suspiciously similar) tags1, for even more examples:

retraction_test
retraction-test
retraction

Additional note for Bowden setups
As Trish notes in the comments:

According to my experience2 it is generally a good idea to add 2 to 4 mm of retraction to a bowden setup in comparison to a direct drive when dialing in the perfect retraction. This is, because some distance is "eaten" by the flex of the Bowden tube.

1 It seems as if Thingiverse could benefit from tag synonyms
2 and Thomas Sanladerer's advice during a stream


Customized Ultimaker 1: Extruder motor does not move

Did you heat the hotend before attempting to move the extruder?  Most firmwares block cold extrusion.  If you send the printer M302 it will allow the extruder motor to move without the hotend being above the temperature set in the firmware.  Jumpers next to drivers are used to set microstepping, no need to adjust these unless you changed to a different type of driver or want to use different microstepping.  Changing them usually requires changing the steps in firmware as well.  Also, swapping drivers or motors while the driver is powered can destroy it.


Can a short-circuited heat bed be salvaged?

What happend was short circuit of course. There is no doubt you overheated HB so copper detached from HB base plate. Because you wrote it doesn't work it means copper tracks are broken.

There is very low chance to fix it. I mean it - near to zero.

What you could do is:

Detach HB from arduino
Find a place where track is broken (which needs to uncover it from protective layer)
Connect it with a wire

Unfortunately even if you do it and your HB will work (electrically) your fixed HB which won't be flat anymore.

So definitely it's to be thrown away.

[edit]

I just realised you have double power HB, which means your HB has 2 heaters... which gives a bit hope.

take a look here

here is schematics which could give you an idea

You could check if your second heater works ok

If yes then you are salvaged! :)

[edit2]
I really suppose the schematics of HB is more or less like this

So if H1 is broken there is a chance to use H2 connecting pins respectively


Would using a leadscrew with 1 or 2 mm lead, en lieu of 8 mm, result in a better printer?

From Accuracy vs Precision and Threaded Rod vs Leadscrews in 3D Printers. I have highlighted the relevant parts:

In general, FFF/FDM printers use relatively infrequent, small, precise
movements on the z-axis and consistent, fast movements on the x and y
axes. A single start leadscrew with the tightest pitch possible
(highest thread density, smallest pitch) is generally going to be your
best bet for the z-axis, while you may or may not need something a
little steeper to get the speeds you'd like from your x and y axes.
While this may seem somewhat arbitrary given the precision of movement
you can get from a stepper motor, an important factor to remember here
is torque.
A more aggressive leadscrew will require more torque to drive. We have
one kit printer we bought a couple years ago that has an overly
aggressive multi-start leadscrew for the z-axis. The small motors
included in the kit do not have the torque required to reliably start
upward movement of the carriage, leaving it sitting there skipping
steps until the carriage is given a little upward nudge to get it
going (no, it's not a lubrication issue or a driver that needs turning
up).

So, a 2 mm lead is preferable to a 8 mm lead, as not only is less torque required, but also more precise movements are obtainable.

With respect to the layer heights, I found this nugget of information, from Ditch the threaded rod in your RepRap 3D printer and upgrade to a lead screw z-axis

It's always better to use layer heights that are a multiple of your
full step. If you trust in your micro-stepping you will get poor
results because torque is very poor and the motor won't stop very
precisely. Best approach is to use a lead screw (whose longer step
allows the gravity to work for you and eliminate backlash) and a
stepper driver configured to 1/4 micro-step for low noise, but not for
micro-layering. I always use multiples of my full step and have
printed 0.040 (1 step), 0.080 (2 steps), 0.120 (3 steps and so on), 0.200,
0.600 and 0.800 mm (of course using 2 different nozzles). Do you need
more than that?

See also Reddit - Lead screw opinions

the general consensus is that a 2 mm lead is preferable to a 8 mm lead:

Lower the lead the better for an Z-Axis screw to allow for more precision.
No need for anti-backlash nuts for a Z-Axis if it has a decent amount of mass/weight to it.

1 mm will slow the printer down, but provide 0.005 mm (5μm) vertical movement:

That's going to be awfully slow when homing. While you really don't
need speed for the z-axis, there's not much point in going with such a
low pitch... you won't be printing anywhere near the layer heights
that can achieve. In the end I guess it's not a big deal, but I don't
see any reason to go below about a 4 mm pitch. A 1 mm pitch with a 1.8°
stepper gives you 0.005 mm increments. Anything under 0.02 mm (which is
sort of ridiculous anyways) is just unnecessary. Just my thoughts.

(As Tom points out) An 8 mm lead can result in the weight of the X-axis gantry (especially in a P3Steel) overcoming the idle torque of the stepper. As a result of this, the X-axis gantry can end up sliding down the leadscrew, in particular at power down:

I have lead screws on my Z and it readily falls down if you kill the power. Regular threaded rod is much better at keeping it in place without power.

and

That's one of the problems with 8mm lead ;) With 2mm lead it will hold itself. The stepper motor provides a fair amount of resistance even when powered down.

TL;DR
Be wary of leadscrews with a lead, as opposed to a pitch, of 8 mm, as there are disadvantages, when compared to a lesser lead of, say, 4 mm, or 2 mm (or 1 mm for leadscrew with a pitch of 1 mm):

Higher torque may be required
Less accuracy
Possibility of slippage, of the X-axis, once power is removed, or stepper is disabled1
Anti backlash nuts required

However, their major (if you can call it that) advantage is a higher maximum movement speed.


Are there many differences between Ultimaker Cura and FlashForge FlashPrint slicers?

The commonality of the 2 slicers is that both are developed and maintained by a printer manufacturer. The largest difference is that FlashPrint is closed/proprietary software, while Ultimaker Cura is released in source (so-called open source project) to the public; this is valid for both the frontend (Cura) (Graphical User Interface) as for the slicing core (CuraEngine). Basically this implies that there is a larger community developing and bug fixing the software. Also, FlashPrint is exclusively available for the FlashForge printers while Ultimaker Cura can be used for different brands as well.

Statement from www.3dprms.com:

  The Flashpoint software is an in-house software program developed by FlashForge for use exclusively with the FlashForge 3D Printers

Statement from the Cura wikipedia:

  Cura is an open source 3D printer slicing application. It was created by David Braam who was later employed by Ultimaker, a 3D printer manufacturing company, to maintain the software.

As FlashPrint is proprietary, it has no shared source repository and can therefore not be based on existing forks of software that are released under e.g. some version of the LGPL license as this implies that you need to share the amendments you made to the software, otherwise you would be in violation:

  ...any developer who modifies an LGPL-covered component is required to make their modified version available under the same LGPL license..

Note that discussing the exact differences in features between the 2 software packages (e.g. implementation differences of model support structures) would be more fit in a forum style discussion board rather than on a Stack Exchange site.


Something is stopping the filament from going down the tube 30 to 40 min. after you start printing.  You are correct that this doesn't sound like a clogged nozzle.  It could be deformed filament, but the closeness of the timing after the start sounds like heat creep.  Other possibilities are also listed at the linked stackexchange article.
Note: with heat creep the filament will not jam in the tube.  It will jam just above the nozzle on a Bowden tube extruder; thus the filament stops going down the tube.  The tube entrance is probably the largest location the tube can kink, although not very large.
What are ways to avoid heat creep?


What are the reasons for my 3D prints having large numbers of strings between parts of a layer?

Stringing is often a result of too-high a temperature, or insufficient retraction. When there is highly liquid filament in the nozzle tip, it can adhere to the remainder of the print while dripping as the nozzle moves, leading to a thin string of the filament forming. As further travel moves are performed in each layer, this turns to a web.

The high temperature causes filament to be very liquid, causing it to move downward in the nozzle chamber easily, as opposed to having to be extruded forcefully due to viscosity. The temperature setpoint of 210 was high enough to cause this to happen.

A second possible cause, insufficient retraction, can also be blamed for this issue. Retraction is a process in which the extruder reverses its movement to pull filament back up the hotend, preventing it from dripping at the tip, and forming a string. Most slicers will allow specifying a numeric value in millimeters of filament to be retracted. Remember that printers with Bowden tubes between nozzle/hotend and extruder motor will require increased retraction and priming (extrusion when starting to print after a retract-and-move). Note that too much retraction can cause other problems, such as insufficient plastic in the hotend chamber at the start of the next printing move, which can cause gaps and other issues.


Filament extrusion always stops at some point during print

Stringing?

The stringing is explained by your relatively low retraction settings, 1.5 mm is not much for a Bowden setup. As do too high printing temperatures.

Stopping mid printing?

What you are experiencing is called clogging, the extruder cannot push the filament through the hotend and cause the grinding you report. Clogging mid printing is usually caused by insufficient cooling (for the temperature you print at) of the cold end (causing heat creep; slowly increasing temperature of the heat break), especially all-metal hotend assemblies are notoriously known for this problem.

Your Bowden tube does make a lot of kinks, maybe you can improve the path of the Bowden tube. Also if you are concerned about the sharp filament intake angle, you could print a filament guide:


I can't get G29 to run BLTouch on my Ender 3 V2

This sounds like a firmware issue to me. I copied and pasted
G28 ;Home
G92 E0 ;Reset Extruder
G29 ;BLTouch

Into my start code, and it worked fine.
I have an Ender 3 V2 and a BLTouch (BL, not 3D.)
If you haven't updated your firmware, that's definitely why.
This is the start code I am using (in Ultimaker Cura)
; Ender 3 Custom Start G-code
G92 E0 ; Reset Extruder
G28 ; Home all axes
G29 ; Auto bed level
G1 Z2.0 F3000 ; Move Z Axis up little to prevent scratching of Heat Bed
G1 X0.1 Y20 Z0.3 F5000.0 ; Move to start position
G1 X0.1 Y200.0 Z0.3 F1500.0 E15 ; Draw the first line
G1 X0.4 Y200.0 Z0.3 F5000.0 ; Move to side a little
G1 X0.4 Y20 Z0.3 F1500.0 E30 ; Draw the second line
G92 E0 ; Reset Extruder
G1 Z2.0 F3000 ; Move Z Axis up little to prevent scratching of Heat Bed
G1 X5 Y20 Z0.3 F5000.0 ; Move over to prevent blob squish

How are you manually initiating the bed level? G-code command? (If so, which command/commands) or on the printer itself?
If you haven't already, I suggest you try placing the line G92 E0 ;Reset Extruder before the line G28 ;Home. I'm wondering if it is possible that this is somehow interrupting the process.
Are you on stock firmware? If so, I would try using firmware for the BLTouch, from the manufacturer.
*You can find a guide on how to do a firmware update here is an external link.
You shouldn't have to change anything in the configuration if you download the pre-configured BLTouch firmware.


Parts of my (apparently manifold) model aren't appearing in my Slic3r preview

I fixed it!

I had my extruder diameter set to 0.5 mm, and the narrowest point of the model was just a hair under a full millimeter, so I guess the program took it to mean that it should only put down one line of material. I made the walls a little thicker and now it looks fine.


What seems to be a difficulty is the stabilizers for plastic absorb UV.  So if added to UV resin, they probably greatly increase the exposure time needed.
The following show characteristics of some plastics, taken from https://www.coleparmer.com/tech-article/uv-properties-of-plastics

Unmodified types of plastics that are regarded as having unacceptable resistance to UV are POM (Acetal), PC, ABS and PA6/6. Other plastics such as PET, PP, HDPE, PA12, PA11, PA6, PES, PPO, PBT and PPO are regarded as fair. Note that a PC/ABS alloy is also graded as fair. Good resistance to ultraviolet rays can be achieved from polymers extruded by Zeus such as PTFE, PVDF, FEP, and PEEKTM. The only plastics found with excellent resistance are the imides, Polyimide (PI) as used in the Hubble Space Telescope and Polyetherimide (PEI).

PTFE has particularly good UV resistance because of its very strong carbon- fluorine (C-F) bond [almost 30% higher than the carbon-hydrogen (C-H) bond], which is the common side bond that surrounds the carbon (C-C) backbone in a helix and protects it. Most fluoropolymers also do not have the light absorbing chromophore impurities in their structure that can act as an initiator for photo-oxidation.


Normally, such patterns are caused by too close printing to the bed (nozzle to bed distance too small), but considering the not fully flattened out extrusion lines (on glass I get a mirror shine fully closed surface) this does not seem to be the reason; you could try to increase the gap a little, in Ultimaker Cura this is very easily done with the Z Offset Setting plugin. Alternatively, you could use a little thicker paper to calibrate the bed levelling.


Is it an issue when X-axis rods are able to slide in their mounting bracket?

If the x-axis rods only move in the x axis then there’s no problem, but if they aren’t firmly secured in the other axes then there could be issues.  If they’re able to move then presumably they aren’t secured that well.  Given the relatively small forces involved in 3D printing though, you may well be fine.


It sounds like you're talking about an iris diaphragm. This has many parts that slide against each other, and would best be printed as separate parts, then assembled.


Scanning 3D with a Kinect v2 on AMD Ryzen 7?

In short with the hardware you have it should be no problem. In actuality your specific setup, how you move the scanner, how stable is the scanner, what software you are using, and how you've calibrated the kinect will most likely have the largest impact on the quality, and speed in which you can scan.


2x scaling of Monoprice Mini Select v2 Firmware v30.50b after factory reset?

Thanks for the comments!  They led me to find this solution using PuTTY on Windows as my serial (COM) terminal.  I guess one of my resets put the settings to 1/16th stepping whereas my hardware has 1/8th stepping.

> M115
NAME: Malyan    VER: 3.0        MODEL: M200     HW: HA04
ok N0 P15 B15

> M503
echo:Steps per unit:
echo:  M92 X93.00 Y93.00 Z1097.50 E97.00
echo:Maximum feedrates (mm/s):
echo:  M203 X150.00 Y150.00 Z1.50 E50.00
echo:Maximum Acceleration (mm/s2):
echo:  M201 X800 Y800 Z20 E10000
echo:Accelerations: P=printing, R=retract and T=travel
echo:  M204 P1500.00 R3000.00 T1500.00
echo:Advanced variables:
S=Min feedrate (mm/s),
T=Min travel feedrate (mm/s),
B=minimum segment time (ms),
X=maximum XY jerk (mm/s),
Z=maximum Z jerk (mm/s),
E=maximum E jerk (mm/s)
echo:  M205 S0.00 T0.00 B20000 X20.00 Z0.40 E5.00
echo:Home offset (mm):
echo:  M206 X0.00 Y0.00 Z0.00
echo:Invert axis: M562 XYZE
XYZABCD++-+-+-
echo:PID settings:
echo:  M301 P20.00 I0.02 D250.00 C100.00 L20
echo:  M304 P10.00 I0.02 D305.40
echo:Filament settings: Disabled
echo:  M200 D1.75
echo:  M200 D0
ok N0 P15 B15

> M92 X46.50 Y46.50 Z548.75 E48.50 ; from https://www.mpselectmini.com/howto/steps_per_unit_mm
> M562 Y ; Invert Y because it was Homing to the wrong corner
> M206 X0.00 Y-2.00 Z0.00 ; Inverting the values from M114 once good Home manually found.
> G0 X0 Y0 ; testing the range of motion
> G0 X0 Y120 ; testing the range of motion
> G0 X120 Y120 ; testing the range of motion
> G0 X120 Y0 ; testing the range of motion
> M500 ; this saves the new values to EEPROM
```


Extruder keeps jamming because of filament dust!

I'm highly unconvinced that dust in the gearing is related to your problem. If the material is still being extruded, then "in the air" suggests the base layers may have slipped, or your belts are slipping, either of which will lead to a huge lateral offset, and thus the "printing in air" problem. It's possible but less likely that the extruder feed gear itself is slipping.

If you can post a picture of one of these situations, that would help a  lot.

I will mention in passing that there are several models for filament guides at thingiverse.com . Putting one of these on your machine will eliminate scraping and the resultant dust.


It can be done, although PE is not the best material to 3D print, as it has very low melting point (HDPE is just over 100°C), it is unpleasantly waxy to the touch and needs specialised paints and glues.

I never tried myself, but I know the RecycleBot is supposed to be able to use PE waste to produce a filament.


Nozzle reducing flow as it comes close to finish layer

If you think it is a slicing problem, look at the G-code. You might want to arrange for the infill to be orthogonal to the axes, but it ought to be easy enough to calculate the ratio between printhead motion and the extruder. G-code is just text, and fairly easy to make sense of. The RepRap wiki has a good reference to the commands, and all you care about are X-Y movement, and E movement.

An alternative explanation might be that your extruder is struggling with the extrusion rate, and after continuous extrusion is failing to heat the filament fast enough to melt. The layer change could be providing a sufficient respite that walls start off OK on the next layer. Also check (in the G-code) that the speed of walls and infill is the same.


Laser 3D scanner is used in the movie to scan a key: technically possible?

There have been instances where people have replicated a key from a photograph of a key. A multi-minute scan of a key seems like overkill, but that appears to be a very large key so maybe so.
Is it possible? Yes.
Is it exaggerated? Probably much simpler than is portrayed.
Is it fiction? As portrayed, yes. Practically, no.


Assuming your electronics are open source (such as RAMPS), you can buy upgrades and spare parts from pretty much every 3D printer spare part provider out there, as long as they suit your needs and the specs of your printer.

In other words, if you want make a headbed upgrade, find some bed that i.e.:

Fit the size of your printer
Can be mounted properly
Can be used with your current electronics (and possibly software)

In general, most DIY hobby desktop 3D printers today use more or less the same components mounted in various ways.


Cura's solution to replace corners->arcs to increase corner speed?

Cura's solution can be found in the "Jerk Control" settings.

Short analogy; when driving, and a corner is coming up, you basically have two options to take the corner smoothly; you can take the corner with a wide turning radius, or you can slow down. Taking a neighborhood street corner at highway speeds just doesn't work even if there's nobody else on the road; you'll very likely overshoot the corner, if you're in a RWD car you'll likely lose the back end and fishtail (or worse), and the occupants of the car, yourself included, are going to be thrown around violently, to no-one's real advantage other than to say you took that turn at 70.

Back in 3D printing land, something similar applies; as the extruder approaches a sharp corner, it will be disadvantageous all around for the extruder to try to maintain 70mm/s around what's basically an instantaneous turn. Your jerk (stopping the moving axis) and acceleration (starting the non-moving axis) settings are going to exceed the physical capabilities of your steppers and drive belts, making the corner less accurate (and in the extreme, losing steps causing layer shifts), and if your belts are not perfectly tensioned, and really even if they are, you'll get "ringing" (the 3D equivalent of fishtailing as you straighten out after the apex of a turn while driving).

The first option, cutting the corner, is your corner-to-arc replacement; rather than try for an instantaneous turn, just soften that corner by enough that you're within what's possible for the stepper motors in terms of acceleration. This keeps the speed and surface quality high, but necessarily reduces the accuracy of the print to the model.

So instead, Cura encourages the second option; slow down before the turn. Enabling Jerk Control and tweaking the associated settings lets the Cura slicer reduce head speed gradually as the extruder approaches a sharp corner, thus reducing the torque required to stop motion in one axis and start it in another, to something the steppers can actually accomplish at a rate you'd call "instantaneous". This keeps the corners sharp and avoids ringing along straight lines after a corner, at the cost of a slower overall print speed (though not as much as reducing overall print speed to the speed at which the extruder will take corners).

Now, I realize that this is the opposite of "increasing corner speed"; jerk control exists to slow the extruder near corners. However, increasing corner speed is rarely what you actually want, for the reasons stated above. If you really want nicely-rounded corners, fillet them in CAD, and then the slicer will generate a sequence of arbitrarily short linear movements (true G2/G3/G5 curve interpolation from the purely polygonal STL geometry has been experimented with, but currently more trouble than it's worth) which limit the change of velocity of the extruder as it rounds the corner, instead of making the rounding an "artifact" of printer limitations. At fine enough detail levels of conversion to an STL, the results are indistinguishable from a true curve.


I have a Prusa i3 and the same case happened to me. I checked the continuity of the wires and discovered one badly soldered wire in the heated bed. After soldering the wire correctly, the heated bed turned on again.

Your problem is in all likelihood the continuity of the wires.

I hope that I helped you with your case.


What is the correct way to export SVG in order to convert to STL?

Considering the simplicity of your sample design - i.e. basically only two different Z-levels, easily distinguished by color - I'd recommend one of the online image-to-3D model converters.  Here are two I've used now and then.  You may have to save your image as png or jpg instead of svg.

selva3d   and 3dp.rocks


The success metrics are entirely up to you, the user of the printed part. For example, the strength of the part under the load it's desgined for will be critical for an end-use part (such as as hook), but doesn't matter at all for a fit or appearance prototype. Conversely, the dimensional accuracy is very important for a fit model prototyping a complex assembly, but might be unimportant for an appearance prototype or for some kinds of end-use parts.

Because there's a wide range of uses for printed parts, there's a wide range of possible metrics. Mostly they depend on the original design, the print options chosen (e.g. infill style), the material chosen, and the capabilities of the printer. Here are a few:

Dimensional accuracy (of the part compared to the design)
Dimensional stability (does the part warp or shrink afterwards)
Total time to print + finish
Material cost of print (build materials and other consumables)
Weight of printed part
Labour of operating the printer and any post-processing
Surface appearance/smoothness (different for horizontal, vertical, angled, and curved surfaces)
Surface friction
Surface hardness (can you scratch it easily)
Colour accuracy (of the part compared to the design, for colour printing processes)
Colour stability (do they fade over time)
Colour resolution (are colour changes sharp or blurred)
Rigidity (different in different axes)
Failure load (different in different axes)
Non-adhesion across small gaps (as in a tolerance test)
Porosity (e.g. if printing a container for liquids or gases)

A big cross-cutting metric is repeatability. If you make the same print again the next day and repeat any of these measurements, how different a result do you get?

There are also some metrics that are more about the material choice than the way it's printed:

Outgassing
Flammability
Toxicity


Artefacts when printing parallel to X axis

I have a TronXY X1 myself. This kind of artifacts appear along the X-Axis as it is a cantilever design - and if not properly secured, will start to osctilate when moving sharply. This can be fixed in several ways:

print slower. By making the movement changes less abrupt, the oscilation can be reduced.
stiffen the X on the Z. Often, the X1 has a somewhat wobbly X-Axis. To fix this, someone calling themselves FabianFriethjoph did design a 'bracket' that is intended to keep the wheels aligned and under a little tension. https://www.thingiverse.com/thing:2275654


The .stl files most commonly used for printing do not have any circles in them at all!
.stl files describe the surface of the things they represent with lots and lots of triangles:

That also means that your slicer doesn't really know which parts of the model are supposed to be round (where G2 and G3 might be applicable).
And, another consideration, though historical: Most 3D printers were (and are) based on relatively weak 8-bit microcontrollers. It's much easier for those microcontrollers to calculate the movements needed for the print if it's just straight lines, rather than elaborate curves.
One issue that can arise with this is when your model is of high quality, and your slicers uses all of that quality - a simple circle can then become hundreds or thousands of tiny segments, which all need to be transmitted, parsed and executed - which may lead to stuttering.


@TomvanderZanden's comment is right.  You have probably damaged your motherboard and/or driver boards by applying 34 volts.  You should never exceed rated voltages.

It might help to study stepper motor driver circuits a bit.  Stepper drivers usually act as current sources, not as voltage sources.  They typically have a high-frequency switch that applies pulses of voltage so that the current through the inductance of the motor matches the current needs for the desired step position.  Motors generate torque from the strength of the magnetic fields, with is linearly related to the current through the coil.  The voltage drives the current, but the current cannot change instantaneously in an inductive circuit.  Unless the motors have an uncommonly high coil resistance, two to five average volts will be enough to provide the maximum current.

The motors are pretty insensitive to the voltage applied, as long as the current meets the specifications.  The motor driver chips are sensitive to the applied voltage.  They are sensitive because the internal switches and logic can only withstand certain voltages, and they are sensitive because the circuits assume that the current won't change too quickly.  If the current gets so high that the magnetic material in motor saturates, the inductance suddenly becomes much lower, and the current can spike to very high levels.  This current spike can destroy drivers.

Heaters also have a voltage spec.  The heaters I've seen are specified for 12 or 24 volts.  To avoid burning out, a heater must have a low enough thermal resistance to the object being heated that the inner heater temperature is not so high that the heating element is damaged.  Powering a 12v heater from 34 volts would cause the current to increase by a factor of 34/12 = 2.83.  The power would be that ratio squared because both the current and the voltage are higher.  The heaters, whenever they were on, would be generating 8.02 times the power.  This might not result in the good behavior of the heater control systems, and could damage the FETs which are driving the heaters.

As for changing the power supply, before doing that I would want to check that the power supply was not supplying the needed voltage and current.

When you've replaced the motherboard and drivers, and configured the drivers for the required operating current, attach a voltmeter to the power supply.  Turn on all the heaters, power up the otors, and watch the supply voltage.  If it remains true (say, within 15%), the power supply isn't the problem.  If the voltage dips, or pulses, or does anything other than staying stable, I would consider a higher current (not higher voltage) supply.  Connecting two supplies in series causes problems with the ground reference of one of the supplies.  Connecting two supplies in parallel, unless they are designed for that use, often isn't any better than a single supply because they will not necessarily share the load well.

Good luck!  I look forward to further questions.


Filament Balling up on random parts of a print

I experienced that several times if my print temperature was too low. Then, the filament does not stick to the plate very well and prefers to stick to the nozzle which pulls it away. Solution is to increase the temperature by 5 to 10 degrees, at least for the first layers..


Can you print at low speeds with e3D Volcano hot end?

Speaking from first hand experience running a Volcano hotend, mostly using a 0.6 mm nozzle, but I have used 0.4 mm as well. I can't really complain about any lower printing speed limit (low speeds are usually a solution to high speeds problems for me).

Just for completeness: I am using a DaVinci 1.1 Plus with custom firmware (modified Marlin) and an E3D Volcano hotend. No problems with the nozzle, clean prints! Note: I am using the Titan Aero as extruder but not using the included pancake motor! Went with the original motor of the DaVinci.

And as always: the parameters are key! Given a bit of tuning you can get amazing results! For PLA and ABS I can work without stringing. Although ABS seems to be prone to pitting (slight underextrusion at start of path). TPU and other flex are sometimes a bit of a challenge, but that's mainly due to my own lack of experience there.

The one important caveat here would be to also reduce the nozzle temperature. A possible theory here might be that the filament has more time and surface to heat up.

(Sometimes I go as much as 15 °C lower as compared to normal/high speeds! Usually lower speeds means small pieces for me and in term means a limit to the layer cooling time.)


Are there multi-filament hardened nozzles or equivalent systems?

Yes, but there is no hardened version of the "Diamond" nozzle design. Basically when you want to use a hardened nozzle, or a Ruby nozzle in combination with color mixing (I specifically refer to mixing solutions as the melting chamber is smaller than filament changing solutions and your request for none or minimal purging towers) you need to order a design that accommodates the replacement of the nozzle. In such a case you can remove the standard nozzle to replace it for a hardened version.

There are a few 2 and 3 filament input designs that are offered on typical auction and Chinese selling sites. Below is an example for the Zonestar M3 mixing color hotend with a replaceable nozzle.


MKS board losing power after endstop installation

Have you tried plugging in the plugging the Z and/or Y end stops into the X position? This could tell you if it's actually the end stops or the board.

EDIT: Also, if the Z and/or Y end stops seem to work just fine in the X position, ensure you have the X position filled and try the other end stops in the Z & Y positions. It may be a case where having multiple positions on the board filled might be causing you an issue. This would point back at the board and not the end stops.


How to set up USB camera for Octoprint on Debian system

You need to install a web-cam server on your Nettop. Octorint recommends Yawcam for windows and mjpg-streamer for linux.

mjpg-streamer: https://github.com/jacksonliam/mjpg-streamer
Yawcam: http://www.yawcam.com/

OctoPrint has instructions for installing mjpg-streamer on a raspberry pi. The process should be very similar for a Nettop running Debian so its a good starting place. The instructions are a little ways down the page: https://github.com/foosel/OctoPrint/wiki/Setup-on-a-Raspberry-Pi-running-Raspbian


I notice that in "configuration_adv.h" for the BIGTREETECH-SKR-mini-E3, which uses TMC2209 drivers, the similar section has:
#if HAS_TRINAMIC_CONFIG

  #define HOLD_MULTIPLIER    0.5  // Scales down the holding current from run current
  #define INTERPOLATE       true  // Interpolate X/Y/Z_MICROSTEPS to 256

  #if AXIS_IS_TMC(X)
    #define X_CURRENT       580        // (mA) RMS current. Multiply by 1.414 for peak current.
    #define X_CURRENT_HOME  (X_CURRENT/2)  // (mA) RMS current for sensorless homing
    #define X_MICROSTEPS     16    // 0..256
    #define X_RSENSE          0.11
    #define X_CHAIN_POS      -1    // <=0 : Not chained. 1 : MCU MOSI connected. 2 : Next in chain, ...
  #endif

  #if AXIS_IS_TMC(X2)
    #define X2_CURRENT      800
    #define X2_CURRENT_HOME X2_CURRENT
    #define X2_MICROSTEPS    16
    #define X2_RSENSE         0.11
    #define X2_CHAIN_POS     -1
  #endif

  #if AXIS_IS_TMC(Y)
    #define Y_CURRENT       580
    #define Y_CURRENT_HOME  (Y_CURRENT/2)
    #define Y_MICROSTEPS     16
    #define Y_RSENSE          0.11
    #define Y_CHAIN_POS      -1
  #endif

  #if AXIS_IS_TMC(Y2)
    #define Y2_CURRENT      800
    #define Y2_CURRENT_HOME Y2_CURRENT
    #define Y2_MICROSTEPS    16
    #define Y2_RSENSE         0.11
    #define Y2_CHAIN_POS     -1
  #endif

  #if AXIS_IS_TMC(Z)
    #define Z_CURRENT       580
    #define Z_CURRENT_HOME  Z_CURRENT
    #define Z_MICROSTEPS     16
    #define Z_RSENSE          0.11
    #define Z_CHAIN_POS      -1
  #endif

  #if AXIS_IS_TMC(Z2)
    #define Z2_CURRENT      800
    #define Z2_CURRENT_HOME Z2_CURRENT
    #define Z2_MICROSTEPS    16
    #define Z2_RSENSE         0.11
    #define Z2_CHAIN_POS     -1
  #endif

  #if AXIS_IS_TMC(Z3)
    #define Z3_CURRENT      800
    #define Z3_CURRENT_HOME Z3_CURRENT
    #define Z3_MICROSTEPS    16
    #define Z3_RSENSE         0.11
    #define Z3_CHAIN_POS     -1
  #endif

  #if AXIS_IS_TMC(Z4)
    #define Z4_CURRENT      800
    #define Z4_CURRENT_HOME Z4_CURRENT
    #define Z4_MICROSTEPS    16
    #define Z4_RSENSE         0.11
    #define Z4_CHAIN_POS     -1
  #endif

  #if AXIS_IS_TMC(E0)
    #define E0_CURRENT      650
    #define E0_MICROSTEPS    16
    #define E0_RSENSE         0.11
    #define E0_CHAIN_POS     -1
  #endif

  #if AXIS_IS_TMC(E1)
    #define E1_CURRENT      800
    #define E1_MICROSTEPS    16
    #define E1_RSENSE         0.11
    #define E1_CHAIN_POS     -1
  #endif
// ...

In the reddit thread Stepper driver current settings?, user brewc found that the stepper motors drivers supplied with the Ender 3 specify peak (maximum) current whereas the TMC drivers specify RMS current.
So, you probably want to change the current settings to those in the above .h file.
Of course, in the spirit of changing almost everything on an Ender 3, you could also swap for stepper motors with a higher current specification and/or add heatsinks to the motors.


Temperature sets to cooling when print starts CR10s Pro v1

File name is too long, I had the same issue, shortened the file name and now printing perfect


Set the overhang parameter in Blender 3D printing tool box

You are looking at overhangs in the design tool.  What matters are overhangs when printing.

When designing the object, the coordinate system is convenient for working with the object.  Before slicing, the object can be rotated and repositioned for better printing.  Only after is it positioned for printing can the actual overhangs and bridges determined.

Unless you wish to limit yourself to the design tools coordinate system, I wouldn't have the design tool generate support material, and I would ignore its comments about overhang angles.  First, bring the object into your slicer, position it on the print bed, and only then evaluate the need for support material.

To be honest, I often have a printing strategy in mind while I am designing an object, but when the object hits the printer I sometimes completely change my plan.


Severe regression in print quality after adding Z probe

Even with Auto Mesh Bed Leveling, you need to level the bed as good as you can. Your leveling grid show it varies between -0.403 and +0.145, that is about 0.55 mm or about 2-3 layers of filament (0.2 or 0.3 mm per layer). That can't be compensated for reasonably.

Re-level your bed so that the corners only have an absolute error of at max 0.1 mm around their average 0 - that's half what I consider the standard layer 1 height of 0.2 mm, regardless of other settings.
Make sure the 0 of the extended probe is a sliver under the nozzle, just to prevent piercing your bed on probing
G28 should bring the nozzle a hair sliver above the bed - if you move the head in X or Y direction (by hand after disabling the steppers, or move the carriage using the LCD) it should not make contact.


That's the temperature problem that you've encountered.

The temperature of bed and hotend is reported every few seconds. Per default, first that sets is the bed temperature, then you need to wait for the bed to reach it, then warm up the hotend, and then start printing.


The image of the sliced print part is not very clear but printing support on air is a feature of Ultimaker Cura. This is done when support is laid on top of your print part if you enabled Support Placement to Everywhere, which you did. The default Cura setting for Support Bottom Distance (which is a sub-setting of Support Z Distance) is the layer thickness specified in Layer Height. If you have a layer height of 0.2 mm, the Support Bottom Distance is also 0.2 mm. For the top, option Support Top Distance this is two layer heights, so 0.4 mm in this example. These options are visible in the expert mode, you can search for them in the search box, see image below.

Why should you want air in between your part and the support?

You'll soon find out when you want to remove supports, if no gap is used, the support will fuse to the print part. This is only interesting (no gap between print part and support structure) when you use a different filament for support like PVA or break-away filament; e.g. PVA dissolves in water.

Note on the updated printed part images, you seem to have a stringing issue that needs to be resolved first. Note that it tries to print support on top of inner side of the toroid. Maybe fusing the support will help you to slice better supports, or alternatively set option Support Placement to Touching Buildplate and use an experimental option called Tree Support. You can also try to change the print orientation by rotating the print. Last resort is to design the supports yourself in a 3D model software program.


Orientation of long thin rod on P3Steel v4

This is half of an answer. I have finally received an answer from my supplier, which says:

  Long thin rod is mounted as in the photo. I do not know what is a
  small hole.

So the small hole is still a mystery.

Here is the photo that was included with the message (which confirms my placement, just not the orientation):

Update

As tjb1 points out in his comment, the hole can be clearly seen on the right hand side of the bar, in the eBay photo:


What do you do If the whole extruder is clogged?

The extruder is not a single component, but a collection of components. From the top, you may have a bowden tube or a direct feed type of design. If the former, there's the bowden tube which extends into the heat sink. If it is a direct feed and not an all-metal design, there will be PTFE tubing inside the heat sink.

The heat sink is a finned assembly, usually cylindrical, sometimes other shapes. Attached below that will be a threaded coupling called a heat break. Both the heat sink and heat break will be configured to have the same inside diameter, to allow the filament to pass through to the next stage.

The heat break passes into the heater block. The nozzle passes into the heater block from the opposite side. The two items contact each other when properly assembled.

If your nozzle is not blocked, but there is a blockage somewhere else, it would indicate that the PTFE tubing has become damaged or a piece of debris has managed to fall into the opening when filament was removed.

The items are easily disassembled and the pathway for the filament can be cleared with a suitable tool.

If a portion of the extruder assembly has previously filled with filament, the nozzle was not solidly secured to the heat break, or the PTFE filament had slipped back or was not fully inserted into the heat sink.


I've been able to reduce stringing by reducing the nozzle temp in 2°C increments until it goes away.
You'll also want to increase your retraction settings a bit.

The problem is caused by the plastic being too hot and oozing out of the nozzle - it's a bit too runny.

Search Thingiverse for Heat Towers.  You'll need to edit the G-code so that your printer adjusts the nozzle temp at each layer.  That will give you a really good indication of the best temperature for the given material.

Keep in mind you'll want to print it for each new brand (and sometimes color) of filament.


TL;DR
You need to have the version 2.x controller board (and the associated CR-10S firmware) to use the filament sensor. If you do not then you will need to upgrade your controller board.

Board Comparison
For an excellent breakdown of the boards, read Creality CR-10 and CR-10S Models – What Printer do you have.
There appear to be two basic model versions of controller board, which use different firmware:

Controller board v1.1.2 (or v1.1.3 with additional filter capacitor) which uses CR-10 firmware. These have a small Atmel ATmega1284P chip, and one Z-axis stepper connector;
Controller board v2.0 (or v2.1 with extra fan ports) which uses CR-10S firmware. These have a large Atmel ATmega2560 chip, and two Z-axis stepper connectors.

See the section Board examples at the bottom of this answer for a visual comparison of the two boards.
It is the v2.x (CR-10S) board that has the filament detector, which uses the X+ endstop connector:

To quote part of the page:

Please make sure you know what printer you have. There are 8 DIFFERENT models from Creality. There are 2 different boards across these models. The easiest way to identify what one you have is if it has a filament sensor or not. If it does then you have a CR-10S machine. If it does not then it is a CR-10.
Just because you have a CR-10 S4 or CR-10 S5 that does NOT make it a CR-10S.
The S4 and S5 sizes come available with either board versions. Again the main way to tell is if you have a filament sensor from Creality or not. Whether you have Dual Z or not does NOT matter. What matters is what board is in the enclosure.
Typically every CR-10S board came with a filament sensor. So if you don’t have a filament sensor then it is the CR-10 and you need use the CR-10 firmware. However we have seen some CR-10 Mini machines ship with CR-10S boards. Use the below pictures of the boards that are in the wild to identify what model you have. The important thing is to use the correct firmware for the board that is in your machine.

Separate upgrade
With respect to the first question, you would be best off contacting Creality directly, via their customer support, to see if the sensor is available separately. This would probably make for the least painful method of implementing the filament sensor.
Alternatively, there is this kit, Creality CR-10S Upgrade Kit, for $120:

Best Upgrade Kit for your Creality CR-10 3D Printer contains Dual Z axis for Stability in 3D Prints & Filament Monitoring Alarm Protection (Sensor) which alerts you when the filament has ran out or broken for Smart 3D Printing

There seems to be a dual-Z option, for an extra $80

Hacked solution
For the second question, the XCSOURCE 1.75mm 3D Printer Filament Detection Sensor Module Filament Run Out Pause Monitor for 3D Printer DIY Kit TE720,

the instructions state that it is designed principally for Lerdge control boards:

Instruction:

When you are using a Lerdge brand motherboard: The green light on the motherboard will turn off when the filament runs out, the
motherboard will stop printing until you supplement the filament and
continue printing. (Please connect to the M-sensor Interface)
When you are using other brand motherboard: The Detection Module uses the level transition detection method. While there still have
filament in the module, the detection port shows as high level; when
there is no filament in the module, the detection port will transform
to low level as "Filament Run Out Command" which will stop the
printing, so you will have time to supplement the filament and
continue printing.

So, it is not particularly clear as to whether it will work with your board - for it to do so, your board would need to have:

A compatible input (i.e. X+ endstop);
The compatible firmware (CR-10S), and;
Use compatible logic levels (i.e. active LOW to shutdown printing).

If not, then given point #2, it would appear to require additional external logic, or microcontroller, to sense the transition to LOW and then shutdown the printer.
For example, this chap on Thingiverse, Cr-10 Filament Sensor Bracket & Tutorial, states that they bought a sensor off eBay, that looks similar, and they provide a printable mount and instructions on how to use it with a CR-10. However, it is not a standalone affair as shown in the CR-10 S4 - because an additional Raspberry Pi and OctoPrint is required.
To use this particular sensor with your board, you would need to:

See if which controller board you have - either the CR-10 or the CR-10S compatible board (see Board Comparison above). If it is the CR-10S therefore it has the compatible input (X+ endstop), and firmware, needed for the filament sensor,

Enable the use of the sensor, if necessary, in the firmware (either by the UI if possible or uploading new firmware) and;

Check whether the CR-10 controller board uses active LOW to detect a lack of filament (or again, this may be a UI, or firmware, setting)
You could test this last point yourself, by applying a LOW level voltage (i.e. grounding) to X+ endstop input on the control board (after checking the UI/firmware for appropriate settings), and see if that halts/pauses the print. If not, try a HIGH level (5 V). If it is active HIGH then you simply need to use an inverter (i.e. 4069), between the sensor and the X+ endstop connector.

Board examples
There are two principle board options, v1.x and v2.x, the latter has dual Z stepper motor connectors and the former does not .For example:
Version 1.x, for CR-10 firmware - Motherboard Controller DIY Creality 3D® CR-10 / CR-10S 3D Printer CR-10 Upgrade Control Board12V (CR-10S Mainboard)

Version 2.x (2.1 in this case) with Dual Z stepper connectors, for CR-10S firmware -  Luxnwatts CR-10S Mainboard Replacement Controller Board Upgrade V2.1 Motherboard For Creality S4 S5 3D Printer


Can 3d printers be operated at voltages above 24 volts?

I believe the main issue is the voltage regulators and capacitors on your standard print main board are not rated for 48V. You can find some CNC shields that can handle up to 36V but these are lacking 3d printer features such as heater ports and only have 4 stepper slots.


OK, I have found the first piece of this puzzle.
"The Raise3D printers listen on TCP port 31625 for remote control from ideaMaker."


Your printer does seem to have a firmware problem and lack important safety features - it should have stopped the moment it went 300°C measurement, beeped like hell, and shut down with an error message about Thermal Runaway Protection. Immediately stop using the printer!
Before you try to print again, you need to make a proper firmware for your printer, one that has both Mintemp, Maxtemp as well as Thermal Runaway Protection actiive and flash that. While setting up your firmware, make sure you use the right temperature table for your thermosensor. How to do that is detailed here.


Vase Mode changed the name in some version before 3.5. Now you can achieve this with 2 modes: "Surface Mode" and "Spiralize Outer Contour". To turn it on do this:

Choose the Custom setting menu on the right
click a gear to set up what settings you want to see
Under the header "Special Modes" you find both Surface Mode and Spiralize Outer Contour
set the checkmarks on both

Turning on the Surface mode to Surface and checking Spiralize Outer Contour gets the "classic" Vase Mode.

Turning on Surface without Spiralize Outer Contour gets an infill-less outer perimeter

Now, the classic Vase mode will only print the single most outer perimeter of a print, so your model will have to be very limited with angles and contain no bridges - with one perimeter, you will only be able to print at best 45° angles!


I had a similar problem some time ago. The problem in my case was, that in the slicer I had a minimum layer time, which was pausing the printer until that time had passed. I can't remember the name of the settings and I'm not at home right now, but the slicer can either print full speed and pause or it can slow down, to maintain a minimum layer time. I guess the idea is to give the plastic time to cool down.


How important is the minimum layer height on a 3d printer?

I believe the Slic3r Manual summarizes this quite nicely:

  A thicker layer height will provide more flow, and consequently more heat, making the extrusion adhere to the bed more. It also gives the benefit of giving more tolerance for the levelness of the bed. It is recommended to raise the first layer height to match the diameter of the nozzle, e.g. a first layer height of 0.35mm for a 0.35mm nozzle.

In other words, larger layer heights for the first layer typically gives better adhesion, and makes inaccurate bed leveling (and auto leveling) still work.


This is an ugly question, and an ugly answer.

Nail polish doesn't come with an ingredient list. Nor are there MSDS's available to refer to what solvents are in it. So it's "unknown 1"
Most every filament company will not give you a list of compounds for colorants or plasticizers used. MSDS is off the table. So, even though we do know what PLA and ABS is inherently, we have no clue about the other ingredients used to make your particular filament. This is "unknown 2".

What both of these comes down to is a very nasty situation indeed. We know for a fact that ABS dissolves into acetone. PLA does not.... Except we have had reports of PLA that does. When we look further into those responses, and ask them to do a burn test, they smell popcorn and something acrid (ABS).

This guarantees unless we have virgin material and MSDS in hand, you only have a close guess at what material you have. And that's to say nothing about "nail polish", and its components.

There are also other solvents that will dissolve PLA. MakerBot back before they turned evil, noted a solution called Beta Solution (90% isopropyl alcohol, 9% KOH, 1% Al(OH)3  ). This stuff is noted for dissolving PLA and leaving ABS intact.

Long story short: "Could Nail Polish damage pure PLA?" We can't guarantee purity of PLA, we can't guarantee contents of nail polish's solvents. The only answer is to print a swatch and test yourself. Calibration cubes are quick and easy.


What are the modifications on this Kossel?

Cool you placed my Kossel Mini on Stackexchange!
What I have modified to the standard kit:

Retractable probe using RC Marlin (Rich Cattels Marlin with auto bed probe functionality). Never have to adjust endstops after it is once setup.
All can be done in firmware.
Made a transport case, in the picture the cover is missing which is a triangular case which fits over the printer.
You can clip it on and the carry it with the handle on top.
I just throw it in the car and bring it to the Hackerspace and Hackerevents/Makerfaires and when I feel to it, I can do an auto-probe to align it again (which is hardly needed BTW)
Another mod is the Vaeder extruder, which is really cool in the way it uses a GT2 timing belt to drive the filament. It uses a round wheel and it drives the filament over 1/4 of the diameter of the wheel, so there is a 3 to 4 cm area where the belt drives the filament.

Advantages:

Lots of retracts don't "eat" into the filament causing feed issues
Doesn't flatten the filament. Keeps it nice and round.

Disadvantages (at this moment):

Not possible/ very hard to do filament swaps on the fly (to experiment with multicolor prints).
First time assembly can be a head ache, once you have it assembled it really works and is easy going.

And last but not least. I made a foldable Roll holder.

It is mounted on top by two M8 screws with knobs. When I am done I undo these two screws, fold in the roll holder and it is then mounted to the side of the flight case. This way I can transport printer and roll holder carrying it only using 1 hand. So I use the other hand carrying the bag with accessories like rolls of filament, 3D spray, tweezers etc.

Maybe this info helps other people new to 3D printing improve their printers, or enables them to bring printers more easily to meets and events to inspire others to build more Delta printers. As it's just mesmerizing to see them print. I love watching the print come to reality because it such beautiful piece of engineering!


How do filament properties change after printing? (In relation to water absorbtion)

Filament that absorbs water prior to printing is subject to boiling temperatures as it passes through the heater block. In extreme cases, steam will be visible and a spitting sound will be heard. The filament will expand as the water exits, causing multiple structural and printing problems.
Once printed, dry filament may absorb water from the atmosphere, but is unlikely to be subject to boiling temperatures.
Waterproofing as a general consideration usually means the ability to keep water out, which is possible if the model is sealed and some printing conditions will adhere each layer well enough to the previous one to provide floating-type waterproofing.
PETG is hydroscopic, which means it will absorb moisture from the air. When printed properly (layer adhesion), the model can be waterproof.
These terms are independent and should not be used interchangeably.


Can 3D printer models be used in video game engines and vs versa?

Yes. You can import it into Blender, but it will need "bones" and "armature" if you want it to move at all.   In Blender, you can manually add armature and "Rig" it, if you want animations.
You can probably convert whatever file type the 3D model is (probably STL) to fbx with Blender
For animating, start with a super basic 2-bone rig YouTube tutorial, then learn about vertex weights or automatic weighting.
But you'll have to UV map it too. The UV map tells textures where to go on the model, STL doesn't have those.
Your time is 100% better spent finding a model that's ready and moving on with your project.
Check Unreal Marketplace.
Also,
https://www.turbosquid.com/3d-model/free/low-poly/character
https://www.cgtrader.com/free-3d-models/character?polygons=lt_5k


Where is filament thickness setting in Cura?

There are two important settings related to filament thickness in Cura 4.8.
They are in Preferences window (open menu Preferences > Configure Cura):

Printers > Machine Settings > Extruder 1 > Compatibile material diameter - this setting will influence visibility of materials available on the list in next point.
Materials > Information > Diameter - width of filament currently selected in the list.

Important remarks:

After selecting a filament from list you may alter its settings. But it will not become the active filament for printing until you press "Activate" button above the list.
Extruder settings (Nozzle size, Compatibile material diameter) will be always displayed with "." (dot) for decimal point. But if your regional settings (in operation system) use "," (comma) for decimal point, then the only way to enter new settings is use comma, otherwise they won't be saved. From my observations this defect concers only this single window.


Prusa's P.I.N.D.A. XYZ axes calibration fails with generic message "Consult the manual"

One thing, and the one that eventually solved my problem, is to update the firmware. Firmware update instructions: Upgrading firmware - Prusa3D

The only thing you might get stuck on is selecting the right COM port.

Go to the device manager (run devmgmt.msc)

In COM and LPT section, you should see port for your printer by name. Select that port number in the firmware update tool.

In my case, I had to run the calibration twice before it worked. I had no problems since then.


What calibration options should I look into given these defects

Your print does not suffer from layer shifts as you call them. This uneven layer deposition is typically caused by the (positioning) accuracy of your printer. All-in-all, this print does not look so bad. You would get better quality prints on a different style of a printer; most high-end printers have a lowering platform instead  of a forth and back moving platform.

Although 180 °C is at the low side of printing PLA (usually it starts at about 185 °C), the print does look okay. However, looks can deceive, it does not say anything about structural integrity (layer bonding).

Note, to calibrate the temperature using a temperature tower, you need a different calibration test print, preferably one that tests overhang. This latter is usually far more important as there is normally not much to see at the walls, you need a slanting part in the print or an overhang to determine the optimal temperature.


I'm not sure exactly sure if you have one problem or two distinctive ones.  However a few notes:

The latest version of Slic3r PE can always be fetched on their GitHub release page.  At the time of writing that would be version 1.38.5, but I concur with you that that is unlikely to be the problem.

Mirrored objects are a clear indication that one of the Cartesian axis is swapped (not that it is translated).  Any of the axis can be swapped, but since the peculiarity of your printer is that the homing point is at the front RIGHT, I would guess the axis that got messed up is the X one.

I have no way to test the following, but if I got the meaning of your first two pictures, then I guess the correct settings in Repetier may probably be these:

If even that fail, check the handedness of the coordinate system of the software generating the model you are trying to slice.  Modelling software like Blender and others are typically right-handed, but many tools for processing those model for on-screen application (movies, videogames) are left-handed.  That means that even if the model display correctly in the native editor, it may be rendered mirrored in another software.


How to remove exess filament from bed after removing model

You should remove it because it can and will affect the quality of future prints. Residue can mix up with new filament and create a ugly of colors and also prevent adhesion in places, thus potentially ruining your next print.

You have several solutions to clean up the bed:

Scrape it off: usually works, but you risk chipping the surface if you're not careful or if you stumble upon a bit of residue that is stubborn and you need to apply strength to get rid of it. I think a scraper is included with the printer.
Sponge and soap: Since the bed cannot be removed, as far as I can tell, you'll need to make sure that the sponge isn't dripping or put towel paper around to avoid damaging the components below, including the heating unit. Rub it gently on the residue until it soften and detaches. It might take a bit to work.
Yellow glass cleaner from Karcher: my favourite, the one I use on my printer and it never failed me. Spray it on a cloth or something, and rub it on the bed until the residue softens and detaches. It might take a bit to work, but you don't run the risk of dripping liquid on any component, and it works way better than soap and without the risk of chipping the bed like when you use a scraper.


The skirt looks ok, which tends to rule out the most extreme flow or blockage issues. However, skirt/bottom layer can be over-squashed so not ideal for calibration.

I assume this is intended to be a 100% layer rather than infill. It looks like you're achieving about 50% infill, which is a good clue.

I guessed (and confirmed in comments) that you are set for 3mm filament, but using 1.75? (I had cura default to this on me not long ago, despite printing perfectly before, and no intentional changes). One easy check would have been to try one of the provided pre-sliced models that came with the printer.

The effect of configuring for 3mm filament is to reduce flow by a factor of 3 (diameter squared), so even a 50% over extrusion still leaves you with less than half the plastic volume required.

After fixing this, you will need to raise the Z-home position slightly to enable the first layer to extrude properly.


Yes, but...
Technically, you can reuse your old heater block and nozzles and just buy a new heartbreak and cooling body or the other way around. However, you might run into problems under working conditions, especially if you install the heater block together with its native heating cartridge and thermosensor. Installing a thermosensor to which the printer is not adjusted to can lead to all kinds of problems - Firmware update is a must!
Another source of trouble could stem from not taking care in the change itself. The Makerbot MK8 seals the hotend by pressing the liner against the nozzle, which itself is seated against the heartbreak, just like the e3D lite6 seals itself. On the other hand an all-metal e3D v6 seals itself by seating the heartbreak against the nozzle on a larger area. If the seal is imperfect, the Makerbot Mk8 style tends to leak out through the top. Such a leak can leave plastic in the threading which has to be removed carefully before reusing.


I'm not aware of libraries that do that for you (but you can create your own, see end of the answer), but creating a relieve hole pattern is not that difficult or tedious using iterator functions (e.i. the for loop). Note that it may not be a good idea to make enclosed holes inside your object, see the edit section at the bottom of the answer.

Small OpenSCAD test script:

 tol=0.2;

 difference(){
   cube([100,100,10]);
   for (x=[10:20:90]){
     for (y=[10:20:90]){
       translate([x,y,-tol/2]){
         cylinder(r=9,h=10+tol,$fn=180);
       }
     }
   }
 }

This can be used for both parts of your question, but in case the pattern needs to be inside an object you need to lower the value of h in the subtracting cylinder and raise/translate it (you could use the center=true in the cylinder function as a parameter and raise the center to the middle of your object translate([x,y,objectThickness/2])). You could make a module of the recurring pattern yourself to create your library.

note: Replace cylinder with cube or any other geometrical solid or (2D) pattern (use linear_extrude) to subtract from your part.

EDIT:

Note that it is not always wise to create your own spacing/grid structure enclosed in the model. Please read the accepted answer of this question. This answer explains that slicer applications work best with true solids!


3D printer filament will not load after running the printer out of filament

PVA is nasty filament to print (from experience). I use it in the Ultimaker 3 in a separate designed core (BB) and even with that core the filament frequently cooks up and carbonizes clogging the nozzle resulting in grinding of the filament at the feeder (it also attracts water really easy, so keep it in the bag with desiccant bags).

To clean the inside of the nozzle, a few techniques exist to remove blockage. E.g. by performing a cold pull or using the atomic method. Both techniques rely on the mechanism to insert the (cleaning) filament when it's hot and remove it quickly at a lower temperature. E.g. see here or here.

The trick is that you pull out all the goo inside the nozzle, you do that by raising the temperature and sticking some (cleaning or high temperature) filament (your ABS will do fine) to the goo. When the temperature lowers, you quickly pull and hope that some of the goo sticks to you cleaning filament. Cut of the tip and repeat until no goo or burnt particles come out and you can push the cleaning filament through the nozzle. You do not need the automatic feeding, it's all manual labor, just raise temperature through the menu and press the lever of the extruder to load the cleaning filament, lower temp and pull back after cooling a bit while pressing the extruder lever.


Measuring the legs of the triangle instead of the hypotenuse in Fusion 360 sketch

For this, use a construction line:

draw the approximate line
press x to go into the construction-line mode
pres l for the line tool
Draw a line from the end to the base
constrict it orthogonal to the base, turning it into the height
press d to go into defining distance mode
click on the dotted line
type in the height
press x again to get back to normal lines.
complete the triangle


Can't level CR10 as nozzle is touching the glass

If the nozzle is touching the bed, you need to further screw down the bed. If the springs under the screws are already fully compressed, you cannot lower the bed further and you will need to move the Z-endstop up. Note that there are handy fine tuning aids you can print to help you with this, see e.g. this fine tune part for your printer. Note that this issue is not uncommon, I've read that more people encountered this.


My printer is making mistakes on the right half of the print, but not the left

I found the problem. This model of printer Monoprice Select v2 has bed warping issues so when the bed heated up it would warp severely. I bought a glass bed and all my problems were solved.


How to remove a PLA print stuck to a BuildTak sheet

I would do as fred_dot_u initially suggested, by increasing the bed temp (or using a hair dryer) to heat the BuildTak. Then, use a small fan to quickly cool the platform (or at least quicker than room temperature). An ice pack on the build plate/part could also work. This drastic fluctuation between the build platform (or BuildTak) and the part should make it easier to remove the part.

This works because the temperature coefficient is going to be different between the build plate, BuildTak, and the 3D printed part. So, each part rises and falls in temperature at different rates. When objects are heated and cooled, they expand and contract (respectively). Essentially, as each object expands and contracts at different rates, the objects begin to separate.

A good example is if you've ever placed a jar into the fridge/freezer to make it easier to open. Typically the jar is glass and the lid is either plastic or metal. You'll notice that the lid is significantly easier to open, as opposed to its original state, because the lid and the jar physically react differently to temperature changes.

Also, here is a good article explaining a few different ways to remove a stuck part. (for prosperity sake, here's a quick list):

Brute force. Just try to yank on it until it pries off.
Sharp objects. Try using a small blade to get under a corner of the part and wiggle the part a bit. Careful not to break the blade and send it flying.
Utilize temperature difference. I already explained this above.
Use solvents. I didn't know this, but apparently there are solvents in the market that are targeted for 3D printing maintenance. Essentially its just an alcohol-based liquid...
Use floss. Another cool idea that's related to using a sharp object, using dental floss. Basically, any small object that you can remotely wiggle under the part and give you more leverage to yank on it.
Invest in a flexible build platform. I've personally heard some mixed reviews on these (in present day of 2016). But material science is getting better every year, so who knows what will be available soon.


Can leaving the nozzle at 160 °C continuously on in between prints affect the viscosity of the prints?

PLA starts to change its properties at above its glass transition temperature of 60-65 °C, if stored there too long. Keeping it at 160°C, close to the melting temperature (173-178 °C) can degrade the material relatively rapidly. During an extrusion, this is usually mitigated by filling fresh material into the melt while the older material gets extruded, but keeping the machine stagnant at the high temperature has not only creep the heat up from the designated melt zone (thus preheating material that should not be preheated yet) but also can damage the material deep in the melt zone. Together with this possible material degradation, the preheated material melts faster and might overshoot the aimed at print temperature until the normal temperature is reached again. Both effects can lead to reduced print quality in the lower layers.

The time saving from keeping the filament heated up for an extended period of time is, in my opinion, not worth the quality reduction that can come from using non-uniform material. You pay more in lost prints than you save in time for heating up the head.

If it is impossible to not keep the hotend heated between prints, it might be advisable try these:

Starting every print with a larger purging operation might get rid of degraded material. It would be as simple as extruding some quantity of material before starting the actual print at the edge of the build plate.
Aside from purging, it might be a good idea to reduce the hold temperature from 160 °C to a lower temperature, allowing the melt to partly solidify and keep the heat creep in check.


Print job stops when given serial command

Opening a serial connection to your printer will usually reset the microcontroller, stopping the print.

The serial interface has a line known as request to send (RTS) that indicates to the microcontroller that the computer is ready to receive data. When the port is closed, this line is HIGH (indicating the computer is not ready), and when you open the serial connection the line goes LOW (indicating the computer is ready now) and the transition from HIGH to LOW triggers a reset.

There are a number of ways to prevent this:

In software: disable hang up on close (HUPCL). This prevents the RTS line from going HIGH after you close it, allowing it to be subsequently opened without causing a reset. However, this does not work for the first attempt (the first, initial connection still causes a reset). How this is configured depends on your software/driver set up, but it is widely supported.
In software: disable the RTS line from going LOW in the first place. I'm not sure if this is readily possible with common serial drivers.
In software: modify your workflow to always keep the connection open, preventing the associated reset from happening.
In hardware: your printer's board will have some circuitry on there that translates the RTS line transitioning from HIGH to LOW to trigger a reset, usually this is implemented in the form of a single capacitor between RTS and RST. RST is normally pulled high with a pull-up resistor (on the order of 10k or so), and when RTS transitions to low the capacitor briefly allows some current to flow, pulling RST low. One way to prevent this is to include a stronger pull-up resistor that overcomes the current drain associated with the RTS line going LOW. DisablingAutoResetOnSerialConnection suggests using a 330 Ohm resistor between VCC and GND.
In hardware: desolder the capacitor mentioned earlier.


There is nothing wrong with the G-code, M109 S195 sets and waits for the temperature to reach the set point. There must be a different reason, other than G-code, why the temperature is not set correctly.

After updating your question by adding another G-code script, the conclusion is that there is nothing wrong with the G-code itself. The problem is that the printer cannot set the 195 °C temperature.

Could it be that the minimum temperature is 200 °C and that it doesn't set a temperature lower than the minimum value?

If you are comfortable enough to flash a new firmware (which you should always do with an Anet A8 as it has no thermal runaway protection) you could try to see if this is a firmware problem.


Looking for a material so I can make ABS parts with rubber grips and feet

Ninjaflex dual-extrudes great with ABS. I've done a fair amount of NF/ABS dualstrusion. Frankly, any TPU will probably work, since molten polyurethane sticks to practically anything.

The main challenge is ooze control since TPUs tend to ooze a lot. You're going to want to use a printing temp on the low end of the range for the flexible filament, and use some sort of wiper wall structure.

Another issue you might run into is re-priming the flexible filament after an extended idle time. It helps to use a large purge structure to ensure the nozzle gets re-primed fully. Don't use an excessively large toolchange retraction distance -- this will make it more likely that the flexible filament jams during reprime.

The best way to accomplish the above will depend on your slicer. Simplify3D is a good choice since it has good dualstrusion wiper and purge functions. Other slicers can be made to work as well.


Raised shell edges on ocarina print. RF1000 sliced with Cura Engine

Managed to solve it by lowering the temperature to 190C. I also lowered the infill down to 25%. Thanks for the advice!

I posted the make with results and settings on thingiverse.


I have made some learning on mechanical setup and discovered some issues on my printer, there are few:

Bed warped, even with glass (thin thickness), making BAL confused with Z-movement over the bed.
Overextrusion making layer oversized in terms of thickness.
Some of missing mechanical fine adjustments.

The main reason for this symptom was the overextrusion (that made my X and Y axis jump some steps when hotend collapses in the already-printed materials on their movements).

I hope this helps some of those who have this similar problem!


Are there practical reasons to NOT use a stepper motor with lead screw for the X and or Y axes?

I am going to answer this as someone who actually did rework their Prusa i3 fleabay clone to use leadscrews for all axes. Before digging into the matter, the backlash issue can be solved easily with spring-loaded brass nuts, kinda like how ballscrews work. That's the simplest problem to solve though as there are a lot of other issues.
Short version / tl;dr

Hardware can't handle that many microsteps.

Crosstalk and motor inductance limit speeds and acceleration.

Print quality suffers in really weird ways because of (2).

Leadscrews are not made for quick movement over extended periods of time and will wear, even with grease.

You'll need additional bearing surfaces to prevent your motors from grinding themselves apart, and to eliminate backlash due to the flex couplings.

The system becomes a lot more prone to highly destructive failure modes.

Long explanations
First
You're going to notice is that you're constrained to horribly, horribly slow movement and acceleration rates. My screws are 8 mm screws, with 8mm pitch. That means it takes 200 steps to travel 8 mm. Multiply by 1/16th microstepping, and that's 3200 microsteps per 8 millimeter of travel. Multiply by whatever speed you're trying to print at, then the number of axes you're using, and you'll find that your RAMPS board starts to stutter on complex moves if you print fast enough.
Second
You'll quickly hit the inductance limits of your motors. At "standard" power levels (ones that don't fry my knockoff NEMA17 motors), even after switching to 24 V for the entire setup, the fastest I could spin my motors was about 5 revolutions per second, which translates to 16,000 microsteps per second with 8mm pitch screws. For reference that means that under ZERO load, the fastest my N17 w/ 8 mm pitch could travel, is about 40 mm/s.
You're basically running the motor coils at several kilohertz, which means you have to be really careful about keeping your wires separate and shielded to prevent crosstalk, in addition to the fact that as your step frequency goes up, your step torque goes down dramatically. Not only does this limit the weight of the bed that the motor is capable of pushing at a given speed, but you even have to worry about the inertia of the motor and bed much more than with a belt-driven system. So instead of 30 mm/s jerk with 200 mm/s2 acceleration, suddenly you're limited to, say, 5 mm/s jerk and 40 mm/s2 acceleration.
As mentioned, for best results, the whole system needs to be converted to 24 V, and not all boards are configured for this to be easily done. My cheap RAMPS clone only needed a single diode removed and everything else was fine, but YMMV in this regard.
You could solve this particular problem by gearing the motors down, but at that point you've now introduced a new source of backlash either between the gear teeth or in the belt drive system, and kinda defeated the point.
Third
Due to this effect, is that you run into extrusion pressure artifacts. Basically, the plastic in the nozzle is a fluid, a very viscous one, being forced through a small hole. The fluid pressure will "lag" somewhat behind what the extruder motor thinks is happening.
The end result is that while you're accelerating, the lines you're laying are thinner than they should be, and will be thicker than they should be while decelerating, and you tend to get weird "globs" on each corner when you come to a stop. For me, with a 0.4 mm nozzle, 0.8 mm line width, and 0.2 mm layer height, these artifacts actually completely offset the additional accuracy I was getting with a tightly-coupled leadscrew with spring loaded dual nuts on it. The parts ended up being even less dimensionally accurate than before, with very strange deformities.
There ARE settings you can use in the firmware to try and combat this specific effect, but the process is tedious and takes a lot of trial-and-error, and recompiling the firmware every 30 seconds is annoying, not to mention the variables are dependent on line width, speed and acceleration settings, and layer height, so you have to recompile your firmware any time you want to change the print quality. Super, super annoying.
Fourth
Leadscrews aren't actually designed for this. The constant back-and-forth motion will wear the brass nuts and even the steel threads of the screws over time. You end up with a black powdery residue on everything underneath the screw, which, in the X axis, typically also means your print. Nobody wants steel powder messing up their layer adhesion.
In my case I used Superlube, which is a silicone/PTFE grease, to help prevent this problem, but that only works so well when you've got spring-loaded brass nuts. Eventually they push most of the lube out. Additionally, the lube tends to grab and hold any metal powder that does form, accelerating wear in areas that are still lubricated.
Fifth
Bearings. Turns out motors have internal bearings, that generally suck and aren't made for heavy loads in any direction. I found that out when my Y-axis N17 motor failed because the bearing did, and spread powder all over the coils, some of which got pushed through the enamel and shorted the wires out.
Additionally, because tiny amounts of misalignment turn motors into shrapnel in a hurry, you're almost certainly going to be using flex couplings. Flex couplings have a certain amount of yield to them axially, and are primarily designed to be under compression loads, and tend to fail when stretched repeatedly.
For the Z axis this is normally not an issue because the whole system is held down by gravity, but in the X and Y axes, you'll get some weird offsets of even a millimeter or two each time the carriage or bed switches directions. So you'll want to make sure that the motors aren't load bearing themselves, and the screw remains locked relative to the frame while still being able to rotate.
You can accomplish this by having a ring fastened to each end of the leadscrew that either pushes on a thrust bearing or rides in a regular ball bearing. Ideally, you can do both, but this turns into an expensive venture with a whole lot of brackets in odd places that you may not have space for. I ended up losing about 20 mm of bed travel solving this problem.
Sixth
You need to think about what happens when a component fails. For me, it was my endstops. The first failure was from the crosstalk issue I mentioned above. Y-stops triggered, bed started shifting towards the front of the printer over time, and eventually the printer started trying to move the bed through the front of the printer frame.
It was successful.
The second time was simply the endstop switch failing mechanically. Belt travel stops at the pulley. Leadscrews go all the way to the end of the screw, and because they're geared so much lower than belts are, there's a lot more torque involved. I destroyed my printer frame three separate times because of this problem, and once more when the Y-axis flex coupling snapped. This allowed the motor to spin the screw easily in one direction but not in another - which this time forced the print bed backwards instead of forwards, yanking the Y motor through its bracket and the frame again.
Conclusion
X/Y screws are not necessarily a bad idea, simply an expensive and tedious one in 3D printing. They're much better suited to low-feedrate applications like CNC mills, mechanical engravers, and the like. You may notice that even high-accuracy applications like laser printers tend to have belt-fed carriages rather than screw-driven ones. Screws are much better suited to high load, low-speed applications, and printers tend to be the opposite of that.
If you're trying to eliminate backlash due to the belts not being tight enough, as I was, the answer is to make a better printer. I couldn't tighten the belts enough to get my prints accurate before the motors started failing, because I didn't have the motor-end pulley supported by a bearing. Start there, literally just support on either side of the pulley on the motor shaft with a small bearing braced against the frame to take the radial load off the motor. If your belts are stretching too much, use steel-core GT2 belt. If your system is overall just sloppy, build a more robust system. My current project is a Hypercube Evo, and I found a supplier that makes steel-core GT2 belt. I'm going to use that to maximize rigidity in the CoreXY belt system. The frame is made from 30x30 mm T-slot extrusions, with 12 mm Z-axis rods and 10 mm X/Y axis rods. Bigger, more expensive components that are way more robust and will flex much less than the 400 mm long 8 mm rods on my cheapo printer.
Hope this helps.
(edited to get my math right on the microsteps)


What happens if you use high temperature PTFE tape with the heater block?

As Andrew stated: PTFE tape should not be needed.
Tighten the nozzle with the hotend hotter than you print at and also clean the threads with a tap if you need to.
To answer your question: it would stop leakage from the threads.


How to switch from PETG to either PLA/ABS mid print?

You should do a complete calibration for ABS (temperature tower, E steps, flowrate %) before starting the print, then when you change filament remember to apply all the parameters I mentioned.
While I'm not in favour of using the flow rate % to correct the E steps calibration, since you are doing it mid print this may be the easiest way, instead of changing E steps AND flow rate %.
As you said, you need to change temperature too, but both PETG and ABS print well at 235 °C so it may not be needed. PLA works too, but PLA bridges at 235 °C are difficult to get properly.
For sure you won't be able to change other parameters, such as fan speed, printing speed and flowrate for bridges, which are all specific to each filament, but hopefully it will work out anyway, since PETG is trickier than ABS or PLA.
Of course you may have issues with adherence: PETG may not bond well to ABS or PLA (in fact, PETG can be used for support for PLA and viceversa because the bonding is not too strong). You may have a weak print with PLA, so go for ABS.
PETG as support for PLA: Can PETG be used as support material for PLA?
Bridge calibration:


Ultimaker Cura infill issues (weird vertical pillars due to underextrusion)

This problem is most commonly caused by infill speeds which are too high.

Instead of printing lines, the filament is caught on one of the lines of the previous layer, leaves a blob there and only restarts extrusion when it hits the next line. Instead of extruding continuously the filament comes out in blobs at the locations where there's filament on the previous layer.

You can have good infill up to some layer and suddenly start getting this problem as of some layer. When the problem occurs the next layer is more likely to show the problem. It's snowballing.


How to correctly print an object with supports

You need to put a check mark to enable supports in Slic3r as you cannot print in mid-air.

This option is found under "Print settings" with header name "Support settings". Please look at the Slic3r manual for more options.