Why would one choose 12 V from 24 V, from a safety standpoint?

The most important "safety" advantage when using 24V (compared to 12V) is that to get the same power, you only need half the current. A 192W heated bed would need 16A at 12V, but only 8A at 24V.

Since one of the most common safety issues is underrated screw terminals being used for the heated bed (just search for "3d printer fire"; you'll find quite a few pictures of charred plastic around screw terminals). For example, the screw terminals on RAMPs board are only rated for up to 12A. That would be okay at 24V, but well over the limit at 12V.

Since the wire gauge is dependent on current, you can also use somewhat thinner wires with a 24V system (or equivalently: wires that would melt in a 12V setup won't in a 24V setup). The power dissipated in a wire scales quadratically with current, so the same wire being used in a 24V setup would only waste a quarter of the heat of that wire in a 12V setup. There is also less strain on switching devices (such as MOSFETs or relays). The same applies here: power loss is quadratic with current.


Use SLA 3D printing to make a flexible mold

Background
SLA relies on the properties of UV-curing Resin. Most currently available UV Curing Resins harden to a solid, hard polymer, but that doesn't mean there are no other UV curing resins that are elastic. Most however will not be suitable for SLA or DLP systems!
Polyurethanes, which can be flexible if cured in the right way, have not come onto the market as suitable SLA/DLP printing material and up to now, I have only found one UV hardening resin on the market - the one offered by FormLabs and identified by OP
Patent History
Indeed, elastic resins are actually quite new. The first patent I could find for an elastic resin was 2003 for an elastic epoxy resin, while subsequent elastic resins were brought to Patent are different like the 2007 elastic olefin resin. In fact, there is a 2013 US patent on SLA Resin, which is still in effect. As a result of such patents being still in effect or just out of protection times, the market is still very much limited because most manufacturers simply lack the knowledge of how to do it or the licenses to be allowed to do it. In fact, Formlabs is named on 43 patents for 3D printers and accessories, of which only 1 is expired as of July 2020. I could not identify the patent that might be in use for their flexible resin, but the marketing material is of May 2020, so it is relatively new on the market and might not have been updated into either the patent database or FormLabs did buy an exclusive license for the material from someone else, meaning they will not show up as Assignee in it. Or it is kept a trade secret.
Material implications
The printed mold will probably be of a different stiffness than a cast mold as you work with a totally different material and your new molds might degrade at a different speed than urethane or latex cast molds. To get a feel for this this, you will need to run some experiments. As FormLabs hands out test specimens of their print materials, you might order the two flexible ones and then test their stiffness and suitability for your uses by having them interact with your casting resin and seeing if they break down and if you can remove them easily.
Food grade
Generally don't consider anything that comes directly from a 3D printer certifiable food safe, as you need to have both a process and a material that is food rated. There are ways to use the resulting parts to manufacture food safe objects, but that's elaborated for example in some of the questions I suggest to look into


ooze shield vs priming tower, do you need both?

I have the same printer you do.  I recall that the ooze shield is printed in alternating layers; first from E0 and then the next layer from E1.  But on a given layer, I don't think that there is a guarantee that the ooze shield will be printed in the filament about to be laid down for the part of the layer.  (But I might be wrong on this.)  But when it comes time to print the ooze shield, what will happen if the filament has already drizzled out during the print of the last layer?  The first part of that ooze shield won't get printed properly and might end up causing a print failure.

As a separate issue, I found that an ooze shield is only helpful if the overall XY diameter of the print is not too great.  This is because it only helps when the print head crosses the perimeter.  If the print head spends a fair amount of time inside the perimeter, then the idle head can still continue to ooze out unwanted filament.

So for many of my prints, I started using the priming tower, but skipping the ooze shield.


Replacement teflon (PTFE) liner For Dremel 3D45

The initial problem you had with filament coming out of the threads at the nozzle is caused by improper seating of the heat break to the nozzle. In a "from the ground up" installation, you'd have an empty heat block, containing your heater core and your thermistor. Threaded into the "bottom" of the block is the nozzle, just a turn shy of being flush with the heat block. The heat break is the thin threaded segment extending from the heavily finned heat sink.
The heat sink/heat break combination is threaded into the heat block until it contacts the nozzle, at which time, the nozzle is snugged into place securely. This keeps continuous the filament path from the heat break to the nozzle. Somewhere in time, a gap opened between the two.
When you have assembled everything (including the PTFE liner), you'll want to heat the extruder assembly to about 250 °C and re-snug the nozzle to the heat block and heat break. Hold securely the heater block, as you do not want to apply force that will snap or otherwise damage the fragile heat break. Use a wrench that fits the heater block without contacting the wiring. Use a wrench that will keep your fingers safe, as the heat block will be hot.
Stepping back in time a bit, when you remove the assembly, you should be able to determine the necessary length for the PTFE tube. I checked the manual for your printer and it is lacking in detail for this information. The diameters you've specified are standard and you should be able to locate a suitable substitute from many online sources. Amazon, Matterhackers, eBay, etc.
Examine the heat break tubing. The diameter should not be so small as to allow you to push the PTFE tubing in from the heater block side, unless you have an unusually manufactured product. Dremel may have decided to create a new bit of engineering, but I'd expect not.
You'll purchase more PTFE than required and examination of the upper portion of the heat sink should give you a clue how much to use. When the cover of the extruder assembly is removed, is there a guide for the filament to make it easier to push through the PTFE tubing? If so, the length of the PTFE is from the bottom of the guide to the bottom of the bore of the heat sink/heat break assembly.
Photos of the upper entry to the heat sink/heat break, with the cover removed, would be useful, but you may have sufficient resources in hand to resolve your problem, once you replace the nozzle and purchase PTFE tubing of the correct size.


Are the layers where this is happening smaller than previous layers? Many slicers have a minimum layer time setting where if the layer takes less than X time, it will either slow the layer down or possibly pause until the time is reached.

This can be useful to allow the previous layer to cool down and harden up a bit before more hot plastic is added.  If you're not having issues cooling the print then you could disable this.  I've only ever used Slic3r, KISSlicer, and Simplify3D so I'm not sure where the setting would be in Cura but those slicers all had/have the option.


Prusa HE3D Xi3 missing step on x and y axis

There's a possibility that your power supply lags after a while, the quality of power supplies on cheaper 3D printers are sometimes an issue.

There's also a possible that the stepper motor drivers aren't putting out enough power. This can be adjusted by turning the trimmer on the driver, check the printer documentation for instructions on how to do that.


How to debond cyanoacrylate glue from pla

Acetone

Acetone will dissolve cynoacrylate (superglue) and should weaken it enough to be able to separate the parts.
A readily available cheap source of acetone is nail varnish remover (just make sure you don't buy the acetone free version!).
Give the pieces a soak in nail varnish remover for 10-20 minutes and they should come apart with some prying.
Acetone does not dissolve PLA, so the PLA parts should be undamaged. If you were to try this on ABS parts however, they would begin to dissolve.


Longer LK4 Pro moving to corner mid print

It's possible that the slicer is using a minimum cooling time per layer and the corner is set as its home coordinates.  In the settings of your printer you can set the home coordinates and in the slicer you can reduce/remove the time between layers.


Marlin firmware: unload filament with G-code

There are three things to fix and one suggestion:

Change follwing lines of M109, using parameter R instead of S, because the latter is not waiting to cool down:
M109 R160 ; Wait for 160C
...
M109 R110 ; Heat hotend to 110C

The behavior of M420 will depend on type of bed leveling, saved mesh, etc. It is off topic to troubleshoot this. The printer operates 10 cm above the surface for this operation. G28 disables bed leveling. Why do you need to re-enable it? Just remove this line:
; M420 S1 - remove (or comment out)

Redefine maximum extrusion length in Configuration.h to allow for scripted long pull (G1 E-430), for example:
#define EXTRUDE_MAXLENGTH 450

Suggestion: Use relative mode for extrusion (M83) instead of absolute positioning (M82). It will simplify your code a lot. You just want to express the distance in E parameter. Then you will not have to reset position with G92 E0 every now and then (do it just once on the start). (I use this Extrusion mode also for slicing becuase it makes easier to re-start a print in case of failure).


Since you said you don't have a cooling fan, try lowering the temperature on your print head to something like 205. The strings in the first and second picture also occur more often when the print temperature is too high as well.

The layer time gets really small at that transition, so make sure the print speed is slowing down while printing that part of the object and pausing in between those layers to allow for cooling.

It looks like the plastic is still molten and is being dragged around too me.


How to move Z up after printing in Cura?

Go towards the right top corner. Click on the printer name. From the drop down, select, "Manage printers". You will get a dialogue box in the middle of your screen. Your current printer's name will be shown in italics. On the right side of the dialogue box, click on, "Machine settings". This will open another dialogue box. In the lower left, you will see a text box with the heading, "End G-Code" scroll down to where you see the line, "G1 X0 Y0". This is the line that moves your print head to the lower left corner. G1 is the command for a linear move. X0 and Y0 are move instructions to move the the 0 coordinate for the two axes. Change this line to G1 Znn where "nn" is the number of the coordinate you wish to move to. Close this dialogue, close the previous dialogue and all newly sliced file will now use this code.
If like to keep track of any changes you make, you can put a semi-colon at the beginning of the line. This turns the line into a comment and will not be actioned. Then press enter and on a new line, put the line, G1 znn.


According to our materials experts, you should always be careful interpreting the start of the force-displacement diagram. It is possible that the test needs to "set" itself, important issues are:

the clamping of the test articles in the test bench vices
alignment of the test article in the test bench
size of the test articles (the load suggests small test articles/small diameter)
how is displacement measured (displacement/elongation sensors "slip" easily depending on the expertise of the operator)
artifacts in the test article?

Instead of proceeding the test till rupture (prior to the in-elastic/plastic region), it would have been beneficial if the test had been stopped at about 8 kN and relaxed to 0 kN to commence a new test.

From my own experience with creep test articles we see similar issues and apply a displacement offset so that the "second section" (using your words) is extrapolated to zero load. Usually this is just a few hundredths or tenths of a mm. In this case you could shift the whole diagram 0.3 mm to the right by applying a similar offset of about -0.3 mm.


Issue with rim of first 5-8 layers of my Prints

The bed and filament temperatures you are using are the usual ones for PLA, so it probably is not the case that the filament is flowing too much and oozing out of place (*).
So most likely the problem is with the slicer. Things to look for:

Most slicers print the first layer in a slightly different way than all other layers (to improve adherence to the bed) and some parameters may be off:

Easiest check: repeat the print with a different slicer; if it goes better it was a slicer setting that needs finetuning.
More involved check:

For Cura make sure "initial layer height", "initial layer line width", "initial layer horizontal expansion" and "initial layer flow" have the default values.
For Prusa Slicer reset "first layer height", "first layer extrusion width" and "elephant foot compensation" to their default values.

Additionally, most slicers will disable the fan for the first few layers. Change the setting so that the fan is only disabled for the first layer.

(*) That is of course unless you got a bad batch of filament. Less probable than the slicer settings being off, but check with a completely different PLA filament to verify.


UM could stand for UltiMaker. I think that you need to either:

download Uranium;
install the UM package;
import the UM package, or;
need to add it to your path (PYTHONPATH).

You may find your answer here: help needed: ImportError: "No Module named UM" in Eclipse #510.

The two things that you seem to need to do are:

Get Uranium from https://github.com/Ultimaker/Uranium.
Add the path: PYTHONPATH=/path/to/uranium/repo cura_app.py


Which 3D filament is 100% (or close to being so) food safe and non toxic?

Answer was moved to this question: Which are the food-safe materials and how do I recognize them?


Sketchup designed object printing first layer incorrectly

A red surface coloring is normal for the bottom when viewed in Ultimaker Cura, nothing to worry about that (e.i. when that face is touching the build plate; if it is unsupported, you should add support structures but a raft is generally not necessary for PLA).

Rafts are useful when you print high temperature materials that have a large shrinkage when cooled from print to bed temperature (this somewhat mitigates the problems of curling up corners or warping prints), for PLA it is not needed. As seen from the print that is printed on the raft, it's clear that the print to raft distance is to large, the first print object layer is not adhering to the top raft layer very well.

The print that is printed without a raft doesn't look too bad. Some printer extruder calibration could further improve the quality.


What is the lifespan of a SLA Resin Tray?

It depends on tray and resin type you are using.

PDMS

If you are using PDMS (eg. sylgard 184) coating for your tray. (B9 and similar printers using this type of tray).

Life of tray PDMS coating depends mainly on:

How long you print without breathing floor.
How reactive is your resin.

You could get 2 3 prints up to 15 20 prints.

It is suitable for printing delicate pieces.

FEP

Large number of manufacturers using FEP.

Life of tray largely depends on.

Thickness of FEP
Piece sizes and movement speed during early layers.

Usually you could use same tray for couple of hundreds of prints.
Optical quality is not comparable to other alternatives but without human error factor you could get almost unlimited prints. Delicate pieces require tough resin.

Teflon

It is halfway between PDMS and FEP.

There are other tray alternatives:

Envision uses special glass you could print on average 50 prints.
Carbon 3D uses super expensive oxygen-permeable window.


There are generally 2 types of operation you might want to do before priming your object:

smoothing to a point that you are comfy with and
roughing pass with very fine grit to give the primer something to stick to

Smoothing via Sanding & Filler

To smooth your object you generally have two options:

Only sand down (and possibly vapor-smooth) and account for the lost size in the design phase.

Vapor-smoothing can flatten away surface details you might want to preserve, so it might not be an option at all.
While vapor smoothing is possible with more than just Acetone on ABS, the price tag for those chemicals is usually more expensive by a factor of 20 or more due to the fact that Acetone is pretty much dirt cheap as far as chemicals go - and easily accessible via home depot.

Fill up with body filler in areas you want and sand smooth afterward.

This is very labor intensive, especially for complex shapes.

Only after you filled up the structure to be somewhat smooth you apply paint primer. In itself, common spray on primers often are not filling enough to hide away the printing layers.

For rough surfaces that need a starting fill, a paste body filler applied with a spatula works best, and for the last pass over a just lightly scratched surface, automotive body filler from a spray can works great. The benefit of spray-can body filler is, that it also acts as a first roughing step, so you don't need to roughen the surface for the primer. If you grab a filler-primer, even skip the primer.

Sidenote from experience:

Some filler-primer and lacquer spray cans seem to contain solvents that are able to soften PLA.

Smoothing via Coating

A random find on Thingiverse showed me another way to paint and flatten the surface faster and without sanding, at the cost of details getting smoothed away:

Apply a thin paint coat.
Apply a thin coat of a fast drying, transparent Polyurethane coating onto the wet paint.
Let the combined layers dry with extra air flow to prevent noses.
Repeat as needed.

It works by picking up the wet paint and embedding it into the thicker Polyurethane layer, which dries much smoother than the paint itself, filling up the imperfections and the steps between layers. This process will however also fill up non-masked surface details you might want to preserve.

Your product in mind

The primer you took a look at works on PLA, but it would not smooth out all the dimples. It might work nicely for the PU-Buildup variant.


A major part of the Arduino IDE is sort of semi-hidden, and that is some guy called  avrdude. Actually, AVRDUDE – AVR Downloader/UploaDEr is a standalone binary.

As an aside, there is also gcc which does the compiling, but that is another matter. The avrdude uploads the compiled binary provided by gcc on to the Arduino, via the USB port (COM port).

You can invoke this from the command line (assuming that you have the Arduino IDE installed).

You will need to specify (see command line option descriptions):

The baud rate of the COM port (-b)
The COM port (-P)
The processor used in the board (for the Arduino Mega2560 board: ATmega2560) (-p)
The path to the .hex file (-U)
The path to the .conf file of avrdude itself (-C)
Verbose mode, so see what is happening (-v)
Specify the programmer to be used (-c). See the -c option on command line option descriptions for more information.
Disable auto erase for flash (-D)

The command will be of the form:

<path to arduino>/hardware/tools/avr/bin/avrdude
-C<path to arduino>/hardware/tools/avr/etc/avrdude.conf
-v -patmega2560 -carduino -b 115200 -cstk500v2
-P<name of serial port>
-D -Uflash:w:<path to hex file>:i

This example above:

Specifies the full path to the avrdude binary
Specifies the full path to the avrdude .conf configuration file
Verbose mode
The ATmega2560 processor used in the Arduino Mega2560 board
The Arduino programmer
The baud rate of the USB port
The Atmel STK500 Version 2.x firmware programmer (may not be required)
The port to which the Arduino board is connected
Disables auto-flash as it is not required – Auto erase is not used for ATxmega devices as these devices can use page erase before writing each page so no explicit chip erase is required. Note however that any page not affected by the current operation will retain its previous contents.
The memory to be uploaded to and the path to the .hex file (see the -U option on command line option descriptions for more information):

flash specifies the flash ROM of the device.
w: read the specified file and write it to the specified device memory
:i specifies Intel Hex

Examples

For Windows

C:\dev\Arduino\hardware\tools\avr\bin\avrdude
-CC:\dev\Arduino\hardware\tools\avr\etc\avrdude.conf
-v -patmega2560 -carduino -b115200 -cstk500v2
-P\\.\COM1
-D -Uflash:w:C:\Users\<username>\Documents\firmware.hex:i

For OSX

/Applications/Arduino/hardware/tools/avr/bin/avrdude
-C/Applications/Arduino/hardware/tools/avr/etc/avrdude.conf -v -patmega2560 -carduino -b115200 -cstk500v2 -P\\.\COM1 -D -Uflash:w:/Users/<username>/Documents/Arduino/firmware.hex:i

Alternatives

If you are not comfortable using a command line interface (CLI) it might be easier to use a GUI solution…

XLoader

For a Windows only solution, see Uploading Arduino HEX files with XLoader

From the author’s website:

  I’ve made a small program that can be used to upload your own *.hex
  files to arduino boards using the bootloader. That means you don’t
  need a flash programmer. I made it for my own use and found it pretty
  useful. So now I’ve made a more user friendly version.. To use it
  compile you’re code in something like AvrStudio. Then simply start
  XLoader.exe, pick a hex file and press upload. That’s it. Good news it
  now also supports Arduino Uno.

Arduino Builder

From Arduino Builder – standalone utility for building and uploading Arduino sketches

  Choose file, either a sketch file (.ino), an HEX file (.hex) or an ELF file (.elf)
  Choose the board type in the dropdown list.
  Click on the serial port (or USBASP button) and theuploading will be proceeded.

Arduino Uploader

From the same page, there is Arduino Uploader which is a command line version of Arduino Builder.


How can I tell if BLTouch is triggering?

Problem is solved, though I still don't know how to test the BLTouch.
I had reversed the power connection (black and white wires) at the connection to the extension cable. Swapping that connector back around restored expected behavior.


Generally, Z-axis zero is when the hot end and the build plate are close to each other.  Some printers keep the hot end up at the top, and bring the build plate up to reach it.  Other printers keep the build plate at the bottom, and lower the hot end down to reach it.  As such, "Z axis zero" doesn't specify top or bottom of the physical printer, it just specifies that the hot end is right up against the build plate, ready to print its first layer.  In the printer you describe, where the hot end remains at the top, that's where Z zero is.

In terms of the model being printed, Z axis zero is always the bottom of the model, the first layer to be deposited on the build plate.  The numbers increase from there, either lifting the hot end up, or pushing the build plate down, depending on the design of the printer.


The duration of a print is affected by the print properties. Speed, nozzle diameter (or line width), layer height,  amount of perimeters, infill percentage, combing, support structures to name a few important parameters.

So, the only way to tell how long the printer will be printing a certain STL is by loading the STL file into a slicer and slice the model with those settings. The most common free slicers are Ultimaker Cura, Slic3r and payed slicer Simplify3D. Alternatively, when you already have G-code files and do not have the STL anymore or don't want to slice it again (e.g. because you cannot remember which settings you used), you could upload your G-code here and it will calculate it approximately for you (as it does not know the dynamics of the printer).

Note that these times are approximations of the real time it takes to print the object as it integrates the tool path and speed to get the time. Sometimes these calculations are off as the actual printer may behave differently than projected by the slicer. From experience I can tell that the Ultimaker Cura slicer predicts fairly accurate print times for the Ultimaker 3, so they have tuned their slicer software to their machines. For your own build or other brands this may result in different/inaccurate print time estimations.


Estimating filament consumption in length per time

Your math looks correct, and is also a good approximation for what I've seen in the first few weeks with my own Ender 3.
Another way to calculate (to check yourself) is to calculate the volume extruded (nozzle area times extrusion percentage times print speed -- be sure you convert everything to the same units!) in a given second, multiply by the density of your filament (common PLA runs about 1.2 g/cm^3), and get a rough figure for how long it takes to print a kilogram of filament.  Your actual print time will always be higher than this approximation, because there are moves during which the extruder isn't running, infill is often set to lower extrusion level, and of course there's setup and cleanup time to account for.


Prusa i3 MK3 latest release first layer calibration issues

Calibrating the first layer height involves two steps:

The first step, as illustrated in that picture, is to adjust the PINDA probe to be roughly the right distance above the nozzle.  The PINDA only has a sensing range of about a millimeter, so if it's too high, it can't detect the printbed; if it's too low, it will interfere with the printed object.

The second step, which you're having trouble with, is to calibrate the exact distance between the PINDA and the nozzle tip.  The printer prints out a test pattern; while it's printing, you turn the the dial on the printer control panel to adjust the "live-Z" value.  Typical values for a properly-assembled printer are between -0.5 and -1.0 (more-negative values are closer to the print bed).  If the live-Z value is outside that range, you need to adjust the position of the PINDA probe.

The official Prusa procedure is good for getting a rough calibration.  If you want more precision, the "Life adjust Z - my way" procedure on the Prusa forums is good.  Basically, you print out a large one-layer square, adjust the live-Z value halfway through, and see which half has a better first layer.  Repeat until satisfied.


Build plate (PEI on glass) isn't flat after several months of use?

Looking at the picture, the first thing that came to mind was, "are you sure it's the bed?".

The height variance looks very regular, and while I'm unfamiliar with this printer's specific mechanics, my thought process trended to the Ender 3 and other v-wheel extruder mounts. If the extruder and gantry carriages are mounted to the gantry spars on V-wheels instead of sleeve bushings or other linear guides, and you've spent a lot of time printing small objects where those wheels are going back and forth over a relatively small travel distance for the entire print, you have been unevenly wearing the wheels so they've become eccentric around their rotational center, and this will cause the extruder to vary its height over the glass in a very regular pattern tied to the circumference of these carriage wheels. This happens especially quickly if you over-tighten the bearings against the gantry spars in an attempt to make the printer more precise.

If the printer uses sleeve bushings, the worn sleeve won't rotate, and any wear on the spar will be very localized to the areas in which you print, but if the printer has spent most of its life printing a grid of small objects (tokens, sets of small figurines), you can still get this regular wear pattern as the printer will spend more time over those areas of the bed.

The fix is to replace the wheels or linear bearings if the printer uses them. If it uses sleeve bushings and the gantry spars themselves are worn in this pattern, you might be able to rotate the spars to put an unworn (or less worn) band of metal on the top of the spar, depending on how the spars are mounted into the endcaps of the frame and y-axis carriages.


I would change the pin assignments by swapping E0 and E1 in pins_RAMPS.h.


What is this called and where can I buy a replacement?

This is the throat block for direct drive extrusion, Anet8 is a cheap clone of Prusa printers, so it's easy to find parts for Anet printers.

This is one extruder kit that may help your needs, 1 Unidades Impresora 3D makerbot MK8 Extrusora De extrusión de Aluminio Bloque de DIY Kit para Reprap i3. This is a link for Aliexpress - of course there are other dealers.


Installed bed leveling probe, now Z homing moves to center

This is a consequence of enabling Z_SAFE_HOMING:

Z Safe Homing prevents Z from homing when the probe (or nozzle) is outside bed area by moving to a defined XY point (by default, the middle of the bed) before Z Homing when homing all axes with G28. As a side-effect, X and Y homing are required before Z homing. If stepper drivers time out, X and Y homing will be required again.
Enable this option if a probe (not an endstop) is being used for Z homing. Z Safe Homing isn’t needed if a Z endstop is used for homing, but it may also be enabled just to have XY always move to some custom position after homing.

My default Cura start G-code contained this sequence:
G28 X0 Y0 ;move X/Y to min endstops
G28 Z0 ;move Z to min endstops

I changed this to
G28 ;safe homing
G90 ;absolute positioning
G0 X0 Y0 ; move to bottom-left corner for nozzle wipe

However any oozing will still happen at the center of the build plate, which is a problem.


Extruder clogging is, at its root, a matter of too much backpressure at the hotend. There are a number of more specific causes, but it very simply comes down to the fact that the printer cannot feed the filament through the hotend as fast as the extruder is pushing it in.

Things to check, pretty much in the order they should be checked/performed for a brand-new printer:

Extruder stepper calibration. With new printers based on RepRap firmware (Enders, Prusas, pretty much any printer in the \$200-\$400 range these days), one of the first things you have to do after assembly is to calibrate your E-stepper (the motor that drives filament through the extruder). The printer is given commands based on millimeters of movement, including the feeding of filament, and it has to translate those into finite steps of the motors. If those steps don't actually move the extruder or the filament as much as expected, the printer will behave poorly, including clogging. E-stepper calibration is pretty easy, especially on Bowden extruders; you basically disconnect the Bowden tube at either end, load filament through the stepper, cut it off flush with the end of the tube or the coupling, then tell the printer to extrude 100 mm of filament. Cut it off flush again and measure, and if it's not 100 mm, look for a command beginning with M92 in your printer configuration (it can be in the settings of your actual printer or a configuration script in your slicer software that gets tacked on to the front of the G-code files generated for use with that printer), and adjust the value you see after the E in that command by multiplying it by 100, then dividing by the millimeters of filament actually extruded in the test. Rinse and repeat until the printer is feeding the amount of fil you tell it to.
Bed height/leveling. This may not sound like it has anything to do with extruder clogs, but in truth, if your extruder is too close to the print bed at any point during the first layer, it can very easily clog the extruder by not allowing enough material to flow out the nozzle to keep up with what's being fed in. Bed leveling is a key step in print prep, and every printer behaves best with subtle changes to the bed leveling procedure. My guess is that you need to re-level for a slightly higher "zero-Z" above the build plate. If you're using the sheet-of-paper method, either use a thicker piece of paper, or go for less friction as you pass the paper between the nozzle and build plate.
Nozzle diameter settings. The standard nozzle tip diameter is 0.4 mm, however there are others. Your slicer probably expects the standard diameter as a default, so if you're running a 0.3, 0.2 or 0.1 mm nozzle for finer detail, the slicer has to be told that so it can adjust the filament feed rate. Otherwise it'll be jamming up to 16 times as much filament into that hotend as it should be. This isn't likely to be your problem but it's something to check; most extruder nozzles these days have the tip diameter engraved or pressed into the side of the nozzle, and if yours is unlabeled, try heading to the local music store and buying a single 0.013" guitar string (typically sold as a high E for acoustics). If that wire end easily fits through the extruder nozzle, you have a 0.4 mm, if it does not, it's something smaller.
Extruder clog/obstruction. That guitar string I mentioned makes a really good extruder cleaner. Just feed it through the extruder tip and gently push it up through the hotend till it pops out the top of the extruder, then feed it back and forth a bit to "floss" the extruder tip, cleaning out any minor carbon buildup. If you can't feed the wire completely through the extruder body from either direction, that's probably your problem, and fixes range anywhere from a little more pressure with the wire, to a narrow drill bit carving out the obstruction, up to removing the entire heat block from the printer, putting it on or in something that won't burn, and blasting it with a soldering torch to burn out the obstruction, followed (after letting it cool) by a bath in some acetone to dissolve any remaining gunk.
Gunked-up extruder hobb. The toothed wheel attached to the extruder stepper is called the "hobb" (you may hear it called a gear, but it's really not one as it doesn't mesh with another gear). As the printer feeds filament, especially if you've had jamming problems, the hobb's teeth will fill with shavings from the filament it feeds through. This can cause the hobb to slip against the filament, which not only reduces the pressure of the filament being pushed through the extruder, it accelerates the accumulation of gunk on the hobb. A short blast of canned air is usually all you need to clean the hobb; if it still looks pretty caked up, a toothbrush will sort it out. While you're at it, check the idler to be sure it's still spinning freely.
Filament type/brand/age. You mentioned it's "silver PLA"; the silver stuff I have is actually a "silk PLA" product, that sheathes the PLA in a jacket of another plastic (often PET) for that high-gloss appearance. These kinds of filaments can be very temperamental, as can filaments with glitter or fiber aggregate in them (also common in metallic fil colors). You have to have the printer settings dialed in just right, and some of these products just don't work well at all in some printers. Try getting some very basic, brand-name PLA filament like Hatchbox, ColorFabb, MatterHackers, MakerBot, etc, in a good primary color (avoid black or white; the color saturation affects how easily the stuff extrudes at a given temp), no silk finish or other modification. If that prints well, the suspect becomes the silver fil.
Extruder temperature. You're printing at 200-205 °C, which is usually good, but if you're getting problems, the first thing to do with PLA is to try printing cooler, not hotter. Case in point, getting PLA too hot can cause it to fully melt and drizzle out (vacating the extruder and causing it to overheat the fil further up, jamming the melt tube), it can gum up (directly clogging the extruder nozzle), and it can carbonize (as you see it doing at 215). If you're already flirting with burning your PLA at 10 degrees hotter, you are probably running too hot. Try backing off to 195 or 190 and see if that helps any.


What you experience is temporary under-extrusion. This could be a typical result of friction in the supply of filament to the extruder. I've run into this also a week ago when the shaft of the spool holder caught a plastic bag next to it which wrapped around the shaft creating a lot of friction. Friction can also be caused by filament that gets entangled on the spool, this is usually a problem if the spool unrolls too freely on the holder (too less friction);it unrolls a few windings, and then tightens those entangling the filament. Also, if you use 2.85 mm filament on small diameter spools, the last stretch of filament has the smallest curvature and as such requires the most force to pull it to the extruder (this can go in steps).

Furthermore, slipping of the extruder gear is also a (rare) possibility (when using a stepper directly to drive the extruder gear, a flat spot on the stepper shaft should prevent this).

Be sure to inspect the filament release from spool to extruder and try to see (and listen!) what happens when you print a part when you experience the under-extrusion.


Tips for making parts that push/snap together

There are many different ways too approach this and the question may be too broad, but here's a stab at it...

Here are a few different ways that I've made parts that connect in the past:

Example 1: Utilize the elasticity of the plastic by creating a semi circle to fit around another object. When fitting the part to the other object, the "wings" will flex out and relax around the back end of the object.

Example 2: T-Slot style designs are a nice choice for semi-permanent or interchangeable parts. The key here is just using trapezoids and make sure the "female" end is slightly larger and/or tapered to make it easier to insert the slides.

Example 3: Create snaps. This can be a bit more difficult, but can provide a more professional look to your design. It's best to start off by designing on L-Shaped slot on the parent part and a smaller L-Shaped extrusion on the child part. Then you can add a taper to the bottom area of the "L" to make it easier to insert into the slot.

Example 4: Creating plugs are similar to snaps, they're just circular. Try starting off with a cylinder and joining either a sphere or a slightly larger diameter and tapered cylinder on top. Then you should be able to snap the assembly into a hole that is slightly smaller than the "top" of the plug.

It's important to weigh the usefulness of some design choices against the purpose of your part. For me, if I'm designing something for the shop or something that I think I'm going to be swapping out often, I'll use the T-Slot idea. Other things that "looking pretty" is more important, I'll try to hide the connections by designing a type of snap that can go into the walls of the part.

The T-Slot designs seem to print quite easily with no need for supports (depending on how gradual the angles of your trapezoid are) and provides a lot of structural strength.

Printing snaps has been difficult for me in the past and its best not to try to unsnap the part too much as you run the risk of shearing the snap upon removal. Printing such a small feature means that it is usually not marginally strong. However, including multiple snaps in an area and designing them with tight clearances can provide a very neat/clean connection that is appealing for consumer products (for example, phone cases).


What do you use to keep your blue tape from lifting?

The tape probably would stick better to the Aluminum bed than the BuildTak clone sheet you have as it would have had more surface area to bond to.

What I found that works best is to print on the bare aluminum bed using a PVA based spray, this can be hairspray or a specific 3D printer product like 3DLAC, or just glue stick. I ditched tape after day one (for reasons you mention) and solely print on aluminium or on glass without a problem, sometimes it sticks too well and the bed needs to cool down to room temperature before I can remove the print. This has been described as an answer to: Should you use hairspray on a metal bed 3D printer?
.

Removing the BuildTak clone sheet may be quite laborious if a very sticky adhesive is used (it took me a long time and lots of solvents to remove the goo/glue from a PEI sheet I used once) it is better to try and print on the BuildTak sheet, maybe use PVA based (hair)spray or glue stick.

Furthermore, ABS is more difficult to print than PLA or PETG. Printing ABS is difficult because of the relative large shrinkage when the filament cools. It therefore requires careful heat management (no part cooling, no draft, enclosure, etc.). This filament needs a good surface to build on and requires brims, "mouse ears", adhesive spray or glue to get the first layer to stick and not curl up. Tape at temperatures of 100 °C will become soft and loose its power to stick. Kapton tape might work better.


What is the correct Marlin firmware setting for Tevo Tarantula with MKS Base V1.2 board

The MKS Base v1.2 is basically an Arduino MEGA2560 and a RAMPS1.4 on a single board.
You can use the RAMPS pin designation.
Note that the endstop to origin distances is explained in question How to center my prints on the build platform? (Re-calibrate homing offset).
In Jims Marlin fork you can find this at:
#define X_MIN_POS 0 - XTRA_BED_LEFT

and
#define Y_MIN_POS 0 - XTRA_BED_BACK

Unfortunately, XTRA_BED_LEFT and XTRA_BED_BACK are defined as zero; this implies that the endstops define the origin (not likely) or it is left as an excercise for you to find out. This answer explains how you figure that out.


Disable Marlin PID, and start print manual

You can edit the temperature control commands out of your gcode, or just tell your slicer to omit them, typically by setting temperature to 0. Then, as you suggested, start the print manually once your industrial PID tells you it's at-temperature.


How to increase the amount of probing points for a BLTouch sensor in Marlin firmware?

You need to change the constant value(s) in your Configuration.h file of your Marlin version from:

// Set the number of grid points per dimension.
  #define GRID_MAX_POINTS_X 3
  #define GRID_MAX_POINTS_Y GRID_MAX_POINTS_X

to:

// Set the number of grid points per dimension.
  #define GRID_MAX_POINTS_X 5
  #define GRID_MAX_POINTS_Y GRID_MAX_POINTS_X

This shows that to go from a 3x3 grid to a 5x5 grid you only need to change one value. Do note that you can set GRID_MAX_POINTS_Y to any value other than GRID_MAX_POINTS_X; replacing GRID_MAX_POINTS_X in the line with GRID_MAX_POINTS_Y to 4 would yield a 5x4 probe grid:

// Set the number of grid points per dimension.
  #define GRID_MAX_POINTS_X 5
  #define GRID_MAX_POINTS_Y 4


Short answer: Use a calibration test.
Long answer: There are a bunch of calibration test files out there you can run. Ameralabs has a guide on how to read one of them and they have a link to download the STL at the bottom of the website. In short, the test file will print with a bunch of features that are hard for the printer to handle (thin posts, angles, small gaps, etc). You can try printing a test file like you would any other file while just guessing at the exposure time. But some printers have a setting just for this where you can run the printer once and print 8 copies of the same object each with a different exposure time. This is the best way to go if you can. either way, you will need to look at the prints when you are done and compare it to what it was supposed to look like. Pick the print that does the best in all types of features on the test.
here is a video showing how to do the test with multiple prints at once. Anycubic Photon S - Resin Exposure Test - R_E_R_F with custom timing
running these calibration tests can be useful even when you have a data sheet for your printer, it can account for other variables such a temperature. I don't usually bother but if you want to spend the time to get the best print you can it's a good idea.


Any family of plastics / filaments that bend and keep their shape?

To have a material be "flexible" and retain the shape after the "flexing", you need to apply a stress in excess of the elastic deformation stress.  You will want a material that has the elastic deformation limit that is much lower than the ultimate tensile strength.  Unfortunately, for plastics, this is difficult to find.

Most plastics are made up of tightly bound, long-chain molecules.  Flexing beyond the elastic limit requires breaking these bonds, which introduces weak points in the plastic.  You can see this by bending almost any plastic.  Either it will snap in two, or you will see a light or white colored line along the fold.  The lighter color comes from light scattering from the broken bonds.

"Flexible" structural plastics such as ABS are a copolymer (more than one type of molecule) in which one of the polymers is rubbery.  The rubbery bits provide places within the bulk material where the stress can create strain that doesn't require breaking bonds.

I doubt that any 3D-printer FDM compatible filaments will satisfy your needs.  A filament must keep its shape during printing, if for no other reason than to permit the extruder drive mechanism to apply pressure to the filament.  There are 3D-printable filaments, but they are very elastic and return to their shape when the stress is released.

Some metals can respond to stress with by flowing rather than by elastic strain.  Lead comes to mind.  Someone suggested copper.  There are several degrees of hardness of copper depending on the alloy and the annealing schedule after it was formed.  Copper also work-hardens, becoming harder and more likely break under stress the more the copper flows under stress.


Continuing a failed print when you have Auto Mesh Bed Leveling

Continuing a failed print has nothing to do with automatic bed leveling. It has everything to do with knowing which line failed, repositioning to resume from that point, and resuming from that line of code.


Can't get Y-Axis to move with Marlin firmware

There is a problem in the Megatronics default config file. I used an other default config file and it worked!


Don't Panic!
First of all, a printhead caked in PLA is usually not a death sentence, it is often a temporary setback. Let's start in steps!
Step 1: remove the extruder
We want to work on the hotend, so we remove the extruder feed first. For direct drive, we unload it, then remove it depending on your printer, so the cooling of the hotend remains. For a Bowden, unload and, if possible, remove the Bowden tube from the cooling block. If not disconnect it from the extruder.
Step 2: remove from the carriage
Now that we have the whole hotend assembly bared, we remove it from the carriage. Usually, it is 2 to 3 bolts, more if the cooling solution is mounted separately and has to be removed to access it.
Step 3: remove the cool-end
If you can, remove the cooling fins - we want to have the heatbreak to hold on to.
Step 4: Clamp it up
Take a fire-proof surface (ceramic tile!) and put down the hotend. Rig it up that it can't jump away, best with a small vise. Don't bend the cables!
Step 5: Free the thermosensor
Let's start to clean! If your cartridge still works, get 12V onto the heater and let the stuff melt a little. Use pliers and a scraping tool to clean the thermistor cartridge.
As you have no heat control only heat in short bursts to prevent fire and destroying the cartridge too.
As an alternative and if you can't get the cartridge to work, use a hot air gun or a hot-air soldering station. A soldering iron with a broad tip also works well to scrape off the plastic with controlled heat an as a scraper to remove large chunks.
If you use an external heat source, free the heater cartridge first and remove it, hoping that it is not also dead.
As soon as you can, get the thermosensor out. If you run on the heater cartridge,  install a fresh Thermosensor, even into the goopy heater block, and wire it to the board to regain temperature control and use the board to provide the power.
Step 6: Finish cleaning
I usually clean up the final stretch (and as far as I can: all steps) under board controlled heat:
Make sure that heater cartridge and thermosensor are installed well and working. Set the hotend to 170 to 180°C and do the last cleaning under the use of regulated temperatre.
Step 7: Do steps 1 to 4 in reverse order.
Reassemble, following the steps backwards.
Step 8: Hot Tighten!
Heat the assembled hotend to 240°C, then tighten the nozzle against the heatbreak to ensure tightness. Let cool, done.
Alternative
Replacement/Upgrade!
One could go down to step 3 and replace the hotend assembly (Heaterblock, Thermosensor, heatbreak, nozzle) with fresh parts and reassemble. This is much more expensive than reusing but cleaner and faster - if you need to print now, you might want to keep one hotend assembly on hand as spare and clean the one replaced while the machine runs.
External heat sources
As mentioned, a hot air gun or soldering iron can provide heat to remove the plastic caking.
The soldering iron has the benefit of doubling as a scraping tool and providing localized heat, allowing to possibly free the thermosensor without unsoldering anything in it, and it won't melt the heater block.
A heat gun provides gentle, overall heating of the beater block, but needs extra care where the hot air is going - it can easily char wood and might remove the solder from the heater cartridge.
A gas torch might be used to burn off any residue on a totally stripped heater block, but it also would be able to melt and deform an aluminium heater block! Do not use it on a still assembled heater block, or it will melt any solder in the heater cartridge and destroy it.
In any case, working on a fireproof surface is mandatory!
Chemically cleaning (for non-PLA)
PLA can be removed chemically, but the solvents are rather nasty and some take quite some time to work. Very toxic dichloromethane was used to make a solution of PLA to create thin layers used in this paper, and most other solvents the study mentions are at least equally nasty. The available working options - ethyl acetate and propylene carbonate - have high price tags associated with them. So chemically cleaning PLA from cheap nozzles is not an economically viable option. However, it is a viable option to use acetone if you have your hotend caked in ABS.


What and how much does coloring in the filament affect in the print?

At this point in time I don't think there is a need to be concerned with purity of filaments based on pigmentation.

For the most part, variations in filament quality due to coloring should be the least of your concerns compared to some of the other variables such as quality of the pellets, extrusion temperature (when manufactured), cooling rate (after extrusion), handling/storage, etc.

Also, assuming your focused on consumer 3D printer use, the typical hardware components aren't equipped to be accurate enough to make fine adjustments with regard to the quality range driven by filament color. Even if there were capable, accurate extruder(s) installed, I think you would need a well designed feedback loop to ensure that you're reading temperatures along the full extrusion process (drive, melt, extrude, etc).

I believe what you're asking involves more material science expertise, from a design aspect.

However, I believe that the more "color" you have obviously reduces the purity of the material and thusly the material properties can suffer. Such properties as thermal resistance found in PLA and ABS. So theoretically if you have Black filament, you'll want to extrude with a lower temperature than you would with a natural "White" filament. I would think that the necessary difference in temperature would be a few degrees (Celsius). However, there are many other factors, such as moisture and manufacturing techniques that can take precedence over color differences.

My advice, figure out how to "cheaply" analyze your material and ensure you have an accurate temperature feedback loop. If can you do that, you'll be able to drastically change the quality of consumer 3D printing.


Have you tried this? It should just work, at least if you're using software like Octoprint to control the printer over serial interface rather than print-from-SD-card on the printer itself. In such a setup you're free to submit whatever commands (in particular, G28 X Y) you like while the print is paused. You'll need it setup to save and restore position across pause/resume, or the next command executed might start from the wrong starting position; this would be no problem if it's a travel command, but if it's an extrusion move it would make a mess.
If you're using the printer's builtin pause/resume functionality, I'm not sure whether it will work. It mainly depends on whether it lets you access the homing function while paused. If not this is more of a logic limitation than any fundamental incapability, and could be fixed in the firmware.


I shook off my laziness and disassembled the mounts holding the stepper motors and tightened the belts. After doing so the drift was resolved.


Found the solution, I had to swap the cables on the board, now they are working.


Did you verify the Cura z-offset actually changed the corresponding G-Codes?

I had the opposite problem on my RF1000. To fix the problem I added the following 2 lines to my start G-Codes:

M3001 ; Activate Z-Compensation
M206 Z-0.3 ; Set z offset 0.3mm closer to the nozzle

The first line was default in some example prints and is (as far as I know) only used by Renkforce printers. The second line moves the nozzle closer to the bed. In your case you'd have to move it further away and would need a positive Z value.


Stringing during travel on first layer with Ultimaker Cura

Yes, if you are using the Combing Mode option, please ensure it doesn't do this in the skin, for a leak/string free first layer, it is required to set the Combing Mode to Not in Skin.

When the mode of the option is set to Not in Skin, combing is "off" for the skin; this implies that the material will retract and move in a straight line to the next print area. When material is retracted (and when properly tuned for your printer), the nozzle will not leak filament causing those (deposited) travel movement lines as indicated by the OP.


You are sitting on a fire risk!
If you are using the stock/original firmware, you should immediately stop printing. The stock firmware of the Anet A8 has no thermal runaway protection (see also this answer), this means it will keep heating until the thermistor senses 200 °C, even if it cannot do that for some reason or another.
When a hotend temperature does not read the correct value, your thermistor in the hotend may not be making correct contact (as you say that it goes up and down). Please ensure that the thermistor is correctly positioned, it makes good contact and the wires correctly fastened.
Similarly applies to the heater cartridge, which can fall out and causing a fire if not properly fastened. Ensure the heater cartridge is properly positioned and held in the heater block.
Fluctuations in temperature sometimes are induced by a wrongly positioned fan duct (but generally not that much). The reason why this is not the case here is that you can still push the filament through while it reads about 120 °C; this temperature is generally too low to push filament through. Apparently the hotend is still hot enough to push filament through while registering a low temperature.


Basically, the answer on your previous question is still valid, but your specific questions will be addressed below.

To answer where the setting has gone by answering:

  However, the layout is different for the new firmware v. 3.4.1, and I
  have no idea where the Z axis settings have gone, if they are even
  still there. Can anyone point me in the right direction to find the Z
  MAX POS settings, please?

To find where the setting is, you need to go to the source code repository of Prusa firmware (which is based on Marlin firmware) or download the zip file with the sources and use a "grep" search utility to search in files.

The setting Z_MAX_POS is located in the board configuration file (so in 1_75mm_MK3-EINSy10a-E3Dv6full.h if you have the MK3). This can be found in the online sources (the github page). The online repository is located here. Using the search functionality to search within the source code files on that page you are able to find any setting you need to find. If you type in "Z_MAX_POS" and scroll down till you see

#define Z_MAX_POS 210

You have found what you where looking for if you located the MK3 board.

To solve your problem by answering:

  How to re-program NEW Prusa MK3 MMU2 to accept taller Z axis?

Prusa development team has got rid of Configuration_prusa.h, you will not find this file in the repository anymore!

Instead, it is you that has to rename one of the board variant files (from the "Firmware/variants" folder) corresponding to the machine you have to "Configuration_prusa.h" and place it in the "Firmware" folder prior to compiling (note that these are simple actions that you can do on any operating system; i.e. copy file, paste file, rename file).  Before you compile the sources, you need to change the value of Z_MAX_POS 210 to Z_MAX_POS 350. Please read the README file as this describes exactly in more detail than worded above what you need to do (e.g. use the correct Arduino IDE, e.g. 1.6.9  as this is used by Prusa development team themselves).

Quoting from the README file:

section describing the renaming of the file:

  in the subdirectory "Firmware/variants/" select the configuration file
  (.h) corresponding to your printer model, make copy named
  "Configuration_prusa.h" (or make simple renaming) and copy them into
  "Firmware/" directory

section describing the compiling:

  run "Arduino IDE"; select the file "Firmware.ino" from the
  subdirectory "Firmware/" at the location, where you placed the source
  codes File->Open make the desired code customizations; all changes are
  on your own risk!

  select the target board "RAMBo" Tools->Board->RAMBo note: it is not
  possible to use any of the variants "Arduino Mega …", even though it
  is the same MCU

  run the compilation Sketch->Verify/Compile

  upload the result code into the connected printer Sketch->Upload

  or you can also save the output code to the file (in so called
  HEX-format) "Firmware.ino.rambo.hex": Sketch->ExportCompiledBinary and
  then upload it to the printer using the program "FirmwareUpdater"
  note: this file is created in the directory "Firmware/"

  To compile the sources correctly please take care in using the correct
  software versions and libraries (Arduino IDE 1.6.9, RepRap
  Arduino-compatible Mother Board RAMBo by Ultimachine v. 1.0.1, Arduino
  AVR Boards Built-in by Arduino updated to v.1.6.23)

Sidenote:

A little more in depth for those who are interested to know (and have some programming skills) why you need to change the name of one of the variants configuration files. Basically, Prusa uses different boards with different settings for the different printers they sell. All the settings for these printer variations are stored in the Firmware/variants folder. When you rename the variant file and put it a folder layer higher to Configuration_prusa.h (e.g.Firmware/variants/1_75mm_MK3-EINSy10a-E3Dv6full.htoFirmware/Configuration_prusa.h), these specific printer and board settings are included into the Configuration.h file (line 43 to be precise) by the C-code include statement:

#include "Configuration_prusa.h"

This include statement will basically insert (like copy in memory) the statements from the Configuration_prusa.h file and thus set important constants like:

#define MOTHERBOARD BOARD_EINSY_1_0a

and many more.


Silver Solder specifications for hot end heating element

The first is not suitable. ASTM96TS Sn96Ag4 has a melting point of 221–229 °C according to Wikipedia. Pb96Ag4 would be OK, but that is not lead free so doesn't seem to match your description. Update from comment to explain the letters and numbers: the data comes from wikipedia, the numbers are Tin(Sn) 62%, Pb(Lead) 36%, Ag(Silver) 2%, for example, see below for an electronics solder compound.

Sn62Pb36Ag2 is an ordinary expensive electronics solder (but not lead free), with an even lower melting point.

You need to find a high temperature silver solder, with a melting point of about 305 °C (which confusingly might be a soft silver solder), for example one of these. Hard silver solders melt at 600 °C, that would be excessive in this application.

The nomenclature 'silver solder' came about before lead-free electronics solder was introduced, since when more alloys containing silver have become popular as general purpose solders.


How to create a support structure in tinkercad?

If you're using the term "supports" to mean the extra material that the 3D printer needs to allow material to be deposited in "mid-air," your slicer will have a setting that permits this. Knowing which slicer is going to be used would enable someone to advise you directly of the location of the settings.
If you are going to be using a 3D printing service, you need not address those types of supports. The printing service will have qualified operators who will select the correct settings for your specific model.


Access Temperature sensor data of 3D printer via Serial connection

Assuming your printer accepts conventional G-code flavor, extruder and bed temperature can be retrieved by sending M105 through the serial port. The printer will respond with ok T:XXX.X B:XXX.X where T is the nozzle temperature and B is the bed temperature.

You can read more about the specific G-code in the RepRap wiki.

EDIT:
I am editing the answer to include information for connecting to the printer using a simple python script.

The following script, first opens a serial connection to the printer. For Marlin firmware, when you first connect to the printer, it needs some time to initialize and respond back. That is why some delay is needed before reading the response. After printing the response, the script sends the M105 command, waits for 100ms, then reads the response of the serial buffer and prints it on the screen.

Note /dev/ttyUSB0 is the serial port name and in your case it may be different. Also 250000 is the baud rate of the connection; 250000 is the default value of my printer so you need to replace this with the baud rate that your printer uses.

import serial
import time

ser_printer = serial.Serial('/dev/ttyUSB0', 250000)
print "Connecting to printer..."
time.sleep(30)  # Allow time for response
buffer_bytes = ser_printer.inWaiting()
response = ser_printer.read(buffer_bytes)  # Read data in the buffer
print "Connection response from printer:"
print response
print "Asking for temperatures (M105)..."
ser_printer.write('M105\n')
time.sleep(0.1)  # Allow time for response
print "Temperature response from printer:"
response = ser_printer.readline()
print response


Temperature problems after switching to RAMPS 1.4

For the overheating, you may need to turn the juice down a little on your Power Supply. Typically, there is a potentiometer inside that trims the voltage level coming from there. Some things can heat up if it's over-volting and needing to drop more voltage for the board.

For the temperature reading stuff, make sure the thermistor is plugged in all way and not possibly dangling near the hot-end block. I have had that happen before and it will report improper temperatures as it goes along, and often results in the hot-end getting too hot and messing with the filament. If it's properly secured it might be just crappy or broken in some other way and you would need to replace it. It's reasonable practice to have a few extra thermistors lying around as having them go out at lousy times will bum you out.


What criteria do I need to be aware of when buying a 3D printer for personal use?

Here are few things to consider from my point of view

Printing technology

The first thing that you need to take into account is printing technology. The most common[citation needed] right now is Fused Filament Fabrication. "Liquid light-sensitive resin" is being used in Stereolitography and Digital Light Processing - the SLA printers I found are less common and more expensive than FFF ones.

Price

Need to decide on budget. You can buy printer for 60k USD and 400 USD. Quality is somehow linked to price but that's not a rule. You can buy a shitty printer for a lot of money.

Printing area

Bigger allows you to print bigger things. You need to ask yourself how big things you really want to print. Remember that 3d printing is quite slow process - how often you will want to print big things that will take 60hrs+ to finish?

Printing materials

What kind of materials you want to print with? Some materials will need higher temperatures so check the max hot-end temperature, some will require heated bed.

Assembled or DIY kit

You can usually get kits for self-assembly cheaper than Ready-To-Print machines. However, it will require additional skills (i.e. soldering), tools and time to assemble. I am not sure if I would buy DIY kit for commercial use, but as an enthusiast I immensely enjoyed putting my Rostock Max together.

Reviews and reputation

It is generally safe to buy printer that already has some users. Beware of new magical Kickstarter printers which will "change the 3d printing forever".
Reddit /r/3dprinting suggests that your new printer should meet 3 criteria:

Printer passes the youtube test - has lots of youtube evidence that this particular printer is working.
Printer is out of the pre-order phase. This means that all pre-orders have been delivered.
Printer has a reputation of working well among current users.

I found it to be a very good set of rules.

Upgrade capabilities

That's very user-dependent, but this point is very important to me. I want to be able to change and improve certain parts of my printer. Check if you can switch the extruder, replace the hot-end etc.

Support

I think one of the most important points. See if you can find a forum for your printer and how active community is. It will be immensely helpful if something goes wrong (and it will).
Also, company support is very important. What will happen if you need a replacement part or your printer will stop working altogether?

This list is definitely not complete.
There are many more things that might be taken into account like configuration (delta or XY), multiple extruders, closed cases etc.


The answer really depends on what you are using it for. Is it for dissolving ABS? A quick google search should show you what you want.

The thread, Could you recommend me a suitable alternative to acetone as solvent?, has a good many points that are worth considering:

For example, you may need to consider the Polarity Index

  Burdick & Jackson solvents are arranged in order of increasing
  polarity index, a relative measure of the degree of interaction of the
  solvent with various polar test solutes.

If you are using it to dissolve a polymer other than ABS, then the family/class of polymer may need to be considered:

  Apart from your desired solvent qualities (non-flammability and low boiling point), the choice will be totally dependent on the family/ class which the polymer  belongs. Based on the principal that 'like dissolves like, the attached document will provide you with good ideas on which solvent to use when a particular repeating unit of the polymer is involved.

Butanone is a possibility:

  One alternative is butanone (button-2-one) - this is similar to acetone, but has a much higher boiling point. It is often used for alkylations etc. It has a boiling point of 79-80°C compared to 56°C of acetone.

or NMP:

  N-methyl-2-pyrrolidone (NMP) can be used. It is a polar aprotic solvent and dissolves many polymers. It has high boiling point ( >200 degree centigrade)  It is soluble in water and easy to dispose which is a great advantage during work up of reactions.

However, some other alternative chemicals are listed here (from Any good alternative to Acetone?:

Butyl alcohol
methyl isobutyl keytone (MIBK)
denatured alcohol
MEK (methyl,ethyl,ketone), i.e. Kleen-Strip MEK Alternative
Ethyl Acetate

Some branded items, from Alternatives to Acetone:

  Surfasolve

    Surfasolve is a 100 percent biodegradable acetone replacement that removes adhesives, degreases tools and works as a resin solvent.
    Surfasolve is a non-regulated product.

  Bio-Solv

    Bio-Solv is an acetone replacement that is 100 percent biodegradable. It is not deemed a hazmat, so shipping will not cost
    you more. This acetone alternative is not listed on California
    Proposition 65, a law passed in 1986 to keep substances that cause
    cancer and birth defects out of drinking water. Nevertheless, you want
    to use Bio-Solv in a well-ventilated area because of an unpleasant
    odor. It is not, however, a hazardous air pollutant. Bio-Solv is not
    petroleum based.

  Replacetone

    Replacetone is another acetone alternative. It is nonflammable and nonvolatile. It can be used as an acetone or MEK (methyl ethyl ketone,
    an industrial solvent) replacement that is biodegradable. Both
    Replacetone and Bio-Solv are referred to as green acetone.

  Methyl Acetate

    Methyl acetate is offered as an acetone replacement. Manufactured by the Eastman Chemical Company, it is utilized in industrial
    applications. It is biodegradable, volatile organic compound exempt
    and non-HAP (hazardous air pollutant)

Important note

However, some of these items may also be banned in your country, so check first. As you do not say which country that you are from, it is not possible to qualify this statement.

It is worth remembering that some of these substances are not as safe as acetone, and the fumes may be more toxic, so they should always be used in well ventilated spaces.


Does the Da Vinci line of 3D printers come with a heated bed?

Yes. The Da Vinci Duo 2 (most common one) has a heated bed.


When the printer ignores the scanned topology (grid) of the bed this means that the levelling is not active. G29 activates the M420 to enable the grid. A G28 after scanning the bed will reset this.

You need to make sure that the start G-code (this is an optional script that is pasted before the sliced object) contains both the G28 and the G29, where the G28 is placed above the G29 on separate lines.

For each slicer this is defined in different places, bit if you use Pronterface for slicing, a good chance is that it uses the Slic3r engine. If I open an STL for slicing in Pronterface, it starts loading Slic3r.exe; this brings up the GUI for Slic3r which has options to define/modify the start G-code.


What types of pigments can be used when making your own filaments?

The normal way pigment is added to filament (or any other extruded plastic product) is by mixing "masterbatch" pellets containing a high concentration of dye with the raw resin pellets. (https://en.wikipedia.org/wiki/Masterbatch) This is significantly easier and more reliable than trying to mix raw pigments into the plastic -- the likelihood of clumping and other issues is greatly reduced.

You can buy these masterbatch pellets and mix up colors in whatever ratios you want to achieve specific output colors. Just make sure the masterbatch pellet carrier material is compatible with your resin. There are a wide variety of vendors, including ebay.


Maintaining fine details while applying smoothing methods

A technique I've used in the past is to make a acetone slurry of the same filament used to print your object, and carefully paint the details you need to smooth.  You must be careful and only do a very thin coat or you may damage your print. You can add extra coat if needed to make sure the acetone has evaporatored from the previous coat of ABS filaments slurry.


Slicer reports 1000s of errors not seen in Cura; Render is missing big chunks

Cura and Slic3r are very different programs. You will not get the exact same print between the two. I find that of late slic3r will try to fill holes when older versions do not. So even versions will not behave the same. I will say I have less issues with simplify 3d, but the price is very high.

Following. When this happens I attempt to repair the model. There is obviously some unresolved issues in the model. I use Netfabb which has been exported to this online tool.

Really though. I would ask for my money back ;-)


Good morning, and welcome to 3D Printing SE.

You said: "I can see information from the printer via USB in RepG and through OctoPrint, but can't send any prints, commands or upgrade firmware (I wanted to flash Sailfish 7.7 eventually)."  This means that the USB communication is working fine.  It isn't a question of drivers or the FTDI interface chip.  That must be working fine or you wouldn't have any USB communication.

I would look toward a problem with slight dialect differences in the firmware that is flashed compared with the expectations of the host software.

I am not an expert regarding the differences in firmware G-code dialects, but there are at least: Marlin, Repetier, Mach3, LinuxCNC, Machinekit, Smoothie, Makerware, Sailfish.  I got this list from the "about" page for Slic3r.

I would start by trying to slice files with different dialects and seeing if one of the resulting G-code files prints.  You may also find a description of the firmware you have flashed with references one of these names, which would save a lot of time.

For flashing, you could try dropping back to the Arduino level and use those flashing tools.

More answer in response to the information you have added to the question.

X3G files are not G-code files.  If you are using a control program that expects G-code, it will not be able to handle X3G code.  Similarly, if the printer expects X3G, it may not understand G-code.

Octoprint has an adapter layer that seems to interconvert between g-code and GPX.  You are running this layer.  At about line 11 of the log file you added to the question:

  Recv: echo: gcode to x3g translation by GPX

The GPX add-in may be perfect, and it may cover all version of firmware and all functions.  I don't use it and am unfamiliar with it.

To flash your board, I would be reluctant to assume that Octoprint/GPX new how to run that protocol.  I would use the host software supplied by the vendor.  Flashing is an infrequent operation, and add-on software is less likely to have it 100% correct.  If I were writing GPX, I would intentionally make flashing be out-of-scope, since the consequences of doing it wrong could easily be to brick the printer.

Since Octoprint/GPX claims to be able to print to the printer, I would being all software up the respective current versions.  Flash current Sailfish firmware using the supplied host tools.  Update to the current/best version of Octoprint/GPX.  Read the release notes of Octoprint/GPX for known issues.

It seems that X3D files are fairly limited in their use, which will constrain your options to be within the scope of the community that uses X3D files.  I tried to add the X3D tag to your question, but so far no one has created the X3D tag.

Makerbot is part of Stratasys, and should be well supported.  It may be well supported mostly within its ecosystem.  You have a clone of a Makerbot machine, so, even though most or all of the printer parts are open source, you may not be able to use the genuine Makerbot host control software.

Your question asked if your controller board was working.  It almost certainly is.  I think you have a software/firmware compatibility problem.


I am looking for the aluminum profile parts specs for this prusa i3 printer?

They are 2020 (20mm x 20mm) T-slot extrusions. They should not be confused with V-slot extrusions, which are similar to T-slot, but have a 45-degree slot profile to accommodate V-slot wheels.

If you are contemplating a new build, I would recommend using V-slot. Note that T-slot and V-slot come in a number of sizes (in multiples of 20mm). A 2040 profile is 20mm x 40mm, and will have two slots on the wider sides. Other sizes are available, such as 2060, 2080, 4040, and even C-shaped profiles.

You may want to use 2040 profiles for greater rigidity, especially if you are contemplating a large build volume.

Note that there are imperial as well as metric T-slot profiles. RepRap uses metric profiles.

ReRap Wiki: T-slot

OpenBuilds: V-slot


G1 -2.000 F2400.000

Is not valid G-code. As you note, -2.000 should be prefixed with an axis (X,Y,Z or E).

Marlin would ignore the -2.000 bit and simply treat the command as equivalent to

G1 F2400.000

which doesn't perform any movement, but sets the feedrate for any future moves to 2400mm/min.

  x and y shouldnt have negative

Not necessarily. Even though normally printing is done in the positive quadrant, negative values can be valid. Not only in relative movement mode, but even in absolute mode (for instance, if you set the center of your bed as (0,0) or if you use a negative z-axis offset the bring the nozzle closer to the bed).


Usually uneven dimensions in X and Y directions are a result of improper belt tension of one of your belts. With improper belt tension, the positioning of the printer head is less accurate and typically results in non-circular prints. You should check the belt tension and adjust the tension, not too sloppy, and not too much tension (as it stresses the stepper motor which can lead to missing micro steps).

Furthermore, the uneven dimensional differences you mention (are these values you mention for similar sized dimensions? e.g. is this measured on a test cube print), if they are smaller than the design, and if it is a complex design, can also be related to shrinkage, e.g. ABS is a well known material that shrinks. Plastic shrinkage is basically the same in all directions, but complex shapes could introduce stresses preventing even shrinkage in all directions. To counteract shrinkage, you should slice your model scaled, e.g. scale to 102% to counteract a 2% shrinkage.

If the belts check out right and you are printing in PLA, you may want to check the steps per mm value. This calibration is only useful when you print a test cube at e.g. 200%, the inaccuracies also increase with the same ratio. If not, than it is a positioning error, caused by some play in the machine. Please check the bearings.


What are main differences between rafts, skirts and brims?

Rafts:

Rafts are a few layers of plastic a placed on the printing surface before the object is printed.  If non water dissoluble filament is used, a bit of an air gap will be placed between the raft and the print itself so it can be removed easily. A raft can help a print stick to the printing surface as it normally has a larger surface area than the bottom of the print.  It also allows the bottom layers of the print to contact another layer of plastic so there is less spreading compared to printing on the printing bed itself.

Skirts:

Skirts are loops of plastic that are extruded around the object that is being printed.  On the first layer this allows the filament to get pushed through the extruder so that a steady flow can be established.  A multiple layer skirt can be used to create a blockage around the print so there is less air movement on the print and the print can cool slower.

Brims:

A brim is a layer of plastic that is placed on the first layer of the print go allow for better adhesion to the printing surface.  It does not extend under the print as a raft does, but only goes from the edge of the print to a set distance away.

Credits: Images from Slic3r


Botched firmware upgrade - did I destroy the stepper drivers?

About 15 minutes after posting this, it started working again. Either the driver had badly overheated and recovered after cooling down, or was never messed up and the firmware was just refusing to operate it with the nozzle cold. For the latter possibility, the stock firmware never had that behavior before, but maybe it's possible that some saved configuration to ignore nozzle-cold got lost in the flashing?


How does a UV LCD 3D resin printer work?

I'm surprised your research hasn't answered your question, as the concept is relatively simple. You have most of the answer in the question. The missing item is a light source. Usually the source is an array of ultraviolet LED modules. There are resin printers that would not be called LCD printers, as they use computer display projectors to generate both the image and the UV to cure the resin.

A rather extensive list of various resin printers can be found at aniwaa.com along with a clear explanation of the technologies.

The image below is courtesy of the link in the previous paragraph.

The light source that answers your question is visible in the third picture. As noted, the LCD panel blocks the light based on the image to be cured. I think the "uses its own light" is somewhat misleading, unless the builder has found a high-UV output LED LCD panel or is using daylight resins and has configured for long burn-in times.


Optimal ratio of fresh to used nylon powder

I currently use the 60/40 recycling mix ratio and find that it works very well.  I do however wonder if there is an even more effective ratio in order to recycle used powder.  I currently discard all "cake" powder (powder remaining in the build piston) and am only "recycling" the push off powder.  I found this paper but it's unclear if they are reusing just the push off or both push off and cake.  Any further opinions/ideas would be greatly appreciated.

http://www.internationaljournalssrg.org/IJME/2015/Volume2-Issue7/IJME-V2I7P106.pdf


How to Calibrate. Oh man that is a good 2-3 page long blog post.. So I will try to give you the bullet point section.

High level

Mechanical
Firmware
Software
repeat

Mechanical
Level everything. Bed. The X axis. Make sure there is no binding, etc. Also make sure the surface you are on is flat before leveling the printer by it.

Firmware
Get that printer moving. This is where you do you Steps per MM. I like Triffids guide.

Now is when you go into the software and start setting your slicer settings. This includes your filament measurements etc. You should go back 2-3 times between this step and the previous to make sure your extruding EXACTLY what you think you are. As mentioned by others filament calculation is hard. You need to measure across a lot of material. Take the averages. You will never get it perfect as the plastic is never perfect. Picking a solid supplier is a factor here too.

Once you think you have that all working. Repeat. Start at step one.

After your done looping though you will start with the slicer calibrations. Which is the meat of your question. You will take collections like this one or this one and tweak settings until you can pass each test. Do your tests in this order

single wall test
hollow cube
solid cube Here is a Bonus solid cube
bridging test (honestly I rarely do this one..)
part fitting test

Now for testing when switching material. Honestly its best to start with their settings, and tweak them. I like to have a spread sheet of xy speed, Z lift, temps. Massage it till you are happy. The firmware settings like jerk and acceleration will be less of a factor between materials. Get it perfect once and don't touch it (till you decide it is not perfect).

You will be testing the new material with the same STLs as I mentioned in the precious section. You also might want to look into Simplify 3d (no affiliation) if you get really into it. Also SAVE THE SETTINGS. Nothing sucks more then losing all this work and having to recreate these profiles for materials. Do not trust slic3r to back them up, or to not randomly delete them. Hard lesson there.

Far as max speeds and accelleration..

Max speed will really be a function of how fast can you hear up plastic. If you have a e3d with Volcano mod you can really crank the speed up. So you go to the point where your extruder just cannot hit target temps AND you are unable to print solid infill. Far as acceleration and jerk. When you knock your extruder causing your print to shift, then you know it is accelerating / jerking too hard.

Best of luck! Let me know if I can clear up a section for you.


Incorrect inner dimensions of 3D prints with Ender 3

There are 3 effects at work, and you misread your micrometer: the measurement is 19.35 in the picture.
You have a little lip
There's a little lip at the top and bottom of the print. You'd need to clean that up with a sharp knife or sandpaper. That is the biggest part of the error you measure.
Movement errors accumulate
Errors also collect on the center of holes due to the order in which walls are usually placed, resulting in outer walls having the correct diameters but inner holes having a small offset.
Plastic shrinks when it cools
A smaller part of the error is the plastic shrinking as it cools, but that can be compensated for by the slicer - if your printer allows for it: Under Materials, there is a Shrinkage Ratio setting.
There's compensation for that in Cura
The option is under Shell and called Hole Horizontal Expansion. Setting that value to 0.6 mm to 0.7 mm should solve the hole sizing error.


https://www.alibaba.com/product-detail/120mm-Small-Squirrel-Cage-Exhaust-Plastic_653850349.html?spm=a2700.7724857.normalList.14.23834341IiKFAu&s=p

After quite a bit of searching the above link from Alibaba was all I could find. I suspect that they don't make them like that because of the direction of the rotation of the blades. Perhaps they are made so that the rotor can be swapped around if necessary.

(https://i1.wp.com/www.homeintheearth.com/wp-content/uploads/2012/11/CentrifugalFanTypes.jpg)
The different curving of the blades affects either the volume or the pressure of the airflow (or both).

Alternatively how about one that is more agnostic:
https://www.amazon.com/2Packs-Wathai-40x40x10mm-Brushless-Centrifugal/dp/B07RNZF97F/

Or just 3d print your own housing!


Can I use a 2D photo to get a 3D printing model?

With just 1 2D photo, you can never get a 100% accurate 3D object. That is because you don't really know about the hidden parts.  Think of a photo of a smiling mischievous child that is facing you, and you can't see that they are holding a sling shot behind their back.    However, with multiple 2D photos, one can reconstruct a 3D object, provided all the parts are seen.  This is called photogrammetry.  You can search wikipedia and youtube for in-depth discussion about this.  It is an entire science.  There are applications that do this for you, but I can't recall the details right now.


I would advise buying a new tube for a few reasons:

PTFE tubes should be either 4 or 6 mm external diameter (for 1.75 or 3 mm filament respectively).  Chances are that if your external diameter is that much off from the nominal value, the inner diameter will also be inaccurate, and this could cause a lot of problems during printing, as the filament will likely bend slightly and unpredictably within the tube and the pressure in the nozzle will be unstable, as well as retraction may work inconsistently.
A non all-metal extruder is designed with the assumption that the inner and external sections of the PTFE tube are concentric.  This may or may not be the case for your tube, but it is likely that any hand-made modification to the tube will cause the above not to be true.
PTFE tubes are pretty cheap (around 2€ per metre or less, when bought online).

That said, should you still want to manually modify your tube, I would proceed like this (beware: untested!):

Insert the end of the tube onto a drill bit that fits snugly into it.
Insert the drill bit into a drill press or a drill held in a vice or otherwise immobilised.
Let the drill spin the bit/tube at a moderate speed
Move a piece of fine grit paper up and down the portion of the tube on the bit, trying to apply consistent pressure.
Check your progress with a caliper or a micrometer often, and reduce increase the grit while approaching the desired result.

Best luck! :)


I have had trouble before not using spacing between arguments. I think no spacing between -b and 57600 is causing the problem. Try

avrdude -p m1284p -b 57600 -c arduino -P COM%x% -e -U flash:w:%filename%.hex


There are lots of ways from mere specifications to designs. Most follow several of the principles below, but designing a printer is not a light undertaking. it's HUGE.
Copy and adapt
The most easy way is to take a known design, for example from the RepRap wiki, and copy it verbatim. But it can easily undergo some adaptions, like different hotends or bed sizes.
Paper sketch & notes
Writing down the specs of some parts is very important to make sure these stay consistent. Paper is also the tool of choice for initial sketches or even finished designs to guide building the actual parts.
CAD
CAD is an almost indispensable tool to map out the placement of parts and combine them. Or later design parts to print. A CAD design doesn't need to be detailed, it can use stand in rough outlines. Only where parts need to be custom-made, details are essential.
Prototype
All projects go through prototyping when groups of parts are built and tested on their own and combined piece by piece. Also, this step is where you finalize the firmware.


In theory, most filaments don't go bad.

It is however always a good idea to store filament dry. To enforce this, some use racks in a well-heated room, others are blessed with very dry weather overall. And others are forced to use dryboxes. Dryboxes can keep the filament reasonably isolated from the surrounding air and so prevent moisture interacting with them. It is also a good idea to store them out of direct sunlight, as UV light might destroy color and/or the plastic.

More information on why to use them is for example at the question Which filaments actually do need to be stored in a drybox?

A couple construction videos using an IKEA box and a bit of foam were offered by Tom (Thomas Sanladerer) and CNC Kitchen (Stefan Hermann) in the last year.

But fear not: most filaments - PLA included - can be freshened up again! Just bake them at a low temperature or store them in a dehumidifier. For PLA, keep the temperature at below 80°C. A couple hours should get all the moisture that has seeped in out again. The Quality might not get back to that of fresh filament in all cases, but you might at least regain reasonable to good printability.


Is nozzle no longer heating up correctly related to hotend insulation being pulled off?

Yes I had this same problem myself.
You will need to re-insulate it using a silicone block and next time don't leave the window open while printing. Just keep the fan or AC on to circulate the air.


You may want to ensure that your filament diameter is correctly set in your printer's CURA profile, and that your hot end is at the correct temperature for the material you are using. Additionally, you should not need a raft to print the cube, and should be able to do without a raft or brim.


Are SLA prints also susceptible to say microbes like FFF prints are with the microscopic flaws?

The best information I could find was this article from Formlabs about food safe 3d printing. It has a fairly detailed discussion of the different food safe requirements and the conclusion basically is that SLA prints are not food safe by default and can create conditions for mold and bacteria growth. SLA resins are toxic when uncured.

The article goes on to list a few options that can increase the food safety of printed objects.

Dipping in a food safe coating such as a food grade epoxy or polyurethane. But it does note that this may not make the object food safe as the coating may be compromised.
Making a mold from the 3d printed part and using the mold for food contact.
Electroplating the printed object with metal.
Printing with ceramic filled resins, burning out the resin in a kiln, and glazing the part with food safe glaze.


Yes, it is a "Sells Mendel" in reference to Edward Sells. As noted on the RepRap wiki:

  Ed Sells, a student of Dr. Adrian Bowyer, designed and built the first Mendel printer, sometimes called a "Sells Mendel" to distinguish the original design from later tweaks.


How to create a web-based PHP that can print to multiple printer(when idle) using silent printing

I'd recommend starting with connecting your printer(s) to OctoPi. From there, try to find either an API or way to create your own plugin. Then just set up a workstation that will manage your print queue and delegate the prints using some form of web request.

I personally don't recommend creating your own slicing engine. If you want to do everything directly from "the workstation" try looking into Skeinforge (most popular from ReplicatorG slicer), Cura (I believe from Ultimaker), and/or Miracle Grue (from MakerWare) as your slicing engine. You can most documentation/source on GitHub.

In the meantime, try to narrow down the general sense of how you want to accomplish this and edit your question. As a reminder for more technical questions regarding code, please use Stack Overflow. For example, "How to create/use REST request?"


My guess is your Z guides are not strictly parallel because there's no instruction how to install X guides correctly. When you install X guides, you can easily make horizontal distance between two Z-mounts either too small or too large, which puts extra stress on one of the Z motors. Move your extruder to home position, measure distance between bottom ends of Z threaded rods and between top ends, and try to adjust right Z-mount position on X guides so that these two distances become equal. Use hammer, but be accurate with plastic.


Connecting my OctoPrint to a Google drive folder

You could mount your google drive using gdrivefs on your pi following this tutorial: https://www.raspberrypi.org/forums/viewtopic.php?t=109587
However, I have to ask: why send the file to the internet? Is your printer/pi on a separate network than your desktop where you are slicing?

If they're on the same network, you'd be better off setting up a samba share on your raspberry pi (https://www.raspberrypi.org/magpi/samba-file-server/) and then mounting that directory from your desktop (https://www.techrepublic.com/article/how-to-connect-to-linux-samba-shares-from-windows-10/).

In either case, you could set the directory (the gdrive directory or the samba share) as the watched folder in octoprint's config.yaml (http://docs.octoprint.org/en/master/configuration/config_yaml.html#folder).


Strange walls/faces when importing self made model from Blender to Cura 3

It is quite common for modelling operations to result in 'non manifold geometry', meaning that some of the faces intersect or are not perfectly joined.

Although there is nothing obvious in your model, you can check in blender by going into edit mode, unselect all, selecting nodes, and 'select all by attribute/non manifold' Ctl-Alt-Shift-M (if I remember right).

Usually this happens with boolean operations where you merge the same object twice (i.e. union for the hole, then difference with the cut part). You would need to apply the boolean to see the non-manifold result.

Any of the standard mesh fixing tools will attempt to clean up your exported STL, and you could then import the model back into blender (but then it is a one way process, and you can't make updates to the base model).


If the printer is printing, it is instructed to do so by the G-code file unless you are printing through an external software program that has extra G-code to print before your print starts. E.g. in OctoPrint print server it is possible to execute G-code before the print starts.
Left line = Priming
The straight line on the left is typically used to prime the printer nozzle to get the filament flow starting, this is typically seen in PrusaSlicer (Prusa's fork of Open Source toolpath generator for 3D printers Slic3r). This straight line is called priming line, purge line or intro line, and is typically (but not necessarily) printed outside or at the edge of the bed area. Furthermore, a prime line print routine will catch errant nozzle ooze, test extrusion (it is the first indication if the nozzle to bed distance is correct; if not you can abort with minimal material loss) and perform a final wipe action to avoid stringing between the prime line and start of the print. Note that this straight prime line is not a standard option in a custom profile of Cura, so this was part of the Ender-3 Preset you imported or possibly you have copied a starting G-code that includes this prime line.
A typical set of G-code lines to create a prime/purge/intro line is found in your start G-code and could look similar to:

G1 Y-3.0 F1000.0 ; go outside print area
G92 E0.0
G1 X60.0 E9.0 F1000.0 ; intro line
G1 X100.0 E12.5 F1000.0 ; intro line
G92 E0.0

After slicing your object, you will find such lines in the generated G-code file, but they are not displayed in the preview. Further information can be found in Writing G-code : swiping at start of print
Equidistant line = Skirt
The lines at distance from the print object is called the "skirt", the skirt is an option found under the "Build Plate Adhesion" options in your slicer. The function of the skirt is similar as described for the straight prime line, but it has additional effects that can be wanted. It also shows fairly fast if the bed is unleveled as a whole or if the bed is greasy. Please look into: "What are main differences between rafts, skirts and brims?
".
Note that it is usually superfluous to use both the prime/purge/intro line and the skirt, both have a similar function. The benefit of the skirt is that you can configure it within the slicer (e.g. length of the printed skirt, height to use as a shield for draft or ooze and distance to product). The downside is, that a skirt limits the useable build area by the distance and width of the skirt.