How to install new ATmega firmware via the ISP pins?

Considering AVR based controller boards...

You might not need an additional Arduino, to serve as an ISP. It really depends upon the board. There are basically three scenarios:

Controller board which is Arduino based - Arduino Mega 2560 with a RAMPS 1.4 - with a bootloader
Controller board which is Arduino based - Arduino Mega 2560 with a RAMPS 1.4 - without a bootloader
Controller board which is AVR based board (no separate Arduino board) - as is the case with an Ender-3 and the TronXY board1 - without a bootloader

Option 1 is the easiest, and you simply upload with the USB cable, directly from the Arduino IDE.

Options 2 and 3 is where you would require an In-circuit Serial Programmer (ISP). Such as a USBasp: USBasp - USB programmer for Atmel AVR controllers

or you can use another Arduino, see Arduino as ISP and Arduino Bootloaders.

An ISP device basically converts the USB to TTL signals (along with a serial protocol (JTAG or derivative)) which then connects to the ICSP2 interface on the controller board:

Scenario 1

As stated above, you simply connect the board to the PC/Mac using the USB cable and, within the Arduino IDE, you hit Upload - ensuring that you have the correct Board (i.e. Mega2560) and Port selected in the Tools menu.

Scenario 2

For the Mega2560 the pins the MOSI, MISO and SCK are broken out on to are:

Arduino / Genuino Board    MOSI            MISO             SCK       Level
Mega1280 or Mega2560    51 or ICSP-4    50 or ICSP-1    52 or ICSP-3    5V

To program the Mega2560 using an Uno, connect as follows:

or using the ISP connector (in this diagram the electrolytic capacitor3 is not shown):

Take note of the electrolytic capacitor3 on the programming device:

  The 10 µF electrolytic capacitor connected to RESET and
  GND of the programming board is needed only for the boards that have
  an interface between the microcontroller and the computer's USB, like
  Mega, Uno, Mini, Nano. Boards like Leonardo, Esplora and Micro, with
  the USB directly managed by the microcontroller, don't need the
  capacitor.

or using the Mega's ICSP connector, from Atmega bootloader programmer (see original image):

Note D10 is used, not RESET4

Scenario 3

So, to use an Arduino Uno on your controller board, which is scenario 3 (an AVR based board, but not an Arduino board per se), you would need to connect the Uno to the ICSP of the controller board like this:

ICSP     Uno

MOSI     D11
MISO     D12
SCK      D13
GND      GND
5V       5V
RESET    D10

or, like this, from Chaos Drucker - CREALITY ENDER3 MIT MARLIN AUSSTATTEN  (see original image):

There is an error in the image and the red line should go to D10 and not D9 as shown

Note, again, that the RESET on the Arduino Uno's ISP connector is not used (and Pin 10 is used to connect to the controller's ICSP's RESET pin instead)4.

Configure the Arduino IDE

Then in the Arduino IDE you will need to select the Programmer to be used, in this case Uno as an ISP, like so:

Once you have connected correctly, and selected the programmer, then you should be able to hit compile and upload as usual.

Footnotes

1 Which both use the same board - see this answer to What voltage does the Creality Ender-3 run at?

2 In case you are wondering, see What's the difference between ICSP vs ISP?:

  The difference between ISP and ICSP is a hyphen.

  ISP stands for In-circuit Serial Programming, and ICSP stands for In
  Circuit Serial Programming.

  Any arrangement that allows you to program a microcontroller while it
  is in a circuit using a serial protocol can be called ISP or ICSP.

See also Wikipedia - In-system programming.

3 See When using an Arduino as an ISP, is the capacitor required or not?

4 Why? From Can the Arduino Uno become an AVR programmer and use the ICSP header to program the target board:

  First of all, as configured, the RESET pin can not be used as an output pin. In order to use it as an I/O pin, you would have to program the RSTDISBL fuse. But once you do that, as jippie said, it becomes near-impossible to reprogram your Arduino (if you have the socketed through hole variety of the MCU, you could pull it out and put it into a high voltage programmer; in all other cases, it's effectively impossible).

  So in theory, you can use the ICSP header the way you suggest. In practice, it's under almost any conceivable circumstance a terrible idea.


What is the difference between M420 S and M420 S1?

TL;DR
Short answer: "There is no difference!".

Long answer
G-code is parsed line by line. The parser in the firmware reads the command and the options (also called parameters) following it, comments are discarded.
Therefore, option S should be followed by a Boolean value 0 for False or 1 for True. Without a value it is undefined and should be reported as incorrect or treated as false (in my opinion). But, the developers have chosen differently. If a Boolean value is expected and the value is not given, the parameter is parsed as true. This has analogy with other software options or switches like e.g. used by Linux commands.
This means that for Marlin  the G-code M420 S is exactly the same as M420 S1.
I've checked this with another command (this is not depending on the G-code command as there is a single parser processiong the G-codes and the following parameters); M211 where M211 S is exactly the same as M211 S1.


I've read people are using them, makes sense, the less air you contain, the less moisture would be in the bag. Myself, I'm using IKEA ziplock bags (and moisture absorbing sachets), they come in many sizes.


According to the chart on this page HDPE has a flexural modulus of between 0.75 and 1.575 Gpa; meanwhile PETG has a flexural modulus of 2.20 Gpa, meaning PETG is the stiffer material.

HDPE, by definition, has a density greater than 0.941g/cc.  PETG has a density of about 1.25g/cc.

So while PETG may be denser (depending on the HDPE used), it is more rigid, while not being too rigid.

PETG is quite printable using FDM.  If you were printing at a higher temperature and high % infill, I could see it holding up well enough.  I've printed heavy duty parts with it using a 0.8mm nozzle.


I know you said you don't want to change the Z height, but it does look like you're printing a bit too far from the plate. I would recommend adjusting your Z-offset if you can, or adjusting the limit switch (or whatever your Z-homing mechanism is)


What is the best method of printing joints for action figures?

(NOTE: Converting comments to an answer.)

An interference fit would probably work. There are a couple of styles I can think of which would do. Here are some ideas from thingiverse.com which may work for your needs.

(image taken from this design by OgoSport)

With this style of ball/socket, you'd have very good articulation. More than enough movement to allow for a posable action figure.

Another idea from thingiverse.com is this:

(image from this design by NEMO_from_saturn)

The idea behind this style of joint is to insert it into each part (part fits over the end). This is premade and would be easy to utilize. The thing about this is, they are covered by the licensing involved with patterns found on thingiverse.

As with anything printed or mechanical, it will wear over time. You won't ever get anything which doesn't wear. It's just a fact of how it works. Some printed filaments will have better wear properties than others, like ABS, NylonX (polyamide with chopped carbon fiber strands), nylon, PET (PETG/PETT), or polypropylene (this is not all inclusive). Each filament has its own printing properties and idiosyncrasies, so pay attention to what needs to be done to print with them. This doesn't mean all of the parts need to be printed out of this material, but rather if using a joint (like the second image), you could print it out of the better wear material and print the rest out of filament which is cheaper and is easier to work with.


Z offset not working after flashing TH3D firmware

I'm pretty sure something is wrong with the firmware I downloaded. I flashed the 3/5/21 version of Marlin firmware from https://marlin.crc.id.au/ and it is somehow working better with the LCD firmware (which I got from TH3D), the Z offset is working as it should, and the leveling process has more points and goes faster.


Here are first 3 the most simplified and generalized options you have:

All you need now is to give use more details about your needs. If you reveal more details we could help you to apply (and modify) one of these  options.

Each of above has its own pros and cons of course. You said you don't want to have spring... so maybe a rubber ;)
But in fact whole-red is one-piece-clip in which the force comes from material elesticity or stiffness.

Please tell me what is the application of such clip.


Using a Full Spool of Filament, Read as "Empty"

From what is read online, it depends on the firmware version your printer has. It seems that later versions keep track of tag serials and reports tampered tags as non-genuine tags. The best and most recent reference found is from 2018 which describes you should be creating new tags instead of resetting existing tags. This involves installing an Android App from unverified source and new "paper" NFC213 tags.


Z-Axis on i3 clone won't move at all, Melzi A4982 driver problem

I've replaced the Z-axis stepper driver with an off-board Pololu-style A4988 driver by soldering leads to pins 2 and 3 on the Melzi board, then connecting those to the driver on a separate board. The Z-axis now moves correctly. When I encountered issues with the step pin (pin 3), I connected it to pin 12 (bed heater) instead, leaving the bed to be heated manually. This has worked so far and the only problems I've encountered were minor issues with electrical noise, which I was able to fix with a shielded cable.


How can I upgrade the drivers in the Printrboard rev. D?

The developers from the Klipper firmware confirmed that Klipper doesn't care about the native functions of each pin, therefore it is indeed possible to use the expansion pins for controlling (including UART) TMC stepper drivers.

At this point I cannot confirm, but maybe Marlin allows the same by updating the pin assignments in the source code.


I think I fixed everything. What I did is I used this guide <youtu.be/y_1Kg45APko> which was a guide by makes'n'breaks on setting the probe z-offset using pronterface and then reverted to the original firmware that was on this page<github.com/bigtreetech/BIGTREETECH-SKR-mini-E3/tree/master/…> Which was the marlin firmware for bltouch for z homing for my mainboard.


3D Printer makes steps at Y axis (in some cases)

When you describe a problem like this, it is best to describe the effect, not what you think is the cause - particularly since others then might mis-read your description.

Each layer being offset in one direction suggests that there is a problem with either the part moving on the bed (unlikely), or in the registration of one axis drifting over time.

Most likely, your Y-axis is skipping steps. It could be several things:

the axis binding on it's runners
the drive belt skipping because it is loose
the drive belt binding because it is too tight
too fast a print/travel speed
the print nozzle catching on the print (bed too high, no z-hop)
not enough drive current to the stepper motor
stepper motor failing
belt drive loose on the stepper shaft

A common 'feature' of 3d printing is that different models might emphasise one problem, but a different shape might hide it.

Check that everything is properly tightened, moves freely, and the belts are undamaged - with luck you can find the problem and it's not electrical.


Does the X/Y bed orientation of a model affect the print detail quality?

In short: Not really.

longer version: It depends.

The main culprit of losing details in this case would be the weight and speed of the thing moving. So if you have a heavy X-axis carriage, acceleration and decelerating the carriage won't be instant. Same with the bed (Y-axis).

Another culprit can be slop in the system, so check your linear bearings and belt tension.

Also keep in mind that you are printing on the bed, so the weight of the Y-axis increases while the print progresses. This shouldn't be a problem for small prints, but if your print becomes bigger it can decrease the quality. Another factor is that every print will bend a little the higher it gets, so if you print a tall slender object, don't accelerate the bed too fast ;)

To summarize, for high detailed prints:

Lower the speed
Check the system for slop (tighten belts, and align linear bearings)
Take the lightest axis for the highest detail (keep the weight of the print in mind)

One thing that you can do to test your machine is to test the ghosting on each axis (https://www.thingiverse.com/thing:277394).


GRBL: inaccurate on X axis by ~4 mm on 400 mm

This seems to be either a case of either belt slop or missed steps or it is a case of the accuracy of the limit switch.

If the limit switch moves even a little into either direction, you have to account twice that as the maximum error. So the 4 mm error could come from 2 mm into either direction from the 0-position.

However, there is a silver lining: Laser engraving, just like CNC, usually first dials in the 0 regarding the workpiece instead of the 0 of the machine. As long as the machine's movement is ok, you should be fine even without tightening the mounting of the X-endstop. I suggest to run the following test to find out what kind of error actually hounds you though:

Mount a waste piece
Go to a position on the workpiece
Run the laser for a split second
X10
Run the laser for a split second
Repeat 4&5 till you have 10 points
Measure the real distances between the dots engraved

If the distances are always the same but short, you have the wrong steps/mm set and need to adjust them accordingly. If the distances are inconsistent, you have either lost steps or a sloppy belt. To fight lost steps, carefully up the signal to the motor a little. If the results don't change from that, tighten the belt a little - it should sing like a guitar string.


Y-axis limit switch adjustment is way off on new Ender 3 V2 causing motor grinding noise and system lockup

It is possible that the buildplate is too low, and cannot travel all way down  the Y axis, but is hitting into the Y motor enclosure.
If you have screwed the Z-stop to printer's vertical frame, shifting the endstop all the way down, there is even bigger chance for this. So one advice is to raise the Z-stop by about a width of wrench key included to the set. Ender 3 V2 has a bit taller glass plate comparing to previous model.
That is not my idea, I just repeat that after the author of "Tomb of 3D Printed Horrors" youtube tutorials. The author also presented quick method Ender 3 easy bed leveling, including fine tuning of the Z-stop position.
Please also note, that there are wires with thermistor taped below the bed with crackling tape (probably capton). So if you raise it too few, you will regularly hear scraping and crackling sounds. Therefore before builtplate leveling, I would advice first to check the initial height if it is already safe.


Ender 5 with 8-bit Creality 1.1.4 board- Issue with speed of extruder motor spinning too slow

I think you might be asking how to adjust your steps per mm, but if the motor is moving the correct distance, but at a slow speed, then it might just be a speed problem with settings, or whatever it might be. I have an Ender 3 but I think I might be able to show you how to calculate the steps per mm. There is a simple equation for this.
New E-steps=(target distance/actual distance moved)*current E-steps
You can use this equation with a couple steps.
Step 1.   Make your printer extrude 100 mm of filament, then measure with a digital caliper how much it actually extruded (or moved). Plug this measurement into your equation in the part "actual distance moved", and put 100 in the part "target distance". You can control the motors by going to: prepare then move axis.

step 2.  Go to the steps per mm section.

Then use this value to fill in the "current E-steps"(but on your printer of course)

In the end your equation should look like this:
New E-steps=(100/your measurement)*your current E-steps.
After you solve the equation, put the answer into the printer. To save your changes, go back two pages from "Steps per mm" and click the "store settings" button. This will save your changes onto your sd card, so make sure that it is in the slot when you do this. Also make sure that your sd card is in the printer at start-up, because it needs to boot up with the settings. (at least on the Ender 3)


Why is support printed over shell if layer preview doesn't show it?

The picture of the line types and the accompanying comment helps to clear this up:

they are "Travel" lines, but why material is printed during travel?

Yes, the dark blue is travel. But if material is deposited during them, then that is not printing, that is material oozing out of the nozzle - which is called stringing most often. Usually, this is an issue with retraction: your length is possibly a little short. However, retraction also only is turned on for moves over a given length, so there might be no retraction happening. And, in Cura support structure generally is printed without retraction due to toggle Limit Support Retractions. Toggling that off can help.
You might also turn on one of the two Avoid modes in the movement (Avoid Printed Parts when Traveling & Avoid Supports When Traveling) to get the movement paths in a way so they don't go over the model and prevent any stringing/oozing onto it or knocking off delicate parts. Possibly increasing retraction a little might help, and so might Z-hop to try to "rip" the strings.


FDM printer?
If you want to print one, maybe you should outsource it (let it print the tag on both sides), even the most affordable printers are in the \$100 - \$150 price range. If you want a printer and use it also to create ID tags, you could go for an FDM printer. Considering your request of having the tag inside (and through) the ID-card you need a dual filament option (one or two nozzle arrangement). If the tag can sit on top you can print it with a filament change with a single filament single nozzle printer. But, don't expect to get crystal clear prints (see experience printing signs below)!

Alternatives
As an alternative, you could print a blank PLA ID-card and laser mark the tag onto both sides, see e.g. this video.

If it is a small batch you can also consider printing/lasering stickers and stick these onto blank ID cards.

From experience
I've done some signs with black letters on a white background for "on-lay", inlay and through arrangements using a more expensive (for home use) dual extruder 3D printer (Ultimaker 3 Extended about \$5000,-) with PETG, but the results were not very satisfying. Usually the black smears out on or in the white no matter tweaking the options. Considering the size of an ID-card, the amount of tag squares, this is even more likely to happen when you print at that small size (the signs I printed were sized similar to the "A5" paper standard).

From my experience I would say that a 3D printer may not be the best solution for your task.


Brass rails, bunting bearings ok for x,y axes?

Extruders tend to be quite light. An E3Dv6 complete with fan, shroud and wires is under 100g. Unless you use a Bowden extruder, you also have to add ~300g for a stepper motor. In any case, it will be quite light.

Sintered bronze bushings can definitely be used in a 3D printer; they're used in the (quite popular) Ultimaker 3D printers. I can't tell whether your particular bushings will work well, but I think the most important consideration is that there isn't too much play between the rod and bushing (but I'm assuming you took care of that). 3D printers don't place high loads onto the motion system.

"Proper" LMxUU bearings aren't very expensive either (reasonable ones can be had for less than $2) so if the bushings don't work out, you could always try those.


You got a few things happening. First that temp seems low. I am printing PLA at 215.. but there are a lot of factors. Start with a simple calibration thin wall test. Which is just a wall, no body.

From there your bed could be closer. Maybe. I don't think that's really the issue. Slower speed and heat will make more of a difference. That said. I take a piece of paper and calibrate it so there just a little, but not too much, friction.

Make sure you are printing at 30% speed for first layer.

Last use a glue stick.


Wanhao duplicator i3 print bed support warped

okay, after ferociously dismantling the whole bed I found out that the bed and the bed support are perfectly straight!
So there is something  warping the bed and support. De Y-axis bars are perfectly flat too.

I found out that my table is not flat! This made the complete printer warped and even bent the print bed. put some cardboard under the frontleft foot and presto! As flat as it should be!


My current workaround is to use union instead of intersection. Unfortunately, that means I have to use an if clause which makes the code have two paths instead of one clean approach. Also, unlike the above method, this does not result in a clean cylindrical shape but must instead by combined with a proper cylinder to get the final pie slice

   size = length + 2;
    if (angle_deg <= 90) {
      translate([0,0,-1])
      intersection() {
        cube(size);
        rotate(angle_deg-90) cube(size);
      }
    } else if (angle_deg <= 180) {
      translate([0,0,-1])
      union() {
        cube(size);
        rotate(angle_deg-90) cube(size);
      }
    } else {
      echo(str("FAILURE - Angle cannot exceed 180"));
    }


You can change your Pi's resolution using raspi-config or the Raspberry Pi Configuration app.

To use raspi-config, access Terminal and run raspi-config. Then navigate to Advanced Options > Resolution.

If you'd rather use the GUI, open the Raspberry Pi Configuration app and select Resolution from the resultant dialog. This may help with the rendering issues.


Since Polycarbonate (PC) has glass transition point of 147°C (according to wikipedia) where it starts to melt, you could in theory use it as a heated bed for PLA or even PETG. BUT, there are other characteristics:
PC is quite good heat insulator, which would result in uneven heat distribution in the heated bed.
Also it expands quite a lot with rising temperature, which could result in warped bed.
And as per usual with thermoplastic polymers such as PC, heating them and cooling them repeatedly can cause material degradation. That would result in the material becoming brittle, deforming, or changes of other properties....
Next problem would be that it is not stiff enough. Depending on the size of the heated bed you would have to support it on multiple points (I would say at least 5x5 grid for 300x300mm bed) and even then it would be unpredictable.
To sum it up: yes, you probably could use PC as heated bed, but it is much better to stick to traditional materials like aluminium or glass fibre sheets (PCB material), because PC would be very inconsistent and therefore hard to level.
I hope this helps.
Note: I am basing this on my theoretical knowledge, I have not tested it and thus do not know if my assumptions are correct or not.


Printing temperature basics
Manufacturers generally specify a somewhat wide range of printing temperatures, and what temperature you should actually need can only be determined by trial and error:

The thermistor in your hotend is not 100 % accurate and may have an offset of a few degrees compared to its actual temperature.

Your hotend has a small temperature gradient, the place where the plastic is melted may have a higher/lower temperature compared to the temperature of your thermistor.

2 is further exacerbated by

As you print faster, you need more heat. The cold filament rapidly moving through your hotend will cool it down locally, meaning that the temperature will be cooler than what the thermistor measures. Faster prints equal bumps in the temperature up to 10 °C, and for a really slow print you might turn it down 10 °C from where you normally are.

This is a minor issue, but different colors of the same brand and material might work better at different temperatures. The pigments used can affect the melting point somewhat. Different brands also might have different temperatures.

Some symptoms may give you a guide as to how to adjust your temperature:
Printing too hot

Small/slow prints may not solidify quickly enough, leaving you with an ugly blob.

Stringing/bad bridging.

Plastic in the heatbreak may soften, leading to clogging.

You might burn/degrade the material (but for this you would really need to go outside of the temperature range).

Printing too cool

Too much force required to extrude, leading so skipping/grinding of the filament drive.

Layer delamination: the plastic needs to be hot enough to partially melt the layer below it and stick to it. Objects printed at a colder temperature tend to be weaker at the layer boundaries.

Furthermore, hot prints can sometimes have a more glossy finish than colder prints.


If you look into the most recent version of Marlin you will find in file Marlin/SanityCheck.h:

elif defined(MANUAL_BED_LEVELING)
  #error "MANUAL_BED_LEVELING is now LCD_BED_LEVELING. Please update your configuration."

This implies that constant MANUAL_BED_LEVELING is obsolete. It is not found anywhere else except for the file linked above. So, no, the constants are not supposed to do exactly the same. Instead an error is shown on compiling to update your configuration to exclude the constant MANUAL_BED_LEVELING.


3D print appears to print very weak walls in long print

What you refer to as weak walls in fact are under-extruded walls. This can be caused by multiple sources, but, since the print recovers this most probably is caused by filament that is entangled on the spool (this causes more friction for the extruder and as such less flow, so under-extrusion; like as if the filament is being pulled back). Any other source that may induce extra friction is equally valid. E.g. kink in filament when using a Bowden configuration (long time extra friction in tube) or friction on the spool itself (I once had severe under-extrusion as the spindle of the spool caught a plastic bag which got wrapped around).


I can't figure out how to name this problem or solve it

I'm an Ender 3 Pro user and I've been through almost every problem this machine has.

If you are on original hotend and Bowden style extruder, then first try the hot end PTFE fix

What the picture may show is a temperature too low, especially on these bad layers. Raise the temperature like you have tried (200 °C is good).

To avoid prints being knocked off the bed, try brim (it's in bed-adhesion in Cura), most people don't use raft anymore. What brim does is to add addition loops on the first layer of your prints and make it sticks as good as possible.

No raft, add brim. Then disable Z-hop, enable combing in Cura.

These steps should be able to mitigate the problem.


Do 3D Printers Prefer Particular Topology?

The most common file format in 3D printing is STL. This file format is using triangles only so when you export an object from your CAD application to STL then exporter has to transform all n-gon faces into triangles.

Once the file is created then it is usually imported by slicer application (or module) which performs slicing using polynomial calculation to find intersection with next surfaces. Here is good example of such intersection finding in javascript.

So answering your question:

no - it doesn't matter as you usually use file format in which faces are triangles but
yes - it matters as all your n-gon faces needs to be transformed into triangles


Well I found the solution on Marlin's GitHub:

https://github.com/MarlinFirmware/Marlin/issues/9155

but it might have been solved without having to hack the file since then.


In addition to @TecTec3's answer:
Parameters that define filament quality:

Diameter variance: If there is too much fluctuation in diameter, the filament might get stuck.
Material Quality: I had really expensive filament that was brittle and did tend to snap when it was extruded. Other filament just didn't melt but started burning up and regulary clogging my extruder.

My opinion:
I'd say you shouldn't go with too cheap filament and stick with one that works out best for you. If you have issues try another brand. It's impossible to tell quality just from the price.


Wanhao Duplicator i3 plus temperature out of control

Thermal Runaway?!
The temperature should not go over the MAXTEMP variable set in the firmware, so permanent damage is probably avoided (when temperature doesn't exceed about 250 °C; that is about the max temperature for the PTFE liners in the hotend). In the factory setup, the Wanhao Duplicator i3 is running an instance of Marlin Firmware. In the configuration.h file the MAXTEMP is defined like:
#define HEATER_0_MAXTEMP 275

for the first extruder where 275 °C is the default value, if Wanhao has changed this to a lower value (as they list their printer to print to max 240 °C) is not known.
Fixing the issue at hand
To expand on your question:

"Any ideas what this is and how to fix it?"

In order for you to fix the problem you need to do some troubleshooting. You need to find out if this problem persists when not using the pre-heat function of the firmware. E.g. When you do not pre-heat, but print a PLA object, does the temperature also keeps rising? Furthermore, try to hook up a computer/laptop over USB to the printer board and try pre-heating from a software application like OctoPrint, Repetier-Host, PronterFace, etc.
From the description alone, it appears as though the gain of the onboard MOSFET is opened once requested to preheat, but never closed. This could hint to a faulty MOSFET. If you are handy with software compiling for Arduino based microchips (please do note that this requires some thorough insight in compiling software for the Arduino platform), you could alter the printer configuration (not only hardware, by connecting the hotend heater and thermistor cables to the bed terminals, but also software, by switching pins in the board configuration file) to use the bed terminals to heat up the hotend (and not use the heated bed during the test, disconnect the cables of the bed), but that will most probably show that the hotend will stop at the requested temperature as the thermistor does not seem to be broken.
Simple tests that you could perform to check the functioning of the hotend/setup are:

Disconnecting the thermistor leadsThis will effectively result in a 0 Volt reading, this is to test the MINTEMP temperature limit of your setup.
Shorting the thermistor leadsThis will effectively result in a full 5 Volts signal resulting in the maximum temperature reading. This exceeds the MAXTEMP temperature by far, as such it should halt heating up the heating element once shortened. You can do this even without heating up or before it reaches 240 °C.
Disconnect the Heater cartridge orTake the heater cartridge out of the aluminium heater blockThis will effectively test the "Thermal Runaway Protection" (or short TRP) of your setup. If the thermistor does not register a temperature rise after a certain amount of seconds (in advanced configuration), the printer should detect there is something wrong and shut down/halt the printer. Disconnecting the heater cartridge is the safer way. Common TRP times are 120 seconds and less.


The silver looking cylindrical nut (with the flat faces) between the brass block and the black metal plate is the heat break of the assembly. The brass block should be tightly fit to this heat break. You could turn the brass block to get a close fit again. The heat break itself can move in the upper part, black plate, the cold end by the set screw on the side. Some hotend assembly types allow that, this screw is then used to fixate the orientation of the brass block. This type of hotend is not very common, it is a MK10.

Without the brass block it looks like this:

Maybe this clears it up how the block is attached in between the heat break and the nozzle; it is positioned where you see the threads. The screw to position the brass heater block and the heat break is clearly visible.

Don't try to wobble the brass block any further as you will wear out the threads, there appears to be a lot of play already.


Can an extruder rated for 24 V work with 12 V ATX power supply?

Electrical engineering can be quite complex, but in this case you can save yourself with same simple equations/relations. Using the following formulae:

Voltage ($\ U$) equals current ($I$) multiplied by the electrical resistance ($R$)

$$ U=I \times R $$

and

Power ($P$) equals the square of the current multiplied by the electrical resistance

$$ P=I^2 \times R $$
can be rewritten using the first formula to:
$$ P= \frac{U^2}{R} $$

Applying these formulae to a 40 Watt, 24 V heater element, the electrical resistance (in $\Omega $) is calculated by:
$$ \frac{{(24\ V)}^2}{40\ W}=14.4\ \Omega $$

Running this heater element with 12 V will lead to a power of
$$ \frac{{(12\ V)}^2}{14.4\ \Omega}=10\ W $$

The heat produced is proportional to the square of the current multiplied by the electrical resistance, halving the voltage is quartering the heat output. This will heat up very slowly! If it is able to reach the required temperature that is. Calculating the temperature is far more difficult, but if you are interested in doing so, please look into this answer from the Electrical Engineering Stack Exchange.


Heater polarity doesn't matter
The heater cartridges are just large resistors and so polarity is irrelevant. Either can be positive or negative.
You can extend the leads by cutting and splicing in ~20 gauge wires* to a two pin JST connector line you suggest.

*At 24 volts and 30 watts, you need wire that is rated to carry at least 1.25 amps. The US National Electric Code dictates that this should be 20 gauge wire, but their standard is very conservative. Since you don't need to adhere to NEC codes, you could get away with something thinner (ie higher gauge number).


What exactly is the relationship between Flow/Feed Rate and (Print) Speed?

By turning the knob in the main screen, you're adjusting "feed rate".
This is essentially a factor that all g-code speed settings are multiplied with - "speed dial" seems an appropriate name for it.

"Flow rate" is something different altogether - this is multiplied with the extrusion commands. It has the same effect as changing your extruders steps-per-mm.
You can adjust under- / overextrusion with this on the fly.


In Ultimaker Cura, unless you print a single perimeter outline and add extra wall infill support you are not going to have different outer perimeter layer heights.

However, Cura is able to reduce the printing time, E.g. you can have fine layers for the wall (all perimeters), and coarse layers for the infill. The option is called "Infill Layer Thickness":

  Infill layer thickness

  Since the layer height of the infill is not important for visual quality, you can use thicker layers on the infill to reduce the print time. When adjusting this setting, always make sure that it is a multiple of the layer height, otherwise Ultimaker Cura will round it up to a multiple of the layer height. This means that you can, for example, print with an infill thickness of 0.2 mm while the layer height is 0.1 mm. The printer will first print the walls for two layers, and then it will print one thicker infill layer.

Note that this is not a standard option, you need to put Cura in the "Custom" mode and filter/search for the option using the search bar. Below you'll find the upper right corner of the Cura Graphical User Interface where I searched for the option:

Note that there are 2 options, one for regular infill of your product and one for infill of the support structures.

An other department at work is working together with a start-up university company to 3D print PEEK molds (from pellets) using 2 nozzles/extruders (to create resin injection parts), one has a large nozzle, the other has a fine nozzle. They use their own developed slicer software to use the fine nozzle for the outer contours and the coarse nozzle for infill and support. It could be that they developed this because it was not available in commercial slicers. For the 2 most common free slicers, Cura and Slic3r, there is no option to have just the outer perimeter of different height than the inner perimeters. If you think of it, it is also pretty difficult to execute, you either get:

(which does not improve the quality of the product, it will make the outside more coarse) or you'll get gaps:

Note that both upper images do not include infill, only 1 outer and 3 inner perimeters. The image below is probably what is possible with Cura, so all perimeters the same; green is infill now:


Commercially available 3D printer fume and UFP extractor

Following on from Harvey Lim's answer, to give a concrete example of a DIY filter, which uses active carbon, see ABS 3d Printer Nanoparticle and Chemical Exhaust Air Filter:

###Description
Enclose your 3d printer and use this exhaust air filter along with a recirculating air filter to eliminate nanoparticles and chemical fumes. 95 to 99.5% of partilces up to 0.1 micron in size are filtered before air is exhausted into your 3d printing room. This is 3 times better than HEPA filtration. Chemical fumes such as phenols, hydrogen bromide, hydrogen cyanide, and styrene are also filtered out. The amount of chemicals filtered out depends on the amount of carbon filtration media you put into the unit and the strength of the fan you install on the unit. If you are using this for business purposes, you'll have to experiment a bit to have it pass inspection. If you are using it for personal purposes, know that the human nose is extremely sensitive. People who have the gene for hydrogen cyanide detection can smell it down to a concentration of 2 to 10 ppm. Suffice it to say, that if you can smell no evil, you are probably not experiencing evil. This has totally cleared my 3d printing room of nasty fumes. I invite you to try it out for yourself as the cost is very low since I've designed it to use surgical masks and aquarium activated carbon filtration media, which is very affordable. You should change the filtration media and surgical mask every month or 50 hours of printing, whichever comes first. I offer no warranty of any kind as this is an experimental device.

This filter is mentioned in tbm0115's answer to What are the best air filtration options for enclosures?


Replicator 2x getting too hot with silent stepper drivers

Most Stepper drivers will have lots of energy passing through them so it is crucial to having a moderately sized heatsink to cool them off otherwise they will get too hot. Most stepper drivers found online come with heatsinks but you could search online for mini heatsinks.


Solution found!

If Display model errors is disabled, the dots appears.
Check the setting, hit OK, click on the box and they disappear.


Why does my printer create notches on the Y surface?

I see two problems with your printer: your filament seems to overheat in some areas, and you overextrude a little. My suspicion is, that your heating behavior is not well tuned and it overshoots the target temperature, leading to an overcooked filament, then the temperature drops below the temperature you need, leading to a wavy pattern and brown lines.
fixing
I suggest running a PID-tune cycle to get better heating behavior and then recalibrating the printer's extruder.


Since we do not know more about the printer and its settings it is most likely that the issues lies within the printer and the temperature/print speed settings. Fill materials do print differently than just colored plastic of the same type. Find valid print parameters for the type of filament that you can modify as needed for the printer that is being used (a good first gauge are the offsets the printer has for other type of filaments (thermistors might be offset for example) added to the 'literature values' of the new filament).

It might also be, that the nozzle was not clean when changing filaments and hence the clogging occured. Have you/your printing guy tried a 'cold pull'? How should I clean my extruder when changing materials?

Usually nozzle clogging comes down to knowledge about your printer and experience with the filament.


The M73 Set/Get build percentage G-code is only defined for a selected few printer firmwares.

As you suspected, next to M73 P19 (tell the firmware at what completage percentage the print is) the M73 R42 tells the firmware the left time to completion.

If you look at the description of the M73 G-code, the following parameters may be used:

P: Percent in normal mode
R: Time remaining in normal mode
Q: Percent in silent mode
S: Time remaining in silent mode

So, running the Q and S parameters, is similar to the P and R parameters with the exception for referring to the printer percentage/time when in stealth (quiet) mode.

These modes, normal and stealth, refer to power modes of Prusa printers:

  Normal vs. Stealth mode
  MK3 printers offer two print modes. Normal mode is required for the detection of lost steps (shifted layers), while still being quieter than the silent mode on MK2/S. There is also the Stealth mode, which utilizes Trinamic StealthChop technology, making the printer almost inaudible with the print cooling fan being the noisiest part of the printer. However, Stealth mode does not provide lost step detection.

Stealth mode times can be a bit higher than normal mode estimation times. Estimation is done by the slicer. As Prusa maintains this feature, their times are accurate for their printers, but that does not have to be the case for custom printers.

To get the current progress, the M73 command is called without parameters:

  Use "M73" by itself to get a report of the current print progress.


The first layers while printing look strange

From the first layer image it can be seen that your nozzle to bed distance is just too large:

the lines of deposited filament e.g. in the brim are not touching,
deposited filament lines are not "squished" or "flattened" to the build plate,
filament is cutting off corners as it is dragged while being hot and not stuck to the bed,
filament leaves the nozzle in "blobs"; it sort of free flows from the nozzle as the bed is too far to give resistance.

Use the plain paper technique while levelling the bed. The paper should give a slight drag/resistance when pulled/pushed. Proper levelling and a proper nozzle to bed distance for the first layer are essential for successful prints.

There is also an option to integrally lower the print level in the slicer software, but it is advised to properly level the bed (hardware solution) instead of using software tricks to sort out the problem.


Not able to insert hobbed drive and filament in the extruder drive

Your parts are not in the Prusa Mendel i2 as found here or here.

Also note, quote:

  Parts included in Github repository have the wrong dimensions for the
  nut traps! Download the correct version from [Thingiverse Greg's
  Hinged Accesible Extruder]

Are you sure you have the correct parts for the original Prusa Mendel i2? Maybe you have a different version? The original extruder mount uses an M8 hobbed bolt, not an MK8 hobbed extruder gear. The first is 8 mm in diameter, the latter is 9 mm in diameter.

Edit:
After you updated your post to hint to the correct printer, it appears that my answer still holds. You did use the incorrect extruder gear. The 9 mm gear doesn't fit in the extruder part as it requires an 8 mm diameter extruder gear.

It might be difficult to find a 8 mm hobbed gear with a 3 mm shaft diameter, they are usually 5 mm (as in the stepper shaft diameter) or 8 mm (as in the diameter of 8 mm bolts that are frequently used for extruder setups). You could redesign the part (load STL in a 3D CAD program and make the changes). By the way, PLA should not shrink so much. As can be seen in the photo's, it looks like your current printer does not print very accurately, that may also contribute.


Nozzle goes down after bed leveling BLTouch

Check and potentially replace your bed springs as this is a common cause with cheap bed springs.
An immediate workaround is redoing your Z-offset but most likely after a while you have to repeat it until you replace the bed springs with stronger ones.

After replacing springs you have to redo Z-offset again.


Where did I go wrong by trying to add an extra motor to my board?

D35, D37, D17 are the pin labels on the Arduino Mega. These do not correspond to pin numbers within Marlin.

I believe that D35 actually corresponds to marlin pin 49 and this is the number you should enter in your firmware. You can find the mapping in fastio_1280.h:

Hardware Pin  : 02 03 06 07 01 05 15 16 17 18 23 24 25 26 64 63 13 12 46 45 44 43 78 77 76 75 74 73 72 71 60 59 58 57 56 55 54 53 50 70 52 51 42 41 40 39 38 37 36 35 22 21 20 19 97 96 95 94 93 92 91 90 89 88 87 86 85 84 83 82 04 08 09 10 11 14 27 28 29 30 31 32 33 34 47 48 49 61 62 65 66 67 68 69 79 80 81 98 99 100
Port          : E0 E1 E4 E5 G5 E3 H3 H4 H5 H6 B4 B5 B6 B7 J1 J0 H1 H0 D3 D2 D1 D0 A0 A1 A2 A3 A4 A5 A6 A7 C7 C6 C5 C4 C3 C2 C1 C0 D7 G2 G1 G0 L7 L6 L5 L4 L3 L2 L1 L0 B3 B2 B1 B0 F0 F1 F2 F3 F4 F5 F6 F7 K0 K1 K2 K3 K4 K5 K6 K7 E2 E6 E7 xx xx H2 H7 G3 G4 xx xx xx xx xx D4 D5 D6 xx xx J2 J3 J4 J5 J6 J7 xx xx xx xx xx
Logical Pin   : 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx

Look on the top row for the pin number (e.g. D35 corresponds to 35), then look on the bottom row to find the pin number to use in Marlin (in this case, 49).


ANet A8 running Marlin v1.1.9 Auto Bedlevel with ROKO SN04-N

Too bad you broke the acrylic plate (nice temporary fix though), but you can easily print a replacement part once your machine is up and running.

Probe positioning is defined in the Marlin configuration as:

 *      +-- BACK ---+
 *      |           |
 *    L |    (+) P  | R -- probe (20,20)
 *    E |           | I
 *    F | (-) N (+) | G -- nozzle (10,10)
 *    T |           | H
 *      |    (-)    | T
 *      |           |
 *      O-- FRONT --+
 *    (0,0)

This implies that your sensor is located on the back-right when facing the machine and need to have the following constants set:

#define X_PROBE_OFFSET_FROM_EXTRUDER 16   // X offset: -left  +right  [of the nozzle]
#define Y_PROBE_OFFSET_FROM_EXTRUDER 58   // Y offset: -front +behind [the nozzle]
#define Z_PROBE_OFFSET_FROM_EXTRUDER 0    // Z offset: -below +above  [the nozzle]

In order to calculate the correct limits of travel for the sensor, you need to subtract the offset values from the bed size at the max limits.

An additional offset may be required for some sensors, so please add an additional offset in the configuration by defining:

#define MIN_PROBE_EDGE 10

As the sensor is off-center with respect to your nozzle, one can only assume that you have no extra space to move the whole printhead and therefore need to confine the head within the limits of the max/min bed size (there should be some extra space, this can be seen from the offsets for the origin as in values for X_MIN_POS and Y_MIN_POS, but for the sake of simplicity these will not be taken into account).

Basically, your positive Y and positive X offset result in the following schematic.

Or, if you include the #define MIN_PROBE_EDGE [value]

Bed limits for the sensor then will need to be calculated based on the values of your offset of the sensor. E.g. when your nozzle is at (X=0, Y-0), or (0, 0), your sensor is at (16, 58). If you don't want to move the head further left and forward (to respect to origin as limit!), this is the minimum position of the sensor. When the sensor is at the back-right position of (220, 220), the actual head is at (220-16=204, 220-58=162).

This means that the limits for the sensor without a minimum offset are (16, 58) and (220, 220):

#define LEFT_PROBE_BED_POSITION (X_PROBE_OFFSET_FROM_EXTRUDER + MIN_PROBE_EDGE)
#define RIGHT_PROBE_BED_POSITION (X_BED_SIZE - MIN_PROBE_EDGE)
#define FRONT_PROBE_BED_POSITION (Y_PROBE_OFFSET_FROM_EXTRUDER + MIN_PROBE_EDGE)
#define BACK_PROBE_BED_POSITION (Y_BED_SIZE - MIN_PROBE_EDGE)

would translate with a MIN_PROBE_EDGE = 0 to:

#define LEFT_PROBE_BED_POSITION 16
#define RIGHT_PROBE_BED_POSITION 220
#define FRONT_PROBE_BED_POSITION 58
#define BACK_PROBE_BED_POSITION 220

and would translate with a MIN_PROBE_EDGE = 10 to:

#define LEFT_PROBE_BED_POSITION 26
#define RIGHT_PROBE_BED_POSITION 210
#define FRONT_PROBE_BED_POSITION 68
#define BACK_PROBE_BED_POSITION 210

The assertion in code: FRONT_PROBE_BED_POSITION >= MIN_PROBE_Y would now translate to (58 >= 58) (or 68 >= 58), in your case it was (47 >= 58) which clearly is not true.

Please look into this answer, this answer or this answer for more information.


Surface Tension Support for FDM Printers

It's not feasible as described with normal FDM technology.
FDM bases on depositing material in a single path. This needs the deposited material to stay at the same XY coordinates for subsequent paths. And exactly here is where a floating piece fails: a free-floating piece is by its very definition unrestricted in XY, and would move to follow the nozzle.
There are is also a whole plethora of factors that make this idea not feasible with the standard technology, meaning you'll have to develop the whole process, not just recombine two ideas. This means, you need to solve the following issues:
Heatsink Water
The extruded plastic needs to stay close to the melting point for some time, so it can fuse and bond with the lines next to them. However, water is known to be a very good method to get the heat away from items, as each liter of water can take about 4.1 MJ and only heat by one Kelvin. PLA on the other hand only stores about 1.8 MJ per Kilogram and Kelvin.
As a back of the envelope calculation, the temperature differential between room temperature and printing temperature PLA is about 180 Kelvin. Each gram of PLA is equivalent to 319.8 mm of filament (assuming a density of 1.3 g/cm³) or an extruded line of 9.6 kilometer length of 0.4 mm width and 0.2 mm height! That one gram contains about 324 Joules of energy that will be dispersed to the room temperature as it cools down. The water vat would not even get measurably warmer from sucking those few joules from a whole print!
While this could be, in the right setup, be used to rapidly cool the print and solidify it in shape, the result of the rapid healing will most likely also impact print quality negatively, as cross-layer bonding is reduced.
Separator water
It is a well-known trick in creating polymer fibers to extrude underwater, as the water not only cools (see above) but also acts as a separator between the fibers, for the very short timeframe they are still malleable. This would also strike when printing into the water - there'll be a water layer in between the deposited filament, which would need to either get pressed out or cooked out before any cross-extrusion bonding can occur. As a result, just extruding into the water should result in a print that has almost no sturdiness, and might fall apart on touch.
Floating
Water has a density of 1 g/cm³. PLA has a density of 1.3 g/cm³. So a solid chunk of PLA sinks. But we don't print solid, we include air. Not just a few percent but infill is usually below 20 %. I have just printed a cube. After smoothing the surface by sanding, the cube is 29,7x29.9x29.9 mm. It has 3 parameters, 20% infill, 5 top and bottom layers with 0.2 mm layer height and comes to 11 grams. 11 g/26.55 cm³=0.41 g/cm³. Or in other words: the cube would float, about 40 % under the water surface, 60 % above the surface. The print would be, as a result, quickly break the water surface and get no support from the water at all.
Submerging the bed?
The main issue of a free-floating object (position) might be mitigated if there was a bed that would be submerged, but one would open a new can of worms, that might be even worse: the volume of the print and the accuracy of pumps.
As the print goes on - quality be dammed - the print grows in volume. However, it doesn't grow entirely linear, depending on two factors:

Is the print happening on/below the water surface? Then we will include water in the print. The volumetric growth of the print is in this case just the deposited filament. You'll need an overflow to compensate for the print growing and keep the water level in position.
Is the print happening just above the surface of the water? then the displaced volume grows according to the depth of the print in the water. This would mitigate most of the problems from water preventing cross-bonding and causing floating, and even use the heatsink properties more beneficial, as any filament starting to sag will be stopped. It also would prevent water from being encased in the print. However, it does not use surface tension. Also, you'll need an overflow system to keep the water level steady.


Prints could end up on tray for couple of reasons.

Vacuum force on early layers - Usually you should lose pieces on the center of platform

Put holes or channels on platform
Very slow speed on early layers
Use smaller platform
Use tilt mechanism
Use larger support structures
Use stickier platform - Anodized aluminum is specially good

Non-aligned platform - Pieces on side of platform end up on tray

Align platform / tray

Low cure times - you could lose pieces around platform for DLP and whole platform for LCD ones
Resin related issues

Resin designed for thinner layers - Decrease layer thickness
Pigment settled down - Shake resin before use


I use cosmetic vaseline - petroleum jelly. Usually it is white to transparent and odorless. It's cheap and available in all drugstores and cosmetics stores.

As suggested by Tom van der Zanden I'm adding additional info about interactions of vaseline and plastics.
I've found many web sites which claim that vaseline can damage plastics but none of them really proved that statement. There is nothing about it neither on producers sites nor wikipedia or any other believable sources I've found. So according to it and my practice I'm pretty sure that vaseline won't damage popular plastics (including common filaments).

The only information I've found is that vaseline can damage natural rubber but I cannot confirm that on my own.

Of course it might not be true for some materials so be careful and check the interactions first on invisible side or on refuses.


I'd say that your axis aren't square, aren't tightened enough and you seem to have overextrusion as well. That would explain why all your layers are wobbly and not neatly stacked on top of each other, why your cube is far being being a cube (the picture of the X face shows it clearly) and the quality of surface finish on the top.

I do not know what kind of printer you are using, but I would advise you to check that the X and Y axis are correctly calibrated and that they're perfectly square, which would ensure that each layer is correctly stacked on top of the previous one to produce a nice cube. And make sure to tighten the axles to avoid the noise in the print due to the vibration produced by the printing.

As for the overextrusion, you'll need to make more test with your printer and the material you're using, changing temperature, and print speed until you find the right combination that will extrude just enough material through your nozzle.


Hotend drops to 175 ºC once extrusion starts (MINTEMP error reported)

Sudden drops in temperature curves like in your picture are usually missing readings on the thermosensor:

Disconnecting the sensor from the board registers as min-temp of the sensor while shorting out as max-temp, so it triggers the mintemp/maxtemp security protocol: shutdown.

One could disable mintemp/maxtemp protection, but that wouldn't solve the issue. The issue is usually the wiring of the sensor. To find the fault, put temperature on the sensor but keep the motors disabled. Watch the read temperature. Move the printhead manually and slowly. If it suddenly drops and throws the error, you might have a faulty lead close to the printhead. If not, you need to open the electronics box to check if the connection to the board is ok. In the worst case, you might need to exchange the whole temperature sensor.


Slicer line width vs. extrusion multiplier for layer adhesion?

Generally speaking, both settings result in the same1: The feed rate of the filament gets adjusted. Either you set a general multiplier, or you demand a wider line which does make it set a higher multiplier hidden in the software.
1 - if you don't look at any other factor that is!
But...
There is always a but, and this one is big:
While we can work with the extrusion multiplier to get wider lines, wider lines do change another setting: it changes the distance between the lines too. Let me show you:

If you print 100% at 0.4 mm line width, lines are about2 0.4 mm wide at 0.4 mm distance.
If you print 100% at 0.5 mm line width, lines are about2 0.5 mm wide at 0.5 mm distance.
If you print 121% at 0.4 mm line width, lines are about2 0.5 mm wide at 0.4 mm distance.

2 - ignoring die swell effects
The result is pretty clear: the theoretical lines do overlap, which will lead to the polymer goop getting squished and pressed around to bulge up. Luckily, that stuff usually ends in the infill on the lower layers, but it can result in very messy sides. You pretty much deliberately chose to massively overextrude!
To say it blatantly: line width changes the overall geometry of the slicing to account for the extra material getting extruded, extrusion multiplier does not.
What is the extrusion multiplier for THEN?
Well, using the extrusion multiplier can be done for many reasons, but mainly 2 are interesting:

Troubleshooting. You can just amp it up or down to test your mechanical properties. Like if your gear ratios on the extruder are correct. Or if your print needs a thicker line to get the first layer sticking.
Dialing in Filaments. In its core, it is meant to allow to change the flow because different polymer blends might have different thermal properties. For example, the filler and paint could lead to more thermal expansion and die swell, or they could reduce it. This behavior can be tackled directly by adjusting the extrusion multiplier. This is one thing you should do when getting a new type (color&manufacturer) of filament. While some manufacturers try to keep the properties along their lines similar, some won't.

It might not look too obvious at first, but I once had printed a model from one roll of white PLA that came from China. Then I got my fingers on some other PLA that was transparent from the same warehouse. I tried to print the exact same .gcode with it again and got a hyper fragile object that just could get squished, every time I used it with the same settings as the white PLA. I had to increase both the extrusion multiplier and change the temperature to get the same strength as with the other PLA.


Troubleshooting poor adhesion at the edge of the bed

There are several things you could try without spending much but even PLA will warp on an unheated bed.  I had a Legacy Kossel that I switched to an acrylic bed and had many issues with warping and prints pulling off the bed.

Some cheap things to try would be...

Adding a brim to the print.
Blue painters tape on the acrylic, remove the other material if doing this.
Place cheap piece of glass/mirror on bed and use hairspray/gluestick.
Use hairspray/gluestick directly on acrylic.  You must be careful here because first layer height is very critical to prevent damage to the acrylic from the plastic welding.  A layer of hairspray or glue should prevent it but dial in your height before printing.
If you aren't currently using a fan, you could try sealing the sides to prevent drafts.  I doubt this would change much since you are using PLA but it's an option.
If these are your designs, there are steps you can take to reduce warping as seen here.

Also many other suggestions here.


Changing FAN0 to FAN1 in TriGorilla printer board

Yes you can use another fan port, this requires some editing of the configuration files of the firmware and reflash the firmware.

If you look at the documentation of the board and an overview of the board layout, you will see that there are 3 PWM controlled FAN ports. The answer is therefore yes, you can use another port (e.g. FAN1 or FAN2) to be used for your broken FAN0 port. The most easy solution is to swap the port numbers in the pins configuration of your firmware, so swap pins 'D9' and 'D7'.

How you edit the configuration is depending on the version of the TriGorilla board you have, there is a version 1.3 and a version 1.4.

Basically you need to define the software FAN (0) to be reached at the hardware location Fan1 using pin 7:

#define FAN_PIN        7

Subsequently, FAN1 in software needs to points to Fan0 in hardware

#define FAN1_PIN        9

If you changed this, the software will think that the Fan1 port on the board is the software FAN.

If you are using the v1.4 TriGorilla printer board, the v1,4 specific pin definition is found in pins_TRIGORILLA_14.h. If you look into this file you will see that this is basically a RAMPS board:

#define IS_RAMPS_EFB
...
#include "pins_RAMPS.h"

So editing for you need to redirect the pins 7 and 9, but you only have a single active fan (as per #define IS_RAMPS_EFB)! Luckily we can forget about the second fan as you want to replace the first by the second.

In pins_RAMPS.h you will find:

#ifndef RAMPS_D9_PIN
  #define RAMPS_D9_PIN      9
#endif

Note that it is wise not to edit this latter file, instead edit your copy of pins_TRIGORILLA_14.h to include assigning of the pin 7 to the Fan1  header as FAN in the firmware.

If you look closely at the assigning of the RAMPS_D9_PIN pin, it says: #ifndef; so if it has been assigned previously, do not override the value.

Now edit the pins_TRIGORILLA_14.h file to include:

// Comment out this line:
//#define FAN_PIN 9
// And enter this beneath that line
#define RAMPS_D9_PIN 7

or

#define FAN_PIN 7
// this bypasses setting of the RAMPS_D9_PIN constant

From this point on, if the software addresses scheduling of the FAN port, the pin 7 schedules the MOSFET attached to the Fan1 header.

Basically, the above procedure describes how one directs hardware ports by changing the addressing in the firmware configuration.

If this does not work, there might be more things broken on your board.


Reprap Ormerod 2 Duet web control not automatically starting, how can I fix?

First thing I would do is to update firmware to the newest version: https://github.com/dc42/RepRapFirmware/releases

See details on Duet wiki page: https://duet3d.dozuki.com/Guide#Section_Updating_Firmware_and_Duet_Web_Control


Heater cartridge connector for Original Prusa i3 MK2S

This is referred to as a Terminal Block Connector.   More specifically this is a 2-position pluggable terminal block connector commonly manufactured by Phoenix Contact and others.

Newark.com Sale Page: Pluggable Terminal Block, 5.08 mm, 2 Positions, 24 AWG, 12 AWG, 2.5 mm², Screw

Larger Picture: 2-Position Terminal Block Connectors


While you probably cannot find an MSDS on the resin for your printer (yet), they are out there for other resin based printers. Here's a generic MSDS on one for Objet RGD515:

It's not a pretty thing.
To back this up, Fabbaloo has two articles out which talk about the toxicity of liquid resin which is light cured. I'm not entirely positive your resin falls into this arena, but would assume since they state in the handling instructions it's toxic, it's probably right along the same lines as the other toxic resins. Please note, in the article it states there are resins out which aren't toxic. They suggest one should handle all resins of this type as though they are toxic unless you have specific documentation which states otherwise.
In one of the articles (Nov 2015) quotes findings which were published by the University of California, Riverside. Their study focused on zebrafish embryos and the toxicity of two different 3D printed materials which are commonly used. The materials were Stratasys Dimension Elite (plastic extrusion) and Formlab’s Form 1+ (photo-cured resin). These printed samples were placed in zebrafish tanks to observe their effects on fish embryos and compare to “control” tanks without the samples.
The University stated:

While the embryos exposed to parts from the plastic-melting printer had slightly decreased average survival rates compared to control embryos, the embryos exposed to parts from the liquid-resin printer had significantly decreased survival rates, with more than half of the embryos dead by day three and all dead by day seven. And of the few zebrafish embryos that hatched after exposure to parts from the liquid-resin printer, 100 percent of the hatchlings had developmental abnormalities.

Note: Here is the second Fabbaloo article from April 2016.
Fomrlabs has quite an extensive list of MSDS sheets for their products. Their page states the following about their resin materials:

Formlabs Standard resins are designed to be similar or safer to handle as other household chemicals or adhesives. When measuring potential acute health effects of inhalation or ingestion, there are no known significant effects or critical hazards. Eye contact may cause eye irritation. Skin contact may cause an allergic skin reaction. The safety data sheets (SDS) are up to date for every resin product and follow the latest government guidelines. Always consult the SDS as the primary source of information to understand safety and handling of Formlabs materials.
Use chemical-resistant gloves - such as nitrile or neoprene; do not use latex - when handling liquid resin, including when removing printed parts from the printer. Exposure to resin in the liquid form can cause mild skin irritation for some people. If you get any on your skin, make sure to wash thoroughly with soap and water before moving on to other activities. Do not use solvents to wash hands, face, or any body parts. Wear gloves and use alcohol, followed by soap and water, to clean tools after handling resin.

While this is not conclusive about your specific resin, like was stated, always treat the material as though it is toxic until documentation tells you otherwise. If all else fails, treat it as toxic and you can't go wrong.


Z axis Stepper motors not working correctly

So after 5 days of trouble shooting, Bob-the-Kuhn over on the marlin github forum solved it for, anyone else who faces the same issue can head over to github for my solutions.
https://github.com/MarlinFirmware/Marlin/issues/9287#issuecomment-359428147
Conversation from link:

Bob-the-Kun:
Problem does not follow the driver. Problem does not follow the
steppers.
I'm thinking that the Z socket has a problem. Sounds like an open/poor
contact.
Try bending the DIRECTION lead on the Z driver a little and see if the
problem disappears. It's one of the corner pins. Sometimes it's called
DIR. If your driver's pins aren't labeled then bend all four corner
pins a little.
Another option is to move the Z function to the E1 socket. Replace
your pins_RAMPS.h file with this one. pins_RAMPS.zip
FYI - if this really is a hardware problem then it's the second RAMPS
hardware problem within a week. Most unusual.
Post reply:
Yes the socket I am now assuming is just broken (not sure what exactly
but possibly one of the connections), After using for pins_RAMPS file
and changed the motors back to series and connected to the E1 slot I
successful got the printer to work!!! Thank you very much Z axis is
working as I would expect! I am now calibrating the printer as it
definitely needs it.


To answer the generic question "Is there a thought process for how to orient the part for printing?", I would say "Yes there absolutely is such a process!".

Part of this though process can be aesthetics, structural strength, limiting filament waste, print duration, etc.

For the given example I would try to think of the load case (if it has to bear a load) that subjects the part and prevent a perpendicular load to the deposition plane. If the load is low or non existent, you could orientate the print such that you minimize wasting material, or get the best aesthetics (removing supports can leave its scars).


The standard choice for this would be TPU, thermoplastic polyurethane.

TPU is a common filament material for use in fused filament fabrication 3D printing due to the fact that it is an elastic thermoplastic which makes it ideal for printing objects that need to be flexible and elastic.
...
Properties of commercially available TPU include:

high abrasion resistance
low-temperature performance
high shear strength
high elasticity
transparency
oil and grease resistance

In addition to TPU, there are plasticizer-modified PLA filaments with similar flexibility, but not necessarily with the other nice properties like abrasion resistance. I've printed with one from 3D Solutech and had good results, after figuring out what to do about stringing.
Also, it's possible to achieve a decent degree of flexibility merely with printed geometry, rather than special materials. It's possible that PETG with an appropriate geometry could work for your application.


Ball screw: Maintaining Z axis position when motor is OFF

My question is a ball screw of pitch 4mm or 5mm, will it be able to Maintain it's position when motor is deenergized under a load of 15 kg shared by two systems.

The detent torque of a typical NEMA 23 stepper varies between around 3 and 7 N·cm. This is the torque produced when the windings are not energized.

Using this leadscrew torque calculator, you can find that the torque required for a 12 mm diameter, 4 mm pitch leadscrew to hold up a 75 N load, is around 5 N·cm - assuming there is no friction. If there is friction, then the required torque will be lower.

So, the torque required is almost equal to or possibly even higher than the detent torque. Therefore, you should not count on a de-energized motor holding up the build platform. In practice, you might see that friction is enough to hold up the build platform, but that any disturbance (such as somebody bumping into the printer) is enough to get the leadscrews to start spinning and have the platform drop like a rock.

  What effect the diameter of rod has on it?

Increasing the pitch also increases the torque required (so, go with a lower pitch leadscrew). The diameter does not affect the torque directly, but having a larger diameter increases the friction and so is beneficial.


I think it depends on your use case.
As Bobt already commented, Meshmixer is a common tool for editing STLs.
But also a lot of CAD-Tools should be able to import STLs.
Then there is also of course Blender.
As you didn't specify what you want to use it for, I would guess you just want to do some quick fixes to the mesh.
The tool I use is Meshmixer. It's pretty powerful, but I personally never really used a lot of it's capabilities.


The 0.1mm refers to the thickness of each layer. However, it does not say anything regarding:

How precise the layers are in the XY plane
How precisely each layer is aligned with the previous in the XY plane
How consistent the extrusion is: are all the layers printed with a consistent line thickness

No matter how fine the layers (and these printers that you refer to can definitely print 0.1mm layers just fine); if they're not well-aligned with each other, or the filament extrudes inconsistently, you're going to see the layer lines. It takes a rigid printer, with low-play bearings, a well-calibrated extruder and filament with a consistent diameter to get smooth-looking prints (but you will always see some layering, especially if you look up close). Also, since filament is extruded in a round shape, the sides of the object are not perfectly flat, but consists of many small arcs, which makes it easier to see the layer lines.


Printer LCD controller required when using a Raspberry Pi + LCD?

No, when you run the print jobs from a Raspberry Pi, e.g. using the OctoPrint print server, you do not need the display of the printer as you can control the printer from the Pi screen or from a browser of any other device. Do note that not all functionality of the LCD controller is built-in in those printer servers, but you normally have a terminal to interface using G-code with the printer, or you can make macros to do that.

In some cases it might be handy to leave it on the printer for small adjustments, homing an axis, or feeding some filament; it saves you some time opening a browser to control the printer when you operate the printer remotely and allows to troubleshoot the machine manually.


3D Printers imported from China - avoiding asbestos exposure

How to avoid asbestos exposure with a high degree of certitude?

If you're not willing to do asbestos testing yourself and can't trust your suppliers either, then this is impossible.

That said, for most of the components on a 3D printer it is easy to verify they're asbestos-free (I've never seen a steel linear shaft containing asbestos). For the remaining components, you may be able to pick an alternative which you know to be safe, for instance an all-metal hotend without insulating tape, or a heated bed that's plain FR4 without insulation. If there are any components that you distrust specifically (such as a heater cartridge) you should source that from a trusted supplier.


Can I replace the cooling fan blade for the hot end on creality ender 3?

It will work, but likely with reduced performances: designing blades is not an easy task and the ones you can print will not be as good as the ones designed for that specific fan.

Overall, do it for fun before you replace the fan anyway.

IF your fan has symmetrical blades (unlikely), another option is to break the opposite blade to balance the fan.


What can I do about a printjob in progress that starts to warp/curl on the edges?

Putting a large brim on it can help, I've seen people rescue prints with larger brims by literally adding weights to the brim around the areas that are peeling up. I've done it by taping brim edges down carefully as the print goes.


Chalk, as a ceramic substance, could be printed with a paste printer and if the substance can hold its shape during drying for a couple of hours.

It might be easier to use a flexible filament like TPE or TPU to print a mold in which the paste can cure slowly to a point it can be safely removed. These filaments make release easier as one can flex them away from the printed object.

Another option could be vapor smoothed ABS and a tapered shape so that the object has no undercuts and easy paths only. If one adds a pusher rod place, which is closed by a plug during casting the chalk and can remove from the back after casting, removal gets easier as air can flow in from the back through the removed plug. It can also be used to use a pen or similar obect to gently release the item with light taps.


How to fix WoW models in photon workshop

I believe you've identified the primary problem with this model. The single surface features are going to interfere with printing this object.

The image above is the result of loading the model into Autodesk Netfabb. The red segments are reversed normals, but also single surface components. There are others, visible when rotating the model.
One portion is uncertain, above the flap on the back. It could be a component of the flap or a reversed normal of the body's back.
To resolve this problem, it would be necessary to add thickness to those features.
I loaded the model into Meshmixer and identified one feature, the rear flap. It's loaded with reversed normals when viewed from the "outside" or rear of the model.
Using the select tool, it was easy enough to highlight those triangles and proceed to Edit, flip normals. That was followed by Edit, Extrude, to a thickness of -0.02 mm which presented this result:

There are a few "floating" features in the model. One which pops out is over the protective garb over the shoulder. Those would have to be anchored by adding features or moving that specific feature to properly intersect the body.
There are a few others, zero thickness portions that resemble solar panels. I suspect they are artifacts rather than intentional model features. Those can be removed in Meshmixer using a similar method, Select, Edit, Delete
The hanging hook is a collection of intersecting faces and present a challenge. It's not my model, but I'd be inclined to completely remove that feature, or remove most of it and add a simple cylinder to attach it to the model.
There are programs other than Meshmixer which will allow one to perform such manual repairs/modifications, but my skill set does not include presenting the answer for those packages.


What are the pros and cons of using a BLTouch in place of a limit switch?

Touch sensors (or inductive or capacitive sensors) are generally used to probe the bed to determine the bed shape. For metallic beds that are not perfectly straight this works excellent. But, if your bed is straight and level (e.g. when you are using a straight slate of glass), you do not need to probe the surface as it is level. Instead you can use the probe to determine the Z level.

Pros for a limit lever switch are:

simple and cheap mechanical switch
no firmware changes necessary
no or few soldering
already present on most bought printers

Cons for a limit lever switch are:

needs fine adjustments counter part to work optimally
something can get in between the lever and counter part
it doesn't look cool

Pros for a more sophisticated sensor:

it looks cool
everybody is using it so it must be good

Cons for a more sophisticated sensor:

expensive and complicated sensor
requires firmware changes (e.g. sensor offset value)
requires soldering, or connecting more cables
inductive and capacitive sensor work usually better at a higher voltage
higher chance of malfunctioning (more parts and electronics)


If a temperature of (rounded) 201 °C is triggering TRP, then one of three things is the culprit:

The TRP Hysteresis is awfully trigger happy. See What is Thermal Runaway Protection?
Your Heater cartridge is not properly mounted and has a bad connection to the heater block and upon heating and expecting a much higher temperature but not measuring the associated increase it triggers TRP as it thinks "DANG! My thermosensor or heater cartridge must have fallen out of the heater block!"
Your Thermosensor has occasionally erroneous readings that are interpreted as temperatures way over or under 200 °C and trigger TRP.

To rule out the problems, do the following:

Check the mounting of the thermosensor and heater cartridge. Tighten if needed. The thermosensor should have no cracks (glass) or deformation (metal cylinder)!.
Check resistance and wiring of the heater cartridge (it should have some depending on the type) and thermosensor (If you use a thermocouple sensor, you might need to flip wiring).
Use a terminal with a graphic interface and look at the temperature output line as you heat up and print. If it has spikes or sudden valleys, you get occasionally erroneous readings and should go back to recheck your wiring or replace the thermosensor.
Only after making sure the physical side is ok, look at the TRP code and Thermal Settings in configuration_adv.h. Only alter these if you know what you are doing, as you do so at your own risk - the settings in the distribution are well proven to be safe, while alterations might turn TRP effectively off and turn your machine into a fire hazard. Which factors to increase carefully is detailed in this answer.


Issues With Cura 4.6.1 Effecting Text Width On The Initial Layer


Perhaps this is due to the aluminum build plate warping/crowning as it heats?  I use a PEI print surface on my Monoprice Maker Select (Wanhao Di3), which has an 8.5"x8.5" build plate, and I've had no issues with the PEI coming unstuck.  However, instead of attaching mine directly to the aluminum heated build plate, I attached it (using 3M 468) to a piece of Borosilicate glass, which is then attached to my aluminum build plate using silicone thermal heatsink pads.  The rational for using a Borosilicate glass print surface is that a heated metal build surface is going to warp or move some, as the heat is coming from one side; the glass will not warp and so you have a completely flat surface on which to print (and the heatsink pads help make up the difference in surface geometry).  I used this 3dprinterwiki article as the basis for my glass bed mod, and applied the PEI/adhesive using another source (which I've forgotten, possibly the RepRap wiki).  While the first link is Wanhao Di3 specific, it covers the idea.  Make sure you tweak your z-endstops if needed on your particular machine, as adding the glass plat raises the bed height by several mm.

Please note that I'm theorizing - I did not ever try applying my PEI directly to my aluminum build plate, so I have no direct comparison.  But the use of glass to eliminate build plate warping/crowning is fairly well documented. See also this 3DPSE Answer.


Makerbot Replicator 2 Halts during print

There are a few options. First your board could be overheating etc. That is harder to verify without some overpriced replacements. So to start lets take everything apart (photo and labeling is Strongly recommended). Then simply put it back together. Hopefully it is just a loose connection.


What causes this "stringing" and can my print recover from this?

No, your problem is not related to slicing, this is a hardware problem. Your complete print has shifted, this is called layer shift.

This could happen when the nozzle hits an obstruction while printing while the Y stepper continues. This could lead to skipping teeth on the belts, slipping of the pulley or missing steps. This results in printing over air as the print progresses. This manifests itself as stringing, but in fact is unsupported printing (in the air). In this case it is unrecoverable as the printer has lost the reference frame, it just continues to print with the new reference frame caused by the layer shift.

A Prusa MK3, or any printerboard using trinamic stepper drivers would be able to recover (if the belt and pulley are correctly attached, and steps are missed) as the skipping of steps is detected, in case of a Prusa  MK3 the machine will re-home when it detects skipped steps and continue printing. See also this answer for more details.

Possible solutions are increasing the belt tension, increase the stepper torque by increasing the current through the stepper drivers or re-tighten the pulley on the stepper of the Y belt.


Finding the cause of under-extrusion is very hard as a lot of parameters of the print process can influence this. There are some nice websites that describe these problems in detail. From your question it is unclear what you have done to solve the problem, or if you have printed products after the vase mode and shown us a picture of that (this eliminates a lot of possible problems).

A nice overview is given by Ultimaker, but other sources may help you to find the root cause, e.g. Simplify3D. If the issue is related to the filament and hot-end, Printrbot, Trideus and Rigid.ink may help you solve the problem.

Important is to isolate your problem! Not knowing what printer you have, your printer has (or potentially has) the folowing modules/elements that may be causing the underextrusion:

the slicer (highly suspicious),
the material/filament and the spool holder (suspicious),
the extruder or feeder (suspicious),
the hot-end (suspicious),
the Bowden tube (suspicious if you have one).

Note that to find the root cause you should tackle this by elimination, this way you make sure that certain modules are not causing the problem. Also keep in mind that the vase mode prints a single outline/perimeter shell and won't make any retracts (so the Z axis will continuously rise), in which defects are shown instantly. Please, take a close look at your normal multi perimeter print.

How to fix under extrusion!

Under extrusion is probably one of the hardest to find the direct cause as there are so many variables to consider. Please find below some of the variables that can affect your printing quality marked in bold face.

Material and material settings

The material you use needs to be resembled correctly, so it is important and easiest thing to check first if your print is suffering from under-extrusion due to incorrect material settings. The material settings in your slicer (or the material profile on your printer for the more fancy printers) should match the material you are printing. So please check the filament diameter with a caliper and measure the diameter at various points; take the mean diameter of at least 3 to 5 measurements. Furthermore, temperature is also an important factor; too low temperatures will cause that the extruder has to push harder as the material is less viscous due to the fact it is not heated properly. Note that this can also happen if the flow of the filament is too high and the heater cannot keep up. It is these high pressures that cause the under extrusion as it may not flow fluidly. In contrast to too low temperatures, too high temperatures, can also cause problems. Very high temperatures can change the structure of the material, this is often referred to as carbonization causing deposits (clogs) in the nozzle. A word of advice, Please check your filament spool/box (or sometimes a paper in the box or bag) for the proper temperatures.

Next to the temperature, other important material settings are the print speed, the layer height and the nozzle size as these properties further define the rate at which the filament volume is deposited. For instance, a too high of a volume flow not only can lead to the previously mentioned cooling of the nozzle, but also is limited by the diameter of the nozzle, you just cannot push more through the nozzle is capable of as the friction will increase (the smallest opening in the system determines the maximum rate of volume flow). If you do, this will lead to under-extrusion. To find the optimum between speed and temperature, a good balance between these needs to be found. A typical way to do that is by the use of printing calibration temperature towers, preferably at various speeds. To print faster, you need a higher temperature, but printing at lower temperatures because of overhangs, you might need to decrease the speed to get a proper extrusion (and maybe also part cooling).

Don't just focus on the hot end part, also take a closer look at the filament spool itself, or better, how the spool unrolls. Is the spool of filament unrolling correctly/freely without a lot of friction (does it make sharp bends, or does it go through a tube having friction from its container to the extruder), or is the filament not correctly wound causing tangled filament (which create a lot of friction preventing enough material to be transported to the hot end) which could stress the extruder.

For some materials that are hydrophilic (they attract water and trap it in the filament, this happens e.g. with PLA, PVA, Nylon and maybe even more) printing the filament with contained water, the water will turn into steam causing bubbles in the deposited filament and interfere with the flow deposition. This effect sometimes makes a distinct sound like popping bubbles. Always store your filament in a sealed container or bag and use desiccants bags. Moisture can cause damage to the printer as the filament swells when taking up moisture; this could lead to various jams. Last but not least, filament with moisture in it has less mechanical properties after printing than dry filament (up to 33% less).
The extruder/feeder and Bowden tube

The extruder/feeder pushes or feeds material into the hot end, or into a tube (called Bowden tube). Under-extrusion caused by the extruder is typically characterized by the fact that filament is not properly fed to the hot end as a result of too much friction in the tube or hot end, too less grip on the filament or filament grinding (the extruder gear 'eating away' the filament). Too much friction could even cause your stepper to tick or click, basically turning back as the pressure on the filament exerts so much pressure that the stepper is rotated back; increasing the feeder tension on the filament (by adjusting the screw on the extruder/feeder would fix that). Grinding is easily spotted when removing the filament; it will clearly show that the gear has worn away circle shapes. Furthermore, filament taken out of the printer should show visible marks on the material as imprints of the extruder gear, if completely smooth, the feeder tension is too less. On the other hand, too much tension on the feeder could flatten the filament, which leads the previously mentioned grinding effect. If you encounter grinding, please assure that you clean the extruder by removing the filament powder and chunks the grinding produced and recheck the extruder/feeder tension before continuing printing again. Be sure that the grinding particles have not entered the Bowden tube as it causes friction. Cleaning them regularly or replacing them once a year is advisable depending on the usage (or once every x kilometers of filament). Furthermore, larger diameter filament (2.85 or 3 mm) can cause additional friction (in the Bowden tube or the extruder/feeder) as towards the end of the spool, the filament is wound tight along a small diameter spool center causing strongly bend filament that exerts pressure as it acts like a spring creating friction at the walls of the tubes.
The hot-end

The hot end can also be a culprit for under-extrusion. Partial blockage of the nozzle as a result of carbonization (buildup of carbon or carbonized material in the nozzle). Even left over material from previous prints inside the nozzle (unflushed residue) may change the volume of the nozzle when the material you printed before needed a higher temperature than the current you're printing. Also try to get good quality filament, it might be that the quality is just not constant for the whole spool. Too clean the inside of the nozzle, a few techniques exist to remove blockage. By performing a "cold pull" or using the atomic method. Both techniques rely on the mechanism to insert the (cleaning) filament when it's hot and remove it quickly at a lower temperature. E.g. see here or here.


3D printing and coating of heat-resistant objects, such as a turbine blisks or blades

This depends primarily on economics and on desired lifetime.  Rather obviously you need a material whose strengths and melting points exceed the operational specs.  Determining the various break strengths (shear, bending, etc) is an engineering problem, not a manufacturing problem per se.
Next, consider the production time and cost of 3D-printing vs. some typical assembly line process.  Nearly always the 3D approach loses for large quantity builds.
Designing and operating devices like this can be extremely dangerous. Very tight tolerances are required.  This site describes the difficulties, starting with material choice, moving on to tolerances, and so on.  I don't think you want to go at this in your basement.


Pile up objects and attach them for mass 3D printing

Don't modify the STL to separate the visors with cylinders. The rest of the part is unsupported, so this will give you lots of support structures or, if omitted, a gigant spaghetti print.
Josef Prusa is already printing stacked visors on his print farm overnight.
I would stack the models of a set of visors in my slicer and for each visor added after the first disable "dropping print to the build plate" and position each consecutive visor one layer height (e.g. 0.2 mm) higher than the last layer of the previous, this way you use the previous visor as a raft for the next.

Below, a reference of someone who prints 8 parts stacked (4 high) overnight:

I wanted to be able to print more than just 2 at a time. Specially over the night when everyone is sleeping. I came up with the idea to stack them on top of each other. Instead of 2 you could print 8 during night. If your printer has smaller build plate and you can only print one its also big help for you.
After printing jsut simply peel them away and they will break loose.
Gap between parts is 0.3 mm .


What should I consider before buying a 3D printer?

Not surprisingly, your question is a difficult one to pin down in a precise manner. I'm going to pull one line from your post as the focus for my answer.

  I would like to get use of your experience with 3D printers and their producer brands

I would suggest that you isolate a few models (or more) that hold your interest. A good example of a popular, quality printer is the Prusa i3 MK2s, although some would consider it to be expensive. It's available in kit form, as well as fully assembled, another topic entirely.

Find the forums specific to the printer models you've selected and read as many posts as you can. Look for user postings describing problems and suggested solutions. Look for user postings describing modifications which implies a problem that had to be solved by the user or community before the printer performed satisfactorily.

I've assisted in the building of a Prusa i3 MK2s recently and am currently assisting in a home-spun design based on a number of other generic printers. The owner of this model is incorporating as many modifications as he can find. That tells me that this model, although not yet completed, is likely to be a handful to tune and operate to his/my satisfaction.

On the flip side, everything I've read about the Prusa told me that for the public library for which it was destined, it would be the lowest level of trouble for any model I researched. I was asked to make a recommendation and performed the suggested research via all the forums I could find.

The above sounds like a direct recommendation, and it could be, but you have not provided too many specifics. The Prusa i3 MK2s (genuine, not clone) would likely print well for your circuit board cases, but there certainly would be other models to do the same job well enough.

Watch out for print bed size, based on your board size requirements. Heated beds usually mean more money, but greater variety of materials can be used as a result.

If you plan to limit your use specifically to circuit board cases, you may not have to be concerned about "expandability" from a feature standpoint. Single extruder models are fine for almost all 3D printing, but it's handy sometimes to have dual nozzle capacity. That's another plus for the Prusa i3 MK2s with an add-on kit, but not a big deal for case building, I think.

Look in the various forums that provide general support for 3D printing (such as this one) for other posts from people who use Brand X 3D printer and have had a problem with, for example, bed adhesion, filament quality, layer shifts, nozzle clogging, just about anything.

As with many things, high quality usually means higher price. The library Prusa has been zero problems for me to support on a volunteer basis, hence my recommendation. The makerspace also enjoyed the building process by buying the kit, saving US$200 in the process and learning more about the printer.

Keep an eye out for users who have experienced broken components or typically troublesome components. You would not want to buy a printer model that ships with a junky hot-end assembly if the suggested modification is to upgrade to an E3D V6 to make it work properly. A user who posts about a continuing belt breakage (rare!) could have a user-induced problem or a printer design problem, which means you'll want to cull out some of the information you see.

Good luck, it's a tough decision, to be sure.


Which hotend does not clog and is good to use with a Bowden 1.75 mm setup?

To make the suggestion of Martin Carney a real answer and shift things away from comments:

Yes, moisture and dust can be a problem. Find elaborations on the moisture here:
Does filament have to be stored in an airtight environment.

Also, dust getting into the hot end won't make extrusion easier. (link with suitable information needed). There are filament cleaning 'devices' for print on thingiverse, have a look at things with the tag: filament cleaner.

There are some other things that are mostly discussed in relation to hot-end clogging, which are printing speed, retract setting and what I would call hot-end resistance. For all of those, read through this thread and refine your question according to what you tried and what the results were:
Repeatedly Clogged Printrbot Simple Extruder.


What will be the best way to remove pla from a volcano nozzle?

If you grab the blob with a pliers and twist, all or most of it may pop off.  If not,  heat the extruder up perhaps 10 degrees higher than usual, and wait for the external gunk to soften up and then pull it off.
edit :
Well, if it won't get hot enough, then try using an external source such as a soldering iron tip to cut off most of the mess, then it may be time for exacto knife blades and small files to remove the remainder.
Unless you're a clean freak :-) a little residue around the nozzle doesn't matter - it won't touch your prints and at some time in the future it'll be "cooked" enough to fall off.


Choosing the most high quality, reliable 3D printer

At work we have a Stratasys Polyjet.  It prints using UV cured gel; so, it is kind of a cross between FDM and SLA.  I have not used it personally, it is mostly used byt the ME group.  The parts I have seen that it produces are VERY good and it support different materials and even multiple materials.  They have a lot of different product levels so they can support different price points.  The only complaint I have heard is the material cost.

It can print some amazing stuff

Here is a nice video https://www.youtube.com/watch?v=HMMJnn_gHWw