text:
Export firmware as a .hex
Because .hex files can be installed without any need of an Arduino (serving as an ISP) to flash the firmware on Creality machines I was wondering, if firmware compiled via some other means (for example the Repetier firmware or Arduino) could be exported as a .hex file.

You might want to mention that this is for the Ender-3 specific controller board, as there is no bootloader, as per TH3D Unified Firmware Package.

Current versions of Arduino IDE
Use the menu option in the Arduino IDE:
Sketch ► Export Compiled Binary
See post #6 from the thread How to get hex file from arduino files ?:

Well, since it was bumped it's worth mentioning there is a new way to
  do this added in Arduino IDE 1.6.5:

Sketch > Export Compiled Binary
If you are doing this with an example then you will be prompted to save the sketch in another location.
Wait until the sketch has finished compiling.
Sketch > Show Sketch Folder
The .hex file will be in the sketch folder

Here is a screenshot for OS X:

There is no need to fully compile, a simple verify will suffice. From post #10:

Reopen Arduino, and open a sketch of your choice (use the Examples->Digital->Blink if you have no other sketches). Hit the Verify button to compile the sketch. Now, navigate to the build.path folder. You should see a bunch of files including one with a .hex extension.

Older versions of Arduino IDE
If using an older version of the Arduino IDE, from post #12:

Try this if using an older version of Arduino
Taking out HEX file from Arduino in 3 simple steps

Open Arduino IDE
File ► Preferences menu

Find "Show verbose output during " and check the "compilation" box
Locate the preferences.txt file and open it
Add the following line (this is the path to the directory where the hexfile will be stored):
build.path=C:\Users\<username>\Desktop\hexfile

Change the following line
export.delete_target_folder=true

to
export.delete_target_folder=false

Quit the Arduino IDE and restart it.
Now when you compile, the directory specified in build.path will contain the .hex file (along with other files which can be ignored)


text:
Should I vary the first layer height
Up till now, I've tended to scale my first layer according to the print quality, so a 0.12 mm first layer for a 0.08 mm print, and 0.28 mm for a 0.2 mm print.
After changing to a PLA which isn't sticking well, I'm wondering if the first layer is best determined by the printer/tolerance/material, rather than the overall print quality settings. Am I going to get more predictable results if I stick to a 0.12 mm first layer regardless? This is with a 0.4 mm nozzle on an Anet-A8.

I made more negative experience for 0.4 mm nozzle and 0.2 mm layer but 0.28 mm initial layer. Change it back to 0.2 mm solves all adhesion problems for me. (Tested on Anet A8 and Ultimaker3)

@Horitsu That could be an answer...

@SeanHoulinhane If this is the solution to your problems and you want to, then I could post this as answer. But till then it is just a litte tip ;)

I always print my entire model with the same layer thickness throughout, regardless of material.

@Horitsu - whilst your comment is a little short as it stands, I would post it as an answer as while it may not directly, or exactly, help Sean, it may help someone else. Maybe expand upon it if you can.

Default settings for first layer height in Slic3r Prusa Edition print profiles regardless layer height is 0.2 mm.
If you need to improve bed adhesion then try tips from this video 3D Prints not sticking anymore? Watch this! 3DP101 by Maker's Muse. It's about using glue stick and spreading it using paper towel and isopropyl alcohol.
There are other possibilities how to improve bed adhesion, e.g. Ultem sheet or other printing surface like BuildTak.

The first layer height can be the same as the whole printing model however you can set different sizes and speeds; it is recommended that layer height should be 75 % or less than nozzle diameter, this means that for a nozzle of 0.4 mm the max height is 0.3 mm (if you are a master you can use higher dimensions)
The first layer with a height of 0.3 mm with a speed of 70 mm/s will have less adhesion than printing at 50 mm/s. Also the same height and speed of 70 mm/s at 210 °C will have more adhesion than at 195 °C. So printing at 195 °C with speed of 50 mm/s could have the same adhesion than 70 mm/s at 210 °C. This depends on the quality of your PLA
On my prints I have set the prints at 195 °C and 55 mm/s with a height of 0.20 mm, then the whole print uses the same temperature at 85 mm/s with 0.25 mm of layer height. With other PLA quality I have to set 210 °C first layer at 50 mm/s, and other layers at 200 °C with 70 mm/s. So adjustments are based temperature and speed once you have determined the smoothness of your prints.

Once you've tuned your 0.20mm first layer, would you stick to it if you went down in thickness for a more detailed model? I'm actually looking at the opposite, if I increase the layer height for the main part of the model for speed - and in that case it seems to make no sense in changing the first layer too.

@SeanHoulihane as mentioned, the layer can be set to specific height but your temperature and speed need to adjusted to get a better adhesion, I used to use Cura and I had the problem with first layer height due changes on layer height extrution; for example when I set for printing 0.35 the first layer height was changed from 0.2 to 0.28, then I set 0.4 then the first layer changed to 0.32, and so on. I changed to simplify3D then My first layer allways is the same at 0.2mm even if I change the layer height of whole printing. Slic3r has this option to set mm or % of layer printing

I made more negative experience for 0.4 mm nozzle and 0.2 mm layer but 0.28 mm initial layer. Change it back to 0.2 mm solves all adhesion problems for me. (Tested on Anet A8 and Ultimaker3)

Layer height in my cura settings means that head of extruder will be going up at 0.3mmm, and how i know that? Because i measure few different settings with height of bed.
When I set bed to -0.2mm, ike everybody is proposing on internet, and i started printing first layer, I did stop it and measure with precise caliper thickness, it was 4.2mm, (human precision with leveling bed :P ) that was for me  to much, because extruded material almost was not sticking to the bed,, and walls was not connected each other.
I did test also with home position of nozzle and setting bed to touch nozzle, to 0 height. ( YEAH) And again I measure thickness of first layer. It was precise 0.3mm. Exactly as I want.
That means that or I have better software witch can take nozzle up with initial layer in cura settings?, or magical printer, but my printer is cheap and is buy'ed almost by everybody.
 That means that peoples who are teaching others how to set bed in a printer are totally wrong. Maybe no one measure thickens of first layer?
 Even seller from who I buy printer propose me use paper with thickens of 0.25mm to set level of the bed.
Previously I have problems with first layer, because that was too high from bed, now when I set 0 position of nozzle exactly with bed, I don't have problems with thickens of layer, and printed element looks allot better from bottom.

Your answer is difficult to read. I don't think this directly answers the question. It appears to be describing levelling and nozzle to bed distance, not initial layer height. As such this answer appears to be off topic, if you can please improve the answer so it may receive some votes.

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

sort: votes


text:
How to build a cheap (but safe) laser engraver with spare parts
I would love to start a small engraving business without having to purchase expensive hardware.
Using scrap parts at home, or parts from broken CD players, are there any ways to make a laser engraver at home? My cousin managed to make one of his own from scraps.

How cheap, what area, engraving what material?

There are ways to do one or several at home (I made one), try to look for laser forums.

I don't know anything about laser engravers, but you might find these links useful: Make your own 3D printer for under $60 using Components with Instructables Design and
Instructables – EWaste 60$ 3DPrinter by mikelllc in 3D-Printing

This question is very opinion based, it's also asking for 'competent person' advice in terms of safety. If you want safe, pay someone who has insurance. Thinking a bit more about this question (and adding my downvote), I think it needs to be split into a few parts. Clearly a laser engraver can be built from scrap, what is easier to answer in the context of this site is some details about 'is a CD player laser strong enough to engrave', what safety do I need with a CD laser (or other type if you go that way). The business aspect of using DIY hardware I think is way off topic.

"cheapest" is a pretty much impossible to answer question. One might arguably get it rather cheap if one converts a printer ot an engraver... This might best be a host for Laser-cutter questions interlinked or a general design consideration question. Basically there is a design triangle of "Cost-Safety-Versatility" to cover here: to go into one direction of this design triangle means to sacrifice in the other two, to to a compromise of two of these means to sacrifice in the third: there is no "Cheap-safe-AND-Versatile" machine.

If you do not have knowledge about the electronics then consider buying a cheap etching machine instead.
Build
Take a look on https://hackaday.com/ and search for laser engravers.
I have found following articles in few seconds:

Hackaday.com: DVD LASER DIODE USED TO BUILD A LASER ENGRAVER
Hackaday.com: LASER PCB EXPOSER BUILT FROM CD-ROM DRIVES
Hackaday.com: HOMEBUILT LASER ENGRAVER USING SALVAGED PARTS
Hackaday.com: ENTRY-LEVEL 3D PRINTER BECOMES BUDGET PCB MACHINE

Cheap laser engravers
And this one is about 2018 list of laser cutters/engravers: 15 Best Laser Cutters, Laser Engravers & AIO Machines of 2018. It lists machines around 100$

Meterk Laser Engraver ($125)
NEJE DK-8-KZ ($70)
QIILU Mini Laser Engraver ($130)
SuperCarver K2 ($160)

Safety
Laser could damage your eyes (imagine laser reflection or if the machine falls from table when it's working). Take a look on wikipedia.
The best option is to use acrylic cover in same color as your laser, so you can observe the etching process and the laser beam is always blocked. For example take a look on orange cover of Formlabs Form 2 3d printer (it uses laser for printing).
Another protection is to wear laser protection glasses. Again the glasses must have same color as your laser.
Using laser for cutting or engraving means to burn material away. You should have good ventilation in the room.
Buy a smoke detector if you use cheap electronics with higher power consumption.

This is a mostly link only answer. If the links die, which they usually do, then the answer will be not much use. Please edit and include a summary of each link, and the highlights

As an alternative to editing this, you can always delete it to earn the 'peer-pressure' badge. I think it's important to address the safety issues if you do answer this question. To clarify - not my downvotes (hadn't voted on the question till now)

@SeanHoulihane thanks for the critics. I rather try to improve the answer then just to delete it.

I have a printer and a diode laser head which will etch aluminum for under $4k, but you're going to have to manage potentially noxious fumes based on what material you're lasering. It's safe if used safely: the focal distance is 15-20mm from the lens, but all present should wear PPE.
Note: I work for Hyrel3D.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
Strange layer separation issues on Ender 3
I got my Ender 3 a couple weeks ago. Within a couple days of test prints, I was able to get it working pretty well. Prints looked great. However, I installed a more permanent solution to my X-Gantry binding issues and now print quality is down again.

The bottom .25" of the calibration part looks absolutely terrible, with hideous layer separation issues, while the upper .75" looks flawless. I have little idea what could be causing this issue.

The only possible failure mode I can think of is that the bed isn't the right distance from the print head, but even fiddling with the knobs doesn't yield any better print quality than the print on the right of the first image. What can I do?
I slice with Cura and can make my profile available if it would be useful.

The answer now seems brain-dead obvious now. Hindsight is 20/20, amirite?
I had a decent filament clog in the extruder past the end of the Bowden tube. This was resolved by sticking a nozzle cleaner rod up and down the filament path from the top of the extruder block several times and clearing the filament jam from the bottom of the Bowden tube. The printer works flawlessly now.

Well, you have several problems with your print. One that could be affecting your print is the nozzle temperature. The print looks wavy and has a lack of adhesion, so the filament is not flowing properly, causing under extrusion and will provoke a clogged nozzle.
Try to increase the temperature by 5°C and do a small test, don't wait to waste material and try another 2-3°C more.
Try to reduce the printing sped; try reducing the feed rate on your printer to 90% or less. While printing you can reduce the feed rate to see which speed works better at your printing temperature. I prefer to do this first rather than change the temperature; If you notice that your print gets better at lower feed rate then change your temperature higher to print a higher speed.

Your answer is a bit confusing. Also, what about the fact that print quality gets exponentially better as the height increases? How does your flow rate and temperature theory account for that?

@ifconfig This is not a theory, if you see your print the temperature and flow is better on top than the base. The top has a higher temperature on each pass due the previous layer is still hot; the combination of both temperatures provoques a better adhesion. so for larger areas the temperature of nozzle need to be higher. A lower speed rate (not flow rate) will give more time to the filaments get added to the previous layer.

Okay.... That sounds good, but these exact settings worked phenomenally before I changed out the z axis stepper adapter. I don't see how that could have affected the max speed and or required nozzle temp.

The adapter should not be the problem since this is not a lack of adhesion of first layer. Is common to see this defect on uncalibrated Z height but only on the first 3 layers but not the whole part. Also this happens when the layer height is to close to the nozzle diameter. for example Nozzle Diam=0.4 and layer height 0.3 or 0.35. your problem is related with plastic feed.Other wise, remove your new improvement that does not work as expected.

I had a real problem with what I was poor bed adhesion and layer separation on my 6month old Ender 3 pro. this problem started all at once, I checked the bed height several times and layer height, temperatures etc still the problem was there.
Then I noticed the filament guide pinch roller was at a slight angle and on further inspection the plastic arm on removal was fractured so instead of holding the filament against the toothed drive it was metal to metal causing a slip on the nozzle feed.
I ordered a replacement aluminium feed roller kit at £6.99 the machine is working as it did when I first got it.
So it’s worth removing the pinch arm and inspecting.

Hi Len welcome to 3DPrinting.SE! SE websites are driven by questions and answers, your answer is more a forum style "Me too" comment to the question. I think you can save your answer by explaining more clearly you had the same problem and solved it by replacing it with new rollers. After all, a clog or filament slip result in the same under extruding condition.


text:
Wear resistant nozzles
I recently purchased some glow-in-the-dark PLA filament (just "because"). Being new to 3D printing, I didn't realize you shouldn't run this type of filament through a standard brass nozzle and should replace it using a "wear resistant" type nozzle. This is true of carbon fiber type filament as well.
My questions are:

What types of nozzle material are considered "wear resistant" and are some materials better than others?
Can I use this type of nozzle all the time (ie: are there any downsides for regular use)?
What types of filament should you use a wear resistant nozzle with?

The last point is maybe a bit broad, although it does tie in with point 2.

Not all G-I-D filament is abrasive.

Related https://3dprinting.stackexchange.com/questions/3854

@CarlWitthoft - That's good to know. I read the reviews after purchase (yah, go figure). It seems the one I bought does promote wear. There was an image of a nozzle after some (I don't remember the amount) usage ... In comparison to the .4mm (they posted a pic of a new nozzle for comparison), it looked like it was about a 2mm nozzle ... ugh. Things you learn after the fact.

split this up into 3 questions, then you are fine XD

E3D have a blog post on the subject of hardened nozzles. The common abrasive materials are carbon fibre, wood impregnated filament (or any other particulate fill), and some pigments. The blog describes that as little as 250g of the more abrasive filaments can wreck a brass nozzle.
For wear resistance, different manufacturers will have different options. Stainless steel is a little harder than brass, and hardened steel is a big step forward. If you fancy spending more money, aluminium oxide (i.e. Ruby) is an option.
The downside is printability and cost. Specifically thermal conductivity of brass (or copper) is very good when compared to steel. However, this may not be the limiting factor for your printing unless you're running a very large machine. The various materials may also give different friction/wetting performance which can affect jams.
Depending on the printer and the type of hardened nozzle, it probably makes sense to avoid swapping between hardened and standard nozzles most of the time.
Hardened nozzles cost between 3 and 20 times what you will pay for a branded brass nozzle (and arguably a bag of no-name brass nozzles can be treated as near enough free disposables in comparison).

The last line is what matters - unless you're exclusively using some nasty filament, it's faster and cheaper to buy brass  nozzles in bulk and treat them as expendables.

Wood filaments are not much more abrasive then plastic. The real issue are materials like carbon fiber, bronze, steel and other metals.

Any material high in additives or with very hard additives can be considered abrasive: these "burn in kiln" 80% metal materials eat nozzles for breakfast, a PLA that contains real mineralic pigments would eat nozzles quickly, ceramic-filled PLA is quite abrasive too.

I saw on kickstarter a while back a tungsten carbide nozzle for about $40 bucks. Good thermal conductivity, about as hard as ruby, much cheaper.


text:
Setting custom x/y bed bounds for Anet A8/marlin
I have an Anet A8 that I just flashed with the latest Marlin firmware (1.1.9). I'm sending prints to my printer with Ultimaker Cura via OctoPrint.
I have affixed a PEI surface to my bed that's about 10 mm smaller in each direction than the full size of the bed (that is, I lose about 5 mm on each side of the bed). This hasn't been a huge problem as usually I account for this myself and just make sure there's lots of room on each side of a print, but having upgraded my firmware, I'd like to take advantage of Marlin's bi-linear bed-levelling. Unfortunately, several of the points it chooses are outside the bounds of my PEI surface and so it's impossible to get a decent setting for those points.
What's the "correct" way to configure Marlin to know that my bed size is actually smaller than it thinks it is? Do I need to additionally adjust settings in Ultimaker Cura and/or OctoPrint?

The answer to the question can be found in How to center my prints on the build platform? (Re-calibrate homing offset). You need to set correct bed size dimensions and offsets from end stops. This question is a possible duplicate.

As you just flashed your own Marlin, you probably have the marlin.ino and its associated files in the Arduino IDE set for your Processor and board and know how to work with them to some degree. This is just the short version where to find what you need to change the bed size, if the marlin.ino is based on the marlinfw-release.
Changing "home"
In Configuration.h there should be a set of lines that reads akin to this:
// Travel limits (mm) after homing, corresponding to endstop positions.
#define X_MIN_POS 0
#define Y_MIN_POS 0
#define Z_MIN_POS 0
#define X_MAX_POS X_BED_SIZE
#define Y_MAX_POS Y_BED_SIZE
#define Z_MAX_POS 200

Usually it is faster to use Ctrl+F and then typing in X_MIN_POS and adding the hook in front of Search all Sketch Tabs and then moving through all the finds till the right one pops up. This not only brings you right to the lines you want to alter, but also covers up the bases in case the distribution you work with did put the movement limits into a different location like Configruration_adv.h.
Changing Bed Size
Alter these minimum positions and make sure that the Maximum positions (usually just after them) to fit the maximum of the bed.
If you reduced your bed size, you also might need to change X_BED_SIZE and Y_BED_SIZE, which (in the marlin.ino) is in the same Configuration.h - I found it to preceede the Travel limits:
// The size of the print bed
#define X_BED_SIZE 200
#define Y_BED_SIZE 200

Adjust these as needed to fit the new sizing.
Hint: Getting the Values for Adjusting
For finding the adjusted values, I have had good experiences using Repetier Host on Manual Control to move the nozzle (lifted 1mm to prevent any accidents) into the correct XY-position and taking this position as adjustments for the minimum positions. Finding your personal settings is a bit of a trial and error still, so take your time.
Finishing up
Now, recompile the marlin.ino (the checkmark in the top left) to check for errors and flash the new firmware it.

Thanks! The starting (x,y,z) values in my config were (-33, -12, 0) and it took me a bit of experimentation to figure out that to adjust the bounds of the bed 12mm right and 5mm back I needed to go to (-45,-17,0), but having sorted that out (and adjusted the max positions accordingly) everything seems to be working the way I'd expect.

@AwesomeTown remember to adjust the ?_BED_SIZE correctly - I forgot to include their lines in the old version, fixed that.


text:
How to install new ATmega firmware via the ISP pins?
While uploading .hex firmware directly onto boards that allow this via CURA, this is not always an option for all machines (for lack of a functioning USB-connectable port for example).
On both my TronXY X1 board (Melzi 2.0 V5 with ATMEGA1284P) and the Creality Ender 3 (Creality 3D v.1.1.2 with Δ ATMEL  ATMEGA1284P  AU 1726) I spotted these 6 pins labeled ISP that are supposed to allow to connect an Arduino or similar to flash firmware. According to the RepRap Wiki, Melzi is a derivative of the Sanguinololu and both are Sanguino Compatible.
After creating the new firmware in Arduino IDE and making sure it compiles for the correct chip in the board, how can I use an Arduino Uno or other microcontroller to flash the new firmware  via the ISP to my printer?
This is asking specifically about ATmega based controller boards, using the Arduino toolchain.

Not all printers are created equal. The process would be very different for a board based on, say, an AtMega2560 than a board based on a Cortex M3. It also depends on what (if any) bootloader is present on the board. I think the question is too broad in its current state.

@TomvanderZanden true, this is meant as a generic "I have some printer and managed to get the firmware to compile - hw do I get it onto the printer? I have this other microcontroller around". If you can add to the question or reitterate it in a better form, feel free to do so - we pretty much need to answer these basic questions to be able to answer more difficult answers more quickly by interlinking.

There isn't a one-size-fits-all answer for this. It would be much better to have separate questions for separate types of board, because a single answer can't cover all possible scenario's you're imagining. Keep in mind that you should only ask practical, answerable questions based on actual problems that you face. You aren't actually facing the problem of having a board you can't upload to using Cura.

@TomvanderZanden I know it is supposed to work, but I fail to understand why it is supposed to be better than for example directly loading it via CURA or a different method to send the compiled .hex to the board... After all you have to open your machine... But it is a rather universal solution and would work for pretty much any machine - even ones that have no possibility to connect it to the PC, for exampe if the USB port was broken.

@TomvanderZanden - the ATmega on the controller of the Ender-3 does not have a bootloader, apparently, as per TH3D Unified Firmware Package: CR-10, Ender 2, and Ender 3 Printers need the bootloader. You will need to follow the CR-10 bootloader guide to flash it before you can load the firmware. You can use our Uno kit to flash the bootloader on your board. The Uno kit is the ISP.

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.

thanks a lot - also I suggest to put up a note reminding to CHECK YOUR CONNECTION WIRES in case some odd error pops up.


text:
Creality CR-10 Clogs and Underextrusion - Filament at fault?
I've been printing successfully on my CR-10 for the past year now. I've had issues now and then but have been able to look around the internet and solve them. I've been using some Flashforge white PLA with great results.
Example:

Last week I got a couple of new rolls of filament, black and orange. SinceI tried printing with them, I've got nothing but jams. The white prints fine, however.

I dug around online and found this was happening to my printer: https://www.youtube.com/watch?v=-vH_spN5wyw
So yesterday I opened up my hotend to clean it out and got quite a bit of gunk out:

I also changed my nozzle. I printed some with the old white PLA and printed fine. The moment I switched over to the new orange filament, it jammed after a few layers.
I ensured my nozzle was tightened and then got to measuring the filament. The older white one is 1.75mm in most places with some at 1.73mm.
The new ones that I got are pretty inconsistent - the orange one ranging from 1.68mm to 1.72mm; I found very few places where it was actually 1.75mm. The black one averaged 1.72mm.
So I made the change in my slicer but even then the first layer was visibly underextruding and it jammed soon after. I took apart the hotend and cleaned it out. Now, I put the white one back and its back printing fine.
Should I go ahead and return the filament?

What is the advertised tolerance on the black filament?

Welcome to 3D Printing, btw!

@arunabha42 Did you check what is the best temperature of printing? I used to print at 190°C but with one kind of brand I had to change to 210°C; now I have another supplier and I had to back to 190°C and 195°C for faster printing.

that black stuff looks to be printed too hot, colors can affect temp...

Not all filaments are created equal. Even with the very same manufacturer, the addition of colorful pigments can change the needed printing temperature a lot! I have had a white china PLA that was giving ok quality at 200°C, but the same brand's clear PLA only took 195°C to print. My white Kaisertech prints better at the 200°C while orange needs a little more, something about 205°C - this is the same brand and manufacturer mind you. The matte "natural" PLA I have even needs some more heat, 210°C.
As a rule of thumb: Printing temerature is filament dependant. Test around (there are temperature tests - use them!) to find the ideal one for each brand and color combo you have.
It is also a goood idea to replace the claps on the Bowden tube, if the plugs appear more often.

From attached pictures I can see that some of the printouts are not sticking enough to the bed (that can be a non-leveled bed).
As you are printing directly on the glass ensure that the area is clean (no fat or other organic substances - clean with alcohol or another grease remover) or use a PVA glue to get better adhesion.
If the Z height is to low it can clog the nozzle, if to high then print will not stick.

good point on adhesion, though in this case probably coupled with temperature as the white material OP uses seems to work fine without changes.

@Trish that all can be down to the add-ons in PLA, another issue can be wobbling Z, but that one is rather a Tevo Tarantula domain :) than CR10


text:
MKS board losing power after endstop installation
I just bought an MKS gen v1.3, and everything on it works fine except for when I plug in the endstops. My X endstop works perfectly in every endstop outlet, but when I plug in my Z and Y endstops, the entire board loses power. Immediately after I unplug the endstop, the board turns back on. I've had these endstops for a while, so could it just be that the endstops are shot, or could there be something wrong with my board?
I'm using repetier firmware 0.92, as well as the latest release of repetier host software.

Have you tested the Y and Z axes' endstops with a multimeter (resistance setting)?

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

I had answered this at first suggesting to put the X end stop into the other positions, not realizing the OP had already tried that ... just suggesting testing the other way which could give you more data.

If the problem's that the board cant supply enough current,it could be any part which is at fault and drawing too much current .


text:
How can you calibrate extrusion multiplier value in Slic3r WITHOUT changing printer settings in memory?
Most tutorials ask you to change the printer settings using the The command M92 E420 will set the new value which can be saved to memory (so that it is available after a printer power off/on cycle) using M500.
But I just want to modify the Extrusion Multiplier in Slic3r's settings. It's default at for each filament, and I'd like to modify this by adding a profile for each roll I have after calibration.

What's the best way to do this? If I measure extruding 100mm and checking how much is left, what is the formula used to get the new EM value?

Divide the amount overextruded by the desired amount. If you wanted 100mm but got 101mm, that's 1mm extra, or 1% over. Use an extrusion multiplier of 0.99 (1% under) to compensate - AND THEN DO ANOTHER TEST to confirm.
This modifier will be used by Slic3r to generate E values in your gcode without flashing anything.
I recommend saving this recipe with an intuitive name, like Acme Green PLA.


text:
Polyurethane-and-steel timing belts?
Has anyone tried the steel-reinforced polyurethane timing belts? If so, how do they compare to the rubber ones?

This question is too subjective. You can try rewording it to ask about the technical properties of the two and how they relate to 3d printing. Btw, you should be using kevlar reinforced timing belts because the steel will stretch.

It's a question of what you want to use the belt for.
All Belts are subject to stress as they run around the motor and idlers and gears and bend. They will get eaten as they are subject to friction against parts, they will stretch as they are subject to tension. All this applies some sort of stress or another on the belt. Anything that is subject to stress wears. And as it wears, it will fail. The question is just: What is your life expectancy? The lifetime expectancy is again dependant on how the belt is used, so usage dictates lifetime of the belt.
Each belt type has an application it is designed for. A bending radius that is to be kept at, a gear it is to be used with, a load it is expected to move, a tension it is expected to uphold, and a lifetime it is expected to serve.
Let's take a short look at some rough ideas what
a soft rubber belt without additions
This is usually a bad choice for printers, but can occasionally be in very cheap kits. This kind of belt has applications. It is for really low loads, it can work tight bends for a long time and provides superb self-tensioning with just a very short tensioning device. On the other side, most rubbers don't take heat well, stretches a lot, wear fast and can only move a light load. If it rubs against a standing object, it squeaks horribly.
a medium hard, somewhat elastic belt reinforced with fibers
The standard belt we often get with printer kits. the fibers lessen the material's stretching ability while offering still some self-tensioning (depending on the fibers). These properties allow to move medium loads yet harder material demands slightly larger bend diameters (not too much, but measurable!). When the piece gets friction against a standing surface the sound will be not that horrible, but the harder rubber might start to shave off, break teeth and destroy the belt after some time. The typical reinforcing is done with cloth, usually cotton, so there are some limits to how much they can take.
reinforcing with aramid fibers
Some fibers are better than others for our applications because of how they stretch and reinforce it. Aramid fibers, for example, are better than cloth. Some consider them as impossible to wear out with the tension in 3D Printing applications alone, but that is not entirely the case. They still stretch under larger loads or on longer lengths enough that it can be a problem (or become one). They also can still be shredded with friction (and heat). For a professional machine, the expected lifetime is quite nice. They are though, but only as good as the rubber used and if properly installed. There are also generally two types: long fibers and short fibers. Long fibers have a somewhat even stretching behavior, while short fibers have totally different stretching behavior. The latter type is looked at in scholarly articles like Yin, Zhou, Lou et al.
a hard belt reinforced with fibers
Let's take... Uhm... a toothed belt from a car. I believe some of these are aramid-reinforced, old ones are on cloth cores, most modern ones I know are steel reinforced. It is somewhat hard. By design, it is made to withstand a strong tension at high speeds. It needs somewhat big bending radii for the hard rubber, but that is easily given by the gears and the large teeth don't break easily. Over the lifetime it will slowly stretch due to the temperature it will encounter, till at some point it gets too loose or looses too many teeth as the parameters don't match up with the teeth anymore and they get ground away. It is made to deliver high torque and could move - if something similar was used on a printer-like machine (like a large CNC), a heavy load for a long time, but the machine needs to be made accordingly.
steel reinforced belt
Steel is going stiffer. Steel reinforcements usually get the stretching parameter to a bare minimum at the cost of increasing their minimum bend and added weight. They can be used to move very heavy loads without the belt starting to slack as it simply can't stretch to give slack on the underside of the belt loop when forces are applied. Steel belts are pretty much Heavy Duty. If you can work with the bending radii belonging to them (as said, usually a little bigger than a similar fiber-reinforced one), you could make use of these properties, for example in a CNC Router with a full spindle or when moving very heavy tool heads.
carbonfiber reinforced
And then there is the super heavy-duty carbon fiber. One can barely stretch it (steel is less stretchy), making these belts super tough in the stretching compartment and granting an extremely long life under most conditions. In comparison to steel, they can work much tighter radii. Usually, they are coupled with urethanes to get a high wear resistance against abrasion. The biggest downside: their price.
Belt Materials
Silicone
Silicone is soft but high temperature resistant but dislikes abrasive forces.
Uretane
Urethanes are not the best to handle the heat, but they can handle abrasive forces. They also don't create dust in the same way as other rubbers.
Neoprene
The most interesting feature of neoprene belts is their reduced noise under work.

Belts come in several formulations.  This page from McMaster-Carr lists several types of belts.  The main materials (rubbers) are Neoprene and urethane, with fiberglass, Kevlar, and steel reinforcement.  I would suggest spending some time looking at these, comparing the specs, and basing your choice on the needs of your application.
I used 1/4" wide MXL series cut-to-length in my machine.  I have yet to see a wear or stretch problem and haven't yet done the high-speed photography to look for dynamic stretch.  IMO, I have a bigger problem with the length of belt resonating like a guitar string than I do with the stretch of the belt.  The compliance needed for resonance can come not only from the belt but also from the mechanical system it is mounted to.  In some cases, a slightly stretchy belt could dampen oscillations that would otherwise result from impulse forces being coupled into the printer frame.

I have recently changed the standard belts on my Prusa MK3 for the aramid fiber reinforced E3D neoprene belts. Those belts are really tough and hard to cut even with a quality side cutter! They have a much smoother surface and a lot more aramid fibers than the standard belts.
Prior to the change, the belt on the X axis was twisting when changing directions, now it is running straight and smooth. Surface quality has improved a little, the ripples are smaller and more regular. Overall a small but noticeable improvement
P.S. I am using belt tensioners on both x and y axis.

I do not believe the standard rubber/plastic belts have any significant stretching over time, nor do they stretch under drive motor force during acceleration (and in any case, extrusion takes place mostly under steady-velocity conditions).
While I suppose it's possible a steel-reinforced belt might have a longer lifetime, replacing a belt is quick and cheap, so why bother?
[incorporating comments]
My suspicion is that standard belts, e.g., as supplied with Prusa-clone kits will outlive us mere mortals. They can move an entire print bed+heater, so a larger print head is not an issue.
The usual problem with any belt material is ensuring there's no significant slack (which leads to backlash/hysteresis), and changing the material won't help or hurt tensioning control systems.

Carl, I'd say that your first point isn't valid over all: Wherever pieces are under tension or stress, they wear. The question is simply in which timeframe. Constant bending and tension will slowly work the belt apart. at some day, it will fail, the question is simply when. Is a steel reinforced belt probably overkill? Sure. Will it have benefits when using a super heavy printhead? Sure.

@Trish  fair points, but my expectation is that standard belts as supplied with Prusa-clone kits will outlive us mere mortals.  They can move an entire print bed+heater, so a larger print head is not an issue.

if you add these considerations as reasoning into your answer, it would increase its quality a lot - feel free work with what cmm and me provided as insight into general belt choices

I had really bad problems with GT2 PU belts (including steel reinforced), under big tension they degrade suddenly with big change in the geometry at some position. When removed they look twisted. Looks like some reinforcing wires slipped inside the PU body of the belt.
Once switched to rubber GT2 belts (fibreglass reinforced) I never had problems connected to the belts. I can tell that rubber GT2 belts have no noticeable change in the geometry over many years of constant use under high tension with the spring.


text:
Adding a battery backup power supply
So apparently the wiring in my home is... questionable. Very rarely, plugging or unplugging things will cause a power dip. This is almost always the result of turning on a fan or something, is only for a moment before coming back, but its long enough to cause my printer to reset. I want to add a backup battery supply using either the 12v cell pulled out of an old apc ups (before the suggestion of just plugging it into that... I did, somethings fried in it and it will ALSO power cycle everything connected to it every few hours) or an old car battery. Is there any reason I shouldn't use this circuit, which was originally intended for amateur radio equipment?
Also is there anything else i should be considering?

What does this have to do with 3D Printing? You need to ask this on SE.Electronics I think.

Agreed, although it is a valid question, you are more likely to get valuable feedback from EE.SE. There is nothing specific to this being about 3d printing (except you will need to specify the load of around 200W).

Unless, you reverse the order and ask if battery backup like this is the most appropriate for a 3D printer.

@SeanHoulihane is correct: the correct question is:  "what's the best way to ensure power backup if  line blackouts are a concern?"

Hello @entropicCreator, and welcome to the 3D Printing Stack Exchange.  Your question is only incidentally related to 3D printing and probably can be better answered in an EE focused group.  One thing to note is that 12v batteries actually charge at about 14.8v and discharge at 12v.  This makes it difficult to simply parallel a battery with a 12v supply.  A car alternator puts out 14.8v. Amateur radio equipment is designed to work with this range of input voltages, but 3D printer motor drivers and heaters are not.  You may have success, but you might consider a different backup method.

It is likely in your best interest to investigate the cause of the dip; sounds like a high resistance or arcing connection, which translates to "eventual electrical fire".  One candidate is where the (aluminum?) feeder wires connect to the breaker panel.  With heating (high load) and cooling (low load) cycles the difference in thermal expansion Cu vs. Al causes the Al feeder to squish and work loose.  Our breaker panel was hot & I could hear arcing; neutral was loose.  Tightened (with the preceding entry panel breaker OFF).

The charging circuit shown is unregulated; it will destroy the battery.  Which would explain why it doesn't carry through power dropouts; that would require the battery to work.  Further, batteries have a limited lifetime, and you mentioned removing it from an old nonfunctioning UPS.  Have you tested the battery in any way?  Try a voltmeter and a 12V bulb.  If a battery charger rapidly takes it from low voltage to 14+V, it's bad (should take a lot of charge transfer, current × time, to do that).  If a bulb rapidly drops its voltage, ditto.

There are a couple of points to consider with this question. First, you will need to make sure the PSU is correctly adjusted to the float charge voltage of the 12V battery. SLA should be safe to float charge, but over voltage will damage it over time.
One alternative solution (since powering the heaters will limit your run time) is to detect power failure, cut the heaters immediately, and save state to EEPROM in the firmware. This is the approach taken in the latest Prusa printers, and is a bit more complex, but might turn out to be more reliable.
If the problem you are solving really is brown-outs, then a simpler solution might be to isolate the high current and control sides of the circuit. The MCU will be run from a regulated 5V or 3V3, so a large capacitor (with diode isolation) on that regulator's input would do the trick.

This circuit is correct as it does the job (provides a charge and switch-over when needed).
The only drawback could be that you need to ensure that the battery is sealed as during the charging process the electlorit will slowly evaporate and decrease battery capacity.
I am personally using a UPC as that gives me more options to power-up more stuff including 240V heater and it has a self-test built-in (it is APC1500VA).

Absolutely: use a UPC and you won't have to worry about spikes, voltage "gaps" upon blackout, and as a side benefit you can keep a desktop controller computer (or arduino or whatever) running as well.


text:
Serious safety concerns with living in same room as PLA 3D Printer?
I have an Ender 3 which I primarily use for printing with PLA. I haven't branched out to other materials yet. :)
I've done some research into PLA fumes and airborne particulates which seemed to mention that PLA is mostly safe, but ABS is rather dangerous to print without proper ventilation. However, I understand that there isn't much research on the topic and that there haven't been many studies.
I have been keeping my printer in my bedroom, far isolated from flammable materials, which I sometimes leave on to print while I'm asleep. Should I be concerned with my health safety with respect to airborne particulates emitted by printing with PLA?
Other questions ask about ABS, but here, I'm asking specifically about PLA.

Related Enclosure, things to pay attention to? and Is 3D printing safe for your health?

Good point, @Greenonline, but I'm asking more specifically about PLA. The Ender 3 isn't very well optimized for ABS, and I don't plan on trying to use it anytime soon. The only other filament kinds I'd be trying are PETG and TPU. Otherwise, I'd just use PLA with my printer.

Possible duplicate of Is 3D printing safe for your health?

Even though PLA is plant based, and not full-on chemicals, living/sleeping in any environment with fumes (i.e. particulates) can't be good for you long term. Vaping with VG (vegetable glycerine) is meant to be (relatively) harmless but, as a chain-vaper, I can still feel negative effects to my respiratory and cardio-vascular systems. I would, IMHO, advise against it, without good filtering/ventilation.

Wow how do you manage to sleep with the sound of the printer running?

Fire is the most obvious risk - firmware can now detect some of the more obvious failure modes such as a detached thermistor, but loose or failing connections can still overheat. A smoke alarm is a fairly obvious (but not necessarily effective) protective measure.
The risk from particulates in particular is probably low, but marginal health risks like this are extremely hard to analyse, and will likely take many years to manifest. The closest analogue would be to look at commercial plastics workers since they are exposed to both heated plastic, and any potential dust generated.
You could also compare the risk to other 'hobby' activities such as soldering, painting, woodworking.

Very good points, @Sean Houlihane, but what's your risk assessment?

Risk is your decision. Why would you care what risks I take personally?

"Most" but not all hot ends will not explode if their temp sensor breaks. Firmware usually detects issues such as disconnected thermistor. The only fires I have been aware of were the Flash Forges and electrical fires on the board it self from cheap / bad solder jobs.
I agree that the risk is unknown. I would not say Low. The issue is with fine air particulates, which are known to be bad for your health. Pro labs that work with plastics and such will have industrial fume extractors. Which you can build your own with an inline fan and an enclosure.

@StarWind0 You comment would probably be better as an answer, otherwise it may eventually be deleted.

@StarWind0 Also, some cheap printer firmware has the "Temperature runaway protection" disabled.

Why would you rate a smoke alarm as "not necessarily effective"?

@vwegert "in smoldering fires ionization alarms respond an average of 15 to 50 minutes slower than photoelectric alarms", again, its a judgement call and I want to leave the reader to make their own assessments.

This entire answer is pure conjecture and I am not sure why it was marked as the correct answer.

You are probably pretty safe printing PLA

Regarding emissions, the following recent report, Emissions of Ultrafine Particles and Volatile Organic Compounds
from Commercially Available Desktop Three-Dimensional Printers
with Multiple Filaments, indicates that PLA is a pretty low emitter (1/20th of nylon) and most of what it out-gasses is Lactide which is low on the harm scale.  That said, everybody's nose sees things a bit different and people tolerate smells differently. Note also that we used to think lots of things (like asbestos) were harmless that we know differently now.  Note also in the figure below from the report that all PLAs are not created equal.  Dremel PLA produce way more nasty stuff than FlashForge PLA did.  I am also sure additives, colorant, and fillers can change this a lot as PLA filaments aren't not all PLA.

Regarding the fire safety issue.  Note that there is a BIG difference between a kit and a "product".  Since you are the manufacturer of the printer for a "kit", the packager of the "kit" is not responsible for the fire or electrical certifications of the final product.  This does open the door to some risks.  The biggest risks are electrical safety; but, fire safety can be an issue as well.  I would say that the risk is likely higher to you personally when the printer is NOT in your bedroom as if it catches fire when you are sleeping, you will likely catch the fire faster if it is in your bedroom.
From a practical standpoint, I have heard several people complain that they can't sleep when the printer is printing when the printer is in a separate room.

I have been printing daily for 2 months with PLA and have noticed respiratory problems!  I feel like slight pneumonia symptoms!
I also have very sensitive lungs that react to things that would not bother normal people.

Having asthma, I'm very sensitive to air quality and when i first started 3D printing i quickly noticed a sore throat, feeling out of breath, headaches and well the smell.
One thing many beginners overlook is material oozing out of the extruder in places other than the nozzle itself. This causes a dirty extruder head which 'burns' that material and thus creating a ton of air pollution and a nasty smell.
As a fix, i took my extruder head apart and reassembled it with PTFE tape on all the threads. The oozing and burned smell of material is now completely gone, my initial health issues have also gone away.
This does not take away the fact that ultrafine particles are still being generated, but you will not notice this problem in an acute way. If you print daily use a fume extractor, your lungs cannot clean out this size of particles. The health effects will be similar as living near a busy street or highway.
One last thing few people mention: cleaning up parts. When you file or sand down parts this creates a lot of very fine dust, and since plastics are electrostatic this becomes very hard to clean up. I now use an extraction fan whenever I'm cleaning up a printed part.

Standard manufacturing practices contraindicate leaving a manufacturing device unmonitored while it's on. That being said, your workshop should be well ventilated anyways since you're probably using acetone, isopropyl alcohol, and other substances that you shouldn't inhale.
If you can not move to a well ventilated workshop, consider installing a fume hood or at least a range hood in your current workshop

There are 3D printers certified for "lights out" manufacturing usage.  The Ender 3 isn't one of them (nor are any of the other hobby-level printers).

thanks @Mark, this is important for non-hobbyists in manufacturing to know. Can you share any of them here? What does the certification process involve?

I don't remember the names, I just saw it mentioned in passing in a discussion of fire safety on https://www.reddit.com/r/3Dprinting/

Most "lights off" 3D printer are industrial grade.


text:
Relation between layer height and bond strength
I've seen many references to a FDM print being weakest in the Z axis, due to poor bonding between layers compared to the extruded walls.
Thinking about optimising this for a specific material (excluding temperature and geometry), is there an optimum layer height? It seems obvious that too thick a layer will give less compression and maybe less heat transfer into the layer below (so 0.3 with a 0.4mm nozzle might be expected to be a bit weak). Is there a single break point (i.e. less than half the nozzle is good), or are super fine layers either good or bad?
I'm specifically using PLA at the moment, in case different materials have different behaviour in this respect.
I am not asking how to model the strength of layer bonds or how to take that into account when designing a part.

related https://3dprinting.stackexchange.com/questions/3861

Possible duplicate of FDM layer bonding strength

@CarlWitthoft, that was the related link I posted. That is asking about modelling the layer strength, not optimising it.

If you look closely to how products fail is that fracture starts by initiation at a corner or side defect or a void in the material. If you look closely to the walls you will see many "defects" as FDM just stacks "pancakes". So, how good the bond may be, there are always crack initiation locations. Yes, there is an optimum layer, but leaving temperature out of the equation is not recommended.

@0scar I'm not saying that temperature is not a factor, I'm saying that for this question, I'm only asking about the height (assuming everything else is optimised around this parameter).

My3dmatter.com performed a series of tests with PLA, using "a universal testing machine". They conclude:

Layer height influences the strength of a printed part when it becomes
  thin. A printed part at 0.1mm shows a max stress of only 29MPa, as
  opposed to 35MPa for 0.2mm (21% increase).
Past 0.2mm, the max stress remains fairly constant around 36 MPa (we
  confirmed this conclusion with an extra test at 0.4mm, not shown here
  because it was not part of the same batch).

Note: It is recommended to read the full article to comprehend the complexity of the subject matter.

Almost the exact opposite of my hypothesis.

@SeanHoulihane Well, the values shows the strength of the whole part taking in count the infill and only one temperature and one speed. The bonding is the strenght adhesion of each layer so this need to be measured like a peel off test.To get the better bonding parameter is necesary to do a Desing of Experiments (DOE) but this expample gives at least the best choice at one temperarure and one speed. Could be opossite with diferents parameters. One day I will do the DOE just to assure the best quality on my prints.

Do you have any information about other materials than PLA?  I'd like to know if PETG and polycarbonate follow the same pattern.  In the Prusa3D forum post
https://shop.prusa3d.com/forum/print-tips-archive--f86/polycarbonate-here-s-how-to-print-it-without-warpi-t6919.html#p88164 metacollin reports that PC works best with much thinner layers, such as 0.1mm with 0.5mm nozzle.  If true, this is a counterexample to the rule of 1/2 nozzle diameter.

According to the people of Ultimaker, the best layer height for PLA is 50% of the diameter of the nozzle. They did extensive testing, although they have not, as far as I'm aware, released any research papers or numbers gathered from their testing.
So, if you have a 0.4mm nozzle, keep your layers at 0.2mm height for best bonding, 0.4mm for a 0.8mm nozzle, and so on.
The max ratio possible is 75% of nozzle diameter, though, at this point, your print has the consistency of a spider web. I tried with a 0.4mm nozzle and 0.3mm layer height and nearly crushed the test print when taking it off the print bed. Anything above that and you end up with the dreaded spaghetti plate.
(Note: I own an Ultimaker 3 Extended, thus why I asked them when I was doing some tests.)

could you place a link to where you quote these numbers from?

Added a link to the post by one of the people from Ultimaker stating that 75% of nozzle diameter is the upper limit and they provide profiles at 50%. I don't have links to post where they state that they did extensive testing on their printers because I couldn't find any post that state it specifically, but it's more or less all over the place when people ask them questions.

Thanks for the link: the quality of a post stands and falls with references, especially when saying what someone else has said.

The question is not easy to answer as it would be difficult to give exact print guidelines. This answer from user @typo already shows results of the print height versus the specimen strength (IMHO his answer should be the accepted answer), as taken from this excellent reference at 3DMatter which basically describes the results of a series of experiments. This answer builds upon his answer. In reference to your question, this reference did not optimize the print settings (all specimens are made with the same print settings), so your question is valid.
It is assumed that you imply in your question that all print parameters that effect the inter-layer bond strength needs to be taken into account for the optimization. Many parameters are in play to bond the filament onto the previous layer, amongst these parameters are e.g.:

Print speed
Filament temperature
Print height
Print cooling

All these parameters influence the deposition temperature which in its turn determines the bonding to the previous layer. Not only printer parameters play a role here, but also the properties of the material itself. Between the various brands, and even within a single brand, material variations (e.g. color doping, or different process batches) influence these parameters.
The question states

It seems obvious that too thick a layer will give less compression and maybe less heat transfer into the layer below

Well, this is not so obvious and assumes that compression is the main driver for bonding a layer. However, the larger the layer height, the more filament can be deposited at once with a higher heat capacity (stays hot longer), so potentially this could have a positive influence on the bond (higher temperature, better adhesion).
The print fan cooling parameter could play a very important role here (or even the filament print temperature). In fact, the results of this are already shown by the 3DMatter experiment referenced above. If you keep all print parameters the same except for layer height, the bond strength increases. This implies that in order to get a better bond for low print heights, you should decrease the amount of print-fan cooling flow, or increase the filament print temperature. How much this is should be done in a similar experiment where you lower the cooling air and increase filament print temperature for more specimens (separately) and test again. This is referred to as a design of experiments.
Theoretically, you can make the bond at any layer height just as good provided you optimize the correct parameters. This implies that there is no relation between the print height and the bond strength, it is just a matter of proper setup.
Also, I would not say that poor bonding strength is the cause of failure in Z direction, as FDM deposits layers in between each layer you will have a lot of potential crack initiation locations, this is usually the starting point of the failure. I have seen prints start the failure between the layers, but not continue to crack along the layers, but traversing through the layers meaning that the bonding strength is not that bad after all.

Just adding another datapoint. CNCKitchen has a new video where he analyses this for cross layer and between layer tension. He also references some other research (which is rather inconclusive). He supports the coarse estimate of 'no more than 50% of the nozzle diameter, with performance also dropping at very low layer height.
He found cross layer tension supported more than 2x the layer-to-layer tension (with a typical 3-wall, low infill pattern).

authors: Hášíl Páůďýál


text:
What glues for bonding printed PLA to injection-molded plastic?
I will be creating a small tube styled piece to use as a junction between two pieces of plastic. The idea is to reattach the two pieces and provide strength so they don't break apart again. I plan on using PLA.
My question is, will superglue (cyanoacrylate) work best for this or are there better choices for attaching PLA to hard (injected molded) plastic? The big thing I'm wanting to make sure is if any of these glues will dissolve the PLA and whether some glues might bond better than others.

PLA is a nice one, and gluing has been a topic on some of our most favorite maker's channels. For example Stefan from CNC kitchen (this video) and Joel the 3DPrinting Nerd (this video). Also, in 2022, Tom's 3D ran a test on glues for PLA, PETG and resin prints. Here some information from them together with my own experiences. Most of these glues are not exactly PLA specific by the way and work for many other materials too. Be careful with PLA containing infil though, as that can seriously alter the properties.
Step 0: Safety First!
Some of these methods are working with chemicals that can irritate the skin (resin, cyanoacrylate), have irritating fumes (acetone), or are flammable (acetone). Others (Cyanoacrylate) are not heat-stable and break down into their components under heat.
Use proper protection when working with glue! Eye protection and respiratory protection, as well as gloves, are to be used when necessary. Read the manual of the products you are working with!
Preparations
For most glues, it is advisable to prepare the surface: sand it to increase the surface area, remove grease from fingerprints etc. Follow the manual!
Glues

Cyanoacrylate - yep, the "one kind for all" is a solution for PLA too: Superglue. However, look out for what type you get! Some are clearly better than others, and using an accelerator can change the properties of the glue spot.

Together with talcum powder, CA glue ("superglue") can fill gaps easily. However, a gap-bridging bond isn't the strongest, and working can be finicky. Yet if the parts do sit flush, a CA glue bond can be a almost as strong as any 2-component glue bond tested, according to Tom.
CA is not stable under heating and when heated too much it breaks apart into a rather noxious fume! This can be handy to break metal-CA-metal bonds in machining of small parts but keep this in mind if you want to use inserts or plastic-soler pieces on the same areas! Don't tack with CA in those cases.

Epoxy resin - Epoxy is a favorite for very tough gluing, a few droplets can stick a car to the roof... and it warms up in curing. If you take a slow
curing resin, you can safely use it to glue PLA without the part deforming.

Uncured Resin and their hardeners are strong skin irritants.

2-Component Acrylic resin is just as good as epoxy often, as Tom noticed. It's very comparable to Epoxy in performance.
Urethanes - 2 Component Urethanes offer strong but flexible bonds and work great according to Joel. Their curing process is also exothermic, so take care to not 'cook' your piece.
2-phase Putty - in a similar vein come 2-phase putties like Green Stuff or Miliputt, which harden after mixing. Their heat generation isn't too big and they allow to fill gaps easily. My favorite stuff though is not the expensive modeling putty but the stuff from the home depot: stuff like Pattex Repairsorry, no English site for this or UHU Repair All Powerkitt harden within an hour, are surprisingly cheap and get a smooth surface.
Acetone - We all know that you can smooth and glue ABS with Acetone or an acetone-ABS slurry. Tom (Thomas Sanladerer) made a few experiments with it. He discovered that it works for at least some types of PLA in the following fashion: apply some acetone to a spot and press the second piece (that also was prepared this way) to it and they might melt themselves together after some time.

Effectivity of this depends very highly on the exact PLA you got.
Acetone is highly flammable.

There's a type of glues commonly called "Kraftkleber" or "Alleskleber" in Germany, for example, UHU Hart or Pattex KraftkleberGerman. While they often stick to PLA, I personally don't like their gluing power and find them often quite messy to work with. Also, they very much fail in loadbearing joints.
Wood Glue - Yes, Wood Glue. PVA Wood glue as well as its non-water-soluble cousin ("Express") have proven themselves to me as a rather nice surface coating to smooth over print lines as well as a good solution to affix paper and wood to prints. It is less of a solution for plastic-plastic bonds but works OK-ish.

Glue? Why glue?!
"Solder"
What better way is there to combine parts than welding or soldering?! Often none. My personal all-time-favorite PLA glue is PLA itself, by using it as PLA solder. This method also works for most other filament types, but is not advisable for ABS and other plastics that emit fumes without wearing respiratory protection! In any case, you need to work with an exhaust, as you heat your plastic in a not always fully controllable way. If you can, use a soldering station where you can set the temperature of the iron.

Take the pieces and make sure on both sides is a cavity that can be filled.
Take a soldering iron and set it to around 200°C.
Take a length of PLA filament.
Melt the filament with the soldering iron and use it as solder when combining the two pieces. Make sure that at least some filament gets into the cavities and sticks there - it can help to stick the soldering iron into the goop in there to force it to merge with the infill/walls and press together to hot PLA goop filled pieces against the iron before pulling it away, pressing the pieces together.
As the PLA cools and hardens, the joint is usually tougher than the actual layer boundaries.

Pen
Instead of using a soldering iron, one might also use a 3D printing penOne that eats filament, not one for PCL or some gel!, but I don't like those personally.
Inserts!
On a different note, a soldering iron is also a very good solution to make inserts into PLA - heat up the metal insert (like a nut) and press it into an undersized hole, and it will mold the plastic around itself into a perfect fit without any glue.
Friction Welding
An alternative to using direct heat from a soldering iron is friction welding. For this, take a rotary power tool and some filament. Insert the filament into the tool, tighten and cut so that about an inch is reaching out of the claw. Turn it on at medium speed, about 800 to 1200 RPM. Now, once you press the tip of the spinning filament against other PLA it gets hot and melts, creating a welding seam. Joel has a good explanation.

Welding is best, but it can be tricky to melt the part enough to merge with the "solder" but not deform or damage the part.

Consider using 3d pen instead of soldering iron. They are pretty cheap these days. Here is a nice list: https://all3dp.com/1/best-3d-pen-reviews-price-3d-pens-buy-3d-printing-pen/  I like 3D simo Mini 2 a lot.

Here's a video about using a superglue, urethane adhesive from BJB Enterprises, as well as 5 minute epoxy to glue 3d printed parts together: https://www.youtube.com/watch?v=s1q2D_pK0BE

I haven't had much luck softening PLA with Acetone.   I like the "wheel of creation" aspect of using filament as plastic welding rod, since the first filament I knew of was made to be plastic welding rod.

Wouldn't methylene chloride also work? :-)

@R.. I have no experience with CH3Cl

I have a concern about Superglue (Cyanoacrylates). Its bloody awful stuff that can go everywhere and sticks to everything. That what makes it so great - however - I have made the mistake of solder-welding a previously Superglued joint. The ensuing hissing cloud of CA steam was so nasty it took weeks to recover. Be careful. I still use Superglue but keep the glue away from the edges is I typically use my trusty Pyro Art Soldering iron (set at 120-150 °C) to sculpt the joins.

@PhilShearer read Step 0 again: Safety first.

Yes Super Glue is best choice.
I personally use it in many PLA projects.
I even apply Super Glue layer to ABS prints to avoid layer separation.
It works well with both ABS and PLA, but exercise some caution whilst using Super Glue because it produces very bad tear gas. Use it in a well ventilated area.

SuperGlues are not really any more dangerous than paints you'd use to paint your walls.  I agree you shouldn't "huff" them, but that's about it.

the dangers of superglues depend a lot on what acrylate one gets and what it its solvent.

I’ve used starbond medium glue on my 3D prints with the accelerator and it dries rock hard in 30 seconds. I would recommend that if your looking for a quick drying method. Here’s a link to show what I’m talking about. https://youtu.be/uI5bwvYwcyM

I used to work at a small thermoforming plastics enclosure company and we used “weld-on” for basically ANYTHING. Delrin and medical grade plastics not included but, PC, PE, acrylic, PETG, etc. use "weld-on number 3" for more easy bond plastic, "number 4" for more crystalline/harder to bond plastics.

PLA Gloop is dedicated glue for PLA. It contains chloroform, so be careful.

3D Gloop! // 3D Printing Adhesive Spotlight
PLA Smoothing 3D Prints with 3D Gloop!

Additionally a PrusaPrinters guide: The Great Guide to Gluing and Assembling 3D Prints


text:
What special considerations must be taken when designing parts for 3D printing?
What are the 'headline' basic design rules for FDM?
Which topics for design principles do you recommend to someone who has purchased an FDM machine and wants to understand what is practical?  In other words, where is the place to start when you don't yet know what questions to ask?
This question and its answer discuss design tools and the workflow but doesn't cover design rules.
Design rules here meaning the principles of what is special about planning a design to be manufactured with an FDM process as opposed to traditional machining or a printing process like SLA, not the detailed/automated checks that would be applied to something like a PCB layout prior to sign-off.

A google search reveals this link 3D Hubs - How to design parts for FDM 3D Printing. Or is your specific question more specific than this?

Seems to be a question like asking for the rules to play with toys. But the questions appears when you have something to do, so you can ask a question for an specific topic.

@ifconfig I should probably move this to meta (somehow).  This question came from reading the purpose of the group, including an encouragement to ask questions to which answers were known, but not answered in 3dprinting.SE.   After some thought, I constructed this questions because:  1) it took me some time to understand these problems, 2) friends with 3d printers have asked this of me and my answers were not as cogent and compact as I wanted, and 3) I thought it likely that someone else here would have an answer readily available.  From the comments and the downvotes, I see that I failed...

@ifconfig What would have improved this question, been consistent with the goals of 3dprinting.SE, and helped put into the record information that I've seen as needed.     And, yes, I have looked for a primer.  The link you provided is very good, and had I found it I would have been referring other to read it.  It could be better is some rules of thumb were included, so that not only the problems were described, but some general values that will usually work were included.

@Greenonline I think meta is appropriate.  I'll ask the meta-question on meta.

@Trish  I see your edits, which are particularly good in that you define what I meant by "design rules".  Perhaps I've been too deep for too long in the engineering swamp to know the smell of fresh air.  What I had hoped to find was a short list of "do this not that" I could refer people to .  Is there a place for discussion and editing where we could develop such a list?

@cmm Do we have a chatroom? Yes we do! Please join us!

Designing a part for 3D printing often doesn't seem to have many special considerations, but I have learned the hard way, that there are some things to do differently. This is just a list of things to that one should keep in mind in addition to basic principles of design1 when designing parts, keeping the subsequently slicing the parts in mind too:
Print orientation
There are many ways how you could orient your print, but usually, there is one orientation, that has the least need for support. Look at your part critically and keep this orientation in mind when designing. Especially look at overhangs and bridging, and if you can get away without.
Overhangs
There are 3 sorts of overhangs:

Small overhangs ones that are neglectable.
Long overhangs which can get support.
Overhangs that can't be supported.

When designing parts, you want to make sure you only have type 1 and 2 Overhangs, as type 3 overhangs will sag and fail. Think carefully if you can rotate the piece to get a print orientation that does not need an overhang that can't be supported by an automatically generated support structure. If that is impossible, try to implement a sacrificial piece that can turn the overhang into a bridge.
Smaller overhangs can be made neglectable by adding a phase to the underside. This phase's angle is depending on the printer. In my experience, 70° is something many printers can manage, but I prefer 45° due to the ease of making them. A fuller can work to give a small overhang the needed support, but often has problems for larger overhangs!
Bridges
Overhangs turn into bridges if they are connected on both sides. These either have a limited length, depending on the printer you use or need a support in the center. Check if you really need a bridge or if you can rotate the piece to get away without.
Avoid vertical holes in bridges
It might be something that might surprise but a vertical hole or slot in a bridging part is something that often fails as the bridging strings just sag as they are terminated mid-air without a support structure and finally fall, ruining the bridge. Yet such a support structure sometimes could not be removed in all cases, so something needs to be done differently.
One such a solution is to add a 1-layer sacrificial layer on the bottom of the hole: printing a solid layer by bridging is possible, and the subsequent hole/slot can still be free. It has to be cut free after printing in post-processing though.
round holes in Walls
Round holes in standing walls can become problematic to print once the diameter gets too large. A trick to keep the upper parts of the hole to sag into the cavity, making it undersized or needing to drill it to size later. To prevent this, the upper side of the hole can be adjusted: instead of a round upper rim, turn the hole into a teardrop. This reduces the overhanging area. Keeping a 60° top angle on the hole should be fine.
If the hole is used to key an item to an axle, put the keyway to the top of the print orientation, so it takes the place of the teardrop-tip.
Some more about holes one can learn from Makers Muse (Angus Daveson)
Reduce internal structure
I have seen prints fail for strange reasons. One of them was a piece taken from a straight up industrial design plan, then scaled down. This one resulted in too much tiny internal geometry, resulting in a lot of material and time wasted on printing these internal pieces that nobody could reach, that were fused together for the original gaps were already 0.2mm and less and besides that, there was the occasional print failure.
Removing any non-essential internal geometry lessens not only the printer's load, but speeds up the print, lessens the material waste and can prevent failures due to clogs or other unexpected behavior. If you can't fix it in design, there are workarounds, but try to need to avoid them!
Avoid Intersecting Shells
As we are at it, often game and graphic designers are lazy and use intersecting shells. These can become quite messy in the slicing step. If possible, try to avoid intersecting shells, even as modern slicers have learned to fix this by themselves by now. The results of that are not always pretty if you forget to flag the "Union intersecting shells" option in your slicer.
Sizing
We might not always be aware of it, but prints do shrink in the XY axis and to a different degree in the Z axis as they cool, during and after the print is done. This is what causes warping in the first place and lead to many lost prints (especially on non-heated beds). This behavior has to be taken into consideration especially when designing bores. My suggestion for this is twofold:

Intentionally design the hole to be too small and add extra wall material in slicing, then drill it up to the right diameter. Drill slowly to not melt the plastic.
Learn your shrinking parameter for the material and design with that shrinkage in mind, possibly iterating the print a few times. Note that different spools/colors of the same material might have different shrinking!

Minimum Wall Thickness
Without Arachne, a 3D-printer can not reliably print walls that are thinner than the extrusion width of a printer. The choice of the correct nozzle for an extrusion width is a question upon itself.. Even with Arachne slicing and variable line width, printing a wall thinner than a nozzle diameter is nigh impossible.
Tapping/Screwing/Inserts
For tapping prints directly, you need wall thickness - according to the norms - you'll need usually about 0.2mm diameter that can be tapped into for smaller standard-size threads. Using 3 perimeters with a 0.45 mm extrusion width will give walls of 1.2 mm, which I consider a rather strong wall, and provides quite some tolerance to drill up to size and then tapping screws into. You will get away with 2 perimeters for smaller thread sizes (M3 and lower), but for large ones (M10+), you will want a fourth or even fifth perimeter.
Remember though, that the printed PLA is not good for very strong threading: Tapping prints directly is pretty much only for low- and non-load-bearing connections. If you combine several pieces with screws, try to design the parts to make some sort of compression fit using a bolt and nut, or use several, small diameter screws with a fine thread. Avoid coarse thread if you can, stay on the small side.
If you need a load bearing connection with screws, the best strength comes from using a metal insert or provide a space for a nut to fit into. Metal inserts are usually placed by heat-setting them: put the heat-set insert onto a soldering iron tip and push it into the slightly under-sized hole, melting and molding the print to fit the insert, providing strong threads that are held really good in the shell of remolded plastic.
As a compromise, modern slicers allow to use modifier meshes, that could be used to increase the strength of modeled threads or holes that need to be tapped.
Do you want to know more? CNC Kitchen (Stefan) had made some tests on the strength of these connection type.
Print strength
Keep these general rules in mind when designing load-bearing parts:
Generally speaking, FDM prints are strongest in carrying along their Z-axis when withstanding compressive forces, as then the print layers of the shell are forced against each other. It also excels at fighting bending forces this way. But this orientation is also giving us the lowest tensile strength, as each layer boundary is a possible breaking point.
The XY-plane usually excels in tensile strength but sacrifices some of its ability to withstand compression (it is not proportional though).
Printing a part at a 45° angle will give often a great compromise of strengths, but might need an additional surface to get a good first layer - this surface can be sacrificial with the use of support.
For deeper information on the strength of parts and materials in comparison and how to manipulate it, there are large playlists of tests made by CNC Kitchen (Stefan) and Thomas Sanladerer (Tom)
Post processing
Post processing can be your best friend when printing, just as it can be your worst nightmare. I won't detail all methods of postprocessing, but some that are quite applicable.
Assembly/Gluing
Remember to design your parts with gaps for the glue when designing parts for assembly, and you might want to include guidance notches/cones or other alignment features to make sure the assembly aligns. This is especially needed as the parts shrink a little and have a rough surface.
If you need to assemble your part due to the available print volume, be especially sure to include ways to key the parts together. Pegs or outcroppings/indents (often called keys) that match up to one another make alignment on assembly much easier too, and are a different type of alignment feature. It can be a good idea to design yourself a "cookie cutter" file that is applied after designing the part that automatically includes the glue gaps and keys.
There are a lot of glues and other methods to merge the parts. A more in-depth look at some of them is What glues for bonding printed PLA to injection-molded plastic? but you will have to keep in mind how you want to combine your pieces in the design step - and account for it.
Print in Place/PIP
In this vein, learn the tolerances your printer can manage to allow print-in-place(PIP), allowing functional parts that require no assembly. PIP is something that isn't possible with subtractive manufacturing usually, but remember that in 3D printing you might need to break the parts free after printing from bridges or sagging. Usually, a single strong turn suffices. To be able to do this, you might want to include a position for an Allen-key to manually turn the parts.
To learn how fine your tolerances are, there are many tolerance gauges/tests around. A rule of thumb for many printers is, that 1 nozzle width is often easily achievable with a good setup, 0.5 nozzles are achievable with some effort and 0.25 is somewhere close to the 'holy grail' - you might want to change the nozzle to a smaller one in case you want to have very thin gaps.
Composite construction
There are ways to turn your (mostly) hollow prints into much stiffer versions of themselves by turning them into composites, for example by using a resin or a different hardening fluid (like foam or plaster) as a filler or coating material.
When planning to do so, remember to include inlets/outlets for it and the air. It can be a good idea to design the part in such a way that it just contains the walls and a pre-planned support structure. In doing so, remember to disable infill in the slicer to enforce the flow you want in your structure. Look at how the ribs inside of an airframe are designed for general rules on hollow parts: include holes. This allows the flow of your fluid into each and every corner instead of blocking the flow. This can also reduce the needed number of inlets and outlets from one per chamber to one per part.
Plastic Properties
Remember we work with thermoplastics. Learn what kind of postprocessing your thermoplastic allows and its mechanical properties. Some examples:

APS can be vapor smoothed with acetone.
Many plastics can be annealed by baking at or little above their glass transition temperature, increasing strength and layer-to-layer bonding.
When using power tools on plastic, use ample cooling and time, as otherwise, one quickly melts the prints!

Surface Finish
The surface of FDM prints is somewhat rough. To smooth it out there are 2 general ways: fill it up or smooth it down. If you want to fill it up, design the part undersized, if you smooth it down, add sacrificial thickness. It is common to combine both, adding body filler first, then sanding down till the print material shows through again. If doing this, make sure to check your sizing.
If there comes a lacquer layer atop, remember to account for that thickness: undersize surfaces, oversize holes!

1 - this means, that thoughts about postprocessing that are not unique to 3D printing are not elaborated on here. Examples are painting, coating or smoothing the surface mechanically.

Further reading/viewing
Further information can be gotten from these playlists, though they aim at times for newbies:

CNC Kitchen (Stefan): 3D Printing for Engineers Playlist
CNC Kitchen (Stefan): 3D Printing Tips
Maker's Muse (Angus): 3D Printint 101
Maker's Muse (Angus): Advanced 3D Printing Tips
Maker's Muse (Angus): CAD for Newbies
Maker's Muse (Angus): CAD for 3D Printing

A very helpful summary which I will pass on to others.  Do you jave guidance on wall thickness for box-like structures?  Design parameters for making holes tappable for screws, or the types of screws to use?  Any surprises you've found for what else to do or avoid?

For post processing, a part tumbler will smooth any 3d printed part.

As you correctly state, if you don't take into account the effect of post processing (e.g. painting) on how it will affect the fit or surface of the final part then you'll be doing revision upon revision trying to figure out how to get it correct. For example, you may have to oversize a hole to account for two layers of spray paint that you'll have to put on it in the end.

@user77232 that type of Post processing is not a special consideration that you take only for 3D printing as is the question here - the most part of post-processing is something that you have to take for any manufactured goods. Like paint.

@cmm as you were very interested in the screwing: Stefan recently did tests on this!

In a presentation(pdf) that I've used as an introduction to 3D printing, I listed out the following points:

Structures have to be built-up from the build platform, with only about 45° overhang (or small flat bridges).

supports can be added (generally automatically), but results can be variable.
changing the print orientation can solve overhand problems.

Infill is used partly to provide additional strength, and partly to support any roof parts. Generally a print will not be solid.
Small parts in particular may need a brim to help with bed adhesion.
Designs must be 'manifold' to be printable. Arguably this is part of the workflow, but it can be the cause of non-obvious failures.

The other detail worth calling out is the precision of what can be printed with FDM, although the best case resolution is ~0.1mm, the overall accuracy will be closer to the nozzle diameter due to the way that extruded filament is squashed during the print.

depending on printer, the achievable overhang can be up to 70°, with thicker nozzles even a little more. 45° is the safe side, 60° is the you go into dangerous territory

Overhang angle is a function of layer height to nozzle width ratio. If layer height is half the nozzle width, a 45° overhang overlaps halfway with the previous layer line. If layer height is 1/4 nozzle width, a 63° overhang overlaps halfway with previous layer line.


text:
Customized Ultimaker 1: Extruder motor does not move
I recently upgraded my Ultimaker 1. The upgrade includes a different stepper motor for the Extruder, the same a Ultimaker 2+ would use. I plugged the new motor and nothing happened.
To eliminate the problem I ordered a new PCB and stepper motor drivers, reassembled all electronics. For some reason the extruder does not move, and actually any other motor I plug into the extruder port doesn't either. I switched the driver, twice, but without a different result.
Can anybody tell me what component could be faulty or how I can find the problem? Could it be the Arduino board, even when I use the Ulticontroller? Maybe remove one of the jumpers next to the driver?

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

That was actually the problem, and the Arduino being toast. Thanks!


text:
Replacing bearings with Drylin bushings
When I purchased my China made Anet A8 printer, it came with the ball bearing style linear bearings for the 8mm guide rods. While pulling parts out of the box and putting them together, I noticed several of the small ball bearings fell out of their respective holders. At the time, I really didn't know what to think of it (ie: were these just extra ball bearings falling out; were they actually needed). I put the printer together anyway and it seems to work okay.
I have noticed while I've been printing, there's a lot of noise during travel of the pieces. I'm not exactly sure where the noise is coming from, but realize it has to be coming from one or more of the bearings. To hopefully fix the issue, I've purchased some Igus Drylin polymer bushings to replace the linear bearings:

My questions are:

When installing these bushings, should they be completely dry?
Should I at least clean the rods?
Are they completely maintenance free?
Anything else I'm not thinking of to worry about?

What was the exact model number of the bushing? RJM-01?  RJ4JP-01? Or something else?

The ones I bought are shown as RJ4JP-01-08 on Amazon.com.

According to igus commercial documentation, these bushings:

do not need any kind of lubrication,
are not susceptible to humidity (but your steel rods might)
work seamlessly in presence of dust (it gets expelled from the bushing with movements)

I've replaced all of my bearings with these, and in my experience, the above claims have been true so far. I must say that I am really pleased with them. Movement is smoother, and the noise is considerably lower.
I did clean the rods to remove any trace of lubrication prior to installing them. I did not dry them.
I believe that igus is also selling rods in a material designed to even further improve the qualities of these bushings, but it starts to become quite an investment.

one should note, that bushings of this type are possibly "self lubricating" as in the plastic will get eaten away with wear.

@Trish - They don't self lubricate, they are lubrication free. An analogy would be a hard wearing, non-stick surface such as Teflon. As there is minimal wear, their life expectancy is greater than that of traditional bearings. There is an online life expectancy calculator.

In addition to this answer and addressing Anything else I'm not thinking of to worry about? I would like to add that you should take care in installing the plastic bearings in suitable housings. It is best to lower the mass of the carriages by replacing the blocks and the bearings, there are a lot of printable bearing housings to find on the internet (e.g. Thingiverse). When installing plastic bearings, it is quite easy to get problems with bearings that bind, so take care when you install them and make sure the bearings do not bind (before you re-install the belt).

I found when installing them, to leave everything loose (mounting screws) until the rods were completely back into place. This pretty much prevented binding. Yes, I was worried about that as well.

That is exactly how to mount them properly!