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Has anyone had success printing PMMA filament using Lulzbot products?
The title of this post more or less says it all.
I am having a heck of a time getting PMMA (polymethyl methacrylate) to print on my Lulzbot Mini 2 (which uses all of the standard/default attachments). Lulzbot offers a demo-STL file (called the "Rocktopus" - found here: https://www.lulzbot.com/content/meet-rocktopus) that is used to evaluate whether or not the printer+filament are behaving as intended. Thus far, I have had no luck with its print.
Layer separation consistently appears to occur at various levels:

sometimes at the interface between the first layer of deposited PMMA (i.e. the first layer of the raft)

sometimes at intermediate layers above the raft (i.e. mid-layers of the Rocktopus)

I have scoured the internet trying to find parameter recommendations (e.g. https://onlinelibrary.wiley.com/doi/full/10.1002/mame.201900263) in order to arrive at successful prints. I have tried several different combinations of bed temperature, extruder/nozzle temperature, layer height, travel speed, etc based on the few articles I have come across: no luck.
I have seen a few recommendations buried on forums to get a heat enclosure cage, but these were not specific to the lulzbot 3d printing line. The heat enclosures are a $200+, so I was hoping I could I find someone on here that could confirm the necessity of this accessory product before I shell out the moneys.
My mini is paired with the most up to date version of Cura Lulzbot (edition 3.6.23).
Any assistance is greatly appreciated! Cheers~

From what I’ve read, PMMA/acrylic shrinks a lot as it cools, like ABS, which translates to warping and layer separation if you don’t have a heated enclosure. The key to printing high shrink materials is getting the ambient temperature up closer to the glass temperature of the plastic, in this case 100-120C. Poly Carbonate is known to have similar challenges. You can always outsource and order some parts made on an industrial printer, rather than diving into elaborate modifications.
Here’s a video of this guy’s adventure in chamber building to print PC: https://youtu.be/79r5D9nCQfM

I was experiencing similar issues on my Raise3D Pro2Plus. I've printed near 20 small cylinders to try and fine-tune the settings to get densities that are close to the theoretical density and right now am sitting comfortably around 80 %. Here is what I've found

Temperature of the build plate and extruder have had a large effect on the quality of the print (obviously), to the point where 3-4 ° have a noticeable effect on print quality. I have settled on an extruder temperature of 252 °C and a bed temperature of 82 °C. I also print in an enclosure which I imagine is necessary due to the shrinkage seen in PMMA.
A lot of my problems were with bed adhesion. The Buildtak that came on the Raise3D worked for a while but the higher temperatures eventually caused the adhesive to fail and bubble up where I was trying to print. Blue tape and purple glue stick worked sometimes but would often detach halfway through the raft. What I've found that works reliably is Kapton tape covered in a purple glue stick. This has yet to fail me and the only downside is that I often have to reapply the Kapton after every 2 or so prints which is a small price to pay for me as my regular prints take 3-4 days.

Just for reference, I print at 30 mm/s, 1 mm nozzle, 0.29 mm layer height. I definitely get your frustration on trying to find a good resource for settings. Most I could find were generic ranges for temperatures and speeds.

Appreciate the input. What company do you purchase your PMMA from? Right now, I purchase from Push Plastic. Perhaps you use a different one. Cheers~

I use push plastics as well. I regularly print in larger formats so I need the 3 kg spools they provide. I believe I mis-spoke earlier, my print speed is 25 mm/s not 30. Just noticed it when I went to print something this morning.

I'm unfamiliar with the Raise3D Pro2Plus. Is it compatible with 2.85 mm filament or 1.75mm? (i.e. is your Push Plastics filament 2.85 mm or 1.75 mm)


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Colour transfer to resin
Is it possible to perform a colour transfer from paper/transparency film to printed resin?
From what I understand there is some sort of transfer process for resin, but I don't quite understand if this works for 3D printed resins.

As shown in the second video, the resin is used to coat a surface. The resin is clear, or appropriately tinted to provide for a visually pleasing background to the transfer. The transparency is printed on an inkjet printer which embeds the ink into a surface designed to accept the ink, rather than allowing it to bead up, as in the first video.
When the transparency is applied to the wet resin surface and the resin is allowed to cure, the specially formulated transparency surface is transferred to the resin surface, akin to gluing the entire image, using the backing of the transparency "paper" as the carrier. Once cured, the backing peels off, leaving the image.
There is no analogy to resin 3D printing. If you 3D print a resin model that has a suitable flat surface, you could certainly apply the same types of resin shown in the video and duplicate that process. If the surface was not flat, you'll have irregularities in the transparency which will prevent the image from being transferred.
I can't envision how the inkjet image could be transferred during the 3D resin printing process, as the transparency film would interfere with the bonding of the resin to the build plate or the vat surface.

source: Stack Exchange

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

sort: votes


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Weedo Tina2/Monoprice Cadet auto bed leveling: Sensor not moving down to touch the print bed
So I bought this printer three days ago as a way to dip my toes into the 3D printing world, and it was working great at first. But at some point, the ABL procedure started behaving oddly: Instead of moving down to touch each corner of the printing bed, it's now only doing so for one corner, then moving to the next, but instead of going down, it goes up. It then continues to the third corner, stops, and moves up again. After that, it returns back to home position. The result is that the extruder hovers way above where it's supposed to be --or alternatively bumps into the printing bed when it's near the origin corner-- thinking it's adjusting for some nonexistent slant, dripping filament all over the place.
The gantry itself is totally level, and I can't see any mechanical faults. As far as I can tell, there's no way to manually level the bed, the only option is to use ABL.
I found out that the Monoprice Cadet printer is the exact same one as the Tina2, so if anyone has experience with that printer in particular, it'll apply here too.

This question is attracting a lot of "Me too" answers lately (apparently becomming a common issue), enough for the community bot to automatically protect the question from low rep. users to answer the question. If you (@stale_mud)) have found an answer by now, please add this yourself, if impossible to answer yourself as in prohibited by the protection, please reply to this comment using my name with an @ in front, I can unprotect the question.

This is a community wiki answer from an answer on Reddit - Monoprice Cadet auto-leveling question, for those who stumble upon this question:

Then I tried their text chat support and the response was basically:
"It is a bad level sensor, which we've never heard of happening to a 3 month old printer and is very rare in general. You are under warranty so here's a preprinted return shipping label, and we'll send you a new printer once we receive your busted one."

From the many "me too" answers, this appears to be a genuine issue rather than a "one-off" issue...

According to the manufacturer's page for the Weedo Tina 2, the bed sensor for the ABL is magnetic -- which means that if you've removed the magnetic build surface you likely have removed the printer's ability to sense the bed height.  You most likely need to replace the worn out magnetic build surface for the (mandatory) ABL to work.
Weedo ought to sell replacements for a part that wears out, but if not, you can buy one made for the Ender 3 (and cut it down to fit) on Amazon (very reasonably priced, too) and have it in your hands in a couple days, though I have no way to know the original didn't have specific poles in particular locations on the sheet.  You'll likely need to remove the base sheet from the Tina 2, if there is one, so as to follow the instructions on the Creality and ensure the upper, removable, flexible sheet actually sticks to the adhesive-backed lower sheet.

The magnetic build surface is still there: I only removed the adhesive paper on top of it, and the magnetic surface itself is fine, it's only three days old as well.

For the magnetic build surface I'm familiar with (on my Ender 3) the texture layer isn't separable from the upper of the two magnetic sheets, and I don't know that I could print on it without the textured surface, anyway.

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


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Converting a 2D black and white image to a 3D model for printing on Linux
Windows has its 3D Builder software which upon importing an image, converts it to a heightmap of the image, aka turning it to a 3D model that can be saved as an stl.
Does Linux have software with similar properties that takes a black and white image and turning it into a 3D heightmap model?

OpenSCAD is linux compatible, free software. There are a number of facilities to permit heightmap to 3D conversion. The results of "lithophane OpenSCAD" returns many options, and it's difficult to narrow down to the "best" choice, as it's a matter of one's skill set/level of understanding. This would be an answer, but I feel it's incomplete without providing results of the search. "Heightmap OpenSCAD" is another useful search set.

The OpenSCAD surface function will do this.  You can feed it a greyscale image or a textfile containing a matrix.  Documentation and examples can be found at https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Other_Language_Features#Surface
OpenSCAD is a cross platform free open source cad package.

Cura will import a picture and use it as a heightmap to build a 3d object.
There are a few options available when importing :
You can even export back the data as STL if you need to process the mesh. Here is the mesh exported in STL, opened in SideFX Houdini:

FreeCAD can import JPG (and IIRC TIFF and PNG as well) image files and produce a lithophane type height-map based on the brightness of each pixel.  I'd be rather surprised if other 3D CAD software aimed at the 3D printing user base couldn't do the same.  Most of the common free-to-use 3D CAD packages have Linux versions; FreeCAD certainly does (I use it on Kubuntu 20.04, and it should work on any recent version of any flavor of Debian-based Linux, if your hardware meets it requirements).


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Can you reuse servo pins on MKS Gen L?
I need to find enough spare pins to add two extra motor drivers for my big printer build. I am using two motors for the Y and three for Z, I can use the E1 for one of them because I won't be using a second extruder.
I need to find six pins to get two external drivers working. I know the MKS Gen L has 3 servo ports, but one will be going to my BLTouch. Can I reuse the other ports? What other ports can I use for adding extra motor drivers?
I know it also has AUX ports as well but I don't know if they are being using by somthing else.

Have a look at the boards pinout:

You'll need 3 pins for each additional driver - enable, step, and dir.
The AUX-2 connector should give your 8 GPIO pins for that, without losing other functionality like the display.
You might also be able to wire your Y axis motors in series, saving one stepper driver. You could then use E1 and three of the four servo pins for the 2nd and 3rd Z axis stepper drivers.

I need the Y motors to move independently so I can have a homing switch on each side. It's a very long bed so dual Y homing is needed to prevent racking

Alright, sounds reasonable. A belt isn't an option either, to keep them in sync?
You could also look at more modern boards like the Fysetc Spider or BTT Octopus, which would have sufficient motor drivers slots for your project.


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Diagonal sawtooth-looking print issue
I got this surface error in my prints using an Ender 5 with BLTouch.

My printer prints a lot and is quite old.
Is it possible that the steppers are done?

Huh! That’s a new one. I can’t see from the picture, but from the top, are the ridges like a zig zag, or are they bulges? Zig zag would be a problem in the XY motion, bulges would be a problem with the extruder or the Z motion, like if the hotend is bouncing up and down.

Hi, sometime the nozzle rattles over the print. Maybe it is a problem with the z steps.

:/ missing force while extruding. Too hot the extruder...


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Up! mini raft sticking to prints
I have an UP! mini and I am using the UP Studio and ABS 1.75 mm.
My prints are always stuck to the rafts and are impossible to remove without destroying the print.
I've had a look at the settings on the Up Studio but I don't know which ones to change to improve the situation.

Normally, the print is made to separate easily from the raft by minimizing layer adhesion between the first layer of the actual part and the last layer of the raft.
If this isn't happening with your prints, you likely need to adjust some settings in your slicer.  You need to ensure that the first part layer is more than a normal layer height above the top raft layer (in Cura Slicer, I believe this would be the First Layer Thickness); this should be comparable to the Z distance allowance for supports to be removable.  You may also want or need to adjust the line width and temperature for the first part layer -- too wide a line may stick too well, and if the first layer is too hot, the same will occur.
It may require several test prints to find just the right settings, though I'd start with resetting your slicer to its default for the printer and materials you're using, and start any adjustments from that base.

There doesn't seem to be much documentation on that particular proprietary software, but in conventional slicers, the setting you are looking for is called the "raft air gap". This should be a distance value slightly higher than your regular layer height.
So if printing with 0.2 mm layer height, do 0.28 mm or something of the sort. Check to see if your UP studio slicer has advanced settings and find something along those lines.


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Metal watches 3D printing
I have noticed major watches watch brands do not seem to offer manuals to 3D print your own parts.
Is there a reason for this?
I would assume in this day and age, with watch repair a dying profession, transitioning parts to 3D printing would be a logical next step (notice luxury watches are still very popular but also fluctuating).
I have found minimal information on 3D printing watches.  Maybe there is another name for this science and it's not typically fit for 3D printing?  It appears some purists aren't into 3D printing.  So it appears watch parts are machined except for the small parts.

Maybe printing plastic watch bands would be practical.

The way you manufacture a part has enormous effects on how the mechanism around it is designed. In a complex enough mechanism you can't just replace any milled part with a 3D printed one.
Furthermore, the answer to your question is already partly in the article you linked:

... the technology is not mature enough for production.
(Tino Bobe)

I guess the watch casing would be the only part that could be possible or reasonable to 3D-print today but would have a distinctly different look than the original, which makes it not desirable.

I would imagine that the main reason that "major watch brands" don't offer free models is so that they don't put themselves out of business. The same goes for car brands and most, if not all, other commercial products. After sales parts and repairs can be a significant revenue earner, and if free DIY repair solutions were provided then that revenue stream would be lost. Not to mention the probable voiding of any warranties, when the owner opens the watch up, in order to attempt the repair themselves.
Off the top of my head, I can't think of any commercial enterprise that offers free 3D models for parts, unless they have gone out of business (and not bought out by another company) and the plans have been kindly made open-source. I came across an example of this recently, via some obscure youtube video, which was an obsolete, yet well-known, computer hardware manufacturer who had made their blueprints available (circuit diagrams, source code, etc.).
Also, it would require a considerable amount of additional work, by the manufacturer, for all of the individual watch parts to be separately modelled accurately (into a printable 3D file format), and just would not be profitable (nor practical, given issue of accuracy raised by the answer by Tillex72). In addition, and I'm guessing here and will probably be proved to be incorrect, I'd imagine that the pool of watch enthusiasts that have a 3D printer is quite small - so the target audience wouldn't be large enough to generate the demand to make it worthwhile, even if the files were made available for a considerable fee.


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Did I fry my Ender 3 V2 Main Board?
I was replacing the nozzle on my E3D V6 clone and the hotend started turning so I held onto it with pliers while I tightened it.
As I did this, the positive wire of the fan that clips onto the E3D V6 melted on the hotend and threw a spark. At this point, the extruder started running so I hit the power switch then unplugged the main cord.
I checked everything to see what caused it, then turned it back on once I figured out what happened and made sure everything was good. Now when it's powered on, it seems like it's still getting power; the BLTouch turns on but the screen doesn't show anything just the backlighting.
Did I fry my board?

The first warning on printer controller boards is to never unplug stepper cables when powered. Please look at Why does (dis)connecting a stepper motor while powered on damage the driver?.

I actually ment the main power cord, not the extruder motor. I also hit the off switch then pulled the cord. Sorry for the confusion, I'll edit that.

Ok I will. I think I actually missed the cutoff to get it today. When I was ordering it there was a few seconds left to be able to get it next day and I was literally like a second late. I checked the email and it said I'd receive it by Tuesday. I dont see why they wouldn't ship it for being a second late if they had other orders to send out though.

Ok I got the new board installed and Jyers Firmware on it. Everything is working correctly except the nozzle temperature. It says zero and wont heat up. That means I fried my thermistor wire, right? Another thing I noticed that I didnt see before is the x y z coordinates flash with a question mark. At first it was no numbers just the flashing question mark then after I homed everything after a few minutes it will flash to the question mark but back to the numbers.

Question marks are not a problem. You need to replace the thermistor.

I replaced the thermistor and the other wire on the hotend and I'm back in business. The whole thing that started this was I went to change filiment and I couldn't pull it out when heated up so I took the nozzle off and finally got it to push a clog out. It ended up pushing the teflon piece out of the throat and I cant find it. Do I need that? I run PLA

I filed down a Capricorn PTFE tube for it

I'm printing a Bullseye Mod for the stock hotend this e3dv6 clone is horrible compared to the stock one. Thanks for all your help.

Yes, you can damage stepper drivers when you unplug stepper motors. Hot (un)plugging of stepper cables can cause voltage spikes that can destroy the stepper drivers. Furthermore, shorting out the fan may have caused damage also to other parts of the board (voltage regulator, fuse, etc ). These controller boards are not that expensive, ordering a spare would get you up and running quickly. Also order a new fan, mind the voltage.
No, pulling the power cord or switching off the controller board will not destroy the board.

Yea I ended up just ordering one on Amazon so I could have it by tomorrow. The fan actually still comes on when I turn the printer on.  I think I must have clipped the fan upside down onto the E3D V6, I cant imagine that the fan wires should be that close to the hot end. Not sure why I didn't catch that when putting everything together in the Bullseye Mod. Thanks for responding. Note, I actually turned it off before unplugging it so I didn't really hot unplug it. I would have thought the fuse should of blown from a short instead of the board

A basic rule of electronics going back at least to the early transistor era (1950s): a $2 transistor will protect a 3 cent fuse by blowing first.

Can you point me in the right direction to info on doing this? Or was this a joke? Considering its costing $2 to protect a 3 cent fuse.

I think the comment was meant to be informative, it gives some insight in the choices made in electronics design, not always the good ones. You frequently see components fail where the fuse didn't, hence the comment I think. It is difficult to find the problem, it can also be a burned trace, SMD fuse, MOSFET, etc. Hard to find and hard to fix if you're not an electronics engineer with soldering skills.

Yea I realized what he ment after I replied lol.


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The chin piece of my print does not print properly
I am printing this piece using a 0.4 mm nozzle. It happens that the piece on the chin does not print properly.
I have already tried the tree mode supports, touching the plate and in all the places but the same thing happens.
I include photos of my configuration in Cura.

This is caused by insufficient support under the whole chin, incorrect slicer settings and the fact that the chin is an overhang than isn't connected to the model at the lower layers (this means that an island is printed in a sea of support that later becomes a peninsula).
The model is a Pokenmon called Dragonite which was found on Thingiverse. When sliced with the tree support option (note that tree support has been an advanced experimental option probably due to the issues with this support type) Cura builds a tree-like structure of which the stem/branch spreads out just before printing the island of the chin:

The problem is that the created support isn't enough for the print settings you are using. E.g. from a different view, you can see that part of the chin is unsupported with this support (note that the chin is also pretty flat, so each consecutive outer wall of each layer doesn't have the best contact with the previous layer, this is something you encounter when you print a sphere or rounded corners, that is why chamfers are preferred over rounded corners on bottom layers):

As seen in the latter image, there is quite some distance of the outer wall perimeter that is printed without support and minimal adhesion to the previous layer.
To deal with this you need to dial in the printer for this filament, i.e. do not print too hot, and use sufficient part cooling. Also be aware that you print the inner walls before the outer walls. You can also choose a different type of support, but that could result in supports that are stuck to the model, which are not easy to remove and possibly leave scars. Rotating the model around the X-axis can also be an option I've used successfully on printing miniatures.

how to solve the problem using different supports?

The answer explains the reasons why the chin isn't printed as expected as per the question request, to print it properly, you should use PLA, lower print temperature (the most interesting print parameters aren't shown), buff up cooling speed (if not possible, print a better flow duct, or use a large household fan) and disable outer wall first, etc. I'm just guessing here as we can't see the value of these options.

I see that you have a minimum support angle of 60 degrees -- that may mean Cura Slicer isn't generating supports for that chin.  Try changing this minimum to a lower figure -- 51 degrees or lower.  From what I've read, most filaments and settings will allow 60 degrees with PLA, but this is the easy first thing to try to get that chin supported.
On looking at the photo again, I also wonder if what looks like a bad overhang print is actually supports that didn't separate as they should -- perhaps you only need to adjust your Z skip for supports to get them to come off the actual part better.
Following up, I saw a likely cause for this on one of my own prints yesterday -- coincidentally on the chin of a sculpture part.  What I observed is that supports for this region, which trailed up the body (as would those for your dragon's chin), likely due to their slenderness, repeatedly got knocked over.  The support structure "healed" over several layers after each such incident, but in a very fragile condition that would again get knocked off by a nozzle brush.  The solution to this is either to enable Z-hop on retraction (so travel doesn't brush the nozzle across supports printed in the same layer), or to reorient the part so the problem support is shorter and doesn't run right alongside the actual body wall.  Z-hop has less effect on other areas of the print.

You need to zoom in on the layers where the support is being generated and check if there is actually support being generated under that area.
Additionally, I noticed your support generation setting is "Touching build plate only". You should change this  setting to 'everywhere' because it could be that build plate support cannot directly reach the area in question (so a portion of it is residing over an already printed surface). With this setting changed though, double check the rest of your print is not generating unecesssary supports, and if it is, use support blocker feature to get rid of them.
And as a last thought, after changing the setting i mentioned above, also play around with overhang angle and carefully observe how the rendering of the support structures changes (like, really zoom in those gaps and check).

Tree supports will reach over a rather a lot of actual part.

If the tree angle is sufficiently high.


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Ender 3 Pro stuck print excess
I have an Ender 3 Pro. When I print, the area that the printer goes around before printing gets stuck and I can't scrape it or use alcohol.
Both of these methods are used with a heated and cooled bed. Does anyone know how to fix this?

Your bed is way too close to the nozzle.

@R..GitHubSTOPHELPINGICE Please consider to add an answer with a little background why it is too close (this is probably the reason), the current answer doesn't include this solution!

With PETG I use Elmer's glue sticks to form a barrier protecting my print surface.
When PETG stuck too hard to the print surface, I have to decide what to destroy; the print or the print surface.  Removing at room temperature can tear the print surface.  Heating the bed to 80 °C  or above softens the print, making it easier to remove, but distorts during removal.
If the print is already removed, you can heat the bed to make the remaining material easier to scrape off. With a glue stick, especially a washable glue stick, you can first clean off the glue stick and undercut the material on the bed.


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What foundation designs are adequate for a 3D-printed one-floor building larger than 200 square meters?
With the increasing price of lumber and construction materials in the U.S., 3D-printed houses become a more viable way of building houses.  Designing the foundations of mini-houses isn't difficult.  However the foundation of a full-size house is different; the larger the more difficult.  The one piece nature of a 3D-printed house makes it almost impossible to repair if the foundation shifts.  Foundation repair is the largest home maintenance cost of existing houses.  Thus, the designs of most existing house foundations are not adequate.
Usually the form for the foundation is printed, rebar is placed in the form, and the foundation poured.  Piers seem to be a most.  While shims can be added or altered on piers with pier and beam, unless the beams hold the house ridge (minimum flexing), this doesn't appear to be an option.  What are adequate designs for 3D printed houses?
Family dwellings in the U.S. usually run from 1,100 to 3000 sq.ft. (aprox. 100 to 280 sq.meters).  More common is 1500 to 2000 sq.ft. (aprox. 140 to 190 sq.meters).  Ceilings are at least 8 ft. (2.44 meters) high.
We can speculate, but a good answer would reference actual construction.  Some speculation:

Print individual wall panels on a bed flat on the ground similar to how warehouses are constructed out of wall panels.  Thus, eliminate the one piece.

One could make concrete pier and beams in a grid pattern within the slap.  The beams would need to be ridged enough to keep the house from flexing.

Structures built as transportable units would survive a shifting foundation and thus be reparable.

China 3D-prints apartments.  Their techniques may give insight into how to design house foundations for 3D printing.
A 380 sq. meters (4000 sq.ft.) building is being printed in Germany, but the webpage gives no description of the foundation: https://www.designboom.com/architecture/first-3d-printed-apartment-building-germany-construction-peri-cobod-11-24-2020/
A huge foundation issue is clay soil in a climate that has both wet and dry seasons.
P.S. The wise customer will want this answered before purchasing.  The construction company would want this answered to prevent a class action lawsuit.  The industry would want this answered to avoid a setback in consumer confidence.

We need more empirical information. The responders of this form are distributed globally. What are the sq. foot dimensions of a mini-house vs a full size house?


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Raising E-steps on my CR-6 SE makes the extruder choppy
I have the community edition of the firmware for my CR-6 SE printer installed on a BigTreeTech SKR-CR6 V1.0 board. This firmware has a nice E-step calibration guide you can use to easily get the correct step/mm value.
However when I raise that value, my extruder motor starts to chop, it's like it doesn't have enough strength to push the filament through and starts chopping.
I tried raising the current on the extruder motor, from 600 mA which is standard, to 900 mA incrementally, but it didn't make any difference.
I just replaced the stock extruder with a dual gear extruder in hopes that the extruder was causing this. but the new extruder faces the same issue.
I think raising the Vref value for the extruder motor might help, but I don't know how to do that. on the BTT SKR-CR6 V1.0 board all stepper drivers are in UART mode so there is no way to change this on the board itself. and there is no way to change Vref in the UI as far as I know.
What should I do to progress with this issue?

You cannot change the Vref of a UART operated stepper driver, setting the current directly is the way to go on UART operated stepper drivers; in fact that is actually what you are doing on non-UART operated stepper drivers, you change the Vref to change the current through the stepper motor, the higher the voltage the higher the current through the stepper the more torque the stepper has.
Depending on the stepper you may increase the current even more, this depends on the stepper motor model/type. There are stepper motorss that allow more than 1000 mA, I don't know the steppers used in the CR6 E, find out before you test higher values.
Please note that there may be something else causing this issue, possibly your filament path is having a lot of resistance. You should check the extrusion manually and possibly clean the nozzle and heat break.

A similar question is found here: Is the Vref trimmer relevant on TMC2208 in UART mode?

I've been thinking of replacing the nozzle with a brass one, this is a (probably steel one) that was included with the all metal hot end that I replaced with as soon as I got the printer, it's not old. but that might help. I do have replacement stepper motors for the extruder as I had problems with my previous printer, but it turned out to be a faulty controller board in the end. so the question is, if I were to crank up current to 1000 mA and motor burns because of it, do I risk causing damage to the stepper driver?

Regarding the high currents, please read this.

That was a good read! Seems like my stepper should be rated at 1.5 A so it should be safe to crank it up to 1.3 A to see if it has any bearing on the choppiness when I raise my E-steps.


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Why is my Ender 3 restarting spontaneously in mid print?
tl;dr How can I test whether my sporadic in-print restarts are a thermal problem or a firmware issue?
The problem
I've had my Ender 3 (not V2 or Pro) for about a month, and gotten a number of excellent small prints with Amazon Basics and SunLu PLA, as well as Overture PETG, slicing with Cura Slicer 4.9.1; the printer has Marlin 1.0.1 according to the "About Printer" display.  I've made no electrical changes to the original hardware, though I've added a few printed parts including a mainboard fan cover, alternative power supply mount, "original screws" display PCB cover, display cable clips, filament guides, storage drawers, and drag chains protecting the cables to the X stepper and extruder/hotend.
However, I've had trouble for most of the time I've had the machine with sporadic reboots in the middle of a multi-hour print.  At a minimum, when I resume the print after one of these incidents, the printer will skip the rest of the current layer and start with the next, producing a weak layer (usually it also leaves a significant blob of plastic, and even if I just flatten that blob with the scraper blade as soon as the nozzle is clear, it will stick out of the print and have to be trimmed off later, and if I try to scrape the blob away while it's still soft, it'll result in layer shifts caused by skipping the Y-axis stepper).
Usually, this happens about four to six hours into a 10+ hour print, though I've seen it happen just a half hour or so after a previous occurrence, and near the end of a 65-minute print as well.  It's becoming a big issue as I venture into larger prints, as it can ruin the appearance of a print (by skipping a large fraction of a layer that's the visible surface of the part) or causing a weak layer at a stress point -- which wastes a lot of machine time as well as filament.
I've also just upgraded my build surface to a Creality coated glass plate -- which is great in terms of flatness, sticks well, and the part comes off very easily when the plate cools.  Unfortunately, if I'm not in the room when the printer restarts, and the bed gets below about 40 °C, the part will unstick and will start moving with the nozzle when I resume the print.
What I've tried
I had suspected issues with my 120 V power, so I purchased a small UPS to condition the power for the Ender 3 power supply, but without seeing improvement.  Prints running overnight often do better, but not always, and this happens with both PLA (nozzle temp 200 °C, bed 50 °C) and PETG (nozzle 235 °C, bed 75-78 °C).  I haven't attempted other filaments such as ABS.
I'm usually not watching the printer when it does this, but several times I've caught it immediately after (I can hear it running when I'm at my computer, so when it stops I can get to it in seconds), and once I happened to be watching when it stopped.  The sequence is that (usually, but not always, when printing a layer with significant infill -- for which I usually use cubic, for best strength with minimal material and time) the printer will suddenly just stop with a normal info screen display for fifteen to thirty seconds (I don't have the exact time, and have only seen it early enough to have an idea a couple of times), then the display goes dark and within two or three seconds returns to the startup splash (Ender 3 dragon logo), from which it changes to the power failure recovery screen with "Resume Print" and "Stop Print" choices.
This is not a reproducible error (nor am I likely to attempt repeating an overnight or whole-day print multiple times to attempt to reproduce the problem).  At no time have I noted the power supply cooling exhaust running hot, nor the steppers getting as warm as a 50 °C bed (I don't have an IR thermometer to check the actual stepper temperature).  I used a photographic thermometer to check the temperature of cooling air leaving the mainboard housing, and found it never exceeded 30 °C during the print I tested.
My hypothesis
I'm aware of two significant possible causes: overheating the mainboard, or overloading the stepper pulse loop in the firmware.  The former should (if things are designed sensibly) result in a complete shutdown, though with a hard switch on the power supply it might not be possible to prevent a restart as soon as the sensor reads below critical (which could be the fifteen to thirty seconds of "freeze" I've observed).  The latter is something I've read about, where the Marlin firmware will restart if the stepper pulse interrupt loop gets so busy the mainboard can't service the sensor interrupt loop.
The only way I know to test which I'm seeing is to find a way to more efficiently cool the mainboard and see if that improves the situation -- but I'm reluctant to either remove the fan cover or run the printer with the mainboard cover off; the reason for installing the fan cover was to keep fragments of plastic from getting into the mainboard housing as, being directly under the build plate, it's prone to collect strings, hairs, and scrapings.
Update
I thought I had solved this problem -- I reduced the print speed (using the "tune" menu while the print was running) to 90% (=45 mm/s instead of Cura's default 50 mm/s) and started getting longer prints without stoppages; that would have pointed to firmware loop overload as the likely cause.  Unfortunately, I still got a freeze about 10.5 hours in to a 13 hour print, but only one rather than the three or so I'd have expected; this may be a clue.  Since then I've had freezes in under an hour into a new print once again, once with the bed running to Ymin (a movement not in the gcode) instead of stopping in place.
Due to the required level of disassembly, I haven't attempted to test continuity while in motion on the stepper or hotend wiring, and I cut away the damaged portion of the Bowden tube when I replaced the hotend and nozzle; I get good extrusion and, when they don't stop in the middle, good smooth prints.
Update 18 June 2021
As suggested in comments, I have initiated a "dry run" of a print that previously generated two or three of these stoppages over the course of about fourteen hours.  Original print was Overture clear PETG, nozzle at 235 °C and bed at 75 °C.  For this "print" I've retracted the PLA loaded into the machine well clear of the hotend and unplugged the extruder stepper; when I get home from work, I'll be able to see if the machine is still running, and if it has restarted, resuming the print will allow me to tell how long it ran before the incident.
Test Result
This is unexpected.  I thought I'd either find the machine still running, or with the power failure resume screen asking to "Resume Print" or "Stop Print" -- instead, I came home from work, some 10 hours after starting the dry run test, to find the printer idle, as if I'd had it properly shut off and then turned the power on.  No way to tell when it stopped or why.
Further Update, June 20
I had another of the new type of failure on an overnight print; I was printing PETG (Sun Lu brand), 240 °C nozzle and 75 °C bed, back on my magnetic textured build sheet because the PETG was warping and coming up from the coated glass -- and when I got up this morning the printer should have still been running, at around 90% complete, but instead it was sitting at the Info Screen, nozzle and bed both reading room ambient temperature with set point 0 °C.
I can only presume that either the "resume print" option has a limited life (though I've seen it at what must have been eight or nine hours after the print stopped and print progress in this case suggests it had only stopped four hours or so before I came back), or I'm getting a second interrupt from the resume screen that's causing the printer to return to "fresh power on" state.
I'm reluctant to pursue further warranty help from the Amazon seller because of the hassle of returning a machine I've customized and my feeling that this is an easy fix if I can just determine what to fix.
Followup, June 21
I'm starting to believe my machine is haunted.  Over the past twenty-four hours, I've had about twenty-one continuous hours of printing, completely successful (in terms of the machine continuing to run; I've got some corner lifting on the print that was running when I left for work this morning, but that's print settings and/or material vs. build surface).  I was more than ten hours into a twelve-plus hour print when I left this morning, and completely a nine and a half hour print yesterday without incident.
In other words, it almost seems as if the problem has resolved.
My partner half jokingly suggested the cats might be somehow resetting the machine, but I don't see any way they could.  Just poking at the Ender 3 control knob won't do anything, and even if they managed to turn the knob and poke it again, if they initiated a "stop print" the machine would retract, lift the nozzle, and home the X and Y.  If they batted at the power switch (which is after the UPS) and got it to momentarily break power, I'd expect to find the "resume print" screen -- and further, this has happened when I'm in the same room and the sequence isn't compatible with a power break.
Additional Followup 22 June 2021
I thought the machine was back to trying to make a liar out of me, after getting around 27 hours of failure-free prints -- and then it stopped at about 60% of a 2 1/2 hour print in PLA, glass bed, at 200 °C nozzle and 50 °C bed, 10% gryroid infill.  It was printing fine when I went to bed, and when I got up I found it at the info screen (not the resume print choice screen), with the nozzle stuck to the infill.
Additional information 26 June 2021
I was able to take a few minutes to open the main board housing while installing belt tensioners today -- I was slightly startled to discover that despite shipping with Marlin 1.0.1 (correction: it's 2.0.1-V1.0.1, 32-bit build and the newest available from Creality for this mainboard), the mainboard is the 32-bit version 4.2.2.  While this is not the most current version, it is the board that was introduced with the Ender 3 V2 in 2020 and almost immediately added to the Ender 3 Pro, and can be updated through the MicroSD or via the USB port.
I'm told (via discussion on the Ender 3 group at Thingiverse) that this rules out firmware overload, as the 32-bit boards are both much faster computationally, and have significantly larger on-board RAM and EEPROM.
I also went over the electrical connections on the mainboard; I found two of the screw terminals weren't as tight as I'd make them (this is probably a result of using tinned wire instead of crimped ferrules); I also was able to push down one of the stepper driver outputs (not sure which one), which wasn't fully seated (though surely making contact, since I've had all steppers operational any time the machine wasn't resetting itself).
Unfortunately, tightening the slightly loose screw connections helped nothing; though I was able to complete a 1 1/2 hour print flawlessly, I had two consecutive failures several hours into a 7 1/2 hour print.
My next thing to check is internals in the power supply.
June 29 update
Power supply check showed perfect 24.0 V output, but I found the two spade terminals on the power switch itself were loose enough to move around with a little tug on the wire.  They were making good contact, as far as I could tell, and required effort to pull off the spade on the switch, but once things heat up after some time under load (running X and Y steppers and bed heater at the same time, for instance, along with near-constant nozzle heat) they might well have gotten looser -- and since I moved the power supply off the vertical extrusion to a pair of printed brackets to improve clearance between the magnetic build sheet and power supply, it does move around a bit when the machine is printing (especially with the rapid direction changes of infill).
On that basis, I disconnected both wires and squeezed the terminals with pliers to close them up a little; they were very tight when I reconnected them.
Too early to be sure, but the machine finished a 7.5 hour print flawlessly after this.
Update June 30
It was better -- I got two 7.5 hour prints in a row without a failure.  Printed a spacer to allow quick switch between magnetic build surface sheet and glass (clips onto X gantry plate to trigger the Z-stop with the nozzle higher by exactly the extra thickness of the glass plate).  Too thick; easier to reprint than to sand or scrape enough.
Machine stopped at the same spot while printing the skirt three attempts in a row.  This is less than one minute into the print.  Further, doesn't reboot, just freezes until I power it off, then comes back up with "resume" dialog.  Tried to reslice, thinking it might be a bad g-code file, and the microSD won't mount on my desktop computer, though it still seems to read okay in the printer and another (full size) SD card mounts on the same USB port and hub (and the problem card doesn't mount even in the microSD slot in the other reader).
This last doesn't appear to be related to the original problem: the microSD had seemingly gotten disconnected without "safely remove" procedure, and Ubuntu apparently isn't capable of recovering from this; that resulted in a corrupted gcode file causing these most recent, very early stoppages, as well as the inability to mount the storage device.  Reformatting the storage device corrected that problem.
Question?
What other tests can I run to differentiate between a thermal restart and a firmware overload?

My Ender 5 plus does it periodically and it seems to be due to other things starting up in the workshop such as extractor fan.

@Davies-Barnard Still doing it after installing a UPS (so now on filtered power).

Are you printing from SD card or from an external interface (e.g. laptop, RPi, etc.). Have you checked all cables, could be a faulty/cracked one.

All prints are from the TF/MicroSD.  Am I correct that I have to open up the mainboard enclosure to check for damaged cables (since they're all connected inside there)?  Won't be able to do that until the weekend.  I did install drag chains two weeks ago (printer was only two-three weeks in service then).

You mention that you purchased "a small UPS to condition the power". Does the UPS have an automatic voltage regulator? Some UPS only supply power during power loss but don't condition the voltage during regular operation (i.e. supply extra voltage during brownouts or suppress voltage during power spikes).

The model I have claims surge protection, at least.  This is the one: https://smile.amazon.com/gp/product/B01FWAZEIU/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1 Looks like limited brownout protection, though -- as with any UPS that isn't just a constant-charge battery inverter.

Are there any signs that could be related to clogging or insufficient extrusion pressure?

@user30878 I had a clogging nozzle, but I've replaced it (and the entire hotend), I get no skipped steps on the extruder and still have this issue.  While it works, extrusion is very good.

What about health of PTFE tubes?

@user30878 I had to cut off the last 40 mm or so of the Bowden tube when I replaced the hot end with the clog (couldn't get it out of the hot end without mashing it with pliers), but AFAIK it's fine now.  Wouldn't a problem there cause skips on the extruder?  I just don't see how this could be related to restarts; even a skipping stepper shouldn't cause that.

Just to confirm, you're not doing this printing near any Ionizing Radiation Sources right? No  X-Rays, Gamma Rays, Beta or Alpha Radiation?

No radiation that I'm aware of.  There isn't even a CRT anywhere in the house any more.  There's a smoke detector about three meters from the machine, and a radioactive (thorium glass) camera lens at a similar distance, but both are pretty weak alpha emitters, and the mainboard housing should block alpha very effectively (it's metal, after all).

@ZeissIkon, Let the machine run the same g-code that was running when the issue occurred but run it without filament (i.e. run it dry). If it doesn't fail that would give us more info. Edit: And turn off the part cooling fan.

@user77232 I already know that this is "sporadic" -- I've reprinted parts ruined by this failure, successfully.  However, I see what you're saying; you suspect something extruder or nozzle heating related.  I've got a belt tensioner part printing now, but I hope I'll remember to run this test before bedtime.

@user77232 Wasn't able to run a "dry test" but yesterday morning and last night I had perfect prints (small parts, X and Y belt tensioners printed as single or paired parts) with one in between that stopped with a run toward (but not all the way to) Ymin but then skipped most of a layer -- less than an hour into a 2.5 hour print (one perfect print was a rerun of this same part).  Problem with a dry run is it'll take hours, if it reproduces the problem at all (and no result doesn't tell anything useful unless it's a 12+ hour print).

@ZeissIkon, I take it you looked for loose cables and the like? It would be useful we could get an oscilloscope on the 3v3 supply rail for the board while printing to determine if it's an undervoltage problem.

@user77232 I don't own an o-scope.  Last time I used one was 1979-1980 time frame.

Let us continue this discussion in chat.

This problem (of spontaneous restarting during printing) appears to be solved.
The Cause
The apparent cause was a combination of push-on spade connectors on the power switch that were looser than ideal, likely specified that way in order to facilitate mass production (the tighter such a connector is, the more difficult it is to assemble, leading to slower work and an increase in damaged parts that then require reworking an assembly), and moving the power supply off its direct mount to the machine frame (in order to increase clearance between the PSU and the heat bed after installation of a magnetic build sheet).
The brackets I used to remount the power supply are free to slide in the 4040 extrusion of the frame base, and have no mechanical connection to the PSU housing or even its plastic extension (which houses the wire connections, power switch, and power cord connector).  This allows the PSU to move much more under frame accelerations (Newtonian reaction to movements of the bed and hot end) than with the original mount -- and this movement sometimes pulls against the wires inside the plastic wiring cover.
Combine that with spade connectors that are loose enough to move when the wire is tugged pretty gently, and you have a formula for momentary disconnects.  Such a disconnect will reset the main board (like a power flicker can do to a computer with no UPS), resulting in the freeze (actually mainboard startup sequence before it begins to update the display), then a startup.
The Complication
I can't prove it, but I hypothesize that the transition from restarting to the "resume print" screen, to restarting as if freshly powered up after a normal shutdown occurred because the connection issue had progressed to the point of producing two or more disconnects close enough together that the second restart lost the "print in progress" flag.
The Solution
What appears to have solved the problem was to remove the wiring cover on the PSU (ensure power is off and power cord disconnected, mains voltage is present inside this cover), disconnecting the spade terminals at the power switch, and (with pliers) carefully squeezing the female receptacles so they are tighter on the male blade.  This must be done carefully, as squeezing too hard will close up the female terminal and prevent reconnection, requiring either much more difficult adjustment with knife and miniature screwdriver, or replacement of the terminal.
Since applying this fix, I've completed a few longish prints (about 7 1/2 hours each) and a number of shorter ones without a single glitch, aside from an unrelated problem that caused a corrupted gcode file.
Adding to this, I did get one in-print reset after this answer; it happened while printing gyroid infill at (IIRC) 40%, which is some of largest ongoing acceleration (=> machine frame movement) of anything you'd do.
My final solution has been to add a third bracket to the power supply, so three corners are supported.  Now the power supply doesn't wiggle and wobble when the machine shifts a little; it's back to a near-rigid mount to the frame (if anything, a little sturdier than the original two screws through an upright).  I haven't tried gyroid infill again, but I've had 100% reliability (including a couple large prints at 7+ hours) since installing this third bracket.

I expected it to be a faulty cable, but connectors are equally suspicious! Glad you fixed it and came back to answer your own question, thanks!


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Does a sturdy table really matter?
There seems to be general consensus that, among other things, a sturdy table is important for print quality.
Within reason, I don't understand why a wobbly table would be bad. Has anyone done a controlled study/investigation on how wobbliness affects print quality?
Ringing artifacts seem to be what people think platform sturdiness helps with. But the frequencies of these artifacts seem to be broadly in the range of 40-100 Hz. The resonance of a cheap fold-out table is seems much lower than that - perhaps 10 Hz or less. And intuitively, it seems that a 10 Hz resonance would have to be very energetic to significantly affect the motion of the extruder.
YouTube links, written studies, or personal experience welcome!

I think your answer could be found here

Purely anecdotal, but my printer is on a not-so-sturdy table and I've never noticed any problems.

Printers usually leave a wavy pattern after turning a right-angle corner.  A flimsy table will make this worse, causing its own pattern.  A flimsy table will cause you to run slower speeds to compensate.

A clear answer is not available, since no one performed a proper test as of June 2021.
The closest answer I can provide is that damping feet result in a change of vibration behaviour, as discussed in this Klipper issue report. How it's not clear.
I paste some of the findings:

I took several measurements with different configurations and the
results are quite surprising IMO. The following graphs show the
respective vibration results for (from left to right):
1- The retrofit back to the standard hard rubber feet
2- The printer
only standing on the "feet clamps" as shown in the picture above
3-
The printer standing on the "feet clamps" but with squash balls
inserted
X-Axis

Configuration 2 vs 3:
The damping is causing an additional spike at ~76 Hz;
Power-Spectral-Density is roughly the same;
Overall vibration is a bit lower in the damped version (11.4 % vs 16% @ 3hump_ei) --> Probably due to damping the additional spike;
A bit surprisingly the shaper recommendation is identical
Configuration 1 (original feet) drives Power-Spectral-Density from e3
range to e4 range
Configuration 1 brought back a dominant spike at
around 75 Hz to 80 Hz (which was surprisingly gone with the printer
sitting on the hard and small area of the "feet clamps"
Configuration
1 nearly tripled the spike at 75 Hz to 80 Hz compared to No. 3
(Power-Spectral-Density 12,000 vs 4,200) The spike at around 30 Hz
stayed pretty much the same
Y-Axis

The effect on the Y-axis is pretty small
My conclusions
The resonance effects very much depend on the type of feet
For
whatever reason every damping in the feet resulted in worse vibration

If you want to know more about it, install Klipper and an ADXL345 accelerometer, make measurements, write a blog post or post here in a new answer.
I may be able to do it within within the year. It's a loose deadline, yes.
I have a printer on a wobbly table, but I haven't performed measurements yet.
I expect it to be better than a stiff table, since part of the energy is dissipated by the table and not by the printer frame (we are not talking about independent feet, but table as a whole), resulting in better quality at high acceleration. Of course if your printer runs at 500-1500 mm/s^2 you won't see anything. If you run at 5000+ mm/s^2, then...

Nice findings you found, it confirms the answer I posted on Fix ghosting problem (damping versus bolting printer to a desk).


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Are part cooling fans available in opposite orientation?
All the blower fans for part cooling I've seen rotate counter-clockwise when viewed from the intake side. I'm looking to replace mine on an Ender 3 with something stronger, and one of the worst parts of the stock design is that it's offset by about 20 mm versus the nozzle position, requiring awkward duct paths that reduce the flow to get uniform coverage around the newly extruded material. A fan that rotates in the opposite direction, with air exiting on the right-hand size when viewed from the intake side, would be exactly right. Are there such models available, and if so, what is the right terminology to search for them by? Or is there a simple way to modify a fan to reverse its direction?

If you are implying radial fans, than this has been asked and answered before, see Does right handed radial fan exist?. If not, please make the question a little more specific.

@0scar: Yes, I believe my question is a duplicate of that.

They exist, but maybe only for industrial use and not so compact. Look for "clockwise".
https://barkerbille.com/technology/designation-of-position/
You could carve the back side of a normal blower with some openings (make a grid out of it) and obstruct the original inlet (or leave both open...).

Commenting on the idea of changing the air holes, that could work for either the intakes OR the outputs, depends on how the fan is built. The exit port might be easier to cut out with a dremel or something, then tape over the old exit hole.  The intake zones tend to be large and any kind of obstruction rather than a fully open face would not be recommended.

I don't see how cutting a different exit hole could change the orientation.

This is probably a stupid answer, but wouldn't switching the ground and hot pins cause the fan to blow the other way. (Which wouln't do much without reversing the blades)


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Odd behaviour of steady feedrate increase
For some weeks I noticed really odd behaviour on my OctoPi controlled Anet A8. I'm using an MKS Gen L board with TMC2208 on this and constellation worked for a year now.
When starting a print, I noticed the movements were really fast in spite of having an extra slow first layer. I adjust the feed rate to 100 % in Octoprint and it works normal. The final print has noticeable imperfections as it moves up. I check the feed rate after the print and it's at like 594 %. My G-code wouldn't specify such a value and I didn't find any related commands in there.
Further, if the printer is idle and I set M220 S100 it returns FR:100 % when asked. If I make a homing move, wait and ask again, the value steadily rises. First FR:102 %, then FR:105 % after a minute and so on...

I think this behaviour might have started after using a G-code post-processed in Cura for different feed rates.
Does anyone have an idea how to tackle this? The printer was switched off several times already. If I implement an M220 in the start G-code I assume it will still rise during the print.


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Can a Prusa be converted to IDEX?
I have a Prusa i3 Mk3s with an MMU2s on it. And to be frank, as far as the MMU goes, I have not had much luck with it.  I've seen people print amazing MMU prints and it works great for them, but I have had MUCH less success.
If a print requires 900 filament changes to go back and forth between colors, even if I have the MMU dialed-in to work 99 % of the time, well that's still 9 failures in that print. I'm sure there are things I could do to dial it in, but I have a different question for now:
I have other printers I work with that have dual extruders and work great, and I've been eyeballing an IDEX kit for my Ender 3, which got me thinking that there's gotta be a way to put IDEX on a Prusa.
I was also eyeballing my MMU and thinking I could scrap it for parts (stepper motors etc) for the IDEX.  I did a quick Google search and couldn't really find anything, but is there a reason for that?  Is the control board not able to handle it, etc?

It would require an adaptation so extensive that I would define it "rebuild".
You would end up savaging basically only the bare frame and the steppers.
I'm not aware, in fact, of anyone ever doing it.


text:
How does direct drive conversion allow higher print temperatures?
I have an Ender 3, currently in stock Bowden extruder configuration.
I want to be able to print nylon and TPU, both of which require temperature too high for the tolerance of the PTFE Bowden tube (as well as the issues with the flexible filament in the tube).
Therefore, I've considered converting my printer to direct drive.  However, the conversions I've seen, both DIY/print the parts type and commercial, seem to include a short length of the same PTFE tube between the extruder (now mounted on the hot end carriage) and the actual hot end.  This same material ought to have the same temperature limit (about 250 C) as it would have in a Bowden configuration -- and for nylon, at the least, this is a problem, since the PTFE would start to soften from contact with the heat break.
Am I missing something in these conversions, or is the PTFE's glass transition not the limiting factor in printing hotter with a direct drive conversion?

TPU does not need more than 250°C, which is ok with stock hotend. No need of all metal hotend. Nylon, depending on the brand and blend, also can be printed at 250°C just fine. What you need is an enclosed chamber for it!

@FarO Please elaborate -- perhaps in an answer, not a comment, since this sounds like a frame challenge.  What's an "enclosed chamber" in this context?

@FarO Oh, it just came to me -- you're talking about a printer enclosure, to prevent premature cooling of the part as it prints (presumably to limit warping).

Direct Drive v.s. Bowden has no relation to the maximum print temperature. What determines the maximum print temperature is the design of the hotend itself. There are "all-metal" designs, where the PTFE tube (Bowden or not) stops in the cold zone and the heatbreak and all other components that get hot are fully made of metal. Other hotend designs have the PTFE tube run all the way down into the hot zone and this limits the maximum printing temperature. It has nothing to do with whether the hotend is Bowden or not.

So, do I need a direct drive extruder for nylon and TPU, or do I need an all metal hot end, or both?

@ZeissIkon: For TPU you absolutely don't need an allmetal hotend (print temperatures are in the same range as PLA or slightly higher) and you don't need a direct drive, but it helps a lot; with a bowden you'll be stuck going really, really slow. For nylon, some variants can be printed at low enough temperature not to need an all-metal hotend, but you'll be limited to those. Bowden vs direct drive should not matter for nylon any more than it does for other non-flex materials. (Direct drive is always better, but not essential.)

Direct drive may not be needed for 98A or 95A TPU, but anything floppier than that will either require ridiculously slow print speeds or a direct drive. I printed nylon on a 60 cm Bowden drive and it works.

So I need direct drive to print very soft TPU (for things like gaskets) at reasonable speed, but for nylon not specifically formulated to minimize print temperature, I need an all metal hot end, not direct drive.  Looks like I get to spend some money before printing nylon.

@ZeissIkon Exactly. However Polymaker Copa, Fillamentum Nylon FX256 and Formfutura STYX-12 Nylon will print easily at 250 °C, or even less. Copa is tested by Polymaker when printed at 240 °C, for example (see datasheet).

Bowden tubes extending to the nozzle to make a seal will damage the Teflon (PTFE) tube if exceeding  250°C for an extended time.  An all-metal hotend for a Bowden would have either the nozzle sealed against the heatbreak or an integrated nozzle and heatbreak.  Then the Bowden tube would attach with a minimum gape with either the heatbreak or heatsink.
Note: The heater block needs to be at the maximum operating temperature When making a seal between the nozzle and heatbreak.


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Extruder 2 is not printing
For my printer (3DGence Double255) there is no ready to use Cura profile available. So I started to edit one.
Until now I left the start code for the two extruders empty. But, the machine is printing everything with extruder 1.
Now I am wondering if the printer needs a special extruder change command in the start code.
And what would be the end code?


text:
PrusaSlicer not making sense
I'm using PrusaSlicer 2.3.1 on a custom delta.
I'm printing a basic 25x25 mm cubic shell for calibration purposes. It keeps setting the print speed to 20 mm/sec despite there being no speed specifically that low (well, except gaps, but these walls are presented as external perimeters in the post-slice viewer.)
I've also ensured the minimum printing speed (cooling section) is 30 mm/s, and set the 'slow down if print is below' to like 1 second but it refuses to change.
In fact, I just turned off all auto-cooling and the software didn't even require a re-slice! I jogged the position a hair which forces a reslice but the end result is the same.  This refusal to require a reslice has been showing up a lot lately, never had this kind of problem in the original Slic3r I've been using for years.

What is the question here? Your contribution reads more like a rant (especially the last sentence).

Yes, sorry about that subject line!  I've lost hair chasing this problem down and it looks like I have a software problem making it really hard to pin down. People in other forums opened my project file (.3mf) and couldn't find a problem and recreating it consistently has been really hard.  I'm in the process of crossing my fingers and re-installing.

So do you really have a specific question then that we can answer? Perhaps making a bug report with Prusa would be a better course of action.

Prusa would ask me to document how to duplicate the problem but I'm having problem duplicating consistently.  My question is:  why did Prusaslicer spit out gcode that prints my single-walled calibration

My question:
To start off simply, if I have auto-cooling enabled and the minimum speed allowed is set to 30 mm/sec, and print speed is set to 30mm/sec, is there EVER a (normal) situation that would slow down my print to 20mm/sec,? Because that is what seems to be happening, if I understand them correctly.
At the moment I can't even recreate the problem, which is where my headaches started.  I sent a .3mf file to the Prusaslicer forum and it sliced fine on their computers.


text:
Help adding additional stepper drivers to Marlin
I am building a large printer that needs 3 independent Z-stepper motors that will home with a BLTouch and 2 Y-stepper motors with an endstop for each side.
I can use the E1 for the extra Y and I plan on adding two external stepper drivers for the two extra Z-stepper.
There should be 8 free pins in AUX-2 to add the two stepper drivers. I purchased some stepper expansion boards and will be using the same A4988 stepper drivers as the rest of the motors.
The hard part is figuring out how to modify Marlin to recognize the new steppers. I also need to get it to do a 2 stepper Y-homing sequence.


text:
"Unable to read TMC UART 'extruder' register IFCNT" - Klipper and Robin Nano
I'm trying to use software UART for TMC2209 steppers on a BigTreeTech v1.2 and apply that to my Robin Nano v.1.1 using Klipper firmware.
I declared a different pin for every driver and I edit my printer.cfg in this way:
[tmc2209 stepper_x]
uart_pin: PA10
run_current:  0.75
hold_current: 0.4
stealthchop_threshold: 9999
interpolate: true

[tmc2209 stepper_y]
uart_pin: PA9
run_current:  0.75
hold_current: 0.4
stealthchop_threshold: 9999
interpolate: true

[tmc2209 stepper_z]
uart_pin: PC7
run_current:  0.75
hold_current: 0.4
stealthchop_threshold: 1
interpolate: true

[tmc2209 extruder]
uart_pin: PC13
run_current: 0.3
stealthchop_threshold: 1
interpolate: true

I watched this video

But I have this error:
Unable to read TMC UART 'extruder' register IFCNT

Why is this happening?

That means that the pins are not correct or that a connection is missing. Some TMC stepper boards require soldering to connect UART from the chip to one of the two pins shown in the enlargement. Have you done it?

@FarO That sounds like the beginning of an answer? Please write an answer if you're sure about this. Indeed this message tells that the pins aren't connected correctly, and for 2208's I'm sure this can be a soldering issue, is that also applicable to 2209's? Please elaborate in your answer.

I had the same issue. In general, that means that the pins you specified doesn't work.
"I declared a different pin for every driver": you don't need just "different pins", you need the CORRECT pins. Check if you specified the correct ones: below the SKR the pins are labelled.
And then check that the TMC module has the UART pin(s) (there are two) are connected to the chip! the TMC modules often are sold with three empty pads on the lower side of the PCB. The central one goes to the chip, then each other pad goes to one pin. You need to bridge with solder the central one and the pad for the pin you want to use.
In the following image you can (barely) see that the central pad near the red line is bridged with the upper one.

Also, for the extruder the stealthchop threshold should be 0, not 1! you don't want stealthchop for the extruder.

yes i solved....the correct pin for extruder is PA8 on robin nano v1.1


text:
Prints have over extrusion only during diagonals
So I have printed multiple benchies with various slicer settings. I have also made sure my bed is leveled well.
But no matter what I do, I get these over extrusion whenever my nozzle is moving in diagonals (left-right). It's always this same angle where it goes wrong.
Has anyone else who has faced this and has figured out know what the issue can be? I'm new to 3D printing so the help would be very much appreciated.

Please tell us what printer, what slicer, and what firmware you are using. Your slicer settings will help as well.

The issue was that the X-axis belt was super loose, figured it after someone pointed it out on Reddit:

swordfish45
You have an extremely loose x belt. That's the root cause of all your problems I can see in these pics.


text:
Using external stepper driver
I need to add two external stepper drivers to my MKS Gen L board. I am using E1 as an extra Y-axis and that is working great. I have three Z motors and I want to move them independently if I can.
I am using:

pins 63, 40, and 42 for Z2, and;
pins 59, 64, and 44 for Z3.

I step up the pins in Marlin and set it to use three motors but when try to move Z only the normal Z motor moves, i.e. the default on-board z stepper driver.
What else do I need to do?

How did you define the pins for the extra steppers, please add the lines you added in your pins_[board].h, e.g. I expect you defined Zx_yyy_PIN for all pins.

I did that, added pins for Y2 and Y3 to the pins I want to use.

Please update the question with the lines you added, and where, the MKS GEN L (version ?) is a RAMPS derivative, possibly are the pins redefined. Adding the information gives others more information to answer, it is basically guesswork at the moment. Have you chosen a driver type for Z2 and Z3?


text:
Creality Ender 3 -X-axis moves too much
I just assembled Ender 3 and noticed that the X-axis movement doesn't correspond to the commands. When I make it move 1 mm with the encoder it moves 16 mm. Everything is in the "out of the box" configuration.
The current steps/mm for the X-axis read (from the display) 80 steps/mm.
Am I supposed to manually fix this with steps per mm setting or could it be another problem. Other axes seem to work fine. I also double checked and everything should be built correctly.

Hi and welcome to 3DPrinting.SE! Beware, please sort this before printing as this may damage your printer!

To answer your question explicitly,

Am I supposed to manually fix this with steps per mm setting

No, you should only do that if the incorrect value has been set, the reported value of 80 corresponds to the values found in all configuration.h files for the boards used by the Ender 3. This value implies the use of stepper drivers with a 1/16 micro-stepping value.

or could it be another problem.

Yes, due to the value of 80 being set, there seems to be a problem with the electronics, this can be a jumper issue or a soldering issue. As this is an "out-of-the-box" issue, you should notify your vendor that the printer isn't functioning properly before you screw it open, it might void the warranty as this is not something you expect from an "out-of-the-box" 3D printer.

The following text is added for a more complete answer to look up the value (initially, the question did not mention this), this is left for others that may stumble upon this question.

You can check these values from the printer LCD (stepper settings menu) or by attaching a console (What is a printer console/terminal?) over USB and enter G-code M92 (or for older Marlin versions M503 without any parameters as the Marlin documentation states:

Get the current steps-per-unit settings using M92 with no parameters or M503 on older versions of Marlin.

The response will give you the values of the steps/mm for all steppers. The value for the X-axis should be 80 (default) according to the Marlin Configurations-release-2.0.7.2 for the Ender 3 printer (note that there are multiple controller boards, so micro-stepping value can be an issue).
If you need to change the value, you need to use M92 X[value] to change the value, use M500 to store the value. Be sure to note which controller board you have, what micro-stepping value is used (1/16, 1/32, etc.). Note that specific calculators exist to assist you.
Based on the comment, the value is already 80, so that should be correct, you really need to check if the board is using micro-stepping, it appears it isn't using this.
You could also test a self generated G-code file containing:
G28 ; home print head
G1 X0 Y0 Z2 F500 ; move to the origin at slightly higher position
G1 X10 Y10 ; move 10 mm in X and Y, if incorrect the machine is at (150, 10) or possibly (160, 10) -> this will hint to micro-stepping issue (full steps, not using 1/16 micro-stepping)

The benefit of using this G-code is that it will amplify the movement by tenfold, if there is a micro-stepping issue, it is easier to measure the movement of the head, a difference of 0 -> 150 1) or 160 is easier measured than 0 -> 15 1) (or 16). If the controller board uses jumpers to set the micro-stepping mode, there might be incorrectly placed. This also tests if the Y-axis is suffering of the same issue, else the print head will be located at (150, 10) 1) or (160, 10).

1) Note that the original question mentioned 15 mm prior to the more logical 16 mm

And the movement distance seems to be indeed 16 times higher like Tom van der Zanden mentioned in his answer.

Not a surprise, I already mentioned the micro-stepping issue before that answer, hence the modified answer with the G-code script, 160 measure more easily than 16! :-) I think you should get a replacement board rather than tinkering, the X-axis stepper is clearly not configured correctly, whether soldering or jumper issue, it is not up to you so solve.

When I make it move 1 mm with the encoder it moves more like 15 mm.

15 is suspiciously close to 16. Perhaps the motor driver is operating in full step mode rather than microstepping. This could be due to a manufacturing defect in the electronics. To diagnose this you would need a multimeter to measure the voltage on the microstepping select pins of the affected motor driver.
Some main boards have jumpers to select the microstepping mode. I am not entirely sure but I don't think the main board that comes with the Ender 3 has them, but (in case I am mistaken) it could be worth checking that you did not forget to put any jumpers in place.
To fix the problem you could also reduce the steps/mm from 80 to 5 but operating in full step mode would seriously degrade print quality, so it is preferrable to find the root cause.

Do you know which pins should I measure, I cannot open the control board box now to check these connections there.

Anyways, I checked the voltages there. Chose one of the outer pins as ground, the two pins in the middle were both 24 V and the other outer pin 0 V.

@KidB You did not measure the correct pins. They are internal to the electronics and you must open the box to have access to them. You need to find the motor driver chip, look up its datasheet to find out which pins are MS1/2(/3) and measure those. Perhaps you can find somebody local to your area with electronics knowledge?


text:
PETG layer adhesion problems
I have recently started printing with Polymaker's PolyMax PETG on my Ender 3 v2. I have not been able to get the layer adhesion anywhere near as strong as it should be. I would guess it is around 20-25 % of the strength in the XY direction. The parts snap easily along the layer lines under loads that PLA and nylon hold up to just fine.
Print settings:

0.15 mm layers @ 35-20 mm/s
Hotend temp 245 °C
4 mm retraction @ 40 mm/s
combing on
jerk control on
no cooling

I made sure to use a nickel-plated brass 0.4 mm nozzle. I have calibrated my E-steps and tried printing in an enclosure, but nothing seems to help with layer adhesion. I have made sure there is no debris getting on the filament as it comes out of the drybox and even tried taping around the heater block so there is absolutely no part cooling.
Any ideas as to what I could be doing wrong?

Have you already tried a thicker layer height to see if that makes a difference?  E.g. 0.2 mm?

Yes, and it makes no difference. A wider line width just leaves lots of blobs on the print. I think it is over extruding slightly.

Maybe you misinterpreted the comment, I wasn't talking about line width; I commented on layer height. PETG prints better when layer height is not too small, I've mainly used 0.2 mm and printed kilometers of 2.85 mm without major  problems.

I got a roll of Hatchbox PETG and the prints are fantastic. Small test prints don't break along the layers even at higher fan speeds. The problem was the Polymax PETG. I took a look at the TDS for it and the impact strength on standing samples was only 29% of the standing ones. I believe the Polymax PETG just has inherent layer adhesion problems.

Please note that Polymax PETG isn't PETG, it's PCTG. I may try doing some firmware changes and printing it at 270 °C later on.

I had this problem with my Ender 3 until I changed to a different extruder and now PETG never has adhesion problems. Even 100 % fan is fine at 245 °C. I think the stock hobbed gear just slips on PETG really badly, giving underextrusion. Go slow, increase the flow to compensate, and possibly increase temperature slightly more. Or buy a decent extruder.

Why would it under extrude if the esteps are calibrated?

@TreeBarkEater: Calibrated under what extrusion rate? Actually pushing material thru hotend at print speed, or just moving it in the bowden? My best understanding of what I experienced was that there was just a lot of slipping under backpressure, and this is really bad for PETG if you're using linear advance since it needs a fairly high spring constant that increases the pressure (and thereby slippage) even more. Also, if you're not using linear advance, that will give rather inconsistent extrusion that also makes the layers adhere poorly.

One more thing: combing is bad for PETG. Because it's so sticky, moving over already-printed material without retracting tends to drag it, making a poor surface for the next layer to adhere to. Try turning combing off (or leaving it on but setting max comb distance without retract to < 1mm).

The OP is already printing pretty slow, the max recommend speed of the PETG I'm using (printed about 20 kg of 2.85 mm filament) is 55 mm/s, so I wouldn't call the OP's speed fast. I fully agree on using a decent extruder.

@0scar: it's not fast, but maybe fast relative to Creality's extruder.

I would think it is being over extruded because when I calibrate the e steps it's extruding faster than when printing.

@TreeBarkEater: I don't follow what you mean by that. If you mean you're doing the calibration with actual extrusion taking place (pushing material out the nozzle not just thru the bowden) that's good, but keep in mind that actual printing is performed by pressing the extruded material against a surface, not extruding into thin air. The backpressure is completely different.

To test this with any certainty, you need to either mark the whole intended extrusion length for a print on the filament, and see that it matches after printing a nontrivial size print, or weigh a print with scale that's sufficiently precise an compare to the theoretical extruded mass.

The layer adhesion with Polymax PETG at 260 °C was great so I didn't go any higher.


text:
Dual extruder does support/secondary extruder stay hot during entire print?
The hot end set-up for my printer consist of 2 Titan Aero extruders. The printer relies on Reprap firmware and a Duet 3 controller board. When I finish setting everything up, my primary extruder will use ABS and my secondary extruder will uses HIPS.
If the model I am printing only has supports near its base, once the supports have been completely printed, will the secondary extruder remain hot/at its printing temperature setpoint until the entire print finishes?  Or has this been worked out.
Even more specifically say the HIPS extruder isn't needed for several hours during a print. Will it cool down and begin heating up when its needed or just slightly ahead of time?
I feel like the HIPS filament left over in the extruder would be ruined after this and likely to clog going forward.

Slicer Cura has a standby temperature that is used when the hotend is not in use. Furthermore, you can write your own filament/hotend change scripts to do whatever you want. You can even do a full cool down of a hotend and full warmup when it is needed again. You can also always edit your G-code file after slicing, use a standby temperature for the beginning of the print where supports are used, and manually change the G-code at the last change to disable the HIPS extruder.

I’m using BCN3D’s fork of Cura, for a Sigma printer, and it is very smart about standby temperature on the idle head- it starts heating the head from standby temp while the other head is finishing up the layer, so you aren’t waiting for it to heat at the tool change.
Does anyone know if that look ahead functionality is something a user could program in stock Cura, or Prusaslicer? The custom tool change G-Code would fire off too late. Not happy with current slicer, the gap fill seems broken.

I use Cura 4.9.  Is Cura set-up to begin heating the stand-by extruder once the printer starts on a layer requiring the secondary extruder?

@ChinchillaWafers what do you mean the custom Gcode would fire too late?

“Fire too late” I should have said the tool change g-code script doesn’t get executed until the previous extruder is done with its part of the layer, so if you’re at standby temp, say 150C, and the tool change gcode tells the second extruder to heat up to printing temp, the printer is sitting there idle while it heats. So not “too late”, but it’s making bad use of the time, by not starting the heating cycle ahead of the tool change.

The BCN version of Cura is set up to do the heating from standby on the idle head in the middle of the layer, it knows how long it takes to heat, and it’s ready by the time for the tool change. It’s slick. It also shuts the extruder down if the print is done with that material. Just wondering if that behavior is possible to program in stock Cura, and take advantage of its slicing improvements, or if I’m stuck with the BCN version, for its good management of standby temp behavior.


text:
How to print Lego bricks?
How can I print Lego bricks in order to make them attach?
I need them to be standalone pieces. I use resin to print. My model is Elegoo Mars 3. What resolution should I use?
Also, how should I color the bricks? I have some colored resin at home but I want to make them all black and color them afterward.

You can't print a LEGOTM Brick, because you are not Lego System A/S. The best you can do is print a brick that is compatible with LEGOTM bricks. Also note that Lego Systems A/S has more than 600 US design patents, which might interfere with the legality of manufacturing bricks in the US.
The original bricks are made from ABS and made with a very tight tolerance and uses the inherent flexibility of the material to create a friction fit. However, Resin prints do lack the required mix of sturdyness and flexibility and thus can't create the required friction fit.
In other words: You can't make bricks that are compatible with LEGOTM bricks with a resin printer based on the material properties.

Given that OP seems to want to use a coating for color already, could it work to do resin prints with additional clearance allowing for additional thickness from the coating to provide the needed flexibility and friction fit?

@R..GitHubSTOPHELPINGICE no. the coating would just get destroyed over time.

The main patent on Legos has been expired since the 90’s, I remember when all these knockoffs were hitting the market. Also US patent law does not prohibit an individual from making a clone for their own personal use.

Design patents are different.


text:
Figure out max bed temperature
I have a Tronxy X8 (yes, I know, poor choice but I didn't know better) and after some years printing PLA, PETG and TPU, I am considering trying ABS, since I got myself a second hotend which can go up to 300 °C.
But I am not sure if my bed can handle the required 110 °C.
According to the manufacturer, 110 °C is the maximum on the bed, but they also claim their teflon-lined hotend can go up to 275 °C, so I don't trust their claims at all.
How can I safely determine the maximum temperature that the bed will go?
I have a MOSFET mod for the bed (and also a Bigtreetch SKR v1.1 Mainboard). The only original parts in the chain, which I don't trust, is the PSU and the heatbed.
The bed looks like aluminium, the surface is a Buildtak clone.
What could happen if I just crank up the heat?

The firmware has a fixed limit for the bed, this is also the maximum value you can set through the LCD interface, the  default is e.g. set in the configuration file for Marlin, it  contains the following constant definition:
#define BED_MAXTEMP      150

But, you will most properly never reach this value, even worse, most beds won't even reach 110 °C. At some point the losses become too high and the heat input is too low to compensate. This is discussed in a previous question that I will link when found. To mitigate the heat loss, you can insulate the bottom of the heated bed and place the printer in an enclosure, this allows for reaching higher bed temperatures. Printing ABS should preferably be done with an enclosure anyways.
To find out the max temperature, just schedule the bed to go to 140 °C and see where the bed temperature takes you, or where the safety features kick in.

The firmware that I have is not the original anymore (since I have a new mainboard). So the original limits don't apply any more. Can anything go fatally wrong if I crank up the heat? I really don't want a burning printer.

You should test to see how far it goes, if it doesn't reach 110 °C you cannot even set the bed at that value. You can heat up the bed from the LCD, take it to the max value (firmware limit) to see what you can get. That is not dangerous, it will not burn your printer, the hotend is something completely different, it requires Thermal Runaway Protection.

I want to add that smaller (say 75 x 75 mm footprint or less) ABS prints can be done on an 80 C bed with some "extra super hold" type hairspray.

@Davo User FarO has similar experience he also uses a skirt shield to create a mini climate. Thanks for sharing!

@0scar nice - we do that for some of our PEEK prints. :)


text:
Can't find replacement nozzle tube
I have a Monoprice Maker Select Plus.
It recently started having issues printing. It turns out that the small plastic tube that feeds the extruder with filament was completely clogged. I couldn't get any of the filament out so I need a new feeder tube. I can't find one specifically for this printer anywhere. Does anyone have any ideas?

Could you add a photograph? Is this tube inside the heat break or between extruder and hotend?

I just added a picture. It is a plastic tube that goes inside of the metal tube I circled.

This printer is using a so-called MK 10 extruder/hotend. These are a little different, there is a liner for the heat break that continues all the way down to inside the MK 10 nozzle:

This PTFE tubular liner has an outer dimension of 4 mm and an inner diameter of 2 mm. The length of the tube is 34 mm. These tubes can be bought at pre-cut size or, more economical, bought per meter.

The per meter tube looks like one of the sizse sold for Bowden tubes.

It is one and the same material, it's a PTFE tube ID/OD 2/4 mm. Alternatives are Capricorn tubes, which supposed to withstand higher temperatures.

PTFE has an advantage of low friction as well has temperature tolerance; thus ideal for Bowden tubes.  Apparently, Capricorn tubes are still PTFE.

Any idea where I can buy this? Everywhere I find it, it is 1.75mm.

@sabo It's designed for 1.75mm filament, the ID will still be large enough to work flawlessly.

@sabo Online 3D print webshops, online market places, Chinese selling platforms, etc. I get my tubes from AliExpress, cheap, but you need to wait a few weeks or months. 2/4 mm PTFE tube is very common, it shouldn't be hard to find it in your city/country (more expensive but fast). You shouldn't buy too tight tubes, but 1.9/4 will work also for 1.75 mm filament.


text:
Fill doesn't reach perimeters on supports (Simplify3D)
My Tevo Flash works well. Right now, I'm trying to print a thin, disc-like part on supports. The 3 perimeters at the edge of the disc are OK. The dense fill zigzag pattern makes many U-turns near the perimeter. It all looks OK in Simplify3D. But in the printed part, in several spots, the zigzag pattern doesn't reach the perimeters, leaving a ~1 mm gap.
My guess: in those spots, the filament has nothing to grab onto underneath, so the U-turn region is dragged back by the nozzle a bit (away from the perimeters) and/or it droops. I'm using the smallest support res in Simplify 3D: 1 mm. Any options I can try?

I think you are right, not enough support. I'm not using the Simplify3D slicer so I cannot answer for this specific software, but in Cura you can create a top layer over the support creating a platform, this helps me much with hot printed filament and support structures, maybe Simplify3D has a similar option. You possibly can also increase the overlap of the infill over the perimeters.

Cura calls this layer an "interface" and offers it for both top and bottom of supports.

Nice sketch, by the way -- not many people have the skill and expend the effort to draw clearly with pen and paper any more.

OK, thanks. What I did: I added a layer of ONLY perimeters, UNDER the ones in the sketch, wider (6 instead of 3), same radius on the outside, but extending more INWARD towards the center. They don't interfere with the function. Now it works, the fill "catches " on the lower perimeters

Posted as a wiki answer from a comment from the OP to a different answer.

The Zig Zag vs Lines patterns was only a part of the problem. The 2nd part was that this layer rested on supports only, so the fill, whatever its pattern, didn't have enough surface to "grab on" near the perimeters. If I had switched from Zig Zag to Lines, the air gap would've diminished a bit, but I would've gotten drooping. I solved it with wider, underlying perimeters.

The zig-zag pattern are known for this kind of fluke...
I will use Cura to demonstrate, but it's gonna happen on the majority of slicers.
See this example:

Because nothing is really a circle on a cartesian plane and there's resolution limitations on the real world, the slicer has to account for these and, assuming you are using zig-zag to save time, they are doing what is expected. The Zig-zag pattern is a continuous, fast way to fill the top/bottom layers.
Now, see this lines pattern top layer:

It has much smaller air gaps. Every time the nozzle finishes a line, it has the chance to reposition itself to make a much smaller gap, just because isn't continuous.
So yeah, the air-gaps are a "feature" for zig-zag patterns, but you can mitigate this effect reducing the line width on top/botton layers.

It seems that increasing "Skin Overlap Percentage" on cura mitigates this effect too, but i really haven't seen the effects of this setting on a real life object

Thanks. The zigzag vs line patterns was only a part of the problem. The 2nd part was that this layer rested on supports only, so the fill, whatever its pattern, didn't have enough surface to "grab on" near the perimeters. If I had switched from zigzag to lines, the air gap would've diminished a bit, but I would've gotten drooping. I solved it with wider, underlying perimeters. I'll keep the line fill in mind as an option. Thanks.


text:
Klipper on Ender 3 v2 wrong signals
I have very strange problem. Motors X and Z are messing up somehow. I mean if I try to home X only, Z moves also. And vice-versa. Y motor homes and moves normally.
Board is stock E3v2 v4.2.2 with TMC2208. With Marlin everything is OK.
Also, I'm not sure if it's important, but I have compiled firmware 3 times and all 3 are different in size - 20424 bytes first, 20540 bytes second, and 21172 last. All with the same settings -> STM32F103, 28kbit bootloader, com only (USB, CAN disabled).
Heaters seem to work too.
Video
(I'm not sure how to add a video window here)
Here is my config for motors:
[stepper_x]
step_pin: PC2
dir_pin: PB9
enable_pin: !PC3
microsteps: 16
rotation_distance: 40
endstop_pin: ^PA5
position_endstop: 0
position_max: 225
homing_speed: 50

[stepper_y]
step_pin: PB8
dir_pin: PB7
enable_pin: !PC3
microsteps: 16
rotation_distance: 40
endstop_pin: ^PA6
position_endstop: 0
position_max: 225
homing_speed: 50

[stepper_z]
step_pin: PB6
dir_pin: PB5
enable_pin: !PC3
microsteps: 16
rotation_distance: 8
endstop_pin: ^PA7
position_endstop: 0.0
position_max: 250

You should probably create an issue about this on the Klipper Github (https://github.com/KevinOConnor/klipper/issues)
Maybe something about the shared enable pins?
The HAL itself for the F103 works fine from my experience.
Make sure your kinematics: in the [printer] section is set to cartesian

Don't open a ticket on Github, read the documentation: help requests go to the Discord channel.

Also, check connections: maybe you inverted some cables.

"Make sure your kinematics: in the [printer] section is set to cartesian"
Thanks, that help!