Threads don't work, not sure where to start troubleshooting  

RE: Threads don't work, not sure where to start troubleshooting

maybe You have to reduce a bit the nozzle temperature, to know how much try printing some tolerance test at various temp.

RE: Threads don't work, not sure where to start troubleshooting

@turro75

Thanks for the suggestion. Any test print in particular or do you mean try re-printing the threads at various temperatures?

I printed: https://www.prusaprinters.org/prints/32321-tolerance-test-prusa-performance-level
And was able to free the first three (.24-.20) by hand, the next 4 with a screwdriver (.18-.12) and the center  (.10) is fused and will not budge under any pressure.

I've also printed the https://www.help.prusa3d.com/en/article/extrusion-multiplier-calibration_2257/ which is reading between .35 and .42 which even if my digital calipers are not the most accurate would indicate a small amount of under extrusion.

Given I appear to be leaning under rather than over extruded, the tolerance test intentionally under extrudes (the model reduces the extrusion multiplier) and the tolerance still seems off I'm not sure where to go next. I thought maybe it was over extruding, but that doesn't seem to be the case.

Do you have any preferred tests? I'll find some more to print to see if I can find anything but I can't find anything that I can tie to thread's not working.

Here are some close up pictures of the tolerance test. I don't see the advertised signs of under/over extrusion or z-axis errors but maybe someone else see's something.

RE: Threads don't work, not sure where to start troubleshooting

I'm a relative newbie to 3d printing so don't have a lot of experience but I've never been very successful when printing fine threads.

I tried printing the small clamp you linked to and mine was very tight also.
The screw looks OK but the thread on the body was malformed when it bridged across the top.

I ran the screw in and out several times and it eventually cleared but it's not an ideal fit.

RE: Threads don't work, not sure where to start troubleshooting

@leem

Thanks for the confirmation. That's how that one prints for me as well, it's the 2nd print that completely doesn't work for me.

I have printed a temperature tower to see how that works.

I have been printing at 215, I think based on this tower I *could* print at 210 but below that gets questionable. It is interesting that the tower looks good all the way up to 230. I might try a reprint of some threads at 210 to see how that works. I also notice this is the first print I've ever seen signs of over extrusion. The right side of the tower clearly has an over extrusion on each layer. I can't explain that at all, maybe I'll reprint the extrusion test but this is the same roll I did the previous tests in and I've never seen over extrusion.

RE: Threads don't work, not sure where to start troubleshooting

Just an update, based on the tower I've tried printing a tolerance test at 208 after the first layer, down from 215. While it started ok it jammed up and didn't complete the print. I've cleaned that out, and I'm now printing one at 225 just to see if there's a difference since the tower printed clean up through 230.

I have noticed something else, the flow rate in the fimrware is reading 100 when I'm sure previous prints were at 95. I increased it to 100 for an extrusion test, and am now manually setting it back to 95 at the start of the print. Prusa slicer has the gcode that sets flow to 95. I'm not clear why the tune menu is now showing 100, if it was saving it from the manual tuning it should have gone back to 95 b/c I've manually adjusted it back down on the last two prints but that's not sticking. If anyone knows why it would keep getting set to 100 contrary to what Prusa Slicer seems to have in the gcode I'd love to know.

RE: Threads don't work, not sure where to start troubleshooting

Finished the test at 225 and the tolerances were worse, which at least does line up with expectations. I'm fairly convinced now that 215 is pretty close for this filament, considering the jam at 208 there's not a lot of room to lower it much. I'm pretty much out of ideas most of the calibrations are coming back good, but I can't get tolerances which are being reported on the prints and threaded prints just don't work. 

RE: Threads don't work, not sure where to start troubleshooting

@csanders

able to free the first three (.24-.20) by hand, the next 4 with a screwdriver (.18-.12) and the center (.10) is fused and will not budge under any pressure.

So not far off.

Your first layer is not quite squished enough, it's close, probably ok for run of the mill prints but for fine tolerance work it needs to be bang on.

Most likely you will be better able to print your own designed threads at first as you will be able to tweak the design tolerances.  Downloaded designs have probably been tweaked to suit someone else's printer.

Printed threads, bearings, gears and similar parts should always print a little stiff and need careful handling to begin with, they will run-in in time.

Cheerio,

RE: Threads don't work, not sure where to start troubleshooting

Well the tolerance test fails when there is too much material (adjust flow) and / or the material expands too much (lower the temperature or improve cooling).

Looking at Your benchy above I can't see anything bad in Your printer, I think You only have to tweak a bit the temperature  and flow setting.

You could also consider to print (in PETG) a fan duct which allows a better cooling such as this https://www.prusaprinters.org/prints/52553-prusa-mini-rhd-front-fan-duct

RE: Threads don't work, not sure where to start troubleshooting

@csanders

I know it seems like a cop out but given what good quality prints you are getting, maybe just scale up or down and live with life's little mysteries.

RE: Threads don't work, not sure where to start troubleshooting

@diem

Thanks, I have been successful with my own prints after tuning fusion 360 myself. I'll take another look at the first layer, and it's good to hear I'm down into the fine details. I was curious that posted prints were so finely tuned, and thought that might mean I had something off by an unreasonable amount.

@turro75

I had not seen the alternate cooling solutions. I think I'll give that a try, I have a spool of Prusament PETG that I haven't opened yet specifically for high temperature prints.

@towlerg

I'm definitely not beyond that, especially with the replies I've been getting. My main concern with this being my first printer was that I was unaware of an obvious fix. It seem that's not the case, and I'm happy to experiment some more and when I can adjust prints for additional tolerance.

I really appreciate everyone that took the time to respond. I'll double check the first layer, fine tune temperature/extrusion a bit more, and probably try the suggested cooling adjustment. That gives me several things to queue up and try. I've also recently purchased a dehydrator so I'll see if dehydrating before a print makes a difference as well. I do live in the southern US which is known for high humidity.

RE: Threads don't work, not sure where to start troubleshooting

Since I couldn't find any calibration tests that demonstrated the issue, I took the threads from the Hot End Pen Holder which was giving me an issue and made a minimal test print. I also printed the threads from the Shulker box mentioned earlier.

Here's what I've tried.

1. Printed stock to see that I reproduce the issue with this small print, it does. Flow .95, Temp 215
2. Decreased Z and dropped temperature to 212 (208 caused a clog on an earlier test)
3. Dropped flow to .9
4. Upped temp to 230
5. Dehydrated the spool for 14 hours, cleaned the extruder gears while I waited
6. Set flow to 100
7. Printed with Prusament, just to verify it's not the spool I'm testing with

With the exception of the Decreased Z height any settings were only for the listed print. The Z height I left lower, here's what the 1st layer looks like on print 6.

I'm really at a loss here. Not only does every one of these test prints get stuck almost immediately, but none of the settings seem to make any difference at all. Visually, I don't think I could tell these apart, and functionally they all stop at the exact same place.

I've attached the .3mf file thread-test to this post. That shows all my settings, although I haven't found anything that makes any noticeable difference.

Edit: What file types can I attach, .3mf and .zip don't appear to be allowed?

RE: Threads don't work, not sure where to start troubleshooting

@csanders

Hi, you need to ZIP the .3mf file, or STL files or .Fcode Files, before you can add them to a post. 
regards Joan

RE: Threads don't work, not sure where to start troubleshooting

There are a few helpful posts on threads.

One the other day with info from Fushr and Bobstro

https://forum.prusa3d.com/forum/original-prusa-i3-mk3s-mk3-how-do-i-print-this-printing-help/nut-and-bolt-threads-dont-fit/#post-415639

And another one I found with a google search yesterday while researching pla settings to get threads working.

https://forum.prusa3d.com/forum/original-prusa-i3-mk2-s-others-archive/guide-to-printing-threads/

Hopefully something that might help

RE: Threads don't work, not sure where to start troubleshooting

@clarmrrsn

Thanks, this should help me too  👍 

RE: Threads don't work, not sure where to start troubleshooting

@clarmrrsn thanks,

I've read through both threads. I'm trying to print https://www.prusaprinters.org/prints/23294-hot-end-pen-holder so I'm not able to adjust the print itself to make it work. 

I've gone back through the file, I don't see overhang issues but to be sure I re-printed with .1mm and .05mm settings in prusa slicer. Both produce the same results. The thread gets stuck right off the bat. I'm trying to zip and upload the .3mf file again maybe someone else sees something I'm not overlooking?

I've done extrusion calibrations and I appear to be slightly under extruding which is the other suggesting I see mentioned. Additionally, I've done test prints from .9 to 100 on the extrusion factor (as well as most of them at the .95 default) and don't see a difference.

Hopefully the .3mf file turns something up? I just can't get this thread to print, and there looks to be a lot of successful prints so it's got to be something with my printer.

RE: Threads don't work, not sure where to start troubleshooting

Just to extend the list of things I've tried for the recommendations from this weekend.

1. Printed stock to see that I reproduce the issue with this small print, it does. Flow .95, Temp 215
2. Decreased Z and dropped temperature to 212 (208 caused a clog on an earlier test)
3. Dropped flow to .9
4. Upped temp to 230
5. Dehydrated the spool for 14 hours, cleaned the extruder gears while I waited
6. Set flow to 100
7. Printed with Prusament, just to verify it's not the spool I'm testing with
8. Sliced with .1 mm layer height
9. Sliced with .05 mm layer height
10. Sliced with .1mm layer height and .4mm extrusion width (mentioned in one of the above links)

I can't say I see a difference with any of them.

RE: Threads don't work, not sure where to start troubleshooting

Hi, not sure if this helps you, but from what you wrote, I had exactly the same issue. I have my Mini for a year now (my first printer), and was having issues with threads and other accurate prints. Few weeks ago, I started to dig more into why I was having such issues and came accross this topic: Prusa Mini : difference between CAD sizes and Printed sizes (both X, Y and Z) : any correction through M92 command on Prusa Slicer? – Assembly and first prints troubleshooting – Prusa3D Forum (prusaprinters.org)

Here is also link for the test object and calculator:

XYZ Calibrator and tools for calibration by weitling - Thingiverse

I found out, that instead of 100mm in X and Y, I was having less than 99,5mm. After fine tuning and getting the test file to exactly 100mm x 100mm, all the threads I was having issues with can be printed with no problem.

RE: Threads don't work, not sure where to start troubleshooting

I've not printed the objects from the thread-test.zip but when I loaded it into PrusaSlicer it notifies me there are 2 errors in the hot-end.stl (the square nut)
Not sure if this is relevant ?

Also I noticed that the filament diameter and extrusion multiplier are both set to default - maybe some tuning could help (extrusion multiplier calibration) and some excellent notes from member Bobstro here (calibrating filament)

RE: Threads don't work, not sure where to start troubleshooting

@leem

Thanks I'll look through the filament tuning to see if there's something I can do there.

You're right the file I sent is w/o any modifications. I have however, varied extrusion from 90 to 100 via firmware on some prints and the most recent print was with all widths set to .4. Should I go smaller than .4?

I had not noticed, or at least didn't remember that there were corrected errors in the file. Thanks I'll review and see if somehow I've mangled the file creating the test print!