I'm currently facing a weird printing quality issue that i can't seem to wrap

3D Printing
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I’m currently facing a weird printing quality issue that i can’t seem to wrap my head around. Printer is an off-the-shelf OrdBOT from RepRapDiscount which printed quite well so far though i haven’t had an eye on high quality during the last months. In the build process of my new Eusthatios now i saw that smaller holes/rounds up to around 20-25mm in diameter show weird deformings. See the picture to get an impression. This is a test part with 25mm diameter and different sized holes. You should see that the circles and holes aren’t really round but have quite a few flat parts - especially a bigger one that seems to happen in the same place over and over again. Good news is that this error doesn’t scale. It only matters on diameters up to max 30mm - on bigger roundings and circles this doesn’t look so bad (see other pic)

I’ve already checked pulleys (i even changed the for new ones as i had some lying around), belts, movement of the makerslides, cleaned the makerslide wheels, checked and reset belt tension and all that other stuff. I also changed slicers (currently mostly using Slic3r), lowered speeds, accel, Jerk and everything else that came to my mind.

I’m a bit stuck mainly because i managed to get such issues worked out quite quickly in the past. Probably any of you guys does have a good hint? Any help is appreciated! Thanks.

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Thanks for the hint, @Mark_Rehorst but the STL definitely isn’t the problem - the final G-Code looks quite nice. If the STL was the problem that flats should also be more regular around the circle.

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Could it be loose or damaged belt/pulley?

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Hysteresys that’s it. Marlin firmware have a new feature to correct this problem. When your axis makes little circurlar shapes , the momentum makes the axis move forward a little bit. With little holes it easy to see.

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Thanks for your hints guys. As i wrote i’ve already checked belts and pulley (even exchanged the latter). Also steps/mm are still as they always were and good at a calculated 80 steps/mm for 1/16 res and 20 teeth GT2.

@Alvaro_Rey_Rodriguez this would mean that this problem has always existed before. Using Repetier firmware and didn’t have such issues so far. At least not on the bigger end of the sizes where you can see the problem.

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@Helmi ​ I don’t nkow, but maybe you didn’t notice. That’s a mechanical problem, in 3dprinters, laser cutters, etc.

Or maybe with the use, it came bigger.

@Branden_Coates ​ the jerks only work in corners, now you can control both hysteresys and jerks

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guys looks like i managed to sort things out. While checking all the mechanics i totally forgot to check the tension for the makerslide wheels - that was set a bit too strong below the table (Y axis) and so it wasn’t moving smooth enough.

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Looks like i can’t post another picker of the resultet from the iOS app. Will post that later.

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It is backlash for sure. Backlash is most evedent on small round feature. Looks like only 1 axis is the culprit, the issues are 180deg from each other at the direction changes of one of the axis.