oliver.r4
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Print of 210 mm circle fail

Apr 29, 2018 10:59 pm

Today I tried to print the door of SpannerHands spool holder MK6 (thingiverse 2839275). And then I noticed, that my MK2.5 was cutting of the print at the max Y side. So I tried a test - printing just a 210mm circle of 0.6 mm hight and 206mm inner diameter. And that failed as well. The printer is just cutting off approx. 1.5 mm of the circle at the max. Y side.
All calibrations went well. And there is enough space for the print bed to move further and complete the circle. I checked the gcode if there are some instructions going outside the printing area, but there aren't. Minimum Y is 0.214, maximum is 209.786.

For me it seems that the printer is just cutting of the print area by stopping to move the Y axis any further like there's a limit reached. Any ideas what I can do? Could it be a firmware issue?
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Knickohr
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Re: Print of 210 mm circle fail

Apr 30, 2018 6:54 am

You printing exact at the last back line, so i'ts all OK, but you have about 3mm to the first front line.

You can move the circle 3mm to the front side.

The purge line is at x=0 y=-2 , so you have about 5mm space left.

Try it.

Thomas

oliver.r4
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Re: Print of 210 mm circle fail

Apr 30, 2018 8:13 am

Knickohr - thank's for the reply. The lines on the metal sheet are not a good orientation because even if placed very carefully, the lines on the sheet do not coincide with the lines on the heat bed. I would assume that if the printer is locating all reference points without problems, then there should not be such a problem.

I placed the circle with Slic3r exactly in the center. And according to the gcode the circle is exactly there. You can see that by the Ymin and Ymax values in the gcode (see my first post). If I follow your advice and shift the circle a bit towards the purge line, slic3r is generating negative Ymin values. That might be a workaround but not a solution.

The circle should be printed completely without moving it slightly outside the boundaries in scli3r. Could it be somehow connected with the "Y distance from min" values? My values are 8.46 on the left and 8.50 on the right. Although I do not get any error messages during calibration I could imagine that there are some calculations inside the firmware that cause such a behavior if the Y distance from min is too high.

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Knickohr
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Re: Print of 210 mm circle fail

Apr 30, 2018 12:23 pm

Yes, you're right, it's only a workaround. And yes, you're right too, it has something to to with the Ymin. My suggestion, the linear rods are a little bit too short. I've replaced it with a 5mm longer version and it works fine.

Do you still use the threaded rods ? In this case, mabe you can move the frame a little bit.

Thomas

oliver.r4
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Re: Print of 210 mm circle fail

Apr 30, 2018 12:38 pm

No - I modified my printer according with the bearmod (with v-slot profiles). Maybe that is part of the problem. And it's the first time that I'm going to print something using the complete print area. Maybe that's why I haven't noticed the problem earlier. I will check my printer for possibilities to reduce the Y distance from min. Maybe that helps.

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Knickohr
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Re: Print of 210 mm circle fail

Apr 30, 2018 1:45 pm

Welcome to the club !

My MK2 is bear-modded too ;) But I'm using a little bit longer rods because the origininal PRUSA was worser. I'm loosing about 5mm in y-direction. So, for the mod I get the longer rods and it works well. My Ymin is about 3.5mm now. But I don't know what it was before.

Thomas

oliver.r4
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Re: Print of 210 mm circle fail

May 03, 2018 7:51 pm

Ok - it seems that I solved my problem somehow. After reading this on github https://github.com/prusa3d/Prusa-Firmware/issues/616 which describes partly the problems I have had, I went back to version 3.1.3. But that did not help at all.
Next I designed a new y-belt holder which is a bit longer and has longer screw holes so that I can shift it by 5 mm. I thought that if I shorten the distance from the end switch until the pinda probe is above the front reference point, I could solve the problem. The result was fail in xyz calibration.

Then I moved by rear v-profil of the bear-mod further back by 3 mm (just adding 2 3mm thick shims). The value for "Y distance from min" changed to 11.21mm left and 10.87mm right. The result for the test print was very unexpected - worse than before (picture Test2).

Then I decided to give the modified y-belt holder another try and shifted it towards the y end switch (completely). And all of a sudden it worked. The "Y distance from min" changed to 6.46 and 6.31. And the circles are round. (picture Test3). As one can see the print is still shift towards the y_min side.

I have not really understood yet why it is like it is but my feeling tells me that there is a virtual room defined somewhere in the firmware starting at the end switches. The xyz-calibration the determines by searching the 4 reference points where the head bed is located within this virtual printing room. And if calibration did not fail, the printer just stops moving towards one end of the head bed if it would move outside of the virtual room.

I could not find the definition these boundaries in the firmware. But I think it is somewhere defined. Maybe somebody of the developers could confirm that. At the end I'm fine for the moment.
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mounia.z
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Re: Print of 210 mm circle fail

Jul 10, 2018 9:41 pm

Thank you! It's just unfortunate that I had to join because of problems instead of pure printing joy. I uploaded the picture the way you said in the first post, and added another one that hopefully gives some more insight into the problem. It has small TubeMate Psiphon Test DPC holes, zits and stringing in the support structure and infill, but none or very little on the objects (if they get finished).

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RHDreambox
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Re: Print of 210 mm circle fail

Aug 14, 2018 1:46 pm

The Y-axis bearings (the ends) determines the centering of the bed. If the bearings are displaced in the tracks, this affects the centerpoint of the bed. The bearings should be located exactly in the middle of the tracks.
In the menu "Support / XYZ cal. Details / [0; 0] point offset" you can see if the bed is centered. The ideal value for X and Y is 0.00.
Happy owner of a Prusa MK3

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