Prints randomly warping

Hi all,
I am trying to figure out and prevent my ABS prints from warping at height. I am printing with the hotend set to 235 at .12 layers. The speed settings are Loops- 40, Solid- 50, and Sparse at 70. Some of the prints come out great but others not so much. I don't believe the motors are to blame because the warping is too uniformed. I looked at the printing troubleshooting guide which points to bed temperature to be the cause but don't think I can go any lower on this without the parts coming loose from the bed. Here are some things I have tried but still getting the occasional warp like the attached pictures. Any suggestions?

1. Closed the ceiling vent to stop drafts
2. Enclosed the sides of printer with plexi glass although the top of the printer is still opened due to mechanics moving making it difficult to cover.
3. Printing with the bed temp set at 50C


-Greg

Here is another that I just finished printing with no warp. The only difference is I changed the layer height from .12 to .2. This 3d printing can test ones' patience at times

Just for he record, most reprappers refer to your problem as layer shifting, not warp (warp usually means the bottom/sides of the print has deformed due to uneven shrinking when the print cools).
Your problem is likely due to one or more of a few causes.
Check that your pulleys are fastened well to the motors (mark with felt tip pen across pulley and axle).
Check current seings on drivers. both over (heat shutdown) and under current (lack of torque) can cause issues.
Check carriage friction along axes.

I may have missed a few, but you get the idea, is anything preventing proper motion along the axes?
/Andreas

lower the travel rate. i think the issue is from the jump from the large body to the thin part.


my guess is some binding in one direction.


slow down travel rate and if that fixed it, then find out why it did and then fix the issue to get up to speed again.

Yes, that is definitely not warping. It's layer shifting. What are your other machine parameters?

Thanks for the replies, I will investigate the axis motions. The chinese linear bearings I am using aren't the smoothest like the Japanese NSK or TDK are but I am hoping they will break in over time. My stepper motors and drivers hardly even get above room temp so I don't think they are over heating and skipping steps. The motors are also rated at 76oz of torque. I am using a H-bot design so the extra long belt maybe causing some problems but I do have it really tight. One of my fixes is to install the piece I am printing to minimize any lash on the X axis during motion reversals. I am currently using a 20 tooth pulley with MXL belt setup, would I see any benefit in going to a GT2 with 16 tooth pulleys? I did order a E3D hotend so hoping this will also help by lowering the Z height and making the prints more contained within the printer avoiding drafts. I had to make some dimensional adjustments to the part I am printing and so far this one hasn't warped either at .2 layer height. Could the lower layer heights be causing excessive heat to be building up on the part?

Thanks guys,
Greg

GT2 belts/pulleys are virtually zero backlash. The same cannot be said for MXL. MXL belts are timing belts, not linear motion belts. You are probably seeing the effects of backlash although I wouldn't expect the error to keep adding like that. Perhaps it would, I don't know. From what I understand, GT2 belts are the ones you should be using for the back-and-forth motion our machines go through.

[reprap.org]

Edited 1 time(s). Last edit at 01/17/2014 01:56PM by umdpru.

After seeing the kind of printer setup you have, it's probably something to do with the fact you have a CoreXY like setup.

You also have some pretty beefy steppers there.

Your drivers are probably overheating.

You say they are at ~room temp. How are you measuring this?

Infrared thermometer reading about 31C and by feel

I ordered some gt2 16 and 20 tooth pulleys and belt to give it a shot. I have printed several other parts today with no other layer shifting. I did slow every thing down which also appears to have helped the quality.

thanks everyone for the advice
-Greg