UM1 looses X position about 23 hours into print

[blackcountrybill 0]

Hi Guys,

My sometimes tempermental UM1 has been printing some 70mm high casings for the last two weeks, they are 24 hours prints. About 23 hours (at different heights, normalls around 63mm) into some of the prints the x stage moves and the print continues as normal but a random amount ofset, sometimes I manage to catch the problem and can manually more the printhead back to where it should be,

I've tried all the belts, different versions of cura, different files, I'm stumped as to what might be causing this.

Here's a video showing what happens and three prints I've managed to save.

Cheers guys!

 

 

[illuminarti 18]

It looks like the print has lifted off the bed quite a bit. Is it warping to the point that the head is catching on some part of the print, and so not able to move correctly at some point. That will cause it to lose track of its position.

Other than that, have you tightened all the pulleys, including the one on the x motor? Also, with the power off, try moving the head around by hand, and see if you experience any areas of tightness or binding. Move the head back and forth while looking at the back corners where the short belts are. If the belts are properly tensioned, they should be running nicely in their grooves, staying totally straight, and you shouldn't see any sign of twisting etc. Indeed, if you half-close your eyes and squint at the belts you shouldn't really be able to see them moving at all (aside from any writing that might be moving in your field of view).

 

[blackcountrybill 0]

It looks like the print has lifted off the bed quite a bit. Is it warping to the point that the head is catching on some part of the print, and so not able to move correctly at some point. That will cause it to lose track of its position.

Other than that, have you tightened all the pulleys, including the one on the x motor? Also, with the power off, try moving the head around by hand, and see if you experience any areas of tightness or binding. Move the head back and forth while looking at the back corners where the short belts are. If the belts are properly tensioned, they should be running nicely in their grooves, staying totally straight, and you shouldn't see any sign of twisting etc. Indeed, if you half-close your eyes and squint at the belts you shouldn't really be able to see them moving at all (aside from any writing that might be moving in your field of view).

 

I see the part is lifting off however this happens during the first part of the build and stabilises later on (within the first 30mm)

All belts are properly tight.

 

[gr5 2,266]

All belts are properly tight.

 

Your problem isn't with the belts. It's the pulleys. There is a small set screw in each pulley. It needs to be as tight as all hell. The problem pulley is on the X axis. The most likely slipping pulley is the one on the X stepper. The second most likely pulley is the other one on the short belt. But there are 6 pulleys (not 4!) on the X axis and it could be any of them.

While you are doing this consider marking the shaft and pulley with tiny dots so you can see which one is slipping if it happens again.

Also consider using the shiny set screws that come as spares. These have a pointier tip and hold onto the shaft better although I still am using the black ones and I haven't had a slip since the first week.

 

[gr5 2,266]

By the way, it's better to halt the print as soon as this happens. Then figure out the height where it fails on the ulticontroller (or other methods) then edit your gcode to skip all the begining parts and then print this new "top portion" gcode file. More details here:

continuing resuming rescuing failed print

First you need to use pronterface to find the exact layer to continue on. Pronterface is here:

http://koti.kapsi.fi/~kliment/printrun/

read all gr5 posts here:

http://umforum.ultimaker.com/index.php?/topic/4213-ideas-for-recovering-failed-prints/?p=34788

post #9 here has specific code change example for um2 (ultigcode):

http://umforum.ultimaker.com/index.php?/topic/5269-um²-printing-more-than-24-hours-non-stop/?p=46704

 

 

[gr5 2,266]

Also your part is sticking well to the tape but the tape not to the bed. So get wider tape. I use 3 inch wide painters tape. Illuminarti has 6 inch wide I think.

 

[nick-foley 5]

Stepper driver in the X is failing or is tuned too low to overcome gantry friction, so you're skipping a few steps when it makes a fast travel move and catches a slightly-warped-up edge.

Options:

1) Try increasing the current slightly, if you feel up for it. You can find guides online that give reference voltages, I tune by ear and feel and it works great.

2) Or, decrease travel speed 30-50mm/s so you have less aggro hops around the build environment.

3) Get yourself a heated bed to stop the warping. (This is a worthwhile upgrade.)

 

[anon4321 16]

I would recommend you follow Illuminati's and GR5's advice before you look into Nick's suggestion. It's not that Nick is wrong. It's that when you mess with the drivers and the current settings there is a chance you could blow up the driver.

However, if all the pulleys check out per Illuminati's/GR5's direction and you are getting good adhesion, there are two things that could be wrong with the drivers. As Nick suggested, the current setting could be too low or it could be too high. If too low as Nick suggests, the printer will not complete steps when needed during high speed moves and it will lose it's position. If the current is too high or something is blocking the cooling airflow, the driver will overheat and shutdown and steps won't occur when needed.

Check that the extruder head moves easily. Lubricate the 8mm shafts with sewing machine oil to reduce the friction and force required to move the head.

Check that the drivers still have the heatsinks attached and that the blower is working and the cover is installed correctly.

Try jogging the head while trying to stop it with your hand. It should stop fairly easily. Assuming the head moves freely otherwise and is lubricated, if it stops easily, increase the current slightly. If it is hard to stall and the motors are excessively hot after a print, the current might need to be reduced.

 

[gr5 2,266]

If you blow up a driver they are very inexpensive to replace. Google "pololu" for replacements.