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almi

Loosing positions after hours of printing

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Hi all,

please help me out with the following issue.

I have a relatively huge object to print. After 2-3 hours of printing the Ultimaker somehow looses its

positions of Gcode and moves sidewards into one direction.

First I thought of an issue with the endstop, but then I printed another small object with the same

issue which cannot reach the endstops at all.

This happened now 4 times witth the same object, always at about the same height.

Is it a mechanical problem or a fault by the slicer? The gcode was done by netfabb.

Could it be an underrun of cpu buffer?

Please help me.

Thanks,

almi

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It is a mix of different problems, and it occasionally happens to me as well.

First, check if the jump happens only in one direction, or two directions.

Second, check if your belts are tight, since they will jump a tooth on fast sudden moves if they arent tight.

Third, check the lubrication of the XY carriage (use thin oil on the rods)

Fourth, check the temperature of the XY steppers during printing... They should/will have around 35C, up to 60C. They they are really cold, it is a sign that they dont get enough current/power, and you need to adjust the small trimpots on the stepper drivers up by "1/2 to 1h" (borrowing the image of a clock face for the trimpot). The ideal spot is between 9 and 10 o'clock

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It's a mechanical problem. First I would check all pulleys, if they have black screws in them tighten them a bit extra. (Which is hard to do on the motors, I know)

There recently has been a batch of slightly lower quality of these screws that need to be tighten a bit better or they vibrate lose.

You could also use a black marker to put a dot on the pulley and axes, so you can see if it shifts (It's how I detect this issue at UM)

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This happened to me recently, after I re-tensioned the main belts, I tensioned them more than

I had done so before, and also I had made some hotend cooling changes.

So I was extruding a bit too much plastic, so the nozzle tip was scraping a bit on the rough top of the

print. Then there was a "boink!" sound, and it had shifted. So the stepper had skipped.

Looks just like your picture.

I oiled the shafts, lowered the belt tension a little, lowerd my "steps per e" by 15 and all is well again.

So basically if the steppers are working too hard they can freak out and skip.

So if the belts are too loose you can loose a tooth position, and if too tight you can run out of

juice for the motors (see above post on motor current).

C.

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Hi all,

thanks for your solutions!

Indeed one of my short belts went sloppy.

And additionally, my rods were dry after hours of printing.

So I guess this all led to loss of steps.

I will now try to make the short belt tensioner posted on thingiverse,

and will use machine oil for oiling my rods instead of the grease shipped with UM,

because out of my experience this grease will be pushed away by the bearings soon.

Thanks for your great support!

almi

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