misaligned printing

got a lulzbot mini for the family for christmas this year. The thing was solid for the first couple of prints but has developed a problem where it seems to randomly shift to the left during printing subsequent layers. Ive run a couple of rocktopus test prints that show this behavior and started one just now to show it at the beginning. Ive read about endstop triggering, and the person I talked to at Aleph suggested I check the tension on the X axis motor. I can see no way to verify these things without disassembling the printer, and as it is about a month old and still under warrenty I am hesitant to do so.

Is this a known problem? Should I be returning the thing?



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Your belt or your motor pully in the axis of the direction the shift is occuring is loose. In this case it looks like its probably the X axis? You need to first check the motor pully setscrews (they can fall out sometimes) and then second, significantly tighten the X axis belt.

this unit is under a month old. Shouldn’t it still be in working order? I understand tinkering to get more life out of an out-of-warranty device but this one is brand new.

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Screws vibrate loose in shipping sometimes. You can call support and get the unit swapped out under warranty, but if you don’t want to deal with the hassle, that’s the fix for what is most likely wrong.

Thank you for the perspective. What you say makes a lot of sense. I’d like to try to fix this myself.

I bought the Printed Solid cover for the thing that it looks like I will have to remove to get at the X motor. It also looks like I need to remove the motor from its housing bracket to be able to access the motor. Is this correct?

In reading some other articles about tensioning the belt, there are reccomendations of using a special tester to validate that the tension is the right ammount. I do not have such a tool. Is this really necessary?

Yeah, you will need to pull the motor to get to the pulley most likely. You may be able to just tighten the setscrews from the side the belt enters. There are two of them, one should be lined up with the flat spot on the shaft.

Having a fancy tension meter helps, but you don’t necessarily need one. Plucking the brlt like a guitar string should make a solid sounding twang noise. If the issue persists you probably didnt tighten it enough. You can probably use the y axis belt to get the general idea of the sound, though it does vary for a few reasons. It could also be an electrical issue but belt or pulley is by far the most common issue there.

To just tighten the belt, use a pair of needlenose pliers to grab the belt end, loosen one of the clamp ends, then roll the belt end around the pliers to add tension, then re tighten and remove the pliers.


After removing the belt, we have discovered that the sprocket on the end of the X-axis motor is missing one setscrew, and the other is loose. We have provided this info to the Aleph support folks who will be processing an RMA for the sprocket (apparrently the setscrews are supposed to be permanently set into the sprocket so the sprocket will be replaced).

I’ll reply back once we have received the replacement part and gotten it installed.

Thanks for the help!


You’re welcome! Those setscrews are metric m2.5 setscrews, you may be able to find them locally at something like an ace hardware or online.