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[Solved] Mk3s y-axis assembly trouble  

New Member
Mk3s y-axis assembly trouble

I was trying to screw in the tensioning screw between the y axis holder and tensioner when the screw encountered some resistance. I began to realign the two printed parts but when I tried to resume screwing, I noticed that the nut now spins within it's printed holding. Do I have to get a new printed part?

The bolt, screw, and printed part having trouble

Posted : 19/09/2020 9:40 pm
Famed Member
RE: Mk3s y-axis assembly trouble

If you can somehow grip or maybe CAREFULLY glue the nut to the piece, you can probably continue with the assembly and then re-print the piece in PETg or ABS once you have it running.

It's always best with all of those plastic pieces to deburr the edges and 'chase out' the holes, making sure that the intended hardware fits properly.

If you start printing with a loose Y carriage, it can cause all kinds of ringing (if you're lucky) or artifacts and shifted layers.

Posted : 19/09/2020 10:29 pm
Eminent Member
RE: Mk3s y-axis assembly trouble

RE: Mk3s y-axis assembly trouble

I had this problem too. I ended up undoing the pulley at the front of the frame to get more purchase. After wrapping the belt ends around each screw I put a piece of rolled up tape between the blocks and tightened the blocks to make the tape press the belt ends against the screws. You then tighten the belt by screwing the front pulley to the frame. Kept tight for months.

This is a poor design, Prusa should have made a two screw down plates that lock the belt ends to the binding screws.

Posted : 20/09/2020 12:18 am
Estimable Member
RE: Mk3s y-axis assembly trouble

It looks like you have the "tensioning screw" going in from the wrong side. The non threaded (shoulder) part of the screw is bottoming out on the nut. The screw should go in from the front with the threads pointing to the back of the printer.

Posted : 20/09/2020 6:34 pm