Video shows , when slowed down, that it is upcut bit … tearing fibers upwards.
unless, by any chance , is your spindle running backwards?
I’ve said it’s an upcut, but I’ve always run upcuts on this path. It’s an apples to apples comparison between the machines. I also ran a downcut as a test.
No it’s not running backwards.
No change with tightening the loose parts you found?
I’ll stick with what I originally said…end play in the ball screw. The top and bottom bearings are contained within the end caps of the slider. They are pressed from the inside and are captivated against a shoulder in the end cap. The end caps are fastened by machine screws to the slider frame. There is nothing specific that would hold the optimum length to insure that there is no end play in the ball screw. The ball screw is shouldered to go through each bearing. If the distance between the shoulders is short, that would mean that the screw itself can move up and down between the bearings. That was the problem I had. I fixed the problem by drilling and tapping the bottom of the ball screw, and adding a screw and washer to draw the screw up against the bearing.
If you don’t have the capability to drill the screw, you could add shims to take up the end play.
Your machine is plenty stiff enough, especially cutting something like color core so chatter can be ruled completely out.
post by Ken5 on Dec 9, 2025
Can you show us a picture of the modification you made
I think I can picture it but a visual would help
post by Derf on Dec 10, 2025
Can’t get a photo unless I take things apart, but I drew a crude diagram.
post by WouldWork on Dec 11, 2025
Thank you for that diagram! I had a very big issue (mm, not 0.mm) z height problems on a OpenBuilds machine due to similar issues, but a more crude setup. Tightening the couplings to the acme screw on that machine such that the couplings reduced play through tension solved most of the issue. The rest was fixed by upgrading to the 1F, and letting someone else continue the effort.