Hi guys, I’ve been cutting a lot of HDPE lately and am having some rough movement of my gantry translate into my cuts and engravings. On wood it is not too bad and can be sanded out, but in the plastic it is very noticeable. I saw a thread here a while ago about this but it didn’t seem to end up resolved. I’ve attached 2 pictures of a part I cut out last night where you can see the rough cuts. It is not from the bits as you can still see the rough movement in the gantry when running gcode in mid air. Straight x or straight y moves are very clean, it is only when moving diagonally or circular that the issue shows up. The circle that is attached has acceptably smooth edges near the x and y planes but is rough elsewhere. Carves are also rough
I purchased all my parts here, 2’x3’ cutting area, stainless rails, dual endstops, all bearings are bolted just until the nuts touch, I have cleaned the bearings and rails.
Should I be changing the resolution of the steppers?
My gantry isn’t perfectly square but the dual end stops square it up perfectly (off by about 1/2" on one endstop)
That is pretty bad, you should easily be able to get it much closer.
You can try rotating your rails a bit to see if it helps. Make sure you use a finishing pass.
You should be able to get really smooth finishes.
More details and machine pictures about everything might help us determine if anything is off. With the info you have provided that is about all I can guess at.
That part had a finishing pass. The finishing pass looks no better than the roughing pass.
I have begun reprinting the center assembly parts, as I had a few issues with them printing before. I’m much better at 3D printing than before, as I bought the printer just for the MPCNC but have now found about 3000 more uses for it. Hopefully if I rebuild the center assembly I can get it to square up using the bolts. I’m wondering if the fact that the dual end stops are forcing the rails square causes there to be excess pressure on the gantry bearings and binds the gantry up? Here goes another 36 hours of printing. I will report back once rebuilt.
Here are a couple pictures of the build. I did happen to run some sandpaper down the rails on the contact strips for the bearings and found that the gantry now runs smoother than it did. I am hopeful that the cleaned up rails and squared up gantry may fix this issue
I spent hours squaring up everything when i built the machine. The frame is square withing 1/32" diagonally. The tubing is very straight and I have spun it to be sure. I never could get the center assembly to square up though. When I square it by hand and move the gantry it is much harder to move the gantry around.
Side note: I have run a piece of sandpaper down the rails and it is noticeably better. There were small bits of debris sticking to the tubing from being run over by the bearings. You can still see the gantry shaking as it moves, but it is much better. I have not had the chance to cut anything since
I am going to print the new pieces anyway as I have no projects for the printer right now and I want to get everything squared up for piece of mind. I will report back when it is back together. Any other thoughts?
I figured I would give this thread some closure in case anyone else runs into this issue.
Reprinted the center assembly parts and it did not make much of a difference.
I spent a little more time running a fine sanding sponge down all of the rails. I ran a razor blade along the faces of all of the bearings while moving the gantry around. I then used an abrasive pad on the rails and bearings to polish them. It took all of about 15 minutes.
Boy what a difference!
I am now very careful about cleaning the rails whenever I cut wood. Even though I use dust collection, the fine dust eventually just gets smashed into the rails and bearings and starts making the gantry run rough. I’ve actually been seeing the movement get better and better as I cut more HDPE because it does not turn into dust and I believe the bearings I could not reach (inside xy parts) are slowly cleaning themselves.
Thanks for posting your experiences here Andrew. I need to clean my rails today, hopefully that will fix my rough movements as well. I need to install dust collection and maybe even brushes on the trucks to clean the rails before the bearings move over them.
Side questions…are those ceiling panels used as walls on your table? If so, how effective do you find them at keeping the noise down?
