Smooth your tubes (SFW :) sanding? stuttering movement

So i just finished upgrading my brand new cnc to a bigger MPcnc haha. just longer tubes. now i have some jittery movements.
I want to sand the tubes, or make them smoother as to eliminate this as a reason, if for no other reason.

Do you guys sand tubes? how else do you smooth them?

EDIT - i have turned up and down the stepper voltage to see if that would make a difference. it doesnt seem to.

Go to your favorite program and make yourself a full size (cut area) box. Set it to cut 85% of your Z height in super shallow depth cuts so it makes a few thousand passes across the pipes in both directions.

Then hit GO and let it run for like 3 hours.

If it’s not smooth by the end of that. Run it again. :slight_smile:

I did not sand my tubes. I had some jittery action at first - turned out to be a bad connection on one stepper wire. You probably should take off the belts and make sure steppers are all moving smoothly without a load.

both very good suggestions :slight_smile: i think ill try the bad wiring first :slight_smile: because that seems easier haha.
And i did have to re-solder the connections when I made it bigger so that would made sense.
but i also replaced the conduit as well. so who knows :slight_smile:

So i am running a few hours of tests like suggested.

  1. It seems smoother in the X direction than the Y. Y grinds more (in a few inches of the run)
  2. My dimensions inside to inside are perfect, within 1/16" however, when i run the larger square test, one side of the carriage doesnt quite keep up with the other, and on one end, it may be up to 1/4" off from back to front or side to side. It certainly could be caused by the grinding just slowing down one side and not the other as much.

So I just spent 2 hours running the grid at 45mm/s and it seems to have smoothed it fairly well.
I then started running it again at 75mm/s after putting some lube oil on it. it helped clean some of the dirt/grime off of them as well.
Its running much better now… so the true test will be to actually cut something… which ill do tomorrow

I used a bolt, nut, washers and tape to make a drill adapter so I can spin the (uninstalled) tubes with a battery drill. Then wrap a kitchen scouring pad around the tube and slowly slide it along the tube length while spinning with the drill. Two passes with the scourer, one pass with a solvent soaked rag and a final pass with a little lithium grease on a rag.

The above process will smooth off the rough/high spots and give a brushed metal appearance. I wouldn’t recommend sanding as you want to leave as much galvanised coating on the tube as possible. Also, just enough grease to coat the surface but not encourage dust to stick to the tubes.

Made a little jig for polishing like RH1N0 suggested. Works great! My local conduit was pretty janky looking so I figured I might as well.

Nice idea! I just looked at it on Thingiverse and I can see how it expands to hold the conduit.

It beats what I did… a big bolt wrapped in masking tape :slight_smile: