Jason- let me know if that fixed it when you get some free time (world’s most valuable commodity).
Zeenon - looks like that is pretty good, could just be the texture underneath showing through, what did you change?
P3D- Attaching the drag chain to the z motor mounts could really be doing some/most of this, plus you have a very large machine which makes it more susceptible to these sorts of issues. That drag chain is acting like a breaker bar and pulling on your entire middle assembly. Nothing should ever touch this. It also looks like you are attaching a vac hose to your router, making it even worse. You really can’t have it all buddy. Giant machine, tall z axis, drag chain, vac hose, and super precision. I use a small machine, hold my vac, no drag chain for a reason.
The drag chain doesn’t affect X only or Y only motion. Only diags and circles are affected. When the pics upload, you can see one of the cuts has a Y only clean cut (to the right of the pic) and a chopy diag and circle (center and left). My issue is only on diags and circles. I would think the drag chain would affect all of them no ?
I want my cake and I want to eat it too!
In some of the videos where I lowered the speeds to F50 you can hear the alternating X Y motor dance. They do not move simultaneously. Is that normal ?
If you watch the little white wire at the top of the Z you can see it only shakes on diags and circles. Pure X and Y it doesn’t move.
I think my biggest issue was the bearings on the XY outside axis were gripping the conduit too tight. I loosened the bolts until I could spin the bearings, but yet, they still made contact with the conduit. Too loose, and the bearing would not come in contact with the conduit. Too tight, and spinning the bearings (if you could), would move the axis.
Got more pics to send but having an issue with getting on my PC.
Did a few things. Redid the zip ties on all belts. Also moved the GT2 16T pulleys in a bit. Also loosened some more bolts. Seems quite a bit smoother. Still has repeating patterns but definitely much better. Will post pics as soon as I can. Time for some sleep.
@vicious1 I started out at 1/32 stepping and the problem happened then as well. Really the only thing that changed when going to 1/8 was the motors seem a little cooler. I was have issues attaining higher speeds while lasering 1/8 helped speed that up as well a little. Other then that anything I have tried has not changed anything. I will have time tomorrow to play… I am going attempt loosening the bolts off a bit on the 8 bearings in x/y that are held in with 1" bolts. I have those tightened up pretty good. Perhaps they are not tracking 100% straight causing a wobble.
@Jason I redid my belt tension, loosened the bolts on the xy that I could get to, and also redid the GT2 pulley. See the pics I just added (dated feb 16). You can see an improvement in the jittering although it is still there and notice the repeating patterns.
20170216_001143 - shows two cuts in different areas of the stock material with identical patterns. The more pronounced one is the plunge location.
20170216_001025 - shows the difference after redoing belt tension and loosening some of the bolts.
20170216_001008 - same as above.
20170215_235329 - shows the location of the GT2 pulley before.
20170215_235436 - and after.
I’m going to dismantle my xyz and redo it. See if that changes things.
I remixed my XYZ pieces, the spacer and nut trap so that the Z bearings aren’t spreading as much and my MPCNC is square at rest now (see attached photo). Was not able to square it before. I think the torsion on the center assembly was part of the cause of the issue.
I tightened all the corners of the frame and added mid span supports on the X axis (see attached photo). That stiffened the frame quite a bit.
I can now cut circles at 1100mm/min pretty cleanly (see attached photo). I can even cut at 7200mm/min but it’s rough looking, but the bit and setup can handle it just fine. Impressive. 3mm per pass on an 1/8 bit at 20000RPM.
When I had the original XYZ parts, the moment I inserted the Z tubes it would force my X and Y axis out of square by 5/8 of an in inch. So I remixed the XYZ parts so that the bearings were backed off a bit by placing the holes for the bearings so the bearings would just touch the tubes. Now when I insert the Z tubes, everything stays square.
The mid span supports are a huge benefit. I might even add more… I’ll post the stl’s tonight on thingiverse and add a link here. They just mount to the standard MPCNC corner mounts. No use in re-inventing the wheel.
