jerky motion on y axis

[GME]

I watched the video and two things come to mind.Were you using the same collet for the spoilboard skim that you used when tramming the machine?If not ,it might be worth trying a new collet in case dirt or wear have reduced the accuracy or concentricity of the one used for skimming.The other issue that might be causing the uneven cut could be resonance of the Z axis and the gantry and if it is occurring it will appear worse with a flycutter simply because of the tips being further from the spindle axis.

I can't see an easy way of isolating the cause.Is there a way to temporarily mount a sturdy piece of steel carrying a dial gauge to the gantry while the cut is running?Any flutter of the needle could point to a little play in the Z axis or spring in the gantry cross beam.

Good points. What about the 'stuttering' and "wiggling'? Neither a bad collet nor an out-of-tram condition should cause stuttering and wiggling. That's what leads me to agree with ger21, i.e., it looks like a R&P issue. I'm still thinking there may be a bind, maybe induced during homing, that is the underlying root cause. A bind could cause the symptoms described, and could result in lost steps, or a sort of hopping. Something as simple as the stepper drives not being tensioned enough could also be an issue - would seem like skipping (stuttering and wiggling) and could be present on one axis (Y) and not the other (X).

Gary

[routalot]

It could be an R&P issue and the clue might lie in the spacing of the scoring and its relationship to the distance travelled per revolution of the pinion.I would still suspect that there is a strong chance of the oscillations of the Z axis plate and the gantry beam have a harmonic that is moving the tool tip.I just can't work out how you would find it or cure the situation.Is there any chance of an image of the whole machine?

[Aerojunkie]

Huge thank you for all the help guys. Looking forward to making this machine what it should be. Headed to the shop to do a little R&D and report back. Im planning to go through the r&p drives to see what may be binding there. My machine is squared with the homing switches but ill check that the gantry is square to the frame, in case that is binding. I can mount the dial indicator on the gantry and move it around to see how much jumping occurs. I have some plate glass I can put on the bed so it has something flat and smooth to ride against.

[ger21]

OK, I'm back home and was able to watch the video. If you put your hand on the spindle, is it shaking the whole time? It sounds like it's bouncing as it moves down the table. If so, then it's almost certainly a mechanical issue. What RPM are you running that at?

[Aerojunkie]

OK, I'm back home and was able to watch the video. If you put your hand on the spindle, is it shaking the whole time? It sounds like it's bouncing as it moves down the table. If so, then it's almost certainly a mechanical issue. What RPM are you running that at?

The spindle is shaking, when going in the y direction. In the video I was running at 10,000rpm and 250ipm.


I did a little more digging and trying to eliminate a few things.

1.I started by removing the spoilboard so I could check the entire machine for squareness. The frame is so close I cant measure any better with a regular fatmax (from my experience they are the most accurate) tape measure. I was getting +/- 1/32" when doing the 1-2-3 method across the whole machine frame.

2.I removed the cutter and ran the same file with the spindle off. You can feel the same vibrations as before, nothing coming from the cutter or spindle running.

3.I removed each y axis drive assembly, the gantry moved very smoothly on its own.

4..I took the belts off each drive and ran the stepper while holding it, very smooth and quiet.

5.I put the belts back on ran each drive seperate, ran smooth there as well from what I can tell holding it.

6.Here is where I think it is, the contact from the rp rail and the 2 stepped gear that engages it. The alignment there is off and they arent meshing real cleanly.

Any ideas on a fix? Only thing I can think of is try some paper shims in a few spots with some trial and error.

I do have one side question if anyone has any ideas. I can jog the machine around and the steppers stop so hard the machine actually shakes a little bit. Normal? I have tightened every bolt I can find and it doesnt seem to matter.


I also wanted to add. You guys were correct from the start about the r&p being the cause of the problem. Thank you for all the help so far.

[ger21]

Call CNCRP and ask them what they suggest?

Certainly seems like an issue with the pinion?

I do have one side question if anyone has any ideas. I can jog the machine around and the steppers stop so hard the machine actually shakes a little bit. Normal?

Either lower the acceleration, or switch to a control with S-Curve acceleration, which is much smoother., Yes, it's normal with Mach3, and higher acceleration.

[Aerojunkie]

I was planning to get a call in to them tomorrow to see what was up. Now I can pass along all thats been tried and suggested, should make getting a solution simple. Over the years I have learned my favorite resource for information is a forum, lots of people using this stuff everyday.

[Aerojunkie]

If anyone ever has a doubt on ordering from cnc routerparts/avid cnc........dont. Sent an email to them with a link to this thread and had parts being shipped to me 1/2 hour later. Ahren and Dan took care of it all and are sending me some replacement drive spindles to help get it resolved, and are willing to help me beyond that if needed. Should be here in a week and I will be updating this thread with the results. Thank you to everyone who has helped me with this.

[Aerojunkie]

Just wanted to report back that the machine seems to be running just fine now. The jerkiness is gone, evidently it was the drive spindles. CNCRP/Avid sent me a new set no questions asked once I explained it to them and they went through this forum thread. Huge thank you to all who helped me on here and at CNCRP.

[nlancaster]

AvidCNC/CNCRouterParts has always had GREAT customer service.

[GME]

Just wanted to report back that the machine seems to be running just fine now. The jerkiness is gone, evidently it was the drive spindles. CNCRP/Avid sent me a new set no questions asked once I explained it to them and they went through this forum thread. Huge thank you to all who helped me on here and at CNCRP.

Just curious, but what was it about the drive spindles that cause the jerkiness?