Vibrations in circular interpolation

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27 Nov 2019 13:20 #151344 by Hakan
I'll join to the backlash idea. The vibrations seems to be at that 45-ish degrees position when the axis switch from pushing one way to pushing the other way.
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27 Nov 2019 13:52 #151347 by Leon82
I would try a conventional cutter pass that way you will be pushing on the screw and see if the vibration goes away
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28 Nov 2019 11:58 #151417 by Samu_97
The conventional milling pass has been a great idea, but unfortunately the result has been the same vibration in the same place.
Today I don't have time to disassemble the axis screw bearings, but tomorrow I can check it.
Thanks to all for the help!

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29 Nov 2019 12:32 #151494 by Samu_97
Today I disassembled the screw bearings of the X and Y axes. Everything seemed correct, I assembled and adjusted it with a little more tightening ... I checked it with a gauge, 0 backlash.
The machining test has been the same vibration, but this disappears if in the middle of the arc, when it is already in the direction of the curve, I tighten the axis screw with the hand trying to stop it, it is indifferent if I press the X or Y screw, the vibration disappears (this confused me)
It is the same as cutting a hard or soft material like PVC, it vibrates the same.
I am using an endmill with 3 teeth, maybe try more teeth to see if it induces less pounding.
I have not yet calibrated the measurements in the movements of the machine, this should not affect this at all, right?
Thanks!!!

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29 Nov 2019 14:17 #151504 by Leon82
If pushing on the table affects the vibration I would look at your linear guideway.

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29 Nov 2019 15:51 #151507 by tommylight
Something is definitly loose on that machine.

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02 Dec 2019 23:44 #151785 by andypugh
You sound to have already tried this, to an extent.

But can you test if the problem switches quadrants if you machine an internal circle first clockwise, then anticlockwise (at a larger radius, to save material)

That would tend to indicate some looseness or backlash somewhere (not necessarily in the screws).
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03 Dec 2019 13:42 #151860 by Todd Zuercher
Another thing to check, see if the defect changes shape or position if it is milled at different positions on the table, (front right, front left, right rear and left rear. (That would point the finger directly at the table ways.)
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03 Dec 2019 15:14 #151878 by Samu_97
Thanks for your help, it will take me a few days to try what you propose.
I will tell you.
Thank you very much to all.

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04 Dec 2019 14:05 #151996 by jools
I have the exact same problem with the closed loop Leadshine drives and I think it's down to resonance.

If I cut a large circle say 160mm diameter then at the North, South, East and West ponts ie where one stepper is running slow and the other fast its fine. On the diagonals I get the same chatter as you. I think this is because when cutting at that speed both the X and Y steppers are in their harmonic danger range. These two frequencies combine and amplify each other (I think)

I ran my program without the spindle on in the air and I can hear and see the vibration caused at these points.

I'm trying tuned mass dampers though with out the tuning to try and overcome this. People have had success with 'rattlers' mass dampers .

I have emailed Leadshine about the problem two days ago but they have not yet come back to me.

In the mean time I am adding rattlers and other vibration suppression devices and strengthening the motor mounts to make them super rigid.

Try just a large circle without the spindle and listen and look for vibration.

Jools
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