Rough Motion on Circular Toolpaths

[cnckeith]

thanks for posting the photo album, very helpful.

my initial impression

a.) 1.1 turn per inch is geared for cutting cabinet boxes at 1500 ipm not doing milling machine type work.

install 5:1 or even 10:1 gearboxes and eliminate the belt down mechanism if you plan on doing this type of work.
sweet spot for this kind of work in the video is 2.5 turns per inch.

b.) i think there was an issue with the probe being tripped while running a job with smoothing on that caused jerky ness which was fixed in v5.10 (you are running v5.08) so make sure you are not running a g code job with CNC12 thinking the probe is tripped as there are lots of probe tripped messages in the error log in the report.

[cnckeith]

gearing for routers post.
https://centroidcncforum.com/viewtopic.php?f=63&t=8649

[cnckeith]

%
(1001)
(T7 D=0.125 ZMIN=-0.01 - flat end mill - 1/8)
N10 G90 G94 G17
N15 G20
(2D Contour9 (6))
N20 G28 G91 Z0.
N25 G90
N30 T7 M6
N35 S20000 M3
N40 G4 P10.
N45 G54
N55 G0 X-5.8625 Y3.925
N60 G43 Z0.696 H7
N65 M8
N70 Z0.296
N75 G1 Z0.121 F60.
N80 Z0.09
N85 G19 G3 Y4.025 Z-0.01 J0.1 K0.
N90 G1 Y4.125
N95 G17 G2 X-2.3875 I1.7375 J0.
N100 X-5.8625 I-1.7375 J0.
N105 G1 Y4.225
N110 G19 G3 Y4.325 Z0.09 J0. K0.1
N115 G0 Z0.696
N120 G17

no need to have smoothing ON with this type of g code. smoothing is for short vector g code. not G2's/g3's
see this for more info.
https://www.centroidcnc.com/centroid_di ... manual.pdf

fyi..smoothing Will NOT make up for bad gearing or other mechanical issues.

[Salted_Pork]

May have found something. I get a bunch of vibration at certain low feedrates (<80 ipm) in the X axis. the chatter marks on my parts line up to where the x axis is at slow speeds for the circle. So yeah seems it is not a centroid issue.

Keith, do you think this is due to the gearing?

Anyone dealt with this before?

Heres a video of what I am talking about. The dial indicator to illustrate the vibration.

https://photos.app.goo.gl/yEc2PDfpjTdvRFeC9

[spikee]

Open the oscilloscope function of your servo. Measure the frequency of the ossilation. And use the built in notch filter to remove that oscillation.

At least, that is how it works wirh delta servos.
All indications, to me are servo tuning related.

[Salted_Pork]

Open the oscilloscope function of your servo. Measure the frequency of the ossilation. And use the built in notch filter to remove that oscillation.

At least, that is how it works wirh delta servos.
All indications, to me are servo tuning related.

Interesting. I’ll look to see if the leadshine servos can do something like that. Thanks.

[Fordmasterkw]

I'm dealing with same issue/different servo though. I have been trying to correct it but have been unsuccessful so far. Just started all of the sudden.
So I will be following this closely.

[suntravel]

Could also be a problem with rigidity tunning...

I use 1 turn/2.5mm on my machines to keep the servo rpm higher = more power while cutting and they run butter smooth, no vibrations.

I tune rigidity till they jitter and then back off the settings a little bit till they run smooth and hold a position without jitter also.

Uwe

[Salted_Pork]

Update.

I disconnected the rack and pinion drive gear to test the linear rail movement. Super solid and smooth.

Then removed the servo/belt/pulley/gear assembly and tested in isolation: Vibration.

Then disconnected the servo motor completely to test it in isolation. And the servo is the culprit! The vibration happens at the same ipm as when it’s all connected.

So. Is this a bad servo? Or can this vibration/resonance be tuned out?

[suntravel]

Do you have a manual from the servo driver?

Uwe