"Jittery edges" on circles - Possibly post processor? (RESOLVED)

[muibubbles]

Hey,

I'm still dealing with "jittery edges/chatter" on my circles (pic 1&2). While this occurs my gantry looks to be making jerky motions as if it were cutting a bunch of line segments. In my CAM program (vetric cut2d) it is a closed circle with only 4 points when I view it in node mode. However when I save and cut it on the cnc the motion dictates otherwise.

I do not understand g-code, however I did some brief searching and managed to put a line of code in for an arc which performed WAY better (albeit a much lower feed). Also I dont see and G2 or G3 commands (CW and CCW arc motions) in my code generated by vetric.

So looking into this further I noticed there are 3 post processors for centroid in vetric. (Pic 3) I also noticed a few other PP have "arcs" in their name. However the one I am using does not (I used the highlighted one). Now I'm wondering if the PP is converting my arcs into lines? (if that's possible)

Things i've tried:
using the Centroid CNC7 Arcs PP (but its in MM and caused way too many problems to get a test cut)
Tried using fusion 360 to generate a PP but had the same issue.
It's not the work holding- all the other pieces cut good. (triangle and square) Which makes me believe my X and Y axis could be ruled out.

My only guesses is the PP or something with acceleration during arcs.. Any help would be great!
If it is the post processor, is there an updated one and are post processors interchangeable with different cam softwares? IE can you use the same PP for Vetric and fusion 360?

[Dave_C]

N0730 G3 X1.1250 Y4.7500 I0.0000 J-0.6250 F60
N0740 G3 X1.7500 Y4.1250 I0.6250 J0.0000
N0750 G3 X2.3750 Y4.7500 I0.0000 J0.6250
N0760 G3 X1.7500 Y5.3750 I-0.6250 J0.0000

I copied the above G3 G-code from your file but there are a lot of small movements in the code as well. I've run code from the old Mach 3 days that was individual moves and never had what you are experiencing.


Dave C.

[cnckeith]

hello.
causes of this
- very short vector moves combined with the items below...
- on the X and Y axes you have turns ratio of .88xx and step per rev of 1600. that is very few steps per inch of travel. can you run the motor drive at 3200 steps per rev?
- backlash, what is the measured back lash of the X and Y axes?


unrelated...
you are running v4.12, time to update to v4.5. free support for previous versions has ended.
viewtopic.php?f=60&t=4457

[muibubbles]

N0730 G3 X1.1250 Y4.7500 I0.0000 J-0.6250 F60
N0740 G3 X1.7500 Y4.1250 I0.6250 J0.0000
N0750 G3 X2.3750 Y4.7500 I0.0000 J0.6250
N0760 G3 X1.7500 Y5.3750 I-0.6250 J0.0000

I copied the above G3 G-code from your file but there are a lot of small movements in the code as well. I've run code from the old Mach 3 days that was individual moves and never had what you are experiencing.


Dave C.

So are you suggesting it's the machine not the coding?

[muibubbles]

hello.
causes of this
- very short vector moves combined with the items below...
- on the X and Y axes you have turns ratio of .88xx and step per rev of 1600. that is very few steps per inch of travel. can you run the motor drive at 3200 steps per rev?
- backlash, what is the measured back lash of the X and Y axes?


unrelated...
you are running v4.12, time to update to v4.5. free support for previous versions has ended.
viewtopic.php?f=60&t=4457

-Is the very short vector moves determined by the cam software? (Ie if I used a different CAM program it will eliminate those short moves?)
-Honestly, I have no idea why it's set to 1600, it's been a while since I set up the machine so I have to relearn everything. I will change it to 3200 steps per rev
-I don't think I have backlash calibrated in, I will look up some videos and report back.

Side issue... So I got the hint and I upgraded to v4.5 lol. But now I cannot get my machine to even move... I restored the report, did all the power cycles and when I open up the wizard I can not click on any of the tabs in the "Primary System" They are grayed out and when I hover over them the are not clickable... Also in CNC12 nothing on the VCP works.

Is this what happens when I wait to long to update or am I missing something here? haha

[muibubbles]

Also let's say I had the steps per rev at 1600 in the wizard but on my driver they were set to 1/16 = 3200 steps per rev...... What would be the effect? Because I've had it running like that for 2+ years.......

[muibubbles]

Update: I ended up uninstalling cnc12 and re-installing it. The restore function didnt work for me but I'm basically starting from scratch since my steps per rev was set up incorrect

[cnckeith]

Also let's say I had the steps per rev at 1600 in the wizard but on my driver they were set to 1/16 = 3200 steps per rev...... What would be the effect? Because I've had it running like that for 2+ years.......

set the wizard to 3200 to match the drive. you just cut your resolution in half with the 1600 setting you will also have to re calculate the overall turns ratio.

[muibubbles]

I fixed the resolution to the correct 3200 setting and basically re-calibrated my whole machine. Needless to say, that seems to have resolved my issue! Thanks for the push to update my software =D

[Upnorth]

Any chance you can post a photo of the results? When I switched to an Acorn I went with the same steps per revolution as it was set to with the other software. I would be interested in seeing what you got for results.