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jagged curve
« on: November 17, 2010, 01:21:12 AM »
Hi,
I'm cutting a curve with a cnc and have set to "fit curves to arcs" in Rhinocam and I keep getting a jagged curve.  I try cutting a perfect circle and the machine cuts a pretty smooth curve but when I cut the curve that I'm using on the plex in the picture it is jagged?  I've attached the gcode to see if you can give me any clues as to why this may be hapening?
Re: jagged curve
« Reply #1 on: November 17, 2010, 07:23:09 AM »
Are you trying to cut in one pass?  Looks like tool chatter to me.  Code looks good in Mach3.

Try slowing down feed rate and cut with multi-pass.

Regards,
John Champlain

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Re: jagged curve
« Reply #2 on: November 17, 2010, 07:33:15 AM »
That is really terrible - looks like a mouse has been at it.

I think John's right. I have tried your code and the result is smooth but I had to reduce your F200 feedrate.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: jagged curve
« Reply #3 on: November 17, 2010, 10:38:18 AM »
The code I posted was the spoiler board cut but I cut the 1/4" acrylic in 3 cuts .08 in. deep each with an offset of .05 and then full cut in one pass without the offset.  I tried cutting slower by putting the feed rate at 10% in mach is that the same as doing it in the cam software or does the computer have to work harder and is maybe not keeping up?  I just got my cnc and I also noticed that when I slow jog in mach at 10% it moves a bit jerky on the y and a bit less on the x.  The x and y are rack and pinion and the z is worm gear.  The z is very smooth.  I was going to try to loosen the rack an pinion to see if it would be smoother.  Do you think any of these things could be to do with the roughness?

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Re: jagged curve
« Reply #4 on: November 17, 2010, 11:38:14 AM »
If it's jerky when jogging, then it's probably not going to cut smoothly. Do you have a gear reduction to the pinion?
Gerry

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Re: jagged curve
« Reply #5 on: November 17, 2010, 12:07:35 PM »
yes it has a belt but it seems good and tight.  The thing that concerned me was the tightness of the gear on the rack.  I was going to try to back it off a bit and see if it glides smoother.
Re: jagged curve
« Reply #6 on: November 17, 2010, 02:39:19 PM »
Got it smooth!  I loosened the gear on the track and it seems pretty smooth in jog mode now.  Also slowed down the cut speed from 200 to about 50in. p.m..  I did a test in the rhinocam without "cut arc fitting" and it was jagged.  With cut arc fitting set to .0002 and the global parameters set to .0001 got a very clean cut.  I think it was a combination of all the things.
Thanks!