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Author Topic: The hurky jerkies  (Read 2996 times)

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The hurky jerkies
« on: October 22, 2008, 06:36:55 PM »
Boy! Color me confused.  I'm doing a 3d part, cutting both sides, about 24" X 24" X 3" in MDF.  Rough cut with 1/2" ball nose, several passes to get down to finish.  First side went fine, perfectly smooth movements on all three axis simultaneously.  Drawn in Solidworks, tuned for cutting in Rhino, IGES export out into Mastercam for first side.  Back into Rhino to flip the part to do the other side. (My Rhino is better than my Mastercam).  Used the same tool paths as for the first side, just reset the geometry.  Now for my problem...on the back side any time I have a direction change in either X, Y, or Z it jerks through it in small increments, then proceeds to a normal speed cut on the straight cuts.  Conservative speeds - 100ipm on the XY, 45ipm on the Z.  Shopbot PRT96 with upgraded control box running Mach3. Rackin' my brain and I can't figure what could have changed.  It acts kind of like ramping is totally missing.  Any ideas?

Donn

Offline Hood

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Re: The hurky jerkies
« Reply #1 on: October 22, 2008, 06:59:11 PM »
First one using CV and second using Exact Stop?
Hood
Re: The hurky jerkies
« Reply #2 on: October 22, 2008, 09:49:03 PM »
Nope, couldn't be that because I didn't change it.  I knew the symptoms matched that, but it couldn't have been because I didn't change anything.  So, after reading your suggestion, just out of consideration for your efforts, I checked CV settings. 

Yup, that was it.  Beats me!

Thanks,
Donn

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Re: The hurky jerkies
« Reply #3 on: October 23, 2008, 02:48:28 AM »
CV and Exact Stop can be changed with your code so that is likely how it happened. G61 is Exact Stop and G64 is Constant Velocity so if G61 was in any of your code it would change to Exact Stop.

Hood

Offline Greolt

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Re: The hurky jerkies
« Reply #4 on: October 23, 2008, 06:43:03 AM »
There was a bug quite a few versions ago that would turn "CV Feedrate" on without the users input.

It has been fixed but perhaps you are using an older version.

CV Feedrate turned on has pretty much the same effect as if CV is turned off.

CV Feedrate is found on the settings page.

Greg
Re: The hurky jerkies
« Reply #5 on: October 23, 2008, 12:43:37 PM »
Thanks, you guys!

I was just glad to get some guidance before I had to run the finish cut.  It went fine.  Here is the result...the other side is dished as you might expect.
I looked at the code and didn't see a switch, so maybe a bug.

Donn