Help. Linux CNC is cutting off my corners
27 Nov 2015 19:08 #65873
by tmanpdx
Help. Linux CNC is cutting off my corners was created by tmanpdx
I'm about Day 4 into trying to figure this out and really would like some help on understanding what Linux CNC is doing and why, then if there is anything else I can do to configure it so that it quits doing this.
I'm trying to cut out a simple bow tie pattern which I then use to do two cuts:
1) Outside profile
2) Inside pocket
So I can then drop the profile I cut into the pocket.
The problem is that when the machine gets to the corners, Linux CNC cuts it off and instead of a 1/16" radius, I'm getting a much larger radius, in the 1/2" size.
After much experimentation, of trying to slow down, etc, I was able to modify the Gcode to slow down to F4 0.01 from the end of each cut, and then speed it back up to F80 for the long cuts, and this appears to be more or less working.
So, my assumption is that somewhere in some config, Linux CNC thinks that it can't handle the change in direction and is deciding to cut off the corner. Rather than experimenting on what it thinks my limits are, I'd like to know where this config is set and how I can understand / change / modify these settings so that it can be repeatable for me.
A little bit of background:
I'm using a custom CNC controller for woodworking using a frame \ gamtry / router from PDJ.
A friend of mine help me set up Linux CNC and we built our own controller (based on Mesa 7i76 and a 5i25) but he helped set up all the hal / ini / gui (using gmocopy). He's pretty rusty & no longer using it in his own shop so I'm left on my own to try & figure this out. I'm trying to ramp up my knowledge on Linux CNC, having read many of the articles here, I can't find the answer I'm looking for.
All help appreciated.
Thanks
Tman
I'm trying to cut out a simple bow tie pattern which I then use to do two cuts:
1) Outside profile
2) Inside pocket
So I can then drop the profile I cut into the pocket.
The problem is that when the machine gets to the corners, Linux CNC cuts it off and instead of a 1/16" radius, I'm getting a much larger radius, in the 1/2" size.
After much experimentation, of trying to slow down, etc, I was able to modify the Gcode to slow down to F4 0.01 from the end of each cut, and then speed it back up to F80 for the long cuts, and this appears to be more or less working.
So, my assumption is that somewhere in some config, Linux CNC thinks that it can't handle the change in direction and is deciding to cut off the corner. Rather than experimenting on what it thinks my limits are, I'd like to know where this config is set and how I can understand / change / modify these settings so that it can be repeatable for me.
A little bit of background:
I'm using a custom CNC controller for woodworking using a frame \ gamtry / router from PDJ.
A friend of mine help me set up Linux CNC and we built our own controller (based on Mesa 7i76 and a 5i25) but he helped set up all the hal / ini / gui (using gmocopy). He's pretty rusty & no longer using it in his own shop so I'm left on my own to try & figure this out. I'm trying to ramp up my knowledge on Linux CNC, having read many of the articles here, I can't find the answer I'm looking for.
All help appreciated.
Thanks
Tman
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27 Nov 2015 21:58 #65889
by BigJohnT
Replied by BigJohnT on topic Help. Linux CNC is cutting off my corners
I'd say you need to read the short User Important Concepts section of the manual.
linuxcnc.org/docs/2.7/html/user/user-concepts.html
JT
linuxcnc.org/docs/2.7/html/user/user-concepts.html
JT
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27 Nov 2015 23:37 #65896
by tommylight
Replied by tommylight on topic Help. Linux CNC is cutting off my corners
And check the acceleration, that usually is related to it.
Or just use the G64 Pxx Qxx as suggested by cmorley, that works like a charm.
Regards,
Tom
Or just use the G64 Pxx Qxx as suggested by cmorley, that works like a charm.
Regards,
Tom
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28 Nov 2015 02:11 #65911
by tmanpdx
Replied by tmanpdx on topic Help. Linux CNC is cutting off my corners
Thanks all. You've given me a bit to think about / read and also test. My first question after reading G64 is that I thought this was what FERROR and MIN_FERROR were supposed to be doing from the [AXIS] section of the INI file.
But I will try it out & finish reading the sections.
Thanks
But I will try it out & finish reading the sections.
Thanks
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28 Nov 2015 16:54 #65955
by andypugh
No, those have nothing to do with the programmed path, they determine how far out of position the machine is allowed to be before an error is triggered and the machine is stopped.
Replied by andypugh on topic Help. Linux CNC is cutting off my corners
My first question after reading G64 is that I thought this was what FERROR and MIN_FERROR were supposed to be doing from the [AXIS] section of the INI file.
No, those have nothing to do with the programmed path, they determine how far out of position the machine is allowed to be before an error is triggered and the machine is stopped.
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29 Nov 2015 01:01 #65985
by tommylight
Replied by tommylight on topic Help. Linux CNC is cutting off my corners
Just remembered, if you have a version 2.7 pre, that was the same problem i had when i was using it, so i had to put G64 Pxx Qxx on every gcode i used, where xx is the tolerance in units, in my case 0.1 and 0.1 for milimeters.
Regards,
Tom
Regards,
Tom
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