Probe for corner

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07 Jul 2013 04:54 #36371 by BigJohnT
Replied by BigJohnT on topic Probe for corner
My SWAG is your retract is not far enough for your probe hysteresis.

JT
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07 Jul 2013 05:10 #36372 by cwmk577
Replied by cwmk577 on topic Probe for corner
Thanks John. I set the retract to an absurdly large value like .25, and I get the same result :P FWIW, the hysteresis on the probe is visually imperceptible to me.
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07 Jul 2013 05:40 #36373 by BigJohnT
Replied by BigJohnT on topic Probe for corner
So much for that guess...

JT
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07 Jul 2013 05:50 #36374 by BigJohnT
Replied by BigJohnT on topic Probe for corner
Are you getting the error on this line?

G38.5 F#1 Y-.010 (retract till probe clears)

JT
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07 Jul 2013 06:14 #36375 by cwmk577
Replied by cwmk577 on topic Probe for corner
John, not 100% sure. I guess I should print it out and try stepping through it one thing at a time.

Where would I look to see what those variables' values (e.g. #5070) are? There's an emc.var file in my machine directory, but it doesn't have any lines for values under 5161 or something like that.

FWIW I tried the center probing routine that was posted earlier in this forum, and that worked fine....
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08 Jul 2013 14:57 #36393 by Rick G
Replied by Rick G on topic Probe for corner
Hello,

Where would I look to see what those variables' values (e.g. #5070) are?

Take a look here ...
linuxcnc.org/docs/html/gcode/gcode.html#sec:G38-probe

Try increasing the
#<Probepause> = #17 (=.05 pause) ; Probe pause, amount of time to pause between probe moves to wait for probe to settle/ stop bouncing
also try reducing
#<Fastprobe> = #1 (=10 Fast prb) ; Fast probe speed
#<Slowprobe> = #2 (=5 Slow prb) ; Slow probe speed

It looks like an early version is posted but this may help...

#<Fastprobe> = #1 (=10 Fast prb) ; Fast probe speed
#<Slowprobe> = #2 (=5 Slow prb) ; Slow probe speed
#<Probedist> = #3 (=.50 Prb dis) ; Probe distance
#<Retract> = #4 (=.050 Prb ret) ; Probe retract distance
#<Diam> = #5 (=.117 Prb Diam) ; Probe diameter
#<Xcord> = #6 (=.25 X Pcord) ; future ignore
#<Ycord> = #7 (=.25 Y Pcord) ; future ignore
#<Xcorr> = #8 (=0.00 X cor) ; correction to X coordinate to fine tune result
#<Ycorr> = #9 (=0.00 Y cor) ; correction to Y coordinate to fine tune result
#<Zcorr> = #10 (=0.00 Z cor) ; correction to Z coordinate to fine tune result
#<Ymax> = #11 (=1.00 Y Smax) ; maximum distance to search for Y
#<Yinc> = #12 (=.125 Y S inc) ; size of step to search in Y
#<Xfin> = #13 (=0.00 X fin) ; X Location to go to when finished
#<Yfin> = #14 (=0.00 Y fin) ; Y Location to go to when finished
#<Zfin> = #15 (=.125 Z fin) ; Z Location to go to when finished
#<Zsafe> = #16 (=.250 Z Safe) ; Safe Z travel location
#<Probepause> = #17 (=.05 pause) ; Probe pause, amount of time to pause between probe moves to wait for probe to settle

Rick G
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09 Jul 2013 04:04 #36428 by Rick G
Replied by Rick G on topic Probe for corner
G38.5 F#1 Y-.010 (retract till probe clears)
G4 P#17
G38.3 F#1 Y[0 - #4] (retract to set up for slow probe)
G4 P#17
O103 IF [#5070 gt 0]
(MSG, Probe not complete unexpected Y hit on retract)
G90
M2
O103 ENDIF
If this is where you are having a problem it is possible that the probe is bouncing on and off on the retract steps.
A slower speed may help or you could try to retract with a G1 move instead. The G38.5 and G38.3 retract moves are for safety and information if there is an unexpected contact or the probe sticks.
You could also try changing the Y-.010 to Y -.025.

Rick G
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09 Jul 2013 22:16 #36449 by cwmk577
Replied by cwmk577 on topic Probe for corner
Thanks. I tried changing the delay but it had no effect. I think the G38.5 was the problem. By the time I was done I ended up writing my own version of this using G1 moves and it seems to be working well. IIRC, LinuxCNC errors if the probe is tripped during a G1 move, or is that only when the G1 is issued from the MDI? I haven't tried tripping it during a programmed G1 move.
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10 Jul 2013 00:08 #36458 by BigJohnT
Replied by BigJohnT on topic Probe for corner
If you trip the probe input when your not in a G38.x move it is an error.

JT
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11 Jul 2013 14:28 #36543 by Rick G
Replied by Rick G on topic Probe for corner
As John said a G1 move should trigger an error with Linuxcnc, however if you normally work in G90 absolute distance mode and the routine is working in G91incremental distance mode you may be left in the G91 mode on error.
G38.5 is to retract the probe from the contact to non contact, if the probe sticks on or bounces back on the move should fail.
IIRC G38.3 will not work if you issue it when the probe is already in contact.
The idea of the two step approach is again for safety, let you know where the problem is and return you to the mode you would normally work in.

Rick G
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