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Author Topic: G68 Angle and Probing  (Read 364 times)

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G68 Angle and Probing
« on: May 10, 2020, 06:45:23 PM »
How can i set a Probing Position when an Agel is set using G68. In Detail i am tying to probe against the Y axis using an G31.1 Y 100 F 100 .. After Probe Contact i would like to set the Y koordinate to 0.
If i Use mc.mcAxisSetPos(inst, 1 , 0) it semms that the 0 position is set, but not valid for the rotation ...

Offline smurph

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Re: G68 Angle and Probing
« Reply #1 on: May 12, 2020, 12:07:03 AM »
You can't change the coordinate offset when G68 is in effect.  Set the G54 offset (or whatever offset you are using) first, then rotate the coordinate system with G68 around the Y0 point. 

Steve
Re: G68 Angle and Probing
« Reply #2 on: May 12, 2020, 03:28:27 AM »
Dear Steve

if that is not possible how do i set the X0Y0 offset for a workpice? For example if i want to use the front left corner of a workpice as X0Y0 offset. Your answer would meant that it is impossible to probe that corner, if the workpice is not in 100 % in angle... So G68 would never make sense, if you cannot probe anymore ...

klaus

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Re: G68 Angle and Probing
« Reply #3 on: May 12, 2020, 03:39:59 AM »
??  Not impossible.  Probe the corner as usual, even if it is out of square.  The corner will then become X0Y0 (changes the work offset).  Then you probe to find the angle and then do G68 X0 Y0, R<angle>.  Done.  This way, the G68 doesn't change the work offset.  This is the way it is ALWAYS done. 

Steve
Re: G68 Angle and Probing
« Reply #4 on: May 12, 2020, 03:52:40 AM »
 Steve, but probing as usual is not the way to get the corect corner on a worpice which is not in angle. if you look athe picture for exampel.... probe P1 and P2 will end in X0Y0 at P3 and not at P4 ...  :(

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Re: G68 Angle and Probing
« Reply #5 on: May 12, 2020, 03:59:58 AM »
Ah yes, I forgot...  We probed on a hole or a dial pin for the offset and then applied rotation.  A differnet animal.  I'm not sure how you would manage this with a corner. 

Just remember, the index dial pin or hole center should also be part X0Y0. 

Steve
« Last Edit: May 12, 2020, 04:03:25 AM by smurph »

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Re: G68 Angle and Probing
« Reply #6 on: May 12, 2020, 04:17:48 AM »
See the "Limitations" section for G68 in the "Mill GCode Programming.pdf" file.  It explains the G codes and offset functions that are not allowed in G68 mode.  The behavior is just like a Fanuc. 

Steve
Re: G68 Angle and Probing
« Reply #7 on: May 12, 2020, 04:18:38 AM »
I Managed it so far by first setting the rotation with G68 ... Afterwards i Probe and set   G92 X0 and a G92 Y0 at the Probing points. Then move to X0 and Y0 and reset the angle to 0 using G69 and reset G92 using G92.1. Then set mc.mcAxisSetPos(inst, 0 , 0)   and mc.mcAxisSetPos(inst, 1 , 0) to get X0Y0. At the end i set the agle again with G68... It seems to work, but its not "nice" way. And in the DOCs i found that G92 should not be used ... :-(  I hoped that there is a better way .....
Re: G68 Angle and Probing
« Reply #8 on: May 12, 2020, 04:39:56 AM »
Steve i was searching fpr the limitations you described in you prost, but i could not find them ... i usesd the following Document ...

https://www.machsupport.com/wp-content/uploads/2014/05/Mach4%20Mill%20GCode%20Manual.pdf

Is ther another one ?

Thanks for your help ...

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Re: G68 Angle and Probing
« Reply #9 on: May 12, 2020, 05:03:39 AM »
Yeah, the one in your Docs folder if your build is newer then 4300.  If not, download a recent dev build from the FTP site and install it to a different directory.  Then look in that directory's Docs folder. 

Also, you could probe the sides of the part in two places each and figure their intersection (corner) with determinants. See https://en.wikipedia.org/wiki/Line%E2%80%93line_intersection#Given_two_points_on_each_line  I believe Renishaw probe routines have this capability built in. 

Steve