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G-Code, CAD, and CAM discussions / Probing for different fixture offsets

« on: March 04, 2012, 11:04:31 AM »

Search isn't working and google isn't answering my question very well. 

Here's what I'm trying to do.  I have a sheet of plastic that varies in thickness from 0.130" - 0.090", I always put the thick side towards the back of my X2 cnc converted mill, and I have a series of milling operations to do including engraving and corner rounding.  Some tools get zeroed on the fixture, IE on the bottom of the part.  But since the sheet varies in thickness I like to zero my corner rounder and engraver on the thick part of the surface, that way I always know that I will get a perfectly rounded corner or less, but never undercut.  I just installed my power drawbar and have a bunch of TTS style toolholders, so I'm obviously using a tooltable.  I have a wired touch probe that I made.

I am trying to use my touch probe to probe several locations on the sheet, load those Z heights into different G55/G56/G57/etc coordinates so that each operation can run from a different fixture offset.  I can't get it to work.  G31 works great, it'll probe down and stop when it touches.  G92 Z0 will reset the DRO to 0, but doesn't seem to affect my fixture offsets table at all.  I've tried following that with G92.1, G92.2, and G92.3 with no success either.  Here is one of the many codes that I've tried, also I'm using this in the Gcode, not as a macro.

(TOUCH PROBE CYCLE)
G90 G00 G40
(FIXTURE SURFACE)
G54
G0 X-0.3 Y0
G31
G92 Z0
G0 Z0.5
(UPPER CHAMFER)
G55
G0 X2 Y-0.2
G31
G92 Z0
G0 Z0.5
(LOWER CHAMFER)
G56
G0 X4 Y-1.75
G31
G92 Z0
G0 Z0.5
(UPPER CORNER ROUNDER)
G57
G0 X1.6 Y0.04
G31
G92 Z0
G0 Z0.5
(LOWER CORNER ROUNDER)
G58
G0 X4.45 Y-1.51
G31
G92 Z0
G0 Z0.5
(UPPER ENGRAVING)
G59
G0 X1.15 Y-0.875
G31
G92 Z0
G0 Z0.5
(LOWER ENGRAVING)
G59P7
G0 X4.7 Y-2.5
G31
G92 Z0
G0 Z0.5

Thanks for any help!!
John