Problem cutting with metric dimensions

29 Mar 2010 14:55 #2467 by cpdude
This is my first post. I'm new to cnc, linux, emc2, gcode...etc. so please pardon me if I use the wrong words.

I've installed from the Ubuntu 8.04 "Hardy Heron" LTS live cd and configured (acceleration, movement/rev, speed, etc) using imperial dimensions. I'm cutting using a diy router with the X & Y dimensions being belt driven and the Z dimension using a 12tpi lead screw. I've had no problems cutting parts to imperial dimensions (G20) however when I cut to metric dimensions (G21) the parts appear off by the tool offset (e.g. the outside dimensions are too small and the inside dimensions are too big).

Here are some more specifics:
I'm using a 1/16" (1.5875mm) end mill.
I'm using CamBam (v 0.9.7) to generate the gcode from dxf files.
I'm using the Inside/Outside cut feature on closed polylines in CamBam--However, I'm also having the problem when I hand code the gcode.

I've include a zip file that has two gcode files--one file uses inches and the other file uses millimeters. These files are supposed to generate parts with the same dimensions. However, the metric one appears to be "off" by the tool width on each cut. I'm cutting model airplane parts so I don't need to be perfect, however, I'd like to get a bit closer than 1/16".

Any help would be very appreciated!


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29 Mar 2010 14:57 #2468 by cpdude
This file didn't upload. So I'm trying again.


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