Using image-to-gcode - tool diameter problem

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20 Apr 2012 15:07 #19400 by grey1beard
I'm designing a bridge for a musical instrument.
I've generated a greyscale image in CorelDraw, consisting of a blend of two elipse set in an outer rectangle, exported it as a gif file, then opened it in Axis.
All OK, except the outer edges of the tool path, and the overall dimensions of the piece are smaller than the design by a size equal to the tool diameter.
Please see attached files.

The finished piece will consist of a set of nine of these, in a line like a mountain chain, and I had assumed that I would run a repeat command of some sort, rather than start with art work that had all nine on it.
Or is this what I will need to create ?
Any thoughts ?
John

File Attachment:

File Name: bridge2.ngc
File Size:12 KB
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20 Apr 2012 15:54 #19403 by grey1beard
Making a 9 unit version was easier than I thought, and the 3500 lines of code take about 40 minutes to run, so as I shall be cutting hard wax for a model, that's acceptable.
The dimensional change is still only one diameter around the whole piece, so I assume I just need to get my head around how it works.


John

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20 Apr 2012 16:14 #19405 by cncbasher
you have not set an outside offset to the toolpath , which is the radius of the tool used

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20 Apr 2012 18:46 - 20 Apr 2012 18:49 #19408 by grey1beard
Ah, good point.
However, when I opened the .gif file, one of the various settings in the window that opens was "Tool diameter" which I set to 4mm, so I assumed that was it.
I've just gone through the process again, and my original settings are still there, with the diameter correctly set.

??

Regards
John
EDIT I've just looked at the gcode in the file that the software produces, and there's no indication that a particular size for the tool has been set.
Should there be, and what would the code read ?
Last edit: 20 Apr 2012 18:49 by grey1beard.

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21 Apr 2012 07:53 #19413 by Rick G

the overall dimensions of the piece are smaller than the design by a size equal to the tool diameter.

You might just scale your model in Corel to be a larger size (parallel line around the object (contour?) by 1/2 the tool diameter as it appears the outside path c/l is following the outside of the design.

Rick G

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21 Apr 2012 08:00 #19414 by grey1beard
Very true, Rick, and indeed that is what I've done in adding a small rectangle outside my original surface model.
However, that doesn't teach me anything about why the software behaves in this way.
A bit like a doctor treating the symptoms rather than the cause !
Regards
John

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