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Chris64
09-08-2007, 11:00 PM
I did something that is probably unusual but it brought a strange problem to light.

I did an inside offset and an outside offset to a shape at the same depth and it left an area untouched between the two that was about 25/1000 wide. I had 0 finish allowance on both. Is this normal? The end mill I was using was 1/2" and it measures pretty exact.

Well, this came into play again toady. I was doing an inside contour that had some pretty tight tolerances for a bearing. It needed a .197" diameter. Corel had the correct measurement, but I couldn't figure out how to read a DXF file to confirm that it had the correct value - but it seems to have this problem regardless of whether it's a shape made up of individual points or true arcs (and only on contours). It ended up making an inside contour of .184". I made this with a .005 finishing pass first, then a 0 finishing pass at 10 IPM so it shouldn't have been due to end mill deflection. It was a 1/8" end mill. From what I see It appears to be doing a minimum of .0125 offset even when it's set to 0.

Any thoughts?

Chris64
09-08-2007, 11:31 PM
OK, nevermind. My problem lies somewhere else. I didn't think of this before, but I verified the actual G-code output and it appears to be correct. So I guess I need to figure out whats wrong on my end. Maybe cutting too fast. And I always use climbing so that could be the problem.

Sorry for the false alarm.

Hack
09-09-2007, 05:01 PM
I know sheet cam allows you to set l diameter you ar using and it uses that to calculate the offsets. Verify that the tool is actually the size that is specified in sheetcam. If using a regrind, it could be undersized and therefore would leave an untouched area.

Dan