shape cutting misadventure

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Gocarter
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shape cutting misadventure

Post by Gocarter »

I'm getting another unexpected result
I'm trying to cut a shape made from a two rail sweep inside a block, with exact dimensions. When I do a roughing cut, the internal diameter is much larger than expected. The shape in supposed to be 2.25" across, but after I cut it with a 12 mm end mill, it is about 2.75". Is there a way to constrain the roughing tool within the boundaries?
Attachments
box is 2.25"
box is 2.25"
actual cut about 2.75"
actual cut about 2.75"

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ohiolyons
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Re: shape cutting misadventure

Post by ohiolyons »

Boundary Offset normally covers that.

Check your bit info. It happens several times a month where the bit is miss named/sized and the hole is cut differently than expected.

Helps if you post the file, less guessing.
John Lyons
CNC in Kettering, Ohio

Gocarter
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Re: shape cutting misadventure

Post by Gocarter »

I'll try to post file here.

I checked the tools as well. All tools seem correct.
Attachments
plane wood 2 test coffin style.crv3d
(1.81 MiB) Downloaded 31 times

Gocarter
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Re: shape cutting misadventure

Post by Gocarter »

the preview shows the thin walls too. So it is actually cutting the way it is showing on the preview.

And, what you tell the CNC to do not always what you want it to do.

Gocarter
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Re: shape cutting misadventure

Post by Gocarter »

my boundry offset was set at 0.0"

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ohiolyons
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Re: shape cutting misadventure

Post by ohiolyons »

So Roughing and Finishing Toolpaths are calculated from the center of the bit, you are using a 1/4" bit, that would account for .25 of your issue. 1/8" on each side. If I remember correctly, someone will surely correct me.

I'm still thinking on this one.

EDIT:

If you include the rest of the block as part of the model with the area you are trying to cut it should solve your problem.
John Lyons
CNC in Kettering, Ohio

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ohiolyons
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Re: shape cutting misadventure

Post by ohiolyons »

Your present project only has 3d components for your "hole".

You maybe able to pull it off with a zero plane and then select the rectangular vector to limit the cut.
John Lyons
CNC in Kettering, Ohio

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ohiolyons
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Re: shape cutting misadventure

Post by ohiolyons »

I tried zero lane it didn't seem to help.
John Lyons
CNC in Kettering, Ohio

Gocarter
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Re: shape cutting misadventure

Post by Gocarter »

I recalculated the opening minus half the diameter of the tool, both for roughing and then for finish toolpaths. Preview looks much better.
Attachments
example 3.jpg

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