Pls check my file

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I designed some cutting boards. First time I wanted to follow all recommendations about how to avoid up/down (“compression”) bits to get stuck, and to get a nice cut.

So I drew an offset around the outer edge of 1mm and 8mm, to cut a pocket between 1 and 8 mm around my edge down to 2mm above (=20mm) the stock back level (=22.5mm), then the contour from 20mm to max depth to cut the level with the tabs. Then I set the last mm, so the “real” edge, to be run by the up/down-bit for the whole depth to get a nice, smooth outer edge and nice, neat edges.

Compared to the plain pockets that all worked fine.

Almost.

Still there are some hickups:

IMG_20241112_174425023
IMG_20241112_1744250231920×2550 358 KB

IMG_20241112_174433393
IMG_20241112_1744333931920×2550 273 KB

I cannot explain how that could have happened. Does anyone have an explanation?

And there are charred strips on both sides where the tabs are down:

IMG_20241112_174456119
IMG_20241112_1744561191920×2550 375 KB

For the stripes I think may happen during the bit movement up and down for the tabs during the first contour cut, but shouldn’t this be gone with the last smoothing round of 1mm?

Here is the project itself:
twofingers.c2d (276 KB)

Any thoughts? Nothing urgent or catastrophic. Just curious, what I could do better.

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The DOC for your .25 end mill is pretty shallow. Per the Settings, you have a SO PRO; I think .125" DOC should be fine.
Your Retract height of .5" / 12.7 MM is pretty high. You can lower it to .125"/3.175 MM.

The rest of the issues look like work-holding issues.

One trick I recommend is leaving an onion skin on the bottom, i.e., the max depth of cut is .05 higher than the stock bottom. Then, you can use a trim router to remove it manually. This will help keep the piece in one place.

two finders sdguy edits.c2d (292 KB)

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Anthony, thanks a lot! Will consider your recommendations!
Yes, I intended to round trim the edges anyway for cutting boards, in this I experimented a little with getting nice edges.

Will set the DOC accordingly, used the ones that came as default from C3D.

And yes, I think workholding would have been an issue.

It almost always comes back to the basics.

Thanks for the corrected file! Will make new pieces, and report back.

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