Pocket (contour) behavior - CNC mode

Hello,
I’m having trouble correctly setting up a pocketing operation, particularly when enabling the contour. The generated toolpath always extends beyond the pocket and performs passes outside of it. How can I ensure that the bit stays strictly within the boundaries of the pocket ?

Here is an example :

Pocket contour example.kmz (1.2 MB)

Veridian.

Hey there,

It seems that you had the contour option checked for one of your pocket operations. By unchecking it, you can make the path stay in the boundaries.

Is this what you were looking for?

Thx for your answer !

In fact, I use 2 different pocketing operations :

  • the first one removes most of the wood, but fails to go to the exact wanted surface (often it leaves a fraction or even 1 to 2 mms, I assume depending on the step down parameter). This alone is often insufficient.
  • the second one, with the contour option, properly finishes the work

I’m not sure if I can do things another way ?

I think I understand better now. It sounds like you are looking for the trace (clear) operation.

If you set the step down to 0, you can trace along the bottom of the areas you want to clear.

Here’s a screenshot and KMZ of how you can use this operation.

pocket_with_trace.kmz.kmz (1.4 MB)

Oh the step down to 0 is a nice trick, the trace operation seems to be working quite well !

Except for a pocket that generates triangular toolpaths, which will undoubtedly leave marks.

Moreover, this doesn’t explain why the pocket with contour overflows from the actual pockets, which is unfortunate because I believe it would be a suitable tool in that case.

Anyway, thx for the trace suggestion, I will certainly use this trick.

pocket + contour is intended for finishing contoured surfaces, not strict flat faces. you can uncheck contour for that and get a strict pocket. so pocket + contour by default will allow the tool center to travel to the bounds of the pocket space. that causes it to “rise” at the edges so it doesn’t cut too much material.

there is a trick with pocket + contour for your use case. it’s odd, but you can set the expand value to negative tool radius. that offsets the pocket edges inward and avoids the step up.

I’m attaching an updated workspace where I split your pocket + contour into two separate pockets with contour disabled and step down set to 0. I think this achieves what you want. the pocket op is split because a single pocket op cannot reliably span multiple separated pockets when the bottom Z isn’t matched exactly.

pocket 0 step down.kmz (1.4 MB)

I wasn’t aware that the pocketing operation wouldn’t always reach the bottom of the pocket if a single operation included multiple pockets. Indeed, generating the toolpaths for each pocket individually works perfectly—no need for the contour here !

And thanks for the trick about setting a negative expand value if necessary, I’ll keep that in mind, it could definitely come in handy. Thanks a lot !

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