Quote:
Originally Posted by Cory
Most CAM packages will by default add "tabs" to a contour toolpath. Basically little bridges of material that connect the part to the stock. You contour at full depth around the exterior of the part and the tool raises maybe .025"-.060" (depending on how many tabs you have and how large the part is) over a small length at various points around the perimeter such that the part is basically done, but doesn't drop out of the stock.
Lets you cut the full depth contour and then you either hammer out the part with a deadblow and snap the tabs off, or you bandsaw them off if the part is delicate. Then you can remove the remainder of the tab with a belt sander, hit it with some scotchbrite, and if you've done a good job you can't even tell the part wasn't fully contoured with an end mill.
It's a massive timesaver when it comes to doing 2D parts on the mill.
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We've had no significant issues sketching bridges (tabs) into HSM works, only takes a few moments for the 2D parts we do (robotics or otherwise) although we do pull to safe z-height and then re-plunge. But, generally we're working with 0.100 in Al or thinner, so the Z-moves aren't a big deal for our applications because we're only doing 1-2 passes per part.
I have also done 'membranes' instead of tabs, leaving 0.010in or so of material holding the part in all around the base, as a 'skirt' if you will. Takes no special programming, and the membrane is thinner than the chamfer put onto the part by deburring so you can't tell it was ever there!
I'm not saying one method is better or worse than the other, just what I've done that I'm satisfied with.