Drilling of Dogbones

CAD (Design) Software Carveco
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I recently got lazy and purchased a DXF file to quickly create a couple of sawhorses. These are cut from 3/4” sheet material and tab/slot together. This involved quite a few inside corners that needed a “dogbone” to allow assembly. The dogbones were already built into the DXF so I simply imported it into Carveco, created the toolpaths and sent it to the Onefinity.

The first several dogbone cuts happened as I’m used to seeing them - as a small deflection of the bit as it traveled around the profile of the part. Then as the tool moved to the next part, it began skipping around the part and drilling out the just the dogbone locations in advance of cutting the profile. It created a whole bunch of holes, and then connected them. This was not only very inefficient, but created a lot of heat and likely took some life out of my compression bit. It didn’t “peck” drill, it simply plunged straight down in one pass all the way through the material.

I have since recreated the vectors, and used the dogbone tool at these corners. With new tool paths created, the simulation now shows a “normal” profile pass with deflection for dogbones rather than this drilling.

I’m curious why this might have happened?

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My guess is that the opening to allow the cutter to enter the dogbone area was too narrow for the cutter to get into. Likely a rounding error as part of the DXF or importing process. If you were to increase the diameter of the dog bone hole by 0.001”, the opening would likely have been wide enough to allow the cutter to stay on the profile.

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Never thought of that. The radius itself was a couple 0.001” larger that needed for the bit, but maybe somehow it still closed the “throat” just to much at the entry. I’ll check. Thanks

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I designed a cutout including dogbones in Fusion 360 and noticed the same thing when I ran the simulation. A .125mm change to the radius fixed it.

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