Thanks for coming back guys,
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I've just had a look at the finishing toolpath up close and I think I was right to stop the job, as Neale has confirmed.
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What I have done is import the Cut3D file into Cut2D and then select the "model" and run a more moderate profile using a 6mm End Mill. That has removed the 0.2mm allowance from the roughing pass on the vertical surface around the edge. So I think I can run the finishing pass now without the material being there, but still get all the nice curves on the shape I had originally intended.
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Or at least that's the theory and what the simulation is showing.
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If that doesn't work I picked up a trial copy of Deskproto last night, which I think does have a compensation function for vertical surfaces, as well as other strategies to try.