Machining Curved Casings and Sashes on CNC

      How to handle hold-down problems when cutting out large curved parts. April 6, 2007

I'm looking for advice on how to hold down curved casings and sashes on a console arm table. The pieces we'll be running are 1.562" wide. Our narrowest vacuum pods are too wide to use on this width piece. We have mechanical clamps, but are limited as far as positioning due to the relatively short y axis, not to mention the fact that the tool would hit the clamp, which would force us to clamp outside, route inside, then move clamps to inside, route outside. A dedicated spoilboard becomes an issue also, since we will be running many different radii and ellipticals. Has anyone dealt with these issues?

Forum Responses
(CNC Forum)
From contributor T:
You have a few options. One is to use the clamps and move them in or out as you have already mentioned. Another is to machine it out of a larger piece of material and then cut it loose as a final operation.

From contributor W:
What I do is cut the stock 1/16" oversize and drill 1/8" holes along the moulding. I then cut a 1" piece of MDF with the same holes drilled in it, then screw the stock to the MDF and then shape it - a little time consuming, but it works great every time.

From contributor B:
I've found the most efficient way to cut narrow radius casings is to use over-thick and over-wide material. We cut deeper than the final casing thickness, but not all the way through. By being over-wide, we can use our standard hold down pods.

Then we band saw the waste away. After that we can either flush the excess left from bandsawing on the shaper, or sand the extra thickness away in the Timesaver, depending upon the moulding being made. Fast, efficient and accurate.

From contributor W:
Contributor B, I use that method as well if there is no profile on the edges. If there is a profile, I use the method posted above. By the sounds of his first post, I think he is shaping both sides of the moulding. Also, if the moulding has a square edge, I sometimes set up the pods to be just behind the shape, then cut it out right through and let the piece drop, then slide the piece forward and cut again.

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