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I have a part made from 5mm alloy plate and I need to cut a large cutout in the middle of said part:

An alloy part requiring a large cutout

As seen above I intend to use a small cutter to cut through the stock (not necessarily plunging as shown here) and cut around the inner diameter of the part instead of roughing out the entire area of the cutout which would take a lot longer.

My concern is that when the cut is complete the large piece of internal cutout could get caught by the cutter and thrown around the machine enclosure, wreaking death and destruction as it goes. Is this something I should be worried about and if so, what's the usual strategy for making this type of feature?

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    $\begingroup$ Clamp it down before finishing the cut? $\endgroup$ – user_1818839 Jan 9 '17 at 14:23
  • $\begingroup$ I think we're going to have to but were wondering whether there was a quicker alternative. $\endgroup$ – HJCee Jan 9 '17 at 14:27
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    $\begingroup$ Have you considered a blanking operation, perhaps with a punch, to remove the bulk of the material before machining? $\endgroup$ – DLS3141 Jan 12 '17 at 13:28
  • $\begingroup$ Old question, but you could just drill a couple of holes in the piece and screw it to the spoil board. (Assuming your machine has such a thing.) Since it's trash anyway... $\endgroup$ – 3Dave Dec 4 '19 at 19:58
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I'm assuming that you are cutting on a base sheet of some sort in my answer, if not, please do. In all my shop applications I have found that double sided taping the product to the base sheet is sufficient when my machine doesn't have adequate suction.

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  • $\begingroup$ Excellent suggestion. We used to use carpet tape which worked great. $\endgroup$ – Eric S Jan 9 '17 at 14:53
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If the alloy is magnetic then you can use a magnet as the cut is nearly complete to fix the cut out part in place as the cut finishes.

If the CNC doesn't allow that then you can instead let a few tabs remain and cut them out on another machine where the center part is properly held in place.

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Some CAM software offers the option of generating tabs or bridges that look like this:CAM Tabs.

The position, qty and size of the tabs are configurable in the CAM software. Here's an example configuration dialog for Fusion 360:

Fusion 360 dialog with 'tab' configuration

The tabs can be 'cleaned up' in a secondary operation.

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