Sheet material hold down on CNC


In ongoing issue with cutting cardboard is that it tends to be fairly floppy. You can clamp down its edges but the center often bulges away from the table.

Of course you can lord over the machine and help hold the material down.

This problem happens when cutting a larger piece of hardboard as well. The endmill sometimes tries to lift the material up as it’s pulling material away from it.

I thought of adding a small wheel to the cnc machine that can press down on the material being cut. So when the endmill plunges down, there will also be a wheel that comes down on the material.

I thought it should be spring loaded and that it should be a castor so it will follow the direction of the cut.

It may not be clear from the diagrams but I need to add some 1/4-20 threaded rod. Two pieces to form the axle for the wheel and the lever axis. Another vertical in the Square hole. A spring is running from the small holes at the lower right to the hole at the top right.

I cooked this quick design up in Sketchup and will cut it out shortly and see if it works.

Material clamping and hold down


My inexpensive plastic mill has 1/4-20 threads spaced on a 10cm grid. This makes it much harder to hold down material.

I now appreciate the value of that channeled aluminum on the bed of my Chinese mill.

I’ve been using some slabs of acrylic with holes drilled in them.

That’s been very difficult since there are only a few sizes of stock that will fit into the machine.

Here’s a technique that seems to be working. I can’t idle the clamps back and forth so I need a multi length clamp. If this continues to work well I’ll make some up.

A week or so later: Jackpot!