Needle Cutter

This is the reciprocating needle cutter (150Hz) which cuts foamboard for RC airplanes with a piano wire needle designed by fans of FliteTest airplanes and the MPCNC. While it does work very well, the foam needs to be help completely flat.

Sheet goods can be held down several ways. The easiest is to fasten a sheet of pink insulation or another sheet of foamboard to the machine workbed and hold down the workpiece with pins. This method, while cheap and easy, limits the use of the edges of the material and, with Texas heat, does not hold down warped pieces very well. The now-standard method is to use a vacuum table, which holds down the material using a ShopVac or vacuum pump for suction.

First Attempt

My first version was a rough attempt at a design proffered by Jason Hitesma. My workmanship was very poor, which resulted in inadequate suction. The stains and folds in the image happened while the attempt was stuffed into the trashcan before I remembered to photograph it.

I also used a complex vacuum plenum which did not work to my satisfaction.

Second Attempt

My second attempt worked better. I used the same design as above with better craftsmanship and a simpler, cleaner vacuum hose attachment. The connection between this piece and the table was still too leaky, even though the table worked enough to hold down foam, only failing at the corners of the most warped pieces.

Note: I now I should only change one variable at a time. But given the overwhelming evidence of multiple problems, I made the bold choice to optimize two characteristics simultaneously.