Vacuum Hold Down
This is my first pass at laying out a vacuum hold down table. I based my design on a number of web sources.
DIY Vacuum Table posted in the CNC for RC Forum.
The CNC Zone - work fixtures and hold down solutions forum.
Vacuum Table - link from a posting by Gaston Gagnon on the Fireball CNC Forum.
You can download an autocad drawing.
It's cut out of a 2 inch thick piece of styrofoam insulation
board. Not shown in either the pictures or on the drawing is the
full grid of slots for distribution the vacuum. It's 1/8 inch slots on
the odd 1/2 inch channels, 1/4 inch slots on the 1 inch channels and
1/2 inch slots on the 2 inch channels. The vacuum area is a
29x20 inch grid of holes on 1/2 inch centers. These are cut into a 1/8
inch thick piece of fiberboard that is 31x22 inches. I used a 2mm
(.078) pc board drill to make the holes.
got very good hold down on larger parts, but I had problems with small
parts (under 2 sqin). That might be attributed to several factors. I
was using a 2 flute end mill. The upcut mills tend to lift the
workpiece. I was using an agressive depth of cut, resulting in more
side force on the workpiece. I was not using tabs on the parts to keep
them in place. At the same time that I was testing out vacuum hold down
I was also having positioning problems on my CNC machine. I have
temporarily abandoned my quest for a vacuum table until the other
problems are fixed and I have more experience cutting parts using
conventional hold down.