Here are some examples of custom vacuum jigs we have made
Click on pictures with blue frames for larger versions
Small Part Jig
One of the problems often found with vacuum hold down systems, is even though you have a large vacuum pump, you may not be able to hold down small or skinny parts, this is because vacuum hold down requires surface area for the atmosphere to push against and hold your part down. We came up to a job requiring cnc machining of a veneer into a very small, intricate shape (the leaping impala logo* from 94-96 Chevy Impalas), extremely accurately, as this veneer was an insert to an inlay job. The first attempt was to make a standard vacuum jig, using foam tape to seal off the vacuum area.
This was not very successful, for 2 reasons, first the vacuum tape held up the veneer around the edges, but it collapsed in the center, second, even with 1/8 x 1/32 vacuum tape, there were about 6 areas where the tape touched itself, cutting off all vacuum to those areas, even trying to trim out a small vacuum channel in the foam tape did not work well, the parts just kept moving. We came up with a new idea...
As you can see there is no vacuum tape on this jig. We cut inside of the shape to be cut, concentric grooves, 1/16" x 1/16" deep, then drilled 1/16 holed into the vacuum grid below. This distributed the vacuum out to the very edges, plus the ribs standing in between the contours held the part flat. This jig worked extremely well, and no attention needed to be given to the parts, they just didn't move. The next challenge, was to make a larger board, with 10 of these nested to cover the width of the veneer, which we did...
This Jig held ok up to about the 7th part, then accumulated leaks started to decrease the vacuum pressure and things started moving, the easiest solution, after the machine past about the 4th part, cover that area with plastic film, sealing off the leaks and increasing the vacuum pressure the other solution was to buy a larger pump. The job was run using the plastic film technique and the tolerances held were excellent as can be seen in the finished product below.
*Copyright General Motors, this design was produced exclusivly for MBA Products,
an offical GM Licensed products manufacturer.
This same plaque required a "Keyhole" to be cut in the back, so we designed a special Cutom Bit to cut it, then a simple program to drop the Z Axis about 1/32 while traveling on the Y Axis, then reversing out... This made a slight taper, so when the plaque is hung on a wall, over the head of a small tack, it is drawn back against the wall.