Today I’ll show the first test of the CNC vacuum plate, but first we’ve got a little bit of work left to do to make the top part. You may recall that I likened it to an air hockey table, but instead of forcing air out of the holes, we’ll draw air down through the holes with a vacuum pump.
Here’s my top plate being drilled with an array of holes. Again, remember that if you use extruded acrylic, you’re likely to have a lot of problems while machining or drilling it because the plastic melts and gets stuck on the bit and also leaves rough edges. Cast acrylic chips away nicely.
Drilling holes in the top acrylic plate.
The next step for me was to make an adapter to go from the vacuum hose to the cavity at the end of the base plate. I won’t go into a lot of detail here but what I did was make the adapter on the 3D printer because it was faster than machining one. 3D printed objects made with the FDM process (using a spool of plastic filament) are usually fairly porous (not airtight) so I’ll use some glue and/or tape to improve the seal and fill up the pores at least well enough for it to function.
Adapter being printed on a small 3D printer.
Finally, putting it all together, it’s looking pretty good!
On the left you can see the hose adapter. My little air hockey table is sitting on top of the base plate. I’ve temporarily fastened the top to the base with a few spots of glue and tape around the edges for a seal. Later I’ll make a more permanent seal after seeing that it works ok.
First test. It works!
For the first test I’ve connected a pretty strong vacuum pump that’s designed for applying vacuum to air conditioning systems to remove all of the refrigerant, air, and moisture. I doubt this is necessary and I’ve seen others use shop-vacs. This was just convenient for me and gives me a chance to see how much leakage there is in my system. I know that with this pump I should be able to get over 29 inches of vacuum, but as you might be able to see, I’m only getting about 14 inches on this test, and sometimes as little as 7 or 8 inches. I’ve got some leaks, probably mostly in that area where the hose adapter sits. You can see I’ve taped over unused holes since the 6 x 6 inch board doesn’t cover the whole area. Imperfections (like board warping) in the pcb also contribute to leaks. As it turns out, 7 inches of vacuum seems to hold it pretty well. I had to apply a lot of force to move it by hand. It was stuck very well.
I hope you’ve enjoyed seeing this and it’s been a fun and useful project. Later on I’ll show some other improvements to the CNC machine itself and refinement of this fixture that allows greater precision when making circuit boards on a machine like this.