Vacuum part holding revisted?

That's not an ideal part for vacuum holding. With a maximum of 2 sq" surface area, the most down force will be about 30 lb. If the slot and hole go through the part, those areas will have to be sealed off too, reducing the surface area. Could several parts be machined out of a larger, thicker blank? The individual parts would be bandsawed off and then second op'ed to face off the back.

Fred

Back in the bomber factory we stacked thin sheets of aluminum, riveted them in places where a cutout would take place, then routed the hell out of them. That might work for you since it sounds like you will have slots. Second ops took out the rivets if necessary.

Wayne

I did a run of sheet parts that were round on the outer dimension. They had a bunch of through holes in them, too. So, I made a fixture with tapped holes where the part had the through holes, and the top of the fixture was a smaller OD than the actual part. I put this on the machine and indicated the center. The fixture had 4 tapped holes for clamps around the edge.

I stacked six bandsawed blanks on the fixture and installed the clamps around the edge. I then ran a program to drill or bore all the holes in the parts. I blew out the holes and inserted bolts that clamped the parts. I could now remove the OD clamps and machine the exterior dimension. This worked great.

If you need to machine the top, you could do that while the clamps are placed outside the final OD, then clamp from the inside to machine the 4 sides. This would require the blank to be made large enough to clamp outside the final dimensions.

Jon

You may want to create some small tabs (places that don't get machined away) to hold the parts in place, just machine something like 95% of the od away and place 2 or 3 small tabs strategically so the parts won't get snatched loose. The tabs can be also machined down to a much thinner dimension for easy removal from the stock sheet after the machine cycle is done. A few hold down allen bolts can be strategically placed to reduce any vibration that may begin while the parts are milled.

Just to reinforce what ff said... I made vacuum table that works very well on pieces larger than 4" by 4". Anything smaller and the piece just gets pushed around by the cutter.

Peter

if the vacuum is almost enough, but not quite, consider a rigid mask the the part can be trapped by.

Now that I'm thinking more clearly the price of a die to punch out these parts is sounding like a reasonable option. That way I only need to drill 1 hole and mill 1 slot. Now if I can get the customer to eliminate the slot...

And why would one not cut the hole and the slot with the same die set?

LLoyd

Hole yes, slot no (0.050" deep)