Hi
Does anyone have suggestions on the best way to hold .093 x 1.750 x 4.250
alum . This part will look like swiss cheese when i'm done since i need to put 45 holes thru at different diam. I also need to mill the outside profile. I'm looking for other suggestions besides doubleside tape. This will be a production order of 500 pcs+.

Thanks
Mike

Vacuum might be a good option, although personaly i have had no luck with it. but you can purchase wax to do what you want (for 500 pieces it might be combersome.

otherwise you can drill all your holes with an full OD capture and a vacuum (which i have had good luck with) then make a fixture to bolt thru you holes and mill the OD profile in a second OP. This method is slow out of the machine but can be sped up by making more than one screw down fixture and have an additional part drilled so you can screw it in the fixture when the other is being OD milled. Then at the end of the op you can mill the final half done part and your done..

I personal use this method allot on small medium runs 25 to 300 parts do to the simplicity, and lack of mess (as with the wax or tape method).

I agree with miljnor -

I would gang drill multiple pieces in a set up which accomodates the dimensional tolerance then profile a plate to locate the pieces - again - several at once. I think this is the way to go. Good suggestion. I would steer away from vacuum - it's a PITA.

Scott

send it to a laser shop and have them burn the holes first and then cut the outside shape and drop parts out

I use alot of vacuum chucks without any problems, but I wouldn't use it for this type of job.

I'd go with Miljnor and Mxtras on this. I would build a fixture for it except have it so that you can run the entire part on the same fixture. Just get a little extra on the profile to clamp on. Drill the part, "M0", then add a cap that screws through some of the holes in the part to the fixture, then profile. With this idea as well, you can gang parts and run this too like Scott suggested.

And I'd build 2 fixtures like that. That way you can load one while one is running.

I do one similar right now. .09 plate thats 4.50 x 16.00 with 430 holes and 4 different sizes. I gang 4 parts at a time. I wouldn't burn it. Too much lead time, paying somebody elses overhead, and just simply not necessary.

Well drill two holes and use them as the basis for the rest of the work. Those 2 holes will be your fixture holes...of course the part must be held down with edge clamping while the 2 holes are drilled/milled, then those 2 holes are your fixture holes.

what i have had good luck with insted of edge clamps is since the work is straight down initialy. you make a 2-3 point restraint (depending on the accuracy of the starting state of your OD's) then make a plate with one hole in the side and a slot in the other.

when you change stacks of parts you simply loosen your bolts rotate the sloted hole off of the part and the hole keeps the hold down plate from moving and put in new parts and repeat. Of course your hold down plate has to be drilled thry but as long as you calc. the depth in with your pieces no prob. Also if the Hold down plate is bothering you with its pivot action you can slot both holes and just remove it and replace with each set up.

I use alot of vacuum chucks without any problems, but I wouldn't use it for this type of job.
....

Agree, I do some weird things with vacuum, but for that I'd use bias-ply tape. We do microwave covers all day long with it.

Thanks all. I didn't mention that some of the holes are c'bored. to stacking is not an option. I was trying to steer away from clamping the outside then "M00" and added screws to mill the profile. My largest dia. is .096 and I would have to use 2-56 screws.
But this seems like my best bet. I will proabably use my pallet changer to save on load and unload. Thanks again for all suggestions.

Mike

I will upload a few more photos of my copper plate fixtures. Maybe it will work for you. Star by clamping the edges (left right) drill all the hole, the place the cover plate over remove side clamps, and machine the outside.


They are in my gallery
My gallery (http://www.cnczone.com/gallery/showgallery.php/cat/500/ppuser/6552)

Clamp stacks of ten from two sides, drill all the holes and do the two accessible sides. Then clamp them individually using two holes that will not get counterbored for alignment and pick up the other two sides and the counterbores.

In a situation like this you can check out the heat activated glue from mitee-bite or some thing like wafergrip


http://www.dynatex.com/products/WBS/wafergrip.html

Howdy Mike,

Trepanning?

Since there are so many holes. My plan would be to cut strips 5.5" x XX" and hold them in a simple clamping plate along the length of both edges.

Create a program nesting XX parts side by side with .28 between each one.

Drill, counterbore and chamfer all the holes in lets say, 10 parts simultaniously to minimize tool changes.

Then change to a 1/4" EM and mill out the full perimeter of all the parts simultaniously, in steps of .035 in an effort to leave about .005-.010 in the bottom of the perimeter path.

Once the fully machined strip is removed from the clamping plate. All the parts should be easily removed from the sacrificial framework and deburred. Care must be taken with the razor like edge though. Plastics are not so bad, but metals can get ya!

I use this procedure very often for flat pattern work. Works fine with vacuum to if not to many holes and adequate surface area. Most of the time I just do this in a vise with a plank and screw clamps. Just make sure the reference surface is decked to make it parallel to the moving axis. This will help maintain a consistant thickness and prevent break through, which will allow things to get under the material and then parts get cut loose etc.

For that many holes. I would drill into the fixture with over sized drills after the first part. This would allow room for drill burrs on the bottom side of the rest of the run to keep from lifting the part.

I do use sticky tape for one off, but that many parts would be a pain to clean.

DC