Need help with holding down aluminium sheet

[levelzero]

I'm milling a bunch of parts from 0.125" 5052 sheet. The size of the stock is 9"x16"

I've made a subplate that allows me to bolt the sheet down using 5 bolts on each of the long edges. The problem I have is the center is bowing 0.007" ..... I know it's not the subplate because I checked it right before taking the measurements. I can't back off the pressure of the bolts as they are only torqued down to a few inch pounds already.

Any ideas? I've though about double sided tape but have yet to find one that can stand up to the coolant/cutting forces and that will also come off easily.

[Geof]

The area you are working with is large enough to get a good hold down with vacuum. You would need a good vacuum. If you are putting a lot of holes through this may not be feasible but if it is mostly surface features and few holes you may be able to isolate the locations with O-rings in the vacuum platen. Ideally some pins around the edges would be good to stop the piece sliding sideways under the cutting force.

Alternatively if you are doing many holes but not much in the way of surface features you could try use a 1/2" Al top plate over the whole part. You simply machine clearance holes where needed to do the machining on the work. Of course if there are too many holes this doesn't work.

[levelzero]

A vacuum table would work but is beyond my means right now both because of time and cost.

A top plate might work ..... although the disadvantage to that approach is the spacing between the items and the need for a new top plate for every shape.

Both are great solutions but I'm hoping for something simple/quick in the short term. All of my cutting is done with either a sport drill (engravinging) or a 0.125 3 flute. I pack as many items as I can onto the sheet to reduce set up times.

[Vac-Clamp]

Hi Levelzero,
Are you doing any cuts that go completely through the 0.125 sheet, or can you onion-skin (leave a thin part) with your cuts? If you have a lot of parts to make a custom vacuum jig will work well but with all vacuum clamping more area gives more holding power.
Errol at Vac-Clamp

[srwalden]

your not serious or you would get a pump some superglue and a roll of universal o-ring matl and make good parts

[Vac-Clamp]

Dear SrWalden,
I am not sure if you have used vacuum as a holding method. For the type of work that has been described it would be quite effective, and efficient.

[prototypeCNC]

how about just superglue, thats how I always hold parts down like that. When machining is done squirt some acetone on it for a minute, and pull the part up. Don't get carried away with the glue or it can be a mess real fast.

[Verfur]

look up "mity bite" as the make a low tepm glue just for this type of job. J@L MSC......

[levelzero]

Originally Posted by Vac-Clamp Hi Levelzero, Are you doing any cuts that go completely through the 0.125 sheet, or can you onion-skin (leave a thin part) with your cuts? If you have a lot of parts to make a custom vacuum jig will work well but with all vacuum clamping more area gives more holding power. Errol at Vac-Clamp

I normally leave 0.001" and break the parts out after the machining is done. But as I said in my previous post I am not interested in vacuum clamping right now.

Originally Posted by srwalden your not serious or you would get a pump some superglue and a roll of universal o-ring matl and make good parts

Thanks for the constructive answer...../sarcasm

Originally Posted by prototypeCNC how about just superglue, thats how I always hold parts down like that. When machining is done squirt some acetone on it for a minute, and pull the part up. Don't get carried away with the glue or it can be a mess real fast.

What kind of super glue? I'm hoping for something that is easily aquired and replaced.

Originally Posted by Verfur look up "mity bite" as the make a low tepm glue just for this type of job. J@L MSC......

I will look into it. Thank you for the information



A friend of mine gave me a roll of medical grade 3M double sided tape. I'm also going to try that out and see if it holds up to the coolant. I've tried tape before and it melted and turned gummy, losing it's holding power and making a mess.

[srwalden]

I am sorry I should have been more specific.
the super glue would be for the orings that you would make for your vac fixture.
you want to place these orings in places that will not be cut through. this method I believe is the solution and probably only reasonable method of manufacturing parts of this type!

[levelzero]

I actually managed to sold this last night. Using my existing fixture I simply pushed down on the middle of the plate while tightening down the cap screws. Everything was within "0.001 which is more then acceptable for this project.