Need Help!- aluminium 6061 milling

[sharathchandar]

dear all,

how to acheive 0.05mm flatness on "1300x950x20"mm aluminium 6061 plate.

currently it's a tight task to me. guide me for machining style.

[cjdavis618]

I would suggest a surface grinder for the best surface. What kind of equipment do you have to use for this purpose?

[Ken_Shea]

.05mm, That is not going to be done in some small shop, it will be a major task for even a surface grinder, a huge surface grinder also, probably need a blanched grinder for that size and as recalled it seems that they cannot achieve the precision of a surface grinder, and I'd bet impossible with a mill.

Just thinking out loud here.

[cjdavis618]

Edit, I read your post wrong about the size. Sorry.

0.00196850 is the inch equivalent. That's nearly 2 thous of an inch.

Granted, I use steel with my surface grinder, but I get more than .001 out of it. But the size he is talking would be impossible on my equipment.

I do have access to a mill that can do this, but that won't help him out much.

[dertsap]

it could be done on a large mill with a decent facemill or fly cutter and side clamps with minimal pressure , miteebite clamps are a good clamp for this type of work ,with the weight of the plate being to your advantage you can get away quite easily with a low clamp pressure
if youve got a hertel facemill , use it
as always mill bowed side up first and lightly shim the gap to avoid any deflection or vibration

the problem is going to be once the part is pulled off the machine it will sag , so is the goal truely for flatness or parallelism ?

[fpworks]

A vacuum plate, or a series of vacuum chucks would be your best choice for workholding.

Just curious, how are you inspecting this?

[cam1]

Havn't ever seen aluminium on a suface grinder before.....too soft. Am I missing something?

regards

[Pressfit]

Sorry to say he will likely never achieve anywhere near that kind of flatness in a "free state" with a plate that big. It will warp all over the place just from machining stresses alone. It will most likely move into a new free state condition with every cut. My suggestion is oversize MIC-6 cast plate and machine it down...that is if he is allowed to substitute type of material. It usually remains pretty flat and stress free.

Yes you can grind aluminum with a Silicon Carbide wheel. But its the workholding to surface grind that gets to be the real bear.

[cjdavis618]

You can use a silicon carbide wheel to do this. But you have to dress it regularly. I wouldn't use it for more than he is asking, and even then, only on some aluminum. Not the real gummy stuff.

[Larry83301]

Just my $0.02 here, but we used "crazy glue" to hold plates on our mills when we needed to get somthing flat without clamping pressure. After you machine the plate, a sharp rap on one edge will break the glue loose, and "crazy glue" is very thin.

Larry83301

[dertsap]

crazy glue! that is brillient


we are talking .05mm or .002" on one single face , obtaining flatness on a plate that size on a machine is not a problem if a guy takes care and uses the correct tooling , parallelism of .05mm would be more of a problem on a plate that size

normally you would want to grind in order to accomplish parallelism and not necessarily flatness

[Pressfit]

Yep! Good old cyanoacrylate. aka Super-Glue or Krazy-Glue works well for certain applications that dont require much thickness or support, just to stay put. Be careful not to use too much or you can damage your parts trying to beat them loose.

So does double-sided sticky tape. But it dont like you to get it wet with coolant or too hot or it lets go. Ooops. I'm still finding those Titanium donut shims I threw off the surface grinder a year ago, once in a while.

Spray on 3M contact cement for a little more thickness and contact but a bit messy to get off.

For really warped applications and 100% support I have used a bathtub style mold filled with Plaster of Paris(cheap). Sit part in it and wait for it to set up. Remove part line with sticky tape or spray on 3M. Trim edges of mold so edge of part is exposed to MiteeBites.

Then last but not least, the metallic fixturing alloy, Cerrobend or Cerrocast works good for those you need to completely surround in a matrix of metal. Kind of pricey though.