[richardmh]

I have a block 6061 that is 6"T x 5"L x 4"W.The part is essentially right angle plate with one wall being .500 and the other 1.75.
The wire EDM operater is saying that the .5 side will warp after cutting on the EDM.Is there some truth to that or is he pulling my lag?

[sybilsurf]

Material does tend to move....the question is how much, and would it affect the quality of the finished part.

The best way to handle material movenment would be to rough out the part, and to then run the finish passes. There is also a practise of adding an extra skim pass with a "step over" amount, usually .0018" or so, to have more material to clean up.

[richardmh]

the .500 wall is +- .005 with no flatness call out or perpendicularity or parallelism?

[KilrB]

If your material has not been thoroughly stress-relieved then yes, your material will move.

As in all aspects of metalworking how much it moves will depend greatly on your material, your machine, and how you use that machine.

You say that the tolerance on the .500" dimension is +/-.005" and that there are no call-outs for flat, perpendicular, or parallel.

Well and good, but does it need to be flat, perpendicular, and parallel ... regardless of call-outs?

As sybilsurf points out, the usual method to insure size, and flat/perpendicular/parallel is to take a "rough cut" several thousandths oversize and follow with one or more "skim cuts" with diminishing offsets and power to bring the part into spec.

This works best if you are cutting the entire profile of your part.

I suspect you are trying to make an "angle plate" by simply cutting a big chunk off of that aluminum block.

It would not surprise me if your 1.75" section were no longer true either after doing that.

Whether you part is still acceptable afterward will depend on just how much it moves.