316L Plate warpage after machining

[prosys1]

Help! I'm trying to machine some plates made from 316L. I purchased the blanks water-jet cut to 9.00 x 7.08 and double disk ground to .400 thick. I'm machining a pocket that leaves .450 on each side and the floor thickness at .113. My problem is the corners are cupping up. The floor has a parallism (sp) call-out of .002 to the bottom of the plate. Can I aneal these parts after machining to get them back to being flat? Do I need to leave some material on the floor of the pocket, aneal, then finish machine? Any help would be appreciated. I have prints I can email if needed. Thx, Derek

 

[EdStainless]

Is the distortion uniform, like a bow or twist, or is it all over the place?
If it is a bow or twist You might try mechanically flattening the parts a couple of times during the machining process.
If it is all over, then maybe rough machine and re-anneal is the only option. Keeping them flat after cooling from anneal will be a real trick.

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[prosys1]

The distortion is pretty close to uniform. Each corner is lifting about .010 from flat. We have placed the part on small plastic blocks on the surface plate and then hammered the middle of each edge with a plastic dead blow hammer. This has helped some, but it's a long process and not totally accurate. If we rough machine and then anneal, wouldn't the annealer know how to keep them flat? Would annealing make the material harder?

 

[MikeHalloran]

For the already completed parts, I'd try stress relieving while in contact with a thick, known flat, platen, with the pocket filled with sand or shot to encourage it to lie down, and maybe another platen on top to keep the margins straight.

... Well, it works on acrylic plastic...






Mike Halloran
Pembroke Pines, FL, USA

 

[prosys1]

Mike,
You had acrylic warp? Man, I had to anneal polycarb, but in all my years of machining plastics, I never had acylic warp.
I talked with the metal distributor, DIX Metals, and they said that it might be possible to anneal the parts after rough machine, and they would stay as flat as the platens that the parts are pressed between. Sounds like Ed had the right idea. It will depend on how slowly they lower the temp.

 

[MikeHalloran]

The stress locked in by casting acrylic will distort it a little when you remove some material. You wouldn't notice it unless you needed the work to remain super-flat.



Mike Halloran
Pembroke Pines, FL, USA

 

[EdStainless]

I was thinking more of using steel blocks under two corners and then a large steel bar across the top and placing it in a hand press. You will need to flex it a bit to get it take a set. Maybe you could rig a dial indicator so that you could tell how much you are bending it and if it has set enough. We straighten bars this way.

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[prosys1]

Man Ed, are you psychic? I found out that the material supplier says he can straighten the plates after machining on your run of the mill bearing press. I know it's an art, because I've seen a guy do it to a crank shaft, but DIX Metals says they can get them flat within .002. I sent a part off to them and I'll report back to all what happens.