Aluminum 6061 T6, thin wall part, rough, heat treat, then finish...?

We have a part that has a machined slot feature on the inside and some features on the outside that result in a thin wall. The specifications on the wall are tight in flatness and we are concerned that stress will warp the thin walls. I understand that a rough machine close, ~.050", to final dimensions, then a stress relieve heat treatment, then a final machine to dimension is the best way to proceed.

Any comments on this method?

laminar-flow said:

We have a part that has a machined slot feature on the inside and some features on the outside that result in a thin wall. The specifications on the wall are tight in flatness and we are concerned that stress will warp the thin walls. I understand that a rough machine close, ~.050", to final dimensions, then a stress relieve heat treatment, then a final machine to dimension is the best way to proceed.

Any comments on this method?

Click to expand...

we do thin stuff and thinner than mentioned all the time in alum and hold tight tols we dont have a problem at all, if we do we find other ways to machine it, block it, clamp it. other ways meaning different tool paths different set ups etc etc.

with out seeing the part theres no way to tell you where to start. if your starting from bar stock one suggestion is to make sure all sides are cut(gets rid of scale so to speak) before you start with the thin stuff.

only stress(if you wanna cal it that) relieving Ive ever had to do with alum is on big 8" and 10" thin rings roughed them out let them sit over night and skin cut them.

I have never done it this way, though I do send 6061T6 parts for heat treatment after welding. Accurate features need to be finish machined after.

For mostly smaller parts that need high accuracy after machining I prefer to stabilize the blanks in liquid nitrogen. I leave the material in the LN for a few minutes (depending on size) let it warm up to room temperature and then dip it again. In cases where there is a lot of metal removal and high accuracy required I might do one more LN dip before the final cuts. But this is only in cases where high accuracy is in the order of microns and for most work the LN stabilized stock stays accurate. Again, I work only on small stuff - like optical elements holders - and never did the stabilizing on a anything bigger then about a kilogram.

This is a part that is about 300 grams. Your business sounds like mine. Liquid nitrogen... any change to the properties? I'll have to look that up. Any published sources?

Loong time ago we had some parts that kept moving, could not hold the close tolerances. We ended up doing cryogenic treatment after roughing, then finishing. They were stable, and fairly easy to hold tolerance after that. I don't remember a property change problem, they were only 6061.

laminar-flow said:

This is a part that is about 300 grams. Your business sounds like mine. Liquid nitrogen... any change to the properties? I'll have to look that up. Any published sources?

Click to expand...

As far as I know there are no property changes in the raw material after cryogenic treatment, including the temper. I have been doing it for years for medical and other demanding stuff where all the procedures must be recorded, approved and maintained.

Dear, I have special technology. Pleas look on picture and send more info(drawing, foto and so on) Regards Libor

Thanks Libor. Nice looking part. We are working on some variances and things may not be as bad as I was thinking. What was that machined on?