Grinding thin aluminum to obtain .02 flatness
Grinding thin aluminum to obtain .02 flatness
(OP)
I'm currently working on a project where the print requires .09 thick 6061-T6 aluminum with a .02 flatness callout. The print also requires a few thousand small holes to be drilled in it, all the same size.
The problem is this: the material seems to be moving around a lot after the holes are drilled, specifically, it goes in and out of the .02 flatness requirement. Some parts are way out of flat, some are in. We can't seem to control the process enough to get a consistent part.
I was considering starting with .125 thick material and fly cutting it. Would this be advantageous?? Any other suggestions for an aluminum to use where it will be easier to hold the flatness??? Any other suggestions that would make holding the flatness on this part easier??
Thanks...
The problem is this: the material seems to be moving around a lot after the holes are drilled, specifically, it goes in and out of the .02 flatness requirement. Some parts are way out of flat, some are in. We can't seem to control the process enough to get a consistent part.
I was considering starting with .125 thick material and fly cutting it. Would this be advantageous?? Any other suggestions for an aluminum to use where it will be easier to hold the flatness??? Any other suggestions that would make holding the flatness on this part easier??
Thanks...





RE: Grinding thin aluminum to obtain .02 flatness
The only solution is to machime the two sides after drilling the holes. However, you have to stress relieve the plate after the drillings before machining the two sides. Two options are given . First, is to let the plates rest for two weeks after drilling and then machine both sides. Second to stress relieve the plates in an oven and then macjine both sides.
You didn't mention the size of the plate which is very important, as larger the plate the worst the problem.
RE: Grinding thin aluminum to obtain .02 flatness
If we end up grinding after drilling the holes, we're going to have a heck of a time deburring the thousands of holes. Any ideas for how to easily deburr these holes after grinding?
Thanks!
RE: Grinding thin aluminum to obtain .02 flatness
http://www.surftran.com/
There are a lot of other ways to get holes in metal.
What are the size of you holes and how many?
What type edge doe you have to have at the hole?
RE: Grinding thin aluminum to obtain .02 flatness
I would try to drill the holes in a such a way that the internal stresses will be relieved equally. Similar to the way you tight the bolts of a car wheel or in a motor head, you tight each time the two bolts which are most far away from each other. In the same way I would try to drill the holes such a way that it will always be in a symetrical way with respect to center of the plate.
One other way is to clamp the plate or few plates between two thicker plates and then drill the whole stack togeter. When the drilling is finished stress relieve the whole stack together and then diassemble the stack. This can be done if the hole diameter is large enough.
RE: Grinding thin aluminum to obtain .02 flatness
Currently, a 3/4" bottom plate is being used and a top plate isn't. But mounting a top plate wouldn't work because the cycle time would be way too long, especially since the current cycle time is already 15 hours.
RE: Grinding thin aluminum to obtain .02 flatness
http://www.lourdessystems.com/home.htm
RE: Grinding thin aluminum to obtain .02 flatness
Robert Setree
www.advanced-grinding.com
RE: Grinding thin aluminum to obtain .02 flatness
I really don't have an answer for you. Just an observation and maybe something to try.
You said, "Some parts are way out of flat, some are in. We can't seem to control the process enough to get a consistent part." It seems as though the only part of the process that would give this type of inconsistency is the raw material. I'd look into having blanks premachined, stress relieved and ground in an unrestrained condition to lower the internal stresses in the material and improve the consistency, lot to lot.
For something to try, how about hording a few of the scrapped parts and making them available to a really good vacuum heat treat operation. Perhaps they can bring them back into flatness? I realize this is a "Hail Mary" suggestion, but these are high value parts that are currently only useful as paperweights or wind chimes. I will recommend a company off forum if requested. Just a thought. There is the possibility that any form of thermal processing coupled with restraining the part back into the flat condition will screw up other features, but hey, what have you got to lose?
RE: Grinding thin aluminum to obtain .02 flatness
Would it be possible to substitute a semi-permeable material for this highly machined plate? Something like an air bearing - maybe a pressed & sintered powdered metal.
If you need to stick with the solid aluminum plate, I'd try drilling the .09" material in T6 condition (you could drill a stack of plates if it is cost-effective), then clamp a stack together in a fixture (with spring preloading) to send through a full solution anneal & artificial aging cycle. This would stress-relieve the plates, re-flatten them, and put them into a dimensionally-stable condition. The spring preloading will ensure that the clamp force is maintained as the plates flatten.
Good luck!
-exploring the cutting edge of old technology-
RE: Grinding thin aluminum to obtain .02 flatness
Have you considered laser profiling--very accurate, no burs minimum distortion.
Apart from increasing production from the time saving this may give desired results.
RE: Grinding thin aluminum to obtain .02 flatness