I think the question is, "Why would more lubricity lead to parts
Maybe someone can tell me the answers or help me ask the right
Here are the details. We deep draw little cans from 0.010" thick pure
niobium. Most of them are cylindrical with a flat bottom. The corner
radius on the bottom varies but 0.020" would be representative. A
typical diameter is about 0.625" with typical height of 0.500".
Our niobium is specified to have an elongation of 24 - 28%, ultimate
strength of about 47 ksi and yield strength of 30 ksi. The modulus of
elasticity is 14900 ksi
The punch and die clearance is about .001" more than the material
thickness. The clearance could increase to 0.003". Generally the
hold down pressure is negligible.
If we have consistent trouble with rip outs, we will go to a double
draw or triple draw. Of course, we would prefer to avoid the extra
We had a part that was ripping out about 15% of the time. I tried a
supposedly superior oil based lube designed for drawing. We washed
the discs before applying it. After wiping it off as normal, we had
100% rip outs with the new lube. Even after wiping as much off as
possible, we there was still a thin film and we had 100% rip outs.
Before going to a double draw, I observed that the partially drawn
disk was very wrinkled. So I assumed the hold down wasn't doing the
job. I tried a different part with a different set of tooling with
more pressure on the hold down. We tried soaking the discs in our old
water based lube and not wiping them as usual. The result was no
wrinkles but 100% of these parts ripped out, too.
The operators tell me that all the cans will rip out if we have too
much lubricant. Therefore, they wipe them with their hands before
It appears that the slipperier the discs are, the more likely they
will rip during drawing. I would think it would be just the opposite.
Can anyone help?
- posted 17 years ago