Three guesses what I did today.

Dang process is very sensitive to several parameters. Centering of the dies turned out to be the biggest challenge. Lubrication was also a real helper. Corners are radiused.  Once I got it right, I can duplicate . Twice anyway. I’d like to get the depth of the female die just right, so it stops and makes a nice flat bottom. It’s a bit deep at the moment

Notice the pile of test pieces in the background.

Next tricks are drilling the 5/16 hole (starting with 5/16 fender washers did NOT work) and cleaning up the excess. I plan on drilling the hole first, then using a 5/16 bolt and nut to make an arbor to mount it in the lathe, the clean up the flash there. No doubt there will learning moments along the way with that too.

I currently only have 0.035 thick tin, the original washers have a .045 thickness at the turned up lip. Will have to go shopping Monday. I will have to reduce the diameter of male part of the die, to make room for the thicker material. I have .035 gap in the dies at the moment to match the material. They feel like they would be too thin and cheap feeling with 0.035 material.

So making is possible it seems. More news on Monday.

Looks great!  Did you mill your own dies?  
 

So I would drill the 5/16 hole in the sheet while it is still flat and then add a slightly smaller diameter  centering pin to your dies. Then press away !  It will help hold the sheet in place and improve repeatability and the hole will be perfectly centered.  

hope this helps ....

PS - you might have to drill a pilot hole slightly smaller than 5/16 because the hole might stretch...

PPS - also use a slightly larger blank...give your dies something to grab on to ?

Edited March 8, 20205 yr by ConVerTT

Having a center screw through the middle was the only way I could make it work.

2 hours ago, zKars said:

Three guesses what I did today.

Nice work. Love it!

Nice pile of practice parts. Once you get the parameters right, you should be able to get very repeatable results. At least until the die is worn out. I see a lot of them torn out like my first attempt. I started with a gap that was the same as the material thickness and that was not enough of a gap. I took off about five thousandths and it made a huge difference. I could actually see the material getting pulled down into the die as the pressure was applied.

And I found the same issue centering the die since I didn't have a center hole to use as a locating feature either. If I were to do it again, I would put a pin in the middle of the male die to locate the blank and center the male portion of the die in the middle of the other half. However, (in agreement with the suggestion above), I would make the pilot hole a little undersize because I'm not sure if the material will stretch in that area or not.

Thicker material might be a little easier since there's more meat there to stretch until it gets so thin that it shears. If you want to know what they started with for the original parts, you should measure the thickness at the flat bottom. A micrometer would be the easiest way. My instincts tell me that the sides will be thinner than the base because the sides are what stretched in the original drawing process.

Couple hundred more tweaks and you'll be in production!  

 

I initially tried using a fender washer that had a 5/16 hole, and die parts that pass through the hole. Seemed like the right thing to do. This didn’t pan out very well, as the distortion that happens caused the material to rip around the hole.

I now have a 5/16” hole in the female side of the die, so I’ll use that as a drill guide to put a hole in the part after it’s formed. 

I measured the original washer base thickness. It is as suspected a bit thicker than the walls, at 0.050.  18 gauge sheet metal is 0.048, guess that will do.

 

Edited March 8, 20205 yr by zKars

Yeah that fender washer trial didn't work out so good. It looks to me like all the stretch occurred at the center hole instead of the sides (as I believe it should). Looks to me like the clearance on the die set was too narrow. I didn't study the guidelines from that webpage I posted earlier, but my own testing indicated that if the gap is way too big, the material will fold and wrinkle and if the gap is too small, the part will stretch in the middle or shear along the edge like a punch.

One other thing that we haven't talked about is the base material... The easiest thing to work with would be something dead soft annealed, and fender washer's aren't. They're heat treated to some spec and then plated.  Anyway, your experimentation is keeping you safe. It's a cheap hobby, and you aren't out and about picking up anything unhealthy!

I would really try to get some sort of hole in the part before you draw the cup. I put the hole in my test part after and it was a bit of a pain. Would have been much easier if the hole were there beforehand. At least some sort of a centered pilot.

Looking forward to the pic of a handful of perfect parts!

I agree with the Captain.  Hole is too big and fender washer is too hard resulting in shear.  I would try a much smaller pilot hole and centering pin with a sheet metal blank and then adjust the die clearances until you get the result. 

Quick update. Lot going on at home right now.

I have a good solution going. Made the first group of 20-ish.

Size is great, appearance comparison to original is pretty good. 

Drilling the hole after the initial forming is the only option. Any hole in the piece to start with is a) too hard to center, and tears out immediately, pretty much like the fender washers. Using a center hole in the FM part of the die makes drilling the hole in the middle very simple.

Once I got the dies centered to each other consistently, I can make millions of identical little wrinkled creatures that only take about 175 finalization steps each. Easy peasy.

I’ll have pictures to post of the whole process stages later in the week. 

 

Edited March 11, 20205 yr by zKars

Again, nice work!

You can tell by looking at the stock washer that the OEM was doing it a little differently. You can see the shear line on the outside perimeter showing that they started with a round blank before the drawing operation. They probably stamped out the round blank OD and ID and then used a second stage die to draw the round blank into the cup shape. Someone more clever than I might even been able to do it all with just one die.

So now that you have spent all that time on making a die set... Have you ever heard of "metal spinning" on a lathe?  

6 hours ago, Captain Obvious said:

Again, nice work!

You can tell by looking at the stock washer that the OEM was doing it a little differently. You can see the shear line on the outside perimeter showing that they started with a round blank before the drawing operation. They probably stamped out the round blank OD and ID and then used a second stage die to draw the round blank into the cup shape. Someone more clever than I might even been able to do it all with just one die.

So now that you have spent all that time on making a die set... Have you ever heard of "metal spinning" on a lathe?  

I was thinking of getting a Greenlee punch set to make easy round blanks. I noticed when I cut my square coupons into a hexagon, there was less distortion. I haven’t actually tried to start with a truly round blank to see what happens. I’m happy with what I’m making.

And yes, I have seen the youtubes of people spinning HUGE aluminum disks in HUGE pots pans and other receptacles. Very long lever arms and very large lathes spinning them. Very impressive.  I will not be trying that, even on a small scale on my lathe. I see another 3 week boondoggle coming up....

Those look great!  Nice work and thanks for posting!!!

11 hours ago, zKars said:

I was thinking of getting a Greenlee punch set to make easy round blanks. I noticed when I cut my square coupons into a hexagon, there was less distortion. I haven’t actually tried to start with a truly round blank to see what happens. I’m happy with what I’m making.

And yes, I have seen the youtubes of people spinning HUGE aluminum disks in HUGE pots pans and other receptacles. Very long lever arms and very large lathes spinning them. Very impressive.  I will not be trying that, even on a small scale on my lathe. I see another 3 week boondoggle coming up....

Haha! I only mentioned the metal spinning in an attempt to guide you towards that 3 week boondoggle. The forming operation you're currently doing could probably also be done using a metal spinning technique. "It's not the size of the tool, it's how you use it."

About the Greenlee punch... All the ones I have require a pilot hole (which has given you difficulties).