View Full Version : I need some math calculations for a punch press die.

08-29-2010, 10:43 PM
I need to make a punch press die to deep draw an piece of sheet metal steel into a funnel shape. Not sure yet what the angle is but large diameter is 2.5" the funnel is 4.448" deep with the small diameter hole of 1.5" diameter. It has been many years sinse I have done this type math I will have to get out my 40 year old college book. There seems to be online calculators these days for just about every thing you can think of I was wondering if there is an online calculator to calculate this??? I recall the metal thickness has a lot to do with how deep this draw can be. Also the blank diameter has something to do with it and the correct lubrcation. Both ends need a lip so the funnel can slide over a piece of tubing and be welded on. I am pretty sure this will have to be done in a slow press like maybe a hydraulic press. Maybe there is a computer program that will calculate this???

08-30-2010, 01:01 AM
That's a mighty long stroke for a punch press. And many hydraulic presses. What kind of machine(s) do you have available? How many do you need to make? It's going to take several steps to get what you want. For something like this, I'd roll the cone, seam weld then swage the flanges. Or maybe just a lock seam. What is it for? Will it carry liquid, gas? Is it structural?

08-30-2010, 01:48 AM
It would it be easier to start with a piece of 4 1/2" long by 1 1/2" seamless tubing (like dom) and drop it into a tapered die. Then take your press and ram a tapered pin down the center of the tube forcing the tubes walls into the walls of the die. Basically shoving a funnel shaped pin into a funnel shaped die with the tubing between the two. This is basically how a large tube flarer works. Might have to anneal the tubing prior to the pressing. There would be a lot less tearing and bunching of the metal starting out this way rather than with a flat disc. You could also get by with a heck of a smaller press.

08-30-2010, 07:25 AM
I have a 100 ton hydraulic press with a 20" stroke.

This is part of an exhaust system. High temperature exhaust goes out though this so it can not leak. I need to make lots and lots of these just like exhaust systems on a car they have to be dirt cheap and I need to make them very fast.

Experement in the shop it takes me 4 hours per part to cut them out by hand in sheet metal then roll it into a cone and weld it together. Then hand swedging it to get a better shape. This is too slow 2 parts a day it too slow. At the moment I could live with 1 part per minutes.

I have to connect a 2.5" exhaust pipe to a 1.5" exhaust pipe. Hand making cones I can not put flanges on the ends so the cone will slide over the pipes and self allign so they can be welded. The parts need to slide together in 1 second like PVC plumbing pipes then get welded quick.

08-31-2010, 02:25 AM
I think my idea has merit. You should be able to make a matching punch and die in less than 4 hours. I suspect regular exhaust tubing would stretch this much as I've had the local exhaust shop put short flares on the ends of 2" tubing that made them 3" max diameter. If you need slip fits on the end just make your tapered punch and die with straight sections on each end.

08-31-2010, 04:50 AM
I need to make a punch press die to deep draw an piece of sheet metal steel into a funnel shape.

.................................................. ....

"Deep draw" implies starting with a flat, round blank. Older texts on die making will show examples of dies to do this type part.

"Die Design and Diemaking Practice" by Franklin D. Jones is one that's readily available at a low price through the online used book sellers.

Deep drawn tapered parts usually are done in a series of dies rather than a single die. Tapered parts present special problems, a non-tapered part is some times much easier to draw than a tapered one.

08-31-2010, 06:12 AM
No metal spinners in your area?

Regfards Ian.

08-31-2010, 07:14 AM
Another approach would be metal spinning:

Probably a couple minutes per part when you get into the groove.

Since you already have a punch press and need to make zillions, you might do better with the press but it is pretty easy to imagine the forces leading to the metal being very uncooperative in the press if you don't have a number of intermediate stages - and I don't even have experience pressing parts. It seems that either a tube or a disc will tend to crumple if you try it in one operation.

Also, I would consider whether or not curves might work better than a taper both in terms of forming and in terms of air flow.

08-31-2010, 07:53 AM
Ditto on the spinning. Cones have a circular cross section, so it just wants to be spun. :D