Wrinkle Formation

Drop the acronyms and use words that are clear to all. What is R.. what is Thk.. what is S.F. I assume that Thk means thickness. But this is only an assumption. Technological guidance should not be based on assumptions.

R For Spherical Radius: 170mm

S.F. for Straight face: 60mm

Thk for Thickness: 7.2mm

170 × π ≈ 534 « 600. Too much surplus material?

We want Straight portion about 50-60mm.

Have you consider it?

Plz Reply.

Too big reduction of diameter from 600 to 340 (ratio= 600/340=1.75 !!!). The thickness has also a negative influence. Such a forming should be done on heated parts so that the material is plastic. And I believe it should be done in steps not in only one tool.

Is your dome half a sphere or just a segment of a sphere? If half a sphere with a spherical radius of 170mm, the base of your dome must have a diameter of 340mm. (2r=d) So what is this 60mm straight face? Straight face of what? OK, never mind. Take a larger plate than you need for your dome and hold it down with a holding ring. Holding ring must hold it down with sufficient force not to allow it to wrinkle or buckle, but still allow it to slide. The surfaces must be well lubricated. Then, through the middle of the holding ring, press out your dome. Now you will have a flat flange with a dome in the middle. Now punch out your dome and you have a dome as smooth as a babies ass. A press die with a holding ring is known as compound die. Usually this is one single operation. The die comes down, holding ring and all. Holding ring is down first, clamping down the plate. The pressing die continues to move down and forms the dome.

The method you suggest is well known but I doubt it would effective with the present ratio thickness (7.2/160) to radius. It is mostly used for quite thin sheets and with very good results.

Extrapolation does not work always, some times there are limits for it.

How many of these metal blisters do you want?

Deep drawing tools are not cheap and hard to justify for a short run.

Explosive forming may be a viable option and is always great fun.

http://en.wikipedia.org/wiki/Explosive_forming

It is just like blow molding with a little more pressure applied.

BAB

For one or a few, the Boilermaker shop method is to work around the blank with a heavy trip hammer, allowing extra thickness because the material is thinned by hammering. US boiler shops have been forming mild steel cold by this method for a century now.

You need a draw die with a pinch plate to keep the metal from deforming.