Press Alignment Problem

[silentbobo941]

Hi everyone, I'm currently trying to align a die set for use in a hydraulic press and am having some difficulties achieving the necessary parallelism. Ideally we need the top and bottom platens of the die set to be parallel within 0.0005 inch. The die set is assembled in stacked parts so that there is a base layer, ceramic insulation layer, heated platen layer, and a metal insert that is in contact with the part to be pressed. Each surface has been ground to a flatness of 0.0003 inch and the dimensions of the pressing surfaces are about 3.5 inch by 3.5 inch.

I am having some difficulties getting everything aligned by shimming. I have heard of a product that would help, but I don't know the name of it or where to find it. Basically it is a heat-activated pad that goes under the die set. Initially it is flexible so that it deforms under load of the press, enabling the bottom platen to align to the top platen. Under load, you heat it and it cures in that position so that it stays aligned. Does anyone know what the name of this product is or where I could find something similar?

Thanks for your help

 

[btrueblood]

Not heard of that, but have seen pressure sensitive paper that leaves an image that shows contact pressure.

 

[Compositepro]

Another name would be liquid shim. A 2-part epoxy will work. You have to carefully consider how your tolerances can be maintained. 0.0005" is very tight. Generally larger presses cannot do this by themselves. Usually the mold or die in the press comes to fixed stops, and this is how close tolerances are achieved.

 

[FMTim]

Is there any way to assemble the components and grind the the surface needed as sub-assemblies to work around the tolerance stack-up?

 

[Pud]

Are you sure it's not the press platens flexing? Or the die set itself?

www.tynevalleyplastics.co.uk

It's ok to soar like an eagle, but weasels don't get sucked into jet engines.

 

[tbuelna]

So you have 4 stacked parts with each of their surfaces ground flat within .0003" over a 3.5" x 3.5" area. But what is the parallelism of the opposing surfaces on each of the 4 parts, and the total tolerance possible in the part stack? As FMTim notes, the best approach would be to surface grind both faces of the stacked parts at operating temperatures.