I'm investigating building a powered hydraulic press for draw die work. The press would be used for tryout only, meaning no production. I could easily imagine the press being hit less than a thousand times over its entire life.
Capacity would be 50-100 ton
Front-to-back working would be about 12" Left-to-right working would be 18" Stroke would be 10" Closed daylight would be about 10-15"
I was considering just using three major plates: the bolster, the ram, and the crown (on which the cylinder is mounted), and using four tie- rods to keep everything together.
My questions refer to the size of plates, and the size of tie-rods/ guide-rods.
As I understand, hydraulic presses aren't really capable of creating severe overload conditions (in contrast to mechanical presses). So, what would be an appropriate safety factor for the tie-rods? 2:1? 4:1? If the tie-rods were 4140, a single 1-1/2" rod should be able to withstand the press's entire capacity.
I have no idea how to calculate the required thickness of the three plates, to withstand the load without severely deforming. The die shoes used would always pretty much consume the entire working area of the press. While the loading wouldn't necessarily be balanced (due to the type of die work), there won't be any pin-point loading on the bolster or ram. Bolster to ram parallelism is actually quite important in this application, although the die shoes will assist in resisting deformation, in addition to the bolster.
While the die shoes will have their own guidance (pins and bushings), the ram should be guided as well to assist in preventing severely unbalanced dies from deforming under maximum loads (remember - this is tryout... Things happen). I'm not sure if it would be a good idea to have the tie-rods act also as guide-rods, or if they should be independent. They seem to be the same thing on commercial presses...
Any thoughts are welcome. I want to build instead of buy because gap- frame and 4-post presses of this capacity seem to be much larger (FB/ LR) than I need, and I don't want to have to deal with a 7500lb monster if it's not required.