pressing sheet metal

I need to press some .048" steel sheet to make a replacemnet body
panel, a replacement will cost more than the materials to make the
press whatever way i end up doing it..
it's a simple enough shape which is formed in a brake but with two
depressions, the pocket is ~4"x24"x.44[widthxheightxdepth] the
depressions have radused corners and i will put a slight taper onthe
sides, i can be a bit liberal with the dimensions to make it easier to
press.
I intend on milling a 4x24x.44, plus an allowance for the steel
sheet, pocket in a piece of 6x24x1 steel to form a die to press the
shape into.
The poket has a bend close to each side of it and one of them is
90degree so it really needs the pockets putting in the sheet prior to bending it.
I wondered if i made a top that basically supported a lip that would
surround the pocket and withstand pressing onto the die. I would put a
sheet of steel on the bottom 'die' then a piece of rubber sheet on top
of it and press the top down and pump oil into the space between the
top and the rubber, it should press the steel into the pocket..
shouldn't it?
alternatively I wondered about a die as above with a top press tool.
and multiple large bolt's though the two to press them. the depression
will have a 2.75x25 hole cut out of the middle of it.
any suggestions?
I do have a cad drawing of the panel if you want to see exactly what i
need..
I did ask before and someone suggested the easiest method was
explosives, don't think it's to easy to get explosives inthe uk.
the second idea saves making a press to press the bits between.
--
richard
Reply to
richard
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I believe that the way this is normally done is with a thick layer of rubber or urethane on the top. The rubber or urethane acts as one half of the die. Forget pumping oil, find a real press with some tonnage.
Another approach (option 2) is to build the pocket separately, and weld it in. You could use a simple 4 inch by 24 inch by 0.5 inch piece of steel or aluminum, even hardwood, as a hammerform to make the pocket. More info on this available on the metalmeet.com site, or look at metalshapers on yahoogroups.
Since I don't have a press, I would select option 2. The pocket could be welded in before or after the the bends are put in.
Richard
richard wrote:
Reply to
Richard Ferguson
If looking for good results first try, expectations are probably a bit high.
Try experimenting with a smaller pocket for the actual drawing operation in order to get the clearances, amount of overbend required, etc.
The draw will suck in lot of material in an irregular way, so xxx amount must be allowed for same. If stock not constrained during the draw, wrinkling is quite possible.
If actual drawing and bending successful, the final shape will probably have to be trimmed.
Good luck!
Reply to
Ace
There may be a fair amount of oil-canning in the part, but that may be mitigated by several annealing steps. Fluid forming, hydroforming as it's commonly known, is the process of forming a material over a male or female tool that has the general shape of the part using a "fluid" medium as the "punch". Most presses use a thick pad of rubber mounted to the upper bolster of a press. Some do use a rubber bladder that is contained within the press and is pressurized during the forming cycle. They are generally used to make short run aerospace type parts, or parts which don't have a straight bend and don't have the complexity to need a matched-die tool. Rough numbers for the force required: Length of formed edge (24+4+24+4) x gage (.048) x mat'l yield strength (30,000 psi) = 80640 lbs. or just over 40 tons. This doesn't account for the work hardening of the material, etc.
An option is to make a set of appropriately sized rollers for a bead roller, or english wheel and progressively roll and anneal the bead in. Possibly would need to keep flattening the outer flat areas.
Ace wrote:
Reply to
nic

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