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Grief from plate fabricators

Question asked by 1-C8YCX8 on Jul 22, 2010
Latest reply on Mar 11, 2018 by J. Mather

Although I have been a solidworks user for 10 years now, its only in the last year that I have started using the "Sheet Metal" capabilities of Solidworks. and this leads to a never ending source of grief with my customers. They get me to save my sheet metal flat patterns as .dxf files, and have the platework (ranging from 1/8" up to 1/2" thick) burned out on a cnc burning table. On plates with a single 90 degree bend, I'm generally okay. However on plates with anything less than 90 degrees (i.e. 73 degrees included angle)  or on anything with more than one 90 degree bend, the flat patterns always seem to be somewhat undersize. For instance, a piece of 1/4" plate formed in a Z shape, say 5" deep with 2" flanges will end up with a 2" flange, 5" deep, but the last flange will be 1 3/4", not 2" like its supposed to be.---Or else, depending on what order they break it in, it will have two perfect 2" flanges but only be 4 3/4" high. I see that Solidworks uses a different radius for almost every plate thickness, but in reality most fab shops use the same top die on almost everything and change only the bottom die (to accomodate different material thicknesses). I also see that Solidworks uses 2 x material thickness for the "BEND DEDUCTION CALCULATION" .  Is anyone else out there experiencing these difficulties? I want to keep my customers happy, but this sheet metal thing is driving me a bit crazy. I know that if what I design was built multiple times, I could keep "fudging" the bend parameters untill the bend piece of steel exactly matched my flat patterns, but I don't have that option. All the work I design is unique, and "one of a kind" stuff, so it has to be right the first time.---Frustrated in Barrie-----Brian