Add the outside dimensions of adjoining flanges and subtract the bend
deduction. The bend deduction is the difference between the outside
dimensions (to a point coincident to both outside surfaces of the
sheet metal) and the actual length of the material required to make
the part. The radius in the formula below is the inside radius.
BEND ALLOWANCE = (.01745 X RADIUS) + (.0072 X THICKNESS) X DEGREES IN
OSSB = RADIUS + THICKNESS
ISSB = RADIUS X TAN 1/2 DEGREES IN ANGLE
BEND DEDUCTION = (2 X OSSB) - BEND ALLOWANCE
The radlius will be somewhat different for press brake work than
stamping, and bottoming bending or air bending parts. So there is
variation depending on your process, but the formula is pretty close
for general fabricating.
Hope this helps. Diego
I think in my drafting class we used a line at 1/3 the thickness from the
outside length of the bend to compensate for the stretching of the metal.
But, it will vary with the material, thickness and bending method.
dimensions for sheet metal are usually given to sharp corners and the die
maker usually deals with it.
Yeah, in most cases, flat patterns should be avoided on product
drawings. You are specifying the final condition of your product to
you vendor, and it is up to them to match it by whatever means, per
current ASME Y14.5M.
This is going to be a dumb question, but if you're doing it in
SolidWorks, why not let it do the calculation for you? Unless you
just want to verify what it's giving you. I can certainly understand