calculating sheet metal bending allowances

Based on the same K factor as the large-radius condition, the flat pattern here produces a part that is too long. It’s thinned at the flat bottom to 0.063 to 0.078 in. We also do sharp bending from sheet stock that is thinned in the bent areas, but V-cut with a small flat bottom. The inside radius for these bends is 0.75 in., and all along the radius the material thins to 0.078 in. I have an accurate K factor for this bend condition. thick, thinned in the bent areas along the circumference and wrapped into a rectangle with radiused corners. Our tanks are formed from sheet stock typically 0.25 in. After a few years of iteration, we have developed an accurate flat-pattern method for our tank bending operations. Question: I am forming plastic, not metal, but I am applying metal bending principles to my application. Instead, without going through any physical change, it simply moves toward the inside surface of the material, causing elongation in the bend. The neutral axis does not remain at 50 percent of the material thickness during bending. Material on the inside of the bend has reached its plastic state while the outside of the bend has not this elastic state on the inside of the bend forces the bend to spring open. Where Theta is the complementary angle of the bend (measured on the outer surface of the bend).įor cases where bend angle is greater than 174 degrees and the inside bend radius is less than half the sheet thickness, we consider the bend to be a Hem or Dutch bend (Benson, 1997).Every bend has tensile stresses on the outside surface and compressive stresses on the inside surface.

The value that describes this repositioning of the neutral plane is called the 'k-factor.' īend Allowance (BA) is calculated using the general equation:ī.A. Typically, the plane repositions at a distance of one-third to one-half the thickness of the material. However, when the bending forces exceed the elastic limit, the neutral plane moves towards the inner surface of the bend. If a sheet material is uniform in section and its elastic limit is not exceeded, then its neutral plane (or axis in 2D) coincides with the centerline of the material. Bend allowance is calculated based on bend angle, material thickness, and inside radius.

Calculating sheet metal bending allowances