What is the formula to calculate the blank development for bending in sheet metal?
The most accurate way to calculate the piece in the flat, is to work off the centerline of the section. Regardless of either the inside or outside dimension’s, by working from the centerline you’ll get the right development every time. The most important thing to remember is calculate the bend radius. As long as you have drawn everything correctly, the development should work out right. One more thing to keep in mind is not only the radius of the top die, but also the bottom die opening as well. If you use a 5mm top die to bend 5mm plate but you use a 400mm bottom die opening, then you’ll get more than a 5mm bend radius in the corner. For bending low carbon steel, the rule of thumb is that the bottom die opening should be 6-8 times the material thickness. But depending on the type of material and the thickness you are trying to bend, the bottom die opening could be more. There are charts available that have recommendations for bottom die openings for specific grades of material and als
