The press brake department has been called the heart of precision sheet metal fabrication. What happens there affects what happens upstream in cutting and downstream in welding and beyond.
How can you create smooth, predictable job flow in the forming department? To find out, The Fabricator spoke with Mike Crossland, bending product manager, and Edwin Diaz, software product manager, at Cincinnati Incorporated about six basic steps you can take to minimize errors in the forming department. They clarified that the list doesn’t cover every scenario, of course, but overall, it still provides a solid foundation for future improvement.
1. Use the Correct V-Die Width
“The biggest errors we see tend to be about tool selection,” Crossland said. “And typically, the lower V die is off. The die opening determines your radius, which in turn determines your blank size. So, when you use the wrong V die width or angle, you throw off your flange dimensions.”
A review of the basics here can help. When you bend sheet metal, the piece elongates at the radius. The k-factor, which describes the extent of that elongation, is incorporated into the bend allowance equation, which gives you the distance around the radius after elongation (or stretching) from forming. You use the bend deduction to subtract (or deduct) the material you need to accommodate for that stretching. This gives you a slightly smaller blank size that, when formed, grows to the overall dimension you need. Buried within that bend allowance calculation is the inside radius.
The bending method matters here. Modern press brakes air-bend almost exclusively. During air bending, the punch’s depth of penetration into the die space determines the bend angle (see Figure 1). And for most mild steels, stainless steels, and harder (tempered) aluminums, the inside radius forms as a percentage of the die width. Change the die width, and you change your radius. When forming materials like soft aluminums, the punch nose can determine the air-formed radius. Regardless, bend calculations need to incorporate the actual radius the shop’s press brake tools create.
Pour lire la suite : https://www.canadianmetalworking.com/canadianfabricatingandwelding/article/fabricating/6-steps-toward-sheet-metal-bending-perfection
