If the bend turns sharp at an inside radius of 0.078 in., then punch nose radii of 1/16 in. Your punch nose radius comes into play here too. The sharper and deeper the crease, the greater the effect. The crease in the center of the bend tends to amplify any angular variations caused by changes in material grain direction, hardness, thickness, and tensile strength. Note also that air forming a sharp bend usually is very detrimental to consistency. If your radius is 125 percent of the material thickness or more, you have a radius bend.Įven if you are producing a sharp bend, the smallest radius you can use for your bend calculations is the minimum bend radius, if you want your numbers to work out in practice. Specifically, the perfect bend’s radius ranges from the minimum radius value up to 125 percent of the material thickness. The perfect bend has a radius that’s equal or close to the material thickness. Try forming a radius smaller than the minimum, and you crease the center of the radius, giving you a sharp bend. A minimum-radius bend has a radius that’s equal to the smallest inside radius that can be produced without creasing the material. There are four types of bends: minimum-radius, sharp, perfect, and radius. Have no fear I will bring the K-factor into the discussion soon.
These are all distinct methods of forming, and each is calculated differently because of how the radius is produced in the workpiece.įirst, let’s step back and talk about the types of bends you can make in sheet metal. On the press brake you are air forming, while on the stamping press you are stamping or coining. Your press brake and stamping press form sheet metal in different ways. Luckily, it’s not too complicated-no differential calculus, just geometry. Math is at the heart of sheet metal bending.
I’ll start with the fundamentals and give some general recommendations, then end with some calculations. Are you able to answer my question on K-factors with a general recommendation without going into too much theory or calculations?Īnswer: The answers to your questions are simple well, sort of simple.
I would say that I have a good understanding of the basics, but there are still issues that I come across in production parts that I tuck away to keep in mind for future designs. I want to help our design engineers create more manufacturable parts. I found your and realized that aside from this question, maybe there is more I could learn. However, this doesn’t work well for our parts that go into a hand transfer stamping press. Our design engineers typically use a factor of 0.4 for our air-formed press brake parts. Question: I had a question on K-factors for our 3-D modeling software. The K-factor is the ratio of the neutral axis location (t) to the material thickness (Mt). When you bend sheet metal, the neutral axis shifts toward the inside surface of the bend.
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