The work piece is situated on top of the urethane and the punch is pressed down into the pad. The way urethane bending works to form a radius is a pad of flexible urethane rubber is placed inside a typically aluminum holder. Urethane pads are often used in large radius bending applications where lack of die marking and smoothness of bend are important factors.

A stronger spring will create a better radius at the cost of added tonnage. Spring loaded bottom cushions set at the center of the die will apply upwards pressure throughout the bend, pushing the work piece against the bottom of the punch, preventing the multi-breakage phenomenon. This ensures an even breakage around the radius and allows for easyВ over bendingВ to compensate forВ Spring Back which can be significant for large radius bends. As the punch pushes down through the metal the rolla-vвЂ™s pads roll with and support the work piece, providing pressure against the punch tip. Rolla-V type diesВ use a rotating, springВ loaded set of pads to cradle the work piece. There are a few common die types whichВ accommodateВ this. This ensures that the final radius is equal to the punch radius. These phenomena can be prevented by specialized dies which push the work piece against the punch during the bend. This Final Radius (FR) can be calculated from the Punch Radius (Rp.) and the Material Thickness (Mt.) by the following formula: You should also note that as the material springs back after the bend the actual radius will be smaller than that of the punch tip. The work piece actually begins to bend in advance of the tip and is then forced out into a polygonal shape underneath the tip.ДЄs you can see the work piece forms a polygonal shape as itвЂ™s pressed into the die. It occurs when the work piece begins to bend in such a way that itВ separatesВ from the punch tip. This means that the phenomena is less likely to occur in a thinner sheet of stainless steel and will be more pronounced in a thicker sheet of cold-rolled steel. The multi-breakage phenomenon occurs in some large radius Air Bending operations, more commonly in thicker sheet metal and less commonly in materials with higher tensile strengths.

There are two significant factors which characterize large radius bending, the first is the multi breakage phenomena and the second is an increased amount of Spring Back. When the inside radius becomes much larger than the material thickness, typicallyВ anythingВ over 8 times the material thickness is characterized by large radius bending. This is due to the relatively low ratio of the inside radius to the material thickness. In acute Air Bending the radius itвЂ™s determined entirely by the v opening of the die. Large Radius Bending, also known as R Bending and Profound Radius Bending, is the process of creating a bend with a large radius to material thickness ratio.

Radius vs steel faith