When selecting a V die for bump radius bends, choose the value that is equal to twice that of the radius Under normal circumstances a V die is calculated at about eight times the material thickness, in which a one-to-one relationship between the material thickness and inside radius is maintained. Per bend angle = Bend angle A/Number of stepsĭetermining the correct V die width follows a different process than normally would be used. Individual Step-bend Angle and Die Widthĭetermining the required bend angle for each individual hit is a simple matter of dividing the number of degrees in the final bend angle by the number of step to be used: For press brake controllers without a radius bend or step-bend function each additional step (hit) from the starting point is one radius pitch value less than the previous hit. The starting point for the step bend is found by adding the leg dimension to the arc length. To find the value of the flat from the outside surface of the larger radius to the edge or next feature, an outside setback (OSSB), or X factor, needs to be removed first, as in Figure 2. This leg also may include other bends not yet formed or, in some cases, bends already in place. The final piece of the puzzle is the leg.Ī leg is the flat distance from the edge of the part to the beginning of the radius. The Outside Setback or X factor is calculated by using the following empirical formula: OSSB = (Tangent (A/2)) x (Material Thickness + Inside Radius) Number of steps = Arc length/pitch The Leg If the pitch is more important than the number of hits (bends), use the following equation: Radius pitch = Arc length/the required number of hits If the radius pitch for a bend's number of steps is the most important factor, the following formula may be used: Is a smooth outer surface the priority, or is the speed of production the priority? First, decide which is the priority-the number of steps or the distance between hits.
The next step is to determine the radius pitch, which is the distance between the bends (or the number of steps required). The following formula can be used to develop that value, where A equals the number of bends and Ir equals the insideĪrc length = 2(pi) x Ir x The arc is the measured distance along the inside radius, the distance from the beginning to end of the radius, which may or may not be 90 degrees of bend angle. If you use the step-bending process to produce the part, the first thing to determine is the length of the arc. Smoother the outside surface of the radius will be (see Figure 1). Obviously, the greater the number of hits, the The number of hits used in this process will determine the tooling selection, smoothness of the final surface, and the depth of penetration into the V die. Step bending is a procedure in which multiple hits (bends) are made along the entire length of the inside radius to produce the bend.
The best option may be to use a step-bending process.
While rolling the bend in a slip roller always is an option (if you have one), rolling is not the most accurate way to place a large radius in a precision part. Perhaps it is a one-of-a-kind part, or the radius that needs to be produced is too large to be done practically in a single punch and die set. It often is impractical to buy or build a custom tool just for large-radius bends.