How to Use the Plate Rolling Curvature Calculator
A pyramid type three roll bender rests the plate on two bottom rolls and presses the top roll down to form curvature. The radius that comes out is fixed geometrically by bottom roll center distance, top roll penetration and plate thickness, so you can predict it before the first trial piece goes through the machine.
With bottom roll center distance a and top roll penetration h, the neutral axis radius is R = aยฒ รท (8h) + h รท 2. This is the sagitta relation that recovers an arc radius from a chord and its mid-span rise. Subtract half the thickness for the inside radius and add half for the outside radius. Entering a target inside radius inverts the same expression to report the penetration you need.
Once the load is released the material springs back and the finished radius opens up. Mild steel plate typically gains 2 to 5 percent, high strength steel and stainless 5 to 15 percent, so rolling a trial piece and measuring it is the surest way to calibrate. The model also omits the contact point shift caused by roll diameter and the flat leading and trailing ends of the plate. Thickness beyond machine capacity calls for preheat or multiple passes, and forming for structural work should be confirmed with the equipment supplier and the material elongation data before final release.
Frequently Asked Questions
Set zero where the plate sits flat against all three rolls, then enter how much further the top roll travels down. That travel is almost identical to the mid-span deflection of the plate between the two bottom rolls, which is what the curvature formula needs.
It depends on the alloy and the R/t ratio. Mild steel plate typically opens up 2 to 5 percent, while high strength steel and stainless can reach 5 to 15 percent. Rolling a trial piece and comparing measured radius to target is the most reliable way to set your own value.
Not if the required neutral axis radius falls below half the bottom roll center distance, which is geometrically impossible in one pass. Narrow the bottom roll spacing or step the radius down over several passes, and confirm the machine capacity for that thickness.