Part 1: Multiply the material height by 10 to get the minimum diameter that can be rolled.
Material Height x 10 = Minimum inside diameter
It may be possible to roll bend smaller diameters but the effects of material deformation and distortion will be more significant. If the required radius is at or below the calculated minimum inside diameter it is best to physically test the material to determine the results and bend quality.
Part 2: Divide the material height by the material thickness. If the result is greater than 20, the material will fail or distort and is not suitable for roll bending.
Material Height / Material = Less than 20
You can think of a scale of 1 to 20, e.g. 1 being very easy and 20 being very difficult. Profiles which score 15 to 20 may require rolling the part in multiple passes to relieve stresses in the profile or using nylon filler or shot medium to provide additional support to withstand the bending pressures. If the score is high, testing is recommended to determine the resulting roll bending quality and profile aesthetics. Scores that fall below 15 indicate that the profile will be easier to roll bend. Easier means that these profiles will require fewer roll bending passes and will take less time to produce.
If your follow the “Eagle 10-20 Rule” you are more likely to stay out of trouble, save time and money, and work within the laws of physics!