Roll Tooling Design (W-Style Method)
The W-style (reverse bending) method of designing breakdown rolls is recommended when forming high-strength very light or very heavy gauge materials. It can be combined with the versatile design for maximum results on light-gauge, high-strength material.
W-style can form more of the strip in the first pass than Edgeform or Versatile designs. It pre-forms more of the strip, giving greater stability, and provides a better presentation into the fin passes.
By comparison, there are some reasons that another design method may be a better choice:
- Drive and ratio are often issues, due to multiple diameters and surface speeds in the first pass
- The tube can have a flat spot, if the second pass is not built for the correct gauge and used properly. This flat spot can remain in the strip through the sizing rolls, so it is very important to work the second pass to take out the center “hump” from the “W” pass.
- Although it is not recommended, this style can be used when running multiple tube and pipe sizes, as long as the smallest size is not less than 80% of the largest size. We recommend replacing the #1 top rolls for various gauges.
- W-style design will raise the properties of the tube, so if bending, expanding, drilling, or other operations are to be done to the tube, another design style should be considered
Even with the limitations of the W-style, it remains a widely used and acceptable method for designing tooling.