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Multiple "W" Style Passes

This technique utilizes the benefits of the "W' in two or three successive forming passes. Each pass after the first one uses a progressively narrower top and bottom edge forming area to add to the previous edge formed area. As in most designs this is a standard metal forming practice.


However the contouring of the flower and the tooling can be complicated and care must be taken by the tooling designer to prevent stepped or uneven forming. This design can add from thirty to sixty degrees of edge form after the first pass to each side of the scalp.

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ADVANTAGES of this design are:

  • When properly executed on super heavy wall tubes edge forming can be accomplished with less thinning and strip edge deformation than other designs produce.
  • A greater amount of metal is edge formed before the fin passes thus reducing fin roll wear.
  • Difficult to form metals are formed with the greatest amount of mechanical advantage available on a tube mill.
  • Overall section height is greatly reduced going into the fin passes. On very light wall products buckling caused by edge stretching or lack of rigidity is greatly reduced.
  • Upper fin rolls will show less wear.


Some CONSIDERATIONS in the implementation of this design are:

  • The mating edge form roll contours can only function properly over a very narrow range of material gauges. To cover a wide range of gauges additional top rolls are usually required.
  • On all edge forming passes upper and lower roll alignment must be accurate.
  • Mill setup needs to be precise.
  • Flower and roll design must be correct or stepping and unevenness will appear in the tube surface.