Part 4: Bent Pipe and D-Bar Web Spreading Rollers

This entry is part 4 of 8 in the series Pros & Cons of Six Common Web Spreading Rollers

Simple Construction Makes Bent Pipe Spreading Roller Popular

Web Spreading D-Bar Spreader

Figure 5 – D-Bar Spreader

The popularity of the Bent Pipe Web Spreading Roller lies with its simple construction. Unfortunately, this simplicity often leads to crude manufacturing practices and dubious spreading qualities. A D-bar spreader takes its name from the characteristic ‘D’ cross-section of the bar as seen in Figure 5. The only functional difference between a D-bar and bent pipe spreader is that the D-bar’s shape can be adjusted by intermediate jacks. With this adjustment, the operator can spread a local baggy or wrinkled spot, or open up a particular slit position. The bow of the bent pipe or D-bar is pointed directly into the web.

One application limitation of pipe, D-bar and other sliding spreaders is that web scratching may be unacceptable for many grades, particularly those that are coated. Indeed, even a hardened steel bar may wear out prematurely on paper grades which can be so abrasive that they generate sparks on the bar. Another issue with the bent pipe on unslit webs is that the path of the center is longer than the edges, thus inducing a degree of temporary slack edges.

Web Spreading Rollers

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