Part 2: Concave Web Spreading Rollers

This entry is part 2 of 8 in the series Pros & Cons of Six Common Web Spreading Rollers

The Concave Web Spreading Roller is the Simplest and Least Expensive

Web Spreading Concave Spreader Roller

Figure 2 – Concave Spreader Roller

The simplest and least expensive spreader is the Concave Web Spreading Roller (sometimes called a Bowtie Web Spreading Roller). As seen in Figure 2, this spreader is a conventional spreading roller whose diameter at the ends is slightly greater than at the center. In its ideal configuration, the diameter profile of the roller is cut as an arc of a circle. However, a simpler version can be made for unslit webs by cutting a roller with conical ends and a cylindrical center. A rough starting point for a diameter reduction at the center would be 10-25% of the MD (machine direction) strain induced by web line tension or draw control.

A useful tip is that one can crudely simulate the concave spreader by banding a roll with a couple of wraps of tape at the edges of the web. However, complete traction is required for this web spreader so that the roller must be well wrapped and the surface grippy. Though this web spreader is an inexpensive fix, it is not particularly powerful.

Web Spreading Rollers

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