There are many different types of spreader systems for different situations By selecting the case within the criteria of Modulus, Application etc. that applies to you the applicability of each type of spreader system is shown as "No" or "Yes". A good spreader for your application will show a "Yes" for each of your chosen criteria.

CriteriaSGFlCCCRBRBPDEEPExTe
Modulus
Soft (rubber, PE)
Stiff (paper, PET)
Very stiff (metal foil)
Application
Full Width
Separate Lanes
Perm. Widening
Width
Wide >1m
Medium >0.2m
Narrow <0.2m
Traction
Traction
Sliding
Drive
Driven
Undriven

The recommendations given here are merely starting point guidelines for most likely success. It does not guarantee that any particular recommended spreader will be helpful as there are many application details that need to be taken care of. Not taking care of details can disable a recommended spreader and can even cause wrinkling and other problems. Also, it is possible that non-recommended spreaders might work in some special circumstances. Again, these recommendations are just starting points.

SG=Spiral Groove, Fl=Flattening, CC=Compliant Cover, CR=Concave Roller, BR=Bowed Roller, BP=Bowed Pipe, DE=Dual Element, EP=Edge Pull, Ex=Expander, Te=Tenter

The suitability choices are based on Dr David Roisum's Web101.10 and The Mechanics of Rollers, TAPPI Press, 1996. Detailed implementations of the mechanics of bowed rollers and concave rollers can be found in TopWeb


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Which spreaders do what and why?
  • Spiral Grooves do not spread. This is an optical illusion that has fooled many. This consensus view of the experts is backed up by lots of data, research and good physics.
  • Flattening is a wrinkle reduction strategy that either attempts to reduce traction to just enough to turn rollers, but no more, or even to encourage whole-scale sliding. The reason is that it acts like a spreader, though not as powerful. Instead of actively making the web wider, as spreaders do, passive flattening allows the web to be as wide as it might want to be.
  • Compliant Cover spreaders are characterized by extremely soft covers that have undercut grooving. They are such weak spreaders that there was for some time a debate as to whether they even worked in the best of cases.
  • Concave spreaders can be as simple as a wrap of tape near the edge or a real concave shape cut into an idler roller. The principle is the same - a larger radius pulls the web toward in when in traction.
  • Bowed rollers are one of the most capable of all spreaders. Unfortunately, they are also one of the most complex in terms of construction and well as application.
  • Bowed Pipe spreaders can many forms such as over-bowed bowed rollers, bent pipes, hypercrowned rollers and D-bars. While powerful, they require either microsliding or whole-scale sliding and that limits application.
  • Dual Element spreaders are quite complicated and are mostly confined to spreading numerous narrow lanes.
  • Edge Pull spreaders are canted, nipped and narrow rollers that grip the edges and pull the web outward.
  • Expander rollers have an outer shell that takes the web in on the narrow side a lets it out on the wide side. This shell has large scale strains (movements) unseen most anywhere else in web handling.
  • Tenter chains running in tracks grip the edges of the web to preserve width (textiles) or permanently widen (such as BOPP and PET films).