Metal Roofing Contractors Can Avoid Cinching AKA Friction Scratches With These Simple Rollforming Tips

Cinching, sometimes also referred to as “friction scratches” or “pickoff,” is the result of the movement or slipping of painted coil laps against each other on a rollforming machine.

This phenomenon can be frustrating to metal roofing contractors because it causes the removal of paint in the shape of small or medium sized scratches on metal roofing coil formed in the same direction of the slipping or movement of the coil laps.

Some clear signs that cinching is the cause of these short longitudinal scratches are:
•    Worn or broken pieces on the spools, idler rolls and guides,
•    Gaps or air spaces between sections of the laps of the coil
•    The ability to move the laps of coil with hand pressure, a sure sign that coil has unraveled.

Cinched metal roofing panel.The vast majority of cinching incidents are caused by improper brake pressure on the un-coiler spool or the expandable arbor brake on the rollforming machine.  For portable roll formers, the improper brake pressure on the un-coiler spool is by far the source of most cinching. And new machine operators not familiar with the use of the brake or trained incorrectly are responsible for most of the problems.

To avoid cinching, the rollforming machine operator must make sure there is proper tension to allow the coil to uncoil without tightening the laps or without loosening the coil so it does not unravel. If either of these actions occurs, the laps will rub against each other and cause cinching.On portable rollformers, the crude brake –tightening a bolt on the shaft—is the only way of adjusting tension on the coil. Because a spool is suspending the coil on a portable rollformer, the operator must take into account the weight of the coil when brake pressure is applied—knowing that when the machine starts, a tug will be observed.

If the brake is set too tight, this tug tightens the coil by moving the laps. As time goes on, the paint can no longer absorb the force of this abrasion and the paint will be removed in the direction of the tug or force applied to it.

Conversely, if the brake is set too loose, the tug of the machine causes the coil to unravel and scrape against the machine. Consequently, the laps of the coil will loosen to the point where they will rub against each other when the machine starts up, again causing cinching.metal roof panel.

It is important to remember that as the coil is used and grows smaller in size, the rollformer no longer has to pull as much weight and brake pressure needs to be adjusted, depending on how the coil is responding.

Cinching problems, causes, solutions and troubleshooting techniques go back many years. The result has been the development of the expandable un-coiler for portable rollforming machines.  An expandable un-coiler will support the coil as it is used but proper brake pressure is still critical to avoid cinching. While new technology like this has done a lot to reduce material waste and improve production, there are still metal roofing contractors who are comfortable using machines that were designed over 20 years ago. In response to that market, there are still companies offering simple metal roofing  machines with features and technology that is 20 to 30 years old as well.

In those cases, good training and experience are the only answers to prevent cinching caused by the operator.

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