Nearly every web manufacturer and most web converters have to cut and remove trim at one time or another. Unfortunately, you can have as much trouble with this small piece of waste as the entire rest of the web. There are three vital tasks for smooth trim takeaway: cutting, pulling and removing.

First we must cut the trim, which is often the same as cutting intermediate positions. However, consider that the trim slitter is almost always cutting, while intermediate slitters may often be idle. You would then expect that even with greater attention to the trims, the reliability may still be lower there. Also, the trim-removal systems may not pull the trim flat and cause problems at the trim blade, which is not a risk for intermediate cuts.

Sometimes the setup of the trim cut is slightly different than intermediates. With intermediate shear blades, for example, the toe in may be ½ degree all to one side, while the top trim blades may toe out by 1 degree at the trims. (These values are for paper; the values for film are less, while those for bulky materials are greater). Staff must take care when changing parts to make sure that the shims used to do this correspond to the correct slitter position. Perhaps the only thing that sometimes makes the trim easier to cut is that it may not be a final cut. A pre-trim or rough trim need only be reliable. It is not so fussy as to width tolerance and cut quality. You might, for example, be able to pre-trim with a water-jet when that type of slitter would not be good enough for a finished cut.

Second, we must pull the trim away. This is where most operators lose it. The trim should ideally be pulled with the same tension vector as the main web. That means the same direction (as if it were not cut) and with the same magnitude. However, it is common to see operators set up the trim to pull a bit sideways. While this might help keep the trim from getting tangled in the main web, it puts an unstable pucker in front of the blade. The other requirement is to pull almost as hard on the trim as the main web. This is hard to do in practice, so again, the result is a diagonal pucker.

Once the trim is passed over a roller or a pan, the trim can be bent or redirected. This isolating component keeps the trim system from talking to the trim slitter. In the order of best to worst, the direction to pull would be: along the path of the web, slightly out of plane, and sideways (the most common operator setup). Judging the quality of design and setup is easy. The trim is dead flat and dead stable near the cut point.

Finally, we must dispose of the trim. If it can be recycled internally, it must be repulped (paper) or reground (film). Unfortunately, mixed materials, such as laminates, are seldom recyclable. Here, it is not just the material savings that are important because trim is usually far less valuable than virgin material. Indeed, recycling often causes process chemistry headaches. The real benefit is the reduction in handling and disposal costs. Here, we may bale the trim to reduce the volume.

All of these steps and more are vital, for if you lose the trim, you've lost the web.

920/725-7671 drroisum@aol.com, www.roisum.com