Controlling static on a paper folding machine has always been an issue. In fact, it has become more common with the introduction of the high speed machines that are being sold today. It is even more noticeable since there are more digital printers and heat-set presses in use. So before we can control static, we must first discuss what it is.
Static electricity is simply a build up (or excess) of charged particles. It can be either positively or negatively charged (that's one of the reasons its so hard to control). It is important to note that these charges can have a very high voltage and can be dangerous! I am sure most of you can remember that funny looking thing the science teacher used to make your hair stand up...it is called a Van de Graaff generator. This is a machine that is used to produce a static charge. The generator causes charged particles to build up on the shiny dome which then discharges to another object. This discharge is because the particles are trying to maintain their electrical neutrality.
The reason why folders are more prone to develop this build up is because of the way the they operate. You see, unlike a printing press which uses grippers to carry the sheet through, a folder pushes the sheet from the feeder through to the delivery. In this process, it exposes the sheet of paper to a considerable number of rub points, be it a belt, a fold plate, rollers or wheels. What adds to the problem is that the processes of digital printing or heat setting inks basically dries out the sheets of paper as they are processed. Paper does not do well with rapid changes, for example changing its moisture balance. This imbalance causes the paper to curl or get wavy. It also makes it electrically unstable which makes it more likely to cause excessive static build up.
The first thing that you should do is make sure that your machine is electrically grounded with a dedicated ground. *** Because your machine uses high voltage electricity, this should be done by a qualified electrician.*** Another major consideration which is often overlooked in the Postpress area is climate control. More specifically humidity. It has been published that a recommended relative humidity of 55% should be maintained to reduce the chances of static build up. If your shop's humidity is not controlled, you could place an ultrasonic humidifier directly beneath the register table so that the moisture vapor is directed toward the individual sheets as they are fed into the folder. Unfortunately though, even these measures will not eliminate static because there are many factors that come into play.
There are a number of ways to control static. One very common way is the use of tinsel. This is usually made from copper and looks like the garland used for decorating Christmas trees. While some people swear by it, it is not really a good solution. But in a pinch, I guess you could use it. Another way is the use of ionizers in the air lines. This has some promise, but again does not eliminate it. There are mink brushes available that also help, but don't eliminate it. Static ionizer bars are also available. They usually come with a transformer and 2 bars. One bar has a negative charge while the other is positive. The trick with these is to know which one should be placed where. Try to experiment with swapping the locations of each of the bars.
The only true solution is to contact a company that specializes in this field. What they will do is come into your facility and use a series of sophisticated (and expensive) test equipment to find the source of the static. They will analyze the data they collect to determine the best solution to eliminate the problem.
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