Plastics Decorating - January/February 2008 - (Page 40) SPECIAL FOCUS continued from page 38 to use, while the second company has a press dedicated to ‘running in’ new pads before they are used in production. Pads have a limited print life; they are susceptible to mechanical damage; and they are not cheap. Such extreme measures make very poor use of your investment. Die Stampco Inc. diestampco.com www. Material This topic refers not only to the material of the pad itself but also, to the base onto which the pad is mounted. For example, you may order pads mounted onto aluminum bases rather than wooden ones, the advantage being that the pads can be mounted very accurately onto the machine. Pads with wooden bases rarely are supplied with drilled holes for attaching to the pad holder of the machine. This means that the printer usually screws the pad in himself, making it difficult to get repeatable pad positioning. Also, wood screws are used with wooden bases. If these screws are taken on and off several times, the base becomes loose. On several occasions, we have seen pads literally fall off the machine during the print cycle because of this problem. Aluminum bases are better because they come with predrilled holes, so there is only one position to mount the pad on the holder or backing plate. Also, unless you have a very heavy-handed press operator, the threads of the screws are not easily damaged. This means that it is simple and quick for press operators to mount or replace pads. Similarly, if a set-up requires multiple pads (such as a matrix), aluminum bases are preferable because they will make pad positioning easier and more repeatable. One further advantage of aluminum bases is that they can be recycled with your pad supplier. If you are using a long-bar pad that does not have an aluminum backing, then back the pad with either aluminum or a thicker piece of wood. This will prevent the base from bending when it comes into contact with either the plate or the substrate. Such bending can cause print distortion or prevent the pad from picking up the image entirely. Recently, pads have appeared on the market that are molded onto a nylon-type base material, offering the advantages of aluminum at less expense. These pads also are delivered in a protective clear vacuumformed plastic that can be used to store the pads when not in use. Certain pads can be recycled (sometimes called ‘recovered’ or ‘resheathed’). Large pads are very expensive. To reduce the cost of replacing pads, some printers will send their worn or damaged pads back to their supplier. The supplier cuts the surface of the pad away and inserts the remaining rubber into the mold where the replacement pads are created, reducing the amount of new silicone rubber that is needed. The new material cures and bonds onto the old rubber and the finished pad performs like new, with a savings of up to 50 percent over the cost of a new pad. If the pad has been split or broken down internally, however, it cannot be recycled. Some pad manufacturers will use recycled material and mix it with new silicone rubber. As long as the pad surface is ‘virgin’ silicone rubber, this practice is perfectly acceptable. Special Pads for Large Images In some situations, a large image area must be printed but the machine does not have the power to compress such a heavy pad in a smooth motion. Two solutions to this problem are available. http://www.diestampco.com http://www.diestampco.com
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