This contribution was made by a pressman in Australia. The first two corrective actions have merit, but I would not record them as new information. These would of course have to be removable. I would recommend an add on to side frames of the unit to restrict the flow of ambient air. I would certainly endorse such design changes. This is a logical move and in some cases has been successful. Many press manufacturers and roller suppliers are trying to cope with the edge drying problem by increasing the bristles on the ends of the brush rollers and reducing the bristles in the centers. Given time and skill, this can work effectively.
#Problems with cd roller Patch#
Unfortunately, this Mylar system is a patch job and requires some innovative skills of design and application, which may be in short supply. The Mylar (or rubber diamond) can be very effective in reducing the water feed in the center of the press. They closely resemble the sophisticated rubber diamond designs that are available from industry sources. A pressman can be very innovative in these designs. The best homemade water stops I have seen are cut out of heavy Mylar and are saw-toothed in varying designed to cut off anywhere from 10% to 70% of the surface water on the dampening rollers. They are mostly designed for narrow web restrictions. Most water stops, as supplied by press manufacturers, are not really effective in providing zone control. I would guess that as a permanent solution the pressman will use each of these together rather than only one. There are several actions the pressman can take. He needs zone control and the dampener is incapable of delivering it. However, in critical areas, such as on the roller ends, the deviation from the optimum pushes the forgiving rate over the edge of acceptable printing. The process can and does tolerate over and under dampening, up to a point. What this system does is take advantage of the forgiving rate of the process which allows a wider range of water to be applied without significant changes to the printed product. It functions on the premise that one size fits all. This design does not in any way adjust the amount of water to demand. Some deliver water directly to the plate, but the roller train configuration is most common. This brush delivers a consistent edge-to-edge fog of water into the roller train. The current most commonly used damper is the spiral brush. Now, let's look at the dampening configuration. in a four-high configuration this constant yo-yo of up and down those ladders, can be a killer and in spite of all of that struggle the job never does look right. In critical configurations he is constantly struggling between emulsification in the middle and scumming on the ends. Typically, he must overfeed water to the center of his product to provide adequate dampening to the ends. The result of this imbalance of air drying is that the pressman is constantly trying to balance his water to ink ratio. Ambient air on the roller ends also dries up rollers. This does work - air flow dries up the roller trains. One example is the recent innovation which uses air bars to blow air into the ink train to reduce excessive water. The higher the exposure the more we dry up. One must realize that this exposure has a drying up effect on the rollers.
If you drew a curve of exposure to atmosphere it would show high atmospheric exposure on the roller ends and low exposure in the center. The centers of the rollers are sheltered from ambient air, while the ends of the rollers are exposed to this ambient air from outside of the roller train. To explain the problem we must examine the structure of our roller configurations and the dampeners that are in use today.īriefly, rollers rotate at very high revolutions per minute and are exposed to the press room atmosphere.
Drying up on both ends of his product causes constant printing problems. You probably should not run Roller in production using this technique, but it's a relatively easy way to try Roller for yourself.One of the most frustrating problems with the dampening solution that a pressman faces today in offset printing is edge-to-edge dampening.
#Problems with cd roller install#
If you want to run Roller in production, then you should down load the latest official release and install it by following the Installation Guide, which you can find at the documentation link.
The Roller Install, User and Template Guides are available in ODT format (for OpenOffice or LibraOffice):
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