The Importance of Proper Drum Lubrication
Failure to properly lubricate a drum cleaning blade and photo receptive drum can result in severe damage to the drum coating from “blade chatter” or “blade flip.” The severity of drum coating damage will vary, depending on which blade-related problem occurs and the type of drum.
Drum cleaning blades are designed to operate by a “stick-and-slip” principle. When the drum begins to rotate, the blade edge lightly “sticks” to the drum surface and moves slightly with the drum as it rotates. With proper lubrication, the blade edge will then “slip” along the surface of the drum, in the opposite direction of drum rotation. Drum cleaning blades are typically urethane, a rubber-like material that is highly durable and wear-resistant. Because urethane is also relatively “tacky,” proper lubrication of the blade edge and drum surface is essential for the blade edge to properly move along that surface during rotation.
If lubricant is not applied thoroughly to the drum surface and blade edge, blade chatter or blade flip can result. When the ends of the blade edge are not thoroughly lubricated, they stick longer and move further with the drum than they should. The ends of the blade then slip slightly, but again stick to the drum longer and move further with the drum than they should. Consequently, the blade “chatters” (skips) across the drum surface during rotation, producing scratches at regular intervals around its entire circumference.
Blade flip occurs when either end of the blade edge sticks to the drum but does not slip. The blade then folds backward along its entire length as the drum rotates, creating a deep scratch in the drum coating that spirals around its entire circumference. A blade will wear this type of scratch around the entire circumference of a smaller, faster-rotating drum more quickly than a larger, slower-rotating drum. After the blade flips completely backward, its back side rubs against the drum during rotation, causing additional scratches in the coating.
Blade flip can also occur when, due to improper lubrication, the center of the blade edge sticks to the drum during rotation and fails to slip. When this happens, the entire blade flips backward at once, producing a single deep scratch in the drum coating. Additional scratches are then produced as the back side of the blade rubs against the drum during rotation. In addition, the blade may be torn out of its holder, causing blade adhesive to stick to the drum.
Blade chatter and blade flip are more common with Organic PhotoConductor (OPC) drums than with selenium-alloy drums, because a “tacky” urethane blade is more likely to adhere to a “tacky” OPC surface than to a more glasslike surface. In addition, damage due to blade chatter or blade flip is likely to be more severe on OPC drums, because OPC coatings are softer and more susceptible to scratches than selenium-alloy coatings.
Types of Lubricant
Drums and drum cleaning blades with preapplied lubricant, and those installed in copiers with an automatic drum lubrication cycle using toner, do not usually require additional lubrication before installation. However, for drums and blades that come without preapplied lubricant and are not subject to a lubrication cycle, service technicians should manually apply one of two lubricants — zinc stearate powder or Kynar powder — or else lubricate the drum and blade with new toner, which contains lubricating additives. When properly applied, zinc stearate, Kynar, or new toner will minimize the likelihood of blade-related damage to the drum coating. Most OEMs recommend one of these types of lubricant. These recommendations vary between OEMs and copier models, and should be followed when installing drums and blades.
Zinc stearate powder should be used only for lubrication of selenium-alloy drums and the blades used with them, because its relatively large particle size can produce minor abrasions on the softer, more physically sensitive coating surface of an OPC drum. Kynar, a powdered fluoropolymer, has a smaller particle size and is much better suited for lubrication of OPC drums and the blades used with them. New toner can be used to lubricate selenium-alloy drums, OPCs, and the blades used with them.
Katun provides zinc stearate powder and Kynar powder in dusting pouches for simple, convenient application to drums and drum cleaning blades. The service technician lightly taps the pouch on the drum surface, while slowly rotating the drum to apply the lubricant evenly. To thoroughly and evenly lubricate the blade, the service technician lightly taps the pouch along the entire length of the blade edge. It is especially important to thoroughly lubricate the ends of the blade edge.
Proper lubrication of photoreceptive drums and drum cleaning blades with zinc stearate, Kynar, or new toner before installation allows the edge of the cleaning blade to move along the drum surface properly. This procedure prevents severe drum coating damage from blade-related problems, such as blade chatter and blade flip.