Printer Drum Definition
Laser printers used to be rare in the office and even rarer in the home. But today, laser printers, both monochrome and color, have become reasonably priced enough for both business and personal use. One of the most important components of a laser printer is the drum, which transfers the desired image onto the paper through a series of negative and positive electrical charges.
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History
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In the 1980s, a revolution in printing occurred with the first inkjet printer. This printer replaced the clunky, often difficult-to-read dot matrix printer with faster printers that delivered ink through tiny jets onto the paper. But in the 1990s, the laser printer burst upon the scene and soon became the hub of office printing. The laser printer is faster, cleaner and, though it has a higher initial price tag, much cheaper to run than an inkjet printer, especially when printing demands are high. The drum, which delivers your images or text to the paper, is an essential component of every laser printer.
Parts
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The drum, an electrostatically charged cylinder onto which the print image is "written" by a laser, is only one part of a laser printer. The printer is made up of paper trays, a laser assembly, the drum, transfer kit, the fuser, discharge lamp, toner cartridges and a network of rollers to pass the paper along its way through the printer. Because the drum's life is measured by each rotation, every time the printer turns on, calibrates or prints a new job, the drum loses a little usefulness. On average, the drum needs to be replaced every 6,000 to 8,000 printed pages.
Drum
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In essence, the drum is a positively charged cylinder that transfers an image or text to a piece of paper that passes under it. Once you have created your design or written your report, you send your document to the printer. A laser assembly charges the drum negatively, but only in the areas where your text or images will appear. The negatively charged areas on the drum then attract the toner in the shape of what is meant to be printed. As the paper passes under the drum on the roller assembly, it is also negatively charged. The toner "jumps" off the drum and onto the paper in the exact same shape. If your document is through printing, the discharge lamp "erases" the drum by giving it a positive charge. The drum is then ready to be "written on" again by the laser.
Replacement
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The need to replace a laser printer drum depends on several things, but primarily on whether your printer is monochrome (black only) or color. For monochrome printers, the drum is part of the toner cartridge and will be replaced each time you replace the black toner cartridge. For color laser printers, the drum is a separate component and will need to be replaced depending on how many pages you print and the ratio of black only to color pages. According to the HP 8500 Color LaserJet manual, for example, the drum will not need replacing until 20,000 black-only pages or 6,000 color pages are printed. Drum life is shortened by doing many short print jobs instead of large quantities of the same print job.
Precautions
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Because the drum is sensitive to light, be very careful when handling it. Never expose it to direct sunlight or strong interior lighting. When removing a drum for maintenance reasons or to clear a paper jam, be sure to touch only the handle. Never open the protective shutter or touch any of the sensors or other parts of the drum. Save the packaging material the drum came in and use it to protect the drum when out of the printer.
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