HP d640 HP D640 High-Volume Printer - User Manual (Printer and Accessories), C - Page 185

Managing Consumables The average number of pages in print jobs has a large effect on drum and developer life. Extra drum rotations occur at the start and end of each job. There are four rotations at the beginning and four rotations at the end. If the D640 primarily prints very small jobs (less than 25 pages), you get lower than rated yields on the drum and developer. If you primarily print jobs larger than 25 pages, you get higher than expected yields. There is also a negative effect on drum rotations if you print complex images that slow the printer down. If the printer controller cannot process the incoming data fast enough to keep the printer running at 40 pages per minute, extra drum rotations occur for the print job. The estimated yields for the drum and developer assume a job size of 25 page sides per job. It is not important if you occasionally print small jobs or complex images; it's important how your print environment averages usage over a long period of time. The drum surface is easily damaged by scratches, long exposure to fluorescent light (30 minutes), or exposure to direct sunlight (which may cause gray background shading). The estimated yields do not account for replacement due to these factors. Scratches can occur from unsupported media and may be significant enough to require the drum to be replaced prior to the printer indicating the drum has reached its end of life. Paper which emits certain chemicals or large amounts of paper dust can cause excessive drum wear. If you this problem, contact your service representative or the paper manufacturer. Fuser The fuser yield is controlled by the number of times a letter or A4 sheet of paper passes through it. The printer maintains a counter which increments based on the size of paper used. Factors which may reduce fuser life can be related to printing repetitious images, media problems or not replacing the cleaning roller when necessary. Hewlett-Packard recommends mixing up the types and positions of print images printed among print jobs. Fuser rollers can wear unevenly when a dark image, such as a company logo or a thick dark line, is printed repeatedly in the same position on every page of every print job. Media can also have an effect on fuser life. Paper which emits certain chemicals or large amounts of paper dust can cause excessive wear. If you suspect problems of this sort, contact your service representative or the paper manufacturer. For optimum fuser life, replace the cleaning roller after every other bottle of toner, and follow the recommended cleaning procedures in "Duplex Area" on page 5-6. The cleaning roller deposits silicon oil onto the fuser roller surface to prevent toner from sticking. It also cleans away small amounts of toner that adhere to the fuser roller surface. Failure to replace the cleaning roller at the specified times can greatly reduce fuser yields. 6-10 Advanced Topics