HP Color LaserJet CM4730 Service Manual - Page 133

ETB life under different circumstances Depending on the MFP workload, the customer will need to replace the ETB once or twice in the life of the MFP. In order to help plan supplies purchases, the HP Color LaserJet CM4730 MFP calculates an estimated remaining number of pages that can be printed with the ETB. The number of pages the ETB can print is a function of two factors: ● The number of times the belt goes from a stationary to a rotating state (spins up) ● The number of pages that have been printed on the belt Unless print jobs are queued back to back, each print job requires the belt to spin up. Think of the ETB as having a limited number of wear units. It has 200,000 wear units when it is new. Each time the belt spins up, it uses two wear units. Each time it prints a page, the belt uses one wear unit. Because most print jobs are not queued, the average number of pages per job, or job length, is a factor in how fast the ETB will wear out. The shorter the average job, the more quickly the ETB will wear out. The following figure shows how many pages an ETB can print, given various average job lengths. Figure 3-1 ETB total page count according to average job length The MFP assumes an average print job length of three pages to estimate how many pages are remaining on the ETB. With an average job length of three pages, the ETB will print 120,000 pages. If all print jobs are exactly three pages long, for each page printed the number of estimated pages remaining would decrease by one, beginning with the maximum 120,000 pages. If the job length is less than three pages, the estimated-pages-remaining number decreases more quickly than the rate at which the number of pages actually printed increases. If the job length is greater than three pages, the number of pages remaining decreases less quickly than the rate at which the actual number of pages printed increases. ENWW ETB life under different circumstances 113