Overview
Printing with low toner coverage leaves a lot of uncharged toner in the development unit. This degrades developer more quickly. To keep toner in the development unit fresh, the machine makes a belt pattern on the drum at the end of a job when image coverage is less than 3%, to make sure that the equivalent toner for 3% coverage is consumed. This supplies a certain amount of fresh toner to the development unit. The belt pattern is cleaned off the drum, and the waste toner is stored in the cleaning unit and from there it goes to the waste toner bottle.
6% Coverage (Toner consumption ratio = 20 mg/m)
In the first example, we have 6% coverage. 20 mg/m of toner is sent from the development unit to the drum. 17 mg/m ends up on the paper and 3 mg/m is cleaned off the drum and goes to the waste toner bottle. 3 mg/m = 20 mg/m x 0.15. This factor of 0.15 is a constant for this development mechanism. In other words, at all times, 15% of the toner applied to the drum does not get on the paper, and is discarded.
1.5% Coverage (Toner consumption ratio = 5 mg/m)
In this example, we have a lot less than 3% coverage. 1.5% coverage is only 5 mg/m of toner. The development unit sends 5 mg/m of toner to the drum. 4.25 mg/m of this gets on the paper, and 0.75 mg/m is cleaned off the drum and sent to the waste toner bottle (this is the 15% factor we talked about above). In this job, only 4.25 mg/m was consumed. The machine has to consume 10 mg/m for each job. So, to make this 4.25 up to 10 mg/m for the preceding job, the machine then consumes 5.75 mg/m by making patterns on the drum (shown in red in the diagram). This toner is cleaned off the drum and sent to the waste toner bottle.
- Red letters indicate the toner amount that the belt patterns forcibly consume.