A drum unit is one of the main parts of modern printers. Structurally, the drum is a metal cylinder (usually aluminum) coated with a layer of a photo-conductive material. It is usually the most expensive and most prone to wear part of a laser printer cartridge.
It is an electrically charged cylinder that transfers the toner powder onto paper. Without a drum unit, the toner powder is unable to be transferred onto a piece of paper.
Drum Unit Page Yield
Depending on the type of the drum, its page yield may be different. There are two main types of drum units:
1. The drum is a standalone part, separate from the toner cartridge. This can often be found on professional printers however there are some exceptions. Most Brother laser printers have a drum unit separate from the toner cartridge. The page yield on separate drum units is often several thousands of copies, after which it must be replaced with a new one. You can purchase original drums from the same manufacturer as the printer, and as a more economic option, a compatible drum from a third-party vendor. These separate drum units last a long time and should be replaced after the use of 3-4 toners.
2. The drum is part of the toner cartridge in most home and small office laser printers. This wears out much faster and its page yield will only be a couple of thousand pages. Since the drum unit is part of the toner cartridge, you cannot replace it on its own. This means that if you run out of toner, you will also have to replace the drum unit even if it was in good working condition.
When to replace the drum unit
You should replace it when your print quality declines and does not improve even after changing your toner. Your printer will notify you when it’s time to replace the drum unit. However, most printers will continue to work with the replacement drum warning long after the light comes on. It is best to be prepared and keep a drum on hand as a backup.