The Difference between a Toner Cartridge and a Drum Unit

The work of a printer is to leave a legible permanent impression on a sheet of paper. Different printers have different ways of doing this. But a LaserJet printer does this via having toner store in a powdery toner cartridge. Deposited on the sheet of paper with the assistance of a drum unit and laser.

How Drum Unit work

To go into more detail, the toner cartridge contains a fine polyester powder. Which is capable of being electrically charged and attracted to the opposite charge.  The required opposite charge is created on a photosensitive electric drum (also known as printer drum) by a laser. Then the toner cartridge deposits polyester powder on the outline formed on the charged printer drum. The printing paper then charges as it passes through the printer. And with the aid of a hot fuser attracts. Appends the polyester particles from the printer drum to itself forming smudge-free prints. 

This process makes it possible to have very fast print speeds.  But also leads to higher cost for a LaserJet printer compared to an Inkjet printer.  

Some Laser Printers with Built-in Drum

Furthermore, some laser printers have their drums and toners built-in together as a single unit. While others have their drums and toners built separately.  Knowing this distinction is important.  As it affects if you need to replace the toners simultaneously with the printer drum. Or if you can separately replace either the toner or the printer drum. Both of these alternatives have cost implications.

But currently, a good rule of thumb to follow is to know that modern laser printers from manufacturers. Such as HP usually come with imaging drum built-in with the toner. Other manufacturers such as Brother, have laser printers that have printer drum and the toner built separately.  But Brother also has laser printers that have the imaging drum built-in with the toner. To aid your search on which printer uses, I recommend you use the toner cartridge finder on To identify the specification of printer drum/toner specification to use for a brand of printer.  

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