Development Units / Assemblies for Laser Printer & Copier

What is the development unit made of?

The development unit is made up of thousands of small magnetic beads attached to a roller - a rotating cylinder made of metal. The beads carry an electric charge and attract the toner powder with opposite charge.

What does the development unit do?

The development unit plays an important role in getting the toner to the page. The development unit (also called a developer unit) attracts toner powder from the toner hopper. It then rotates and passes on the toner (that is coated on the beads) over to the drum unit, which has the electrostatic image written on it by the laser. The stronger charge on the photosensitive drum draws the toner away from the development unit and on to the image (to be printed).

Development units in a colour printer

Colour laser printers have four instead of one toner cartridges (cyan, magenta, yellow and black) and have separate developer drums for each toner cartridge. If you are buying a replacement developer unit for a colour unit, you need to usually buy and replace for the exact colour based on what the display screen error message mentions.

When is it time to change a developer unit?

Look out for these signs that might indicate that your printer’s developer unit needs to be replaced:

Refer to your printer's instruction manual or check your brand and model number online for instructions as to how to replace your developer unit.