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The drum-unit is an important component in the copier/MFP/laserprinter. Its primary role is to attract the toner particles by electrostatic polarities. Also known as Photoconductor-Unit (PCU) or Imaging-Unit (IU), the design of the drum-unit vary depending on the brand and model of the device.

Recent models in laserprinter and MFPs make use of toner cartridges with built-in drum-units. The combination cartridge and drum allows the printer to operate at higher print speeds. This is because the cartridge and drum-unit can synchronize better and therefore operate at reduced response times as compared to devices that are loading a separate toner cartridge and imaging-unit. In case of a defect service-cost tend to be lower as the complete toner-/drum-unit can be replaced instead of searching for the failure in the drum-unit and toner-section separately. However, combined toner cartridges and imaging-units are not cost-efficient in the long run because the drum-unit is still serviceable when the cartridge’s toner supply runs out. Consequently working drum-unit are being disposed with the empty toner cartridge.


The laser printer drum operates as the photo conductive unit which serves as the image processing core. Basically, it is a set of parts that specifically work to transfer and paint a digital image right onto the surface of the drum. The document to be printed is transformed into a raster image by the computer and sent to the printer. These repetive processes take place at very high speed and frequency during printing.



Charging the Drum – The printer drum unit will be positively charged. The electrostatic character of the drum unit can be achieved in 2 different ways depending on the printer mechanism. Some printers use a corona wire with electric current running through it. The newer printers use a separately charged roller instead of the corona wire. These are two completely different ways to charge the drum unit but both basically follow the same principle.

Recreating the Image – Tiny laser beams from the printer laser scanning unit draw patterns on the surface of the drum unit to recreate the image. Initially, the surface of the drum and the toner particles have positive polarities.

As the drum rotates, the laser beam is used to paint the image or texts. Through the action of the laser beam the formed image becomes negatively charged, thus allowing the positively charged toner to «jump» to the surface of the drum. Excess toner is then wiped away by the drum-blade to guarantee the best print-quality.

Transferring Image to Medium – Toner on the printer drum unit will then be transferred to the medium which is usually paper (cut-sheet, labeles, other types) or transparency. Once completed, toner and paper move into the fuser-roller for fusing/fixation of the toner onto the medium. The printout will come out a little warm but smudge-proof.

Laser printers rely on the printer drum unit in creating and transfusing images into the medium. This means that without it, the printer will not be able to produce any printout. While toner cartridges are important, it is the drum that makes printing possible.


Laser printer drum units like toner cartridges have finite shelf life. Most image unit last 2 to 3 toner cartridge replacements or refills but they eventually wear off. The laser printer will turn out poor quality prints even after replacing or refilling the toner cartridge when a defective or exhausted drum unit is used. Replacing the drum in this scenario is therefore necessary.

Compatible vs Originals

OEM printer parts are usually very expensive. Consumers can opt for cheaper alternatives such as a compatible new-built drum-units or remanufactured drum-units depending on the printing-device and availability of suitable afermarket drum-units.

Depending on the OEM brand and machine model Drum-Units today have life-times up to 300’000 prints and more. To work over such a long time and different operational conditions stable is even for the OEMs a big challenge for the major components built-in such as OPC-drum, developer and blade. Quite often we therefore see an hear from OEM dealers that also the OEM drum-units to not achieve the specified life-time which in some cases is prompting then the OEM to modify their drum-units.

Our drum-units are made to meet or at least reach a life-time that is very close the life-time that is specified by the OEM. As with the toner we are partering with the best manufacturer to ensure high and consistent quality while offering our distributors a substantial cost-saving against the respective OEM drum-units.

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