The two essential components of a laser printer are the toner cartridge and the drum unit. This is because toner creates the print on the paper, and the toner cannot be transferred to the paper without a drum unit. Toner cartridges and Drum Units are not the same. Toner cartridges contain a toner powder, while the drum unit is an electrically charged rotating cylinder.
Working of drum units
Drum Units work on the principle of electrostatic charges. The drum is an aluminum cylinder that is given a positive charge through an electric wire. After that, a laser beam discharges its certain points and draws the letters or images in the form of electrical charges.
The toner is coated on the drum. The toner is a positively charged powder. Thus, it adheres to the negatively discharged points on the otherwise positively charged drum unit. An electrical wire gives the paper presentation below the drum a negative charge on a belt. The drum then rolls over the paper. Since the negative charge on the paper is stronger than the negative charge of the electrostatic image, the paper draws the toner away from the drum and prints the pattern.
The paper is discharged to prevent it from clinging to the drum after the pattern has been transferred.
Types of drum units
Drum units last much longer as compared to toner cartridges. Drum Units either come as a single unit with toner cartridges or separately from the toner cartridges. In the case of a single unit, the drum unit is also replaced as soon as the toner cartridge exhausts even though the former is still working. The drum unit needs replacement in the case of a separate toner cartridge and drum unit, usually after the 3-4 toner cartridges are used up.
The following types of drum units are available in the market for replacements.
- Genuine Drum Unit is manufactured by the same brand as the laser printer. It can either be available in combination with the OEM toner cartridge of the printer or as a separate OEM drum unit depending upon the brand and model of the laser printer. The genuine drum units are expensive but reliable and provide high-quality prints.
- Compatible Drum Units are designed to work with multiple models and brands of laser printers. They are manufactured by third-party manufacturers and not by printer manufacturers. Compatible drum units come either with compatible toner cartridges or as separate units. Compatible drum units provide acceptable print quality and cost less.
- Recycled drum units are made from discarded drum units. They are repaired, tested, and sold again in recycled drum units.
When to replace the drum unit?
If the drum unit is integrated with the toner cartridge, the drum unit naturally gets replaced together with the toner cartridge. However, if the drum unit is a separate entity in your laser printer, then the rule of the thumb is to replace it after changing toner cartridges 3-4 times. Most laser printers give an alert when the drum unit nears the end of its lifecycle. Black spots or lines on the page also indicate the imminent demise of the drum unit.