Laser printers use laser beams to print information on a piece of paper. The lasers in addition to high voltage, charged ions, powdered ink, heat, and paper combine to produce high quality output prints. Laser printers also provide for fast printing speeds.
Laser printers are very complex with many moving parts. It requires on printer memory and can be very messy on the inside.
Imaging drum, fuser assembly, transfer belt, transfer roller, pickup rollers, separate pads, duplexing assembly
The imaging drum is the middle man between the laser and the printed image on the page. The laser draws out what it wants to print onto the imaging drum which is photosensitive. The imaging drum is then put through toner. The toner sticks to the area where the laser hit the imaging drum. The toner is transferred to the paper where it is heated and permanently affixed to the paper. The imaging drum can be a part of the toner cartridge itself, but some laser printers separate the toner cartridge and the imaging drum, so that you can replace a toner cartridge without have to replace the imaging drum as well.
Permanently attaching the toner to the printed page requires heat and pressure. The fuser assembly is what completes this process. The fuser assembly melts the plastic toner powder to permanently bond it to the paper. The fuser assembly will be very hot so make sure to cool down the system before doing maintenance on the fuser.
Color laser printers usually have 4 colors that they use to print: cyan, yellow, magenta, and black. So there may be 4 different toner cartridges inside of a laser printer. Instead of printing one color at a time to the paper, laser printers prints them onto a single transfer belt. The transfer belt then transfers all four of the colors to a single transfer roller which makes it onto the printed page.
You usually will place a stack of blank paper into your printer. The pickup rollers are responsible for feeding one paper at a time from the paper stack and into the printer. If your printer isn’t picking up any paper to send through the printer or if too many sheets are being fed through at once, then you may have an issue with the pickup rollers. Too many sheets being fed into the printer at once could cause paper jams.
Pickup rollers should be periodically cleaned or replaced when they have worn down.
The separation pad works in conjunction with the pickup rollers. The separation pad works to pull just the top sheet from the stack of paper supply. The separation pad is usually on the paper tray. It’s small and inexpensive and easy to clean or replace.
Generally, printers only print on one side of a paper. If you want to print on both sides of the page, your printer may have a duplexing assembly which will automatically flip the paper over once one side has been printed, and then send the paper back through so that the backside of the paper can be printed on. The duplexing assembly is the mechanisms by which the printer flips the page over automatically. The duplexing assembly can be built in to the printer. However, some printers allow you to add on a duplexing assembly if it was not originally included in the printer.
Imaging process: processing, charging, exposing, developing, transferring, fusing, and cleaning
There’s a 7 step process for laser printing:
- Processing: The data to be printed is sent to the memory of the laser printer. The paper is sent into the printer. The entire page has to be rendered in memory before it starts printing.
- Charging: A primary charging roll charges the photosensitive drum with negative ions.
- Exposing: The laser writes out what it wants to print by neutralizing the negative ions on the photosensitive drum only in the specific areas it wants to print to.
- Developing: The toner from the toner cartridge is transferred onto the sections of the photosensitive drum that have been neutralized by the laser. The toner has a negative charge so it wont stick to any parts of the drum that have negative ions. The toner only sticks to areas that have been neutralized by the laser.
- Transferring: The transfer roller transfers the toner from the photosensitive drum onto the paper.
- Fusing: Heat and pressure are applied to melt the toner onto the paper to permanently fasten it to the paper. You may notice that when you pull a freshly printed paper out of a laser printer, the paper will be warm. That is due to this fusing process.
- Cleaning: There may be toner left over on the photosensitive drum. So this last stage cleans the photosensitive drum to prepare it for another print.
Maintenance: Replace toner, apply maintenance kit, calibrate, clean
One of the most common maintenance tasks for a laser printer is to replace the toner cartridge. The printer will display error messages when the toner becomes low. Low doesn’t necessarily mean empty, so you can still print until the toner is empty.
The toner can also contain the OPC (Organic Photoconductor) drum. The drum is sensitive to light so keep it in the bag until it’s time to install it in the printer. As a best practice it’s good to power down the printer and disconnect it from the power source prior to changing the toner cartridge.
Toner cartridges are modular and easy to remove and replace them. Remove any packing strips before placing it in th printer. Generally you slide out an old toner cartridge from the printer and slide the new one in place. If it’s a color laser printer, there may be a tray of toner cartridges, and you simply pick up and replace the cartridge on the tray.
Laser printers components often wear out. Most laser printer manufacturers provide a standard maintence kit. The maintenance kit provides everything you need to swap out during this scheduled maintenance process. For example replacement feed rollers, new fuser unit, etc. The maintenance should be scheduled according to the number of pages that have been printed. The printer will have a page counter to let you when maintenance should e scheduled. Remember to power down the printer and remove the power source before replacing the components in the printer. Reset the page counter once maintenance has been completed.
Once you replace a toner cartridge or perform maintenance on the laser printer, it’s common to print out a test page. A new toner cartridge might print a little differently than the previously installed cartridge. To adjust the density of the colors you can perform calibration. The calibration process prints out a set of colors and marks on a page that can then be used to determine how dense the output should be. The calibration process may be automated or manual so check your printer manual to see how calibration is performed.
Laser printers can get dirty. There may be toner in the printer and paper scraps can be found on the inside and outside of the printer. The printer manufacturer will mostly likely provide recommendation for printer cleaning. This could be using water or isopropyl alcohol (IPA) to clean. Avoid using harsh chemicals. For the outside of the printer, you can use a damp cloth to wipe it clean of stray toner.
On the inside of the printer, we can use the damp cloth to wipe away any paper dust or toner. Don’t use a normal vacuum cleaner or compressed air inside of a laser printer, which could put toner particles into the air. If you get toner on yourself, you can wash it off yourself with cold water. To clean the rollers, IPA can be used to clean them.