The Canon Laser Printing Process Explained Step by Step

Canon laser printers and copiers use static electricity to place fine toner powder on paper, then use heat and pressure to bond it permanently. The same basic process is used by laser machines from every major manufacturer.

The technique is called electrophotography, also known as xerography: a dry printing process that uses a light-sensitive, electrically charged surface to attract toner into the shape of an image. It was invented decades before the first office laser printers and is still the foundation of almost every office copier and laser printer sold today.

Canon has a long history with this technology. The company supplied the print engine for HP's original LaserJet, a story covered in the history of the HP LaserJet, and it builds the laser engines in its own imageCLASS printers and imageRUNNER copiers. Whatever badge is on the front, the steps inside are the same, so understanding them helps you choose machines, buy the right supplies and diagnose print problems.

Each page goes through charging, exposure, developing, transfer, fusing and cleaning, in that order, in a few seconds. The drum rotates continuously, so different parts of its surface are at different stages at the same moment.

1. Charging. A charge roller or corona wire gives the surface of the drum a uniform electrical charge across its whole width.
2. Exposure. A laser beam, guided by a spinning mirror, or a row of LEDs switches on and off to discharge tiny points on the drum. The pattern of discharged points is an invisible electrical copy of the page, called the latent image.
3. Developing. The developer unit brings charged toner close to the drum. Toner is attracted to the exposed areas and ignores the rest, so the invisible image becomes a visible one made of powder.
4. Transfer. A transfer roller or belt gives the paper an opposite charge as it passes the drum, pulling the toner off the drum and onto the sheet.
5. Fusing. The paper passes between heated and pressure rollers or a heated film in the fuser, which melts the toner and presses it into the paper fibers.
6. Cleaning. A cleaning blade scrapes away any toner left on the drum, and the remaining charge is neutralized so the drum is ready for the next page.

The precision of the exposure stage largely determines print sharpness. Resolution, measured in dots per inch (dpi), is the number of individual dots a printer can place along a one-inch line; the more precisely the laser or LED can place those dots, the crisper small text and fine lines appear. Toner particle size plays a part too, since finer, more uniform toner reproduces edges and gradients more cleanly.

Timing is also tightly controlled. The paper must reach the transfer point at exactly the moment the matching part of the drum arrives, which is why paper that slips or feeds unevenly can cause misplaced or skewed images as well as jams.

The laser printing article on Wikipedia has diagrams of these stages if you would like to see them visually.

Five main parts do the work: the drum, the laser or LED unit, the toner and developer, the transfer roller or belt, and the fuser. Several of them are consumables that are replaced over the life of the machine.

• Drum. A drum (photoconductor) is a cylinder coated with a light-sensitive material that holds the electrical image of the page. It wears gradually with every page.
• Toner. Toner is a very fine powder of plastic resin and pigment that melts under heat to form the printed image.
• Developer. In some machines, developer is a separate material that carries toner to the drum and helps give it the right charge; in others, this job is built into the cartridge.
• Transfer roller or belt. This part moves the toner image from the drum to the paper, directly or by way of an intermediate belt.
• Fuser. The fuser is the heated assembly that permanently bonds toner to paper, which is why fresh prints feel warm.

Many smaller Canon printers use all-in-one cartridges that combine toner, drum and developer, so most of the wearing parts are renewed with every cartridge change. Larger Canon copiers usually separate them into toner cartridges, drum units and developer, each replaced on its own schedule. You can find compatible toner and drums by searching your model.

A copier adds a scanning stage before the six printing stages. It reads the original document into a digital image, then prints that image exactly as a laser printer would.

Early analog copiers projected light reflected from the original straight onto the drum. Modern digital copiers, including Canon imageRUNNER models, scan the original with a sensor, store it as a digital file in memory, and then drive the laser or LED unit from that file. You can read more about how the technology evolved in the copier guide.

Going digital is what made multifunction copiers possible. Once the page exists as a file, the machine can print it, email it, save it to a folder, fax it or store it for later. It also means many copiers keep document images on internal storage, which matters for data security when the machine is replaced. Our guide to the scanning process covers the scanning stage in more detail.

Color laser printing builds each page from four toners, cyan, magenta, yellow and black (CMYK), using the same six-stage process for each color. The four color images are layered precisely before fusing.

Most color office machines use a tandem design, with four imaging stations in a row, one per color. Each station charges, exposes and develops its own drum, and each color is transferred in turn onto an intermediate transfer belt. The belt then transfers the full-color image to the paper in one step, and the fuser bonds all four toners at once.

Because colors are layered, the machine must line them up very accurately. When colors are slightly out of alignment, you may see colored fringes around text or images. Most color copiers have a calibration or color registration routine in the settings menu that corrects this. Running calibration after moving the machine, or when colors drift, keeps output consistent.

Most laser print-quality problems point to a specific stage, which tells you which part to check. Use the table below as a starting point before replacing supplies or calling for service.

Repeating marks are especially useful clues, because the distance between them often matches the circumference of the part causing them. If a fault persists after replacing the obvious consumable, our article on top copier frustrations and solutions covers more fixes.

Good paper, genuine-quality supplies and regular cleaning keep every stage working as designed. Most problems that seem mechanical start with damp paper or worn consumables.

1. Store paper flat, sealed and away from humidity, and fan the stack before loading it.
2. Set the correct paper type in the driver or tray settings so the fuser uses the right heat.
3. Replace toner, drums and other consumables when the machine prompts you or quality drops.
4. Clean the scanner glass and document feeder rollers regularly if you make copies.
5. Run the machine's cleaning or calibration routines when output starts to look uneven.
6. Let a hot fuser cool before reaching inside to clear a jam.
7. Keep service records so recurring faults are easy to spot.

For more on paper care, read how to prevent paper jams, and see how to keep your copier clean for routine care.

CopyFaxes supplies Canon printers, Canon copiers and the toner and drums that keep them running. If you are not sure which supply your machine needs, or you are choosing a new laser machine, ask our specialist team and we will help you find the right fit.