How Printer Copiers Work
Printer copiers essentially have two elements: the scanning element of the copier, and the printing element. The copier function uses the same mechanism as the print function to print the copy, whether it uses a laser printing mechanism or an inkjet mechanism. To understand how the copier works to scan an original document and pass the image copy to the printing element of the printer copier, click here.
Here we detail how the two main printer mechanisms work.
Laser Printers
The printing mechanism inside Laser Printers is very similar to the common form of digital copier, only with a different sequence of process.
Below describes the process used for laser printing:
- When the print command is give by the user at the computer, the document to be printed is sent page by page as a series of images to the printer’s data memory
- The images are processed as rasters, and the information on the raster rows stimulate a laser to fire light towards a mirror at a given angle to represent the position on the image
- The light reflects off the mirror towards a rotating photoconductive drum
- The Charge Corona creates a charge on the drum where the drum surface is activated by light
- The image begins to form on the rotating drum as a series of negative charges
- As the drum rolls passed the toner unit, the positively charged developer material is attracted to the drum and carries toner powder onto the drum
- The toner attaches to the drum in the arrangement of the image, and is carried by the rotating drum to where it meets the print paper
- The Transfer Corona then separates the charges by attracting the toner away from the drum and onto the paper, forming the image on the paper as the drum rotates passed the corona.
- The drum continues to rotate on and passes a cleaning unit, which collects residue toner and developer left on the drum, and removes any residue charge from the drum to be clean for the next copy
- The paper with the toner is passed on to the Fuser Unit, which uses the heating element on the upper roller to melt the toner plastic and release the ink pigment onto the paper, and press it onto the paper
- The paper is then transported on, and often brushed for any residue, before exiting the printer onto the paper/catch tray.
Inkjet Printers
The information transfer and printing mechanism in inkjet printers is very different to laser printers. Instead of using light and static electricity like the laser printer, the inkjet printer uses systematic mechanical movement of a container called a Printhead, holding the ink cartridges over the paper, controlled by an electronic circuit, and releases ink where necessary by heat.
Inkjet printing takes the following process:
- When the print command is give by the user at the computer, the document to be printed is sent page by page as a series of images to the printer’s data memory
- Each horizontal line of data from an image is read by electronic circuitry, which then sends signals through a ribbon to the mechanical structure of the printhead
- The signal makes the printhead move along a pole according to where the data exists on the line of image, with the paper sitting underneath
- Where there is data, the heat is transferred through the ribbon to the printhead, which contains the ink cartridges
- The heat is transferred to the appropriate colour ink tubes, and creates a bubble to displace a portion of ink
- The ink is released through an opening in the printhead as it is positioned over the paper
- In this way, each line of image data is translated through the printhead movement and positioning, and heat transfer to release the ink where appropriate as the paper passes under the printhead
- As the paper passes and is printed on, it exits the printer
