Understanding The Basics of How Laser Printers Work
Getting inside that amazing piece of technology we all love, (when they work) The laser printer.
Parts of this article as well as the images were sourced from HowStuffWorks.com
Laser Printers! What does that even mean? Are there really laser beams shooting around inside of that big box sitting on your desk? We all know how an inkjet printer works, little jets spray tiny drops of ink on the paper but who really knows how a laser printer works?
How many times have you pressed the print button, made a copy or run across a laser printer in your every day life without ever thinking about the inner workings of a laser printer. There is a mechanical and technological symphony being played every time you hit that print button. that noise you hear is a combination of components (Drum, fuser, rollers and more) the exchange of data and the creation of static electricity are all happening seamlessly in order to deliver the perfect print.
This article wont make you a laser printer expert but it will shed a little light on the mystery that is, laser printing. The principles are basic but the combination of their interactions are quite extraordinary.
It Starts With a Spark: Static Electricity
The same energy that gives you a little shock when rubbing your socks on carpet, binds your clothes together in the dryer and causes lightning to strike, is the main workhorse of laser printing. Static electricity is simply an electrical charge built up on an insulated object, such as a balloon or your body. Since oppositely charged atoms are attracted to each other, objects with opposite static electricity fields cling together.
A laser printer uses this phenomenon as a sort of “temporary glue.” The core component of this system is the photo-receptor, typically a revolving drum or cylinder. This drum assembly is made out of highly photo-conductive material that is discharged by light photons.
The drum is positively charged by a wire with an electrical charge running through it known as the charge corona wire. As the drum revolves, the printer shines a laser beam across certain portions of the surface area essentially de-charging these portions of the drum. Essentially the laser is drawing the information to be printed in a pattern of (negatively charged) electrical charges that then attract the positively charged toner particles. The positively charged toner then affixes itself to the negatively charged areas on the drum.
Now that the drum has the toner affixed in the specific pattern the drum rolls over a sheet of paper. the paper is given a negative charge that is only slightly stronger than that of the drum in order to attract the toner from the drum. Since the drum and the paper are moving at the same speed the image transfer is exact. The detac corona wire then discharges the paper immediately to stop the toner from sticking to the drum.
The fuser is what makes the final print feel warm to the touch. In order for for the toner to be permanently fused to the paper it needs to be heated up. After the paper passes through the drum and receives the electrically charged toner it rolls through the fuser. The fuser is made up of two heated rollers and feeds from the drum to the paper output tray.
After the toner transfer is made and the paper is headed to the fusers the drum surface passes the discharge lamp. The bright light from the discharge lamp erases the electrical image by exposing the entire photoreceptor surface. The drum is now ready to start the entire process over.
On paper its actually quite simple but in practice there is kind of a lot going on.
Communicating With Your Printer
The print controller is the printers internal brain. In order for a printer to do anything the printer controller has to receive the page data and translate it to information that the printer can then use to reproduce the print on a sheet of paper.
The printer communicates with the host computer a number of ways. There are wired connections through serial ports or USB cables but there are also wireless communications through BlueTooth or WiFi connections.
Most laser printers can be connected to multiple host computers or to a network of host computers and communicate with multiple computers at once. The ability to share printers and manage print solutions within the office environment is one of the reasons they are so popular.
Putting the Laser in Laser Printer
The laser scanning assembly is what actually draws the the page. It is amazingly precise and is made up of at least these three components.
- A laser
- A movable mirror
- A lens
The laser of a laser printer is a stationary object. The beam is directed and reflected by the mirror and a variety of lenses. Much like an inkjet printer drops tiny dots of ink in precise locations in order to make up a printed page, the laser pulses across the surface emitting a pulse of light for every dot where there part of the image will be revealed and not pulsing where there is no image to be transferred.
Writing the Page
There is no up and down in laser printing, only side to side. The laser assembly only moves along a horizontal axis. It is essentially writing the page line by line just like the inkjet printers you are more familiar with. Due to the speed at which most laser printers operate there has to be a small print-engine computer to synchronize and manage all of these interactions
Some lower quality laser printers use a strip of light emitting diodes (LEDs) to write the page instead of a single laser. These printers are constricted to a single resolution as each dot position has a fixed LED. they are less expensive to manufacture but deliver inferior results.
Photocopiers and Laser printers work almost the exact same way except of course the method in which each device captures the image to print. A copy machine grabs its image by reflecting a bright light off of the original image while a laser printer receives its print information digitally. There are also differences in the way the electrostatic image is created but that’s for another article.
Toner, at its core is not really ink at all. It is a combination of pigments and polymers (plastic). It is a weird concept to understand if you are not familiar with laser printing. I mean most of us would think that to print you would transfer liquid ink to a piece of paper so when you tell people that instead the paper grabs the ink with static electricity they typically look at you like you are crazy.
The plastic is infused with the pigment so that once the toner is fused with the paper it is less likely to smudge, fade or bleed very easily. The make up and consistency of the toner is important and can affect the overall print quality. You can save money with remanufactured toner cartridges but be careful as some can do more harm than good.
Many toner cartridge manufacturers are combining the developer, drum and toner hopper in one simple replaceable cartridge but many still have to be replaced individually. There are different life spans for each individual part of the laser assembly so buying a printer with separate laser printer components could be beneficial for high volume print applications.
Putting Toner to Paper
The toner is stored in a toner hopper inside the plastic toner cartridge. The developer unit then gets the toner from the toner hopper and transfers it to the drum. The developer unit works with static electricity just like the drum but has a slightly less powerful charge so the transfer can be made from it to the drum. The developer unit is actually a collection of small, negatively charged magnetic beads. The beads are attached to a rotating metal roller, which moves them through the toner in the toner hopper.
The drum then moves over the paper, which has an even stronger charge and so grabs the toner. After collecting the toner, the paper is immediately discharged by the detac corona wire. At this point, the only thing keeping the toner on the page is gravity — if you were to blow on the page, you would completely lose the image. The page must pass through the fuser to affix the toner. The fuser rollers are heated by internal quartz tube lamps, so the plastic in the toner melts as it passes through.
But what keeps the toner from collecting on the fuser rolls, rather than sticking to the page? To keep this from happening, the fuser rolls must be coated with Teflon, the same non-stick material that keeps your breakfast from sticking to the bottom of the frying pan.
So I know that was kind of a lot to take in but have no fear, Rite Technology is here. Find out how you can save money and combine all of your toner, print and copy expenses in to one simple managed print solution.