How Do Laser Printers Work

Think of an office, and the first thing that you’ll notice is a printer. Printers are a staple for physical document processing. As a result, they have been widely used since their invention.

The first noted use of analog printers can be found as early as 1440. But a faster and more mechanized printer was first developed by Univac computers in 1953. Today, the technology has gone through more refinements and has become a standard as modern printers.

But have you ever wondered how laser printers work? How can a simple laser beam copy something with precision and high resolution?

Well, this article is for curious minds. In this article, we will look at the history of laser printers, how they work, their different components, and of course, the technology behind such a widely used product. So buckle up and get ready to go.

How Do Laser Printers Work?

Laser printers are thought of as the successor of the inkjet printer. The working process of an inkjet printer and a laser printer are also similar. They both use light to trace out an image in the drum, which is then used to print out the paper.

But the key difference is in their work process. While inkjet printers use a simple line-by-line tracing by ink droplets, laser printing uses a far more complex process to print out the complete image in one go.

The process of laser printing happens in a few key successive steps. But before we get into the details, you need to understand the basic principle behind a laser printer. A laser printer works by the process of static charge. Many of us did the paper bits sticking to comb after brushing experiment back in school. The same static charge that holds the bits in place is used here to make the print.

But it’s not just about the static charge. The charge needs to be applied to a medium, and more importantly, it needs to apply in the trace of the image to print. Let’s see in detail how this complex process occurs behind the scene.

Step 1 – Raster Imaging

Raster imaging is the process of turning an image into a bitmap. A bitmap is essentially a codification of something so that it can recognize and execute by machines. Rastering the image is the first step of the laser printing process.

Every laser printer comes with a small memory system with it. Now you might be thinking, why would a printer need memory? Unlike other printers, a laser printer continuously prints out an image, so the entered bitmap of the image needs to pre-store to the printer to start printing.

Other traditional printers, which convert the image line by line, do not require memory to store the bitmap. As a result, they are often remarkably slow compared to a laser printer.

After the bitmap is stored in the printer, the internal process of a printer starts.

Step 2 – Charging the Drum

The actual process of printing starts with charging the drum. A drum is a barrel-like structure within the printer that enables the print to take place on the paper. We will discuss these components in detail in the latter part of the article.

As we mentioned before, a laser printer uses a static charge to print. This static charge needs to place on the drum. The negative charge allows the drum to hold the raster image.

A corona wire or a charging roller is used to spread the negative charge on the drum to charge the drum. The drum can hold this negative charge because it is not exposed to the external light source. In the subsequent step, laser light is exposed to this drum to create a duplicate of the bitmap.

Step 3 – Creating Bitmap on the Drum

Things get technical from here on. Once the drum is negatively charged, it exposes the laser beam. The laser beam is a high-precision and high-intensity light source that traces an outline of the bitmap on the drum. Light acts as a positive charge on the negatively charged drum.

The laser makes the outlined part charge-neutral by removing the negative charge. The high precision of the laser outline allows for a precise print. That is why laser prints look far superior in quality compared to a traditional printer.

A charge negative toner roll is placed on the surface of the drum. The charge-neutral part of the drum will attract the charge negative toner and attach it to its surface. This will essentially complete the main part of the printing.

Step 4 – Image Processing

The toner gets rolled onto the drum until it reaches an even 15-micron thickness. The toner is a dry powder mixture, which acts as either a monochrome or coloring agent, depending on the print.

Once the standard thickness is achieved, the drum can transfer the paint from the roller to the paper.

Step 5 – Transfer the Print to the Paper

In this step, a paper roll is rolling on the toner-infused drum. The toner particles have a very low point of attraction to the drum. Direct contact with the paper easily shifts from the drum to the paper surface.

Some advanced laser printer uses a positively charged plate on the backside of the paper. This ensures a better pull on the toner from the drum. The pulled toner on the paper surface is the exact copy of the print to make. It might seem like the process of printing is complete at this stage, but there is one final step in the process.

Step 6 – Fusing the Toner With the Paper

A separate hollow roller tube is used to bond the toner with the paper permanently. There are two complementing rollers in the hollow tube – a heated roller and a rubber roller. The heated roller heats up the paper, and the toner and the rubber roller press against the paper to make a concrete bond.

To save cost, many low-end laser printers use a slow roller. It allows the heated roller to operate at a lower temperature which essentially cuts down the cost, compromising the speed of printing in the process. However, all high-end models use the high-temperature roller, making almost instantaneous prints.

Step 7 – Resetting the Drum

Once the print is shifting to the paper, the function of the drum is essentially over. Now the printer has to reset the drum for the next print. The drum gets scrapped by a plastic scraper to clean out the residual toner from the drum. The toner dust is stored in a separate waste compartment.

What are the Main Components of a Laser Printer?

The steps of how a laser printer works should be clear by now. Within the steps, we mentioned different components of a laser printer. Now let’s look at some of these components in detail.

We will skip some of the basic components like power units, papers, and other chassis components. Instead, we will outline some of the more complicated parts and how to handle them best in case of any complication.

Corona Wires

The function of the corona wire is to charge the drum positively. The light-emitting from the corona wire wraps the drum with a positive charge which is responsible for attracting the toner particles.

Some advanced laser printers use transfer corona wires. The transfer corona wires essentially use a negative charge on the drum so that the toner particles can easily shift to the paper.

Toner Cartridge

The toner cartridge is essentially what inks are in a traditional printer. The cartridge holds toners that are positively charging carbon particles. These particles can be color or monochrome depending on the print.

Standard cartridges have a page print limit between 2500 to 4000. After that, you will need to replace the toner in the cartridge. Some cartridges are replacing completely with a new unit. Others simply use refill material.

The Drum

The drum is a hollow metal cylinder situated inside the laser scanner. The primary function of the drum is to create a copy of the raster image stored as a bitmap. Once the corona wire charges the drum, it becomes ready to attract the toner to its surface.

The drum cylinder is photosensitive. So it cannot expose to direct sunlight. Most drum cylinders are fitting inside the scanner body. But some drums are fixing on the toner cartridge as well.

The Laser

The laser is another key component. The print itself was named after the laser because of the revolution it brought to printing. The laser emits a series of highly concentrated light rays from the diodes. The light rays get to reflect on several mirrors until it falls on the drum.

The laser creates a precise outline of the bitmap image. The concentrated light momentarily makes the outline charge neutral for the drum to attract toner particles.

Transfer Belt

The transfer belt is usually situated on the underside of the printer. The main function of the transfer belt is to roll the paper on top of the drum. The belt rolls the paper in such a way that it gets pressed against the drum.

The toner particles then shift from the drum to the paper. Sometimes, the transfer belt comes with a positively charged slider under it. This is done to ensure that the toner gets firmly attached to the paper.

Fuser Unit

The Fuser unit is the most important part which determines a perfect print. It is situated opposite the transfer belt across the drum. Once the toner transfers from the drum to the paper, the fuser unit gets into action.

The primary function of the fuser unit is to heat up and roll over the paper so that the toner can melt and stick to the paper.

Waste Toner Bottle

Not all the toner from the drum gets used up. Some of it remains on the drum, which needs to be removed for a fresh print. The scrapped toners are transferred to the toner bottle. In case you’re wondering whether these toners can be used again? The answer is no.

Once the toner waste box becomes full, it needs to be replaced immediately for smooth printing.

Advantages of Using Laser Printer

Laser printers were thought of as the next big jump in the printing system. It drastically reduced the printing time and misprinting. If you need any incentive to choose a laser printer over anything else, have a look at some of them.

Super Fast

The laser printers are super fast compared to many other printers out in the market. It might sound like a long process when we describe it, but everything happens at lightning speed in reality.

The laser printers revolutionized the industrial printing process. Today almost all the offices and printing presses uses later printing. Other technologies simply cannot match the speed and reliability of laser printers.

Cost

Laser printers are not cheap. So why are we mentioning this in advantage? Because laser printers may have a high initial cost, the long-term running cost of laser printers is much less than other types of printers.

For example, an inkjet printer cartridge lasts several hundred prints. A similarly priced toner cartridge for a laser printer can make prints in several thousand. The number of prints alone makes laser printers a cost-effective choice.

Reliability

Laser printers are more reliable compared to other types of printers. It’s not just because of the use of lasers for accuracy. There are several other factors.

Firstly, the toner particles are far more refined compared to inkjet inks. It can print precise and vivid colors onto the paper unlike any other. The second is the premium material used for laser printing. It has been tested for continuous prints with relatively less downtime than other printing forms.

Print Quality

The print quality of laser printers is far superior to any other printers. The quality is achieved through the use of laser and toner. These two components work in unison to create the perfect outline of an image as well as the perfect color drop in the image. The result is an accurate copy of the same.

Laser Printers vs Inkjet Printers: Which is Better?

This is a common question of everyone wanting to buy a printer. Inkjet printers are much cheaper compared to laser printers ones. But some other features give laser printers the edge over inkjet printers.

For a long time, inkjet printers were the market leader globally. Inkjet printers were first invented in 1976. By that time, laser printers were already on the market for 7 years as it was invented in 1969.

But laser printers never really took off. The reason was the printing system of the laser printers. Components like a drum, laser, and toner weren’t that expensive. But laser printing requires to raster the whole image before it starts printing. And that is where the problem began.

Back in the early 70s, even a few megabytes of storage were highly expensive. Since laser printers required a dedicated memory, it became almost impossible to cut down the cost of the printers.

On the other hand, inkjet printers didn’t require any dedicated storage. It could print by rasterizing a few lines of the image at a time. As a result, inkjet printers became hugely popular. But that only lasted until microchips were developed in the mid-80s.

The reduced cost of memory chips meant the cost of laser printers fell drastically. Yes, it wasn’t as low as inkjet printers, but it was within the affordable grasp of offices and schools. People started to use laser printers more. Today almost all modern offices use laser printers.

Laser printers always had a few distinct advantages over inkjet printers. It was fast and reliable. The prints on the laser printers were far superior in quality compared to the inkjet printers. But perhaps the most important advantage was the speed. Laser printers could print 10 times faster than inkjet printers, and the difference has only increased with time.

So, even though the initial cost of setting up a laser printer might be higher compared to an inkjet printer, it still provides better value for money, reliability, and quality compared to inkjet printers.

Conclusion

Laser printers are undoubtedly one of the greatest inventions of the last century. It has radically changed how we see the printing process. Technological advancement over the years has made laser printers even more efficient.

This article mainly outlined the working process of a laser printer. We also focused on various components of a laser printer and the advantages of using one. We hope this article helped you to learn everything about how laser printers work and maybe even inspired you to get one.