Laser Printers – CompTIA A+ 220-1101 – 3.7

A laser printer provides high resolution output using charged toner particles. In this video, you’ll learn how these printer components work together to complete the laser printing process.

One of the most popular printer types you’ll find at home and in the office is a laser printer. A laser printer combines high voltages with powdered toner, heat, and pressure to create output on a printed page. This combines high quality output with very fast printing speeds, which is perfect for an office environment. So this is a relatively complex process with a lot of moving parts and a lot of things that could go wrong. That means as a technician, you’ll need to be very familiar with the laser printing process.

The image that ultimately is printed on this sheet of paper starts with the imaging drum. This is the colorful photosensitive drum that’s inside of a laser printer. The laser writes or paints exactly what it would like to have appear on the piece of paper. And this drum is responsible for taking that image, picking up some toner, transferring that toner to the paper where eventually it will be fused and presented as the final output. This imaging drum can be its own part inside of the printer.

And if you need to replace the drum, you simply replace that single component. But sometimes this is integrated into your toner cartridge. And when you replace your toner cartridge, you’re not only replacing the toner but you’re also replacing the imaging drum. In either case, this imaging drum is usually something that’s easy to access. This allows you to examine, clean, and even replace the drum that might be in your printer.

Once that toner is transferred from the imaging drum to the paper, it still needs to be permanently affixed to the page. We accomplished that with a fuser assembly. The fuser assembly uses heat and pressure to effectively melt the toner so that it is permanently part of the printed page.

Here’s a close up of the entire fuser assembly inside of this laser printer. It’s that dark brown drum that’s inside of this piece that allows for the heat and the pressure to be used with that toner. Here’s another view of the fuser assembly that’s inside of my laser printer. This one has little hooks that you can move to release the entire fuser assembly and easily replace it if you have any problems.

If you’re working with a color laser printer, then you probably have multiple colors of toner that are used during the printing process. And the way that you take toner from those individual colors and combine them all into a single page is through the use of a transfer belt and roller.

Normally, the colors inside of your printer will be cyan, yellow, magenta, and a black color. These are usually installed into the laser printer as four separate cartridges. This not only allows you to remove and replace cartridges as you use them but you’re able to pull exactly the right amount of color from each individual cartridge. The color from each cartridge is transferred to the belt. And from the belt, it’s moved to a transfer roller.

Here’s a better view of this belt. This printer does not have any toner cartridge inside of it. But you can see where the yellow, the cyan, and the magenta cartridges would be installed. And the toner from those cartridges would be transferred onto this belt.

Before the paper makes its way through the printer, it starts in a printer tray. And the way that we get a single page from that printer tray into the printing process is through the use of a pickup roller. This pickup roller is responsible for picking up just one single page and sending that single page through the printing process.

If you’re trying to print and no pages are being picked up or multiple pages are being sent through the printer at the same time, your problem is probably with this pickup roller. If you perform maintenance on a laser printer, you’ll find that the pick up roller is something that you’ll either clean or replace during that maintenance process.

Here’s a view of the pickup rollers in my laser printer. These are relatively new. And they’re in very good shape. You can see the individual lines that are in this pickup roller. As your printer is used more and more, these begin to wear down and become smoother so you’ll need to replace those with a new set of rollers to bring your printer back up to normal operation.

The pickup rollers work in conjunction with a separation pad to be able to pull just the top page off of that paper tray. The separation pad is also helpful to keep multiple pages from being sent through the printer all at one time. These are relatively inexpensive parts. And if you’re performing maintenance on a laser printer, this is a very common part to replace.

Here’s a close-up of the separation pad that’s used in conjunction with the pickup roller to be able to pull that top page of paper and send it through the laser printing process.

We often think of printers as only printing on one side of the page. But there are many printers that can perform duplexing, which is printing on both sides of the page when it finally presents you with the output. This is something that happens inside of the printer itself. And it doesn’t require any human intervention to be able to print on both sides of the page. When a printer is configured for duplexing, it usually prints on one side of the page, goes through an extra step to be able to turn the page over, and then prints on the other side of the page.

There has to be some type of hardware inside of the printer or connected to the printer tray that gives it the capability to perform this duplex printing. This could be something that is built into the printer and is shipped with the printer automatically or it may be an optional add-on that you can either purchase with the printer or add to the printer later.

This is the duplexing assembly that’s on the paper tray that I use in my laser printer. And it has a method of flipping the paper over using this duplex assembly. I can either print on one side of the paper or I can check a box during the printing process that enables duplex mode. And it will automatically flip the paper over and print on both sides of the paper.

The entire printing process on a laser printer can be separated into seven different steps. This is a cross-reference of a laser printer as if we cut it right down the middle. And you can see there are a lot of different components that we’ll be working with.

Let’s start with the first step, which is the processing step. At this point, nothing is moving inside of your printer. We’re simply sending the data to the printer itself. The printer does not begin printing until the entire page is rendered in memory. And at that point, the processing phase transfers over to the charging phase.

During the charging phase, a corona wire or charge roller is used to provide a negative charge to the photosensitive drum. This negative charge effectively clears the drum and prepares it for the image that will be provided by the laser. In the third phase or the exposing phase, the laser begins writing the image to the photosensitive drum. Since the charging phase created a negative charge, the laser is creating a positive charge everywhere it touches that photosensitive drum.

This leads to the developing phase where you have toner that’s in a toner cartridge that is also negatively charged, the same charge as the blank slate that was created during the charging phase. That means that the negatively charged toner will stick to the positively charged sections that were exposed by the laser, effectively causing the toner to stick to the photosensitive drum. That means that we can begin phase five or the transferring of that toner from the photosensitive drum to the paper that is going through the printer itself. When that paper comes out of the other side of the transferring process, the toner that was on the photosensitive drum is now part of the paper.

But the toner has not been permanently affixed to the paper yet. To be able to accomplish that, we need to apply heat and pressure in phase six, or the fusing phase. This is where the paper passes through the fuser, which is then going to melt the toner. And now it will be permanently attached to the paper. That’s why the pages that have been freshly printed on a laser printer are slightly warm because they’ve been through this fusing process where all of that toner was melted to the page.

Although most of the toner that was on the photosensitive drum is transferred into phase five, there’s still a little bit of toner that still may be left behind on the photosensitive drum. To make sure that excess toner doesn’t somehow make its way into another rotation of the photosensitive drum, we have step seven, which is the cleaning phase, which removes any excess toner from that drum.

At this point, the process cycles through again and this photosensitive drum may rotate a number of times just to print a single page on the printer. So you might have step one for processing that spends quite a bit of time rendering that page in memory but steps two through seven may occur multiple times to be able to print that single page. Once that page is complete, the entire process resets. And the next page that needs to print starts with phase one and begins the process all over again.

These seven steps are useful to know, especially if you need to troubleshoot any part of that process. The first step is the processing step where we are rendering the entire printed page in the memory of the laser printer. Step two is the charging step where we’re writing a negative charge to the photosensitive drum.

That leads us to step three or the exposing stage where we’re using a laser to paint the image onto that photosensitive drum. That leads us to step four or the developing step where we take toner from our toner cartridge and have it stick to all of those areas that was hit by the laser in step three when it was exposed.

In step five or the transferring phase, we can now take all of the toner that’s on the drum and transfer that toner to the printed page. To be able to have it stick permanently, we go to step six or the fusing step where we apply heat and pressure to melt that toner to the page. And lastly, we need to clean any excess toner that may still be on the photosensitive drum so that we can then begin this process again.