CompTIA A+ Rapid Review: Printers

The Printers domain covers approximately 11 percent of the A+ 220-801 exam. A PC technician will be expected to perform regular maintenance on printers and needs to be aware of common printers used in different organizations and how to install and maintain them. The corporate world uses laser printers extensively, so it’s extremely important for PC technicians to have an in-depth understanding of laser printers. Because of this, you can expect the exam to have more questions related to laser printers than other types. However, the objectives also mention inkjet, thermal, and impact printers, so you’ll need to understand the differences between these printers.

This chapter covers the following objectives:

• Objective 4.1: Explain the differences between the various printer types and summarize the associated imaging process

• Objective 4.2: Given a scenario, install, and configure printers

• Objective 4.3: Given a scenario, perform printer maintenance

Objective 4.1: Explain the differences between the various printer types and summarize the associated imaging process

For this objective, you need to understand each of the four basic printer types (laser, inkjet, thermal, and impact) and their differences. Laser printers have the most complex imaging process, but if you understand this process, you’ll be better prepared to troubleshoot common laser printer problems. Inkjet printers are used within homes and small offices and provide superb printouts. They are often used in place of laser printers by home users and some small businesses. Thermal printers and impact printers are less common than laser printers and inkjet printers, but they do have specific abilities that make them useful in certain situations.

Exam need to know...

• Laser

  For example What is the purpose of a fuser assembly? What occurs during the cleaning process?

• Inkjet

  For example: When should an inkjet printer be calibrated? What is needed to print two-sided copies with an inkjet printer?

• Thermal

  For example: Where are thermal printers used? What are the components in a thermal printer?

• Impact

  For example: What is the primary usage of impact printers? How is carbon paper used with an impact printer?

Laser

Laser printers provide high-quality output at a relatively low cost per printed page. They are commonly used in corporate environments, and their reasonable cost makes them economical for many small businesses too.

True or false? Laser printers can print two-sided output as long as they have a transfer belt.

Answer: False. A duplexing assembly (not a transfer belt) is required to print two-sided output on a laser printer. Many inkjet printers also use duplexing assemblies to print two-sided paper.

A transfer belt is used on some high-end color laser printers. Colors are applied to the transfer belt and then to the paper. This step is repeated for different colors.

True or false? The primary purpose of the fuser assembly is to melt toner onto a piece of paper.

Answer: True. The fuser assembly generates heat, which melts the plastic particles in the toner and fuses them onto the paper.

Other components of a laser printer include the following:

• A raster image processor (RIP) accepts data to be printed and converts it to a raster image. The raster image is a group of dots organized as characters, words, and graphic images.

• An imaging drum is a round rotating cylinder covered with a photosensitive surface. Images are written onto the drum by shining a focused light from the laser onto the drum. Laser printers have a drum.

• A primary charge roller (or in some cases a corona wire) applies between -500 and -1,000 VDC to the imaging drum. This charge neutralizes the photosensitive surface of the drum and prepares it to receive an image.

• A highly focused laser shines light onto the imaging drum through one or more mirrors. The laser writes the raster image created by the RIP onto the drum by removing the negative charge wherever the light from the laser hits it.

• The toner is charged with a high negative charge and applied to the drum. Because of the electrical charge, the toner is only attracted to the drum where the laser wrote the image.

• Pickup rollers applied to the top of the paper are used to pick up paper from the paper tray and begin feeding it through the printer.

• Separator pads spin in the opposite direction from under the paper and push extra paper back. These pads help prevent more than one piece of paper from being sent through the printer at a time.

• The transfer roller charges the paper with a high voltage. As the drum turns and the paper is moved through the printer, the charged paper attracts the toner away from the drum. The result is that the toner is transferred from the drum onto the paper.

• A static eliminator or electrostatic discharger removes the charge from the paper as it passes the drum. This helps prevent the paper from sticking to the drum.

• A fuser assembly melts the toner onto the paper with a combination of friction and heat.

• An erase lamp shines light onto the drum to neutralize the voltage on the entire drum. This removes the previous image from the drum.

• Similar to a windshield wiper, a scraper removes residual or excess toner from the drum.

True or false? The order of the imaging process in a laser printer is processing, charging, exposing, developing, transferring, and fusing.

Answer: True. This is the proper order of the laser printer imaging process.

Figure 4-1 shows the seven steps of the laser imaging process. Each of the steps occurs as the imaging drum turns.

Figure 4-1 Laser imaging process.

The first two steps in the laser imaging process are processing and charging, which consist of the following operations:

• Processing. The image is converted to a raster image by the RIP and stored in the printer’s memory.

• Charging. The imaging drum is charged with a high negative voltage (between -500 and -1,000 VDC ) with a primary charge roller. In older laser printers, a corona wire applied the high negative voltage instead of a primary charge roller.

Figure 4-2 shows these two stages.

Figure 4-2 Processing and charging stage in the laser imaging process.

True or false? The laser writes the image onto the imaging drum during the developing stage.

Answer: False. The image is written onto the drum during the exposing stage, not the developing stage.

The next two steps in the laser imaging process are exposing and developing, consisting of the following operations:

• Exposing. During this stage, the laser writes the raster image onto the drum as shown in Figure 4-3.

• Developing. The toner is applied to the drum during the developing stage, as shown in Figure 4-4.

Figure 4-3 The exposing stage in the laser imaging process.

Figure 4-4 The exposing stage in the laser imaging process.

True or false? The toner is applied to the paper in the transferring stage of the laser imaging process.

Answer: True. During the transferring stage, toner is transferred from the imaging drum to the paper.

After the toner is transferred to the paper, it is melted onto the paper during the fusing stage. During the transferring stage, pickup rollers and separator pads pick up a single sheet of paper and start moving it through the printer. A transfer roller (or a transfer corona) applies a charge to the paper as it passes. The charged paper attracts the toner and the toner is transferred from the imaging drum to the paper. At this point, the only thing holding the toner in place on the page is electrostatic charge. As the paper passes the drum, an electrostatic discharger removes the charge from the paper to prevent it from sticking to the drum, as shown in Figure 4-5. At this point, only gravity and friction hold the toner in place on the page.

Figure 4-5 The transferring stage in the laser imaging process.

True or false? If toner falls off the printed pages, the most likely cause is a faulty fuser assembly.

Answer: True. The fuser assembly melts the toner, so if the toner is not sticking to the paper, the most likely cause is a faulty fuser assembly.

Figure 4-6 shows the fusing stage of the laser imaging process. The fusing assembly provides both friction and heat to the paper as it passes through, melting the toner onto the paper.

Figure 4-6 The fusing stage in the laser imaging process.

True or false? If print jobs show a ghost image of a previous printed page, the erase lamp or scraper might be the problem.

Answer: True. The erase lamp and scraper work together to remove remnants of the previous print job during the cleaning phase of the imaging process.

Figure 4-7 shows the cleaning process. A plastic or hard rubber scraper removes excess or residual toner. If the toner is not being removed, the scraper might need to be replaced. The lamp shines over the entire photosensitive surface of the drum, exposing it all and neutralizing the electrical charge. In contrast, the laser has a focused beam to expose only parts of the drum.

Figure 4-7 The cleaning stage in the laser imaging process.

Inkjet

Inkjet printers are popular with home users and small businesses. They provide excellent quality printouts and are relatively inexpensive to purchase. The biggest drawback is that the cost of the ink is exceptionally high, resulting in a high cost per printed page.

True or false? Inkjets use small pins to hammer the ink onto the page.

Answer: False. Impact printers (not inkjet printers) use small pins to hammer ink onto a page from a ribbon.

Inkjet printers have one or more print heads that move from side to side on a carriage and belt assembly. In some printers, each ink cartridge includes a disposable print head. In other printers, the ink is separate and is fed to a fixed print head when needed. Disposable print heads will last as long as the ink but aren’t built to last for a long time. In contrast, fixed print heads are meant to last much longer.

Paper is fed though an inkjet printer with a roller and feeder assembly similar to how paper is fed through a laser printer. A pickup roller works with one or more separator pads to ensure that only one piece of paper is picked up at a time. Many inkjet printers include a duplexing assembly used to print on both sides. When used, the rollers feed the paper through the printer to print on one side. The paper is then routed to the duplexing assembly where it is turned over and then rerouted through the printer to print on the back.

Inkjet printers use one of the following two methods to print:

• Thermal printing. This is also known as bubble jet printing. Small heaters within the print head heat the ink, creating small ink bubbles. These bubbles are then ejected onto the paper.

• Piezoelectric printing. In this method, a crystal oscillator vibrates, causing the ink to break up into small droplets. These small droplets are given an electrical charge as they leave the print head, causing them to either stick to the paper or fall off. Ink that falls off is recaptured.

True or false? Printouts with colors that aren’t aligned on an inkjet printer indicate that the printer should be calibrated.

Answer: True. Inkjet printers commonly have calibration programs that can be used to align the print heads when colors are misaligned. A calibration program performs electronic adjustments to improve the print quality.

Inkjet printers include one or more test pages that you can print to check the quality of the printouts. These usually include specific patterns, with notes on what to do if the printout isn’t perfect.

Thermal

Thermal printers are frequently used to create receipts at point of sale (POS) locations. After the sale is completed, the printer creates the receipt.

True or false? The print head in a thermal printer includes a heating element used to heat the paper.

Answer: True. Thermal printers use a special type of paper that responds to heat. The print head heats the paper to create the printout.

The paper on thermal printers is typically wound around a spindle. The spindle is attached to a sprocket type of feed assembly, and as the printer prints, the sprocket turns, feeding the paper through the printer.

Impact

Impact printers include pins within the print head. These pins strike an ink ribbon, and the ink ribbon leaves a dot on the paper.

True or false? Impact printers are also known as dot matrix printers.

Answer: True. Impact printers use pins to print dots within a matrix, and by printing different dots, they can print characters and images.

Figure 4-8 shows how a 9-pin print head can be used to print the capital B by printing specific dots in a dot matrix. Near letter-quality impact printers have print heads with 24 or 48 pins. The extra pins fill in the holes between the dots, providing a higher-quality printout.

Figure 4-8 A dot matrix from an impact printer.

True or false? Businesses that need multiple copies of printouts commonly use impact printers.

Answer: True. Impact printers are ideal for printing multipart forms using carbon or carbonless paper to create multiple copies at a time.

Many businesses use multipart forms that have carbon paper between each copy. When the print head strikes the top paper, the force is felt through each page and presses the carbon paper onto the other copies.

True or false? It’s common to use a tractor feed mechanism to feed paper through an impact printer.

Answer: True. Impact printers often use continuous feed paper with holes along the sides. The tractor feed mechanism has sprockets that fit into these holes to pull the paper through.

Impact paper used in impact printers can be continuous feed paper or individual sheets. When continuous feed paper is used, the paper is fed through the printer with the tractor feed mechanism. Single sheets of impact paper are fed through with friction from the platen, similar to how paper was fed through old typewriters. For best print quality, continuous feed paper and a tractor feed mechanism are used to ensure the paper is fed through at a consistent rate. Continuous feed paper is available with carbon paper to print multipart forms, or multiple copies at the same time.

Can you answer these questions?

You can find the answers to these questions at the end of this chapter.

1. What voltages are inside a laser printer that aren’t in other printers?

2. Name two safety concerns related to laser printers.

3. What are two common types of inkjet printing?

4. Where are thermal printers used?

5. What can be easily printed by impact printers but not by laser printers?