4 Printers and Multifunction Devices

Question 1

What are impact printers ?

Answer 1

The most basic type of printer is in the category known as an impact printer. Impact
printers use some form of impact and an inked printer ribbon to make an imprint on the paper. Impact printers also use a paper feed mechanism called a tractor feed that requires special paper.
There are two major types of impact printers: daisy-wheel and dot-matrix.

Question 2

What are Daisy-Wheel Printers ?

Answer 2

One of the oldest printing technologies in use. These impact printers contain a wheel (called the daisy wheel because it looks like a daisy) with raised letters and symbols on each “petal”. When the printer needs to print a character, it sends a signal to the mechanism that contains the wheel. This mechanism is called the print head. The print head rotates the daisy wheel until the required character is in place. An electromechanical hammer then strikes the back of the petal containing the character. The character pushes up against an inked ribbon that ultimately strikes the paper, making the impression of the requested character.

Letter Quality (LQ).

Question 3

What are Dot-Matrix Printers ?

Answer 3

The other type of impact printer to understand is the dot-matrix printer. These printers contain rows of pins that are triggered in patterns that form letters and numbers as the print head moves across the paper

Near Letter Quality (NLQ).

Question 4

What are Inkjet printers ?

Answer 4

These printers spray ink on the page to form the image. Inkjet printers typically use a reservoir of ink, a pump, and a nozzle to accomplish this.

The printer parts can be divided into the following categories:
Print head/ink cartridge
Head carriage, belt, and stepper motor
Paper feed mechanism
Control, interface, and power circuitry

Question 5

Parts of an Injet Printer:

Answer 5

Print head/ink cartridge
Head carriage, belt, and stepper motor
Paper feed mechanism
Control, interface, and power circuitry

Question 6

What is a print buffer ?

Answer 6

A small amount of memory (typically 512 KB to 16 MB) used to store print jobs as they are received from the printing computer. This buffer allows several jobs to be printed at once and helps printing to be completed quickly.

Question 7

Once the printer is ready to print:

Answer 7

The control circuitry activates the paper feed motor. This causes a sheet of paper to be fed into the printer until the paper activates the paper feed sensor, which stops the feed until the print head is in the right position and the
leading edge of the paper is under the print head. If the paper doesn’t reach the paper
feed sensor in a specified amount of time after the stepper motor has been activated, the Out Of Paper light is turned on and a message is sent to the computer.

Question 8

What are page printers ?

Answer 8

Printers that receive their print job instructions one page at a time rather than receiving instructions one line at a time.

Question 9

Two major types of page printers that use the electrophotographic (EP) imaging process:

Answer 9

The first uses a laser to scan the image onto a photosensitive drum

The second uses an array of light-emitting
diodes (LEDs) to create the image on the drum.

Question 10

Most printers that use the EP imaging process contain nine standard assemblies:

Answer 10

the toner cartridge, laser scanner, high voltage power supply, DC power supply, paper transport assembly (including paper-pickup rollers and paper-registration
rollers), transfer corona, fusing assembly, printer controller circuitry, and ozone filter.

Question 11

What is the fuser ?

Answer 11

The fuser is made up of three main parts:

a halogen heating lamp,
a Teflon-coated aluminum-fusing roller
a rubberized pressure roller.

The fuser uses the halogen lamp to
heat the fusing roller to between 329° F (165° C) and 392° F (200° C). As the paper passes between the two rollers, the pressure roller pushes the paper against the fusing roller, which melts the toner into the paper.

Question 12

What is the printer controller assembly ?

Answer 12

A large circuit board that converts signals from the computer into signals for the various assemblies in the laser printer using a process known as rasterizing. When a computer prints to a laser printer, it sends a signal through a cable to the printer
controller assembly. The controller assembly formats the information into a page’s worth of line-by- line commands for the laser scanner. The controller sends commands to each of the components, telling them to wake up and begin the EP imaging process.

Question 13

What is Duplexing Assembly ?

Answer 13

Usually located inside or on the back of the printer, the assembly is responsible for taking the paper, turning it over, and feeding back into the printer so the second side can be printed.

Question 14

Electrophotographic Imaging Process:

Answer 14

The electrophotographic (EP) imaging process is the process by which an EP laser printer forms images on paper.

1. Processing
2. Charging
3. Exposing
4. Developing
5. Transferring
6. Fusing
7. Cleaning

Before any of these steps can begin, however, the controller must sense that the printer is ready to start printing (toner cartridge installed, fuser warmed to temperature, and all covers in place).

Question 15

Step 1: Processing

Answer 15

The processing step consists of two parts: receiving the image and creating the image.

Question 16

Step 2: Charging

Answer 16

The next step in the EP process is the charging step. In this step, a special wire or roller (called a charging corona) within the EP toner cartridge (above the photosensitive drum) gets high voltage from the HVPS. It uses this high voltage to apply a strong, uniform negative charge (around –600VDC) to the surface of the photosensitive drum.

Question 17

Step 3: Exposing

Answer 17

Next is exposing the drum to the image, often referred to as the exposing step. In this step, the laser is turned on and scans the drum from side to side, flashing on and off according to the bits of information that the printer controller sends it as it communicates the individual bits of the image. Wherever the laser beam touches, the photosensitive drum’s charge is
severely reduced from –600VDC to a slight negative charge (around –100VDC). As the
drum rotates, a pattern of exposed areas is formed, representing the image to be printed.

Question 18

Step 4: Developing

Answer 18

Now that the surface of the drum holds an electrical representation of the image being
printed, its discrete electrical charges need to be converted into something that can be transferred to a piece of paper. The EP process step that accomplishes this is the developing step. In this step, toner is transferred to the areas that were exposed in the exposing step.

Question 19

Step 5: Transferring

Answer 19

At this point in the EP process, the developed image is rotating into position. The controller
notifies the registration rollers that the paper should be fed through. The registration rollers move the paper underneath the photosensitive drum, and the process of transferring the image can begin; this is the transferring step. The controller sends a signal to the charging corona wire or roller (depending on which one the printer has) and tells it to turn on. The corona wire/roller then acquires a strong positive charge (+600VDC) and applies that charge to the paper. Thus charged, the paper pulls the toner from the photosensitive drum at the line of contact between the roller and the
paper because the paper and toner have opposite charges. Once the registration rollers move the paper past the corona wire, the static-eliminator strip removes all charge from that line of the paper.

Question 20

Step 6: Fusing

Answer 20

The penultimate step before the printer produces the finished product is called the fusing step. Here the toner image is made permanent. The registration rollers push the paper toward the fuser rollers. Once the fuser grabs the paper, the registration rollers push for only a short time longer. The fuser is now in control of moving the paper.
As the paper passes through the fuser, the 350° F fuser roller melts the polyester resin
of the toner, and the rubberized pressure roller presses it permanently into the paper The paper continues through the fuser and eventually exits the printer.

Question 21

Step 7: Cleaning

Answer 21

In the last part of the laser imaging process, a rubber blade inside the EP cartridge scrapes any toner left on the drum into a used toner receptacle inside the EP cartridge, and a fluorescent lamp discharges any remaining charge on the photosensitive drum.

Question 22

Summary of the EP Imaging Process:

Answer 22

1. The printer receives and processes the image and stores a page in memory.
2. The printer places a uniform –600VDC charge on the photosensitive drum by means of a charging corona.
3. The laser “paints” an image onto the photosensitive drum, discharging the image areas to a much lower voltage (–100VDC).
4. The developing roller in the toner
   cartridge has charged (–600VDC) toner stuck to it. As it rolls the toner toward the photosensitive drum, the toner is attracted to (and sticks to) the areas of the photosensitive drum that the laser has discharged.
5. The image is then transferred from the drum to the paper at its line of contact by means of the transfer corona wire (or corona roller) with a +600VDC charge. The static-eliminator strip removes the high positive charge from the paper, and the paper, now
   holding the image, moves on.
6. The paper then enters the fuser, where a fuser roller and the pressure roller make the
   image permanent. The paper exits the printer.
7. The printer uses a rubber scraper to clean the photosensitive drum. At that point, it is
   ready to print the next page or it returns to the ready state.

Question 23

Thermal Printers

Answer 23

Thermal printers print on special thermal paper, which is a kind of waxy paper that comes on a roll; it’s heat-sensitive paper that turns black when heat passes over it. Thermal printers work by using a print head that is the width of the paper. When it needs to print, a heating element heats certain spots on the print head. The paper below the heated print head turns black in those spots. As the paper moves through the printer, the pattern of blackened spots forms an image on the page of what is being printed. Another type of thermal printer uses a heat-sensitive ribbon instead of heat-sensitive paper. A thermal print head melts wax-based
ink from the ribbon onto the paper. These are called thermal transfer printers or thermal wax-transfer printers.

Question 24

3D Printers

Answer 24

3D printing is really a fabrication process, also called additive manufacturing. In it, a
three-dimensional product is produced by “printing” thin layers of a material and stacking those layers on top of each other.
There are two primary categories of 3D printers intended for the home and small business use.

The first uses rolls of plastic filament to create objects, and the second uses a reservoir of liquid resin and UV light.

Question 25

Parts of a 3D Filament Printer

Answer 25

Frame
Printing plate or print bed
Extruder
Cooling fan
PCB circuit board
Filament

Question 26

The 3D Printing Process

Answer 26

1. Design the object using a computer-aided
   design (CAD) program.
2. Export the file from the CAD software. Doing so will cause the CAD program to “slice” the object into layers, preparing it for printing. The exported file will be an STL file.
3. Send the job to the printer. This is basically just pushing the Print button.
4. The printer will perform a calibration and self-test.
5. Printing begins.

Question 27

What charge is required to transfer print from drum to paper ?

Answer 27

Because the toner on the drum has a slight negative charge (–100VDC), it requires a
positive charge to transfer it to the paper; +600VDC is the voltage used in an EP process
laser printer.

Question 28

Best printers for multipart forms ?

Answer 28

Dot-matrix printers are impact printers and therefore are the best for multipart forms.
Daisy-wheel printers can be used with multipart forms as well.

Question 29

What are Audit Logs ?

Answer 29

Audit logs keep a record of all print activity, as well as print origination location.

Question 30

Two ways for users to authenticate are:

Answer 30

to use user authentication (which requires typing in the username and password) or badging, which requires the MFD to have a badge-scanning feature. Secured print will save print jobs until they are ready to be released. SMB is a file and print-sharing protocol used by MFDs to send scanned documents to a shared network folder. There are no printer authentication logs, but audit logs may be used to see who has
used the MFD.

Question 31

What is The high-voltage power supply (HVPS) ?

Answer 31

The part of the laser printer that supplies the
voltages for charging and transferring corona assemblies.

Question 32

Which type of scanner is best suited to scan multiple pages quickly?

Answer 32

An Auto Document Feeder (ADF) scanner will scan multiple pages quickly through the use of a feeder.

Question 33

What two substances can a 3-D printer use?

Answer 33

Depending on the type of 3-D printer, it can use either filament or resin to print.