CompTIA+ Printers

Print Technologies

A printer outputs data that is seen on the computer screen on to a paper. Most printers are used through a parallel port, but some newer ones use USB connections. The most crucial printer measurement is its dots per inch rating. Printers are best chosen by actually seeing the quality of the printer output. There are many types of print technologies like Daisy wheel, Dot matrix, Laser, Inkjet etc. Printers are normally categorized into impact and non-impact types. You will learn more about this as you go further in this lesson.Printers can be divided into two categories:

• ImpactThe impact printers incorporate a built-in mechanism to print images on paper using a series of pins or hammers, which strike on an inked ribbon to create the image. For Example: Dot Matrix, Daisy Wheel etc.
• Non-impactThe non-impact printers include those printers that do not have any kind of contact with the paper while printing either text or image. For Example: Inkjet, Laser, Bubble Jet, etcThese printers use different technology to print an image. For example, a laser printer uses heat to attach microscopic particles of dry toner to specific parts of the page. An inkjet printer has tiny nozzles through which it sprays droplets of ink onto the page.

Solid Ink Printer

This type of printer contains sticks of wax-like ink that are melted and applied to the paper. The ink then hardens in place. This technology has the capability of creating brilliant, vibrant prints on a wide range of media, including cardstock, envelopes, and transparencies, as well as recycled paper and custom page sizes.Inside The Solid Ink PrinterPrint Head: The solid ink is applied through a precise stainless steel print head with tiny holes smaller than a human hair. It uses 1,236 nozzles jetting more than 30 million drops per second. The print head primarily is used in applying ink to the print drum.

1. Print Drum: The ink is jetted from the print head to a heated drum where it remains in a malleable state that ensures precise transfer to the paper. This reduces the amount of ink that can wick into the paper fibers and controls dot spread.
2. Phaser Controller: The Phaser controller is based on a 500 MHz processor and high-speed 64 bit bus. It is like the brain of the printer that converts data from the computer to information required to print the image on paper.
3. A cabinet and a tray will complete the assembly and make a complete Solid Ink Printer.

A Solid Ink Printer is fast, has lower cost per page and the color sticks are easier to load owing to its unique shape-coded and numbered ink stick which ensure the right color goes only in the right place.

Dot Matrix Printer

Dot Matrix is the oldest printing technology and is still widely used, owing to its low cost per page. These printers produce an image by using a mechanism called a Print Head which contains a row of “pins” (short sturdy stalks of hard wire) that are triggered in patterns to form letters and numbers as the Print Head moves to and fro on the paper.Printing Procedure

• The pins in the Print Head are coiled by wire and are held in the rest position by a small magnet and a spring.
• The Printer Controller activates a particular pin by sending a signal to the Print Head.
• The Print Head in turn stimulates the wires around the appropriate print wire turning the print wire into an electromagnet.
• This electromagnet fires the print pin, thrusting it into the ink ribbon and leaving a dot on the paper.

It is this arrangement of dots in various shapes that we see on the page

Dot Matrix Printer (Cont...)SpeedThe speed of a Dot Matrix Printer can be measured in characters per second (CPS no change). The dot matrix printer's can be differentiated on the basis of their speed which usually varies between fifty to about five hundred characters per second (CPS).QualityThe image quality of a dot matrix printer depends on the spacing of the pins in the Print Head. For example, early dot-matrix printers used only 9 pins. It is one single picture and not multiple pictures. This spacing resulted in an output that looked “fuzzy” or have “draft quality” because the dots were spaced at a distance from each other. For better quality more pins had to be put closer together on the print head. Further, these printers are noisy when compared to the others.However, there is one redeeming point. Dot matrix printers have the ability to print carbon copies of the original document. So, when it comes to printing multiple copies of the same document simultaneously then dot matrix printers' scores higher than any other printer which are using technology other than that used by these printers.

Ink DispersionInks are a complex mixture of pigments, varnishes, waxes, solvents and other additives. During manufacturing, these ingredients are blended carefully and milled crushedto ensure a smooth, homogenous product free of lumps or large particles.Ink Dispersion, like the name suggests, disperses ink through tiny nozzles onto the paper. This is the primary way of printing adopted by a majority of non-impact printers. Examples of printer technologies that employ ink dispersion are Ink Jet and Bubble Jet printers.

Ink Dispersion (Cont...)

INKJET PRINTERAn Inkjet printer is a complicated medley of a number of components. These components fall under two categories -

• Print Assembly
• Paper Feed Assembly.

Print AssemblyPrint head:The print head has a series of nozzles that are used to spray dots of ink on paper.Ink Cartridge:This acts as a store or a repository for ink.Stepper Motor:The Stepper Motor transports the print head assembly (Print head and ink cartridge) from one corner of the page to the other.Belt:Keeps the print head assembly and stepper motor securely fastened to one another.Stabilizer Bar:Makes sure that the print process goes through with precision, accuracy and control.

Ink Dispersion (Cont...)

INKJET PRINTER (Cont�)Paper Feed AssemblyPaper tray / Feeder:Like the name suggests, a Paper tray is where the papers can be loaded while a Feeder pulls open at an angle and can be located at the back of a printer. The main advantage that a paper tray has over a Feeder is that a feeder cannot hold many pages.Roller:Roller aids in smooth transfer of pages from the paper tray into the printer.Paper Feeder
Stepper Motor:
This supplies power to the roller and ensures that the papers are fed into the printer at a uniform speed so as to enable the printer to print a seamless image.A Transducer is located at the back of the reservoir of each nozzle.The transducer receives a tiny electric charge that causes it to expand. When the transducer expands inward, it forces a tiny amount of ink out of the nozzle. When it recedes out, it pulls some more ink into the reservoir to replace the ink sprayed out.

Ink Dispersion (Cont...)

BUBBLE JETA bubble jet printer is designed in the similar manner as an ink jet printer It contains an ink cartridge and a print head. The ink cartridge is divided into several small chambers and each chamber has a metal plate and tube. Ink is supplied from the top of this tube. At the bottom of each chamber is a small pinhole which is used to spray ink on the paper.How Bubble jet works:

• For a chamber to spray ink, it is stimulated by an electric signal sent to its heating element.
• Heat vaporizes the ink from the element and causes it to expand, thus pushing the ink out of the pinhole in the form of a bubble.
• As the vapor expands, the bubble eventually gets large enough to break off into a droplet.
• The rest of the ink is pulled back into the chamber by the surface tension of the ink.
• When another drop needs to be sprayed, the entire process as stated above is repeated.

Upon completion of the printing job, the printhead docks itself in the maintenance station. A small suction pump and an ink absorbing pad pull the ink through the nozzles using vacuum suction and absorb the expelled ink. This keeps the printer in good condition all the time.

Ink Dispersion (Cont...)LASER PRINTERThe main principle behind the working of a laser printer is Static Electricity. It works on the principle that atoms with opposite charges attract each other.The Laser Printer makes use of this energy as temporary glue. The most important part of the laser printer without which it cannot function is something known as the photoreceptor. The photoreceptor basically consists of a cylinder or a drum that revolves. Using highly photoconductive material that is dispersed by light photons creates the drum or the cylinder.A laser printer consists of:

• Toner
• Corona wire
• Quartz lamp
• Laser unit
• Fuser
• Developer roller
• Photoreceptor drum assembly

Each of these parts has a very important role to play in the printing process.

Ink Dispersion (Cont...)LASER PRINTER (Cont�)The Process:

• A computer sends printed matter to the printer as vector information.
• The vector information is converted into dots.
• A Laser Unit, located at the back of the printer, shoots the laser beam while printing. The laser fires when there is a dot and remains off when there is blank space.The vector information is converted into dots.
• The onboard electronics control the movement the laser and the beam is passed through the lens filter to the Photoreceptor drum.
• A complete positive charge is given to the drum, by the corona wire, when it starts rotating. The corona wire is a wire that carries electrical current and which runs through it. When the drum rotates, the miniscule laser beam hits across the surface in order to discharge certain places.
• The laser moves in a horizontal pattern creating the dot patterns on the photoreceptor drum. Once the entire line of dots is completed the drum rotates to receive the next line.

Ink Dispersion (Cont...)LASER PRINTER (Cont�)The Process:

• When the laser hits the positively charged drum, a negative charge is created.
• The toner is to the Laser Printer what ink is to an Inkjet. Basically toner is an electrically charged powder that has two main components; plastic and pigments. The Pigment is responsible for imparting colour onto the page. The pigment is blended with plastic particles to avoid smudging and make the of an image look sharp.
• When the laser hits the drum, the positively charged toner attaches itself to the negatively charged regions of the drum.
• Now the paper is passed over the drum. The paper is negatively charged by the transfer corona wires.
• This charge is greater than the negative charge on the drum, and thus attracts positively charged toner pigment.
• The pigment doesn't stick to the paper here, the paper is neutralized and passed through the fuser assembly.
• The Fuser Assembly is nothing but Teflon quoted metal roller, heated by a quartz lamp.
• The heat fuses the pigment to the paper.
• After this, the pattern is cleaned off the drum using the charged corona wire and the printer is ready for the next page.
• You should remember the process as:
  Clean-Charge-Write-Develop-Transfer-Fuse
  An mnemonic for remembering this is:
  California-Cows-Won't-Dance-The-Fandango

Printer InterfacesA printer interface enables a printer to communicate with a computer. It defines the time interval and the amount of data to be transferred between the printing device and the computer.A printer's interface is a combination of both software and hardware. A printer, generally, has one interface but sometimes a printer can support more than one interface in order to be more flexible and compatible with all kinds of computers.Several components make up an interface, including its communication type and its interface software. Each aspect must be matched on both the printer and the computer. For example, if a printer has a parallel port then the appropriate parallel cable coupled with the relevant software, based on the platform, has to be used.The following are the various 'communication types' or the hardware part of an interface:

• Serial
• Parallel
• USB
• Network

Serial

In a serial interface, the data is sent serially i.e. one bit after another. In other words, the bits form a queue and enter the printer one by one.Serial ports are also known as Communication (COM) ports and are bi-directional. Bi-directional ports allow transfer of data in both directions i.e. receive and transfer data. Most standard serial ports have a maximum transfer rate of around 115 kbps (kilo bits per second). In other words, at any point in time, a serial port cannot receive or transfer more than 115kbps of data, although, newer ports support greater speeds.Serial ports come in either 9 pins or 25 pins. Each pin has a specific purpose. For instance, pin numbers 2 and 3 are used to transfer and receive data respectively. Pin 4 is used to tell the computer that the printer is in ready state or is ready for a new print job.

ParallelParallel ports support higher data bandwidths than serial ports and they are much faster. When a printer uses parallel communication, it is receiving data eight bits at a time over eight separate wires (one for each bit). Parallel communication is the most popular way of communicating from computer to printer, mainly because it's faster than serial.A male DB-25 connector and a male 36-pin Centronics connector at either ends of a parallel cable enable communication between the computer and printer. The DB-25 connector connects to the computer and the Centronics goes with the printer. Most of the cables are shorter than 10 feet long.

USBUSB or Universal Serial Bus is the most popular interface for a printer or for that matter, any computer peripheral. Its popularity is largely due to its higher data transfer speeds and its ability to recognize new devices automatically.The Universal Serial Bus provides a single, standardized, easy-to-use way to connect up to 127 devices to a computer. USB devices are hot-swappable meaning devices can be plugged into the bus and unplugged any time. Further, many USB devices can be put to sleep by the host computer when the computer enters a power-saving mode.The newer USB devices support data speeds up to 480mbps (megabits per second).