1. Group Members: Osama Bin Imran (Leader) Fouzan Akhtar Faris Faisal Sameer Hussain Haris Abassi INKJET PRINTERS LASER PRINTERS DOT-MATRIX PRINTERS

2. INKJET PRINTERS: 1) Continuous(C.I.J) 2)Drop On Demand(DOD) 1. Thermal Inkjet 2.Peizoeltric Inkjet 3)Advantages & Disadvantages3)Advantages & Disadvantages 4)Uses and Features BACKBACK NEXTNEXT

3. Inkjet printing is a type of computer thinking that recreates a digital image by propelling droplets of ink onto paper, plastic, or other substrates. There are two main technologies in use in contemporary inkjet printers: 2.Continuous (CIJ):-  In CIJ technology, a high-pressure pump directs liquid ink from a reservoir through a gun body and a microscopic nozzle, creating a continuous stream of ink droplets.  A piezoelectric crystal creates an acoustic wave as it vibrates within the gun body and causes the stream of liquid to break into droplets at regular intervals: 64,000 to 165,000 droplets per second.  The ink droplets are subjected to an electrostatic field created by a charging electrode as they form; the field varies according to the degree of drop deflection desired.  This results in a controlled, variable electrostatic charge on each droplet. Charged droplets are separated by one or more uncharged "guard droplets" to minimize electrostatic repulsion between neighbouring droplets.  The charged droplets pass through another electrostatic field and are directed (deflected) by electrostatic deflection plates to print on the receptor material (substrate), or allowed to continue on undeflected to a collection gutter for re-use. The more highly charged droplets are deflected to a greater degree. Only a small fraction of the droplets is used to print, the majority being recycled.

4. Drop on Demand(DOD): BACK NEXTBACKNEXT  Types:- i) Thermal Dod:  In the thermal inkjet process, the print cartridges consist of a series of tiny chambers, each containing a heater.  To eject a droplet from each chamber, a pulse of current is passed through the heating element causing a rapid vaporization of the ink in the chamber and forming a bubble, which causes a large pressure increase, propelling a droplet of ink onto the paper.  The ink's surface tension, condensation, and resultant contraction of the vapour bubble, pulls a further charge of ink into the chamber through a narrow channel attached to an ink reservoir.  The inks must have a volatile component to form the vapour bubble; otherwise droplet ejection cannot occur.  The inks involved are usually water-based and use either pigments or dyes as the colorant. ii) Peizoelectric Dod:-  A peizoelectric material in an ink-filled chamber behind each nozzle instead of a heating element is used.  When a voltage is applied, the peizoelectric material changes shape, generating a pressure pulse in the fluid, which forces a droplet of ink from the nozzle.

5. Peizoelectric inkjets are not effected by Kogation(build up of ink residue)where as Thermal and C.I.J printers are. C.I.J printers’ ink lasts longer due to its ability to recycle the majority of ink used. C.I.J and Thermal inkjets are less expensive then Peizoelectric printers as Peizoelectric heads are more expensive to manufacture. Peizoelectric inkjets have a wider variety of ink than Thermal inkjets as there is no requirement for a volatile compound like in Thermal inkjets. BACKBACK NEXTNEXT

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7. LASER PRINTER: 1)Process 2)Features & Uses 3)Advantages BACK NEXT

8. Laser printing is an electrostatic digital process. It produces high-quality text and graphics (and moderate-quality photographs) by repeatedly passing a laser beam back and forth over a negatively charged cylindrical drum to define a differentially-charged image. The drum then selectively collects electrically charged powdered ink, and transfers the image to paper, which is then heated in order to permanently fuse the text and/or imagery. Laser printers employ a xerographic printing process. Laser printing differs from analogue photocopiers in that the image is produced by the direct scanning of the medium across the printer's photoreceptor. Process:  A laser beam projects an image of the page to be printed onto an electrically- charged, selenium-coated, rotating, cylindrical drum(or, more commonly in subsequent versions, organic photoconductors).  Photoconductivity allows the charged electrons to fall away from the areas exposed to light. Powdered ink (toner) particles are then electrostatically attracted to the charged areas of the drum that have not been laser-beamed.  The drum then transfers the image onto paper (which is passed through the machine) by direct contact. Finally the paper is passed onto a finisher, which uses intense heat to instantly fuse the toner/image onto the paper.  There are typically seven steps involved in the process: 1)Rastor Image processing, 2)Charging, 3)Exposing, 4)Developing, 5)Transferring, 6)Fusing, 7)Cleaning BACKBACK NEXTNEXT

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11. DOT-MATRIX PRINTER: 1)PROCESS 2)ADVANTAGES &DISADVANTAGES 3)USES BACK BACK NEXTNEXT

12.  Type of computer printer that uses tiny hammers in its print head to strike pins over an inked ribbon to form characters or images on paper, and is used mainly for multipart forms.  The term "dot matrix" is normally used for a particular kind of impact printers - printers that use mechanical pins to squeeze ink out of a ribbon and onto the paper. Inkjet and laser printers also use a matrix of dots, but individual pixels are smaller and less evident in the printed page. Dot matrix printing or impact matrix printing is a type of computer printing which uses a print head that moves back-and-forth, or in an up-and-down motion, on the page and prints by impact, striking an ink-soaked cloth ribbon against the paper, much like the print mechanism on a typewriter. Letters are drawn out of a dot matrix, and thus, varied fonts and arbitrary graphics can be produced. Process:  The paper is positioned at a blank line on the paper. The input logic takes in a stream of characters and assembles the line to be printed in memory.  When a line is available the print-head sets off from the left margin. As the head travels across the paper its position is tracked. For ten characters per inch the tracking might be in 1/100ths of an inch, but for closer character spacing it will be more accurate.  Each print-head position corresponds to a both a character to be printed and a column of dot- positions within that character. Columns of pixels are made by firing the pins in each position.  The shapes of the characters are usually stored at manufacture in a ROM in the printer.). As the print- head is moved to successive locations the character and column position required are looked up and drive circuits push the pins accordingly.  The high speed action required from the pins on a dot matrix printer demands quite a lot of electrical power.The total power is not that great because the duty cycle on each circuit will probably be under 5%.  Printheads can get hot after a couple of minutes operation. BACK NEXT BACK NEXT

13. ADVANTAGES The Dot matrix printers are cheap and easily available in the market. They can make carbon copies of the print out unlike non-impact printers. The printing costs are the lowest as compared to other printers. The printout fades gradually rather than coming to a halt suddenly. You therefore get plenty of time to change the ribbon before crisis emerges. They use paper continuously unlike other printers that require frequent change of paper. The maintenance cost is low as compared to other printers. They tolerate dirty and hot conditions as are found in industrial environments. The output is not high resolution. Colour printout is limited and the print speed is also lesser as compared to non-impact printers. Therefore, the quality of print out in general is not very good. This affects the scanner readability of the print out. The printer creates great deal of noise while the pins strike the ribbon to the paper. The pins get bended easily destroying the print head. The single sheet of paper has to wound and aligned by hand which is time- consuming and hectic. This also makes it prone to jamming frequently. Although paper jamming can happen with any printer, fixing it here is not an easy task. The density of barcodes is low and may fail to match user’s standards. DISADVANTAGES BACK BACK NEXTNEXT

14. USES:  Applications such as receipt printing, especially when multipart forms are required.  Dot matrix printers are used in banks and stores where they print duplicates on two part forms for record keeping.  Used in voting machines where they make a copy for the voter to take home, and a second copy for permanent records for recounts.