REPORT

ON

Printers

INTRODUCTION

In computing, a printer is a peripheral which produces a hard copy (permanent readable text and/or graphics) of documents stored in electronic form, usually on physical print media such as paper or transparencies. Many printers are primarily used as local peripherals, and are attached by a printer cable or, in most newer printers, a USB cable to a computer which serves as a document source.

Another aspect of printer technology that is often forgotten is resistance to alteration: liquid ink such as from an inkjet head or fabric ribbon becomes absorbed by the paper fibers, so documents printed with a liquid ink are more difficult to alter than documents printed with toner or solid inks, which do not penetrate below the paper surface. Printers vary in size, speed, sophistication and cost. In general, more expensive printers are used for higher–resolution color printing.

The six printer qualities of most interest to most users are:

1. Color: Color is most important for users who need to print pages for presentations where color is part of the information. Color printers can also be set to print only in black and white. Color printers are most expensive to operate since they use two ink cartridges (one color and one black ink) that need to be replaced after a certain number of pages. Users who don’t have a specific need for color and who print a lot of pages will find a black and white printer cheaper to operate.

2. Resolution: Printer resolution (the sharpness of text and images on paper) is usually measured in dots per inch (dpi). The minimum the size of the dots the better the detail of the figure reproduced. And higher dpi values increases the sharpness and detail of figure and enhance the number of intensity levels that a printer support.

3. Speed: Measured in characters per second (cps) or pages per minute (ppm), the speed of printers varies widely. Line printers are fastest (up to 3,000 lines per minute). Dot-matrix printers can print up to 500 cps and laser printers range from about 4 to 20 text pages per minute. Color printing is slower.

4. Memory: Most printers come with a small amount of memory that can be expanded by the user. Having more than the minimum amount of memory is helpful and faster when printing out pages with large images or tables with lines around them.

5. Graphics: Some printers (line printers) can print only text. Other printers can print both text and graphics.

6. Fonts: Some printers, notably dot-matrix printers, are limited to one or a few fonts. In contrast, laser and ink-jet printers are capable of printing an almost unlimited variety of fonts.

Categories of printers

There are several major technologies available. These technologies can be broken down into two main categories with several types in each:

1.Impact Printer: These printers have a mechanism whereby formed character faces are pressed against an inked ribbon on to the paper in order to create an image. Impact printers make use of certain force while printing. In this printer head touches the paper while carrying out the process of printing. For example dot matrix and line printers.

1. Identification: An impact printer uses a head or a needle coated in ink to apply pressure on a piece of paper in enough places to create an image of the letters, words and phrases sent to it from a computer.

2. Types: These printers include various models. Dot-matrix printers work by striking a pin against an ink strip and a piece of paper to create a series of dots that make up an image. A daisy wheel printer, on the other hand, has a disk covered in raised letters, which spins and applies the correct letters, one at a time.

3. Resolution: Dot-matrix printers can achieve varying resolutions based on the number of pins found in a print-head. These range from about nine to 24, with 24-pin print-heads creating a much higher resolution. Considerations

Impact printers have been replaced, for the most part, by laser and inkjet printers, which offer increased speed, efficiency and resolution.

o DOT MATRIX PRINTERS

o A dot matrix printer or impact matrix printer is a type of computer printer with a print head that runs 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.

Each dot is produced by a tiny metal rod, also called a "wire" or "pin", which is driven forward by the power of a tiny electromagnet or solenoid, either directly or through small levers (pawls).

The moving portion of the printer is called the print head, and when running the printer as a generic text device generally prints one line of text at a time. These machines can be highly durable.

EARLY DOT MATRIX PRINTERS

The LA30 was a 30 character/second dot matrix printer introduced in 1970 by Digital Equipment Corporation of Maynard, Massachusetts. It printed 80 columns of uppercase-only 5x7 dot matrix characters across a unique-sized paper. The print head was driven by a stepper motor and the paper was advanced by a somewhat-unreliable and definitely noisy solenoid ratchet drive. The paper was moved by a stepper motor.

The LA30 was followed in 1974 by the LA36, which achieved far greater commercial success, becoming for a time the standard dot matrix computer terminal. The LA36 used the same print head as the LA30 but could print on forms of any width up to 132 columns of mixed-case output on standard green bar fanfold paper.

Though hardware improvements to dot matrix printers boosted the carriage speed, added more font options, increased the dot density (from 60 dpi up to 240 dpi), and added pseudo-color printing through multi-color ribbon. Still such printers lack the ability to print computer generated images at acceptable quality. It is good for text printing in continuous sheets.

Advantages of Dot matrix printers:

1. Dot matrix printers, like any impact printer, can print on multi-part stationery or make carbon-copies.

2. Dot matrix printers have one of the lowest printing costs per page.

3. They are able to use continuous paper rather than requiring individual sheets, making them useful for data logging.

4. They are good, reliable workhorses ideal for use in situations where printed content is more important than quality.

5. The ink ribbon also does not easily dry out.

Disadvantages of Dot matrix printers:

1. Impact printers create noise when the pins or typeface strike the ribbon to the paper.

2. They can only print lower-resolution graphics, with limited color performance, limited quality, and lower speeds compared to non-impact printers.

3.While they support fanfold paper with tractor holes well, single-sheet paper may have to be wound in and aligned by hand, which is relatively time-consuming, or a sheet feeder may be utilized which can have a lower paper feed reliability.

4.They are prone to paper jams when a print wire snags the leading edge of the label while printing at its very edge.

o Line printers

The line printer is a form of high speed impact printer in which one line of type is printed at a time. They are mostly associated with the early days of computing, but the technology is still in use. Print speeds of 600 to 1200 lines-per-minute (approximately 10 to 20 pages per minute) were common.

The major design existed under this printer is:

Chain printers

Chain printers (also known as train printers) placed the type on moving bars (a horizontally-moving chain). As with the drum printer, as the correct character passed by each column, a hammer was fired from behind the paper. Chain printers had the advantage that the type chain could usually be changed by the operator.

Bar printers

Bar printers were similar to chain printers but were slower and less expensive. Rather than a chain moving continuously in one direction, the characters were on fingers mounted on a bar that moved left-to-right and then right-to-left in front of the paper.

Drum Printer

1. Drum printers are line printer that prints an entire line at a time.It Consists of a solid cylindrical drum with characters embossed on its surface in the form of circular bands.

2. Each band consists of all the printing characters supported by the printer in its character set.Total number of bands is equal to the maximum number of characters that can be printed on a line.In addition, the printer has a set of hammers mounted in front of the drum in a manner that an inked ribbon and a paper can be placed between the hammers and the drum.

3. The drum rotates at very high speed and a character is printed at a desired print position by activating the appropriate hammer when the characters embossed on the band at the print position passes below it.

Advantages of line printer

1. Typical main-frame line printers (IBM) use a metal "band saw" character loop, and solenoids for each character position, typically 132 columns. The band spins at several RPS and as each letter aligns with the column it's intended to be, the solenoid, or hammer behind that column fires striking the letter through the ink ribbon, onto the paper.

3.The speed is high. Since each letter passes each column several times per second, the entire line of print can be struck at once. 10 lines per second is typical and the sound is quite high;

necessitating heavy sound insulation.

Disadvantages: The standard "line printer" can only use pin feed paper, cannot use other than standard widths {17"} typical, and is pretty specialized to the system being used. No color other than black.

Difference Between a Line Printer & a Dot Matrix Printer

A line printer and dot matrix printer differ in how they print pages. Line printers are more commonly used with computers, while dot matrix printers function similarly to a typewriter.

1. Printing: A line printer print pages exactly as its name implies, one line at a time. Dot matrix printers use pins arranged in a matrix that physically strike an ink ribbon between the pin and the paper to print characters.

2. Speed: Line matrix printers can print roughly 1,200 lines per minute, or generally about 20 pages per minute. Dot matrix printers print about 40-300 characters per second, or about six to seven pager per minute, at best.

3. Quality: Dot matrix printers have a lower print quality than line printers. The characters' shapes on pages printed using a dot matrix printer appear as a number of dots connected together. Line printers print solid characters and can use a wide variety of font face and sizes.

2. Non-impact printer:

There are many types of printers available. However, all printers fall into two basic categories: impact and non-impact printers. Non-impact printers give both higher print quality and faster printing speed than impact printers. Because of this, non-impact printers are popular with both professionals and consumers.

1. Function: On an impact printer, the print head comes in direct contact with the paper. On a non-impact printer, the type is formed without the print head coming into direct physical contact with the paper

.2. Types : Types of non-impact printers include: ink-jet, bubble-jet, laser and thermal

printers.

3. Benefits: Non-impact printers offer better print quality, faster printing and the ability to create prints that contain sophisticated graphics, such as photographs.

4. Technology: Non-impact printers use either solid or liquid cartridge-based ink. This ink is either sprayed, dripped or electrostatically drawn onto the page.

5. Maintenance Non-impact printers typically require little maintenance beyond replacing the print or toner cartridges.

6. ConsiderationsWhen choosing a non-impact printer, take into consideration how you will be using it. Ink-jet printers offer a nice compromise between print quality and price.

If speed and quality are more important than cost, you might need a laser printer. Laser printers are available in black and white or color (used for graphics).

o Inkjet printer

An inkjet printer is a type of computer printer that reproduces a digital image by propelling variably-sized droplets of liquid material (ink) onto a page. Inkjet printers are the most common type of printer and range from small inexpensive consumer models to very large and expensive professional machines.

The concept of inkjet printing dates back to the 19th century and the technology was first developed in the early 1950s. Starting in the late 1970s inkjet printers that could reproduce digital images generated by computers were developed, mainly by Epson, Hewlett-Packard and Canon. In the worldwide consumer market, four manufacturers account for the majority of inkjet printer sales: Canon, Hewlett-Packard, Epson, and Lexmark.

There are two mian technologies used in inkjet printers: thermal and piezoelectric inkjet printers.

Thermal technology:-

Most consumer inkjet printers, from companies including Canon, Hewlett-Packard, and Lexmark (but not Epson),use print cartridges with a series of tiny chambers each containing a heater, all of which are constructed by photolithography. In this technology with every nozzel there is a heating element which is constructed of a series of resistors. Each nozzel has a reservoir of ink where ink is filled.Printer driver decides which of the nozzels will be activated and then those nozzels will be send electric signals by the driver itself And then the current starts flowing through the heating element of those nozzels. The heat generated by the heating element will heat the ink and then it starts evaporating and results in the form of bubbles. When ink is heated the bubbles goes on expanding and pushes the ink out of the nozzel and so gets sprayed on the paper and printing is done.

Piezoelectric technology:-

In this technology each and every nozzel has a piezo-actuator instead of heating element. It is filled inside with piezo-crystal which is a type of material which follows piezoelectric effect property. This property states that when stress is applied electric current is generated and vice-versa .In this technology also printer driver decides which of the nozzels have to be activated. Those nozzels are sent an electric signal by the printer driver. As a result electric current is generated and a result stress is generated inside the piezo-actuator. Due to this stress the piezo crystals starts vibrating due to which pressure waves are created inside the nozzel which force the ink out of the nozzel. When the ink is pushed out the electric signal is withdrawn.

Advantages of inkjet printers:-

1. They are quieter in operation than impact dot matrix printer.2. They can print finer, smoother details through higher printer head resolution, and many

consumer inkjets with photographic-quality printing are widely available.

3. Inkjets have the advantage of practically no warm up time and lower cost per page

4. Red, Green, Blue and Cyan are the colors that are helpful in generating all the other colors.

Disadvantages of inkjet printers:-

1. The ink is often very expensive.2. The lifetime of inkjet prints produced by inkjets using aqueous inks is limited; they will

eventually fade and the color balance may change.

3. Because the ink used in most consumer inkjets is water-soluble, care must be taken with inkjet-printed documents to avoid even the smallest drop of water, which can cause severe "blurring" or "running." Similarly, water-based highlighter markers can blur inkjet-printed documents.

4. The very narrow inkjet nozzles are prone to clogging with dried ink.

o Laser printer

A laser printer is a common type of computer printer that rapidly produces high quality text and graphics on plain paper. As with digital photocopiers and multifunction printers (MFPs), laser printers employ a xerographic printing process but differ from analog photocopiers in that the image is produced by the direct scanning of a laser beam across the printer's photoreceptor. These are non impact printers. In this printer there is a photo conductor drum that keeps on rotating. It is so called because it gets electrically charged when light falls on it. There is a laser unit which generates laser beam, ink tonner which is in powder form, charging corona which when supplied current deposits positive charge on photo conductor drum. The laser unit receives data from CPU.

The printer driver sends signal i.e it switches the laser beam either on or off as per the data is received from CPU. As a result those areas of drums that are exposed to laser beam gets negatively charged. Now the drum is partially negatively charged and positively charged. The ink tonner consists of plastic granules. This tonner is applied positive charge. Now the drum will be exposed to the tonner, and since the tonner is positively charged it sticks to those areas of photoconductor drum which are negatively charged. The paper passes through rollers in the fuser assembly where heat (up to 200 Celsius) and pressure bond the plastic powder to the paper. The heat from the fuser assembly can damage other parts of the printer, so it is often ventilated by fans to move the heat away from the interior. The primary power saving feature of most copiers and laser printers is to turn off the fuser and let it cool. Resuming normal operation requires waiting for the fuser to return to operating temperature before printing can begin.

When the print is complete, an electrically neutral soft plastic blade cleans any excess toner from the photoreceptor and deposits it into a waste reservoir, and a discharge lamp removes the remaining charge from the photoreceptor. Waste toner cannot be reused for printing because it can be contaminated with dust and paper fibers. A quality printed image requires pure, clean toner.

Advantages of laser printers:-

The main advantage behind these printers is probably its efficiency and speed at printing. Laser printers are also known as 'page printers' as they print documents a page at a time, and performs it at a very fast rate.

They produce highest quality output in comparison with the other types of printers. This is mainly due to the technology behind it as laser printers utilize electro-photography for printing which results in quality output.

While it is a small issue, noise can be very unproductive and disturbing specially at a work place, laser printers are highly optimized and barely emits any sound.

They also offer user-friendliness with other features like self-printing, where printing maybe done without supervision thus increasing productivity at the workplace.

Disadvantages of laser printers:-

With the extra benefits in comparison with other printers, they are a lot more costly. Laser printers are powerful and utilize complex technology and perform fast output, the result

of which is a relatively large hardware device which can take up a lot of space.

As they are non-impact printers, multipart stationary cannot be used thus duplicate printing cannot be simultaneously performed.

While the cost is an issue, an initial investment only maybe worth it based on your organization's or personal requirements, however maintenance, servicing and repair of this hardware device is also very high thus laser printers aren't very economical.

Laser printers are also known to be hazardous to the atmosphere and your health. Due to the high voltages when running the machine, small amounts of ozone are generated which can

damage the ozone layer. Some laser printers are also known to emit particles that are suspected to cause respiratory diseases.

Difference between an Inkjet and Laser printerInk Emission

Inkjet printers emit ink through the spraying of ink bubbles or piezoelectric crystals that change shape based on electric signal. Laser printers have a laser that charges the paper and allows the toner to stick.

Ink Type

Thermal inkjets use aqueous ink and piezoelectric inkjets use specialized inks such as solvent-based and UV responsive. Laser printers use toner rather than liquid ink.

Paper Type Thermal inkjets only print on paper or substrates with special coatings, while

piezoelectric inkjets and toners print on a wide variety of uncoated paper

Efficiency Inkjet printers produce high quality prints, but take a relatively long time to do so. Laser

printers print at a higher speed than inkjets and are less expensive per page to use.

Image Application

Inkjet printers come with disposable or non-disposable print heads. Laser printers contain a heating element to fuse the ink to the paper.

Advantages and disadvantages of printers:

Computer printers are a common sight in homes and offices. They often come as part of a computer bundle that includes a mouse, keyboard and monitor. Computer printers also come in several varieties, including simple inexpensive models and high-end versions with many features. Having a printer has definite advantages, but also carries certain drawbacks.

Convenience The primary advantage of a computer printer is convenience. Printing documents at home can save time and money compared to visiting a commercial printer or office supply store. It is also a good way to manage documents and paperwork by producing hard copies to use as backups or by printing documents or letters that need to be mailed out.

Initial Cost The first disadvantage of printers comes from the initial cost. For users who only print documents occasionally, establishing a good relationship with a local print shop may be a good idea, and a more cost-effective option than investing several hundred dollars in a home printer. While some basic models are very affordable, the sky is the limit with color laser printers and high-quality photo printers, representing a substantial investment.

Long-Term Cost Printers continue to cost money after they are purchased. Users will need to provide a constant supply of paper, which can be especially expensive for photo printers that produce images on high-quality, glossy photo paper. Ink and toner, for inkjet and laser printers, respectively, are also expensive and need to be replaced with use. Finally, any printer may require occasional maintenance or repairs, leading to even greater cost.

Waste Having a printer connected to a computer is a way of encouraging waste. Users may be more likely to print hard copies of documents that they could easily read online or off of the computer's monitor. Excess printing wastes electricity, ink and paper, and can add up to a substantial cost over time. When only essential documents get sent out for printing, and only after extensive proofreading, there is much less waste.

Features

Another significant advantage of a printer is the long list of features certain models include. Besides printing documents and photos, some printers can also scan, fax and make copies. This means that a computer printer may actually replace several different machines, reducing clutter and streamlining a home office.