Thoery- 4 :- Types of printers, Dot Matrix printer’s laser printer, Ink jet printer, line printer

 

1. Introduction to Printers

A printer is an external hardware output device that takes electronic data from a computer or other device and generates a hard copy (permanent text or graphics on physical media like paper).

Printers are broadly categorized into two main types based on how they transfer characters onto paper:

• Impact Printers: These printers create images by physically striking an ink ribbon against the paper (similar to a typewriter). They are noisy but cost-effective for multi-part forms (carbon copies).

• Non-Impact Printers: These printers do not hit the paper. Instead, they use heat, lasers, ink spray, or static electricity to transfer text and images. They are much quieter, faster, and offer superior print quality.

2. Impact Printers

A. Dot Matrix Printer (DMP)

A Dot Matrix printer is an impact printer that prints characters and images as a pattern of tiny dots.

• Working Principle: The print head contains a matrix of tiny metal pins (typically 9 or 24 pins). An electromagnet fires these pins forward selectively, striking an inked fabric ribbon against the paper to form characters out of dots.

• Key Characteristics:

  • Resolution: Relatively low; text can look pixelated or grainy.

  • Speed: Measured in CPS (Characters Per Second), ranging from 200 to over 500 CPS.

  • Advantages: Extremely low printing cost per page; can print carbon copies using carbonized paper.

  • Disadvantages: Highly noisy, slow, and cannot print high-quality graphics or color effectively.

B. Line Printer

A Line Printer is a high-speed impact printer that prints an entire line of text at once rather than character by character.

• Working Principle: It utilizes a fast-spinning drum, chain, or band containing embossed characters. A row of hammers behind the paper strikes the paper and ribbon against the moving characters at precisely the right millisecond to print a whole line simultaneously.

• Key Characteristics:

  • Speed: Exceptionally fast for impact technology, measured in LPM (Lines Per Minute), often ranging from 500 to over 2,000 LPM.

  • Advantages: Massive throughput capability, highly durable, and ideal for heavy-duty data processing centers.

  • Disadvantages: Limited to basic text/fonts, cannot print complex graphics, and is incredibly loud.

3. Non-Impact Printers

A. Inkjet Printer

An Inkjet printer is a non-impact printer designed for low-to-medium volume printing, highly favored for home and small office use.

• Working Principle: The print head moves back and forth across the paper, precisely spraying microscopic droplets of liquid ink through hundreds of tiny nozzles.

  • Thermal Bubble: Uses heat to vaporize ink, creating a bubble that forces a droplet out.

  • Piezoelectric: Uses electric currents to vibrate a crystal, forcing the ink droplet out.

• Key Characteristics:

  • Ink Type: Uses liquid ink cartridges (CMYK: Cyan, Magenta, Yellow, and Black).

  • Resolution & Speed: High resolution (excellent for photos); speed is measured in PPM (Pages Per Minute), typically 10 to 20 PPM.

  • Advantages: Excellent color blending, low initial hardware cost, capable of photo-quality printing.

  • Disadvantages: High cost per page (ink cartridges are expensive), slow print speed compared to lasers, and liquid ink can smudge if wet.

B. Laser Printer

A Laser Printer is a high-speed non-impact printer designed for sharp text and high-volume business printing.

• Working Principle: It uses photographic and electrostatic principles:

  1. A laser beam draws an electrostatic image of the page onto a rotating, photosensitive drum.

  2. The statically charged drum attracts fine, dry powder called toner.

  3. The drum transfers the toner onto the paper using static electricity.

  4. The paper passes through a fuser (heated rollers), which melts and permanently bonds the toner to the fibers of the paper.

• Key Characteristics:

  • Ink Type: Uses dry toner powder.

  • Speed & Resolution: Very high speed (20 to 60+ PPM) with crisp, sharp text quality.

  • Advantages: Very fast, extremely sharp text formatting, low cost per page over time, and the print does not smudge.

  • Disadvantages: Higher initial machine cost; requires a warm-up time; color laser printers and their replacement toners are expensive.

4. Summary Comparison Table

Feature	Dot Matrix	Line Printer	Inkjet Printer	Laser Printer
Category	Impact	Impact	Non-Impact	Non-Impact
Speed Metric	Characters/Sec (CPS)	Lines/Minute (LPM)	Pages/Minute (PPM)	Pages/Minute (PPM)
Consumable	Fabric Ribbon	Fabric Ribbon/Band	Liquid Ink Cartridge	Dry Toner Powder
Noise Level	Very High	Extremely High	Low	Low to Medium
Best Used For	Carbon copies, invoices	Continuous bulk logs	High-quality photos	Sharp office documents