How Printer Work?
The printer is a peripheral allowing to make a printed output (on paper) of the data of the computer. There are several printer technologies, the most common of which are:
- the daisy wheel printer
- the matrix printer (also called printer needle )
- the printer inkjet and bubble jet printer
- the laser printer
- the LED printer
These days, daisy-chain printers and dot-matrix printers are hardly used anymore.
The printer is generally characterized by the following:
Print Speed: Expressed in pages per minute ( ppm ), print speed represents the printer’s ability to print a large number of pages per minute. For color printers, a distinction is usually made between the print speed in monochrome and in color.
Resolution: expressed in dots per inch (noted dpi or dpi, for dot per inch ), the resolution defines the fineness of the print. Sometimes the resolution is different for monochrome, color or photo printing.
Warm-up time: it represents the waiting time necessary before the first printing. Indeed, a printer cannot print “cold”, it is necessary for it to reach a certain temperature in order to function optimally.
On-board memory: This is the amount of memory that the printer can use to store print jobs. The greater the amount of memory, the larger the job queue can be.
The paper format: depending on their size, printers are able to accommodate different sizes of documents, generally A4 (21 x 29.7 cm), more rarely A3 (29.7 x 42 cm). Some printers also allow printing on other types of media, such as CDs or DVDs.
Paper Feed: This is the printer loading mode, characterizing the way in which blank paper is stored. It is particularly important depending on the location planned for the printer (rear loading should be avoided if the printer is stuck against a wall). * The main paper feed modes are as follows:
- The feed tray (also called cassette tray ), uses an internal paper feed source. Its capacity represents the maximum number of sheets of paper it can accommodate.
- The tray by feed is a manual feed mode, to insert the sheets by a small amount (about one hundred). The platen is sometimes horizontal, sometimes vertical, at the rear of the printer.
Cartridges: Cartridges are rarely standard and depend heavily on the make and model of the printer. Thus some manufacturers favor multicolored cartridges, while others offer separate ink cartridges. Individual ink cartridges are generally more economical because it is not uncommon for one color to be used more than the others.
It is interesting to look at the cost of printing per sheet. The size of the ink drop is particularly important. The smaller the ink drop, the lower the printing cost and the better the image quality. Some printers allow you to obtain drops of 1 or 2 picoliters.
- Interface: this is the printer’s connections. The main interfaces are as follows:
- USB ;
- Parallel ;
- Network: this type of interface makes it very easy to share a printer between several computers. There are also WiFi printers, accessible via a wireless network. If your printer does not have a network interface, you can still connect it to your network (local or Wi-Fi ) using a specific box called a “print server”.
The daisy-chain printer
The daisy wheel printers are based on the principle of typing machines. All characters are embossed on a daisy-shaped matrix. To print, an ink-soaked ribbon is placed between the daisy and the leaf. When the die hits the ribbon, the latter deposits ink only at the level of the relief of the character.
These printers have become obsolete because they are much too noisy and very slow.
The matrix printer
The matrix printer (sometimes called a needle printer , impact printer or in English Dot-Matrix printer ) allows documents to be printed on the paper thanks to a “back and forth” of a carriage comprising a head of impression.
The head is made up of small needles, pushed by electromagnets, striking a carbon ribbon, called an “ ink ribbon ”, located between the head and the paper.
The carbon ribbon runs so that there is continuous ink on it. At each end of the line a roller rotates the sheet.
The most recent dot-matrix printers are equipped with print heads with 24 pins, which allows them to print with a resolution of 216 dpi ( dots per inch or in English dots per inch , denoted dpi ).
The inkjet and bubble ink printer
The technology of inkjet printers ( Bubble jet printers ) was originally invented by Canon, it is based on the principle that a heated fluid produces bubbles.
The researcher who discovered this principle had accidentally put in contact a syringe filled with ink and a soldering iron, this created a bubble in the syringe which caused ink to squirt out of the syringe.
The heads of current printers are made up of numerous nozzles (up to 256), equivalent to several syringes, heated between 300 and 400 ° C several times per second.
Each nozzle produces a tiny bubble that ejects an extremely fine droplet. The vacuum created by the drop in pressure sucks in a new drop.
There are generally two technologies:
- The jet printers ink , using nozzles having their own built-in heating element. The technology used is thus thermal.
- The Bubble Jet printers , using nozzles having a piezoelectric technology. Each nozzle is associated with a piezoelectric quartz, which, excited on its resonant frequency, deforms and ejects the ink drop.
The laser printer provides quality paper prints at low cost and with high printing speed. On the other hand, the cost of acquiring such a printer reserves it for semi-professional or professional uses.
The laser printer uses technology similar to that used in photocopiers. A laser printer is thus mainly made up of a photosensitive drum (in English “ drum ”) which, electrostatically charged, is capable of attracting the ink in order to form a pattern which will be deposited on the sheet of paper.
The overall operation is as follows: a paper ionizer charges the sheets positively. The laser charges the drum positively at certain points thanks to a pivoting mirror. Thus, the ink in the form of powder ( toner ), negatively charged, is deposited on the parts of the toner which have been previously charged by the laser.
As it turns, the drum deposits ink on the paper. A heating wire (called coronary ) finally fixes the ink on the paper.
Thus, the laser printer, having no mechanical head, is fast and low noise.
There are in fact two technologies for laser printers: “carousel” (four passes) or “tandem” (single pass).
- carousel: With carousel technology, the printer makes four passes to print a document (one per primary color and one for black, so printing is theoretically four times slower in color than in black).
- tandem: A laser printer using “tandem” technology deposits each color in a single pass, the toners being arranged in parallel. The outputs are as fast in black as in color. However, this technology has a higher cost price, the mechanics being more complex. It is therefore reserved in principle for mid-range or high-end color laser printers.
Another printing technology competes with laser printers: LED ( Light Emitting Diode ) technology. With this technology, a strip of electro-luminescent diodes polarizes the drum by means of a very fine light ray, making it possible to obtain very small points. This technology is particularly well suited for obtaining high resolutions (600,1200 or 2400 dpi).
Since each diode is at the origin of a dot, the printing rate hardly suffers from differences in resolution. In addition, this technology has no moving parts, which makes it possible to design products that are less expensive, but also more robust and more reliable.
Page description languages
The page description language is the standard language that the computer uses to communicate with the printer. Indeed, the printer must be able to interpret the information that the computer sends to it.
The two main page description languages are:
- PCL language: it is a language made up of binary sequences. The characters are transmitted according to their ASCII code
- PostScript language: This language, originally used for Apple LaserWriter printers, has become the standard for page description language. It is a full-fledged language based on a set of instructions
It should be noted the existence of boxes, called print servers, making it possible to make available on the network a printer having a USB or parallel connection.