Matrix Printers Dot-matrix printers were the first that came on the market, there have lately lost ground compared to inkjet printers, remain the only ones that can print continuous forms, making them an option for shops that need to print invoices. Operation
This type of printer is bi-directional printing, as printed in the rightward shift.
The PC sends a series of ASCII codes. These codes are stored in a buffer, a random access memory of the printer (RAM). These codes are commands that tell the printer that uses a bitmap font table, contained in a chip. Then, the table, sent to the printer the dot pattern to be used to create the characters represented in ASCII code.
to form each letter, number or symbol, some needles are activated, hitting the paper. In between is a ribbon. The result is not very high quality (24 needles are better quality than 9), but is more persistent than can be achieved and needs no special role. However, the ability to play graphics (photos, illustrations complex) is almost zero.
Advantages and disadvantages The main advantages of this technology are its ability to obtain multiple copies and print continuous forms. His speed is text and also the highest maintenance cost is lower than the market offers today.
other hand the disadvantages are: the noise is certainly high, and the inability to handle color or several types of sources.
In general, needle-matrix printers are positioned as low-priced printers, medium-low quality, low maintenance and high printing capacity. The largest manufacturer of these printers is Epson, with different models and prices.
Inkjet Printer General Features
Although inkjet printers were available in the 80's, it was only in the 90's when prices fell far enough to bring these printers to occupy an important place in the market. Models already exist less than U $ S 100, and many of them compete with laser-quality text and produce photorealistic images.
The concept of inkjet printers is simple (throwing liquid ink on paper) but in reality dependent on advanced technology, despite its affordable price.
Operation
printing inkjet, and laser printing is a non-impact method. The ink is emitted from nozzles that are in the printhead. The print head scans the page in horizontal strips, using a motor to move laterally, and another to move the paper in vertical steps. A strip of paper is printed, then the paper moves, ready for a new slot. To speed things up, the print head does not print only a single line of pixels in each pass, but also a vertical line of pixels at a time.
In general, inkjet printers today have resolutions of 600 dpi or more high print speed and approaching that of laser printing to black and white. An inkjet printer can produce a fast, full-color 8 x 10 inches and 300 dpi in 2 to 4 minutes. This means that producing 7.2 million points in a time of 120 to 240 seconds, or 30,000 to 60,000 points per second. The printhead of a typical printer has 64 nozzles for each color, each of which must be able to cycle on and off at speeds as high as 900 times per second, which is surprising because it is a mechanical device.
When emerged inkjet printers, print heads were designed to provide a continuous stream of ink droplets. The drops were static electric charge and "mixed" on paper or in a recycling tank through loaded areas. This procedure was weak and very inaccurate. Currently, the inkjet printers rely on technology as demand drops. DOD (Drop on Demand) that produce small droplets when needed. There are two methods that use inkjet printers to ensure that the drops are thrown quickly: thermal and piezo. Thermal Technology
One of the legends of computer technology explains how the printer was invented Thermal inkjet. An engineer experienced with ink formulas and had loaded some into a syringe. By accident, the needle touched the hot tip of a soldering iron, and left a tiny drop of ink. Canon claims to have invented this technology, which he called Bubble Jet, in 1977.
The jet is initiated by heating the ink to create a bubble that generates a pressure force to emerge and hit the paper. Then the bubble collapses and the resulting vacuum draws new ink into the chamber to replace the one that was expelled. This is the method of choice for Canon and Hewlett-Packard. Tiny
heating elements are used to eject droplets ink from the nozzles of the print head
, these tips are about the size of a human hair (approx. 70 microns, a micron being one millionth of a meter) and expel droplets of approximately 8 / 10 picoliters and points approximately 50 to 60 microns in diameter. The smallest drop that man can see with the naked eye is about 30 microns, so these drops are reaching the limits of our perception.
The incredibly small size of these droplets allows increasing the resolution of the print job. It takes a drop of nearly 35 microns to create a 720 dpi print, so that they overlap slightly drops in that resolution.
based dyes cyan, magenta and yellow are usually presented via a head CMY. Some small ink drops of different color, usually between 4 and 8, can be combined to generate a point of variable size, a larger color palette and smoother halftones. The black ink is generally based on larger molecules of pigment, is generated by a separate head with drop volumes of about 35 picoliters.
Print speed is primarily a function of the frequency with which the nozzles can fire ink, and the width of the strip printed by the printhead. Usuamente is about 12.5 MHz per inch giving print speeds between 4 and 8 ppm for black and white text and 2 to 4 ppm for color text and graphics.
Piezo technology is an alternative strategy, developed by Epson, the technology bubble jet or thermal.
Piezoelectric crystals have a rather unique property. If physical force is applied on them, can generate an electric charge. The process also works in reverse: an electric charge applied to the glass and you can make it move, creating a mechanical force.
Printhead an inkjet printer uses a piezoelectric crystal in the back of a tiny ink reservoir. A current is applied to the glass, pulling it inside. When power is interrupted, the crystal returns to its original position, and a small amount of ink out the nozzle. When the power resumes, attracts the glass and throw back the next drop.
Latest Epson printers are most important black ink heads with 128 nozzles and header color (CMY) with 192 nozzles (64 for each color), achieving a resolution of 720 dpi. Since the process can produce piezoelectric small and perfectly formed points very effectively, Epson can offer an enhanced resolution of 1440 x 720 dpi. This is accomplished by the head using two passes, with a consequent reduction in speed. The inks that Epson has developed to exploit this technology are extremely quick to dry, they penetrate the paper and hold their shape causing the points interact with each other.
The result is very good picture quality especially with the right paper.
This strategy has some advantages. Piezo print heads can use ink dries faster and pigments could be damaged by temperatures in a thermal head. Also, as a piezoelectric head is integrated into the printer, you need only replace the ink cartridge. (Thermal printers include the nozzles on each cartridge, which increases the cost of the cartridge and, therefore, the cost per page.) The downside is that if a piezo head is damaged or clogged, your printer needs service .
laser printer technology.
Operation
laser printer works much like a photocopier, the difference is the source of light. With a photocopy a page is scanned with a bright light while a laser is scanned, obviously, for a laser. After that the process is virtually identical, with the light, creating an electrostatic image of the page in a charged photoreceptor, which attracts the toner in the form of electrostatic charge. Operation
When the image to be printed is communicated through a language
description page, the printer's first job is to convert the instructions into a bitmap. This is done by the printer's internal processor, and the result is an image (in memory) of each item to be placed in the paper. The models designated as Windows printers do not have their own processors, so the host PC creates the bitmap, burnt directly in memory of the printer.
The heart of a laser printer is a small drum stock - the cartridge organic photoconductor (OPC) - with a coating that allows it to maintain an electrostatic charge. A laser traces the drum surface, selectively placing a positive charge points, which represent the output image. The size of the drum is the same as the paper on which the image appears, each point on the drum corresponding to a point in the paper. At the appropriate time, the paper is passed through an electrically charged wire which deposits a negative charge on it. In the real
laser printers, the selective charging is done by interrupts on and off the laser while scanning the drum, using a complex system of rotating mirrors and lenses. These mirrors spin incredibly fast and in sync with the interruptions of the laser. A typical laser printer, may well make millions of interrupts per second.
inside the printer, the drum rotates to build a horizontal line at a time. Clearly, this has to be done very efficiently. The smaller the rotation, the higher the resolution of the page. The rotation of a modern laser printer is typically 1 / 600 of an inch, giving vertical resolution 600 dpi. Similarly, the faster breaks are on and off the laser, the higher horizontal resolution.
As the drum rotates to present the next area for laser treatment, the writing area moves toward the toner. Toner is a very fine black powder negatively charged, which causes it to be attracted to the points with positive charges on the surface of the drum. So, after a full rotation, the drum's surface contains all the printed image on the page.
A sheet of paper (positively charged) then comes into contact with the drum, fed by a series of gears smooth. While completing their rotation is taking the toner from the drum because its magnetic attraction, thus transferring the image onto paper. The areas of the drum do not attract negatively charged toner, which is in the white areas of the print.
The toner is specially designed to melt very quickly, and a fuser (or fuse) heat and pressure applied to paper to make the toner adhere permanently. This is why the paper comes out of a laser printer warm to the touch.
Forget the pens and adhesives. 
