How Printers Work
Inkjet printers technology development starts in the early 1960s. The first inkjet printing device was patented by Siemens in 1951, which led to the introduction of one of the first inkjet chart recorders. The continuous inkjet printer technology was developed later by IBM in the 1970s. The continuous inkjet technology basis is to deflect and control a continuous inkjet droplet stream direction onto the printed media or into a gutter for recirculation by applying an electric field to previously charged inkjet droplets. The drop-on-demand inkjet printer technology was led to the market in 1977 when Seimens introduced the PT-80 serial character printer. The drop-on-demand printer ejects ink droplets only when they are needed to print on the media. This method eliminates the complexity of the hardware required for the continuous inkjet printing technology. In these first inkjet printers ink drops are ejected by a pressure wave created by the mechanical motion of the piezoelectric ceramic.
I. Dot matrix printer technologies used today
There are several printer technologies used in today's home, office and banking printers. Dot matrix printers, known also as impact printers, represent the oldest printing technology, are still the widespread today, grace of it's best cost per page ratio. Dot matrix printers are divided on two main groups: serial dot matrix printers and line dot matrix printers (or simply line printers). In serial dot matrix printers the characters are formed by the print head (or printhead). Such a print head has a number of print wires ( pins) arranged in vertical columns and electro-magnetic mechanism able to shoot these wires. There are two main printhead technologies - in the first one electromagnetic field shoots the print head's wire. In the second one, the so called permanent magnet printheads, a spring shoots the printhead wire and the magnetic field just holds the spring in stressed and ready to shoot position. When the electromagnetic field equalizes the magnetic field, the spring is released to shoot the wire. Both print head mechanisms are shown in action at the picture bellow. Dot matrix printer head mechanisms in action: Classical printhead mechanism is showed from the left side. The permanent magnet printer head mechanism you may see at right. In general the permanent magnet printheads are faster and are used in heavy-duty printers. Some of the most popular print heads of this type are: Epson DFX, IBM 4226, Fujitsu 5600 and 6400, and all Oki print heads. How the serial dot matrix printers work? As the printer head moves in horizontal direction, the printhead controller sends electrical signals which forces the appropriate wires to strike against the inked ribbon, making dots on the paper and forming the desired characters. The most commonly used printer heads has 9 print wires in one column ( 9-pin printheads) or 24 print wires in two columns ( 24-pin printheads), for better print quality. In some heavy-duty dot matrix printers there are also used 18 wire print heads ( 18-pin printheads) which have 2 columns, 9 wires in each. The printing process of a 9-pin printer head is shown at the picture bellow: Serial 9-pin dot matrix printer in action

The distance between wires in column may give us the vertical printing resolution. For example: 9 wire print head with distance 0.35 mm between adjacent wires will result in 25.4/0.35=72.5 dots/inch ( dots per inch DPI) vertical printing resolution for one pass printed line of characters. 24 wire print heads has 2 columns - 12 wires in each, with a vertical displacement of ½ step. So if the distance between adjacent wires is 0.21 mm, then one column will print with 25.4/0.21=120.9 dots/inch (DPI) vertical resolution, but since the second column print between the dots printed from the first one, the overall vertical resolution will be 240 DPI. Please note that the first laser printers released on the market had the same resolution.
| Serial dot matrix printer Features: |
Specifications |
| Print Technology: |
Serial impact dot matrix |
Print Speed CPS (characters per second) |
200 - 1120 CPS (draft) |
| Graphics Resolution |
72 - 360 DPI |
| Copies (Original +) |
4 - 9 |
| Printhead life |
200 - 400 million characters |
Workload (Duty cycle) PPM (Pages per month) |
6,000 - 60,000 PPM |
| Price [US$] |
50 - 3,500 $ |
| Cost Per Page (Cost/cents ¢) |
0.15 - 0.2 ¢ |
2. Line printers, the parallel impact printer technology
There are several printer technologies used in today's home, office and banking printers. Dot matrix printers, known also as impact printers, represent the oldest printing technology, are still the widespread today, grace of it's best 'price per page' ratio. Dot matrix printers are divided on two main groups: serial dot matrix printers and line printers (or line dot matrix printers). Line printers as well as serial dot matrix printers use pins to strike against the inked ribbon, making dots on the paper and forming the desired characters. The differences are that line printers use hammer bank (or print-shuttle) instead of print head, this print-shuttle has hammers instead of print wires, and these hammers are arranged in a horizontal row instead in vertical column. The hammer bank uses the same technology as the permanent magnet print head with the small difference that instead of print wires the print-shuttle has hammers. The printing mechanism works as follow. The permanent magnetic field holds the hammer spring in stressed, ready to strike position. The driver sends electrical current to hammer coil, which then creates electromagnetic field opposite to the permanent magnetic field. When both fields equalize, the energy stored in the spring is released to strike the hammer against the ribbon and prints a dot on the paper. The hammer printhing mechanism is shown in action at the picture bellow. The line printer mechanism in action:

How the line dot matrix printers work? During printing process the print-shuttle vibrates in horizontal direction with high speed while the print hammers are fired selectively. So each hammer may print a series of dots in horizontal direction for one pass of the shuttle, then paper advances at one step and the shuttle prints the following row of dots The line printing process

Line matrix printers are the right solutions for high-volume impact printing and are superior in speed, reliability and quality. As price-performance leaders, line printers cost less to service and less to use. The fastest line matrix printers available on the market are Tally T6218 and Printronix P5220, with a claimed print speed between 1800 and 2000 lines per minute ( lpm).
| Line dot matrix printer Features: |
Specifications |
| Print Technology: |
Line impact dot matrix |
Print Speed LPM (lines per minute) |
500 - 2000 lpm (draft) |
| Graphics Resolution |
60 - 240 DPI |
| Copies (Original +) |
5 - 9 |
Workload (Duty cycle) PPM (Pages per month) |
60,000 - 600,000 PPM |
| Price [US$] |
3,000 - 13,000 $ |
| Cost Per Page (Cost/cents ¢) |
0.1 - 0.15 ¢ |
3. Laser printers and LED printers technology
Laser printers as well as LED printers rely on one and the same technology used at first in photocopying machines. This process is known as electrophotography and was invented in 1938 and developed by Xerox and Canon in the later 1980s. Electrophotographic process in laser printers, involves six basic steps: A photosensitive surface ( photoconductor) is uniformly charged with static electricity by a corona discharge. Then the charged photoconductor is exposed to an optical image through light to discharge it selectively and forms a latent or invisible image.

Development is done by spreading toner, a fine powder, over the surface, which adheres only to the charged areas, thereby making the latent image visible. At the next step an electrostatic field transfers the developed image from the photosensitive surface to a sheet of paper. Then the transferred image is fixed permanently to the paper, by fusing the toner with pressure and heat. The last step is cleaning of all excess toner and electrostatic charges from the photoconductor to make it ready for next cycle. Laser printers as well as LED printers offer the best print quality i.e. the highest resolution. The unique difference is the method of exposition or formation of the latent image. Laser printer scanning assembly: Laser printers rely on a laser beam and scanner assembly to form a latent image on the photo-conductor bit by bit. The scanning process is similar to electron beam scanning used in CRT. The laser beam modulated by electrical signals from the printer's controller is directed through a collimator lens onto a rotating polygon mirror ( scanner), which reflects the laser beam. Then reflected from the scanner laser beam pass through a scanning lens system, which makes a number of corrections to it and scans on the photoconductor.

This technology is the major key for ensuring high precision in laser spot at the focal plane, accurate dot generation at a uniform pitch and therefore better printer's resolution. Laser printer scanning process: the latent image creation

LED printers,developed by Oki and Panasonic, use an array of small Light Emitting Devices to form the latent image, hence no scanner is required. Thus LED technology offers some potential advantages over laser one. However, several problems are related to this method. A main problem is the integration of the 2400 diodes (A4 format with 300 dpi) into a staggered or single row, along with lens arrays for focusing the LED emission onto the photosensitive surface. The image scanning process is similar to that in line dot matrix printers as shown bellow. The LED printer scanning process

Laser printers as well as LED printers are the right solutions for applications demanding high quality with high-speed output of images and text data, such as desktop publishing.
| Printer Features: |
Laser printer Specifications |
LED printer Specifications |
| Print Technology: |
Electrophotography Laser |
Electrophotography LED |
Print Speed PPM (pages per minute) |
4 - 50 PPM
for industrial printers up to 1000 PPM |
10 - 26 PPM |
| Graphics Resolution |
300 - 2400 DPI |
300 - 1200 DPI |
| Copies (Original +) |
0 |
0 |
Workload (Duty cycle) PPM (Pages per month) |
6,000 - 300,000 PPM
for industrial printers up to 18 million PPM |
6,000 - 100,000 PPM |
| Price [US$] |
200 - 8,000 $
for industrial printers up to 1,000,000 $ |
250 - 8,000 $ |
Cost Per Page (Cost/cents ¢) |
1.0 - 8.7 ¢ |
1.0 - 9.0 ¢ |
4. Inkjet and Bubble-jet printers technology
Inkjet printers technology development starts in the early 1960s. The first inkjet printing device was patented by Siemens in 1951, which led to the introduction of one of the first inkjet chart recorders. The continuous inkjet printer technology was developed later by IBM in the 1970s. The continuous inkjet technology basis is to deflect and control a continuous inkjet droplet stream direction onto the printed media or into a gutter for recirculation by applying an electric field to previously charged inkjet droplets. The drop-on-demand inkjet printer technology was led to the market in 1977 when Seimens introduced the PT-80 serial character printer. The drop-on-demand printer ejects ink droplets only when they are needed to print on the media. This method eliminates the complexity of the hardware required for the continuous inkjet printing technology. In these first inkjet printers ink drops are ejected by a pressure wave created by the mechanical motion of the piezoelectric ceramic. Inkjet printer drop-on-demand technology with piezoelectric actuator

At the same time Canon developed the bubble jet printer technology, a drop-on-demand inkjet printing method where ink drops were ejected from the nozzle by the fast growth of an ink vapor bubble on the top surface of a small heater. Shortly thereafter, Hewlett-Packard independently developed a similar inkjet printing technology and named it thermal inkjet. Bubble jet printer drop-on-demand technology

The most popular inkjet and bubble-jet printers use serial printing process. Similarly to dot matrix printers, serial inkjet printers use print heads with a number of nozzles arranged in vertical columns. The printing process is the same as in dot matrix printers. Serial Inkjet printer in action

There are also available inkjet and bubble-jet printers analogous to line dot matrix printers for high speed printing applications. The image printing process is similar to that in LED printers as shown bellow. Line inkjet printer printing process

The greatest advantages of inkjet printers are, quiet operation, capability to produce color images even with photographic quality and the low printer prices. The down side is that although inkjet printers are generally cheaper to buy than lasers, they are far more expensive to maintain. When it comes to comparing the cost per page, ink jet printers work out many times more expensive than laser printers. There are some exceptions of course for some heavy-duty industrial printers. From Tally claim the T3016 SprintJet prints at only 1/3 of a cent per page.
| Printer Features: |
Specifications |
| Print Technology: |
Inkjet or Bubble-jet |
Print Speed PPM (pages per minute) |
1 - 20 PPM |
| Graphics Resolution |
300 - 1200 DPI |
| Copies (Original +) |
0 |
Workload (Duty cycle) PPM (Pages per month) |
6,000 - 60,000 PPM |
| Price [US$] |
30 - 3,000 $
For large-format printers up to 19,000 $ |
| Cost Per Page (Cost/cents ¢) |
3.0 - 30.0 ¢ |
source: http://mimech.com/printers/
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