How to choose an inkjet printer | Inkjet Printers | Blog | DNS Club

Laser printers

Laser printing can be divided into laser printers and LED printers. Laser printers use a two-stage method of applying an image to a medium: obtaining a latent image and developing it. The structure of the printing unit of a printer using laser technology is shown in the diagram:

Corotron
– a device for creating a corona discharge. The structure of the corotron is very simple – it consists of metal threads and a screen, to which high voltage is applied. Under voltage, the gas located between the filament and the screen is ionized and a corona discharge occurs. Gas ionization is used to apply a charge to the photosensitive drum. Because under the influence of high voltage, oxygen in the air is converted into ozone, which has a characteristic odor.
Photosensitive drum
– the main part of the printing unit. Drum coating allows for laser printing
. The drum coating must not conduct electric current, and also have photoelectric properties (change its charge when exposed to light). These properties make it possible to create a latent photoelectric image on the surface of the drum. Currently, three types of coatings are used in drums: selenium coating – one of the first types of photosensitive coatings (selenium is a chemical element, semiconductor). The selenium coating consists of four layers. The first layer from the surface reduces charge leakage. It is a natural film of oxides. Behind it lies a layer of selenium, which has photovoltaic properties. It is in this layer that charges are formed. The third layer consists of aluminum oxide. It prevents the rapid leakage of charges from the selenium layer into the substrate. The fourth layer is the metal backing of the drum. It is connected to the printer body (grounded). The organic coating consists of a synthetic photovoltaic material. It also consists of four layers. The first layer serves to redistribute charges when the drum is illuminated during the formation of a latent image, the second consists of a substance capable of forming charges under the influence of light, and the third, as in the selenium coating, consists of oxides and serves to prevent charges from leaking into the substrate. The fourth layer is a metal substrate. Silicon coating is a new type of coating used, for example, in Kuosega printers. It is formed by a layer of amorphous silicon deposited on the base. Silicon, like selenium, is a semiconductor and has photoelectric properties. To obtain high-quality printouts, the surface of the drum must be smooth and free of scratches.
Laser Beam
used to create a hidden on the photosensitive drum; electrostatic image. The process involves the redistribution of charges in the photosensitive layer of the drum under the influence of light. Different types of lasers are used to produce the beam. Currently, semiconductor lasers are most widely used. The beam must be well focused (the size of the spot illuminated on the surface of the drum and, accordingly, the horizontal resolution of the printer depend on this). To form an image of the required intensity on the drum, the beam must have sufficiently high energy, which requires the use of a powerful laser in the printer (its beam can be dangerous to human eyes and skin).
Bunker
with dye (toner). Different printer models use different dye compositions. Typically the hopper is part of a replacement cartridge. To develop a latent image, it is necessary to apply a layer of powdered dye (toner) to the surface of the photoelectric drum. To deliver it to the photosensitive drum, magnetic powder is used – developer
. It consists of particles of magnetic material coated with a polymer. Depending on the type of printer, the toner can be single-component or two-component. Single-component toner is most often used in laser printers and consists of a mixture of dye, polymer powder and developer. This composition allows you to simplify the design of the printer. A two-component toner consists of a toner (dye and polymer) and a developer that are charged separately into the printer. They are mixed by a special dispenser in a hopper. Due to electrification during friction of the developer and toner particles, they stick together. After transferring the toner to the photosensitive drum, the developer is reassembled and reused. This requires the use of a magnetic drum cleaning system and a dosing system.
Magnetic drum
serves to transfer toner to the photosensitive drum. It consists of a hollow shaft, inside of which permanent magnets are placed. The magnetic drum attracts developer particles with toner particles adhering to them and carries them past the photosensitive drum. A special plate is installed above the shaft to regulate the amount of dye on the shaft. Also, voltage is applied to the plate to charge the toner particles. This charge facilitates their transfer to the photosensitive drum.

Image carrier (paper or film). The media comes into direct contact with the photosensitive drum, so you should be careful about the weight and type of media.

The transfer roller is used to transfer dye from the photosensitive drum to the media. The media is pressed against the photosensitive drum and the toner transfers to it. The quality of the surface of the transfer shaft and the photosensitive drum determines how tightly the media will be pressed against the drum and, accordingly, how well the image will be transferred.

Squeegee – a special plate (knife) used to clean the surface of the photosensitive drum. Cleaning removes any remaining toner from the drum that has not transferred to the paper. To ensure that the squeegee does not damage the photosensitive layer of the drum and at the same time ensures high-quality cleaning, it must be installed with great precision. The working edge of the squeegee must be strictly straight.

The waste dye hopper is designed to collect dye scraped off the surface of the drum. The collected dye must be removed periodically.

The heating roller together with the pressure roller forms the heating block of the printer. This block is often called a fuser or fuser. The high temperature of the oven is necessary to fix the dye on the carrier. The heating roller is a hollow shaft with a coating that prevents dye from sticking to the roller.

A special coating is necessary because the curing is done by melting the polymer contained in the toner, and particles of molten polymer adhering to the surface of the drum can damage it. A quartz lamp placed inside it is used to heat the shaft.

Some printers use a stationary heating element instead of a heating roller. Heating elements with a lamp consume more electricity and take longer to warm up, but have a longer service life than an element with film and can operate at higher paper speeds.

The pressure roller is used to press the media against the heating roller (or heating element).

Laser printer controllers must be very powerful because the printing speed is very high. Modern printers are equipped with powerful processors (similar to those used in computers or specialized microcontrollers), and also require a large amount of buffer memory

Electrostatically controlled inkjet printing.

The technology is based on the property of electrically charged bodies: bodies with like charges are sawed off, and those with opposite charges are attracted to each other. If a drop of ink in a printer’s print head is charged with an electrical charge and then forced to move between charged electrodes, then by changing the charge of these electrodes, the trajectory of the bodies can be changed.

Electrostatically controlled print head

https://www.youtube.com/watch?v=Uoj5DmkiB9Y

The numbers in the figure indicate the following components of the print head.

The filter is designed to protect the nozzles and other parts of the printing system from dust particles and other impurities that may end up in the ink.

Vibrator that generates ultrasonic vibrations. To obtain a uniform stream of ink ejected from the nozzle, it is continuously shaken by a vibrator with a frequency of about 100 kHz.

The nozzle is designed to produce a smooth, uniform stream of ink. To achieve an even flow of ink. To form a jet of the desired shape, as well as give the droplets the required speed, ink is supplied to the nozzles under pressure. This pressure can be created using a pump or by supplying compressed air to the ink container (to prevent the ink in the container from drying out, the air is not supplied to the ink tank itself, but to a special compartment separated from the rest of the volume by a flexible partition or a movable piston).

The charging electrode is a hollow cylinder to which voltage is applied. Flying through this cylinder, the ink jet is split into droplets, which acquire an electrical charge. This is what allows you to control the further movement of the droplets.

Control electrodes are designed to deflect ink droplets (control their movement). To give the electrodes the necessary charge, high voltage is applied to them. As can be seen in the figure, flying past the control electrodes, ink drops either do not change their trajectory and land on the media, or deviate from the straight path and are diverted into a special ink collector.

Electrical deflection of drops is used to switch the state of the head between “printing” and “not printing”.

The ink collector is designed to collect ink that deviates from the media. The ink collected in it can then be used again.

The rotating drum, depending on the type of printer, can be either a paper roller that pulls the paper (or film) past the print head, or an intermediate shaft. In some printers, the image is initially formed on an intermediate shaft and then transferred to the media by rolling the shaft over it.

The nozzle continuously ejects a stream of ink, which is then broken up into droplets. If the droplets from the nozzle do not need to reach the media at the moment, they are deflected to the side and taken to the collection for reuse. To ensure ink reuse, the printer must include an ink pump.

Inkjet printers can also be divided into groups: ink is ejected through a nozzle continuously or only when needed.

If ink is ejected continuously, the printing method belongs to the “continuous ink flow” group. In such printers, ink is ejected continuously from the nozzle and directed onto the media as needed.

If drops of ink are shot from the nozzles onto the media only as needed, the printing method belongs to the “drop on demand” group. Printers in this group are slower.

During the movement from the nozzle to the collector, the drops come into contact with air, the ink may thicken, to eliminate such cases, special ink viscosity control systems are used. When a certain critical viscosity value is reached, a solvent is added to the ink.

The print head consists of three main units: nozzle unit, electrode unit and ink collector unit. The main material is silicon and its compounds. All blocks are made using sputtering and etching technologies from multilayer blanks.

Protective coating. A row of nozzles. The print head may have one or more nozzles, depending on the print quality.

Nozzle. In this case, the nozzles are formed by holes in a layer of silicon nitride. This layer is applied to the silicon base of the entire structure of the nozzle block, after which the holes that form the nozzles are etched into it. In order for droplets emitted from different nozzles to have the same size, it is necessary that the nozzles themselves have the same size.

Silicon nitride layer. Channel for supplying ink to the nozzles. It is a recess in the silicon base of the block. Through this channel, the ink supplied to the print head flows through the filter to the nozzles. To transport the ink through the channel to the nozzles and form droplets, the ink must be supplied under pressure.

Ink supply hole. To supply ink to the nozzles, you must pass it through a glass substrate (see below) on which the nozzle unit is located. This is precisely what holes drilled in glass using ultrasonic drilling machines serve for.

Pyramidal recess with nozzle. Provides ink supply to the nozzles. The shape of the recess helps to collect ink from the surface of the filter and direct it to the nozzles.

Filter. Its main function is to trap dust particles and other solid impurities that may accidentally end up in the ink. If you do not install a filter, these impurities may reach the nozzles and clog them.

Glass backing. The silicon structures from which the main components of the nozzle assembly are made are fragile and therefore require support. The substrate, which ensures the strength of the block, is made of glass with a low coefficient of thermal expansion.

Silicon block base. All components of the nozzle block (except for the glass substrate) are made of silicon and its compounds. Silicon is relatively easy to use for deposition and atomization, which is necessary to produce channels and recesses for nozzles.

In addition to the nozzle block, the print head contains blocks of electrodes and ink collectors that serve to deflect drops and collect those drops that do not fall on the paper.

Thermal and piezoelectric inkjet printing comparison – 4apple – looking at apple through the eyes of a geek

How to choose an inkjet printer | Inkjet Printers | Blog | DNS Club

Two inkjet printing technologies: thermal inkjet and piezoelectric. Which one to choose? Pros and cons of both technologies.

According to the principle of operation, inkjet printers resemble dot matrix printers, only instead of needles hitting the ink ribbon, ink in inkjet printers is applied directly to the paper with drops of ink through very small holes called nozzles.

Currently, two printing technologies are most widespread in the inkjet printing device market: thermal inkjet
, in which activation of the paint and its release occur under the influence of heat, and piezoelectric
, in which paint is released under pressure created by the vibration of the membrane.

These are fundamentally different technologies, which have their own pros and cons.

Piezoelectric printing takes advantage of the ability of piezocrystals to deform when exposed to electric current. This allows you to control the size of the drop, the thickness of the jet, and even the speed at which the drop is ejected onto the paper. All this allows you to obtain high-resolution images. Another advantage of this technology is the naturalness of color rendering, and this is one of the conditions for high-quality photo printing. Piezo printing technology was invented and patented by Epson. Brother uses both technologies.

Today, piezojet printing is the most reliable in relation to others. With proper care, the service life of the head is comparable to the service life of the printing device itself. As a rule, the piezoelectric print head is stationary, that is, it is not replaceable along with the cartridge. But along with this there are a number of problems, such as very expensive repairs and head replacement. In addition, piezo inkjet heads are prone to high ink requirements, the possibility of air penetration when replacing cartridges or when ink runs out in the CISS. When printing infrequently, the nozzle heads tend to become clogged or skewed. But if you print frequently, you won’t find a better piezo inkjet head.

In thermal inkjet technology, ink is supplied to paper by heating, using temperatures up to 600 C. At the same time, the quality of thermal inkjet printing is an order of magnitude worse than piezo inkjet printing. And all because of the explosive nature of the drop and the appearance of satellites, or companion drops. Hence the distortion of high-quality images when printing. In addition, as a result of the temperature, carbon deposits and scale form, which clog the nozzles and lead to a deterioration in color rendering, and the printer begins to streak. In addition, temperature changes contribute to the destruction of the print head, which burns out when overheated. This is the main disadvantage of such PGs. But, as a rule, thermal inkjet PGs are less expensive than piezojet PGs and are combined with a cartridge. As a result, they are replaced more often and with lower financial costs.

Attention!
If thermal inkjet cartridges are mistakenly filled with ink for piezoelectric printing, the consequences can be disastrous.

There are two main printing technologies common in the inkjet printing market: piezoelectric and thermal inkjet.

The differences between these systems are in the method of delivering a drop of ink onto the paper.

Piezoelectric technology was based on the ability of piezocrystals to deform when exposed to electric current. Thanks to the use of this technology, complete control of printing is achieved: the size of the drop, the thickness of the jet, the speed of drop ejection onto the paper, etc. are determined. One of the many advantages of this system is the ability to control the droplet size, which allows for high-resolution prints.

The reliability of the piezoelectric system has been proven to be significantly higher compared to other inkjet printing systems.

The print quality when using piezoelectric technology is extremely high: even universal, inexpensive models allow you to get prints with almost photographic quality and high resolution. Another advantage of printing devices with a piezoelectric system is the naturalness of color rendering, which becomes really important when printing photographs.

The print heads of EPSON inkjet printers have a high level of quality, which explains their high cost. The piezoelectric printing system ensures reliable operation of the printing device, and the print head rarely fails and is installed on the printer, and is not part of replaceable cartridges.

Piezoelectric printing system was developed by EPSON, it is patented and its use is prohibited by other manufacturers. Therefore, the only printers that use this printing system are EPSON.

Thermal inkjet printing technology is used in Canon, HP, Brother printers. Ink is supplied to paper by heating it. The heating temperature can be up to 600°C. The quality of thermal inkjet printing is an order of magnitude lower than piezoelectric printing, due to the inability to control the printing process due to the explosive nature of the drop. As a result of such printing, satellites (satellite drops) often appear, which interfere with obtaining high quality and clarity of prints, leading to distortion. This drawback cannot be avoided, since it is inherent in the technology itself.

Another disadvantage of the thermal inkjet method is the formation of scale in the print head of the printer, since ink is nothing more than a combination of chemicals dissolved in water. The resulting scale clogs the nozzles over time and significantly deteriorates the print quality: the printer begins to streak, color rendition deteriorates, etc.

Due to constant temperature changes in devices using thermal inkjet printing technology, the print head is gradually destroyed (burns out under the influence of high temperature when the thermoelements overheat). This is the main disadvantage of such devices.
The service life of the print head of EPSON printers is the same as the device itself, thanks to the high quality of manufacturing of the PG. Users of devices with thermal inkjet printing will have to buy a new print head each time and replace it, which not only reduces the durability of the printer, but also significantly increases printing costs.
The quality of the print head also matters when using non-original consumables, in particular CISS.

Using Epson CISS allows the user to increase print volumes by 50%.
The print head of EPSON printers, as has been mentioned more than once in this article, is of high quality, due to which an increase in print volumes does not negatively affect the operation of the printer, but on the contrary allows the user to get maximum savings without compromising print quality.

Due to the nature of printing devices using thermal inkjet technology, an increase in printing volumes can lead to failure of the PG printer.

As observations show, to obtain maximum savings with perfect print quality, it is more advisable to use EPSON printing devices with CISS. EPSON printers operate with a continuous ink supply system more consistently than printing devices from other manufacturers.

The differences between these systems are in the method of delivering a drop of ink onto the paper.

Piezoelectric technology was based on the ability of piezocrystals to deform when exposed to electric current. Thanks to the use of this technology, full control of printing is achieved: the size of the drop, the thickness of the jet, the speed of ejection of the drop onto the paper, etc. are determined. One of the many advantages of this system is the ability to control the size of the drop, which allows you to obtain high-resolution prints.

The reliability of the piezoelectric system has been proven to be significantly higher compared to other inkjet printing systems.

The piezoelectric printing system was developed by EPSON, it is patented and its use is prohibited by other manufacturers. Therefore, the only printers that use this printing system are EPSON.

Another disadvantage of the thermal inkjet method is the formation of scale in the print head of the printer, since ink is nothing more than a combination of chemical substances dissolved in water. The resulting scale clogs the nozzles over time and significantly deteriorates the print quality: the printer begins to streak, color rendition deteriorates, etc.

How to choose an inkjet printer | Inkjet Printers | Blog | DNS Club

Laser printers

Electrostatically controlled inkjet printing.

Thermal and piezoelectric inkjet printing comparison – 4apple – looking at apple through the eyes of a geek

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