Non-Impact Printers

Non-impact printers are those printers which can print characters, number or images without any physical contact between any striking devices and papers. Since these types of printers do not require hammering action to print any character, they do not produce any noise while printing. These types a any printers can give high quality of print at a very fast rate. They can print around 24 pages in a minute.

The most common examples of non-impact printers are:

• Laser printer
• Inkjet printer
• Thermal printer

 

Laser printer

Laser printer is a type of non-impact printer in which a laser beam is use to print a character or an image on the paper. Gary Starkweather developed the laser printer in the year 1971 at Xerox PARC. A laser printer operates a very fast speed and it does not produce sound while printing

Basic components of a laser printer are:

• Toner cartridges
• Imaging Drum
• High-voltage control supply DC control supply
• Paper-transport assembly
• Exchange corona assembly
• Fusing assembly
• Printer controller assembly
• Ozone Filter
• Duplexing assembly

 

 

 

Toner cartridge: Toner cartridges contain the toner particles. These particles are some powders that are used for creating texts and images. It is required’ to replace the toner cartridge from time to time when the toner runs short and the quality of printing becomes poor.

Imaging drum: Imaging drum is an important component that is used to transfer the toner particles from the reservoir to the paper. The drum consists of a photosensitive material which holds a static charge when it is dark but can’t hold a charge in light.

When we send a text or image to a laser printer for printing, it is converted into neutral dots. Then the electrostatic charge containing the text or images to be printed is sent to the imaging drum through a primary charge roller called as corona wire.

Later the imaging drum passes over the toner particles and the charged lines pick up the tonner particles and are transferred to the sheet of the paper where they melt and set into the paper. Finally, when the next images or text is required to be printed, an alternating current is sent to the drum which will remove all the residue of the previous image or text and the same process continues.

High-Voltage Control Supply (HVCS): High-voltage control supply (HVPS) offers high voltages used in the processing stage of printing. The segment shifts AC current from a standard divider outlet (120V and 60Hz) to a higher voltage which can be used by the printer. This high voltage empowers the charging corona and the transfer corona.

 DC control supply: The high voltage which is utilised as a part of the electro photographic procedure cannot regulate alternate segments in the printer. i.e., the logic circuit and motors. The logic circuit and motors need low voltage, amongst +5VDC and +24VDC. The DC Power Supply (DCPS) changes over house current into three voltages: +5VDC, -5VDCand +24VDC. +5VDC and -5VDC are used for the logic circuitry and +24VDCfor the paper- transport engines. This part runs the fan that cools the interior segments of the printer.

Paper-transport assembly: The paper-transport assembly is in charge of shifting the paper through the printer. It contains an engine and a few rubberised rollers that play out alternately. The primary type of roller found in many laser printers is the feed roller or paper-pickup roller. This D-molded roller, when actuated, spins against the paper and pushes the paper into the Printer. This roller then works synchronously with an extraordinary elastic rubber separator cushion to ensure that only one sheet is offered into the printer. A second type of roller used is called as the registration roller. There are mainly two registration rollers that work together. These rollers synchronise the paper development with the picture arrangement preparation in the electro photographic cartridge. The rollers don’t offer the paper beyond the electro photographic cartridge unless the cartridge is prepared for it. Both rollers are functional with an exceptional electric engine called electronic stepper engine. This kind of engine can move precisely. It controls both the fuser rollers and a majority of paper-transport rollers.

 Exchange corona assembly: When the laser composes the pictures on the photosensitive drum, the toner sticks to the unexposed zones. There are two kinds of exchange corona assemblies: one carries the wire and the other contains a roller. The exchange corona wire is small in diameter and gets charged by the HVPS. The wire is placed in a notch on the floor of the laser printer. Since the exchange corona roller is directly in touch with the paper, its speed is high. That is why; the exchange corona wire is rarely used in printers now-a-days.

Fusing assembly: Since the toner in the electro photographic toner cartridge has a negative static charge as compared to the objects having net positive charge, the electro photographic toner cartridge will stick to anything. These toner particles can be brushed to get them removed from the object across the page. But, if the user wants the image to stay permanently it can be a problem. In order to solve this issue, electro photographic laser printers include a device known as a fuser. The fuser has two rollers that exert pressure and heat to fuse the plastic toner particles to the paper. Due to the fuser, pages from either a laser printer or a copier turn out warm. The fuser contains three principal portions: a halogen heating lamp, a teflon-coated aluminium-fusing roller and a rubberised pressure roller. The fuser heats the fusing roller between 329° F (165° C) to 392° F (200° C) with the help of the halogen lamp. The pressure roller pushes the paper against the roller when the paper passes between the two rollers which softens the toner into the paper.

Printer controller assembly: Printer controller assembly is a large circuit board which helps in converting computer signals into various assemblies’ signals using rasterizing. It is normally attached under the printer. At the point when a PC gives the print command to a laser printer, it sends a signal through a cable to the printer controller assembly. The printer controller assembly then arranges the data into a page of line-by-line charges for the laser scanner. Then the controller sends instructions to each component and alerts it and starts the electro photographic printing.

Ozone filter: Personal laser printer uses different high-voltage inclinations. High voltages create ozone which is a synthetically responsive gas. In, a laser printer, it is created by high-voltage coronas. Since ozone is synthetically receptive or chemically reactive and it depletes the longevity 01 various parts of the laser printer, the earlier versions of laser printers used to include a channel to expel ozone gas from within the printer at the time of manufacturing. However, the channel was required to be removed and cleaned with compressed air frequently. Newer laser printers do not contain ozone channels. This is because these printers use exchange corona rollers, which drastically lessen ozone leakage.

Duplexing assembly: Now-a-days most of the laser printers can print on both sides of the paper. This is possible due to a feature called duplexing assembly. Generally, it is situated inside or on the back of the printer. The duplexing assembly takes the paper, turns it over and feeds it again into the printer to print on the other side. The imaging process of a laser printer consists of the following seven stages:

• Processing
• Charging
• Exposing
• Developing
• Transferring
• Fusing
• Cleaning

 

Processing: The two important functions of the processing stage are getting and generating the image or text. The print task is conveyed to the laser printer by the computer system through various interfaces like USB, wireless, etc. Then the raster is manufactured by Raster Imaging Processor (RIP) which generates the image of the final sheet in the memory. The process of raster creation is based on the page explanation language that the system is using, such as PostScript (PS), Printer Control Language (PCL), etc. Then the collection of lines is written to the photosensitive drum and onto the sheet.

Charging: In this process, a special kind of wire or roller called as charging corona that resides inside the toner cartridge and above the photosensitive drum receives high voltage from the High-Voltage Control Supply (HVPS). It utilises this high voltage to implement a powerful, evenly distributed negative charge (around —600VDC) to the surface of the photosensitive drum.

Exposing: The exposing stage is also called as writing. In this process, the drum is exposed to the images or text to be printed. When the drum rotates the laser reduces the charge and the places where the laser beam touches, the photosensitive drum’s charge is severely minimised from —600VDC to a bit negative charge (around —100VDC). As the drum spins, a pattern of exposed areas is formed which demonstrates the image to be printed.

 Developing: In this stage, the surface of the drum captures an electrical demonstration of the images to be printed. In this process, the toner is shifted to the localities or spots which are manifested in the writing step. Then a metallic roller called as developing roller receives a -600VDC charge from HVPS. The toner of the printer is attached to this metallic roller with the help of a magnet which is situated inside the roller. When the developing roller spins towards the photosensitive drum, the toner perceives the charge of the roller (i.e., -600VDC). When the toner arrives between the developing roller and the photosensitive drum, the toner is pulled towards the spots that have fallen under the laser as they have a lesser charge, -100VDC. The toner is also refrained from the spots which are unexposed to laser because they have the same -600VDC charge and a similar charge repels. This toner shift creates a smog of toner between the drum and the developing roller. Now the photosensitive drum has an attached toner with it where the laser has inscribed. The photosensitive drum goes on spinning until the developed image is ready to be moved to the sheet in the next step.

Transferring: This stage deals with developing the picture and its rotational positions. The controller informs the registration rollers about the feeding of sheets. The registration rollers pass the sheet under the photosensitive drum and the procedure of carrying through the image starts.

The controller relays an impulse to the charging corona wire or roller and asks to switch on. The corona wire/roller then receives a powerful positive charge (+600VDC) and implements that charge to the sheet. When the sheet is charged, the paper draws the toner from the photosensitive drum. Because of the opposite charges of sheet and toner; the paper gets aligned with the line of contact between the roller and paper. When the registration rollers move the sheet beyond the corona wire, the static-eliminator strip eliminates all charge from that line of the sheet. But in case the strip didn’t remove the charge away, the sheet would draw itself to the toner cartridge which would create jams of sheets. The toner will then place in the appropriate position by weak electrostatic charges and gravity. It will not remain at that position unless it is made permanent, which is the objective behind the fusing process.

Fusing: In this stage, the paper is pushed by the rollers toward the fuser rollers. Once the fuser gets the paper, the registration rollers push the paper for some more time. The fuser now regulates the moving paper. When the Paper runs across the fuser, i the 350° F fuser roller make the polyester resin of the toner melt and the rubberised pressure roller pushes it permanently into the paper. The paper still goes through the fuser and gradually leaves the sensor that printer. When the sheet entirely leaves the fuser, it trips commands the printer to complete the electro photographic method with the cleaning process.

Cleaning: There is a rubber blade situated inside the electro photographic cartridge which is used to omit any residual toner left Oil the drum. Then a fluorescent lamp discharges the remaining charge on the photosensitive drum and this process is termed as cleaning. The electro photographic cartridge cleans the drum without any break. It may need more than one spin Of the Photosensitive drum for creating a picture on the paper the method of wiping and cleaning refreshes the drum for each use if the drum remains unclean, the spirits of past pages would get printed with the current picture.

 

Inkjet Printer

Inkjet printer is a type of non impact printer that prints by spraying ionised ink on the sheet of the paper. This type of printer is less costly than laser printer and it can produce a resolution of 300 dpi. In this type of printer, the ink stored in a disposable cartridge and for each major colour separate cartridge s is used. Colour print is generally done in this printer by combining four inks i.e., Cyan, Magenta, Yellow and Black which is commonly known as CMYK. Inkjet printers are also referred as bubble-jet printers.

Inkjet printer contains fewer components as compared to the laser or impact printers. The assembling of an inkjet printer is less expensive. A typical inkjet printer consists of the following parts:

• Print head or ink cartridge
• Head carriage, Belt and Stepper Motor
• Paper feed mechanism
• Control, interface and power circuitry

Print head or ink cartridge: The print head is the most visible part of the inkjet printer. Ink is sprayed in small droplets on the page by the small in the printer. The reservoir ink is placed in a removable package in the Print head. Each print head consists of CMYK (cyan, magenta, yellow, and black) print patterns. The ink cartridge must be changed when it runs out of ink. There are small chambers inside an ink cartridge. Each chamber consists of a metal plate and a tube to lead the ink out to print. The bottom of each Chamber has a pinhole which is used to Spray ink on the paper.

Head carriage, belt and stepper motor: Head carriage, belt and stepper motor are the devices which keep the printer moving while printing. The head carriage in an inkjet printer which is electronically as well as physically well connected with the print head and also with the ink reservoir. Small clips are used to keep the electronic connections and ink cartridge in place. These connections are responsible for the nozzle to fire. The belt and the stepper motor is responsible for the movement of the head carriage. Whenever the stepper is activated it makes some small movements. This makes it easier to move in the same position in as much time as it wants. Stepper motor is also referred to as a carriage motor

Moreover, the print head carriage connected to the belt is moved by pulleys. The carriage belt is moved by the carriage motor and is responsible for moving the print head from place to place for printing. Apart from that there is a small metal stabiliser installed near the head carriage just to keep it stationary when not in use.

Paper feed mechanism: The paper feed. mechanism is the process to pick the paper from the drawer and place it into the printer. There are different functionalities involved in this. At first, the pickup rollers which are made of rubber rub against the surface of the paper and place it into the printer. These pickup rollers work against the separator pads to keep the paper stable and in position.

In large and expensive printers, there are paper trays which are used to hold the papers until they are fed into the printer. But in portable or smaller printers, papers are generally placed in a paper feeder vertically. The paper fed mechanism consists of a paper feed sensor which takes care of all the papers waiting to get printed. This sensor prevents any jamming or interruption during the paper feed.

Control, interface and power circuitry: The stepper motors are operated with small circuit board present in the printer control circuits. This includes and the functionality of loading the paper, moving the print carriage back and ON/OFF of the system. These circuits are used for connecting the printer to the PC and managing the health of the printer.

There is an interface circuitry where all the physical connections are made the from the PC like serial, USB, Network, etc. It is responsible for converting interface signals to data streams.

There is also a power circuitry. The power circuit converts 220V or 110V into standard voltage of 12V and 5V that most of the inkjet printers use and a distributes the voltage to other devices that the printer is connected with. A transformer of 110V AC is used to accomplish this task. It converts 110V AC into 12V DC.

Calibration: By calibration we mean how the printer stands up to all its functional specifications. Before using an inkjet printer, it is necessary to make sure that the printer is fully calibrated otherwise you may get irrelevant Printout. For example, if the print heads of an inkjet printer are not aligned then unstructured, unevenly spaced letters will get printed. Calibration is done to make sure that everything is in control before printing. It is a routine check-up and must be done every time new cartridges are installed. It is a phenomenon which is initiated manually.

Thermal printer

Thermal printers are those printers that use heat for printing images and text. This type of printing is generally used in several POS terminals and facsimile machines. It is also used to print labels, barcodes, safety signs, etc. In this process of printing the ink is not sprayed through nozzle, rather it uses heating elements to transfer the pigments. Printing in thermal printer is inexpensive and does not produce sound while printing. That is why it is highly used in printing receipts and bills. The two types of thermal printing are:

Direct thermal: In direct thermal printer, images or text are printed by burning dots when it moves over the heating elements. In this type of printing, ink, tonner or ribbon are not used for printing. It is mainly used to print receipts and shipping labels.

Thermal wax transfer: In thermal wax transfer, a thermal transfer ribbon consisting of wax-based ink is used to print images or text. In this process using a thermal print head heat is applied on the ribbon in which the ink melts and gets transfered to the paper. The ink gets marked permanently onto the Paper when it cools.

Feed assembly: The feed assembly of thermal printer is the same as that of the laser and inkjet printer. Feed assembly is used to get the paper in easily and also to take out of the paper from the printer.

Heating elements:  There is a heating element in thermal printer. This heating element is responsible for heating up the printer. It heat many part of the printer. There is a long strip in the thermal printer and the heating elements heat up some parts of the strip. When the paper are passed through those parts in which the heat strikes on the paper, the papers hot while printing.