Basic Printer Types:

Impact vs. Non-impact

There are several major printer technologies available. These technologies can be broken down into two main categories with several types in each:

Impact - These printers have a mechanism that touches the paper in order to create an image. There are two main impact technologies:

• • Dot matrix printers use a series of small pins to strike a ribbon coated with ink, causing the ink to transfer to the paper at the point of impact.

  • Character printers are basically computerized typewriters. They have a ball or series of bars with actual characters (letters and numbers) embossed on the surface. The appropriate character is struck against the ink ribbon, transferring the character's image to the paper. Character printers are fast and sharp for basic text, but very limited for other use.

Non-impact - These printers do not touch the paper when creating an image. Inkjet printers are part of this group, which includes:

• • Inkjet printers, which are described in this article, use a series of nozzles to spray drops of ink directly on the paper.

  • Laser printers, covered in-depth in How Laser Printers Work, use dry ink (toner), static electricity, and heat to place and bond the ink onto the paper.

  • Solid ink printers contain sticks of wax-like ink that are melted and applied to the paper. The ink then hardens in place.

  • Dye-sublimation printers have a long roll of transparent film that resembles sheets of red-, blue-, yellow- and gray-colored cellophane stuck together end to end. Embedded in this film are solid dyes corresponding to the four basic colors used in printing: cyan, magenta, yellow and black (CMYK). The print head uses a heating element that varies in temperature, depending on the amount of a particular color that needs to be applied. The dyes vaporize and permeate the glossy surface of the paper before they return to solid form. The printer does a complete pass over the paper for each of the basic colors, gradually building the image.

  • Thermal wax printers are something of a hybrid of dye-sublimation and solid ink technologies. They use a ribbon with alternating CMYK color bands. The ribbon passes in front of a print head that has a series of tiny heated pins. The pins cause the wax to melt and adhere to the paper, where it hardens in place.

  • Thermal autochrome printers have the color in the paper instead of in the printer. There are three layers (cyan, magenta and yellow) in the paper, and each layer is activated by the application of a specific amount of heat. The print head has a heating element that can vary in temperature. The print head passes over the paper three times, providing the appropriate temperature for each color layer as needed.

Out of all of these incredible technologies, inkjet printers are by far the most popular. In fact, the only technology that comes close today is laser printers.

(tyson n.d.)

(http://ecomputernotes.com n.d.)

 Laser Printers:

The Basics: Static Electricity

The primary principle at work in a laser printer is static electricity, the same energy that makes clothes in the dryer stick together or a lightning bolt travel from a thundercloud to the ground. Static electricity is simply an electrical charge built up on an insulated object, such as a balloon or your body. Since oppositely charged atoms are attracted to each other, objects with opposite static electricity fields cling together.

A laser printer uses this phenomenon as a sort of "temporary glue." The core component of this system is the photoreceptor, typically a revolving drum or cylinder. This drum assembly is made out of highly photoconductive material that is discharged by light photons.

The Basics: Drum

Initially, the drum is given a total positive charge by the charge corona wire, a wire with an electrical current running through it. (Some printers use a charged roller instead of a corona wire, but the principle is the same.) As the drum revolves, the printer shines a tiny laser beam across the surface to discharge certain points. In this way, the laser "draws" the letters and images to be printed as a pattern of electrical charges -- an electrostatic image. The system can also work with the charges reversed -- that is, a positive electrostatic image on a negative background.

After the pattern is set, the printer coats the drum with positively charged toner -- a fine, black powder. Since it has a positive charge, the toner clings to the negative discharged areas of the drum, but not to the positively charged "background." This is something like writing on a soda can with glue and then rolling it over some flour: The flour only sticks to the glue-coated part of the can, so you end up with a message written in powder.

With the powder pattern affixed, the drum rolls over a sheet of paper, which is moving along a belt below. Before the paper rolls under the drum, it is given a negative charge by the transfer corona wire (charged roller). This charge is stronger than the negative charge of the electrostatic image, so the paper can pull the toner powder away. Since it is moving at the same speed as the drum, the paper picks up the image pattern exactly. To keep the paper from clinging to the drum, it is discharged by the detac corona wire immediately after picking up the toner.

The Basics: Fuser

Finally, the printer passes the paper through the fuser, a pair of heated rollers. As the paper passes through these rollers, the loose toner powder melts, fusing with the fibers in the paper. The fuser rolls the paper to the output tray, and you have your finished page. The fuser also heats up the paper itself, of course, which is why pages are always hot when they come out of a laser printer or photocopier.

So what keeps the paper from burning up? Mainly, speed -- the paper passes through the rollers so quickly that it doesn't get very hot.

After depositing toner on the paper, the drum surface passes the discharge lamp. This bright light exposes the entire photoreceptor surface, erasing the electrical image. The drum surface then passes the charge corona wire, which reapplies the positive charge.

Conceptually, this is all there is to it. Of course, actually bringing everything together is a lot more complex. In the following sections, we'll examine the different components in greater detail to see how they produce text and images so quickly and precisely.

Inside an Inkjet Printer

Parts of a typical inkjet printer include: Print head assembly:

• • Print head - The core of an inkjet printer, the print head contains a series of nozzles that are used to spray drops of ink.

  • Ink cartridges - Depending on the manufacturer and model of the printer, ink cartridges come in various combinations, such as separate black and color cartridges, color and black in a single cartridge or even a cartridge for each ink color. The cartridges of some inkjet printers include the print head itself.

  • Print head stepper motor - A stepper motor moves the print head assembly (print head and ink cartridges) back and forth across the paper. Some printers have another stepper motor to park the print head assembly when the printer is not in use. Parking means that the print head assembly is restricted from accidentally moving, like a parking brake on a car.

  • Belt - A belt is used to attach the print head assembly to the stepper motor.

  • Stabilizer bar - The print head assembly uses a stabilizer bar to ensure that movement is precise and controlled.

Paper feed assembly:

• • Paper tray/feeder - Most inkjet printers have a tray that you load the paper into. Some printers dispense with the standard tray for a feeder instead. The feeder typically snaps open at an angle on the back of the printer, allowing you to place paper in it. Feeders generally do not hold as much paper as a traditional paper tray.

  • Rollers - A set of rollers pull the paper in from the tray or feeder and advance the paper when the print head assembly is ready for another pass.

  • Paper feed stepper motor - This stepper motor powers the rollers to move the paper in the exact increment needed to ensure a continuous image is printed.

  • Power supply - While earlier printers often had an external transformer, most printers sold today use a standard power supply that is incorporated into the printer itself.

  • Control circuitry - A small but sophisticated amount of circuitry is built into the printer to control all the mechanical aspects of operation, as well as decode the information sent to the printer from the computer.

  • Interface port(s) - The parallel port is still used by many printers, but most newer printers use the USB port. A few printers connect using a serial port or small computer system interface (SCSI) port.

Heat vs. Vibration

• • Different types of inkjet printers form their droplets of ink in different ways. There are two main inkjet technologies currently used by printer manufacturers:

  • Thermal bubble - Used by manufacturers such as Canon and Hewlett Packard, this method is commonly referred to as bubble jet. In a thermal inkjet printer, tiny resistors create heat, and this heat vaporizes ink to create a bubble. As the bubble expands, some of the ink is pushed out of a nozzle onto the paper. When the bubble "pops" (collapses), a vacuum is created. This pulls more ink into the print head from the cartridge. A typical bubble jet print head has 300 or 600 tiny nozzles, and all of them can fire a droplet simultaneously. Click the button to see how a thermal bubble inkjet printer works.

  • Piezoelectric - Patented by Epson, this technology uses piezo crystals. A crystal is located at the back of the ink reservoir of each nozzle. The crystal receives a tiny electric charge that causes it to vibrate. When the crystal vibrates inward, it forces a tiny amount of ink out of the nozzle. When it vibrates out, it pulls some more ink into the reservoir to replace the ink sprayed out.

Impact Printers

 With this type of printer something strikes paper & ribbon together to form a character, like a typewriter.

Types of Impact Printers

Thermal Printers - How Do Thermal Printers Work?

Your average home user will probably never own a thermal printer. One of today’s primary uses of thermal printers are in businesses or stores that need a POS (point of sale) receipt printer. Some offices may have thermal technology in their fax machine or MFP.

Thermal printers work in one of two ways, for older models heat sensitive paper is used by placing a roll in a container inside the machine and the end of that roll is stuck into a slot. The heat that has built up in the machine reacts with the heat-sensitive paper and the pigments transfer the image to the sheet.

For newer machines, they use ribbon printer cartridges. Inside of the ribbon cartridge there is a waxy material stored inside. When the printer is in use, paper is fed through the a slot located between the print head and a roller and the heat then melts the substance and sticks it onto the paper.

Despite their reputations as solely special use printers, thermal printing does have some distinct advantages. The first advantage is in the price; thermal printers are fairly inexpensive. Second, thermal printers by and large are easy to use. Usually to run a thermal printer it is just a combination of a few buttons and that’s all. A third advantage is that they are quiet printers so they won’t disturb customers or office co-workers.

Others will argue that the disadvantages outweigh the advantages. For one thing, thermal printers are not extremely efficient when it comes to using ink. Because these machines rely on heat to operate, if the machine becomes too hot while in use more ink will come out. This ties into the second problem which is prints that are not always precise. Thermal prints are prone to smudges, even from the heat given off by a person’s fingers can trigger a reaction from the paper. The third disadvantage with thermal printers is the fact that they are almost exclusively monochrome printers. The majority of the ink used with thermal printers is carbon pigmented ink which does not work well with color. For thermal printers to use colors, they utilize more wax based cartridges. The final disadvantage of thermal printers is also related to heat. The high heat used in the printing process can be harmful to the printhead, costing owners money to repair the machine when it breaks down.

 (http://www.castleink.com n.d.)

Xerox Solid Inkjet Printers, also known as phase-change printers, are unique since they represent a ink technology not used by any other manufacturer. As always, pros and cons exist for all printer technologies with solid ink printer as no exception.

Article chapters:

1. How Solid Ink Printers Work

2. Solid Ink Printers - Pros and Cons

How Solid Ink Printers Work

Solid ink technology was first developed by a company called Tektronix which was later bought up by Xerox in the year 2000.

A solid ink printer is based on a simple technical design consisting of three major components:

• • a maintenance roller applying oil to the print drum

  • a printhead transferring ink to the print drum via 1,236 nozzles jetting more than 30 million ink drops per second.

  • a print drum transferring the image to the paper

The printing process looks as follows:

• 1. The maintenance roller applies a layer of silicone oil to the heated drum for reliable ink release

  2. The printhead applies all colors at the same time on the rotating drum.

  3. A sheet of paper is rapidly fed between the rotating drum and a transfix roller, transferring the ink to the paper.

  4. The ink penetrates and solidifies very fast with the paper minimizing the risk for smearing problems. The ink fuses with the paper by heat and pressure.

  5. If the printer is set to print in duplex, the paper is feed back into the duplex paper path. The paper takes one more turn in the printer and gets printed on the other side.

Solid Ink Printers - Pros and Cons

Below listing is based on the comparison with standard inkjet and laser printers. As for buying and operation costs, solid ink printers can be compared to the costs of owning a laser printer.

Solid ink printers are generally Strong in the following areas:

• • Eco friendliness, read more about this in our solid ink sticks article. Tip: Read more about Green Printing!

  • Few parts lowering the maintenance cost and creating a reliable printing process

  • Capable of handling more paper types and thicknesses compared to laser and inkjet printers. Examples of media to use is recycled paper, envelopes and transparencies

  • Excellent print quality with vivid colors

  • Fast printing (when the initial warm up is done)

  • Ease of use, all ink color sticks have different forms making it impossible to insert them in a wrong way

Solid ink printers are generally Weak in the following areas:

• • Lengthy warm up time that in worst case can take 3-5 minutes.

  • As with inkjet printers, printheads can become clogged. To clean them a cleaning program needs to be run which might drain the ink sticks.

  • The printer can’t be moved around without the running of a special cooling program that cools the melted wax. Failure to do so can damage the printer.

  • High power consumption due to the nature of the technology requiring that several parts of the printer must be heated to a temperature that is close to the melting point of the ink. If the printer is set to low power mode a warm up period is needed again to get the printer print ready.

  • Printouts are harder to interact with if you have the need to make notes on them with a pencil. This due to the wax that repel pencil ink.

(http://www.inkguides.com n.d.)

3D Printers

A 3D printer cannot make any object on demand like the "Star Trek" replicators of science fiction. But a growing array of 3D printing machines has already begun to revolutionize the business of making things in the real world.

3D printers work by following a computer's digital instructions to "print" an object using materials such as plastic, ceramics and metal. The printing process involves building up an object one layer at a time until it's complete. For instance, some 3D printers squirt out a stream of heated, semi-liquid plastic that solidifies as the printer's head moves around to create the outline of each layer within the object.

The instructions used by 3D printers often take the form of computer-aided design (CAD) files — digital blueprints for making different objects. That means a person can design an object on their computer using 3D modeling software, hook the computer up to a 3D printer, and the watch the 3D printer build the object right before his or her eyes.

(Hsu 2013)