7.1 Printer types, characteristics & Connection methods

Exposing phase (laster printers)

A laser beam changes the charge on the surface of the drum in a pattern of the page's image.

USB connection

Most printers use a USB connection, allowing for configurations that also include scanners, external drives, or additional printers. The USB connection increases speed considerably over a standard serial or parallel port. A smaller number of printers that use a FireWire interface are also available.

When purchasing a printer, consider the following factors:

*-Connection interface:*Make sure that the printer you choose has an interface supported by your computer. The two most common interfaces in modern printers are USB and network interfaces. *-Print quality:* Often measured in dots per inch (DPI). The higher the DPI, the higher quality the image. *-Print speed:* Expressed as the number of pages that can be printed in a minute (PPM or pages per minute). Printers often rate both the black and white and color print speeds. *-Memory:* Printers can improve performance by having significant built-in memory. Additional memory improves performance and reduces the processing load on computers. In some cases, you can add or upgrade the memory in a printer. *Printers can include additional features such as:* -Additional paper sizes -Double-sided (duplex) printing -Document or sheet feeders -Built-in scanners, copiers, or faxing capabilities -Automatic collation or stapling -Color printing -Built-in network support -Built-in hard drives or memory for storing and recalling printed documents

By making a printer accessible on the network, you allow multiple devices to share a single print device. Network printing uses the following 3 special processes and components:

*1) The client application* generates the print job on the local system. This process is known as spooling. 2) The print job is sent to a *print queue.* The queue is a location for storing waiting for print jobs. 3) A print server is responsible for managing the flow of documents from the queue to the printer. When the printer is ready, the print server takes the next document out of the queue and sends it to be printed.

Dye-sublimation printer (digital photo printer)

*A non-impact* printer that uses film-embedded dye. -The print head heats and passes over the film, causing the dye to vaporize and soak into the film paper. -Dye sublimation printing prints in transitioning colors rather than pixels. -Produces photographic quality images.

Thermal printer

*A non-impact* printer that uses heat to cause a reaction on specially treated paper. -Monochrome thermal paper is chemically treated to darken where heated (photosensitive). Many cash registers use this type of printer for creating receipts. -Color thermal paper is chemically treated to absorb color from a ribbon when heated. -Ink is applied using the ribbon in a similar manner to a solid ink printer. -The color system used by thermal printers is CMYK (cyan, magenta, yellow, and black). -The paper must make one pass for each application of a different color. -The feed assembly takes the thermal paper off the roll and it sends it through the printer to the outside of the printer. -Color thermal printers are very expensive, high quality, and operate quietly.

Dot-matrix printer

*An impact printer that transfers characters by striking a pattern (from a matrix) through an inked ribbon and onto paper.* -The most common number of pins on a dot matrix printer is 9, 18, or 24, with more pins providing a higher resolution. 24-pins create a near-letter quality print and anything with less than 24-pins provides a draft quality print. The overall print quality of a dot matrix printer is quite poor when compared to that of other types of printers. -The speed of dot matrix printers is measured in characters per second (CPS). Common speeds for a dot matrix printer are 32 to 72 CPS. -Dot matrix printers operate in either a font (letters, numbers, and symbols) or dot-addressable (graphs and charts) mode. -Dot matrix printers can use either a friction feed or a tractor feed system to move paper through the printing assembly. -Because dot matrix printers strike the image onto paper, it is a good printer to use when carbon-copy documents are being printed. -The print head can become dangerously hot due to pin friction. -Dot matrix printers can be loud because printing takes place by pins physically striking the ink ribbon, paper, and the platen (a metal plate behind the paper).

Wireless connection

*Many printers allow you to connect using a wireless connection. This is especially useful when working with laptop computers.* -Bluetooth is a wireless technology for creating simple connections between two devices. Unlike infrared, line-of-sight connections are not required. -802.11a/b/g wireless standards use radio waves and are used to create wireless networks between multiple devices.

inkjet printer

*Quiet non-impact printers with ink stored in a reservoir. Bubble jet printers are the most popular form of inkjet printers.* -The ink reservoir is in a disposable cartridge that includes the printing mechanism. -Bubble jet printers print by heating the ink and squirting it through tiny nozzles in the print head and onto the paper. -The crispness of an inkjet printer's image is usually rated as dots per inch or dpi. Inkjets range from 150 to over 1400 dpi. -A new generation of inkjet printers produce photo-quality printouts when used with photo-quality paper. -Photo-quality inkjet printers mix up to 16 drops of ink to form a single dot of color on the page. -Inkjet printers feed single cut sheets of paper, from a feed tray, by clamping them between rollers and advancing them one print line at a time, from top to bottom, and then placing the newly printed paper into a tray, other than the feed tray. -Inkjet printers are an inexpensive way to produce color printouts.

Solid Ink Printer

*Solid ink printers melt ink onto the print head (which is as wide as the paper). The head jets the melted ink onto the paper as the paper passes by on the print drum (similar to the laser printing process).* *Solid ink printers offer the following advantages:* -Simple design & Excellent print quality -Easy setup and maintenance -The head takes as long as 15 minutes to heat prior to printing.

Laser printers share the following components:

-Laser printers use a laser and electrical charges to transfer images to paper. -Laser printers move paper through the printer via motorized rollers. -Each laser printer has a high-voltage power supply to charge the drum. This power supply converts AC current into higher voltages required for the printing process. -Each laser printer has a DC power supply to operate most of the electronic components inside the printer. -Each laser printer has a controller, which is a circuit board that acts like a motherboard in the printer. This controller board makes it possible for the printer to have and add its own memory. -Laser printers are classified as *page printers* because they print text and graphics simultaneously one complete page at a time. -Laser printers use a laser to charge a metal drum. The drum picks up plastic toner, and the toner is then fused onto the paper (using rollers and heat). -Of all the types of printers discussed in this course, laser printers have the highest print quality. -A duplexing assembly is required to print two-sided output on a laser printer. Many inkjet printers also use duplexing assemblies to print two-sided paper. Duplexing assemblies are typically mounted on the back of a laser or inkjet paper. -A transfer belt is used on some high-end color laser printers. Colors are applied to the transfer belt and then to the paper. This step is repeated for different colors. -The layout of physical parts in laser printers can vary greatly, however, the basic process remains the same.

Network connection

Some printers also have their own network interface card, which allows them to connect directly to a network. Network printers can also be connected to a computer that is connected to the network. Another way to connect a non-network-ready printer to a network is with a network interface device. Network printers are useful for allowing multiple people to share the same printer. This is a common way to connect printers used in a business environment.

Cleaning phase (laster printers)

The cleaning phase prepares the drum by removing the previous image printed. It uses a rubber-cleaning blade to remove any excess toner on the drum and then it scrapes off the debris into a debris cavity. Next, a heat roller is lubricated to ensure that enough heat will be evenly applied to transfer the next image printed. Then an electrostatic erase lamp neutralizes the electrical charges that remain on the drum from the previously printed image.

Developing phase (laster printers)

The developing roller applies toner to the drum. The toner sticks to the charged areas on the drum.

Fusing phase (laster printers)

The fusing assembly attaches the toner to the paper using rollers that press and melt the toner to the paper. As the paper leaves the printer, a static eliminator strip removes the static charge from the paper.

Charging phase (laster printers)

The primary corona prepares the photosensitive drum for writing by causing it to receive a negative electrostatic charge. Depending on the printer, the primary corona will be wires or rollers.

Processing phase (laster printers)

The printer receives a document to be printed from the connected computer and converts it into a bitmap raster image, which is divided into horizontal raster lines.

Transferring phase (laster printers)

The transfer roller charges the paper to attract the toner.