Working Of Laser Printers
By Roberto Sedycias
Laser Printers are commonly used printers that are known for its rapid printing abilities. The other marked feature of a laser printer is the high quality text and graphics printing. It works basically on the principle of xerographic printing process. However, it is different from the analog photocopying machines in which the image produced is the result of direct scan of a laser beam on the photoreceptor of the printer.
Using a laser printer has a number of advantages over any other types of printers available. The speed of a laser printer varies from one model to another as it depends on a number of factors like the graphic intensity required in processing the job and others. The latest models of laser printers can print more than 200 single color pages in one minute, which is more than 12 thousand pages in an hour! The color laser printers are relatively slower, but even they can print at more than 100 pages per minute. The high speed laser printers are generally used for printing of mass mailings like utility or credit card bills etc.
The cost incurred in using the laser printing technology is dependent on more than one feature such as the cost of the toner, paper, once in a while replacement of the drum, and change required in other consumable parts of the printer like transfer assembly and the fuser assembly. Laser printers having drums made of soft plastic can be costlier in the long run than one can comprehend; its high overall cost becomes apparent only when the printer requires a drum replacement.
Another feature in the family of laser printers is the duplexing model. This allows printing on both sides of a paper without the need to remove the paper at all. This technology can cut paper cost directly into half and also lessen the filling volumes. Formerly, the duplexing technology was available only on the high-end laser printers. However, now they can be seen on a number of mid-range office laser printers. Although, the duplexing technology can reduce the printing speed to some extent as the paper path length increases.
The dot-matrix and inkjet printers take the incoming spooled data for the printer and directly print that on the paper making it a slow process which can stop as soon as the printer is waiting for more data. On the other hand, a laser printer cannot work this way, the reason being the large amount of data required to output to the printer in a continuous fashion. The printer cannot wait for data arrival and if that happens, there can be gaps and misalignment on the page.
To take care of the above problem, a printer buffer is used. The data is built up and kept in the large printer buffer that is generally present in the printer. This data bank is large enough to account for every single dot that can be printed on a page. However, this requirement of storing the dots in the memory before printing can begin has limited the printing capability of laser printers to small size like A4 or A3. Most laser printer cannot print long banners as there is no memory to hold that amount of data.
The printing takes place in seven steps. A Raster Image Processor scans the entire page line by line and stores a bitmap of the page in the raster memory. The drum is then charged negatively and the bitmap is written on the photosensitive drum using a laser beam whose functionality is dependent on the bitmap image. The charged toner particles are charged negatively and wherever the laser has not discharged the drum, the charges will repel and printing won`t take place, hence creating the required print out. The toner contains a plastic powder that is attracted to the parts where the laser beam hit and in the end the plastic powder is fused at 200 degree Celsius to bond the ink with the paper.
About the author
This article can be accessed in portuguese from the Article section of page www.polomercantil.com.br/impressora.php
Roberto Sedycias works as IT consultant for www.PoloMercantil.com.br from http://www.FreeArticlesAndContent.com
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