PRINTING PAPER

2/1/2002

Printing Paper: General purpose computer printing uses three major technologies -- impact, ink jet, and laser. Each imposes some limitations on the material printed upon.

Impact printing: The principal issue with impact printing is paper handling. The principle use of impact printing in the 21st Century is printing multipart forms and labels. This material is generally continuously fed -- often using tractor feed holes on the edges. The major issue is proper spacing of the head and platen. Mispositioning can result in poor printing, torn ribbons, torn paper, ripping the paper off the tractor feeds, or head jamming. In addition, peel off labels can peel off and jam the printer. This is less of an issue with bottom feed configurations that have a fairly straight paper path than with rear feed configurations. Removing jammed labels is simple in some printers, quite difficult in others.

Inkjet Printing: Inkjets are notoriously unfussy about what they print on. Early inkjets had difficulty with long fibre papers that are widely used in offices wicking the ink to undesired places resulting in fuzzy print. This is generally not an issue with modern inks. Most problems with inkjet printing come from the use of curved paper paths to make printers more compact. In general, the issues are similar to those of laser printers, but less severe. The use of peel off labels in inkjets with a curved paper path is possibly a poor idea. Inkjet paper feed mechanisms are often difficult to disassemble. Removing a jammed label requires disassembly.

Laser Printing: Laser printers are designed for high volume, low cost printing. The are generally configured as sheet feeders. To accommodate the high volume requirement, paper feed mechanisms often are designed to work with narrow range of paper thicknesses, sizes, and materials. The paper in a laser printer will typically follow a twisted paper path moved by a number of rollers and passing through two areas -- image transfer and fuser -- where the paper thickness is important. It is important that paper, transparencies, etc used in laser printers have the proper thickness, weight, and slickness. The most common problem with laser printing is paper jams. These can be caused by using material that is too thick, too thin, too slippery, too damp, electrostatically charged, etc, etc, etc. Even when everything appears to be right, laser printers may not work well with expensive coated, embossed, or "laid" papers unless they are specifically designed for laser printer use. The heated fuser rollers have been known to alter or remove colored inks in preprinted letterheads. In the case of unusual materials like envelopes and transparencies, it is often best to single feed the sheets using the simplest possible paper path.

Paper consists of a mat of cellulose fibre impregnated with a filler. If large amounts of clay or calcium carbonate mixed with a whitener are used in the filler, the paper is called "coated". But even uncoated papers use a filler and usually have a top and bottom side. For example, watermarks may only be visible from one side. In the case of "copier" paper (an "uncoated" paper), one side is smoother than the other. When using copier paper, it can be necessary to check the arrow on the paper package and put the paper in properly oriented. Failure to do so can put the paper's smoother side against feed rollers that work better with the rougher side. In addition, the paper has a natural curl which the arrow also reflects. Printers are designed to allow for the curl and will feed less well when the curl is inverted.

Envelopes stored in a humid airspace can weld themselves shut when fed through a laser printer. This can be cured by inserting a sheet of copier paper under the flap, but that results in a four sheet plus glue stack of material that is likely to be thicker than the printer is designed to use.

http://cp.ru/goods/Inform/prl/books/07-chp7.html#Pape

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