Different Types of Presses… ask and discuess
Types of paper feed
“Sheet-fed” refers to individual sheets of paper or paperboard being fed into a press. A lithographic (“litho” for short) press uses principles of lithography to apply ink to a printing plate, as explained previously. Sheet-fed litho is commonly used for printing of short-run magazines, brochures, letter headings, and general commercial (jobbing) printing.
“Web-fed” refers to the use of rolls (or “webs”) of paper supplied to the printing press. Offset web printing is generally used for runs in excess of 5 or 10 thousand impressions. Typical examples of web printing include newspapers, newspaper inserts/ads, magazines, catalogs, and books. Web-fed presses are divided into two general classes: “Cold” or “Non-Heatset,” and “Heatset” offset web presses, the difference being how the inks that are used dry. Cold web offset printing dries through absorption into the paper, while heatset utilizes drying lamps or heaters to cure or “set” the inks. Heatset presses can print on both coated (slick) and uncoated papers, while coldset presses are restricted to uncoated paper stock, such as newsprint. Some coldset web presses can be fitted with heat dryers, or ultraviolet lamps (for use with uv-curing inks). It is also possible to add a drier to a cold-set press. This can enable a newspaper press to print color pages heatset and black & white pages coldset.
Web press v. sheet-fed (photo offset)
Sheet-fed presses offer several advantages, because individual sheets are fed though, a large number of sheet sizes and format sizes can be run through the same press. In addition, waste sheets can be used for make-ready which allows for lower cost makereadies, so that good paper is not wasted while setting up the press, for plates & inks (waste sheets do bring some disadvantages as often there are dust, offset powder particles that transfer on to the blankets and plate cylinders, thereby creating imperfections on the printed sheet in the form of “hickies”).
Web-fed presses, on the other hand, are much faster than sheet-fed presses, with speeds in excess of 20,000 cut-offs per hour. Their speed makes them ideal for large runs such as newspapers or magazines. However, web-fed presses have a fixed cut-off, unlike rotogravure or flexographic presses.
Types of commercial offset processes
A perfecting press, also known as a duplex press, is one that can print on both sides of the paper at the same time (Bruno, Romano, and Riordan 137). Web and sheet-fed offset presses are similar in that many of them can also print on both sides of the paper in one pass, making it easier and faster to print duplex.
Small offset lithographic presses that are used for fast, good quality reproduction of 1- and 2-color copies in sizes up to 12”X18”. (Romano, & Riordan 139–141) Popular models were made by A.B. Dick, Multilith, and the Chief and Davidson lines made by A.T.F./Davidson.
Offset duplicators are made for fast and quick printing jobs; therefore have faster make-readies and turn-around time, printing up to 12,000 impressions per hour.
They are able to print business forms, letterheads, labels, bulletins, postcards, envelopes, folders, reports, and sales literature.
In sheet-fed offset, “the printing is carried out on single sheets of paper as they are fed to the press one at a time.” Sheet-fed presses use mechanical registration to relate each sheet to one another to ensure that they are reproduced with the same imagery in the same position on every sheet running through the press. (“What is Offset Printing”)