WHAT IS DESIGN FOR PRINT?//PRESENTATION & RESEARCH//OUGD504

NOTES FROM PRESENTATION:

DESIGN FOR PRINT AND WEB PRESENTATION:

PRACTICAL TECHNICAL ECONOMICAL

types of printing: rotary printing, digital printing, screen printing, pad printing

ROTARY PRINTING:

three types of printing: offset lithography, rotogravure, flexography

OFFSET LITHOGRAPHY: not printed directly-aliminium  (wrapped around cylinder)

WEB OFFSET MACHINE: high speed, run on rolls not sheets, folding built in.

Detailed printing e.g stamps

ROTOGRAVURE PRINTING:

copper plates (with mirror image) transfers ink directly to print surface, usually on rolls, durable plates, good for longer print runs, high volume, durable.  How bank notes are printed.

FLEXOGRAPHY:

positive, mirror image, rubber polymer plate, on a cylinder, transfers 'sticky' ink directly to print surface - usually roll feed

flexo plate - silicone feel with the image raised 2-4mm, stock flexibility with flexography 

DIGITAL PRINTING:

reproducing images by translating the digital code direct from a computer, specials on a range of print media from paper to metal

PAD PRINTING:

a printing process that that can transfer a 2D image onto a 3D object, print to any surface (golf ball)

COLOUR PROCESS:

key aspects of digital colour theory, subtractive colours-CMYK

CMYK vs. RGB - selecting appropriate colour

FURTHER RESEARCH:

ROTARY PRINTING:

rotary press

n.

A printing press consisting of curved plates attached to a revolving cylinder that prints onto a continuous roll of paper.

A rotary printing press is a printing press in which the images to be printed are curved around a cylinder. Printing can be done on large number of substrates, including paper, cardboard, and plastic. Substrates can be sheet feed or unwound on a continuous roll through the press to be printed and further modified if required (e.g. die cut, overprint varnished, embossed). Printing presses that use continuous rolls are sometimes referred to as "web presses". Rotary drum printing was invented by Richard March Hoe in 1843, perfected in 1846, and patented in 1847. (Note – Some sources describe Parisian 'Hippolyte Auguste Marinoni', (1823, 7 January 1904) as the inventor of the Rotary printing press.)

Today, there are three main types of rotary presses; offset including web offset, rotogravure, and flexo (short for flexography). While the three types use cylinders to print, they vary in their method.

Offset lithography uses a chemical process in which an image is chemically applied to a plate (generally through exposure of photosensitive layers on the plate material). Lithography is based on the fact that water and oil do not mix, which enables the planographic process to work. In the context of a printing plate, a wettable surface (the non-image area) may also be termed hydrophilic and (the image area) a non-wettable surface hydrophobic.

Gravure is a process in which small cells or holes are etched into a copper cylinder which is filled with ink.

Flexography is a relief system in which a raised image is created on a typically polymer based plate.

In stamp collecting, rotary-press-printed stamps are sometimes a different size than stamps printed with a flat plate. This happens because the stamp images are further apart on a rotary press, which makes the individual stamps larger (typically 1/2 mm to 1 mm).

http://en.wikipedia.org/wiki/Rotary_printing_press

ROTOGRAVURE PRINTING:

Process in which the image to be printed (unlike in letterpress and flexographic printing) is etched into the printing plate, and the printing ink (unlike in offset printing) is transferred direct to the paper. Used mainly for long runs of high quality multicolor printing. Also called photogravure printing, specially where photographs are reproduced.

rotogravure printing,  system of printing based on the transfer of fluid ink from depressions in a printing plate to the paper. It is an intaglio process, so-called because the design to be printed is etched or engraved below the surface of the printing plate. At the start of the gravure printing process, the plate is covered with ink and the surface is then wiped clean. When paper is pressed against the inked plate, the paper penetrates the sunken parts slightly and draws out the ink.

All copy (the material to be reproduced, or printed) in rotogravure printing is prepared as positive film. A gravure printing plate made of copper is then prepared to accept photomechanical transfer by means of a gravure screen; this is a grid of closely intersecting lines that create thousands of tiny squares on the plate, which will in turn react differentially to an etching bath after the plate has been exposed to light through the positive film. The varying depths of the etched cells determine the tones of the printed image, with deeper cells holding more ink (and thus printing darker) than shallow cells, which may hold no ink at all.

In the printing process, the cylinder bearing the printing plates is usually arranged so that during its rotary movement it passes through a trough filled with a thin solution of fast-drying ink, or is sprayed with ink instead. A thin steel blade (called the doctor blade) moves across the cylinder and removes the ink from the plate’s surface but not from the tiny depressions in its cells. The plate cylinder then comes in contact with the paper, and the paper draws the ink out of the depressions in the plate. In colour rotogravure printing, a separate cylinder is prepared for each colour.

Because cells of different depths can hold varying amounts of ink, the rotogravure process can print a rich, full range of tonal values, making it ideal for reproducing photographs and other continuous-tone copy in large quantities. Rotogravure is thus widely used to print newspaper supplements (e.g.,colour magazine sections), catalogues, illustrated magazines and books, advertising, calendars, and so on. It is also employed for printing labels and wrappers on cellophane and similar materials. A high-speed printing process, rotogravure is best used for printing long runs of material bearing black-and-white or colour illustrations.

http://www.britannica.com/EBchecked/topic/510645/rotogravure-printing

FLEXOGRAPHY PRINTING:

flex·og·ra·phy

A rotary relief printing method using rubber or plastic plates and fluid inks or dyes for printing on fabrics and impervious materials such as plastics, as well as on paper

Flexographic presses are capable of producing good quality impressions on many different substrates and is the least expensive and simplest of the printing processes used for decorating and packaging printing. The use of flexographic printing presses is on the rise. There are two primary reasons for this: 1) it is a relatively simple operation; and 2) it is easily adapted to the use of water-based inks. The widespread use of water-based inks in flexographic printing means a large reduction in VOC emission compared to the heatset web or gravure printing processes.

Publication flexography is used mainly in the production of newspaper, comics, directories, newspaper inserts, and catalogs. Packaging flexography is used for the production of folding cartons, labels, and packaging materials. Large quantities of inks are used during normal runs on flexographic presses; however, some printers are able to recycle a majority of their spent inks and wash waters. Major chemicals used in flexography include platemaking solution, water and solvent based inks, and blanket/roller cleaning solvents.

Flexography is a form of rotary web letterpress, combining features of both letterpress and rotogravure printing, using relief plates comprised of flexible rubber or photopolymer plates and fast drying, low viscosity solvent, water-based or UV curable inks fed from an "anilox" or two roller inking system. The flexible (rubber or photopolymer) plates are mounted onto the printing cylinder with double-faced adhesive. Plates are sometimes backed with thin metal sheets and attached to the cylinder with fastening straps for close register or ink alignment. This adds additional cost to the plate and requires more makeready time, but when quality printing is critical this type of plate can make the difference.

http://www.pneac.org/printprocesses/flexography/moreinfo6.cfm

DIGITAL PRINTING:
Digital printing describes the process of transferring a document on a personal computer or other digital storage device to a printing substrate by means of a device that accepts text and graphic output. As with other digital processes, information is reduced to binary code, or "digitized," to facilitate its storage and reproduction. Digital printing has steadily replaced lithography in many markets, especially at the consumer and business level, as a result of its substantially lower production costs.

Digital printing refers to methods of printing from a digital based image directly to a variety of media. It usually refers to professional printing where small run jobs from desktop publishing and other digital sources are printed using large format and/or high volume laser or inkjet printers. Digital printing has a higher cost per page than more traditional offset printing methods but this price is usually offset by the cost saving in avoiding all the technical steps in between needed to make printing plates. It also allows for on demand printing, short turn around, and even a modification of the image (variable data) with each impression. The savings in labor and ever increasing capability of digital presses means digital printing is reaching a point where it could match or supersede offset printing technology's ability to produce larger print runs of several thousand sheets at a low price.

The main differences between digital printing and traditional methods such as lithography, flexography, gravure, or letterpress are that no need to replace printing plates in digital whereas in analog printing plates are continuously replaced, resulting in a quicker and less expensive turn around time, and typically a loss of some fine-image detail by most commercial digital printing processes. The most popular methods include inkjet or laser printers that deposit pigment or toner onto a wide variety of substrates including paper, photo paper, canvas, glass, metal, marble and other substances.

In many of the processes the ink or toner does not permeate the substrate, as does conventional ink, but forms a thin layer on the surface that may be additionally adhered to the substrate by using a fuser fluid with heat process (toner) or UV curing process (ink).

PAD PRINTING:

a recessed surface is covered with ink. The plate is wiped clean, leaving ink in the recessed areas. A silicone pad is then pressed against the plate, pulling the ink out of the recesses, and pressing it directly onto the product.

Pad printing is a printing process that can transfer a 2-D image onto a 3-D object. This is accomplished using an indirect offset (gravure) printing process that involves an image being transferred from the cliché via a silicone pad onto a substrate. Pad printing is used for printing on otherwise impossible products in many industries including medical, automotive, promotional, apparel, and electronic objects, as well as appliances, sports equipment and toys. It can also be used to deposit functional materials such as conductive inks, adhesives, dyes and lubricants.

Physical changes within the ink film both on the cliché and on the pad allow it to leave the etched image area in favor of adhering to the pad, and to subsequently release from the pad in favor of adhering to the substrate.

The unique properties of the silicone pad enable it to pick the image up from a flat plane and transfer it to a variety of surfaces, such as flat, cylindrical, spherical, compound angles, textures, concave, or convex surfaces.

Pad printing cycle

1. From the home position, the sealed ink cup (an inverted cup containing ink) sits over the etched artwork area of the printing plate, covering the image and filling it with ink.
2. The sealed ink cup moves away from the etched artwork area, taking all excess ink and exposing the etched image, which is filled with ink. The top layer of ink becomes tacky as soon as it is exposed to the air; that is how the ink adheres to the transfer pad and later to the substrate.
3. The transfer pad presses down onto the printing plate momentarily. As the pad is compressed, it pushes air outward and causes the ink to lift (transfer) from the etched artwork area onto the pad.
4. As the transfer pad lifts away, the tacky ink film inside the etched artwork area is picked up on the pad. A small amount of ink remains in the printing plate.
5. As the transfer pad moves forward, the ink cup also moves to cover the etched artwork area on the printing plate. The ink cup again fills the etched artwork image on the plate with ink in preparation for the next cycle.
6. The transfer pad compresses down onto the substrate, transferring the ink layer picked up from the printing plate to the substrate surface. Then, it lifts off the substrate and returns to the home position, thus completing one print cycle.

http://en.wikipedia.org/wiki/Pad_printing