“Develop success from failures. Discouragement and failure are two of the surest stepping stones to success.”
INTRODUCTION OF PRINTING PROCESSES
DEFINITION: Printing is a reproduction of a no. of copies from original with the help of suitable substrate.
EFFECT OF PRINTING IN OUR LIFE:
1. Educational: It is relation with human life (man need to communicate their views to each other).
2. Social: Invitation card, welcome address.
3. Political: Advertisement, newspaper, magazines, pamphlets or many govt. orders.
4. Economics: Customer attractive more-well packed and pay more rather than loose or unpacked. This is used in cash books, receipt books, registers, currency printing, bank draft, cheque books and many such other important.
5. Cultural
6. Scientific: Printing process has taken much help from different of science of manufacturing food printing machine. Science of mechanical and electrical engineer was needed in preparing ink and photographic material. Science of Physics, Chemistry, Math. Geology, and Chemical technology is needed.
UNIT-1
BRIEF HISTORY OF PRINTING: some time ago, printing was considered an art or craft but now it is science and technology.
Three main Material used in printing.
1. Paper: It was invented some time ago in china.
2. Ink: Kajal was used as ink.
3. Printing surface: A printing matter was engraved on a smooth surface of square wooden block.
A: After japan, the art of developed in china 11th.
B: 1400, Johannes Guttenberg made some alphabets called moveable type in Germany. He is father of printing and was death in 1468.
C: William Caxton established "the red pall" at Westminster in England.
D: 1805 G.P Jorden invented platen machine.
E: 1806 George Climer discovered the lever principle for moving up and down.
F: 1814, a German call Fredrick Coeing, achieved cylinder machine.
G: 19th, Thomas nelson invented printing by a bent plate.
Reheating the resin mixture loosened the pieces of type so they could be reused.
Other material including wood, tin, copper and bronze were used for the same purpose.
The idea of movable type traveled to neighbouring countries.
In korea in 1403 AD king R, aijong ordered that everything should be printed. Three hundred thousand pieces of bronze type were cast and printing began.
It is interesting to specilate on the relationship between this event and a similar one that took place in northern Germany which brought Johann Gutenberg the title of “Father of Printing”.
The casting process involved cutting a letter by hand inverse on a piece of hard metal, then punching the letter shape into a soft copper mould to form a die, called a matrix. He printed 42 line Bible, 200 copies took 3 years to print.
Terms such as ‘form’ ‘leading’ ‘uppercase’ ‘lowercase’ ‘type size’ ‘impression’ and make ready originated with Gutenberg.
The first high speed printing press was designed around 1450 by Johann Gutenberg. It was made of wood and named wine press. The bed of this press moved forward and backward under the impression plate, activated by a lever and a tympen holded the paper in place.
Senefelder used Kellhein stone or say lithostone with unique quality of porous surface and availability.
He named this process chemical lithography first of all in 1798.
The litho-stone was replaced by zinc plates and aluminium plates. This was a tremedous advancement in efficiency, speed and quality of reproduction. Total lithography is also known as offset printing.
The initiatives was takes by E. Porthole in 1896. When he attempted to project to a sensitized plate by using light after the second world war the prototype setting machine became a commercial reality. The prototype set matter could be stored as films for reuse in future unlike their Hot Metal Counter parts.
In 1984 Steve jobs launched Macintosh the next generation first personal computer to have GUI (graphic user interface). The GUI were pictorial depictions of a function that told the user what operation the GUI can perform.
The mouse was another revolutionary device that came with the Machintosh. The mouse acted as the easy way to interface to the computer, the combination of the mouse and GUI made personal computing almost like a child play.
INTRODUCTION TO PRINTING PROCESSES: METHOD OF PRINTING
The back side of the printed image becomes depressed and printed side remains raised.
The image for this method has to be prepared on stone or metal plates. First of all, a roller made wet with water, is operated on the complete surface and after that the roller of ink is operated similar. The water get applied on the non-image area and the ink gets applied on the image area and the paper is placed on their surface and pressure is applied on it.
(The reverse design has to be made on the stone or metal).
In modern days, aluminum, zinc and bimetal plates are used in. its place, we make a design on stone by the help of photographic negatives, call it photo lithography.
(Alois Senefelder in 1976).
1. Plate cylinder linked with Ink Train and Dampening System.
2. Plate Blanket cylinder
3. Impression cylinder.
1. Web Presses: Print from rolls or web of paper.
2. sheet-fed Presses: Print precut sheets.
3. Duplicators: Generally sheet-fed machines without all extras.
All printing inks are made of:-
1. Pigment or colorant.
2. Vehicle such as solvent or water
3. Additives like waxes, driers that provides specific properties such as hardness dry speed, Color intensity etc.
A Two basic type of inks:
Types of Lithographic Inks:
1. Petrolium based inks.
2. Water based inks.
3. Energy-Cured inks.
4. Waterless inks.
5. Vegetable oil based inks.
6. Single fluid inks.
7. Process color Inks
8. Spot color inks.
3. Heat set and non-heat-set-inks.
10. Specialty inks.
11. Security inks
12. Thermocharomic Inks.
13. Photocharonic inks
14. Scratch-off inks
1. Ink and water balance problem.
2. Screen angles (moire pattern).
3. Maintaining registration is an also critical.
1. Avoid overuse of colors.
2. Font size: Larger than 5 point.
3. Resolution upto 300 dpi and some can print upto 6oo dpi.
4. Trapping: Done at prepress stage most of cases.
5. Ranges from 0.25 -0.50 point trap should be allowed.
6. Reverse type and line art should not be less than 1/2 pt.
The gelatin is that after the effect of light, its surface does not absorb water. Therefore in the highlight areas of the negative, water will note be absorbed at all.
Light area = ink – 25%, water – 75%.
Middle area = 50%, 50%.
Solid area = 100%, 0%.
After this the plate is immersed in Glycerine, water and ammonia serially. This help to control the quantity of ink layer. This method is used Graphers. These printed paper are also used as plates in books, which are few in number. A special type of machine is used for this collotype printing. The ink used for litho printing is also suitable for collotype printing process. The printing by this method is very slow and it is also expensive.
The ink used is very thin is volatile liquid and drying fast and very Imflamable.
Now a days, the method of preparing screen by stencils is no more. Instead of this, the matter to be printed is photographed with a process camera and the positive of the design is prepared. A light sensitive surface is prepared on the screen. The positive is place on it and it is now placed in light. The light effects to the transparent part of the positive and coating of the screen becomes hared. After the screen is developed in tape water. Coating of the image areas is dissolved in water in water and the light effected areas are hardened. Thus, the holes in parts of the screen which have to be printed get opened. The holes of these non-image area are get closed by the hardened coating.
After this, the whole wooden framed screen is fitted on to a large table with the help of hinge. The paper to be printed is placed on the table. Special type of ink used for screen printing is placed on this of ink used for screen printing is placed on this screen. Now this ink spread all over the screen with the aid of an equipment, which is called squeegee. The squeegee is taken to one direction for printing one sheet, and bringing it back in the same way for printing another sheet repeatedly. The ink is passed through the holes of the stencil and the design of this stencil is printed on the paper below. The paper is now removed carefully and left to dry.
This method slow but good and shinning and high density for specially used small image print not perfectly. Basic stencil used for printing 65 lines in one square inch.
LETTERPRESS PRINTING:
Printing from Hot Metal Type is generally called Letterpress printing. Until the middle of 19th Century L/P was the only commercial method for putting ink on paper, even until the middle of 20th Century, it was still being used to print newspaper book, magazines, and most commercial printing. Letterpress is based on the concept of relief printing.
Designed in 1950, the platen Jobber became the most common type of Letterpress used in US.
Type of Presses:
Flong- for casting streo-plates.
Wax mold: for electroplates
Image carrier: Type-form - cast type
1885-1890: Linotype, Monotype
Zine blocks copper blocks or engravings.
Substrates: Mostly paper, folding Cartons, Cardboard material and textiles like book binding cloth.
Inks: Linseed oil or varnishes. Petroleum baked inks, require denser ink, heavier in pigment.
UV and water-based inks.
Press Technology:
Flatbed press: use flat screens that require back and forth motion. used for printing graphic applications such as bill boards, posters, t shirts, banners and caps, some presses have vaccum table which improves print quality and registration, Manual, semi-automatic fully automatic.
Rotary: use screened cylinders with the squeezer mounted inside the cylinder, Ink is pumped automatically and the squeezee controls the flow of ink used to print continuous pattern like gift wrap, textile, thin paperboard, and wall covering vinyl. Have multiple printing units.
Cylinder: Have configuration similar to offset, flexo and gravure. A series of grippers grab the sheet which is held tight to the cylinder by a vaccum. As the cylinder rotates, the screen carriage passes over the substrate; the stationary squeeze
LETTERPRESS PRINTING: The term letterpress brings to mind images of raised letters pressing against a surface, onto which their shape is transferred in ‘ink’, letterpress printing is also called relief printing.
Types: letterpress printing is meant for printing text comprising of not only letters but also other visual such as borders, rules and illustrations in black and white or color. Other visual can also be made separately and then arranged together on a page or pages. Then, a form can be made for printing.
There are three types of processes involved in letterpress printing.
It is faster and the continuous action of the cylindrical image carrier.
A rotary press require elaborates make ready procedures before printing can begin. To achieve this, the copy is set on a hot metal composing system and block are made for illustrations, etc. and then arranged according to the layout plan on a metal frame called chase. Now, the paper flong with depressed images is fed into a casting box where it is converted into a lead version, called a stero.
UNIT-2
Applications of printing processes: suitable of printing processes to different classes of work.
UNIT-3
1. Mainly used for Printing text and rough graphics onto cartons (corrugated) and plastic bags.
2. Created by Bibby's, Baron and Sons in 1890 in England.
3. Now vast improvements has taken place in flexographic plates, press design, ink metering, anilox Rolls, prepress software and ink formulations which can produce sophisticated designs on everything from fold up cartons, and flexible packaging to tags, labels and commercial printing.
4. Aniline printing was its initial name because aniline- a poisous colorless liquid used in dyes.
5. In 1950 aniline ink were replaced with ink based on non-toxic polyamide resins and the name was changed to flexography
6. Ability to handle non-paper substrates.
7. Making inroad into commercial printing particularly in books, newspaper insers and publication market.
8. To more than 70% printing is done packaging segment.
9. Flexography printers call themselves Converters - convert the substrate into a package.
(1) The fountain roll
(2) The ink metering roll anilox roll.
(3) Plate cylinder.
(4) Impression cylinder.
The anilox roller accept ink into tiny engraved cells which can vary from 80-1200 cells PLI. Anilox roll in paired with doctor blade to remove excess ink.
1. The plate is held to the plate cyl. with special double sided tape called sticky back.
2. The impression cyl. hold the substrate at the right tension against the plate to form a clean impressions.
3. Prints roll to roll.
4. A drying it system at the end of flexographic print station dries the ink between one color and the next.
5. There is a main drier at the end called overhead drier.
6. Cutter and stackers at the end.
7. Some presses have die cutting operations and deliver finished product.
Ready Set, Repeat: Multiple repeat of product according to the circumference of plate cyl & also width of cyl.
- cyl can range from 2" to 110" in circumference
1. Inline Presses: Printing units in line one after the other. Ability to print the reverse side of substrates.
2. Stack Presses: Printing unit are placed vertically, one on top of the other. Six and eight stack configuration used four advantages.
• Press occupy smaller space.
• The web may be reversed to allow perfecting.
• The stations are very accessible.
• Can print a variety of substrates.
(Lower quality work)
3. Central Impression Presses: (CI)
- Used for extremely tight color registration.
- Have two to sight printing stations.
- Cannot print both sides at one pass.
- Suitable to print stretchy films.
4. Sheet-fed presses:
- Mostly used to print corrugated containers attached with cutting folding and gluing units.
Wide web vs. Narrow web:
Narrow web: 24" wide - Labels, business forms, small folding cartons, tags, tickets, pressure, sensitive, lables, multilayer coupons and flexible packaging - faster changeover
Mid-web: 24" to 36" wide: for flexible packaging markets - faster changeover.
Wide-well: 36" to 100-120 inches, extremely used in flexible packaging."
1. The image area - face
2. Caliper - the thickness of the plate.
3. Floor- Non printing area.
4. Relief - the distance between floor and face
5. Shoulder- visible edge between face and floor.
6. Plate backing: the dimensionally stable material that adheres to the back of the flexible plate to provide stability.
Plates exposed with Negatives made now digitally now or on films. The image area is polymerized" during exposure. Non-polymerized area is washed away by water / sol, while clean.
Now-a-days computer to plate process is used to produce image carriers.
(a) Moulded plates.
(b) Photopolymer plates.
(c) Digitally engraved (laser etched) photopolymer plates to produce high quality printing. 150-300 LPI.
Plate thickness: 0.107-0.25 inch.
Print: millions of impressions.
1. Anilox roll apply ink.
2. Three three primary components - pigments or soluble dyes, a vehicle for carrying the ink and additives.
3. Bright and vivid.
Types: Solvent based inks.
1. Water based inks.
2. Energy cured inks (UV or EB) contain chemicals that reacts to UV or EB lights.
3. Process color inks create the entire color gamut.
4. Spot color inks.
5. Specialty inks -security inks.
6. Thermochromic inks.
7. Photocharomic inks.
8. Scratch-off inks.
- UV coating
- EB Coating
To produce gloss finish, scratch resistance and quick drying.
Resolution: 300 LPI but average resolution is 110-150 LPI.
Live weight & type size: 0.008 in 0.012 in avoid printing of script type with fine serifs.
Dot gain: is more than offset ptg.
Tonal Range: not to print below 3% size dots above 85% have a tendency to fill is.
Printing from recesses of an engraved cylinder. It is sometime called "Intaglio" printing.
1. 16th century, chemical etching was invented.
2. Modern gravure printing press emerged around 1860 with the dev. of halftone screening.
3. Very high quality printing process.
4. Extremely consistant printing.
1. Engraved cylinder.
2. Ink fountain
3. A doctor Blade
4. Rubber Impression Roller cylinder prepared by.
- Chemical etched.
- Electromechanically.
- Laser Engraved.
- Steel Base
- covered with copper layer
- chrome plating done.
- Reel Stand: Unwinds roll of substrate.
- Two position reel stand are paired with splicers for attaching the new roll onto the old roll on the fly.
- Web guiding systems, web conditioning and web surface treatment system to improve the printability of the substrate.
- To change the dyne level of printing films.
- Reducing surface tension.
- De-curl paper
- Clean the web debris.
- Heat treat papers to even out moisture content.
- The gravure cylinder rotates through the ink fountain.
- The doctor blade wipes the surface of the cyl clean.
-The rubber impression roller propels the web and transfer image to the substrate.
- Web then passes through an interstation dyer to set the ink.
- This process is repeated for the number of colors to be printed. (8 to 10 colors).
- After printing the wet enters any of a variety of online finishing operations, slitters gatherers, folders etc.
Repeated work.
1. Publication Presses: 72" - 143"
- High sheet, 3000 LPM.
- 8-10 units
- Inline finishing.
- Adaptability of wide variety of substrate.
2. Packaging: 18"-60", 44" - 216" for heavy weight rubs.
For producing light weight substrates like flexible packaging, paper and foil.
Producing heavy weight substrates like folding cartons, beverage containers and soap cartons.
- Five or more units.
- configured with inline converting operations
- Slitters and re-winders.
- Option for reverse printing on the back of substrate
- Precondition systems to beat the substrates.
- Cooling units to cool films.
- Steel cylinders are plated with copper.
- Traditional etched using chemicals.
- Copper layer
- Chrome plated
- Inking
- Pressing against the substrate.
- Engraving electromechanically directly from digital files (1560)
- Chemical etching replaced by a diamond styles (after 1992)
- De-chroming
- Re-chroming increases life of cylinder.
- Today gravure cyl, are coated with light sensitive coating and on graved using lasers. Because of the current lasers cannot engrave coppers, gravure printer are using zinc. During the engraving process, the high powered laser removes the zinc from the cells, and any waste material is caught up in a vaccum, leaving the cylinder clean and ready to be chromed expensive.
- Gravure printers now have the ability to remake cylinders exactly to original.
-fluid inks, thin viscosity.
- Bright and vivid
- Stronger solvents used to adeker to plastics.
- Solvent based miles: Petroleum and other organic materials.
- Water based inks.
- Spot color inks.
- Speciality inks and coatings:
- Security inks
- Heat transfer inks.
Posters and graphics printing in short print runs:
Screen printing is a primary method of printing T-shirts banners, decals and other form of decorative printing.
Printing bottles, plastic container, pens, posters, counter displays, menu-covers, Cap, shower curtains, leather, metal, glass, wood, ceramic, plastic labels, Outdoor signage.
Screen printing is originated in ancient chine where silk was abundant. Modern screen printing methods were developed in the mid 1800 in Germany and Scotland.
Printing from the stencils produced on the sturdy frame screen - whether made of nylon, dacron or stainless steel in a sturdy frame. The non-image areas are mashed off and the ink is pressed through, the stencil and into contact with substrate using a squeegee. It is a versatile ptg. can print anything, shape and size. Leather, metal, glass, wood, ceramics and plastics.
(1) A sturdy frame, wood or metal.
(2) Scream printing fabric.
(3) Stencil.
1. Wooden: inexpensive and readily available but difficult to achieve high tension levels.
-Dimensionally unstable
2. Metal frames: -Durable and stable
-Resistant to distortion.
-Impervious to screen solvents and cleaners.
-metal screens are tensioned with special devices and glued.
3. Retensionable frames: introduced in 18805 with this technology the four sides of the frame can be independently moved or rotated typically by hand. The screen fabric is locked into each side of the frame prior to tensioning, and the corners can be loosened as needed.
- Characteristic of ink. (Particle size)
- Level of fine details in the art work.
- Thickness ink film designed.
- Elasticity
- Resilience to chemicals.
There are two types of weaves used in screen printing
Plain weave: Use the standard "over and under" weave pattern.
Twill- Uses an alternative pattern of Quer one or two threads.
Thread material can be:
Monofilament: made of single filament like sewing thread.
Multi-filament: multiple strands twisted together to form a single strand live rope.
Classification of screen fabrics:
Coarse: 110- 240 TPI (threads per inch).
Medium: 305-355 TPI
Fine: 390-470 TPI
C. Creating the stencil:
(1) Direct Stencils: stencil is created on the fabric itself directly.
(2) Indirect stencils: in which stencil is created on paper, or film and then adhered on the fabric. Stencils can be made either by, imaged from a film or a digital file.
Shellac coated paper or Lacquer coated film for direct stencil and indirect stencils.
Lacquer Coated film.
Why use screen anyway?
Screen holds everything in position. It will not shift during printing. It also helps to control the thickness of ink film. The thicker the ink film required the thicker the mess necessary to print it. Thinner inks printed with higher mess count screens. Thick inks are printed with coarse mess screens.
-The square is often used for printing flat surfaces.
Above the screen carriage apply pressure to the ink. Once the image is laid down the drum lets go material the substrate is unloaded from the press, and the screen carriage shuttles back to its starting position. Used for paper, plastic and flexible board. Many round oval, or tapered substrates like bottles, toys, and sports equipments are printed.
(1) Transparent inks: for graphic printing and four colour printing.
(2) Non-transparent inks: for textile printing.
Thick consistancy, almost like paint.
1. Solvent based inks: petroleum / or other organic mat as a vehicle. excellant printability for non-paper substrates contain voc's.
2. water-based inks: water as a vehicle Have few voc's. Dry by absorptions.
3. UV inks: contain chemicals that reacts to ultraviolet light. Provide excellent hardness gloss and resistance characteristics. Dry using controlled light source. Dry instantaneous.
4. Process Colour Inks: Four basic colours to create the entire gamut of process ptg.
5. Spot colour inks: Colour are formulated from individual combination of pigments rather than combination of CMYK. Provide perfect colour combination to achieve exact colour match.
• Poster inks
1. Over/ under-stretching of the screen.
2. Selection of correct fabric.
3. Squeezed too softy too hard cause damage to image/ poor inking
4. Improper angle of squeegee.
Not designed for high resolution graphics, and fine text printing.
Halftones upto 85 4pi.
Trap between 0.5pt to 10 pt.
Font bigger than 5 pt. /6 pt.
UNIT-4
SCREEN PRINTING: Main part of screen printing
Screen printing has its origins in simple stencils, used for textiles, mostly for clothing.
Principle of screen printing: in this type of printing, the image and non-image areas are carried on a mesh (woven/screen, the image areas being open or ‘unblocked’ in the form of a stencil. The non-image areas are formed by ‘blocking out’ the mesh by coating. The paper is placed under the screen. After the screen is lowered into contact with the paper, ink is passed across the upper surface of the screen. Where the screen is open ink goes through to the paper beneath.
Classification of stencils: It is material the fineness of the screen (the number of scree thread per centimeter of fabric length), the thickness of the screen, the distance between the top and bottom sides of the screen, and the degree of opening of the screen that determine printing properties and quality of the fabric (screen). Fabric can be obtained in level of fineness from 10 to 200 fibers/cm. the most frequently used fabrics are those between 90 and 120 fibers/cm.
Screen fabric: the screen fabric is a woven material. It is a tightly stretched across the frame. This screen fabric serves as a carrier for stencil. The selection of fabric for particular works plays a major role. The woven screen printing fabric serves two primary functions: the fabric supports the stencil system, and the fabrics mesh permits ink to flow through the image area. The mesh plays a dominant role in metering the amount of ink that will flow into the surface.
Frame: the frame serves as a support for the screen. It can be made from wood, metal or any other rigid material.
Types of fabrics:
Brief outlines of preparing hand cut stencil: Preparing the screen by knife-cut stencil method: the first printing screen used in the early days screen printing consisted of knife cut or paper out or stencils representing the design or originals to be printed.
Photographic stencil method: the primary reason for the growth of the second printing industry has been the development of photographic stencil. He found that certain materials, such with a potassium bichro-mated solution hardened when exposed to light.
All photographic stencil processes are divided into three types:
The liquid light-sensitive emulsion fall into the following types of chemical formulation.
Preparing the emulsion on screen.
In the present days market the gelatin or gum is sold in commercial named such as silk coat, red star etc.
The method of preparing a sensitized emulsion is as follows:-
Emulsion: composed of polyvinyl chloride, a gelatin-based substance
Sensitize – 2% (ammonium bichromate), (3 to 4 drops) liquor ammonia
The emulsion thus preparing is coated to the cleaned screen with a scale or a sharp edges squeegee in a dark room.
Drying: A circulation air fan can be to hasten drying, when the first coat is dry, apply a second coat to the inside of the screen and allow it to dry.
Exposure: Place the right reading side of the transparent positive against the outside surface of the screen.
Development: The stencil is developed by first wetting both sides of the screen is warm (95 to 105 F) water.
Drying: When the emulsion is dry, the screen is ready for printing.
Using the thin emulsion coating with a carefully applied on the backing sheet under controlled condition consists of the colloidal gelatin, pigment and plasticizer for importing softness and flexibility to the coating.
The film should be stored according to the manufacturer directions.
Cut the film according required size and keep the film side in contact with the readable side of the positive.
Exposing: Then the place it in a contact box so that light will pass through the positive and strike the five-star film. Then expose it to sunlight or artificial light source.
The exposure time varies from design to design, from 1 to 10 minutes in some cases.
Developing: After exposing remove the five-star film from the contact box and place it in a tray care should be taken so as not to expose it to actinic light. Then pour a diluted solution of hydrogen per oxide, that is, one part of hydrogen per oxide mixed with three part of water. That is, one part of hydrogen peroxide mixed with three part of water. Develop the film for about one minute. Remove the hydrogen peroxide solution from the tray and pour warm water, over the film. Now image areas will open up and after all the image areas have been opened up, cool down the film by pouring the cold water.
Digital Printing is an umbrella term for the assortment of technologies now available for commercially printing documents using toner, inkjet or other digital processes.
Shorter runs.
Faster turnaround.
Economical segmented and targeted runs.
Ability to use marketing.
However output quality do not match with that of conventional printing.
No film is generated and no plates are made; it is all a push button operation!
No make-ready cost.
Reimage each page from digital data; means your per page cost remains the same, whether you print 10 copies or 500 copies.
Press operation:
Toner-based presses: 1990s.
Over time, these presses have improved in speed, quality, reliability and cost. The latest presses range from basic four colour models to those that can print six and seven colours. Inaligo, Xeikon chromatress and Zerox Docucolor.
First the drum is coated will an electrically sensitive chemical (Selenium) that becomes charged when exposed to light. Electrodes are then used to expose the image areas on the drum, creating + electrical charges. The toner particles are (-) charged.
As the drum rotates, the toner is attracted to the image areas. This forms the image areas to be printed. When the paper is inserted into the press it gets strong electrical charge by corona wires. When the paper come in contact with drum it draws the image onto the paper. The paper is then passes under a heating element which fuses the toner onto the paper.
Then the drum passes under a blade which scraps off any remains toner.
Then the drum passes under a charging were which erases all memory the image and all the process to start over.
- Each printed image is unique.
- one to one printing market.
- Personalize printing.
- Variable data markup.
These presses are in the same categories as toner band presses, but the imaging is clone with a high end laser. The laser writes positive images on a photographic imaging plate wrapped around the cylinder.
The image rotates and pick up inks from the Binary Ink Dev. (BID) system.
Once the colour has been transfered to the imaging plate, the image is transferred to a blanket cylinder and onto the substrate. Presses available upto 7, 8 colours Liquid inks used, there is no fusing of toner, It dries from pressure and heat.
HP Indigo presses were the only digital press Recently Xerox machines have been developed.
Sheet-fed toner based, on web positive is negative charges to transfer the image. The paper must be treated to make them compatible with the digital printing processes. Size: 12 x 18" / A-4-, A-3.
Web-fed presses: for publishing work. 13" width roll printing. Toner based can print high resolutions from. 600-800 dpi.
High greed black & white printers.
Continuous inkjet: which uses continuous stream of ink.
Drop on Demand: made up of individual dots. Produce higher resolutions at higher speed.
High speed Inkjet presses: Print 750 per minute at 300 dpi.
Capable of imaging at 2540° dpi. Push button operation short 540 copies. DI presses use traditional plates for transferring the image, they capable of producing variable information. Heidle-berg QuickMaster D1 Ryobi, karat, Xerox and Adast have den. D1 models.
In true digital presses there is image carrier, Imaging is done directly from the digital file (Excepting the direct imaging presses which use imaging" cylinders).
Toner based presses use toner.
DI to presses use traditional water less inks.
Various types inkjet inks.