“Develop success from failures. Discouragement and failure are two of the surest stepping stones to success.”
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 & 3
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”.
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.
INTRODUCTION TO PRINTING PROCESSES: METHOD OF PRINTING
1. Relief printing.
a. Letterpress,
b. Die-stamping
c. Flexography
d. Letterset
2. Planography printing.
a. Lithography printing (direct printing)
b. Offset printing (indirect printing)
c. Collotype printing.
3. Intaglio (gravure) printing.
4. Stencil printing (silk screen).
5. Electrostatic (Xerography) (digital printing).
1. Relief printing: The method printing according to this principle has two surface. One is printing surface and other is non-printing surface. Ink is applied only image area because the non-image area is in groove. Printing paper is placed on the printing surface and pressure is applied on it. The ink is now transferred from the printing surface to the paper.
a. Letterpress: Generally, this method is very easy and simple. This was the method of printing which was invented in the beginning. Printing done by this method, the edges become sharp and a slight raise is found on the indentation. The pressure is so adjusted that a good print is obtained.
b. Die-stamping: This process is used for printing envelops and trade-marks etc. two dies are made for printing by this process. One is made die and another is female die. Female die is made of metal and male die is prepared by pasting paper sheet.
The back side of the printed image becomes depressed and printed side remains raised.
c. Flexographic printing: The printing surface of this process is made of flexible rubber. The rubber plate is prepared by duplicating process. The jobs which are printed on one side of the paper are generally done by this process.
d. Letterset printing: It is also called dry-offset process. The printing surface of this method is similar to the letterpress. But the printing is done similar to the offset method. Dry-offset machines do not have damper unit. Aluminum tubes and other metallic surface are printed by this process.
2. Planography printing: the person who invested this method was named Alois Senifelder. In 1798, he invented this method. It is obvious from its name that the printing and non-printing surfaces are prepared on plain surface. By the aid of chemicals, the printing surface is separated from the non-printing surface. The nature of water and grease which repel each other, is used for this method. The principle of printing by this method is “grease and water repels each other” and therefore they cannot be mixed together.
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.
a. Lithographic printing: this process is also called direct printing process. In this method, the design to be printed is made reverse on the stone or the metal plate with the help of crayon chalk or a special ink. When the water roller is passed over. The surface, the water gets applied to the non-image areas. Now, when the ink roller passed over the same surface, the ink gets applied only on image areas.
(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).
A Two basic type of inks:
1. Liquid inks. (Petrolium products).
2. Paste inks. (Solvent based).
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
b. Offset printing: this indirect process of printing. In this method, the image is not directly transferred from the printing plate to the paper. First at all, the image is transferred from the plate cylinder to an intermediate cylinder (blanket cylinder) then, the image is transferred to the impression cylinder from where it is printed on the paper. The machine which is used in this type of printing process has three cylinders.
c. Collotype process: it is also called photo-gelatin process. It similar to the planography. Joseph albert invest this method of printing in 1873. It partly based on the photo lithographic principle. It is used for printing pictures having continuous tone, it is based on the principle of light. A glass is plate is coated with a thick layer of Bichromated gelatin. The negative is placed on this surface and it is exposed to bright light, light enters the transparent parts the negative and reacts stick to the glass plate. After getting dried, these parts stick to the glass plate. Light cannot enter the opaque parts and therefore the layer of gelatin does not stick permanently to the glass plate.
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.
3. Intaglio printing/gravure process: the principle of this printing process is just opposite to the letterpress printing. In this process of printing, the printing surface is made in depressed form. The non-printing surface remains in relief shape. This is an ink duct placed below the printing plate cylinder. A little part of the cylinder lower side is left to dip in the ink duct. A little above the ink duct, the whole length of the cylinder remains in contact with the doctor blade. The work of this doctor blade is to clear off the extra ink of the non-image area. As soon as this ink is wiped off, this cylinder remains revolving and comes in contact with the paper. The ink paper of the printing surface is impression cylinder.
The ink used is very thin is volatile liquid and drying fast and very Imflamable.
4. Stencil process: it is also called silk screen process. This method is used for the printing of glasses, marriage cards, greeting card, visiting cards, posters etc. in this method, the number of stencils made on a shellac coated paper. A square wooden frame is and a silk screen is spread over it. The screen is tightly fitted overt it with nails. The prepared stencil is placed over screen and heat is given from below. Due to this heat, the stencil sticks to the screen, because the heat melts the chemical applied on the surface of the stencil.
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.
Applications of printing processes: suitable of printing processes to different classes of work.
1. Offset printing: it is largest and widest ranging of the printing processes in market.
a. Small offset: short run work 10,000 copies of stationery product such as letter headings, business cards, overprinting of envelopes, pads, set, and leaflets and booklets.
b. Larger-size sheet fed: up to 50,000 copies. It can prove economical in print runs up to 250,000 range of work includes books, booklets, brochures, cartons, catalogues, folders, magazines, annual reports, instruction manuals, posters and leaflets.
c. Narrow-width web offset: business forms and continuous stationery, direct mail, etc. plus if sheeter and UV drying is fitted.
d. Heat-set web-offset: print runs of above 50,000. Suitable work covers magazines, holiday brochures, catalogues, brochures and direct marketing products.
e. Cold-set web offset: newspaper, longer-run, paper-back books.
2. Flexography printing: it is reel-fed labels, newspapers, flexible packaging such as food wrapping, carrier bags and rigid packaging such as cartons and collapsible corrugation cases.
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.
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.
- cylinder 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.
3. Letterpress:
a. Sheet-fed letterpress: short run works such as business cards, letter headings, leaflets, booklets and posters in mainly one or two color extremely popular for non-printing operations such as cutting for creasing, die cutting, embossing, numbering and perforating.
b. Narrow-and larger-width web letterpress: books and self-adhesive labels.
4. Gravure printing:
a. Sheet-fed gravure: work such as printing on metallized ad other substrates to produce high quality decorative effects in gold silver and fluorescent color.
b. Web-fed gravure: general commercial products. Such as magazines, mail order and catalogues and specialist products such as security printing including stamps and cheques board packaging products such as folding box cartons for foods and cigarette industries. Flexible packaging such as printed cellophane and polythene used in food wrapping, display and protection.
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.
5. Screen printing:
a. Sheet fed screen: It print a thicker an ink film than any other printing process this makes it ideals for printing light color inks on dark colored material, ex-posters, show-cards, printed circuit, T-shirts, vinyl, metal, glass and plastic.
b. Rotary web-fed screen: specialist used for self-adhesive labels, scratch-off lottery ticket, packaging, transfer printing, fabric printing, security printing, direct mail.
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.
A. Frames: Two types of frames
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.
B. Screen Febrics: Nylon, Dacron (polyester), and stainless Steel
- 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
1. Plain weave: Use the standard "over and under" weave pattern.
2. Twill- Uses an alternative pattern of Quer one or two threads.
Thread material can be:
1. Monofilament: made of single filament like sewing thread.
2. 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.
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.
1. Halftones upto 85 4pi.
2. Trap between 0.5pt to 10 pt.
3. Font bigger than 5 pt. /6 pt.
6. Digital printing:-
a. Print on demand: children’s books of varying page quantities and binding techniques.
b. Advertising: outdoor banner, personalized direct mail campaigns.
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:
2. Wide format Presses: High quality is speed: Printing of Billboards, pop 370 dpi.
3. Direct Imaging Presses: (DI): are compact version of tradition offset presses, although they use waterless plates and waterless inks.
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.