Printing Processes

Today we looked at different commercial printing methods used within design with Ian.

We look at the five major printing processes: flexography, gravure, screen printing, offset lithography and digital printing – the latter two being the most commonly used. Depending on the job a designer has in hand, there will be a most suitable printing process for that particular job, given the requirements for the cost, quality and timing for the job.

After talking us through the general basics of printing, Ian split us into 9 groups and gave us each a printing method to research. These included:

  • Flexographic printing
  • Web fed gravure printing
  • High-volume multicolour silk screen printing
  • Foil block printing
  • Varnish printing
  • Die-cutting and crease printing
  • Perforating, punching and drilling
  • Lasercut printing
  • Holographic printing

My group got given Web fed gravure printing, and it was safe to say, that none of us had any idea what the process was or what it involved. The main objectives of our task were:

  • Find a video displaying the process
  • How the process/technique works
  • It’s uses
  • Advantages and disadvantages

As well as researching our own given printing process, I have also made noted from other group’s presentations and added in my own research that I have gathered in my own time about each of the nine processes.


Web Fed Gravure Printing (AKA Rotogravure Printing)

How does it work?

I wrote out a simple step-by-step guide on exactly how the gravure printing process works.

  • There are two cylinders: one engraved positioned below and one not engraved above.
  • The cylinder is engraved with the desire printing pattern and set above an ink fountain, partially submerged.
  • Ink is applied directly to the cylinder – this happens as the ink from the ink fountain below gets drawn into the engravings as the cylinder rotates.
  • There is a blade that removes any excess ink as the cylinder rotates too.
  • The non-engraved areas do not print, whereas the engraved sections do.
  • A substrate is sandwiched between the two cylinders – the engraved printing cylinder and the impression roller – and the ink is transferred onto it.
  • The now inked up substrate goes through a dryer and then goes through the process again – the process must happen four times in order to get a full colour print using CMYK.

We were able to find a great diagram that clearly shows exactly how the printing process in gravure printing works.

roto-gravure-printing.jpg

What is it used for?

High-volume printing, packaging, wallpaper, gift wrap, post cards, magazines, photographs, etc.

Advantages

  • Produces high quality results rapidly – has an unbelievably high volume of production.
  • Ideal for extremely long runs.
  • Delivers full range of tonal values in photographs – reproduces excellent quality of image.
  • The cylinder lasts for millions of impressions.
  • It’s very low cost once it’s actually running.

Disadvantages

  • High cost initial investment.
  • Preparation of the engraved cylinder is time consuming.
  • Costs are higher unless printing in huge quantities – it’s not cost efficient for short runs.

Video:   https://www.youtube.com/watch?v=bY3n6Z_Au9M


Flexographic Printing (AKA Surface Printing)

How does it work?

Flexography uses a flexible relief plate, often made out of rubber or flexible plastic. This allows the inked surface to print on many kinds of substrates.

Step-by-step, the substrate is fed into the press from a roll and the image is printed as it moves through a series of stations. The first roller (fountain roll) transfers the ink from an ink pan onto the second roller (Anilox roll). The substrate then moves between the third cylinder (plate cylinder) and the fourth cylinder (impression cylinder). The impression cylinder at the far end of the cycle applies pressure to the substrate, transferring the image onto it from the plate roll. Similarly to gravure printing, it is dried and then the process is repeated – it’s printed four times in order to get full colour using CMYK.

flexoprocess

What is is used for?

It can be used for printing on almost any type of substrate, including plastic, metallic films, cellophane and paper. Often used for printing on packaging and other uneven surfaces. Some examples of what it is used to print are: plastic bags, milk cartons, disposable cups and containers, labels, envelopes, newspapers, wrappers, etc.

Advantages

  • Flexographic printing is faster than rotogravure (but quality isn’t as high).
  • Versatility – it can be used on almost any non-absorbent material.
  • It supports full range of colours.
  • It can be used with both water-based and oil-based inks – water-based inks are great for their non-toxicity.

Disadvantages

  • Not very advanced – can’t produce complicated and extensive artwork (compared to rotogravure printing).
  • Colours in final print aren’t as bold or crisp (compared to rotogravure printing).
  • The whole process is less dynamic as it’s quite an old printing process.

Video:  https://www.youtube.com/watch?v=vuGptR330VU


High-Volume Multicolour Silk Screen Printing

How does it work?

For this process, a mesh is used to transfer ink onto a substrate. Areas are made impermeable to the ink by using a blocking stencil – these blocked areas will not be printed, whereas the other sections will be. The ink is pored over the mesh and stencil and the substrate is placed on a firm surface beneath. A squeegee is moved across the mesh screen, filling the unblocked areas of the mesh with ink – a second reverse stroke causes the screen to meet with the substrate beneath, transferring and printing the ink onto it.

What is it used for?

Mainly used for printing onto fabrics, e.g. t-shirt printing. Also used for show cards, posters, etc.

Advantages?

  • It requires relatively low cost equipment.
  • Very economical for short runs.
  • It permits printing on practically any surface.
  • Almost any ink can be used – from glossy oil-based weatherproof inks, to delicate water-based inks.

Disadvantages?

  • Quality is not very high – unsuitable for fine detailed reproductions.
  • Delicate graduations, such as half-tones, are difficult.
  • The stencils have a limited durability.
  • It is a relatively slow printing process.

Video:  https://www.youtube.com/watch?v=tkuqA8w20W8


Foil Block Printing (AKA Foil Stamping)

How does it work?

Foil stamping comes down to three key things: heat, pressure and time.

Foil film is positioned between the heated metal die and the substrate – the die presses the foil onto the substrate and the heat activated the adhesive. With the correct level of heat and amount of time, under the pressure, the foil fuses onto the substrate.

foil-image.jpg

What is it used for?

You can print/stamp onto almost anything. Often used on book covers for example.

Advantages?

  • Unlike many printing processes, there is no ink used.
  • Foil does not change colour based on colour of substrate beneath – you are able to use light-coloured foil on a dark-coloured substance.
  • Can create a variety of finishes – metallic, matte, glossy, pearlescent, holographic, marbling patterns, semi-transparent tints, etc.
  • Big visual impact – have a shiny, lustrous finish.

Disadvantages?

  • Labour-intensive – can require multiple runs through press.
  • Can be expensive – not very cost effective.
  • Can’t be applied near print already applied by thermography – the foil stamping method uses heat and this will melt the thermographic resins.

Video:  https://www.youtube.com/watch?v=zEF0WMilG1k


Varnish Printing

Varnish is essentially ink without pigment and is available in many finishes including gloss, satin and dull – varnish manipulates how light reflects or is adsorbed into a sheet.

How does it work?

Different methods can be used in applying varnish to achieve different results. There is ‘wet trapping’, which is when varnish is laid in-line on top of wet ink and then there’s the opposite method, ‘dry trapping’, which is when the ink is allowed to dry prior to putting it through the press a second time to print the varnish. Dry trapping results in more contrast and a glossier look, but takes longer and requires two passes through the press.

Strike-through varnish is a technique in which a dull or matte varnish is applied on all areas of the substrate, except for the areas that are intended to be glossy. A high-gloss water-based coating is flooded over the sheet and as it dries, the varnish strikes through the aqueous coating to achieve a dull finish where varnish was applied and the areas where the varnish was not applied appears glossy. This process is more cost-effect than a dry trapping, but it does not achieve the same contrast.

Advantages?

  • Offers a range of varnishing choices, including tinted, flooded or spot.
  • Additional substances can be added to varnish, such as glitter.
  • Can be used to enhance specific areas such as text, logos or images, rather than cover a whole page.

Disadvantages?

  • Relatively low degree of protection – tends to yellow over time.
  • If printed over a crease in a document, it will crack.
  • Longer drying time.

Video:  https://www.youtube.com/watch?v=x7HAVcxuq3I


Die-cutting and Crease Printing

How does it work?

Die cutting is used to make multiple, identical shapes – it works in a similar way to a biscuit cutter. A shaped sharp blade called a ‘die is used to cut the substrate. The substrate is placed under the die, which is then lowered and pressed down firmly. For the creasing, blunt or slightly curved blades are used. Rather than cutting all the way through the substrate, it merely creases it – perfect for end pieces that need to be folded.

The cutting can also be done by a CNC (computer numerical control), which is the use of computers to control the cutting and shaping machines.

What is it used for?

It is considered ideal for packaging templates, for example a cigarette packet template. It can also be used for pop-up books and cards, press-out shapes for model making, etc.

Advantages?

  • Uniformity – creates multiple identical forms and you get lots of cutouts from the same die-cut.
  • Cost effective – Can be less expensive because only one tool or machine is needed to create the shape.
  • Less waste – leaves less waste than other cutting methods as the dies can be lined up very closely.

Disadvantages?

  • Can be time consuming if not using an automated machine – only having one die-cutter means each shape will have to be repeatedly cut out individually.

Video:  https://www.youtube.com/watch?v=vaMpdmI4XUs


Perforating, Punching and Drilling

How does it work?

The process of perforating involves, puncturing the substrate with a tool in order to make a strip of tiny holes in an organised fashion. Perforating allows easy separation of two sections of the chosen substrate to be easily torn along, allowing them to be separated in a straight clean line. Composed of a series of small impressions, tearing the paper from the perforation is quick and easy. Perforation can be created by pins, needles, die and punch or laser there are also rotary pinned perforation rollers which are precision tools that can be used to perforate a wide variety of materials.

Hole punching and drilling is used to prepare your documents for a variety of binders.

What is it used for?

Perforating is commonly used for mesh, invoices, receipts, stamps, purchase order books and tickets, etc. The substrate used would usually always be either paper or card. Packaging with perforations in paperboard or plastic film is easy for consumers to open.

Hole punching or drilling could be used for hole making, such as holes down the side of a page for a binding to be attached. Drilling could also be used to create holes for products like clothing swing tags.

Advantages?

  • Can create a professional and reliable holes for almost all purposes – endless opportunities.
  • Hot perforation melts a hole in the material, causing a reinforced ring around the hole.

Disadvantages?

  • Some perforation techniques can be very expensive, such as laser systems.
  • Cold perforation can cause slitting rather than creating a round hole – hot pinning is often more popular because of this.

Video:  https://www.youtube.com/watch?v=B7F8ifGCTcQ


Lasercut Printing

How does it work?

Laser cutters work by directing a very powerful laser beam, at a precise focal length, onto a material which they either cut or etch, depending on how the laser cutter has been set up. Laser cutters cut materials similarly to other computer controlled tools, only they do so using a beam of light, as opposed to a blade.

What is it used for?

Laser cutters can be used to cut and/or etch into a huge range of materials. The list below shows which materials can be used, as you can see, some are only safe to either etch or cut into, whereas some you can do both.

  • Acrylic (plastic) – can be etched and cut
  • Aluminium (metal) – can be etched and cut
  • Wood – can be etched and cut
  • Glass – can be etched

Advantages?

  • Capable of cutting through many materials and thicknesses.
  • Fast and reliable – easily and accurately repeatable.
  • Efficient processing – multiple jobs or parts can be nested and cut in a single program.

Disadvantages?

  • Extremely high power consumption.
  • Rate of production depends on the material.
  • Poorly adjust lasers can cause burning.
  • Difficulty cutting reflective metals (like copper, brass, and sometimes aluminium).

Video:  https://www.youtube.com/watch?v=cszsZMshm2k


Holographic Printing

A hologram is a physical structure that diffracts light into an image.

How does it work?

Holographic printing cannot be done on ordinary paper – in order to work, the substrate must be coated with a layer of metal (usually aluminium or steel) or reflective plastic. The hologram is embossed into the shiny metal or plastic, forming a complicated, extremely detailed, pixelated image.

What is it used for?

Holographic prints are extensively used for identification and security purposes. For example, credit/debit cards, driving licenses, passports, and security badges commonly have small holographic prints embedded on their surfaces.

Engineers and architects use large holographic prints to demonstrate or promote their projects in a more enhanced fashion than conventional photographs can do.

Advantages?

  • Small holographic prints, such as those found on identification documents and credit cards, can be produced at moderate cost.
  • Security – can not be replicated by being scanned or photocopied.

Disadvantages?

  • Large holographic prints, such as engineers might use, can range upwards of £2500 per piece.

Video:  https://www.youtube.com/watch?v=oGYLeTjELj4

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