PRINTING PROCESS

There are various options for digital printing nowadays. These consist of using Toner, Electro-ink, and Inkjet technologies.

Digital printing means that the job is printed directly from a computer to a device that is connected via a network. As soon as a job is imposed (laid up) on a page, it can be sent to the digital printer.

Toner is finely powdered ink used in digital printers.

During the digital printing process, the toner is electrostatically charged to adhere to the printer drum charged with opposite polarity (so negative attracting positive). After transferring to the paper, the toner particles are then fused in place (adhered to the paper) by a heat fuser such as a heat roller.

ElectroInk technology (used on Indigo Digital Presses) uses small colour particles suspended in Imaging Oil (also known as Isopar) that can be attracted or repelled by means of a voltage differential (again negative attracting positive and so forth).

The ink forms a very thin and smooth plastic layer on the paper surface. The fact that these particles are so small ensures that the printed image does not mask the underlying surface of the paper (whether it be rough/ smooth, gloss/ matte, etc.), which is possible with some toner-based processes, bringing Indigo Printing closer in appearance to conventional offset lithography, whereby ink is actually absorbed into the paper.

Inkjet technology works by spraying very fine drops of ink on a sheet of paper.

These droplets are ‘ionized’ which allows them to be directed by magnetic plates in the ink’s path. As the paper is fed through the printer, the print head moves back and forth, spraying thousands of these small droplets on the page. Inkjet can print finer, smoother details and are often chosen to produce high quality photographic prints.

Large format is a term generally used for jobs that are larger than A3 in size. However, any job that is printed on a large format inkjet printer can be called large format. Whilst offset printing presses can print as large as A0 (1189x841mm) in size, there are substantial make-ready costs that prohibit small volumes printed. Therefore, lesser volumes are printed on large format printers.

A2 to A0-sized posters can be printed on either an offset press or with a large format printer. The point at which it becomes cheaper to print offset instead of using a large format printer varies due to the actual printer being used and the size of the product. Below is an example of when a poster job might be printed using the offset process instead of a large format printer.

A0 Posters

(1189x841mm)

Over 50 posters will generally be printed using the offset printing process A1 Posters

(841x594mm)

Over 100 posters will generally be printed using the offset printing process A2 Posters

(594x420mm)

Over 200 posters will generally be printed using the offset printing process

Of course, as technology is evolving, it is becoming more economical to print higher quantities with Large Format Printers.

Another product that is printed with a large format printer is a banner. Banners are an affordable form of outdoor advertising. They can be finished with eyelets and ropes for attaching to structures such as walls and fences. They can be easily rolled up afterward and used multiple times if necessary.

Large banners can be made by welding separate pieces together. This usually occurs when a large billboard is being constructed or the side of a building is to be covered.

The wind can be troublesome with vinyl banners so many are printed on a special mesh material so that the wind can pass through them. Double-sided meshes for when the artwork needs to be seen from both sides. In fact, there are many, many different kinds of vinyl and mesh to deal with almost every application. Its useful life ranges from 3-5 years.

Digitally printed banners can printed with aqueous (water-based) inks, eco-solvent inks, solvent-based inks, or UV-curable inkjet inks. The last three inks contain durable pigments that are weatherproof and scratch-resistant.

In some cases, the banner might be screen printed because a large quantity is required and digital large format printing would cost prohibitive or because special colours such as fluorescents might be desired.

Vinyl banners are commonly seen on billboards, as building banners, table banners, trade show banners and shop front banners.

Sometimes a banner may not be suitable and a board may be more appropriate. Examples of this might include directional signage, information boards, company logos at a trade show, or a mounted image on a wall.

Boards are made from any of the three processes.

1. They can be printed onto a vinyl sticker which is then mounted onto a rigid substrate such as foam core or MDF.
2. They can be printed directly using a flatbed printer. Here the substrate is placed onto a table and the print heads print directly onto the substrate. This method is relatively new and allows printing onto substrates with uneven surfaces such as a door or corrugated iron.
3. For larger quantities where the cost of digital large format printing is cost prohibitive, screen printing is used.

Clear (transparent) types of vinyl, translucent vinyl, coloured vinyl, and block-out vinyl are other options that are available if required.

Vinyl Duration

The length of time that a sticker needs to be on display helps us choose what kind of vinyl sticker to use. If a sticker is going to be up for a short-term promotion, we will likely use a “monomeric vinyl” which is cheaper but tends to shrink over time. “polymeric vinyl” shrinks less than monomeric vinyl and is generally recommended for jobs that will be up for three to five years. If a vehicle needs to be wrapped, then cast vinyl will be used as this has the least shrinkage and is also “conformable” i.e. it will apply around rivets and complex curves. It is likely to last up to seven years.

Vinyl Adhesives

For jobs that need to only be displayed for a week-long special, you might only require a mild adhesive so that it can be removed easily. These stickers are called “removable” and don’t leave a residue when they are removed. Floor signage, however, requires a very aggressive adhesive so that it does not lift due to the excessive traffic it is exposed to. Permanent adhesives can also be initially removable and then achieve a permanent bond after a period of time.

When deciding on what adhesive to use, another thing to consider is what surface the sticker is being adhered to. You wouldn’t put an aggressive adhesive on a polished floor unless you were prepared to redo the floor boards afterward.

Quality Of Printing

Having a high-quality photographic image on a billboard would be excessive as it is unlikely to be viewed at close range. It is smarter to print a large image such as a billboard at a lower resolution because it is faster to turn around and at the same time uses less ink, which makes it cheaper as well.

Installation

Installation can be expensive – sometimes more expensive than the printing itself!

Large format stickers can be challenging to stick up yourself if you are not familiar with the correct procedure and this can result in visible wrinkles, bubbles or stretched areas. Often a professional installer is required to complete the work and if the job is a complex one, extra installers may be required for assistance, resulting in higher costs.

When a job is to be installed at a height of over 3 meters, a scissor lift or a boom lift will be compulsory for safety reasons and this may require council permits if the work is in a public place. It will usually have to be installed outside of normal hours too which can increase costs again.

Travel time is another factor when it comes to installs. Often, particularly in the case of a complex installation, the installer may have to inspect the site before the job can be accurately quoted and will charge accordingly, especially if the site is distant.

Offset printing is perfect for your longer run print runs such as flyers, brochures, catalogs & magazines. 

It is a traditional process of printing and produces the best-looking results but also involves the most work in setting up a job and therefore has higher “make-ready” costs.

Making ready involves creating individual plates per separate colour for each side of the sheet. Each plate is then loaded into its colour station on the press. Once this is done, the correct water/ink balance has to be determined at each station as well as the registration (positioning) of each colour on the page. In short, it is a fine-tuning process to ensure that each impression of each colour looks good and is positioned so that all four images are on top of each other. This process can take anywhere from five to thirty minutes to make a press ready to start printing. The cost of the plates and the time to set them up is what is called the “make-ready costs”. This is the reason that you pay hundreds of dollars when “you only wanted 100 flyers”.

As the ink in offset printing is mixed with water and applied to paper in a wet state, it takes time to dry. Some stocks might take two days to dry properly before you can cut them in a guillotine otherwise the ink on one side of the sheet might “set off” onto the back of another sheet.

Offset printing is also used for printing Pantone Matching System (PMS) colours. These are specific colours with a unique code number such as PMS 186 which can be found in a Pantone Swatch book. These swatch books enable printers to replicate these colours accurately every time, no matter what country they are in. This is handy for companies who want to ensure that their branding colours remain consistent.

Whilst the set-up costs are higher in offset printing, the running costs are reasonably low. This means that the digital printing process may be preferable for printing a job when it is under a particular quantity but if the quantity were to increase, then it might be cheaper to use the offset printing process. The threshold that determines when the process should change is different for each job. It is largely dependent on the size, quantity, and complexity of the project.

Screen printing is a technique that uses a woven mesh to support an ink-blocking stencil. The stencil forms open areas of mesh that transfer ink which can be pressed through the mesh as a sharp-edged image onto a substrate. A squeegee is moved across the screen stencil, forcing ink past the threads of the woven mesh in the open areas. 

Screen printing is also a stencil method of printmaking in which a design is imposed on a screen of silk or other fine mesh, with blank areas coated with an impermeable substance, and ink is forced through the mesh onto the printing surface. It is also known as silkscreen printing. 

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 printing process that involves an image being transferred from the printing plate via a silicone pad onto a substrate (the surface to be printed). Pad printing is used for printing on otherwise impossible products in many industries including medical, automotive, promotional, apparel, electronics, appliances, sports equipment, etc.

Physical changes within the ink film both on the printing plate 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 (i.e. flat, cylindrical, spherical, compound angles, textures, concave surfaces, convex surfaces).

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 sticky 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 sticky 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.

There are two methods of Dye Sublimation printing. 

The first method involves a digitally driven thermal print head to transfer dispersed dyes directly onto a substrate. A common product that is printed this way would be the instant personalized plastic cards that you get when you join a gym. A simple dye sublimation card printer can do this while you wait.

The other method uses a normal print head to disperse dyes onto a transfer sheet, which is then placed against the substrate and together they are heated so that the image transfers across. This method is frequently used to dye fabrics, in particular polyester.

Disperse dyes are not soluble so they are still in a solid state while they are mixed in an aqueous solution to create the dye sublimation ink.

As the ink is heated to a specific temperature, the dispersed dyes ‘sublimate’ which means the particles vaporize, causing the image to transfer onto the substrate. When the substrate cools, the dye becomes solid again.

Platen presses can be used to dye sublimate individual pieces such as cut apparel parts, T-shirts, sports apparel, tote bags, etc. Platen presses are also used to print on rigid substrates such as ceramic tiles.

Rolls of fabric are printed using sublimation heat transfer machines, through which the printed transfer sheet and the unprinted fabric substrate pass between two heated rollers. Variations in temperature control the amount of dye that sublimates, thus varying the colour intensity. It is an effective way of printing onto fabrics, as the dye molecules sink into the porous material.