The Printing Process in the Corrugated Industry
What is the most commonly used printing process in the corrugated industry?
I’m sure all of you would have come across many times in your life, various cartons printed using the processes I’ll be talking about. As I mentioned before, a little knowledge can go a long way.
It’s important when you are in front of a customer discussing products that you can identify the type of print processes used on the box. Depending on whether it’s lithographic or flexographic will have a huge effect on price. You want to ensure that you quote the customer what they need and equally important is to get it right the first time.
I’m not going to bore you with a lot of technical jargon. What I would like to do is help you understand and provide a little knowledge so you can confidently have an open discussion with your customers.
If you’re not too interested in the technical differences between both processes just focus on the information contained in both sections below. The information focuses on explaining some of the advantages and disadvantages of each print process.
If you are interested in a little more technical knowledge then read on.
Let’s begin by talking about the most commonly used printing process for shipping type corrugated boxes. Most of the shipping boxes “if printed” would be printed via the flexographic process.
Flexography often abbreviated to “flexo” is a method of printing most commonly used for packaging (labels, tape, bags, corrugated boxes, banners and so on).
A flexographic print is achieved by creating a mirrored master of the required image as a 3D relief in a rubber or polymer material commonly known as print plates or stereos. The inked plates have a slightly raised image and rotate at high speeds to transfer the image to the print surface. A measured amount of ink is deposited upon the surface of the printing plate using an anilox roll. The print surface then rotates and the doctor blade ensures the ink transfer on the anilox roll is consistent when contacting the print material which then transfers the ink onto the print surface.
Flexographic plates are made utilizing a relief type plate. The technology employs plates with a raised image (relief) and only the raised image come in contact with the substrate during printing.
Flexographic plates are made of a flexible material, such as plastic, rubber or UV sensitive polymer (photopolymer), so that it can be attached to a roller or cylinder for ink application.
The flexibility enables the plate to wrap around the print cylinder.
There are 2 main plate manufacturing processes which the corrugated industry use. One being
liquid resin or polymer which is the more commonly used plate. It’s perfectly suited for letterpress
or block style printing and is the less expensive of the two.
Solid plate is also used but the plate material and manufacturing process is more expensive. This type of plate has a higher gerometer which means it’s a harder compound then the liquid resin. Solid plates enable the print machines to produce a higher quality print.
For every colour to be printed, a plate is made for each colour and eventually put on a cylinder which is placed in the printing press. To make a complete picture, regardless of printing on flexible film or corrugated paper, the image transferred from each plate has to register exactly with the images transferred from the other colours. To ensure an accurate picture is made, registration marks are made on the flexographic plates.
These registration marks can be various types depending on the manufacturer’s standards. They could be round dots and/or crosses. When setting up the run these marks become very important for several reasons. Firstly, the machine operator uses them to line up the colours which ensures the colours fall where they are supposed to on the substrate. Secondly, they help reduce set up time on the machine. They are also used during the run for quality control and shows the operator if the print is still running within registration.
Lithography is an "offset" printing technique. Ink is not applied directly from the printing plate to the substrate as it is in flexography. Ink is applied to the printing cylinder to form the "image" and then transferred or "offset” to a rubber blanket mounted on the print cylinder. The image on the blanket is then transferred to the substrate (typically paper or paperboard) to produce the printed product.
In offset lithography (litho) a printing plate, which is most often made from aluminium, contains an image of the content that needs to be printed. When the plate is inked, only this image part holds ink. That inked image is subsequently transferred (or offset) from the plate to a rubber blanket and then to the printing surface. The process can be used to print on paper, cardboard, plastic or other materials, but these have to have a flat surface.
On sheet-fed presses, the substrate is fed into the press one sheet at a time at a very high speed. Web fed presses print on a continuous roll of substrate or web which is later cut to size.
High volume lithography is used today to produce posters, maps, books, newspapers and packaging and just about any smooth, mass-produced item with print and graphics on it.
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