A basic understanding of Contact Coding.

This quide will give you an insight into what is involved.

Click here to download the guide in PDF format

A good understanding of the equipment is, of course, very important but to understand the fundamental aspect of printing with ink is invaluable.

What happens when ink is transferred by a typeface from an ink capsule to a surface to be printed?

Think about it in an enlarged way: ink is deposited onto a surface, a chemical mixture of solvent, or water, resin and dye or pigment.

It is wet but it resides there in a mound because that is the way the surface tensions work.

It starts to dry by exposure to the air and, of course, it is the surface of the ink mound exposed to the air that dries first, although at the same time the substrate may be absorbing ink to a greater or lesser extent – more if it is uncoated paper, less if it is glass.

Under these conditions it can readily be seen that the surface of the ink character can dry quickly but that, in so doing, it retards the drying of the centre of the ink mound; thus the print can become touch-dry quickly but a full ‘cure’ takes much longer.

The more ink (ink weight) deposited, the longer it takes to dry out.

Similarly, if you think of a flat rubber surface, the type face, being pressed hard into the felt transfer surface of an ink capsule, picking up a lot of ink on the flat surface and flowing down the sides of the type face, and this being squelched onto the print surface, squeegeeing the ink sideways, it is not too hard to see that using high forces is not conducive to a good print.

A gentle touch has everything to commend it; brute force will never achieve an acceptable result. Beware when you hear the phrase “stamping machine”.

WHAT SORT OF JOBS CAN THE CC100 DO?

The CC100 is a reciprocating contact ink coder, therefore most suited to coding stationary products. It will quite easily code 120 products per minute, so stationary means momentarily stationary as experienced on production machines such as yogurt, produce filling machines or form-filling/labelling machines, etc.

IS IT LIKE AN INKJET CODER?

No, an inkjet coder prints a vertical row of dots and relies on the movement of the product past the print head to provide the second ordinate necessary to form the characters. This is done by computer control.

The CC100 uses contact printing techniques and so is able to print logos, etc, as well as codes, and the control is simple.

IS IT LIKE A HOT-FOIL CODER?

No, a hot-foil coder transfers ink from a dry ink tape on foil to the product, using quite high temperatures and pressure. It follows that the product being printed has to be very firm or well supported by a platen, to allow pressure to be exerted. The print height has to be finely tuned to get an even print.

The CC100 transfers ink by gentle touch and can therefore print products that are relatively delicate and, because it prints in a straight-line motion, there is no requirement for precise height setting.

WHAT ARE TYPICAL APPLICATIONS FOR THE CODER?

It is used in the Food Industry for printing ‘Best Before’ dates and in the Household and Personal Toiletries/ Cosmetic industries for management codes. Overprinting labels on the machine before application is a common use and companies pursuing quality management systems use them to print traceability codes on all sorts of products.

WHAT MATERIALS WON’T IT PRINT?

Polypropylene is difficult and siliconised surfaces on labels are bad news, although in this case it is usually possible to leave a patch free for coding.

WHAT COLOURS CAN BE PRINTED?

DYE INKS – The dye-based ink is formulated from resin, ethanol solvent and natural dyes, which impart the colour:

Blue – This is the best colour. It is a basic dye colour, gives the best capsule life and works well on most products, with a very good drying time.
Black – This colour is achieved by mixing various other colours, which slightly retard the drying time and which can subsequently separate under very wet conditions, giving red-tinted effects.
Red – This is quite good, and looks gold when printed onto black plastic, such as video cases.
Yellow, Green, etc – These tend to be rather translucent and lack the density normally required for a good code – some Cosmetic companies prefer these colours.

HOW LONG WILL AN INK CAPSULE LAST?

We periodically test the life of a dye-based capsule on a test rig, printing onto a renewed paper roll so as to continuously consume ink, using 2.5mm type to reprint a typical ‘Best before’ date from which we expect at least 50,000 codes before replacing the capsule.

CAN OTHER INKS BE USED IN THE CAPSULE?

Possibly, but Cap Coder ink is a top quality ink, specially formulated for the printing industry. Do not mix different inks, or add different solvents to the ink capsule.