Rollers

When buying a printing press, the inking. damping and distribution rollers with which it is fitted will have been designed for use with that particular model and make of machine. Although most modern rollers are made of nitrile rubber. press manufacturers specify the hardness. diameter and correct roller pressure for their machines. Consequently. when replacing rollers, the new ones must adhere to the correct specifications.

The hardness of rubber is represented by ascale of one to 100 on a Shore 'A' scale Most inking rollers fall within 25 to 30 Shore and most distribution rollers between 25 and 40.

Today's roller technology is very advanced and a modern roller. manufactured to fine tolerances will provide a fine. even surface which is hard wearing. However, there are different grades of rubber and one compatible with the ink. solvent and substrate must be used.

If changing to alcohol damping on the press. then the rollers should be replaced with ones which are more hydrophilic. If ultraviolet facilities are added, you may be able to change just your wash-up, but check this with the roller supplier. In fact, it is wise always to check with your roller supplier before changing any inks or solvents.

CHEMICAL RESISTANCE

Roller coverings are subjected to various chemicals during their use, from inks and damping solutions to washing up and cleaning agents. Be sure only to use recommended chemicals and always wash off thoroughly afterwards.

To scavenge a roller to remove dried ink. there are cleaning pastes which can be put on the roller after it has been taken out of the press. These pastes are effective but never use one designed for off press use with rollers still on the machine. Do not let the roller become contaminated with substances like machine oil or silicon spray.