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Printing rollers are referred to as the “heart” of the printing press, yet the rollers are the most neglected part of the printing press.

Misuse of the roller is usually due to a lack of information on how best to care for them. Pressmen should check their roller daily; watch out for and prevent accumulated ink and glaze. The roller must be cleaned at once or it will crack and pit and continue to deteriorate.

Glazed rollers occur when the printer is working with materials soluble in water and minerals soluble with solvents.

Cleaning the roller of both types of glaze-causing materials is a difficult task. The recommended TRC Process is a two-step procedure.

Some products sold for use in the pressroom may have a detrimental effect on rollers and blankets. The harshness of the solution can be determined by soaking a section of blanket or roller covering overnight and checking to see if swelling has occurred. The TRC representative can demonstrate this test.

Most offset presses have automatic wash-up devices that do not clean beyond the face length of the roller. Heavy build up begins to flake off into press, causing “nickels”. To prevent this, the roller shoulders beyond the wash-up device should be cleaned by hand at least weekly. Where these ends are inaccessible, a long handled brush will come in handy. The wash-up blade should be examined for wear monthly, if necessary, replaced. Daily wash up of a press, sometimes leaves a residue of ink on the rollers. Ultimately, the surface of the rubber rollers becomes filled with dried ink, become hard and glazed and they do not accept and distribute ink properly. The rollers (rubber and urethane) are, then hand-washed with a stronger proprietary wash-up. (Ketones, acetates or any chlorinated hydrocarbons are never used). However, if glazing has gone too far, then this may not be effective. The roller should be removed from the press and sent for factory re conditioning.

Composition roller should be cleaned with a recommended roller wash after usage. At the end of the day, oil should be applied to the ink plate and the press should be run for a few minutes. Rollers will pick up a film or oil and this procedure will prevent ink drying on it.

When parts of ink rollers refuse to hold ink, this is called stripping. Usually it is steel rollers that strip, losing their affinity for ink but at times, even parts of rubber rollers refuse to hold ink properly. There are two main reasons for stripping :

A film of dried ink on the rollers often remains after each washup. The surface of the roller become hard and glazed and does not accept ink as well as it should. Once a glaze has been built up it must be removed.

If the above method is not completely effective, return printing rollers to the factory for re conditioning or re covering.

No roller can function properly if any part of its surface is clogged with dried oils, solvents or gum. Always check with the roller manufacture for proper wash-up solutions to fit your requirements.

Pressman know that if rollers are not accurately set, efficient operation of the inker units will be partially lost and they will not perform at operating capacity. Ductors, distributors and forms are driven from the surface of power rollers. Improper setting of the rollers may cause damage, adversely affecting the quality of printing. Rollers should be set as lightly as possible to accomplish their intended function of transfering ink to plate.

Press manufactures have made it easy to set rollers through fewer and more accessible adjustments. Great care must be given to the proper setting of rollers.

	Take a “picture” of the contact by washing the plates clean. Then, lock the inked rollers against them to print. Check several areas around each roller to determine the contact at both high and low areas.
	Place one narrow strip of paper between two wider ones. Place these between the roller and the surface against which it is to be set. Change the adjustment until the proper contact is felt on the centre or narrow strip.
	On flatbed presses, a quick picture can be made and checked by running the inked plate under the roller backing the roller sockets off on both sides. Then bring the sockets back one at a time to just touch the roller shaft.
	The lowest roller area must touch the lowest form area.
	Fountain rollers should be set in such a way as to be allowed to stop at a different position each time. To observe whether or not it is stopping in the same spot, make a little dent or smear some ink on the end of the roller and see if these marks move. Proper adjustment of the brake will take care of the problem and correction will result in a more uniform supply of ink.
	After the roller has been set and is running for a short time, check the setting and reset if necessary.
	For high speed newspaper printing very light settings are recommended especially for R.O.P color.
	When setting rollers there must be uniform tension on both ends. This is very important.
	Composition rollers must be set more carefully and reset more frequently because humidity and atmospheric conditions expand these rollers.

Rollers on larger presses are ground with crown to compensate for “whip” created at high speeds. Setting form rollers too hard is a common and faulty practice. Overloaded rollers especially during make-ready will not lift ink uniformly, resulting in a scumming condition. This will eventually work into the grain of the offset plate.

Roller should always be positioned without jarring, to avoid springing the core, causing it to run out of tune.

To get best results from a roller is to keep it in a soft smooth tacky, velvety condition, just the way the roller manufacturer made it. This can be done if these few simple rules are consistently followed.

Proper Selection
The type of roller required varies with its function; that is whether it picks up, distributes or deposits ink as a ductor, distributor, intermediate or form roller. The best roller also varies with kind of ink, press speed, type of presses etc. Roller manufacturers are continually developing new rubber compounds and improved urethane compounds to broaden the types of rollers available as original equipment and replacement.

Storage
Rollers should always be stored away from damp and heat, from sunlight, from ozone generated by electric motors, switchgears or generators. Special care has to be given to the physical location of storage facilities. Rollers should not be stored on open racks, close to non-offset spray guns, or in congested areas where they may be damaged by material handling equipment. Special care must be taken during storage so that only the roller shaft supports them. The roller should never be left in contact with anything that will cause a depression or a mark in the roller surface. Rollers should be kept away from dust and sunlight. They should be wrapped in paper or covered.

Spares
Printers should always have an adequate supply of spare rollers on hand; a quarter of a set for each press. When new or re conditioned rollers are received they should be put to immediate use and the ones on the press should be removed, cleaned and stored. Spares should be stored at normal room temperature and in a clean place. Spares should be rotated with the rollers on the presses at least every six months. Spares should be suspended on the journals either horizontally or vertically and the covers should never be in contact with each other or any other surface. Spare rollers should be covered when stored.

Setting
Improper roller setting may cause much downtime. All rollers should be set very lightly when cold because when in use, frictional heat and absorption of ink expands them. After the press reaches operating temperature in 20 or 30 minutes, roller settings should be rechecked and reset if necessary. In all instances, rollers should be set as lightly as possible to transfer ink to plate.

Wash-up
Pressman should check their rollers daily to watch for and prevent accumulated ink/gum glaze. Stripping, streaking, hickies, emulsification, excessive plate abrasion, ink glaze and gum glaze are some problems caused by improper wash-up. Prevention of a build-up of gum/glaze is better than attempting to remove it after it has occurred. This method provides clean performance from day to day and would be similar to always having a new set of rollers on the press. A roller cannot function properly if any part of its surface is clogged with dried oils, solvents or gum.

Reconditioning
If the surface of the rollers becomes hard and glazed because of accumulated dried oils, dried ink, solvents or gum, that’s the time to send the rollers back to roller manufacturer for roller re conditioning. Re conditioning of rollers at regular intervals not only maintains quality reproduction but actually extends the useful life of the rollers.

A good pressman takes pride in his press and every part of it. Unless the rollers are properly maintained, top quality printing is impossibility.

Inks of today are different from inks of years past. Higher speeds required by today’s printing market dictate faster drying time. To obtain higher gloss and faster drying, new synthetic resins have been used in the formulation of quick-drying inks. To enable printers to select the most efficient chemicals from the multitude available, given below are these chemical guidelines.