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ROLLER CARE

 
 
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For a Longer Roller Life
 
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.

Chemicals
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.
 
  • Solvents used on rollers and blankets must be compatible with the material upon which they are used. If unsure of solvent reaction, before using, test it on a piece of the material. Solvents containing benzol, toluol, xylol, ketones and toxic chlorinates should never be used.
  • Select chemicals with the highest flash point consistent with good performance. Chemicals should also have the highest Threshold Limit Value (TLV) possible. Both the flash point and the TLV are available from manufacturer’s Material Safety Data Sheet.
  • Chemicals seriously affect printing profitability. The price of chemicals is not an indication of result, cost effectiveness is.
  • Cost effectiveness = Price x Quantity required to do the job.
  • All chemicals should be treated with caution, respect and proper safeguard.
 
 
 
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