TRC
 
 

ROLLER CARE

 
 
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Testing Roller Settings
 
  • 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.

Reading Roller Stripes
 
Proper Maintenance of Rollers
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.
 
  • Properly maintained rollers, are the ”heart” of the printing press. In A-1 condition, they will go far to ensure top quality printing. If they are mishandled or ignored, they will be blamed for costly downtime, and for inferior work.
  • A consistent roller care program can improve printing quality and reduce roller costs. It has frequently been said that $500 worth of rollers will print $50,000 worth ink and $500,000 worth of paper.
  • The ultimate success of the printing process depends on the control of ink distribution. A good roller has the ability to pick up a film of ink and deposit what is necessary for a proper impression. This establishes the necessity of always having the right roller under the best possible operating conditions.
  • When rollers get hard, dry, cracked, dead or dirty, they become full of tiny surface cracks or a hard glaze. These will prevent the roller from performing properly and it has lost its ability to hold on to and spilt ink properly. These conditions invite water logging and stripping and can ruin even the most beautiful, sharp halftone to muddy prints.
 
 
 
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