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Resource Guide
Chemical Impact on Rubber Rollers
Roller Maintenance Guide
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Roller Settings
The setting of a roller is the most important factor in a press. Nothing can
contribute to premature roller life and reduce quality of the finished product as
much as this commonly overlooker area. A roller set too hard causes great
dynamic stress and friction and can lead to heat build-up sufficient to cause the
roller to break down. Inking from rollers set with excessive pressure can produce
roller-strike streaks and also prematurely wear the plate. This heavy roller to plate
contact can further cause roller end damage.
An overly light setting will lead to poor or uneven ink or dampening solution
transfer. It may also effect the efficiency of your washups. Too light a setting on
the dampening rollers may set up conditions condusive to roller stripping.
The lightest setting possible to transfer the ink uniformly is the best setting. Care
should always be taken to ensure that rollers are set parallel to its adjacent roller.
With a parallel setting a nip of constant width is evident over the whole length of
contact.
Ink and water form rollers should be set to the vibrator first so that 0.1 mm milar
strips have an even drag at either end of the roller. Dampener roller settings can
be obtained by applying an even ink film on the dampener rollers and adjusting the
setting as you would for inking rollers. Typically a 3-4 mm nip between ink
transfers and vibrators is required and a 3-5 mm nip between ink forms and
vibrators is sufficient. This should be determined by the setting instructions of each
printing machine amnufacturer and through experience.
With the ink form rollers in a non-contact position to the plate the roller train
should be adequately inked. Gently drop the form rollers to the plate to determine
the nip width. Typically a 4-5 mm stripe between ink form and plate is required;
again, determined by the setting instructions of the manufacturer and through
experience. An alternate method for checking inking form roller settings is to ink
the plate up solid and lift the form rollers while the press is idling. This eliminates
the variable of excessive and/or uneven pressure being applied when the form
roller contacts the plate. Further, the chance of roller bounce is also removed. A
parallel setting is crucial for proper ink or dampening solution transfer.
Heat build-up and surface friction and surface friction will slightly swell a roller
covering, therefore, roller settings should be rechecked and reset, if necessary,
after the press reaches operating temperature. |