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Synthetic rubber is used in roller creation: a complex mixture of organic
rubber and several chemicals that obtain their strength and
resiliency through the vulcanization procedure. It is the raw rubber that
adds the rubbery material its necessary qualities. The vulcanization
agents are added to this for the upcoming vulcanization process.
Plasticizers (liquid oils) play a major role as they – in addition to the extenders
and the vulcanization agents – determine the upcoming degree of hardness
of the material. The more plasticizers are added, the softer the rubber after
the vulcanization method.
Shore Hardness
The Shore hardness of a roller identified with a Shore meter
designates the resistance towards penetration of a needle using the
form of either a conic section (Shore A) or a point (Shore D),
pressed with a defined force (1 kp) for a period of three seconds
on the rubber surface. Soft rollers are measured with Shore A,
and hard rollers with Shore D. Inking rollers are required to be adjusted
to be oil-friendly (or oleophilic). In an inking system having conventional inks,
rollers of Shore A hardness in between 30 and 35 are used.
For UV inks, rollers with Shore A hardness of 25 and between 40 and 45 are used.
• Dampening rollers should be water-friendly (hydrophilic). For alcohol
dampening systems, Shore A hardness of between 25 and 30 is suitable.
In direct dampening systems, hard rubber rollers are employed.
Roller Protection
For washing the rollers it is recommended:
1. Use a water miscible wash to get rid of the top layer of solvent-soluble and water-soluble particles that came from the nap of the roller.
2. Apply a non-grit roller paste to take out the insoluble particles.
3. In the end, wash a second time with a water-miscible wash to eliminate the remaining soluble particles.
Glazing
Over time, rollers pick up particles from the ink, the paper coating and the
dampening agent which block their pores. This contamination ends in a
smooth shiny surface. Inappropriate detergents and hard water contribute
to this effect. Transport of ink and dampening solution is noticeably inhibited
because of this.
Problems with irregular rollers
-A worn out roller, a roller with damaged bearings, rollers set with too much pressure or, a roller that has not been adequately cleaned, can cause:
* color inconsistency
* poor solids, or mottling
* streaks
* muddy print
* extreme dot gain
Apart from the obvious expenses of poor print quality, as well as wasted paper and ink, bad or improperly maintained rollers could cause excessive press downtime, raised running costs, and shorter roller life.
Storing of rollers
If possible, do not expose rollers to direct natural or artificial light.
• The special paper that the rollers come served in prevents light
entering
and therefore helps keep the rubber’s qualities.
Because of this, do not remove the paper before applying the roller in the
• Always enter the roller with its pivots on a structure support: Installing it
down right onto the rubber can result in permanent deformations
(pressure marks).
• Keep rubber rollers in a cool and dry place.
• Within specific situations ozone leads to microscopic scratches on
the rubber surface. Due to this don't store rollers closer to
motors or other electrical gadgets.
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