Roll cares
from Modinagar Rolls
A big name in the Indian printing industry, Modinagar Rolls Ltd is a manufacturer of all kinds of printer rolls. Diversity of printing systems requires different roll types where formulation of rubber, roller hardness, surface structure and elasticity change according to the type of printing system. Thus the rolls should be manufactured according to needs, sheet offset rollers, web offset rollers and flexography rollers. Vaibhav Agarwal, director, Modinagar Rolls shares some tips to guide everyone using the rolls get best of results.
Basic notes
It should be noted that the contact gap of the cylinder must have the values that have been stipulated to avoid problem of its edges dropping off fast. In multi-colour machines, rolls help a great deal to wash the cylinder that works continuously and periodically. Beware of cleaning substance like gasoline and solvent causing rubbers to swell by damaging its structure.
In cylinder coating, outer diameters of the rolls mentioned in the manufacturer’s manual must be taken as basis. Error in outer diameter measurement causes undesired results in ink density. The required cylinder’s area of usage is important because if the producer makes the coating in the rigidity level that is appropriate for the area of usage, the running efficiency of the cylinder will be increased.
Bearings and shaft ends of new coated or used rolls must be straight and rotate without balance. Otherwise that will cause problems of faulty transfer of ink. Rollers should be cleaned during stoppage of the machine otherwise the ink which dries quickly will stick on it which in turn causes affusions on rubber surface.
Storage tips
Rolls should be stored in places free from humidity and sunlight and which are not to be used immediately should not be opened. Put in upright position or hung vertically in order to avoid any external force upon the coated rubber. Putting rolls on top of each other or placing them on the ground should be definitely avoided. Otherwise due to weight of the rolls, traces will occur by touching each other or the ground.
Common faults
During assembling of bearings and shaft, the rubber of the roller may get damaged because laying the roller on the counter without putting a protective material under it resulting in damage of the rubber coat. Running of recently coated roller without carrying out new setting, letting it run with the old setting causes damages on coating and cracking on the edges because when the rollers become worn out or they are ground, the diameter will get smaller and the setting must be changed accordingly.
During running arising of the patterning fault the ink will not be transferred correctly resulting in vibration during running of the roller. Rubber gets cracked continual in some alcohol rollers. The reason is that separators of the rollers are worn out and escaped notice, the incorrect running of the roller will damage the rubber coating.
Cleaning techniques
Depending on ink types, solvents used for cleaning vary in different chemical constructions. In order to cover these needs, it is also necessary to use different rubber types and mixtures. While selecting the roller type, it would be useful to know what kind of ink you are working with in order to get best running performance from the roller— conventional ink rollers, UV ink rollers and rollers for mixed usage (20% UV +80% conventional).
