Graphic Design & Printing Technology

Graphic Design & Printing Technology

Blanket and Roller Problems

Glazing

The ink system rollers and the blankets get shiny and hard and as a result it
looses its ability to absorb ink. Causes are:

• Improper cleaning of blanket and rollers.


• Excess use of solvents.


• Over exposure to UV light sources.
  Remedies:- Clean the surface with deglazing compounds
  Swelling

This defect takes place in the blanket due to the use of unsuitable chemicals.
This result in lose of image sharpness.
Remedies:- Remove excess swell of the blanket by reducing the packing, blanket
wash should be used which dries faster.
Paper sticking

Sometimes the paper is picked up by the image and non image areas of the
blanket. Causes are:

• Use of strong solvent in the blanket wash.


• The driers of previous ink may have been oxidised and created tackiness
  in the blanket surface.
  Remedies:- Use mild blanket washes, use blanket lacquer to remove tackness
  of blanket, apply pumic powder and keep the blanket to rest for some time.

Preventive maintenance

The use of proper setup procedures, proper ink formulation, and quality offset
paper as well as proper cleanup procedures, increase the production and
maintains printing quality. The following items should receive careful attention
when preparing to run a job on the press.

• Oil the press periodically.


• Check for lubrication points and examine the belt and pully systems.


• Chains of infeed and outfeed tables needed to be greesed and free from
  paper pieces and dirt.


• Oil reservoirs of vacuum pumps should be kept filled. The pump itself
  should be flushed out several times a year.


• All rollers and cylinder bearings must be lubricated on daily basis.


• A consistent maintenance schedule is essential.

Cleaning and caring the press

The most common procedure is to give the entire printing unit a thorough
cleaning at the end of each work day. Before the inking system is cleaned the