Print Industry

Selective Plating Repair

A large printing company recently installed a multi-million dollar eight colour printing press. On commissioning the press disaster struck. A stray screw dropped from some where above the machine and embedded itself in the print cylinder roller.

This caused 150 almost identical impressions around the circumference of a 2.2 metre diameter central impression drum rendering the machine not quite useless, but capable of producing 50% work capacity.

 How to repair the damage raised several options:

1. Removal of the roller was out of the question as the whole machine would have to be dismantled, and other machines would be disrupted during its removal, resulting in total shut-down of the printing line.

2. The cost of a replacement roller would have been in excess of $100,000 (if available), and of course the machine would still have to be dismantled.

Another option was:

Filling the impressions with epoxy type fillers, but it could not be guaranteed that the filler would not fall out and cause further damage. Finally it was decided the only suitable method would be to use selective brush plating techniques.

The company in question had previously used Hawker de Havilland Processing Department to repair small localised damaged areas on printing cylinders and it was felt that HDH could undertake this task.

PROCESS:

The size of the task was formidable 2.2 metres diameter represents a 6.9 metre length with small indentations every 4.8 cm. Each indentation was varying in depth from 0.2 mm to 0.3 mm and approximately 5 mm in length and 5 mm at its widest point. Each indentation had to be blended out, removing sharp corners and depressions. The DALIC selective plating process requires a dish shape to effectively make the repair. It was decided to use copper to fill the depressions and finally use a nickel layer of approximately 12 microns thickness to cap off.  This nickel deposit would match the existing cylinder surface. The work of course, was done in-situ and had to be carried out on the upper cylinder surface to allow for plating solution flow and catchment. Plasticine masking tape and plastic sheet were used to ensure the solution did not go onto other areas of the machine and cause damage. The actual task was not easy for the operator as he had to lay down and reach forward to do his job - which was very tiring.  Initial progress was very slow and it was decided to introduce another operator to work on the opposite side of the cylinder. With each repair carried out, the cylinder was rotated slightly until the task was complete. This in all took just on 14 working days and the machine is now back in full operation.