Post Moulding Operations
Sometimes known as Secondary Ops., once a moulding is produced it can be subjected to several additional processes.
Welding or Heat Staking
These processes are used to join individual plastic items together. Ultrasonic welding uses high frequency vibrations to weld plastic components together. Long ‘seams’ are possible, for example, to join two halves of a sphere. Staking can take several forms, but in effect, plastic is locally melted and then hardened to form a joint. A simple example would be a simple riveting type procedure.
Laser printing can be used for the addition of relevant information in the form of text or numerals, but the addition of coloured text and/or graphics is usually accomplished using Pad Printing.
Plating or Painting
Plastic components are first cleaned to remove any surface contaminants. The procedure for “Plating on Plastic” consists of a highly complex chemical and electro-chemical process, during which the components go through total immersion in numerous tanks of solution. This includes etching the surface of the mouldings, at a molecular level, to chemically deposit a conductive coating, prior to building up a layer of Copper and Nickel before the final decorative finish.
Painted finishes are usually achieved by applying layers of paint in a highly controlled environment, usually starting with a base coat that can sometimes be electrostatically charged. (To allow the use of electrostatic paint guns that add the opposite charge to the paint, therefore causing it to be attracted to the parts surface). Various finishes can be achieved, and a top gloss coat can be applied if required.
Sometimes more complex assemblies are required. These can still be a manual operation, e.g. involving the use of metal fasteners, but high-volume examples can be fully automated.