Monday, April 4, 2011

Miscellaneous Paint Application Techniques

Paint wipe operation should be considered when a product with a fairly flat surface, a lower surface is to be painted. The wipe set up is an automatic operation. Its use is more expensive than the cost of a mask, but it can handle very large volume. It can also be used where very fine lettering or designs are involved, where designing a mask for the job is almost impossible. Manual wipe is only feasible where the labour cost is very low.
Automatic wipe: Here the product indexes from the paint station to a wipe station where an absorbent fabric passes over the top of the product taking the paint off the flat surface and leaving the paint in the indented parts. A light solvent spray can be used to aid in paint removal. Disposable soft paper is usually used as an absorbent fabric, however some processors also use reusable fabrics.
Here the raised surface of the part is coated with paint while the depressed surface of the part remains uncoated. No secondary operations are required and the process does not paint depressed surfaces when even slightly raised sections are present.
Paint is applied from the overhead nozzles on the racked parts. The excess coating is drained off, after painting and is re circulated for use in the next cycle, thus resulting in very little waste. The process is not continuous, but many parts can be handled in a single cycle. Sharp corners should be avoided in the parts since it can result in excessive paint build up.
The part is dipped in the paint bath so as to minimize the wastage due to the overspray. Automatic system for raising and lowering the parts are used to control the uniformity of the coating thickness. Parts that entraps excessive air cannot be dip coated because they will require prolonged drain time.
It is a decorating technique also classified as a variation in painting. It involves coating of a plastic part with adhesive lacquers tinted to match the flock colour, and then the fibre (flock) is applied with a special flock spray gun. Flock imparts the appearance and feel of material such as felt (matted fibre), suede (soft or furry surface of cloth) or short napped mohair (Angora goat with long silky hair), to the plastic part.

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