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Coating plastic mouldings: get the best results

You can apply rmi/emi shielding, or completely transform plain plastic mouldings, with an electroplated or painted finish. But electroplating & painting won't cover up the flaws in mediocre plastic mouldings. Here's our guide to get the best results.

1. Check your mould design

If you're planning to electroplate or paint your mouldings, make sure the designer is aware of this beforehand. The designer needs to ensure there are no blind holes or sharp corners in which a build-up of coating material can occur. Sharp grooves or raised sections can prevent electroplating. Also, it's necessary to allow for a means of jigging the mouldings during the coating process, such as a special plating peg, or simply by leaving a feed sprue attached to the mouldings.

2. Make sure your mouldings are the right quality

Your injection moulder needs to be ruthless about discarding mouldings that are not perfect. Any sink, flow and weld lines will be magnified by both the electroplating and the painting processes. The plastic surface quality is also paramount to good adhesion of the plating. Silvering (occurs if polymer was not thoroughly dried before being moulded), cold slug and high stress (caused by imperfect tool design) and the addition of too much colour to the base polymer will all prevent the coating from bonding to the moulding properly.

3. Make sure your mouldings get the right treatment

All mouldings need to be packaged with care to avoid scratches, both before and after being coated. The mouldings should be completely clean of oil, dust and any mould release agents to ensure good adhesion of the coat. As you see, selecting the right moulder can prevent a lot of coating headache. At Toolcraft, we manufacture coated mouldings for numerous customers. Our designers know how to design injection mouldings for coating, our production operators know which mouldings to discard and how to treat the ones that are correct for the coating process.

To find out more about different finishes, visit our emi/rfi shielding and plating page, or if you want to get going with plastic mouldings,

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