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Reliable method and supplier for painting zamak 5 component

We are producing electronic modules. These modules include a component produced by zamak diecasting. This component is visible inside the car compartment (mounted on the dashboard). Customers require it to be matte black. We started with powder painting. The component is a subject of appearance criteria. During one year we worked with two suppliers, but we faced same problem - very low and unstable yield after 100% visual screening of painted parts. There are many causes for that: the component is small size (dia 10mm), it must be painted only at outer surface and no paint allowed in the inner, painted surface should be smooth and with an equal color, and without defects visible with naked eye from 30cm. One of the main visual defects we have is inclusions in the paint layer which look like very small "white dots". Microscopic investigation shows these are dust, metal micro chips, etc.

Now our supplier uses tribo gun manual spraying - due to manual operation we have not a repeatable thickness of paint layer, which is very important as the outside dimension is defined as a special characteristic by the customer.

We are looking for reliable method of painting...

For the short term a supplier (painter) of powder coating. We are looking for automated industrial facility of painting service...

... and for a proven alternative method for the next time. The forecast is for 200K this year of ramp up.

Penka Bahtchevanova
QA eng, automotive products - Sofia, Bulgaria
2004

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2004

We supply a waterborne stoving black that is used to coat original interior mirror arms.

Try to get your local paint mfgr. to formulate a matte black water based material for you. No paint inside -- controlled film weight and matte-ness.

You will obtain the correct matte-ness - film weight is no problem as you apply the paint film using an air assisted wet spray gun.

We control matte-ness 15% + - 1%. The white bits are probably poorly dispersed matting agent used by the mfgr. to obtain matte-ness. Finding the correct agent for this is the art plus the blend of resin to melamine resin.

Terry Hickling
Birmingham, United Kingdom

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You might also try e-coat.

-LOW COST: black e-coat is an industry standard, resulting in many companies around the world having huge lines that could coat your part at low cost. The efficiency is much higher than powder coat and the paint is supplied in such volume that costs are low.

-THICKNESS CONTROL: Where powder coating may require a tolerance of 1-2 mils (thousandths of an inch), e-coat can typically hold 0.2-0.3 mils tolerance. We use eddy current thickness testing equipment and get excellent gage R&R with minimal cost basic fixturing.

-GLOSS: The automotive standard paints are more a satin appearance than a full matt, but are definitely not glossy. Worth a try. They can custom formulate to get the matte finish you desire.

There are many custom e-coaters. Best of luck.

John Thornton
- Boston, Massachusetts
2004