Caliper Considerations These are used to give some idea as to the relative performance of different surface effects and coatings. They can be used as a “quick” test for quality control Surface Considerations Slightly rough castings when painted give orange peel effect. Dressing of a casting is highly visible Porosity can give bubbled paint Casting oils /wax may give arise to fisheye effects Local filling gives smooth spots - A smooth surface is much preferred; any high gloss finish will highlight defects Masking Cost ; the more masks required the more costly it becomes. Block internal masking is used to cut down time Use of robotics for accurate spraying on volume components Use of die cuts to speed up processing Watch for shadowing behind port /screw plugs and other features
Colour Base casting colour, light on dark ! White primer needed to lift bright colours Reds and particularly yellows are difficult to get opacity correct on thin films Yellowing of some material with age and heat, noticeable on whites /silvers Gloss level, a semi gloss or matt will hide paint and casting faults Clean reds /yellow -Single pigment colours will require multiple coats to acheive finish White or grey primers may give different colours (hues) Metamerism – parts appear same under one light source and different under another. (Tip - In the absence of a light box a good consistent is north facing daylight)
Decoration Screen Printing: Pros; cheap, fine detail, can use the same casting Cons; can be scuffed off Infill / Machined in logo Pros; robust, Cons; has to be machined or cast in limiting caliper use to named supplier. Raised and Linished Pros; stylish, robust Cons; needs protective coat. Cast in, limiting caliper use to named logo. Fluid resistance tests: Brake fluid – passed elongated submersion tests in DOT4 and DOT 5.1 fluids (The part is left for 3 weeks before removing and washing in water. There should be no dissolving or blistering of the logo or paint finish. Slight softening is expected however the original or very near original hardness should return within 1 week) Wheel cleaners – tested and passed against popular products using Phosphoric and Hydrochloric based cleaners, as well as Alkali systems