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Tips on Rapid Prototyping | Surface finish

Rapid Prototyping is the process of manufacturing a trial version of a product or its components in a short time, so as to clarify the requirements of the product or to verify a product designer’s idea. Prototyping can give both the designer and the user an opportunity to prove that it is what the user needs. Alternatively, engineers can use prototypes to improve their understanding of the technical and the feasibility of production. Therefore, prototyping is a critical procedure for product development. In this paper, we would like to share some tips about surface finish treatment of prototypes, as reference for product designers.


1, Choosing the right type of aluminium for anodizing.

Anodizing is an electrolytic passivation process that forming a layer of oxide on the metal surface, so as to make it decorative, durable and corrosion-resist. Aluminium alloy is the most ideal metal material to be anodizing, but not all the type of aluminium can be resulted in the same surface finish, that’s because they have different ratios of alloy elements, such as silicone, magnesium, cooper, zinc, etc.  Let’s check what’s the difference of anodizing result between these types of normal aluminium.

2000 series, strong and hard because of the big amount of copper element, the anodizing coating tends to be yellow and low protection.

3000 series, the major alloying element is manganese which leads to strong and small grains. The anodizing coating comes out brown, and difficult to match the required color in pantone.

4000 series, the major alloying element is silicone, the anodizing surface comes out dark grey and usually with dark black smut which is hard to eliminate.

5000 series, the major alloying element is magnesium, which leads to strong, ductile, and fluid. The anodizing finish is relative solid and protective for the part. 


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6000 series, the major alloying element is magnesium and silicon. It can get ideal and excellent finish with relative precise color match to Pantone color chart after anodizing. Therefore, this series is recommended for cosmetic products and prototypes.


Finally, 7000 series, the major alloying element is zinc, so it is considered very hard and strong. However, the anodized finish is not steady and hard to control. Clear and black anodizing is relative fine, but if anodized into blue, orange, green, yellow and so on, the color will be inconformity, sometimes even generate some white stain. If your parts tend to be decorative, 7000 series aluminium is not recommended.


2. Surface finish for transparent parts.

1) Acrylic (PMMA), which is one of the most frequently-used plastic for those products that requiring high transparency with relative low impact resistance needs. The application ranges from glass, lights to bill board, home appliances. PMMA parts can be polished from rough surface to high glossy and even optical transparent. And any colors are available to be painted on it after polishing.


2) PC (Polycarbonate) well known and widely used for car lamp, gear, dashboard, windshield and so on because of its transparency and high impact strength. In rapid prototyping area, hand polishing doesn’t work if we need to make PC part with transparent finish, because PC is rigid. We need to use “vapor polishing”, to reduce the surface roughness or improve transparency. Even that, however, the transparency is not as good as PMMA parts, and after that, the PC part shouldn’t be painted, otherwise it will crack. 


We will present some more tips on rapid prototyping in the following articles, please click www.dankemold.com to get more information.

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