Finishing Techniques for Plastic Prototypes

After designing a plastic product from scratch, it’s time to have it prototyped. But what’s the best way to make the prototype’s look match that of the final product? Whether it be color, finish, or information, there are plenty of options available. Here are some of the techniques that we use at Produktworks.

Color and Texture

Spray Painting – After 3D printing a plastic part using SLA, FDM, or PolyJet, spray painting is the best option for adding color to the part. Some 3D printing materials are colored themselves. However, the finish of a PolyJet part is often lacking compared to an SLA part. Spray paint can match any color and the finish texture anything from matte to satin to gloss. Spray painting can also be applied in sections by masking off parts of the surface in between spraying colors.

Vacuum Casting – A neat alternative to spray painting is vacuum casting the part out of Polyurethane (PUR). Polyurethane can mimic both hard ABS and soft TPE, so the vacuum casting process is especially useful for overmolded parts. The PUR can be mixed with the desired color of the final mass produced product but is a suitable process for small quantities and prototyping. The tools are made out of silicone instead of machined aluminum, reducing their cost, but also reducing durability, as each mold can only be used 20-30 times.

Hydrographics – After spray painting a part, extra color and visual depth can be added by applying hydrographics. These patterns can be anything from wood grain to camouflage to carbon fiber. The pattern film is laid on top of a warm water bath, and the spray painted part is carefully dipped into the bath. The pattern adheres to the part, and a clear coat, ranging from matte to gloss depending on preference, protects the part from wear and tear. This process is useful for items that will be handled frequently, as it is robust, but is also valid for prototyping small quantities.

Conveying Information

Embossing or Cutting – If logos or written information is needed, a simple option is to design the information into the part itself through embossing or extruding. In final manufacturing, the tooling may be more expensive, but an SLA logo is easy for a concept prototype so long as the print is detailed enough.

Pad Printing – Used mainly for larger quantities of prints or mass production, pad printing applies ink using a silicone pad. It can be applied to convex and concave surfaces, especially silicone buttons. However, this may not be a financially viable option for a short run of prototypes.

Screen Printing – Screen printing is more suitable to prototyping and small quantities than pad printing. The information is printed onto a screen, and when the screen is exposed to UV light, the area without information becomes hard and prevents paint from passing through. The printed information is washed off to form a stencil. When paint is applied, it only passes through the part of the stencil that contained the desired information.

Rub-On Transfers – If only a few prototypes are being made, then rub-on transfers may be the best option. Similar to screen printing, a rub-on transfer is essentially an adhesive-backed screen print that can adhere to your desired surface. This is useful for adding logos or decals to small projects and can be applied by hand. However, the logo is more prone to rubbing or peeling off the surface.

Final Thoughts

There are many more options for applying color, texture, and information to prototypes, and here at Produktworks we know all of them. We’ll choose the best application method to make your prototype look just like the real thing.

Posted on January 6, 2018 in Design, Engineering, Prototyping

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