Monday, December 26, 2011

Thermoforming Conversion Story:

Trike Conversion Kit Light Bars

California Sidecar, a 30-year industry leader in motorcycle trike conversion kits, was looking to find ways of cutting costs with a specific focus on the type of materials used to make their conversion kits. Obviously, due to lower volumes and high impact and structural requirements, fiberglass is a choice material for most of the applications on their kits. However, because fiberglass dominated, several components were sourced as fiberglass where plastics were more suitable and economical. One such component was the light bar assembly, a cosmetic rear panel that adds additional LED lights to the conversion kit for style and safety. It was determined that an ABS vacuum form would not only prove to be more economical but also resulted in an easier assembly process and weight elimination.

The process of converting the light bars from fiberglass to an ABS thermoformed plastic component required addressing a few design characteristic requirements necessary for the light bar’s function and aesthetics. Firstly, in order to achieve a class-A painted surface on the exterior of the light bar, a female mold would be necessary with a polished surface free of even slight imperfections. Secondly, the opposite ends of the light bars required undercut (or die-lock) features so that the final assembly would show no trimmed edges in order to achieve a high-end appearance. Since the undercut edge geometry was on a curve, hydraulically–controlled indexing details were selected to mold the undercut geometry. These undercut  details would then subsequently open up and allow the vacuum form to index from the mold cavity. Due to the mold size and deep-draw geometry a cast aluminum mold proved to be far more economical than an aluminum mold cut from billet. However, given that a CNC-cut surface was necessary to achieve the required finish it was determined to use a Renboard-cut foundry pattern with hand-constructed run out data. A very high quality cast aluminum mold with minimal porosity was developed and the mold surface was benched to perfection. Lastly, during the thermoforming process, a matched surface plug assist is utilized to achieve adequate material distribution and consistency. In the end a very high-end and aesthetically pleasing light bar was introduced to two of their Trike models providing the cost savings they needed while maintaining critical appearance and performance requirements.

Light Bar Close-Up Shot

Overall Trike Conversion Shot

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© 2011 Techniform Industries Michael Robinette

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