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make a bicycle frame?’” he said. “At some point, I decided it was now or never and I started actually doing something instead of dreaming about it.” Tat “something” started in 2010 and has become the “ideas2cycles” project, a non-profit organization for developing novel bicycle concepts with the latest technology and production methods. Five years in, Antin, along with two collaborators, has produced a number of innovative bicycle designs featuring a variety of materials and manufacturing processes. Among his most notable designs,

the original “Te Fixer” prototype was an ultra-light model featur- ing five investment cast magnesium lugs whose molds were created with 3-D-printed models. Now designing the Fixer’s third iteration, Antin again is using 3-D printing to create sand molds for aluminum castings that will improve performance and appearance. Antin began working on a design

for the first prototype during spare time from his studies. He wanted to produce something different from the conventional bicycle frame, which initially proved more difficult than expected. Te area between the chain ring and the back axle was particularly troublesome. Tere, the chain and back wheel must be free to rotate, while still allowing the cranks (which connect the pedals to the chain ring) to move freely. After a few months of designs and

redesigns, the ideas2cycles team had its first prototype, though it hardly impressed its creator. “I was scared it was going to

break in half. It was a little crooked and went a bit sideways,” Antin said. “Te wheels weren’t aligned, but still, it worked to some degree and that was encouraging. I always knew I didn’t just want to do one prototype. I wanted to do several iterations of an idea and develop it.” Refining that prototype and produc- ing other designs eventually led Antin to explore 3-D printing as a possible method of producing lugs, which con- nect the bike’s lightweight carbon-fiber tubes. 3-D-printed plastic components were not an option, considering the required mechanical and physical properties. CNC machining to produce

The 3-D-printed patterns reduced the time for the ideas2cycles team to produce prototype lugs.

The magnesium castings minimized weight while achieving necessary mechanical and physical properties.

molds was entirely too expensive. But Antin then looked into marrying 3-D printing with investment casting after he visited Aalto University’s met- alcasting lab, just down the hall in the engineering building. “I took a basic course on casting

but I didn’t really know much,” he said. “Fortunately, at the lab, I was able to talk to people with several decades of experience with metalcasting, includ- ing one researcher who had studied magnesium castings.” Considering the relative simplicity

of the components, Antin did thickness analysis in the CAD program instead of using casting-specific software to estimate which parts would cool first and which parts would need a feeder. Tanks to the casting expert’s contacts with a German 3-D printing company, two sets of patterns were printed for free and delivered in a week. Te pattern cluster was built and

hand-dipped in the slurry to build the investment shell. De-waxing and casting took place in a single day, producing ready-to-use lugs after minor machining. Unfortunately, two of the first set’s five castings failed due to insufficient wall thickness. Antin added some wax to the second set of patterns, repeated the investment casting process and produced accept- able components. But that initial failure highlighted

an advantage of rapid prototyping through 3-D printing and investment casting, especially for someone looking to produce unconventional designs. “I want to push the limits of what

can be done,” Antin said. “With rapid iterations, I’d rather just test some- thing. If I fail, I can backtrack a little and play it a little safer, instead of playing safe from the beginning and ending up with a heavier structure.” Te acceptable castings weighed

April 2015 MODERN CASTING | 29

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