A D V A N C E D M A T E R I A L S & P R O C E S S E S | M A R C H 2 0 2 3 2 8 SMA ENTREPRENEURSHIP: SHAPING THE FUTURE I first encountered shape memory alloys (SMAs) in 1972, when I was hired as an alloy production manager for the Metals Division of Raychem Corp. At that time, our division was making product using a special low temperature version of Nitinol. Within a short time of melting, forging, and characterizing the material, I decided that for a materials scientist, working with shape memory alloys was as interesting, challenging, and rewarding as one could hope for. Following are a few examples of the fun I enjoyed as an SMA entrepreneur. When Raychem learned of the invention of the shape memory alloy Nitinol, developed in the early 1960s, the immediate question was whether or not they could make a “shrink tubing”with it. Raychemwas known formaking plastic shrink tubing used mostly by electricians for insulating wire joints. The invention that sprang from that question was Cryofit, a tubular metal coupling designed to expand in diameter while below its transformation temperature (TTR). Then, the ends of high strength metal tubes to be joined wouldbe inserted into it, andallowtheCryofit towarmabove its TTR so it would “remember” to be smaller in diameter and clamp down on the tubes to make a weld quality joint. The Cryofit system for joining high strength titanium tubes had been sold to the Navy as the system for plumbing the hydraulic system of F-14 Tomcat fighter planes. This presented one serious requirement. As the Tomcats would be flying stratospheric with temperatures down to -500°C, the TTR of the alloy needed to be much lower so that the couplings could never transform and loosen in service. Another invention was needed. A strong, ductile, machinable Nitinol with a transformation temperature below -1000°C was found. The equiatomic alloy discovered at the Naval Ordnance Laboratory had a TTR just below +1000°C, so this was no trivial change. During the ‘70s at Raychem, my job was to make bigger and cleaner ingots of the needed alloy faster and at lower cost, and fabricate them into machinable rod stock with the required mechanical properties. The Metals Division also developed other SMA-based products, including electrical connectors, safety devices, and package closures. One thing became clear as we created new products for new markets—if there is a way to solve the problem with a standard material, DON’T try to force an SMA solution. It will almost always be more difficult and more costly. Another lesson was that good applications will rely on one of the unique properties that SMAs have for their value proposition. Whether using the shape memory effect, superelasticity, variable modulus and stiffness, or energy absorption of repeat deformation cycles, success will invariably result from utilizing an SMA property not available in a standard material. After leaving Raychem and co-founding Beta Phase, I was lead engineer on developing SMA eyeglass frames. The initial idea was that shape memory frames could be easily brought back to ideal shape, if they were bent, by running hot water on them. We quickly realized that the better benefit for the customer would be to make superelastic frames that would rebound immediately to ideal shape if bent. This required a different Nitinol alloy with a much lower TTR, plus additional processing for enhanced elasticity, but created a much better product for the customer. Around the same time, we were using a small wire actuator to regulate the flow rate in an IV medical fluid controller. We found that the actuator need not be just an “on or off” component, but with proper position detection and feedback, an extremely small, light, silent, and accurate proportional controlling actuator could be made. One thing became clear in developing the small actuator: It is not only necessary to use the SMA material with the correct TTR, but the processing history (i.e., deformation, heat treatment, and post-processing steps) must be clearly understood and scrupulously followed to ensure reliable product performance. After the Beta Phase work, a friend asked if I would help him launch a company based on small diameter (< 0.3 mm) Nitinol wire, and this became Dynalloy Inc. While sales have been slow and steady, I’m convinced that Dynalloy has now sold more Nitinol components and finished products than any other SMA-based company. Success has been hard fought and based on rigorous adherence to proven manufacturing processes—along with a deep understanding of the strengths and weaknesses of the company’s actuators. Perhaps the advice for aspiring SMA entrepreneurs could be summarized in three points. First, find a real need for a product that can only be made using one of the unique SMA properties. Second, determine not only which SMA to use and what TTR is needed, but also the processing steps required to reliably obtain the final characteristics essential to market success. Third, stress the unique selling proposition and performance of your product, but be prepared for a lengthy adoption time by the market. Success is not often achieved overnight and may be best measured in years. Darel Hodgson, FASM Co-founder, SMST GUEST EDITORIAL Hodgson 2
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