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How To Make Lighter and Thinner Magnesium Components?
Magnesium is the lightest structural material offering very good damping characteristics, weldability and excellent shielding against electro-magnetic interferance, and is unlimited in supply. It has been an excellent material for making portable electronic and telecommunication devices, and automotive and aerospace equipment such as MD player casings, chassis for cell phones, video cameras and notebook computers, automotive gear housings, car wheels and engine blocks.
The most common methods to produce magnesium parts are die casting and thixomolding processes. However, these runner and gating processes provide a low material yield of only 30% for thin-wall casting and can only produce thin walls of between 0.7mm to 1.2mm.
If we can form magnesium parts from sheet metal just like metal stamping of steel and aluminum parts, we can achieve better material yield of about 80% and possibly safer operation due to the lower processing temperature. However, magnesium is known to be non-formable as it is very resistant to deformation due to its hexagonal close-packed structure. The only way is warm forming of magnesium as deformation of magnesium above 225 degrees Celsius will cause additional slip planes to become operative.
Extensive process research in this area have resulted in a few warm forming hydraulic presses available in the market for draw forming. Recently, research in warm draw forming of magnesium to make cell phone chassis has successfully shown that 0.4mm thin walls can be achieved consistently. Metallographic tests of the chassis have also demonstrated that there is zero porosity and increased rigidity.
While the current warm forming press systems are complicated to operate as they require the preliminary building of stroke and force profiles for the specific products using data acquisition modules and forming simulation softwares, the increased replacement of aluminum and plastics with magnesium for handheld electronic devices may well accelerate this process. Progressive early adopters of this technology would have a first mover advantage in the competitive global manufacturing industry.
About the Author: Author Ken Yap is a director of Suwa Precision Engineering in Singapore and represents Japanese manufacturers of niche precision engineering components such as stepper motor housings, connector shells and miniature precision balls.