Injection molding speedster Proto Labs is now offering magnesium injection molding as part of its rapid manufacturing services. Called thixomolding, the new service is aimed at both prototypes and low-volume production runs of anywhere from 25 to 5,000 parts.

Magnesium injection molding isn't new; in fact, it's a mature manufacturing process. It can be used as an alternative method for engineers whose projects would otherwise depend on machining or die-casting processes. It produces fully dense, net-shape metal parts that resemble those made with die-casting. Strong and lightweight, magnesium is one-third lighter than aluminum and has an extremely high strength-to-weight ratio. It is increasingly being used for lightweighting in aerospace and automotive.

"In recent years, lightweighting has become a significant factor in automotive product development, for example, as engineers are being tasked with drastically reducing vehicle weight in order to improve vehicle gas mileage," said Becky Cater, Proto Labs' engineer and product manager in a news release. "We see magnesium injection molding as an important tool for achieving this."

In Proto Labs' process, magnesium AZ-91D feedstock is heat-chipped in the barrel of the injection molding press. A reciprocating screw transforms the material into a thixotropic, or gel-like, state. Under high pressure and at high speed, the material is forced into a steel mold to create the part. This process lets design engineers prototype with the same materials and processes that will then be used for producing the final part. Besides making prototypes, Proto Labs also offers production quantities of up to 5,000, with a typical turnaround time of 15 days.

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Magnesium thixomolding, along with thixocasting, rheocasting, and others, is one type of semi-solid metal casting. It can produce complex net-shape parts with thin walls and minimal porosity, and is considered safer and more environmentally friendly than magnesium casting. Although its design rules are generally less stringent than those for plastic parts, there's a greater need for smooth material flow. Design guidelines for Proto Labs' process can be found here.

Aside from magnesium injection molding, Proto Labs also provides more than 100 thermoplastic, liquid silicone rubber, steel, and stainless steel materials in its injection molding services.

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Ann R. Thryft is senior technology editor, materials & assembly, for Design News. She's been writing about manufacturing- and electronics-related technologies for 27 years, covering manufacturing materials & processes, alternative energy, and robotics. In the past, she's also written about machine vision and all kinds of communications.