Injection Molding Metal (Well, Metallic Glass—Like Metal)

While there is a considerable amount of attention being paid to the prospect of using additive manufacturing to produce metal parts, there is another alternative: injection molding.

That’s right: injection molding metal.

ENGEL (engelglobal.com), a producer of plastics processing machines, has become the exclusive machine manufacturing partner of Liquidmetal Technologies (liquidmetal.com). Liquidmetal makes zirconium alloys with a non-crystalline structure (amorphous). Another name for the material is “metallic glasses.”

This material results in parts that are hard and elastic. Whereas a component made from steel has an elasticity of 0.2% and titanium 1%, Liquidmetal alloy parts have an elastic value of 2%. What’s more, they are said to have a low specific weight and high corrosion resistance.

ENGEL has developed a new all-electric injection molding machine based on its e-motion machine to handle the material. The primary difference between a machine for plastics and the metallic glass machine is that there is an inductive melting chamber wherein the material, in the form of slugs cut from round rods, is melted under high vacuum conditions. Then the molten material is injected with a piston, instead of a screw, into a temperature-controlled mold.

There’s rapid cooling without oxygen. This leads to the creation of the amorphous structure. Robots are used to remove the finished parts. The sprue can be removed with waterjet cutting or mechanical shears. Sprues can be recycled.

Although there is a process called “metal injection molding” (MIM) that may seem similar (metal . . . injection molding), apparently, the “metal” is not a metal alloy but, rather, a metal/plastic powder. This powder is injected, but then the plastic is melted out of the part and a sintering process is required to attain the finished part. That can leave the surface rough and in need of additional processing.

According to ENGEL, the parts produced with Liquidmetal injection have a high surface quality and can be produced in a two- to three-minute cycle time.