How Will Magnesium Extrusions Be In The Future.

 

For one, they have screws and barrels that can accommodate processing temperatures as high as 590C. "That's about 100C lower than die casting but far higher than plastics," Vining notes. The thixo-machines also feature more robust hydraulic systems in order to meet high injection speed requirements (up to 1 m/sec).

Large parts represent another Thixomolding opportunity. Decker notes that the largest Thixomolding machine today is the equivalent of a 1,600-ton plastics molding machine. With Thixomolding needing five tons of clamp force per square inch of projected area, that size machine can produce some big parts. Decker reports that the next "big-part" project will be for automotive seat backs, which should go into production sometime this Spring.

"Magnesium alloys can be re-chipped and molded over and over again," Vining says, noting that recyclability gives Thixomolding an edge over plastics in Europe and Japan, where very tough environmental laws are more stringent (Magnesium Thixomolding). Designing for Thixomolding. With Thixomolding, processing conditions have strong relationships to design strategy. As Decker tells it, the processing temperature dictates the amount of solids in a given alloy's slurry, and fluidity decreases with higher solids.

Filling a mold and winding up with a dense part can be a balancing act. A typical thin-wall part, for example, would have solids of roughly 10% for a porosity that is just below 1. 5%, according to Decker. That porosity drops to about 0. 5% as the solids approach 30%.

With its move into automotive parts and new alloys, Thixomolding will increasingly go head to head not just with injection-molding, but increasingly with die-casting. Vining concedes that die-casting can produce simple, high-volume parts at a lower cost. Magnesium Thixomolding. But for complex parts designed from scratch for Thixomolding, "we have a cost advantage," he says, explaining that Thixomolding can mold in features that have to be machined into die cast parts in expensive secondary operations.

By saving material and runner-trimming operations, the hot runners are predicted to shave as much as 50% from the cost of smaller parts where the runner-to-part ratio is high, Vining says. Thixomolding from Thixomat Inc. Circle 546 Thixomolding Die-casting Density 98% 95% Elongation 6% 3% Minimum wall thickness 0. 02 inch 0.

Magnesium Thixomolding

"So at that point, we made a decision to add an external cooling fan, which gave us more leeway in the design of the heat sink. Magnesium Thixomolding."With the freedom to make the fins shorter or even take a hit on the thermal conductivity, Johnson evaluated both die casting and Thixomolding the heat sink out of magnesium.

A die cast part is going to be very spongy. Also, the economics were there." Phillips Plastics Corp.'s Magnesium Injection Molding business unit (Racine, WI) produces the part. While engineers have not tested this configuration to extreme limits, they have found it to be satisfactory in a wide variety of work settings to date.

1 - Magnesium Thixomolding. 2 History of success, PIM followed behind the first developments in plastic injection molding. Early polymers were thermosetting compounds; Bakelite, the first man-made polymer, was invented about 1909. Subsequently, as thermoplastic such as polyethylene and polypropylene emerged, forming machines appeared to facilitate the shaping of these polymers a few years later.

Since the mid-1990s, the use of paraffin wax has migrated to variants such as polyethylene glycol to give water solubility to part of the binder system. This has improved the concerns over solvents used to remove the binder from the molded component—simply immerse the shaped component in hot water to dissolve out most of the binder.