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Injection molding wax patterns for investment casting

Better accuracy, versatility, integrity, and finish are potential benefits for the investment casting industry from a breakthrough development in injection molding technology. Battenfeld Austria, working with the University of Leoben in Austria, has invented a new reciprocating-screw injection system for injection molding wax (IMW).

The present state of the art in IMW machinery involves a wax melting pot with a capacity of 50 to 100 liters feeding a plunger injection unit and aluminum tooling. Since the wax first has to be fully melted in the pot, startups can take 3 to 6 hours. The wax has to be kept at a constant temperature, so energy consumption is sky high. Plunger injection is used, so there?s no chance of quickly changing melt temperatures, and it?s impossible to control melt homogeneity.

In addition, since a very low viscosity must be achieved to ensure process stability in plunger injection, temperatures must be maintained at the upper limit. That means longer cooling times and slower cycles, not to mention, it typically takes a minimum of one day to change waxes. Using screw plasticating is difficult because waxes come in such a wide variety of grades, flow and hardening behaviors, and other performance properties.

In response to these challenges, Battenfeld?s system was designed with a heated screw and barrel. Its patented IMW injection unit features a reciprocating screw with a channel running inside the length of it. Hot water (140F to 158F) is circulated inside the channel, which provides a maximum of 2 minutes? residence time in the barrel, as opposed to weeks with a plunger. Material changes take only 15 minutes. Other potential benefits include more

design freedom, higher dimensional accuracy and consistency, and less scrap.

Nine prototypes are already being field tested.

Battenfeld Kunststoffmaschinen
Kottingbrunn, Austria
Phone: 43 (2252) 404 4810
Fax: 43 (2252) 404 3002
www.battenfeld.com

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