A German company, Injection Moulding Innovations Ltd., has introduced Simplex TandemMoulds, which replace complicated stack molds with two standard hot-runner molds by shooting the melt right through one part to mold the second part.
Injection Moulding Innovations estimates that at least 30 percent of all molds built worldwide could use the technology. The company claims part production costs can be reduced more than 30 percent, compared with a larger injection press with a stack mold or two standard presses with single, regular molds.
TandemMoulds can be run on standard machines. The processor can mold family parts such as waste bins, containers, buckets, cosmetic cases and margarine tubs with lids on a single machine with two simple hot-runner nozzles and needle valves positioned behind each other. There is no need for a manifold.
Normally, when two cavities are positioned behind one another in a single stack mold, the mold maker has to fashion a complex network of runners.
The company gives an example of a container and a lid molded in two alternating cycles, the lid first, followed by the container. Regular injection pressure shoots a hole through the lid, allowing the plastic to flow to the container. With thicker-walled parts, a needle valve also can be applied to pierce a flow path to assist melt flow.
According to the company in Versmold-Loxten, Germany, melt energy is sufficient to re-melt the part so the slug can reform, and the finished lid has no hole.
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