When designing molds of multicavity layout using cold runner systems, the mold size often is increased to accommodate the runner, slides and mechanisms—and the cavity is more difficult to orientate for complex part shapes.

The molding process operating window becomes very restricted and warpage control is dependent on part modification or long process times.

Three-plate mold construction is sometimes used to permit higher levels of cavitation, better cavity layout and automatic mold operation. Using a hot runner system with direct thermal gating in place of the traditional mold constructions will permit the utilization of the multicavity mold in a more economical form—smallest parting line surface per part, low mold height, better cycle time, least scrap and best automatic function.

Using a traditional valve gated hot runner will provide additional advantages in cycle times, reduced part stress and higher quality parts. However, new valve gated hot runner systems that cause no mold height increase and are less expensive can help alleviate the initial cost and mold height increases of traditional valve gated hot runners that reduce economical effectiveness.

To provide better mold delivery times, the hot runner order may be for the entire “A” half minus cavities. This spreads the workload to a larger facilities base, which can reduce mold construction time.