One of the keys to manufacturing is efficiency of operations. The efficiency derived from Stackup Mold technology comes from the advantage of utilizing smaller foot-print molds to produce multiple parts in smaller molding machines, thereby lowering your part costs. Stack mold are like two single-face molds. mounted back to back. One core half is mounted to. the injection-side machine platen, ... injection nozzle during mold close. Benefits of Stack Molding: Stack molds can meet a variety of molding demands because they are available in a variety of configurations to best meet the demands of a specific project, and produce the most economical and efficient manufacturing solution. Increase output efficiency (productivity) Decreases number of machines required Lower machine size requirement vs. multi cavity single face molds Mold ejection functions are self-contained.