Stack molds in injection molding are often described as a way to double output without adding more machines. In theory, that statement is correct. In practice, the decision to use a stack mold is far more complex. At CINDY MOULD, we view stack molds not as a shortcut for productivity, but as a long-term production strategy. When properly engineered, a stack mold can significantly improve injection molding productivity and reduce cost per part. When poorly evaluated, it can introduce instability, excessive maintenance, and unnecessary capital risk. Understanding the difference is critical. What Is a Stack Mold in Injection Molding? A stack mold is a multi-level injection mold that contains two or more cavity layers within a single mold base. Unlike a traditional single-face mold, a stack mold produces parts on multiple parting lines during one injection molding cycle. In most configurations: The concept is straightforward. The engineering is not. Because the projected area effectively