Doubled Output. Reduced Part Cost. Multiple Components In One Shot.

Stack molds double (or more for increased stack mold levels) the output of standard plastic injection molds, increasing molding efficiency and reducing the overall part cost. Stack molds can also produce multi-component assemblies or a family of parts in one shot on one plastic injection molding machine.

Stack Molds

A stack mold can be described as a series of interconnected, same-sized, single-face molds, where the molds are “stacked” next to the other. Thus, without increasing the plastic injection molding machine platen size or tonnage, stack molds double the number of cavities producing parts. Three-level and four-level stack molds triple or quadruple production volumes, respectively.

Most stack molds have an equal number of the same cavities in each side of the mold, or parting surface, but they can also have different cavities in each mold parting surface to produce a family of parts per shot, with each part being a different shape and size.

See the stack mold process in action:



  • Doubled part production (more for three- and four-level stack molds)
  • Optimal molding efficiency
  • Reduced production and part cost
  • Ability to mold multi-component assemblies or a family of parts in one shot on one plastic injection molding machine


Stack molds benefit many applications, some of which include:

Proper stack mold design and construction are critical to success, and EVCO Plastics in-house engineering and mold design and building teams are highly experienced. Robotic automation is often employed for increased speed and accuracy.

Lower your part cost and gain competitive advantage via EVCO Plastics’ experience with stack molds in custom plastic injection molding, focus on early supplier involvement in the engineering and design process, design for manufacturability, project management, material selection support, and global systems and global locations in the United States, Mexico and China.


Stack molds in plastic injection molding offer advantages for a wide range of plastic injection molded parts and products, including reduced overall part cost and the ability to mold multi-component assemblies, or a family of parts, in one shot on one plastic injection molding machine

When plastics matter to your business, partner with EVCO.
Where innovation takes form.