Stack molds might be for you if you have annual part quantity requirements in the millions, for products like the food containers with very thin wall.

If you are looking to expand your injection molding business then they can save you hundreds of thousands of dollars in capital investment.

They virtually double production capacity per machine.
They will save you buying extra machines and takeout robots.
The clamp tonnage required for a stack mold is half the tonnage required for a straight face mold with the same number of cavities. For example, if a 4 cavity mold requires 300 tons clamp force then 2 +2 stack mold requires 150 tons (for the same part) and then add a bit for the nozzle contact force (10%).

Stack molds can run in normal injection molding machines provided they satisfy the following criteria:

There is sufficient mold space
There is sufficient opening stroke
There is sufficient shot size barrel capacity
There is sufficient injection speed
Machine shut off pin (optional)