Manufacturing of a Stadium Cup

Sometimes I am asked if we can make a few thousand of a special design or mold a few thousand of a special color. My hope is this section gives some insight why this is not possible with most production operations. The plastic cups are injected molded using rather large machines, using large expensive tooling. The tooling consists of multiple copies of the cores & cavities… which form the cup. In this picture, you will notice this tooling is a 16 cavity mold, with eight cores on each side and the cavities in the middle. Every time the machine cycles, it produces 16 cups. The process consists of the mixing of polypropylene resin & colorant, the melting of such, then injecting the melt into the space between the cores & cavities, the quick cooling of this, followed by the opening of the tool. When the tool opens, robotics grasp the 16 cups & stack them on a conveyor belt. The tool then closes & the cycle starts all over again, and does so every 8 seconds, 24 hours a day & 7 days a week.


Molds such as this contain an enormous amount of steel & other exotic metals and they are manufactured to extremely tight tolerances. A mold such as this is designed to produce millions of cups before needing refurbishing and can easily cost over $100,000 to produce. Now that is just the rather small mold… not the machine itself. So when you hear a muffled laugh whenever you ask if we can make a few special cups for your client, maybe now you will understand.


It is important to understand why special cup color requests can have such high minimum quantities. As we produce our stock colors, our normal minimum run is 50,000 pieces. The reason for this is as you switch from one color to the next, it is not an immediate change. The machines stores a large amount of resin & colorant, so as you make the change, it is a gradual process for the cups to transition from one color to the next. During this changeover, the machine keeps running & all cups produced during this period are unusable, and this product is ground up & reused in other applications. It would make little sense to produce small runs where you would waste more cups than you made. Now this discussion is based upon a rather large scale production. Some smaller producers might use much smaller machines with much smaller tools. I have seen cups made on a one cavity tool, so a producer such as this could easily offer smaller quantities & more economical startup of a new design. Larger machines & larger cavitation tools obviously benefit from the economics of scale. It takes a small machine making one part per cycle about the same amount of time as it does a larger machine making 16 parts per cycle.