Eat Up
Food Packaging
Every time you open the refrigerator, a heroic engineering effort looks back at you. The global market for plastic caps and closures is worth $40 billion per year–and growing. Sophisticated packaging keeps consumers safe from foodborne illness, reduces spoilage and waste, makes it possible to deliver food to faraway markets, and provides distinctive experiences for customers.
Behind each plastic bottle cap is a careful engineering process that balances cost, user experience, and manufacturability at massive scale. Let’s take a look at what goes into a few of these mechanical marvels with the help of our industrial CT scanner.
Heinz Ketchup Cap
Heinz ships roughly a billion squeeze bottles every year. Heinz says it has put 185,000 hours and 45 prototypes into reinventing its squeeze bottle cap to improve recyclability. Heinz’s reasoning is understandable. Looking at the existing design with an industrial CT scanner, we see that it’s a complex assembly of multiple plastic materials, making recycling difficult.
But the lack of recyclability doesn’t take away from the brilliance of this cap’s design. In the early 1990s, Paul Brown revolutionized the condiment world by inventing a squeeze-bottle cap that could be stored upside-down without leaking. His company, Liquid Molding Systems, created 111 prototypes before finding exactly the right design, which it quickly licensed to NASA, Gerber, and of course Heinz.
Polyethylene Terephthalate (PET) is dense, making it easy to isolate it with our CT scanner. When we peel away the softer plastics in the cap, we see a floating ring in the center. What looks like a single-part cap turns out to be a complex three-part, three-material design.
The red blends into yellow area showing the perfect engagement between bottle threads and cap threads. Stiffener ribs provide a broad, stable base for the bottle to sit on while keeping the cap rigid enough to snap closed reliably. A flexure joining the cap lid to the main body is at the very top–a clever design that keeps the cap from flying away when open.
Sriracha Bottle Cap
Huy Fong Foods has a unique origin story: the company is named after the boat that the founder used to flee Vietnam. It produces Sriracha, a fiery red sauce whose packaging–a clear squeeze bottle with a green cap–is so distinctive that the company trademarked its design. The family-owned company popularized the sauce in the United States, and its factory outside Los Angeles now ships 20 million of its famous bottles every year.
The PET plastic bottle features a transfer ring just below the cap to enable factory automation; robots use this feature to lift the bottle without gripping it. Above that, a two-part screw on the cap forms the nozzle. In between the cap and bottle is a thin foil that ensures freshness and ensures the product hasn’t been tampered with.
This slice shows the essence of Sriracha’s nozzle design. The upper housing, which includes the outer ring, spins around the body of the cap, which contains the inner spoked wheel. The channels between the spokes allow the sauce to pour through, but only if the upper housing has raised itself from the axle at the center of the cap.
We see this protective multi-layered foil sandwich in many packaged foods. Seals like this are often applied by induction sealing, a non-contact method that heats an aluminum layer in the foil with an electromagnetic field, which in turn melts wax and polymer layers to create a clean seal.
Vita Coco Bottle Cap
After surviving the coconut water wars of the 2000s, Vita Coco emerged as the #1 coconut water in the United States. Its packaging design includes a protective seal that magically breaks open when the cap is removed. Developed with Tetra Pak, it remains one of the most innovative containers on the market, inspiring YouTube teardowns and Twitter exchanges with customers who wonder how their protective foil was removed.
Our CT scan of an unopened Coco Vita bottle confirms that the foil does indeed remain intact until you open the cap. The complexity of the cap design is evident in this cross-section: each cap contains a combination of threads, cams, followers, and even a saw blade.
The cap threads onto the bottle just like any other. What’s unique is its inner ring of cam walls. Between the bottle and the inner ring, you see a cam follower outfitted with a miniature hole saw. The follower is visible here above the saw and to the right of a stiffening rib.
What are all these extra rings for? The outermost and innermost rings are the same part – the cap. The consumer grips and twists the outermost ring, which spins the innermost ring and advances the cam tracks. The second ring from the inside is the saw, and here you can see its rotationally symmetric followers ready to push the saw into action when the innermost circle begins to turn.
