Project: The McDonald's STRAW
McDonald's STRAW designed for the Chocolate Shamrock Shake
Did the world need another straw? Not really. But that left McDonalds with a problem: if you have a shake with the top half Shamrock and the bottom half chocolate, how do you get equal parts of both with every sip? This is the problem that NK Labs and JACE were asked to resolve for McDonald’s in spring 2017... and we had only had a few weeks to get a product to market in time for Shamrock Shake season.
The Design Process
The team initially challenged itself to come up with many concepts with few restrictions. We generated many ideas such as a two piece slider (one with holes, one without), another with a float to control fluid intake, and yet another with a wide horn to pull fluid from a large volume. Having generated some initial concepts, we next had to find one to balance the requirements for the product: food grade materials, quick-turn manufacturing process, cost, and of course dual-layer shake-drinking performance. We selected a concept based on a two simple ideas: first, a series of holes whose areas follow a Fibonacci sequence, and second, to shape the straw in the shape of the J to keep it drawing fluid once the first hole was exposed to air.
NK Labs engineers working through the design process
Concept Development and Testing
With the concept in hand, we began the detail design process to create a practical device that actually worked. We have a number of tools in house to rapidly turn concepts into manufacturable solutions. We created the original solid models using SolidWorks mechanical design software, and conducted computational fluid dynamics (CFD) simulations using COMSOL multiphysics. We also did a lot of rapid prototyping using our Formlabs 3D printer, and tested candidate designs by walking down to our local McDonalds restaurant. We optimized the diameter of the straw, which has a big impact on how much force is needed to draw a thick fluid through the tube. The area of each hole required fine tuning, and we needed an extra-large hole at the bottom to avoid leaving too much liquid at the bottom of the cup. After testing on well over 100 shakes, we had a design that worked well and also met the requirements for manufacturability and cost.
Computational Fluid Dynamics (CFD) simulation of two phase beverage flow
The result was the STRAW, which stands for Suction Tube for Reverse Axial Withdrawal. McDonalds introduced the STRAW to the world on a Facebook live feed, and it soon received coverage by Fast Company, Edgadget, Gizmodo, WIRED, and Slashdot. Then, it was featured on Good Morning America. Dedicated customers drove for miles and camped out in line for hours at the participating restaurants to be one of the first people to experience the STRAW.
IN THE MEDIA
McDonald's commercial for the STRAW, featuring several NK Labs engineers