Background

OXO partnered with Smart Design to develop a non-electric coffee gadget that brews hot and cold coffee concentrate in 5 minutes or less. At the start of the project, OXO mocked up an initial works-like prototype and Smart’s CEO discovered a “hack” using a competitor product with a unique brewing process. This groundwork planted the initial seeds of over a year and a half of design and engineering development.

Initial Concept Exploration

I started the project by diving into the world of coffee science. I quickly learned that there are numerous variables at play when it comes to brewing a “good” cup of coffee, including bean type, roast, freshness, grind size, water ratio, and steep time. I kept as many of these variables as consistent as possible to develop specific elements of the system at a time.

We aligned to start development focused solely on cold brew. I began making rough frankenstein prototypes by modifying competitor products and off the shelf parts. We focused on developing two different concepts; plunger and pump. Each concept had a different pressure delivery mechanism, but a similar architecture comprised of a stacked water chamber, brew basket, and carafe.

Early Iterations

For the plunger concept, I designed and printed molds to cast different types of silicone gaskets. I also tested different piston diameters and heights to see how they affected both brewing pressure and usability. For the pump concept, I tested different off the shelf ball pumps and digital pumps.

Testing

To quantify performance across prototypes, I used a light refractometer to measure TDS, or total dissolved solids. I also calculated extraction by multiplying TDS and output yield and dividing that by the mass of coffee used to brew.

Using these metrics, I ran numerous tests with different iterations of each prototype to determine the ideal size of the water chamber and coffee basket, as well as the ideal water to coffee ratio.

Rainmaker and Filter

Between the water chamber and the coffee basket is a porous divider called a “rainmaker.” The purpose of the rainmaker is to evenly distribute water across the tamped coffee puck without agitating its surface and causing channeling, or isolated funneling of water through the puck. There is also a steel filter at the bottom of the brew basket to catch fine coffee particles. I tested various different materials and perforation patterns for both of these components to find an ideal configuration that balanced extraction and brewing pressure.

Preliminary User Testing

After developing the overall architecture to a higher fidelity, we ran user testing with printed prototypes of each concept. The goal for this initial round of testing was to gather feedback on each step of the user interaction. This included filling the coffee basket, tamping the coffee basket, attaching all parts together, pouring water, pressing or pumping, and dumping the coffee grounds. For each concept, we compared the force and stability of the plunger vs. pump.

Machined Prototypes

To begin gathering more qualitative data on taste, we outsourced machined food-safe prototypes for each concept. We then ran more user testing involving taste, output volume, and more accurate cleanability.

For this round of user testing, I helped conduct user interviews and owned the full research synthesis and presentation to OXO.

Pump Development

We ultimately found that the pump interaction was both an easier and more enjoyable experience compared to the plunger, so we aligned on proceeding only with the pump concept.

I created a feels-like handmade prototype using turned parts on the lathe. I used this a diving off point to then develop two working pump prototypes with another engineer, equipped with pressure gauges to monitor brewing pressure. These prototypes were build internally with SLAs, turned ABS parts using the lathe, casted silicone parts from printed molds, off the shelf components, and outsourced CNC’ed parts.

We explored using duck bill valves and umbrella valves as both an output check valve but also to test pressure relief systems, I collaborated with OXO to ultimately land on a pump design that utilizes excess internal negative space that determines a maximum pressure the pump can physically produce following Boyle’s Law.

Tooling CAD

I owned the full preliminary tooling CAD package for the rapid brewer, including all exterior surfacing, internal components, and DFMA. Before tooling, OXO made some design refinements by adding a cosmetic shroud around the pump, a steel wrap over the pump knob, and an updated tamper design.

From a DFMA perspective, this project involved insert molding, two-shot parts, umbrella valves, compression seals, radial seals, dynamic seals, and one-time snaps.

Product Launch

Before launching, OXO and Smart experimented with brewing using hot water. We found the overall build and pressure system to still work well under higher temperatures. The Rapid Brewer has now launched with recipes for both cold brew concentrate and hot coffee contrate.