Background

OXO partnered with Smart Design to develop a manual 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 proof-of-concept prototype and Smart Design 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

The start of the project was primarily focused on brewing cold brew concentrate. I began by immersing myself in the world of coffee science, learning about the numerous variables at play when it comes to brewing a quality cup of coffee, including bean type, roast, freshness, grind size, water ratio, and steep time.

I mocked up “frankenstein” prototypes by combining modified competitor products and off the shelf components. I explored different methods of pressurization including manual and electric plungers and pumps, which included testing different piston diameters and heights to evaluate their impact on brewing pressure. While different concepts had different pressure delivery mechanisms, they shared a similar architecture comprised of a stacked water chamber, brew basket, and carafe.

Coffee Extraction Testing

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

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.

Prototype Development

I developed and iterated through numerous works-like prototypes to optimize the performance each of the brewer’s subsystems. Making air-tight, functional prototypes involved rapid prototyping in FDM and SLA, manual machining, laser cutting, and silicone casting.

Early prototypes used off-the-shelf bike pumps, but were later refined into prototypes with custom pumps made in-house equipped with umbrella valves and duckbill valves. Final pre-tooling machined prototypes were outsourced to test near-final fit and finish.

Rainmaker

Between the water chamber and the coffee basket is a perforated 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 (isolated funneling of water through the puck). OXO and I tested various different materials and perforation patterns to find an ideal rainmaker geometry that yielded optimal coffee extraction.

Filter

At the base of the coffee basket is a stainless steel etched filter used to filter out fine coffee particles. We worked closely with OXO to measure various off-the-shelf filters and identify the ideal filter pattern that brewed best with our grind size while not producing too much back pressure when brewing.

User Testing

User testing was conducted throughout each phase of the project, from informal testing with Smart and OXO teammates, to longer-term, at-home testing with cold-brew users.

We focused on each step of the user journey and key interaction points, including filling the coffee basket, tamping the coffee basket, attaching all parts together, pouring water, pumping the water, and cleaning the coffee basket.

For one of the formal rounds of user testing, I helped conduct user interviews and owned the full research synthesis and presentation to OXO.

Pump

A spring-loaded, manual air pump atop the product is used to pressurize the water chamber and push water through the tamped coffee puck within the brew basket.

To understand the desired proportions and user experience of the pump, I created an non-functional UX prototype by hand 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 SLA prints, turned ABS parts, casted silicone parts from printed molds, off the shelf components, and outsourced CNC’ed parts. Through user testing, we evaluated the different sized pumps to compare pumping force, number of strokes, and general ergonomics.

We tested different one-way valves including duck bill and umbrella valves for both the pump outlet and pressure relief systems. From a safety perspective, I collaborated with OXO to create a pump design that utilizes negative space in the pump shaft to prevent over-pressurizing the system.

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 and found the construction and pressure system to still work well under higher temperatures. The Rapid Brewer has since seen a successful launch with the capability to brew both hot and cold coffee concentrate. Users have already created in-depth video reviews of the product, and have experimented with their own recipes and brewing methods.