Biosystems and Agricultural Engineering

Growing Oklahoma

Biosystems and Agricultural Engineering

Growing Oklahoma

senior design team rotary arm redesign for coffee roastersus roaster corp logo

Rotary Arm Redesign to Improve Mixing Capabilities of Coffee Roasters

Cameron Buswell, Jonathan Lim, Sibongile Hlatywayo, Drew Sutterfield



A few years ago, the U.S. Roaster Corp conducted a customer survey about their current coffee roaster machines, in which they asked their customers about which aspect of their coffee machines could be improved. According to their clientele, their current coffee bean cooling system was the aspect that could use the most improvement. Thus, the Coolroast design group was tasked to construct a new rotary arm design for the U.S. Roaster Corp’s coffee bean roaster machines. This rotary arm mixes the beans as they empty into a cooling bin after being roasted. The necessary design specifications for the rotary arm were set forth in a meeting with the U.S. Roaster Corp on September 9, 2012, and are as follows: the rotary arm that the Coolroast design group should perform better than the current rotary arm design in several key criteria in order to improve the cooling process. The new arm design should improve airflow within the coffee bean cooling bin, which can improve the rate of cooling. It should also mix the coffee beans in such a way so that the beans cool more uniformly. The arm should also mix the beans so that they cool from a temperature of 450 degrees Fahrenheit to about 90 degrees Fahrenheit within 5 minutes. It should also empty out the cooling bin in a timely fashion, and minimize the amount of coffee beans that are broken while the beans vacate the bin. The new rotary arm should also not deviate too far from the aesthetics of the rotary arms commonly used in other coffee roasters.



Problem Statement

The need for this design was made apparent to the U.S. Roaster Corp after they assigned a previous engineering group from Oklahoma State University to discover which aspect of their coffee roaster machines needed the most improvement. According to a survey conducted by this group, the U.S. Roaster Corp’s clientele described that they thought that the cooling mechanism in the coffee roaster machines could be improved. This presents a bit of a unique problem: in a meeting between the Coolroast design group and the U.S. Roaster Corp that occurred on September 19, 2012, it was said that the consumers in the coffee roaster machine industry tend to shy away from purchasing roasters that stray too far from the traditional roaster look. Thus, the U.S. Roaster Corp cannot drastically change the design or aesthetics of the current cooling system, even if it does end up significantly improving the cooling aspect of their machines. It was decided that the rotary arm that mixes the coffee beans in the cooling bin attached to the roaster machine was the component that could be safely modified without breaking conventional roaster aesthetics. By improving the design of the rotary arm, it may become possible to improve the cooling rate of the coffee beans as they fill the cooling bin while cutting down on production costs of the coffee roaster machine. In addition, designing the arm to adhere to NSF standards could offer a unique distinction to the U.S. Roaster Corp’s machine over its competitors.

Scope of Work

The goal of our project is to improve the design of the U.S. Roaster Corp rotary arm that is currently used in their cooling bin designs. The type of work that we would need to do to accomplish this would involve: • Drawing preliminary sketches/concept sketches of new rotary arm designs. • Testing the current rotary arm design that the U.S. Roaster Corp uses in their cooling bin and gathering data from those tests. We will also need to do the same for our own rotary arm designs. • Researching NSF International guidelines as well as consulting professors within OSU to determine how the rotary arm can be designed to adhere to NSF standards. • Creating CAD models of preliminary sketches of prototype rotary arm designs. • Testing these prototype rotary arms using heated coffee beans and analyzing the rate of cooling using an infrared thermal imaging camera. • Creating a suitable mixing test by modifying an ASABE mixing assessment protocol to gauge the mixing strength of the rotary arms. • Determining how well the beans are being mixed using a mixing test using spray-painted beans as a visual tracer. • Testing and collecting data from our final design model using the thermal imaging camera, visual area evaluation method, and comparing it to the default rotary arm included with the cooling bin. • Comparing data gathered from testing rotary arm designs and judging which design is best suited for the cooling bin according to cost, bean cooling uniformity, bean cooling speed, bean mixing capability, and bean vacating speed. • Determining which rotary arm prototype is the most practical/efficient design. • Creating a final prototype from the best design model in the appropriate final material. • Presenting our final design to U.S. Roaster Corp.



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