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Coffee Roaster Design
Project Background

During my junior year in college, my two roommates were obsessed with home-roasted, home-ground, home-brewed coffee. One of them, an electrical engineering student, wanted to design circuitry for and construct a coffee bean roaster with temperature and timing control using a microcontroller and thermocouples. He ended up working on that project through multiple years of college. I’m not sure whether or not he has settled on a finished product yet. At the time, though, I was the “expert” in 3D modeling in our household, so I implemented his design ideas in the form of multiple iterations of his ideal roaster.

As he changed design plans, I would draw them up in Creo and give him the files to use as a building reference. Mainly, the models were meant to be a proof of concept that the dimensions that he had selected would actually work correctly with each other, and that the involved mechanisms were actually feasible. Most designs utilized a horizontal rotating drum to allow even airflow to pass over all of the beans and to mix them up, preventing hotspots. This would reside in an enclosure designed to contain the heat.

Mounted in the enclosure would be a few thermocouples along with a few resistive heating coils which would heat the air inside. Most of the designs that I modeled included a fan on the outside meant to pick up the chaff and carry it out of the chamber as well as to act as the main source of airflow, drawing the hot air over the beans but not allowing it to stagnate and overheat.

We experimented with a few different designs for adding and removing the beans. My favorite such design included a hinged door on the drum which could be opened after the enclosure was opened, and then the drum could be rotated like a lottery ball machine thus spilling the beans into the bottom of the enclosure. To automate collection, I modeled tapered walls into the bottom of the chamber to funnel the beans into a hole and into a bowl placed under the roaster. While I don’t think that he ended up using most of the design ideas and instead went with a cheap toaster oven as an enclosure, it was still interesting to consider the design challenges involved.

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