Precision Coffee Roasting Gets Even More Precise With Help From the Makerspace


In an effort to improve the precision of coffee roasting at Swift & Finch, Mark McLucas upgraded the Victory 10 roaster by replacing the analog environment thermometer with a SOLO 4824LR PID controller and T-type thermocouple, which are capable of providing real-time temperatures within 1/10 of a degree.  The bean pile temperature is monitored by a near identical setup from the manufacturer.  He used the laser to cut an acrylic face plate and etch labels for both PID controllers, enabling him to differentiate between displays at a glance.

Precise monitoring and control of both bean pile and environment temperatures is
critical to producing clear flavors and a clean cup quality.  The temperature curves of both BT and ET move somewhat independently throughout the roast, and are manipulated through adjustments to airflow and gas charge.  Ideally, the two curves, though being 100-150 degrees apart at certain points, can be manipulated to move in tandem, the bean temperature gradually climbing to meet the environment temperature at the end of a roast.


To help with process control, he used the laser cutter to create a dial face for the gas control knob, making it easier to track and repeat exact set points procedures and train others in the fine art of bean browning.

To some, roasting coffee is considered to be a sensory operation: something conducted purely by watching bean color change, smelling for the development of compounds, and listening for first and second cracks.  However, the last few decades have brought about a more scientific approach to growing, processing, roasting, and preparing coffee, with roasting being one of the most crucial.  At the risk of sounding melodramatic (as is the inclination of some coffee professionals or people that fancy themselves as one), a coffee that has the perfect biological parentage, the ideal environment, and the best of care in growing, harvesting, processing, packaging, and transport can be blunted and even completely botched by roasting it without the same level of care and control.

All in all the project took approximately 6 hours, with approximately 3 hours spent designing the pieces and testing various laser settings to get the dimensions right, the edges clean, and the engraving deep enough.  The remaining three were spent on reassembly and testing.

What laser settings worked well? I found for the acrylic I used, a quicker speed (70), a lower power (35), and more passes (19) worked best for the vector cut.  I left the piece in place, added my engraving to the design, and ran the raster engraving back over the vector cuts as well to help clean up the edges.  Any pointers to other folks based on your experience?  Experiment a lot and be patient.

A well done laser cut is a beautiful thing.


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