If you are concerned about uneven roasting of beans the first thing to consider is the coffee you are roasting. Sometimes green beans are themselves very inconsistent, consisting of a wide range of bean sizes, ripeness at picking, and processing variations. Do not spend time trying to get inconsistent coffee to roast consistently.
However, if you know that your coffee is well graded and should roast consistently, but it is not, or if you are seeing a small number of obviously burnt beans in among otherwise well roasted coffee, your fan speed is most likely too low for the coffee you are roasting. This could indicate a need for re-calibration, but it could equally well indicate an unusual coffee for which you need to make some adaptations.
See Fan speed calibration for how to check if re-calibration is needed.
When roasting on BOOST at lower sized batches we find that sometimes the auto adjusted fan speed might still be too high with some coffees. Lowering the entered load size or altering the fan profile can resolve this issue.
Adaptations
If you need to make adaptations to accommodate specific beans, do not do this by altering calibration. Do one of:
Use the BOOST feature to adjust the entered load size setting until you have the correct circulation.
Alter the size of the load you are roasting; less beans means more circulation.
Alter the fan profile in Kaffelogic Studio. This is the preferred method, especially if you plan on sharing your adaptations with other Kaffelogic users.
How to alter the fan profile in Kaffelogic Studio
In KL Studio, click on the ‘Fan profile curve’ tab, here you can make manual adjustments to the curve.
In the same tab, click on ‘Tools’, ‘Transform profile’, and in the second RPM block on the right you can enter a value to move the profile up, or a negative value to move it down.
The default fan speed for the unit is 14,700 RPM and the input is multiplied by 10. Inputting a value of 25 will raise the fan profile by 250 RPM. A good starting point is inputting a value of 10 (100 RPM) and going from there.
Each coffee is unique and you may need to spend some time dialling this value in to achieve the perfect roast for that particular coffee.
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