The first set of grinders from the sample production run have arrived! We had 15 grinders (5 black, 5 white, 5 nickel) shipped to us for the SCAA Coffee Event. These are the first samples of the white and nickel finish that we have recieved and they look great. The two step electroplating process gives the nickel rings and top a beautiful brushed metal finish. The nickel parts are also heavier and have a metal *clink* when they come into contact with one another.
The rings and hopper are screen printed as the final products will be. The nickel and white are printed in black ink and the black components are printed with white ink. The screen printing really ties everything together and makes the grinder look like a completed product.
It was a bit of a rush to get the screen printing done in time for SCAA so there are two problems with it. The first is that the numbers and arrow that indicates the current grind size is out of alignment. They are both shifted clockwise and the current grind size arrow sits very close to the measurement marks. The second problem is the handground logo is not screen printed onto the top cap.
Overall these are small problems that have simple solutions. We are glad to catch them at 15 units instead of thousands.
The first set of sample burrs we received were too small by 2-3% in all dimensions due to a miscalculation of the shrinkage factor when the ceramic goes through the drying process. In attempt to quickly solve the problem we worked with the ceramic factory to modify our existing mold and change the composition of the ceramic and drying process to reduce the shrinkage rate.
We received the second set of samples and found that they were larger by 0.3mm in all dimensions but our target increase was 1.0mm. The sizing issue causes the inner burr to sit too high into the outer burr which prevents grinds from falling through at finer settings.
Despite the problem with the shrinkage issue we decided to spend the day testing the sample set of burrs to record the grind speed, torque and consistency. We found that it requires 68 - 90 revolutions per 10g of beans. The torque was under our target of 1.1n/m on grind setting 4 which is used for a pour over and produces coffee particles that are 1mm in diameter. We used a manual sieve system to test the particle distribution and compared the results to setting 20 on a Baratza Encore and a Hario Skerton calibrated to the best of our ability.
The results are displayed in the chart above. You can see the particle size peak at the target range of 1.52 - 1.02. These are good initial results but we expect them to improve once the geometry of the burr is correct. The Skerton (yellow line) produces a large number of fines (<0.76) because it's axle is only supported at one location.
Since we were not able to fix the shrinkage issue with minor modifications we will have to make an entire new tool, starting with a solid steel block. We already ordered the new mold and it is in the process of being machined right now and is expected to be finished within 2-3 weeks. This is the final component that we are waiting on; all other components are at the assembly factory waiting.
We spent the day setting up our booth (pictured above) for the SCAA Annual Coffee Expo. Over the next 3 days people from all over the world, from coffee growers to coffee equipment manufactures will be meeting and greeting on the exhibit hall floor. Our booth is #1564 and we are neighbored by our friends who also started on Kickstarter, Fellow and Acaia. If you are at the event make sure to stop by and say hello!
If you can't make it to the event add "handground" to your list of snapchat friends to join in on the SCAA experience from our perspective over the next 3 days. We will be posting videos of the grinders in action in our booth, our 3D printer making pour over stands live, and all the action from the Event, including the US National Barista Championships.