What is it for?
From the explosion overview of the Open Fuel Cell it appeared that milling and cutting processes were used to either produce some components or give them the final touch. To be more specific, CNC-based milling processes are used for the production of the anode and cathode flowfield plates and the post processing of the anode-endplate namely the milling of the M6-thread and the sealing groves. In combination with a drag-knife this CNC-machine was used for cutting the edge sealing.
What are the requirements?
Some of the criteria that came to our mind were that the machine itself should be of a simple design, easy to operate and maintain as well as available at an affordable price – at least for hobby and educational purposes. Furthermore there should be the possibility to mount several different tools into the CNC-base machine in order to adapt it to several different applications. An additional “nice to have” is the availability of the CNC-machine as an assembly kit. Why? Not only that reduces the cost compared to the completely assembled one, but it also gives the unique opportunity to really get a deep understanding of its design, functionality and construction. As the Open Fuel Cell is meant to offer a simple entry into the fascinating world of the fuel cell technology at an astonishing low (financial) price, the used equipment should fulfil the same requirements.
Now please observe our statement in the introduction. We do not have any connections to the mentioned companies what so ever. The following statements are based on our own experience and therefore reflect our own opinion. There may be a bunch of great CNC-machines out there which may be as well suited to be used for the described processes.
What equipment did we choose?
Our machine of choice is the D-series (D420) by “STEPCRAFT GmbH & Co. KG” (https://www.stepcraft-systems.com/). This entry level series is, according to the manufacturer, specifically designed for hobby applications. Among the various tools that can be mounted into that machine the “HF-Spindle” (https://shop.stepcraft-systems.com/hf-spindel-500-w_1) and the drag knife (https://shop.stepcraft-systems.com/schleppmesseraufnahme) were used. In order to facilitate the milling processes, especially if tool changes are required, additional sensors such as tool length sensor (https://shop.stepcraft-systems.com/werkzeuglaengensensor-ts-39) and 3D-sensors (https://shop.stepcraft-systems.com/3d-taster) were used.
Additional tools like the contraptions to reproducible fixate the workpieces such as shown in the picture are homemade according to the actual requirements.
What to learn from it?
As you can see from the overall workflow diagram, building the Open Fuel Cell requires a whole bunch of engineering technologies. In this case you will become an expert especially in the area of the machining technology. As with all machines the CNC requires some kind of maintenance. Due to the simple design you can do all this work by your own ensuring that you get a really deep insight of how such a CNC-machine is constructed. Does this give you a good base knowledge if you decide to work with the real big ones later on, e.g. to pursue in the area of fabrication technology? – Well the basic setup and the principle of all these CNC-machines are basically the same. This also holds for the application of such a machine for the specific milling tasks. The suitable cutters in accordance with the correct settings such as revolution, cutting depth and feed rate have to be selected for the specific workpiece.
