Today is the first Open Fuel Cell Meeting after I started working at ZBT. So I was able to pick up Leander and Frauke from the entrance and lead them to Burghard’s office. Today is the day on which we want to test a first OFC assembly for tightness. There are two main differences between our parts and the parts on Burghard’s original cell: the sealings which we printed with printed with PTU with a scab hardness of 95 instead of Burghard’s recreus Filaflex (scab hardness 70A) and the pressure plates which were printed on the SLA printer at the Chair of Energy Technology and not on Burghard’s Prusa using PETG.
So we are all excited while Alexandra assembles the cell. We applied about 0.3 bar of compressed air aaand…
…it does not look too bad. However, when we submerged it in a water bath, we have to admit that what we see is air bubbles and that this is not really what air-tightness looks like.
OK, our first suspect is the TPU sealings since we assume they have a higher influence than the SLA pressure plates. So, we disassemble the whole thing, exchange the sealings with some recreus sealings from Burghard and reassemble the cell. We go over each screw several times with the torque wrench and tighten it in several steps to 1.7 Nm. Almost done. Then the SLA plate cracks. Urgh. Back to start. New SLA plate. This time Leander holds the screw driver.
Compressed air. Water bath. Aaand. Wohooo, looks good. Ok, so as we epected that SLA pressure plates are fine but the TPU sealings are probably too hard. Frauke says that she will have a look at the filaments they have at the FabLab and potentially order the stuff that Burghard used.
