Yesterday I managed to print a cylindrical vessel with the volume of two 30mm spheres with a 10mm wall thickness:
From the highly reliable blow test it seems to be pressure tight but we will see.
I had a brief play around with some of the slicing settings but I have only just begun to explore them. I am using the "repetier" software to control the printer with the "Slic3r" slicer to generate the G-code. It was printed with 0.3mm layer height and +- 45 degree solid infill. For some of the print I increased the flow rate of plastic so it would be more compacted but its pretty arbitrary anyway. Aside from stress concentrations I can't see any advantage to printing with smaller later heights got better resolution; they take a lot longer.
I also played around with using acetone to melt together a failed print. Just a few seconds immersed made a huge difference to the surface roughness. Acetone might help with sealing but I can't see how it would change the strength between layers for a solid print. One idea I had is that I could probably soften the plastic to enable a threaded fitting to be inserted with no epoxy to hold it in, since the thread should hold its shape after
So hopefully Buren and I will get to do some testing this weekend. Other things we need to do are build a tensile tester and a hydro-tester. I was going to base the tensile tester on two pneumatic rams connected to a regulator. I just need some way to make sure the whole thing doesn't fly apart when the test piece breaks. I was planing on basing the hydro-tester on a pressure washer with a accumulator to smooth out the pressure. I haven't managed to find a suitable accumulator yet. There some designed for hydraulic systems but they are expensive. I was thinking about using one of the super high pressure pipe-tanks from the nitrous project (good to 10,000PSI) but I would prefer the air and water to be physically separated. Much do, so stress, such little time.