Slowly Slowly

The 3D printer came about a a week and a half ago but I only got time to set it up on the weekend. I had a few problems initially but one of the people at work has the same printer so he helped me get it going. The pain problem I was having was that the prints weren't sticking to the kapton coated heated bed bed. Apparently glass coated with hairspray is the way to go for ABS printing, I cut a piece of plain glass to size and haven't had any problems. My first few attempts at printing the pressure pressure vessel from previous posts failed due to printer or filament feeding failure but I think i've got the hang of it now.

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.