Printing in the Air

I've been doing a bit of 3D printing recently and I've had a need for some lens caps for, er, lenses that I seem to have bought recently. I found a design on Thingiverse that looked promising, downloaded it, sliced it and Una, my lovely if rather tempestuous 3D printer, refused to print it properly. 

To be honest, I've been expecting problems. I made the mistake of saying to Peter last week that I've reached the point where the printer "just prints" these days. At the time I said this I worried that I may have spoken too soon. And it looked like I was right. 

The print just refused to stick to the printing bed. The filament just went out into the air and all over the place. This is usually a symptom of poor alignment of the print head and so I spent a non-happy half an hour today getting the bed height precisely positioned. And it still didn't work. Very annoying. 

And then I noticed something odd about the print design. It seemed to be hovering in the air a millimetre or so above where it should be. Turns out that the printer was set up perfectly all along and the fault was with the design itself. I've found a different, less levitated, one and it prints out pretty much perfectly. Oh well, another good lesson hard learned....