I have been slowly building a 3D printer based on this design. A friend has a printer of the same design, which I have been using to print the plastic parts for my printer.
While printing the parts, I ran into a bit of an issue: the plastic filament is pushed through a tube to the print head, where it is melted and deposited to build up the object. The plastic only has a tiny hole to come out of at the print head, and can build up considerable pressure in the tube, and this eventually broke the mechanism that is supposed to secure the tube in place. So, in the middle of the print, it comes lose; the motor just keeps spooling out filament, but instead of being pushed through the print head, it just coils around until someone notices it. The original mechanism that holds the tube is not 3D printed, and has to be ordered from China, which could take weeks.
First thing I tried was, of course, duct tape, but the persistent pressure was just too much.
But that's OK, surely I can design a 3D printed part to hold the tube in place! I found a nut that was just the right diameter to securely thread onto the outside of the tube.
Then I design and arm to hold the nut in place using OpenSCAD, a fun little programming language for designing 3D models.
So I can 3D print a fix for the 3D printer! Which requires a working printer... But I still only had the one, and it wasn't working. Luckily this piece is small, and I was able to get the print time down to about 1 hour. So I sat down with a podcast and some locking pliers to hold it in place, while I printed the brace.
And it worked! Here is the final piece
And here it is, holding the tube in place.
The STL model, and OpenSCAD source (so you can adjust the dimensions) is available on Thingiverse.