nested cubes

cube^3,
three hollow cubes, printed in one go



Instructions
A cube in a cube in a cube
This is a updated version, with rounded edges. Further, the support structure has been improved.
A friend of mine had this as a key chain out of metal, and challenged me to print it on the Makerbot.
First idea was to print the three cubes separate, and whilst printing the larger cubes, place the previously built smaller cubes in it. Through that, one probably could print this without any additional support. However, I wanted to try making it print on one go, and this is what this thing is.
On the lower side, there is a support structure built in which holds the inner two cubes in place while printing, which can be removed with a knife
Although not perfect, if came out fine with PLA, 3 shells, 0% infill, 0.1mm layer height.
The print also developed some weird stringing effect where in the openings, there are 45deg upward-growing artefacts. See the picture with the orange color thing. Any1 knows why this happens?