Ouch I feel for you. 14 hour days is insane.
As for why no linear bearings on the Z-Axis, I'm guessing that bushings are cheaper and it's easier to assemble. Also the Z-Axis assembly can handle a lot more friction than either of the other axes. (Axises?)
E: "Did they... did they just endorse the combination of the JSDF and US Army by showing them as two lesbian lolicons moving in together and holding hands and talking about how 'intimate' they were?"
B: "Have you forgotten so soon? They're phasing out Don't Ask, Don't Tell."
As for why no linear bearings on the Z-Axis, I'm guessing that bushings are cheaper and it's easier to assemble. Also the Z-Axis assembly can handle a lot more friction than either of the other axes. (Axises?)
E: "Did they... did they just endorse the combination of the JSDF and US Army by showing them as two lesbian lolicons moving in together and holding hands and talking about how 'intimate' they were?"
B: "Have you forgotten so soon? They're phasing out Don't Ask, Don't Tell."