I've been picking away at this thing all week, and it's starting to drive me up the wall. I flipped the Y lead-screw around, and it didn't break as much as I thought it would. But, I have a small issue with Alibre that's REALLY irritating. This is the latest assembly drawing of my new CNC's 3D model.

You see that yellow object in the middle? That's not where it's supposed to be! The lower surface of the flange should be coincident to the upper surface of the dark blue lead-nut plate. The Z carriage, basically everything in front of the cyan colored plate, is one sub-assembly. In THAT sub-assembly, everything behaves like it should, including the lead-nut. However, when the Z carriage assembly is added to the main assembly, the Z axis lead-nut turns into the misbehaving red-headed step-child that you see above,
I thought this problem felt kinda familiar. About a year ago I was working on designs for 1/16 scale RC truck differentials, based on a modified cheap Chinesium 1/10 scale RC car differential. I started out wanting just the front and rear axles for a tandem dual drive set-up. Later, after seeing how a fellow builder had modified the front axles from a similar 1/10 scale RC crawler into powered steer axles for his 1/14 scale RC telehandler, my designs morphed into adding a powered steer axle for a 6x6 Bruder truck conversion. I had designed a powered steer axle, and tested it as an assembly, where the steering worked fine. When I added that sub-assembly to the main truck, it would no longer steer. The same thing happened with the rear axles assembly. As seperate sub-assembly it would articulate, when added to the main assembly it would not. I had a buildlog detailing the designs of the differentials.
I checked back through that Frankendiff build log and found I had run into a similar road-block there. I have a perpetual off-line license for Alibre Design Pro V.22, I am NOT going to pay any more to upgrade it - and maybe not have it work any better. I've checked, seems like sometimes it works, sometimes it don't. AND, then I would have to upgrade to a version of WINDOZE that I like even less than the WIN7 Pro I've got now.