I didn't get a lot done this week with the build, but I did get the time to bolt together the main part of the frame for the first time. There were a few spots where certain parts of the machine didn't want to line up exactly right. At first I thought it might just be the floor being slightly unlevel, but after reviewing some video I shot I realized that something wasn't quite right. It's hard to explain, so I highly recommend watching the video below to see exactly what was going on. However, the long and the short of it was when I moved the gantry along the y-axis the two y-axis rails shifted quite a bit, and one of them even would lift up in the air slightly when the gantry was all the way back.
After investigating I realized that the upper to rail slots on one side of the gantry didn't line up correctly with the threaded holes on the x-axis rail. It would appear that this was a major problem that was causing what I was observing. It's very likely that there is other factors at play here, but until the machine is mounted to a table I really don't think I can work those out yet.