Here's the last issue I sorted out on my machine: http://www.mycncuk.com/threads/7420-...ith-my-machine
.
Some profile rails rather than round rails sorted that on the Y axis. I will likely upgrade the z axis as well at some point and Jazz pointed on my thread, profile rails are a lot better than round due to better resistance to play.
.
I didn't have many issues with alignment/binding once I had taken the time to do it properly. I did have a job drilling the ballscrew holes off centre on the left hand corner posts, through the extrusions, but luckily the holes were not critical in diameter and I oversized them so I had some adjustment room when aligning the ballscrews.
.
Repeatability is good on my machine and on a part I am milling, which has 56 identical pockets on it, each pocket was within 0.02-0.04mm of each other dimensionally.
.
At the risk of "I told you so" from Robin and a debate about capabilities ;) , I am happy with the machine for wood, plastics and ali work. However, there are limitations in using >8mm cutters due to general rigidity and although I have cut 1mm slots accidentally through some holding steel washers, I am planning to buy a commercial milling machine (Warco GH) to convert to CNC and do steel and other harder materials. So I would think carefully about how much ali and metals you want to cut generally as a milling machine conversion maybe better (although you will need custom brackets etc made up, which needs CNC to start with).
.
Best of luck with your design and I'm sure others more in the know will give finer advice on your design, which looks much better to my layman's eyes than your first.
.
Cheers
.
Chris