Though I cannot be certain, I think the drift may have been caused by the pulley on my z-axis. And that would make sense. I just read that it is frequently a cause, and that is currently an issue for my big machine. I’ll let y’all know what I find out.
Everything you add is just another potential point of failure. Beyond the added complexity I rejected using pulleys just for what they cost. That’s why you’ll find rubber hose couplings on my machine. You can get a foot of rubber hose for a buck. You can make a bunch of couplings out of a foot of rubber hose. Then you need some hose clamps too. I had enough for my CNC machine just kicking around here. So they cost me nothing. I got a lot of junk. A good bit of the material I used in my CNC machine was just junk I had laying around. Some I bought special for it though. Heck some of what I used I literally found lying on the side of the road. One day I stopped for a yard sale and when I parked I found this sheet of plastic just laying in the weeds. It’s my control panel today. I saw that and I was like it’s perfect! Oh yeah I beat the metal out of some old pool caps. I forgot about that. http://i.imgur.com/lCbaRHu.jpg