[SpeedyDad]

I've had some problems with my edges coming out bumpy and not so straight. I could see the machine jerking as it moved, especially in the Y axis. I had to solve it.

It had been suggested many times that the cold rolled steel rails were the problem and I thought I had it solved by smoothing some problem areas. It helped a little but not enough. It was finally time to try some things to fix this issue.

I got lucky and my other two rails are pretty smooth. I had filed the top of the right gantry rail flat but it was time to check the bottom. I shined a flashlight along it and saw what looked like the Himalayas. Lots of peaks and valleys. Definitely not as smooth as I thought. I pulled the screws that hold it in place and slid it out of the machine. I then chucked it up in my hand mill and took just enough off to get a nice smooth roller surface. I then dressed the edges with a file. and reinstalled. The gantry now ran much smoother but when I moved the machine under power, some of the jerkiness was still there.

On to the belt tightness. I thought that maybe the belt was too tight and causing cogging as the pulley turned on the gear or roller bearings. I loosened it and that made it worse. Tightening it back up made it better but I was back where I started after the rail smoothing. Something else was wrong. With no belt on the gantry, it was very smooth moving. It would roll without stopping. I then checked my bearings and found the bottom two on the right side of the gantry were a little loose. Could it be racking and causing binding? I tested it by pressing down on the gantry as I ran it forward and back. Much smoother. I tightened up the bearing to rack clearance and it runs pretty darn smooth now. I ran a test piece and I now have almost perfectly smooth edges. Problem solved!

So, in summary, don't buy cheap rail stock, This link has been posted in my thread and one other:

O-1 Tool Steel - Oil Hardening on Amtek Tool & Supply, Inc.

Don't bother with the cheap stuff, get ground flat stock and be done with it. Also make sure your bearings are tight to the rails.

Since I work mostly with carbon fiber, I also clean the rails after every run so that carbon dust doesn't build up in those area.

[OCNC]

So, in summary, don't buy cheap rail stock, This link has been posted in my thread and one other:

O-1 Tool Steel - Oil Hardening on Amtek Tool & Supply, Inc.

Don't bother with the cheap stuff, get ground flat stock and be done with it. Also make sure your bearings are tight to the rails.

Since I work mostly with carbon fiber, I also clean the rails after every run so that carbon dust doesn't build up in those area.

It also helps to put grease on the rails where the bearings ride. I use ordinary automotive wheel bearing grease. It probably sounds counter intuitive regarding dust and other swarf but I find that the rails don't load up at all. The grease seems to provide a vehicle for the debris to get pushed out to the edges of the rollers.

Chris