First Build 5 x 12 Steel Frame CNC router

[Scott Damman]

Have you Earthed the Frame.? Common cause of troubles like this.

No I hadnt, I added a separate ground for the frame and grounded each part of the machine, i.e. Gantry and Z. Thanks for the suggestion.

I learned some hard lessons last night while continuing to tune the servos.

1st, make 400% sure that the ballscrew mid-supports can not get hung up on a sudden change of direction.


This bent back pretty easily but I will need to make some modifications to make sure it cant happen again. Basically the machine stopped before the support flipped and on change of direction it caught on the ballnut mount. No other damage observed which is good.

2nd, and this is the big one, when butting linear rail together remove the lead in on each rail. I had known this was the case but being that I got the rails for cheap and not having a way to accurately grind the rails I chose to try it.... bad choice.



What the pictures show (or what I assume happened), as the block went past the joint a ball dropped into the joint, caused alot of extra force and blew the end of the block off. At lower speeds it seems to be fine, but I was running past it at ~1000 ipm. I think the block counldnt handle it I was able to stop it before the other 2 blocks hit the joint. I have 4 extra blocks that came with the used rails so I can put it back together for now but I need to make a plan for future.

I think my options are
1 - remove rails and have them ground and put back together - this is a no go as the cost would be more than just buying Hiwin rails
2 - buy Hiwin rails and blocks - definitely the best option but costly
3 - try to fill the groove/lead in
- Im thinking of trying this method, couple options, epoxy, babbitt, other options?
- I think I just need to keep the balls from dropping in there, I think there shouldnt be too much stress on the fill otherwise.
4 - just use the 8ft of full length rail for now???

Any thoughts are appreciated...