Linear rail question

[njhussey]

There is not much price difference between 15mm and 20mm the trouble with 15 mm is it can be very tight in the z axis unless a lot of material is milled away. The Chinese stuff is fine you can buy it all at the same place including screws and bearings etc this is one place BST http://es.aliexpress.com/store/314742

I've got 15mm on my Y & Z and if I was doing it again I'd buy 20mm all round. The Z axis I've got round by using a 40mm thick plate and recessing it for the ballscrew and mounts so I could put the bearing carriages flat on the back plate...

[Clive S]

That pic explains the problem very well. ..Clive

[Nr1madman]

Hello again!
I understand the problem, but why doesnt ppl just use 25mm rail and thinner ballscrew?
If you use 1204 ballscrews with bk/bf10 you would get 3mm extra for ballnut clearence and just have to make a bracket?

Or am I missing something vital? :D

[JAZZCNC]

Hello again!
I understand the problem, but why doesnt ppl just use 25mm rail and thinner ballscrew?
If you use 1204 ballscrews with bk/bf10 you would get 3mm extra for ballnut clearence and just have to make a bracket?

Or am I missing something vital? :D

There are many ways to do the same thing but your way is adding expense and weight to an area where you want to limit the moving mass. The larger rails don't really add much strength but they are considerably more heavy.

Maching slots for clearence while trouble some if not kitted up to mill the slots does give the advantage of reducing weight without sacrificing too much strength. The lighter and shallower 20mm setup gives a very strong and low profile setup making for a nice balanced Z axis.

Either way would work.! Thou IMO the 20mm rails with lighter plate setup gives better balance of strength and acceleration/speed with nema23 motors.