Aluminium CNC log.

[Jonathan]

Mounting the rails behind the spindle plate in my Eyes isn't correct.
I don't know why it would be stronger and on our scale machines it may make no difference at all but I just prefer it that way.



I know this drawing is unfair but I'm provin a point here.

The scale doesn't mean it makes no difference, just a little less. With profile rails it would make a lot less difference as they are so much more rigid. Unless the Z-axis travel is very short it will make a difference.
The reason why is most people start by mounting them like this:

So clearly there there is a large overhang = weak.

However you've mounted it like this:



Which is better than the previous, as at the bottom of the travel (where you'll use it most for thin materials i.e. cutting aluminium for which it is the most rigid). However further up you're relying on er... the spindle for rigidity instead of with the configuration I suggest the aluminium plate and rails.

EDIT: Actually the second diagram is just the same as the first except instead of using aluminium plate to hold the spindle you're relying on the strength of the spindle itself.

Chip did it like in the first drawing and unfortunately found out the hard way when he tried to cut aluminium. I started by drawing the same on my Z-axis (400mm travel), but fortunately someone pointed it out so I changed it.