mounting profile rail - Hiwin Manual vs. typical approach

[m_c]

It's to do with ensuring the blocks/rails can't move, and allows easier assembly.

Relying on bolts alone means that under high loads (especially shock loads), the blocks/rails could slip. By ensuring they're mounted firmly against an edge ensures they won't move.

Also by using datum edges, it makes assembly quicker and more accurate. Most machines using linear rails will be getting machined anyway, so adding a datum edge isn't a major issue, and saves quite a bit of time in mounting and adjusting the rails/blocks. For one offs, it's probably not a major benefit, but if you're producing multiples of the same machine, that additional time mounts up.

[AdCNC]

I always incorporate a datum edge when i build a new machine i have done ever since i built my first machine.. and always used hi-win gear.

[Jonathan]

I always incorporate a datum edge when i build a new machine i have done ever since i built my first machine.

Where are they on the first machine, they look well hidden to me...
http://www.mycncuk.com/forums/router...tempt-cnc.html

To make a datum/reference edge you need a milling/grinding machine with as much travel as the length of the rail or maybe a long precision straight edge to use as a reference. Either way it's not realistic for the vast majority of people on the forum.

[GTJim]

So how do people get around this problem. I'm very interested as I will be facing this problem soon.

[dsc]

Gents,

thank you for the replies.

Looking at the manual, you can do without having a datum edge for the rails (ie. use the edge of the plate as datum), but the carriages still need a 'lip' and side bolts to secure in place.

Regards,
dsc.

[AdCNC]

This is how i mount my rails..

[dsc]

Few things I still don't get:

1. mounting against an edge assumes the edge is perfect, otherwise things go wonky. Surely there will be errors when machining the edge every single time.

2. with no side plates pressing the rail against the edge, I don't really see the point of the edge. Surely if the rail moves under load, it will move anyway. Sure the edge will spot the movement towards the edge, but the other way is still unsupported

3. the manual suggests simply bolting the rails down (ie. no edges) if there's no side space, but shows the carriages supported and mounted against edges. Again point 1 comes into play.

Regards,
dsc.