"Henge", 3 Axis Cnc, Fixed Gantry, Moving Table

**Greeny** · 19-03-2017

Sinking the rail blocks into the plates i think i could reduce overhang by about 16mm (8mm + 8mm)

I don't think i can reduce it further as the rails are fixed to the 2 outside orange plates and move with respect to the center plate.
If i sank the blocks any deeper the rails would interfere with the centre orange plate.
They move over the whole length of the centre plate so, if i went any deeper, i would have to put a groove in the whole length of centre plate weakening it.

Basically i'm saying the orange plates must be at least a rail height apart, so i could only sink them about 8mm each.
Or have i misunderstood?

Cheers

**Robin Hewitt** · 19-03-2017

Click image for larger version.

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If you can't do it, you can't do it. Picture shows it is possible. The white arrow points to a 1mm clearance between the X axis linear rail in purple and the 8mm linear Z axis shaft in yellow

**Greeny** · 20-03-2017

Thanks Robin,
However, am i right in thinking that's only possible when using unsupported round rails on z?

I think I'm probably interpreting your drawing wrong, as there's a lot of stuff there and I'm not sure how it all fits together in 3d, do you have a side on view?

Cheers

**Robin Hewitt** · 20-03-2017

What you could do is slip pairs of linear blocks on to two pairs of linear rails, lay two rails on top of 2 rails at right angles then slide the blocks around a bit and see where the metal of the Y and Z slides can fit in around it.

Does that make sense?

**Greeny** · 20-03-2017

ok, will give it a go, thanks.

**Greeny** · 20-03-2017

Aha!
I think i see now. Playing with two pairs of rails it took about 60 secs.
I will take some photos & do a couple of drawings later this evening. (i'm supposed to be working now... shhh)
Cheers

**Greeny** · 20-03-2017

Well i think Robin's idea is pretty nifty, but i don't think it's going to work for me, as the rails i have are not long enough!
A good example of not buying until the design is finished!

The only way i can get to sensibly work is as per the drawings below.
The Z table must fit between the Y blocks which means the y blocks are spread quite wide.
In this case restricting my Y movement to about 250mm which is too small (I'm aiming for 350mm)

I do quite like it though, it makes for a wider Z assembly than usual, but makes it very compact in other respects . (always some tradeoffs!)

Cheers