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

[Greeny]

Hi Robin,
Don't worry your secret is safe with me

I think i understand the intention of what you are suggesting and like the idea, but not exactly sure on the details.
Could you explain a little further?

Cheers

[Robin Hewitt]

Right now you are simply stacking layer on layer and moving the router further and further away from the gantry, ignoring the fact that overhangs are not your friend. This is the peril of designing a 3d object on a 2d sheet.
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The Y and Z linear blocks could be sunk in to the plate until the rails hit the plate. Less overhang. If they didn't line up with each other then extra metal could be bolted on behind to compensate for the loss. The clever bit would be removing still more metal below the blocks so you approach the limit which is where the rails rub against each other.
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I am all in favour of pushing the limits of the design rather than slavishly following what everyone else has done in the past. I am not building a router so some might say I should keep my fat mouth shut, feel free to tell me where to stick this stuff.
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Your base is overhanging the X axis bearing blocks presumably to hold the X axis screw. All you have to support is a straight push pull, you seem to have a lot of excess metal thereabouts

[Greeny]

Ah I think I see now.
I will have to think about that. I can see the benefits, but it complicates construction quite a bit and i'm very limited on skill, experience & tools! Will ponder if i'm brave enough

Good point on the base, i will take a look at that and see what i can do.

I appreciate your input, & most certainly won't tell you where to shove anything
I also fully agree with your attitude of thinking "outside the box" or "racing your own whippet" as we say up here

Cheers

[Greeny]

A half way to Robin's suggestion to reduce the overhang would be to place the Z screw outside the blocks so the risers (in red on "A") can be removed.

This would reduce the overhang by 30mm, but widen the Y plate by 75mm to accommodate the screw. Although some weight could be saved by having a cut out as in drawing C1
However the risers also serve to stiffen both Y & Z plates, so i'm not sure.

I would be interested to know anyones thoughts on this (or any other part)

Cheers

Note: The orange X & Y plates are 10mm steel guage plate it would be easy to up them to 12 if i removed the risers, only adding 4mm to overhang
Drawing B & C are the same just different angles.

[Greeny]

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]

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]

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