Joe's 1000x600x200 steel and aluminium router started

[JAZZCNC]

Mr Newton I believe.

That's the bloke, another clever sod. Lol

[NordicCnc]

Attachment 26987

Is there any pros/cons to mounting the x-axis linear rails on top and bottom, compared to mounting both on the front side? One thing that I can think of is:

- Mounted on front side is easier to get aligned but will not use table area as efficiently as top/bottom mounted rails. Any difference in stability?

[Voicecoil]

Both on the front tends to reduce spacing between them, hence more leverage for a given cutting force - but this leverage is in the plane of the screw fixing. It also pushes the spindle out from the gantry which could increase the twisting moment on the gantry. However it does increase clearance under the gantry and can allow a greater range of movement in Z. Top and bottom has greater spacing and hence less leverage on the rails, but it's then sideways which might not be so good unless you've milled slots as Joe has in this build. And you'll lose something like 30-45mm clearance under the gantry depending on the size of rails & thickness of mounting plate you're using. So there's pros and cons both ways, in the end it will all depend on your design as a whole.

[JAZZCNC]

Is there any pros/cons to mounting the x-axis linear rails on top and bottom, compared to mounting both on the front side? One thing that I can think of is:

- Mounted on front side is easier to get aligned but will not use table area as efficiently as top/bottom mounted rails. Any difference in stability?

Don't lose any sleep over either choice, choose whichever suits your requirements best because the difference is minimal and both will work fine provided you got a good strong gantry foundation.
I've built several machines using both methods and there is no obvious difference in cut quality or performance so build to suit your needs.

[NordicCnc]

Don't lose any sleep over either choice, choose whichever suits your requirements best because the difference is minimal and both will work fine provided you got a good strong gantry foundation.
I've built several machines using both methods and there is no obvious difference in cut quality or performance so build to suit your needs.

The gantry foundation will be a 160x80 aluminium extrusion and the sides will be raised so that the x-axis is as close to the y-axis as possible. Right now my design ia with front mounted rails but I figured I am loosing quite a bit of work area because of it. Do you think it would be sufficient to change it to top and bottom mounted?

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[NordicCnc]

Both on the front tends to reduce spacing between them, hence more leverage for a given cutting force - but this leverage is in the plane of the screw fixing. It also pushes the spindle out from the gantry which could increase the twisting moment on the gantry. However it does increase clearance under the gantry and can allow a greater range of movement in Z. Top and bottom has greater spacing and hence less leverage on the rails, but it's then sideways which might not be so good unless you've milled slots as Joe has in this build. And you'll lose something like 30-45mm clearance under the gantry depending on the size of rails & thickness of mounting plate you're using. So there's pros and cons both ways, in the end it will all depend on your design as a whole.

Thanks for this very detailed answer. So to draw a conclusion for this is that if you are more concerned about work are that Z-axis clearance/travel, one should go for the top/bottom mounted rails, since it will most likely result in a little bit stiffer construction?

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[JAZZCNC]

Do you think it would be sufficient to change it to top and bottom mounted?

My last post said it all really. Do which suits your needs best.

[Voicecoil]

You needn't lose too much work area, but there will always be a certain zone where the cutter cannot reach (unless you make your Y axis rails longer than the bed). This is because you want to have a decent distance between the carriages on your Y axis for stability (I went for 200mm IIRC), hence the machine will be at least this much longer than your cutting area.I arranged things on mine so the cutter reaches to within 30mm of the front of the bed, with the "dead space" behind.Decide on what X, Y and Z capability you want then as Jazz said choose whichever layout fits it most convieniently.

[Kitwn]

Something else to consider is the complexity of the Z-axis back plate. Rails on the face can allow this to be a simple flat plate whereas rails on top and bottom will require two accurate and rigid square joints.

[Sterob]

Good point..... 'Complexity and Less Overhang' verses 'Simplicity and more Overhang'...