over kill?3040 fixed gantry cnc

[Robin Hewitt]

It wouldn't be right if I didn't mention the blinking obvious, you are under no obligation to listen though.
The profile rails are upside down. You should have the rails bolted to the table and the carriages bolted to the gantry.
The way you have it makes for an unnecessary overhang which you are trying to compensate with huge box sections.

[dazza]

ta lads.
i dont think ive ever seen an x axis arrangement in the way you describe robin

[Jonathan]

Robin's usual suggestion is quite common on milling machines, including mine. It makes sense so long as the bed is very strong, though it's not normally seen on extremely high precision machines as the weight of the overhanging will cause some deflection, but that's hardly a concern to us.

Careful with the bearing spacing you've chosen for X - with a single ballscrew either the bearing spacing should be increased or the rail spacing decreased, else the stiffness of the X-axis is reduced when Y is towards either extreme.

By the way, when it comes to aligning the rails and bearings, I have a quite high precision straight edge and square now, so you're welcome to borrow them.

[dazza]

thanks all i.ll edit rail spacing at some point,still playing about in cad