over kill?3040 fixed gantry cnc

[dazza]

i might have got a bit carried away with my new revised version of a fixed gantry...its a 3040 sized work area for milling plastics and aluminium, box section is 100mm x 100mmx 5mm sat on the rack at work.
and im hoping my gaffers will help us out with using their laser cutters with the plate.
still loads to.

[JAZZCNC]

i might have got a bit carried away with my new revised version of a fixed gantry

No what makes you think that.? Plastics can be bitch to cut.!!

[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