New build - fixed gantry mill using extruded profile

[Robin Hewitt]

In my humble opinion it won't cut aluminium very well because it is not designed to cut aluminium.

Overhangs are your enemy. A good solid base is your friend if you want to get the best out of a fixed gantry.

The tool is unlikely to stick out more than 2" from the chuck, and that's being generous. Try dropping the gantry down to 2" clear of the table and cut the Z axis travel down to 2". See how much more rigid it looks.

If you go vertical and have a good brick wall, consider dumping the frame altogether and Rawbolt everything to the wall. Maybe add extra diagonal braces to stop the gantry flexing sideways.

If you really think you will want to engrave the top of something 130mm thick at some later date, add provision to move the gantry rail up another 80mm. All it takes is a few extra bolt holes. You don't need to worry about extending the Z travel because the tool isn't going to be 130mm long.

[toolchimp]

@Jazz - thanks for the input. I can see the benefit of what you have suggested and I will look to incorporate the changes. I haven't purchased any hardware yet (thought it would be wise to get some feedback first!) so the move to 20mm rails all around is an easy one.

@ Robin - I undertsand the benefit of low overhangs, but I am looking to 3D machine parts up to about 70mm deep (a shallow trough form so I don't need a 70mm long cutter as long as the spindle body clears!). That combined with the 50mm tool height (and a little margin) gave me the 130mm height. I will still look at the deflection of the gantry at worst-case conditions to see if there are stiffness improvements to be had.