Quote Originally Posted by georgetheforge View Post
hope that all makes sense?George
Makes perfect sense George.!

Some will complain the Ballscrew is too far back from the Y axis carriage, which it is slightly, but because you are using profiled rails they will help absorb some of the effects. Thou be aware this will apply twisting forces to the bearings which over time could cause premature wear.? You may want to consider moving the screw forward and higher sitting directly on top of the upper bearing plate.?

When you say 150mm of clearence between gantry is that from the Bed to the underside of gantry.? If so then again you may want to consider upping this if your wanting flexabilty.
The things that tend to cause the most problems regards clearence are drills and clamping devices.!! Often drills have long length's so by the time you have material, sacrificial base material then clamps etc you don't much left for clearence.
Also if you ever want to work with really small items you may want to add a vice to hold them and with only 150mm of clearence then again it's very tight even with normal endmills.

150mm is a good Z axis travel amount but really I would look to more clearence if your wanting flexabilty. It's very easy to pack the work material up towards the cutter but not so easy to move the gantry up.!!!