Quote Originally Posted by biketrialsdave View Post
Thanks Jazz! I had thought of something similar but was afraid monting the ballscrew like that would cause problems. Is the general idea of the gantry sides to keep them as short as possible? Well not the sides, but the distance between the top and bottom profile carriages on the X axis?
Yes if you want the best possible strength then you want short stubby sides but this is only really required if you want to cut hard materials most of the time. Gantry height just needs to be high enough to provide support to the Y/Z axis and resist Twisting/flexing. With this design the height of the gantry supports and takes the full load of the Z axis bearings with just the ballscrew and motor above the gantry.
The red machine in the pictures is twin ballscrew driven and this cuts aluminium no problem with resoanable quality of finish but it's not designed to do this all the time and it would eventually take it's toll on the machine, where has with woods etc it will happily cut 24/7.

With regards to the ballscrew at the rear then IME it hardly makes any difference unless wanting to cut hard materials with deep DOC. Which in this case then you'd want a stronger gantry design. For all wood and lighter aluminium use then it's no problem at all, if it was I wouldn't be using this design.!

To be honest if your wanting to cut all materials then you have to lose something somewhere. If you build for cutting the hardest materials then you need strength and weight, this comes at the cost of speed unless you increase the strength of motors etc and this costs cash.
This is wasteful if your only ever going to cut hard materials 5% of the time. So IMO you get a much better machine if you target the main use and design for the optimum doing this.! . . . Jack of all trades works but truely is master of none and you have to accept this other wise you'll be sadly dissapointed.!