Kit's Machine

[Kitwn]

With the frame welded up it's time to fit the fixed (X -axis) rails. As described earlier, the rail, ballscrew and motor for each side are all mounted on a single piece of 65 x 65mm hollow steel, effectively forming a 'linear actautor' for each side. This is done to keep them all in a fixed alignment while the relative alignment of the rails is adjusted.

I wasn't sure how accurate all the welding had been so made 3 of 12mm shims to lift the rails beams above the frame. The fourth corner would then be adjusted to make the rails co-planar. A first approximation was done with a standard spirit level using a stack of washers to lift the fourth corner. Absolute level is not required here, a slight tilt in the whole machine is no problem, but the tilt must be the same at both ends. This showed that a shim of about 6mm was needed at this corner. Bearing in mind the primitive setup used for the welding an error of 6mm was not too bad, though I'd have been a bit more smug at 2mm.

Once a ballpark figure for the shim was found the precision spirit level was brought out and some pieces of copper shim used to make the rails as parallel as possible. The whole point of this design is adjustability rather than highly accurate initial construction.

Now the gantry can be put in place and the rail spacing adjusted. This is done by simply moving the gantry to one end, making sure the ballscrews move easilly and tightening the rail beam fixing bolt. Then run the gantry to the other end, by hand to check for any tightness, and tighten that end fixing bolt.

The fixed rails are now aligned and fixed in place ready to provide a reference plane for aligning the gantry.