1. Ah yes, I see, that sounds good.
  2. Ok cool but the further away the Z plate drive point is from the bearings the more compound the tolerance will be on the drive forces. You are right it should not affect the travel accuracy.


The Z axis travel looks quite short compared to the X&Y if you are designing for large surfaces and need to jump up and down the job work plane will this have enough for your need? I originally had 250mm Z distance and have since increased to 400mm for those extra long tools and thicker jobs. My Z axis runs from the collet face at 20mm above the table to 420mm +Z my machine has a fixed 200mm throat under the gantry. This now allows for quite a long tool for example drilling through 200mm you obviously need at least 410mm travel. As the -Z movement starts to put the pressure on when drilling the whole gantry structure starts to go under stress, which is why I advocate centering the spindle in middle of the Y axis bearings, if it is off centre the gantry start to tilt back against all those bearing tolerances and pulls the drill out of square and jams up the drill.

I have a distance of around 400mm between the bearings on a 1.3m Y axis total length so I get an affective length of approx 900mm which is perfect for the standard linear scale I have fitted.

This is a good design as most fixed table machines have the "Throat" restriction under the gantry. How are you going to adjust the table up and down and keep things square? I would think a secondary Z knee adjustment for the work piece height, suggest a manual mechanism that can be locked after part fitting otherwise although flexible just like a knee milling machine, will bring in further rigidity issues.