Stell frame cnc 1500X1000. Adjustable table your opinion please

[Jonathan]

Roughly in order of priority...(i.e. in order of how much I expect these changes will impact the overall stiffness of the machine:

1. The thin plates the linear bearings are mounted on are definitely weak points.
2. Keep the Y-ballscrew where it is - it's well positioned. Moving the ballscrew to prevent exposure to swarf is totally the wrong priority - just guard it if necessary.
3. The spacing of the bearings on the Z-axis is a bit low - bear in mind the deflection of the linear guide system is proportional to that bearing spacing squared, so every little helps.
4. Try to compact the Z-axis to reduce overhang - by making cutouts in the plates you should be able to avoid putting the rails on spacer strips.
5. The Z-ballscrew could be made shorter if you want, but it doesn't really matter.

You only need the adjustment slots for mounting the X-axis linear bearings to the gantry at one side - on the other side you could use normal holes and mill a reference edge for the bearings to rest against. That will help slightly with getting things square. It's also a good tactic for the other axes - particularly Z in your design.