Hi,

I'm working on spec'ing a new Chinese machine. 1100x1800 with a full table structure, hiwin rails, etc. I've also chosen ball screws on all axis for higher accuracy, but have now been informed that the gantry structure had to be aluminum instead of steel due to the weight and ball screws not being rigid enough.

This seems odd to me since it's the bearings and rails that are taking the weight and all VMC's use ball screws (and are dealing with much higher forces). The design is supposed to be a full square tube structure on the uprights, but I had expected steel like in the larger format machines.

We're not planning anything as heavy as done with a full VMC, but am going to do aluminum. What I wanted was the heavy structure of the large format machines but in a smaller package (therefore increased rigidity), but suggestion of an aluminum structure for the gantry has me worried.

Thoughts?

Thanks,

-Gord