CoreXY...Z?

I was having a think about CoreXY solutions and had a look at the X3D XS CoreXY which looked good but still has Z axis moving.

I was wondering if I removed the stepper motors from the gantry with the CoreXY and had this sliding on rods (probably unconstrained at the top end) if I could not extend the idea to the Z axis as well and allow a fixed build platform.

Obviously the rear two 'rods' would need to be able to turn the spindles on the gantry to be able to control the X and Y Axis so I would suggest a Triangular rod. This would then have to allow Z axis movement so I came up with a quick bearing support. I would implenment the gantry movement on the underside and alow gravity to hold them in place. As the gantry is suspended, unless it drops at a rate to allow the spindles to move up then this shouldn't be an issue.

What do you guys think? As I said, it was a quick lunchtime musing and I haven't worked out finer details; that is why the concept is hand drawn.

Cheers,

Dave

What's wrong with Z moving?

You have to move something. And with the bulk of the movement happening in XY, It would seem that having XY moving up and down you are going to cause banding in your prints because it is very hard to constrain the wiggle of the XY carriage if you have designed it to actually move vertically as well. You're talking about adding at least four linear rails or rods, and a mechanism to move it.

What do you suppose is the real problem that you're attempting to solve? I personally don't see a problem with z moving a fraction of a mm at a time.