Linear and rotary movement of a shaft

[harshith]

hi
i am going to design a parallel plate rheometer as a part of my project.in parallel plate rheometer, the fluid is sandwitched between the plates and rotation is given to the top plate.top plate is made with shaft, rotation is provided to the shaft by servomotor and for placing the fluid and removing the fluid,the top plate has to move up and down.here my problem is how to move the plate up and down , how to maintain the gap (0.8mm ,0.9mm)precisely and how to maintain parallelism of two plates with in microns.
please help me in this.very urgent.

 

[Danger]

Welcome to PF, Hargarbageh.
My first thought in this matter would be an optical stage as used in holography. The drive is usually by a screw-jack mechanism, and can be incredibly precise. I'm afraid that I don't know enough to give you more information. I'm sure that others here can, though.