Cetus Z axis Clamp

Improved high performance clamp with smooth friction adjustment.

Aug 9 2019: Added a reverse flexture socket feature. This geometry tends to seat the sprag bearing better. Added clearance on the back side of the ball part to better seat the sprag bearing (minor interference eliminated).

(Added a flexture feature version to the socket part to allow some in-out movement)

The problem source is the axis of the Z stepper motor shaft and the axis of the outside diameter of my sprag bearing are not parallel. With the original cetus Z clamp the clamping force reduced the Z layer accuracy.

To have a consistent braking force the bearing clamp needs to follow the sprag bearing surface and constrain a single degree of freedom, rotation. With this design I can now adjust the clamp to slowly over 3 or 4 seconds land or park the extruder head on the build surface.

Three implementations:

Use with the original cetus screw.
Get a new 4-40 nut and bolt and a spring which could be a