Metal z coupler question

[jprochnow]

Is the threaded rod supposed to be sitting on top of the motor shaft or is there speed to be a gap? I have a gap on mine but I can see the z axis changing from the coupler springing up and down.

[printbus]

Mine are set up without a gap.

[ex-egll]

Mine sit on the motor for the reason you mentioned.

[TopJimmyCooks]

I put a ball bearing (an airgun BB actually) between the motor shaft and the threaded rod.

[jprochnow]

Thanks for the input. I'll get mine changed.

[AbuMaia]

I leave a small gap in mine. The weight of the X axis should be enough to compress the metal couplers enough to take out most bounce. If you have a bent Z rod, you want a small gap there to let the z rod and coupler flex so it doesn't affect the X axis as much. If the rod were in contact with the motor shaft, it may not flex as easily, and you'd get some artifacts in your prints.

[ex-egll]

I leave a small gap in mine. The weight of the X axis should be enough to compress the metal couplers enough to take out most bounce. If you have a bent Z rod, you want a small gap there to let the z rod and coupler flex so it doesn't affect the X axis as much. If the rod were in contact with the motor shaft, it may not flex as easily, and you'd get some artifacts in your prints.

Good point on the bent Z rod. I may try TJC's idea of the ball bearing

[TopJimmyCooks]

Ball bearing allows the rotational and torsional compliance with an out of true z threaded rod (they all are out a little) without introducing Z height concerns.