Z axis drops at power off

[Mr.Ben]

Hi, all.
Finished building a new bench top router and am having the following problem. When I power down, the Z axis drops until it hits something. The Z has 25mm Hiwin rails and carriages, and weighs about 35 lbs. It is powered by a Clear path nema23 driving a 1605 x 350 rolled thread ball screw, supported at both ends.
What is the best option for stopping this? I hate to add a spring to the side as this would eat up X travel.
If I turn off the motor enable power it drops very slowly, but killing the power to motor allows it to drop fast enough to hurt you if you got in the way. I gotta fix this. Your ideas are welcome.

Ben

[Sam0117]

Hi Mr.ben I have infeeling that your stepper motor is faulty or wired wrong? When a stepped motor has its pairs correct the motor won’t turn unless it has a signal to move, so when you power off you shouldn’t have the z axis drop, sorry I can be more helpful but I’m confident you have a problem either with the stepper motor or how it’s been wired up

Hope this helps 👍🏼

[Clive S]

Hi Mr.ben I have infeeling that your stepper motor is faulty or wired wrong? When a stepped motor has its pairs correct the motor won’t turn unless it has a signal to move, so when you power off you shouldn’t have the z axis drop, sorry I can be more helpful but I’m confident you have a problem either with the stepper motor or how it’s been wired up

Hope this helps 👍🏼

This statement is incorrect. When a stepper is not energised it can free wheel and will when the Z is heavy. Some machines have an electric brake on the Z motor for that reason.

[Ger21]

He's using a servo, so it's not relevant.

What you really need is a servo with a brake.

[johnsattuk]

As pics