Z-axis dropping on its own weight

Has anyone had an issue with their z-axis dropping on its own from the weight of the router or being able to push down on the router by hand.

I can push it down but it takes some force to do so. Mine won’t drop because of it’s own weight.


Thanks Mike yeah for some reason there’s very low friction and with the router running it will come down on its own.

@Rob1 Is this a new problem or has it always been this way?

No it’s kind of a new problem

I have noticed that it’s pretty easy to overpower the Z stepper when idling. Is this normal? I’ll have to compare to my little machine but I thought that the steppers should hold at idle.

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The Z stepper on my small machine is not difficult to overpower at idle. The big difference is the lead per revolution of the leadscrew. It uses a 2 start lead screw instead of a 4 start lead screw. It provides better mechanical advantage. More revolution per unit of linear distance.

Would it be feasible to replace the Z axis lead screw and nut with one with a 2 start thread instead of a 4 start thread?
That would mean that there would be 4mm lead per each revolution instead of 8mm per revolution.

Check the play of the lead screw with the backlash backed off. Then set the back lash back to operating tension. .I f this is ok check the motor and drive couplings. One of those maybe loose or need replacing.

You can change the GRBL Step Idle Delay so the stepper motors stay energized even when not moving. This holds everything in position, but your stepper motors will get warm from being energized.

The command is: $1=255

I usually recommend this anyway, that way nothing moves when you’re doing bit changes, because you can easily move things when tightening bits.

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Do you need to disengage after the bit change? And do you put the command in every time before a bit change?

It’s a Grbl setting so it will stay once you set it, unless something gets reset.

You can set it and leave it that way indefinitely.

More information on Grbl settings can be found here: Grbl v1.1 Configuration · gnea/grbl Wiki · GitHub

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