Recently, my HDZ started back driving and falling when I power off the machine. I’ve got a new 80mm 1.5kW spindle in it - so, not as big as what some folks are putting in.
It wasn’t doing this at first with the new spindle, this happened after a few days.
Anyone else have a similar problem? I might set up a counterweight or a spring or something to help, but there’s a slight concern this might be the symptom of something else I should be fixing.
Hi Alex
Are you saying the HDZ slowly moves lower on the axis over a few days or immediately?
Luke
Immediately upon power off, the HDZ falls (slowly) until it stops when the end mill hits my wasteboard.
Because there is no force being applied to the motor the ball screw is free to rotate leading to the carriage dropping.
It’s not something I would be too concerned about, and I have seen this a couple of times. Can you do me a favour and email a video of this to support@carbide3d.com? I’d like to check it out just to be sure.
Luke
Mine started doing that occasionally a week or so ago. I figured since I checked it for play, that everything finally got lapped smooth and now doesn’t have the friction needed to stay still anymore.
Think a thicker linear block grease might help?
Probably. I have NLGI 0, 2 and 3 grease from my son and I playing with bearing and diff grease for our RC trucks. The NLGI 3 grease is like cold peanut butter.
Thanks everyone. Sounds like this is within the realm of normal.
I am using a fairly light oil: Super Lube 51004.
It doesn’t fall when I power it off when the HDZ is near the top of its travel, which I don’t normally use during cutting, so that points to it just being the HDZ “settling in”.
I’ll probably rig something up so it’s not crashing my end mills on power off… I’d feel pretty silly breaking a smaller end mill that way 
@Luke If I run the HDZ down past the 150mm point, is there a chance I’ll run the guides off the rails? Here is a video of it falling:
3D print or machine a spacer that holds the spindle up, but have it balanced so that when you initialize the machine, and the spindle raises up, it falls out automatically.
My “woken up by the baby” thought:
Hook up a relay to one pair of your stepper’s coils and wire it such that when your machine powers down it will short the pair. The extra resistance might be enough to stop it.
Ok, back to bed.
It depends on the version and I can’t tell from the video which you have - I added a hard stop into the design, I would run the HDZ down 1mm at a time and see if the carriage go off the rails by more than 1mm.
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