Spindle Gradually Falls on Power-down. Normal Behaviour?

[mistuhd]

After I power down the controller on my AR8 PRO V5, the spindle gradually falls until the bit is in contact with whatever material is lying beneath it (project/spoilboard, ...). My fear is that this could potentially damage a project or a fragile bit if I forget to move the bit away from the project material.

So my question: Is this behaviour normal? Do I just have to be scrupulous about not leaving a bit in the collet and moving the spindle away from project material? This seems more than a minor inconvenience if I pause work on an ongoing project.

[dadealeus]

May 17, 2023 10:21:51 GMT -5 mistuhd said:

So my question: Is this behaviour normal? Do I just have to be scrupulous about not leaving a bit in the collet and moving the spindle away from project material? This seems more than a minor inconvenience if I pause work on an ongoing project.

Honestly, this just sounds like a really well lubricated z-axis, or one that's in a very hot area that makes the grease less viscous. I can see why you might be concerned, however.

There is nothing holding the z-axis up on my machine other than friction, so I don't believe it's any cause for concern. Whenever I move my machine from building to building (once every year or so), the spindle will work its way down to contact with the machine as I drive over bumps in the road.

I imagine yours will eventually stop this behavior as the grease stiffens up a bit from use or cooler temperatures.

Just my opinion.

[zaxis4]

Mine is not quite that loose, but it is movable when the power is off. When the servos are not energized it is normal for that to happen. I asked support about it when I noticed it. They said that it is normal for this to happen. Call Chad and ask if there is a way to help your machine from doing it so easily

[mistuhd]

May 20, 2023 8:51:58 GMT -5 zaxis4 said:

Mine is not quite that loose, but it is movable when the power is off. When the servos are not energized it is normal for that to happen. I asked support about it when I noticed it. They said that it is normal for this to happen. Call Chad and ask if there is a way to help your machine from doing it so easily

Thanks. It's somewhat reassuring to know that it's relatively normal behaviour. If I leave a bit in the machine, I'll just have to make a habit of putting some softer scrap material (like MDF) underneath the spindle when I power down.

[dadealeus]

May 26, 2023 7:48:33 GMT -5 mistuhd said:

Thanks. It's somewhat reassuring to know that it's relatively normal behaviour. If I leave a bit in the machine, I'll just have to make a habit of putting some softer scrap material (like MDF) underneath the spindle when I power down.

Stepper motors have very little holding power when they aren't energized, so they aren't going to hold a load well without power. Like I said, yours simply indicates that your z-axis is very well aligned and lubricated - which is far better than the other extreme of increasing the load on the z stepper while running (which would reduce vertical movement speeds and slow down your cuts).

Honestly, if all the axes on my machine were that lubricated, I'd be quite happy.

If you read your machine's manual, there's likely a way to store a "finishing position" for your spindle. For example, I have mine set to the far back of the machine so that when it finishes any cut, it automatically retreats to the far end of the machine, allowing me plenty of room to remove the workpiece without having to manually move the spindle out of the way.

If yours has a similar feature, you could place a ring or something on a far corner so that the spindle automatically retreats to that location upon cut completion and when you power off the machine, the spindle would sink with the bit in the center of the ring while the ring supports the spindle, itself - allowing the bit to hover safely in the air (similar to how the machine ship).