Bed Levelling? Z home point?

Can someone explain to me what the deal with bed levelling is? After a few prints my Z screw pointers are now about 45 degrees either side of the Z bars when Z is homed.
1. Why does this happen?
2. Does it mean that I have to level my bed again? or adjust my z home point? or both? Or does it mean something different altogether?
3. Does this continue to happen? And if so how often do I have to re-level the bed?
4. Is it worth my while buying a dial gauge?

Edited 1 time(s). Last edit at 01/23/2014 04:10PM by tforde90.

sounds like your z motors are out of sync. Which is caused by motors loosing steps. You need to increase the current or slow them down. Or both

Are they 45 degrees in opposite directions relative to the bars? If so they are still in sync but the distance to the top limit switch has changed a little, which may mean the Z home point might need tweaking. The bars are on opposite sides so as both pointers rotate in the same direction they move in opposite directions relative to the bars.

The bed should stay level unless you move the machine to a non-planar surface or from a non-planar surface surface to a flat one.

The Z height tends to change a little when the machine is new. I think the plastic parts take time to bed in. 0.05mm make a big difference to a print but is a tiny amount for plastic parts under tension to deform by. For example I think hot ends stretch a little when new and I think the extruder beds into the X carriage, etc.

My production machine has printed for more than a year and I don't remember ever needing the re-level the bed. I have changed the Z height a few times.

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Is it possible the pointers are turning freely and thus not showing the rods actually position? I ask because mine are lose (I probably stripped them during installation) and don't grip the rods tightly. I actually don't pay attention to them. As long as the machine prints fine I haven't worried about the pointers.

Garry, I have the exact same situation. They almost turn by a blow of air so to speak. But figured too that if the prints come out right...ah well

I recalibrated the Z home point and it is printing well again.
Thanks for the help everyone.

I've resorted to wrapping a bit of PTFE (thread seal) plumbing tape around my threaded rods where the z pointers are to keep them in place. The z pointers are a great idea and help me out tremendously since my left stepper seems to be off just slightly quite a bit and the pointers let me square it right up.

Good tip, thanks!

Another option is fingernail polish or a dab of light thread locker. Either are easy enough to break free if you need to tweak the position but will hold firm until then.