z height problem

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Re: z height problem

Postby IslaWW » Tue Sep 03, 2019 5:13 pm

". It's probably a good idea to check the zero point if the power is turned off."

Much more than that.

When the controller is turned off you can assume with certainty that the machine position has lost sync with the DRO. in many cases, even if by some luck there was no physical movement, energizing steppers or servos will cause them to "seek" a step detent or encoder position, thereby rendering an erroneous display of actual position. You can assume this happens every time and if you listen carefully, you can hear it. You cannot always see it.

If the controller remains on and the computer and software is power cycled, the onscreen position will be accurate. This is why it is important to home your machine each and every time the control is cycled off.
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Re: z height problem

Postby martin54 » Wed Sep 04, 2019 1:50 am

It was the end of the day yesterday so I didn't want to start machining, but I did set my material and zeroed all the axis. This morning my zero axis was off .3 mm. Apparently when the power is off, there's no pressure on the servo motor (stepper motor in some cases) and it backs off the screw slightly. It's probably a good idea to check the zero point if the power is turned off.

did you home your machine in the morning before checking it was 0.3mm out? First thing I do every time I turn the machine on is home it as IslaWW has just said. Homing the machine ensures my machine co-ordinates are set correctly & therefore my G54 offset should be the same as it was when I set it. Of course that is assuming my machine is perfect in every way which it may well not be :lol: :lol:
It is a very old machine so manybe a little inaccuracy in the home switches or some backlash has crept in over the years. Anyway from now on it won't be powered off part way through a job :lol: :lol: :lol:
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Re: z height problem

Postby garylmast » Wed Sep 04, 2019 1:59 pm

did you home your machine in the morning before checking it was 0.3mm out?

I had everything setup the night before, and the only reason I checked the clearance before I started was because of your original post, otherwise I would of just hit start and wouldn't of gave it another thought. And that's amazing because my memory is only good for a few minutes anymore. :oops: :oops: :oops:
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