Z-Axis Safety

[professorburnout]

I have an issue with the Z-axis on my mill occasionally falling. This is a problem I have to work out with the hardware but I am thinking of a safety that could be implemented with Mach3.
My thought is to add an encoder to the motor that would be calibrated to the same units as the stepper motor. Mach3 would then compare the DRO’s and if the 2 numbers were different by a set tolerance an E-stop would be triggered also engaging the Z- axis brake.
Any thoughts if this is possible or ideas to make this happen?

Thanks,
Paul

[BR549]

HERE you go already been done

http://romaxxcnc.com/encoderinfo.html

(;-) TP

[professorburnout]

I worked on this a little this weekend and I also reviewed the suggestion for using the encoder  board from romaxxcnc.com. The romaxxcnc board cost $159   more than I wanted to spend at this time and at this time I am only concerned with 1 axis.

The first few steps I have done to get this going was to get an encoder working with Mach3 then couple the encoder to the motor, and finally calibrate the units for the encoder and motor. The next steps will involve having the software compare the data from encoder to the DRO in Mach3. My thoughts for the software is to modify the home sequence of the z-axis to zero the encoder to get the Z machine position equal to the encoder position. Then have the comparison done in Mach3 Brains. But at first I may do the comparison in a Macropump because it may be easier for me at this time.
Is there much of an advantage to using a macropump over doing the comparison in Brains? My original thinking is that Brains run faster.

Thanks,
Paul

[poppabear]

another option would be (since your talking about a following error kind of thing), to run in brians.

Encoder (on z axis) x (factor to tune it to the axis) = v0

abs (v0-z absolute coordinate DRO), compare if greater than some value, then E-Stop

** Use the formulas and compare statements in brians for the above.