Macro for multi stage rotary axis homing

# Thread: Macro for multi stage rotary axis homing

1. ## Macro for multi stage rotary axis homing

I already have my 4th axis homing working with ref A using index pulse, but I want it to be quicker and more accurate. With anything faster than extremely slow, it overshoots beyond the index pulse. I want it to home in one direction at high speed, then home in opposite direction at medium speed, then one last home in original direction at very low speed. Doing it this way should be very fast and accurate. How can I do this in vb? Do I need to break it down completely into do while loops and such? Or is there a way to call a homing cycle at specific speed and direction?

2. ## Re: Macro for multi stage rotary axis homing

The steps you describe is a normal homing cycle. I thought there was a homing function in Mach3 to do this. I don't remember what drives you are using, but some drives have a homing function built in.

Worse case, just write the script you described.

3. Originally Posted by Jim Dawson
The steps you describe is a normal homing cycle. I thought there was a homing function in Mach3 to do this. I don't remember what drives you are using, but some drives have a homing function built in.

Worse case, just write the script you described.
Mach3 does a normal single stage homing cycle. It moves at a specified percentage of rapid speed until it triggers a home switch (in my case an index pulse) then it stops and zeros machine coordinates dro. Mine is already working like this, but it's very slow at the speed required for accuracy. At higher speed, it triggers the stop when passing the index pulse, but overshoots and home position ends up pretty far off the actual index pulse position. Lowering the speed gives better accuracy, but a much longer wait.

What I want it to do is run the homing cycle clockwise at high speed as it already does, then after it overshoots and stops, run the homing cycle again counterclockwise at reduced speed to reduce the overshoot. At this point it will be very close to the index pulse and it can run the cycle one more time clockwise at very slow speed so it can stop dead on the index without overshooting. This will allow very good accuracy without waiting a long time for it to home. The reason it's important for me to reduce the time is because it needs to run through this cycle every time my mill turn switches from turning to index milling which can happen multiple times in one program depending on the part. Running a normal homing cycle at low enough speed for good accuracy will easily add minutes to cycle time. Mach3 allows you to specify the direction and speed of the cycle, but I don't know how to change these settings within a vb script for the 3 different stages. If it's not possible, I will have to break it all down myself, but if there is a way to simply specify speed and direction of a standard homing cycle within the script, the macro will be much simpler.

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