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Author Topic: 360 rollover bug  (Read 1388 times)

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Offline Sage

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360 rollover bug
« on: March 07, 2013, 03:59:58 PM »
I have the 360 degree rollover set in my A-axis configuration

I have a machining setup where I have a bar set horizontally in the rotory table and I move the side of the bar into a grinder using the Y axis.. The Gcode rotates the A axis a degree at a time and manipulates the Y axis to generate a profile in the side of the bar.
The code starts the A axis at 0 deg and steps one degree per step and manipulates the Y position around to the final command
G1 A360 Y.075
 It then moves Y quickly to a safe position away from the bar.
At this point Mach has rolled over to zero degrees and the A axis DRO display shows 00.00

The next command is G1A0 Yxx. Where xx is the proper starting Y position.
This should not move the A axis as it is already at zero but it moves the Y axis back into the work from the safe position to start again.

What I've noticed very intermittently (only a couple of times in several hundred passes) is when it makes the move shown above it rotates the A axis without moving the Y axis. It rotates the A axis from zero around to 360 or zero again and then continues as it should positioning the Y axis. It's a good thing I have Y set at a safe position otherwise rotating the bar without moving Y would jam the grinding wheel into the part profile.

I'm thinking that perhaps when it rolls over and auto-zeros that maybe somewhere in the umpteenth decimal place the A axis is not
 really zero so it has to make a move to zero to get in sync again.

I can't duplicate it at will.

This might be something that Briian may have a clue about since he knows how the math works. Something to look at for Mach 4 perhaps.