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Rotary axis zeroing problem
« on: February 15, 2010, 08:13:11 AM »
Hi,

in the German CNC-Ecke we are discussing a problem with the rotary axis.

If "Ang. Short Rot on G0" is active and the DRO for the A-axis is a multiple of 360, there is no movement when executing "G0 A0".
That's exactly what it should do.
But there is also no change in the DRO value. It stays just as it was before the move and does not switch to '000'.

Any ideas about this effect ?

Thanks
Uli

Offline Hood

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Re: Rotary axis zeroing problem
« Reply #1 on: February 15, 2010, 08:46:12 AM »
I am not really understanding what you are meaning. As far as I understand the setting "Ang Short Rot on G0" should move the axis to zero if you are not already there. If for example you were at 100 then it would move backwards to zero, if you were at 200 it would move forward to zero, ie taking the shortest path.
Hood
Re: Rotary axis zeroing problem
« Reply #2 on: February 15, 2010, 09:03:26 AM »
Yes. It should move on the shortest path, what it does in fact.
But if the actual position is a multiple of full turns to the commanded position, there is no move to do.
The axis doesn't move which is what it should do.
But the DRO value remains the old one, it does not change to the target position.

Example:
DRO for A is '0'
G1 A3600   --> Axis moves. After move DRO shows 3600
G0 A0        --> Axis does not move at all, because way to go  is 10x360°
                     After move,  DRO still shows 3600

Uli

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Re: Rotary axis zeroing problem
« Reply #3 on: February 15, 2010, 09:12:53 AM »
Surely 360.000 is exactly the same as 000.000 as far as Mach is concerned when the axis is set for continuous rotation ?.
My A axis often reads 360.000 when it has be zeroed but it has no effect (that I have yet discovered) on subsequent moves.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

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Re: Rotary axis zeroing problem
« Reply #4 on: February 15, 2010, 09:22:21 AM »
Ah ok obviously you are not using the rotational roll over, that is where I would see the use for the short rotation move. I will have to think about what you are trying to do.

Hood

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Re: Rotary axis zeroing problem
« Reply #5 on: February 15, 2010, 09:24:14 AM »
What version Mach version are you using as i don't remember that happening here ( ver 033), but, will recheck it later on.  Maybe i had the 360 rollover checked.

Rot 360 rollover – if checked the A axis DRO will display from 0 to 360 degrees and then start over at 0. If not checked the A axis DRO will be additive such that 2 revolutions will display as 720 degrees.

Ang Short Rot on G0 – The axis will move in the shortest possible move to a new position. So if at 0 degrees and you jogged  to 359 deg then it would just rotate  -1 degree.

Hood, you beat me to it,
RICH
 

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Re: Rotary axis zeroing problem
« Reply #6 on: February 15, 2010, 09:25:40 AM »
Also what mode are you in, incremental or absolute.
RICH

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Re: Rotary axis zeroing problem
« Reply #7 on: February 15, 2010, 09:32:44 AM »
Are you just trying to reset the A DRO to zero?
If yes do you home the A Axis?

Hood

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Re: Rotary axis zeroing problem
« Reply #8 on: February 15, 2010, 10:11:16 AM »
If it is a lathe, use Phil's screen as it has the button already there for it.
RICH
Re: Rotary axis zeroing problem
« Reply #9 on: February 15, 2010, 11:43:58 AM »
Rich,

here on my PC it's R 3.042.020 with the 1024 standard screen but it seems to happen with other versions as well.
This is in absolute mode.

About what the guy is trying to do:
He uses the rotational axis to mill a thread on a rod. He does it to a depth of 1mm in let's say portions of 0.25mm.
So it is something like

g0 z1
g0 x0
g1 z-0.25
g1 x10 a3600    ; make 10 full turns to get a spacing of 1mm on a length of 10mm
                       ; We are at x10 and a3600 now
                       ; Then a second path is needed.
g0 z1
G0 x0 a0          ; Without the Ang Short Rot it's a full 10 turns back :-((
                      ; with Ang Short Rot  we are already there and do not haveto do more  than moving x to zero. That's much better :-))

But if a stays at 3600, the next pass has to go to 7200 and so on.
And there is no explanation why a stays at the old value.

Uli