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Offline russh

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Losing Zero
« on: November 14, 2015, 07:39:40 AM »
Hello All,

Can some one offer some help on an issue I seem to have

Basically, when set my zero positions, I then come to run a program and now and then (more times that not!) it seem to loose its zero positions. I've had a few cases where Z or Y have lost Zero and the tool has crashed in to the work piece.

Initially I though I might be cancelling or calling up an incorrect fixture offset in the G-code with G54, but even when I remove this from the safe line, it still happens

Any help would be greatly appreciated

Thanks

Rusty

Online Tweakie.CNC

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Re: Losing Zero
« Reply #1 on: November 14, 2015, 07:54:19 AM »
Hi Rusty,

Sounds like you are loosing steps.
To resolve the problem just one step at a time ( no punn intended)...
Try reducing your Velocity and Acceleration settings ,for each axis, by 50% (in motor tuning) and save the changes -  and then see if the problem persists.

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

Offline russh

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Re: Losing Zero
« Reply #2 on: November 14, 2015, 08:00:44 AM »
Tweakie,

Huge thanks for the quick reply

Would the "losing sets" issue occur in manual mode as well, I.E If I jog the table around with the MPG wheel, I don't seem to loose zero (well not that I have spotted, but I will recheck this statement as well), it only seems to be during code running

By the way, The problem occurs even if I manually over ride the feed rate right down to a snail pace during program run as well

Cheers

Rusty

Online Tweakie.CNC

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Re: Losing Zero
« Reply #3 on: November 14, 2015, 11:27:02 AM »
Hi Rusty,

Reducing the feed-rate is not quite the same thing so try reducing the Velocity and Acceleration by 50% as suggested and report back on what happens regarding loosing position.

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

Offline russh

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Re: Losing Zero
« Reply #4 on: November 15, 2015, 02:52:11 PM »
Hi Tweakie,

Right, I ran a few tests and record a bit of position information first. I turn the machine on and zero'd the tool to each edge of the vice I had in, then ran a simple movement program with G00 and G01 commands. The machine lost position from the zero points by X: 3-4mm, Y: 3-4mm, and Z: 16mm.

I then changed the Velocity and Acceleration values as you said by 50%.

Original Values
X: Velocity=6000, Acceleration=300
Y: Velocity=6000, Acceleration=300
Z: Velocity=5100, Acceleration=300

New Values
X: Velocity=3000, Acceleration=150
Y: Velocity=3000, Acceleration=150
Z: Velocity=2550, Acceleration=150

I then ran the same simple program (after re-zeroing), and repeated the program a few times. It still lost position, but not as much this time. X: 0.5mm, Y: 0.5mm and Z: 2.4mm

Should I reduce by half again? or do we need to look at something else now?

Offline bfgstew

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Re: Losing Zero
« Reply #5 on: November 15, 2015, 04:38:21 PM »
Reduce it by half again I would say.
I run mine at 1000 max for velocity, and even that I find is too fast when the machine is cold!

Offline russh

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Re: Losing Zero
« Reply #6 on: November 15, 2015, 05:40:08 PM »
So 6000 velocity was WAAAAAAY to high then!
That was what was in the manufacturers config file!

I will give it a go at half again, and if it still runs out will knock it down a little more

Online Tweakie.CNC

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Re: Losing Zero
« Reply #7 on: November 16, 2015, 02:13:48 AM »
Hi Rusty,

Wow those Velocity figures you have been using are high.

Perhaps try;  Velocity 2000 and Acceleration 300 and see how that goes.

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

Offline russh

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Re: Losing Zero
« Reply #8 on: November 17, 2015, 02:11:44 PM »
Right,

I'm now down to 1000 mm/m velocity and just had a more stable run in X and Z, but I still lost about 0.8mm on the Y.

I'm now trying 800 mm/m but is this beginning to look like another issue, or is sub 1000 common?

Offline bfgstew

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Re: Losing Zero
« Reply #9 on: November 17, 2015, 02:30:00 PM »
How are the motors sounding?  Smooth and humming or jerky and noisy?