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Offline Davek0974

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Look-ahead settings...
« on: March 19, 2014, 08:57:47 AM »
Can anyone advise re the setting of look-ahead.

I am having issues on a plasma cutter running small 20mm circles at around 3700mm/min and there is a pronounced flat on one side, I have been advised to up the look-ahead settings but have no idea what to?

I am running in CV mode as far as I know.

Thanks

Dave
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Hood

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Re: Look-ahead settings...
« Reply #1 on: March 19, 2014, 09:13:14 AM »
Lookahead is in General Config and it defaults to 20 if I recall, you could try setting it higher. If however your circle code is G2 or G3 then that is unlikely to be the problem and more likely a mechanical issue or possibly if it is where the pierce occurs then it could be a delay of some sort.
If your circle code consists of lots of short lines then the lookahead may well be the issue.
Hood

Offline Fastest1

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Re: Look-ahead settings...
« Reply #2 on: March 19, 2014, 09:15:16 AM »
  I always use a value of 200 but have no idea as to why. I just figure it is better to look further down the road when driving fast. More time to think.

  Are you saying you dont know how to change the value (or dont know where this value is)?

It is on the general config page in Mach 3.   Mach3/Config/General Config. Dont forget to hit enter after changing the value.
I want to die in my sleep like my grandfather, not like the passengers in the car! :-)

Offline stirling

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Re: Look-ahead settings...
« Reply #3 on: March 19, 2014, 10:01:56 AM »
You might want to do a google for learned papers on cutting small holes with plasma - it's a whole subject/artform in itself. That said - 20mm isn't really regarded as small from this point of view.

As Hood has said, if your circles are G2/G3 lookahead isn't an issue. Your hole has a leadin, a circle and a lead out so even if lookahead was an issue it wouldn't matter what you set it to because it's only going to actually lookahead by TWO - the join between the leadin and the circle and the join between the circle and the leadout.

Lookahead like everything else involves a compromise. Make it too small and it's less effective. Make it too large and your needlessly burdening the system. To take Fastest1's analogy. I don't give a toss about how fast I can negotiate the driveway into Hood's mansion if I'm currently driving onto the M5 roundabout - 500 miles away. ;D

Offline Davek0974

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Re: Look-ahead settings...
« Reply #4 on: March 19, 2014, 10:14:07 AM »
Thanks

I'll check the g2/g3 thingy out and also see if an increase in look ahead makes any change.

Also, should plasma mode be on or off or does it not make any difference?

It's off at present but CV mode is on.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline stirling

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Re: Look-ahead settings...
« Reply #5 on: March 19, 2014, 10:27:07 AM »
and also see if an increase in look ahead makes any change.

Sorry - thought we were clear - if you're using G2/G3 (which you should be) lookahead is irrelevant.

Offline Hood

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Re: Look-ahead settings...
« Reply #6 on: March 19, 2014, 10:48:02 AM »
I don't give a toss about how fast I can negotiate the driveway into Hood's mansion if I'm currently driving onto the M5 roundabout - 500 miles away. ;D


Ian, you should be concerned, if you are 500 miles away from my mansion you are turning into the driveway :)

Hood

Offline stirling

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Re: Look-ahead settings...
« Reply #7 on: March 19, 2014, 01:37:05 PM »
Ian, you should be concerned, if you are 500 miles away from my mansion you are turning into the driveway :)

Me very 'umble apologies m'Laird.  ;D

Offline RICH

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Re: Look-ahead settings...
« Reply #8 on: March 19, 2014, 07:54:20 PM »
Quote
turning into the driveway


Always thought that is was the field clearing before the woods. DAHH........ guess I am confused. >:D
No wonder me and the friar  can't find your house......drank all the wine....shoot.... Big John is no help.........only see green men now......darn must be  a dream! ::)

Back to sleeping, ;D

RICH