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Author Topic: Just when you think you are finally getting there....  (Read 5759 times)

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Re: Just when you think you are finally getting there....
« Reply #20 on: November 28, 2016, 08:37:01 AM »
... centripetal acceleration....

Increase acceleration or decrease feedrate in the corners to get LEDs following error
Rob

Albert Einstein ― “If you can't explain it to a six year old, you don't understand it yourself.”

Offline Davek0974

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Re: Just when you think you are finally getting there....
« Reply #21 on: November 28, 2016, 08:39:57 AM »
As far as i know, its only SheetCam that can do whacky, useful things with feed-rates on demand.

I'll tune her up a notch and see what happens.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives
Re: Just when you think you are finally getting there....
« Reply #22 on: November 28, 2016, 11:39:06 AM »
Onecnc XR7 has just added corner feedrate adjustment. Only helpful if you have the program of course.
We never have the time or money to do it right the first time, but we somehow manage to do it twice and then spend the money to get it right.

Offline Davek0974

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Re: Just when you think you are finally getting there....
« Reply #23 on: November 28, 2016, 01:26:09 PM »
I've doubled the acceleration to 700mm/s/s and checked the servo pid settings - following error did not alter and is still sub 250 on X&Y.

Air cutting the same code seems ok, you can feel it is a lot sharper when direction changes but will need to do some test cuts to verify.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Davek0974

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Re: Just when you think you are finally getting there....
« Reply #24 on: November 29, 2016, 12:47:19 PM »
Instant improvement, same code as before, same feeds etc just the increased acceleration in motor tuning.

Nice corners, no sign of rounding at all. :)

At least it now works up to 1000mm/min feed rates, no idea how much beyond that as i have no job that needs it.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Hood

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Re: Just when you think you are finally getting there....
« Reply #25 on: November 29, 2016, 01:51:46 PM »
Good news, never realised you originally had such slow acceleration but good its sorted now.

Offline Davek0974

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Re: Just when you think you are finally getting there....
« Reply #26 on: November 29, 2016, 02:03:50 PM »
Seems so, without any firm figures i just plonked it somewhere it seemed happy at - seems it was ok at the lower speeds but then i upped the feed rate to book specs because i was seeing premature tool wear and thats when it started rounding corners.

It probably will do it again but unless i do wood or plastics on her, I can't see much work needing to go faster than 1000mm/min. - this is on aluminium with a 2mm carbide tool so pretty much the fastest CAM needed i think.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives
Re: Just when you think you are finally getting there....
« Reply #27 on: November 29, 2016, 02:07:03 PM »
Good to hear Dave.

Looks like it really is all about acceleration.
Rob

Albert Einstein ― “If you can't explain it to a six year old, you don't understand it yourself.”

Offline Davek0974

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Re: Just when you think you are finally getting there....
« Reply #28 on: November 29, 2016, 02:14:44 PM »
It does, I was just babying her i think ;) Looking at the setup with it's 32mm ball screws and proper A/C thrust bearings in there now, I am confident that it will be ok.

Would be interesting to see what sort of figures are in use on the big boys vmc's.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives
Re: Just when you think you are finally getting there....
« Reply #29 on: November 29, 2016, 02:38:05 PM »
It seems like few want to post their acceleration and velocity settings, I was look for numbers on the plasma, and managed to find Jim Colt stating 40miliG as a starting point target, and some hyperthem literature as 10miliG as a plasma minimum, hence why I was reading about centripetal acceleration

 40 miliG = 0.04 x G (~9.81m/sec) => 392.4mm/s/sec.

But not found an idiot's guide explaining the importance of acceleration in cnc world (yet)
Rob

Albert Einstein ― “If you can't explain it to a six year old, you don't understand it yourself.”