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Author Topic: CV mode tuning  (Read 2753 times)
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stirling
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« on: June 22, 2007, 07:07:42 AM »

Hi all

I'd be grateful for any comments re: the fine tuning of CV mode. I've had a few issues of CV rounding too much and would like to understand setting it up better. I understand what CV is, I'm just not sure how to take full advantage of it's settings.

As I understand it CV will more accurately follow the required curves if feed rate is slower and acceleration capability is greater. Is that right?

Also am I right in thinking that the UG is a little behind the latest lockdown of Mach3? e.g. Chapter 10 - "No Angular Discrimination" - I can't find this on Mach3 but am assuming it's been replaced by "Stop CV on angles >". I understand generally what the idea of stopping CV over some angle is about but some advice with how I configure this with relation to G02 and 3 would be useful. Finally there's two buttons and DROs on the Settings screen labelled CV Distance and CV Feedrate which don't appear to be documented.
If all these questions are answered somwhere I havn't looked then apologies. I know there are lots of threads about CV but trying to wade through them all to see if my questions are answered is making me cross-eyed. - is that lazy? sorry.

Many thanks
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stirling
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« Reply #1 on: June 25, 2007, 07:01:08 AM »

bump - anyone?
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Graham Waterworth
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« Reply #2 on: June 25, 2007, 07:30:06 AM »

Unless you are turning staircase spindles I would turn CV mode off for turning.  Exact stop mode is more accurate for forming chamfers and radii on turned parts.

Graham.
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stirling
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« Reply #3 on: June 25, 2007, 10:13:50 AM »

sorry - maybe should have said - I'm milling not turning.
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Graham Waterworth
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« Reply #4 on: June 25, 2007, 10:34:38 AM »

CV mode is the blending of lines and arcs into a polly line, the smoother the original line the more accurate the CV line, sudden changes in direction result in large blend rads, thus the original shape is distorted.

The slower the feed rate the better the match to the original path (more time to change direction).

Under general config several CV config options can be set, these can be set the cause the axis to slow before a corner and reduce rounding.

Graham.
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stirling
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« Reply #5 on: June 25, 2007, 02:37:49 PM »

ah graham - guess it's been one of those days...

As I said in my OP - I know what CV is and I know where all the options are... but thanks anyway.

cheers
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stirling
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« Reply #6 on: June 26, 2007, 03:33:00 AM »

OK - I emailed Art with my questions and he's clarified the technicalities regards some of my issues with CV. He also pointed me at earlier threads. It seems http://www.artsoftcontrols.com/forum/index.php?topic=1724.0 is the nub.

Scott could have been speaking for me. The thread kinda runs out round about February this year and it's not clear to me whether there was any real resolution. Anyone?
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Chaoticone
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« Reply #7 on: June 26, 2007, 09:09:34 AM »

Hey Stirling,
   
Quote
As I understand it CV will more accurately follow the required curves if feed rate is slower and acceleration capability is greater. Is that right?


That is correct. I'm not sure about the UG, but I'm sure it is a little behind. Things change so quick.

CV distance tolerence - Notice it says units, this is the number of setup units (inches,mm) Mach will ignore to get from point A to point B in CV mode.
Stop CV on Angles Greater than _____ If your Code spells out an angle greater than this number, it will run it in exact stop.
G100 adaptive nurbs has been ripped out, no longer needed. It will be removed from the screen at some point.

I have sent you a personal mesage.
Brett
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