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Author Topic: help in understanding CV stop at >  (Read 2712 times)

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help in understanding CV stop at >
« on: January 11, 2012, 07:03:51 PM »
I recently enabled the CV stop at > "60" on my machine. I also changed lookahead from 20 to 200. This is an attempt to compensate for gantry vibration that occurs at high speed when I change sharp directions. (my gantry weighs about 60 pounds and is 60 inches wide)

I cannot tell if anything changed at all. I am using a plotter pen and drawing for my test. I does not appear that Mach decelerates to a stop and then changes direction and accelerates from 0 when it changes direction > 60. Also, the corners of my squares are rounded, shouldn't they be square if Mach is stopping at corners?

Thanks,
Scott Sutton

Offline Hood

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Re: help in understanding CV stop at >
« Reply #1 on: January 11, 2012, 07:22:07 PM »
Exact stop will likely make your issues with vibration worse I am afraid, really the only way to solve the issue is to try and stiffen the gantry up. You could try the tempest planner but it was just a test and a lot of things dont work in it. Having said that there are people who use it all the time.
Hood.

Offline Chaoticone

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Re: help in understanding CV stop at >
« Reply #2 on: January 11, 2012, 07:26:02 PM »
Scott, this may help you understand the settings.

http://www.machsupport.com/forum/index.php/topic,7923.0.html

Brett
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Re: help in understanding CV stop at >
« Reply #3 on: January 12, 2012, 03:44:03 AM »
Brett I read the post about the explanations. From what I read I believe that Mach should ramp to a stop at any angle > 60 on my machine and then ramp back up to speed. All other arcs, angles < 60 should run in full CV mode and ignore exact stop. This is not the case with my machine, it does not stop at angles > 60. I am really only having issues with vibration at high degree angles at high speed.

Does Mach have to be re-installed after making changes like these or are they instantaneous?

Thanks

Offline stirling

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Re: help in understanding CV stop at >
« Reply #4 on: January 12, 2012, 04:01:38 AM »
The section about CV angles in the doc is wrong. I've brought this up many times in the past and even submitted a corrected doc once but I don't know that anything came of it. Last time I brought it up and attached a correction to the doc was here I think.

http://www.machsupport.com/forum/index.php/topic,18378.msg126805.html#msg126805

Ian
Re: help in understanding CV stop at >
« Reply #5 on: January 12, 2012, 06:04:20 AM »
Yes, it does appear that the docs are  wrong. In the shop this am and found this out;

With CV stop at >60 the machine would NOT stop at 90 degree corners, at 150 ipm and above I would get a small amount of vibration in my gantry when I turned a corner.
Playing with the setting I found that even at CV stop at > 45 it would not stop at corners. But, with it set to >44 it worked as described. Now, even with complex splines composed of many line segments it runs smooth unless it encounters a segment with a change of angle > 90. My corners are not rounded at all and all of the vibration is gone from my gantry even at 400 ipm. It appears that the CV stop at > value is off by 100% unless I am just not getting it.

This is what I was looking for!

Thanks for all the input into this puzzling configuration.

Scott

Offline stirling

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Re: help in understanding CV stop at >
« Reply #6 on: January 12, 2012, 06:55:43 AM »
Pleased you're getting somewhere Scott

It appears that the CV stop at > value is off by 100% unless I am just not getting it.

CV is not "off by 100%", it works absolutely correctly as long as you understand WHICH angle the "stop CV on angles >" is actually referring to.

Ian