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Author Topic: CV Mode .. thought I understood, but ..  (Read 7316 times)

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Offline Zaae

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CV Mode .. thought I understood, but ..
« on: June 07, 2008, 04:35:24 PM »
I've been running my machine with CV mode on, CV Dist Tolerance at 180, G100 Adaptive NurbsCV on (whatever the heck that is), and Stop CV on angles at 180.

I've been cutting a lot lately, and I thought I had everything all tuned in, but today I thought to myself "Self, that thing sure is jerky still" and decided to go fiddle with the CV settings again.

After a few changes, I turned on Plasma mode just for kicks and WOW - my machine smoothed out SO NICE!

As a test, I turned CV mode off entirely, and I saw no difference between it being off, or on. The only time I noticed a difference was when plasma mode is on.

Here's the question: What did I just do? Am I going to run into trouble having this on since it's not a plasma torch? Why am I not seeing any change without it enabled?


Hope this made sense, and thanks :)

Offline jimpinder

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Re: CV Mode .. thought I understood, but ..
« Reply #1 on: June 08, 2008, 05:13:24 AM »
I am a little at a loss here. CV mode should not be jerky, unless you have the parameters wound up so as to more or less cancel it out.

1. Absolute Stop mode means that the axis - as they change direction (or speed) to give an apparent change in direction - come to an absolute stop - before setting off on their new setting.

2. CV mode means that the acceleration required for the new setting is computed and mixed in with the deceleration of the old setting, so the axis never comes to a stop.

C.V. mode should be smooth - Absolute stop is often jerky is, for example a curve is made up of many little straight lines.
Not me driving the engine - I'm better looking.

Offline Greolt

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Re: CV Mode .. thought I understood, but ..
« Reply #2 on: June 08, 2008, 07:00:01 AM »
Make sure "CV Feedrate"  is not being turned on without your knowledge.

A bug was turning this on when saving settings a few versions ago.

It has been fixed in the most recent versions.  Found on the settings page.

I run all my machines with CV turned on and every CV option turned off and get good results.

But I run fairly crisp acceleration settings.

Greg
Re: CV Mode .. thought I understood, but ..
« Reply #3 on: June 08, 2008, 08:23:49 AM »
I thought it was just me but, I could never see any effect from CV mode UNLESS I selected the plasma mode.  Untill I checked this box, nothing (& I tried it all) seemed to effect the machine.  As soon as the plasma mode box was checked- BAM things started smoothing out and working in what I assume is a CV manner.

HTH,
Sid

Offline Zaae

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Re: CV Mode .. thought I understood, but ..
« Reply #4 on: June 08, 2008, 01:07:05 PM »
It sounds like sshneider is having the same results as I am. No matter what I change about CV mode, the only time the machine shows any difference is when plasma is enabled.

I've noticed a couple minor glitches here and there too. One that's got me a couple times is that *sometimes* when the CNC computer is rebooted, the setting for TOOL CHANGE is lost. Even after manually saving the settings, once in a while, tool change is set back to IGNORE, and it doesn't stop and wait for a new tool. This makes a bit of a mess as I'm sure you can imagine. Trying to do detail work with a 1/2" end mill doesn't work so well.

I've taped some notes on my monitor as a checklist before I start any programs to make sure things are set up correctly before I start.
Re: CV Mode .. thought I understood, but ..
« Reply #5 on: June 08, 2008, 02:25:34 PM »
Not sure how CV works with Lathe.  Seems to me that movements on a lathe are smaller and slower and that generally CV would not be as noticable with a lathe.

All I can say is that I never saw any change in my machine using CV until I checked the plasma mode box and then it all seemed to work. 

All that being said, I still prefer exact stop as I find it to be more predictable.

Sid

Offline docltf

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Re: CV Mode .. thought I understood, but ..
« Reply #6 on: June 08, 2008, 06:10:59 PM »
HEY GUY'S

i have two ver. mach loaded on my compute.ver 2.02 and ver 3.41 -- 2.02 for cash 3.41 for play.since i picked up a smoothstepper to play with 3.41.when doing CV mode stuff i switch on and off with the g-code.
the machine is set as absolute in the config.i posted my config setting for abs and CV.most of my work gets done in absolute.CV gets the play stuff like V-carving.the CV setting number i came up with is a goofy number,but it sure works good for me.
both ver of mach have the same settings.the CV setting makes my machine run like smooth absolute.but not wide open CV.i will play with the plasma box later ,that will be new for me.

bill
Re: CV Mode .. thought I understood, but ..
« Reply #7 on: October 11, 2008, 04:31:25 PM »
What does CV Dist tolerance 0.023 units stand for I think mine is set on 180 would it help if I change this?

Thanks for your help,
Nick
Re: CV Mode .. thought I understood, but ..
« Reply #8 on: October 11, 2008, 06:29:16 PM »
 :)
Re: CV Mode .. thought I understood, but ..
« Reply #9 on: October 11, 2008, 08:27:45 PM »
Sorry I read that AFTER I posted the question . Then I changed my settings and I think I learned a little more today!!!

Thank you for your response,
Nick