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Author Topic: cant understand mcCvDisToleranceV001 behaviour  (Read 361 times)

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cant understand mcCvDisToleranceV001 behaviour
« on: May 12, 2020, 03:08:27 AM »
i work with mach 2 years but until now cant find solution for corner
if i make exact stop ,then when some curve  the machine go in pulses...like stop in the middle of curve then continue ,very bad work
when i try use the wizard then ....god know what will happened
please see atach ,the part shuld be total simple rectangle ,but for some reason on corner its become round
(in this part for some reason the pp divide the line into 2 parts ,but this not error)
thanks
alot for any help

Re: cant understand mcCvDisToleranceV001 behaviour
« Reply #1 on: May 12, 2020, 03:20:05 AM »
i forget to send you the phot of the wrong part ,to understand how big its the confusion ,when client send you this photo ,and i have no tools to do something

Offline smurph

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Re: cant understand mcCvDisToleranceV001 behaviour
« Reply #2 on: May 12, 2020, 03:52:36 AM »
Wow...  if you have to use CV for a part like that, then I suspect you are trying to drive your machine faster than it can go with regard to your acceleration parameters on your motor tuning.  Bad CV settings in combination with horridly slow acceleration parameters in your motor tuning will round corners like that.

Do Help->Support->Package profile and attach the packaged up profile.  Then I can take a look at your motor tuning.  BTW, you could work all of this out with the Sim plugin as your motion controller.  Just plugin your motor tuning numbers into the Sim profile.  You will see the cut path vs. the programmed path on the tool path. 

Steve
Re: cant understand mcCvDisToleranceV001 behaviour
« Reply #3 on: May 12, 2020, 04:14:51 AM »
thanks steve
that what i did,the simulation i sent you its not from the machine ,because this part already cut(i sent the part picture)
in this parts i real no need cv and can change to exact stop ,but i cant do it because the nc files export from the desighn software ,and
some panels need cv some not ,its not something we can leave for worker ,if run cv or not
thanks
yaakov
Re: cant understand mcCvDisToleranceV001 behaviour
« Reply #4 on: May 12, 2020, 04:17:43 AM »
forgot to attach the package
Re: cant understand mcCvDisToleranceV001 behaviour
« Reply #5 on: May 13, 2020, 06:12:10 PM »
is any coment? no one have problem with corner?its only in mine???very starnge

Offline smurph

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Re: cant understand mcCvDisToleranceV001 behaviour
« Reply #6 on: May 13, 2020, 11:03:58 PM »
I haven't looked at yours yet.  But to answer your question, no.  I don't believe anyone else is having these issues. 

MOST of the time, you don't even have to do ANY CV settings.  I have never run the CV wizard on my mill, for example.  The reason is my machine is very rigid and has powerful servo motors on it so I can have good acceleration parameters in the motor tuning section.  The CV tolerance wizard is usually used on a machine that has poor acceleration settings to try and modify the trajectory's profile so that the corner can be cut at a speed that doesn't excessively round the corner. 

Steve
Re: cant understand mcCvDisToleranceV001 behaviour
« Reply #7 on: May 14, 2020, 02:30:17 AM »
i  also do not need that cv
but when i have curve work that build from many small segment (its depened on cadcam software ,but many export only G1 not  G2 or G3)
then movment become not smooth and with shaking
so if you can have solution for the smoth then i real no need that cv and can work with exact move

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Re: cant understand mcCvDisToleranceV001 behaviour
« Reply #8 on: May 14, 2020, 03:34:12 PM »
I'm talking about the special CV settings.  I run my machine in CV mode all of the time.  Constant stop only on special occasions.  My point is, I do not need to run the CV wizard in order to have good CV. 

The CV wizard is used when the machine is not capable of doing what is asked of it.  Like a machine with real low acceleration parameters but capable of high speeds.  A lot of people want to cut with their routers at 500 inches per minute but are running steppers that don't have much torque at those highers speeds.  They end up reducing the acceleration parameters so the steppers won't lose steps.  Then they program the 500 IPM feed rate and CV will cut a WIDE corner.  So the CV tuning Wizard allows the user to compensate for this by slowing the corner approach automatically based on angle.

CV is a function of the programmed speed and the acceleration parameters in the motor tuning.  CV will sacrifice accuracy in favor of speed.  So natural CV, without using the CV Wizard, will look at the path and calculate the maximum velocity that it can maintain to get around the corner.  If the acceleration parameters are lacking, CV will make a wide turn around the corner.  If you decrease the feed rate, CV will follow the path more closely. 

So what is the for this? 

1. Slow down and increase the acceleration parameter. 
2. Get stronger motors that are capable of having higher acceleration parameters. 
3. Program the part path to slow down before the corners. (Some CAM packages actually have a setting for this).
4. Use the CV Wizard to try and mitigate the issue.

Steve
Re: cant understand mcCvDisToleranceV001 behaviour
« Reply #9 on: May 15, 2020, 10:54:08 AM »
we cut aproxmaly this speed(10-15 m/min)and we change our accl dccl in mine pp
so g0 its about 300000  g1 its about 20000 (this the values i use in mc.mcMotorSetMaxAccel(   ))
we use big servo motor (850 w each side) so we dont have any problem with the motor ,we only have problem in some works (most  is "pocket" in MDF) that i think because i cant control the acc dccl s curve in mach ,i have not good surface finish
but in any case first how can i disable the new cv and use only the old cv(the new cv also have change my tool path in linear cut)
and second is there any difference in corner behiviour if i change the look ahead parameter?
thks