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Help with CV mode
« on: April 04, 2009, 09:59:28 AM »
I have used many Robot and motion controllers over the years.
All of them have a method of path mode (cp) that allows the connection of many moves to be blended together to get smooth continuous motion. Basically Accelerate up to commanded velocity from the start to the first position and then move thru each position to the next and Decelerate to a stop at the last move.
Can Mach do this?
I am not a machinist but it seems that "finish grade" is a function of feeds and speeds, if the axis accel and decel on every move in a path, the finish would be anything but acceptable.

I have a simple function of Cv mode that needs to be done.
I want to connect a series of ten arcs and I do not want to change velocity from one arc to the next (Constant Velocity).

I am frustrated with Cv and its setup, as I can read many others as well are having similar and varied results.

What are the settings that I need to make to see a change from exact stop to CV mode?

I am cutting holes in Tangential mode  most openings are less than 20" * 20".
Example an ellipse 7" high by 5" wide.

I see no change when I turn CV on in the general configuration settings.
I have changed the look ahead lines, cv distance, and max cv angle.

Can anyone help?

Offline ger21

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Re: Help with CV mode
« Reply #1 on: April 04, 2009, 10:26:58 AM »
Try turning OFF all the CV options, bith on the settings page, and uncheck all the options in general config.
Gerry

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Offline Hood

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Re: Help with CV mode
« Reply #2 on: April 04, 2009, 10:28:58 AM »
can you attach an example of your code?
Hood
Re: Help with CV mode
« Reply #3 on: April 04, 2009, 11:14:16 AM »
Thanks for looking at this.
I am heading to the shop and will have details later.
One example is utilizing the ellipse wizard code.
This program works very well, in that it allows you to set the ht and width as well as the number of line segments.
This is for example a connection of 360, 1 degree moves that are G1 x & y type.
If CV could remove the acel and decel on each move it would be perfect.
I then created an ellipse in autocad and found 10 arcs with varying radius dimensions that overlay the original ellipse.
This provides 10 arc segments with end point and radius and can be done with G2 or G3 moves.
This works very well, ellipse done with arcs instead of line segments. (circular vs linear interpolation)
To clean it up I need to roll thru all moves at the same velocity.
I can give you the set of points that I am going to test next.

The code is from memory and may not be complete to the detail.
I have not tested these numbers yet, If the arcs present inverted, change from G3 to G2 moves.

G1 1.000,1.75
G17 G3 0.804, 1.69, r 0.35
G17 G3 0.60, 1.45, r 0.625
G17 G3 0.50, 1.00, r 1.0625
G17 G3 0.60, 0.55, r 1.0625
G17 G3 0.804, 0.310, r 0.625
G17 G3 1.00, 0.25, r 0.35
G17 G3 1.196, 0.31, r 0.35
G17 G3 1.40, 0.55, r 0.625
G17 G3 1.50, 1.00, r 1.0625
G17 G3 1.40, 1.45, r 1.0625
G17 G3 1.196, 1.690, r 0.625
G17 G3 1.00, 1.75, r 0.35

Thanks again.
Chuck














Offline ger21

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Re: Help with CV mode
« Reply #4 on: April 04, 2009, 11:22:59 AM »
In AutoCAD, change the PELLIPSE variable to 1 and you'll get an ellipse made up of polyline arcs.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html