how to stop arcs from being interpolated

[cryptopsy]

Hello,

I draw a circle, extrude, then generate a 2.5D operation "face mill" . The type is spiral. It should be producing gcode with 02/3 arcs. What's wrong here? The program is like 2500 lines.

-Point interpolation is unchecked.
-Approximate arc by line is unchecked.
-Geometry is not silhouette
-It is not a spline since it is just a circle created in solidworks.
postprocessor is aweaFANUC

In visi, the postprocessor does not interpolate, producing the same path of about 50 lines or less. Here it is 2500 and producing poor surface.

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[Mikay19]

Hi cryptopsy,

Unfortunately, there is no gcode command for a spiral. To be a true spiral, the arc (G2/G3) would not work because the spiral is actually a spline that is continuing to change as it gets bigger or smaller. Thus producing a point-to-point gcode.


Highest Regards,
Darrin - SolidCAM

[cryptopsy]

Hi cryptopsy,

Unfortunately, there is no gcode command for a spiral. To be a true spiral, the arc (G2/G3) would not work because the spiral is actually a spline that is continuing to change as it gets bigger or smaller. Thus producing a point-to-point gcode.


Highest Regards,
Darrin - SolidCAM

What spiral type should i use to replace the spiral with g2/3 moves? There must be some type that permits this, since i generated it in visi.
What if i want to do a helical path, would it interpolate arcs? Like in this exact example :

[CitizenOfDreams]

Edit: What kind of spirals are we talking about? A flat one ( R=var, Z=const)? Or a downward spiral (R=const, Z=var)?

[Mikay19]

I am assuming that visi did an arc fit during the creation of the spiral. Which means it is not really a spiral but a series of larger/smaller arcs that are connected. I don't see a way to create a true spiral using arcs.

Regards,
Darrin - SolidCAM

[cryptopsy]

It is a spiral for a facing operation, so it is const Z and it doesn't have to be a true spiral.

[RCaffin]

A true spiral has a constantly changing radius of curvature.Neither CAM programs nor g-code can handle that.
However, one can do a very good approximation by doing a number of 180 degree segments at decreasing radii.

Cheers
Roger

[mactec54]

A true spiral has a constantly changing radius of curvature.Neither CAM programs nor g-code can handle that.
However, one can do a very good approximation by doing a number of 180 degree segments at decreasing radii.

Cheers
Roger

Give me any possible curvature or spline you can come up with and I'm sure I can make the G-code for it in my cam program

Here is a Spiral took me all of 2 minute's start to finish, of course it is not a true spiral, but anything is possible with a good cam program, the cam software I use has had this operation for about 15 years may be longer has many more useful operations like this

[Mikay19]

cryptopsy,

RCaffin is correct, you can draw the path in pretty simply if you really want a spiral like path without so many lines.

Darrin - SolidCAM

[cryptopsy]

A true spiral has a constantly changing radius of curvature.Neither CAM programs nor g-code can handle that.
However, one can do a very good approximation by doing a number of 180 degree segments at decreasing radii.

Cheers
Roger

Visi generates this automatically. I should not have to draw my own spirals, because if i want to change the width of cut , or i change the tools, i have to redraw the spiral.

[RCaffin]

I use a parametric program for spirals. Take radius R of spiral area, divide by 0.8*D, where D is the tool diameter, and you have the number of full loops needed. Both R & D are editable parameters. The 0.8 allows for path overlap. It's just maths, which g-code is well able to handle.

Cheers
Roger