ARC Failed

[Leandro]

In the attached file the blue surface is part of a "torus".

The center of the red arc is X0 ; Y0

The yellow arc is a Proyection (View) from the red arc.

 

Did somebody know why I get a different center point and a different radius??

 

ftp://ftp.mastercam.com/Customer%20Area/T...tercam/ARCO.MC9

[camguy]

Leandro, when you project a curve onto a surface the result will be an aproximation only, especialy if the result is an arc as opposed to a spline. If you create 3 points along the red arc, and then project those points onto the surface, and then create an arc from those 3 surface points, they will have the same center and radius.

Hope this is of help to you.

Steve

[Jim at Gentex]

Leandro,

I believe what is happening is that the arc projects onto the surface as an approximation that follows the surface as closely as possible, but not exactly. Thus, the center of the arc shifts slightly.

 

Try this:

 

Create>Curve>Project

Select the surface

Select the curve

Select Options

 

In the Projection Curve menu:

 

Select 'fixed step'

(You will see Parametric Spline option selected automatically when you select 'fixed step')

 

Select OK

Select Do it

 

Now you have a parametric spline projected onto your surface which will represent the original arc much more closely. There is one more step to complete the process:

 

Create>Arc>3 points>

Select the endpoint, midpoint, and endpoint of the projected spline and there you have it! Now you can delete the spline and analyze the arc. The center should be X0. Y0.

 

HTH

 

edit: Steve and I answered at the same time, but his solution is even quicker!