Involute curve accuracy

[not2fast]

Hi All
I found a macro for an Involute curve that works great however I see that the created curve in the sketch is a series of points & lines. I converted this Inv curve to construction geometry and recreated the Inv Curve with a Spline along the points that looks better.

My question is whats more accurate when it comes to machining ? I have 2 choice's here, one is Wire Cut and the other is a CNC Mill for the particular part.

the macro is here

http://www.cnczone.com/forums/archive/index.php/t-20351.html

How can I edit the macro so as to create a curve with a Spline instead of the Line in the sketch?

thanks
not2fast

 

[rollupswx]

G-code uses lines or arcs. At some point it will have to be converted from a spline to lines or arcs. The resolution should be set at the resolution of the manufacturing machine or as loose as then design intent will allow (the higher the resolution the more expensive the part - there is no point in making a curve for the space-shuttle when the part is going in a vending machine).
Forget about making "perfect" parts.
Just cause you can doesn't mean you should.

 

[TheTick]

If you get the curve points, overlay a spline on the points. Some programs only do arcs and lines, so you may need to overlay arcs instead of splines.

I did one project to replace a gear that was no longer available for an old press. The gear was wire cut. The model is at <

http://www.esoxrepublic.com/models/>

if you want to see. That involute was done analytically, by "unwrapping" a string from a base diameter. The spline is mirrored to maintain curvature at the root.

 

[not2fast]

I hear what your saying here, my thinking is that the spline is a more accurate representation rather than the line from point to point, as the model looks like it has Facets... I'm hoping that this look appearance would not be recreated in the part. I guess I would need to look at the G-Code to really understand whats going on, the guy who will make this part uses MasterCamX. I know the wire cut machine is accurate to approx 2uM as for a CNC milled part I'm not sure.

thanks for the help

not2fast