Helical Sweep/Conical Thread

[theledman]

I'm currently modeling a screw thread with a conical
style thread. When I machine this part, the tool cutting
the thread follows a conical path so that the core
diameter is increasing as it goes up the shaft of the
screw. Also, the width of the tool is wider than the
pitch itself so that at the start of the thread, the
outer diameter is also slightly conical (due to parts of
the cutting tool overlapping itself as it travels along
the tool path). I have attached a picture of the
prototype showing what was done.

<a href="http://postimage.org/image/m3k9c6rvl/" target="_blank">
[img=http://s8.postimage.org/m3k9c6rvl/IMG_20121213_162626.j pg"></a>

I'm trying to model this in ProE, but since the width of
the tool is wider than the pitch, the helical sweep cut
feature returns an error when trying to render it. I'm
not sure how to get around this. Any thoughts?
[b]Edited by: theledman [/b]

 

[dr_gallup]

My company is blocking your link but i think I understand the problem. The helical sweep feature does not like to self intersect as you are finding. Before there was a helical sweep feature, we used to use a curve by equation and then sweep along it. I think (but don't have the time to verify) that feature will allow self intersection.

The only problem I see is that the sweep profile will always be normal to the curve and you probably want it normal to the axis so you will have to draw the cutting tool normal to the axis and then project it normal to the curve start point.

 

[theledman]

Thanks for the response. I'm not sure how to derive the
curve from equation though since it's the tool path is
fairly complicated. (I'm assuming you're suggesting to
create a curve from an equation that graphs the path of the
tool?)

 

[dr_gallup]

Insert a datum curve by equation and use a cylindrical CSYS.
/* For cylindrical coordinate system, enter parametric equation
/* in terms of t (which will vary from 0 to 1) for r, theta and z
/* For example: for a circle in x-y plane, centered at origin
/* and radius = 4, the parametric equations will be:
/*&nbs p; r = 4
/* theta = t * 360
/*&nbs p; z = 0
/*---------------------------------------------------------- ---------
r=4+2*t
theta=t*6*360
z=t*12

View attachment 5800