find axis of helix 2

[cowski]

Does anyone know of a way to determine the axis of a helix feature? I have a part that is a little mismatched and would like to line up the axis of an existing helix with the axis of another existing feature.

 

[hudson888]

I think the best thing to do is probably to re-construct the axis. You'll know what I'm about to relate but for the sake of confirmation I've passed on what I know.

If you have a parametric helix then info object sadly seems to offer no clues. Of course if you know that the number of terms is an integer then you can construct a curve parallel to the central axis using the two ends of the helix curve. Then by projecting the helix to a normal plane you should get a circular arc or at least a spline from which you can quite closely locate the centre point.

Much of the time the best first guess would be that somewhere relative to known co-ordinate systems is discernible from the part that you're working with. Sometimes I'd have to say it can be pretty hard to find the axes of helices especially from non-parametric splines of indeterminate orientation.

For mating purposes I usually retain a datum axis with springs that I use in assemblies.

Best Regards

Hudson

www.jamb.com.au

Nil Desperandum illegitimi non carborundum

 

[mmauldin]

Try this.

Temporarily change the number of turns to a whole number. Skip this step if it already is a whole number. Draw a non-associative line between the endpoints.

Then change the number of turns to whole number plus/minus 1/2. For example 5 turns for the first step, 4 1/2 for this step. Then draw a line from the end of the helix that changes position that is perpendicular and point-on-curve to the first line drawn.

Add a datum axis using point and direction, select the mid point of the second line for the point and the axis of the first line as the direction.

Change your helix number of turns back to its original value.

 

[cowski]

Thanks for the suggestions, that will get me what I need.