Helix Definition

[dgs]

Working in SW 2006.


I have a helix defined. It runs inside a cylinder from one radial wall to another (about 1/5th of a revolution). I really would like to tie it to the two walls so that if they change the helix grows or shrinks with it. Theclosest way I've seen to create a helix, however, is to give it a start angle and number of revolutions. If my part changes (as I now need to do) my helix stays put and the cut createdwith itfails.


Is there a way to tie the helix to the existing geometry?


(I'd love to give you a screen shot, but the upload mechanism seems to be broken.

)

 

[michael3130]

Hi Doug,


Thehelix is initially defined using a circle in a sketch. If you add a constraint between the circle sketch and the inner edge of the cylinder, then when you alter the cylinder diameter, the helix will alter with it. So steps are:


1: Draw circle to define diamter of helix


2: Construct helix


3: Show initial sketch (now contained and hidden in helix feature in tree) and draw cylinder, providing a constraint between it and the cylinder sketch.


I use this for bottle spouts and closures, the customer usually has a range of sizesso I set up a family table to adjust the outer cylinder and the thread form grows or shrinks with it.


I think this is what you're trying to do. Let me know how you get on.


Michael


PS - if you have difficulties, let me know and I will send you an example.

 

[dgs]

Constraining the diameter isn't the problem. My helix is a partial revolution and I want the start and stop points constrained to geometry that intersects and interrupts the cylinder. These are planar surfaces that intersect the cylinder radially.


The only way to create it now is to measure the angle from the origin plane of the helix to the first intersecting wall and set the helix start point to that value. Then, I need to measure the angle from that wall to the end wall, divide by 360 and set the number of revolutions to that number (in this case, 0.20). Of course, none of that will update if the model changes.


It's frustrating to sit in front ofa powerful computer with a sophisticatedgeometry software and have to do the math myself. I suppose I could come up with an equation to drive it, but I was hoping there was a way to tie it directlyto the geometry.