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# spiral straw

Creator

I've attached a picture to show what I'm trying to do.  It's a non-linear tube with two spirals wrapped around it.  I'm trying to subdivide the face of the tube, so that I'll have a tube surface, and the spriral surface.  I was unsuccessful with the divide face operation.  I'm also open to creating these two surfaces with a helix/swept combination, etc., vs. subdividing the tube - whichever approach works.

8 REPLIES

# Re: spiral straw

Siemens Phenom

Hi,

I have an alternative way to model this.

You can use variational sweep in a special way. Helix-like can be modeled with variation sweep through a capability that is not very well-known: you can vary the sketch depending on the position along the path. The sketch plane contains an expression that you can use inside the sketch.

I recorded a movie for you.

Powerful stuff!

Regards, **bleep**

(view in My Videos)

# Re: spiral straw

Creator

This is a pretty sophisticated answer - thank you.  Now, I just need to tweak the paramaters such that I get the desired pitch of the spiral.

# Re: spiral straw

Creator

All right.  I've been playing with that formula for a little bit, but can't seem to figure out how to manipulate that "pos" parameter to get the period I want.

Prior to this approach, I created a tube along my spline, then created two helixes of identical periods, but offset along my spline to give my sprial the width I wanted.

With this rotated sketch approach, I can understand how to get the width, just not the period.

Thanks, again.

# Re: spiral straw

Creator

When you tie that angular dimension to the curve percentage alone, meaning, let the angular dimension be equal to p6, does that mean 1% or curve is equal to 1° of angular separation?

# Re: spiral straw

Siemens Phenom

if P is the length that moves form 0 to 100 then you can make the angle A go a full cycle (360 degrees) by using the formula: "A=360*P/100"

Regards, **bleep**

# Re: spiral straw

Creator

I'm stumped...what causes the sketch to off its path?

# Re: spiral straw

Siemens Phenom

I am not sure... but a likely cause it that you did not correctly constrain you sketch to the references of the 'datum on path'.

When creating a sketch on path ensure that all your references are internal to the sketch so that you know what will happen when the sketch is moved along the path. When creating sketches like this one it is wise to set your selection scope to within active sketch.

You probably snapped to a point outside the sketch or the center point was not constrained to the internal datum point in the sketch.

Regards, **bleep**

# Re: spiral straw

Creator

It was definitely related to the selection scope when creating the sketch; the problem apparently went away when I chose the vertex of the sketch datum CSYS origin vs. the endpoint of my spline.

All this has been good learning.  Thanks!