Swept extrudes

[Charlie_P]

Am I going about this the right way?

What I am after is a rotated extrude of a polyline (see attached). As far as I can see the best way to do this is :

1. draw the profile (arcs, lines etc.) and compose to a polyline

2. convert to nurbs

3. duplicate array using a Z offset and a rotation to produce a spiral stack of nurbs

4. loft surface tool in loft with no rail mode, select the curves in order, click the green tick

5. go through each curve setting alignment by percentage to the same value, select create solid

This produces the solid OK but when rendered there is a visible ripple along the side of the object. I've tried other methods - create helix/spiral, extrude the rib along the path with the idea of adding it to an extruded circle (rib doesn't retain the same orientation to the axis all the way down) - loft with rail on the rib profile alone with the same purpose in mind (all sorts of strangeness).

Essentially this is a cylinder with a rib.

I've got a working method but it's not perfect - a little too fussy perhaps?

Charlie

[Pat Stanford]

How about making the flutes as a separate pieced and adding them to a circular extrusion?

Assuming that you want your object to be standing vertical (long dimension to screen Y), go to a Top/Plan view and draw a circle. Switch to front and put a locus at the center of the circle. Draw a rectangle the size of your flute at the edge of the circle.

Select the rectangle and the locus. Do a Sweep. Set the pitch and the Number of degrees to get the number of rotations you need, plus a an extra turn or so on each end.

Go back to Top and extrude the circle. Go back to Front and move the sweep in the Y direction to cover the extrude. Go back to Top/Plan and Duplicate array to create the other three flutes. Select All and Add Solids.

If you need to go back and fillet the edges as necessary.

HTH

Pat

[Charlie_P]

Thanks Pat,

I've had a few attempts and have a respectable result, considerably easier than my technique! I'm also after another version that I can't produce by that method (see attached) - any ideas?

Cheers

Charlie

[Dieter @ DWorks]

I tried it, and you can make it with just a sweep.

You'll need to make the profile a height of Y. Then you'll need to set the height of the sweep to Y. This way you'll get what you want.

[Pat Stanford]

Or make the sweep angled and with a radius equal to the external dimensions and do a subtract solids instead of add solids.

Pat

[Charlie_P]

Thanks DWorks & Pat, your help is very much appreciated

Charlie