Twisted Extrusion

David Bowser

11 Feb, 2018 10:53 PM

Twisted Bar modeled 3 ways - Extrude and flex, Sweep with twist, Loft with helical guide curves

1. Step 1: Finished Product Revealed

   The three bars below were modeled using three separate methods: apply flex to extrusion, sweep with twist, and loft with helical guide curves.

   

   
   

   
   

2. Step 2: Extrude and Flex

   This tutorial assumes the "student" is familiar with making sketches and extrusions.

   Draw some closed curve to extrude - a 1/2" square on the top plane was use for this tutorial.

   -Extrude it - Extrusion below is 15" long

   -Insert Features Flex..

   

   -Select the Extrusion.

   -Select the "Twisting" Button and "Hard Edges"

   -Enter 720 degrees for the amount of twist

   

   Careful here, a large number - say 7200 accidentally entered instead of 720 - could cause SolidWorks to take a long time to apply flex.

   -Click the check mark to apply flex.

   Congratulations, bar is twisted, it is that easy.

   

   
   

   
   

   
   

3. Step 3: Sweep with Twist

   Draw another 1/2" square on the Top plane centered on where it meets the Front plane.

   Draw a vertical line on the Front Plane from the center of the square 15" high

   

   Select Insert Boss/Base Sweep

   

   Select the square as the sketch profile and the vertical line as the path

   Select Options, Profile Orientation, Follow Path,

   Select Profile Twist, Specify Twist Value

   Enter 720 degrees in Direction 1

   

   
   

   Select the check mark to apply the sweep

   

   
   

   The second method to model a twisted extrusion is now complete.

   
   

4. Step 4: Loft with Helical Guide Curves

   Draw another 1/2" square on the Top Plane

   Create a new sketch and draw a circle centered on the square and coincident with one of it's corners.

   

   
   

   Select Insert Curve Helix/Spiral

   

   
   

   Select the sketch that contains the circle

   
   

   

   In the Helix/Spiral dialog box

   Select Defined by Height and Revolution

   Select Constant Pitch

   Enter 15" for Height

   Revolutions 2

   Start angle 45 degrees

   Select Counterclockwise

   Select the checkmark to apply Helix

   

   
   

   Create 3 additional Helical Curves at the remaing three corners of the 1/2" square by repeating the above steps (including making three new sketches with a circle at the center of the square) Increment the Helix starting angle by 90 degrees each time. The first helix started at 45 degrees. The others should start at 135, 225, and 315 degrees.

   The 4 Helix should look like this:

   

   Start a sketch on the top surface of one of the existing twisted extrusions (or on a new plane parallel to and 15 inches above the Top plane). Use convert entities to copy the 1/2" square to the new sketch

   

   Select Insert boss/Base Loft

   

   Select the sketches containg the 1/2" square as the Loft Profiles

   Click on the Guide Curve section of the Loft dialog box

   and select the 4 Helix

   

   Click on the check mark to apply the Loft.

   There you have it - three methods to model a twisted extrusion.

   

   
   

   
   

   
   

5. Step 5: Epilogue

   Why 3 methods and when to use each?

   The first method, use of the flex tool, is best when the extrusion already exists and is straight.

   The second method, Sweep with twist, can be used to twist along a curved path. A common use is to model twisted wire cable or rope.

   The third method, Loft with helical/spiral guide curves, can change the rate of twist along the extrusion or vary the cross section of the extrusion along it's length, although it was not used that way in this example.

   The model shown above is posted on GrabCAD at https://grabcad.com/library/twisted-extrusion-1