Expert: Bill DeShawn - 2/16/2010

Question
How do construct a helical extrusion? It has been a while since CAD was used last and need step by step refreshing if possible.

Answer
Use 3Dspiral.lsp to create a 3D spiral made up of joined polyline segments.  At one end of the spiral draw or place your object that you want to extrude.  Then rotate it perpendicular to the spiral.  Extrude the object using the spiral polyline as a path.

In older versions of AutoCAD you can't extrude along a splined path.  But in newer versions you can.  I did it in AutocAD 2010, but could not do it in AutoCAD 2006.  In AutoCAD 2006, the polyline could not be splined.  In 2010 comes out very nice, but boy! it sure takes time.  And regenerations sure take a long time after that is made.  If you have an older version don't use PEDIT to spline the polyline.  On my dual core, it took more than 30 seconds.  To get a copy of 3DSpiral.lsp go to my website below and scroll down to my email icon and send me a request for the routine and I'll email it to you.

Another source for the routine is here courtesy of Reini Urban:
http://mail.xarch.at/~rurban/autocad/code/jfoster/3dspiral.lsp

I hope this helps.

Bill DeShawn
http://my.sterling.net/~bdeshawn