Rotate Extrude?

Bryan_Yeung

I'm trying to duplicate the result of a rotate extrude operation from openscad/openjscad in OnShape without much luck.  In particular, the property that each cross-section of the extrusion has the same area (i.e. is just a rotated cross-section of the original sketch).

So far, I've been trying to use the Loft tool with a guide, but any of the unguided edges up through the vertices take a shorter path which deforms the cross-sections in a way I'd like to avoid.

(Actually, I'm trying to scale simultaneously with the rotation during the extrusion, but that seems to be the easy part so far with Loft.)

john_mcclary

Forgive me if I misunderstand, but are you trying to do a revolve?

Bryan_Yeung

Nope, not a revolve.  I'm trying to do an Extrude where the extruded sketch is simultaneously rotated (about a point within the sketch) and scaled during the extrusion.

john_mcclary

Do you have a link or an image of the desired shape? even if it's imperfect

Bryan_Yeung

Does this help?  (That's openjscad.org if you want to replicate the rendering in a way you can move around.)

john_mcclary

You can do that by creatinf a helix, then doing a sweep.

As for the scale issue. Try looking into "non uniform scale" in featurescript.

I'd help more tonight but as yousee my computer is off and i'm on my cellphone going to bed. Sorry

konstantin_shiriazdanov

if needed a smooth shape - Variable section sweep gives the highest control on all degrees of freedom of your sketch (speaking poetically)
https://cad.onshape.com/documents/cd5c97012fe2330882e8ac38/w/87481dbbb7107f1e8c06452c/e/481996a23b965d6670d262cc

john_mcclary

Here try this if you want to see what I came up with in my dreams last night.. (Literally all I remember when I woke up
https://cad.onshape.com/documents/28050bca2b1ddeb0acbab720/w/72369ffa7faabbf84de28ab1/e/46ac818ef0ae6686c27ac407

Took a few attempts because onshape would throw self intersecting errors, but this is what I ended up with:
It has some clutter, but my attempts of lofting around a taper-helix would fail. What ended up working was matching verticies in loft, but that was only good for 1/4 turn at a time.

Bryan_Yeung

Unfortunately,
- the actual sketch I'm trying to use for this is much more complicated than a simple square
- I definitely want more than 1/4 turn total

Is there documentation somewhere on the variable section sweep?  That looks like it's worth learning about, but it's a bit opaque to me how one would use it.

konstantin_shiriazdanov

Here  i describe it usage requarements.