Drawing a spiral staircase

tony_g

I'll be honest; I'm stuck...  I'm trying to design a 3DP test part whose side plane view is at  https://cad.onshape.com/documents/676978fedd5417d8039896d8/w/f2925e7ed8fabc51cb99a883/e/b5dda3a805eb693c40c5c02d
but I can't figure out how to offset each rectangular step (which is obtained by rotating the base rectangle pattern in 5 degree steps) so that they can then be extruded to a depth (e.g., 8 mm) less than the plane spacing (e.g., 10mm).  Obviously, they all share the same axis of rotation, but I've stumbled at the offsetting step, so to speak...

MichaelPascoe

There are multiple ways to do this, here is one approach I like to use:

• Sketch the bottom or top tread
• Sketch a circle for an axis
• Extrude the circle as a surface to the height you want
• Create a helix around the axis cylinder with it's starting point at the tread
• Curve pattern the first tread along the helix

https://cad.onshape.com/documents/ac8a354a1ed2b1e04bf74db5/w/6020e67766db3d4b5e7bf9fc/e/5c11daa46800db110cc50ac4





Also, here is a configured circular stair model I made quite a while back. You are welcome to copy the document and use it. I have learned better techniques for almost everything in this document, but it should work still.
https://cad.onshape.com/documents/93e0f0c7f7b694eb5e967338/w/9a790a123e1e7d340510fe28/e/139193a84d5c60084b0379d4

tony_g

Wow!  Thanks.

MichaelPascoe

Absolutely