help with a model using sweep

brett_sutton

I'm an amateur, half way through building a deck and I need to change my hand rails.

I'm trying to create  the hand rails using a spline and a sweep that needs to pass through three points (in the same plane).

The three points are attachment points on posts that the hand rail attaches to.

I have the sweep for the handrail working between the three attachment points.

My problem is that the attachment points are in the centre of the posts but I need the hand rail (created with the sweep) to extend to the edge of the posts (start and end posts).

The problem is that the 'extensions' aren't in the same plane as the three attachment points.

How do I get the sweep to pass through the attachment points and then extend to the outside of the (start and end) posts?

Here is the part studio - named 'steel'

https://cad.onshape.com/documents/f3b03c15b5a38d98937576aa/v/bc565b072ca25e34c7013b42/e/05dec5ec995dd1c4173db46f

S1mon

Here's a version which works.



A few things:

1. You can sweep along multiple connected, but not tangent curves, but Onshape seems to be fussy about how the thing you're sweeping is angled to the sweep path. When I first tried to do this using your existing sections, it didn't like it.
2. The regular spline tool creates curves that go to zero curvature at the ends which is not very attractive for something like this which wants to look like a natural bend. I replaced the curve with a Bézier which is aligned at the ends and in the middle and you can adjust the shape still.
3. Assuming this is made from bent tube or rod stock, the cross-section wants to be a circle which is normal to the path. I added an extra plane and sketch in the middle of the curved part of the path. (See #1.)
4. I redid the ends to be just straight lines with 3DFitSpline, but if you really want those short bits to be curved, you could redo them.

brett_sutton

OK, wow, thanks for the effort.
 
I will go through the answer in detail later today. I need to look a few of those terms up