sweep on a 3d curve or bridging curve - any way to control normal/tangent?

Lyle_Walsh

I am trying to make a tubing support that has an open groove facing upward while turning it down and then toward the back (traveling neg x then neg z then neg y} all while maintaining the groove at the top.  What I want is a continuation of the grey curve into the blue curve or the blue curve where the slot/groove is always up.

Bridging curve and 3d curve seem to be missing controls for 3d bezier handles or normal/tangent handles.  Can I do this with Onshape?

philip_thomas

I am going to say 'yes' - but as with all requests for help on this forum, posting a link to a public document is by far the best way to get help!

mahir

It's not a one stop solution, but you could try my Sweep Normal featurescript. You would still need to create a surface that dictates which way is "up", but it's better than being left to whims of your path's normal vector.

Alternatively, you could create the sweep in several "planar" sections. That way the normal vector variation would stay planar, and "up" would stay up.

mahir

I'm sure there's an easier way to do this, but here's one method.
https://cad.onshape.com/documents/57acdfaae4b005c413ed9b6f/w/3fd585a46d3af1b3ba413c53/e/b9d81dfab0fcc542dc827099

Lyle_Walsh

Thanks, Mahir, that is a brilliant idea, it will do what I need. 
Questions: 1) how close to the sweep curve does the normal surface have to sit?  Do variances in distance disturb its operation, for example how does it choose which  point on the normal surface to use for the normal direction?
2) where do you suggest I start learning about using featurescripts?

Thank you also philip_thomas, I realize I was being lazy and I need to make a clean simple example.  I will put something together tomorrow.  It seems Mahir has a solution that will work and I will try to learn how to use the featurescripts next.  Just FYI the mesh modeling program Blender does this by including normals within curves and you use a modifier feature called bevel object as the "sweep" feature.  Its an old and fiddly feature, Id much rather use sweep in onshape.  This is an interesting area where the organic modeling at which  Blender excels overlaps with the needs of Cad with its high precision.

mahir

1) I would try to make sure your sweep path is actually on top of the normal surface. The only way to ensure that is to use an edge of the normal surface as your path, or project the path onto the normal surface. It's possible to get around this sometimes, but the sweep command can be finicky. So may as well stick to what works.

2) I tend to learn by doing and from examples. I'm sure there are some FeatureScript tutorials laying around. Here's one. But the easiest way would be to find a FS that does something similar to what you want to accomplish, and dissect its code.

Jake_Rosenfeld

@Lyle_Walsh

A note: you don't need to learn any FeatureScript to use mahir's custom feature.  Just press the '+' button in your toolbar while visiting his document to add his feature to your toolbar, then you can use his feature in any of your part studios! (custom features that you've added show up in the toolbar dropdown that looks like a pair of {brackets} surrounding a cube.) No need to learn any new coding concepts! (Unless of course you want to )

Jake_Rosenfeld

See 'start using custom features' here:
https://www.onshape.com/featurescript

mahir

@Lyle_Walsh, if you want to take another look at my example, I've simplified it a good deal. I originally thought you had to use a single, non-faceted surface as the reference surface. Turns out my FS is more flexible than I gave it credit for.

Lyle_Walsh

mahir said:

@Lyle_Walsh, if you want to take another look at my example, I've simplified it a good deal. I originally thought you had to use a single, non-faceted surface as the reference surface. Turns out my FS is more flexible than I gave it credit for.

Great example, thank you that is exactly what I am trying todo!  And thanks Jake_Rosenfeld , that explanation of how to add custom features to the toolbar was what I needed.

Lyle_Walsh

update:  turns out that I could do what I desired using the path feature of loft!

Lyle_Walsh

https://cad.onshape.com/documents/5a55a128a3c604c74f83e3fa/w/5fb8568b79431b1f2646ebcc/e/8ee154e52529bb67c270d06d
is my rather busy file

Lyle_Walsh

and Curve patter almost works!

mahir

If the cross members aren't getting oriented correctly along the path, you can try this FS.
https://cad.onshape.com/documents/57ef018093832a1090983bfe/w/58bcbe4474554bfb72f7ecbe/e/ce32f2b154fa3142e58c8c6b