Is there any reasonable way to work with complex surfaces?

AIify

Hello everyone,
Thanks for your help already in advance, I am rather new to onshape but not inexperienced with CAD.
What i intend to do is modifying and working with complex surfaces created in blender, such as hands or faces. I am looking for tools that you use to do these kinds of operations as 2D sketches and splines arent really cutting it sadly. I would need 3dimensional curves, for example to create a hat that is not exactly circular (or oval) in one plane, or for a shape that wraps around another the wrist, or even for a simple grip that is somewhat ergonomic. More specific, how do I cut a complex shape such as an (irregular sinus curve) into the circumference of a hollow tube - i cant even manage to create a sketch that cuts towards the center of a ball ? How do you do these kinds of tasks? what tools do you use?

Thanks again for any help

konstantin_shiriazdanov

In respect to surfacing Onshape is really not less capable then SW, SE or Inventor. In any of those CAD's you would make base spline cage and then make lofts, sweeps and patches. So firsly it all about spline cage definition, and the main instrument for this is "Intersection curve". Sadly OS doesn't have builtin freeform tools or nonlinear deformation features but there are a number of custom features made by community which you may find usefull: 
- tools for nonlinear curve transforms - wrapping onto cones and cylinders, folding them based on some reference curve
https://cad.onshape.com/documents/0bb13c1b6ed6d4a6dd75cf99/w/b4493d47a45c27ce485c84b9/e/1299ae499a697e3b28bca1e4
- tool for rolling/unrolling closed contours onto cylinders:
https://cad.onshape.com/documents/0a110db94725cadd8c9a9b73/w/38370845e3bd9825fbb136d9/e/76245601fe54f319c9eff2db
- feature for parametric curve definition  https://cad.onshape.com/documents/d8aab1e0e7ae10038a6830e0/w/9dfdd631d025960813b8f2df/e/ba4054f79173536a994fd0da
- the thread on the forum about Organic surfaces:
https://forum.onshape.com/discussion/7188/organic-surface
and Sculpt face feature:
https://cad.onshape.com/documents/2c277b8c65f802c616cd16d4/v/8460dd533e59ecf92219c86b/e/cf6e6e7f9227d2ebbc72d1fa
Variable section sweep feature:
https://cad.onshape.com/documents/2d81c59d7fc5df36ecbaecf3/w/a2de18e932e02a4bd51d3af3/e/c17e4dc293d0b843fc524ca6

Also usually you can get several recomendations from surfacing pro's about specific problem if you'll be willing to share a link to the document.

AIify

Thank you for the very elaborate answer!
That's great to hear, I will spend the next while working though these and seeing what works for me!
This really helped a great deal as i am not too familiar with the community features.

billy2

to add to @konstantin_shiriazdanov great post:

I tend to use 2 noded splines on 2D planes and extrude to produce a 3D intersection. May seem like a simplified create method for complex geometry, but with these 2D displays we're looking at, 3D splines are tough to control. Some times I worry that people might think I'm trying to ride a bicycle with training wheels. In a big project for a consumer product, it's a great structure to create maintainability, inheritability and robustness while creating some complex stuff. I mean something that looks really cool.

This morning I'm creating a new tail piece for my motorcycle and building the 2D constructs for the complex shapes.


If you're a math major and want to see what those equations look like, then go for it. Me, I'm a product designer with a simple mind.

billy2

So.....

I spent the morning creating 2 surfaces. Once this is right, the rest is easy. I'll share with you what I was doing.

My constructs are:
-2 sketches
-2 surfaces derived from the 1st cap I made



The derived surfaces from the 1st cap, why redo'm?, 1st cap fits great. Why deal with curves when you have surfaces? I don't need the curves from the 1st cap and  prefer working with surfaces. Why? You get position & direction with a surface, a curve, you only get position. The new cap, well, there aren't any surfaces yet so I'm back to building curves to create new surfaces.



These 2 surfaces are created with edges, sketch curves & every normal to, tangent to that exists. These 2 surfaces are tightly controlled for curvature and profile matching. They're mirrored because my bike is symmetrical.


How'd we do?



I'm trying to eliminate that harbor freight trailer light from my bike. I've got an LED strip coming and need a new tail piece.

side view:


top view:


rear view:


3D:




I don't like the top view, it's too round. 



Have we talked about parametrics yet? Let's make a change. Top view, pull spline handle:


I like this better:



Look at the side view. The high lighted edge has a 500mm radius and matches the rear wheel making it looks like it belongs there:


Hope you're not blowing a gasket. I can only encourage you to figure it out. It's not that hard and comes with practice.

billy2

Continuing....

The mounting points are highlighted on the mesh which represent the heads of the bolts that'll be used to mount the new tail piece:


If you look at previous tail piece designs, the bottom wouldn't wrap around these bolts so I have to add more control to "Loft2":


Previously this surface edge wasn't controlled and was left natural meaning the system was allowed how to figure out this transition. Typically, that won't do and I need more control to pull the surface outward and clear the bolts. I elected to use a "3D fit spline" (3D sketch) to accomplish this task. Curves need both position & direction. In fact, so do surfaces and I should write up what this means in more detail to help people trying to understand surfacing. 

Extending the bottom surface and checking the geometry:


I've also included a mounting datum which represents the bike's frame where the holes are located. This will be used when designing c'bores for the rear tail piece.

So here's a 1st shot at thickening just to see how things are going:




There's still a lot of work to do and I'm not ready to solidify these surfaces quite yet. The thickening is temporary and will be deleted after writing this post.

billy2

Done!

bruce_williams

Inspiring!  Thanks for sharing @billy2 - your tips have helped me on a couple of projects over the weekend.

owen_sparks

Wow that's impressive. Well done.

To my admittedly childish mind It also looks a bit like a Cylon crossed with Kermit the frog.

Owen S.

billy2

Thanks guys,

The resemblance to cylon was totally unintentional:

brucebartlett

Nice Work, Nice Form. Thanks for sharing

billy2

Ok, this is starting to sound like a broken record, "It fits".

I've been using onshape's meshes to aid in designing motorcycle parts and since I'm paying for them, it's good to get the 1st one right. This part is really expensive and having the 1st one fit, I saved a lot of $'s.







It's great to get that harbor freight tail light off the back of my bike. Maybe now they'll allow me into heaven.

brian_jordan

@billy2 Broken record or not I am more than happy to see your posts here; they are inspirational. I have probably missed a previous post so may I ask how you do the scans to model the bike?

billy2

Thanks Brian, I'm using a structure scanner $300 buck. The file is .obj and OS reads it. Do you have any other questions?

Wired up the lights:

brian_jordan

@billy2 Thank you, that is very helpful. No more questions for the moment - I'm off to research this a bit more.

billy2

@brian_jordan

The scanner fits on an ipad, let me know if you have any issues.