How to smooth a model

kenn_sebesta167

I have a model I generated from Fusion 360's generative design package, and I'd like to smooth all its curves. Is there a convenient way in OnShape to do something like that?

EvanReese

I'll DM you some outputs. It was very very easy:

1. import .stl with way too many triangles into Rhino
2. type "quadRemesh" and hit enter
3. tweak settings if you want. I just changed the poly count
4. run the command and you're done.
5. if you want, you can also convert it back to NURBS using Rhinos sub-d capability

I use Onshape for like 95% of what I do, but Rhino is an awesome tool to have access to and to know a bit. I think it's like a one time payment of $1k or something pretty reasonable if using it professionally (of course you'll have to pay again for Rhino 8 etc if you wanna upgrade).

dirk_van_der_vaart

Why would you do it this way?
You have lost the feature tree while importing the model into Onshape.
Share the model please if you want us on the forum have a look at your problem.

EvanReese

I think the answer here is no, Onshape isn't the tool for that. I've not used the generative design tool personally, but I believe that Fusion will generate mesh geometry, which would be an okay thing to add onto with Onshape since they added mixed modeling (i.e. remove holes or add other geometry). Without images I can only guess at what you mean, but if you have a mesh that needs to be smoothed out, you need something that does subdivision surface modeling: Blender, Rhino, Cinema 4D, Modo, and so on. I think I've got to agree with Dirk here though. If you started in Fusion, I'd try to finish there too instead of passing the model around.

kenn_sebesta167

@dirk_van_der_vaart, I used Fusion 360 to automatically generate the CAD, and that's as far as I want to go with that dumpster fire of an interface.

My design approach is to use OnShape to develop the geometric constraints, import this into Fusion 360 as the base of the solver, export the result as a STEP file, and then use OnShape to do all the clean-up necessary. This works surprisingly well, and keeps Fusion 360 from driving me insane.

However, the nature of Fusion 360's generative design is that there is a lot of waviness in the outcomes. This is likely because these tiny surface changes don't make enough of a difference to register with the solver.

But even if they don't matter to theoretical strength, they make real-world CAM much harder. It would be nice to smooth the irregularities with a low-pass filter so that my ball end mill doesn't have as many nooks and crannies to try to get into. Plus, my gcode files would stop being frickin' ginormous.

Here's a screenshot of some generative design, you can see what I'm talking about.



@Evan_Reese thanks for the alternative suggestions. Maybe I'll see about Blender.

EvanReese

You could use it as an underlay to model over it with traditional tools. That's the best I can think of in Onshape. To smooth it like that you'll need something that edits meshes. For starters you'll probably need to remesh from triangles to quads, and simplify the number of polygons and only keep detail in mating areas. I'm not sure of the best way.

S1mon

As much as I like Onshape, Rhino has much better tools to smooth and manipulate mesh models. 

https://www.youtube.com/watch?v=aeWAC028XHQ&list=PLWIvZT_UEpWWt1rKiyalBixOrENwgbStm&index=18

kenn_sebesta167

S1mon said:

As much as I like Onshape, Rhino has much better tools to smooth and manipulate mesh models. 

https://www.youtube.com/watch?v=aeWAC028XHQ&list=PLWIvZT_UEpWWt1rKiyalBixOrENwgbStm&index=18

That is *exactly* what I would like to do. Now to find someone who has Rhino and knows how to use it. (SIGH!)

dirk_van_der_vaart

You could try Freecad, that's opensource lots of tutorials on Youtube and mesh editing

S1mon

You can download a free trial of Rhino, and it’s not too hard to learn to do basic things.

EvanReese

I use Rhino and would be happy to take a crack at it to improve my own understanding. I've done some quad re-mesh stuff before, which isn't hard, but keeping your detailed areas (mechanical mating areas) precise will make it a little trickier.

dirk_van_der_vaart

In the end it could be faster to use the geometry of the part and make a new part in Onshape.
It looks to me that the part is a forged metalpart with some welded part's, and if it is made of sheetmetal there is no or minimal variation in the tickness of the material.

steve_shubin

dirk_van_der_vaart said:

In the end it could be faster to use the geometry of the part and make a new part in Onshape.

Yup

I sure would spend a fair amount of time trying to figure out how to do it completely in Onshape.

Because in the long run, it just may be a whole lot less complicated doing it this way

And the end result may end up looking a whole lot better too

And tweaking the design later on and having various configurations would no doubt be easier going this route

steve_shubin

I’d be curious to see the basic shape you’re trying to accomplish because I’d bet that any of the people up above and people like @MichaelPascoe and @eric_pesty and a number of other people here in the forum could probably show some great ways to go about it.

kenn_sebesta167

I'm leery of redesigning a generatively-designed part in OnShape. For a simple part, such as a hook, I can see the DFM benefit. In this case, it's easy to see leaving the load cases behind by accident. 

I also think that's the wrong answer to this process. Redesigning it purely because the tool lacks a feature to reduce CAM size seems like the wrong answer. If it were for serial production then I can see why getting an optimal structure answer is not always-- or even frequently-- the right final part. But in this case, I should be able to easily take something designed to be milled (the fabrication process is something which can be defined in Fusion 360) and mill it without too much more ado.

For the curious, this part is is a motor mount for a self-launching glider. The part dimensions are approx 5x15x30. It is designed to meet all FAA load cases for engine mounts, so in theory should be overbuilt when moving from an ICE to a motor. It's made from a single large billet of 2024-T351, and is a one-off (although I expect this first part to go wrong somehow, so I have a second billet ready for the milling). 

@Evan_Reese, thanks for the offer! I'll DM you.

EvanReese

Rebuilding in Onshape would definitely be a desperate, get-it-done-asap solution, not a long-term solution for a workflow. I'll take a crack in Rhino once you send it my way, because it seems like a good way to learn some new stuff and maybe help somebody out doing it, but no promises on my level of dedication. 

dirk_van_der_vaart

For the curious, here is a video of an electric glider.
https://www.youtube.com/watch?v=gMmu98hiLko
You can see the function of the motor mount

kenn_sebesta167

Wow, I would *not* stand in front of a glider and test the motor like that. I hope there's something out of frame I'm not seeing, like the tail being tied down. Otherwise, that guy is one elbow jerk away from losing, well, an elbow.

Also, wow, that's a beautiful motor mount.

steve_shubin

Thanks for the link @dirk_van_der_vaart . Really love watching gliders. There is at least one that flys not too far from where I live. If I remember correctly, I think it’s part of the civil air patrol

To my untrained eye, it certainly looks like they had aerodynamics as a priority when they designed that arm holding the motor in the video. It really looks good

It’s too bad that somebody couldn’t take the strength and the lesser weight that generative can bring and combine it with the smooth surfaces that conventional tools have, such as loft and sweep

Maybe one day somebody will figure out how to use generative as a template, as mentioned in other posts above, and make profiles from sections of the generative, and then use conventional tools such as loft and sweep and what not, so that one ends up with the beautiful zebra patterns at the surface with the strength of generative underneath

In the meantime, I’d be curious to hear what type of zebra patterns Rhino will generate upon tweaking of the generative mesh, And I’d be curious to know if in tweaking that surface, if one is  able to maintain contact points at the same position

On the other hand, maybe that bumpy surface that fusion develops, will work similar to how the dimples work on a golf ball

How do dimples in golf balls affect their flight? - Scientific American

But I guess one would need a virtual wind tunnel to find that out

EvanReese

Without much tweaking of settings the result is pretty good. I'm not sure of the best way to handle how this messes up the mating areas. There's an option to detect hard edges, but I guess it's based on the angle between faces and there's not a setting for that, which smoothed out some of the flat areas. Maybe these could be exported from Fusion as separate parts so they don't get re-meshed? Or you could add them back in with Rhino, (or Onshape or whatever you want).

EvanReese

@kenn_sebesta167
It seems promising enough to get a trial of Rhino, I'd say.

kenn_sebesta167

@Evan_Reese that's almost magical. Was it hard?

Concerning the impacts on the mating surfaces, that's very easy to recover from. I've already gone through and regenerated them all in OnShape, as cheap insurance in case Fusion360 modified them at all. It's very easy to regenerate the regeneration.

EvanReese

I'll DM you some outputs. It was very very easy:

1. import .stl with way too many triangles into Rhino
2. type "quadRemesh" and hit enter
3. tweak settings if you want. I just changed the poly count
4. run the command and you're done.
5. if you want, you can also convert it back to NURBS using Rhinos sub-d capability

I use Onshape for like 95% of what I do, but Rhino is an awesome tool to have access to and to know a bit. I think it's like a one time payment of $1k or something pretty reasonable if using it professionally (of course you'll have to pay again for Rhino 8 etc if you wanna upgrade).