topic Re: convert from T spline into B rep in Fusion Design, Validate & Document Forum

convert from T spline into B rep

Anonymous — Thu, 23 Nov 2017 15:29:59 GMT

Hi everybody,

I'm working on a Fusion shape optimization and after have ran the optimizion I would like to do a static strass test in order to see if the piece is ok. But i don't want to change it. What i did was to export as an .stl file, reduce the number of faces with meshmixer, convert it with 3ds max into quad mesh and import it again in to Fusion 360. I convert the mesh into a T spline but now I can't convert the T spline into a B rep. I tryed to repair the T spline, but it looks like there are too many errors and the repair function is not arriving to a result.

This is the T spline that I obtained.

I really would like to thank you in advance,

Federica

Re: convert from T spline into B rep

SaeedHamza — Fri, 24 Nov 2017 22:33:19 GMT

Hi,

Why convert it into a T-Spline from the beginning

I tried converting your mesh into a BRep and it succeeded with no problems

Go to the model environment if your timeline is turned off and right-click your mesh then select mesh to BRep, this will give you a solid body

Regards

Re: convert from T spline into B rep

TrippyLighting — Sat, 25 Nov 2017 00:25:41 GMT

Shape optimization is a FEM method. For that to work at least currently the solid body's have to be to be meshed. The mesh is a tetrahedral volumetric mesh but the visual presentation of the surface of the body is just simple triangles.

You cannot assume that this can be automatically remeshed in 3DSMax into a quad mesh , then be exported as .obj and imported into Fusion 360 and still provide meaningful results in a stress test, which again is a FEM method that will require meshing of the volume of the solid boy.

The re-meshiong in 3DSMax will modify your input data and so will the conversion into a T-SPline.

Re: convert from T spline into B rep

Anonymous — Wed, 06 Dec 2017 09:16:57 GMT

Hi,

i'm sorry that I didn't replay you back fast, I was working on an other project and I had to finish that first! So what you are suggesting to do is to pass from the simulation environment to the model environment then do the mesh and export the file as an stl file. Import the new file on an other project (unable first the history capture) and transform it from a mesh to a Brep?

I tryed to do like this but it didn't show me the piece when I went back to the simulation environment in order to do the static stress.

Thank's a lot,

Federica

Re: convert from T spline into B rep

Anonymous — Wed, 06 Dec 2017 09:23:11 GMT

Hi Peter,

I was using this method cause I saw a tutorial in which they were doing like this, but it looks like it's not working my method. I don't want to change the shape and the data neither. So what you are suggesting is to work with the mesh of Fusion, obtained after the simulation shape and trasform this mesh into a Brep in order to obtein some correct results with my static stress simulation? Which are the steps to follow? I'm complitly lost =).

Thank's in advance for your usefull help!

Federica

Re: convert from T spline into B rep

SaeedHamza — Wed, 06 Dec 2017 14:00:02 GMT

@Anonymous wrote:

pass from the simulation environment to the model environment then do the mesh and export the file as an stl file. Import the new file on an other project (unable first the history capture) and transform it from a mesh to a Brep?

No, that isn't what I meant mate

I said just go to the model environment and then right-click the body ( with the design capture history turned off ) and select Mesh to BRep

Please try this and then check if it appears in the simulation workspace

Regards

Re: convert from T spline into B rep

Anonymous — Thu, 07 Dec 2017 14:36:34 GMT

Ok, thank's a lot!

It looks like it's working, it appears on the simulation environment but now I have a new problem!

I post you a picture of the simulation environment.

I should put a pressure on the surface at the end of the bracket, this pressure has to cover all the surface. And then I have to fix the four holes in all directions, because the piece will be fixed to a support.

The problem is that I don't have all these surfaces, the pressure in applied on a tria only and the fix constraint is applied to a vertex only.

It looks thenn the simulation fails cause an error on the mesh.

Thank's in advance mate!

Federica

Re: convert from T spline into B rep

TrippyLighting — Thu, 07 Dec 2017 15:01:04 GMT

@MikeSmell_ADSK could you comment on whether the workflow presented in this thread is able to provide meaningful results ?

Re: convert from T spline into B rep

MikeSmell_ADSK — Thu, 07 Dec 2017 20:19:16 GMT

Hi @TrippyLighting -

Thanks for looping me in on this.

As to whether or not the workflows described in this thread will produce meaningful results is a tough question to answer definitively.

Let me explain why.

Both of the workflows attempted by @Anonymous and @SaeedHamza are potentially valid paths to get from Shape Optimization results to a solid body. However, as already noted, there are a few drawbacks, in that neither of these processes are completely reliable. First, it is important to realize that the resultant mesh from a Shape Optimization result may not always yield a shape that is easy to convert. This is especially true when a coarser mesh is used or when many small sections get generated. So as @Anonymous has experienced, a number of the conversions to post process the mesh ultimately did not yield something that could be easily turned into a solid. As a quicker alternative to getting a solid, @SaeedHamza's suggestion was pretty good, however, there is a very important point to pay attention to. When a user starts off doing a Shape Optimization with some 3D modeled brep geometry, it is often very clean with a reasonable number of faces and these are the faces that get used to load and constrain the model. Directly converting the resulting mesh to a BREP turns every mesh facet into a surface, so without doing any merging of faces or mesh smoothing/coarsening, there will be a huge number of surfaces in the model. This has two immediate downsides. First, the mesh will need to put elements on all of those faces which will drive up the mesh size and also create some odd elements that might generate spurious results. It may also simply fail to mesh. Second, as @Anonymous noticed, it is no longer easy to apply a pressure across a large face or easily apply boundary conditions to the hole surfaces, as rather than being single surfaces for each, now they are hundreds or thousands of triangular surfaces.

So to answer if it is possible to be successful with these workflows, the answer is a soft yes, however, it may take a lot of trial and error and will be very sensitive to the complexity of the Shape Optimization result. I have simple models that have worked pretty nicely using these workflows and I have simply models that just do not work with either of these workflows.

My personal recommendation is to just use the resulting mesh in the Model workspace as a guide to create sketches, surfaces and extrusions to cut material away from the original shape. This will make analyzing a result shape much easier and more reliable to simulate and will likely be much more efficient than chasing these other two workflows that are far less reliable.

I hope this helps guide folks in this thread in a better direction.

Thanks,

Mike Smell

Product Manager, Fusion 360 - Simulation

Re: convert from T spline into B rep

Anonymous — Mon, 11 Dec 2017 10:15:09 GMT

Thank you so much @MikeSmell_ADSK for the answer and @TrippyLighting for the big help! I thought I was doing something wrong during all the steps.

So the way you are suggesting is to redesign the piece following the shapes obtained by the shape simulator?

Thank you very much,

Federica