Making efficient imported STEP and deeper understanding solid body, surface body

[michal879ZE]

Hello, I would like to know what is more efficient to work with (faster work in assemblies). We are using these STEPs (3th party using whatever SW) which we are not modify only have them in assemblies as silhouettes. Problem is that something is as surface or solid body ... or solid feature in surface body.

 (from left: tree, base2, base1)

Solid feature has solid body icon - 1) why and are there some benefits as to solid body?*

(Those "base1" and "base2" are not closed bodies and if I remove one surface (at repair environment) then it convert to surface icon (instead of solid icon). Closing the caps saw in "base2" I can create "true" solid body".)

Other thing - there is "base3" and "surface1" (see below). Those bodies overlaps each other and so - 2) what is better to use and what body to delete? 

Thats all, thank you for your answers!

* I had a conversation with support and I learnt some insight when using imported cad:

- Inventor works better with solid bodies then surface bodies

- Better open step and let use inventor mechanics than import data to ipt file and also better using native assembly from step then again trying to import it to ipt file and have all parts as bodies.

- Lower file size does not always indicate most "efficient" model to work with. 

Inventor 2022.

[johnsonshiue]

Hi Michael,

I think it isn't so much solid bodies work better in Inventor. It is about the body quality. If the body quality is low (errors or unnecessary complexity), all bets are off.

The nice thing about solid bodies is that it is more intuitive. You can look at the model in 3D as if it is real. Surface bodies are less intuitive. The intersection may not be apparent.

Based on the images you attached, it looks like the original data is probably mesh. Mesh is not precise. It represents a model approximately. Inventor does not have comprehensive mesh modeling workflows (you may want to look into Fusion 360). Inventor is strong on traditional B-rep modeling with precise data. Mesh is more as a reference for further modeling.

Many thanks!

[michal879ZE]

So for 2) question, just use "better looking" part (Surface1). Thank you. Further to your thought process, when original cad is mash does it explain two overlapping bodies? When inventor see mesh it converts it to whatever it can, in this case to one body with errors (looking like stl) and one surface having better result?

Still I would like to know what this means and how it works - solid feature icon in surface body.

[JDMather]

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@michal879ZE wrote:

 Still I would like to know what this means and how it works - solid feature icon in surface body.

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If I dive into this question - are you willing to contribute to the discussion (by running some experiments that I will suggest) or are you just looking for a white paper that explains everything?

[michal879ZE]

If you have some text to explain everything give it to me please 😄 But I guess the meaning is no this explicit. Anyway I am totally for experiments to get to bottom of this. I just need to know general things to apply it to different step files not only this specific example I posted.

[johnsonshiue]

Hi! I would avoid overlapped bodies. They are just confusing. If you want to work on solid bodies, stick to solid bodies, or vice versa. Also, you want to run through Repair Bodies workflow to ensure the apparent badness is fixed up.

Many thanks!

[michal879ZE]

Sure and I like you make it clear. You partially answered to my question and I will mark your solution in the end but I would like to have some clarity in the other thing. I am waiting for @JDMather and his proposed experiment if it may lead to something.

[JDMather]

@michal879ZE 

As I go through this - it might seem as though I have gone off on a tangent - but I will circle back around to your problem.  (It will be very helpful if you can Attach some actual files.)

Let's do some mind experiments.

Let's assume that you make automobile engines but you get the Alternators from a third party supplier.

Let's assume the Attached file is a typical "Alternator" that you use with your engine designs (I intentionally picked an abstract representation that you would have great difficulty in modeling from scratch).

Open the file.

Right click on the top node and select iProperties > Physical tab.

Click Update (if needed).

What do you observe?

There is a circle in Sketch1.

Extrude-cut midplane through all.

Check the iProperties again.

What do you observe?

Step 2 in the experiment to follow...

Edit:  I forgot to ask - what version of Inventor are you using?

[michal879ZE]

Don't worry I like good story, interested where this might go. Except some weird unit I don't observe nothing extraordinary. 

After extrusion: 

My version: Professional 2022.3, 64bit, build 350

And I forgot to mention in my original post that such files are confidential.

btw you have nice youtube channel, glad to find it out through your link.

[JDMather · Accepted solution]

The key observation is that with solid bodies you can get the Mass Properties information.

You could have exactly the same surface body, but you do not get that information.

But surface bodies are perfectly fine (and sometimes preferred) in many design cases.

As I progress - I will lay out the advantages/disadvantages of each.

Open the Attached file.

Note from iProperties that there is no Mass Properties information.

You can edit the surface, but you must use a different set of editing techniques and it might be a bit more laborious.

But there are advantages to working with surfaces that I will cover.

You can create 2D drawings of surface bodies (might require an extra step with assemblies) for documentation, so there might not be a need for solid bodies if the Mass Properties is not needed.

Next I will cover Mesh Bodies and then we will tie everything together.

[michal879ZE]

Thank you for your files and examples. Interesting to see all types and looking at different behavior.. of course leading me to more questions 😄

It is interesting that area is computed only for solid bodies or surface body:

Just my, giving your conclusion from last post, probably fail thought process: 

So surface body has some resemblance with solid body, guessing it remains (going from solid to surface body) the surfaces by solid ... which is "simpler " than "real" surface?? .. so it is able to compute area??... simpler for inventor less file size: 7 MB for solid or surface body and 12 MB (or 11 MB) for surfaces.....? Is there really no difference except file size? And please don't take it as poking holes in your text 😄

I really don't need iProperties information in fact I use those files only as background reference, never opening it and modifying it.

[JDMather]

@michal879ZE 

Examine these two imported mesh data files.

If you examine them very closely - you will note that there are ONLY straight lines and triangular planar facets in the file.  No curved faces.  Not one.  Only lines and planes that sort of look like curved surfaces.

However - we can still create 2D drawing views of the mesh geometry...

[michal879ZE]

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