topic Re: What can bodies do that components cannot? in Fusion Design, Validate & Document Forum

What can bodies do that components cannot?

Noah_Katz — Wed, 08 Feb 2017 23:44:39 GMT

I've done a lot of reading and watched a lot of videos on bodies/components, which is a confusing

Most of the content is about the pitfalls of not using components, and as far as I can tell, anything you can do anything with components that you can do with bodies.

So why do bodies exist?

One of the videos had me momentarily thinking there was a reason, i.e. you might want to shell just one of the bodies of what would later become a multi-body component, but I believe you can do the same with components.

As a test I created a cylinder and a box as new components and was able to combine them, so I'm puzzled why it says "Unfortunately the combine command is going to limit you to bodies."

here https://forums.autodesk.com/t5/design-validate-document/combine-components-instead-of-bodies/m-p/6742017#M86689

Re: What can bodies do that components cannot?

TrippyLighting — Thu, 09 Feb 2017 00:06:22 GMT

The information here explains the difference between bodies and a components in Fusion 360.

When you combine two components, you really are combining the bodies in those components.

Re: What can bodies do that components cannot?

Noah_Katz — Thu, 09 Feb 2017 00:32:18 GMT

Not to be difficult, but I already read that and believe I understand the differences, but it doesn't answer any of my questions.

As far as I can see, the unique behavior of bodies could be realized with components, i.e. if you didn't want it to be moveable you could constrain it.

Re: What can bodies do that components cannot?

TrippyLighting — Thu, 09 Feb 2017 00:38:16 GMT

@Noah_Katz wrote:

As far as I can see ...

Therein lies the problem 😉

My suggestion would be to simply start designing a project and see where it takes you and what obstacles you come across.

A body is simply just one contiguous piece of geometry. However, a body in itself does not have knowledge of how it was created. It does not have any sketches to construction planes or features that can be edited. A component is the collector of such information. Or maybe in other words the body in a component is just the end result of all the other stuff collected in a component.

Re: What can bodies do that components cannot?

Noah_Katz — Thu, 09 Feb 2017 00:51:00 GMT

> Therein lies the problem 😉

Maybe, but I believe I saw what you're referring to in several of the videos.

Is the question that difficult?

Let me try again with a less wordy version - what benefits do bodies confer that couldn't be achieved w/o them?

Re: What can bodies do that components cannot?

TrippyLighting — Thu, 09 Feb 2017 00:57:45 GMT

You would not have any 3D geometry in you model without a body. If you import geometry from other sources, e.g. step files, the only thing you get is a dumb 3D body, geometry.

It can be edited to some degree because Fusion 360 is very smart in recognizing certain features but there are limits to what you can do with it.

A body is just one piece of information that is needed for an editable CAD model.

Re: What can bodies do that components cannot?

Noah_Katz — Thu, 09 Feb 2017 01:33:36 GMT

OK, I see that the combined component I created contains a body.

Let me put it this way then.

What's the benefit of having a body that is *not* contained within a component?

Some of the videos recommend immediately starting with an empty component.

Why even have the option not to do it that way?

What would be lost other than a lot of confusion and time spent on discussions like this?

I guess my original question needs to be modified to "Why allow bodies to exist outside of components?"

Re: What can bodies do that components cannot?

Beyondforce — Thu, 09 Feb 2017 04:06:12 GMT

@Noah_Katz,

I would like to add to what @TrippyLighting said... The reason you are allowed to create a body "outside" a component (no matter what, you'll always be inside the Root Component), is to give you more control and workflow options.

I'm guessing you have read This post by @TrippyLighting about RULE #1 & #2, if not then you should. I hope this will help:

Cheers / Ben
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Re: What can bodies do that components cannot?

jeff_strater — Thu, 09 Feb 2017 04:26:22 GMT

@Noah_Katz: The short answer to your question: "What's the benefit of having a body that is *not* contained within a component?" is if you are just designing a single part, not an assembly. If you were, for instance, creating a bolt (not that you would model that yourself, but it's a simple example), you would just create a new design, and create the body of that bolt in the top level of that design. Then, you could insert that bolt into other designs. This is how existing CAD tools like Inventor or Solidworks require you to model - you have separate part and assembly document types. Fusion does not make that distinction.

If you were creating a design that was an assembly of a bolt, a nut, and a washer, you would create sub-components for each piece, and have a body inside each of those for the bottom-level part.

Jeff

Re: What can bodies do that components cannot?

Noah_Katz — Thu, 09 Feb 2017 05:09:56 GMT

Ben,

I hadn't seen that particular video, but it still doesn't answer my question.

Re workflow, what do bodies let you do that you couldn't do if they belonged to components?

Mention has been made of having a unified design environment where components and assemblies coexist in the same design space, which is indeed wonderful, but I don't see how that bears on my question.

Before discovering F360 I had a trial of IronCAD, and it has the same unified design environment, with plain old parts.

Jeff,

> ...if you are just designing a single part, not an assembly.

Could you not create a bolt as a component?

> This is how existing CAD tools like Inventor or Solidworks require you to model - you have separate part and assembly document types. Fusion does not make that distinction.

Per above, neither does IronCAD.

Re: What can bodies do that components cannot?

michallach81 — Thu, 09 Feb 2017 11:04:30 GMT

Hi Noah,

The first thing to say is that you can't have bodies outside of the component, not in Fusion. When you starting your design you are already inside the component. When you hit New Component button Fusion creates subcomponent. Then you can create other subcomponents or a subcomponent of that subcomponent:

To answer your initial questions "What can bodies do that components cannot?", with bodies, you can do geometry with components you can't. For components to have any geometry you need to create a body within it.

It may be easier to understand if I would make reference to another cad tool. Components are, in fact, like a Part files (SW or ProE) by default they contain origin and basic planes and axis. As it is in other programs to create geometry we are creating bodies. In Fusion if you don't create a new component, whole design will work like a Part file. That component/Part file can contain multiple bodies. If on other hand you would create a new component, our top level component will serve also as an Assembly file and all new components will be like Part files/subcomponents. Of course, these subcomponents may contain more subcomponents, then we can treat our file like an assembly full of subassemblies.

All that could be a little confusing. We can reverse your question, What can components do that bodies cannot? You can't assembly bodies. If in your design you have only bodies and no new components you have no Parts to assembly.

Another important thing to say is that through all that time you can edit one component in a context of others, you can create multiple cross references.

It's like you would be in an assembly in Solidworks and could edit Parts inside, in a context of that assembly.

It is a very powerful concept where whole structure is like matryoshka toy. Each component is a Part file and Assembly file in the same time, each component is built in the same way.

That creates one problem you can have bodies and components on the same level. To address that "inconsistency" and couple of others following consequences Peter (@TrippyLighting) is proposing workflow where you treat your First top level component as Assembly file only. That require slightly more constraint/focused workflow because you need remember about activating components and making cross-references wisely.

You can also try to go old fashion and treat each design as a Part or Assembly file only. Then in "Part" designs you would stick to bodies only and creation/modification tools in "Assembly" designs you would assemble "Part" design with the use of linked components, and you would use only mating tools (joints).

Re: What can bodies do that components cannot?

Noah_Katz — Thu, 09 Feb 2017 18:42:45 GMT

Thanks, Michal.

I still don't see the answer to my question, which has become "Why allow bodies to exist outside of components?"

But before anyone spending more time on this, let me work my through the Assembly lessons; maybe more hands-on will clarify things for me.

Re: What can bodies do that components cannot?

Beyondforce — Thu, 09 Feb 2017 19:00:31 GMT

"Why allow bodies to exist outside of components?" - The bodies are NEVER outside a component! If they are not inside a component you have created, then they will stay under the Root Component - Like I explained to you in the screencast.

Re: What can bodies do that components cannot?

michallach81 — Thu, 09 Feb 2017 19:08:22 GMT

Everyone is telling you, you can't create a body outside the component. Your rhetorical speech is pointless, you didn't come for help?

Re: What can bodies do that components cannot?

Noah_Katz — Thu, 09 Feb 2017 19:52:35 GMT

Well yes it is rhetorical/academic, since my question is really why, not what or how.

That aside, the responses have been educational and are appreciated.

Re: What can bodies do that components cannot?

michallach81 — Thu, 09 Feb 2017 19:57:54 GMT

The question "why" implies that whatever you've stated is true. A simple parallel, question why the earth is flat implies that earth flattens is a fact, but a possibility to ask such question don't make assumptions in that question, valid. That's exactly your case you can ask us "why allow bodies to exist outside of component", but before asking that question you should show us that it is possible to have bodies outside of the component. IT'S NOT POSSIBLE.

Re: What can bodies do that components cannot?

Noah_Katz — Thu, 09 Feb 2017 20:33:25 GMT

> The question "why" implies that whatever you've stated is true

Valid point.

Let me reframe the question again:

What is gained by distinguishing between bodies and components, with its ensuing confusion; why can there not just be parts (to which belong associated coordinate systems, sketches, etc., and which can exist on their own and within assemblies)?

Re: What can bodies do that components cannot?

etfrench — Thu, 09 Feb 2017 21:45:51 GMT

I think a better question is why is the default output from an Extrude and other Create operations a body instead of a new component?

Re: What can bodies do that components cannot?

Oceanconcepts — Thu, 09 Feb 2017 22:49:14 GMT

“Body” is Fusion’s term for 3D geometry.

“Component” is Fusion’s term for a container that can hold multiple bodies as well as other relationships, history, sketches, joints, etc. Components are really the basic unit of Fusion.

Bodies are always in at least the root component. Adding additional subcomponents enables more levels of interaction and control, because components are containers for other information as well as for bodies. This architecture helps to define complex relationships and has considerable power. It also gives the user control over many of these relationships, because the user decides how these relationships between components are structured and- to some extent- what information is included in any given component.

Sometimes just the root component is enough, and if those other levels of information are not necessary in a design, Fusion allows us to keep it very simple. Fusion also gives the option for direct modeling, without history, which is simpler still and very useful for some workflows. In that environment making bodies in just the root component for use in, say, boolean operations is a quick and simple way to try out ideas.

If Fusion (or any other CAD program) is to keep track of relationships between sketches and resultant geometry, or parts and related elements like joints or appearance, or assemblies, there must be some data structure that maintains these relationships. It could be hidden so it looks as if you just have parts, but Fusion makes this structure explicit and visible to the user. Doing so adds control and power and no doubt enables better implementation of Fusion’s future roadmap as a concept-to-manufacturing design solution. It does so at the expense of new users needing to wrap their minds around the distinction between Bodies and Components. Since this is 1) unique to Fusion and 2) important to get straight to use the program effectively, those of us on the forum have emphasized the importance of understanding the distinction between components and bodies early in the learning path.

Re: What can bodies do that components cannot?

Oceanconcepts — Thu, 09 Feb 2017 22:56:43 GMT

"I think a better question is why is the default output from an Extrude and other Create operations a body instead of a new component?"

Because when you are working within a component, which you always are, even if the root component, it's a reasonable default to place the new body in the same component as the sketch it is derived from. New geometry is always created inside the currently active component. You can select "new component" if that's what you want, but I think that would be less useful as a default.