Fusion 360 Bodies vs. Components

Keqing Song June 30, 2015 5 min read

What is a component in Fusion 360? Why do we need them? Simply put, a component is a position and motion independent part of an assembly within our single design environment. We use joints to define its motion and its relationship with other components in the assembly so that the design is mechanically accurate.

i am a component.jpg

For example, take a look at this pump design. The Pump Housing V35 at the very top is the whole assembly design, and each part of the pump is a component of the overall assembly. Some components are just single bodied bolts, but some, like the pump housing, contain other components, making it a sub-assembly. Other people designed some components, and some were imported from existing data. We introduced a distributed design to make managing an assembly more efficient and make it easier to control future changes.

For more knowledge on components, check out this awesome article by Paul Sohi!

Still with me? Okay, now let’s get to the fun part.

1. A component can contain bodies as well as other components.

The Pump Housing is the holistic assembly design, and inside it, we can see various components such as the Base, Housing, and Coupler. If we expand into the Base component, we’ll find that it contains only one body. If we expand the Housing component, we’ll notice many other components within it, such as Housing Front and Housing Rear, which contain their own respective components and bodies. Since Fusion 360 has a single environment for design and assembly, this is how we can give our designs organizational structure in terms of what is a single part (body or component), sub-assembly (component), and assembly (design). Oh, and by the way, we can also rename any component and do not have to worry about feature dependencies or where they are saved.

2. Components have their own origin planes, whereas bodies do not.

pump origin.jpg

We established earlier that components are parts in Fusion 360 that can have motion relationships with one and another. This is made possible due to them having their own origin planes. Components are not dependent on the assembly design’s origin, but they can refer to it. When we create a body, it does not have its own origin planes because it is dependent on the top-level assembly’s origin planes and can not have motion relationships unless it is converted into a component.

3. Create a component right for the start of the design.

When we create 3D geometry in Fusion 360, we always have the choice to make it a body vs a component. However, if we already know that our design is going to become an assembly, we can and should begin with components right off the bat. By going to the top-level design node, we can right-click and select New Component. This will create an empty component in the browser and will allow us to define what the component should be with more features. Think of an empty container that we can fill up with Lego bricks where the container eventually takes the result’s shape. The advantage of this workflow is that we can begin to give our features some structure right from the beginning. If we’re not sure about where our design is going yet, we can start with new bodies and then convert them to components when they’re ready.

4. Activate a component to work within it.

As mentioned in our Assembly Modeling video, we can think of components as containers for bodies and other components. In scenarios where we have multiple components in a single assembly, Activating the component in which we want to work will allow us to associate all the features we use to build that component specifically to itself. If we don’t activate the component, all the features will be associated with the top-level design by default. Take this example, for instance. There are 2 identical boxes with holes in them. The one on the left was a component I created from the start, which I then activated and continued by applying a box, sketch, and extrude feature to obtain its geometry. The one on the left is a body I created using the same features. After converting the body into a component, notice that I now have 2 identical components…or do I?

If I activate component1:1, the timeline will show the 3 features I used to create it. However, if I activated component4:1, the timeline will only show the body-to-component conversion. When I created Component4:1’s body, it was created when the top-level design node (Unsaved) was active; thus, the 3 features I used to create that body were associated with the top-level design node and not the new component of which the body became. This is why it is always best practice to activate the component we want to work with first before creating new geometry.

If we look at the pump design again, we can see that when the top-level design node (Pump Housing V36) is active, the timeline stretches out quite a bit. Yet if we activate the Top Mounting component, the timeline focuses on what was used to create that specific part.

5. Turn Component Color Cycling on.

Component color cycling is a nice and easy way to tell which features in the timeline belong to its component. Let’s go back to our 2 boxes example and turn component color cycling on. When we activate Component1:1, we can see that the timeline’s features following its creation are the same blue color as it is the component item shown in the browser, indicating that they are associated with Component1:1. In Component4:1’s case, all of its features are associated with the assembly and is highlighted yellow because they were committed as a body and then converted into a component.

When we look at the pump design, we can start to see the value of component color cycling when we activate.

I hope this post helped you better understand the differences between components Vs. bodies, how and when to better use components, and why they behave the way they do. 

Download Fusion 360 today to explore the relationship between bodies and components in your next project.


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