Day 23 of Learn Fusion 360 in 30 Days for Complete Beginners! – 2023 EDITION – Create Assemblies with As-Built Joints

Demo File – Tripod

1. Open the Data Panel
2. Scroll down and double-click on the ‘Basic Training‘ section which is included with the Autodesk Fusion download.
3. Find and double-click on the ‘06 – Assemblies‘ folder.
4. Find and double-click on the ‘06_tripod‘ file.
5. Demo files are read-only by default. Select File > Save As, and save the design.

Transcript

Welcome to Day #23 of Learn Fusion 360 in 30 Days. I’m Kevin Kennedy,

and today we’ll look at how to start assembling multi-part models in Fusion 360.

We’re going to use the tripod demo file included in your Data Panel.

Open your Data Panel and scroll down to the ‘Basic Training’ section. Inside this Project, you’ll find an Assemblies folder that contains the Tripod file.

Upon opening the file, you’ll find demo files provided in the Data Panel default to read-only. 

Select File, Save As, and then rename the file and choose the desired location.

The file is now saved to your Data Panel as a regular file and we can start modifying it.

Notice our tripod parts will move around freely as we click and drag on them. 

Any time you move your parts around to test things, you can select “Revert Position” in the toolbar to move them back into place.

We’re going to use the Joint feature to position components. In Fusion 360, the Joint features define the relative position and motion between each part, allowing you to create functional models, such as a working tripod.

If you’re coming from another CAD program then you may be familiar with the term ‘Mates.’ Fusion 360 uses the concept of ‘Joints’ in place of ‘Mates.’

Before we discuss the Joint commands, it’s important to note that our Browser already consists of Components for each part. Components are required by the Joint command. Fusion 360 does not allow you to assemble individual 3D bodies that are not placed in a component.

There are many approaches to creating assemblies in Fusion 360. One of the most common includes creating all of your parts first, followed by joining them together at the end.

Another common approach is to design individual parts and join them together as you create each sequential part.

Which one you choose is often determined by your design objective and other factors. This includes whether you’re working with a team, have all the known measurements, import any 3D files, and more.

When starting a new assembly, you’ll want to consider which part should be stationary or ‘fixed in place.’ This will allow us to join all the parts together, restricting degrees of freedom based on the design intent.

Oftentimes a part that touches the ground or a part that has the most number of pieces attached to it will serve as the best starting point.

With our tripod, our red Stand component in the middle is not expected to move as the user slides the tripod legs or moves the ball joint.

We’ll start by preventing this component from moving, which will allow us to join the rest of the parts together.

Let’s find the component in the Browser, noting that it is nested in a few sub-assemblies. You’ll always want to “Ground” the individual component and not a sub-assembly, ensuring it “freezes” the item itself and not a parent component that may change.

Right-click on the component and select the Ground option.

Grounding our component will prevent it from moving. Try to click and drag on the red Stand component and confirm that it’s frozen in place.

Notice that ‘ground’ also places a red thumbtack icon on the component in the Browser. The thumbtack lets us know that it’s grounded.

At any time we can right-click and ‘unground’ the component, if needed.

Now that our stand is grounded, we’ll want to use Fusion 360’s Joint commands to create functioning tripod legs.

Under the Assemble dropdown list, you’ll find a handful of different Assembly features.

Both the Joint and As-Built Joint features include 7 different types of motion.

The key difference is that the Joint feature will physically move one of the selected components.

On the other hand, the “As-Built Joint” feature lets you define the relative motion between components without repositioning them. As-Built Joints make it easier to add Joints when parts are designed in their final location. This includes when designs are imported with the parts already in their desired location. 

Our tripod model has the legs in the desired position, so in this lesson, we’ll focus solely on using the “As-Built Joint” feature.

We’ll start by activating the ‘As-Built Joint’ command. You can also activate it with the keyboard shortcut Shift + J.

Before selecting the components, we’ll want to set our desired Motion type in the dialog.

The lower tripod legs should slide within the upper leg, so we’ll select the “Slider” motion.

We can then select each tube that makes up the tripod leg.

After selecting each tube, notice we get an additional “Snap” option in the dialog. 

Defining a ‘Snap’ places a Joint Origin. Joint Origins allow us to define how these two parts understand each other in 3-dimensional space. They represent our X, Y, and Z axis.

Notice how different snap locations appear as we hover our mouse over the 3D model.

We want the lower tube to slide into the top tube so we can select any of the snaps on the upper tube. I prefer to select the end of the tube as it makes defining the Joint Limits easier, as you’ll see in a second.

After selecting the Snap, we’ll see it gives us a preview of the slider motion. This helps us confirm it’s working in the desired direction. If not, we can clear the snap and select a different location.

The lower tube unrealistically slides past the other tube. We can fix this by defining the “Joint Motion Limits” in the dialog.

Let’s check all three options to turn them on.

Flag icons will appear representing the minimum and maximum joint limits. 

Let’s drag the top slider upward, setting the Maximum value at 55mm. Keep in mind you can type this in the dialog as well. This value means our lower tube will not go beyond 55mm into the upper tube.

We can then drag the other flag down, setting the Minimum value. This lower tube needs to remain in the upper tube to ensure the tripod legs won’t collapse. Since these legs were designed in place, we can keep this value at 0mm, which leaves some of the lower tube inside the upper tube.

At any time, we can preview the motion to ensure our joint limits are working as expected.

Lastly, setting the rest position will determine the position of the parts when the Joint is not moving. Oftentimes, this value will be the same as either your minimum or maximum. In our case, we’ll leave this set to 0mm as we want the tripod legs to ‘rest’ in the open position. If we wanted the tripod model to have the legs closed, we could set the rest value to 55 millimeters.

After selecting OK, you’ll find that our slider joint was automatically applied to the other two tripod legs. This is because the components were copied and pasted to make the other two legs. Copied parts will always inherit any Joints or design changes.

If we now click and drag a tripod leg, you’ll see the tubes remain together.

Let’s proceed by adding a ‘Rigid’ As-built Joint to attach the rubber feet. Rigid motion is used when you want to simulate something being fastened together.

Set the motion type to ‘Rigid.’ Select the bottom leg and the rubber foot components.

Previewing a Rigid motion will shake the two components, helping you double-check that the correct components are selected.

Select OK and we can move the tripod leg to check the results.

Next, we’ll want to add a Joint to the top leg and the black connector.

Again, we’ll use a Rigid “As-Built Joint,” selecting the two parts before double-checking our joint.

Let’s go ahead and hide the red Stand sub-assembly in the Browser, allowing us to see the remaining parts.

The Leg connector component needs to be attached to the black connector. We’ll then add another motion joint to connect the leg to the stand.

Activate “As-Built Joint” and select the two components. Again, we’ll use the Rigid motion type as these two parts will be fastened together.

For our final Joint on the lower assembly, we’ll want to add a ‘Revolute’ Motion type, allowing the tripod legs to swivel up and down at this connection.

With “As-Built Joint” active, set the motion type to “Revolute” and select the two parts.

Similar to our Slider motion, Revolute requires us to set a snap, which defines where the part will swivel. Typically this will be the center of the shared cylinder, as they would revolve around the pin or bolt holding them together.

After defining the snap, we’re given a preview of the motion.

We can also set our Joint Motion Limits.

For the Minimum, we may want to allow the leg to move up until it collides with the bracket.

For the Maximum, we can set it to just beyond vertical, resulting in 25 degrees.

Remember to always preview the motion to ensure everything is moving as expected. It’s easier to fix Joints as you create them, versus later, as they may impact other Joints or features.

Again, we can also set our Rest position. Let’s leave this set to 0 as we want the tripod to ‘rest’ in its current position as if it were being used.

While checking our results, you’ll find this Joint was not copied to the other three legs. This is because our top bracket is a single instance and is not copied and pasted like the three-leg parts.

Take a minute or two and apply the same Revolute “As-Built Joint” to the remaining two legs. They should have the same Snap location and Joint Motion Limits.

Once complete, we’ll need to add another Rigid “As-Built Joint” between the top connector and bolt.

We can then turn our red Stand component back on.

Remember we grounded our red stand component, so it’s frozen in place. We’ll need to apply one last rigid joint to the bolt and the red stand.

Once that is complete, you’ll find that we can move the tripod legs more realistically. Notice the lower tube slides into the upper tube, with respect to our Joint Motion Limits.

Lastly, we need to apply an “As-built Joint” to the top camera mount and the red stand.

We want the ball to revolve around the socket of the stand. Looking at our motion types, you’ll find the “Ball Joint” to be most appropriate for this use case.

After selecting the two components, we’ll select the center of the ball as the “Snap,” as the ball should revolve around its center point.

In this beginner lesson, we won’t discuss how to prevent this camera mount from colliding with the red stand. If you’re interested in learning more, you’ll want to watch my lesson on “Contact Sets” in Fusion 360.

Lastly, you’ll find our Joints are all listed in the Fusion 360 Browser. If you right-click on any Joint, you’ll find we have options to animate the Joint and Joint relationships, edit our Joint Limits, and Lock the motion if needed.

In this demo file, you will also find a few other tripod parts that have their visibility hidden by default. I encourage you to turn them on and practice applying “As-Built Joints” to the remaining parts, including any applicable Joint Motion Limits.

[Upbeat Music]

I’ll see you on Day #24 where we’ll take an introductory look at Fusion 360’s Sheet Metal tools.

[End Upbeat Music]