Dynamic Simulation in AutoDesk Inventor

This is just one hub in a series of 15 hubs on using AutoDesk Inventor for 3D modeling. The index hub is here.

Of course, modeling a part or assembly in Inventor isn't much good if you don't do anything with it. We need 3D modeling for other purposes beyond just entertainment in our free time. Inventor lets us add forces and torques and then watch what happens. We can track the motion in 3D, and then graph displacement, velocity, and acceleration. In other words, Inventor does all the math for us, but only as long as we know how to use it.

In this tutorial you'll learn how to add a force to an object, play the animation, and then see where the object goes. We'll be using the lamp that we added to our shelving system to test out the dynamic simulation. We'll also be tracking the location, velocity, and acceleration of the lamp so we can graph them at the end.

Dynamic Simulation

Ok, so we want to make that lamp move. Go to the "Environments" tab and click on "Dynamic Simulation," all the way to the left. This should open a new tab, just like the one in Picture 1. Inventor will probably ask you if you want to see the tutorial, which you may or may not want to do. I didn't find it too helpful, but then again, I like figuring things out for myself anyway. Let's go right to adding a force.

Adding a Force

Find the "Load" panel on the "Dynamic Simulation" tab and click on "Force." A menu should come up just like the one in Picture 2. This menu gives you options for the location, direction, and magnitude of the force. I chose the location to be on the side of the lamp, just because it was handy. The direction I chose as the rod that the lamp slides on, since that is, of course, parallel to the motion of the lamp.

The magnitude was a little tougher. Since everything is operating in perfection, a tiny little force will send anything flying if you don't add constraints and limits. You can try a few forces, but chances are you'll have to make them pretty small. I recommend the input graph option.

Just to the right of the input box for the magnitude, there is a little arrow. Click on it and choose the input grapher. In this menu, shown in Picture 3, you can make a graph for the force you want to add. My final graph was a bit more complicated than the one shown here. Add points by double clicking the line, then clicking the point you just added. You can give it a time value and a force value. Repeat this process several times to produce a graph. Remember that F = ma, and if your part is already zooming in one direction, you'll have to stop that acceleration first before you can go the other way. In other words, this is not a velocity graph, but a force graph.

Try a few different graphs until you are happy with the outcome. You'll need to close the Input graph menu and click on play. After testing the forces, you'll need to click on the "Construction Mode" button at the left side of the Simulation Player to return to editing your forces. To edit an already existing force, double click on its icon in the Dynamic Simulation tree on the left of the screen. Once you are happy with your editing, it's time to add traces.

Tracing and Graphing

In the "Results" panel, click on the "Trace" button. You should get the menu shown in Picture 4. Click on any point on your lamp - they should all be very similar, since this part isn't bending or twirling. Choose to trace the motion, then check the boxes for Trajectory, Velocity, and Acceleration as well.

Run the simulation again. Notice how there is a line in the 3D drawing that tracks wherever the lamp goes. This can be very handy for predicted many different types of motion. In this case, the up and down motion of the lamp is pretty boring.

If you want to see the graphs that were produced, click on "Output Grapher," up in the "Results" panel of the "Dynamic Simulation" tab. This will show up as it does in Picture 5. Expand the tree on the left side until you get to the traces that you set up earlier. You should find them under something like Model Name ->Traces->Trace:#.

There are a number of different traces for you to check under each trace - the top one should be the 3D motion, and the next three are the x, y, and z motions broken out separately. Check the ones you want, and inspect the graph.

If you chose to input a force that was non-linear, such as the "Input Grapher" method, these graphs will be pretty interesting. If you are actually working on a real project, these graphs can be very useful.

Another day, another Inventor tutorial! We're not done yet, though. The most fun section if coming up soon-wait, they're all fun. Keep reading for more!