Manufacturing

Animate with Alibre Motion (Alibre Options Tutorial)

1 Jan, 2007 By: Michael Todd

Add motion to your assemblies with this new module.


Alibre Motion is a new module available to users with an Alibre Design Expert 9.1 license. To use Alibre Motion, you should have a solid understanding of assemblies and assembly constraints. In addition, you need a decent understanding of part design and a basic understanding of assembly design for this Tech Tip, plus a license of Alibre Design Expert. The module helps you bring your assemblies to life, and even create a video of your product in action. In this Tech Tip, we'll create a basic assembly from scratch and then use Alibre Motion to animate it.

Create Your Assembly
The key to using Alibre Motion is to properly build and constrain an assembly that can move in the desired manner. As an example, let's create a simple clock. For this assembly you need five parts: the baseplate for the clock, the faceplate and three hands for seconds, minutes and hours. Make each part with one extrusion from a sketch on the x,y plane. You can add numbers and fillets for visual purposes, but these additions aren't covered here. (Note: The numbers on the sample clock were generated using the Text Import Wizard for Alibre Design. More information on this Alibre Design plug-in can be found here.)

figure
Completed clock assembly.

The baseplate is a simple cylindrical extrusion. Draw a circle on the x,y plane with the center on the origin. Extrude the circle. Once the part is created, save it and place it in a new Assembly Workspace. Mate the backside of the baseplate to the x,y axis with a 0 offset. Now, right-click on this part in your Design Explorer and select Show Reference Geometry. Align the z-axis of this part to the z-axis of your Assembly Workspace. You can now anchor this part, as it is the base for the rest of our clock. Save your assembly.

figure
The baseplate assembly for a clock.

Next, create the faceplate in the same manner. Make the circle for the faceplate slightly smaller than you made the baseplate. Extrude the part, save it and bring it into your assembly. Now mate the back face of the faceplate with the top face of the baseplate. Once again, right-click on this part in the Design Explorer and select Show Reference Geometry. Align the z-axis of the faceplate with the z-axis in your Assembly Workspace. Save your assembly.

figure
The faceplate mated and aligned with base.

Now let's create the hands for the clock. You can use whatever shape you like for the hands, but keep in mind that the z-axis will be used for rotation, so start your parts just below the origin and have the hands go up along the y-axis. Try to keep them symmetrical over the y-axis. Traditionally the minute hand is long, the hour hand is short and stubby and the second hand is long and skinny. Once you have all three hands built and saved, bring them into your assembly. Decide which hand you want on the bottom of your stack of hands and mate it with the top face of your faceplate. Now mate the bottom face of your next hand to the top face of the hand you just mated. Do the same with the third hand. Now right-click on each of your hands in Design Explorer and select Show Reference Geometry. Align the z-axis of each hand with the z-axis of your Assembly Workspace. These axis alignments are what we will apply motion to. Save your assembly.

figure
Sketch for hands.

Apply Motion
Now that the clock is constructed, it's time to get moving! In your Assembly Workspace, choose Motion / Motion Explorer. When you enter Motion Explorer you will get an error message about the density of your parts, because we haven't adjusted the densities on the parts. Ignore this error message for this Tech Tip.

Notice that your parts are now separated into two lists: Fixed Parts and Moving Parts. The baseplate should be the only part listed in Fixed Parts, because it's the only part we anchored. Under Moving Parts you should see the hands that we created. Under each part there is a list of constraints applied to it. For each of your hands you should have one or two mates and one align. Open the Constraints for your minute hand and right-click on Align Constraint. Go to Insert / Rotary Motor. Make sure Enable Motor and Specify rotation are checked. Then click on the Prescribed Rotation tab and set the Constant rotation to 8 Degrees Per Second.

Repeat this process for your hour and second hands. Apply Rotary Motors to the Align Constraints on each of these hands. For the second hand, set the Constant rotation to 120 Degrees Per Second. For the hour hand, set the Constant rotation to .5333 Degrees Per Second. If you would like your clock to run faster or slower, you can increase or decrease these numbers. If you modify these numbers, try to maintain the ratio between them (each hand should be 15 times faster than the hand below it).

Now we're ready to see our assembly in action! Click on Motion / Enable Simulation, then click the Play button in the Motion Toolbar and watch your assembly come to life!

figure
A running clock.

You can create a video of your assembly in action by clicking the Record Playback to Video icon in the Motion Toolbar. Choose the location to save to, and a title to display as the video runs. This creates an AVI file of your assembly with motion.

Using Alibre Motion
Rotary Motors are not the only type of motion that can be applied. You can also apply Springs (for a back-and-forth motion) or Dampers (for linear motion in one direction). Using constraints, you can also have moving parts that move other parts in the assembly without applying additional motors.

Alibre Motion is a powerful tool that can be used many ways. For more information and practice with Alibre Motion, visit our Alibre Motion Tutorial.


About the Author: Michael Todd


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