Motion Study Troubleshooting

The following are frequently asked simulation questions and answers.

General Questions:

Q: Calculations and animations run slowly on my PC. Is there a way to get fast, shaded animation?

A: Yes. Try the following:

• Save the animation to an .avi file.

• Turn off RealView graphics and Shadows In Shaded Mode. These modes are very graphics-intense, and can be hard on graphics cards, and increase calculation time and playback time.

For new simulations, work in small steps. Try to get the general model working without using some of the more advanced features.

If you encounter problems, determine some of the basic causes. Focus on the portion of the model that has the problem by suppressing other motion entities.

Strike a balance between the number of frames captured and the time to calculate the animation. The more frames you have, the better, but the calculation time increases. Using 100-200 frames has insignificant overhead on most systems.

Motion Analysis- Specific Questions:

Q: The reaction forces in the joints that are calculated are incorrect. What might I be doing wrong?

A: Check that you set the units and values for your motion study properly. Also check that you set the density of each of your components correctly. You can also check that you do not have redundant mates.

To check the density of a component:

1. Right-click the component and select click Open Part .

2. Click Tools, Mass Properties while viewing the component (not the assembly).

Incorrect settings of units or density can significantly affect the reaction forces.

Q: How do I plot my results?

A: Use Motion Analysis to produce a plot. To export your data for use in an external program, right-click the background of a plot and select Export CSV.  

If working with linkages, remove redundancies to improve the accuracy of the force results.

Have a rough idea of the expected animation and magnitude results. This helps validate simulation results for the design.

When you have small time events, such as collisions, run multiple simulations with variations in settings to verify the solution. Use sufficiently small time steps to capture the motion.

Save a history of your designs. Create different study tabs and use a nomenclature that is intuitive. You can always go back to an earlier design if you encounter a problem.

You can use higher frame capture rates when you clear Animate during simulation in the Motion Study Properties PropertyManager.

For motion studies that do include 3D Contact, try modifying elastic properties if your simulation does not perform as expected.