# Animating Rotary Motion in SolidWorks

“Easy,” you said. You needed an animated motion study within which a component needed to rotate 360 degrees, or some multiple thereof. “I’ll just set a key point at the desired ending position, and then rotate the component. SolidWorks’ transpositional animation will do just what I need.”

But it doesn’t seem to. In replaying your animation, the part doesn’t seem to have rotated at all. It’s not that the part didn’t move, per se – it did. Right back into the same position. SolidWorks will calculate the shortest distance between two key points. Which, in this case, is? None. In another example, a part that was to rotate 270 degrees has instead just rotated 90…in the wrong direction!

So, we discover a method that works just fine for linear translation is not so desirable for rotations beyond 180 degrees. What’s an animator to do?

We have not one but two answers for you. The first is this: Instead of trying to do a full 180-plus degree rotation in one key frame, break it into multiple smaller ones. Figure 1 shows a 360-degree movement broken into four 90-degrees segments.

Fig 1

The second is to use a rotary motion driver instead of explicit positioning. A much more complex movement can be more simply programmed in terms of RPM and distance traveled. Figure 2 shows where Motors can be selected and how they appear in your Motion Study timeline.

Fig 2

BONUS TIP: Whichever of these two methods has been most appropriate, if you wish to repeat but reverse the motion (i.e., unscrew something which had earlier been fastened), the following steps may help you. Window-select and then right-click and “Copy” all the key points related to your movement. Then, select the point on the timeline where the reversal is to start, right-click again and “Paste.” With the key points still selected, right-click and select “Reverse Path” from the context menu.

EXTRA BONUS TIP: For visual accuracy in certain mechanical situations – fasteners, threaded rods, etc. – consider using and driving an assembly-based “Screw Mate” in your animation. This will allow you to control translational distance as a function of revolutions, and may at times be more intuitively calculated than the above motor method. Remember, though, that animation is above all a visual medium – and you may need to balance mathematical accuracy with clarity of message.

Click Here for more SolidWorks 2014 Tips and Tricks on the SolidNotes Blog!

By: Sam Hochberg, Applications Engineer at Graphics Systems

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