SolidWorks 2010 Bible

Chapter 33: Animating with MotionManager

Using Animations to Flex Parts

You cannot change part dimensions when animating. You cannot use features like the Flex to bend

parts for an animation. If you can’t do any of this, how do you make parts flex during an anima-

tion? This calls for another workaround, but it is the only way to actually make parts change shape

with the MotionManager. You have to find a way to model the part such that you can make the

changes using distance and angle mates in an assembly. That means that you have to do in-context

modeling.

A lot of people treat in-context modeling as if it is some terrible infectious disease, but as I pointed

out in Chapter 16, it is nothing to be afraid of if you know how to handle it. Still, when you’re

flexing parts with in-context tricks, it is best if you can keep it simple.

Figure 33.20 shows an assembly that uses this technique to twist the strap as the fork rotates. The

assembly used to create this animation is on the CD-ROM, and is called Chapter 33 yoke

link.sldasm. The finished movie file is also on the CD-ROM, and is called Chapter 33 yoke

link.avi.

FIGURE 33.20

Twisting a strap during an animation

The main trick here is that the strap is made from three separate features. One feature is a revolve

that fits the bottom shape of the pin. This feature is part of a part that moves with the fork and pin

as they rotate. Another feature is an extrude made from an in-context feature. The in-context rela-

tion goes to a dummy part that remains stationary with respect to the rotating fork. And the final

feature (really a pair of features) is a loft that goes from the ends of the rotate feature to the ends of

the extrude feature.

As the fork part rotates, the in-context relation causes one feature to stay still while the other

rotates, and the constant rebuilds the MotionManager does make it look like the strap is flexing.

You can use the same sort of idea to flex living hinges in plastic parts, or just about anything. A

cleaner way to do this is to create planes in the in-context part, and then everything else is

sketches. If you can drive the flex illusion with planes, you can get this trick to work in a wide

range of situations. You usually wind up needing a loft feature, because no other feature is quite as

flexible as a loft. It is possible to sometimes use other types of features, but I like the loft the best.