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More DMU Kinematics Questions


New member
I'd like to start of by saying Thanks for all the help. Learning Catia really is a lot of work and I appreciate all of the input from you knowledgeable folk.

So I've been mucking around with the DMU Kinematics module and I've figured out how to create joints and simulate with clash detection BUT I can't seem to figure out how to make parts move other parts upon contact. For instance, lets say I was simulating the pushing of a button... anything where there is space between the parts and then a pushing force upon contact.

Also, is there a way to put springs into a kinematics simulation?



Super Moderator
DMU Kinematics is pretty cool to animate mechanisms, but it has several limititations: it only handles closed loop, single-solution mechanisms containing only rigid bodies.

To simulate the button motion, you must create two mechanisms: one before the button makes contact, and one after the contact is made which moves the other parts. You might be able to simulate both mechanisms by using laws to combine both mechanisms and establish some time parameters for when the first mechanism moves and then when the second one.

Springs are not rigid bodies, so the spring motion can not be simulated. (you can fake it by breaking the spring into two halves and adding a prismatic joint between them)

You might want to check out the DMU Fitting Simulation workbench if you want to animate moving parts with collision detection. Or check out some other software that does dynamic analysis (such as LMS Virtual Lab that can be added as a CATIA workbench)


New member
Hey could you suggest any other pieces of dynamic analysis software? I don't think I'll be able to get LMS Virtual Lab for Catia R17 or R18.


New member

Unfortunately thats not true with kinematics. You can simulate two contact components using 1 mechanism. This is the way we recommend you use the tool.

Create 1 mechanism that will define you movement.
Create two commands, 1 for the movement of the finger (pris) and one for the movement of the button (pris). Ensure both are driven joints.
The mechanism now displays 2 commands in the simulation dialogue box.

Create a law that ties the two together. Set one joint going on a linear movement. (single line in a sketch) and set the other so that the value remains 0 until the other component comes into contact with it. The set this command moving at the same linear rate.

Sounds complex but is very simple if you have done it once before.

Take a look at the example model here:

CADHandy.com - Downloads | Catia V5