How to simulate a spring in DMU Kinematics?

[MrCATIA]

davood-se sent me a private message with the following question: (I don't usually respond to private messages, but this is a great question)

im learning dmu kinematics
its simple for some mechanisms but for some of them which is necessary to write formula its not easy
how ever when you learn one type you will able to do the other ones in that type automatically
my question is
how to simulate spring in dmu kinematics

 

[MrCATIA]

One of the first things I learned when I attended my first CATIA Kinematics class was:

CATIA Kinematics purpose is to analyze the motion of rigid parts within a mechanism.

Some of the basic assumptions of CATIA Kinematics are:

• the mechanism has 1 degree of freedom
  • (that means 1 mathematical solution for each driving motion)
• the mechanism consists of rigid parts
  • (no flexible parts such as parts that bend or deform - no springs)
• Motion analysis only
  • (no forces, no gravity, no friction)

So the answer to the question is: CATIA V5 doesn't do springs.

However, several users have figured out different ways to "fake it" so it looks like a spring.

Here's a video of one method Spring Animation CATIA V5R20 - YouTube You can find ,more by doing a Google search.

 

[MrCATIA]

One of the easiest ways to "fake" a compression/extension spring in CATIA Kinematics, is to model the spring as two CATPart files. One file for the right side, and the other file for the left side. Then use a Prismatic Joint based on centerlines and centerplanes to simulate the spring motion. But having the two springs "collide with each other" doesn't look too good when simulating the motion of the mechanism, so I like to make one side be a "holder" for the spring to slide in and out of.

Here's an example of a Bolt Cutter mechanism that contains a spring:

Obviously the spring is not compressing or stretching, but most people will not notice that. If you look again at the video I suggested, the 8 sections of that spring are just rotating about each other in order to make it "look like" the spring is being compressed.

Again, the purpose of CATIA Kinematics is to analyze the overall mechanism and how the parts move relative to each other - not to make nice animations of springs.

 

[PLM Technology]

Hi Mr Catia,

Like always, great article you wrote! I used very little kinematic in CATIA V5, but what you did is very impressive

I did my master thesis on kinematic and dynamic behavior on 3DExperience at Dassault Systèmes in the CATIA Team in Paris back in 2015 - I assure you, nothing too fancy, no science or mathematics, just testing the app and making video for presale

So my point is that Springs and Dampers have been added to 3DExperience in Mechanical System Design application.
I made a video with a dynamic behavior to show you how it works:

4:45 for spring creation
9:52 for simulation

Hope this will give one another reason to move to CATIA 3DExperience one day

Have nice christmas vacation!
Maxime at PLM Technology

 

[MrCATIA]

Hello Maxime,

It's always good to hear from you and to learn more and more about the 3D Experience. Your video demonstration showed several new capabilities that can not be done with the old CATIA V5.