Monday, March 19, 2012

How do you simulate rolling in CATIA?

This is anupdate of an older post. I've created a brand new tutorial with step-by-step instructions detailing how to use CATIA V5's DMU kinematics workbench to simulate a rolling object.

First, in assembly design, create a new product and insert two new parts, one name Wheel and the other Ramp. 

I've explained this before but as a real quick overview, to create my ramp I used three sketches (overhead, side profile, and rotation about itself sketch) and combined them with laws. The wheel is a simple sketch and pad command. On my ramp I have two parallel curves 5mm apart. On my wheel I also have two parallel curves offset from each other 5mm. I added a point to one of the edges of the wheels so you can see it spin around in a circle when we simulate it. 

Add a Fix constraint to the ramp to ensure it does not move. It's absolutely vital that the curves on the wheel and the curves on the ramp are tangent to each other. Even a 0.001 gap and it will not work. Use coincidence restraints to pair them together if you have to. Also make sure your ramp is nice and smooth and much bigger than your wheel.

Now it's time to go into the DMU Kinematics workbench. Create a new mechanism and set the ramp as the fixed part. I can constrain all degrees of freedom using only two joints. The first joint is a roll curve joint between curve 1 on the wheel and curve 1 on the ramp. This is a length driven joint meaning you will input the rolling distance over time from the start point. The second joint is a slide curve joint between curve 2 on the wheel and curve 2 on the ramp.

Once you get the hang of it you can simulate more complex systems, like a full-scale roller coaster


View my Introduction to CATIACATScript Macros Video Tutorial.

Thursday, March 1, 2012