CSWP Segment 3: Origins and Coordinate Systems

Segment 3 is about assemblies.  It becomes nearly impossible to judge if your assembly is correct based on mass.  Therefor we switch to reporting the Center of Mass or Center of Gravity.  Because of this, we have to pay very close attention to the polarity of our answers.  A negative sign can mean the difference between right and wrong here...

For example, the question in the box below can be answered without opening SOLIDWORKS.

You can see that Z and Y must be positive and X must be negative.  If Z is positive, then this eliminates the top two answers.  If X must be negative, this eliminates the bottom left answer, leaving us with only one option, the bottom right.

So, it is important that you create and assemble your models with the origin in mind.  If for some reason, you find yourself 3 questions deep and realize your coordinate system is wrong, there is a simple fix.  We can use a Reference Coordinate System.  Click Insert, Reference Geometry, Coordinate system to open the feature.

Select Edges to make the Reference Coordinate System match the test.

Hit the check box and you have a secondary Reference System.  When computing the Center of Mass, make sure you have the new coordinate system selected in the window shown here.

On the next post, we will talk about how to insert a sub assembly and make it flexible.

Have Fun,

Bryan