Understanding the various coordinate systems in NX is an important first step to using the CAD software. New users may find it confusing at first because there are 3 coordinate systems in NX Design, and there is also a Machine Coordinate System (MCS) for CAM. Depending on how you model, you may never even need a coordinate system! That being said, it's important to understand the differences between each. That is precisely what you will learn from reading this article.
You have the ability to define a parametric location for an object, such as a Point or the Center of an Arc, using absolute coordinates and this is where the Absolute Coordinate System comes into play. If an object has been defined using parametric coordinates rather than referencing some other object like a Datum CSYS, then the parameters stored with that object will be with respect to the Absolute Coordinate System.
The Absolute Coordinate System does not change or move. It provides a fixed point in space from which to begin modeling.
The Work Coordinate System (WCS) is a coordinate system object. First introduced with the Unigraphics D2 release, the WCS is essentially a legacy object that is still used to determine the orientation and origin of any newly created object which is not created using another object for reference.
When the WCS is moved, nothing else goes with it. The WCS simply defines a new 0,0,0 origin and X Y Z orientation.
With the introduction of parametric and geometric features, you needed some additional tools to define the intended location and orientation of objects as well as how they could be controlled. With a Datum CSYS, objects are created relative to some aspect of the datum object, such as a Point, Plane, or Axis.
The Datum CSYS contains 3 datum planes and 3 datum axis along with a coordinate system.
When the Datum CSYS is moved, anything that referenced it will move as well.
This article is based on a question and replies in the NX Student Forum.