Coordinate System (CSYS) in NX

Coordinate System (CSYS) in NX:

A curious mind will first come up with this question when one reads the above title.

Question is- “What is a coordinate system?”

In geometry, a coordinate system is a system which uses coordinates (e.g.: X/Y/Z Coordinates), to determine the position of a geometric element in a 3D space.

There are a number of types of a coordinate system like- Cartesian, polar, cylindrical and others.

What we will look into here is a cartesian coordinate system when it comes to NX design.

A Cartesian coordinate system for a three-dimensional space consists of 3 axes which pass through a common point called origin.

NX Design has 3 coordinate systems while NX CAM has a separate one named as Machine Coordinate System (MCS).

Here we will look into 3 coordinate systems related to NX design.

1. Absolute Coordinate System:

As the name suggests this coordinate system is absolute. It does not move (from one point to another point). Further, its orientation is also fixed. Thus it gives you a fixed reference in a 3D space. 

Ultimately, Location & orientation of an object can be measured with respect to this fixed reference which is the Absolute Coordinate System.

In NX, you can see this coordinate system by clicking on the drop down arrow of Datum CSYS command. 

“View Triad” in NX is a representation of this system. There is no need to keep Absolute CSYS “ON” all the time. View triad does that job by giving you orientation (if not the absolute 0,0,0).

1. Datum Coordinate System:

When you open the NX modelling application, you will see a datum CSYS in show mode by default.

Unlike Absolute CSYS, it can be moved from one point to another and its orientation can also be changed. We can create a number of such CSYS. You can assess Location & orientation of an object with respect to this CSYS too -same to absolute CSYS.

Only difference is- absolute CSYS gives you reference with respect to absolute 0,0,0- while datum CSYS may /may not be at absolute 0,0,0. Same is true when it comes to absolute orientation.

Datum CSYS has its own significance though. Whenever you approach any CAD test for any MNC, the requirement is -  “To construct your model with respect to a single point. You may be instructed, once you finish your modelling, to move that single point and accordingly move your whole model”. Datum CSYS helps us to fulfill that criteria. (Kindly put a comment, if you are interested in knowing other criteria of a CAD test for a MNC.)

1. Work Coordinate System (WCS):

WCS was first introduced with the Unigraphics D2 release. We do not see any of its utility other than being a legacy feature.

WCS can be moved and the same is true for orientation. 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. We can not have more than one WCS.

There is lots of material available on the internet showing - how to move WCS, how to orient it. However, there is no point of discussing the same here as it does not have any utility.

Summarised Comparison: