UG NX 6 Tutorial – Unigraphics Top Down Approach for 3D CAD Assembly

UG NX 6 Tutorial – Unigraphics Top Down Approach for 3D CAD Assembly
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Like ProE, Unigraphics also permits you to create an assembly using two different approaches: top down assembly and bottom up assembly. In this UG tutorial we will discuss the top down approach of UGS assembly and its application.

What is the Top Down 3D CAD Assembly Approach?

In short, in the top down approach you have to create the blank assembly first and then you have to go on creating the sub-assemblies and parts in it. So, if the main assembly is at the top most level and the components are in bottom most level, then you are coming from top to bottom and it’s top down assembly.

How to Do it Actually in Unigraphics

Let’s say we have to create a Unigraphics assembly of three rectangular plates like below:

This sort of assembly is used for press tool die models. Anyways, for creating the assembly by top down approach in UGS, do as below:

  • Open the UG NX 6 (or whatever version you have) and click the Create New File icon and you will get a window (New) like below:

UG New Assembly

  • Here you select Assembly template from the Templates list. Also, you need to set the Folder, where you wish to save your Unigraphics files. You can change the name of the UG part/assembly as well. Click Ok.
  • Next, it will ask for the already created components to be added in the assembly, for top down assembly you need to click Cancel here.
  • Press Ctrl + m key from the key board now. Observe the change in the UGS window.
  • You have to create all the required Unigraphics datum plane now. For the above example you have to create the six datum planes as below:

UG Top Down Assembly Datum

Please don’t forget to check the Associate check box while creating the datums.

  • Now, let’s create the first rectangular plate. Go to Assemblies → Components → Create New Component and you will get a window similar to the New file creation window, select the Model template and change the name to Plate1 and click OK.
  • You will find the Create New Component window open, just click OK. You will find the Plate1 has added in the assembly navigator under the assembly.
  • Right click the Plate1 and click the make work part.
  • Right click the Datum1 and select Link to work part.
  • Now go to insert → design feature → extrude and select the Datum1 as sketching plane and sketch the rectangular outline of the plate1. Finish the sketch.
  • Change the End limits option from value to until selected and select the Datum2 and click ok. You have just finished modeling Plate1.
  • Similarly, create the model of Plate2 by taking the Datum3 as sketching plane and the Datum4 for end limit.
  • Also repeat the procedure for plate3 by using Datum5 and Datum6.
  • Save the file and your top down assembly is ready.
  • Now, the best part, if you wish to change the thickness of the plates or the distance between them, no need to remodeling each of the plates just change the distances between the datum planes and you can see the change.


Top down assemblies of Unigraphics (or any other 3D CAD packages) find its application for conceptual designs and for designs where frequent changes are part of the design process. Real life top down UG assemblies are much more complex and larger compare to the example discussed in the UG tutorial. However, I feel you can start working on the large top down assemblies if you understand the concept explained in the Unigraphics tutorial.