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If you’ve been using Siemens NX for a while, you’re likely intimately familiar with the traditional Assembly Constraints dialog. It’s powerful, but it can feel heavy with clicks. In NX 2206, Siemens emphasized a newer, more streamlined tool: the Assemble command.

In this post, we take a deep dive into this command. While we’ve traditionally stuck to the old-school methods, the Assemble command has some hidden efficiency perks—especially for quick component placement. Here is your step-by-step guide to use it.

What is the "Assemble" Command?

Step 1: Access the Command

You can find the Assemble command in the Assembly tab of the ribbon.

If you can't find it, use the Command Finder and type "Assemble."

The Assemble dialog in Siemens NX, showing the 'Part to Add' and 'Position Component' sections for integrated assembly management.

Step 2: Selecting Your Component

Once the dialog is open, click Open and your first step is to select the parts you want to bring into the assembly.

You can open multiple parts in one go.

Selecting multiple Siemens NX part files (.prt), including brackets, wheels, and bolts, in the file explorer to add to a Caster Assembly.

Step 3: Positioning and Dragging (The "Loose" Move)

Before applying hard constraints, you might want to get the part into the "ballpark" area.

To Move: Click and hold the Left Mouse Button (MB1) on the part and drag it.

Importing multiple caster assembly components into the NX graphics window using the Assemble command for initial positioning.

Step 4: Applying Inferred Constraints

Now let's apply constraints. First, let's fix one item. In this case, we fixed that Caster Bottom Bracket.prt.

Using the 'Fix' action in the NX Assemble tool to ground the base plate at its current position, creating a stable foundation for the assembly.

Next, instead of picking "Touch" or "Align" from a list, just start picking geometry:

Select a face on your moving part.

Selecting the bottom face of a caster bracket in Siemens NX to begin the mating process with the fixed base plate.

Select a face on the stationary part.

Defining the target face on the fixed base plate in Siemens NX to receive the bracket component using automatic constraint detection.

NX will automatically apply a Touch/Align constraint.

The result of a Touch-Align constraint in the NX Assemble tool, bringing the bracket into contact with the base plate while maintaining degrees of freedom for sliding.

If NX picks "Touch" but you wanted "Align" (or vice versa), look for the Flip icon that appears near your cursor or in the dialog. You don't have to restart the command!

Step 5: Working with Brackets and Mid-Planes

In this post, we demonstrate a common scenario: centering a part between two faces of a bracket.

This is where the command falls apart. There is currently no way to do this in NX 2206. Because of this, you must switch to the classical method.

Using the Center Constraint in Siemens NX with the '2 to 2' subtype to perfectly center a caster wheel between two bracket faces by selecting pairs of planar surfaces.

The Verdict: Should You Use It?

The Assemble command is significantly faster for basic constraints and standard hardware. It feels more "modern" and less "menu-heavy."

However, for complex mechanical relationships or very specific "Distance" constraints with offsets, you might still find yourself reaching for the traditional Add Component or Assembly Constraints dialogs.

How to use Assemble