Siemens NX Assembly, WAVE, and Routing Complete Guide

NX · Assembly & WAVE

Overview

The core of the Siemens NX assembly environment is a Master Model structure that binds files together by reference only, without duplicating them.

This page consolidates assembly workflows — Assembly Constraint, Assembly Navigator, Arrangement, and Flexible Component — together with the WAVE Geometry Linker that underpins top-down design and the Routing Mechanical/Electrical tools for piping and harness design, all from a practitioner's perspective.

For part modeling fundamentals see 02-modeling-synchronous.md; for shortcuts and Navigator usage see 01-shortcuts-ui.md.

Basic Assembly Structure

An NX assembly (.prt) only references its child component part files and does not hold duplicates inside itself.

This structure is called the Master Model Concept, meaning the same part is shared as a single source across multiple assemblies, drawings, and CAM files. When the source is modified, every upstream document that references it stays in sync.

Term	Meaning
Top Assembly / Displayed Part	The top-level assembly currently shown on screen
Work Part	The part set as the edit target (where features are actually added)
Component Part	A child part instance loaded inside the assembly
Sub-assembly	A mid-level assembly (itself a component of another assembly)

> Tip: Displayed Part and Work Part can be different. An NX strength is keeping the top level displayed while setting a child component as Work Part and modeling in place — this is called In-Context Modeling.

Adding Components

The entry point is Menu → Assemblies → Components → Add Component (default shortcut Ctrl+Alt+A). Key options are below.

Positioning: Absolute Origin (auto-place at origin) / By Constraint (set constraints immediately) / Move (mouse drag) / Select Origin (pick a target point)
Count: place multiple instances of the same component at once
Layer: choose which layer to place into (follow the organization standard — Layer 1–10 recommended)
Reference Set: choose load level — MODEL / Entire Part / Empty

Assembly Constraints

After NX 7.5 replaced legacy Mating Conditions with Assembly Constraints, most shops use the constraints in the table below.

Constraint	Purpose
Touch/Align	Planar touch or axis/edge align
Concentric	Concentric match between two circular edges
Distance	Numeric distance between faces or axes
Fix	Fully lock a position in space
Parallel / Perpendicular	Parallel / perpendicular
Center	1-to-1, 1-to-2, or 2-to-2 centering
Angle	Angle between two vectors
Fit	Auto-concentrically align cylinders of equal radius
Bond	Bond multiple components into one rigid group that moves together

> Tip: A single Concentric on a cylinder end often resolves axis alignment, concentricity, and face contact all at once. It is faster than stacking several Touch/Align pairs and has lower over-constraint risk.

Constraint Navigator

Since NX 8, the dedicated Constraint Navigator (CN) panel collects constraints, making Suppress (temporary release), Convert to (constraint type conversion), and status icons (Fully / Under / Over / Conflicting) easy to work with.

When temporarily releasing constraints to check mechanism motion, Suppressing individual Constraints makes it easy to restore later.

Using the Assembly Navigator

The Assembly Navigator (AN) on the left panel shows the entire assembly tree at a glance.

Checkboxes toggle Load / Unload
Right-click a component → Replace Component: swap with another part (the filename can differ)
Make Unique: detach an instance that shared a .prt into an independent part
Colored icons distinguish Fully Loaded, Partially Loaded, Unloaded, and Error states

> Note: Even after Replace Component swaps the part, if existing Constraints cannot find the new part's edges or faces, a warning appears in the Constraint Navigator. Always open CN and clear all errors before saving.

Pattern Component

For repetitive placement, use Menu → Assemblies → Component → Pattern Component.

Linear Array / Circular Array: linear and circular patterns
Reference Pattern: auto-replicates components along an existing feature pattern

If bolt holes were created with a Hole Pattern Feature, applying Reference Pattern to the bolt component lets the bolts automatically follow changes to the holes. This is especially valuable on fasteners that exceed 100 instances.

Flexible Component

A capability that lets the same component file have different positions and constraints per assembly. Classic examples are springs, hoses, and bellows.

When one assembly needs the free length and another needs the compressed length, set it via Assembly Navigator → right-click component → Make Flexible.

> Tip: Overusing Flexible Components makes it confusing which version is the "normal state." Restrict it to parts that physically deform, like springs, hoses, and harnesses.

Arrangement

A capability that stores multiple position scenarios within one assembly. Door-closed and door-open states, or actuator retracted and extended states, can be stored inside the same .prt and selected from drawings.

Menu → Assemblies → Arrangements → Edit Arrangements
Each Arrangement stores its own constraint values, positions, and Explode state
When creating a drawing view, specify which Arrangement to reference

Explode View

Exploded views for assembly drawings and operator manuals are created in Menu → Assemblies → Exploded Views → New Explosion.

Auto Explode lets the algorithm compute distances, while Manual Explode drags individual components.

Turning on Explosion Path draws path lines along the assembly order automatically — useful as visual content for manufacturing manuals.

Component Group

A capability in large assemblies to bundle related parts for batch Show/Hide or Load/Unload. For example, grouping a vehicle model by "front suspension," "powertrain," and "interior" lets you lightly load only the system you need during design reviews.

Creation path: Assemblies → Component Groups → New.

Interpart Copy and WAVE Geometry Linker

What is WAVE?

WAVE stands for What-if Alternative Value Engineering, and it is the engine of NX's top-down design methodology.

In an assembly context, it performs a linked copy of geometry from Part A into Part B, and when the source changes, the copy updates automatically. Unlike plain Interpart Copy, the core distinction is that associativity is preserved.

Using WAVE Geometry Linker

Entry: Menu → Insert → Associative Copy → WAVE Geometry Linker, or the Assemblies tab → Interpart Links → WAVE Geometry Linker.

Object types you can copy:

Point, Line, Curve, Sketch
Face, Body, Mirror Body, Region of Face
Datum (Plane/Axis/CSYS)

Key options:

Option	Behavior
Associative	Auto-updates when source changes (default on)
Fix at Current Timestamp	Freezes the copy at the snapshot moment, ignoring later source changes
Hide Original	Hides the source object
Inherit Display Properties	Inherits color and layer from the source
Make Position Independent	Keeps the child geometry at its original position even if the parent component moves

> Note: Keeping Associative on is convenient, but in large assemblies thousands of WAVE links can make Update take several minutes. For areas where design is already frozen, use Fix at Current Timestamp to regain performance.

Top-Down Design Workflow

Create a Master (Skeleton) part that defines only the key faces, axes, and points.
Place the Master into a new assembly.
Use New Component to create an empty part inside the assembly.
Switch the new component to Work Part.
Use the WAVE Geometry Linker to bring faces, axes, and sketches from the Master.
Model the component in detail against the linked reference geometry.
When the Master is edited, every child component updates automatically.

Relations Browser

Menu → Tools → Relations Browser is a tool that visualizes interpart link relationships as a graph.

If Part A references Part B while Part B in turn references Part A, that is a Circular Reference and Update becomes impossible.

The Relations Browser detects these cycles and lets you double-click a node to jump to the offending part.

Product Interface (PI)

A Product Interface is a contract that formally declares, in a Master part, "only these objects may be referenced externally".

Only objects registered in the PI can be copied by children via WAVE, and as long as PI targets are preserved, internal Master implementation can change without forcing children to update. It is analogous to a public interface in object-oriented programming.

WAVE Best Practices

Create WAVE links top-down only. Bottom-up links between already-finished parts cause cross-linking, blowing up load time and raising circular-reference risk.
Concentrate WAVE sources in Skeleton/Master parts and keep ordinary design parts mostly as consumers.
Define clear team naming rules and Item ID schemes. Complex WAVE trees easily tangle when names look similar.
When cloning, always run General WAVE Relinker (Menu → Assemblies → WAVE → General WAVE Relinker). If you skip it, the cloned parts continue to reference the original .prt and unintended edits propagate back to the source.
Using WAVE PMI Linker (NX 2206+) lets PMI (dimensions, tolerances, notes) link across parts, completing the MBD pipeline.

Interpart Expression

Where the WAVE Geometry Linker links geometry, Interpart Expression links numeric parameters between parts.

For example, if the Master part holds L_Frame = 1500, a downstream cover part can reference it as L_Cover = "master_frame"::L_Frame - 20. The path uses the part name and the :: symbol.

Menu → Tools → Expression → Interpart → Create/Delete Interpart Expression
Keep the reference direction strictly one-way. If A references B's Expression, make sure B does not reference A.
A common convention is the naming prefix IP_ to signal "this is an interpart reference."

> Tip: On large projects, create a dedicated "Control Part" that gathers all key dimensions, and have every part reference values from it. This way, opening one file gives you control of the project's core parameters.

Routing Mechanical / Electrical

Overview

Routing is a module that automates path-based design for piping, wiring, and ducts. It has two branches.

Routing Mechanical: Pipes, tubes, ducts, conduits, and Steelwork
Routing Electrical: Wires, harnesses, cables, connectors, and cable trays

Routing Mechanical Workflow

Specification setup — pick a piping standard library like ANSI B16, DIN, or JIS.
Stock definition — specify pipe bore, material, and schedule.
Create the Path — Insert → Routing → Path. Draw the centerline using points and existing edges.
Qualify Part — register a generic .prt as a "routing part" with connection point information.
Place Part — snap Tees, Elbows, Valves, Reducers, and Flanges onto path intersections.
Assign Stock — apply pipe specifications to individual segments.
Generate BOM / Cut List — the parts list and cut lengths are computed automatically.

Routing Electrical Workflow

Import the Netlist — bring it in as JSON/XML/CSV from ECAD such as Capital Harness or Mentor Xpedition.
Place Connectors — place Qualified Connectors at their coordinate positions.
Auto-route / Manual route — generate paths automatically or sketch them directly with Path Curve.
Bundle — group wires together and auto-compute the bundle outer diameter.
Min Bend Radius Check — flag segments that violate the manufacturing curvature limit.
Harness Drawing — generate a 2D harness drawing via Flattening Harness.

Routing Field Tips

Always keep piping Spec-driven. Free-hand modeling without a Spec will tangle both BOM and cut list.
The Path is a 1D centerline and the 3D pipe is the Stock wrapped around it, so editing only the Path propagates to the whole pipe.
For electrical harnesses, the Flexible Cable capability computes length in real time based on curvature, leading naturally into jig design.
For piping clash checks, run Analysis → Clearance → Clearance Analysis on a regular cadence.

> Note: The Routing module requires a separate license. If your shop has limited seats, finish prerequisite tasks like netlist consistency validation in Excel/Capital (which do not require the license) before entering NX.

Clearance Analysis and Interference Check

A capability that automatically detects interferences and minimum clearances between components in large assemblies. Analysis → Assembly → Clearance → Clearance Analysis.

Type	Content
Hard Interference	Two bodies physically overlap (design defect)
Soft Interference	Below the configured minimum clearance
Touching Contact	In contact (useful for assembly and weld review)

Saving a Clearance Set enables regression testing by rerunning the same conditions after design changes.

Large assemblies should be run per Component Group to keep execution time within a reasonable range.

Deformable Component & Advanced Positioning

Beyond springs and hoses, use the Deformable Part capability when shape must deform according to assembly conditions.

By defining deformation rules (reference points, degrees of freedom, deformation laws) inside the part, it will deform automatically to match constraints in the assembly context. Especially useful for belts, wires, and flexible brackets.

Advanced Positioning provides precise placement features beyond plain drag. For example, Align Edge aligns two edges directly and skips Touch/Align, while Pack/Unpack lets you treat a Pattern Component as a single temporary bundle.

Assembly Sequencing (Assembly Order Simulation)

Assembly Sequencing validates the assembly process as animation. Menu → Tools → Sequence → Create Sequence.

Install/Remove Step: defines along a time axis the order parts are installed and removed
Motion Envelope: auto-computes the spatial envelope used during assembly → checks interference with surrounding parts
Exploded Path: visualizes the disassembly route
Output can be exported to MP4 or AVI for manufacturing manuals and training materials

In fields like automotive trim lines and aircraft engine assembly, where assembly order directly drives product quality, this has become a validation means at the design stage.

Field Checklist

Verify that component names and Item IDs follow team standards
Confirm no Under/Over/Conflicting statuses remain in the Constraint Navigator
Standardize assembly Reference Set on MODEL (avoid Entire Part)
Verify in the Relations Browser that WAVE links are strictly one-way Master→Child
Review that only externally-public objects are registered in the Product Interface
Name Arrangements by function so intent is obvious, like "Closed/Open" or "Retracted/Extended"
Routing: confirm the Spec library path points to the team-shared path (UGII_ROUTING_DIR)
After Clone Assembly, always run General WAVE Relinker
Before large-assembly reviews, use Open by Proximity to limit viewing scope and cut load time

Clone Assembly

Used when Project B is derived from a similar assembly in Project A. File → Utilities → Clone Assembly duplicates the entire assembly under new naming rules, and child parts, WAVE links, and drawings are all auto-relinked.

Default Method: choose Clone, Reuse, Import, Export per part
Naming Rule: add prefix/suffix, character substitution, and auto-generate new Item IDs when integrated with Teamcenter
Replacement Assistant: bulk-manually relink broken links

> Note: Never copy folders with Windows Explorer. Any duplication outside Clone Assembly leaves WAVE links still referencing the original, so unintended edits propagate back to the source.