Getting Started with Nx for Electrical Harness Design

Electrical harness design is a critical part of many engineering projects, especially in automotive, aerospace, and industrial applications. Siemens NX is a powerful CAD/CAM/CAE software that offers comprehensive tools for designing electrical harnesses efficiently and accurately. This article guides you through the essential steps, best practices, and advanced techniques to use NX for electrical harness design, from initial project setup through to manufacturing outputs.

Before starting, ensure you have the latest version of Siemens NX installed with the Electrical Harness Design module activated. This module is typically included in the NX Electrical Design or NX Manufacturing suites. Familiarize yourself with the interface by opening the Harness application within NX. Key toolbars to locate include Harness Routing, Component Placement, Wiring, and Electrical Schematics.

Planning and Setting Up Your Harness Project

Successful harness design begins with thorough planning. Define the overall parameters before touching the 3D model.

Creating a New Harness Project

Start by creating a new NX part file for the harness. Use File > New > Harness to launch the dedicated harness template. This template automatically enables the relevant electrical design tools. Name your project clearly, e.g., FrontDoorHarness.prt.

Defining System Requirements

When creating a new project, you must define:

  • Harness length – overall length and branch lengths.
  • Number of circuits – based on the electrical load and signal requirements.
  • Connector types – e.g., Molex, Deutsch, or custom inline connectors.
  • Wire specifications – gauge (AWG), color, temperature rating, insulation material.
  • Protective coverings – braided sleeving, shrink tubing, or corrugated conduit.

Import the 3D model of your assembly (the product that will contain the harness) as a reference. Use File > Import > Part to bring in the mechanical envelope. Align the coordinate system so that the harness routes correctly within the assembly confines.

Creating the Electrical Schematic

NX provides integrated electrical schematic tools that are linked directly to the 3D harness model. This link ensures that changes in the schematic automatically update the routing and vice versa.

Building the Wiring Diagram

Use NX Electrical Schematic Design (also called NX Schematics) to create a logical wiring diagram. You can create:

  • Symbols for connectors, splices, and devices.
  • Wire connections between pins.
  • Signal names (e.g., CAN_High, Power_12V).

These schematic elements are stored with the harness part file. When you later route wires in 3D, NX automatically matches the schematic connectivity.

Linking Schematic to 3D Harness

After creating the schematic, open the Harness Routing environment. Use Tools > Electrical > Link from Schematic to import the electrical data. NX will list all wires, connectors, and pin assignments. You can then assign physical component models to each connector from a library or create new ones.

Routing Wires and Cables

Routing is the core of harness design. NX offers both automatic and manual methods to place wires along defined paths.

Creating Path Networks

First, define the route network – a set of connected line segments that represent the desired wire paths through the assembly. Use the Route Path tool to draw lines in 3D, snapping to points, edges, or reference geometry. Key considerations:

  • Set minimum bend radii for wires (e.g., 4x the wire diameter) to avoid sharp kinks.
  • Add clearance constraints to keep wires away from moving parts or heat sources.
  • Use branch points to split the path into multiple legs.

Automatic Wire Routing

NX can automatically route wires along the defined path network based on the schematic connectivity. Use Route Wires to let NX calculate the optimal path for each signal. This is especially useful for harnesses with dozens of wires. You can then manually fine-tune problem areas.

Manual Routing Adjustments

For complex areas (e.g., around a tight bracket or through a grommet), you can override automatic routes. Select a wire and use Edit Path to drag intermediate points, add intermediate points, or apply fixed length constraints. Always verify that manual adjustments don’t violate minimum bend radii or interfere with other components.

Managing Connectors and Splices

Connectors and splices are the backbone of a harness. NX provides dedicated tools to place and manage these components.

Placing Connectors

Use Place Connector to insert a connector model into the harness. You can either:

  • Select from a library of standard connectors (e.g., JST, TE Connectivity) if you have the library installed.
  • Import a custom connector from a separate part file.

Each connector has ports (pins) that correspond to the schematic pins. NX automatically matches the wire ends to the correct ports when routing.

Working with Splices

Splices connect multiple wires together. In NX, you can create inline splices or multi‑way splices. Use the Splice tool to define a shared connection point. You must specify:

  • Splice type (crimp, solder, etc.).
  • Number of incoming and outgoing wires.
  • Physical splice model (if needed).

Splices are represented as special components in both the schematic and 3D model.

Adding Protective Coverings and Ties

Real harnesses include sleeving, tape, and cable ties. NX can model these coverings to produce accurate form‑fit representations.

Applying Sleeving or Conduit

Select a group of wires and apply a Covering (sleeving or conduit). Define properties such as:

  • Material (nylon, polyester, heat shrink).
  • Inner and outer diameter.
  • Start and end locations along the bundle.

NX will create a 3D solid or faceted representation that follows the wire bundle geometry.

Using Cable Ties and Clips

Place clips or cable ties as constraints in the route network. They act as connection points where the harness is fixed to the structure. NX can simulate the clamping force and ensure the harness doesn’t sag.

Validating the Design

Before finalizing, use NX’s analysis tools to catch errors and ensure manufacturability.

Checking Electrical Rules

Run Electrical Rules Check (ERC) to verify:

  • All schematic connections are matched in 3D.
  • No pin is left unconnected.
  • Wire length meets requirements (not too short, not excessive).

Physical Interference Check

Use NX Check Clearances to detect collisions between the harness and other parts. This is critical in tight enclosures.

Length and Bend Radius Analysis

NX can report the length of each wire path. Ensure that wire lengths are within acceptable tolerances. Also, check that all bend radii exceed the minimum specified by the wire manufacturer.

Exporting for Manufacturing

Once validated, NX provides several output formats for manufacturing and documentation.

Generating Flat Patterns

For harness assembly, a flat pattern (nailboard) is often required. NX can flatten the 3D harness onto a 2D drawing using the Harness Flat Pattern command. This produces a true‑length representation with connectors, splices, and measurement annotations.

Creating Wiring Reports

Export a wiring list or from‑to report as a CSV or Excel file. This helps the manufacturing team know exactly which wire goes where.

3D PDF and Step Files

For collaboration, export a 3D PDF or a STEP file of the harness. This can be shared with suppliers or assembly operators who do not have NX.

Advanced Techniques: XML Authoring and Capital Harness Integration

NX allows advanced users to define harness logic using XML authoring, and it integrates with Siemens’ Capital suite for end‑to‑end electrical system design.

XML Authoring

The NX Electrical XML Authoring tool enables you to create custom wiring rules, component libraries, and connectivity logic in XML format. This is useful for large‑scale design automation where standard GUID generation is required. You can define:

  • Unique GUIDs for each harness component.
  • Custom attributes (e.g., supplier part number, cost).
  • Rules for automatic assignment of wires and connectors based on signals.

Integrating with Capital Harness

Siemens Capital Harness is a dedicated electrical design platform. NX can import and export harness data to Capital using the Capital XML exchange format. This allows you to maintain electrical logic in Capital while using NX for the 3D mechanical routing. The integration ensures that any design change in Capital (e.g., adding a new signal) is reflected in the NX harness.

Real‑World Example: Automotive Door Harness

Consider a typical car door harness containing wires for windows, speakers, locks, and mirrors. Here is a step‑by‑step workflow:

  1. Import mechanical assembly: Load the door sheet metal, glass run channel, and speaker bracket.
  2. Create route paths: Snap paths along the door inner panel, going through grommets at the door hinge.
  3. Place connectors: Insert a 20‑pin connector at the door hinge (body side) and a 10‑pin connector at the window motor.
  4. Wire routing: Use automatic routing for ~30 wires. Fine‑tune positions near the window mechanism to avoid pinching.
  5. Add protective sleeving: Apply corrugated conduit on the bundle that crosses the hinge (high‑flex area).
  6. Validate: Run clearance check – ensure no wire touches the window glass edge. Run length check – adjust a couple of wires that were too short.
  7. Export flat pattern: Generate a nailboard drawing for the assembly line, including connector callouts and wire length labels.

Best Practices for Efficient Harness Design in NX

  • Standardize libraries: Create reusable connector libraries and wire definitions to avoid re‑entering data.
  • Use design layers: Separate schematic, 3D routing, and covering details into different layers to improve performance and clarity.
  • Leverage templates: Start new harness projects from a template containing predefined routing paths, common connectors, and cable tie intervals.
  • Perform incremental checks: Do not wait until the end to run validations – run ERC and interference checks after every major routing step.
  • Collaborate via Teamcenter: If using Siemens Teamcenter, store harness data there to enable concurrent engineering and version control.

Conclusion

Using Siemens NX for electrical harness design streamlines the process, improves accuracy, and facilitates collaboration when correctly applied. By mastering the routing, component placement, wiring documentation, and validation tools, engineers can create efficient and reliable harnesses for complex assemblies. The integration with schematic design, flat pattern generation, and external tools like Capital Harness further extends NX’s capabilities. Adopt the practices outlined in this article to reduce design time, minimize errors, and deliver production‑ready harnesses.

For more detailed instructions, refer to the official Siemens NX documentation on Electrical Harness Design and explore the Siemens NX Community Forum for tips from other users.