The Essential Guide to Wire Harness Manufacturing Process

By Mer-Mar Electronics Date posted: Last updated: February 22, 2022
Wire Harness Manufacturing Process

Wire Harness Manufacturing process is an extremely specialized process that involves several measured steps. Before we get into them, let us look at the difference between a cable assembly and a wire harness.

Simply put a cable assembly is an external connection to devices and needs to take into account factors such as:

  • Thickness
  • Flexibility
  • Type of insulation

A wire harness, on the other hand, offers connectivity between systems in an electromechanical assembly. Wire harnesses are built on panels that has pegs. The harness, therefore, is laid out to bespoke dimensions. It is important to remember that the more detailed and precise the specifications, there will be fewer issues on the assembly floor. Some of the information that the contract manufacturer will require in order to build the wire harness, includes:

  • Connector images with pin locations
  • Wire lists
  • Detailed BOM with part numbers
  • Assembly drawing
  • Test specifications

Best Practices in Wire Harness Design

The benefits of good wire harness design includes the fact that it improves the service life of wires, optimizing the space required for wires, organizing all wires in one place for easy access. It is imperative therefore that best practices be followed when it comes to wire harness design.

Some of the best practices in wire harness design include:

  • Identifying problems that could be posed by the physical environment such as moisture, temperature, electrical interference and more.
  • Choosing the correct routing option.
  • Ensuring that exact measurements are adhered to when it comes to cutting wires and calculating the bend radius.
  • The harness must fit correctly in the space it is intended for. It is important, therefore, to take the size of the outer protective casing into account.
  • The type of terminals and how they fit into the wire radius is also an important design decision.

Important Steps in the Manufacturing Process to Build Your Wire Harness

The broad steps followed by contract manufacturers to build a wire harness include:

  • Robust design review – Basis your design, the contract manufacturer will examine the entire documentation and Bill of Materials to see that everything is in place.
  • Preparing the material – Post finalization of the Bill of Materials, the components and materials required for production and test of the harness are purchased.
  • Assembly documentation – The Contract manufacturer will also create a detailed Assembly Documentation including:
    • Assembly steps
    • Images
    • Test procedures.
  • Prototype – Typically before producing the wire harness, the contract manufacturer creates a prototype. This helps to perfect the assembly and to ensure that the quality expectations are met.
  • Production of Wire Harness – The building of the wire harness involves cutting the wire to length and laying it on the assembly panel. The next steps involve adding connectors, tying bundles of wires and attaching labels.
  • Testing – A detailed testing protocol is finally undertaken. The harness is checked for a number of issues including:
    • Construction
    • Labeling
    • Checked for usage on-site

Dos and Don’ts to be followed in building the Wire Harness:

Below are some of the tips to be followed when it comes to building the wire harness assembly:

  • The termination recommendations for attaching the wires need to be followed. The recommendations could be in the form of stripped and bare or stripped and tinned.
  • Similarly, the recommendations for torque values on fasteners need to be followed.
  • Generic specifications for wires such as 300V or 600V need to be adhered to. It is best not to give the contract manufacturer a specific UL code. That way the contract manufacturer can use wires that fit the requirement, are available and that are cost-effective.

As a thumb rule it is imperative that you work with the contract manufacturer from the early stages of development so that the electronic contract manufacturer can help with the selection of best performing parts. Additionally, it is advisable to go with a contract manufacturer that has experienced engineers with the necessary expertise who are equipped with industry best practices so that you do not land up making any costly mistakes in the wire harness manufacturing process.

Mer-Mar Electronics has been in the business for over 40 years and has a skilled & experienced engineering team who works on different design systems. Our manufacturing experts build your PCBs, cable assemblies, wire harnesses, and more. In case if you have any questions or require more information about cable and wire assemblies services, get in touch with us via or call us on (760) 244-6149.

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