Overcoming the final barrier to full automation: the wiring harness

Electrical and electronic products have been at the forefront of manufacturing automation for decades, but one important factor has stood in the way of full automation for many of these products: the need for wiring harnesses. Wiring harnesses are still mostly made by hand. This raises issues of cost, consistency of quality, and robustness of supply chains. Manual work goes where it costs the least, and managing the subsequent supply chain issues adds further cost and risk. The war in Ukraine has recently brought supply chain problems to the fore, constraining the ability of European car makers to meet their market demands.

Business drivers of wiring automation

The wire harness market will be worth $200 billion by 2031, according to Transparency Market Research. Growing demand is driven by growing electrification in cars, aircraft, domestic appliances, industrial automation, and everything IoT. In all these applications and more, circuit complexity is increasing, so anything that automates the interconnection between electrical functions has the potential to deliver significant productivity increases. Cost reduction will be just one of the benefits. If OEMs and contract manufacturers can automate the wiring aspect of products, they can shorten supply chains, reduce their reliance on third parties, and take direct control of product quality and consistency.

The reliability challenge

Traditional wiring harnesses are flexible, making them susceptible to wear and tear. Also, they are rarely fixed in position along their entire length, so damage may result from metal fatigue in conductors or from chafing of insulation. The U.S. Department of Transportation cites electrical systems as one of the leading causes of vehicle recalls in 2022. An earlier analysis of data for the US Navy found that chafing was the leading cause of wire harness failure in its aircraft between 2000 and 2004. Shortly before that, in the late 1990s, they estimated that wiring problems cost them $94 million annually and that chafing caused one-third of the problems. So, in addition to saving costs during manufacture, wiring automation has the potential to deliver considerable cost savings over the operating life of products by minimizing these reliability problems.

Figure 1: Wiring harnesses are heavy, expensive to produce, and often unreliable.

Why weight matters

Wiring harnesses are heavy, and the need for individual wires to be insulated is a major contributor to this. If wiring is embedded into products and fixed rigidly in place, bare wires will often suffice. Weight is a key consideration for aircraft and an increasingly important one for road transportation as the world moves away from internal combustion engines. Many countries are committed to phasing these out by 2040. ?

Electric vehicles are the leading alternatives. These are demanding from the power and connectivity perspectives as carmakers add features to differentiate their offerings and then need to manually compress more wires into the limited space available. At the same time, the battery capacity limitations of electric vehicles mean that weight reduction is a key design consideration. Lower weight means greater driving range before a recharge is needed. This is important because range anxiety is often cited by consumers as a reason to delay their purchase of electric vehicles.

Early attempts to address wire harness problems

Not surprisingly, there have been several attempts to address the issues outlined above. Laser direct structuring (LDS), printed circuit boards, and large-area flexible conductors have been explored for more efficient wire harness production. But success has only been achieved in limited applications and none of these methods automate the entire production process.

Can 5-axis robotic manufacturing cells provide the answer?

Using a newly-developed 5-axis robotic manufacturing cell, an innovative new approach to wire harness automation involves laying down conductive tracks on vehicle components and appliances. It integrates wire harnesses within the products so that harness manufacture and final assembly are both automated as an integral part of an additive manufacturing process.

The steel-framed robotic cell, which is 2.3 wide, 2.17m long, and 2.32m high, has a working area of 1m x 0.3m and its high-speed, 5-axis operation has demonstrated manufacturing productivity improvements of between five and ten times, compared with manually adding conventional wire harnesses to products.

?Figure 2: This 5-axis robotic cell seamlessly adds wiring automation to additive manufacturing.

It can install bare conductors up to 3.00mm in diameter, which can carry up to tens of amps of current, or insulated wires. The wires can be held in place by channels or wire traps, both of which are created as part of a polymer deposition, additive manufacturing process. Furthermore, the combination of wiring placement and 3D additive polymer deposition facilitates customization without excessive tooling costs.?

?Figure 3: Bare copper or insulated wires are accurately affixed throughout their length into even the most complex shapes

This promising new approach to automated wiring, called electrical function integration, makes it faster and easier to add components to complex shapes, such as the drill body shown in Figure 4. At the CAD/CAM stage, digital twins are employed to give designers the freedom to experiment with their products and to maximize the speed at which wiring can be designed for integration into parts. The digital twins also facilitate fast and accurate customization of components, giving OEMs opportunities to differentiate their products and services within their chosen markets.

Figure 4: Application example: an electric drill casing could be automatically manufactured complete with embedded electrical wiring.

Electrical function integration has been in development for several years, but the first commercially available manufacturing cells are due to be launched in June this year (2023).

For OEMs and contract manufacturers, the technology looks set to deliver lower costs, improved product reliability, fewer supply chain challenges, and greater design flexibility than ever before. Manufacturing automation could be about to take a big leap forward by ditching one of the few remaining manual processes that have hindered the efficiency and effectiveness of the production of electrical components and systems.?