Cable harness design: Wire harnesses range in complexity from simple ones with a few individual wires to highly complicated ones with hundreds of wires, connectors, and multi-conductor cables, all combined for data and power transmission.
You may need wire harnesses to conceal behind walls, fit in the electrical box, or for any other purpose.
Whether a wire harness will be functional in an application depends on the cable harness design.
Thus, designs must be customizable to suit the specific application requirements. Let’s learn all about it in detail.
What is the cable harness design?
The designing of the wire harness is mainly a process where an engineer evaluates the requirements of the electrical systems and the space available to assemble wires and cables functionally.
A functional wire harness design connects all components without interfering with other systems needed for the product operation.
Let’s understand this with an example. Suppose you need a wire harness for an airplane. The harness must power all flight controls, landing gears, and passenger comfort devices.
While designing such a harness, an engineer must take into account weight distribution, crew and passenger comfort, mechanical systems, and safe transportation.
The specific process of wiring harness design:
- Before a designer starts designing a harness, he must have all information related to the electrical system’s functioning, electrical loads, location of installation, type of connection between harness and electrical system, etc. An electrical system engineer provides all this information.
- Considering all the functions and requirements, designers create a schematic diagram by putting all the necessary components in place and connecting them together.
- After defining the schematic, the designer creates the harness design. Even in one platform, customers may have different requirements. However, making a separate harness for each user’s requirements is impossible. Thus, while designing the harness, the designer keeps all multiple variants in mind.
- Following this, a 2D design is prepared representing all the wiring connections and wire bundles and shows how they are secured. You can also see the end connections in this 2D representation.
- These designs can interact with 3D tools for importing and exporting data. You can import wire length details from 3D tools while exporting connection details from the harness tool to the 3D tool. With the help of this data, the 3D tool can add passive components in the wire harness designs, such as cable ties, cable lacing, straps, electrical tape, sleeves, conduits, etc., at required locations. Once added, this data is then fed into the wiring harness tool.
Complex wiring harness for car building industry
10 Best practices for cable harness design:
You need to focus on 10 main factors before designing your cable harness assembly.
Know the purpose:
Of course, this must be the first step in any wire harness design and manufacturing. You may need a harness for transmitting electrical or power signals or stereo systems.
Based on your applications, the harness may have specific needs like protection from EMI or reduced vibration, withstanding certain environmental conditions, etc.
Selection of wires:
Before choosing wires, it would be good if you go through relevant standards. These standards let you know what wires suit which applications.
Always pick the right gauge wire, considering the electrical requirements of your application. Based on the amount of current a wire can carry (measured in amps) in an application, a wire gauge is chosen.
Like the wire gauge, wire length is equally important to get the desired results in an application.
Your wire selection must be based on the applications’ environmental conditions. If a wire is exposed to high-temperature conditions, pick one with a high-temperature rating, while a moisture-resistant wire will do in a moisture-laden environment.
If applications demand bending, twisting, or other mechanical stress on the wires, the selected wires must be able to bear that stress. To prevent scraping and rubbing, go for abrasion-resistant wires.
Wire connection:
Connectors are an important component in a wire harness assembly. Their role is not confined to completing the circuits but also protection from EMI, abrasion and other environmental factors.
Factors like electrical and mechanical properties of connectors, wires’ length, gauge & material, circuit size, need for regular connection and disconnection, and insulation should be considered before their selection.
Further, the connectors’ selection depends on whether you are making board-to-wire, wire-to-wire or board-to-board connections.
Also, ensure that the clamping device and other connector hardware you choose are high quality.
Also, we advise you to go for common-use connectors so that you can source them easily.
Routing:
Make sure that all wires are routed to allow easy access for repairs and replacements, but at the same time, installation is also easy.
Further, while routing, focus on any potential EMI components that can interfere with the signal transformation. Segregate twires based on their signal type, voltage, and function to prevent any interference and ensure correct connections to the devices.
Strain relief:
Wiring harness assemblies must be designed for strain relief so that wires and connections do not become loose or break in case of vibrations or any pull force. Strain relief becomes more important in applications undergoing mechanical stress.
Protect your harness assemblies with cable ties, grommets, or cable lamps. The use of protective components depends on the application, its environment, and the harness’s design.
Also, ensure that the material you use for strain relief is chemically and mechanically strong to withstand the environmental conditions.
Wire harness diagram:
Get your wire harness diagram ready at an early stage. You can do it by a wire harness tool like a computer-aided design.
Having the right tool allows you to check voltage drops in real time, improve design quality, and ensure high accuracy.
Such tools also help you identify issues like wire-to-wire interference and wire limitations, which may lead to issues in further stages.
With the design tools, you can optimize your design and create a flexible wire harness while ensuring its structural integrity.
Undoubtedly, such tools also make the designing process faster as they give you access to the fine details of connectors and splices. Allowing you to make changes as and when required.
There is harness design software that helps the designers design harnesses with
- 50% fewer design errors
- 85% improvement in form board design,
- 30% improvement in quote-to-production cycle time.
Protective covering:
Outer protection is the key to the long life of wire harnesses. Always cover the harness with a protective covering or sleeve to protect it from harsh environmental conditions.
The material selection for protective cover depends on the environmental condition.
If designing an engine harness that undergoes fluids, chemicals, and vibration exposure, the protective cover must be able to handle this stress.
Protective covering also differs in type; you can use spiral wraps, pull-on braided looms, heat-shrink sleeves, etc.
Testing:
Keep testing your top priority from the early design stages to the prototype. It will lead to fewer errors and problems during the quality control stage.
You must have all the required equipment to check the electrical integrity of the harness.
Using cloud-based testing interfaces is good for manufacturers as it not only saves time but reduces manual errors.
Essentially, the testing aims to
- Calculate impedance
- Check intermittent connections
- Allow you to set up dual thresholds and limits
Documentation:
Documenting everything you have done so far helps in after-sales service, create technical publications mentioning schematic diagrams, connectors and wires information with their information with their specific location.
Such technical publications help you engineers to make repairs and replacements convenient.
Compliance:
Without compliance with regular industry standards and regulations, your wire harness assembly is of no use. For wire harness assemblies, the industry standard is IPC/WHMA-A-620. If your business has global clients, you may need to follow guidelines from one of these:
- International Electrotechnical Commission (IEC)
- European Committee for Electrical Standardization (CENELEC)
- International Commission for Rules for the Approval of Electrical Equipment (CEE)
multi-wire cables
Challenges in cable harness design
As the electronics in the automobile and other industries are growing daily, the wiring harnesses are becoming more complex, adding to the challenges in the design.
Wire harness designing is a tough, task-oriented and time-consuming task, and if we talk about a globalized design with consolidated platform, the wire harness design faces three main challenges:
- Absence of system integration
- Delayed identification of problems and errors in the physical prototypes
- Limited reuse and inconsistency in data
Problems
When you are working on a consolidated platform, it is essential that all platforms or teams have consistent data, if each will work on its design with its own CAD and EDA tools, the shared data will soon become inconsistent.
And when designs do not match, the resume seems impossible. Also, inconsistent data can lead to delays in time to market (TTM).
Further, the issues detected late during the production make designers return to the first stage and resolve them.
Inconsistencies and design issues usually arise when the designs from the different teams combine into a full and final electrical design.
This merger of designs occurs very late in the production schedule, negatively affecting the delivery time. Also, by then, most of the engineering resources have been consumed.
Sometimes, due to changing industry standards and growing competition among industries, requirements change during the project.
If you need to update any of such requirements at any point, you have to change all the databases and tools, which can lead to mistakes.
One must understand that the probability of problems and errors does not end here, even after a successful merger without any inconsistencies.
There may be issues in the final physical prototype during testing. Resolving these problems can also delay TMM and consume further resources.
How to solve
There should be some continuous system integration method to avoid inconsistent data multiple merge points and reduce overall challenges of the wire harness designing.
Further, it is also essential to use advanced EDA tools for thorough validation and verification before the prototyping step. Laboratory testing should be only for the final system verification.
Conclusion:
Once the final design is ready, the harness manufacturing starts in the manufacturing plants. The process starts with cutting, twisting, and pre-assembling to the final assembly of wires and cables.
Digitization is important for the realization of today’s Industry 4.0; the harness manufacturers’ success depends on their ability to design.
