Wire harnesses have become an integral aspect of vehicle safety and efficiency. Malfunctions such as car stereo problems are always annoying. Hence, the a dramatic increase in quality assurance of automotive wire harnesses. However, the question remains: how does a manufacturer ensure the creation of a high-quality auto wiring harness?
Phase 1: From Design to Production
The car manufacturer provides the wire harness manufacturer a 150% drawing of the on-board wiring design, including any variants of the harness based on any possible options for a certain car model.
The engineers use the wire harness manufacturing, work plan, and corresponding parts list.
Most people know that any activities are done manually, especially under time pressure, so you can expect a high rate of errors.
So, frequent changes aren’t always properly managed and documented in real-time. Of course, manual implementation is contingent on individual working methods.
Since all the aspects mentioned above tend to determine the quality of the wire harness, it makes sense to use a software-controlled planning system.
A manufacturer can use a scripting language to set the production plan rules with such a system. All the guidelines should be flexible to allow easy adjustment.
For instance, it could look like:
If one wire
And 0.35 < cross-section < 6 mm2
Then, use a standard machine
A system reads the automotive manufacturer’s design, analyzes it, and generates production data.
In addition to saving a significant amount of work time, quality advantages are high due to standardizing the implementation procedure and eliminating sources of manual errors.
Also, such software can calculate production documents according to a set just-in-time delivery schedule.
An appropriate wire harness is produced and delivered in time for a certain vehicle in a batch size of one.
Phase 2: The Production of Automotive Wire Harness
Below the ERP level, the work of the MES (manufacturing execution system) is to control and document the production of the automotive wire harness.
However, since wire harness production has several set aspects, one can’t use standard MES (manufacturing execution system).
Such systems will fail, for instance, in the technical IT description of the wiring harness.
Hence, the advantage of various wire harness manufacturers developing individually unique MES systems.
However, such custom-made software solutions don’t work once ERP systems and production processes change.
Another problem is that know-how is frequently undocumented and linked to certain employees.
Therefore, it forces automotive wire harness manufacturers to rely on specifically developed systems for the automotive wire harness industry.
Wire harnesses are produced in three stages: cutting, pre-assembly, and final assembly.
Cutting
Cutting during wire processing is mostly automated. CST machines cut the wires to certain lengths, strip off the insulation, and terminate and seal the wire.
Complex machines can perform additional steps, such as twisting the wires. Once the wires are produced, they’re grouped in a bundle, awaiting the next step of production.
The CST machine is primarily responsible for quality and precision.
However, the MES contributes significantly by transferring control data like crimp data straight to the connected machines.
Also, the MES can ensure quality assurance processes like scanning terminal and wire barcodes, monitoring tool maintenance cycles, and enforcing pull tests and crimp heights.
In addition, an MES assigns unique to every produced wire bundle and continuously manages it throughout its history to enable traceability.
Pre-Assembly
The next step is highly manual. Wire bundles are assembled into kits via twisting, crimping, and ultrasonic welding during the first pre-assembly step.
For each step of the process, the history is updated. Once a kit is produced, it is assigned a new ID and the components in the kit are recorded to complete the history.
Since manufacturers often move their production to countries offering low labor costs, factors are seamlessly built overnight, and they must recruit new employees.
However, the absence of technical qualifications and relevant experience threatens product quality.
Therefore, the MES system must emphasize instructions directly to every employee.
Final Assembly
Employees mount the wires onto the harness boards mounted on moving assembly lines in the final assembly area.
At every workstation, every employee has to perform the correct steps because, generally, harnesses are made to meet certain customer specifications.
The MES controls such complex processes on display monitors that provide detailed instructions on work steps for the employees.
Also, the system can prompt workers to confirm some steps, input relevant QA data, and perform step tests.
Therefore, the system enhances the quality of such manual processes.
Once more, during the final assembly, the history is updated. The complete wire harness now has multiple components recorded in the complete history.
The system tracks which employ machine and tool used to make the components and circuits for every wire harness.
Therefore, manufacturers can backtrack what vehicles have a wire harness made with wires from a certain batch.
Furthermore, it isolates any recall and repair and clarifies the product liability easily.
Quality control managed by the software is important for making auto wire harnesses in highly digitized car technology.
Without this, you can’t guarantee quality for such demanding tasks.
Also, traceability is important to manage product recalls and ensure product quality.
Regular MES systems cannot manage the increasingly specialized nature of auto wire harness production.
Phase 3: Wire Harness Testing
Despite the target application, cables, or wires in the wire harness, testing is an important part of the manufacturing process.
Ensuring the harness was correctly assembled mitigates the risk of field failure with the associated delay, reputation harm, and cost.
Also, it proves compliance with the necessary product quality standards.
Caption: Wire Harness Testing
Manual Testing or Automated Testing
Manual testing is a cost-effective and feasible solution for simple wire harnesses with low-frequency data signals and a few cores for main power.
However, testing increasingly becomes challenging with wire harnesses of significant length, multiple wires and cables, and harnesses that convey high-frequency data signals.
With such harnesses, the number of terminals that could short or disconnect significantly increases, and you have to test more parameters.
Furthermore, the wire harness might have LEDs, Zener diodes, contactors, and other components, not forgetting the cables and wires.
When working on complex wire harnesses, technicians will find it impossible to perform manual tests while maintaining pace with production output, maintaining consistent test accuracy, and finding and fixing any issues discovered during testing.
The solution uses automatic electric testing systems that provide faster necessary testing and greater accuracy.
The Range of Test Typically Performed on Cable and Wire Harness
Resistance measurement and continuity testing are standard functions that check for incorrect wiring, bad joints, faulty crimps, loose connections, faulty components, and wrong wire gauges.
Short circuit testing also finds unwanted connection paths or connections and crossed wires.
Also, testing equipment can provide distance to fault indication, reducing the time it takes to short and open circuit failures.
You can use two wire resistance tests if accuracy up to 0.1 Ohms is enough. If you need higher accuracy, you can use four-wire Kelvin testing.
If you eliminate fixture resistance from your measurement, you can get up to 0.001 Ohms accuracy.
High voltage direct current insulation resistance testing can locate faulty or damaged insulation by measuring the insulation resistance value of every conductor or bunch of connectors.
Also, alternative Hi-pot and high voltage direct current dielectric tests can identify faulty or damaged insulation by measuring the current leakage value of every conductor or group of conductors using high-voltage AC and DC.
Cable capacitance for higher-frequency data transmission can become an issue.
The cable’s natural capacitance plus the driver’s output impedance can create parasitic low-pass filters.
If the cable capacitance is high enough, it could significantly distort the measurement pulse, thus making way for errors.
Accordingly, tests could include checking cable capacitance in twisted pairs, coaxial, shielded, and capacitors/components.
Testing Equipment and Test Management
Modern equipment testing should be capable of accommodating wire and cable harnesses, and this includes fuses, indicators, transistors, transformers, resistors, sensors, diodes, and more, not forgetting electrical devices like contactors, solenoids, actuators, motors, and relays.
You can perform functional testing by simulating active components and detecting or measuring responses.
Automated equipment testing with software-controlled power supplies can accelerate and automate simulation and measurement procedures.
Although the test functions mentioned above are important to the harness tester’s utility, they’re not the only factor.
Conclusion
A quality wire harness is important for autonomous driving and vehicles. Since quality assurance is a rather complex and mainly manual process, using a specialized MES is essential.
For all your quality automotive wiring harness needs, contact Cloom Tech.
