‘Volunteer’ Engineers Tackle Wire Harness Automation
Engineers are using a six-axis collaborative robot to automate assembly steps such as terminal insertion and wire routing.
Automotive wiring harnesses are challenging to automate.
Terminations must be aligned precisely so they can lock into the connector and function properly.
Because of their complexity, wiring harnesses are traditionally difficult to assemble with automation. However, a team of young engineers at the University of Tennessee is tackling the challenge. They’re using a six-axis collaborative robot to automate assembly steps such as terminal insertion and wire routing.
“Wiring harnesses are essential for controlling the electrical components of an automobile and transmitting power to every part of the vehicle,” says Keith Stanfill, Ph.D., P.E., a mechanical engineering professor and director of UT’s integrated engineering design program. “The bundled sets of wires and cables are responsible for air bags, ABS brakes, climate control and engine management.
“Their assembly is one of the most labor-intensive and complex aspects of manufacturing,” explains Stanfill. “Being able to automate the process would help the auto industry with labor shortages, rising production volumes, cost efficiency and quality control.”
An interdisciplinary senior design team at UT was recently tasked with that challenge. They are working with engineers at Nissan Motor Co. to develop a way to fully automate the wiring harness assembly process.
The project features six students from the Tickle College of Engineering and one student from the Haslam College of Business. The engineers hail from several disciplines, including computer, electrical and mechanical engineering.
“The mission of the integrated engineering design program is to increase the number of horizontal and vertical design interactions for engineering undergraduates,” explains Stanfill.
“Horizontal interactions allow students across the University of Tennessee to collaborate in interdisciplinary courses on authentic design challenges,” Stanfill points out. “Vertical interactions provide opportunities for seniors to first-year students within their own discipline to work together on real-world design problems.”
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To graduate, all engineering seniors have to complete a capstone design project. The majority do a project within their own discipline. However, the interdisciplinary senior design (ISD) program provides a way to work with students from nonengineering programs.
“Each team has at least one business student, because all engineering projects ultimately have a business driver behind them,” says Stanfill. “Each group is coached by faculty from the business and engineering schools.”
The projects cover a variety of topics ranging from additive manufacturing to robotic leak detection and e-bike batteries to orthopedic implants. One group of students is currently in the process of analyzing, designing and testing joining mechanisms for use in hypersonic vehicles.
The sponsoring company provides one or more liaisons for the technical and business aspects of the projects. For instance, the wire harness automation team meets regularly with Aaron Hall, an engineer at Nissan’s assembly plant in Smyrna, TN.
“At Nissan, engaging with student teams from the University of Tennessee on real-world challenges through ISD projects offers significant benefits,” says Hall. “It brings fresh perspectives and innovative solutions to our projects, helps us build a talent pipeline by identifying and nurturing potential future employees, and enhances our brand visibility and reputation within the academic community.”
Two ISD teams are currently working on the wiring harness project. One is focused on streamlining the design of connectors, wire cutting and termination for automation. The other group is attempting to fully automate the routing and management of wires during harness fabrication.
The latter team is using a UR10e cobot. In addition, they’re exploring applications that involve force sensors and vision system technology.
The goal for the two teams is to have a fully integrated system with a fully pinned wiring harness ready for wrapping before the students graduate in mid-May.
The engineers started the project by creating a software program that provides the robot with information about where the connectors are located and where the wires need to go. Then, the program autogenerates a path for the robot.
“Both ends of the wires have to be inserted into two specific connectors, but there’s a general path the wire has to follow to make the subsequent taping of the harness easier,” says Stanfill. “The program knows the location of the connectors and the pegs, and [the robot] uses that knowledge to generate an optimal path.”
According to Stanfill, automotive wiring harnesses are challenging to automate for several unique reasons. “Wires are flexible, but robots and other automation systems are optimized for more rigid elements,” he points out. “There are many opportunities for tangling.
“Wiring connectors are also designed to provide acoustic feedback, such as a clicking sound, when terminated wires are properly inserted, requiring a system with precision and compliance to thread the needle and feedback to sense proper insertion,” explains Stanfill.
“The terminations on the wires are tiny and must be aligned precisely so they can lock into the connector and function properly,” says Stanfill. “Operators manually building the harness hear a click when the pin is inserted correctly and feel a minimally perceptible bump.”
Some of the biggest obstacles that the engineers have encountered involve high precision and the repeatability needed for pinning wires into connectors. Other challenges include wire management, and proper staging and alignment of wires prior to gripping with a robotic end effector.
The end effectors were custom designed to grab the terminated ends of precut wires from a staging area and insert them.
“The staging area used by the team required careful pre-alignment of the terminated wires,” notes Stanfill. “A follow-on project team is investigating ways to eliminate the staging area for a more continuous termination-to-pinning process.
“The team stuck with the smallest wire diameters used in the low-complexity cable selected for prototyping,” adds Stranfill. “This cable has 47 wires and seven connectors. There are two different wire gauges used on this harness.
“The biggest lesson learned from the project so far is that automating wire harness fabrication is possible,” says Stanfill. “But, harnesses and connectors need to be designed for automation from the start.
“Reshoring wiring harness production only makes sense logistically and financially if automation is possible,” adds Stanfill.
For more information on automated wire harness assembly, read these articles.
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