For some electrical assembly and wire harness applications, exposure to vibration is minimal. For those engineered to operate within heavy duty vehicles, however, the high RPMs, rough terrain and other conditions under which they operate can cause extreme vibration and chafing over time, leading to potential electrical failure. If not detected early in the design phase, speed to market can be impacted, or worse; a product can get to market and experience significant breakdowns.
While reducing an assembly’s exposure to harsh environmental conditions should be considered, it may not always be an option. Minimizing the impact of vibration in electrical assemblies can be achieved, however, through proactive measures taken during the design and testing phases by assessing the following areas.
1. Materials and Insulation
Choosing proper wire materials will not only help ensure compliance with regulatory requirements such as UL, CSA or CE, it will also minimize failures. With myriad variances among materials including voltage ratings, bare or plated copper and more, knowing which will stand up to abusive environments requires expert knowledge and testing data. Some applications are better suited to commercial off-the-shelf parts (COTS) and can save significant time and money. Additionally, approved COTS parts have been tested for reliability, so there are some assurances that they will meet with compliance and performance expectations.
The type of wire covering also plays a critical role in protecting an assembly from the persistent wear and tear of vibration. Some insulation materials are more prone to cracking under stress and they should be avoided for components that are susceptible to prolonged vibration exposure. Select materials that are less rigid and can stand up to harsher conditions. Identifying appropriate materials can be a challenge, so consider seeking input from an outside engineer or designer experienced in designing electrical assemblies for critical use applications.
2. Routing and Configuration
Even with proper insulation, chafing can occur if wires aren’t properly routed. As more features and complex technology are integrated into instrument panels and under the hood, the need for more electrical wiring increases while the allowable space to house it decreases, making proper wire routing a major challenge.
If wiring is routed in an area where chafing of the protective wire insulation is allowed to occur, it can cause a short circuit and the potential ignition of surrounding materials. Such a fire can be a major safety hazard and result in the catastrophic loss of a vehicle. Make sure that wire harness configurations do not rest on surfaces exposed to excessive vibration and that bend radius installation issues are avoided. Also consider how exposure to particulates, grime and dirt over time can cause build up of debris on nearby surfaces and eventually come into contact with wires.
Allowing just the right amount of tension that falls within strict compliance regulations is a must when designing a wire harness or electrical assembly for critical use applications. Appropriate tolerances will help ensure that components and wiring won’t deteriorate under certain conditions. Those who specialize in designing and manufacturing assemblies use automated wire tensioning and cutting systems to ensure consistent results that are compliant with specific industry standards.
Sometimes the least expensive component can play a major role in preventing wear. Something as seemingly insignificant as choosing the right clamp or connector can spell the difference between failure or functionality. If a coupling is too large, excessive bending and eventual breakage can occur during repeated movements; too small, and wires can become pinched. In addition to choosing the right connectors, make sure you allow for proper spacing and placement of clamps and other harness restraint devices.
We’ve only touched on a big picture view of what goes into preventing abrasion from excessive vibration in electrical assemblies. There are many other considerations when designing an electrical assembly, and preventing failure starts before the pen hits the paper. Work with qualified electrical engineers that have experience with heavy duty vehicles and can perform a design analysis to help you mitigate the risks associated with vibration on electrical systems and improve your speed to market.