The wire harness set of a modern automobile is the most expensive item in the vehicle after the powertrain, according to SAE 2012 World Congress exhibitor Mentor Graphics (Booth #437), and with today’s extreme pressure to reduce costs, wire harness manufacturing is now the focus of much attention. Mentor Graphics has responded to this need with its Capital Harness Manufacturing Process Management (MPM) software application.
With each harness containing hundreds or even thousands of components assembled via a sequence of operations, wire harness manufacturing is logistically complex. Harnesses must be manufactured in a variety of configurations, reflecting the vehicle’s optional content, and designs often change daily, making the process hard to optimize by experience.
“[Harnesses] are getting larger and larger and getting more content and variability, so managing the complexity of the variability is one of the main things that we do,” said Glenn Reynholds, Engineering Manager, Integrated Electrical Systems Division, Mentor Graphics. “If we built a harness for every variation offered in a vehicle, there would be 50 to 60 million combinations, so you obviously don’t build 50 or 60 million harnesses. A lot of it is about managing that complexity and bringing it down to a level that you can actually build and do those trade-offs, saying if I give away this functionality or that functionality, how can I reduce that complexity to a buildable set.”
Capital Harness MPM helps identify what, where, and how harnesses and their constituent subassemblies should be built. It also helps minimize inventory and obsolescence costs and achieve economies of scale by identifying subassemblies that are common across different harness designs.
“Manufacturing Process Management is about actually building that harness,” Reynholds said. “How do I go about taking that pile of components sitting on the floor and assemble it into a harness, and what’s the sequence by which I do that?”
Every harness design can be decomposed into a hierarchical set of manufacturing steps, each of which consumes components or subassemblies and results in new subassemblies until the finished harness has been built. This process results in a structured bill of materials optimized for the machinery and manufacturing resources available in the factory.
“So it’s taking a flat bill of materials and saying how do I structure this to actually build this thing? To be able to do that, you have to be able to model the capabilities and operations that are available in a factory,” Reynholds said. “Building wire harnesses is this combination of automated and manual labor. An ERP [enterprise resource planning] system is used to drive a factory. Previously, internal systems, spreadsheets, tribal knowledge—all went into making harnesses. What this does is formally model the process by which you go about building it and you basically define the sequence of operations, whether those be performed by a machine or human.”
In addition to the automotive industry, wire harness manufacturing is an area of emphasis in the aerospace and off-highway industries.
“In aerospace, you get into different problems. They don’t have as much variability, but the volume is far greater and how they build them is very different than how you build automotive harnesses,” Reynholds said. “They are much more custom and one-off types of things, and the same thing with the truck industry as well. They are kind of halfway between cars and airplanes. They have a lot of electronics, but they actually build very custom things as well. Very rarely do you see a truck on the road that has the same electronics in it, so managing that level is something we also do.”