Mixed-model Assembly
Assembly Line
Toyota Reveals Future EV Production Strategy
During the automaker’s most recent earnings announcement last week, Yoichi Miyazaki, chief financial officer, briefly explained how the strategy will reduce Toyota’s parts count by 35 percent while adding 35 percent more floor space at its assembly plants. The aim is to maximize flexibility and mixed-model assembly, while minimizing costs to avoid over-investing in electric vehicle production.
“Our goal is to shorten lead times companywide,” said Miyazaki. “To achieve this, among other things, we need to eliminate waste, end redoing of work and make it possible for anyone to get their job done.
“Specifically, amid a shortage of human resources, we have been working companywide across divisions and functions to create environments in which anyone can work and to improve what we call the ‘rate of value-added work,’ which is the ratio of work that is truly meaningful and that increases added value.
“There are two main things we want to accomplish,” explained Miyazaki, “The first is to increase how quickly we can respond to environmental changes in an age in which it is hard to predict the future. The second is to improve our fundamental capabilities that will enable us to carry on into the future “Toyota’s philosophy of ‘leaving no one behind’ and ‘producing happiness for all,’ even as advances in vehicle functionality mean that full-lineup, multi-pathway car making is not easy. As a specific example, we are currently advancing what we call within Toyota ‘Area 35’ project, which aims to improve our rate of value-added work through integrated efforts involving development, production and sales.
Mixed-Model Lines Enable Multiple Power Train Configurations
Mixed-model automotive assembly plants must have the workstations, tools and components necessary to efficiently build hybrids in the same facility as electric and internal combustion engine (ICE) vehicles. However, assembling cars with different power trains is much harder than making multiple types of pens, syringes or toothbrushes on the same assembly line. Mixed-model assembly lines typically also need to be laid out differently than lines that only produce one type of vehicle.
“Mixed-model assembly is used regularly across industries, most notably the discrete electronics industry where products such as smart phones with multiple form factors and internal configurations are manufactured,” notes Khalid Sebti, executive vice president and managing director of Capgemini Engineering. “Use in the auto industry is different, but not necessarily more complex, due to designs shifting to multi-use platforms to accommodate different power train options.
One complex problem that Porsche had to solve involved fastening. The marriage of a gas or hybrid vehicle requires the underbody and chassis to be screwed together in 20 places. However, in the all-electric variant, there are 50 joints that need to be tightened. Porsche engineers developed an automatic screw loading system that, depending on the product line and fittings, can handle any screw size and shape, torque and angle at high speeds. A measuring device regularly passes along the assembly line to check the screw spindles during ongoing production operations. As a result, there are virtually no idle times or delays.
How do you produce three drive types on a single assembly line?
This is what’s called the marriage. Wherever vehicles are manufactured, this is the centerpiece of production. So far, so good. But the marriage at the Porsche Plant Leipzig is special. Unusually complex, multifaceted, and efficient. Three different drive concepts are manufactured on a single production line: gasoline-driven, hybrid, and electric vehicles. Some 600 Macan and Panamera cars are produced in top quality in this way every day, for customers around the world.
One especially complex problem: whereas the marriage of a gasoline-driven or hybrid vehicle involves the vehicle’s underbody and chassis being screwed together in 20 places, there are 50 in an all-electric model. While this change may seem unspectacular at first, it involved the major challenge of handling these additional work steps on one and the same assembly line.
To solve this problem, Sebastian Böttcher and his team had to reinvent the marriage. What was previously four assembly stations stretching across 24 meters became nine stations across 60 meters. Six additional robots and 18 automatic screw stations were incorporated.
Ford Focuses on Flexibility
Another Ford plant that’s located just 17 miles away from the remnants of the Highland Park facility represents the future of auto manufacturing. The 4-million-square-foot Michigan Assembly Plant (MAP) in Wayne, MI, is Ford’s showcase for flexible, green, lean manufacturing.
Engineers transformed an old plant that once made large sport utility vehicles (SUVs) into a state-of-the-art factory that assembles fuel-efficient small cars. Ford invested $550 million to make the 60-year-old complex the first assembly plant in the world capable of building a full line-up of vehicles on the same line. Thanks to an integrated production strategy, MAP assemblers build three different types of electrified vehicles alongside traditional gas-powered cars.
New tools and equipment, coupled with world-class quality standards and a revised lean production philosophy, allow Ford to make small cars profitably while adjusting production volume and production mix based on market demand. Reprogrammable tooling in the body shop, standardized equipment in the paint shop and a common-build sequence in final assembly make MAP Ford’s most flexible plant.