Toyota is one of the the most visionary car makers with respect to its manufacturing. They continuously and radically evolve and update their production system. Recently I learned about their new “flexible assembly line.” Now, you’ve probably heard about Toyota’s flexible assembly lines producing multiple products on the same line. That is old hat; they’ve done that for thirty years. Their new flexible assembly line involves a completely different aspect of flexibility, with which Toyota surprised me (again). Let me show you …

Introduction

Toyota continuously evolves and changes its production system in a way that is more frequent, more radical, and more successful than its competitors.

They already have the ability of doing lot size one on their production line. The ability to produce multiple car models on the same assembly line in any sequence without set-ups was a radical new idea when it started with Toyota in the 1960s, but nowadays it is industry standard, although some major car makers still prefer batch sizes of more than one (e.g., the Honda Sayama plant).

I have previously written on how Toyota split its assembly line layout into smaller segments and how it changed its shift schedule to make the work easier for its workers. I was quite surprised by how radically they push for lot size one, including aluminum casting in lot size one on demand.

Currently they are implementing their Toyota New Global Architecture (TNGA). They realized that they had around one hundred different subplatforms on which to build vehicles, and eight hundred different variants of engines (based on sixteen models, but blooming out into eight hundred variants). Now they are taking major steps to reduce this multitude of products using TNGA.

Their first car based on this TNGA is the 2015 fourth-generation-model Toyota Prius. By 2020, they want to switch half of their models to TNGA. Currently, there are three variants of this platform, GA-L (for “long-mounted engines”) and GA-C and GA-K (both transverse-mounted engines). They work together with Mazda, which is considered to have the best platform approach worldwide with their Skyactiv approach.

This is all very exciting, but today I want to look at how Toyota is changing its assembly line (again). First of all, it is a bit difficult to find a good name. Toyota calls it a “flexible assembly line” in English (more on that later), but the word flexible is heavily overused nowadays and most people think of flexible assembly lines as mixed-model assembly. But before I go into what Toyota does, let me introduce the idea using easier examples.

Flexibly Configurable Assembly Lines

The basic idea is to have an assembly line that can be moved around, rearranged, and reconfigured on short notice. The idea itself is not new, and I have seen it many times in industry for work cells and chaku-chaku lines. Since the workstations are on wheels, they can simply be unplugged and moved if the product lineup changes, if demand requires an increase or decrease in capacity, or if a new arrangement is simply more efficient. Many of these lines were automotive suppliers. Since car manufacturers like to have a tight grip on their suppliers, sometimes the biggest challenge was to have the customer accept that the line may change without an expensive re-certification of the quality by the customer.

One non-assembly example would be some Japanese supermarket checkouts. As shown below and explained in a previous post, they have one or two workers manning a cashier station. If there is high demand, they have two people for higher throughput; if there is low demand, it is only one. To keep the station at a good size, they have the cashier on wheels.

Flexibly Configurable Automotive Assembly Lines

Now, it’s one thing to roll around a supermarket cash register, but it is a completely different task to do this with an automotive assembly line including all its material flows. Yet, automotive companies in Japan have done it.

Toyota developed what they call a “flexible assembly line” in 2010. However, there is a lot lost in translation from the original Japanese name 伸縮自在な組立ライン (Shinshuku jizai na kumitate rain). The first part means not only “flexible,” but also “elastic; telescoping; expandable; retractable; extensible.” “Expandable” and “extensible” fit the intended meaning much better. It is also part of the TNGA, which not only includes the new platform but also technical improvements and new manufacturing approaches and methods.



Mitsubishi in their Okazaki plant developed a similar concept called Tatami Conveyor (畳コンベア ), where all equipment is also placed on the floor. Even overhead body assembly is done using floor-mounted supports.

But let’s start with the basics. The image below shows a model from the Toyota Kaikan Exhibition hall, displaying a conventional assembly line. You can clearly see a lot of overhead structure. Not visible but also there are structures in the ground, especially railings, markings for the AGV, and space for turntable gear.

The second picture below shows the new type of line. All of the overhead structures are missing. Also gone are most underground structures. The numbered items are described below the image.

Collaborative robots working together with humans. Tapeless automated guided vehicles. Rather than following markings on the floor, these AGV have a navigation system (not in the picture). Solar power is used for some signal lamps and wirelessly connected computers, making the devices easy to move (the number is not visible in this shot, as it is behind the seats on the left). Rail-less transport turning equipment. The carts no longer sit on rails but move directly on the floor. Turntables for changing the direction of the car bodies also sit on the floor rather than in an excavated hole. Air conditioning towers direct air rather than overhead tubes. Call switches (andon lines) are now wireless buttons directly on the carts of the workers. All assembly equipment is floor based rather than hanging from overhead. Much of it is on rollers for easy moving.

Toyota already implemented this in its Tsutsumi plant near Nagoya in 2015, and they now want to implement it in all new plants. Below are two still images from a video at the Toyota Kaikan from the Tsutsumi plant. The left shows the assembly line before extension, the right after the extension. The entire change happened over a weekend.

Additional improvements are a much smaller and more energy-efficient paint shop, and a new type of laser welding that is faster than before (laser screw welding). Injection molding machines are able to change tools so quickly that they sit close to the line and produce parts just as they are needed in any sequence, followed by painting in the desired color. Lot size one is used for injection molded bumpers.

Why Do They Do It?

The overarching goal of Toyota is to reduce investment in new lines by 40% to make them “simple and slim.” The resulting plants should also be 25% smaller. There are also a lot of sub-goals.

Lines can be extended and reduced easier if the demand goes up or down, or if new features are added or removed (i.e., the work content changes). Of course, they still need the empty space to put the line, however. You may also be wondering why they don’t just make a long line and idle some stations if they are not needed. Toyota hates excess inventory, and if these four or so vehicles at these stations are not needed, Toyota would prefer not to have them there. This reduces lead time and also makes for easier communication.

Overall, the line is easier to change beyond a mere extension. If some stations need to be added in the middle, everything else is just moved a bit.

It increases reliability. Toyota assembly lines already have a utilization of 95% or more, but occasionally a robot or a machine breaks down. In the old line, this would have stopped the line until the problem is fixed. With the new line, they simply move the robot aside and human workers can take over. While this increases the work, Toyota has such manpower available, and the line keeps running.

The reduced overhead structure allows a better use of natural light, reducing the electricity consumption.

Heating, cooling, and general energy consumption is reduced, reducing the carbon footprint too.

The new lines are cheaper than the old ones.

Does It Work?

Toyota claims that these lines are significantly cheaper than the previous ones. Now, such claims are easy to make. Most improvement projects claim success even though the actual benefit does not always come true. In this case, however, it seems to work.

Tsutsumi in Japan and Georgetown in Kentucky both produce Camrys. Japan has a labor cost very similar to the USA (hourly compensation costs 2012 Japan 35.34 USD, USA 35.67 USD). The South in the USA is about 10% cheaper than the average, which was one of the reasons why Toyota moved there. Overall, labor cost in Kentucky is probably around 10% less than in Japan. A Camry produced in Tsutsumi and shipped to the United States has the disadvantage of the increased labor cost and the shipping cost compared to Georgetown. It should be a no-brainer that Camrys for the US market should be produced in Georgetown.

Not so. Toyota issued an advanced warning to the Georgetown plant that despite their labor and shipping advantage, Tsutsumi can deliver Camrys cheaper to the United States than Georgetown can make them in the United States. Georgetown will have to improve its costs to stay competitive.

In sum, Toyota has changed the game again. This is what probably amazes me the most about Toyota, that they are able to constantly challenge the status quo, question conventional wisdom, and have a good sense of the right direction. I hope you are also able to see such things for your own area of responsibility. Maybe my blog can even help you a bit with this. Now, go out, challenge the status quo, question conventional wisdom, and organize your industry!