The Principle-Stopping the Process to Build in Quality (Jidoka)
Jidoka, the second pillar of TPS, traces back to Sakichi Toyoda and his long string of inventions that revolutionized the automatic loom. Among his inventions was a device that detected when a thread broke and, when it did, it would immediately stop the loom. You could then reset the loom and, most importantly, solve the problem to avoid repeating the defect (waste). Like many elements of TPS, a simple invention and simple idea led to profound and broad insights. Quality should be built in. This means that you need a method to detect defects when they occur and automatically stop production so an employee can fix the problem before the defect continues downstream. One of the leading American students of TPS, Alex Warren, former Executive Vice President, Toyota Motor Corporation, Kentucky, defined jidoka and how it relates to employee empowerment:
In the case of machines, we build devices into them, which detect abnormalities and automatically stop the machine upon such an occurrence. In the case of humans, we give them the power to push buttons or pull cords—called “andon cords”—which can bring our entire assembly line to a halt. Every team member has the responsibility to stop the line every time they see something that is out of standard. That’s how we put the responsibility for quality in the hands of our team members. They feel the responsibility—they feel the power. They know they count.
Jidoka is also referred to as autonomation—equipment endowed with human intelligence to stop itself when it has a problem. In-station quality (preventing problems from being passed down the line) is much more effective and less costly than inspecting and repairing quality problems after the fact.
Lean manufacturing dramatically increases the importance of building things right the first time. With very low levels of inventory, there is no buffer to fall back on in case there is a quality problem. Problems in operation A will quickly shut down operation B. When equipment shuts down, flags or lights, usually with accompanying music or an alarm, are used to signal that help is needed to solve a quality problem. This signaling system is now referred to as andon. Andon refers to the light signal for help.
While it may seem obvious that you should catch and address quality problems immediately, the last thing management in traditional mass manufacturing would permit was a halt in production. Bad parts, when they happened to be noticed, were simply labeled and set aside to be repaired at another time and by another department. The mantra is “produce large quantities at all costs and fix problems later.” As Gary Convis, President of the Toyota, Georgetown factory, explained to me:
When I was at Ford, if you didn’t run production 100% of the shift, you had to explain it to Division. You never shut the line off. We don’t run 100% of the scheduled time out here. Toyota’s strength, I think, is that the upper management realizes what the andon system is all about …. They’ve lived through it and they support it. So in all the years I’ve been with Toyota, I’ve never really had any criticism over lost production and putting a priority on safety and quality over hitting production targets. All they want to know is how are you problem solving to get to the root cause? And can we help you? I tell our team members there are two ways you can get in trouble here: one is you don’t come to work, and two is you don’t pull the cord if you’ve got a problem. The sense of accountability to ensure quality at each station is really critical.
So here we have a paradox. Toyota management says it is OK to run less than 100% of the time, even when the line is capable of running full-time, yet Toyota is regularly ranked among the most productive plants in the auto industry. Why? Because Toyota learned long ago that solving quality problems at the source saves time and money downstream. By continually surfacing problems and fixing them as they occur, you eliminate waste, your productivity soars, and competitors who are running assembly lines flat-out and letting problems accumulate get left in the dust.
When Toyota’s competitors finally did start using Toyota’s andon system, they made the mistake of assuming that the line-stop system was hardwired to each and every workstation—push the button and the entire assembly line comes to a screeching halt. At Toyota, the andon in all of its assembly and engine plants is called a “fixed-position line stop system.” When an operator in workstation five pushes an andon button, workstation five will light up in yellow, but the line will continue moving. The team leader has until the vehicle moves into the next workstation zone to respond, before the andon turns red and the line segment automatically stops. This is likely to be a matter of 15-30 seconds on an assembly line building cars at one a minute. In that time, the team leader might immediately fix the problem or note it can be fixed while the car is moving into other workstations and push the button again, canceling out the line stoppage. Or the team leader might conclude the line should stop. Team leaders have been carefully trained in standardized procedures on how to respond to andon calls.
The assembly line is divided into segments with small buffers of cars in between (typically containing seven to 10 cars). Because of the buffers, when a line segment stops, the next line segment can keep working for seven to 10 minutes before it will shut down, and so forth. Rarely does the whole plant shut down. Toyota achieved the purpose of andon without taking needless risks of lost production. It took U.S. auto companies years to understand how to apply this TPS tool. That may be one reason why workers and supervisors were hesitant to stop the line—because it actually stopped the entire line!
The built-in quality created by jidoka has never been more important to Toyota than with the Lexus and the necessity of meeting the extremely high expectations of Lexus owners. Until recently, Lexus vehicles were built only in Japan, where the culture and quality systems are undisputedly world-class. But can a Lexus be built in North America and still maintain the unbelievably meticulous levels of quality customers have come to expect? The answer is yes and it is being done in Toyota’s Cambridge, Ontario, facility. Among the innovations used to maintain this “pursuit of perfection” are some technologies and processes that are taking andon to the next level.
Ray Tanguay, President of Toyota Motor Corporation, Canada, knew that the bar was now higher as he moved from making the Toyota Corolla and Matrix models to the Lexus RX 330. There are many innovations designed into the people, processes, and technologies of the new Lexus line to ensure that Lexus buyers will get Lexus quality. For example, production tools and robots on the line have been designed with built-in sensors to detect any deviation from standard and use radio transmitters to send an electronic signal to team leaders wearing headphone sets. Since not every problem can be caught in process, there is a highly detailed 170-point quality check for every finished RX 330. Tanguay wears a Blackberry personal digital assistant on his belt wherever he goes and every time an error is found on a finished vehicle, a report is instantly sent to Tanguay’s Blackberry, along with a digital photo of the problem. Tanguay can transfer the photo to an electronic billboard in the plant so huge displays can be seen by workers and they can be cautious to prevent the same mistake from occurring. While the technology is new, the principle is the same: bring problems to the surface, make them visible, and go to work immediately on countermeasures.