It was love at first sight. The first time I met a model line I fell in love with it. In 1993 I was on a tour at a grimy car-parts factory in the US Midwest with Toyota TSSC advisors, who exposed me to the concept of the model line, which was pioneered in the late 1960s by Taiichi Ohno and the team he created to spread the Toyota production philosophy throughout the Toyota supplier group in Japan.

At this factory the TSSC team had directed the movement of machines out of process villages to create a cell composed of technologies (molding, paint, final assembly, and test) that did not normally live together. In so doing they had created single-piece-flow with dramatically reduced lead times, reduced cost, and higher quality. This was for one product family amidst the chaos of a mass production facility with many product families.

And yet. In walking around the rest of the factory I noted that nothing else had changed. Work elsewhere proceeded in the traditional way, and did so in a deep dim gloom compared with the one new cell that had introduced bright lighting. The performance improvements in the model line were so compelling that I had mistakenly assumed the plant’s managers would soon convert the entire facility to lean cells. (This, by the way, was my first awareness of the need for yokoten – the spread of a good idea, once demonstrated in one place, across an entire organization.)

In the following years I observed the Shingijitsu consultants from Japan, and many other advisory groups inspired by Shingi, creating model lines in many manufacturing firms to demonstrate the power of lean thinking to clients. These followed on in the tradition of the TSSC model lines and the original lean assembly line that Toyota managers created at NUMMI in California in 1984, which was designed to illustrate the power of lean thinking to General Motors managers in GM’s traditional assembly plants around the world.

I subsequently found the model line concept extended to a remarkable range of activities, including patient flow through primary care facilities and hospitals in healthcare, document processing in financial service firms, permit processing in governments, and applications writing in software firms. In my mind’s eye I envisioned a world where the transition from batches and queues to steady flow and leveled pull would soon be completed.

But instead I have gradually shifted from a model line enthusiast to a model line archeologist. I have often found in my company visits that the model line never spread from the original example, and that in many cases the model itself regressed, with the progressive addition of inventories between steps and even deconstruction to isolated villages. Perhaps the worst case is the sad assembly line for the Model 3 at Tesla (in the same NUMMI building) with its enormous re-work areas, a truly massive retreat from the NUMMI model line of John Shook’s era. Clearly there has been something missing in the lean conversion process.

This missing element turns out to be a complete lean management system, with line management thinking that supports the needs of the model line. As I have taken this insight on board in recent years, I’ve rethought the purpose of the model line.

Rather than simply demonstrating the power of lean thinking, and designed to solve a specific quality, cost or lead time problem, I now see the model line’s highest purpose is to serve as a splendid diagnostic tool that exposes all the problems in modern management systems. Let me give an example from recent experience.

Imagine a large factory assembling a range of product families on a number of assembly lines. And imagine that one of these lines is selected to become a model of lean thinking. In the current state there is a striking lack of repeatable standardized work, an absence of team leaders to support the front line associates, no line balancing of the sequence of machines being assembled (which creates real problems because the labor content for the most complex machine is twice that of the simplest machine), many parts that don’t fit properly due to poor design and that require fiddling by line workers, and very poor reliability of various pieces of automation and test equipment used on the line. As a result, productivity and quality suffer even when the line is able to make the number of machines demanded by customers everyday (usually with considerable overtime and a large number of machines in the rework are at final test.)

Further imagine that this firm introduces repeatable standardized work developed with the production associates, proposes a level schedule with products carefully sequenced to support the standardized work, introduces a team leader system to respond to front-line worker struggles within takt time, addresses part fit issues by prescreening parts to ensure they meet specifications, and repairs all equipment to support smooth flow to meet daily production needs without overtime. In addition, the management introduces visual management in each work station and a daily management walk to look at the visual management boards in each area.

This sounds like a valid model line and for a brief period it may appear to be successful, with lower defects, higher quality, and production of exactly the items requested by customers. But what happens when the line is turned over entirely to traditional line managers and the pre-existing management system reasserts itself?

The locked schedule to permit parts delivery in the right amounts at the right time is unlocked to accommodate “hot list” orders from sales. The parts system cannot respond to this, meaning the balanced sequence cannot be run, and so standard work begins to unravel as workers scramble to deal with imbalances, the off-standard parts reappear, the equipment begins to experience downtime, and team leaders can’t deal with disruptions in a timely manner. Problems (which are listed neatly on the right side of each production control board) pile up but can’t be addressed, and the performance of the line deteriorates steadily toward the original level. Good grief. I nearly screamed as I observed this happening over a period of a few months.

What was needed instead was an understanding of lean management to lock the schedule (which Toyota has always done ten days out from production) and to create a pull system all the way back to production of parts in the supply stream. The problem of off-standard by design parts needed to be resolved through collaboration with product and manufacturing engineering, and team leaders needed the training on methods for introducing temporary countermeasures to deal with problems as they emerge. Finally, a preventive maintenance system was needed to deal proactively with equipment problems and daily management walks needed to be redesigned to immediately address any deterioration in performance.

In short, a complete lean management system was needed to align sales, production control, product engineering, purchasing, and maintenance to support the needs of the final assembly line, where all the sins of modern management emerge for everyone to see (if anyone takes the time to look.)

So the model line in this case has served a critical purpose: to raise awareness of fundamental management problems. The question for the organization in question – and many more like it – is whether the evidence will lead to a fundamental rethink of management. Perhaps I will be able to answer this question in a future Lean Post.

P.S. Tesla is once again in the news. I have offered several times in recent writing for Planet Lean to visit Tesla for free to offer a bit of advice on how to create a model line. But I’ve gotten no response. I see today that Tesla is advertising for 400 new assemblers to staff the new plan for 24/7 operations on the Model 3 line in hopes of producing the long promised 5,000 vehicles per week. So: I’m prepared to do an assembler job for free in return for freedom to offer advice and write about it. At age 69 I would seem to be a bit old for the task. But there seems to be lots of down time at Tesla, so I think I can stand the pace until they act on my advice, transform their management thinking, and get the line to run steadily.