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Michael Balle

Michael Ballé: Takt time is a thinking device to combine flexibility and productivity

By Michael Balle, co-author of The Gold Mine and The Lean Manager - Last updated: jeudi, février 23, 2012 - Save & Share - Leave a comment

As time goes by fact becomes legend and legend becomes myth. Takt time is one of the core concepts of lean, which origins are now misted in myth – uncertain and unknowable, but thought-provoking anyhow. Legend has it that Ohno hit upon Takt time thinking when trying to improve productivity. Toyota was assembling trucks for the US army, and Ohno realized they’d spent three weeks in the month getting all parts in and then producing like crazy for the last week they started again. He figured out that rather than be an end-of-month company, if they were a end-of-day company they could triple productivity. Takt time was originally a device to make all the parts supply processes move at the day rhythm. The important aspect of this just so story is that Takt here is linked to productivity.

Another legend has it that Toyota (and other automakers) did really well in the fifties because the Japanese engineers trained by German engineers for the production of war plane during WWII migrated to the two second-most interesting industries: building ships and building cars. “Takt” therefore supposedly is a local interpretation of cycle time in Kiichiro’s Toyoda just-in-time frame: the pace at which the market takes a product, calculated as production time divided by average customer demand. Now, customer demand is not for just one product, but many. As Toyota did not have the capital to invest in dedicated lines, it started building different options, then different models on the same lines, which means following the same Takt whilst mixing models to also follow each model Takt. Back in the eighties when my father visited the Toyota plants he figured out that they scheduled the line to have a mix of high work content vehicles and short work content vehicles in order to stick as close as possible to the overall Takt. “And the kanbans” kept saying the Toyota engineers. It took him a while to figure out they were also leveling the pull of parts on suppliers, as per the previous intuition: each part assembled had to follow a regular Takt. Which gets us to the second key idea of Takt: productivity and flexibility.

And this is where the cookie crumbles – the massive competitive advantage of lean as an industrial system is that it resolves the fundamental contradiction between productivity and flexibility. We know that economies of scale show a reduction of 20% of costs when you double the number of consecutive cycles, but conversely costs increase by 20% if you double variety. By working hard at maintaining overall Takt as well as product Takt, Toyota has figured out a way of both having its cake and eating it, but at the price of constant hard work and kaizen. This is not a natural state for any production line, and it needs to be taught to do so constantly. Indeed, a newborn Toyota plant will assemble one vehicle, then a second on the same line, then a third. A mature Toyota line in Toyota City will handle up to eight vehicles of different platforms on the same line.

Now, this is hard enough to do so it is assumed that you need overall Takt (i.e. overall volume stability) to achieve running a flexible line. The general idea is volume stability, mix flexibility, and some of the old times have repeatedly told me that you can’t run a line if you change overall Takt more often than once a year, because changing overall Takt involves redesigning every operator workstation, for every model that goes on the line: a mammoth task.

But what is true of an assembly line is not a general rule, for instance the Polish Toyota engine plant I visited changed Takt every week or so. The idea here is that as they had less product variation, they tried to stick more closely to volume variation, and so modified Takt regularly (in a kind of quantum way, there are several levels of Takt allowable).

Also, as we’ve seen in Toyota’s French plant, Takt change can be used as a deliberate mechanism to get learning again. In the turmoil of the 2009 crisis, the plant’s new president decided to use Takt (i.e. volume) variation frequently to get engineers back on the line working with operators. His point was that a good Japanese plant could absorb a Takt change every three months in less that a week (the time it takes to solve all the fine-tuning problems) so the French plant, with a single model, should be able to do the same – which fit well with the no-layoff priority of the plant, but demanded an enormous amount of work.

Takt time thinking is a linchpin of lean and applies whatever your industry: as the senseis taught us, don’t plan production by your capacity. The ideal is equal productivity through mix and volume change. Sure, Takt time changes if you close a shift, but that’s besides the point: it doesn’t get you to increase your flexibility and now you’ve got your capital sitting idle for an entire shift. I’m not saying we shouldn’t do this and I’ve been involved in such actions myself, but the question is always one of motivation.

Sure, you can do rebates to stimulate your sales, but what are you saying? You give profit back to the customer in order to persuade them to purchase earlier than they had in mind. If you can give this value back to take market share, go ahead and lower your prices. By giving rebates you’re teaching the customer to wait for your rebates and thus increase your volume variation problems. There are all sorts of ways of cheating with Takt time, and if you practice lean long enough, you’ll come across most of them, from saying that Takt is only an ideal that doesn’t apply to all cases, to fiddling with the open time calculation (should we subtract change-over times from the open time figure? What about pauses during the shift?).

To my mind, this is missing the point. Like most lean tools, Takt is NOT supposed to help you run your operation better. It’s a tool to make you explore how to be more flexible on your market AS WELL AS more productive. As Orry Fiume has repeatedly said PRODUCTIVITY = WEALTH and Takt time change should be seen as an opportunity for kaizen and seek further waste elimination – in my experience, people who tackle Takt time changes with this in mind end up discovering new sources of productivity, mostly in the form of uncontrolled variations.

Falling sales, means lengthening Takt time, and that’s that. The issues here are: how? Over what period, by what mechanisms; and why? Why are sales falling? What is the fundamental problem? Are products not attractive enough? Are we not responsive enough on the market? Too pricy? What? The point of applying Takt time to your situation is not to get you to solve your scheduling issues, this will be done one way or the other, but to think more deeply about what’s happening on your market and what options you’ll take.

So let’s starts from the ideal: what would be a Takt that sticks monthly to customer demand? And why can’t we achieve this – what are the current barriers stopping us from doing this? Dimension of equipment? Inflexible labor? What? Chances are that as we explore each barrier we’ll discover new rigidities and inefficiencies in our company, and as we tackle them highlight new areas for increased competitiveness. Don’t shy away from brutal Takt time calculations, whatever your industry or business might be, but don’t try to apply it right away either. Use the Takt time calculation as a support for deeper thinking.

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