Why Is Takt Time So Confusing?
First, everything I’ve read about blogging says that bloggers aren’t to point out (apologize for) long periods between blog posts. “Just start posting again and forgo the mea culpas,” the experts tell me. But….two years between posts? Who does that?
I was recently reading some typically boring article on lean that, like so many others, harped on the importance of takt time. Now, I’m not one to deride the idea of takt time, especially given that many others seem to find it useful. (Or I guess they do….else why does it continue to show up in the literature so often?) It’s just that pretty much everything I’ve ever read provides the same tired definition without really explaining what it means.
Here’s an example of that tired definition (I picked this one pretty much at random…I just web searched on “takt time definition and went to the first one I saw):
“Takt time is the rate at which you need to complete a product to meet customer demand. For example, if you receive a new product order every 4 hours, your team needs to finish a product in 4 hours or less to meet demand.”
First, who gets a “new product order” every four hours? (Given that the first sentence refers to “customer demand”, I assume the author is speaking of new product orders from customers, not production work releases.) Second, in what world is a manufacturer in a position to start on an order that has just been received immediately after the previous one is finished? Mind you, I’m not saying the definition is totally bogus, I’m just saying that it’s confusing.
Here’s the definition in Wikipedia:
“Takt time is a manufacturing term to describe the required product assembly duration that is needed to match the demand. For example, if the customer demand is 10 units per week, then, given a 40-hour workweek and steady flow through the production line, the average duration between production starts should be 4 hours, ideally.”
Once again, we’re left to figure out what to do if we don’t get new product orders every four hours. Or what to do if customer orders come in willy-nilly in a wide variety of quantities and characteristics.
Some books and articles provide a formula for takt time as if customer demand were constant across time and not something that changed moment by moment.
Once again, I’m not saying that the definition is wrong, I’m just saying that it’s not very helpful. No client I’ve ever worked for has the steady, predictable flow of customer orders that takt time definitions always seem to refer to.
We’d be better off if practitioners were more forthcoming about the underlying purpose of takt time (assuming that they actually know it): smooth, predictable flow of material through the manufacturing process. It wouldn’t be difficult to get workers to brainstorm, for example, those things that prevent smooth flow: downtime, scrap, errors, problems with material, tooling, machinery, and so on. It would be easier (and better) to get operators talking about how to reduce or eliminate those things than it would be to try to teach takt time. So let’s do that.