In this chapter, we will discuss collecting key cycle time data to be used in the calculation of takt time, an important production metric. In this example, the process for manufacturing precision tools has three steps. Attaching a lever, inspection, and packaging. For each of these tasks, we enter the observed times for each in a worksheet. We typically would record about ten sets of samples as a minimum, but to keep it simple we are only using six in this example. Then we will want to add some key parts of the data that we observed, including the most frequently recurring value, the high value, and the low repeated time. The most frequent value can likely be repeated without a whole lot of difficulty by operators. The high time helps us to understand the worst case scenario. And the low repeats represent a best case scenario. So if we want to improve performance, we may employ some Lean Six Sigma tools to be able to perform more consistently at this level. It’s important to recognize that we can have multiple operators performing the same work simultaneously or a single operator performing multiple tasks.
So our cycle time worksheet needs to be designed to reflect the actual production processes. When we sample six instances of this total cycle time, we can conclude that the most frequently recurring time is 7.6. So what is takt time? Takt time is the required rate of production per time period needed to meet customer demand. Usually it’s expressed as a function of units per hour. But it could be daily, weekly, or in some cases even monthly depending on the process. Process cycle time needs to be balanced to meet takt time so that we’re not over-tasking or under-utilizing our resources. If our cycle time is greater than takt time, then we’re going to have a problem with bottlenecks and not meeting customer demand. We can use our Lean Six Sigma tools to break that bottleneck or figure out how to balance the work differently. Conversely, if the cycle time is less than the takt time, we run the risk of having resources sitting idle waiting for work and excess production. Being able to balance takt time and process cycle time will allow the operation to run at the appropriate pace to meet, but not exceed, customer demand.
Let’s go through a quick little calculation. So let’s say that our customer demand rate is about 120 per day. And we need to produce this to keep up with customer demand over an eight-hour shift. So this is the grand total of about 480 minutes of available time that we have for the day. What we now want to do is divide this by 120 to get to our takt time. If we do that calculation, we’re going to find out that this works out to about 4 minutes. However, it’s not the entire story here. From this 480 minutes, we’ll often subtract the breaks and the lunches and maybe planned meetings that people will not actually be working. So we could have a more accurate number for the takt time. So let’s say that we’re going to have 40 minutes a day for breaks and other purposes. So I’d want to change that calculation and subtract that 40 minutes from the 480, and instead we’d have 440 minutes available to do the work. This would give us a different result because we’d now divide this by that 120 per day needed by the customer and get a different statistic. This will give us about 3.667 minutes, or if we round that up a little bit, 3.7 minutes average takt time that we want to look at. This would be what we would actually want to be paying attention to as we run through the day for hour to hour production. You might want to use this as a much better number to know that we’re keeping up with the work throughout the day.