There remain many folks who think Takt Time is the same as Tact or Touch Time. Takt Time and single-piece flow are core drivers in Kaizen events. They are what connects you to the customer and drives speed. Let’s start with Takt Time first.
Takt Time — I like to think of Takt Time as the customer’s pulse. It is the rate your line must produce. Simply stated, every so many seconds or minutes, your line needs to produce a ready to ship product to satisfy your customer. The math is simple – Divide your available work minutes for a day by the number of units the customer wants a day. You can move the units to hours or seconds. You can also use weekly averages if it makes more sense.
As I have mentioned in other postings, much of my career has been in high-mix, ETO businesses. Because of this, I have used weekly averages to gain a blended or smoothed view of the variety of items going through a process. To get to “available” time, you need to eliminate any paid lunches, breaks, daily toolbox meetings, etc.
From this Table, if you have a 1-shift operation with 2 paid breaks, your “available” time is 2,300 minutes a week. If the total average units flowing through the line was 1,140 units, your Takt Time equals 2.02 minutes. Simply stated in single-piece terms, we need to have a line that produces a part every 2.02 minutes to satisfy customer’s rate of demand. The next element that we need to evaluate is whether the process sequences violate TAKT time.
If you have a process family that is continually delinquent, working overtime, and/or using premium freight, you probably have a TAKT time violation. The sequence that takes the longest to complete sets the pace for the rest of the sequences. As shown below, operation sequence “A” violates Takt Time of 2.02 minutes by a wide margin.
It really doesn’t matter how fast the other sequences are. If you happen to be a fan of Theory of Constraints, Sequence “A” is your Herbie or pacing item in this line. To serve the customer, the first thing you must address is this violation.
Ideally, all sequences should equal our TAKT time. Since customer demand is rarely consistent, I like to position sequences below Takt Time by at least 10% – 15%. Before we worry about the lack of rhythm among these sequences, we need to reduce the time in sequence “A.” The two most obvious strategies are:
1- Add capacity to sequence “A”. You might consider adding a second machine or an additional shift. You have to be careful with the latter idea in a continuous flow environment. If sequence “A” were to become a two-shift operation while sequences “B” through “D” remained one-shift operations, you would find continuous flow very difficult to implement.
2- Reduce the work content in sequence “A” through process redesign or by moving tasks to one of the other sequences.
Single-Piece or Continuous Flow — Once you have resolved the violation of TAKT time, you begin to assess the balance of sequences. Your goal is to achieve a balanced flow throughout the process such that a single piece is processed without delays or storage times. In a batch environment, you start each sequence separately. When that sequence is finished, you move the goods in line for the next sequence. In single-piece or continuous flow, you deploy an entire process of sequences. My favorite tag line has been, “Decide to Start – Decide to Finish!” Anything short of this, doesn’t serve the customer, nor any other stakeholder in the business.
In our example, you might consider combining sequences “B” and “D” to create one sequence that takes 1.80 minutes to complete. Your TAKT time and rhythmical capacity chart would now look like this.
Sequence “A” was redesigned to take 1.90 minutes and sequences “B” and “D” were combined to create sequence into “B”.
Once you have your sequences lined up and combined properly, you can relocate equipment based on the new combination of tasks. This final step is crucial to flowing the goods through the line on a continuous basis, while minimizing material handling costs and times.
Summary – First, using Takt Time, make sure your process is aligned with your customers’ needs. Second, make sure your process steps are well-balanced and co-located to support single-piece or continuous flow. These 2 steps will resolve chronic delivery issues, reduce premium costs, and position your plant to out-execute your competition!
As you explore some of these ideas in your own facilities, I hope to hear from you. If you have questions, feel free to reach out to me by email or through the Contact Me button or page. Please post your own success stories in response so other readers will benefit from your experiences.
Thanks & Good Wishes for a successful 2018!
Mike