Discussion

Takt is the German word for “pace” or “rhythm” like the beat an orchestra conductor uses to regulate the speed of the musicians’ playing. Takt time, often referred to by lean practitioners as the heartbeat of the process, is a measure of customer demand (see Section 4.3.2.1 for more detail on the calculation of takt time). Takt time is calculated as:

Takt time predates the theory of constraints and was developed as a manufacturing flow tool in the 1930s and adapted by Toyota as a manufacturing management tool in the 1950s. The primary purpose of takt time is to serve as a management tool to indicate, at a glance, whether the value stream or process is meeting customer demand at any given time. It also serves as a tool to align upstream processes with downstream processes in a value stream with the customer demand requirements.

The intent of takt time analysis is to take a good look at an organization’s products or

services through the eyes of the customer (i.e., customer demand rate). The idea is to match the value stream’s process time (cycle time) with takt time (or customer demand) as closely as possible.

The analysis is performed by comparing various segments of the value stream and organization with takt time and identifying areas of focus for optimization to takt time.

Takt times of individual products, services, and processes can be compared to identify issues with production leveling, load leveling, and various forms of waste. Figure 2.3.1.4-1 is an example of takt time analysis by processes in a value stream. Process C needs to make countermeasures in order to reduce cycle time and meet takt time, and Processes A and B may be combined to reduce the risk of overproduction. Table 2.3.1.4-1 is an example of a takt time analysis by service type to identify areas for production leveling in a mixed model production schedule.

The purpose of performing a takt time analysis is to balance the work within a process, or line balancing. Line balancing is used to ensure continuous work flow through the process.

Originally, line balancing terminology was used, as lean was focused on manufacturing environments that had production lines. As lean grew beyond manufacturing, the use of the line balance was applied to service processes. In short, the goal of line balancing is to ensure that the workload through a process is balanced, with faster steps “feeding” or being “fed” by slower processes eliminating backups and excess inventory.

Although line balancing can be performed independently, combining it with other lean tools, like takt time analysis, process flow, and value stream mapping, provides the best benefit. To perform line balancing, one must understand the total time each process step takes. Total time for each step should include the time from when the “product” reaches that step to the time it leaves that process step. This can be a manufacturing process step (e.g., component placement) or a service process step (e.g., hotel check-in). Since total

time includes waste (muda) like waiting, as noted earlier, the partnering of load leveling with other lean tools eliminates waste within the overall process and within each individual process step.

A quick line balancing assessment was performed on a process with five steps, as shown in Figure 2.3.1.4-2. This figure shows the original process and the times (measured through observation using a stopwatch) to perform each step within the process. Figure 2.3.1.4-3 shows the same assessment in bar chart format.

The organization decided to increase throughput, so it added a second station for process step 3, allowing two products to be produced in 30 minutes. This can be accomplished because process steps 1, 2, 4, and 5 take five minutes for processing.

With the addition of a second process step 3, each one receives an input and provides an output every 10 minutes. Figure 2.3.1.4-4 shows the results of the line balancing analysis and the associated process changes. Figure 2.3.1.4-5 shows the same results in bar chart format.

In the next example, the organization decided to keep output levels the same but reduce the area (footprint) and the number of personnel needed to process the work in order to allow the personnel to do other work. To accomplish this goal, the organization combined steps 1 and 2 and steps 4 and 5; thus, all process steps now take 10 minutes. This move reduced the steps from five to three, reduced work-in-process, and reduced the area footprint (reduction of input and output shelving, operation process space, etc.). Figure 2.3.1.4-6 shows the result. Figure 2.3.1.4-7 shows the same results in bar chart format.

Line balancing analysis can be performed with more detail by adding in takt time, number of operators, and waste (or non-value-added work content). Figure 2.3.1.4-8 is an example of the original process with the detail added to the bar chart.

The ideal state for a level loaded process is one in which all processes are as close to takt time as possible, with little or no waste time, and stacked in a sequence where the downstream process is slightly faster than the process preceding it (Figure 2.3.1.4-9). This scenario creates a natural pull where the downstream process must pull from the upstream processes.

Line balancing analysis helps improve work flow. Depending on the organizational goals, line balancing can reduce the process footprint and in-process work, free up personnel (see Figure 2.3.1.4-6), and increase output (see Figure 2.3.1.4-4). Line balancing analysis is performed through observation, motion studies, or process flow analysis. While a powerful tool on its own, load leveling can be combined with other lean tools to have a greater impact on reducing waste (muda).