Time Study

While most people are probably not familiar with the Therblig style of motion analysis, almost everyone is familiar with the practice of time study. Indeed, most of the time when someone mentions a “time-and-motion study,” in reality he or she is mainly conducting a time study with the main work element listed on an analysis form. The Therblig level of detail is not included in the study. In this section, we outline the basics of conducting a time study and contrast it in particular with work method analysis and motion study.

The concept of time study is quite old in manufacturing and predates the Kaizen course at Toyota. Time studies were also common in the loom business of Toyota long before the automotive division was established as a separate company in 1937. The basic concept of a time study is accredited to Fredrick Winslow Taylor and the methods outlined in his work, The Principles of Scientific Management.⁴ As Frank Gilbreth commented in 1912, “Time study is the art of recording, analyzing, and synthesizing the time of the elements in any operation, usually a manual operation but it has also been extended to mental and machinery operations.”⁵ The concept of time is important in Kaizen and the entire Toyota Production System. Time is a major underpinning of improvement efforts in Toyota, whether through the usage of

“takt time,” “lead time,” or “just-in-time” concepts, for example. Time is often an objective, simple way to quantify and measure a process. Along with quality, productivity, and cost, time is at the forefront of metrics evaluating processes.

Time can be used to measure duration of events or intervals

between events or to help identify sequencing order of concurrent events and so on. Normally, time study in conjunction with Kaizen focuses on either operator motion or machine cycle times. Due to the nature of this workbook, it is not possible to adequately describe all the details of a proper time study; however, we can point out its typical uses, highlight a couple of examples, and review the strengths and weaknesses of the technique.

Filling out a time observation form (Figure 5.10) requires significant instruction and practice. In the Kaizen course, Toyota focused considerably on this basic technique of time study and the practice of using a stopwatch. First, practice was conducted in a classroom setting, then application was made on the shop floor. Since the majority of the participants of the Kaizen course were often not industrial engineers, the basic technique and suggestions for time study were kept simple. The points in Figure 5.11 outline the main concepts for simplicity and practicality.

The practice of time study is unfortunately difficult to explain in text form. However, explaining the basic mechanics, key points, strengths, and weaknesses is still possible. For starters, to explain the basic concept of time study a simple exercise can be used in the classroom as a demonstration. Further shop floor practice is of course required for mastering the technique.

Figure 5.10 Time observation form.

Figure 5.11 Tips on time study.

In the example, a person simply walks to a flip chart and writes down something on the chart, such as “time study.” For the sake of practice, the start and stop points for measurement are identified, and a simple time study is conducted via stopwatch. The total cycle time for the demonstration and each individual measurement segment are kept uniform the first several iterations. Then, the demonstrator alters his or her walking pattern, fumbles with the marking pen, and writes time study backward (yduts emit) slowly and deliberately for the last cycle. The result is a cycle that takes a few seconds longer (Figure 5.12).

This example was conducted specifically to drive home certain points for discussion. By design, the instructor would keep certain work elements to a consistent level and vary other ones as measured in the example. The purpose of the variation was to drive conversation and discussion regarding

several points. For example, what work element was the longest? Why did it take so long? What work element varied the most? Why did the work element vary? Time reflects motion and thus is an important key to look at for improvement opportunities. Analysis by time does not provide an answer to a problem; however, it provides highly valuable clues regarding where to look.

Time study has certain strengths and weaknesses, as does any operational analysis method. The main strength of time study is that it is quantitative. Time reflects motion and provides a layer of insight beyond writing down work elements or minute motions. Time is also a constant unit of measurement that can be applied as needed to measure manual work, machine cycle times, or auxiliary tasks such as setup and changeover. This is also true whether the focus of the time study is writing a purchase order, taking an order over the phone, or entering an engineering change order into a system.

Time is also a great way to compare before and after situations and highlight the level of improvement accomplished by any change in method that has been implemented.

Figure 5.12 Time Study Exercise.

A weakness of time study is that it is often more difficult to conduct than work analysis, for example, and often it intimidates people. Individuals not familiar with time study may be reluctant to use the technique, and employees are often sensitive to the practice as well. Toyota’s goal with time study was to simplify the tool and put the skill set for measurement into work teams for the purpose of measuring their own work and indentifying improvements. If members of the production team could conduct the time study under the direction of the team leader, this was usually more effective than its being measured by external parties.

Time study is also difficult to conduct when the measurement points are poorly defined for the work elements or the job has not been adequately defined up front. Time study loses some of its meaning when the operation is not performed the same

way each time during the study. For these instances, it is highly useful to enlist the aid of someone with an industrial engineering background to provide help in difficult cases.

Time study was a major tool in both the P-courses of Shingo and the Kaizen course of Toyota. Despite its initial difficulty, the skill is valuable in every manufacturing shop for Toyota.

The concept of time as a measurement and comparison technique is also vital for the Toyota Production System as a whole. With no time analysis, there can be no just-in-time style of production or standardized work which relies upon takt time. Time dimensions along with quality and cost are extremely important factors for the success of any system.