Motion Analysis

A second basic technique utilized in Kaizen by Toyota is motion analysis. Most students of Kaizen think of “time and motion studies” as the same technique. However, as we highlight, they are in reality different. Motion analysis was introduced to Toyota via the P-courses taught by Shigeo Shingo starting in the mid-1950s. However, motion analysis is several decades older than that and dates to the work of Frank and Lillian Gilbreth, a husband-and-wife team in the early part of the 20th century in the United States.

Most people are somewhat familiar with the story of Frank Gilbreth’s work in the study of the motion involved in laying bricks. Gilbreth once famously reduced the number of motions involved in laying bricks from eighteen to four and a half.¹ An article in the New York Times in 1911 extolled the virtues of this motion analysis technique, proclaiming that the art of bricklaying had yielded to science for the first time. “If the Pharaoh could only come back now he would rub his eyes at the change made in a trade that had been stationary since he built the pyramids.”²

Less well known, however, is the fact that Gilbreth and his wife pioneered a basic system called Therblig (Gilbreth spelled backward with the t and h reversed) for describing basic motions of workers. The husband-and-wife team also pioneered the use of video capture in motion analysis.

Through use of their methods, the Gilbreths helped pursue what they termed the “quest of the one best way” of doing things.³

Motion analysis is important to study for several reasons in Kaizen. First and foremost, motion is one of the seven wastes coined by Ohno. That alone makes it an excellent fit for Kaizen in the Toyota Production System. However, there are other benefits to studying the topic, as we will explain. For example, as we will indicate, the study of motion is an excellent way to develop participants’ eyes regarding the opportunity for improvement in any process involving human activity. Motion is also a key ingredient for properly understanding other topics for improvement, such as standardized work. Mechanical motion analysis of robots or equipment is of course also possible but beyond the scope of this basic workbook.

Basic motion analysis as taught in the Toyota Kaizen course is most easily understood via introduction of the Therblig symbols. For decades, these symbols were taught to heighten sense of motion and to identify ways to improve. Figure 5.6 represents the basic Therblig symbols and their definitions.

These 18 basic symbols are used to describe most forms of human motion in detail. Items such as walking, however, are not included since this technique mostly applies to stationary jobs involving detailed motion. Demonstration of each of the

symbols is the best way to introduce the technique and to quickly memorize them. Then we can use a common example to illustrate the concept. Further detail about the symbols is available online at the Gilbreth Network Web site (http://gilbrethnetwork.tripod.com).

Figure 5.6 Therblig symbols.

As a classroom example, the following simple demonstration can be used. A person uses his or her right hand to pick up a pencil from a table and then sets it down a few inches away.

When most people observe this motion and are asked to explain what just occurred, they simply state something along

the lines of “The pencil was picked up and set down” or “The pencil was moved.” Those statements are correct, but they are closer to examples of what we used in work analysis to depict the main steps of the operation. The advantage of motion analysis is that we can go much deeper. Figure 5.7 is an example of the Therbligs that might be used to describe the motion involved in the example. As you can see, there is more going on than initially meets the eye. To move the pencil, the following detailed motions occurred as seen by the Therblig symbols:

The eyes had to locate (search, find, and select) the pencil to be lifted.

The arm had to be extended (empty transport) forward toward the pencil.

The pencil had to be secured (grasped) by the thumb and fingers.

The pencil had to be lifted (disassembled) from the table.

The pencil had to be moved (transport loaded) over several inches.

The pencil had to be set down (assembled) on the table.

The fingers had to let go (release) the pencil.

Finally, the empty hand returned (transport empty) to the starting location.

Figure 5.7 Therblig pencil example.

Using this description, it takes 10 basic Therbligs to describe the simple motion that just occurred. More complex movements, of course, comprise more Therbligs and often involve the use of the right and the left hand at the same time and use more of the symbols.

Therbligs are an excellent way to describe motion details in a graphical manner. As we mentioned, however, Therblig symbols are also a powerful tool for improving the skill of observation in most people. The technique is often referred to as developing greater “motion awareness” or a “motion

mind.” Part of the objective of the application of Therbligs is to make students realize just how much wasted motion there is in almost any process involving human work. Figure 5.8is an example of a sequence of events where a nut is picked up and transfered from one hand to the other, then inspected and set down.

Although the act of “assembly” is thought of as mostly value added, this is not always the case. If you break down a job in your company, you will quickly see how much waste there is even in well-thought-out jobs. If you look closely, most of the Therblig symbols are not value added and simply involve looking, transporting, or holding or imply empty-handed motion. Only a couple of the Therblig symbols actually illustrate valued-added work in the given example. In addition, most of the work in most operations is done by one hand or the other at a time and does not make use of both hands simultaneously, as would be ideal in many cases.

Therbligs can thus highlight waste in terms of efficiency of overall motion.

Figure 5.8 Therblig nut example.

Figure 5.9 depicts what we mean regarding value-added motion. Therblig symbols can be categorized into three groups: true value-added motion, incidental motion, and wasted motion. Studying Therbligs in detail not only highlights just how much waste exists even in supposed value-adding processes but also provides some hints in general on how to improve.

The clear strength of motion analysis using Therbligs is the ability to focus participant behavior on extremely detailed aspects of work. Even operations that have been improved over the years still demonstrate large potentials for improvement when studied under the specific lens of Therbligs. Once students grasp the concept of Therbligs, then basic aggregate motions (e.g., picking up a pen or assembling parts) are never looked at in the same way. In other words, students learn to see with greater motion awareness.

Figure 5.9 Analyzing Therbligs.

There are several weaknesses of Therbligs and this particular type of motion study. For starters, it works best on detailed tasks but does not work well when applied to longer jobs.

Analysis would simply take too long if hundreds of steps were involved. You can easily wind up looking at individual blades of grass instead of bushes or trees by way of analogy.

Second, as critics long ago noted, the method lacks a certain quantitative element, namely, that of time measurement.

There is nothing stopping you from adding time to a Therblig style of motion analysis, but the original technique did not include time as a measurement. Indeed, time-and-motion studies are what most people attempt to conduct in many instances today. Last, there are a few instances (e.g., walking) for which the motion is not really captured by Therblig symbols since the method was developed for more stationary jobs.

Whether you use Therblig symbols or a more modern technique such as videotaping to study motion, you should find tremendous opportunity for improvement in any process.

The problem is usually one of getting people to see the real details of the process and to realize that much of what is going on is not value added. This sort of analysis trains the mind to spot motion in greater detail and to hone in on various wastes in the process. We recommend analyzing operations in general and then selectively diving down into detail when needed using this type of motion analysis. We call this T-shaped analysis with more general framing at the higher level and then detailed drill downs as required. The goal is not to use the technique everywhere as that would not be practical. The pragmatic path is to focus this powerful improvement method where it is most suited.