The worker on a fast line such as a candy cane maker has little control over their environment. They must perform more like machines themselves. The welder on an auto manufacturing line may have more control over their environment. For instance they may make the welds necessary and then press a button to send the car on down the line. They control how fast the line moves. However, it is much more important for the welds to be performed correctly. If an imperfect candy cane goes out, the consequences are less serious than if a car frame is welded incorrectly. This is the different amounts of control that a worker has in the speed of production.
More experienced welders would be able to make the welds faster than inexperienced welders. However, speed is not the most important element when welding automobile frames. They must be done right, even if a few seconds, or even minutes are sacrificed. Therefore, we can surmise that the amount of control a worker has over the speed of the tasks is directly related to the importance of quality over quantity. This is directly related to the consequences that the end consumer could face as a result of error.
The measurement phase means determining the average time that it takes a worker to complete a task. Line speeds are the result of work measurement. If a human cannot possibly perform a task in the required amount of time, then the production speed must be slowed so that it is possible to complete the task. There are many phases of the operation than can best be performed by robotics. For instance, if a package needs to be turned over at some point, a robot may be best suited for the task, rather than a person. Many packing tasks are performed by robots. Robots make measurement an easy task as they can perform the same task thousands of times in a row exactly the same way (Polakoff, 1990). They can often perform many steps of the work much faster than their human counterparts. They are not as prone to injury as humans either. The use of robotics is an important element of job design.
The efficiency of robotics and their ability to perform a task over and over in exactly the same way without complaint is a major consideration in using them in the manufacturing process. However, there are many things that a robot cannot do that only a human can do. For instance, a robot cannot make a decision as to what is a perfect package and what is not. The use of scanners is making this task easier. For instance, it is now possible for a robot to detect certain flaws in a package, but they still cannot replace the reasoning skills of a human being in many areas. Humans are necessary and machines cannot operate completely independent of their human counterparts at the current time. They can help with tasks that could cause injury to the worker, but they cannot make decisions the same as a human being (Vicente, 2002).
Job measurement is easier when it comes to machines performing the task than if humans perform it. However, it is not always possible for the machine to perform each and every task. Often the job is performed by a combination of machine and human elements, all of which must work together in perfect harmony (Vicente, 2002). Synthesis is the final phase of work measurement. This means putting all of the various elemental times together with appropriate allowances for the human factor. This results in a standard time to complete a job.
The above example is an example of an actual measurement of a work system. In some cases operations managers will use predetermined data to use for work calculation. These standard data are derived from simulation models or visualization of the actual work. This makes the task of calculation easier, but can result in errors that do not reflect actual working conditions. Work measurement is a systematic approach that breaks the task down into its individual components. This results in a motion-time study, which is no more than an analysis of the time that it takes to perform every motion required for a task. This applies whether the worker is human or a robot. Each motion takes a certain amount of time, regardless of the distance.
The time that it takes to perform a motion can be lessened by decreasing the distance traveled. For instance, an arm that swings 2 feet takes longer than the same arm traveling 2 inches. The arm that travels 2 inches can perform the take in a shorter period of time and therefore more times a minute than the arm that travels 2 feet. This is easy to visualize using robotics, but the same is true of human workers as well. The result of this calculation is expressed in standard minutes or standard hours. A standard minute or hour includes the number of units produced and motions made, rather than simply the ticking of the clock. It is an essential element of work planning for operations managers.
Non-operations managers use this technique many times throughout the day without even realizing it. For instance, everyone knows how long it takes to walk to class, how long it takes to read a chapter in your text book, and how long it will be until the pizza is delivered. We schedule our day based the average amount of time that it takes to perform a task. It may take 12 minutes to walk to class one day and 14 minutes in the rain, but we know the average and plan to leave accordingly. This is how motion-time studies work as well. They work on an average amount of time with known limits.
There are several factors that influence the most appropriate methods of work measurement. For instance, it may be more appropriate to measure the work in seconds or hours. Some projects, such as building a sky-scraper may be measured in man-hours, which may be converted into years to complete the job. Scale is an important element in work measurement. Tasks such as screwing in a bolt exist in standard data banks based on thousands of measurements. Longer tasks may require estimation to arrive at a reasonable length to completion. These data banks are derived from the actual event being timed, often by a third party observer with a stopwatch.
These data banks of tasks can be used to create a computer model of a particular process (Feirer, 2002). This can allow the engineer to arrive at an approximation of the time it will take to complete a task-based combining the average times from the different components of the task. Using computer analysis of a task can allow the operations manager to dissect the various parts of the task, change the values and maximize the efficiency of the task (Fitzgerald, Leven, Riedel, and Toenshoff, 2003).
The Human Factor
Up until this point in the discussion, the work of the human and the work of the machine are performed in the same way. The human is treated as just another step in the production process. We mentioned the human factor as far as reliability is concerned and that human needs can reduce the reliability of the human, as compared to the machine that can perform the same task tirelessly day in and day out, as long they have proper lubrication to do so. However, humans need much more than a little machine oil from time to time.
Over the course of the working day the worker will experience fatigue. Adverse working conditions such as extreme heat, or fumes may increase the fatigue experienced by the worker. Operations managers must make an allowance for this to allow the worker to recover from the fatigue. The work and conditions determine the allowanced needed for the average worker to recover. Allowances cannot compensate for unsafe or unhealthy working conditions, and they must be sufficient to recover. There is often a trade-off between worker fatigue and maximum production efficiency. A worker that is fresh can perform the tasks more quickly and efficiently than a tired worker.
Anticipating worker fatigue, machine maintenance and times between machine failures are also allowances that must be made if one is to obtain the most reliable work measurement. Many of these factors can be estimated with a high degree of accuracy. Careful observation over time is the key to accurate work measurement. Each observation represents a data point. Just like any other scientific study, the more observations made, the more accurate and reliable the results. After a sufficient number of observations outliers can be easily identified. A greater number of observations mean more reliable estimations of work and better data to use in the design process.
Work measurement is an important part of business process engineering, or in some cases, re-engineering. The more knowns that a designer knows…