Introduction to Industrial Engineering
By Jane M. Fraser
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I have stressed that an organization is a system; an IE who looks at a part of the system must be sure to consider how that part fits into the overall system. The analysis and improvement of a work station and the methods used by an individual worker requires the IE to focus on a small part of the production system, but such analysis and improvement can provide tremendous gains in the efficiency, safety, and quality of the organization’s output.
In this type of analysis, the IE looks at exactly how each individual worker handles work and performs the assigned tasks, including the worker's body movements and movements of each hand. The goal is to improve efficiency, quality, and safety by determining the best way to do the task.
When the IE focuses on one or a few work stations and on one or a few individuals, very sensitive issues arise. Some plants have a tradition of sending a new IE out to the shop floor with a stop watch. Many workers will see such an approach as a threat and the new IE may be faced with a near revolt. Also, experienced workers may not take kindly to a new college graduate’s well meaning suggestions for improvement.
Deming stressed “measure, measure, measure” but he also stressed that measurement should be used to improve the system, not to evaluate an individual's performance. The IE can work with a team of production workers to measure differences among workers with the goal of identifying and spreading best practices. For example, Parkview Hospital measures the time that elapses from when a patient in the emergency room is assigned a bed in the hospital to when that patient is actually in the new room; this time is called the “move time.” Analysis of the average move time for different nurses showed that two nurses were achieving significantly lower averages. Discussion among the nurses uncovered that the nurses with shorter average move time were anticipating which patients would be moved soon and initiating some of the required process before the start of the move time; they were efficiently overlapping tasks. The result is that the patient is settled into the hospital room more quickly. Allowing nurses to develop better practices and share them with each other can only occur in an atmosphere without competition.
Work sampling can be used to determine existing work methods. Observations are taken at fixed or random intervals. A small device that beeps is often used to prompt the worker or the observer to record the activity being done by the worker at that time. The resulting data can be used to determine the proportion of time being spent in each type of work. As described in this article about mine safety practices, work sampling can be used to determine if workers are following recommended practices. Video taping can also be used.
More sophisticated IE methods can uncover small inefficiencies in repetitive work and small improvements add up. The same type of visualization tools that helped map the entire production system can also be used to map tasks. For example, a worker assembling a lock will use both hands; a chart showing the actions of left and right hands may uncover times when one hand is idle and tasks could be redesigned. Such changes in the work procedure might also require a change in the layout of the work station.
While some latitude can be allowed in how workers do tasks, specified work methods are necessary for training new workers, for ensuring that products and services are of high quality, for enabling the identification of sources of problems when quality issues arise, and for ensuring safety.
IEs are often involved in setting work standards. A work standard is a statement of the how long a worker working at a reasonable pace over a work day should expect to take to complete a well defined job using a specified work method. Work standards are needed for several reasons:
Two methods can be used to determine work standards:
Because the time for even an experienced worker to do the same task will vary from time to time, actual measurement involves measuring several workers several times. Such measurement usually also involves measuring the elements of the task, especially distinguishing portions of the task paced by the human and portions with time determined by a machine. An element should have an easily determined start and finish, should take an amount of time that can be conveniently measured, and should contain movements that make up a unified sequence. This web page teaches irrigation contractors how to determine the time for different tasks so they can calculate labor costs for bids.
Sophisticated hand held devices can be used for such measurement, with data then being downloaded to a PC. For example, UmtPlus and WorkStudy3.0+ allow a PDA to be used to collect data. Over time, the company may build up a database of the standard times for different tasks.
Actual measurement is time consuming, so some organizations use predetermined motion time systems. Again, the work is broken into elements, such as a grasp, movement, or placement. Depending on the details of the grasp (for example, the size of the item), the movement (for example, the distance the item is moved), and the placement (for example, how accurately must the item be placed), the IE can use a database to determine how long the element should take. The times for each element can be added up to determine the “normal time” for a job. A work standard must also include allowances for rest time, personal time, unavoidable delay, and so forth. This web page describes predetermined time systems in more detail and gives an example chart showing movements of left and right hands in a task.
This case study describes how Maynard worked with Cardinal Health Care Systems to determine the time savings that clients of Cardinal could expect from purchasing Cardinal's prepackaged kits of supplies needed for specific surgical procedures. These kits eliminate the need for the hospital staff to gather the supplies.