Introduction to Industrial Engineering
By Jane M. Fraser
Chapter 7
Operate a production system
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Finally (!), the workers actually do the work. They make steel, they make computer chips, they take and fill orders for food, and they take care of patients. Since the IE doesn’t do this work, what is the IE doing?
The goal of the IE is a perfect system, humming along, producing goods or services for satisfied customers. Two issues make that vision not quite accurate. First, problems can occur. The IE has to make sure the system is collecting data that will enable the detection and correction of problems. Second, the IE is never happy: "if it ain't broke, it can still be improved." The system needs to be monitored and data need to be collected.
Recall the three targets from section 5.5. After we have helped the second and third archers achieve the tight cluster of arrows in the bulls eye that the first archer had, we need to continue to monitor the system to detect if the archer's performance wavers. A production system that is reliably producing products or services within specifications might slip (1) in its mean or (2) in its variance. In the first case, the archer still has a tight cluster, but is not aimed at the center; in the second case, the archer is still aimed at the center, but the cluster has spread out.
Control charts are designed to detect either kind of slippage in the production system. A control chart is a plot of the performance of the system over time. Typically two charts are created, one showing the average (are the arrows aimed at the center of the target?) and the other showing the variability (are the arrows still tightly clustered?).
[example of X bar and R charts]The two charts above show a process that is in control. The upper chart, called the X bar chart, shows the average measurement from several recent parts. Notice that the average in this chart is always between the lines, called the Upper Control Limit and the Lower Control Limit. The lower chart, called the R chart, shows the range from several recent parts. The range is computed as the difference between the largest and smallest part. Notice that the range in this chart is also always between its limits.
Now let me explain how those charts were generated.
Release, control, monitor, exception handling, replanning...
The article “Real-Time Data Collection for Real-Time Customer Response,” from MMS Online describes how KVK Precision Specialities, in Shenandoah, Virginia, uses the collection of data to integrate sales, production scheduling, and tracking.
“Bar code scanners throughout the shop facilitate automated data collection, which enables the software to keep track of every job in real time as it moves through the shop.”
“All of the software’s capabilities, which include order entry, scheduling, resource planning, real-time tracking, inventory of more than 4,000 component parts and imaging capabilities are utilized. The software tracks a job from the time a purchase order is received until the product is shipped to the customer.”
Such systems are often also used to allow customers to track their own orders and thus to plan their operations better.
The International Organization for Standardizatoin (ISO, from the Greek work for equal) has developed many international standards, but the two that IEs should be aware of are 9000 and 14000.
ISO9000 is a set of standards for the tracking of business processes. Put colloquiially, the standards require that you say what you will do and that you actually do what you said you would do. The organization must have documents that say what procedures are followed for each step in the production process and the organization must be able to show that these steps actually were followed.
Companies can have their operations certified by registrars, that is, certified that the operations follow the ISO standards. Especially in international markets, many large customers require that their suppliers be ISO9000 certified.
ISO describes the 9000 and 14000 standards as follows:
The ISO 9000 family is primarily concerned with "quality management". This means what the organization does to fulfil:
- the customer's quality requirements, and
- applicable regulatory requirements, while aiming to
- enhance customer satisfaction, and
- achieve continual improvement of its performance in pursuit of these objectives.
The ISO 14000 family is primarily concerned with "environmental management". This means what the organization does to:
- minimize harmful effects on the environment caused by its activities, and to
- achieve continual improvement of its environmental performance.
Note that ISO9000 deals with "quality managment" not with "quality," and ISO14000 deals with "environmental management" not with "clean environment." An organization that is ISO certified is not guaranteed to be producing products and services with high quality or guaranteed to be minimizing its harm to the environment, but the organiztion is guaranteed to have consistency in their processes for quality management and environmental management. Since reducing variability and achieving consistency are required for quality, the ISO standards are certainly related to quality.
This web page has a good short description of the actual requirements of ISO 9000. An example requirement is:
The products shall be identified and traceable by item, batch or lot during all stages of production, delivery and installation.
This requirement and others mandate the collection of significant information during the manufacturing process so that if a customer has a problem, the organization can trace that problem back through the system, determine the cause of the problem, and prevent the problem from occurring again.
The ISO standards are strongly rooted in IE principles, as shown by this list of quality principles on which the most recent ISO9000 standards are based.