Volume 6 · Issue 3 · March 2001

Contents

Does Your Organization Know How to Apply SPC
ISO SPC Guidance Will Assist ISO 9001:2000-Based QMSs

By John E. (Jack) West

For a number of industries, statistical process control (SPC) is an activity that is critical to the effective operation of a quality management system (QMS) and to satisfying customer requirements for product quantity as well as quality.

SPC is a well-established quality management tool, and some sectors have had SPC reference manuals for use in meeting QMS requirements for some time (e.g., the SPC reference manual used with QS-9000 was first issued in 1992). Yet, despite the existence of the ISO 9000 series since 1987, ISO has not had a good SPC guidance standard to support this critical QMS activity as well as the requirements of ISO 9001/2.

This situation should soon be rectified when ISO 11642-1, which is presently a Final Draft International Standard (FDIS), is balloted for approval and published by ISO as a new standard. As noted in the Introduction, Subcommittee 4, Applications of Statistical Methods in Process Management, of ISO Technical Committee (TC) 69, Applications of Statistical Methods, drafted ISO/FDIS 11462-1 "to guide an organization in planning, developing, executing, and/or evaluating a statistical process control system", so an organization can achieve the goal of "increasing production efficiency and inherent capability, and reducing interval and cost."

From March 8 to May 8, 2001, ISO will be conducting a 2-month up-or-down vote by participating member bodies, including the US Technical Advisory Group to TC 69, on the approval of ISO/FDIS 11462-1 as an International Standard. The Statistics Subcommittee of the American Society for Quality’s Z1 Committee will be balloting the adoption of ISO/FDIS 11642-1 as an American National Standard during a slightly different but overlapping time period, with an expected US vote of approval on a national and international level. (Copies of the draft standard, BSR/ISO/ASQ S11462-1-2001, are available from ASQ by calling 1-800-248-1946 (United States and Canada only).)

ISO/FDIS 11462-1, Guidelines for implementation of statistical process control (SPC)–Part 1: Elements of SPC, deals with achieving control of processes to ensure product conformity. An organization that uses this type of control will be able to improve the economics of achieving conformity and, with the use of data, also improve its processes. It is important to understand that ISO/FDIS 11462-1 has been developed to provide guidance for all types of organizations.

SPC is most often thought of as being important for organizations that engage in "mass production"–that is, the same exact processes, whether related to a product or service, that are repeated frequently and regularly enough to allow the application of statistical techniques. While its application in high-volume production is most common, SPC can be beneficial in other situations as well. A NOTE to Section 1, Scope, of ISO/FDIS 11462-1 indicates that SPC "is also applicable to processes producing services or transactions (for example, those involving data, communications, software, or movement of materials)."

In the past, the use of statistical methods has been a common weak point in many QMSs. It is expected that Parts 1 and 2 of ISO 11462 will be able to help organizations strengthen their systems in this area (Part 2 of ISO 11462, drafting of which is expected to be taken up soon by TC 69, will provide a catalog of SPC tools and techniques).

This has become even more important with the advent of ISO 9001:2000, Quality management systems–Requirements, which moves away from the manufacturing-oriented language and approach to quality management and quality control. This new edition of ISO 9001 increases emphasis on the determination and use of such statistical methods based on the following clauses/subclauses:

• Clause 7.1, Planning of Product Realization, requires planning of the processes for product realization, including the required verification, validation and inspection and testing processes specific to a product. This planning needs to include monitoring and measurement of both products and processes.
• Clause 8.1, Measurement, Analysis and Improvement–General, requires planning of the monitoring, measurement, analysis and improvement processes as well. It also requires that "applicable methods, including statistical techniques,…" be determined. How extensively these methods will be used must also be determined. Clearly the emphasis is not just on identification of the techniques–there is a focus on their use!
• Subclauses 8.2.3, Monitoring and Measurement of Processes, and 8.2.4, Monitoring and Measurement of Product, require monitoring and measurement of the characteristics of processes and products to demonstrate the ability of the processes to meet requirements and to demonstrate that product requirements have been met.

ISO 11462-1 has been designed to provide guidance for organizations wanting to use SPC to meet these requirements.

ISO 9001:2000 also requires a planned approach to improvement of the QMS. Planned improvement means that the organization is required to use a number of elements together to manage the improvement processes. Subclause 8.5.1, Continual Improvement, requires use of:

• The quality policy, which must include a commitment to continual improvement of the QMS’s effectiveness
• Measurable quality objectives
• Audit results
• Data analysis
• Corrective and preventive action.

This combination of elements could be called a "loop of continual improvement" for the overall QMS. Many users of ISO 9001:2000 may see definite relationships among the elements of this loop but may not be able to easily translate their understanding into action. ISO 11462-1 should be a big help in translating this conceptual loop into actions that can achieve real results for the organization. Understanding what ISO 11462-1 will provide to organizations with an existing ISO 9001/2:1994- or ISO 9001:2000-conforming QMS or beginning the ISO 9001:2000 implementation process can make an incredible difference in how they manage their processes.

Aspects of an SPC System

Let’s take a look at the aspects of SPC on which ISO 11462-1 provides guidance. These should be useful not only in developing processes to comply with ISO 9001:2000, but in developing processes for process improvement.

Three aspects are discussed below in relation to what ISO 11462-1 provides.

1. Defining the SPC Goals

As with many other things, implementing an SPC system starts with the setting of goals. ISO 11462-1 provides guidance on defining the general and specific goals an organization wants to achieve by implementing SPC. These may include aspects of control, such as:

• Reducing variation around target values for product and process characteristics as well as compensating for process variation to ensure product conformity
• Reducing costs while reducing variability thus achieving process optimization
• Indicating how the process is likely to behave in the future
• Quantifying process capability.

Once these more abstract goals are established, ISO 11462-1 recommends the identification of specific goals that the organization wants to achieve related to improvement. These may include:

• Managing process efficiency to ensure greater consistency and improvement
• Using data to identify and eliminate assignable causes of variation
• Using data to identify variation or nonconformity so that needed corrections or corrective actions can be defined
• Providing information to assist in determining potential root causes of variation or nonconformity
• Understanding the relationship between the final product and the process parameters
• Meeting financial and other overall organizational objectives.

2. Conditions for a Successful SPC System

Ongoing benefits of an SPC system are best achieved when the necessary infrastructure is developed and maintained. ISO 11462-1 points out that this can be achieved by establishing the SPC effort as part of a formal QMS, such as that specified in ISO 9001: 2000. The needed infrastructure includes management support, which can be a means to demonstrating the commitment to continual improvement required by ISO 9001.

In other words, to obtain improvement, management must use data to make decisions, support activities (e.g., data recording), react to process disturbances and assign SPC coordination responsibility. In addition, there should be a link to the management review process required by Clause 5.6 of ISO 9001:2000.

For any organization to effectively identify areas for improvement, there needs to be a periodic top management review of SPC results. Each of these is a job of top management and relate to the requirements in Section 5, Management Responsibility, of ISO 9001:2000.

Programs to ensure the competence of those who will be using the statistical tools are also necessary. All employees involved with the application of statistical techniques must have a general understanding of SPC tools, with detailed training for those employees needing special skills pertaining to the application of specific tools. There must be sufficient expertise to understand the organization’s objectives and select the correct statistical techniques to meet all related goals. Planning should include these personnel competency needs as well as the activities necessary to address the other elements of an effective SPC system.

3. Elements of an SPC System

The core of ISO 11462-1 is Section 7, Elements of a Statistical Process Control System, which discusses the processes an organization should implement and the actions it should take to ensure a successful SPC system is in place to support the QMS. ISO 11462-1 covers both the operational and support activities needed for SPC success.

A Look at the Core

To help introduce you to this core, I will review the general concept behind each of the 20 elements of an SPC system. While ISO 11462-1 details each element, I will just be highlighting the key points of Section 7.

The ultimate key point is that Section 7 provides guidance on the operational elements of an SPC system. These elements can be thought of as roughly paralleling the Plan—Do—Check—Act (PDCA) model shown in Figure 1 (at end of article). Considering these key operational elements as part of an SPC version of PDCA will not only provide consistency with an ISO 9001:2000-conforming QMS, but will make the implementation of SPC easier to conceptualize and execute.

Plan

Planning the SPC system encompasses the first 3 of the 20 clauses in Section 7, but it is probably the most critical content. In a sense, it rephrases the old saying "An ounce of prevention is worth a pound of cure" as a warning that "If you don’t plan your system right, you won’t be able to control your processes effectively."

Clause 7.1, Process Documentation and Control Plan, outlines a planning step related to the ISO 9001:2000 clause bearing the same number on planning of product realization processes. Implementing organizations must fully understand the process and develop a plan of control to ensure the process will meet requirements. This includes use of techniques to understand process inputs, outputs, flows, measurement points and boundaries.

Understanding these aspects of each process can help identify which process parameters affect product conformity. It is then that you should determine the process parameters that can be monitored and measured to ensure conformity of product. It also recommends that organizations plan the actions to be taken when out-of-control signals are detected.

Clause 7.2, Definition of Process Targets and Limits, provides guidance on developing the target values and limits for each parameter, beyond which an organization would consider a process unacceptable or unfeasible. ISO 11462-1 indicates that the target-setting process should be dynamic so that targets and limits are properly set and updated as conditions change.

The final clause that provides guidelines on the planning process is 7.3, Measurement System Evaluation and Control. Since the measurement system needs to be evaluated to ensure that its uncertainty is known–which will help prevent false alerts that a process is out-of-control or the output of nonconforming product–the standard gives some simple guidelines for accomplishing this.

Do

Measurement, monitoring and controls also involve 3 of the 20 clauses in Section 7, but they relate to the application of the SPC system to the QMS. They are also spread out within Section 7. The guidance in these clauses involves the actual role of SPC in supporting the day-to-day operations of an organization and the functioning of the QMS.

First, Clause 7.6, Process Data Recording and Collection, discusses the need to design a data collection system usable in an organization’s actual operational environment. The data collection system should be carefully designed so that it will yield the needed data.

The organization implementing an SPC system using ISO 11462-1 will need to answer such questions as:

• What will be measured?
• What is the sample size?
• Where in the process is the measurement to be taken?
• Who is responsible for the sampling?

Clause 7.6 introduces a number of other considerations for an organization, including the need to provide proper measurement equipment as well as any training needed for the equipment’s use.

Clause 7.12, Process Output Monitoring System, then states that an organization should track the outputs of its processes and collect the data so that the processes can be analyzed. The monitoring system should include a mechanism to initiate a reaction to problems and to identify and take advantage of opportunities for standardization on best practices.

Finally, Clause 7.13, Process Control System, involves controlling the process that creates the product. The standard provides several options for such process control systems, each of which addresses the need to monitor and measure process parameters to ensure that they meet process requirements. If a parameter is outside of its limits or undesirable patterns are detected, correction and/or corrective action is needed to bring the process back into control.

As its title indicates, Subclause 8.2.3, Monitoring and Measurement of Processes, of ISO 9001:2000 also requires these Clause 7.13 processes, so the guidance provided in ISO 11426-1 may be helpful in meeting Subclause 8.2.3’s requirement.

Check

Assessment of variability and communication of analysis results is perhaps most important to the SPC system’s effectiveness. It is the information that an organization obtains as a result of planning and doing and on which it will act which will lead to improvement of the SPC system and also of the QMS. In this stage, there are also 3 clauses that focus on checking activities.

The first two clauses relating to checking deal with differing time periods:

• 7.14, Short-Term Variability Assessment, recommends activities that should be considered in developing a process for assessing process changes that occur during a short period of time and typically involving a limited number of factors.
• 7.15, Long-Term Variability Assessment, provides guidelines for assessing long-term process capability once assignable causes have been eliminated and the process is in a state of statistical control. Long-term assessments are viewed as building on the changes taken or identified as needed because of the findings of the short-term efforts.

Clause 7.16, Communicating the Results of Process Analyses, covers communication of the results of process analysis to those who design and operate the processes as well as to leaders and others, as necessary, to achieve the goals of the SPC system. Communication of process analysis results is one of the things organizations should consider when addressing Subclause 5.5.3, Internal Communication, of ISO 9001:2000.

Act

Using the analysis results is the focus of the guidance in Clause 7.20, Process Improvement, Optimization and Troubleshooting, which by itself is the action clause. All the data collection and analysis is just wasted activity if it is not used to achieve results and thereby completing the CI loop successfully. Once long-term process variability has been studied, it is possible to prioritize processes to be optimized and improved. Clause 7.20 suggests several types of approaches that can be used to take actions to correct, control and improve the processes.

After establishing priorities, an organization can use ISO 11462-1’s guidance to improve or optimize the priority processes. SPC and business goals should be considered during the improvement activities. These concepts related to process improvement and optimization may help organizations develop effective mechanisms to meet the requirement of ISO 9001:2000 Subclause 8.5.1, Continual Improvement.

Other Core Elements

While the operational elements are very important, ISO 11462-1 also points out and explores a number of other elements important to a successful SPC system. The following may be viewed as supporting processes or support elements:

• Clause 7.4, Documented Work Instructions–Work instructions are a key support element of an SPC system. ISO 11462-1 gives guidance on the creation of work instructions that are appropriate to the SPC environment.
• Clause 7.7, Traceability and Production Sequence Identification–ISO 11426-1 includes guidance related to a variety of traceability concepts, including the use of traceability to improve the ability to analyze processes. Whether or not the traceability requirements of ISO 9001 apply, organizations should consider Clause 7.7’s guidance on this subject.
• Clause 7.9, Process Input Sequencing–This concept is linked to the notion of traceability. Under some conditions, process sequence is critical to production and, if inputs to the process are used in the order in which they were produced, there will be less process variability or at least the variability should be easier to analyze. Such sequencing can have great advantages, but extensive work is needed in many organizations to reach the point where it is fully implemented.
• Clause 7.10, Process Logs–In most cases, a systematic process is needed for logging process disturbances, process adjustments and operational changes. Consistent and useful logging can yield information for after-the-fact analysis to identify patterns over time. ISO 11462-1 lists the types of information that should be recorded and how to use the data.
• Clause 7.5, Employee Training and Involvement in Process Data–The proper addressing of personnel issues is critical to success when an organization introduces an SPC system. Organizations frequently fail to achieve the desired results from their SPC activities, even though the technical activities are accomplished, generally because the people elements of SPC have not been adequately addressed. Since employee involvement in the proper data-related activities is critical to success, the missing link is often detailed training in the use of data for those involved. The SPC guidelines standard points out that it is necessary to instruct employees on how to plan for data collection, design control systems using the proper techniques, identify measurements requirements and assess measurement capabilities. Perhaps most important, the right employees must be able to use the proper techniques to ensure data integrity as well as conduct proper data analysis and interpretation. This means there must be people in the organization with sufficient education to be able to understand what tools to use and how to use them.
• Clause 7.19, SPC Projects and Teams–ISO 11462-1 recognizes the project-by-project nature of improvement by recommending that organizations maintain projects to reduce variation and improve processes. It also recognizes that, where appropriate, these projects should be conducted by cross-functional teams from the functions involved in or affected by the process being considered. Teams may be especially important to ensuring that projects improve or optimize processes.

There are several other systematic activities examined in the clauses of Section 7 that ISO 11462-1 recommends should be included in an organization’s SPC system. Organizations should consider including:

• Subcontractor performance evaluation–This involves establishing a system for obtaining information about variation of parameters in incoming product from suppliers and/or subcontractors.
• Process reliability–This addresses the maintenance of process equipment.
• Customer information system–Consideration should be given to implementing a system to provide customer feedback on the suitability of the organization’s product.
• Internal SPC audits–There should be a supporting audit program to periodically determine how effectively the organization has been in implementing SPC.

When it becomes available in the near future, organizations will find ISO 11462-1 useful in developing their QMSs for both compliance with ISO 9001 and for achieving improvements.

Figure 1. The Operational Elements of SPC

Planning the SPC System

• Understand process
• Define targets
• Evaluate the measurement system
• Execute

Measure, Monitor, Control

• Collect/record data
• Monitor outputs
• Control the process

Assess and Communicate

• Assess short-term variability
• Assess long-term variability
• Communicate results

Use Analysis Results

• Prioritize
• Improve, optimize, troubleshoot

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John E. (Jack) West is a quality professional who helps organizations improve productivity and quality. He is Chair of the US Technical Advisory Group to ISO/TC 176, the technical committee responsible for the ISO 9000 family of quality management standards, and serves as the US lead delegate to TC 176. Mr. West has nearly 30 years of experience in industry with Tenneco, Inc., in a wide variety of industries that include shipbuilding, packaging, automotive parts manufacturing, chemicals and manufacturing of farm machinery and construction equipment. In his consulting work, he has led implementation of TQM and Cost of Quality processes. His extensive international experience includes working with organizations around the world to implement effective ISO 9000 quality systems that focused on lowering costs and increasing customer satisfaction. In 1993 and 1994, Mr. West served as Tenneco’s Director of Quality for European operations based in Brussels and served for 4 years (1990-1993) on the Board of Examiners for the Malcolm Baldrige National Quality Award. He has implemented internal TQM Assessment processes based on the MBNQA criteria. Mr. West is also a member of the Board of Directors of the Registrar Accreditation Board (RAB), the author of many papers and articles, co-author of ISO 9001:2000 Explained and ISO 9001:2000, An Audio Workshop and Master Slide Presentation, both published by the American Society for Quality, and a member of THE OUTLOOK’s Editorial Advisory Board.

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