The evolution of acceptance standards and specifications, the pressures of Public Law 101-592, and increasing customer expectations have all forced a long overdue reassessment of fastener quality.  While there are many aspects to this issue, perhaps the most encouraging development in this arena is the wide-spread adoption of Statistical Process Control.  Very simply, there is nothing on the horizon which offers as many long-term competitive advantages while simultaneously improving both efficiency and accountability.

Unfortunately, despite considerable effort and well-documented successes, the full potential of SPC as a competitive weapon has yet to be realized.  All too often, the use of statistical techniques as a means to improve the productive process is viewed as a band-aid solution, a short term commitment used to satisfy a temporary problem.  Very few have embraced a process which has the potential to create miracles in manufacturing.  Fewer still have integrated the broader concepts of Total Quality Management into day-to-day operations.

The root of the problem lies in a basic misunderstanding of the role of Statistical Process Control in the broader context of company operations, customer expectations, and product acceptance.  In all areas, a lack of commitment to the concepts and mandates of SPC may be dangerous.

Excessive initial cost is often cited as the primary reason for the lack of commitment to Statistical Process Control.  While there is a burden cost associated with the initial investment in SPC, any consideration of cost must also reflect any potential benefit which may accrue downstream.  When viewed in this manner, the investment in SPC shows a remarkably high rate of return.  Real-time data collection reduces redundant inspection, increases productive efficiency through the use of tooling and control studies, and permits maximum utilization of all productive resources.  More important, it fosters an environment for the establishment of an economically sound system for decision-making in light of changes in the productive process.

Ignorance and intransigence also retard commitment to SPC.  While draconian styles of management may have served industry well in the past, the current competitive crisis and drive toward World-Class Quality requires radical departures from previous practice.  Refusal to delegate responsibility to the lowest level of authority and reluctance to embrace SPC and its ensuing result-oriented prejudice as a standard business practice both condemn a company to mediocrity.

In a broader context, the lack of commitment to SPC at the company level may be rooted in fear of change.  SPC is not a passive program.  It creates a blueprint for change.  In fact, its premise is that it is a mandate for change and aggressive management.  Those who prefer reactive rather than proactive response may be uncomfortable in the bias for action contained within the concepts of process control. 

Finally, management must acknowledge its own role in the manufacturing and quality evolution defined by SPC.  It is estimated that only 15 per cent of all possible reduction in variability can be affected at the basic manufacturing level.  The remaining 85 per cent of possible corrective action is the responsibility of management.  Put another way, changing a defective tool offers limited results.  Changing a defective tool supplier is much more effective.

In many cases, customer expectations and requirements demand commitment to Statistical Process Control.  In automotive procurement, the Ford Motor Company virtually mandates the utilization of Statistical Process Control by their entire fastener supply base.  A lack of commitment at any level of the vendor organization may jeopardize the very existence of the contractual relationship.  While such a stance may seem extreme, Ford has a very good reason for its position.  Very simply, SPC has been a successful business strategy.  Costs have been reduced, problems have been solved, and the entire fastener supply base now competes on a level playing field.  Several divisions of General Motors and the Chrysler Corporation have enacted similar programs.

Within the Department of Defense procurement structure, there is also strong commitment to Statistical Process Control.  According to DoD Instruction 5000.2 "Military Specifications should not contain requirements for use of specific sampling plans nor should they provide AQLs or LTPDs as a requirement."  Further, the Army is in the process of revising existing Military Specifications in accordance with acceptance based on proven contractor statistical process control techniques.

The aerospace community has also strongly encouraged the incorporation of SPC as pre-condition of procurement for fastener-type items.  Contractually-mandated utilization of Statistical Process Control procedures are now the norm for General Dynamics, FMC Corporation, and Boeing.  Further refinement and extension of these programs is expected not only at these companies, but throughout the industry. 

In very real terms, the commitment to SPC must be viewed as an issue of survival.  Procurement specifications in such diverse areas as automotive and aerospace virtually demand adherence to the practice and principles of Statistical Process Control.  Clearly, those suppliers who fully comply and commit their resources to SPC will remain active in the procurement function.  Those who choose to cling to the archaic practices permitted in the past will be forced to seek other customers.  SPC not only will revitalize your business, it will allow you to stay in business and prosper.

The relationship between Statistical Process Control and standards or specifications for product acceptance is complex.  SPC retains validity only when a viable index for the assessment of process variation is firmly in place.  In most instances, this index is predicated on dimensional tolerances. If the standards and specifications defining these tolerances are erroneous or misleading or the inspection methods defined in the documents are flawed or inadequate, the entire concept of Statistical Process Control losses all meaning.  Consequently, adequacy of inspection standards and specifications is paramount in the establishment of a successful Statistical Control program, and commitment to SPC requires a complete analysis of this factor.

The controversy surrounding MIL-S-8879C is illustrative of this complex relationship.  Unlike previous editions, the newly-revised specifications provide a solid basis for Statistical Process Control by providing default inspection limits which are consistent with dimensional accountability and are sensitive enough to provide a platform for SPC.  Further, Continuous Improvement toward a measurable goal is encouraged through establishment of clearly defined limits.  In this respect, Statistical Process Control, as encouraged by MIL-S-8879C, is simply the final chapter in the evolution of that particular specification.

Despite these and other strengths, there is opposition to the revised Specification.  By creating toothless documents completely lacking any relationship to engineering logic or dimensional verification, those promulgating alternatives such as NAS8879 have sought to avoid the very accountability and improvement which SPC mandates and creates.   Even worse, such departures imply permission to seek loopholes in the path to continuous improvement, ignore progress, and avoid enlightened quality initiatives.

Additionally, inadequate standards or specifications pose an economic and logistical burden upon those companies and organizations mandating or encouraging the utilization of Statistical Process Control.  If clear and consistent definitions of acceptable quality levels are not specified in the procurement specification or related documentation, or if acceptable quality levels are defined in a manner inconsistent with the development of Statistical Process Control techniques, these companies and organizations must prepare and maintain their own proprietary documentation to support their SPC directives.  The net result is confusion regarding acceptability, varying standards of acceptance for identical product configuration depending upon the whims and expectations of the procurement agency, and an underlying mistrust of Statistical Process Control.

The recent introduction of a new Flexible Fastener Manufacturing Workstation at the Portsmouth Naval Shipyard is an example of commitment to Statistical Process Control.  The concept was initiated by the Shipyard in 1987.  Upon approval of Manufacturing Technology Program Office of the Naval Sea Systems Command, the National Institute of Standards and Technology with the collaboration of the Brown and Sharpe Manufacturing Company and the Johnson Gage Company developed the automated workstation.  The Flexable Fastener Manufacturing Workstation produces Safety Critical threaded fasteners of various types and sizes for the United States Navy in accordance with MIL-S-1222H, ANSI B1.18, ANSI B18.2.1, ANSI B18.3, and MIL-B-857A, and other specifications.

While the fasteners are produced on a Numerically Controlled Turning and Milling Center, the heart of the System is the computer controller which closes the loop between actual manufacturing operations and inspection of the fastener.  The unique NIST-developed process control system, which incorporates engineering and data collection portions of the Johnson Gage Thread Analyzer software, constantly monitors dimensional acceptability and adherence to Statistical Control Limits.  Thread dimensions are inspected using a Johnson Digital Thread Inspection System in accordance with ANSI B1.3 System 22.  The gages are directly linked to the computer controller utilizing standard interconnect wiring.  Initial pieces in the production lot are carefully analyzed using the gaging system to assure not only acceptability but also adherence to proper form and dimensional tolerances.  When fully implemented, this initial statistical sample can be combined with additional subgroups to assist in the creation of statistical control limits for the balance of the manufacturing lot. 

As the production process continues and eventually degrades, the controller analyzes the actual thread dimensions and compares the data to the acceptability limits as well as a pre-defined Statistical Capability Plan whenever appropriate.  When required, the program automatically calculates the proper adjustment.  Corrections and changes are then sent to the machine tool through Direct Numerical Control to compensate for thermal growth, tool wear, and other machining variations.  All tool changes can be anticipated by the Statistical Process Control Program prior to degradation of product quality.  According to Kang Lee of the National Institute of Standards and Technology, United States Department of Commerce,  "the error-compensation software keeps the part dimensions within the Navy's demanding specifications,"  and "defect rates are reduced to almost zero."  As more and more fasteners are manufactured using the Workstation, SPC limits will be refined, setting the stage for continuous improvements in manufacturing operations.

As a result of a 300 percent improvement in productivity stemming from reduced manufacturing and inspection time, more efficient machine  utilization, and a three-fold increase in tool life, Portsmouth Naval Shipyard anticipates annual savings of over $900,000 from the Fastener Workstation when utilized at full capacity.  Beyond the Navy, applications for the NIST-developed process-control and error compensation system include virtually all United States fastener manufacturers producing critical threaded components for the aerospace, automotive, and construction industries.

While it is almost universally acknowledged that Statistical Process Control can benefit virtually any manufacturing operation, the role of SPC for the distributor is less clear.  Since the distributor is not involved in manufacturing operations, employment of Statistical Process Control practices and principles does not directly apply in this instance. However, the distributor should still advocate and even demand that all vendors supplying product should implement SPC.  Very often, SPC mandates from prime manufacturers and end-users are simply passed along the procurement chain regardless of source of supply.  The distributor should take active measures to assure conformance of his own inventory to the evolving requirements of SPC-driven procurement requirements.  Demonstrated control of the manufacturing process through the utilization of Statistical Techniques by suppliers will assure the distributor that product in inventory that will meet or exceed customer requirements regardless of application. 

However, the imposition of Statistical Process Control initiatives upon the vendor base does not relieve the distributor of the ultimate responsibility for quality conformance.  Supplier compliance to the dictates of SPC must be actively monitored and reviewed, standard documentation formats developed and maintained, and continuous improvement encouraged.  Further, until the adoption of process control is an accepted and universal industry practice, the installation or maintenance of a detection system for the discovery of discrepant material should be a priority for any distributor.  Currently, many distributors are utilizing computerized inspection systems for dimensional analysis.  These systems reduce inspection time, simplify data recording and retrieval, document traceability, and provide a real value-added service to the end-user

Without question, the wide-spread adoption of Statistical Process Control can enhance the competitive posture of the American fastener industry.  There are glowing success stories of what SPC can do in terms of cost reduction and process improvement.   While there are widely divergent theories regarding the most appropriate SPC plans and practices, in the short term it is not important exactly what you choose, but simply that you choose.  Statistical Process Control is a bold initiative that simply will not go away.

It is relatively easy to initiate Statistical Process Control and the broader initiative of Total Quality Management.  The basic principles are relatively easy to grasp and understand, tangible improvement may be almost immediate.  Fortunately, there are a host of excellent procedural guidelines, and the bandwagon effect is certainly in evidence.  Conversely, long term success is more difficult.  Basic modifications in the corporate structure are necessary.  The entire organization must readily acknowledge the transformation brought by the introduction of Statistical Process Control.  Most important, company management must demonstrate its commitment to SPC on a daily basis.  Anything less will erode any progress which has been achieved.  Even worse, erosion of progress will be perceived as failure by all concerned.  According to Deming, Statistical Process Control is intolerant of failure.  If the initiative falters in its initial introduction, it will be extremely hard if not impossible to resuscitate the program.