by Russell T. Westcott
Total Productive Maintenance (TPM) and its subset of autonomous maintenance are described as all-encompassing, companywide, team-based practices for decreasing equipment-related waste and losses linked to downtime, speed degradation, fixture-wear, and resulting product defects by stabilizing and improving uptime and other conditions. TPM blends maintenance-prevention activities and maintainability improvement with conventional preventive maintenance activities. Consider these three examples of TPM organizational plans and practices:
- A study is done to gather metrics on the time it takes for the cutting tools used in the metal-cutting operation to wear down to the point where further use will not hold the required tolerance or the tool will break. Based on the study, the specification for each machine is established so that the tool can be replaced before it becomes unusable. This solves the previously recurring problem of producing defective material and the safety hazard of a broken tool causing operator injury.
- A study is done to determine the most effective time to lubricate each machine, depending on what is being produced and other conditions, considering the effects of too much lubricant or too little. Operators are trained on how use the matrixes showing machine type and number, time period allowable between applications, type of lubricant to apply, quantity to apply, and other pertinent stipulations. Also, these matrixes/tables must be under document control to ensure the most recent matrix is used. Properly attending to equipment cleaning and lubrication lessens the potential of machine damage, reduces defective products, and improves uptime.
- By coincidence, in touring a copper-wire producing plant, I expected to see the many operators stationed at critical points along the enclosed machine watching measuring instruments. The surprise came when a loud horn sounded and the machine ground to a halt. The covers along its entire length popped up to reveal the continuous string of copper wire. The operators immediately switched to the role of maintenance inspectors and repair people. Why not? The malfunction had to be attended to anyway, and it was better for the operators to check for other potential problems than just stand around waiting for maintenance personnel to show up. The machine was up and running before we left the building. In this case, both a well-tended machine and a well-trained, dual-function workforce demonstrated an example of TPM’s autonomous maintenance.
A primary metric for TPM is overall equipment effectiveness (OEE). This metric addresses downtime from breakdowns, setups, reduced operating speed, idle time, lost time from defects, and rework. An OEE of 40 percent is said to be typical; 85 percent is in the world-class category. For example, with a scheduled runtime for a process of 6.5 hours, if you allowed an average of 4.1 hours for breakdowns, setups, maintenance shutdowns, minor stoppages, rework, and defects time, the OEE would be 4.1 ÷ 6.5 × 100 = 63%.
As production equipment has become increasingly sophisticated and costly, quality-related concerns have expanded the focus from the product produced to include the machines used in the production. This is especially a concern when the up time of multi-function robots are so critical in the production process. One major aim of automation is to replace humans to reduce error, shorten runtime, and provide consistent quality. If a robot breaks and shuts down the entire line, there is often no speedy way to place humans back in the process to replace the robot.
It’s important to realize that preventive maintenance itself cannot eliminate breakdowns. The life-cycles parameters of individual equipment, according to reliability engineering principles, can be displayed with the “bathtub” curve (named for its shape).
Early period failures are usually caused by equipment design, process design, and production errors. In the stabilized period, causes may occur due to operator errors, including improper operation of the machine. Wear-out period failures are the result of the natural limited life span of the equipment (e.g., worn parts, inadequate lubrication, or deterioration of material used to manufacture the equipment). Effective maintenance actions and reengineering can prolong equipment life until it becomes ineffective to continue use.
Hidden defects must be exposed to eliminate failures, such as:
- Ignored needs such as cleanliness, air quality, poor lubrication, and inadequate attachment of the machine to a firm foundation
- No up-to-date operating and maintenance procedures or improper application of procedures
- Unexpected machine deterioration, unanticipated detection, and delayed restoration
- Delayed detection and correction of machine design flaws and process design errors
- Failure to detect the need to take action to improve operators’ operating and maintenance skills
- Operator’s inadvertent or deliberate (sabotage) damage to equipment
- Equipment operated beyond normal and acceptable range of capability due to management’s pressure to speed-up, employee piece-work pay incentives to produce more and faster, or operator inattentiveness to warning signs of potential for malfunction
- Raw material processed by the equipment differs from the specification range of materials for which the equipment was designed, causing product defects (poor match-up of machine capability with material it has to process or an undetected drop in the quality of supplied raw material).
Overall points for auditors to consider
- Does the culture of the organization to be audited enable the introduction and adherence to the concepts, principles, and practices of a TPM process?
- Does top management support the full integration of TPM with the overall product realization process? TPM causes a change in how people, from top management to operators, think and act. Operators should ultimately be responsible for equipment operation and routine maintenance.
- Are the following five TPM objectives deemed feasible for the organization to achieve:
- Train all equipment operators in the safest and most cost-effective operating methods, including how to properly maintain their assigned equipment?
- Maximize the overall equipment effectiveness (OEE) of each machine?
- Ensure that the maintenance process for all equipment is designed to span the equipment life cycles?
- Involve all work units that plan, design, use, and maintain equipment?
- Continually monitor, measure, improve, and sustain the TPM process?
- Is there a linkage between engineering, operations, and procurement that considers the potential economic benefits and process yield, the operator’s ability, safety, and maintainability when purchasing new or replacement equipment?
Suggestions for audit checklist questions
- From available objective evidence (records and observations) what are the primary objectives of the existing maintenance program to:
- Prevent equipment breakdown?
- Ensure that equipment can be operated safely?
- Minimize setup and adjustment time
- Reduce or eliminate idling and stoppages of any kind?
- Optimize speed of equipment?
- Prevent process defects?
- Increase process yield?
- Increase workplace safety?
- Improve ease of operation of equipment?
- Conserve use of natural resources?
- Lower process costs?
- Apply 5S practices?
- All of above?
- Should the objectives be modified?
- Is the productive maintenance subsystem considered part of the quality management system? If not, why not?
- What categorical statement best describes the existing state of the maintenance process:
- Breakdown maintenance (fix it when it breaks)?
- Preventive maintenance (scheduled overhauls, lubrication and cleaning, and scheduled parts replacement)
- Productive maintenance (corrective maintenance required to restore equipment to its functional state after failure occurs, all actions needed to retain equipment in its functional state and prevent failure from occurring, and use of reliability measures)
- Total productive maintenance (effectiveness of equipment operation, profitability of equipment operation, actions based on predicted need, autonomous maintenance by operators)
- Is all equipment used in the organization’s product/service realization processes included in the TPM subsystem (including delivery, service vehicles, and material transfer vehicles)? If not, why not?
- Are TPM practices fully integrated into the product/service realization processes? If not, should they be?
- Are the internal procedures and standards applicable to TPM documented, under document control, monitored for compliance, and scheduled for periodic review and update?
- Are the operator skills needed to sustain autonomous maintenance carefully delineated, communicated, and practiced by well-trained operators?
- Is the training for operators well-designed, instructed, evaluated, and improved as needed?
- Is the training available in a medium suitable for self-instruction and refresher training (available to train one-at-a-time newly-hired operators and re-train operators’ fading skills)?
- Is the OEE of all equipment monitored and measured on a scheduled basis? If not why not?
- Are the principles and practices of the 5S methodology being used effectively? If not, why not?
- Are studies of equipment and fixtures re-done when stoppages are occurring or increasing due to wear-out, defective machine design, material used to manufacture the equipment, or operator misuse? Are the procedures and internal standards updated as needed? (For example, before the previously set replacement schedule, a cutting tool is wearing out causing defective product. A number of factors could be the root cause: material being cut has changed to harder than expected, tool is not inserted correctly, equipment is run at higher speed than previously established, lubrication plan was not followed or is inadequate, inadvertent/ intended operator tampering with tool setting, etc.)
The following are a few additional questions for auditors to consider:
- Are new employees, who were hired from colleges or technical schools for their technical knowledge of advanced equipment use, being appropriately deployed to use their knowledge and skills? If not, they are underutilized and can soon depart for another employer or be disruptive because of their boredom or disappointment.
- Has a full-scope TPM program been implemented and then allowed to falter as time passes, and management’s interests focused on something else?
- In quality management system reviews, are TPM results discussed and evaluated?
- In an established TPM-oriented organization, has the TPM program been expanded for areas other than main-line product realization, areas such as vehicles and equipment used in other functions (e.g., mail rooms, shipping work-unit, parts and tool cribs, IT and telecommunication functions, call centers, leased vehicles, and so on.)
- For an organization that provides technical and process management system assistance to their suppliers, has TPM been considered as an additional service to mutually improve supplier material or products?
- Has TPM feedback from the auditee-organization’s use of equipment been considered as an incentive for its equipment manufacturers to improve the equipment for subsequent purchases?
- If the auditee-organization is using the Theory of Constraints methodology, has the TPM program results been usefully associated with the search for and elimination of constraints?
- As the voice of the customer is cascaded throughout the organization to the product/service realization level there is a linkage with TPM, such as: setting takt time, line-balancing, just-in-time process design and loading, process corrective and preventive action, and so on). Have these relationships been considered?
For TPM to be most effective, it shouldn’t be regarded and operated as a stand-alone function. It should be fully integrated into the organization’s quality management system as a subsystem. It is probably wise for most organizations that haven’t had experience with TPM to implement in phases, perhaps choosing a few machines in a small work unit that have not been a major concern. This way experience can be gained from improving the productivity of machines that were previously not a problem and learn how productivity can be improved using TPM practices. This kind of success will help build confidence in the TPM approach and can offer cost-effective benefits in furthering the program.
This “make something good even better” concept runs somewhat counter to the traditional “tackle the largest problem area first” approach, which can go either way, but represents more of a gamble than that suggested above.
About the author
Russell T. Westcott is an ASQ Fellow, Certified Quality Auditor, and Certified Manager of Quality/Organizational Excellence. He edited The ASQ Certified Manager of Quality/Organizational Excellence Handbook, Third and Fourth Editions (ASQ Quality Press, 2005 and 2014), and co-edited the ASQ Quality Improvement Handbook. Westcott authored Simplified Project Management for Quality Professionals (ASQ Quality Press, 2005), and Stepping Up To ISO 9004:2000 (Paton Professional, 2003). He is active in ASQ’s quality management division and the Thames Valley, Connecticut, section management. Westcott instructs the ASQ Certified Manager of Quality/Organizational Excellence refresher course nationwide. He writes for Quality Progress, The Quality Management Division Forum, The Auditor, and other publications.
Westcott is president of R.T. Westcott & Associates, founded in 1979, based in Old Saybrook, Connecticut. He guides clients in implementing quality management systems, applying the Baldrige criteria, strategic planning, and project management practices.