Wednesday, April 9, 2008

Total Productive Maintenance

Many companies implementing lean manufacturing work on improving their equipment uptime. When equipment breaks down or stops, it injects variation into the process causing downstream inventory fluctuations and quality problems. When eliminating variation, eliminating machine downtime is a key step. One way to address equipment down time is through implementing Total Productive Maintenance, or TPM. TPM is a systemic approach to maintenance with the goal of maximizing overall equipment effectiveness, OEE. OEE is the product of availability, quality, and performance. Availability is defined as operating time divided by planned production time. Quality is defined as good pieces divided by total pieces. Performance is defined as the number of total pieces per unit operating time divided by the ideal run rate. OEE is the product of these figures, availability x quality x performance. One of TPM’s objectives is to increase OEE, thus reducing systemic variation in the process.

There are three phases to implementing TPM: the first phase is training people and gathering data, the second phase is to cure breakdowns and micro-stops (equipment stops less than 5 minutes), and the third phase is prevention of future breakdowns. Phase 1 involves collecting data on the current status of equipment uptime or OEE. It also involves training maintenance professionals and equipment operators in TPM philosophy and actions required. The best training results in a change in mindsets among the team. The team comes to realize the importance of the goal of increasing OEE and knows their part in doing so.

Next, the team works to implement curative actions. Here, equipment is brought up to par with new equipment, or better. All major systems are reviewed and upgraded, new or rebuilt components are installed to cure breakdowns. Data is collected on micro stops, and systems are put in place to minimize these small disruptions. This is where TPM makes the most impact, by measuring and addressing micro stops, capacity is uncovered and the manufacturing system performs closer to ideal.

Once downtime is reduced and equipment is running stably, a prevention phase begins. Here 5S activities (workplace organization) are key to maintaining the improvements set in phase 2 of TPM. Maintenance schedules should be established and reviewed periodically to ensure preventive measures are effectively supporting the new OEE. Here, too, effective teams review and revise their maintenance activities to ensure continued improvement.

Implementing the three phases of TPM sounds like a lot of work... or it should. TPM is an investment; it takes time, money, and expertise to implement. It pays dividends in improved quality, better delivery, lower inventory, and reduced need for capital. For the lean enterprise, TPM is a necessity.

No comments: