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5.28 - Planned Preventative Maintenance

Unplanned machine and process downtime or breakdowns interfere with the ability to give customers what they want and when they want it.

The objective of preventative maintenance is to minimise the number of unplanned stoppages by increasing the reliability of all manufacturing resources. If machines are continually braking down then production is disrupted in many ways:-

  • Bottleneck machines become even more overloaded.
  • Bottlenecks are created where work cannot be re-routed to other machines.
  • Broken down machines may sit in many process routes and so create wide ranging havoc.
  • Planning of production is difficult, since complex schedules have to be recalculated to meet customer needs.
  • Lead times become elongated and unpredictable.
  • Scrap and re-work is increased.

Plant Maintenance Sub-Systems Elements

Preventative Maintenance is an investment and NOT an expense. Prevention is better than Correction!

Planned Maintenance Strategy

  • A planned preventative and corrective maintenance programme, including planned outage time, must be integrated with the levelled schedule for the manufacturing processes - viewing the cell machine system as a whole.
  • A predictive approach to machine reliability using accurate plant history and performance measurement is required. For example, allocate a Personal Computer with spreadsheets and a database to build up diagnostic charts and history.
  • Decentralisation of the maintenance task, where possible, to the specific cell and to operators and manufacturing craftsmen requires methodical training and procedural aids located close to the machine.
  • Allow Manufacturing Systems Engineers to ‘design out’ maintenance problems.
  • Provide an effective and efficient emergency breakdown service in which communications and roles of staff and priority categories are clear.
  • Where possible use simple machines and avoid planned loading above 75% capacity of any machine or process.
  • The well founded process cell is one that uses the optimum combination of simple and complex machines. The latter carefully justified by task requirements, balancing cycle times and flexibility.

Insist on ALL machine suppliers subjecting their equipment to reliability and risk analysis and also providing maintenance diagnostics in standardised decision tree format.

Further Reading