What Are The Six Big Loses?
The Six Big Losses are a very effective way to categorize equipment-based losses: Unplanned Stops, Planned Stops, Small Stops, Slow Cycles, Production Defects, and Start-up Defects. They are aligned with OEE and provide an excellent target for improvement actions.
The six big losses originated from the world of total productive maintenance (TPM).
Seiichi Nakajima developed TPM and the Six Big Losses in 1971 while at the Japanese Institute of Plant Maintenance. He characterized maintenance as the responsibility of all employees; best carried out through small group activities with the goal of maximizing equipment effectiveness.
Six Big Losses categorize productivity loss from an equipment perspective. They align directly with OEE and provide an additional and actionable level of detail about OEE losses.
Why Use Six Big Losses?
The Six Big Losses are very well-aligned to discrete manufacturing and provide a more detailed perspective on equipment loss than OEE. Since the Six Big Losses are derived from TPM, each loss maps very well to a specific set of countermeasures. Not only do you get more information – you get a foundation for more effective actions.
The Six Big Losses
Unplanned Stops are significant periods of time in which equipment is scheduled for production but is not running due to an unplanned event. Examples include equipment breakdowns, tool failures, unplanned maintenance, lack of operators or materials, being starved by upstream equipment or being blocked by downstream equipment.
Planned Stops are periods of time in which the equipment is scheduled for production but is not running due to a planned event. Examples include changeovers, tooling adjustments, cleaning, planned maintenance, and quality inspections. Many companies also categorize breaks and meetings as Planned Stops.
Small Stops occur when equipment stops for a short period of time (typically a minute or two) with the stop resolved by the operator. Small Stops are often chronic (same problem/different day), which can make operators somewhat blind to their impact. Examples include misfeeds, material jams, incorrect settings, misaligned or blocked sensors, equipment design issues, and periodic quick cleaning.
4. Slow Cycles
Slow Cycles occur when equipment runs slower than the Ideal Cycle Time (the theoretical fastest possible time to manufacture one piece). Examples include dirty or worn out equipment, poor lubrication, substandard materials, poor environmental conditions, operator inexperience, startup, and shutdown.
Production Defects are defective parts produced during stable (steady-state) production. This includes parts that can be reworked, since OEE measures quality from a First Pass Yield perspective. Examples include incorrect equipment settings, operator or equipment handling errors, or lot expiration (e.g., pharmaceutical).
Startup Defects are defective parts produced from startup until stable production is reached. They can occur after any equipment startup, however, are most commonly tracked after changeovers. Examples include suboptimal changeovers, equipment that needs “warm up” cycles, or equipment that inherently creates waste after startup (e.g., a web press).
In the short term, Six Big Losses provides additional information that aligns with and extends OEE (improved information).
In the long term, Six Big Losses makes it easier to identify effective countermeasures for equipment-based losses (improved actions).
1. Monitor the Constraint
Every manufacturing process has a constraint, which is the fulcrum (i.e., point of leverage) for the entire process. Measure Six Big Losses at the constraint and focus your improvement efforts to IMPROVE THE CONSTRAINT†. This will be the fastest path to improved throughput and profitability.
2. Don’t Hide Loss
Time that can be used for value-added production (i.e., manufacturing to meet customer need as opposed to manufacturing for inventory) should be used for value-added production. If it is not – that time should be categorized as a loss. This strict standard drives innovation and improvement. Every loss can be targeted and improved.
This is the reason that many companies choose to categorize breaks and meetings as Planned Stops, and are also very careful to ensure that their Ideal Cycle Times are based on the fastest possible time to manufacture one piece (not “standard” or “budget” times).
Standardize Changeover Time Measurement
Measure changeover time accurately and consistently by standardizing the measurement. It is usually measured as the time between the last good part of the prior run to the first good part of the next run. You can define your own standard – the important thing is to be consistent.
3. Create a Six Big Loss Rulebook
Consistency is important when using the Six Big Losses as a benchmark (comparing across shifts, equipment or plants) or as a baseline (comparing over time). Create written standards to ensure consistency.
Create a simple Six Big Loss Rulebook and uniformly apply it across your company to ensure that every team measures loss consistently.