The main idea with Overall Equipment Efficiency (OEE) is to reduce losses and thereby increase effectiveness and productivity. It's essential to provide decision-makers at all levels with the right and relevant information at the right time to succeed with your OEE initiative. A systematic breakdown of OEE into relevant categories for losses will enable this data-driven decision-making process.
After breaking down the OEE into APQ (Availability, Performance, Quality), the next level is loss reason categories.
When deciding your loss reason structure, it is essential to focus on the strategic target your factory should achieve. Below we provide some examples of commonly used structures to break down loss reasons relevantly.
6 Big Losses
6 Big Losses is a concept that steams from TPM (Total Productive Maintenance), which is a Japanese concept about autonomous machine maintenance.
6 Big Losses is a loss categorization with a machine perspective and is used to break down the losses into 6 categories. A benefit with 6 Big Losses is that it separates Planned stops from Unplanned stops, as these should be handled in strategic and operational forums, respectively.
|Unplanned Stops||Small Stops||Production Rejects|
|Planned Stops||Slow Cycles||Startup Rejects|
8 Losses from the 16 Major Losses
This model also derives from TPM and breaks down all factory losses into 16 categories. 8 of these categories are relevant to OEE and machine efficiency; the remaining 8 relates to organization and people.
The losses relevant to machinery and equipment usually gets referred to as the 8 Losses.
All losses must be described in terms of lost machine time when working with the 8 Losses. Approved, reworked, and rejected amounts needs to be translated into machine time. Since it is not possible to know how much time a rejected unit consumed (rejection could occur before the cycle ended, or the cycle time could be longer than normal), the recommendation is to use the unit's optimal cycle time.
1. Machine or equipment failure
2. Setup and adjustment
3. Tool change
6. Minor stops
7. Speed losses
8. Defect and rework
The 14 Losses structure focuses on the receiver in contrast to 6 Big Losses and 8 Losses, which takes the perspective of the source. The 14 Losses categorization can be helpful when allocating resources and responsibility.
- Infrastructure and media (e.g., power outage, lack of water/gas, network problems).
- Machine failures (e.g., mechanical, electrical, unplanned machine maintenance).
- Maintenance (e.g., planned maintenance).
- Social activities (e.g., breaks, meetings, training).
- Staff shortage (e.g., unplanned stops due to lack of operator or other key personnel).
- Lack of material.
- Lack of production order (e.g., the machine is ready, but there is no production demand).
- Changeover (e.g., from one product/order to another, CIP, if there are any preparations before the startup or close down each day).
- Other stop time (e.g., anything causing a stop that is not covered by the above categories).
- Stops not yet coded with a reason code, and therefore, has no category code either. There should be no stops without a proper reason code at the end of any shift.
11. Minor stops (e.g., stops too short of providing with reason code and category).
12. Speed losses (e.g., when production is running at a slower speed than ideal).
13. Rework (e.g., the machine needs to perform more than one cycle for the item to be approved).
14. Rejects (e.g., the machine has completed the process, but the unit cannot continue in the value chain).