OEE loss categorization
Learn how categorizing production losses helps manufacturers understand where efficiency is lost, identify root causes, and prioritize improvement activities. Explore three commonly used loss categorization models: 6 Big Losses, 8 Losses, and 14 Losses.
Why Categorize OEE Losses?
The main purpose of measuring Overall Equipment Effectiveness (OEE) is to identify and reduce production losses, improving manufacturing efficiency and productivity.
An OEE value tells you how effectively your equipment is performing, but it does not explain why losses occur or what actions should be taken.
To make OEE useful for continuous improvement, production losses need to be broken down into meaningful categories.
A well-structured loss categorization helps manufacturers:
- Understand where losses occur: Identify the main reasons for lost production time and output.
- Prioritize improvement activities: Focus on losses with the greatest impact on production.
- Assign responsibility: Make it easier to identify which teams or functions should address specific problems.
- Support data-driven decisions: Provide relevant information to Operators, Production Managers, Maintenance, and leadership.
- Measure improvement: Track how different types of losses develop over time.
The goal is not simply to collect more data, but to create information that supports better decisions and concrete improvement actions.
Understanding the OEE Loss Structure
OEE is calculated using three components: Availability, Performance, and Quality.
Each component represents a different type of production loss.
| OEE Component | What It Measures | Typical Losses |
|---|---|---|
| Availability | Whether equipment is running during planned production time. | Breakdowns, changeovers, material shortages. |
| Performance | Whether equipment is running at its expected production speed. | Minor stops, reduced speed. |
| Quality | Whether production meets quality requirements. | Scrap, rejected products, rework. |
These three components provide the first level of loss categorization.
The next step is to divide each component into more specific loss categories, making it easier to understand what causes the losses.
There are several established approaches to doing this. The most suitable structure depends on your production environment, improvement objectives, and organizational responsibilities.
1. The 6 Big Losses
The 6 Big Losses is one of the most widely used frameworks for categorizing manufacturing losses.
It originates from Total Productive Maintenance (TPM), a manufacturing improvement methodology focused on maximizing equipment effectiveness through proactive maintenance and continuous improvement.
The model categorizes production losses into six groups, organized under the three OEE components.
| OEE Component | Loss Category | Description |
|---|---|---|
| Availability | Equipment Failures (Unplanned Stops) | Unexpected breakdowns or equipment problems that interrupt production. |
| Availability | Setup and Adjustments (Planned Stops) | Production time lost during changeovers, setup, and adjustments. |
| Performance | Small Stops | Short interruptions that reduce production efficiency. |
| Performance | Reduced Speed (Slow Cycles) | Equipment operating below its ideal production speed. |
| Quality | Production Rejects | Products rejected during normal production. |
| Quality | Startup Rejects | Defective products produced during startup or stabilization. |
When is the 6 Big Losses model useful?
The 6 Big Losses provides a straightforward way to understand equipment-related losses.
It is particularly useful when:
- Introducing OEE measurements for the first time.
- Establishing a common language for production losses.
- Identifying whether improvements should focus on downtime, speed, or quality.
- Supporting TPM and equipment improvement initiatives.
Key benefit: A simple, standardized structure that makes it easier to communicate and compare production losses.
Important: In the traditional 6 Big Losses model, setup and adjustment losses are distinguished from equipment failures. Whether scheduled activities affect OEE depends on how planned production time is defined.
2. The 8 Losses
The 8 Losses model is derived from the TPM framework known as the 16 Major Losses.
The broader framework considers losses associated with equipment, labor, and other production resources. Eight of these losses focus specifically on equipment effectiveness.
Compared with the 6 Big Losses, the 8 Losses model provides a more detailed breakdown of Availability losses.
Availability Losses
| # | Loss Category | Description |
|---|---|---|
| 1 | Machine or Equipment Failure | Unexpected breakdowns or technical problems that interrupt production. |
| 2 | Setup and Adjustment | Time lost when preparing or adjusting equipment for production. |
| 3 | Tool Change | Production interruptions required to replace tools or equipment components. |
| 4 | Startup | Losses associated with starting equipment and reaching normal production conditions. |
| 5 | Shutdown | Losses associated with stopping equipment and completing shutdown activities. |
Performance Losses
| # | Loss Category | Description |
|---|---|---|
| 6 | Minor Stops | Short interruptions that reduce production efficiency. |
| 7 | Speed Losses | Equipment operating below its ideal production speed. |
Quality Losses
| # | Loss Category | Description |
|---|---|---|
| 8 | Defects and Rework | Production losses caused by rejected products or additional processing required to achieve approved quality. |
Expressing losses as production time
An important principle when comparing different types of losses is to express them using a common measurement.
For equipment-focused analysis, this is often equivalent lost production time.
Availability losses are already measured in time, while Performance and Quality losses can be converted into equivalent time using the ideal cycle time.
For example, if 20 products are rejected and the ideal cycle time is 30 seconds per product:
Quality loss = 20 × 30 seconds = 10 minutes
This allows different loss categories to be compared using the same unit.
The calculation represents equivalent production capacity lost, not necessarily the actual time spent producing defective units.
When is the 8 Losses model useful?
The 8 Losses model is particularly suitable for manufacturers that want a more detailed understanding of equipment-related losses.
It can help organizations:
- Separate technical breakdowns from setup and tool-change losses.
- Identify opportunities to improve startup and shutdown procedures.
- Compare different types of equipment-related interruptions.
- Prioritize maintenance and operational improvements.
Key benefit: More detailed equipment loss analysis without introducing an overly complex categorization structure.
3. The 14 Losses
The 14 Losses model provides a broader operational perspective on production losses.
Unlike the 6 Big Losses and 8 Losses, which primarily focus on the nature of equipment losses, this structure also emphasizes the organizational areas associated with different causes.
This can make it particularly useful when assigning responsibility for improvement activities.
Availability Losses
| # | Loss Category | Description |
|---|---|---|
| 1 | Infrastructure and Utilities | Interruptions caused by power failures, network problems, water, gas, or other infrastructure issues. |
| 2 | Machine Failures | Unplanned equipment failures, including mechanical and electrical problems. |
| 3 | Maintenance | Production interruptions caused by planned maintenance activities. |
| 4 | Social Activities | Breaks, meetings, training, and other personnel-related activities. |
| 5 | Staff Shortage | Production interruptions caused by insufficient personnel. |
| 6 | Lack of Material | Production cannot continue because required materials are unavailable. |
| 7 | Lack of Production Order | Equipment is available, but there is no production order or demand. |
| 8 | Changeover | Time spent changing Articles, Orders, cleaning equipment, or preparing for a new production run. |
| 9 | Other Stop Time | Interruptions that do not fit into the established loss categories. |
| 10 | Uncategorized Stops | Production stops that have not yet been assigned a reason or category. |
Performance Losses
| # | Loss Category | Description |
|---|---|---|
| 11 | Minor Stops | Short interruptions that reduce production efficiency. |
| 12 | Speed Losses | Production operating below the defined ideal speed. |
Quality Losses
| # | Loss Category | Description |
|---|---|---|
| 13 | Rework | Additional processing required to bring products up to the required quality standard. |
| 14 | Rejects | Products that cannot continue through the value chain because they do not meet quality requirements. |
Important considerations
Some categories, such as planned maintenance, breaks, and periods without production orders, may fall outside planned production time depending on how your production schedule and OEE calculation are configured.
These activities can still be important to monitor, even when they do not reduce OEE.
Uncategorized Stops should be treated as a temporary classification rather than a permanent loss category.
The objective should be to assign the correct stop reason to all relevant production interruptions, ideally before the end of each shift.
When is the 14 Losses model useful?
The 14 Losses model can be particularly valuable in organizations where several departments contribute to production performance.
For example:
- Maintenance can focus on equipment failures and maintenance-related losses.
- Production teams can address changeovers and operational interruptions.
- Logistics can investigate material shortages.
- Management can address staffing and production planning issues.
Key benefit: A broader operational view that supports assigning responsibilities and coordinating improvement activities across departments.
Comparing the Three Models
Each model provides a different level of detail and supports different improvement objectives.
| 6 Big Losses | 8 Losses | 14 Losses | |
|---|---|---|---|
| Main focus | Equipment effectiveness | Detailed equipment losses | Operational losses and responsibilities |
| Level of detail | Basic | Intermediate | Detailed |
| Main strength | Simple and widely recognized | More detailed technical analysis | Supports cross-functional improvement |
| Particularly useful for | Starting with OEE and TPM | Equipment-focused improvement | Factory-wide operational improvement |
There is no single categorization model that works best for every factory.
The most important consideration is whether the chosen structure helps your organization understand production losses and take meaningful action.
Choosing the Right Loss Categorization
When defining your loss structure, consider the following questions:
- What are your improvement objectives? Are you primarily focused on equipment reliability, production speed, quality, or overall operational efficiency?
- Who will use the information? Operators, Production Managers, Maintenance, and leadership may require different levels of detail.
- Can losses be categorized consistently? Categories should be clear enough that different users classify similar events in the same way.
- Does the structure support action? Each category should help identify an appropriate improvement activity or responsible function.
- Is the structure manageable? Too many categories can make data collection difficult, while too few can hide important information.
A practical approach is to start with a manageable number of categories and introduce additional detail when it creates clear value.
Using Loss Categorization in Good Solutions
Good Solutions enables manufacturers to categorize production stops and analyse production losses across Measure Points, shifts, Articles, and Orders.
By defining meaningful stop reasons and categories, you can build a consistent structure for production loss analysis.
This makes it possible to:
- Identify the largest sources of downtime.
- Compare loss categories across machines and production areas.
- Analyse recurring production interruptions.
- Improve the accuracy of production reporting.
- Prioritize improvement activities based on actual losses.
Operators can contribute to data quality by assigning the correct reasons to production stops, while Production Managers can use the Timeline and Reports to investigate losses and follow up on improvement opportunities.
Remember: The value of loss categorization comes from using the information to improve production, not simply from collecting and classifying data.