In Total Productive Maintenance (TPM), loss refers to any event or condition that reduces the effectiveness of equipment, thereby hindering its ability to produce goods at maximum efficiency, quality, and speed. These losses are critical targets for improvement in TPM, as they directly impact Overall Equipment Effectiveness (OEE).
TPM aims to eliminate these losses to maximize equipment uptime, performance, and product quality. Identifying and categorizing these losses is the first step toward continuous improvement and achieving world-class manufacturing standards.
The Foundation of Losses in TPM: The Six Big Losses
The concept of "losses" in TPM is primarily understood through the Six Big Losses, which are universally recognized categories that prevent equipment from operating at its full potential. These losses are directly linked to the three core elements of Overall Equipment Effectiveness (OEE), namely Availability, Performance, and Quality.
Here's a breakdown of the Six Big Losses:
| OEE Category | Loss Type | Description | Common Examples |
|---|---|---|---|
| Availability | Breakdown Losses | Time when equipment should be running but is stopped due to failures. | Mechanical failures, electrical malfunctions, unscheduled repairs. |
| Setup and Adjustment Losses | Time lost when equipment is stopped for changeovers, adjustments, or tooling. | Product changeovers, material changes, quality adjustments. | |
| Performance | Idling and Minor Stoppages | Brief pauses in production or short stops that don't require maintenance. | Jammed parts, sensor obstructions, component replenishment. |
| Slow Running (Reduced Speed) | Equipment operating below its ideal or designed speed. | Incorrect settings, equipment wear, alignment problems, operator inefficiency, inadequate lubrication. | |
| Quality | Production Defects | Products that do not meet quality standards and require rework or are scrapped. | Scrap, rework, defects from incorrect settings, process variations. |
| Reduced Yield (Startup Rejects) | Defective products produced during startup or until stable production is achieved. | Scrap, rework, defects during warm-up, early production batches not meeting spec. |
Let's delve deeper into each category:
1. Availability Losses
These losses occur when the equipment is supposed to be running but is stopped.
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Breakdown Losses (Equipment Failure)
- Description: These are unexpected and often significant stoppages due to equipment malfunction or failure. They are typically the most disruptive as they are unplanned.
- Impact: Leads to substantial downtime, missed production targets, and increased maintenance costs.
- TPM Approach: Focuses on preventive maintenance, predictive maintenance techniques, and autonomous maintenance to identify and address potential failures before they occur.
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Setup and Adjustment Losses
- Description: Time taken to prepare equipment for a new product run, including changeovers, tooling adjustments, and material setup.
- Impact: While often planned, excessive setup times reduce available production time.
- TPM Approach: Utilizes Single-Minute Exchange of Dies (SMED) principles to drastically reduce changeover times, converting internal setup steps (machine off) to external steps (machine running).
2. Performance Losses
These losses occur when the equipment is running but not at its optimal speed.
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Idling and Minor Stoppages
- Description: Brief, short-duration stops (often less than a few minutes) where the equipment is temporarily idled or stopped, usually without requiring maintenance intervention.
- Impact: Cumulatively, these small stops can add up to significant lost production time. They are often overlooked due to their brief nature.
- TPM Approach: Involves operator training to quickly identify and resolve minor issues, root cause analysis for recurring stoppages, and improvements in material flow or sensor reliability.
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Slow Running (Reduced Speed Losses)
- Description: This loss occurs when equipment operates below its theoretical maximum speed or ideal cycle time. As mentioned in the provided reference, examples include incorrect settings, equipment wear, and alignment problems.
- Impact: Reduces throughput and overall production capacity without necessarily stopping the line.
- TPM Approach: Regular equipment inspections, lubrication, component replacement, standardizing optimal operating parameters, and addressing factors like equipment wear or alignment issues.
3. Quality Losses
These losses occur when the equipment produces defective products or reduced output.
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Production Defects (Process Defects)
- Description: Refers to the production of items that do not meet quality specifications, leading to scrap or rework. These defects can occur throughout the production run.
- Impact: Increases material waste, labor for rework, and potential customer dissatisfaction.
- TPM Approach: Implementing poka-yoke (mistake-proofing) mechanisms, statistical process control (SPC), operator training on quality checks, and root cause analysis of defect generation.
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Reduced Yield (Startup Rejects)
- Description: Specifically refers to the initial production of defective items at the start of a production run or after a changeover until the process stabilizes. The reference also highlights scrap and rework as examples.
- Impact: Wastes raw materials and production time at the critical startup phase.
- TPM Approach: Standardized startup procedures, effective changeover techniques, and optimization of warm-up and calibration processes to minimize initial defects.
By systematically identifying, measuring, and eliminating these six big losses, organizations can significantly improve their OEE, optimize resource utilization, and foster a culture of continuous improvement across their manufacturing operations.
