The Six Big Losses of OEE in Maintenance Explained

Overall Equipment Effectiveness (OEE) provides a clear measure of how well manufacturing equipment performs. But behind this important operations and maintenance metric lie six major losses that can erode equipment efficiency and lead to productivity losses.

These losses fall into different categories and highlight where machines fail to meet their full potential. The article explains these losses, their impact, and how maintenance practices help curb them.

What are the Six Big Losses of OEE (Overall Equipment Effectiveness)?

The Six Big Losses fall into three buckets: downtime, speed, and quality. Each bucket ties directly to one of the three OEE factors as

• Downtime: Equipment Failure and Setup and Adjustments
• Speed: Idling and Minor Stops and Reduced Speed
• Quality: Process Defects and Reduced Yield

Each of these losses have been elaborated in detail below:

Equipment Failure

Equipment failure is an unplanned stoppage of an equipment. The unexpected failure results in unplanned downtime and must be addressed to prevent productivity loss. Reasons can be numerous -mechanical faults, electrical issues, or tool breakage. Since the production process halts, every minute lost contributes to Availability loss.

Common causes of equipment failure include worn-out bearings, overheating motors, misaligned shafts, poor lubrication, missed inspection, and skipping planned maintenance tasks.

Setup and Adjustments

Setup and adjustment losses occur during planned downtime. Machines don’t run because they’re being prepped for a new job or adjusted for a new spec. Changeovers, tool swaps, calibration, and cleaning all fall under this category. Though scheduled, these stops still eat into Availability.

Long setup times usually point to inefficient procedures. If operators need to hunt for tools or wait for instructions, the clock ticks. If adjustments require trial and error, more production time slips away. The goal isn’t to eliminate setup. The goal is to reduce its duration.

Idling and Minor Stops

This is a speed loss where minor stops don’t shut down a machine completely, rather, they cause brief interruptions. A sensor trips, a part jams, or an operator resets the system. These issues add up and cause slow cycles. They fall under Performance losses.

Unlike full breakdowns, minor stops don’t trigger alarms. They don’t call for a technician. But they still reduce the actual run time. A machine that stops for 30 seconds every 10 minutes loses hours over a shift.

Reduced Speed

Reduced speed means the machine runs slower than its designed cycle time. It doesn’t stop and keeps crawling. Over time, performance takes a hit, and the machine produces fewer parts per hour than expected.

Causes range from worn tooling to poor lubrication. Sometimes the operator runs the machine slower to avoid defective parts. Sometimes the material doesn’t feed properly. Environmental factors like temperature and humidity also affect machine performance. Whatever the reason, the machine underperforms, bringing down production quality.

Process Defects

Process defects occur when products made during normal production fail to meet required specifications and must be scrapped or reworked. The machine is running, but the output is unusable or requires additional labor to correct. These defects directly lower Quality because the time and resources spent on producing faulty parts do not contribute to good output.

These defects stem from tool wear, incorrect settings, or poor material. Sometimes the machine drifts out of tolerance. Sometimes the operator misses a step. Each bad part wastes time, material, and labor.

Reduced Yield

Reduced yield covers defects that occur during startup. The first few parts off the line don’t meet spec. They get tossed and so product quality suffers. The machine wasn’t ready, but production started anyway.

Startup defects usually point to poor warm-up procedures. Reasons could be that the machine wasn’t calibrated, the tooling wasn’t seated properly, or the material wasn’t conditioned. Whatever the cause, the first batch fails.

What is the Impact of Each Loss on OEE

Each of the Six Big Losses chips away at your overall equipment effectiveness (OEE) score in a different way. We analyze this impact for each loss to keep maintenance teams ready for preventing losses.

1. Equipment Failure

   Availability is drastically affected, because a machine that’s down for repairs doesn’t produce anything. If a line runs 16 hours a day and loses 2 hours to breakdowns, Availability drops by over 12%. That’s a direct hit. When failures occur, the ripple effect spreads: operators are left waiting, schedules begin to slip, maintenance teams scramble to recover, morale declines if issues are frequent, and planning suffers.

2. Setup and Adjustments

   Hits Availability directly. The machine isn’t broken, but it is just not producing. If changeovers take 45 minutes and happen twice a shift, that’s 90 minutes of lost production time. Over a week, that adds up. Based on a team’s judgement things differ. Some teams treat setup time as fixed. Others treat it as flexible. The difference lies in how they approach the process. Standard work, quick-change tooling, and pre-stage kits shrink setup time. But only if someone tracks it.

3. Idling and Minor Stops

   Even though these stops don’t stop the machine for long, they interrupt flow and affect Performance. If a machine stops for 30 seconds every 10 minutes, that’s 18 minutes lost per shift. Multiply that across machines and shifts, and the loss grows. These stops could thus be very frustrating to operators. They break rhythm and create uncertainty. If the cause isn’t clear, operators guess. If the fix isn’t simple, they wait. Either way, production slows.

4. Reduced Speed

   This loss hits Performance harder than most teams realize. A machine rated for 100 parts per hour that runs at 80 produces 20 fewer parts every hour. Over a 10-hour shift, that’s 200 defective parts. As mentioned earlier, Speed losses don’t trigger alarms. They don’t show up in downtime logs, but they show up in output. If the numbers don’t match the plan, speed is the culprit.

5. Process Defects

   Process defects result in Quality loss. The machine runs, the parts look fine, but inspection says otherwise. If 5% of parts fail inspection, that’s 5% of machine time wasted. If rework takes time, the loss grows. Defects also affect customer trust, because bad parts lead to returns, and returns lead to complaints which lead to strained relationships and loss or orders.

6. Reduced Yield

   Reduction in yield hits Quality during startup. In this case the machine starts cold, and the first few parts fail. If startup takes 15 minutes and produces 10 bad parts, that’s 15 minutes lost. If the line starts 4 times a day, that’s an hour gone. Startup losses point to preparation. If the machine is not ready, the parts won’t be right. If the tooling isn’t seated, the parts will not hold spec. If the material is not conditioned, the parts will not pass inspection.

How Maintenance Practices Address Each Loss

Each maintenance practice offers an avenue for overcoming a loss, as summarized:

To Wrap Up

OEE score tells a story not just about your equipment but about the efficiency of your manufacturing process, and the Six Big Losses fill in the details. They reveal where time slips away, where machines underperform, and where quality falters. Maintenance plays a central role in tackling each of these losses—not through guesswork, but through careful data analysis, disciplined processes, and decisive action.

A computerized maintenance management system (CMMS) becomes indispensable in this effort. It helps track equipment performance, schedule preventive maintenance, and provide real-time insights into recurring issues. Using a CMMS, you can track each type of loss and can come up with measures to mitigate and eliminate them.