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Why the Six Big Losses are crucial to your preventative maintenance regime

Peter Thompson, (7 min read)

Manufacturers face a daunting task. They’re expected to achieve increasingly short production time frames, while still meeting quality, safety and compliance standards… It’s a big ask, to say the least.


The key to achieving this goal lies in understanding the Six Big Losses: the fundamental causes of production loss in manufacturing.


Paying attention to the Six Big Losses will:

  • help you more accurately identify the causes of production loss;
  • give you the information required to make the right decisions; and
  • allow you to increase production time with minimal impact on quality.

This blog post will outline each Big Loss and recommend actions to help reduce its impact on production.


But first, some background:


The Six Big Losses were developed along with the Total Productive Maintenance (TPM) approach by the Japan Institute of Plant Maintenance in the 1970s. TPM aims to achieve near-perfect production through proactive and preventative maintenance and employee empowerment. The Six Big Losses are a continuation of this approach.


The losses are also directly tied to Overall Equipment Effectiveness (OEE) – the benchmark rating for measuring manufacturing productivity. OEE is calculated using three main causes for productivity loss: Availability loss, Performance loss, and Quality loss.

The Six Big Losses

We’ve listed the Six Big Losses under their corresponding OEE categories:


Availability losses:

1. Equipment failure, and unplanned downtime

2. Setup and adjustments, or planned downtime


Performance losses:

3. Idling and minor stops

4. Reduced speed


Quality losses:

5. Process defects and rework

6. Start-up losses


Reducing any one of these will help increase output capability and even product quality.


Let’s explore each ‘Big Loss’ in detail.


Availability losses


1. Equipment failure, or unplanned downtime


… is time lost due to unexpected stops in production, largely due to equipment failure or breakdown.


Breakdowns are most often caused by operator error; poor maintenance; and hardware, electrical or software error. Operations managers have the least control over production time during unplanned downtime. This is why it’s the most important Big Loss to get on top of through prevention.


Reducing impact: Consistently measure how much downtime is occurring, when it most occurs, and the root cause/s of failure. If you have a manufacturing execution system (MES), great. If not, make use of the data from your SCADA. This should move you towards more predictive and preventative analysis.


Holistic analysis of operations can help identify breakdown patterns to be addressed.


Finally, operator training and maintenance regimes like TPM have also had proven results for preventing downtime.


(If you want to learn more, read: 10 ways to reduce downtime with preventative maintenance.)


2. Setup and adjustments, or planned downtime

… is the changeover time between the last piece of a product run to the first piece of the next product run. This is the period where all Clean-In-Place procedures, major adjustments or materials changes take place to meet production requirements for the new batch.

It also includes planned maintenance, cleaning, quality inspections or tooling adjustments.

Reducing impact: Make full use of scheduled downtime; for example, if a tooling adjustment is required, do the maintenance, calibration and cleaning too.

Arnott’s took a more drastic approach to reducing setup and adjustments: they upgraded their conveyor and recipe management systems to allow multiple products to be produced on the same line, thereby eliminating the need for changeover altogether.

Performance losses

3. Idling and minor stops

… is the amount of time lost due to small stops (<5 mins). Not to be confused with unplanned downtime, minor stops are typically the small adjustments, jams, misaligned or blocked sensors, incorrect settings or misfeeds fixed by the operator. These regular occurrences can seem inconsequential to operators, making them an ideal Big Loss to target.

Reducing impact: Minor stops is one of the hardest Big Loss to address, because it largely involves changing workplace practices. Getting operators to notice small stops and document them is a starting point. Even better, automate this documentation by building it into the operator’s HMI. It’s an easy way to guarantee data integrity and operator compliance.

From there, you can start correcting behaviour or fixing larger problems, such as faulty equipment.

4. Reduced speed

… is the time wasted when a machine or process is running below its speed capability or Ideal Cycle Time (the standard fastest time to manufacture one piece). Reduced speed can also be due to a machine or process causing a bottleneck, thereby holding up production.

Common causes of reduced speed are incorrect lubrication, inefficient or incorrect start-up and shut-down procedures, worn equipment, dirty machines, operator inexperience and/or environmental conditions, such as extreme heat or dust.

Reducing impact: There are three parts to this solution:

1. Automate the manual tasks that can be automated
2. Educate your operators, as they have the most power to improve cycle time
3. Identify the constraints in process.

Analyse each component of the entire operation using SCADA, MES or manually collected data. For machines, use the Ideal Cycle Time as a benchmark for measuring a machine’s process time. If none is available, use a value generated from the best few days of the year.

If you’re opting for an education approach, consider implementing a TPM program, which focuses on employee ownership to improve machine health and indirectly improve cycle time.


Quality losses


5. Process defects and rework

… refers to defective products that are created during normal production. These can be products that don’t meet quality standards, are damaged or are scrap. Some people only include non-reworkable rejects in this Big Loss. Others will include the rework time and resources required to remake the product.

Reducing impact: Incorrectly calibrated sensors can cause defective products. So, ensure you’re doing regular instrument calibration as part of your preventative maintenance regime.

In addition, try doing more quality checks during production using TPM’s Quality Maintenance technique. This could include visual checkpoints and sensor readings at known problem points during production.

6. Start-up losses

… are the product rejects or scrap created due to adjustments made during start-up. It also includes damaged products created after planned maintenance or changeover.

Reducing impact: Put data collection systems in place to help distinguish between defects occurring during start-up and defects occurring during production. Both require different solutions.

Reduce start-up losses by adding regular loop tuning to your preventative maintenance regime. Finally, ensure Standard Operating Procedures for start-ups are up-to-date and are being read and followed by staff.


One final caution


Mapping your operations against the Six Big Losses is pointless if the data can’t be trusted. Where possible, automate data-collection processes. If that’s not possible, communicate to staff why accurate data collection is important.

The real value of a Six Big Losses program is in the information it provides to make the right decisions. Having a clear understanding of what is draining your production time, and when, will ensure your efforts to increase available production time are successful.


When a machine stops, it can quickly escalate to calling in external help – sometimes unnecessarily. The Breakdown Checklist is designed to get you back online faster. It will get your team thinking about what caused the breakdown and assess the need for external advice. Download the free checklist here.
Get the checklist!

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