Overall equipment effectiveness

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Overall equipment effectiveness [1] (OEE) is a measure of how well a manufacturing operation is utilized (facilities, time and material) compared to its full potential, during the periods when it is scheduled to run. It identifies the percentage of manufacturing time that is truly productive. An OEE of 100% means that only good parts are produced (100% quality), at the maximum speed (100% performance), and without interruption (100% availability).

Contents

Measuring OEE is a manufacturing best practice. By measuring OEE and the underlying losses, important insights can be gained on how to systematically improve the manufacturing process. OEE is an effective metric for identifying losses, bench-marking progress, and improving the productivity of manufacturing equipment (i.e., eliminating waste). The best way for reliable OEE monitoring is to automatically collect all data directly from the machines.

Total effective equipment performance(TEEP) is a closely related measure which quantifies OEE against calendar hours rather than only against scheduled operating hours. A TEEP of 100% means that the operations have run with an OEE of 100% 24 hours a day and 365 days a year (100% loading).

The term OEE was coined by Seiichi Nakajima. [2] It is based on the Harrington Emerson way of thinking regarding labor efficiency.[ citation needed ] The generic form of OEE allows comparison between manufacturing units in differing industries. It is not however an absolute measure and is best used to identify scope for process performance improvement, and how to get the improvement. [3] OEE measurement is also commonly used as a key performance indicator (KPI) in conjunction with lean manufacturing efforts to provide an indicator of success. OEE can be illustrated by a brief discussion of the six metrics that comprise the system (the "Six Big Losses").

Calculations for OEE and TEEP

The OEE of a manufacturing unit are calculated as the product of three separate components:

To calculate the Total Effective Equipment Performance(TEEP), the OEE is multiplied by a fourth component:

The calculations of OEE are not particularly complicated, but care must be taken as to standards that are used as the basis. Additionally, these calculations are valid at the work center or part number level but become more complicated if rolling up to aggregate levels. [4]


9 Major Downtime Losses Affect Availability
[ citation needed ]

  1. Machine broken
  2. Setup time
  3. Machine adjustment
  4. Quality issues from material
  5. Material missing
  6. Operations team member missing
  7. Tool change
  8. Startup loss
  9. Other-Miscellaneous

Overall equipment effectiveness

Each of the three components of the OEE points to an aspect of the process that can be targeted for improvement. OEE may be applied to any individual Work Center, or rolled up to Department or Plant levels. This tool also allows for drilling down for very specific analysis, such as a particular Part Number, Shift, or any of several other parameters. It is unlikely that any manufacturing process can run at 100% OEE. Many manufacturers benchmark their industry to set a challenging target; 85% is not uncommon.

Alternatively, and often easier, OEE is calculated by dividing the minimum time needed to produce the parts under optimal conditions by the actual time needed to produce the parts. For example:

Total effective equipment performance

Whereas OEE measures efficiency based on scheduled hours, TEEP measures efficiency against calendar hours, i.e.: 24 hours per day, 365 days per year.

TEEP, therefore, reports the 'bottom line' utilization of assets.

TEEP = Loading * OEE [4]

Loading

The Loading portion of the TEEP Metric represents the percentage of time that an operation is scheduled to operate compared to the total Calendar Time that is available. The Loading Metric is a pure measurement of Schedule efficiency and is designed to exclude the effects how well that operation may perform.

Calculation: Loading = Scheduled Time / Calendar Time

Example:

A given Work Center is scheduled to run 5 Days per Week, 24 Hours per Day.

For a given week, the Total Calendar Time is 7 Days at 24 Hours.

Loading = (5 days x 24 hours) / (7 days x 24 hours) = 71.4%

Availability

The Availability portion of the OEE Metric represents the percentage of scheduled time that the operation is available to operate. The Availability Metric is a pure measurement of Uptime that is designed to exclude the effects of Quality and Performance. The losses due to wasted availability are called availability losses. [5]

Example: A given Work Center is scheduled to run for an 8-hour (480-minute) shift with a 30-minute scheduled break and during the break the lines stop, and unscheduled downtime is 60 minutes.

The scheduled time = 480 minutes - 30 minutes = 450 minutes.

Operating Time = 480 Minutes – 30 Minutes Schedule Loss – 60 Minutes Unscheduled Downtime = 390 Minutes

Calculation: Availability = operating time / scheduled time [6]

Availability = 390 minutes / 450 minutes = 86.6%

Performance and productivity


Calculation: Performance (Productivity) = (Parts Produced * Ideal Cycle Time) / Operating time [7]

Example:

A given Work Center is scheduled to run for an 8-hour (480-minute) shift with a 30-minute scheduled break.

Operating Time = 450 Min Scheduled – 60 Min Unscheduled Downtime = 390 Minutes

The Standard Rate for the part being produced is 40 Units/Hour or 1.5 Minutes/Unit

The Work Center produces 242 Total Units during the shift. Note: The basis is Total Units, not Good Units. The Performance metric does not penalize for Quality.

Time to Produce Parts = 242 Units * 1.5 Minutes/Unit = 363 Minutes

Performance (Productivity) = 363 Minutes / 390 Minutes = 93.1%

Quality

The Quality portion of the OEE Metric represents the Good Units produced as a percentage of the Total Units Started. The Quality Metric is a pure measurement of Process Yield that is designed to exclude the effects of Availability and Performance. The losses due to defects and rework are called quality losses and quality stops. Reworked units which have been corrected are only measured as unscheduled downtime while units being scrapped can affect both operation time and unit count.

Calculation: Quality = (Units produced - defective units) / (Units produced) [6]

Example:

242 Units are produced. 21 are defective.

(242 units produced - 21 defective units) = 221 units

221 good units / 242 total units produced = 91.32%

"Six Big Losses"

Example of OEE and Six Loss calculation OEE SixLoss Calculation Example.png
Example of OEE and Six Loss calculation

To be able to better determine the sources of the greatest loss and to target the areas that should be improved to increase performances, these categories (Availability, Performance and Quality) have been subdivided further into what is known as the 'Six Big Losses' to OEE.

These are categorized as follows:

AvailabilityPerformanceQuality
Planned DowntimeMinor StopsProduction Rejects
BreakdownsSpeed LossRejects on Start up

The reason for identifying the losses in these categories is so that specific countermeasures can be applied to reduce the loss and improve the overall OEE.


Total Productive Maintenance

Continuous improvement in OEE is the goal of TPM (Total Productive Maintenance). Specifically, the goal of TPM as set out by Seiichi Nakajima is "The continuous improvement of OEE by engaging all those that impact on it in small group activities". To achieve this, the TPM toolbox sets out a Focused improvement tactic to reduce each of the six types of OEE loss. For example, the Focused improvement tactic to systematically reduce breakdown risk sets out how to improve asset condition and standardise working methods to reduce human error and accelerated wear.

Combining OEE with Focused improvement converts OEE from a lagging to a leading indicator. The first Focused improvement stage of OEE improvement is to achieve a stable OEE. One which varies at around 5% from the mean for a representative production sample. Once an asset efficiency is stable and not impacted by variability in equipment wear rates and working methods. The second stage of OEE improvement (optimisation) can be carried out to remove chronic losses. Combining OEE and TPM Focused improvement tactics creates a leading indicator that can be used to guide performance management priorities. As the TPM process delivers these gains through small cross functional improvement teams, the process of OEE improvement raises front line team engagement/problem ownership, collaboration and skill levels. It is this combination of OEE as a KPI, TPM Focused improvement tactics and front line team engagement that locks in the gains and delivers the TPM goal of year on year improvement in OEE.

Heuristic

OEE is useful as a heuristic, but can break down in several circumstances. For example, it may be far more costly to run a facility at certain times. Performance and quality may not be independent of each other or of availability and loading. Experience may develop over time. Since the performance of shop floor managers is at least sometimes compared to the OEE, these numbers are often not reliable, and there are numerous ways to fudge these numbers. [8]

OEE has properties of a geometric mean. As such it punishes variability among its subcomponents. For example, 20% * 80% = 16%, whereas 50% * 50% = 25%. When there are asymmetric costs associated with one or more of the components, then the model may become less appropriate.

Consider a system where the cost of error is exceptionally high. In such a condition, higher quality may be far more important in a proper evaluation of efficiency than performance or availability. OEE also to some extent assumes a closed system and a potentially static one. If one can bring in additional resources (or lease out unused resources to other projects or business units) then it may be more appropriate for example to use an expected net present value analysis.

Variability in flow can also introduce important costs and risks that may merit further modeling. Sensitivity analysis and measures of change may be helpful.

Further reading

See also

Related Research Articles

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Focused improvement in the theory of constraints is an ensemble of activities aimed at elevating the performance of any system, especially a business system, with respect to its goal by eliminating its constraints one by one and by not working on non-constraints.

Kaizen is a concept referring to business activities that continuously improve all functions and involve all employees from the CEO to the assembly line workers. Kaizen also applies to processes, such as purchasing and logistics, that cross organizational boundaries into the supply chain. It has been applied in healthcare, psychotherapy, life coaching, government, manufacturing, and banking.

Productivity is the efficiency of production of goods or services expressed by some measure. Measurements of productivity are often expressed as a ratio of an aggregate output to a single input or an aggregate input used in a production process, i.e. output per unit of input, typically over a specific period of time. The most common example is the (aggregate) labour productivity measure, one example of which is GDP per worker. There are many different definitions of productivity and the choice among them depends on the purpose of the productivity measurement and data availability. The key source of difference between various productivity measures is also usually related to how the outputs and the inputs are aggregated to obtain such a ratio-type measure of productivity.

<span class="mw-page-title-main">Performance indicator</span> Measurement that evaluates the success of an organization

A performance indicator or key performance indicator (KPI) is a type of performance measurement. KPIs evaluate the success of an organization or of a particular activity in which it engages. KPIs provide a focus for strategic and operational improvement, create an analytical basis for decision making and help focus attention on what matters most.

Reliability engineering is a sub-discipline of systems engineering that emphasizes the ability of equipment to function without failure. Reliability describes the ability of a system or component to function under stated conditions for a specified period. Reliability is closely related to availability, which is typically described as the ability of a component or system to function at a specified moment or interval of time.

<span class="mw-page-title-main">Operations management</span> In business operations, controlling the process of production of goods

Operations management is concerned with designing and controlling the production of goods and services, ensuring that businesses are efficient in using resources to meet customer requirements.

Quality, cost, delivery (QCD), sometimes expanded to quality, cost, delivery, morale, safety (QCDMS), is a management approach originally developed by the British automotive industry. QCD assess different components of the production process and provides feedback in the form of facts and figures that help managers make logical decisions. By using the gathered data, it is easier for organizations to prioritize their future goals. QCD helps break down processes to organize and prioritize efforts before they grow overwhelming.

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Capacity planning is the process of determining the production capacity needed by an organization to meet changing demands for its products. In the context of capacity planning, design capacity is the maximum amount of work that an organization or individual is capable of completing in a given period. Effective capacity is the maximum amount of work that an organization or individual is capable of completing in a given period due to constraints such as quality problems, delays, material handling, etc.

High availability (HA) is a characteristic of a system that aims to ensure an agreed level of operational performance, usually uptime, for a higher than normal period.

Takt time, or simply takt, is a manufacturing term to describe the required product assembly duration that is needed to match the demand. Often confused with cycle time, takt time is a tool used to design work and it measures the average time interval between the start of production of one unit and the start of production of the next unit when items are produced sequentially. For calculations, it is the time to produce parts divided by the number of parts demanded in that time interval. The takt time is based on customer demand; if a process or a production line are unable to produce at takt time, either demand leveling, additional resources, or process re-engineering is needed to ensure on-time delivery.

Overall labor effectiveness (OLE) is a key performance indicator (KPI) that measures the utilization, performance, and quality of the workforce and its impact on productivity.

Manufacturing execution systems (MES) are computerized systems used in manufacturing to track and document the transformation of raw materials to finished goods. MES provides information that helps manufacturing decision-makers understand how current conditions on the plant floor can be optimized to improve production output. MES works as real-time monitoring system to enable the control of multiple elements of the production process.

The following outline is provided as an overview of and topical guide to production:

In a business context, operational efficiency is a measurement of resource allocation and can be defined as the ratio between an output gained from the business and an input to run a business operation. When improving operational efficiency, the output to input ratio improves.

Total productive maintenance (TPM) started as a method of physical asset management, focused on maintaining and improving manufacturing machinery in order to reduce the operating cost to an organization. After the PM award was created and awarded to Nippon Denso in 1971, the JIPM, expanded it to include 8 Activities of TPM that required participation from all areas of manufacturing and non-manufacturing in the concepts of lean manufacturing. TPM is designed to disseminate the responsibility for maintenance and machine performance, improving employee engagement and teamwork within management, engineering, maintenance, and operations.

In production and project management, a bottleneck is a process in a chain of processes, such that its limited capacity reduces the capacity of the whole chain. The result of having a bottleneck are stalls in production, supply overstock, pressure from customers, and low employee morale. There are both short and long-term bottlenecks. Short-term bottlenecks are temporary and are not normally a significant problem. An example of a short-term bottleneck would be a skilled employee taking a few days off. Long-term bottlenecks occur all the time and can cumulatively significantly slow down production. An example of a long-term bottleneck is when a machine is not efficient enough and as a result has a long queue.

In lean manufacturing, machine operator efficiency (MOE) is the performance of an employee who operates industrial machinery. The operator's efficiency is measured as the time spent producing product divided by the time the operator is on duty. For example: if an operator is assigned to run a CNC machine tool for seven hours, but they only have four hours' worth of continuous uninterrupted output of workpieces—their MOE rating is 57% for this seven-hour period of time.

Power system operations is a term used in electricity generation to describe the process of decision-making on the timescale from one day to minutes prior to the power delivery. The term power system control describes actions taken in response to unplanned disturbances in order to provide reliable electric supply of acceptable quality. The corresponding engineering branch is called Power System Operations and Control. Electricity is hard to store, so at any moment the supply (generation) shall be balanced with demand. In an electrical grid the task of real-time balancing is performed by a regional-based control center, run by an electric utility in the traditional electricity market. In the restructured North American power transmission grid, these centers belong to balancing authorities numbered 74 in 2016, the entities responsible for operations are also called independent system operators, transmission system operators. The other form of balancing resources of multiple power plants is a power pool. The balancing authorities are overseen by reliability coordinators.

References

  1. Guimarães, Nilo (16 August 2019). "OEE, TEEP e IROG! Importantes Métricas Para a Indústria". CONAENGE-Congresso Online de Eng. Mecânica e Automação (in Brazilian Portuguese). Retrieved 30 May 2021.
  2. "Origin of OEE". OEE Foundation. Retrieved 15 July 2015.
  3. "Understanding OEE". Archived from the original on 23 September 2016. Retrieved 7 July 2015.
  4. 1 2 "OEE Overview - with Calculation Methods" (PDF). Archived from the original (PDF) on 27 September 2013. Retrieved 23 September 2013.
  5. "Understanding Availability" . Retrieved 9 October 2014.
  6. 1 2 "Calculate OEE - Simple Calculator & OEE Formulas". Mingo Smart Factory. Retrieved 15 October 2016.
  7. "OEE Primer: Calculating OEE" . Retrieved 9 July 2013.
  8. "Top Three Methods on how to Fudge Your OEE" . Retrieved 5 January 2014.