1

Concept

Overall Equipment Effectiveness (OEE) is a stand-alone measurement tool that expresses the ratio of actual production capacity to theoretical capacity, which must be achieved without any interruptions or quality losses.

OEE is composed of three key elements: Availability, Performance and Quality Index:

OEE =

where:

Availability = Operating Time / Planned Working Time

It is used to evaluate the cost of downtime and includes any event that causes a downtime in planned production, such as equipment failure, raw material shortages, and changes in production methods.

Performance Index = Ideal Cycle Time / (Operating Time / Total Production) = (Total Production / Operating Time) / Production Rate

Performativity is used to evaluate losses in production rate. It includes any factors that prevent production from running at maximum speed, such as wear and tear on equipment, material failure, and operator error.

Quality Index = Good Goods/Total Production

The Quality Index is used to evaluate the loss of quality and it is used to reflect products that do not meet quality requirements (including reworked products).

OEE

OEE =

Where, Time On Energized = Time on Energized / Load Time

And, load time = calendar working time - scheduled downtime

Start-up time = Load time □ Failure downtime □ Equipment adjustment initialization time (including time spent on activities such as changing product specifications, changing tooling and dies, changing tools, etc.)

Performance start-up rate

And, net start-up rate = machining quantity × actual machining cycle / start-up time

Speed start-up rate = theoretical machining cycle / actual machining cycle

Conformity rate

Global Equipment Efficiency OEE is a simple and practical production management tool, which has been widely used in manufacturing industries in Europe and the United States and multinational enterprises in China. Global Equipment Efficiency Index has become an important standard for measuring the productivity of enterprises, and it is also one of the important methods for the implementation of TPM (Total Productive Maintenance).

The first application of OEE dates back to 1960. It is used as a key metric for TPM (Total Productive Maintenance), which is a factory improvement method. Mobilizing employee ownership by mobilizing employees. This leads to continuous and rapid improvements in manufacturing processes.

2

Scope of Application

1

-The same process of the same type of machine for a single machine.

-The same process for different types of machines on a single machine.

-Different processes for the same machine type on a single machine.

2

The same process for the same type of machine; - The same process for a different type of machine

-The same process for different types of machines.

-Different processes for the same machine type.

3

The function of practicing

-Convenient for the leaders to check the production status and understand the production information.

-Keep the machine and equipment in good and normal operation.

-Make manpower and machine equipment scientific cooperation, give full play to the maximum potential.

-Can help managers find and reduce the six major losses in production.

-It can levy the right problem, analyze and improve the production condition and product quality.

-Can maximize the utilization rate of resources and equipment, tapping the maximum production potential.

4

Benefits

1

Provide objective and scientific decision-making basis for enterprise planning.

-Can provide a lot of value-added opinions and suggestions for the enterprise.

2

-Can collect real-time data of the production line in order to establish a shop floor monitoring and management system.

-Can analyze/track the effective utilization of production line equipment in order to maximize the production potential of the equipment.

-Able to analyze/track the potential risks and six major losses of the production line in order to reduce production costs and improve productivity.

-Can provide visual production reports for enterprise lean production management.

3、Equipment: Reduce equipment failures and maintenance costs, and enhance equipment management to extend equipment life.

4、Employees: Improve labor proficiency and effective work performance by clarifying operating procedures and SOPs to increase productivity.

5、Process: Improve productivity by solving bottlenecks in the process.

6、Quality ： Improve the product straight through rate (FTT), reduce the rework rate, and reduce the quality cost.

5

Cautions

-OEE should be applied to one machine (which can be regarded as a production line of one machine) and not to the whole production line or the whole factory, so as to be meaningful.

-OEE has to be applied as part of an integrated series of comprehensive KPIs and not in isolation, otherwise it will result in the production of larger batch sizes or products with quality defects

-OEE must be consistent with Lean principles, ensuring that the calculation of OEE does not lead to rationalization and institutionalization of waste, e.g., never allowing time for line changes.

6

Influencing factors

1.

Loss of start-up time due to equipment failures and loss of quantity due to generation of defective products, these failures include sudden failures and multi-frequency glitches, for which there is a need to change the traditional concepts of faulty maintenance and to improve the reliability and repairability of the equipment in order to reduce these failures to zero.

2.

When switching from the production of one glass variety to another, due to changeover and adjustment and produce downtime and product defects loss, in order to eliminate such losses should be shortened changeover and adjustment time.

3.

When the production because of temporary error action or equipment idle stoppage, equipment often occurs small stoppages, these are different from the failure of the shutdown, as long as the removal of the blocking workpiece, the production will be restored, and therefore often ignored, in fact, these small stoppages on the equipment efficiency has a great impact on the quantitative treatment should be given. Make it reduced to zero.

4.

Loss of speed is due to the difference between the design speed of the equipment and the actual operating speed, which is ignored in actual production, it should be prudent to increase the operating speed of the equipment, so as to detect potential problems in the state of the equipment, so that the actual operating speed to meet the design speed, and through the improvement of the activities to exceed the design speed.

5.

Defects in work-in-process and loss of rework quality are caused by malfunctioning of production equipment; for sudden defects, they are easily corrected by adjusting the equipment to its normal condition: for chronic defects, they are difficult to recognize and must be eliminated by careful investigation and innovative methods.

6.

Start-up loss is the loss of quality from the start-up of the equipment to stabilize the production period, the size of the loss depends on the stability of the state of the process, the level of maintenance of the equipment, the operator's skill level, and so on.   Usually in actual production, the amount of such losses is still quite large and should be minimized as much as possible.

7

Calculation example

Let's take an example to illustrate the calculation method of OEE:

Set a certain equipment a day working time of 8h, pre-shift planning downtime 15min, fault downtime 30min, equipment adjustment 25min, the theoretical processing cycle of the product is 0.6 min / piece, a total of 450 pieces of products processed a day, there are 20 pieces of scrap, for the OEE of this equipment.

According to the above can be seen:

Program running time = 8x60-15 = 465 (min)

Actual running time = 465-30-25 = 410 (min)

Efficiency = 410/465 = 0.881 (88.1%)

Total production = 450 (pieces)

Ideal speed x actual running time = 1/0.6 x 410 = 683

Expressive = 450/683 = 0.658 (65.8%)

(Alternative solution: expressivity = ideal processing cycle * number of units produced / actual running time = 0.6 * 450/410 = 0.658 (65.8%))

Quality Index = (450-20)/450 = 0.955 (95.5%)

OEE = Effectiveness x Expressiveness x Quality Index = 55.4%

Another OEE algorithm:

OEE = products meeting quality requirements / maximum theoretical output

Maximum theoretical output in this example = (8*60-15)/0.6 pieces = 775 pieces

Products meeting quality requirements = 450-20 = 430 pieces

OEE=430/775*100%=55.4

8

Others

In the calculation of OEE, encountered outside the planned downtime external factors, such as no orders, water, electricity, gas, steam, stoppage of materials and other factors resulting in downtime losses, often do not know to put this part of the loss of which part to calculate. Some people include them in the planned downtime, but they are not really planned downtime. If counted as a failure downtime, but not the equipment itself caused by the failure of the downtime. The calculations are so varied that they are not comparable across organizations. These problems can be solved when we extend the calculation of OEE with a new concept and algorithm called “Total Equipment Effective Productivity (TEEP)”.   The structure of TEEP and the relationship between the characteristic time, loss and each efficiency.