Overall equipment effectiveness
|Overall equipment effectiveness|
Overall Equipment Effectiveness (OEE) - that is, total equipment efficiency, it is an indicator that allows the producer to evaluate the machine's efficiency. Thus, the percentage shows how many machines have made what theoretically they are able to do. This indicator consists of three parameters: accessibility, efficiency and quality. It is calculated using the formula:
OEE = availability x performance x quality x 100%
This indicator is the basic measure in the Total Productive Maintenance system, which helps maintain the highest efficiency of machines.
OEE was first described in the book Seiichi Nakajima "TPM tenkai" in 1982. At the end of the 80s The 20th century the concept of TPM has become more and more popular among others thanks to Productivity Press publishing the English translation of Nakajima books. This led to the use of the TPM method outside Japan. The OEE index used in the TPM system was calculated to eliminate losses in the production process. In 1995. SEMATECH has published "Semiconductor Manufacturing Productivity Overall Equipment Effectiveness (OEE)" , where guidelines for the implementation of OEE were in. At present, this indicator is used around the world in virtually any type of production process.
Availability includes loss of availability, i.e. all events that stop further production for a period of time. Includes unplanned interruptions (e.g. failures) and planned (e.g. changes).
Performance takes into account the loss of performance, that is all the factors that make production run slower than the maximum speed at which it can work. It includes small breaks as well as slow cycles related to, for example, starting machines.
Quality takes into account the loss of quality, i.e. those manufactured products that do not meet the quality standards. It includes production recovery as well as reduced performance when starting the machine.
Six great losses
In order to be able to specify in more detail what contributes to the largest losses, a specific loss has been assigned to each OEE parameter. They are classified as follows:
|Availability||Unscheduled breaks||Shortage of materials|
|Performance.||Smaller breaks.||Speed reduction|
|Quality||Production defects||Reduce performance|
The OEE indicator is used all over the world as an indicator for measuring the machine's efficiency. However, the nature of its calculation makes it very difficult to achieve a high OEE score. For example: if all three parameters are 90%, the OEE will be only 73%. Therefore, the "global standard" of this indicator has been set, which is:
- 95% efficiency
- 99% quality
- OEE 85%
To effectively calculate the OEE indicator, the following steps should be taken:
- Determine the total production time.
- Specify the planned production time (taking into account the planned downtime).
- Perform an efficiency loss analysis.
- Determining the availability indicator.
- Determining the performance indicator.
- Determining the quality index.
- Calculation of OEE - Overall Equipment Effectiveness.
An example of the OEE calculation
- Test carried out for one shift - 8 hours, or 480 minutes (total production time)
- Lunch break - 30 minutes
- Measured total failure time - 40 minutes
- Nominal machine performance - 40 pieces / minute
- Speed losses - 40 minutes
- Waste - 520 pieces
Schema of task solution:
Determination of the planned production time:
working time (length of change) - planned stoppages (break for meals) planned production time = 480 min. - 30 minutes. = 450 minutes
Determining the operating time: planned production time - unplanned downtime (machine failure) operating time = 450 min. - 40 minutes = 410 min
Determining the availability indicator:
operating time / planned production time availability = 410 min. / 450 min. 1.
Determination of speed loss:
working time with lower efficiency x reduced performance loss of speed = 40 min. x 50% = 20min Working at 50% efficiency is the equivalent of working at maximum efficiency for half the time and downtime for the rest of the time.
Calculation of net operating time:
operational time - speed losses 410 min. - 20 minutes = 390 min.
Calculation of the performance indicator:
net operating time / operational time efficiency = 390 min. / 410 min. 1.
Determination of qualitative losses:
number of defective products / performance quality loss = 520 pcs / 40 pcs./min. = 13 min
Calculation of the effective production time:
net operating time - quality losses effective production time = 390 min. - 13 min = 377 minutes
Calculation of the quality index:
time of effective production / operational time net quality = 377 min. / 390 min. = 96.7%
Calculation of the OEE indicator:
availability x yield x quality OEE = 91,1% x 95,1% x 96,7% = 83,8%
RESULT: Total Equipment Effectiveness for an 8-hour change in the plant is 83.8%.
Data collection methods
To calculate the OEE indicator, collect data, process it, and then prepare the results. These processes can be carried out in many ways using, among others (W. Mazurek 2014, pp. 12-14)
- The "paper" method
- The method of manually supported software
- MES (Manufacturing Execution System)
- Golem OEE SuperVisor Next - a simple MES system
- Andon system
- OEE calculator
- Muchiri, P., & Pintelon, L. (2008). Performance measurement using overall equipment effectiveness (OEE): literature review and practical application discussion. International journal of production research, 46(13), 3517-3535.
- Bamber, C. J., Castka, P., Sharp, J. M., & Motara, Y. (2003). Cross-functional team working for overall equipment effectiveness (OEE). Journal of Quality in Maintenance Engineering, 9(3), 223-238.
- Singh, R., Shah, D. B., Gohil, A. M., & Shah, M. H. (2013). Overall Equipment Effectiveness (OEE) calculation-Automation through hardware & software development. Procedia Engineering, 51, 579-584.