By Matthias Kohlbrand In
The ideal technical cycle as the cycle time for the manufacturing process for a cycle quantity is the foundation for the calculation of equipment effectiveness metrics, like Overall Equipment Effectiveness (OEE), Net Equipment Effectiveness (NEE) and Total Equipment Effective Equipment Productivity (TEEP). If the cycle is set incorrectly or even unknown, the resulting metrics will also be invalidated.
COSMINO AG is a provider of software in the functional area of Manufacturing Execution Systems (MES). Predominantly, the acquisition and calculation of process losses (equipment effectiveness) plays an important role for COSMINO's customers. The foundation for the calculation of equipment effectiveness is respectively the time required for processing a performance unit. If this cycle has been specified as part counts, meters or kilograms (or other units of measure), does not matter to the Cosmino MES Plus software.
The following definitions of cycles are used by Cosmino.
Technical Cycle (Tc) equals machine time + operating time
Machine time equals the work center's pure processing time (without equipment and tool changes)
Operating time equals the personnel time for the total of the primary and secondary activities needed for manufacturing a cycle unit (such as handling time, clamping and so forth)
In this, the technical cycle has the most significant effect on the initial value of the equipment effectiveness statistics. Each deviation from the targeted technical cycle will be assessed as unscheduled modifications to the cycle, regardless of whether the equipment is running more slowly or even more quickly than defined by the technical cycle.
Analysis of the cycle delays proves which machines have been affected most often and to which degree. Measured cycle delays may however also indicate a non-optimal technical cycle setting.
To each Product its own Cycle
The technical cycle of a component can depend on a variety of factors.
- Components may be produced at various speeds using various equipment. The selection of the equipment will affect the technical cycle.
- The number of employees used for the assembly line will affect the speed of production. The number of employees will affect the technical cycle.
- Tools of different levels of quality are available for the assembly steps. The quality or type of tool will affect the technical cycle.
- Surcharges and additions (time for individual distribution and recovery and performance factors) will be added to the processing time. These surcharges and additions will affect, or even distort, the technical cycle.
Entry of the technical cycle into the Enterprise Resource Planning (ERP) system will only work when the cycles managed by such systems are in relation to the means of processing and tools, and when the staffing of the equipment is taken into consideration. This happens in very few cases.
In addition, the ERP cycles often contain surcharges and additions in the form of time for distribution and recovery and performance factors, because such issues are important when calculating an order. The additions to processing time contingent on people should not be taken into consideration for the determination of the 100% effectiveness of a piece of equipment.
When properly calculating the effectiveness of the equipment, the change of equipment, tools or number of employees during a production process should be taken into consideration, such as when an employee is removed from an assembly line or breakage of a tool induces the use of a tool of poorer quality, which in turn causes processing to continue at a slower speed. If an order is distributed between several production systems with different performance capacities then different technical cycles will be required to properly identify the effectiveness of the equipment. In doing so, companies cannot avoid determining the technical cycle in consideration of all conditions and maintaining the technical cycle in the system. Because the ERP system often does not provide this capability, there are advantages to using MES installations, which have been prepared for detailed management of cycles as a rule and which also make additional adjustment of the ERP cycles possible.
Woe to the Person who does not know their Cycles
If erroneous assumptions have been made about the technical cycle or not all the circumstances have been taken in account, this will heavily affect the calculation of the equipment effectiveness and not permit proper assessment of the metrics OEE, TEEP and NEE. Because each of the factors indicated above can heavily influence the technical cycle and the metrics along with it, OEE values totaling more than 100% are possible. In the worst case, the erroneous assumption will go unnoticed and be incorrectly entered into the follow-up calculations for an order, which may lead to significant financial losses over the long term. For this reason, it is often better to not rely on the cycle times from the ERP system when calculating the equipment effectiveness metrics.
Chart showing which products are running ahead of, or behind, scheduled cycle times. Conclusions based on the analysis of the technical cycles should immediately be included into the product cost calculations.
For good MES system installations, like Cosmino MES Plus, various cycles can be stored for the respective constellations of products, equipment, tools and number of operators.
By doing so, the same technical cycle can be used for a certain constellation of products, equipment, tools and operators throughout the plant, even if the ERP cycles exhibit different cycle values based on, for example, different surcharges and additions.
Every Beginning is Difficult
The ideal technical cycles cannot always be calculated from the planned cycle times stored in the ERP system. Because nowadays production time is seldom measured (such as using the REFA methods), work schedules are often based on outdated values. In practice, this means that the technical cycle is often affected by an assumption. In many companies, the fastest cycle ever measured is used. In order to discover this, a machine data acquisition system must be installed. The ideal technical cycle for each combination of products, equipment, tools and various teams of employees can then be approximated in steps after the introduction of the software.
Accordingly, adjusting the cycles should be the motto. As a rule, correction of the cycle means reducing it, which will unavoidably lead to fall offs in the values of the effectiveness metrics, such as OEE, TEEP and NEE.
Knowing the cycle for each combination of products, equipment, tools and number of employees is barely possible for a large number of different products or manufacturing to order. For this reason, products, equipment and tools can also be combined into groups that share a uniform cycle time. If the product will be made again, the previous fastest cycle will already be known, which can be used as a reference time for the technical cycle.
One Cycle fits All
Because of the various problem issues related to calculating the technical cycle, COSMINO AG developed something special for their Cosmino MES Plus manufacturing execution system. This feature allows each metric for effectiveness to be calculated at various cycles, independent of the technical cycle. For example, for benchmarking comparable processes using comparable equipment or for the final comparison of the OEE increase based on the first historical technical cycle created.
The effectiveness of the equipment is one of the most important technical metrics for production, because continuous improvement is essential for the sustainable success of the company. Reliable calculations can then be used to discover and evaluate your unique potential for improvement. Finally, the reliability of these effectiveness statistics will primarily depend on the technical cycle. Software partners, like COSMINO AG, know this and support the detection and determination of the proper technical cycle even before the installation of data acquisition systems. Only in this manner can customers achieve reasonable results using manufacturing execution systems and benefit from the long-term use of the Cosmino software.
Talk with us about it. We will be happy to advise you.
