One of the metrics, also called Key Process Indicators (KPI), which are often used to calculate production efficiency is the so-called OEE, an acronym for Overall Equipment Effectiveness. This metric has now become an industrial standard and therefore widely spread in the factories and implemented in the various MES.
However, this metric is mostly used to evaluate the efficiency of use of an industrial asset, therefore very often a limited part of the entire production process, mostly consisting of a series of mechanical processes, treatments, manual operations, transport, inspection and testing.
In my past experience I have worked in industrial contexts where the OEE of the plants was higher than 70-75%, however the total lead time was months, compared to a cycle time of hours.
- Can we define this process as an efficient production process? In my opinion absolutely not.
- Can we therefore rely only on the OEE as a control parameter? Obviously the answer is no.
In this post we try to define what the metrics and tools can be used to give a more comprehensive answer to the measurement of the efficiency of a process.
Effectiveness, efficiency and lead time
- Low system efficiency (plants, flows, workforce)
- Low quality (additional process controls, management of non-conformities, rework etc.)
How to measure the efficiency of the production system?
- Processing: machining, bending, die casting etc.
- Special processes: heat treatments, chemical processes, washing etc.
- Logistics: transport of parts from one operation to the next (both internal and external to a supplier)
- Manual operations: bench work, assembly etc.
- In process inspection and final testing: manual or automatic
How to measure the plant efficiency?
How to measure the process flow efficiency?
How to measure the workforce efficiency instead?
- Tideal: Tva
- Treal: Tva + Tnva
- Efficiecy: Tideal / Treal
How to measure the efficiency of process controls and final tests?
- Automatic inspection, for example thanks to NC machines. In this case, the OEE can be used as a control metric
- Manual inspection, for example bench tests. In this case, the above formula can be used
Overall efficiency of the production process
Where to start?
In this post we have emphasized that the use of the OEE parameter alone does not provide us with a reliable value of the entire production process, unless this involves the use of automatic assets only.
Using a system approach, we can calculate the efficiency of each phase of the process in an extremely simple way, so as to intervene in a timely manner to improve the effectiveness and efficiency of the production process, thus satisfying at the same time the customer, who will see his requests met and company management that will see its resources used in an appropriate manner.
To do this, the new technologies of industry 4.0 come to our aid:
- Assets interconnectivity to the company IT system
- Use of real-time locating systems (RTLS)
- Using Discrete Event Simulations (DES)
- Computer Vision
In this sense, SkillS4i makes a series of contents available on its platform to help companies improve their knowledge: