When looking for a method and measurement that can be used in the improvement potential of a production process, many turn to Overall Equipment Effectiveness (OEE). By measuring these areas with OEE, one can identify ways to improve processes in manufacturing, such as how to improve productivity by eliminating waste, a core objective of Lean Manufacturing. The OEE method can also provide a link between measurement and improvement. It ties to Lean’s “Six Big Losses”, which when practiced can offer a roadmap for improvement.
Usually OEE is applied to the manufacturing processes, such as the ones creating individual parts. OEE can also be used to look at the continuous processes like in refineries. It is important to remember OEE uses the ratio of Fully Productive Time (actual output) to Planned Production Time (theoretically possible output). The difference between the two (the actual and possible) is waste.
Identify the machine that creates the throughput; this step is also known as the constraint. This is important for OEE because this is the point at which it is necessary to capture all losses (internal and external):
- Internal Losses = Six Big Losses (Equipment Failure, Setup and Adjustments, Idling and Minor Stops, Reduced Speed, Process Defects, and Reduced Yield)
- External Losses = Starved and Blocked
If a line or equipment is balanced to run at identical speed, good practice is to focus on the ones doing the primary work in order to measure OEE. This would be a balanced filling line, monitor the filler.
Performance of your constraint equates to the performance of the line. Additional equipment can stop and start, but if your constraint is running, you are profitable.
Some factories count of the number of pallets or boxes shipped to the customer. As a result, they think they should measure OEE at the end of the line, however this isn’t necessary. Counts and OEE can actually be looked at as independent metrics. The only reason one should measure the OEE at the end of the line is if this is your constraint.
Not sure this is necessary. By creating an OEE score at multiple steps in the process, this could provide conflicting information and could lead focus to be on aspects of your process that are less critical. Measure OEE at the constraint and then measure mechanical efficiency for other assets. By doing this, one will get the OEE score for the line and an additional benchmark number without confusing the OEE measurement.
If the constraint moves due to an improved or elevated initial constraint, enjoy the good news and then move the OEE measurement to the new constraint and begin again. The key is consistently and constantly measure one point of the process.
Constraint moves with different products, in theory one should correct to additionally move the measurement point. Is it worth moving the OEE measurement for every product? If you can move the point easily or with little cost or complexity, then the answer is yes. Keeping the OEE measuring process simple is the best option, that provides the best results.