This page is a “quick start guide” for measuring OEE. It provides a roadmap of key decisions and is organized in three parts:
When implementing any new initiative, it is usually best to start small and expand from a base of success. For OEE, that means starting with a pilot implementation on a single machine, cell, or line. Creating an OEE score at multiple points will give you conflicting information and potentially lead you to focus on less critical aspects of your process.
Select a pilot area where your employees are engaged and motivated; ideally an area where employees are interested in learning new things and applying ideas towards improvement. Preferably, select a pilot area that manufactures either one part or multiple parts with the same cycle time.
OEE should be measured at the constraint step of your process (sometimes referred to as the bottleneck). The constraint is the single step or machine that governs (i.e., limits) the throughput of the overall process. Improving the constraint will improve the overall process. If the constraint moves because you’ve improved the former constraint, move your OEE measurement to the new constraint and start again.
Identify the constraint step of your process.
WIP often accumulates at the constraint. On lines where equipment is balanced to run at identical speed, measure OEE at the step that does the primary work.
OEE measurement can be manual or automated.
We recommend starting with manual OEE measurement. It reinforces the underlying concepts and provides a deeper understanding of OEE. Later, you may want to to improve accuracy, track the , and to generate top losses and other reports.
Only three pieces of information are needed to calculate OEE: Good Count, Ideal Cycle Time, and Planned Production Time
Good Count should only include parts that are defect-free the first time through the process. This is similar in concept to First Pass Yield, which defines good parts as units that pass through the manufacturing process the first time without needing rework.
Identify how you will collect Good Count. For manual measurement look for a counter immediately after the constraint that reliably counts good parts. For automated measurement look for a sensor immediately after the constraint that is triggered only for good parts.
Ideal Cycle Time is the theoretical minimum time to produce one part (it is NOT a ‘budget’ or ‘standard’ time). It is important that Ideal Cycle Time be a true and honest measure of how fast the process can run, even if the process currently runs slower due to product, material, or equipment problems.
Determine the Ideal Cycle Time. The preferred method is to use Nameplate Capacity (the design capacity specified by the equipment builder). An alternate method is to perform a time study (measuring the absolute fastest speed the process can support).
Planned Production Time is the total time that the manufacturing process is scheduled for production. It is the yardstick against which Fully Productive Time is measured.
Start with shift time and decide if certain types of planned stops will be excluded (i.e., will not count against OEE). Most companies exclude only breaks (including lunches) and meetings.
In order to leverage OEE to improve manufacturing productivity it is essential to calculate the : Availability, Performance, and Quality. This requires two more pieces of information: Run Time and Total Count. Since in practice Run Time is calculated as Planned Production Time less Stop Time, we need to collect Stop Time.
Stop Time is defined as all time where the manufacturing process was intended to be running but was not due to unplanned stops (e.g., breakdowns) or planned stops (e.g., changeovers).
Decide how to record stop time. For manual measurement a tick sheet is usually the easiest way to collect stop time (an alternative is to record start and end times for each stop). For automated measurement the will automatically record these times.
Decide the time threshold for recording stops. Any stop that reaches the threshold is recorded and is included as Stop Time (an Availability Loss). Any stop shorter than the threshold is considered a small stop (a Performance Loss) and is not recorded. A typical stop threshold is five minutes for manual systems and two minutes for automated systems.
Total Count is required to measure OEE Quality. It can be measured directly, or Reject Count can be measured instead, and added to Good Count to calculate Total Count.
Decide if you will measure Total Count or Reject Count. For manual measurement of Total Count look for a counter that counts all parts going into the constraint. For automated measurement of Total Count look for a sensor before the constraint that is triggered for all parts. Reject Count is measured in the same place as Good Count (see above).
Measure changeover time consistently by defining the start and end points of each event.
Document a policy for measuring Changeover Time. Three common options are:
Stop reasons provide insights as to why the process has stopped – especially for unplanned stops. They are an essential part of any manufacturing improvement program.
Create a starting list of stop reasons. Here are some tips:
Now you have a good understanding of how to define a project, how to gather the data you need in order to calculate OEE, and how to capture and calculate detailed loss data. You also have a roadmap of key decisions to make along the way. Use this information to start small and measure the OEE score in your pilot area, and then expand until you know the OEE of every line in your plant!