Thursday 10 May 2018

OEE and Six Big Losses

What is OEE?

OEE and Six Big Losses

OEE is used to measure the utilization of machines. OEE gives the overall utilization and shows the loss factors in detail.

In this way, the potential for improvements is very visible. It is not only visible on which machines to focus, but also how the capacity is increase on the machines.

Advantages when using OEE

  • Knowledge of machine utilization and loss factors when using an OEE measuring gives all possibilities to improve the capacity.

  • An improvement of the utilization at a bottleneck by 10% – increases the capacity in a value stream by 10%!

  • Knowledge of loss factors gives a clear picture of the way to prioritize the effort to improve capacity.

Results when using OEE

In typical manufacturing companies the machine utilization at bottlenecks is often below 50%!

Normally this can be raise to at least 80%. This means that the overall capacity can be improve by 60% - without major investments!

Six Big Losses

Defining the Six Big Losses

One of the major goals of TPM and OEE programs is to reduce and/or eliminate what are call the Six Big Losses – the most common causes of efficiency loss in manufacturing. The following table lists the Six Big Losses, and shows how they relate to the OEE Loss categories.


Eliminating unplanned Down Time is critical to improving OEE. Other OEE Factor cannot be address. If the process is down. It is not only important to know how much Down Time your process is experiencing (and when) but also to be able to attribute the lost time to the specific source or reason for the loss (tabulate through Reason Codes). With Down Time and Reason Code data tabulate, Root Cause Analysis is apply starting with the most severe loss categories.

Setup and Adjustments

Setup and Adjustment time is generally measure as the time between the last good part produce before Setup. To the first consistent good parts produce after Setup. This often includes substantial adjustment and/or warm-up time in order to consistently produce parts that meet quality standards.

Tracking Setup Time is critical to reducing this loss, together with an active program to reduce this time (such as an SMED - Single Minute Exchange of Dies program).

Many companies use creative methods of reducing Setup Time including assembling changeover carts with all tools and supplies necessary for the changeover in one place, pinned or mark settings so that coarse adjustments are no longer necessary, and use of prefabricated setup gauges.

Small Stops and Reduced Speed

Small Stops and Reduce Speed are the most difficult of the Six Big Losses to monitor and record. Cycle Time Analysis should be utilize to pinpoint these loss types. In most processes recording data for Cycle Time Analysis needs to be automate. Since cycles are quick and repetitive events that do not leave adequate time for manual data-logging.

By comparing all complete cycles to the Ideal Cycle Time and filtering the data through a Small Stop Threshold and Reduced Speed Threshold. The errant cycles can be automatically categorize for analysis. The reason for analyzing Small Stops separately from Reduce Speed is that the root causes are typically very different, as can be seen from the Event Examples in the previous table.

Startup Rejects and Production Rejects

Startup Rejects  and Production Rejects are differentiates. Since often the root causes are different between startup and steady-state production. Parts that require rework of any kind should be consider rejects. Tracking when rejects occur during a shift and/or job run can help pinpoint potential causes, and in many cases patterns will be discover.

Often a Six Sigma program. Where a common metric is achieving a defect rate of less than 3.4 defects per million opportunities. It is use to focus attention on a goal of achieving "near perfect" quality.

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