Tag: Implementing OEE

OEE Integration – Where do We Measure OEE? – Part I

OEE Integration Part IX – Where do we measure OEE?

Our recent posts have included numerous examples to calculate OEE correctly. We also discussed integration of OEE as an effective metric for managing your processes and ultimately how to analyze and use the data to improve your profitability.  We spent little time discussing where this measurement should occur.  OEE can be measured for both manual and automated lines as well as any stand alone operation.

The OEE factors (Performance, Availability, and Quality) are process output results.  The expectation, of course, is to manage the inputs to the process to assure the optimal result is achieved.  Availability, Performance, and Quality can be measured in real-time during production. However, the results should be subject to a due diligence review when production is complete.

At a minimum, it makes sense to measure OEE at the end (output) of the line or process but this is not always ideal.  The complexity of OEE measurement occurs when single or multiple sub-cells are constrained by an upstream or downstream operation or bottleneck operation.  The flow, rate, or pace of a process is always  restricted or limited by a  sequence / process constraint or bottleneck operation.  Just as a chain is only as strong as its weakest link, so too is the line speed limited by the bottleneck operation.

We contend that the “Control-Response” loop for any process must enable immediate and effective corrective action based on the measured data and observations.  Measuring OEE in real-time at the bottleneck process makes it an ideal “Trigger Point” metric or “Control-Response” metric for managing the overall process even in “isolation” at the bottleneck operation.  Any variations at the bottleneck correlate directly to upstream and downstream process performance.

A disruption to production flow may occur due to a stock-out condition or when a customer or supplier operation is down.  While these situations affect or impact the OEE Availability factor, external factors are beyond the scope of the immediate process.

Real-time OEE requires that these events and others, such as product disposition, are reported in real-time as well.  External events are more difficult to capture in real-time and by automated systems in particular.  Operator interfaces must accommodate reporting of these events as they occur.

Reporting PITFALL – After-the-Fact events

If a quality defect is discovered several days after reporting production and all parts are placed on hold for sorting or rework, the QUALITY Factor for that run should be changed to ZERO.  In turn, the net OEE for that run will also be ZERO.  If the system is not changed, the integrity of the data is lost.  This also exemplifies that real-time data can be deceiving if proper controls are not in place.

“Where do we measure?” is followed by “When do we measure?” The short list of examples provided here are likely events that are far and few between.  If this is a daily occurrence, consider adopting the banking policy of, “adjustments to your account will be reflected on the following business day”.  Your process / system is in need of a rapid fix.

OEE is one of the few vital signs or key performance metrics for your manufacturing operation.  As such, measure where you will reap the greatest benefit and focus your attention on the process or operation accordingly.  OEE is as much a diagnostic tool as it is a monitoring tool.

Until Next Time – STAY lean!

Vergence Analytics
Versalytics

Weighted OEE: How To Calculate Total Plant OEE

In this post we will present a simple method to calculate a truly weighted OEE, including weighted factors Availability, Performance, and Quality.

The QUICK weighted OEE method:

Recalling our original definition of OEE, we are measuring how effectively our planned production time (net available time) is used to make a quality (saleable) product.  The weighted OEE then is the total time required to make a quality product divided by the total net available time.

From our examples in the “Calculating OEE” post, the following table summarizes the time required to produce quality products ONLY for machines A, B, and C:

  1. Machine A:  365 minutes
  2. Machine B:  318.75 minutes
  3. Machine C:  254.34 minutes

The total time to produce good quality (saleable) products is 938.09 minutes.

The total net available time for the three machines is 1365 minutes (3 * 455 minutes). 

The total weighted OEE for the 3 machines = 938.09 / 1365 = 68.72%

Calculating the Weighted Factors:

A similar process to the one described above can be applied to the individual factors.  It stands to reason that when the individual factors are multiplied together that we should get the same result.  We will use this to check our answer.

Weighted Availability:

Availability measures machine uptime efficiency.  The definition applied to an individual process also applies to the total of all the machines.  Availability is calculated using the formula:

Availability:  Net Operating Time / Net Available Time

From our examples in the “Calculating OEE” post, the following table summarizes the Net Operating Times for machines A, B, and C:

  1. Machine A:  423 minutes
  2. Machine B:  437 minutes
  3. Machine C:  433 minutes

The total Net Operating Time = 1293 minutes.

The total Net Available Time for the three machines is 1365 minutes (3 * 455 minutes). 

The weighted AVAILABILITY for the 3 machines = 1293 / 1365 = 94.73%

Weighted Performance:

Performance measures machine operating time efficiency when compared to the “ideal” cycle or operating time.  The definition applied to an individual process also applies to the total of all the machines.  Performance is calculated using the formula:

Performance:  Ideal Operating Time / Net Operating Time

From our examples in the “Calculating OEE” post, the following table summarizes the Ideal Operating Times for machines A, B, and C:

  1. Machine A:  373.33 minutes
  2. Machine B:  337.50 minutes
  3. Machine C:  267.17 minutes

The total Ideal Operating Time to produce ALL parts = 978 minutes.

The total Net Operating Time for the three machines is 1293 minutes (See Availability Calculations Above). 

The weighted PERFORMANCE for the 3 machines = 978 / 1293 = 75.64%

Weighted Quality:

Quality measures how efficiently the “ideal” operating time is used to produce quality (saleable) products.  Again, the definition applied to an individual process also applies to the total of all the machines.  Quality is calculated using the formula:

Quality:  Ideal Operating Time to Make Quality Parts / Ideal Operating Time

From our examples in the “Calculating OEE” post, the following table summarizes the Ideal Operating Time to produce Quality Parts ONLY for machines A, B, and C:

  1. Machine A:  365.00 minutes
  2. Machine B:  318.75 minutes
  3. Machine C:  254.34 minutes

The total Ideal Operating Time for Good Parts = 938.09 minutes.

The total Ideal Operating Time to produce ALL parts for the three machines is 978 minutes (See Performance Calculations Above). 

The weighted Quality for the 3 machines = 938.09 / 978.0 = 95.92%

Weighted OEE cross check:

Let’s compare the results.  From the calculations above, the results are summarized as follows:

  1. Weighted Availability:  94.73%
  2. Weighted Performance:  75.64%
  3. Weighted Quality:  95.92%

Now, we multiply the individual weighted OEE factors together:

OEE = 94.73% * 75.64% * 95.92% = 68.73%

You will see the result is the same as the Quick check introduced at the start of this post.

In our next post we will show you how to calculate the weighted factors for each individual process and introduce yet another way to confirm the weighted OEE calculation.

We have created a number of Excel spreadsheets that are immediately available for download from our FREE Downloads page or from the Free Downloads widget on the side bar.  These spreadsheets can be modified as required for your application.

If you have any questions, comments, concerns, or suggestions for a future topic, please forward them by e-mail to leanexecution@gmail.com  We look forward to hearing from you and trust this information will get you going.

Until Next Time, STAY Lean!

"Click"