What is OEE (Overall Equipment Effectiveness)?
OEE is a
"best practices" way to monitor and improve the effectiveness of your
manufacturing processes (i.e. machines, manufacturing cells, assembly lines).
OEE is simple and practical. It takes the most common and important sources of manufacturing
productivity loss, places them into three primary categories and distils them into
metrics that provide an excellent gauge for measuring where you are - and how
you can improve! OEE is frequently used as a key metric in TPM (Total
Productive Maintenance) and Lean Manufacturing programs and gives you a consistent
way to measure the effectiveness of TPM and other initiatives by providing an
overall framework for measuring production efficiency.
How to calculate OEE?
OEE is calculated as the product of its three contributing
factors:
Availability:
Availability= (Operating Time) / (Planned Production Time)
Availability takes
into account Down Time Loss, which includes any Events that stop planned
production for an appreciable length of time (usually several minutes – long
enough to log as a trackable Event). Examples include equipment failures,
material shortages, and changeover time. Changeover time is included in OEE
analysis, since it is a form of down time. While it may not be possible to eliminate
changeover time, in most cases it can be reduced. The
remaining available time is called Operating Time.
Performance= (Total Pieces) / (Operating Time x Ideal Run Rate)
Performance takes
into account Speed Loss, which includes any factors that cause the process to
operate at less than the maximum possible speed, when running. Examples include
machine wear, substandard materials, misfeeds, and operator inefficiency. The remaining available time is called Net Operating Time.
Quality:
Quality= (Good Pieces) / (Total
Pieces )
Quality takes into account Quality Loss, which accounts for produced pieces that do not meet quality standards, including pieces that require rework.
OEE analysis
starts with Plant Operating Time; the amount of time your facility is
open and available for equipment operation. From Plant Operating Time, you
subtract a category of time called Planned Shut Down, which includes all
events that should be excluded from efficiency analysis because there was no
intention of running production (e.g. breaks, lunch, scheduled maintenance, or
periods where there is nothing to produce). The remaining available time is
your Planned Production Time. OEE begins with Planned Production Time
and scrutinizes efficiency and productivity
losses that occur,
with the goal of reducing or eliminating these losses. There are three general
categories of loss to consider - Down Time Loss, Speed Loss and Quality Loss.
World Class OEE:
In practice, the
generally accepted World-class goals for each factor are quite different
From each other,
as is shown in the table:
OEE Factor
|
World Class
|
Availability
|
90.0 %
|
Performance
|
95.0 %
|
Quality
|
99.9%
|
OEE
|
85.0%
|
Of course, every
manufacturing plant is different. For example, if your plant has an active Six
Sigma quality program, you may not be satisfied with a first-run quality rate
of 99.9%. Worldwide studies indicate that the average OEE rate in manufacturing
plants is 60%. As you can see from the above table, a World Class OEE is
considered to be 85% or better.
Clearly, there is room for improvement in most manufacturing
plants! How about yours?
Example of OEE Calculation:
The table below
contains hypothetical shift data, to be used for a complete OEE calculation,
starting with the calculation of the OEE Factors of Availability, Performance,
and Quality. Note that the same units of measurement (in this case minutes and
pieces) are consistently used throughout the calculations.
Item
|
Data
|
Shift Length
|
480 min
|
Breaks (2 short breaks)
|
20 min
|
Meal Break
|
30 min
|
Down Time
|
40 min
|
Ideal Run Rate
|
10 pieces per minute
|
Total Pieces
|
3500
|
Reject Pieces
|
200 pieces
|
Planned Production
Time = (Shift Length – Breaks) = (480-50) = 430 minute
Operating Time =
(Planned Production Time – Down Time) = (430-40) = 390 minute
Good pieces =
(Total Pieces – Reject Piece) = (3500-200) = 3300 pieces
Availability = 390 / 43 = 0.9069 (90.69%)
Performance = (3500 / 390)/10 = 0.8974 (89.74%)
Quality = 3300 / 3500 = 0.9428 (94.28%)
Any Question?
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