| Overall
Equipment Effectiveness |
INTRODUCTION In
today's economy, you're expected to continuously improve your Return on Total
Capital. And as capital to build new, more efficient plants becomes more difficult
to obtain, you often have to meet growing production demands with current equipment
and facilities - while continuing to cut costs.
There are several ways
you can optimize your processes to improve profitability. But it can be difficult
to understand the overall effectiveness of a complex operation so you can decide
where to make improvements. That's especially true when the process involves multiple
pieces of equipment that affect each other's effectiveness.
One metric
that can help you meet this challenge is Overall Equipment Effectiveness, or OEE.
OEE measures the health and reliability of a process relative to the desired operating
level. It can show you how well you're utilizing resources, including equipment
and labor, to satisfy customers by matching product quality and supply requirements.
Overall Equipment Effectiveness (OEE) measures total performance by relating
the availability of a process to its productivity and output quality. OEE
addresses all losses caused by the equipment, including
" Not being available
when needed because of breakdowns or set-up and adjustment losses
" Not
running at the optimum rate because of reduced speed or idling and minor stoppage
losses
" Not producing first-pass A1 quality output because of defects
and rework or start-up losses.
OEE was first used by Seiichi Nakajima,
the founder of total productive maintenance (TPM), in describing a fundamental
measure for tracking production performance. He challenged the complacent view
of effectiveness by focusing not simply on keeping equipment running smoothly,
but on creating a sense of joint responsibility between operators and maintenance
workers to extend and optimize overall equipment performance.
First applied
in discrete manufacturing, OEE is now used throughout process, batch, and discrete
production plants. DEFINITION
The overall performance of a single piece of equipment or even an entire
factory will always be governed by the cumulative impact of the three OEE factors: Availability,
Performance Rate and Quality Rate. OEE
is a percentage derived by multiplication of the three ratios for the factors
mentioned above. The OEE percentage is used for analysis and benchmarking. What
is OEE? OEE
= Availability X Performance Rate X Quality Rate
OEE is calculated by multiplying
three factors: availability, productivity, and quality. %
OEE = ( % Availability ) * ( % Productivity ) * ( % Quality )
The values
used can reflect an entire processing plant, a process line, or an individual
piece of equipment.
For individual equipment, the performance of the
equipment is compared to earlier values for the same equipment or to similar pieces
of equipment. Changes in OEE or its elements are tracked and trended over time.
OEE for a process line treats the entire line as a single unit, regardless of
how much equipment it includes. For multiple-recipe or batch operations, OEE is
calculated for each product produced. Like a process line, a process plant performs
as a whole, and OEE is therefore calculated for the entire plant as a unit.
AVAILABILITY
Percent of scheduled production (to measure reliability) or calendar hour's 24/7/365
(to measure equipment utilization), that equipment is available for production
Equipment availability
isn't just assumed to be the length of the shift in which it is operated. Instead,
it's based on actual operating time, as a percentage of the possible production
time.
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