O.E.E.
OEE is a tool to measure the performance of individual equipment or an entire process.OEE can be used to measure losses caused by poor quality, equipment problems or non-optimal run rates. The calculation for OEE is:
%OEE = (% availability)*(% productivity)*(% quality)
This equation can be applied to a single machine or an entire process. It should be tracked over time to see the impact of changes in equipment, training, and maintenance, purchased materials and management direction. OEE will help identify the areas requiring improvement, the potential revenue from an improvement and serve as a benchmark against competition. One of many ways of expressing OEE is (Operating Time/Total Time)*(Std Cycle/Std Mult)
Typical items measured by OEE will be actual downtime vs. planned, slower production rates than standard, defects, and minor but important problems. The Emerson Company offers the following guidelines for OEE. Other references can be found on the web by searching on OEE.
Quartile
Process Type Worst 3rd 2nd Top
Continuous <78% 78-84% 85-91% >91%
Batch <72% 72-80% 81-90% >90%
Chem., Power <85% 85-90% 91-95% >95%
Paper <83% 83-86% 87-94% >94%
The elements of OEE are Availability, Productivity and Quality.
Availability takes into account Down Time or stoppages, time the machine is not running as scheduled.
% Availability is defined as Actual Production time/Planned production time, or Operating Time/ planned production time, or the percentage the equipment is available for production. It can be affected by changes in process variables, preventive maintenance, and machine failure detection.
Plantstar Panorama defines availability as
.
Idle time is not a part of this calculation. ie. A machine is not available when idle for whatever reason. Idle time can be scheduled or non-scheduled.
Productivity or Performance takes into account Speed Loss.
% Productivity is defined as Actual Production/Optimum Capacity or (Minutes/part)/(Total parts/Operating time), or Ideal cycle Time/(operating time/Total parts), or (Total parts/Operating time)/Ideal run rate, or parts per time to produce. Material availability, operator training, equipment breakdowns and machine speeds affect it. If production was planned for a machine and it is down, the productivity clock is still running.
Plantstar Panorama defines productivity as (gross parts produced/up time)*(std cycle/std mult).
Or (gross parts/up time)*(seconds/cycle)/pieces/cycle).
Productivity is a unit less quantity, a number. Expanding just a little:
Gross Parts Gross Parts Time to make a part
Productivity = --------------------- = ------------------------ X ------------------------
Scheduled Pieces Time to make a part Scheduled Pieces
Gross Parts Time to make a part
Productivity = ------------------- X -------------------------
Time to make a part Std Mult x Num of Cycles
Gross Parts Time to make a part
Productivity = ----------------------- X ------------------------
(up time)/Std Cycle Std Mult x Num of Cycles
Gross Parts Time to make a part x Std Cycle
Productivity = ------------------------- X ----------------------------
up time Std Mult x Num of Cycles
where Std rate = Std Mult/Std Cycle
Gross Parts 1
Productivity = ----------------- X ----------
up time std rate
Quality takes into account bad parts or wastage.
% Quality is defined as (Product produced (rejects)/Product produced, or Good parts/total parts. It is affected by changes in process variables, material quality, and equipment performance.
Plantstar Panorama defines Quality as (net pieces/gross pieces).
The total calculation can be expressed as:
(up time/up time + down time)(net parts produced/up time + down time)(std cycle/std mult)
For Example:
Shift Time = 8 hrs
Breaks = 30 minutes
Lunch = 1 hr
Down time = 35 minutes
Ideal Run Rate = 10 seconds
Gross parts = 2200
Rejects = 37
Availability = Operating time/Planned production time = (480 30 -60 - 35)/(480 -30 -60) = 0.91
Availability = Up Time/Up Time + down time = 355/390 = 0.91
Productivity = Gross Parts/Scheduled Parts = 2200/(60*390)/10 = 2200/2340 = 0.94
Productivity = Gross Parts/operating time/run rate = 2200/390*60/10 = 0.94
Quality = Good Parts/(good parts + rejects)= 2163/2200 = 0.98
OEE = Availability * Productivity * Quality = 0.91 * 0.94 * 0.98 = 0.838