OEE Calculation

Overall Equipment Effectiveness (OEE) Calculation

OEE is an abbreviation used in most of the manufacturing industries around the Globe, for a special metric called Overall Equipment Effectiveness that takes in to account the three major indices which are as follows:
1. Availability
2. Performance
3. Quality
And their relationship is well described in the following equation:

Overall Equipment Effectiveness (OEE) = Availability Rating X Performance Rating X Quality Rating

Now ,
• Available time = Plan Time = Time per shift x Number of  Shifts
• Standard Allowance = Lunch Time + Tea Time  + Meeting Time…… etc.
• Loading Time (Plant Running Time for actual) = Available time – Standard Allowance
• Down Time =  (Break Down Time + Setup and Adjustment Time + Die and Tool Change Time + Startup Losses + Management Losses……… etc.)

• Availability Rating 
Availability rating can be improved with bringing down the line stoppages and break downs . Availability takes into account Availability Loss, which includes all events that stop planned production for an appreciable length of time (typically several minutes or longer). Examples include Unplanned Stops (such as breakdowns and other down events) and Planned Stops (such as changeovers).
                            =[{ (Net Available time)/ Loading Time} X 100 ] %
                           =[{(loading Time – Down Time)/ Loading Time} X 100]%

• Performance Rating
Performance Rating Can be improved eliminating no small stops or slow running. Performance takes into account Performance Loss, which includes all factors that cause production to operate at less than the maximum possible speed when running. Examples include both Slow Cycles, and Small Stops.
                            = [(Actual Produced Volume / Total Opportunity for
                                  Production) X 100 ] %
                             = [{Actual Produced Volume /
                                   (Net Available Time/ Standard Cycle Time )} X100] %
                             = [{(Actual Produced Volume X Standard Cycle Time ) /
                                  (Net Available Time)} X 100 ] %

Note :  Net Available time  = Loading Time – Down Time

• Quality Rating
Quality Rating can be improved by allowing no defects to get created in the production process. Quality takes into account Quality Loss, which factors out manufactured pieces that do not meet quality standards, including pieces that require rework. Examples include Production Rejects and Reduced Yield on startup.
                              = [{Actual Produced Volume – ( Defect + Rework )} /
                                     Actual Produced Volume] X 100 %

Hence  ,
• Overall Equipment Effectiveness (OEE)
OEE takes into account all losses i.e. Availability Loss, Performance Loss, and Quality Loss resulting in calculating the measure of truly productive manufacturing time.
                                         = Availability Rating X Performance Rating X
                                                                      Quality Rating

Now let us take an example on this ,

Example : Question -Calculate OEE of XYZ Plant as per the following Details Given Below :  
1. Number of Shifts ( the company operates in) : 3;
2. Working time per shift : 8 Hours;
3. Break time for food : 0.5 Hours  for  each shift ( ½ an Hour per shift);
4. Break time for tea : 15 Minutes ( two times for each shift);
5. Meeting Time : 15 Minutes for each shift;
6. Break Down time (A) : 2 Hours;
7. Setup Adjustments (B): 2.5 Hours;
8. Die and Tool Change time ( C) : 0.5 Hours;
9. Setup Losses (D) : 0.25 Hours;
10. Management Losses (E) : 3.75 Hours;
11. Production Volume : 750 Numbers of Components;
12. Defects produced on one Monday : 50 Number of components;
13. Total Rework done on components on  Monday : 100 Number:
14. Standard Cycle time per component : 50 seconds

Solution –
We Know ,
Original Equipment Effectiveness (OEE) = Availability Rating X Performance Rating X Quality Rating
 Now ,
• Available time = Plan Time = Time per shift x Number of  Shifts
                                                              = (8 X3) Hours = 24 Hours  ;
• Standard Allowance = Lunch Time + Tea Time  + Meeting Time
                                     = {(0.5X3)+ (0.25X2X3) + (0.25 X3)} Hours
                                     = 3.75 Hours ;
• Loading Time ( Plant Running Time for actual)
                                    = Available time – Standard Allowance
                                    = (24-3.75) Hours = 20.25 Hours;
• Down Time =  (Break Down Time + Setup and Adjustment Time +
                                +Die and Tool Change Time + Startup Losses
                                 + Management Losses)
                          =  (2+2.5+0.5+0.25+3.75) Hours = 09 Hours;
• Availability Rating
                           =[{ (Net Available time)/ Loading Time} X 100 ] %
                           =[{(loading Time – Down Time)/ Loading Time} x 100]%
                           = [{(20.25-9)/20.25} X100]%
                           = 55.55 %
• Performance Rating
                            = [(Actual Produced Volume / Total Opportunity for
                                  Production) X 100 ] %
                             = [{Actual Produced Volume /
                                   (Net Available Time/ Standard Cycle Time )} X100] %
                             = [{(Actual Produced Volume X Standard Cycle Time ) /
                                  (Net Available Time)} X 100 ] %
                              = [{ ( 750 X 50) /  (11.25 X 60 X 60 ) } x 100 ] %
                              =  92.22 %
Note :  Net Available time  = Loading Time – Down Time
                                                 = (20.25 – 9) Hours  = 11.25 Hours;
• Quality Rating
                              = [{Actual Produced Volume – ( Defect + Rework )} /
                                     Actual Produced Volume] X 100 %
                              = [{ 750- (50+100)} / 750] X 100  %
                              = 80 %
 Hence  ,
• Original Equipment Effectiveness  (OEE)
                                         = Availability Rating X Performance Rating X
                                                                      Quality Rating
                                         =  [( 0.5555 X 0.9222 X 0.8) X 100 ] %
                                         = 40.98 %

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