OEE

Overall Equipment Effectiveness

Enrique Mora

How to Measure The Generated Improvements of The TPM Implementation in Terms Of The Overall Equipment Effectiveness?   

All performed effort should have certain parameters in order to evaluate your achievements. The TPM effort won't be the exception to this rule. To be able to measure that advance, we have the OEE, Overall Equipment Effectiveness. It is a useful concept and helps to define restrictions in the plant.   

The OEE contributes to measure how the improvements will positively affect the productivity thanks to the appropriate operation of the equipment.  

TPM plays an important role in this process, since the effectiveness of the equipment is improved. A basic goal of the TPM is "Zero interruptions or production stoppages" which makes it possible to increase the effectiveness of the equipment so that each machine can be operated at its full potential and maintained at that level. We will use the denomination: OEE. 

The attitude in the implementation of TPM should be centered in zero breakdowns. Only with that conviction can a good implementation of TPM be achieved.     

  The Formula To Measure OEE:    

»     OEE = EA X PR X QR

Being: 

»     OEE = Overall Equipment Effectiveness    

»     EA = Equipment Availability  

»     PR = Performance Rate  

»    QR = Quality Rate  

The Equipment Availability (EA) is improved through reducing or eliminating the breakdowns, setups and adjustments, and all kinds of stoppages. This can be achieved thanks to realistic Preventive Maintenance and the opportune scheduling of repairs when the equipment begins to show some abnormality, earlier than the failure point. 

The Performance Rate (PR) improves through eliminating the losses of speed, stoppages and smaller failures.  TPM allows the operators to notice any reduction of the capacity of their equipment, and they also learn how to use it at its full capacity. As they know it better, the operation is safer and fluid.  

The Quality Rate (QR) improves eliminating defects in the process, especially during the beginning of a new product.  

The indexes can be determined in each workstation. The high level of effectiveness OEE will only be achieved when the three indexes are high.

The following principles should be applied when improving the effectiveness: 

• Make detailed and exact measures  
  

• Establish priorities 
   

• Establish clear goals  

To calculate the indexes to use, it is necessary to review the following concepts:  

• Production Time:  refers to the net availability of the equipment during a given period. In other words it is the available total time for operation minus the necessary times for breaks, chats, lost cycles, etc. (unavoidable).    
  

• Operation Time: the production time minus the time in which the equipment is stopped due to breakdowns, adjustments, setups and other stoppages. It is the time in which the equipment is in operation.    
  

• Net Operation Time: the time in which the equipment is operated at stable and constant speed. From the Operation Time subtract the time lost by smaller stoppages and for loss of speed, (especially in the kick off).

• Productive Operation Time: the Net Operation Time minus the estimated time that is required to rework the faulty products. It is the time during which the acceptable products are manufactured.    
  

• Ideal Cycle Time: the time designed for the production of one unit. We should bring it the closest possible to the "Takt Time".   
  

• The "Takt Time": a theoretical time that results of dividing the Net Operation Time by the number of pieces that are required to be produced.    

The levels for the effectiveness of the equipment differ 
depending on:

• The industry  
  

• The characteristics of the equipment  
  

• The production systems involved.  

The effectiveness of the equipment averages from 40 to 60 percent in plants that remain working with traditional corrective or reactive maintenance procedures. This standard can be as high as 85 or 95 percent through several Kaizen Events focused in the reduction and elimination of the effectiveness losses in the equipment.     

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