Q 233. Overall Equipment Effectiveness (OEE) aims at eliminating 'The Six Big Losses' in any organization. What are these 6 big losses? Identify the ways in which these losses can be avoided?

 

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In OEE there are traditional 6 big losses:

1. Equipment Failure
2. Setup & Adjustments
3. Idling & Minor Stops
4. Reduced Speed
5. Process Defects
6. Reduced Yield

 

They can be grouped further:

1. Availability Loss
   • Equipment Failure
   • Setup & Adjustments
2. Performance Loss
   • Idling & Minor Stops
   • Reduced Speed
3. Quality Loss
   • Process Defects
   • Reduced Yield

 

Few ways in which we can avoid/ reduce these 6 big losses

1. Equipment Failure – Avoid Tooling Failure, breakdowns, unplanned maintenance. Keep material ready so that machine is not starved by upstream equipment or being blocked by downstream equipment. Eliminate unplanned downtime.
2. Setup & Adjustments – Changeover – Time between the last correct unit until the first correct unit has been produced after the changeover. Keep necessary tools or parts needed for changeover ready or within reach  
3. Idling & Minor Stops- Where machinery ceases to operate for very small duration like 1-2 minutes because of any reason. Do minor cleaning activities, reduce misfeeding, diminish incorrect configurations, lessen material jams
4. Reduced Speed - Compare all cycles times with ideal cycle time. Operator experience should be considered for any change, worn-out equipment should be replaced, avoid low quality material or lessen environmental effects.
5. Process Defects – Manage your equipment settings, operator knowledge or equipment handling
6. Reduced Yield -  Reduce Sub-optimal changeovers, Incorrect settings, keeping equipment warmup to required cycles etc

 

https://www.novotek.com/uk/solutions/overall-equipment-effectiveness/explanation-of-the-six-big-losses/

https://www.oee.com/oee-six-big-losses.html

 

Overall equipment effectiveness (OEE) is one of the most effective and commonly utilized tool in lean  methodology and lean manufacturing. Importance of OEE lies in :

 

1.Identifying the source of inefficiency

2.Quantifying the degree of inefficiency

3. Labelling the quality of goods produced/service rendered

 

OEE combines three factors namely -1) availability 2) performance 3) quality

 

Ideal OEE score is 100%, meaning production of cent percent defect less products/process, at maximum speed possible,  and  with no interruptions/breakdown. The output emerging from Ideal OEE is called as planned output

 

Availability: availability accounts for planned and unplanned breakdowns or interruptions. The unplanned fractions may be due to equipment failure, material shortage, manpower crunches, change over time etc.

 

Availability can be calculated in different ways:-

 

Availability=  Runtime/Planned production time

 

 Where  Runtime =Planned production time- breakdowns

 

 Gross output= Planned output- loss of output due to availability losses

 

Availability Rate(a)= Gross output /planned output

 

Performance: It takes into account the performance loss because of process operating at submaximal or slow speed and also accounts for small stops in between leading to loss of efficiency and sell optimal production.

 

The probable causes of poor performance can be:

 

-       Low quality input material

-       Old equipments with wear and tear

-       Small duration stops, may be due to some minor jams or process congestion(Long duration stops are generally classified under availability domain)

 

Net Output= Gross Output-loss of output due to speed loss

 

Performance rate(p) = Net output/Gross output

 

Quality: Quality accounts for any defects/scraps due to some flaw in any of the process.

 

Valuable output= Net Output-loss of output due to scraps/quality issue

 

Quality Rate(q)= Valuable Output/Net Output

 

                                  OEE=a*p*q

 

Six Big Losses: The three types of major losses have been further subdivided to yield 6 types of big losses, that an organization is prone to suffer because of equipment/process related issues.

 

       -Availability loss:

 

1)    Unplanned stops

2)    Planned stops

 

-       Performance loss

 

1)    Slow Cycles

2)    Small stops

 

-       Quality loss

  

1)    Production Rejects/scraps

2)    Startup Rejects/scraps

 

Ways of eliminating/mitigating the six big losses:

 

-       Availability losses:

  

1.    Equipment failure:

 

-       Regular preventive maintenance of the instrument,  with linkage to computerised maintenance system(CMMS)

-       Tracking the downtime

-       Investigating the reasons for each shutdown/downtime

 

2.     Setup and adjustments:

 

-       Batch production  instead of  equipment delivering throughout the day, to minimize the retooling adjustments throughout day.

-       Single minute exchange of die(SMED): switchover/change from one process to another process in production in  a single minute or single digit time frame, less than 10 minutes.

 

-       Performance losses:

      

1.     Idling/Minor stops:

 

-       Prompt  signaling and initiation of action

-       Patterns of performance loss, needs to be analyzed

-       Process standardisation

 

2.    Speed reduction:

 

-       Adequate maintenance of equipment to prevent wear and tear and maintain the speed and efficiency

-     Continuous improvement by regularly looking for the ways to remove waste, inefficiency and  improve operation 

 

-       Quality losses:

 

1.    Production rejects/process  defects:

 

-       Direct inspection of the equipments and materials, providing regular maintenance.

-     If defects become overwhelming and  routinely detected, then change of the equipment remains the best  economically viable option in long run.

 

2.    Reduced yields/start up rejects/scraps:

-    Usually predictable ones, sometimes an inherent part of the process and commonly attributed to setups, changeovers and initial warm up of  equipments.

        Can be  prevented by:

-          Reduced initial production- Production of small  batches at startups, rather than large batches

-       Reduced Variation: maintaining uniform equipment settings, standard and uniform material quality in all batches and stringent quality control.

     

 

 

 

      

 

 

  

Overall equipment efficiency

OEE is the best tool to measuring manufacturing productivity. In simple words it represents the percentage of manufacturing time that is actual productive. Measuring OEE is good practice in industries. We get important insight on how to improve our manufacturing process. OEE is a best matrix for identifying losses benchmarking progress and improving the productivity of manufacturing equipment. Main part of OEE calculation are availability of equipment, Performance of equipment quality of product.

OEE = Availability Score × Performance Score × Quality Score

6 Big Losses in OEE: -

6 Big Losses in OEE
Overall Equipment Efficiency	Recommended Six Big Loses		Traditional Six Big Losses
Availability Loss	1	Unplanned Stops	Equipment Failure
	2	Planned Stops	Setup and Adjustments
Performance Loss	3	Small Stops	Idling and Minor stops
	4	Slow Cycles	Reduced speed
Quality loss	5	Production Rejects	Process Defects
	6	Startup Rejects	Reduced Yield

 

The six big losses are directly linked to discrete manufacturing and provided an equipment loss in more detail. Six big loses are derived from TPM.

1. Unplanned Stops:

   Unplanned stops are a time period in which equipment is scheduled for production, but it is not running due to unplanned activity. Examples -Equipment breakdown, unplanned maintenance, tool failure, lack of operator or materials.

    

2. Planned Stops:

   Planned stops are a time period in which equipment is scheduled for production but not running due to planned activity for example -cleaning, Planned maintenance, product changeover, quality inspection.

    

3. Small Stops:

   When equipment stops for a small time such as 1 or 2 minutes with the stop resolved by the operator. Small stops are often long-lasting. Example include misfeed, material jam, incorrect setting, blocked sensor, periodic quick cleaning.

    

4. Slow Cycle:

   Slow cycle time happen when machine run slower then rated cycle time for example        dirty equipment, poor lubrication, poor environmental condition, operator experience, start up and shut down.

    

5. Slow Production Defects:

   Production defects are defective products produced during the production (stable production). It includes all product which required reworked for example Include correct equipment setting, operator & equipment handling error, or lot expiration.     

       6. Start Up Defects:

Startup defects are defects which produces at the time of startup of equipment. It can happen after any equipment startup. Generally, it can see after change over for example includes suboptimal change over , Warm up time of equipment

 

 

Benchmark Six Sigma Expert View by Venugopal R

 

Total Productive Maintenance (TPM) is a terminology introduced by Seiichi Nakajimma. As part of improving the Overall Equipment Effectiveness (OEE), the six big losses have been defined, by which it becomes easier to identify the inefficiencies.

The Six Big Losses that aim to improve the OEE are:

 

 

1.       Unplanned stoppages:

Unanticipated stoppages of equipment for a long time. The causes for such unplanned stoppages could be Equipment breakdowns, Tool failures, unscheduled maintenance, Lack of power, Lack of raw materials or other required consumables.

 

Since these are unexpected stoppages, we need to learn lessons from these incidents, by doing a root cause analysis and identify pro-active measures to prevent recurrences or similar occurrences. A structured FMEA exercise will help identify potential causes and the associated Risk Priority Numbers.

 

2.       Planned stoppages:

Planned stoppages may happen for scheduled maintenance, Quality checks, Tool Adjustments, planned breaks, change of input materials.

 

Since there could be multiple reasons for planned stoppage, it would be economical to sync up these activities to happen in parallel, apart from the efforts to decrease the time for the activities that consume larger duration. SMED (Single Minute Exchange of Dies) is one of the well known methods to keep the planned stoppage time low. Predictive maintenance approach is recommended.

 

3.       Small Stoppages:

Small stoppages usually happen for problems that are attended by the operator himself / herself. It could be minor cleaning of sensors, correcting minor misalignment, blockages, wrong feeding of raw material etc.

 

Since these are mostly dealt by the operators, it is best to involve them on a Small Group Improvement program such as QC circles, to continuously and systematically identify various causes and work on solutions for each of them through employee involvement and incentive programs. A good 5S program would help to keep the work place organized.

 

4.       Reduced speed:

‘Reduced speed’ means that the equipment is taking longer time to produce an item. Possible reasons could be wear & tear of the equipment, lubrication issues, operator skill to handle the equipment, influence by raw material or operating conditions

Root cause analysis needs to be done to identify and stratify the causes.

 

Some of the causes could point improvement in the effectiveness of the preventive maintenance schedules, that could have led to the deterioration of performance of the equipment. Issues related to Operator skills will have to be addressed by training. Enhance raw material control for associated causes.

 

5.       Production defects:

These are defective products that come out during normal production. Any output that is not ‘First-time right’ is considered as defective. The reasons could be due to inadequate process capability, improper setting of the machine, improper handling or defective raw materials.

 

Incorporating strong methods for detection, control and prevention would help improve the First Pass Yield (FPY). SPC and Process Control Plans will improve control at upstream stages to prevent defective from flowing down the process.

 

6.       Start-up defects:

These are defects that occur during the start of a setting. Could be due to warm up cycles, improper settings, change over process.

 

Training using very clear standard operating procedures with validated check points, based on the historical learning would minimize the start up defects. Introducing automated methods where possible, will further reduce variation and uncertainty.

 

All correct answers have been published. Best answer has been provided by Dr. Shashikant Adlakha for first explaining the concept of OEE, detailing the 6 big losses and finally highlighting the ways to avoid these losses.

 

Please go through the answer by Benchmark Expert- Mr. Venugopal as well.