Ipp Extra 1

Front 1

Six Sigma in general

Back 1

The Six Sigma approach was first popularized by Motorola, the electronics and communications systems company. Motorola` Six Sigma quality concept was so named because it required the natural variation of processes (+- 3 standard deviations) should be half their specification range.

Ultimate goal of virtually eliminating all defects. So, now Six Sigma should be seen as a broad improvement concept rather than a simple examination of process variation, even though this is still an important part of process control, learning and improvement.

Front 2

Six sigma: measuring performance

Back 2

So, now Six Sigma should be seen as a broad improvement

concept rather than a simple examination of process variation, even though this is still an important part of process control, learning and improvement.

· A defect is a failure to meet customer-required

performance (defining performance measures from a customer’s perspective is an important part of the Six Sigma approach).

· A defect unit or item is any unit of output that contains a defect (i.e. only units of output with no defects are not defective,defective units will have one or more than one defect).

· A defect opportunity is the number of different ways a unit of output can fail to meet customer requirements (simple products or services will have few defect opportunities, but very complex products or services may have hundreds of different ways of being defective).

· Proportion defective is the percentage or fraction of units that have one or more defect.

· Process yield is the percentage or fraction of total units produced by a process that are defect-free.

· Defect per unit (DPU) is the average number of defects on a unit of output (the number of defects divided by the number ofitems produced).

· Defects per opportunity is the proportion or percentage of defects divided by the total number of defect opportunities (the number of defects divided by (the number items produced) the number of opportunities per item)).

· Defects per million opportunities (DPMO) is exactly what it says, the number of defects which the process will produce if there were one million opportunities to do so.

· The Sigma measurement is derived from the DPMO and is the number of standard deviations of the process variability that will fit within the customer specification limits.

Front 3

Critics of Six Sigma

Back 3

Critics: One common criticism of Six Sigma is that it doesnot offer anything that was not available before. Its emphasis on improvementcycles comes from TQM, its emphasis on reducing variability comes fromstatistical process control, its use of experimentation and data analysis issimply good quantitative analysis. The only contribution that Six Sigma hasmade, argue its critics, is using the rather gimmicky martial arts analogy ofBlack Belt etc. to indicate a level of expertise in Six Sigma methods. Thereare also technical criticisms of Six Sigma. Most notably that in purelystatistical terms the normal distribution which is used extensively in SixSigma analysis does not actually represent most process behaviour. Othertechnical criticisms (that are not really the subject of this book) imply thataiming for the very low levels of defects per million opportunities, as recommendedby Six Sigma proponents, is far too onerous.

Front 4

Critics of Lean

Back 4

Critics allege Lean to be a throwback to the group piecework systems of the 1920s where supervisors engage in full-time monitoring and disciplining under-performing workers; a return to Taylor’s scientific management approach from the more advanced behavioral approach to managing workers.

1) Stress: The single biggest criticism of lean manufacturing is that the constant focus on improvement and elimination of waste becomes an obsession and causes stress in the workforce.

2) No Margins for Error: Lean tools such as Just in Time Inventory and Six Sigma allows for no safety stock or margin of error, and vilifies any deviance from the codified optimal process.

3) Over-Focus on Waste: Lean strives to ensure productivity and efficiency primarily trough cutting flab, but in the process, ignores other crucial parameters such as employee wellness, and corporate social responsibility.

4) Over-Focus on Present: Lean’s constant pressure to eliminate waste and ensure optimal output places all energy on the present. Lean does not allow reflection or experimentation for the sake of development in the future. Such a focus on only the present may lead to missing out on the bigger picture, failing to comprehend the relevance of the task in the first place, or taking time to anticipate future challenges and make necessary changes to respond to such challenges

Front 5

Statistical Process Control (SPC)

Back 5

Statistical process control (SPC) involves using controlcharts to track the performance of one or more quality characteristics in theoperation. The power of control charting lies in its ability to set controllimits derived from the statistics of the natural variation of processes. Thesecontrol limits are often set at +- 3 standard deviations of the naturalvariation of the process samples.

Control charts can be used for either attributes orvariables. An attribute is a quality characteristic which has two states (forexample, right or wrong). A variable is one which can be measured on acontinuously variable scale.

Process control charts allow operations managers todistinguish between the ‘normal’ variation inherent in any process and thevariations which could be caused by the process going out of control.

Acceptance sampling helps managers to understand the risksthey are taking when they make decisions about a whole batch of products on thebasis of a sample taken from that batch. The risks of any particular samplingplan are shown on its operating characteristic (OC) curve. However, some of itsassumptions make acceptance sampling controversial.