Statistical Process Control was ab initio developed by Dr. Walter Shewart in the early 1920s. He was working at the Bell Telephone Laboratories, carry oning research on statistical methods to better quality and to take down the costs. He recognized that fluctuation in a production procedure can be understood and controlled through the usage of such tools. The wider acknowledgment and usage of SPC came during World War II, when the demand for higher quality production to back up the defence industry was necessary.
The American industry, in comparing to Japan, was non convinced about the importance and the benefits of SPC. After the war, Dr. W. Edwards Deming, one of Shewhart ‘s adherents, was invited to develop Nipponese applied scientists with the constructs of SPC. Nipponese were eager to reconstruct their economic system, and so they applied the statistical methods, they developed plans in human resources and they focused on uninterrupted betterment to better respond to client demands, therefore ensuing to the growing and development of Nipponese companies into powerful planetary rivals.
Around 1980 the parts of Statistical Process Control became eventually recognized in America. From that minute on the scheme started turning and spread outing. Those who used it added on it, bettering the system or even developing new, different schemes to guarantee quality and better productiveness. So Statistical Process Control is non the lone technique available. Presents such schemes are widely used in fabrication companies and service organisations. Statistical Process Control is a really popular scheme, because it is easy to utilize and it can hold accurate consequences without disrupting the procedure under scrutiny. However, it is my sentiment that SPC, or any scheme for that affair, can no longer stand entirely. A combination of different techniques and schemes should be preferred, since every individual 1 has something different to offer. Generally, the best consequences will be delivered when a statistical information analysis is being used combined with an action sing managerial or proficient corrections. I do non believe that SPC has an expiring day of the month at the close hereafter, but possibly as other techniques and package are developed it might be incorporated to an a more advanced betterment scheme.
Statistical Process Control uses package such as Minitab, with which a set of maps and tools can be used, enabling us to supervise and better merchandises or procedures by measuring procedure variableness. Such tools are the computation of steps of location, scattering and distribution, ways to expose informations ( charts and graphs ) and analyze their fluctuation and the finding of the capableness, which can be either the existent public presentation of the procedure or the possible public presentation of the procedure. Some techniques used are the Measurement Systems Analysis, which guarantee that measurement mistake does non excessively contribute to the procedure fluctuation, the attribute understanding analysis ( AAA ) , which is used to measure the evaluations given by multiple valuators, and the Kappa statistics, which tests the understanding of the valuators. Finally, the most celebrated SPC tool is the control chart, which is the key to quality betterment. The control charts are run charts which include the mean or mean of information points, the upper control bound ( UCL ) and the lower control bound ( LCL ) .
Statistical procedure Control has been applied to many fabricating industries or services. For illustration it has been applied in health care to better patient aid and operations, in aircraft care direction by utilizing p-charts and Pareto diagrams, in the analysis of machines for replacing, in fictile injection modeling companies and in package development. In other words SCP can be applied in any field that has facts, figures, steps, counts or Numberss about the three jobs originating in public presentation: hold, defect and divergence. In order for SPC to hold successful consequences and for the organisation to demo uninterrupted betterment it has been shown that top direction committedness is critical. The following tabular array shows the effects of SPC on some industries where it was applied. It is obvious that quality improves, since SPC purposes to that betterment.
Table: A sample of surveies describing the effects of the SPC intercession ( 1 )
Survey
Effectss on
Procedure quality
Product quality
Other effects
Benneyan and Chute ( 1993 )
a†‘ productiveness
a†“ costs
Kumar and Gupta ( 1993 )
a†“ bit rate
Dondero ( 1991 )
a†“ costs
a†‘ merchandise quality
Rucinski ( 1991 )
a†‘ truth
a†“ bit rate
a†‘ rhythm clip
Cantello et Al. ( 1990 )
a†‘ procedure stableness
a†‘ procedure capableness
[ Sower, 1990 ] A andA [ Sower, 1993 ]
a†‘ merchandise consistence
a†‘ positive attitudes towards the organisation
a†“ client ailments
no effects on control over work
no effects on attitudes towards direction
Neidermeier ( 1990 )
a†“ procedure variableness
a†‘ client satisfaction
Oakland and Followell ( 1990 )
a†‘ procedure uniformity
a†‘ merchandise uniformity
a†‘ market portion
a†‘ faulty rate
a†“ failure costs
Chaudhry and Higbie ( 1989 )
a†‘ procedure efficiency
a†‘ merchandise uniformity
a†‘ client dealingss
Manson and Dale ( 1989 )
a†‘ procedure outputs
a†“ bit rate
a†‘ occupation satisfaction
a†“ procedure variableness
Depew ( 1987 )
no effects on productiveness
no effects on merchandise quality
Keefer ( 1986 )
a†“ faulty rate
Followell and Oakland ( 1985 )
a†‘ procedure uniformity
a†‘ merchandise quality
a†“ external failure costs
Harmon ( 1984 )
a†“ bit rate
The term entire quality direction ( TQM ) was foremost used by the Naval Air Systems Command in order to depict its Japanese-style direction attack to quality betterment. TQM derived straight from SPC and it can be defined as a direction system for a customer-focused organisation that involves all employees in continual betterment. By utilizing rules and cognition of behavioural scientific disciplines, analysis of qualitative and quantitative informations, economic theories and procedure analysis, within effectual communicating, it succeeds in incorporating the quality subject into the cardinal thoughts and the mundane activities of the organisation. The preliminary elements of TQM are:
Cross-functional merchandise design
Process direction
Supplier quality direction
Continual betterment
Customer focused
Information and feedback
Committed leading
Strategic and systematic planning
Cross-functional preparation
Entire employee engagement
TQM tools can be divided into two classs, tools for quality planning and tools for uninterrupted betterment. As in SPC there are CTQ ‘s ( Critical to Quality ) in order to interpret client linguistic communication into qualified demands for the merchandise and KPI ‘s ( Cardinal Performance Indicators ) to measure how good the CTQ ‘s are being met, in TQM the quality map deployment ( QFD ) is measured by using the existent client statements, referred to as “ Voice of the Customer ” to comprehensive matrixes called “ The House of Quality ” . Another tool of TQM is the Concurrent Engineering ( CE ) , which is a systematic attack to the integrated design of merchandises and their procedure including industry and support. That means that through consideration of the costs of production, the aesthetics of the produce-ability, assemble-ability, maintainability and recyclability of the merchandise, CE aims to better the design stage of the merchandise. Finally, the most common tools of TQM in usage today are referred to as “ The Seven Management and Planning Tools ” and they include pie charts, saloon graphs, histograms, run charts, spread diagrams, control charts, tendency charts, Pareto charts and analysis, flow charts, patterning diagrams, the 5 Whys and procedure capableness. All the above can be found in the Statistical Process Control tool chest every bit good. However TQM makes common usage of two more types of graphs: the dealingss diagram, which helps to do clear the relationships between assorted factors, issues, events, etc. so as to understand their importance in the overall organisational position, and the fishbone diagrams ( or else known as ishikawa or cause and consequence diagram ) . The latter, is being used in order to exemplify multiple degrees of possible causes ( inputs ) and ultimate effects ( end products ) , of jobs and issues that may originate in the class of the analysis. Other tools and techniques being used are the SIPOC table analysis ( Suppliers, Inputs, Process, Outputs, Customers ) , FMEA ( Failure Modes and Effects Analysis ) , which analyses the failure manner within a system for categorization by the badness and likeliness of the failures, PDCA ( Plan-Do-Check-Act ) , which is used in concern for the control and uninterrupted betterment of procedures and merchandises.
Six Sigma – DMAIC ( define, step, analyze, better, control )
Six Sigma is a high-performance, informations based attack and methodological analysis for extinguishing defects in any procedure, by analysing the root causes of concern jobs and work outing them. In other words it ‘s a manner of scientifically mensurating the current success ( or failure ) rate of a concern in relation to what client expect, irrespective of industry sector, and so guaranting that the appropriate betterments are made. Two Six Sigma sub-methodologies are being used in order to accomplish that: DMAIC ( define, step, analyze, better, control ) and DMADV ( define, step, analyze, design, verify ) . The Six Sigma DMAIC procedure methodological analysis is an betterment system for bing procedures falling below specification bounds and looking for incremental betterment. On the other manus, Six Sigma DMADV procedure is an betterment system used to develop new procedures or merchandises within Six Sigma quality degrees.
Six Sigma DMAIC approaches solution with the usage of informations and facts and drives defects to less than 3.4 per million chances. The primary elements of Six Sigma DMAIC are five. The definition of the undertaking ends and the internal and external client deliverables, followed by the measuring of the procedure to find current public presentation, the analysis and finding of the root causes of the defects, bettering so the procedure by elimitating defects and eventually keeping the high public presentation by commanding the hereafter procedure.
Tools and methods used in Six Sigma DMAIC include charts and graphs used in TQM and SPC or in one of them, such as histograms, run charts, Pareto charts and analysis and fishbone diagram, control charts, procedure capableness, gage R & A ; R, the CTQ tree, 5 Whys, QFD and root-cause analysis. Apart from the above tools and methods, DMAIC besides uses pick charts, analysis of discrepancy ( ANOVA ) , self-evident design, which uses matrix methods to transform client demands into functional demands, correlativity, which refers to any wide category of statistical relationships affecting dependance, cost-benefit analysis, arrested development analysis, for gauging the relationship among variables, SIPOC tabular array analysis, stratification, Taguchi methods and Taguchi Loss Function and TRIZ.
The differences in tools and techniques are summarized in Table 2.
SPC
TQM
DMAIC
Critical to Quality tree
Quality Function Deployment
Voice of the Customer
CTQ tree + QFD
Cardinal Performance Indexs
The House of Quality
Cost of Poor Quality ( COPQ )
pie charts
pie charts
saloon graphs
saloon graphs
spread diagrams
spread diagrams
choice charts
Pareto charts and analysis
Pareto charts and analysis
Pareto charts and analysis
flow charts
flow charts
frequence histograms
histograms
histograms
tally charts
tally charts
tally charts
control charts
variable
control charts
control charts
property
patterning diagrams
patterning diagrams
dealingss diagram
fishbone diagrams
fishbone diagrams
cheque sheets
Checklists
Check sheets
machine and procedure capableness
procedure capableness
procedure capableness
gage R & A ; R
gage R & A ; R
5 Whys
5 Whys
5 Whys
analysis of discrepancy ( ANOVA )
self-evident design
correlativity
cost-benefit analysis
arrested development analysis
SIPOC tabular array analysis
SIPOC tabular array analysis
stratification
Taguchi methods
Taguchi Loss Function
TRIZ
FMEA
FMEA
PDCA
Abdominal aortic aneurysm
Kappa
The chief difference between TQM and Six Sigma is the attack, since TQM is chiefly a direction attack to long-run success through client satisfaction. As for SPC and the other two Continuous Improvement strategies the chief differences lie on the fact that SPC trades with properties every bit good, which is a different sort of quality measuring.
In this essay I am traveling to show briefly a instance survey on the application of Statistical Process Control on some basic chemicals used in pure H2O production in Nigeria, by some Privately Owned Water Enterprises ( POWE ) . These POWEs produce sachet H2O, which is low-cost but with unsure pureness. So in this instance survey, statistical procedure control charts are used to supervise the production procedure of pure H2O, combined with the appraisal of some chemicals used in the production and procedure of the H2O. The informations were collected from indiscriminately selected packaged H2O manufacturers and they are referred to as “ pure H2O manufacturers ” . Each sample undergoes some research lab trials ( physical and chemical ) in order to find some overall belongingss, such as pH and conduction ( I?S/cm ) and the degree of some basic chemicals used in the production of pure H2O. The trials showed that most chemicals used, were out of procedure control and endangering the wellness of the clients. The physical ocular scrutiny included odour and appearance such as coloring material, turbidness and presence of drifting atoms. The samples were besides subjected to chemical trials, in conformity to the standard methods of the American Public Health Association and these included the chemical analysis of Lead ( Pb ) , Chloride ( Cl ) , Iron ( Fe ) and Aluminum ( Al ) . The consequences derived from the usage and reading of the several control charts and taking in conformity the Western Electric Rules, which province that a procedure is out of control when one of the undermentioned occur: eight back-to-back points are on one side of the centre line, one point is outside the 3-sigma control bounds, two out of three back-to-back points are outside the 2-sigma warning bounds on one side of the halfway line or four out of five back-to-back points are at a distance of 1-sigma or more from the centre line on one side of the centre line. Overall, pH, conduction, Fe ( Fe ) and lead ( Pb ) , were out of control. The representative control chart of lead, which exceeds the upper control bound by a batch, ensuing to likely hurtful wellness effects, is presented below.
It is clear now that by utilizing control charts the procedure variableness can be monitored and reduced. It is besides possible to find whether a procedure needs seting and when non, every bit good as set up procedure stableness and detect and procedure alterations. In the specific instance study some of the chemicals used in the production of packaged H2O are at times out of control and do non conform to criterions for quality imbibing H2O, ensuing to possible wellness hazard of the consumers. It is hence recommended that statistical procedure control charts should be plotted sporadically, to supervise the fluctuation of the merchandises and to better the procedure and the concluding merchandise, cut downing at the same clip bit and rework.
A similar process can be followed in all procedures, no affair how large, little or complex are. For illustration the merchandises of every crude oil industry need to run into some criterions ( EN ISO ) . Nowadays the European ordinances province that conveyance Diesel must be a blend of up to 5 % biodiesel and these blends need to compromise with the European Standard 590 for Diesel fuels incorporating up to 7 % of biodiesel. SPC can hence be applied in the production of automotive Diesel fuel, in order to supervise merchandise variableness and command the production. The upper control bounds are determined chiefly by environmental and wellness hazards and the lower control bounds by the public presentation demands of the engine. The specification demands stated in EN 590 include many belongingss of the fuel, but in this essay the application of SPC will be limited in three of them. The most of import belongingss that need to be within bounds are the sulfur content of the fuel, Fatty Acid Methyl Ester ( FAME ) , which determines the quality of biodiesel used and the cetane index. Cetane index has merely a lower control bound, as the bigger the cetane index of our Diesel is, the better the public presentation of the fuel. The lower control bound is 46 and it can be calculated by the EN ISO 4264 trial method, which uses the four-variable equation. Sulfur content and FAME content merely have upper control bounds, as values beyond these bounds can do either engine failure or increase the wellness hazard of the population, whereas really little values are either the purpose of the industry ( sulfur content ) or have no negative impact on the engine ( FAME ) . These control charts will hold a signifier as shown below.
Sulfur content is measured by EN ISO 20846 and has every bit upper bound the value of 10mg/kg. FAME content is measured by EN 14078 and the maximal value is 7 % ( V/V ) . Within all these methods, other tools of SPC are applicable, such as when mensurating the preciseness of the trial method, by utilizing gage R & A ; R, the bios and the one-dimensionality. Apart from control charts, run charts can besides be drawn, in order to observe any form and to distinguish common from random causes of variableness. The capableness indices can besides be measured by utilizing the graphs and the specification bounds, which in this instance coincide with the control limits. In decision, by supervising the production the industry can ever be within control bounds, better the public presentation of the production and minimise the scarp and the demand of rework.
1. Rungtusanatham, Manus. The Quality and Motivational Effects of Statistical Process Control. Journal Quality Management. March 1999, Vol. Volume 2, Issue 2, p. 243-264.
2. Abubakar Usman, Nasir Mu’Azu Kontagora. Statistical Process Control on Production: A Case Study of Some Basic. Pakistan Journal of Nutrition. 2010, Vol. 9, 4, p. 387-391.
3. European Standard. Automotive fuels – Diesel – Requirements and trial methods. BrusselsA : Technical Committee CEN/TC 19, 2009. EN 590.
