Quality theories

Quality management

Lecture 3.

History of quality managementEarly 1920 Scientific management (Taylor, Gilbreth)

1920s Statistical process control (Shewart)

1930s Acceptance sampling (Dodge, Roming)

1940s Military standards introduced

1950s Quality management in Japan (Deming, Juran)

1960s Taguchi method, and quality tools

1970s Quality becomes strategic (USA)

1980s Introduction of LEAN, TQM, Baldrige Award

1990s Reengineering, Six Sigma

2000s Supply chain management, improvement of supplier development, LEAN, Six sigma become popular, contingency theory

Quality and taylorism

• Basics of taylorism– The whole process is divided into short steps (division of labor)– It is not the worker who determine the process/movements -specialist do

that (task management)– Workers are selected and trained for work – Standard movements and tools, detailed instructions (standardization)

• Quality effects:– Product and process design were separated from the repair of product– Workers were not responsible for repairing of product– Quality control department was established to control the product at

the end of the process– The responsibility for quality were spread over in the company

Deming

• Not just worker but managers have the responsibility for establishing quality– Workers responsible for

special problems– Managers responsible for

the whole system (proper methods, equipments, motivation system etc.)

• Quality improvement must be divided between the two level

Juran

• Quality problems are rooting in insufficient and ineffective planning for quality

• In traditional way:– Planning determine the tools

for producing goods– 20% of the operating process

is waste, it is planned into the product or process

– Instead of quality improvement they only do quality control

• Juran trilogy– Planning– Control– Improvement

Ishikawa• Democratizing statistics: everyone is responsible for

statistical analyzes, • total involvement of the operating employees in

improving quality• Basic 7 tools of quality

– Process map – flow chart, step of process– Check sheet – to collect errors for analyzes– Histogram – graphic representation of data– Scatter Diagrams – examine the relationship between variables

(what cause the problem)– Control Chart – is the process stable or not– Cause-and-effect (Ishikawa) diagram – find all reason of the

problem, directed tool for find all causes– Pareto Chart – prioritize causes, determine problems must be

focused on

Feigenbaum

• Father of Total Quality Control (TQC)

• the entire organization should be involved in quality improvement

• The quality is poor – If the product is designed

incorrectly (engineering)– If the product is released in

the wrong market – If the customer relationship

is not proper. (marketing)• 3 steps of improvement• 4 deadly diseases

Crosby• Crosby’s four theorem

– Quality is the conformance to the requirements of customers. The whole system must be developed according to this approach.

– The main goal is zero-defect. Do the right product at the first time.

– Thus the applied method for quality assurance is prevention not control.

– Quality can be a source of profit. Quality costs must be evaluated, and on the basis of these costs, corrective actions should take place.

Taguchi

• Quality definitions: quality is measured in terms of loss to society if the service not performed as expected.

• Quality Loss Function (QLF): any deviation from target value results in loss to society

• Robust Design: products should be designed to be defect-free– Concept design (technology and process choices)– Parameter design (select parameters which have an effect on

quality – amount of training, heights of a paper)– Tolerance design (deals with decrease variation in order to fulfill

the specification limits – use a higher-grade materials)

QLF (Qualtiy Loss Function)

• L=K*V2

– K – constant, and – V2- mean squared dviation from target value

• K=C/T2

– C - unit repair cost– T – tolerance interval

Target valueLSL USL

Exercise - QLF

• Suppose the cost to repair a radiator on an automobile is $200. Compute the QLF for losses incurred as a result of a deviation from target setting where a tolerance of 6±0,5 mm is required and the mean squared deviation from target is (1/6)2.

• Solution:• K=200/0,52=800• L=K*V2=800*(1/6)2=$22,22/unit

TAGUCHI PROCESS• 1. Problem identification• 2. Brainstorming session

– identify factors, its settings, interactions, • Control factor• Noise factor

– Identify objectives• The less is better• Nominal is best• The more is the better

• Experimental design – Offline experimentation (number of replications)

• Experimentation– Orthogonal array (determined by the number of factors and levels)– Record the result– Compute average performance for each factor– Showing the best outcomes

• Analysis (which level of each factor is the proper one)• Confirming experiment (validate results)

Contingency theory• There are no schemes, firms do not have

to use only one quality approach

• Successful firms adopt aspects of each approach that help them improve, understand them, and apply them creatively.

• It depends on the situation which approach is the best.

Thank you for your attention!