11 Quality POM Handout 11

7/31/2019 11 Quality POM Handout 11

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Quality Introduction

What is quality? Quality is important to businesses but hard to define. Customers want quality that is appropriate to the price that they are prepared

to pay and the level of competition in the market.

Every good or service is consumed to derive some satisfaction.The objective of every businessmen is to maximise profit.Profit can be maximised by creating the greatest satisfaction in customer.Customer satisfaction is thus the ultimate goal.

Every good or service has attributes like performance, reliability, appearance,commitment to delivery time etc.Every good or service has attributes like performance, reliability, appearance,commitment to delivery time etc.Quality is a measure of how closely a good or service conforms to specified standard.

The attributes, variables and characteristics are various dimensions of quality.Organisations insure quality assurance as built in the good or service by policy,program, procedure are guidelines.

What is the need for quality control?1. To compare quality of goods/services2. Maintain consistency in quality in output.3. Increased maintenance and operating cost which create dissatisfaction.4. To reduce rework cost in mfr.5. To increase lifetime of the products.6. To improve flexibility to use std. Spares.

Therefore controlling quality is essential.Key aspects of quality for the customer

Good design looks and style Good functionality it does the job well Reliable acceptable level of breakdowns or failure Consistency Durable lasts as long as it should Good after sales service Value for money For the firm, good design is fundamental, so that the product can be produced

efficiently, reliably and at the lowest possible cost.Why is quality important?Quality helps determine a firms success

Customer loyalty they return, make repeat purchases and recommend theproduct or service to others.

Strong brand reputation for quality Retailers want to stock the product Retailers want to stock the product As the product is perceived to be better value for money, it may command a

premium price and will become more price inelastic Fewer returns and replacements lead to reduced costs Attracting and retaining good staff These points can each help support the marketing function in a business.

How is quality measured?

Dr. M KOTEESWARAN MBA II SEM POM 2012 Hand Out - 10Page 96


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Failure or reject rates Level of product returns Customer complaints Customer satisfaction usually measured by a survey Customer loyalty evident from repeat purchases, or renewal rates Quality is subjective. It is a matter of personal opinion What constitutes an acceptable level of quality will vary from one individual to

another.Not all aspects of quality are tangible

for example the degree of assurance given by a firms name or reputationcan be very important even though it is hard to measure.

Quality is always evolving because of things like improved technology, better materials, new manufacturing techniques and fresh competitors. No firm can afford to stand still as far as quality is concerned.

Whilst controlling quality has benefits to the firm, it can also be costly to do.So it isimportant that the benefits outweigh the costs in the long term.

Inspection is a function to interpret specifications, verify conformance to thespecifications and communicate the result to those responsible to make corrections.What is inspection?Inspection involves defining standards and specifications, selection of products,verification of the product against set standards, decide the variance, decide whethersuch variance is acceptable or not, advise concerned of the result.Inspection1. It is comparison with standards.

2. It is postmortem operation.3. After production/process, verification carried out.

4. Defective are segregated, either rectified or scrapped.5. A phase of QC6. Provides info. Reqd. By QC7. Does not add value.Quality Control

1. It is a function contributing to quality of goods.2. It establishes standards / criteria3. Aims at investigating root cause for defects to eliminate for future production.

4. Helps reduction of insp. Cost.5. Adds value

Objective of inspection1. Prevention of defects.2. Detect defects in time / in process3. Remove defective parts from further processing.



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4. Inform concerned.5. Records for evaluation of m/c and man's performance.Definition for quality"degree to which a set of inherent characteristic fulfils requirements" as ISO 9000Conformance to requirements"

Philip B. Crosby.

The difficulty with this is that the requirements may not fully representwhat the customer wants; Crosby treats this as a separate problem.

Fitness for use" (Joseph M Juran). Fitness is defined by the customer.A two-dimensional model of quality (Noriaki Kano and others). The quality has two

dimensions: "must-be quality" and "attractive quality".The former is near to the "fitness for use" and the latter is what thecustomer would love, but has not yet thought about.

"Value to some person" (Gerald M Weinberg)6. W. Edwards Deming defines "Costs go down and productivity goes up, as

improvement of quality is accomplished by better management of design,engineering, testing and by improvement of processes.Better quality at lower price has a chance to capture a market. Cutting

costs without improvement of quality is futile.""The loss a product imposes on society after it is shipped" (Taguchi).

Taguchi's definition of quality is based on a more comprehensive view ofthe production system.Definition for qualityHowever, the American Society for Quality defines "quality" as "a subjectiveterm for which each person has his or her own definition."Stages of inspection

1. Receiving Inspection Goods inward inspection is carried out when spares / bought out items arereceived at stores before taking to stock.

2. Pre-production inspection Inspection of materials prior to actual processing. First piece / first off

inspection of materials, equipment tools and pilot batch.3. First piece inspection

The first part/ piece produced is inspected to verify set up, tools andequipment and dimensional accuracy.

4. Production Inspection:Inspection after every operation is completed and quality checked.100% inspection is due to ensure no defective item passes to the next

stage.(a) Patrol or Floor inspection(b) Centralised inspection.

5. Product Test:Apart from dimensional verifications, functional tests are performed

physical and chemical, performance and endurance tests, destructive andnon destructive tests.Role of inspection in QCAs the frequency of inspection increases, cost of inspection increases and

cost of undetected defects decrease.



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There is a trade-offwhere the cost of total QC is minimum.

It would be uneconomical where destructive test are done.1. After operations that are most likely to produce faulty items.2. Before costly operations start.3. Before operations that can cover up defects taken place.

4. Before starting assembly operations that cannot be undone.5. When finished product is ready for delivery.Cost of Quality

1. Cost of prevention 2. cost to prevent defective goods / services from being produced / delivered.3. Investment in m/cs, technology, education/trg,4. To reduce no. of defects,5. Cost to administer quality programme, Data collection / Analysis.

Cost of Quality2. Cost of detection / Appraisal

Costs associated with evaluating quality and performace of products /m/cs; inspection of equipment maintenance.

Cost of failure cost of non performing and non conforming products internal and external failure costs internal repair,scrap, retest, downtime, process variability,

Cost of failure external

with customer cost of returned goods,law suits,loss of sales due to dissatisfaction of customer, loss by concessions.

Quality Control Techniques

Process capability It is the capability of the process to meet the requirements of the product it

produces. Capability therefore depends upon the design tolerances associated with the

product. In any production process it is impossible to produce identical products

because of a variety of reasons. A range is normally specified by a set of variables like surface finish, length,

diameter etc. A process designed to produce a product should consistentlyproduce products, which fall within the defined range.

Process capability may be judged by the variations recorded by the output. A manufacturing process is in statistical nature. A process will never produce

any identical pieces. Hence it is possible to construct frequency distributionsfor variations.

2.The width of the distribution shows the process capability. A wide distribution shows, process out of control and shows it has less

capability to produce consistent parts. A narrow spread suggests control tunes to be better and



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if it is centered around the centre of variance, it is close to the best valuerequired.

3. Centre of variance sampled The centre of variance is where most variance occurs. Variable data are continuous in nature and are measurable on a sliding scare.

These data have a range of values and provide more information than attribute

data. Dimensions, voltage, weight etc. Attribute data are discrete in nature and can be binary like accept / reject as in

Go / No go ranges.What are tolerances?

Tolerance are the upper and lower limits within which acceptable qualitymeasurement can be expected to be if the product or process is acceptable.

Tolerances are generally design specifications. Example: diameter of a rod 20.00 cm 0.05 The upper measurement is 20.05 and lower is 19.95. All pieces produced where dia. Is anywhere between 19.95 and 20.05 cm is

acceptable.Process Capability

is the ability of a process to function within the design parameters withrespect to both its central tendency ( target value = 20.00 cm) and theinherent variable (tolerance 0.05 cm).

Process capability is described by a frequency distribution of the variable understudy.

SamplingA process is said to be in control so long as the output measured falls withinthe acceptable limits or tolerance.However, variation in output is typical and could face a problem if thevariation falls outside the limits.At the same time, it is impossible or prohibitively costly and timeconsuming to check or inspect every piece of output.It is not practical. Hence, sample of a lot is inspected or tested as the casemay be.Sampling has several advantages:-

1. Sampling consumes less time and is less costly.2. Testing of all output may be infeasible as in destructive test.3. Sampling is a scientific process which may yield highly accurate results at apredictable level of confidence.

However, in sampling, sample should truly represent the entirelot/population. Hence sample are randomly selected or computergenerated random nos.Random Sample

A random sample is one in which each element or combination of elements, inthe population or lot has an equal chance of being selected.

Control Charts

Control charts are simple tools used in SQC to record the performance of aprocess. They serve two purposes.



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1.They reveal instantly the performance of the process at the movement ofdata collection.

2.They also show the overall trend of the process, which is more important. The trend shows the out of control status if any which required correction.

The observations are recorded in sequence on x axis and the respectivevalues on y axis. The central line, upper and lower control limits are drawn,

as these values are known. The area within which the observedcoordinates should fall is thus demarcated.Acceptance sampling.

Acceptance sampling is accepting or rejecting a production lot based on thenumber of defects in a sample.

It is assumed that the quality of items produced in a lot in same and uniform.Hence any piece of the lot is assumed to reflect the overall quality of the

entire lot. Hence, a random sample is chosen and inspected. It is assumed that in choosing a piece at random, every piece in the lot has the

same chance of being chosen. This process enables statistical inferences to be made about the lot as a whole. If the sample is acceptance, the lot is accepted, if not the entire lot is rejected. The acceptance sampling is based on attribute plan.

It is also performed that the production will contain certain defects.The producer decides as to what percentage of defective items could beallowed as acceptable.

This is crucial if the sample has an acceptable number or percentage ofdefective items, the lot is accepted.

This is called Acceptance Sampling. Acceptance sampling is not consistent with the TQM philosophy and zero

defects. While acceptance sampling allows certain free determined level ofdefective items, TQM aims at zero defects to be present in any passed item.

AS is after production while TQM is preventive. AS is to identify a lot tothrow away or rework, nor to prevent poor quality in production and infuture.

TQM measured defects as parts per million. Under the AS an acceptancelevel of 2% defect, would amount to 20,000 defective parts in a million,where as TQM aims at zero defects per million or 3 or 4 .However, AS is still a popular SQC tool in many industries before ultimatelymoving towards TQM. Thus, for industries AS may be initial steps TQM thedestination.In AS however, what is important is how, when and what size the samplingis done. This is called the sampling plan. This provides the guidelines foraccepting a lot or not.

There are 1.Single Sample attribute plan 2.Average outgoing quality 3.Double and multiple sampling plans.

Acceptance sampling. Acceptance Quality Level: Acceptance sampling decision is accept or reject. The crucial factor is the

decision of the producer in fixing the acceptance no. of defective items in asample and sample size.



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If the actual no. of defective items exceed the pre determined no. of defectiveitems, the lot is to be rejected entirely. The producer, in the process, incurs arisk.

If the results of the sampling did not actually reflect the overall quality of thelot and in fact was acceptable but rejected by sampling , the producer incurs aloss of rejecting the entire lot which was otherwise acceptable.

If the predetermined defective no. acceptable in a sample is c and actual is d,when d>c, the risk is rejection of a lot otherwise acceptable and when d


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From producer / Service provider's point of view:- Quality of conformance is making sure the product / service is producer as per

design. This involves design, materials, equipment and training, supervisionand control.

TQM Movement: Walter Shewherrt, W.E.Denning, Joseph Jerren and Philip Crosby, A.V.Feigenbaum and / Shikauvav propagated TQM as a

philosophy and movement. Shewhart developed statistical control charts andintroduced the concept of Quality Assurance a commitment to quality to theorganisation.

Demings14 point planW. E. Deming started teaching SQC to Japanese companies. He advocatedcontinuous improvement of production process to achieve conformance tospecifications and reduce variability.Deming advocated a 14 point charted to achieve quality:-

1. Create a constant purpose to product improvement to achieve custom org. goal.2. To be internationally competitions adopt prevention of poor quality instead ofAQL.

3. Eliminate the need for inspection than SQC.4. Select suppliers who are committed to quality than price.5. Continuously improve production process by attending to - Quality problems - the system and workers.6. Train the worker on preventing quality problems.7. Instill leadership among supervisors to help workers perform better.8. Encourage employee's involvement by eliminating fear of reprisal.9. Eliminate barriers between depts. Promote cooperation and team approach.10. Eliminate slogans and numerical targets.11. Eliminate numerical quota for employees.12. Enhance worker pride and self esteem.13. Institute commitment from top to bottom in implementing 1 to 13 above.

Deming developed Deming wheel PDCA cycle.


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11 Quality POM Handout 11