BY AMAR P. NARKHEDE

INTRODUCTION All the items raw materials, bought out items,sub part, components are purchased from outside suppliers as well as those manufactured at the home plant must be verified for quality before passing them for next operation. This ensures that Only acceptable pieces go to the next operation which guarantees specified outgoing quality to the customer Defective pieces are withheld and additional cost is prevented from being expanded on the defective pieces Causes for the defectiveness are known to those concerned and appropriate action is taken to prevent re-occurrence of such defects

Inspection of incoming material serves other objectives It exerts moral pressure on the suppliers to inspect goods before supply It enables buyer to assess suppliers quality assurance capability and thereby decide future share of business to the suppliers The inspection results enable buyer to discuss defects with the suppliers, extracts promise to improve, watch their performance in the subsequent suppliers, and remove those who fail to show improvement event after repeated promises Periodical feedback is also very important its aims to good quality of the product

TYPES OF INSPECTION Cent percent inspection Sampling inspection A.CENT PERCENT INSPECTION It is one wherein each and every piece is verified against the preset specifications. However, cent percent inspection does not mean verification of each and every quality characteristics. Only important characteristics those necessary for satisfactory performance of the function may be verified

WEAKNESS OF CENT PERCENT INSPECTION It involves huge costs and expenditure incurred on inspection which is a DEAD WEIGHT COST (Inspection does not add any value to the product but adds to the cost) It is time consuming and tedious It is not suitable for items whose conformance to the quality specifications needs to be ascertained from defective tests Cent percent inspection is not fool proof either. Since inspection work is highly repetitive and boring, even competent inspectors sometimes reject good pieces or accept defective ones

An alternative to cent percent inspection is to use statistical inspection methods wherein the quality of the lot is decided based on the inspection results of few pieces drawn from each consignment lot. If the sample conforms to specifications, the whole lot is accepted otherwise it is rejected. Since acceptance is based on the interface drawn from the sample, the technique is known as acceptance sampling

SAMPLING INSPECTION It is subjected to sampling errors as there is always a chance that the sample may not be the true representative of the population from which it is drawn. This at times my cause acceptance of a lot of bad quality or rejection of a lot of good quality Sampling errors is acceptance sampling are minimized by selecting a sample which is true representative of the lot (choosing the sample at random so that every portion of the lot will have equal representation in the sample) such a sampling is known as random sampling. If the sample is true representative of the lot then only a few good sampling plans exactly do this. A carefully designed sampling plan utilizing appropriate sample size(n) and allowable number of defectives called acceptance number(c) usually takes care of quality assurance function

Acceptance sampling plan is a set of rules which prescribe the procedure to be adopted in preparing the lot, selecting the samples, conducting inspection of the samples and fixing criteria for acceptance or rejection of the lot

BASIS OF SAMPLING INSPECTION Variable basis (on the basis of actual measurements like weight of packet in kgs, length of component in mm, cm,meter, life test of part in hours Attributes basis (on the basis on “go” and “no go” i.e. determining whether or not the product in the sample conforms to the specifications for example pressure gauge is either checked or not checked, furniture has a desired color or it has not. Appearance surface finished of cover is either satisfactory or not

NEED OR IMPORTANCE OF INSPECTION To sort out acceptable from defective raw material or work in progress. This may be called remedial inspection To help in locating the causes of defective work and extend cooperation and assistance in removing these causes. It is preventive inspection To control the quality standards of manufacturing processes To submit reports to the management regarding a. Quality of product manufactured b. Quality of raw material received c. Efficiency of plant operation

FUNCTIONS OF INSPECTION Raw material inspection Process inspection (machines, handling equipments) Tool inspection Finished Goods inspection( to control quality, quantity small matters like colour, surface, shape)

QUALITY CONTROL QC is one of the important function of the management. It is a system set of tools and techniques by which products are made to comply with the specifications at the minimum costs of the firm According to Alford and Beaty “Quality Control is the mechanism by which products are made to measure up to the specifications determined from customer’s demand and transformed into engineering and manufacturing requirements. It is concerned with making things right than discovering and rejecting those made wrong”

BASIC ASPECTS OF QULITY CONTROL Acceptance function: it is inspection of goods that they are up to the specifications thereby segregate and reject those which are defective it is called as Inspection and it includes elements like receiving inspection, process inspection, finished goods inspection Preventive inspection: it refers to identification of defects in materials thereby avoiding or minimizing occurrence of defectives it includes elements like capability study, failure statistics analysis, methods studies

Assurance function: it refers to verification that every quality characteristic or a product is assured to meet a predetermined performance standard at each stage in manufacturing cycle it includes the elements like customers complaints, quality audit, quality determination, accuracy of inspection, executive reports on quality

INSPECTION AND QUALITY CONTROL INSPECTIONQUALITY CONTROL It is the art of comparing materials, products or performance with established standards. It is the process of measuring the qualities of a service in terms of established standards Inspection is one of the important step in quality control The maintenance department is responsible for inspection of plant, machinery and equipment It includes Raw material inspection, process inspection, tools inspection, finished good inspection Quality control is a industrial management technique or group of techniques by means of which products of uniform acceptable quality are manufactured Quality control is not step in inspection QC is department responsible for various quality control activities It covers Inspection and statistical Quality control

STATISTICAL QUALITY CONTROL Statistics is the collection, organization, analysis and interpretation of the data. The body of knowledge of statistical methods is an essential tool of the modern approach to quality. The increased precision demanded of manufactured parts and product require better methods to measure, specify and record it, statistics, the science of the most valuable techniques used in quality control jobs The statistical techniques and methodology have become more and more widely used got acceptability in industries. The availability of power of computers and advanced data processing equipments have enhanced

FOUR STATISTICAL TOOLS USED IN QC Frequency Distribution Control charts Sampling methods Special methods (Profitability paper graphing, testing of hypothesis, design of experiments) The understanding of these tools is necessary for full technological comprehension of quality control. Because the statistical techniques are used in controlling quality, it is called Statistical Quality Control

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