Quality inspection are measures aimed at checking, measuring, or testing of one or more product characteristics Relate the results to the requirements to confirm compliance.

This task is usually performed by specialized personnel and does not fall within the responsibility of production workers.

Products that don't comply with the specifications are rejected or returned to improve.

The key assumption relating to quality inspection is to adopt the principle that the ultimate controller is a client.

The optimum form of quality inspection is the man who's aim is the best customer satisfaction.

It is the cost art of controlling the product quality after comparison with the established standards and specifications.

It is the function of quality control.

If the said item does not fall within the zone of acceptability -- it will be rejected and corrective measure will be applied to see that the items in future conform to specified standards.

Inspection is an indispensable tool of modern manufacturing process.

It helps to:control quality, reduces manufacturing costs, eliminate scrap losses and assignable causes of defective work.

Quality inspection serves three main purposes: 1. Identification of the problem 2. Preventing its occurrence 3. Elimination of the problem

Effective identification of the problem requires verification checks after each stage of production.

most common method of attaining standardisation, uniformity and quality of workmanship.

Purpose of Inspection(1) To distinguish good lots from bad lots(2) To distinguish good pieces from bad pieces.(3) To determine if the process is changing.(4) To determine if the process is approaching the specification limits.(5) To rate quality of product.(6) To rate accuracy of inspectors.(7) To measure the precision of the measuring instrument.(8) To secure products – design information.(9) To measure process capability.Stages of Inspection(1) Inspection of incoming material(2) Inspection of production process(3) Inspection of finished goods.

Inspection of incoming materials ( Receiving Inspection )It consists of inspecting and checking of all the purchased raw materials and parts that aresupplied before they are taken on to stock or used in actual manufacturing. Inspection may take place either at supplier’s end or at manufacturer’s gate. If the incoming materials are large in quantity and involve huge transportation cost it is economical to inspect them at the place of vendor or supplier.

Inspection of production processThe work of inspection is done while the production process is simultaneously going on. Inspection is done at various work centres of men and machines and at the critical production points. This had the advantage of preventing wastage of time and money on defective units and preventing delays in assembly.

Inspection of finished goods. This is the last stage when finished goods are inspected and carried out before marketing to see that poor quality product may be either rejected or sold at reduced price.

Types of quality inspections methodsQuality inspection of product design Assessing the status of compliance with the requirements enunciated by users or by the designers. The resulting quality of the design is essentially unmeasurable

Quality inspection of the design process Checking whether accepted methods and means of production, Quality performance in accordance with the quality of design.

Quality inspection in the production stage Used to determine the compatibility of the resulting quality of the product.

Thorough quality inspection Shall be carried out after completion of all stages of the production process. Subject of inspection is : Final product and its compatibility with the standard design

Inspection one hundred percentConsists of subjecting the inspection of all units produced. Due to time-consuming, this method is applied only to products manufactured individually or in small series.

Statistical inspection A lot of statistical inspection is assessed on the basis taken in a random sample. Therefore, this form of control is called a sample inspection. Depending on the size and frequency of sampling and the use of audit information to reverse effects on the production process, control may be statistical in nature

Statistical inspection of the products Statistical process control (SPC)

Metrology - Science of MeasurementAccuracyCloseness of agreement between an observed value and a standard

Precision Closeness of agreement between randomly selected individual measurements

Interchangeable PartOne which can be substituted for a similar part manufactured from the same drawingTypes: 1. Universal Interchangeability: it is assume that similar parts, derived

from any source whatsoever, are interchangeable.2. Local interchangeability: i.e parts made at the specific source (in

particular factory, for instance) are interchangeable, but such parts are not necessarily interchangeable with similar parts manufactured else where.

Interchangeability of Component Parts depend on two factors: i.e,1. It is necessary for the relevant mating parts to be designed

incorporating specified limits of size.2. Parts must be manufactured within the specified limits, which must

be controlled rigidly

Accuracy is the agreement of the result of a measurement with the true value of the

measured quantity the closeness with which the reading approaches an acceptable standard

value or the true value. It is numerically equal to the degree of error in the final result In any experiment, accuracy of the measured quantity is influenced by the

limits of the intrinsic error, limits of variation in the indication, accuracy of the observer & the environment

Precision: is defined as the repeatability of measuring process orThe quality or state of being precise orDegree to which an instrument gives repeated measurement of the same

standard SOURCES OF ERROR

ErrorDifference b/w the measured value & the true value of a quantity is

called static (orabsolute) error or simply error of measurement

The error may be positive or negative1. If the error is on positive side, the instrument reading is on higher

side2. where as if it is on lower side then the corresponding reading is on

lower side

Error falls into two categories:1. Controllable Errors2. Random Errors

Controllable Errors (System Error )Are controllable both in their magnitude & stress. These can be determined and reduced if attempts are made to analyze themControllable Errors can be due to:1. Calibration errors: actual length of standard such as slip gauges and engraved scales will vary

from the nominal value by small amount.2. Ambient Conditions: The variations in the ambient conditions from internationally agreed

standard value3. Stylus Pressure : When ever any component is measured under definite stylus pressure the

deformation of the work piece surface & deflection of the work piece shape will occur4. Avoidable Errors: These errors include the errors due to parallax & the effect of misalignment

of the work piece centres. Instrument location errors such as placing a thermometer in sunlight when attempting to measure air temperature also belong to this category of errors

Random Errors: The random errors occur randomly the specific causes of such error can not be determined.

The likely sources of this type of error are: 1. Small variation in the position of setting standards & work piece2. Slight displacement of lever joints in the measuring instrument3. Transition fluctuation in the friction in measuring instrument 4. Operator errors in the reading scale & pointer type displays or in

reading engraved scales positions

Classification according to use:1. Linear Measurement:

A. Direct Readingi. Ruleii. Combination setiii. Depth gaugeiv. Vernier caliperv. Micrometervi. Measuring Machine

a. Mechanical b. Optical B. Instruments for transferring

measurements:i. Calipers & Dividersii. Telescopic gauge

2. Angular Measurementi. Protractorsii. Sine bariii. Combination setiv. Angle gauge blockv. Dividing Head

SELECTION OF INSTRUMENTS

• The selection of measuring instrument depend upon its technical specifications eg:

• Scale value, scale division, graduation range• Linearity, threshold value, Sensitivity• Accuracy, Precison, measuring force• Working capacity, free strokes, • Error of measuring surface,• Error of the straightness of the guide ways, etc

* Testing of a completed application to determine that it provides all of the behaviors required of it

* Search for defects that are variances between the actual operation of the system and the requirements for the system

* System is treated as a black box

* Functional testing is a quality assurance (QA) process

* A type of black-box testing

* Functions are tested by feeding them input and examining the output, and internal program structure is rarely considered (not like in white-box testing).

* Functional testing usually describes what the system does.

* Functional testing does not imply that you are testing a function (method) of your module or class. Functional testing tests a slice of functionality of the whole system.

* Functional testing differs from system testing in that functional testing "verifies a program by checking it against ... design document(s) or specification(s)", while system testing "validate[s] a program by checking it against the published user or system requirements“.

Functional testing has many types:1. Smoke testing2. Sanity testing3. Regression testing4. Usability testing

Functional testing typically involves six steps1.The identification of functions that the software is expected to perform2.The creation of input data based on the function's specifications3.The determination of output based on the function's specifications4.The execution of the test case5.The comparison of actual and expected outputs6.To check whether the application works as per the customer need.

Functional Testing (also know as Behavior testing) is based on the Functionality of the program.

It is involves only observation of the output for certain input values.

There is no attempt to analysis the code, which produces the output

The Significance of a Non-conformanceThe existence of a nonconformance means that some aspect of an organisation's standard operating procedures are not being followed.

How are Non-conformances Identified?Non-conformances are typically identified in the context of a quality management system audit. The auditor documents the non-conformance in a Non-conformance Report which is subsequently issued to a management representative who directs corrective action.

The occurrence of a problem with a process or product is referred to commonly in the quality realm as a ‘nonconformance’.  

A process designed to manage nonconformances is what is referred to as nonconformance management (NCM).

There are four core elements within a nonconformance management process :Standard Reporting Method: It is essential for the occurrence of a nonconformance to be tracked in a standardized way. The occurrence of a nonconformance is commonly recorded using a Nonconformance Report or (NCR).

Nonconformance Review Process: The data from the NCR is then commonly reviewed by a Material Review Board (MRB) to assess the impact of the problem. This board commonly has representation from the Quality, Production, Engineering and Regulatory departments.  Generally, many companies will review nonconformances in batches at the end of a day or shift

Disposition: This is where it’s decided what is to be done about a specific occurrence of an issue.  Examples of disposition types within a manufacturing company include: rework, scrap, recall, Return to Vendor (RTV). products/processes, categories, time periods, and suppliers.

Ongoing Analysis: Ongoing analysis of trends in nonconformance data gives an organization the ability to make changes to their process to reduce the occurrence and costly impact of nonconformance.

Challenges and Pitfalls of NonconformancesAll companies large and small have to deal with managing nonconformances.  The larger the company, the more complicated this process can become.  As companies grow from one small team of people to multi-site corporations and continue to expand through acquisition, the processes and data being tracked almost certainly diverges.  Suddenly, the process that worked so well at the founding location is not easily adopted at the new locations, and then you wind up with stacks and stacks of nonconformance reports all being measured and managed in different ways

Effectively Managing NonconformancesStart with the end in mind: Define the ways you want to organize your data should management (or a customer) request it.  Build the nonconformance report (NCR) with that information included.

Review the NCR form: It is amazing how often we continue to use systems that are in place just because “we’ve always done it that way”.  A fresh look at your nonconformance report may illuminate pieces of data that don’t serve a long term purpose, and therefore, can be eliminated.

Standardize Reference Codes: Using checkboxes or selected code values be sure you have a place on your nonconformance form to track:

The type of nonconformanceThe type of disposition that was decided uponTraceability Information: It may seem like a no-brainer but make sure to track pieces of information such as: part number, lot/job #, serial #’s, customer, department found, supplier, quantity of product impacted.  These pieces of information are commonly used to look up nonconformance records.

Problem Solving 1. Define the problemDiagnose the situation so that your focus is on the problem, not just its symptoms. Helpful techniques at this stage include using flowcharts to identify the expected steps of a process and cause-and-effect diagrams to define and analyze root causes.

2. Generate alternative solutions Brainstorming and team problem-solving techniques are both useful tools in this stage of problem solving.

3. Evaluate and select an alternativeSkilled problem solvers use a series of considerations when selecting the best alternative. They consider the extent to which: A particular alternative will solve the problem without causing other unanticipated problems.All the individuals involved will accept the alternative.Implementation of the alternative is likely.The alternative fits within the organizational constraints.

4. Implement and follow up on the solution

The most effective approach, by far, has been to involve others in the implementation as a way of minimizing resistance to subsequent changesFeedback channels must be built into the implementation of the solution, to produce continuous monitoring and testing of actual events against expectations.