INTRODUCTIONInspection or testing is an act of checking material, parts, components or products at various stages of manufacturing, detecting poor quality manufactured products for taking corrective action. Inspection is done before, during and after manufacturing to ensure that the quality of the product is consistent the accepted design standard. The design standards are defined by the product designer, and for the mechanical components they relate to factors such as dimension, surface finish and appearance. The objective of nay inspection process is either to take actual measurements of the values of the specified product characteristics or to check whether specific characteristics meet design standards. When inspection and testing is carried out manually, the sample size is often small compared to the size of the population. In high production runs, this size may be very small which may result in slipping of defective parts. In principle the only way to achieve 100% good quality is to use 100% inspection where only good quality parts will pass through the inspection procedure. But when this done manually, the problem of expenses involved and error associated with procedure is of major concern. Automation of inspection offers an opportunity to overcome these problems. Automated inspection procedures are carried out by sensors that are controlled by computers.AUTOMATED INSPECTIONAutomated inspection can be defined as the automation of one or more of the steps involved in the inspection procedure.There are a number of alternative ways in which automated or semi-automated inspection can be implemented:1. Automated presentation of parts by an automatic handling system with a human operator still performing the examination and decision steps.2. Automated examination and decision by an automatic inspection machine, with manual loading (presentation) of parts into the machine.3. Completely automated inspection system in which parts presentation, examination, and decision are all performed automatically.WHEN & WHERE TO INSPECTInspection can be performed at any of several places in production: Receiving inspection, when raw materials and parts are received from suppliers. At various stages of manufacture, and Before shipment to the customer.COMPUTER-AIDED TESTING (CAT)It is the application of computers to control either analog or digital test techniques in order to evaluate the quality of components and products. Computer-aided testing is used to check that the component parts, subassemblies, and full systems are within specified tolerances and also perform up to specification. Note that performance to specification may require that the unit or system operates under stressful conditions that would not be encountered in normal use. The parameters (test criteria) for computer-aided testing are often derived fromcomputer-aided designandcomputer-aided manufacturingsystems.COMPUTER-AIDED INSPECTION(CAI) Computer Aided Inspection (CAI) is a new technology that enables one to develop a comparison of a physical part to a 3D CAD model. Its primary purpose is to create a faster production process and components with more precise dimensions and material consistency. This process is faster, more complete, and more accurate than using a Coordinate Measuring Machine (CMM) or other more traditional methods. An automatic inspection method and apparatus using structured light and machine vision camera is used to inspect an object in conjunction with the geometric model of the object. Camera images of the object are analyzed by computer to produce the location of points on the object's surfaces in three dimensions. Point-cloud data is taken from a laser scanner or other 3-D scanning device. During a setup phase before object inspection, the points are analyzed with respect to the geometric model of the object. The software provides a graphical comparison of the manufactured part compared to the CAD model. Many points are eliminated to reduce data-taking and analysis time to a minimum and prevent extraneous reflections from producing errors. When similar objects are subsequently inspected, points from each surface of interest are spatially averaged to give high accuracy measurements of object dimensions. The inspection device uses several multiplexed sensors, each composed of a camera and a structured light source, to measure all sides of the object in a single pass.BENEFITS OF CAI The CAI process saves both time and money. The computer software processes data from a 3-D point cloud from a laser scanner, eliminating the need for slower and more time-consuming CMM measurements. Inspecting with CMMs requires that designers create a 2-D drawing in addition to the 3-D CAD model of a part. The drawing is used to inspect the part at specific locations to verify that it matches the design. Point-cloud data is taken from a laser scanner or other 3-D scanning device. The software provides a graphical comparison of the manufactured part compared to the CAD model. By producing point clouds of the entire part, measurement of the part can be done everywhere and not be limited to the specific locations on a drawing.

COMPUTER AIDED QUALITY CONTROLComputer Aided Inspection (CAI) & Computer Aided Testing (CAT) are performed automatically using the latest computer & sensor technology. CAI & CAT methods from only part of Computer Aided Quality Control (CAQC). CAI & CAT are example of what have been called Island of Automation.The implications of the use of computer aided quality control are important. The automated methods of CAQC will result in significant changes from the traditional concepts & methods describe above.The following list will summarize the important effects likely to result from CAQC.1)With CAI & CAT, inspection & testing will typically be accomplish on a 100% basis rather than by the sampling procedures normally used in traditionally QC.2)Inspection during production will be integrated into manufacturing process rather than requiring that the part to be taken to some inspection area. This will reduce the elapsed time to a complete the part.3)The use of non contact sensor will become much more widely used with CAI.4)The online noncontact sensors will be utilized as the measurement component of computerized feedback control system.5)Because of 100% inspection & online quality control system will become prevalent; a basic assumption in statistical QC must be challenged.Inspection during the process of manufacture was also impossible. There are several factors to be considered. They are,1.Expensive inspection cost.2.Delay in production scheduling & delivery of finished components.3.Customer demands for high quality product.4.Need for automatic inspection procedure.All the above factor lead to the introduction & implementation of what is known as CAQC.To achieve the objective CAQC is considered essential.1.To improve the quality of the product.2.To increase productivity in the inspection process.3.To increase productivity & reduce manufacturing lead time.Hence it is necessary to automate the inspection process using computers & some sensing devices. The common situations that require inspection area are:Incoming raw materialDuring process of manufacturing.After production of component.Before shipping the component to the customer.CAI & CAT are performed automatically using the latest computer & sensors. The advantages of CAQC are,1.Inspection & testing will be accomplished in100%.2.Inspection area will be an integral part of processing area, hence reduction in inspection time.3.Inspection rate will be high.4.Manual inspection activity is eliminated.5.Besides CAI & CAT, computers can also be used in other areas of quality control