 Welcome you all for the series of lecture on Metrology. Now, let us start lecture 3 in module number 12. In this lecture, the following topics will be discussed. What are the features that can be checked by CMM complex form measurement using coordinate measuring machine, preventive maintenance of coordinate measuring machine and some details about portable coordinate measuring machines which can be moved to the shaft floors for measurement purpose. And then finally, we will discuss about virtual metrology laboratory. Now, let us discuss what are the features that can be checked by using coordinate measuring machine. We can measure the flatness of 6 surfaces. We can see we have a prismatic workpiece here which has 6 surfaces, flatness of 6 surfaces can be checked and parallel sum of 3 sets of surfaces can be checked and perpendicularity also can be checked, perpendicularity between the 12 surfaces can be checked by CMM. Roundness can be checked for example, say we have a hole here and we want to measure the diameter of the hole also the roundness of the hole. So, by selecting the data points on the surface of the hole you can find what is the roundness of that particular hole. And then, straightness of surface can be checked, we can say this is the workpiece surface by selecting some data points on the surface of the workpiece. CMM can estimate what is the straightness of that particular surface. You can see here, these points are data points obtained by the CMM and using the software the straightness is estimated. That means, the best fit line is fitted using the data points. Now, in one setting 5 faces can be inspected all the 5 surfaces, the features available in the 5 surfaces can be checked. Now, you can see here we have a very complex workpiece and this is the pro contact type pro. This workpiece has many features. So, it has angles, so angles can be measured and linear measurement is possible that is what is the slot width and what is the diameter of the hole, what is the distance between two surfaces and what is the distance between two slots, distance between centers say this is the center of one hole and the center of another hole, what is the center distance, pitch circle diameters, those things can be checked by CMM. Also, geometrical features like roundness, straightness, flatness, taper, slingicity, perpendicularity and parallelism can be checked using appropriate subroutines. We can see here by selecting the measurement points on the surface of external surface or internal taper surface, the CMM can estimate what is the taper and then the slingicity also can be measured. Now, very complex profiles can be measured using coordinate measuring machine. You can see here a very complex tooth profile. So, by selecting appropriate probe, the form or the profile can be estimated. So, measurement of sperm gear, hypoid gear, bevel gear and alkyl gears is possible using the coordinate measuring machine. Now, we can see the coordinate measuring machine is inspecting the sperm gear. The stylus is scanning the bore surface. Now, the stylus is moved. Now, it is scanning the tooth profile. It is scanning the tooth profile on the other side. Now, the ruby tip is scanning the tooth along the vertical direction. Now, it scans the other flank of the same tooth along vertical direction. Now, the inspection is over. Probe is moving to the home position. Now, we can see the inspection of a spiral bevel gear mounted horizontally using the fixture. Now, we can observe the automatic stylus changing. Probe bar is selecting another stylus from the rack. Now, the stylus is moved towards the workpiece to be inspected. Now, one stylus is inspecting the flank surface because of the very complex nature. Now, the inspection of the same flank surface is continued by another stylus. Now, some measurement examples are shown here. We have an engine block wherein we have to measure the internal surface of the bore and the details of these features. Here, another example is in the diesel engine body. This inclined surface is there in which we have bores and bores are to be checked. You can see the orientation of the probe is adjusted automatically. Here, the gearbox cover is placed horizontally. Then, using this content motorized probe, we can measure the features like diameter, the hole distance, the center distance and then the depth of the hole etc. can be checked. Here, the job is placed vertically and you can see motorized probe is oriented and you can measure the depth, surface details, center distance etc. etc. Depending upon the measurement requirement, the probes are selected automatically. We can see here the inspection of an engine block. By using long stems, you can see the probe has entered into the hole to check the features available at a deep surface. Using motorized probes, we can orient the probe and check the various features. You can see the use of a star type probe. Here, using an extension bar and the probe stylus at the end, we can check the inner details. It has entered into the hole to check the details available here. Here, the micro hole measurement using the combination of optical and contact probes in a CMM. You can see this is the workpiece placed in a fixture which has a micro hole. This is the spray hole and this is the optical probe CCD image sensor and this is the objective lens. This is the optical probe and then there is a contact probe also and there is a holder probe holder. This is the workpiece with a micro hole. This is the top surface and this is the bottom surface of the component. The details of the workpiece which has the micro hole are given here. This is the schematic diagram of diesel fuel injector which has micro holes. These are the micro holes of injector nozzle and this is the needle and here the fuel diesel will flow and it will come out of the nozzle. So, these are the spray holes. How these micro holes are made? The details are available here using micro hole EDM using wire electrode. This is the wire electrode and this is the workpiece in which the micro hole is to be made. So, using this EDM process, micro holes are fabricated. Now, here we can see the arrangement set up for micro hole measurement. So, in this first picture, we can see the overview of nozzle. This is the nozzle of the diesel engine injector nozzle and this is the contact probe made of glass fiber, glass fiber probe and this is the probe holder and this is the optical vision sensor, optical lens vision probe and in this picture we can see the close view of glass fiber probe. We can see the diameter at this point is 200 micrometer. At this point diameter of the probe of the stem is 500 micrometer and this is the tip of the probe and this is the workpiece and here we have nozzle micro hole and this picture shows spherical glass fiber probe tip. This is the probe tip, spherical probe tip with 74 micrometer diameter and this image is captured by the CCD image sensor. So, the measurement results are diameter of three micro holes are measured and the diameter is 157 micrometer, 158 micrometer and 160 micrometer. So, using CMM very small holes, micro holes also can be measured. Now, let us discuss how we can carry out preventive maintenance on coordinate measuring machines. Each of the three axes of CMM has a scale and encoder head for determining its position during travel. We should rub the scale lightly in one direction with a denatured alcohol soaked cotton ball to clean the scale. This generally needs to be done only twice in a year. The encoder head is not to be cleaned except by a trained service technician. So, keeping the scale clean will keep the encoder clean. Although the x and y axis scales are exposed, the z axis scale is covered. So, we should remove the tower cover to clean the z axis. There are ground surfaces located on the bridge leg rail and probe bar. These should be kept free of rust and debris and they should be cleaned at least once in a month. To clean these surfaces we should use denatured alcohol and a lint-free cloth and then we should follow up with an application of a thin coat of light oil again using a lint-free cloth. The probe bar should be cleaned and lubricated daily at least each day that is used in the same manner as ground surfaces to prevent rusting. Since the granite table is a porous material, we should clean the greasy layer and oily layer from the work parts to be inspected. Otherwise, the oil will enter into the pores in the granite. So, we should not place the foreign objects on the granite plate and we should remove inspected parts quickly from the table surface. Rust can form and stain if the work pieces are left on the plate. Stains can be reduced using a light amount of denatured alcohol and medium grade scoring pad. We should use only a light amount of special surface plate cleaner and lint-free cloth to clean the work piece table surface and we should allow it to fully dry before placing the parts on the table. The granite plate should be kept level for best results. We could use a 0.125 millimeter per 30 centimeter bubble level and we should adjust the knobs at the bottom of the table legs. If required, we should check this condition periodically. We can always use a gram gauge for adjustment, reset and checking of probe trigger force settings on touch trigger probes. Setting the optimum trigger force using the gram gauge maximizes a probe's performance. The gram gauge can be used to set trigger force settings over a range of 4 to 35 grams. The scale graduation are set at 1 gram intervals which is sufficient for all probe trigger force measurements on coordinate measuring machines. Here we can see the gram gauges. These are analog gram gauges. The least count of this gram gauge is 1 gram and in this case it is 10 grams and the digital gram gauges are also available. Using these gram gauges, we can set the force trigger force. The conversion factor is 1 gram force is equal to 0.01 newtons. Now, let us study what are the advantages of coordinate measuring machines. The first very first advantage is the flexibility. Coordinate measuring machines are essentially universal measuring machines and they need not be dedicated to any particular task. They can measure almost any dimensional characteristic of a part configuration including cams, gears and warped surfaces. No special features or gauges are required to use coordinate measuring machine. Since probe contact pressure is very light, most parts can be inspected without being clamped to the table. So, clamping devices are rarely used. Single setup measurement, most parts can be inspected in a single setup thus eliminating the need to reorient the parts for access to all features. And we can achieve reduced setup time. Part alignment and establishing appropriate reference points are very time consuming with conventional surface plate inspection techniques. Since coordinate measuring machine software allows the operator to define the orientation of the part of the coordinate measuring machine, all subsequent data are corrected for misalignment between the parts reference system and the machine coordinates. Because of this, the setup time is reduced very much. And we can achieve improved accuracy. All measurements in a CMM are taken from a common geometrically fixed measuring system. So, this eliminates the introduction and accumulation of errors that can result with hand gauge inspection methods and transfer techniques. And there is reduced operator influence. The use of distant readouts eliminate the subjective interpretation of readings common with dial or vernier type measuring devices. Since the measurement data is directly transferred to the computer system, the operator errors are minimum. And operator field is practically eliminated with modern touch triggered probe systems. And most coordinate measuring machines have routine measuring procedures for typical part features such as boards or center distances. In computer assisted systems, the operator is under the control of a program that eliminates the operator's choice. In addition, automatic data recording prevents errors in copying readings to the inspection report. In conventional measurement system, the operator reads the dial indicators or whatever the gauge is using. And then you should copy the reading to the inspection report. So, during that time, you may make a mistake. In the computer assisted system, such errors are completely eliminated. Due to a computer assisted system, less skilled operators can be easily instructed to perform relatively complex inspection procedures. And there is improved productivity. Due to the above mentioned advantages, coordinate measuring machines are more productive than conventional inspection techniques. Additionally, productivity is realized through the computational and analytical capabilities of associated data handling systems. And no separate gauges are needed. All the features can be measured in one setup in a CMM and reduced inspection time and pick retrieval of stored data. Now, let us study what are the errors possible in coordinate measuring machine. The granite table or cast iron table should be very much flat. If the table is not flat and there is some error in the granite table surface, then when we keep the workpiece, it will be resting like this. So, it will rest on the table at some inclination. So, because of this errors will be introduced. And error in probe movement, that means the probe when it moves in the x, y, z direction, there is some error in the guideway. The guideways may not be straight or they may not be moving along a straight path. Because of this, there will be error in the measurement. And then deflection in probe, if we use unnecessarily long probes, so it will bend too much. And because of this deflection, error is introduced. And workpiece weight induced errors. So, when we keep the workpiece on the granite table, if the weight is too much, then the granite table may deflect like this. Because of this, the measurement error will be introduced. So, we should take care to see that weight of the workpiece does not exceed the limit specified by the manufacturer. Then if there is any temperature variation because of the thermal expansion and contraction, error will be introduced. So, it is very essential that whenever we use a coordinate measuring machine, the temperature variations are minimized or proper compensations are given for the variation. And the fingerprint test particle and human ear may cause error in the measurement. We should clean the workpiece surfaces, we should clean the probe surface with utmost care and then we should conduct the measurement. Perpendicularity, error if the three axes are not orthogonal because of this also measurement error will be introduced. Then coordinate measuring machine in a computer aided manufacturing system. Dimensional measurement interface system that is DMIS is used between the computer aided manufacturing and CMM. This provides a bi-directional communication of inspection data between CNC machine and coordinate measuring machine to see that what has to be made and what exactly is made. That means, what is intended and what is made. This difference can be assessed by using this DMIS system. Now, you can see here this is the CAD system which will provide the CAD data to the CNC machine tool and this generates the CNC program based on CAD system and the program CNC program or the part program is supplied to the CNC machine tool for machining the workpiece. This CAD system also generates a inspection program based upon the CAD data and that is supplied to the coordinate measuring machine. Now, we have understood that the data collecting unit in a coordinate measuring machine is the probe inspection probe. Therefore, the selection of probe and its positioning in the CMM machine is very critical. Proper instructions must be given to the CMM system for positioning the probe properly and what is the path to be followed by the probe and what angle the probe should approach the workpiece. All these instructions should be properly given by the software and after a part is produced on the CNC machine, the finished part is moved to CMM and CMM inspects the workpiece using the inspection program. Then the data about the checked part, inspected part is sent back to the computer in this diagram. You can observe that the inspection program generated by the CAD system is given to the CMM and the part that is produced using the CNC program is supplied. It is moved to the CMM and coordinate measuring machine inspects the workpiece using the CMM program and the data on the inspected workpiece is sent back to the CAD system for making necessary correction. If there is any deviation in the workpiece from the desired size the data is utilized to alter the CNC program so that the error is minimized or error is nullified. The data about the checked part is sent back to the computer where the original part geometry is stored. The part geometry as designed is compared with the part produced and the resultant deviation that is error data is identified. This helps in identifying problems in the manufacturing and eliminating problems in the manufacturing. Now let us move to another topic, very interesting topic known as portable coordinate measuring machine. In the previous discussion we studied about the various configurations of coordinate measuring machine, how the measurement data is obtained, what are the different types of probes and then we also learnt about the CMM software. And we learnt that the coordinate measuring machine will be set up in the meteorology lab or if it is a sharp floor CMM it is moved to the sharp floor and it is placed in the production line. The workpieces are workpieces to be inspected or moved to the table of CMM and then inspection is carried out. Sometimes if the workpiece cannot be moved to the table of CMM that means we have a very huge workpiece very huge casting which cannot be placed onto the table of CMM. In that case the CMM itself is moved to the part then it is called portable CMM. In this illustration we can see the various elements of portable CMM. We have a CMM system, this is a dual camera system we can observe the two cameras here and this is a mobile unit we can see the wheels it can be moved to the place where the huge workpiece is placed and then this is installed or placed near the workpiece. And then we have an optical probe this is a non-contact type probe wireless probe and this probe we have to move around the workpiece. The CMM system dual camera system will be monitoring the workpiece as well as the probe probe movement as well as the workpiece will be continuously monitored by the dual camera system and then it establishes dynamic referencing using optical triangulation technique. And then this optical probe it takes the images from the workpiece and then that data is sent to the data acquisition storage processing and display system. There is a dedicated computer system with the software all the data obtained by this optical probe is transmitted wirelessly to this data acquisition system. This system after acquiring it will process the data and then results are displayed in the monitor. Now what are the features of portable coordinate measuring machine? So these portable CMM are currently used on production lines of automotive, aerospace and manufacturing industries. They are insensitive to changes in the environment that means the vibrations of the workpiece because of the nearby installations and part displacement and then setup or CMM instability have no impact on the measurement. These portable CMMs they are highly efficient at measuring parts that can't be moved to a granite or cast iron table. They are very much ideal for geometric and surface quality control. These portable CMMs offer scanning capabilities when paired with a 3D scanner. The part size the workpiece size ranges from 1 meter to 3 meters and any type of material can be inspected like hard material or very soft materials can be inspected. Since they are this is non-contact type of measurement even very soft materials can be measured without any difficulty. The measurement range can be extended up to 10 meters. In this picture you can see the CMM system. This is the mobile CMM system and this is the huge workpiece which is to be inspected and then we have wireless probe. Both the probe and the workpieces are monitored or continuously viewed by the dual camera system and then the image captured by the wireless this vision probe is sent to the computer system for processing. Now optical triangulation technique is used for dynamic referencing. This is required for self positioning or dynamic referencing of the workpiece and the probe system. This dynamic referencing enables the measuring device to be continuously locked to the part by an optical link. Now cameras in the optical localization system can simultaneously observe the targets positioned on the probe and object that means the targets or in other words reflectors are placed on the workpiece to be inspected and also they are placed on the probe and these targets and reflective surfaces they are continuously observed by the cameras. Since the targets are measured at the same time the targets placed on the object and targets placed on probe system they are measured at the same time. It is possible to calculate not only the probe position but also the part position at the same time. Now this illustration shows the dynamic referencing. We have this dual camera system which will be continuously monitoring the workpiece as well as probe system or scanner system. Now this is the workpiece to be inspected. You can observe that targets or reflectors are placed at specified locations on the workpiece to be inspected and also on the scanners reflectors are placed and then reflectors are placed on the probe system also. The XYZ coordinates of each reflector are recorded. The dual camera system will be recording XYZ coordinates of the reflectors placed on workpiece and XYZ coordinates of reflected placed on probe system or scanner system and also the part position the after monitoring the reflectors the probe position and the part position are calculated simultaneously that means the probe is locked with the workpiece. With this optical system it is possible to take continuous measurements of a number of 3D points at a relatively high speed. As the probe is moved around the workpiece for measurement there is a dynamic locking between the probe and then the workpiece because of the dynamic referencing and when the probe moves the distance moved is calculated and hence the measurement is made. Since there is the probe is wireless it is arm-free probing system so there is a total freedom of movement and the operator can hold the probe system and he can move around the workpiece easily for making measurement and this wireless system allows a significant increase in the productivity and self calibration using traceable certified artifact is possible that means a calibration bar equipped with several reflectors placed at known distances at various locations is used for self calibration of the system and there is a continuous monitoring of temperature and the temperature compensation is also possible and automatic alignment functionality is also present which saves a lot of time and there is a real time visualization and validation of acquired data the measurement volume can be extended depending upon the requirement increased accuracy in the sub volumes is possible easy volume extension by automatic leapfrog system and the total system weight is very very less including the tripod it is less than 30 kg a dynamic measurement mode is possible there is no physical link between probe and cmm system hence there is total freedom of movement for the operator. Now let us discuss about the very important element in the portable cmm that is dual camera sensors camera sensors are fitted with high quality optics and special lighting systems enabling them to measure all reflectors so these cameras they will be sensing all the reflectors provided on the workpiece as well as on scanner and probing system in addition to tracking the whole systems reference model the system ensures the exact location of the probe because of the triangulation technique used the portable cmm system ensures the exact location of the probe with respect to the work part it performs continuous image acquisition and transmission see the probe and scanner will be sending the images to the computer system and also the dual camera sensor will also be sending the images to the computer system for processing this dual camera system performs continuous image acquisition and transmission a lighting of reflectors management of the data transfer with the computer and storage of the sensor parameters now what are the benefits of portable cmm so this portable cmm eliminates the need to inspect parts in the lab that means we need not have to move the parts to the inspection lab or metrology lab since the portable cmm itself is moved to the sharp floor where the huge casting a huge part is present and it performs quality control right on the sharp floor this portable cmm ensures reliable results regardless of production environment that means even if the vibration is present or dusty environment is present irrespective of that regardless of that it gives good results no bottlenecks at the cmm so no waiting time at the coordinate measuring machine this decreases the back and forth movement between inspecting produced parts and sending back to the third party suppliers for corrective measures so this picture shows mobile pro contact type mobile probe so the probe can be contact type a varying mechanical probe is present or it can be non-contact type in which case we will be using optical probe and this is non-contact probe 3d scanner so without any physical contact this scanner will be scanning the work part and it will be sending the images to the computer system now this portable cmm improves the efficiency of the quality control process right up to product delivery this ensures 100% compliance with these standards and regulations and it guarantees top quality finished products and volumetric accuracy of up to 0.085 millimeter in real life sharp floor conditions regardless of instabilities vibrations thermal variations etc now it measures up to a few hundred parts per day directly on the production line so such is the speed of the portable cmm with the dynamic referencing mode the coordinate system can be literally locked onto the part being measured thus maintaining part alignment during the entire scanning process and very fast measurement is possible that is 36,000 measurements per second is possible now this picture shows the scanner mounted on the robot arm and we can give the inspection program for the robot arm and robot arm will move as per the program and it scans the work part now let us discuss about portable cmm software this software guides the operators at every step throughout the process it clearly and immediately notifies the operators to take additional pictures whenever needed to increase measurement accuracy real-time visualization and validation of positioning model make it possible to see the rebuild volume and all estimated points with the utmost accuracy the software measures and recomputes all the identified points each time an image is taken now what are the applications of portable cmm these portable cmm are used in the aerospace automotive and energy sector and in the manufacturing sector for part inspection tool verification etc and this portable cmm can be used for part to CAD analysis and then first article inspection and supply quality inspection is possible and then large scale tooling inspection and adjustment can be made using portable cmm very large castings can be easily inspected by portable cmm large models and dyes can also be inspected and then conformity assessment of 3d models against original parts and production tooling is possible and then conformity assessment of manufactured parts against originals and then large part alignment can be achieved full free form inspection and generation of high density color maps can be generated and then reverse engineering of geometric entities like spears cylinders planes etc is possible the portable cmms allow faster and more accurate reverse engineering of mixed parts where in the geometrical and free form parts are there now let us discuss about another topic known as virtual metrology lab in the previous portable cmm only one dual camera set is used and measurement is made now let us assume that the workpiece is very large for example in this picture we have shown a car body so in such very large workpieces if you use only one set of dual camera then the measurement is possible only in this region when they want to measure the front side of the car body then we will have to move this dual camera to this place and then we have to carry out the inspection that means the inspection is not seamless we will have to break the inspection process and then finally we have to assemble them in order to avoid such things virtual metrology labs have been developed where in up to four portable cmms are connected in a single network we can observe here this is the workpiece to be inspected we have one dual camera system here second dual camera system here third dual camera system here and fourth dual camera system are mounted on walls in the lab and then the operator holds the probe or scanner and then he moves around the workpiece around the car body for making measurement without any pauses continuously he will be moving around and he takes the readings that is up to four portable cmms are connected in a single network to create a virtual metrology lab this enables seamless probing and 3d scanning operations using the probe or 3d scanner and portable cmms without having to move the optical tracker that is dual camera system around the part to be inspected if we use only one optical tracker or dual camera system we will have to move around the workpiece so that is avoided by networking four trackers networking four trackers in the system total freedom of movement with a measure of up to 360 degree when linking multiple coordinate measuring machines this simplifies the setup and measurement process therefore ensuring a more seamless contact and non-contact inspection process which translates into significant time saving now let us discuss about laser vision lasers are also being used for measurement of workpieces for single dimension measurement 2d measurement as well as three-dimensional measurement is possible using the laser or the laser vision setup is schematically shown here this is the workpiece to be inspected we have a laser source and then the filter lens and then this is the image sensor CCDR CMAS is used since the image now in the laser vision optical triangulation principle is used the principle is like this this is a laser source and it is a B image sensor and this is the object which is to be inspected now we want to check what is the distance of the object from the line joining this AB now knowing the distance between AB and these two angles alpha and beta it is possible to get this D this principle is used for the measurement 100 to 1000 images per second can be captured in this system so normally this is used for weld joint preparation check whether the joint weld joint preparation is okay or not what is the leg distance what is the angle whether any mismatch is there such things can be inspected using this laser vision now the vision system can be moved along with the processing machine for example if we are checking the weld joint this is the welded portion and we want to check whether weld is okay or not so this is the welding unit which is moving in this direction and then behind this we can have this laser vision system which checks whether the welding is proper or not so this vision system can be used to check preparation of joint as well as the bed inspection this 3d contour digitization detects weld defects and acquires enough information to track the joint at a speed of 1 to 20 meters per minute which is compatible with the welding speed apart from weld joints this system can also be used to check the profiles so here you can see there is a two workpieces are placed and we need to check what is the what is the depth and what is the width see the width information is required as well as this depth information is required now you can see this is the point laser source and then structured pattern generator so this pattern generator will generate the required pattern of laser and then it is reflected back optical lenses are there for so that the image the reflected light reflected light falls on the images sensor and here the image sensor captures the picture and it can be analyzed to check the width and depth measurement now we can see here a handheld welding inspection device so this is the weld to be inspected and we can move this inspection system we can get the we can see the image and image can also be captured and stored it can measure joint fit up priorealty welding to ensure that the preparation joint operation is suitable joints and weld widths are measured for a variety of features including length size porosity and intricate mismatch and bevel angle the measurement results can be automatically compared to the tolerances prescribed and the comparison is made and the system provides go or no go feedback these results can be augmented with a picture of the weld all the measurement records can be retrieved easily now laser vision sensors can automate the visual inspection of pipes tubes and pipeline welding they can be used for real-time process control and measurement of welding processes ranging from arc to laser welding now we can see here the welding system as well as the laser vision system together they are mounted on a robot so in the robot modes the welding is carried out simultaneously the bead is inspected for its quality so if there is any defect in the weld the feedback is given to the system so that the rectification can be carried out now apart from a welding inspection there are many other applications of laser vision the vision system can be used to check the PCBs PCB circuit can be checked automotive parts can be inspected parts like camshaft crankshaft axle brackets windscreens etc can be inspected by laser vision system the vision systems can also be used to check the profiles you can see here we have a workpiece with a profile like this so using the laser system we can check whether the profile is okay or not so using this optical triangulation technique the measurement of workpieces is possible the measurement system is mounted in the CMM and 3D inspection of workpieces can be carried out now let us conclude this lecture number three in this lecture we discussed about what are the features that can be checked by coordinate measuring machine complex form measurement of workpieces and how to maintain the coordinate measuring machine what are the advantages of coordinate measuring machine what are the common errors in the CMM and then we also discussed about portable CMM its benefits and applications and then we studied about virtual metrology laboratory and laser vision we will conclude this session thank you