 Now, let us start the lecture number 2 in module 12 and the advanced metrology topic. In this lecture, we will be discussing about the different types of CMM probes. So, we will discuss about the probe working and how the collision of probe with the machine or workpiece is avoided and then what are the various types of probes like touch trigger probe, scanning type of probe, probe and then we will also discuss about the calibration of probes and how do we change the stylus or probe depending upon the inspection required and then we will discuss about the vision probes and then we will move on to the CMM software wherein we will be discussing about the various capabilities of software and then what are the various subroutines used in CMM software. Now, let us study how the CMM probe works. In this picture, we can see we have the CMM table on which the workpiece is placed and then this is the probe. When the probe is moved in this direction, this tip of the probe or tip of the stylus will come in contact with the job and then it slightly deflects, the probe will deflect like this and then we can see here we have three micro switches placed inside the housing of the probe. One the micro switch is available here, second one and one more behind the spring. Now, when the stylus deflects, the micro switch gets opened and then a signal is sent to the CMM software. So, this is a mechanical probe wherein the micro switches are used and then we have another type wherein the piezoelectric element is used or wire strain gauges are used to sense the contact of the stylus tip with the job. Now, in the case of touch trigger probe, as the probe contacts the job as shown here, the continuity breaks or resistance changes. If it is a probe with micro switch type, the micro switch gets opened and the signal is sent to the CMM software. If it is a probe based on the strain gauges, when the probe deflects the resistance of the strain gauges changes and hence the signal is sent to the software. The computer records this point coordinates that means whenever the probe comes in contact with the component that particular point coordinates are stored with the computer and a LED light and audible signal indicates the contact. In the case of scanning probe, this is used to measure contour surfaces and very complex irregular shapes and this scanning type of probe remains in contact with the part surface as it moves. For example, this is the probe and say this is the surface, work part surface. When the probe moves in this direction, the stick it scans over the surface and then it will be sending the signals to the computer system and hence very complex 3D shapes can be assessed using the scanning probe. Now, let us try to understand how the probe collision with the CMM structure or the job is avoided. We can see here we have the table of the coordinate measuring machine and this is the column of the coordinate measuring machine and this is over arm on which the probe head is provided. We have the probe fixed to the probe head and this is the probe rack. Now, the workpiece, this is the workpiece to be inspected which is mounted on a fixture. The height of fixture and the location of the fixture plays a very major role. Now, when the stylus is checking the inside pole feature, the other stylus for example, this stylus should not touch the table and the other third stylus should not touch the column. So, in such a way we have to locate the fixture and we should select the fixture of proper height. Similarly, when the probe moves, see it selects the appropriate probe from the rack and then it will be moving in this direction for carrying out the inspection. So, after carrying out the inspection in this particular hole it will be retrieved and then they should be moved up to a sufficient height so that this stylus will not touch the surface of the workpiece. So, like this the automatic path selection is done using the CMM software based upon the CAD detail that is provided. So, you can see here the probe is inspecting very complex part. So, when it after completing the inspection over here it has to move up to a sufficient height and then it should be brought to this position for inspection. Now, we can see the probe assembly. This is the probe body which is fixed to the probe head using the spanners and then we have this is the probe module which can be coupled with the probe body using the kinematic coupling. We can see the alignment marks here to check whether the assembly of the probe module with the probe body is correct or not and then we can select the appropriate stylus and it can be fixed to the probe module. The term probe refers to the entire probe configuration and the term stylus refers to the stem and tip of the probe configuration. So, this is the stem portion and this is the tip of the stylus. Now, let us study the different probe types under mechanical probes. We have touch trigger probe, scanning probe and five axis probes. This touch trigger probe, it contacts the job at the selected points which are decided by the operator or by the inspection program. The operator operates the joystick and he will move the probe and then probe will move and it makes contact with the workpiece and then the like this measurement is carried out. If it is a CMM with a dedicated computer system, these selected points are decided by the software or the inspection program. Now, the scanning probe, there is continuous contact of the probe tip with the job but this can also be used as a touch type probe and then we have five axis probes, the details of which we will be discussing shortly and there is another type of probe called optical probe or vision probe. So, you can see here as is a profile which is to be measured. So, the probe we have to select the scanning probe, it continuously it moves over the profile and then it is sending the data points to the computer. Now, touch trigger probes, they measure discrete parts decided by operator or the software making them ideal for inspection of 3D geometric parts. As the probe touches the surface of the component, you can see here probe will move and it makes contact with the workpiece surface. So, as the probe touches the surface of the component, the stylus deflects and simultaneously sends the XYZ coordinate information to the computer. Now, you can see here this is the stylus and it is a probe model and probe body. So, depending upon the inspection we have to select appropriate stylus and appropriate model which can be assembled into the probe body and care must be taken to see that proper stylus with proper tip and stem length is selected. We can see in this particular diagram the stem is contacting the workpiece surface which is incorrect. So, whereas here only the tip of the stylus is contacting the surface that means we have to select the appropriate stem and tip for achieving the proper measurement. Now, in the case of continuous contact probe, these scanning probes are miniature measuring machines that can acquire several hundred surface points per second. That means such as the speed of acquiring the data points several hundred surface points are sensed in each second enabling measurement of form as well as size and position. Scanning probes can also be used to acquire discrete points similar to touch trigger time. Now, you can see here the probe when it moves like this it is scanning the surface and hence we can get the profile information. Very high speed scanning is possible with advanced scanning probes which can give which can sense at the rate of 300 millimeter per second. An extremely robust design to withstand moderate collisions. The low probing forces give maximum application flexibility because of these low forces the wear of the stylus is also very less and excellent product life with a mean time before failure in excess of 50,000 hours. So, this gives low cost of ownership. Now, let us discuss the five axis probe systems. In the conventional coordinate measurement methods, the CMM structure performs all the movements that is x, y, z movements necessary to acquire the surface data. CMM structure accelerations induce inertial deflections into the machine frame which in turn induce measurement errors. Many techniques have been developed that reduce these dynamic errors, but there is an upper speed limit imposed by the machine and servo system stiffness beyond which measurement cannot be taken with reliability. Recently, five axis probe system have been developed which uses an articulating head that moves in the two rotary axis as it measures. That means, five axis probe system has additional two rotary axis a axis and b axis along with x, y, z motion given by the CMM structure. This allows the CMM to move at constant velocity in a single vector while measuring. As the probe head is much lighter and more dynamic when compared to the CMM structure, it is possible to quickly follow changes in the part geometry without introducing harmful dynamic errors. This results in much faster surface speeds and hence shorter measurement cycles. Five axis scanning technology allows the user to achieve extraordinary levels of throughput. Now, you can observe a motorized five axis probe head here. This is the probe head and appropriate styluses can be incorporated inserted into the probe head. We can observe here that apart from x, y, z motion given by the CMM structure, these motorized probe heads, they have their own a axis movement as well as b axis movement. So, the stylus can be swivelled as shown here and the stylus can rotate in plus 180 degree or minus 180 degree. Apart from that, the radial adjustment is also possible. There is an integral LCD display which enables easy programming of probe orientation. So, depending upon the inspection requirement, the probe orientation can be adjusted and this is the digital display built into the probe head. Now, you can see here with the use of extended bars, extension bars probe head can reach to deep holes and recesses and the internal details, deep hole details can be measured and accurate 3D form measurement even with the long stylus is possible. You can see here by using the extension bars, the measurement volume can be selected. Now, apart from single stylus probe heads, multiple stylus probe heads are also possible. You can see here we have a probe head with multiple stylus. This is a disc stylus with an extension bar and this is a ruby ball stylus with the knuckle joint. Similarly, you can insert appropriate stylus here depending upon the inspection requirement. A wide range of stylus have been developed to suit many different aging applications. These can be mounted on multiple stylus head. The selection of the stylus is done based on the application for which the probe is to be used. Now, you can see here with the help of motorized probe head infinite number of repeatable positions and repeatable stylus changing is possible. You can see here a motorized 5-axis probe head is fixed to the jet axis. It can orient its angle. Angle can be adjusted depending upon the workpiece inclination, workpiece angle. Here also you can see the inclined surface and bore is to be checked. So, the 5-axis heads will help in inspection of these holes which are at some inclination. Advanced probe head increases inspection throughput up to three times using fast infinite rotary positioning and unique head touch capability. Now, you can see here this is the deflected probe body if we use conventional probes and here we are using a 5-axis scanning type probe. So, non-linear motion on a Cartesian CMM induces acceleration and deceleration that twist and deflect the machine structure and these dynamic deflections result in measurement error. So, this is eliminated by using the 5-axis probe system. Now, you can see these pictures show variety of mechanical probes. The motorized probe wherein the angle can be changed. Start type probe heads are possible. Motorized probe head wherein the angle can be adjusted depending upon the workpiece type. These touch probes are extremely robust and are ideal for use on general purpose manual coordinate measuring machines. The feature to be inspected dictates the type and size of the stylus used. However, in all cases maximum rigidity of the stylus and perfect specificity of the tip are very vital in order to have accurate measurements. You can see here the there is excessive deflection of the probe. It means selection of stem of proper thickness and proper length is very important in order to avoid excessive deflection and perfect specificity is also very vital so that we get accurate measurements. The performance of gauging can easily be degraded if a stylus is used with poor ball roundness, poor ball location, bad thread fit. See the fitting of the stylus into the probe body should be proper otherwise it will need to improper measurement or a compromised design that allows excessive bending during measurement. To maintain accuracy at the point of contact it is recommended that stylus be kept short. So, unnecessarily when the stylus should not be used which causes the large amount of deflection which will lead to incorrect measurement joints should be minimized between probe and stylus tip the minimum joint should be there as large as possible stylus ball should be used. Now, you can see a variety of probes here this is a stylus stem ruby tip is ruby tip and this stem is made of stylus stylus steel so which is used to measure the recesses as well as the surface heights, widths etc. etc. Now, you can see here is star stylus and here we are observing how we can use a star stylus to measure the external grooves. So, similarly here measurement of internal groove using the star stylus and here we have a ceramic hollow ball stylus for measurement of the diameter of the holes a disc type stylus and a cylindrical type stylus used for measurement of threads. Now, how do we select the probes depending upon the material see if we have a soft material then we should select the probes with low force requirement low measurement force requirement. So, for general use we can select the SF type and for heavier longer and heavier style like we should use the probes with medium force requirement and similarly for grooves and undercuts and depending upon the type of the inspection we should select the probes of appropriate length with appropriate force requirement. Now, let us see the details of striped probes. Now, this diagram shows striped probe stylus. Now, this is the thread threaded portion which will go into the probe body different threads are possible and two m2 to m6 threadings are possible and then this is the stem portion stems are available with different materials like steel, ceramic, aluminum, carbon fiber, titanium and tungsten carbide and they are available with different diameters also and at the end we have the tip this is the probe tip. Probe tips are available with different tip material like ruby, silver steel, silicon, nitride, tungsten carbide, ceramic and zirconia and tips are available with different shapes also. So, this shows a ball type tip and balls different diameters up to 6mm and above are available depending upon the inspection requirements. So, effective working length of the probe is D. So, the probes of different working lengths are available up to 11 millimeter, 11 to 29 millimeter, 30 to 50 and 50 mm and above. So, depending upon the application we can select probes of different length. Now, striped stylus are designed to inspect simple features where direct unobstructed contact with a measure surface is possible. A tungsten carbide stem provides exceptional rigidity particularly for stylus with small ball and stem diameters. Ruby is regarded as the industrial standard for stylus tips. It is one of the hardest materials available and it is suitable for most applications. Due to adhesive nature, ruby tips are not recommended for scanning aluminum bars. Now, these pictures show cylindrical head stylus. You can see the tip is cylindrical type which can be used to measure threads and this is a spherical ended stylus and then we have datum dend. Hemispherical tips are also available for measurement of holes of larger diameter and then we have star type where in the different tips can be mounted on this head probe head. Then we have pointed tips for measurement of threadings and then extension rods are possible to measure very deep hole details. So, extension rods can be used and at the end we can have the stylus and adopters are also possible between the probe head and the stylus tip. Now, before we use CMM with selected stylus, we should calibrate whether the probes are capable of giving the proper readings or not. So, for that a master ball is used. The master ball is placed at the specified location normally at the center of the table and the probe is selected, probe is fixed into the stylus, stylus is fixed into the probe body and then the stylus is made to scan the surface of the master ball and the readings are analyzed to check whether the probes are giving proper readings or not. Whenever we select a new probe, we should find whether the probe is capable of giving correct readings or not. So, we should calibrate the touch probe to determine the CMM scanning probe error, a sphere of diameter 25 millimeter with negligible certified form error is scanned along four recommended scanning lines. So, in this picture you can see this is the master ball which is used to calibrate the probes selected. So, this is the probe that is selected and which is to be calibrated. So, the master ball is placed at the specified location on the CMM table and the probe selected is made to scan the surface of the master ball along the four lines. This is line number one, line number two, line number three and we have line number four. So, the probe selected scans the surface of the master ball along these four lines as per ISO 103604. The time required T for this test must be specified as speed has enormous influence on the results. Many CMM manufacturers do not quote this time unjust specifically requested since they may quote an excellent T value, but it is obtained at a slow scanning speed. Now, how do we calibrate the CMM? Now, a reflector is placed at the probe dwelling. So, this is the jet axis of the CMM and this is the place where the stylus is inserted. So, this place reflector is placed and the inspection program is run. The reflector will move as per inspection program. So, the motion of the reflector is tracked by the laser tracker and then what should be the movement of the reflector as per inspection program and what is the actual movement as inspected by the laser tracker they are compared to check whether there is any error in the CMM movement. So, like this CMM can be calibrated using the laser tracker. Now, we can also calibrate coordinate measuring machines by using the slip gauges that means this is the table of CMM on which slip gauge of known length say a length is equal to 10 millimeter. So, the slip gauge of known length is placed and then we should insert the stylus in the probe body and then it is moved probe is moved in this direction and it makes contact at this place and reading one is recorded. Similarly, the probe is moved to this place and then it is made to touch the slip gauge at this place and reading R2 is taken. Now, the difference between these readings R2 minus R1 okay R2 minus R1 minus the tip diameter minus tip diameter should be equal to this slip gauge here then if this is the case then the CMM movement is okay like this coordinate measuring machines can be calibrated using the slip gauges. Now, depending upon the inspection requirement we sometimes we need to change the stylus that is if workpiece is very complex we need to change the stylus to suit different measurement tasks. For example, assessing deep features that require long and complex stylus as well as using different tips like spherical tips, disc type tips and cylindrical type tips for measurement of threads. So, stylus should be optimized for the application to ensure very sound measurement results. So, these stylus can be changed manually using a threaded connection. So, whenever we change manually recalibration is essential. Probe systems are now available with repeatable automated means to switch stylus reducing manual intervention and eliminating the need to recalibrate. Now, in this demonstration we can see the movement of the probe. Now it is moving in B axis plus or minus 180 degrees plus minus 180 degree movement. Now it is A axis movement. Now we can see the calibration of probe using a master ball before using probe we should calibrate. Now you can see the operator is operating joystick is moving the stylus and is inspecting the inclined surface on the workpiece. Stylus is contacting at four different places of the inclined surface. When the probe touches we can see the red light blinks. Now after this inclination is calculated and probe is adjusted for proper orientation and again joystick is operated and stylus is moved so that stylus touches the inner surface of the bore on the inclined surface. It is contacting the inner surface of the bore. You can see the blinking of red light. Now after getting the measurement points software is calculate the diameter and center point coordinates. Now recently optical probes also known as vision probes are developed and by using these vision probes CMM can be used as a microscope for measurement of electronic circuits for measurement of micro holes and for measuring very rubbery materials or elastic bodies. The optical probe capture you can see here in this diagram we have an optical probe and this is the electronic circuit which is being inspected by the vision probe. So this probe moves on the electronic circuit and captures the image and the captured image is analyzed and measurement readings are taken. The optical probe captured image will have various automatic edge detections performed by the dedicated software and then various calculation processes such as calculation of dimensions like thickness, width, depth, length, etc. and geometrical deviations will be performed by general purpose measurement program. These optical probes can be mounted on automatic probe changer. You can see we have probe changer where in the different kinds of touch type and scanning type probes are mounted. We can also see a vision probe is mounted in the automatic probe changer which allows fully automatic measurement including both contact and non-contact types of measurement. That means depending upon the requirement sometimes the contact type probes are selected and inspection is carried out and whenever non-contact type measurement is required this vision probe is selected and inspection is carried out. Dedicated software available in the computer system displays the image window when it detects a workpiece edge when a vision type probe is used for inspection. After detecting an edge it starts various calculations like diameter, thickness, angle, etc. with the regular general purpose measurement programs. Here you can see an edge is detected. This is the hole available in the workpiece. So the dedicated software it detects the edge like this and then the various points or the coordinates of various points on the selected edge are obtained and then the software will calculate what is the diameter of this hole and what are the expected coordinate points of this center point. So like this software will calculate the required details, required features. Now using the vision probes and with powerful image processing tools it is possible to have 3D metrology. That means it can measure the vision probe can measure in the height that Z axis also by means of its autofocus function. By using this autofocus function while the height of the workpieces, height of various features can be measured and hence three-dimensional measurement is possible. In ordinary microform measurement it is often difficult to remove bursts and dust for example. So we have a workpiece like this wherein there is a hole and here some bursts are there. See in ordinary measurement these bursts cannot be compensation for these bursts cannot be made whereas if we use vision type probes. So these bursts and dusts can be removed automatically. The advanced optical probes of this can recognize these obstructions like bursts and dust and bypass them during the measurement. Now 3D vision measuring systems are developed wherein vision system vision probes are provided as well as text trigger probes are also provided in the machine. So vision probes are used for measurement of the various features and then the touch trigger probe is provided to reach undercuts and similar features which are not accessible by the vision probe or the camera. You can see here we have a vision probe and then the touch trigger probe. So using the combination of these the complex workpieces can be measured wherein the undercuts or some such things are there in the workpiece which are not accessible by the vision probe. This advanced machine is extremely productive on most workpieces because of its high intensity LED stroboscopic image capturing technique that operates while the stage is moving. That means when the stage is moving along the workpiece the measurement is possible. That means we need not have to stop the table for making measurement. Programmable ring lighting is also provided to give the flexibility in lighting direction angle and intensity that enables achievement of maximum surface contrast for best imaging resolution and hence accuracy on the more problematic workpiece. The fixed bridge moving table design is used for the ultimate in rigidity. A programmable power turret provides control of magnification for optimal viewing. That means whether we require 10x magnification or 20x magnification. So that can be programmed. So the turret will rotate as per the program and then we can have the required magnification. In this demonstration we can observe a coordinate measuring machine with the vision probe and a touch trigger probe. Now you can see the moments of the coordinate measuring machine. The vision probe of coordinate measuring machine. Now the touch trigger probe is inspecting a spur gear. It is inspecting the profile, tooth profile of spur gear. Now the vision probe is inspecting the tooth profile, gear tooth profile using the optical system. Finally the software will present the measurement results on the computer monitor. Now let us study what are the capabilities of CMM software. In the advanced CMM software it is possible to select the required resolution that is whether accuracy requirement is up to 0.01 millimeter or 0.001 millimeter or 0.001 millimeter. Like that required accuracies and regulations can be selected. Unique selection is also possible depending upon the requirement we can select English system or meta system. Conversion of rectangular coordinates to polar coordinates is possible. Axis scaling is possible. Datum selection and resetting is possible. Save and recall previous data is also possible. We can do the tolerance entry. Out of tolerance competition is possible and measurement of diameter, center distances, length and geometrical and form errors in prismatic components can be calculated. Online statistics for statistical information in a batch is possible. Parametric programming to minimize CNC programming time for similar parts is possible. Measurement of plane and spatial curves is possible. Data communication is possible. A digital input and output commands for process integration is available. Program for the measurement of spur gear, helical gear, bewill gear and alphoid gears is available and then interfacing to CAD software is also possible. Now various sub-routines are used for making the computations. Some of these sub-routines are discussed here. Multi-point circle that means we have a workpiece with a hole here by selecting minimum of three points. For example, point 1 here and then a second point at this place and then a third point at this place. So using the minimum of three measured points, center point and diameter of best fit circle can be calculated and multi-point sphere using the minimum of four measured points. So one point here, second point at this place, third point at this place and fourth point at this place. Using the minimum of four measured points, center point we can, the software can calculate what is the coordinates of this center point and then what is the diameter of best fit sphere can be calculated. Multi-point cylinder using minimum of five measured points, a best axis, a point on the axis and diameter of best fit cylinder can be calculated. That means on this cylinder we have to select five measured points. Then the software will calculate best axis and point at the axis and diameter of best cylinder can be calculated. Then what takes cone angle computation is possible using the four measured points. So on this conical feature four points should be selected. Using these four points software will calculate the vertex angle and taper of an inside or outside surface of a cone. So if you have an extended outside cone, so four measuring points should be given and software can calculate what is the coordinates of this vertex and what is this angle and then what is the taper that can be calculated. Multi-point line using a minimum of two measured points, the software determines the best fit line through the selected points. The point of intersection between the line and the major axis can also be calculated. We have this major axis here and we have the best fit line here. So these are the two measured points and this is the best fit line and what is the angle between the major axis and the best fit line that can be calculated using the software. And perpendicularity of two lines. You can see here we have one plane here and we have second plane here and this is the line in the first plane and this is the line in the second plane. So what is the perpendicularity between these two planes can be calculated by the software. That means we have to give a minimum of two measured points on each line two points here and two points we should give. Then software will calculate the perpendicularity between these two lines or planes. Angle of intersection or point of intersection of two coplanar lines using a minimum of four measured points software determines the point of intersection. So here we should give two points and on the line two we should give two points as software will determine the point of intersection. So coordinates of point of intersection can be calculated and the angle of intersection up to this angle also can be calculated. Then parallelism of two lines. You can see here we have line one and we have line two and using the minimum of two measured points on each line. So we should give but we should select two points on line one and two points on line two. That means total four points we should give. Then the software determines the angle between these two lines. Then the parallelism is tan of this angle and then multipoint plane. So we have a plane surface here. We should give minimum three measured points. We should select one point here, one contact point here, one second contact point here, third contact point here. That means we should move the probe and then we should make contact here, here and third point here. Then the software will establish a best fit plane passing through these three given points and then 3D alignment. So software aligns the third axis. So this is the third axis. Software aligns the third axis through a line determined by the part origin. This is the part origin and the measured point on the part surface. Parallelism of two planes. Now in this diagram you can see this is plane number one and this is plane number two. We want to check whether these two planes are parallel to each other. That means we have to select one point here and another point on this plane. Similarly, two points on this second plane. Then the software will determine a best fit line passing through these two points. Similarly, best fit line passing through these two points and then it will calculate what is the angle between these two lines. In other words, the angle between these two planes. The software determines the angle between the two planes. Parallelism is tan of this angle and then perpendicularity of a bore axis to a plane. I can see we have our piece here with a bore and this is the bore surface. The software determines the angle between a bore's center line. So this is the bore's center line established as a line between the bore's upper and lower center points. So this is the bore's upper point and this is the bore's lower center point and it establishes an axis passing through these two center points. That will be the bore's axis and what is the perpendicularity between the bore axis and the bore's face. So that will be calculated by the software. What is the angle between the bore surface, face of the bore and the center line and perpendicularity is tan of this angle. Now let us summarize the module 12 lecture number two. In this lecture, we discussed about the probe working, how the probe works, wherein we discussed about the micro switch arrangement in the probe or piezoelectric element or provision of strain gauges in the probe and then what are the different types of mechanical probes like touch type probe and scanning type probe and how the calibration of probes and calibration of CMM is carried out. We also discussed about the stylus changing depending upon the inspection requirement and we also discussed about the vision probes and finally we discussed about the CMM software, wherein we discussed about capabilities of software and what are the various subroutines used in the software. With this, we will conclude this lecture. Thank you.