 Welcome you all for the lecture series on metrology. Now we will start module number 12, lecture number 4. In this lecture, we will be covering in-process gauging and control, which includes introduction to the in-process gauging and how the in-process gauging systems are classified. And then we will discuss about the working principles of various gauging systems in which we will be studying about mechanical gauging systems digital systems, pneumatic systems in line probing and electro pneumatic system and measurement during transit. Finally, we will be discussing about the various benefits that can be obtained by in-process gauging. Now, let us try to understand what is the meaning of in-process gauging and control. In-process gauging, in other words, it's also known as auto sizing. It means inspecting the dimension of the workpiece while machining itself. In the normal process, what we do? The workpiece is machined and the machine is stopped to check whether the correct size is achieved or not. That means if you take the example of a turning process, after giving a few cuts, the operator will stop the machine, he will stop the rotation of the workpiece, then he will take the appropriate instrument like micrometer or vornier caliper and then he will check what is the diameter that is obtained. If the size is okay, then he will remove the workpiece and he will put new raw material. If the size obtained is not to the correct extent or there is extra material, again he will stop the machine and he will give a few more cuts. So, in the process, a lot of time is wasted and the cycle time will increase. So, to avoid the unnecessary time that is non-productive time and the effort of the manpower used in conventional inspection process, this in-process gauging is used. It helps in getting higher productivity. The goal of the in-process gauging is to remove variation from the process. In the conventional inspection process, the size of the workpiece may vary from workpiece to workpiece, whereas in the case of in-process gauging, that variation can be minimized. Now, these in-process gauging systems are classified as given below. In-process gauging systems for grinding machines, including gauges for external grinding machines, gauges for internal grinding and gauges for centralized grinding process. And the gauges for turning process are also available and gauges for honing process are also available. Now, let us study the in-process gauges for grinding operation. So, this picture shows a mechanical swinging lever. This is the grinding wheel and we have the workpiece which is rotating. Both are rotating in the proper direction and there is a pivot which carries this lever. When the correct size is attained by the workpiece, the contact lever will swing to the position shown by the dashed line. So, this is the initial condition of the swinging lever. When the correct size is reached, the lever will swing to the position shown by this dashed line. And when it swings, it makes electrical contact at this place. This contact will move and it makes a contact which causes the wheel head to move away from the workpiece. That is how when the workpiece attains the correct size, the wheel head moves back and the machining process stops. Now, this diagram shows another system wherein there is a mechanical lever with indicating the system. This is the grinding wheel and there is a job which is to be ground. And there is a probe or stylus which is in contact with the rotating workpiece and there is a hinge. And we have this lever 1. See, when the grinding process continues like this, the diameter goes on reducing and the stylus will be in contact because of the spring force. And this lever 1 will move to the new position shown with this dashed line. So, this indicator will show the change in the size of the workpiece diameter. When the correct size or the reset size is reached, this lever will move in this direction and the lever 2 will fall down and it makes this contact. This contact will make a contact over here and because of this, solenoid will be activated which will withdraw the grinding wheel head in this direction and the machining process stops. This is how the in-process gauging in mechanical lever indicator system works. Now we have another type of system which is caliper gauge. You can see this diagram. We have the grinding wheel and then we have the wheel head. Now this caliper system, this is the workpiece and then the caliper system which is fitted to the wheel head. And this caliper can be swivel in this direction and whenever measurement is required, this can be swing and it will be in this position. Whenever the measurement is not required, it can be removed from this position. Now this picture shows the details of the caliper gauge. This is the grinding wheel and this is the workpiece to be ground and this is the caliper. And here there is an anvil which is in contact with the workpiece and this spindle will move in this direction, vertical direction. So this anvil will be in contact with the workpiece due to this spring force active in this direction. So initially when the diameter is more, when there is excess material, there is the desired size. So this is desired size and this is the raw material, varying extra material is there which is to be ground. The anvil will be in contact with the periphery of the workpiece. So if the job is oversized, that is this extra allowance is there but the job is oversized, the electrical contact between A and B occurs. So electrical contact between A and B occurs and then the wheel head is moved in the forward direction and then grinding continues. If the job is undersized, which is less than, when the job becomes smaller than the desired size, electrical contact between C and A occurs, electrical contact between C and A occurs and the saw line will be activated and wheel head is withdrawn also. Such contacts, that means the electrical contacts will help in moving the wheel head in the proper direction. That means when there is enough material to be ground, the wheel head will move in the forward direction. When the workpiece becomes equal to the desired size or less than the desired size, the wheel head is withdrawn. The wheel feeding is stopped when the job gets within the prescribed limits. Now you can see commercially available caliper gauge, this is the clamp for clamping this caliper gauge to the wheel head and this is the caliper, there is a carbide point here which will be in contact with the workpiece and this is the spindle. So which will move in this direction depending upon the size of the workpiece and here there is an electrical cable which will go to the electrical contacts. So the caliper gauges are available in this from 10 millimeter to 1000 millimeter range. Accuracy, that means the workpiece accuracy will be of 2 microns or 2.5 microns when we use the caliper gauges like this. The narrow design for use with the crank granting the study is narrow gauge designs are also available and the transducer is sealed. Since these gauges are to be used wherein there is lot of coolant splashing, the transducer sensors used are properly sealed. Offset tips are provided for oil holes and the gauges contain replaceable carbide tips. Whenever they get worn we can replace these carbide tips and profiled shoes are also available. So commercially the caliper gauges are available for very small diameter gauges. The systems are available for measurement of 2 millimeter diameter and up to 1000 millimeter diameter. Now in this picture we can see the caliper gauge in the vertical setting. This is the workpiece mounted between centers and the grinding wheel and the caliper gauge which is fitted to the wheel head. And we can also see the arrangement for proper setting of the caliper gauge. And in this picture you can see the horizontal mounting of the caliper gauge using the adjustment facility provided with the adjustment gauge to the workpiece. Now we can see a caliper gauge with display unit. This is the caliper gauge fitted to the wheel head and then we have a monitor placed over here. There is a clear display of size and set points. This will also show the digital display as well as the analog display. And we can observe that there is a sealed transducer for maintenance pre-operation. These look as such are. The monitor can display the component count that means how many pieces are crowned by the preview displayed. Wheel dressing alarm will also be given. Wheel balance in the status is indicated. Wheel speed is indicated. Coolant temperature, time and date display is also possible. And we can change the setting from imperial to metric as needed. Multiple diameter displays also possible. That means if we use multiple caliper gauges to measure or to gauge the multiple diameter. So multiple diameter displays also possible. That means we have to use the multiple gauges so that multiple diameter displays possible. Now this picture shows the schematic arrangement of Landis Olex air gauging system. So this is the grinding wheel and this is the workpiece. And then we have the gauge head. At the end of the gauge head we have carbide tipped shoes which are in contact with the rotating workpiece. And between the shoes we have air outlet. Air will be escaping from this outlet. The amount of air escapement depends upon the condition over here that is the gap between the nozzle and the workpiece. So that dictates the amount of air that is escaping. So the pressure in this line depends upon the gap between the nozzle and the workpiece. And there is a pump which will pump the air. So we get the compressed air here which will move in this direction and the compressed air will be escaping from the nozzle. The compressed air will also enter into the mercury switch box. We can see here in the switch box we have two electrical contacts D and E which are set at different heights. So the height setting depends upon the size of the workpiece desired. Now the working principle is shown here. Here is escaping from the pressure line. The pressure in the line P is affected by nozzle conditions at outlet through which it is escaping. That means the pressure here in this line depends upon the gap between the nozzle and the workpiece. The change in the pressure is used to change the level of mercury in the mercury switch box. Thereby closing contacts D and E and these contacts D and E will control grinding wheel feeding. Air pressure of 0.15 bar is supplied by a pump A to the calibre frame B which has two corporected shoes that rest lightly on workpiece. The air outlet is between the two shoes. This is the air outlet placed between the two shoes. Now as the grinding proceeds spring tension moves the gauge head forward. So you can see this diagram. As the grinding proceeds the size of the workpiece will be reducing and the gauge head will move forward because of this spring tension. When the gap reduces between the work and air outlet pressure builds in the air line B causing the mercury to rise in the switch box C. At the end of roughing operation the mercury touches the contact D and electric circuit is then completed. The solenoid is energized and finish feeding starts and grinding continues until the finished size is reached. Gap between air outlet and work further reduces increasing the pressure in the line. Then mercury rises further in the switch box and electrical contact at E occurs. So when the size of the workpiece approaches the desired size the pressure builds up and the mercury level rises and then the electrical contact will happen with the contact E. Then when contact at E occurs a solenoid is energized and grinding wheel is withdrawn from the workpiece and machine stops. Factors such as wheel wear variation in the amount of work to be removed do not affect the machining accuracy. Since the final size of the workpiece depends only on the setting of the electrical contacts D and E using master workpiece. Now we will discuss another type of auto-sizing device based on electronic system. We can see in this diagram we have this is based on Wheatstone bridge circuit. In the circuit we have A and this system is based on Wheatstone bridge. So in this circuit we have A and B fixed condenser. This is A and B fixed condenser. And then we have C and D fixed plates. We can see here we have C and D fixed plates. And in between C and D we have a movable plate that is E. So this plate E will move up and down depending upon the size of the workpiece. When E is at the middle position that is workpiece size is equal to the desired size. That means initially we will be setting this system auto-sizing device by using a master workpiece. So we have to keep the master workpiece between center and then we have to adjust the position of this plate E. Such that plate E is midway between C and D. When the workpiece size is equal to the desired size, capacitance between E and C that is these two plates and E and D that is these two capacitance between E and D are equal and bridge is balanced. So this initial setting can be performed by using a master workpiece of the desired size. So after doing this initial setting we have to know the master piece and then we have to place the workpiece to be ground in between the two centers and then we have to start the we have to set the gauge and then we have to start the grinding. At the start of the grinding there is extra amount of stock on the workpiece that means this is the grinding allowance. So the plate E will move above and it becomes closer to C. So when the plate E moves up it is closer to C but the distance between D and E will be more. At the start of the grinding there is extra amount of stock on the workpiece. So this causes plate E to be nearer to C thus increasing the capacitance between the E and C and the capacitance between the E and D reduces due to the greater amount of gap. Due to this the bridge circuit based on bridge is imbalanced. Now when the grinding continues the workpiece reaches the exact size then the bridge is balanced. That means the plate E will be at the middle position when the workpiece size reaches the exact size then the capacitance between C and E and capacitance between E and D will be equal and then bridge is balanced. At that point of time a maximum current is permitted in the output stage to operate a relay causing the withdrawal of grinding beam. It is interesting to note that any variations of temperature, humidity, ionization of air, frequency and voltage act simultaneously on both sides of the bridge. That means any variation will affect on both sides. That means the variation will occur between C and D as well as between E and D. So this variation has no effect on the reading. That means these variations will not affect the variation of the workpiece size. A bracket for fixing the gauge to the machine is needed and the final setting is done by means of a compensator hatch. As you can see here there is a compensator is provided by operating this we can do the final setting so that we can achieve an accuracy of 1 micron repeatedly. Now let us study another type of auto sizing system wherein we have dual fingers. So this is known as dual finger gauge head. The diagram is shown here. This is the body of the gaging head which houses the transducer either capacitive or strain gauge sensors are used in this system. And two fingers are there. These two fingers will be in contact with the workpiece which is being ground. As the diameter reduces due to the continued grinding, the fingers will be always in contact with the workpiece because the spring force is active. And since the fingers move closer, the capacitance or strain will be changed and the changed electrical characteristic is supplied to the electronic circuit that is control unit which will display the size. And when the correct size or the desired size of the workpiece is reached, a relay will be operated to withdraw the gaging head from the workpiece. So in this photograph we can see this is the workpiece being ground and we can see the grinding wheel and we can see the coolant jet and then the fingers which are in contact with the workpiece. And gauge controllers are provided along with the gauge head for data storage and for zero setting. A multi-diameter gaging is also possible by using multiple fingers, finger sets. Now what are the features of real finger gaging device? The precise diameter control is possible and real time control is possible. And setting of the gauge head on the workpiece takes very little time, around half a minute per setup. Stainless steel body is used so that the complete setup does not get corroded due to the usage of water based coolants. And a repeatability of 0.0004 mm is possible at 5.15 sigma level. Integrated air retraction system is available for retracting the wheel head when the correct size is reached. Externally adjustable contact force, over travel and retraction is possible. This gaging system can be used either for dynamic parts or it can also be used for gaging the static parts. The range of operation is 5 to 200 mm on OD and 12 to 165 mm on ID. The wave finger gage system can be used for plane outer diameters or interrupted outer diameters. And this can also be used for gaging inner diameters. So the retraction amount of finger is 2.5 degree per finger. So when the correct size is reached, the fingers get retracted. That means the finger will move, swing back and then the gaging unit is withdrawn. Retraction mechanism air pressure is about 5 watt and the total weight of the dual finger set is about 1.56 kg. And the system can be used for gaging armatures, bearings, bushings, camshafts, crankshafts, cylinder linings, drills, impeller shafts, motor shafts, pistons, reamers, rotors. So like this it can be used for gaging many industrial parts. Now with the schematic diagram we can see the grinding wheel, the workpiece mounted suitably. And then we can see the dual finger gage head. The signals from the gage head will be sent to the machine control unit via the measurement control unit. When the desired size is reached, machine controlled will send a signal to the wheel head for retraction. You can see in this photograph the two fingers in contact with the workpiece which is being ground. And here you can see the gage head in action. The grinding wheel is grinding the workpiece and this is the gage and two finger gage head. In this photograph we can see that the dual finger gage head can be used for... In this photograph we can see that the auto-sizing device that is calibrated gage head can be used for online inspection of crank shafts. The close view of the crankshaft gaging is the grinding wheel and is the gaging head. We can see the shoes and the plunger which will be in contact with the ground surface. Now in this diagram we can see the arrangement for online gaging of the crankshafts. The crankshaft will be rotating and the gaging head will rotate along with the workpiece that is the crankshaft. Also it will move up and down because of the crank. So this is the gaging head which will be mounted on the wheel head. There are some gaging heads in process measurement systems for measurement of diameter as well as for measurement of roundness. So one such gaging unit we can see in this diagram. So the diameter measurement different models are available. In this model workpiece diameter range will be 24 to 90 mm. Stroke that is the stroke of the gaging head will be up to 120 mm. Measurement speed is up to 80 rpm and resolution is 0.1 micrometer. The other model stroke will be up to 340 mm and measurement speed is up to 80 mm and resolution is again 0.1 micrometer. And then at the end of the grinding is over roundness of the ground workpiece can be measured. That is the resolution. The evaluation points in the first model will be 3600 points. The data points will be collected and the measurement resolution is 0.1 micrometer. And measurement speed while measuring the roundness is up to 60 rpm. And least square circle method is used for evaluation of the, for assessing the roundness. Now let us discuss about the in-process gaging systems for internal grinding. This diagram we can see is the workpiece. The internal bore is being ground using this grinding wheel. And this is the gaging point which is in contact with the bore. So this is a single point contact system. The stylus is in contact with the internal surface of the bore. And you can see the arrangement. This link will move up as the grinding proceeds. The gaging point will be always in contact with the internal surface of the bore. Because this is spring force. Now as the grinding proceeds this link will move up. And there is a hinge here. And the B, the another link which is carrying the contact point will swing in this direction. And it makes contact. This contact will make contact with the other point, other contact. And a circuit will be closed and a relay can be operated to withdraw the grinding wheel. Now when there is, when the bore size is small that is, there is grinding allowance. The contact will be between A and B indicating that the bore is small. And when there is contact between over here it indicates that the correct size is reached. Also when the grinding is in progress we can see the change in the diameter by reading this indicator. Now this schematic diagram shows two point contact system. You can see the two points are in contact with the internal bore of the workpiece. This is the grinding wheel. And because of the spring tensions the two plan stylus points will be always in contact with the inner surface of the bore. As the grinding proceeds the diameter is getting enlarged and we can see the change in the diameter which is indicated by the indicator. There is no feedback to the machine tools so continuous monitoring is very essential in this system. Now there are pneumatic systems available for gauging the internal bore that is the gauging systems for internal grinding. The pneumatic pressure will be point 61.5 bar. And you can see in this diagram there are five lamps to indicating different stages of grinding. There is a pivoted lever we can observe here. There is a pivoted lever with a pad which makes contact with the bore of the component. This is the pivoted lever. The other end of the lever is in contact with the internal bore of the workpiece. As the bore is enlarged during grinding the lever turns about the pivot and the other end progressively restricts the outlet. So because of this pivot element this side it will swing downwards and it will be restricting the air escapement from this nozzle. This nozzle which causes the air pressure to build up and indicator gives the change in the pressure. This can be calibrated to show the change in the diameter. Now the increase in the pressure because of the restricted passage over here. The electrical circuits or relays will be operated and the feed rate will be adjusted. Finer feeds will be given to the grinding wheel so that the grinding enters into the finish cycle. The response time being 0.5 second very quickly the feed rate is adjusted. The indicator lights are eliminated. You can see here 5 lamps are there. 1, 2, 3, 4 and 5 lamps are there indicating the different stages of internal grinding. That is the roughing operation, semi-finishing operations, parking out with no feedback and work within limits. These are indications given by these lamps. So finally when the correct size is reached the automatic unloading cycle is initiated. Now there is another gaging system known as gagematic system for internal grinding operation. You can see the arrangement here. This is the table of the grinding machine. And there are two contacts E1 and E2 two contacts are there. And this is the gaging head which carries two solid flake gauges A and B. The size of B is smaller than A. Now this is the workpiece and this is the dressing wheel diamond point and this is the grinding wheel which will grind the internal surface of the workpiece. Now at each stroke of table two solid gauges A and B they try to enter the rear end of the workpiece board. So at each stroke these gauges they try to enter the bore. They are unable to enter the bore until sufficient metal has been ground. Initially there will be the size of the bore will be smaller because of the grinding elements. So these gauges will not enter. On nearing the finished size gauge B enters and allows a contact to be made by E2. When they due to the grinding continued grinding the bore size increases and at one point of time the gauge B enters into the bore. At that point of time there will be a contact made by E2 which actuates the wheeled dressing cycle. And then the diamond point comes into position and it addresses the wheel so that the finishing cut can be given. During the finished grinding gauge A tries to enter. When the correct size is reached gauge A will enter. When A enters it actuates another contact given this also contact end. Now when contact E is made this will activate a relay and the grinding wheel is withdrawn and the machining stops. Now let us study an auto sizing device made for inspecting interrupted surfaces. This is basically an electro pneumatic unit so wherein the compressed air is used for measurement purpose. So here you can see the anvil wherein we have jets. I am just writing this I am enlarging this portion. So here there will be a nozzle and compressed air will be escaping and this is the workpiece. This is a spline shaft, a spline shaft being ground. Now so in this spline shaft we get two pressures. When there is landing position the gap between the nozzle and the workpiece surface is less and hence the back pressure is more. When the space comes into position that means when the space comes into position the gap will increase and the pressure will reduce. So this electro pneumatic unit is capable of distinguishing between the pressure, the increased pressure and the reduced pressure. So in the schematic diagram we can observe that two open jets are mounted in a non-contact type caliber gauge. When grinding commences the gauge head is away from the workpiece that means this gauge head is in the retracted position until the component is within 0.5 to 0.1 mm of the required size. Now you can see when the workpiece size comes within this range or within the 0.5 to 0.1 mm of the required size the gauge head is moved to the position by operating an air cylinder. At this stage an electrical signal is produced and the gauge head advances the measuring angles to the preset position. Now you can see these dashed gauge heads indicate the gauge head is in position. Grinding continues when the correct size is reached the gauge head sends a pressure signal to the controller to withdraw the wheel head. That means when the pressure, when the size of the workpiece is lined shaft approaches the correct size there will be a certain pressure and when that pressure is equal to the preset pressure, a pressure signal is sent to the machine control unit which will withdraw the wheel head. An accuracy of 0.0005 mm is possible with a system like this. Now we can observe from the diagram that knurled B and thimble D. So this is knurled B and this is the thimble that is D. These are used to adjust the gap between the gauge head angle and the spline surface. The system differentiates between the large and small variation in pressure which occur alternately as the spaces and lands of surface pass the jets. Pressure variation is applied to a sensitive capsule carrying a set of contacts which breaks relay circuit when preset pressures are reached and wheel head is metron like this, this electromagnetic circuit works. Now let us study a system which is used to gauge the turned workpieces. This is called the digital lathe system and this system is preset using a master workpiece. Direct reading of dimensions can be obtained by reading this display unit. Now we can observe from this diagram that linear encoders are used for the two axes X and Z. For X axis there is a linear encoder and for Y axis for Z axis there is a linear encoder and we can get the direct reading from the display panel. And using a master workpiece we can set the values, preset values can be input to the system. So we can see the two buttons are there for setting zero when the master piece is used. All measurements are with reference to the preset data. The machine runs continuously and the operator stops the machine when the desired size is reached. That means the operator will be observing the readings in the panel. When the correct size is reached he will stop the machine. Now here we can see the linear encoders. You can see this is the one linear encoder fixed to the lead bed. This is for the Z axis and similarly for X axis there is a linear encoder. And this is for Z axis and we can observe the appearance of the linear encoders and this is the display. This is for X and this is for Z. Turning the continuous values, the radius and length values are displayed here and the operator will be observing. When the correct size is reached he will stop the machine.