 Let us start the module number 12, lecture number 5. In this lecture, we will continue the discussion on in-process gauging and control. So in this lecture, we will discuss about in-line probing and then we will move on to the various benefits of in-process gauging and then we will move to the next topic that is stage position metrology in which we will be discussing about various precision stage positions or table positioning systems. So what are the various kinds of stages or tables available and what are the driving systems used in these tables and then what are the errors associated with these stages and then how we can calibrate the stages and finally we will discuss about the various applications and how we can select the micro or nano stages. Now let us discuss about in-line probing. The main objective of in-line probing is to get probing routines into the cutting cycle. This is not exactly the gauging during the machining. So what we will do, in between the different operations, we stop the machining and we bring the stylus into position to check whether a particular feature is within the limits or not. If it is within the limit, then we allow the next operation to be continued. So we will just take a very simple example. So we have a work piece where we have two operations. First operation is drilling operation. Now that we have carried out the drilling operation, before we move to the next operation that is reaming operation, the first operation is drilling operation followed by reaming operation. So after completing the drilling operation, we remove the drill from this position and then we allow, we bring a probe which is similar to CMM probe into this position which will check whether the diameter of the hole is within the limits or not. If the diameter is within the limits, then the next operation that is reaming operation is allowed. So in in-line probing what we have to do is first the inspection program should be built to remain the CNC program. For that we have to import the CAD model. Then the programmer has to pick what are the various features to measure the features like the diameter or the depth of the hole or the B-circle diameter like that. So the programmer will pick the various features and he will drag and drop them into the inspection program. Then running an inspection program generates measurement data that can then be used to automatically update offset. That means the probe is brought into the position and the feature is checked. If the feature for example the diameter is within the limits, then no change is made. If the diameter is not as per the specification, then the feedback is given to the CNC controller to make changes in the offset so that the workpieces can be produced to the to the specification. So this can be done automatically or the feedback is given to the operator so that he will manually make changes in the CNC program. The precise dimensional relationships between features at each step of operation can be performed to avoid rework or scrap. Now high precision machine tool probes are available which offers a micron or CMM like precision to inline part inspection. The strain gauge based designs deliver low trigger force and uniform 3D trigger pattern with part 5 micro meter repeatability with a 50 millimeter stylus. Inline probing are used for very complex and high value parts so that the reception is almost nullified. Now in this picture you can see a probe which is inspecting the hole in the IC engine body. Now let us move to the discussion on benefits of in-process gauging. The in-process gauging can tell how well the machine tool is performing before actually cutting the workpieces. That means we have to use the probing tool to probe the master part. A program inspection program touches off a series of points on the master workpiece. A deviation in the machine measurement from the control dimensions determines the need for offset. The inline gauging can be used when parts are to be made to the specifications. It can also reduce trips to a metrology lab that not only takes time but can mean an error inducing the re-setup. Now there are real-time benefits of real-time gauging which allows control and optimization of the following cycle. Part control at start of the machining that means check the in-process gauging checks for correct part loading or excessive machining allowance to prevent collisions of the probe with the work part. It can define the amount of machining allowance to increase machine productivity and then part control during the machining. Grading will feed and speed changes when the pre-set machining allowance values are reached consequently reducing the machining times and hence increasing the productivity. A management of super finishing time relative to the actual part value to improve the surface of the part. Management of removal value to optimize grinding speed and to control firm errors. So proper form can be provided to the workpiece by usage of in-process gauging systems. Then cycle stop at the nominal part dimension increasing process quality and automatically compensating grinding will be here. An in-built post-processor system allows evaluation of the machine capacity and receipt of statistical indications for correct feedback on the process. So with this we will wind up the discussion on in-process gauging. Now we will move to the next topic that is stage position metrology. In the recent times advanced manufacturing systems are used to produce very high precision parts. When it comes to high precision machine tools accuracy of the positioning table or positioning stages is very very important so that precise components can be produced to micrometer or nanometer accuracy. Also there is a need for accurate positioning systems for probing high precision components to micrometer or nanometer accuracy. Now what are micro positioning devices? They have drives and guiding systems such as stepper motors, ball screws, inertial drives, frictional drives, ball bearings, roller bearings etc. These micro positioning devices have micrometer resolution like pint, one micrometer resolution, half micrometer resolution, one micrometer resolution depending upon the design and construction of the device. In this diagram we can see a micro positioning device. This is basically x-y table. It has two movements in the x-direction as well as y-direction. I can see this is the table on which workpieces can be mounted. We can directly place the workpiece on the table or we can use some suitable fixture for mounting the workpiece. We can see the two wheels for moving the x-y table in the x-direction as well as y-direction. We can also observe the cylindrical guide. You can see there is a guide here, there is another cylindrical guide and one more cylindrical guide here. So cylindrical guides and ball bearings also I can observe here. Re-circulating ball bearings are used so that it precisely moves to micrometer resolution. Now what are the nano positioning devices? They are basically positioning devices capable of nanometer or sub-nanometer resolution. A dry system and guiding systems are frictionless and normally air bearings, linear motors and piezo drives are used in nano positioning stages. So here we can see a nano commercially available nano positioning device wherein we have the table or the stage to keep the workpiece. So this will move with the nano meter resolution. So the range will be in terms of few micrometer like 0 to 50 micrometer, 0 to 100 micrometer ranges are available with nanometer or sub-nanometer resolutions. Now this picture shows a motorized precision stage. We can observe this is x-axis motor with x-axis high resolution rotary encoder and we have a y-axis motor with y-axis rotary encoder where the motor is coupled to the lead screw. You can observe the lead screw within that. So when the motor rotates the nut will move and hence the stage will move along with the workpiece that is mounted. We can also see adjustable end limits on both sides we have end limits and here also you can observe end limits for the y-axis. So encoders are provided for feedback purpose. I mean these pictures we can see there is a digital display. As the table moves the digital display we indicate what is the amount of movement. At any location we can set the reading to 0 and from that position when we move the table what is the amount of table movement is indicated in this digital display. Now here we can see a manual x, y, z table the z movement the vertical movement is by operating this knob and this is the table on which we have to keep the workpieces and then I can see the two micrometers are provided one for x and one for y. So we can always take the reading what is the movement of table can be read by reading the main scale and the symbol of these micrometers and the accuracy positioning accuracy in these cases will be like one micrometer, two micrometer depending upon the micrometer units what we use. Now here we can see the rotary tables manual rotary tables and motorized rotary tables. So you can see here this is the motorized rotary table this is the motor fixed to the body of the table. So inside there will be worm and worm build mechanism to convert the rotary motion of the motor into the circular motion of the table. So this is 0 range is 0, 2, 3, 6, 3 and least count is 1 degree. With vernier attachment a least count of 10 seconds or 5 seconds can be obtained. You can see the holes are provided to mount the rotary tables on the machine to the tables. So here we can see another manually driven rotary table. So this is a rotary table is mounted on the machine tool table by using the T bolts. We can also see vernier is attached so that very precise rotary position can be obtained. So this is called HV rotary table. H stands for horizontal and V stands for vertical. So these tables can be used in horizontal or vertical position. Now we can observe that this is placed in the vertical position and we can tilt it and we can use it in the horizontal position also. This is the wheel to obtain the rotary motion of the table and we can see the scale and vernier. So the tables are available with 4 degree rotation per handle rotation and 20 second vernier scale using vernier scale and accuracy rotary accuracy of 20 seconds can be obtained. And here we can see a tiltable rotary table. So this is the table on which we have to mount the workpiece using the T bolts. We can see the T slots and this is the wheel to rotate the stage and we can tilt this table by operating this lever. Again here you can see there is a vernier scale so that very precise tilted position can be obtained. Now what are the drives used for these stages? These stages can be manually driven stages or magneto-strictive drives can be used. Thermodynamic drives can be used. Linear motors can be used to move the stages or tables. Visual electric drives are also available for precise movement of micro nano movement of these tables. Stepper motors also can be used. Also these same motors are used to drive the stages. In this picture you can see manually driven xy table. You can see micrometers are attached for by operating these micrometers we can get the precise motion of table in x and y directions. The range of movement in x and y will be like 25 millimeter by 25 millimeter 50 by 50, 100 by 100 like this different ranges are available. The resolution of these manually driven xy table will be normally 1 micrometer and load capacity that is the workpiece weight which can be mounted on the table will be like 1 kg, 2 kg and different sizes are available. Now let us study the magneto-strictive drive used for micro displacement of these tables. You can see the arrangement here this is the unit of the machine or table of the machine which which is moved precisely and here we have this is the total length of the unit and here we can see the coil is provided through which the electromagnetic potential is applied and when we apply the electromagnetic potential the unit machine tool unit undergoes a finite change in length that is delta m that we can see here. In some cases this change is positive that means there will be extension of the unit of the machine and in some cases it can be anything that means this unit machine tool unit contracts. So that depends upon the material's characteristic. Delta lm is equal to lambda times l where lambda is the magneto-strictive strain and l is the length of the machine tool unit. The value of lambda depends on the property of material and the actual number of ampere tons per centimeter that is the hedge. Now here we can see lambda hedge occurs for various allowance. Lambda is the magneto-strictive strain and hedge is number of ampere tons per centimeter. So x-axis decays the hedge values in ampere tons per centimeter and y-axis indicates the value of lambda. You can see the different materials used for construction of the machine tool table. Now the delta lm can be calculated using the this relationship delta lm is equal to lambda lm this is equal to see if we take 60 ampere tons per centimeter for perm alloy then the lambda value will be 40 units. So that is 40 lambda value is 40 times 10 power minus 6 and let us assume the value of l of the machine tool as 100 millimeter then the delta lm will be equal to 0.004 millimeter that means four micro meter like this by adjusting the value of hedge we can get the required positioning accuracy. Now these diagrams show the application of magneto-strictive device for giving the final displacement this is the machine tool table which is to be positioned precisely. So you can see the arrangement this is the motor for table feed we have clutch and gearing arrangement and then lead screw with net. Rough displacement can be given by using the lead screw and net and final movement can be given by the magneto-strictive drive and in this diagram you can see the rough displacement being provided by the hydraulic cylinder and final displacement of the unit is provided by using the magneto-strictive drive. Now let us study another type of drive used in machine tool tables. Now this is a thermodynamic drive used for very precise moment of machine tool stages also known as machine tool tables. Now the arrangement is like this this is the body of the machine tool and this is the support B and this is the machine tool stage which will move on the guideline and X is the moment that is needed and inside the support B we have electric coil and current will be passed through this coil and this coil gets heated up and hence the support B will also be heated and it expands. Support B has electric coil inside depending upon the temperature attained by the support B which depends upon the current that is passed. It undergoes a change in length delta X you can see here this table moves to this position depending upon the temperature that is attained by this support B. Because of the expansion of support B the machine tool will move by micro displacement delta X. So delta X can be calculated by alpha times L times delta T where alpha is coefficient of linear expansion which depends upon the support material L is the length of the support B. So L is equal to length of the support B and delta T is changing temperature. Now I can see some of the displacement characteristic for a particular material based on various feed velocities. You can see X axis is a time of heating in seconds elongation in terms of millimeter. So the temperature varies between 300 to 400 degree Celsius and various curves are available for different feed velocities. Now if you take very slow heating as shown by curve 1 if we heat for about 60 seconds that is one minute then the elongation of the support material will be about 0.2 millimeter like this by adjusting the heating time different displacements can be achieved. Now let us study another kind of drive used in precision X-ray tables. So the linear motors can be used to try the precision tables. A linear motor is effectively an AC induction motor that is cut open and unwrapped. In this diagram you can see the conventional rotary AC induction motor. This is the stator coil and the rotor. So when the stator is energized the rotor starts to rotate. In the linear motor the stator is laid out in the form of a track of flat coils as shown here. You can see the stator in the unwrapped form. This stator is also known as the primary of the linear motor. The rotor takes the form of a moving platform known as secondary. So this is the rotor portion which is known as secondary and it is also known as a force plate which will move linearly. When the current is switched on the secondary that is the rotor slides past the primary supported and propelled by a magnetic field. Now let us study how the linear motor works. So in this diagram you can see the stator which is in the form of a flat portion and then we have a rotor placed above the stator. So this rotor is supported by mechanical bearings or air bearings. So when we pass the current to the stator a magnetic field is induced because of this secondary magnetic field is induced in the rotor. Now these two magnetic fields interact or they react between each other and this produces a linear thrust on the rotor and hence the rotor starts to move. Since the magnetic field in the stator is traveling along with that the rotor also starts to move and hence we get the linear motion of the rotor. Now the linear motors also known as linear induction motor they are designed to directly produce the motion in a straight line. Typically linear induction motors have a finite stator length that means depending upon the application we have to design that the stator. In this picture you can see the tubular type of linear motor the red colored parts are linear motors and these are thrust rods and this is the work stage on which we have to place the work piece. Now ultra high accuracy linear motor positioning stages are available in the market. The typical positioning range is 50 to 300 millimeter and they are able to carry a load of 15 kg. The maximum velocity is 600 millimeter per second. Positioning resolution is 0.001 micrometer and they have a position free reproducibility of 0.015 micrometers unidirectional and plus or minus 0.024 micrometers bi-directional. Center mounted linear position feedback encoders are provided for feedback. Specifically these are designed for subsurface wafer inspection, fiber alignment and high precision robotics. Now let us discuss another type of drive used in the positioners that is piezoelectric effect. Now you can see in the diagrams we have a solid mass to which electrical current or voltage is applied. In the first case the electrical current applied is 0 and here we can observe that when electrical voltage is applied there is deformation of the solid material. So this effect is known as piezoelectric effect. This effect describes the relation between a mechanical stress and an electrical voltage in solids. An applied mechanical stress will generate a voltage and when you apply voltage the voltage will change the shape of the solid by a small amount which we can observe here. The most well known piezoelectric material is quarch material. Now this piezoelectric effect is used to prepare piezoelectric actuators which are used for micro positioning and nano positioning application. In this we can see piezoelectric actuator made out of flexural mechanism. The advantage of this flexural mechanism is it does not require any lubrication there is no wear and tear of the parts. Now it is almost made out of a single material and inside we have the piezoelectric material to which we have to apply the voltage and there is a deformation of the piezo material. With the result that these surfaces will move in the perpendicular direction as shown here. So the vertical moment is proportional to the applied voltage. So this flexural mechanism provides an exceptionally large range of motion something like 200 micrometer 300 micrometer range and the response is very fast and the sub nanometer resolution is possible. So such piezoelectric actuators are used for nano positioning, biomedical application, microscopy, precision machining, vibration control and they are also used in high speed valves and optical engineering. Now some specifications we can see here you can see the dimension of the piezoelectric actuators very small actuators are possible. You can see the total length is 20 millimeter and height is 7 millimeter and the width is 6 millimeter. Such a miniature actuators are available. The voltage that is applied varies from minus 50 volts to plus 115 volts. So displacement range that is vertical moment displacement range is from 0 to 120 micrometer. So depending upon the applied voltage we can have the displacement in terms of nanometers and we can say another piezoelectric actuator of bigger size total length is 52 millimeter width is 16 millimeter and height is 14 millimeter and the displacement range is up to 830 micrometer and you can see it can a force that can be applied using such a piezoelectric actuator is 90 newtons. Now you can see a piezoassisted micrometer in this picture. This is a manual micrometer whether they operated and there is a piezo mass mounted in series with the screw. So inside there will be a micrometer screw to which a piezo mass is fixed in series. You can see this is the conventional micrometer wherein we can give the larger displacement and the finer displacements are given by the piezo mass. You can see the timble here graduated here. You can see the timble has clearly marked graduations every five micrometer while the barrel is engraved with marks for every one millimeter. It is equipped with a strain gauge to give the positional feedback over a range of 0 to 30 micrometer of piezo travel with 10 nanometer resolution. So here you can see the micrometer manual micrometer traveled ranges up to 12.7 millimeter and micrometer resolution is 1 micrometer whereas the piezo mass travel range is 30 micrometer up to 30 micrometer and the piezo resolution is 10 nanometer. So piezo driving voltage is up to 75 volts. Now in this picture we can see a high load precision piezo nano position in the jet stage that means we can get a vertical movement in the jet direction. So nano positioning is possible in the vertical direction. So it has an encoder for feedback with a resolution of 3 nanometer and minimum incremental motion is 100 nanometer and the total travel range is up to 12.5 millimeter in the vertical direction and it can carry a load of up to 12 kg hence it is high load precision nano position jet stage. Now what are the various advantages of piezo electrical systems? We can get a very fine resolution of sub nanometer range. So with this extremely fine positioning is possible the workpieces can be moved to very fine accurate positions and these piezoelectric actuators are able to produce large force generation. They can generate a force of up to 10,000 new tons and piezoelectric systems or stages are available which can bear loads up to several tons and position within a range of more than 100 micrometer that is range travel range is up to 100 micrometer with sub nanometer resolution. These piezoelectric actuators offer the fastest response time that means positioning can be achieved within a fraction of microseconds and then they settle typically in milliseconds minimal tilt and out of plane motion and zero wear components is the added advantage of piezoelectric actuators and the power consumption is very very low the piezo effect directly converts the electrical energy into motion only absorbing electrical energy during the movement otherwise there is no absorption of electrical energy and in static operation even holding heavy loads does not consume power only during motion the power is consumed and no wear and tear there are no gears and no rotating parts and then operation at cryogenic temperatures is possible the piezoelectric effect is based on electrical fields and they can function down to almost zero Kelvin and the capacity feedback is possible which is a direct measuring type and not contact time vacuum and clean room compatibility is there with these piezo actuators and piezo actuators are the ceramic elements that do not need any lubricants and there is no problem of wear operation so this makes them clean room compatible and ideally they are suited for the ultra high vacuum applications and their reliability is very very high and they can be used in industrial and space applications where the cycle of operation is as high as 100 billion cycles and they perform frictionlessly because of the flexure designs the there is better multi-axis transitory control and parallel metrology which keeps motion of all controlled axes inside the servo loom and digital control is possible with wider dynamic range and better linearity and auto calibration facility is also available with these piezo actuators now let us discuss about the stepper motor which are used in positioning stages you can see the main parts of the stepper motor this is the state art form which is having the field windings and these field windings are energized by supplying the electrical pulses and when electrical pulses are given to these windings the rotor of the motor is attracted and hence it starts to rotate the shaft of the motor rotates in the discrete step increments when the electrical command pulses are applied to the state art in a proper sequence so when the higher rpm is required we have to apply we have to increase the electrical pulse rate and when very slow speed is needed we have to decrease the pulse rate applied to the state art like this we can control the speed of the motor and we can also control the rotation angle by controlling the applied electrical pulses I can see the working of the rotary stepper motor at position 1 this is the position 1 the rotor is beginning at the upper electromagnet this is the upper electromagnet this is the wherein we have supplied the voltage and this becomes the electromagnet and it attracts the rotor so rotor is in line with this particular upper electromagnet now say we want to move the rotor in the clockwise direction that means we want to rotate the rotor in the clockwise direction so what we have to do is we have to turn off the voltage applied to this upper electromagnet and we have to switch on the electrical supply to this right side pole so this becomes electromagnet and it attracts the rotor and now we can see the rotor has turned through 90 degrees and then it gets aligned rotor gets aligned with this particular electromagnet like this the motor steps a bit at a time in this case 90 degree per pulse so if you want very minute rotation then we have to increase the number of poles so here we have shown a very limited number of poles by increasing the number of poles this rotation angle per step can be reduced like that we can have one degree rotation half degree rotation so fraction of an angle rotation is also possible by proper designing of the motor now this process is repeated in the same manner at south and west electromagnets now we can see in the position number three so the power supply electric voltage supply to this is switched off and the power voltage supply to this south pole is on so this becomes electromagnet and it attracts the rotor now we can see the rotor has further rotated and it has become aligned with this south electromagnet and in the fourth position you can see the voltage supply to this south pole has switched off and we have a west electromagnet is in action so the rotor has further rotated in this direction like this we can continue we can rotate the electromagnetic field by using a microcontroller and hence we can have continuous rotation of the rotor at required rpm and we can stop the rotor at any desired angle depending upon the positioning requirement now this picture we can see x y table is the table surface on which we have to mount the workpiece which is to be positioned and we have one rotary stepper motor for x axis and one more stepper motor for y axis so you can see another ring material this is x y table and a x direction movement and in the y direction movement so we have one stepper motor for x movement and one stepper motor for y movement and you can also see the t slots for mounting the workpiece on the table so here we can see the stepper motor is coupled with the ball screws so there is a coupling over here and it is properly coupled so when the stepper motor rotates the rotation of the stepper motor is converted into a linear motion of the table by having this ball screw and net mechanism now some specification typical specifications we can see this table the travel of 50 millimeter by 50 millimeter any desired travel amount can be obtained by proper design bi-directional repeatability of such a such an arrangement is plus or minus one micrometer flatness and straightness movement of table is five micrometer and orthogonality movement orthogonality is about 20 arc seconds and the tables can be designed to carry a load of 75 kg and maximum velocity that is possible is 50 arc ps 50 revolutions per second is possible we can always integrate the encoders for feedback arrangement with a required resolution like one micrometer point one micrometer resolution 0.01 micrometer resolution 0.001 micrometer resolution depending upon the positioning accuracy required we can select appropriate encoders and appropriate lead on the ball screw now we can see some specifications here the XY table with stepper motors are available with different stroke lengths so 100 millimeter stroke 200 millimeter up to 800 millimeter even more than that is also possible and here we can see the repeatability of plus or minus two micrometer can be achieved with a positioning accuracy of 30 micrometer 40 micrometer 50 micrometer so by having proper design even the positioning accuracy of one micron two microns also possible and here you can see the maximum speed so when the ball's lead screw is having a lead of 5 millimeter then a speed of 250 millimeter per second is possible with 10 mm lead so you can see here we have ball screw of 10 mm lead with 10 mm lead ball screw a speed of 500 millimeter per second is also possible now what are the advantages of stepper motor by controlling the rate of input pulse we can control the rotation angle and we can position the rotor of the motor at any desired angle the motor has full torque even at stand still when the windings are energized so precise positioning and repeatability of movement is possible since the stepper motors have an accuracy of three to five percent of a step and this error is non cumulative from one step to the next step excellent response to starting and stopping and reversing is possible in terms of milli seconds now very reliable these stepper motors are very much reliable since there are no contact ratios no gearbox so the life of the motor is purely dependent on the life of the bearing what we use the motor response motors response to digital input pulses hence open loop control is possible making the motor very simple and less costly to control and it is possible to achieve a very slow low speed synchronous rotation with a load that is directly coupled to the shot by adjusting the pulse rate we can have a very slow speed of rotation a wide range of rotational speeds can be obtained as the speed is proportioned into the frequency of input pulses by adjusting the frequency of input pulses we can have very low speeds we can have very high speeds also so these stepper motors have many applications in x5 recorders CNC machines scientific instrumentation for positioning of the work pieces and they are also used in robotics for proper positioning of the work pieces now let us start another type of drive system used in precision stages so the in the picture we can see the linear stepper motor its constructional features we can see here we have a platen having t cut on its top surface and then we have a forcer unit with two phases of electromagnets phase a and phase b in between we have a permanent magnet you can see here rotary stepper motor the state r is having so this is the state r which is having the field windings whereas here the forcer unit which moves has the field windings and they become electromagnets whereas the state r the platen is the state r and which is not having any electro any field windings basically the linear stepper motor is a rotary stepper motor unwrapped to operate in a straight line they operate on electromagnetic principle and they consist of a moving the forcer and a stationary platen so the stationary platen is fixed to the precision stages and forcer will be moving and the work piece table will mounted on the forcer unit the plata is passing to the destilba that means it doesn't have any windings and it extends over the desired length of the travel forcer incorporates electromagnetic modules that means phase a and phase b electromagnetic modules it has and it runs along the length of the stepper so state r by the forcer unit moves along the state r and it is supported by bearings and it can move in both the directions now in this picture you can see a forcer unit so here there will be electromagnetic modules will be there and we can see the bearings bearings and the side as well as the bottom portion a linear stepper motor has either mechanical roller bearings similar to this or air bearings also are used in linear stepper motor side and bottom mechanical bearings are built into the forcer and they are fixed to the forcer and they doesn't require any adjustments over the lifetime of the motor they are permanently lubricated and exhibit very little amount of friction and you can see here in if air bearings are used you can see there is a small gap air gap between the forcer unit and the platon and the forcer unit at the bottom of the forcer unit there will be orifices so through this orifice compressed air is alone and because of the air pressure the platon or the or the forcer it will float and then it will move in the linear direction air bearing motors can operate continuously at high speed without any wear because there is since there is no contact metal to metal contact there is no wear of parts air bearing permits a smaller air gap resulting in larger motor forces now linear motor linear stepper motors are microstepped by proportioning currents into two phases in the in this picture we observed that two phases of that phase here and phase b so like this by proportioning the current microstepping can be achieved to have higher resolution with microstepper linear stepper motors following benefits can be achieved higher resolution for very high precision positioning and very it runs smoothly at slow speeds and then wider speed range can be obtained here we can understand that the microstepping when one phase of the forcer when one coil is powered I can see here there is a attraction between the two deep surfaces and here there is a repulsion with the result that the forcer will move by one step this is known as full stepping and when both the coil one and coil two are powered at a time together then you can see here at a there is a pulling force and b also there is a pulling force because of this the forcer they move by half step this is known as half stepping so this process is known as microstepping by microstepping the very high resolutions can be obtained now we can see here the complete arrangement of open loop single axis stepping motor is the linear stepper motor and you can see here bearings are provided in this so here at a pressure of 3 bar is supplied so that bearings can be operated and here this is an open loop control there is no feedback of position of the forcer whereas in this case this is a closed loop control of single axis stepper motor again this is a bearing operated and you can see encoder are provided for feedback of the position of forcer and this is a open loop plain or axis stepping motor that means dual axis stepper motor which can move in the x direction as well as in y direction now I can see some performance details of commercially available linear stepper motor maximum thrust on the force it can be 60 newtons or 18 newtons depending upon the model what we use and the holding force will be 17 newtons and 100 newtons force the resolution per step you can see as low as one micron resolution can be obtained and repeatability of two microns micrometers are possible and the positioning accuracy of plus or minus five micron is possible with these type of stepper motors and I have a velocity of 1.5 meters per second can be achieved now with this we will conclude module 12 lecture 5 in this lecture we discussed about the inline probing and benefits of thin process aging and then we discussed about the basics of stage position metrology and motorized linear and rotary stages and then we have different kinds of price used for moving the stages with this we will conclude thank you