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Publisher Summary The purpose of this chapter is to discuss the methods and errors associated with cylindricity and sphericity. Some basic form errors and positional errors that occur in cylindricity are concentricity and co axiality. The errors in cylindricity are taken as the deviations in peak and valley from it using the original data. There are a number of factors that cause errors in cylindricity, such as coaxiality, asperity effect, ambiguous fits, and run out. The maximum peak to valley that decides the minimum concentric cylindrical zone is used as the measure of the cylinder. Sphericity can be measured by many ways. The coordinate system usually used is spherical, having two angles and one radius. There are three coordinates for sphericity, namely: latitude variables, longitude variables, and cylindrical variables. The minimum zone method of measuring sphericity can be tackled by exchanged algorithms. The problem related to the measurement of sphericity is often encountered in surface metrology of measuring a workpiece using an instrument, which is not matched to the component shape. The problem of the mismatching of the instrument with the workpiece is often true of cylindricity measurement. Therefore, special care has to be taken with cylinder measurement as most engineering components have a hole somewhere that is often a critical part.

This chapter gives a description of different classification of parameters for the profile. The basic elements used in the characterization at different levels of manufacture, surface, and functions are discussed. It is not possible to isolate the characterization of the surface from either the manufacture or the workpiece function. Surface characterization can get out of hand without these two constraints. Areal parameters are those obtained from an area of the surface rather than a line profile. Areal measurement has two demand axes “x” and “y” and one dependent measurement from it, “z.” Areal information can be useful in monitoring the condition of the machine tool. Process information can be investigated via the profile. The Areal (3D) parameters determine the flow behavior as they switched attention from profile parameters. Areal information is important in contact situations because the longest wavelength in either lateral direction determines the positions of the initial contact. The estimation of Areal parameter values from the corresponding profile values is commonly practiced for parameters, such as peak density.

The purpose of this chapter is to focus on the surface metrology, and different ways of its manufacturing and measurement. The surface can be used to assess all aspects of quality progress in manufacture. The surface texture can be used to have a check on the process, but there are a number of issues to consider: where to measure, when to measure, and what to measure. In order to control the process such that changes can be detected quickly and effectively, simple parameters such as R a or R z can be used. The number of parameters could be measured and displayed in process. Several processes are categorized in the process and surface finish, namely: turning, diamond turning, milling and broaching, general abrasive process and surface finish, grinding and surface finish, nano-grinding, honing and superfinishing, polishing (lapping), unconventional machining, and atomic bit processes. The process control can be achieved by using critical parameter of the workpiece. Control using the measured parameter is achieved by means of the Shewhart charts and Cumulative charts. The cumulative-sum method is to plot the accumulation of the R a values. Some of the parameters are need to be used to monitor and prevent machine tool problems from developing. If the function is understood and the process is controlled, no metrology would be required. Once the measurements are made on the specimen, these are then plotted on a Shewhart chart, Cumulative chart, or any other control method. Hence, there is so much “capability” in the system that no measurement is needed as the link-up between manufacture and use has been properly made.

Publisher Summary This chapter outlines the development and methods of scanning microscopes. By using the scanning microscopes, the astonishing pictures are produced. A new dimension to surface metrology has been added by the advent of scanning microscopes based on quantum effects. The instrument design helps to develop new generations of the same instrument. There are a number of microscopes that make use of electrons, rather than light, in order to improve the lateral resolution. The electrons in transmission (TEM) and another in electron scanning mode (SEM) are used. The microscopes used in scanning microscopes are the atomic force microscope, laser force microscope, magnetic force microscope, electrostatic force microscope, scanning thermal microscope, scanning ion conductance microscope, and near-field scanning optical microscope. All these microscopes possess different qualities and requirement. Scanning probe instruments can help to miniaturize the new generation of probes to turn into new machines of assembly. One of the rule of metrology is that the unit of measurement should be close to the size of the feature being assessed and the same logic can be carried to the instrument size. In scanning microscopes, the area involved, curvatures due to shape, and form are very small and are ignored. They are largely areal in application and not three-dimensional. As the size of motors and actuators shrink because of miniaturization, the presence of the longer wavelengths will start to impinge on the scale of the scanning microscopes.

This chapter describes the errors of form in different engineering shapes. It summarizes the deviations from, or concerned with, a linear variable. Form can be considered to extend into straightness and then flatness, the short wavelengths are known to be subject to instrumental constraints such as stylus dimension in roughness. It is the long-wavelength boundary of waviness that is difficult to define. This is the short-wavelength boundary of form. In form errors, the long wavelengths are determined by the ideal shape specified. The short wavelength of form is defined in terms of the size of the piece because of the difficulty of defining anything in absolute terms. Errors of form are easy to characterize as they are broken down into Euclidean shapes, such as circles and planes. Errors of straightness are due to errors in machining and slideway. In measuring straightness, it is a common practice to measure the errors by methods that take account of the length of the surface to be measured. Flatness is an extension of straightness errors to two dimensions. All flatness problems do not involve surface plates. Errors are in the form of a bow and the maximum errors are generally at the edges of the plate or mirror where the coverage is most extensive. The actual flatness error value reported depends on the method of assessment used. Hence, straightness and flatness are very important in engineering.

This chapter discusses the logical evolution of methods to isolate roughness from the profile. Until the late 1920s, no attempt was made to measure the surfaces; instead, they were examined by eye or by touching with the fingernails. An estimate of surface variety can be obtained by viewing the image of a strip light in the standards and by varying the angle. The roughness can now be estimated by either stylus or optical methods. Hence, it is necessary to define all stages in the measurement procedure, although it requires the agreement on the nature of the measurement. The simplest starting point is a profile of the surface texture that requires a different way for developing a profile. The profiles, roughness, notation, and procedures of surface metrology in depth are discussed in the chapter. A major problem in surface metrology has been the procedure determining the shape and length of the mean line. The two methods commonly used for the identification and measurement of surface are Envelope system (E) and Motif methods. The E system failed because the meters in use were better suited to measure the average parameter values of the roughness rather than peaks to which the E system was suited. The Motif method is flexible, and the functional parameter makes them very susceptible to high-frequency effects. The assessment of the surface texture involves blocking certain wavelengths and accepting others. The separation of different wavelengths are covered by “filtering,” by operating in space and in frequency, mean lines, standard electrical 2CR filter, and phase-corrected filters. In surface metrology, the arbitrary values turn up at certain instances that are embedded in the standards system to push forward quality of conformance. This has resulted in a bewildering variety of filters and parameters.

In this chapter, the function and surface texture are surveyed. Relating surface texture to performance, which is called function, has always been difficult because of the simultaneous development of the key ingredients of tribiology, surface instrumentation, random process analysis, and digital analysis. As a consequence the development has been uneven and resulted in a lack of structure. The major problem has been a lack of focus when discussing function, which is probably due to the fact that a systematic approach has been impossible as the number of applications where surfaces are important is large and diverse; and because the link has been suppressed because of confidentiality in certain cases where a relationship between the surface and function has been found. However, a generic approach is given to classify the tribological applications and in particular, contact, friction, wear, lubrication, and failure mechanisms. The characterization of function has been broken down in to two variables: the normal separation of two surfaces and the lateral relative velocity of the two surfaces. An attempt has been made to characterize function by means of a map as the “function” part of the problem has been neglected. The amount of information linking surface texture to performance is minimal and only “types” of parameter can be safely associated with different types of function. Furthermore, an idea of the distribution of averages, extremes, and defects on the surface with relation to the function has been provided. Hence, the geometric properties of the surface can aid or inhibit the functional properties.

Publisher Summary This chapter provides a synoptic view of different ways of surface measurement. Surfaces are important in the manufacture and performance of workpieces, but a problem is created by the multitude of requirements that are not compatible with each other. After several investigations made earlier to develop an instrument, the surface instrumentation was started by Schmaltz in 1929 and the first stylus instrument was developed. The stylus method and optical method were developed along different paths and were used for height information and areal information, respectively. However, some parameters can be estimated without using an instrument. The surface roughness can be evaluated by Lambert's law, directionality, and lay pattern (isotropy). In addition, profile record contains enormous amount of data to determine the actual roughness value by calculation of the instrument but other parameters such as the statistical parameters skew and kurtosis can be examined from the chart. Furthermore, the surface finish instrumentation is described. Certain points should be considered to overcome the issues for measuring texture and roundness by stylus method, optical method, and scanning microscopes. Three types of measurement having different properties determine the nature of measurement: dynamic, static, and integrated. Therefore, the differentiation between the types of instrument is necessary, and two major issues should be considered in order to measure the surface, it should not damage the surface and has high fidelity.

This chapter emphasizes on the roundness and the processes associated with its measurement and assessment. The roundness of a workpiece is directly linked to the performance of the machine tool that makes it more relevant than roughness. It is the prerequisite of rotation, which in turn dominates dynamic function and therefore, it is one of the cornerstones of surface metrology. The roughness and roundness influence at right angles to each other in the function map that is consistent with the direction of measurement being at right angles to each other on a round workpiece. A suitable stylus should be used while measuring roundness to avoid mixing with the roughness. There are a number of ways of displaying roundness, such as Cartesian and Polar. As the characterization of roundness is important, there as three basic ways to measure roundness that have been used industrially, namely, Fourier analysis, diametrical methods, radial methods, and chordal methods. The assessment of roundness is done by four ways of least squares, ring gauge, plug gauge, and minimum zone. Roundness instruments form the basis for measuring many metrological features apart from roundness, such as, concentricity, squareness, alignment, cylindricity, sphericity, and conicity. The basic problem associated with roundness is the persistent use of peaks and valleys. In miniaturization, measuring the roundness is difficult than measuring the roughness of small components.

Publisher Summary This chapter considers the different optical methods of examining the surface. The properties of optical methods are described here, such as optical path length, optical penetration, and resolution and depth of focus. The optical methods are held to optical laws and it gives a larger value than the stylus as it tends to differentiate. Optical methods are tip resolution- and angle-dependent. The probe cannot be broken in optical methods and a very limited tilt is allowed, but it can scan fast. It is capable to measure everything good or bad but calibration by standards is difficult. Optical methods tend to have poor lateral resolution. There are various optical methods used in the surface metrology, such as gloss meters, total integrating sphere, diffractometer, interferometry, optical followers, heterodyne method, and other methods also that are not mentioned here. The major disadvantage of this method is that the test surface has to be of the same shape as the reference surface, or at least near to it. Otherwise, too many fringes are formed. As the requirement grows for detail, much greater than the wavelength of light can provide, it becomes difficult to justify the continued use of optics. Therefore, optical methods can have greater sensitivities of the limit but this extra sensitivity can cause extraneous noise to enter the system. The optical methods are limited by the wavelength of the light.

Publisher Summary This chapter reviews the issues involved in the design and identification of error in instrument design. Major issues are kinematics, error reduction, mobility, elastic effects, and materials. The metrology instrument design and error reduction can be rectified by various design methods, kinematics, pseudo kinematic design, hexapod considerations, mobility, simple Abbe and cosine instrument error, metrology loop properties, material selection and other problems, mechanical stability, optimized design, improvement in accuracy, inverse method, and multistep method. The four major problems that need to be overcome are design problems, improving accuracy, set-up problems and usage, and calibration and traceability. The overall trend is to become smaller and to be able to measure dimensions as well as texture is for the instrument and components. Certain points should be considered here. Metrology loops should be small, avoid force loops, and the force should be kept at minimum. The vibration or heat sources should be eliminated and errors should be removed by inversion or multi step. Moreover, the hysteresis errors should be reduced by elastic design. Hence, it is important to design instruments in a way that best reflects the measurement.

This chapter provides a description about sampling, numerical analysis, and display parameters. The sampling rate table used in roundness for the Gaussian filter is also explained in the chapter. It is necessary to take five sample values of roundness in order to capture all detail as per the table. Some numerical formulae vary from one type of an instrument to another. The representation on drawing shows the standard notation where roughness value, production method, sampling length, sampling length of lay, and machine allowance are represented. Moreover, the sampling guides are also given to help the operator. The metrological characterization of phase correct filters and transmission bands for use in contact (stylus) instruments is described. The sources of different measurement philosophical background within the standards in surface roughness have also been discussed. The two major sources of roughness assessment are UK/USA and Germany/France, with Russia in between. In the standards, there are two distinct threads; one in which the reference line is determined from the peaks with the major parameters, and the other where the reference is determined from all the data and the parameters are averages derived from the data. However, this work has highlighted the importance of surface geometry without detracting from all manufacturing and functional aspects covering physical and chemical properties of “surface skin.”

Publisher Summary The chapter describes the usage, methodologies, and issues related to stylus instruments. A fast stylus instrument is needed in order to give the possibility of scanning over an area. Cone stylus and pyramid stylus are two different types of stylus differing in shapes and properties. The skid is much blunter than the sharp stylus so that it tends to bridge the gap between peaks on the surface and, in certain circumstances, it can damage the surface. In stylus instruments, two types of pick up systems are commonly used, side-acting gauge and cantilever gauge. In stylus methods, it is possible to make the stylus angle and tip dimension independently. The stylus method is reported in damage to the surface usually due to skid usage. However, the damage can be prevented by lowering the dynamic force by reducing the speed of transverse of the system. In stylus instrument usage, the number of instrument types are kept minimum, namely, measurement issues, in process measurement, in situ measurement, hand-held instrument, integrated instruments, and fast tracking stylus systems. Furthermore, the stylus method scores do not encounter environmental problem like other methods. The stylus method has advantages over other methods, such that it can push aside debris and penetrate films that would mask the geometry. Therefore, the aspect of stylus has extended the application of the stylus method to encompass other fields. Stylus methods can be used to scan areas, as they may be slower than non-contacting methods with better mechanical fidelity.