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Surface Characteristics and Quality Assurance

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CHAPTER 4
Surface Characteristics and Quality Assurance (표면 특성 및 품질검사)

Surface Structure of Metals

Figure 4.1 Schematic illustration of a cross-section of the surface structure of metals. The thickness of the individual layers is dependent on processing conditions and processing environment.

Terminology in Describing Surface Finish
Figure 4.2 Standard terminology and symbols to describe surface finish. The quantities are given in µ in.

Coordinates for Surface-Roughness Measurements
Figure 4.3 Coordinates used for surface-roughness measurement, using Eqs. (4.1) and (4.2).

Standard Lay Symbols for Engineering Surfaces

Figure extra

Measuring Surface Roughness
(b)

Figure 4.4 (a) Measuring surface roughness with a stylus. The rider supports the stylus and guards against damage. (b) Surface measuring instrument. Source: Sheffield Measurement Division of Warner & Swasey Co. (c) Path of stylus in surface roughness measurements (broken line) compared to actual roughness profile. Note that the profile of the stylus path is smoother than that of the actual surface. Source: D. H. Buckley

Surface Profiles
Figure 4.4 Typical surface profiles produced by various machining and surface-finishing processes. Note the difference between the vertical and horizontal scales. Source: D. B Dallas (ed.), Tools and Manufacturing Engineers Handbook, 3d ed. Copyright © 1976, McGraw-Hill Publishing Company. Used with permission.

Three-Dimensional Surface Measurement

Figure 4.4 extra Surface of rolled aluminum.

Figure 4.4 extra A highly polished silicon surface measured in an atomic force microscope. The surface roughness is Rq = 0.134 nm.

Contact Between Two Bodies
Figure 4.5 Schematic illustration of the interface of two bodies in contact, showing real areas of contact at the asperities. In engineering surfaces, the ratio of the apparent to real areas of contact can be as high as 4-5 orders of magnitude.

Ring Compression Tests

(b)

Figure 4.7 Ring compression test between flat dies. (a) Effect of lubrication on type of ring specimen barreling. (b) Test results: (1) original specimen and (2)-(4) increasing friction. Source: A. T. Male and M. G. Cockcroft.

Friction Coefficient from Ring Test

Figure 4.8 Chart to determine friction coefficient from ring compression test. Reduction in height and change in internal diameter of the ring are measured; then µ is read directly from this chart. Example: If the ring specimen is reduced in height by 40% and its internal diameter decreases by 10%, the coefficient of friction is 0.10

Effect of Wear on Surface Profiles
Figure 4.9 Changes in originally (a) wirebrushed and (b) ground-surface profiles after wear. Source: E. Wild and K. J. Mack.

Adhesive and Abrasive Wear

Figure 4.10 Schematic illustration of (a) two contacting asperities, (b) adhesion between two asperities, and (c) the formation of a wear particle.

Figure 4.11 Schematic illustration of abrasive wear in sliding. Longitudinal scratches on a surface usually indicate abrasive wear.

Types of Wear Observed in a Single Die

Figure 4.13 Types of wear observed in a single die used for hot forging. Source: T. A. Dean

Types of Lubrication

Figure extra Types of lubrication generally occurring in metalworking operations. Source: After W.R.D. Wilson.

Rough Surface
Figure 4.15 Rough surface developed on an aluminum compression specimen by the presence of a high-viscosity lubricant and high compression speed. The coarser the grain size, the rougher the surface. Source: A. Mulc and S. Kalpakjian.

Surface Treatments for Various Metals
TABLE 4.1 Metal Aluminum Beryllium Cadmium Die steels High-temperature steels Magnesium Mild steel Molybdenum Nickel- and cobalt-base alloys Refractory metals Stainless steel Steel Titanium Tool steel Zinc Treatment Chrome plate; anodic coating, phosphate; chromate conversion coating Anodic coating; chromate conversion coating Phosphate; chromate conversion coating Boronizing; ion nitriding; liquid nitriding Diffusion Anodic coating; chromate conversion coating Boronizing; phosphate; carburizing; liquid nitriding; carbonitriding; cyaniding Chrome plate Boronizing; diffusion Boronizing Vapor deposition; ion nitriding; diffusion; liquid nitriding; nitriding Vapor deposition; chrome plate; phosphate; ion nitriding; induction hardening; flame hardening; liquid nitriding Chrome plate; anodic coating; ion nitriding Boronizing; ion nitriding; diffusion; nitriding; liquid nitriding

Vapor deposition; anodic coating; phosphate; chromate chemical conversion coating Source: After M. K. Gabel and D. M. Doorman in Wear Control Handbook, New York, ASME, 1980 p. 248.

Roller Burnishing
Figure 4.16 Roller burnishing of the fillet of a stepped shaft to induce compressive surface residual stresses for improved fatigue life.

Figure 4.16 Examples of roller burnishing of (a) a conical surface and (b) a flat surface and the burnishing tools used. Source: Sandvik, Inc.

Thermal Spray Operations

Figure extra Schematic illustrations of thermal spray operations. (a) Thermal wire spray. (b) Thermal metalpowder spray. (c) Plasma spray.

Physical Deposition
Figure extra Schematic illustration of the physical deposition process. Source: Cutting Tool Engineering.

Sputtering

Figure extra Schematic illustration of the sputtering process. Source: ASM International

Ion-Plating Apparatus

Figure extra Schematic illustration of an ion-plating apparatus. Source: ASM International.

Chemical Vapor Deposition

Figure extra Schematic illustration of the chemical vapor deposition process.

Electroplating

Figure extra Schematic illustration of the electroplating process.

Electroplating Guidelines
Figure extra (a) Schematic illustration of nonuniform coatings (exaggerated) in electroplated parts. (b) Design guidelines for electroplating. Note that sharp external and internal corners should be avoided for uniform plating thickness. Source: ASM International.

Hot Dipping
Figure extra Flowline for continuous hot-dip galvanizing of sheet steel. The welder (upper left) is used to weld the ends of coils to maintain continuous material flow. Source: American Iron and Steel Institute.

Painting

Figure extra Methods of paint application: (a) dip coating, (b) flow coating, and (c) electrostatic spraying. Source: Society of Manufacturing Engineers.

Engineering Metrology and Instrumentation

Slideway Cross-Section
Figure extra Cross-section of a machine tool slideway. The width, depth, angles, and other dimensions must be produced and measured accurately for the machine tool to function as expected.

Types extra Measurement and Instruments Used of TABLE
Measurement Linear Instrument Steel rule Vernier caliper Micrometer, with vernier Diffraction grating Bevel protractor, with vernier Sine bar Dial indicator Electronic gage Gage blocks Autocollimator Transit Laser beam Interferometry Dial indicator Circular tracing Radius or fillet gage Dial indicator Optical comparator Coordinate measuring machines Plug gage Ring gage Snap gage Toolmaker’s Light section Scanning electron Laser scan

µm

Sensitivity

µin.

Angle Comparative length

0.5 mm 25 2.5 1 5 min 1 0.1 0.05 2.5 0.2 mm/m 2.5 0.03 0.03 1 125 0.25

1/64 in. 1000 100 40

Straightness

Flatness Roundness Profile

40 4 2 100 0.002 in./ft 100 1 1 40 5000 10

GO-NOT GO

Microscopes

2.5 1 0.001 0.1

100 40 0.04 5

Caliper and Vernier

Figure extra (a) A caliper gage with a vernier. (b) A vernier, reading 27.00 + 0.42 = 27.42 mm, or 1.000 + 0.050 + 0.029 = 1.079 in. We arrive at the last measurement as follows: First note that the two lowest scales pertain to the inch units. We next note that the 0 (zero) mark on the lower scale has passed the 1-in. mark on the upper scale. Thus, we first record a distance of 1.000 in. Next we note that the 0 mark has also passed the first (shorter) mark on the upper scale. Noting that the 1-in. distance on the upper scale is divided into 20 segments, we hve passed a distance of 0.050 in. Finally note that the marks on the two scales coincide at the number 29. Each of the 50 graduations on the lower scale indicates 0.001 in., so we also have 0.029 in. Thus the total dimension is 1.000 in. + 0.050 in. + 0.029 in. = 1.079 in.

Analog and Digital Micrometers
(a) (c)

Figure extra (a) A micrometer being used to measure the diameter of round rods. Source: L. S. Starrett Co. (b) Vernier on the sleeve and thimble of a micrometer. Upper one reads 0.200 + 0.075 + 0.010 = 0.285 in.; lower one reads 0.200 + 0.050 + 0.020 + 0.0003 = 0.2703 in. These dimensions are read in a manner similar to that described in the caption for Fig. 35.2. (c) A digital micrometer with a range of 0-1 in. (0-25 mm) and a resolution of 0.00005 in. (0.001 mm). Note how much easier it is to read dimensions on this instrument than on the analog micrometer shown in (a). However, such instruments should be handled carefully. Source: Mitutoyo Corp.

Angle-Measuring Instruments
Figure extra (a) Schematic illustration of a bevel protractor for measuring angles. (b) Vernier for angular measurement, indicating 14° 30´.

Figure extra Setup showing the use of a sine bar for precision measurement of workpiece angles.

Dial Indicators

Figure extra Setup showing the use of a sine bar for precision measurement of workpiece angles.

Electronic Gages
Figure extra An electronic vertical length measuring instrument, with a sensitivity of 1 µm (40 µin.). Courtesy of TESA SA.

Figure extra An electronic gage for measuring bore diameters. The measuring head is equipped with three carbide-tipped steel pins for wear resistance. The LED display reds 29.158 mm. Courtesy of TESA SA.

Laser Scan Micrometer and Straightness Measurement
Figure extra Two types of measurement made with a laser scan micrometer. Source: Mitutoyo Corp.

Figure extra Measuring straightness with (a) a knife-edge rule and (b) a dial indicator attached to a movable stand resting on a surface plate. Source: F. T. Farago.

Interferometry
Figure 4.18 (a) Interferometry method for measuring flatness using an optical flat. (b) Fringes on a flat inclined surface. An optical flat resting on a perfectly flat workpiece surface will not split the light beam, and no fringes will be present. (c) Fringes on a surface with two inclinations. Note: the greater the incline, the closer the fringes. (d) Curved fringe patterns indicate curvatures on the workpiece surface. (e) Fringe pattern indicating a scratch on the surface.

Measuring Roundness
Figure extra (a) Schematic illustration of “out of roundness” (exaggerated). Measuring roundness using (b) V-block and dial indicator, (c) part supported on centers and rotated, and (d) circular tracing, with part being rotated on a vertical axis. Source: After F. T. Farago.

Measuring Profiles
Figure extra Measuring profiles with (a) radius gages and (b) dial indicators.

Figure extra Measuring profiles with (a) radius gages and (b) dial indicators.

Horizontal-Beam Contour Projector
Figure extra A bench model horizontal-beam contour projector with a 16 in.-diameter screen with 150-W tungsten halogen illumination. Courtesy of L. S. Starrett Company, Precision Optical Division.

Coordinate Measuring Machine

Figure extra (a) Schematic illustration of one type of coordinate measuring machine. (b) Components of another type of coordinate measuring machine. These machines are available in various sizes and levels of automation and with a variety of probes (attached to the probe adapter), and are capable of measuring several features of a part. Source: Mitutoyo Corp.

Coordinate Measuring Machine
Figure 4.19 A coordinate measuring machine. Brown & Sharpe Manufacturing.

Gages
Figure extra (a) Plug gage for holes, with GO-NOT GO on opposite ends. (b) Plug gage with GONOT GO on one end. (c) Plain ring gages for gauging round rods. Note the difference in knurled surfaces to identify the two gages. (d) Snap gage with adjustable anvils. Figure 35.19 Schematic illustration of one type of pneumatic gage.

Figure 4.20 Basic size, deviation, and tolerance on a shaft, according to the ISO system.

Tolerance Control

Figure4.21 Various methods of assigning tolerances on a shaft. Source: L. E. Doyle.

Tolerances as a Function of Size

Figure 4.22 Tolerances as a function of part size for various manufacturing processes. Note: Because many factors are involved, there is a broad range for tolerances.

Tolerances and Surface Roughnesses
Figure 4.22 Tolerances and surface roughness obtained in various manufacturing processes. These tolerances apply to a 25-mm (1-in.) workpiece dimension. Source: J. A. Schey.

Engineering Symbols
Figure extra Geometric characteristic symbols to be indicated on engineering drawings of parts to be manufactured. Source: The American Society of Mechanical Engineers.

Quality Assurance, Testing, and Inspection

Deming’s 14 Points
TABLE extra 1. Create constancy of purpose toward improvement of product and service. 2. Adopt the new philosophy. Cease dependence on mass inspection to achieve quality. 3. 4. End the practice of awarding business on the basis of price tag. Improve constantly and forever the system of production and service, to 5. improve quality and productivity, and thus constantly decrease cost. Institute training on the job. 6. 7. Institute leadership (as opposed to supervision). Drive out fear so that everyone can work effectively. 8. 9. Break down barriers between departments. Eliminate slogans, exhortations and targets for zero defects and new levels of 10. productivity 11. Eliminate quotas and management by numbers, numerical goals. Substitute leadership. 12. Remove barriers that rob the hourly worker of pride of workmanship. Institute a vigorous program of education and self-improvement. 13. 14. Put everybody in the company to work to accomplish the transformation

Robust Design

Figure extra A simple example of robust design. (a) Location of two mounting holes on a sheet-metal bracket, where the deviation of the top surface of the bracket from being perfectly horizontal is ±α. (b) New location holes, whereby the deviation of the top surface of the bracket from being perfectly horizontal is reduced to± α/2.

Taguchi Loss Function
Figure extra (a) Objective function value distribution of color density for television sets. (b) Taguchi loss function, showing the average replacement cost per unit to correct quality problems. Source: After G. Taguchi.

Frequency and Normal Distribution Curves

Figure 4.23 (a) A histogram of the number of shafts measured and their respective diameters. This type of curve is called frequency distribution. (b) A Normal distribution curve indicating areas within each range of standard deviation. Note: the greater the range, the higher the percentage of parts that fall within it.

Frequency Distribution Curve

Figure 4.25 Frequency distribution curve, showing lower and upper specification limits.

Statistical Quality Control

Figure 4.26 Control charts used in statistical quality control. The process shown is in statistical control because all points fall within the lower and upper control limits. In this illustration sample size is five and the number of samples is 15.

Constants for Control Charts
TABLE 4.3 Sample size 2 3 4 5 6 7 8 9 10 12 15 20 A2 1.880 1.023 0.729 0.577 0.483 0.419 0.373 0.337 0.308 0.266 0.223 0.180 D4 3.267 2.575 2.282 2.115 2.004 1.924 1.864 1.816 1.777 1.716 1.652 1.586 D3 0 0 0 0 0 0.078 0.136 0.184 0.223 0.284 0.348 0.414 d2 1.128 1.693 2.059 2.326 2.534 2.704 2.847 2.970 3.078 3.258 3.472 3.735

Control Charts

Figure 4.27 Control charts. (a) Process begins to become out of control because of such factors as tool wear (drift). The tool is changed and the process is then in statistical control. (b) Process parameters are not set properly; thus all parts are around the upper control limit (shift in mean). (c) Process becomes out of control because of factors such as a change in the properties of the incoming material (shift in mean).

Digital Gages with Microprocessors
Figure 4.28 Schematic illustration showing integration of digital gages with microprocessor for real-time data acquisition and SPC/SPQ capabilities. Note the examples on the CRT displays, such as frequency distribution and control charts. Source: Mitutoyo Corp.

Data for Standard Deviation Calculation
TABLE 4.4

Sample number 1 2 3 4 5 6 7 8 9 10

x1 4.46 4.45 4.38 4.42 4.42 4.44 4.39 4.45 4.44 4.42

x2 4.40 4.43 4.48 4.44 4.45 4.45 4.41 4.41 4.46 4.43

x3 4.44 4.47 4.42 4.53 4.43 4.44 4.42 4.43 4.30 4.37

x4 4.46 4.39 4.42 4.49 4.44 4.39 4.46 4.41 4.38 4.47

x5 4.43 4.40 4.35 4.35 4.41 4.40 4.47 4.50 4.49 4.49

x
4.438 4.428 4.410 4.446 4.430 4.424 4.430 4.440 4.414 4.436

R 0.06 0.08 0.13 0.18 0.04 0.06 0.08 0.09 0.19 0.12

Acceptance Sampling

Figure 4.29 A typical operating-characteristics curve used in acceptance sampling. The higher the percentage of defective parts, the lower the probability of acceptance by the consumer. There are several methods of obtaining these curves.

Liquid-Penetrant and Magnetic-Particle Inspection
Figure extra Sequence of operations for liquid-penetrant inspection to detect the presence of cracks and other flaws in a workpiece. Source: Metals Handbook, Desk Edition. Copyright ©1985, ASM International, Metals Park, Ohio. Used with permission.

Figure extra Schematic illustration of magnetic-particle inspection of a part with a defect in it. Cracks that are in a direction parallel to the magnetic field, such as in A, would not be detected, whereas the others shown would. Cracks F, G, and H are the easiest to detect. Source: Metals Handbook, Desk Edition. Copyright ©1985, ASM International, Metals Park, Ohio. Used with permission.

Radiographic Inspection
Figure extra Three methods of radiographic inspection: (a) conventional radiography, (b) digital radiography, and (c) computed tomography. Source: Courtesy of Advanced Materials and Processes, November 1990. ASM International

Eddy-Current Inspection

Figure extra Changes in eddy-current flow caused by a defect in a workpiece. Source: Metals Handbook, Desk Edition. Copyright ©1985, ASM International, Metals Park, Ohio. Used with permission.

Holography

Figure extra Schematic illustration of the basic optical system used in holography elements in radiography, for detecting flaws in workpieces. Source: Metals Handbook, Desk Edition. Copyright ©1985, ASM International, Metals Park, Ohio. Used with permission.

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