Technology & Engineering
Surface Finish
Surface finish refers to the texture or smoothness of a material's outer layer, which is often achieved through processes like grinding, polishing, or coating. It is crucial in engineering and manufacturing as it can affect the functionality, appearance, and performance of a product. Surface finish measurements are used to ensure that the final product meets specific quality standards.
Written by Perlego with AI-assistance
Related key terms
1 of 5
6 Key excerpts on "Surface Finish"
eBook - PDF- Ken J Stout, Liam Blunt(Authors)
- 2000(Publication Date)
- Butterworth-Heinemann(Publisher)
In recent studies, some of which are funded by the EC in relation to the setting up of 3-D surface characterization standards, it has become recognized that the functional situation in which surfaces are employed should be investigated. [11 What is it then that makes a functionally successful surface? It is a combination of the surface topography, the material selection that provides the underlying bulk properties of the material, the properties of the near- surface layers, and the control of the manufacturing process by which the final surface is generated. Traditionally, the majority of manufacturing processes that are specified for a wide variety of engineering components first define a selection of appropriate machining techniques by which to generate the surface. This is often achieved by more than one process being undertaken in sequence. The surface that results has in many cases been further modified by subsequent surface treatments to enable it to be better suited to the function for which it is intended. The purpose of this subsequent treatment, often referred to as surface engineering, is to modify the upper layers of the surface to impart specific properties such as wear resistance or fatigue resistance to improve functional suitability. As a consequence of this time-served and widely accepted procedure, the subject of surface engineering has gained prominence and credibility. Major facilities have been set up in many countries which are now regarded as centres of excellence in this important subject. In addition, a highly respected international journal (Surface Engineering) is directed at reporting recent techniques and achievements in this field. The importance and scope of this subject was demonstrated in an international survey of surface engineering, particularly directed to surface coatings, which was conducted at the University of Hull (UK). t21 The findings of the report produced as a result of the survey indicated that in the UK alone the expenditure in this area would reach at least s billion by the year 2005. Clearly, a large part of this expenditure will be related to re-
- J. T. Black, Ronald A. Kohser(Authors)
- 2018(Publication Date)
- Wiley(Publisher)
If we view the process as having five main components (workpiece, tool, machine tool, environment, and process variables) as outlined in Table 34.1 we see that surface properties can be altered by all of these parameters by producing the following: • High temperatures involved in the machining process. • Plastic deformation of the work material (residual stress). • Surface geometry (roughness, waviness, cracks, distortions). • Chemical reactions, particularly between the tool and the workpiece. More specifically, surface integrity refers to the impaired or enhanced surface condition of a component or specimen that influences its performance in service. Surface integrity has two aspects: topography characteristics and surface-layer charac- teristics. Topography is made up of surface roughness, wavi- ness, errors of form, and flaws (Figure 34.1). A typical roughness profile includes the peaks and valleys that are considered separately from waviness. Flaws also add to texture but should be measured independent of it. Changes in the surface layer, as a result of processing, include plastic deformation, residual stresses, cracks, and other metallurgi- cal changes including hardness, overaging, phase changes, recrystallization, intergranular attack, and hydrogen embrittle- ment. The surface layer will always contain local surface defor- mation due to any machining passes. The material removal processes generate a wide variety of surface textures, generally referred to as Surface Finish. The cutting processes leave a wide variety of surface patterns on the materials. Lay is the term used to designate the direction of the predominant surface pattern produced by the machining process see Figure 34.2. In addition, certain other terms and symbols have been developed and standardized for specifying the surface quality. The most important terms are surface roughness, waviness, and lay. For machined surfaces, Rough- ness refers to the finely spaced surface irregularities.
- J. T. Black, Ronald A. Kohser(Authors)
- 2019(Publication Date)
- Wiley(Publisher)
CHAPTER 32 613 32.1 Introduction Surface Finishing processes are used to tailor the properties of the surfaces of manufactured components so that their function and serviceability can be improved. Processes include solidifi- cation treatments such as hot-dip coatings, weld-overlay coat- ings, and thermal spray surfaces; heat treatment coatings such as diffusion coatings and surface hardening; deposition surface treatments such as electrodeposition, chemical vapor deposi- tion, and physical vapor deposition; and Electroplating means the electrodeposition of an adherent metallic coating onto an object that serves as the cathode in an electrochemical reaction. The resulting surface provides wear resistance, corrosion resist- ance, high-temperature resistance, or electrical properties dif- ferent from those in the bulk material. Many manufacturing processes influence surface proper- ties, which in turn may significantly affect the way the compo- nent functions in service. The demands for greater strength and longer life in components often depend on changes in the sur- face properties rather than the bulk properties. These changes may be mechanical, thermal, chemical, and/or physical and therefore are difficult to describe in general terms. Many metal-cutting processes specified by the manufactur- ing engineer to produce a specific geometry can produce altera- tions in the surface material of the component, which, in turn, produces changes in performance. 32.2 Surface Integrity The term surface integrity was coined by Field and Kahles in 1964 in reference to the nature of the surface condition that is produced by the manufacturing process. If we view the process as having five main components (workpiece, tool, machine tool, environment, and process variables) as outlined in Table 32.1 we see that surface properties can be altered by all of these parameters by producing the following: • High temperatures involved in the machining process.
eBook - ePub- David A. Stephenson, John S. Agapiou(Authors)
- 2018(Publication Date)
- CRC Press(Publisher)
2 ]. The repeatable portion of the distortion is often not easily eliminated without major changes in the fixture or cutter, but may still be reduced by compensation without major changes. Engineering surfaces manufactured by different processes have different topographies. For example, a milled surface is spatially inhomogeneous, a ground surface may have pits and troughs, and a honed surface has cross-hatched grooves. Such surface features often cannot be modeled analytically; therefore, statistical parameters have traditionally been used to describe their influence on part function. It is important to use the most suitable surface characterization method that links the process to functionality.The first part of this chapter describes methods of measuring and predicting the machined Surface Finish. The measurement of Surface Finish is discussed in Section 10.2 ; the discussion concentrates on stylus-type measurements, which are most common in practice. The Surface Finish in turning, boring, milling, drilling, reaming, and grinding operations is discussed in Sections 10.3 through 10.6 . These sections consider only the texture of the machined surface. Of equal importance in many applications is the surface integrity, which can be defined broadly as the metallurgical and mechanical state of the machined surface. Surface integrity can be assessed using microhard-ness measurements or microstructural analyses, which reveal microcracks, phase transformations, melted and redeposited layers, and similar features. Residual stresses in machined surfaces are discussed in Section 10.7 . White layer formation in steels and surface burning in grinding are considered in Sections 10.8 and 10.9 . Surface integrity is influenced by thermal effects in cutting (Chapter 7 ).Finally, surface flatness measurement is discussed in Section 10.10 , and flatness compensation methods for face-milling operations are described in Section 10.11 .10.2 MEASUREMENT OF Surface Finish
10.2.1 STYLUS MEASUREMENTSThe finish of machined surfaces is most commonly measured with a stylus-type profile meter or profilometer, an instrument similar to a phonograph that amplifies the vertical motion of a stylus as it is drawn across the surface [3 –5 ]. The output of the profilometer is a two-dimensional profile of the traced surface segment, amplified in the directions both normal and along the surface to accentuate surface contours and irregularities (Figure 10.1 ). On a gross scale, the surface profile of a nominally smooth surface gives an indication of the surface’s shape, waviness, and roughness (Figure 10.2 ). The shape of the surface is the macroscopic surface contour. Shape errors may result from errors in the machine tool guideways or machined part, distortions due to clamping forces or subsequent heat treatment, and from tool wear. For nominally flat surfaces, the shape is referred to as the slope or lay of the surface. Waviness refers to variations in the surface with relatively long wavelengths or, equivalently, lower frequencies. Waviness may result from clamping errors, errors in the tool or cutter geometry, or vibrations of the system. As discussed in Section 10.4 , spindle tilt in face-milling operations also produces a waviness or shape error. Roughness
eBook - PDF- David J. Whitehouse(Author)
- 2004(Publication Date)
- Butterworth-Heinemann(Publisher)
Surface metrology and manufacture 97 For more rigorous tests involving perhaps roundness as well as roughness and waviness, the workpiece would be taken to a properly equipped inspection room. Here, some tests for machine tool capability would be possible. Failing this facility, the tests could be carried out at a 'centre of excellence' in which personnel as well as equipment are 'capable'. 4.2 The process and Surface Finish 4.2. 1 General Table 4.1 shows typical surface roughness values for commonly used machining processes. These processes can be categorised into a number of subdivisions. Table 4.1 Typical roughness valuesproduced by processes Key: ~ average application ~ less frequent application 98 Surfaces and their measurement 1. Cutting with single or multiple tool tips - this includes turning, milling, broaching, planing. 2. Abrasive machining- this includes grinding, polishing, honing. 3. Physical and chemical machining- this includes electrochemical machining, electrodischarge machining etc. 4. Forming, casting, extrusion. 5. Other macroscopic machining to include laser machining, high-power water jet. 6. Ultra-fine machining (nanomachining) including ion beam milling and energy beam machining. Within these categories, there is considerable overlap, for example, diamond turning is capable of producing very fine surfaces, yet it is included here in group 1. In fact, the groups have been assembled according to generic likeness rather than magnitude of roughness, because it is the former that impart the unique char- acter of the process to the workpiece. 4.2.2 Turning This is the commonest process and, as the name implies, involves an axis of rota- tion.
eBook - PDF- Brian Griffiths(Author)
- 2002(Publication Date)
- Butterworth-Heinemann(Publisher)
6 Surface Finish Specification 6.0 Introduction Considering the trace of a supposedly flat surface in Figure 4.11, the 'flat' surface is far from a perfect straight line. Things related to the machine tool, such as vibrations and slide-way inaccuracies cause the long wavelength deviations where the undulations are of the order of millimetres. However, the figure also shows wavelengths of a much smaller magnitude. These deviations are the Surface Finish (SF). They are of the order of tens of microns and they are the machining marks. They are caused by a combination of the tool shape and the feed across the workpiece. In many instances the SF and texture can have a significant influence on functional performance (Griffiths, 2001). The SF is normally measured by a stylus, which is drawn across the surface to be measured. The stylus moves in a straight line over the surface driven by a traversing unit. This produces a 2D 'line' trace similar to that in Figure 4.11. A line trace produces an X-Y set of data points that can be analysed in a variety of statistical ways to produce parameters. These parameters are descriptors of a surface. They can be used to describe the SF of a surface in much the same way as a dimension describes the form of a feature. In the same way that a dimension can never be exact, the SF, represented by a parameter, can never be exact. Tolerances also need to added to SF specifications. To ensure fitness for purpose, the SF needs to be defined with limits. This chapter is concerned with the specification of SF and texture. 112 Engineering drawing for manufacture 6.1 Roughness and waviness A trace across a surface provides a profile of that surface which will contain short and long wavelengths (see Figure 4.11). In order for a surface to be correctly inspected, the short and long wavelength components need to be separated so they can be individually analysed.
Index pages curate the most relevant extracts from our library of academic textbooks. They’ve been created using an in-house natural language model (NLM), each adding context and meaning to key research topics.
