Precision Machining Process and Technology

Precision/ultra-precision machining technologies are the fundamental methods for achieving high form accuracy and surface quality. With the continuous development of modern science and technology, precision machines now involve complicated systems engineering and have been widely used in the production of components in various aerospace, national defense, optics, mechanics, electronics, and other high-tech applications. This chapter presents an overview of the conception, development and application of ultra-precision machining, and the typical structure of ultra-precision machines, the developments of ultra-precision machining technologies, especially ultra-precision cutting, ultra-precision grinding and polishing are also reviewed. The current state and problems of this field are analyzed, and the future development trend is prospected.

In the last few decades, the demand for high-precision components has increased. These components have a wide range of industrial applications in space and aeronautics, optics, electronic devices, and medical and life sciences. Ultra-precision machining technologies play an increasingly important role in the precision manufacturing process. Ductile materials, such as aluminum, copper, and other metals, can be machined by single-point diamond turning (SPDT) or other deterministic ultra-precision machining technologies such as ultra-precision raster milling and tool servo machining. However, for difficult-to-machine materials, such as ceramics, silicon carbide, glass, and semiconductor materials, they are primarily machined by ultra-precision grinding technology. With the continuous development of modern science and technology, precision, ultra-precision machining technology is increasingly becoming the mainstay of machining. Nowadays, precision, ultra-precision machining technology is more and more precision, from the micron level, nanoscale processing gradually to the atomic level of machining process technology. Ultra-precision machining technology is an indispensable and important foundation of modern equipment manufacturing industry, and it is also an important development direction of modern manufacturing science as well as machining. Precision, ultra-precision machining is no longer limited to the national level of very important causes but has entered the national economy and all aspects of our lives.

The advent of diamond turning is one of the most significant breakthroughs in modern materials processing technology, especially for ultraprecision applications that demand extreme form accuracy and surface finishing. This chapter emphasizes the operating principles of diamond turning in which the underlying mechanics of material removal are governed by the tool edge radius and microstructural effects. Recent advances in diamond turning, particularly in productivity improvement for some important applications through high-volume production, are addressed. The design principles of both the machine tool and cutting tool, which are critical components of a diamond turning system, are also explained in sufficient depth. Despite that, the latest advancements in slow tool servo technology, a widely applied method for manufacturing large nonrotationally symmetric parts, are also comprehensively detailed. Finally, considering the increasing demand for complex optics, there is also a brief introduction to the recent advances of the fast tool servo turning technology.

Ultra-precision large-sized milling technology is the machining technology of parts with high precision and high surface quality. The flatness of the processed parts in general milling is technically required to be more than 5 μm. The surface roughness (Ra) of the processed parts is technically required to be more than 5 nm. Advanced single-point diamond turning technology (SPDT) has been widely used internationally for machining flat parts. This technology refers to the use of natural single-crystal diamonds as a tool for the cutting, milling, and processing of optical surfaces under computer control. It is a new technology that was developed in the early 1980s. After more than 20 years of development, it has been widely used in processing a variety of high-precision optical components.

The increasing demand for high-precision parts has significantly grown within the past decades. Precision grinding, as one of the most widely utilized abrasive machining techniques in precision machining, provides reliable method to achieve the deterministic precision requirements of the high quality and functional parts in optical, semiconductor, automobile, and medical device industry. Precision grinding involves the use of abrasive tools to removal material from a workpiece to achieve high dimension accuracy and surface finish. It employs grinding wheels as regular tools, which are embedded with abrasive grains to act and grind down the surfaces of parts. The precision aspect refers to achieving a relatively higher tolerances and fine surface finishes and pushing the machining accuracy limit to micron and submicron levels. This chapter begins by introducing the fundamentals of the grinding process, including a detailed explanation of the abrasive grains, bonding systems, and grinding tools. Additionally, the design and dressing techniques of precision grinding tools are explored. Following this, the process parameters, such as depth of cut, material removal rate, force, and temperature, are discussed in detail. Given the critical role of material removal mechanisms in determining machining capabilities and accuracy limits, this chapter also delves into the distinct material removal processes for ductile and brittle materials. Finally, the chapter highlights the application of precision grinding in producing optical lenses and semiconductor wafers, showcasing its essential role in modern manufacturing.

For the micro-nano-fabrication technology in the field of precision engineering, this chapter mainly introduces the planar microfabrication technology and probe processing technology. At present, high aspect ratio structures are widely relied on in emerging technology fields such as large-scale integrated circuits. The measurement methods of complex micro-nanostructures are mainly divided into two categories. One is the noncontact measurement methods represented by various laser interferometers and electron microscopes. This method is limited by the depth of field and small lens focusing range when the depth width ratio is large. The other is the contact measurement method represented by high-precision probe profiler and scanning probe microscopy. This method has high resolution, but the length diameter ratio of conventional probe is small, which cannot meet the measurement requirements of structures with high aspect ratio. This chapter introduces the representative etching technology of planar microfabrication technology, the representative micronano-processing technology of probe processing technology, the micro-nano-processing technology based on atomic force microscope probe, and the scanning probe processing technology for micro-nanostructure with large aspect ratio.

With the continuous development of optics, optical components have been widely used in military and civilian fields such as national defense construction, aviation and aerospace, industrial and agricultural production, and people’s lives. Especially, the large and medium-sized optical components are the core components of astronomical observation systems, laser nuclear fusion devices, precision optical measurement instruments, and other high-tech products. Optical mirrors require strict control of the surface/subsurface quality of the lens to ensure the optical performance of the mirror while achieving low surface roughness, high surface accuracy, and high surface integrity. However, optical materials are difficult to process due to their high hardness and brittleness, and surface/subsurface damage such as scratches, microcracks, breakage, residual stresses, etc., often occur after processing, resulting in a decrease in the material’s strength and refractive index, which directly affects important performance indicators such as the coating quality of the optical element, long-term stability, laser damage resistance threshold, and lifetime, and has a significant impact on the performance of the entire optical system. In the last few decades, high-precision free-form optic components such as high-resolution observation and precision-guided munitions play an important role in national defense. The fundamental goal of high-efficiency, precision, low-damage manufacturing of brittle optical materials is to maximize the material removal rate while maintaining a certain degree of surface integrity and subsurface quality of the material. However, the higher material removal rates usually used to improve machining efficiency are often prone to heavy damage, which affects the surface/subsurface quality of the workpiece. Therefore, a clear understanding of the cutting mechanism of brittle optical materials is necessary for the efficient, high-precision, and low-damage grinding of large and medium-sized optical components. There has been a great deal of research and development in this area, such as material removal mechanism and qualitative and quantitative analysis of surface/subsurface damage in manufacturing process. Currently, the ultraprecision grinding is the main manufacturing process to cut the optical materials. However, it is a challenge work to fabricate the free-form surface with high quality and closed tolerance due to the rapid change in the concavity-convexity and curvature of the surface, the effective cutting zone of the grinding wheel changes frequently in ultraprecision grinding, and the current flat surface-based theoretical model cannot be applied to the prediction of the surface topography generation in the ultraprecision grinding of the curved surface with rapidly varied curvature, which may seriously restrict the machining quality and efficiency of the optical elements. In this chapter, take the silicon carbide (SiC) as an example, which is a typical difficult-to-machine material that has been widely used in the fabrication of optical elements and structural and heat-resistant materials. The parallel grinding has been frequently adopted to produce a high-quality surface finishing. The surface generation is a vital issue for assessing surface quality, and extensive modeling work has been developed. However, most of them were based on the disc wheel with the cylindrical surface, and the surface topography generation based on the arc-shaped tool has paid relatively little attention. In this study, a new theoretical model for surface generation in ultraprecision parallel grinding has been established by considering the arc-shaped effect, synchronous vibration of the wheel, and cutting profile interference at the tool feed direction. Finally, the ground surface generation mechanism and grinding ductility were analyzed in the grinding of SiC ceramics. The results showed that the spiral and straight-line mode vibration patterns were the main feature of the machined surface and its continuity was mainly affected by the phase shift. Furthermore, for the in-phase shift condition, the grinding ductility is more significant than that of out-of-phase shift due to the continuously decreasing relative linear speed between the wheel and workpiece. High-precision optical components with complex shape or microstructure have been extensively used in numerous fields such as biomedicine, energy, and aerospace. In order to accurately achieve the specific functions of the components, the form accuracy and uniform surface quality need to reach an ever-high level. To achieve this, ultraprecision normal grinding is used for machining various types of complex optical surfaces. However, the intricate variation of the workpiece curvature and grinding wheel vibration give rise to great challenges to obtain higher precision and uniform surface condition. Finally, the micro-sinusoidal array with the setting value for scallop height is achieved by controlling the feed speed, which is determined by the local curvature of surface profile.

This chapter presents an experimental and theoretical study of surface generation in ultra-precision grinding of hard and brittle materials. The study considers material properties, the relative vibration between the grinding wheel and the workpiece, machining parameters, and the phase shift of the grinding process. The Taguchi approach is employed to study the influence of machining parameters on the surface quality and shows the workpiece’s feed speed and rotational speed as vital factors. Experiments have been conducted to examine individual variables, and the results further show that the feed rate and the cross-feed distance have significant effects on surface generation. It is found that the spirals around the central area of the workpiece are the primary mechanism for surface generation, which originates from the synchronous relative tool-work vibration. The integral part of the ratio of the rotational speed of the grinding wheel’s rotational speed to the workpiece’s rotational speed determines the number of spirals, and its fractional part controls the spiral geometry. A theoretical model for predicting the single spiral generation has been developed to explain the accumulation of the phase shift and the geometry. The changeable feed speed near the end of grinding is also modeled, revealing the approximate straight lines around one circle in the central region. The simulated results indicate the theoretical models and the ground surface are in close agreement. Finally, a comparison of different surface generation mechanisms in grinding mold steel, tungsten carbide (WC), and reaction-bonded silicon carbide (RB-SiC) is investigated. It is interesting to note that the Spanzipfel effect contributes to the surface generation not only on ductile materials such as mold steel but also on brittle materials such as WC and RB-SiC. The Spanzipfel effect is most significant in grinding mold steel. For WC and RB-SiC, the ground surface contains both tensile and brittle regions in microfracture.

In this chapter, precision manufacturing processes for the large-size rotary table, spindle, and guideways were analyzed and concluded. Firstly, specifications of typical components were listed as well as the design principles. Cases for the slide guideways, air rotary table, and spindle were given separately. The investigation mainly focuses on the aerostatic and hydrostatic bearing components which are generally customized, the design strategies, critical dimensions measuring techniques, material selection method, and machining procedure will be introduced compressively.

In this section, the precision manufacturing processes for small-size rotary tables, spindles, and guideways were analyzed and discussed in detail. The section began by listing several types of small-size linear and rotary components commonly used in high-precision machinery. These components, which are crucial for various applications such as CNC machines, robotics, and aerospace systems, require careful consideration of their materials, geometries, and performance characteristics. A particular focus was placed on the manufacturing process of small-size aerostatic spindles, which are essential for applications demanding ultra-precision and minimal friction. The aerostatic spindle’s production involves several key steps, each contributing to its high performance. The materials selected for the spindle are critical to its durability and precision, typically involving high-grade alloys and composites that offer both strength and stability. Precision in manufacturing is paramount at every stage, with tolerance levels often in the micrometer range to ensure smooth operation and minimal wear. Advanced techniques, such as CNC machining, surface grinding, and aerostatic bearing design, are employed to maintain the spindle’s performance and efficiency. The use of aerostatic bearings, in particular, allows for contact-free operation, reducing friction and heat generation, which is crucial for maintaining high rotational speeds and precision over time. Each step in the production process is closely monitored and refined to ensure the spindle meets the stringent requirements for its intended applications, ensuring optimal performance in demanding environments.

Subsurface damage is easily induced during the processing of hard and brittle materials, and has a significant impact on the lifetime, secular stability, coating quality, transmission performance, and laser-induced damage threshold of a machined part. To realize high quality manufacturing, it is necessary to detect the subsurface damages and remove them in the subsequent processes. However, subsurface damage is rather difficult to detect directly since it is often covered with a smearing layer. This chapter introduces the formation mechanism, measurement methods, and control strategies of subsurface damage. Firstly, the theoretical model and mechanism of subsurface damage formation based on the indentation fracture mechanics of hard and brittle material is discussed. Then, the detection methods of subsurface damage including both destructive and non-destructive are reviewed, and their principles, characteristics, research progresses, and applications are illustrated. In comparison, destructive methods can provide quantitative and reliable information; non-destructive methods have the advantages of fast and convenient operation and can realize in-process detection to meet the growing demand on high quality manufacturing. Finally, the control strategies for subsurface damage are summarized and the future development trend is prospected.

In this chapter, polishing technologies used for artificial implants surface finishing are introduced. It starts with an overview of hip replacement and knee replacement. The biomaterials for arthroplasty components and the general processes for the manufacturing of arthroplasty components are reviewed. The ultra-precision polishing technologies for finishing the load-bearing surfaces of artificial joints are then discussed in terms of polishing technologies, material removal mechanism, surface roughness improvement, and form correction. Different types of polishing technologies, which can be potentially used for artificial joints in the future, are also reviewed and special attention is paid to the bonnet polishing technology.

High-speed grinding is an important process for high-performance machining of advanced materials due to its capability for high efficiency and excellent surface integrity. In this chapter, the fundamentals of high-speed grinding were introduced, followed by a review of the practices of high-speed grinding in recent years. First, authors’ experience gained from the high-speed grinding of engineering ceramics and thin film materials, including alumina, alumina–titania, yttria partially stabilized tetragonal zirconia, and thin film multilayer solar panels, was presented. High-speed grinding of combination materials was then introduced focusing on the selection of grinding wheel and parameters and development of unique coolant supply technology.

Plastic films with microstructures are widely applied due to their outstanding performance in different fields. One of the applications is the manufacturing of flat panel displays for which conventional manufacturing methods using injection molding technology are inadequate. However, the rolling imprint method is an emerging technology that can overcome some shortcomings of traditional technologies in the fabrication of plastic films and flat panel displays. The quality of the precision roller has a direct impact on the accuracy of the microstructure pattern on the films. Research in this field currently focuses on the design and fabrication of precision rollers with little emphasis placed on the factors that affect the surface generation and measurement of the microstructure pattern. This chapter therefore presents the influence of machining factors on microstructure patterned surfaces on precision rollers by single point diamond turning, and introduces a model-based simulation system for the machining process.

Ultra-precision machining, as an effective way to obtain components with high dimensional accuracy and outstanding surface smoothness, is developing rapidly with the progress of science and technology. Polymers have unique properties compared to conventional materials like metals, glasses, or ceramics. Particularly, with great improvements in specific strength, specific modulus and surface modification, polymeric materials are possessing broader applications. Relevant requirements are higher in geometric precision and surface quality. Accordingly, ultra-precision machining of polymeric materials is urgently needed, and great efforts are necessary to be contributed in this field. In this chapter, the knowledge about polymers and related processes for making polymer parts are introduced. Then the necessity of ultra-precision machining for polymers is presented by comparing the advantages of ultra-precision machining over conventional processes under current application requirements. The biggest challenge for successfully ultra-precision machining of polymers is viscoelasticity. This property and its affecting factors are introduced. Based on understanding of the viscoelastic behavior of polymers, two representative examples of ultra-precision machining of polymeric materials are provided: cryogenic machining and fabrication of contact lenses. It can be indicated from the examples that viscoelasticity of polymers need to be controlled during ultra-precision machining. Possible methods can be altering environmental conditions like temperature, designing suitable tools or collets, and optimizing machining parameters. Even though challenges remain to be solved for ultra-precision machining of polymeric materials, it can be predicted that a broad future is coming with more input to meet increasing application requirements from various fields.

Due to the geometry complexity and high precision requirements, it is still a challenge to manufacture ultra-precision freeform surfaces with submicrometer form accuracy and surface finish in nanometer range, which largely depends on comprehensive consideration of advanced optics design, modeling and optimization of the machining process, freeform surface measurement and characterization. This chapter presents the theoretical basis for the establishment of an integrated platform for the design, fabrication, and measurement of ultra-precision freeform surfaces. The chapter firstly gives a literature review on machining and measurement of freeform optics and then presents the layout of the proposed integrated system, which mainly consists of four key modules, including optics design module, data exchange module, machining process simulation and optimization module, and freeform measurement and evaluation module. The proposed Platform is implemented and validated by a series of experiments, and its capability is realized through a trial implementation in the design, fabrication, and measurement of an F-theta lens production. The results show that the proposed integrated platform not only helps to shorten the cycle time for the development of freeform components but also provides an important means for optimizing the surface quality in the ultra-precision machining of freeform surfaces.

The pursuit of ultrasmooth surfaces of polycrystalline materials is of paramount importance for enhancing the functionality of components and devices, particularly in the fields of optics, electronics, and mechanics. This study delves into the formation mechanisms of ultrasmooth surfaces on polycrystalline copper using ultraprecision diamond cutting techniques. Specifically, a crystal plasticity finite element (CPFE) model integrated with the Johnson-Cook failure criterion to simulate the anisotropic cutting process of polycrystalline copper is introduced. The model captures the influence of microstructures, such as grain boundaries (GBs), on the machining characteristics, including machining forces, chip profile, and machined surface quality. CPFE simulations, corroborated by experimental investigations, reveal that the anisotropic plasticity and elastic recovery within grains, which is coupled with GB accommodation, significantly impact the formation of surface steps at GBs during cutting process. The study demonstrates that optimizing cutting parameters, such as the cutting edge radius and misorientation angle of GBs, is crucial for achieving superior surface finish of polycrystalline copper. By adjusting these parameters, an ultrasmooth surface of polycrystalline copper is successfully obtained with a surface roughness less than 1 nm through ultraprecision diamond turning. This work not only advances the understanding of microstructure-dependent machining behaviors in polycrystalline materials but also provides actionable insights for optimizing ultraprecision diamond cutting processes to achieve ultrasmooth surfaces. The findings have broad implications for the manufacturing of high-performance components and devices where surface integrity is critical.

Laser surface texturing is a promising method to functionalize surfaces by changing chemical, physical, and mechanical properties of materials at the microscopic scale. In the present chapter, we perform finite element simulations and experiments to investigate the ablated surface morphology of silicon by nanosecond pulsed laser ablation using low laser fluences ranging from 14.92 to 23.21 J/cm². The utilized finite element model comprehensively considers the following aspects: (1) combined effects of thermal conduction, convection, and radiation on heat conduction; (2) temperature-dependent thermomechanical properties of material; (3) instantaneous update of the laser focus due to evaporation-induced surface recession; and (4) spatial and temporal Gaussian energy distributions of the laser pulse. Experimental works using the same laser processing parameters with the conducted finite element simulations are carried out to validate the simulation results. Through the optimization of the laser processing parameters by 2D and 3D finite element simulations and the respective experimental validations for eliminating heat-affected zone and promoting forming accuracy, high accuracy aligned microgrooves are fabricated on silicon with high antireflective properties in a wide range of wavelengths between 400 and 2000 nm. This is fairly comparable with the performance of similar silicon microstructures manufactured by femtosecond laser ablation. Consequently, the current chapter presents a feasible way to fabricate precise surface microstructures with high antireflective properties on silicon at low cost by nanosecond pulsed laser ablation.

Ultraprecision cutting is a new technology with a wide range of contents, and its machining accuracy and surface quality are determined by ultra-fine machine tool equipment, diamond tools, cutting processes, measurement and error compensation technology, environmental support conditions, and other factors that influence the comprehensive results. With the continuous development of aerospace, information communication, and biomedical fields, a variety of complex optical components have begun to appear, which puts forward higher requirements on the performance of precision manufacturing technologies. In the future, the characteristics of precision manufacturing technologies will be very high precision, high efficiency, large-scale, miniaturization, intelligence, process integration, online processing, and testing integration. With the development of new materials and technologies, precision machining will continue to improve its machining accuracy and productivity.