Processing, characterization and function of ultra-smooth surfaces

Abstract: The goal of ultra-precision machining is to obtain predetermined surface functions through surface quality control. A certain processing process produces corresponding surface features, which in turn largely determine the actual function of the surface. In order to obtain the required functional surface through pre-design and processing control, a comprehensive and in-depth study of the processing, characterization, function and interrelationship of ultra-smooth surfaces is required.

1 Introduction

With the rapid development of precision, ultra-precision and nano-scale processing technology, advanced control systems, laser measurement technology, scanning probe microscope and other related technologies, research on ultra-precision machining surfaces has made new progress, and its processing precision is gradually increasing from Asia. The micron level has been increased to the nanometer level, and it has become possible to obtain an ultra-smooth surface by superfinishing. However, these ultra-smooth surfaces are usually obtained on the basis of repeated processing and testing. How to obtain high-quality surfaces stably and reproducibly and realize the design function of the surface is still a difficult point in ultra-precision surface processing research. At present, an important research direction of ultra-precision machining surface is to study the surface forming mechanism, and according to the different uses of the surface and the corresponding functional requirements, the surface is designed and predicted before processing, so as to achieve stable desired surface. To meet the needs of practical applications. To this end, a comprehensive and in-depth study of the processing, characterization and function of the surface of ultra-precision components is required.

2 Ultra-precision machining surface and its characteristics

Related definition of the machined surface

A surface is a peripheral interface in which an object is separated from other objects or spaces. For the convenience of research and analysis, the definition of nominal surface, actual surface and measuring surface is given in American National Standard ASME B46.1-1995, namely: 1 nominal surface: expected surface interface (excluding any surface roughness), The shape and extent are generally shown and labeled in the drawings or are described in detail. 2 actual surface: the actual boundary surface of the object, its deviation from the nominal surface is derived from the processing of the surface formation. 3 Measurement surface: A description of the actual surface obtained based on the measuring instrument.

Machining surface characteristics

The actual surface of ultra-precision machining differs from the nominal surface in that it exhibits surface features, defects and shape errors. Among them, the surface feature is the main content of controlling the surface quality of industrial products. It is a combination of some typical deviations on the actual surface, including roughness and waviness. Roughness refers to the fine irregularities of surface features, usually derived from the effects or material conditions inherent in the process, which may be characteristic marks left on the surface during processing. Waviness is a more extensive spatial configuration of surface features resulting from deviations or vibrations in the machine or workpiece. Roughness can be thought of as a superposition on a wave surface.

As a physical entity, the surface has many features. The geometry of the surface is one of its important features. Its natural state is three-dimensional (3D), and its characteristic details are called topography. In many applications, the topography represents the main external features of the surface.

3 Processing, characterization and function of the surface of ultra-precision components

The surface of the workpiece is produced in a large number of machining processes. Once the machining is completed, the surface features reflecting the machining process are reflected on the surface. Therefore, the surface features of the machining component are the reproduction of the entire machining process, and the change and processing of any machining variables. Tool errors will be reflected in the surface features. At the same time, these surface features determine the final function of the surface of the processing component, that is, the specific surface features produce corresponding surface functions, so the surface is the link between its processing control and functional design, and the surface is characterized by acquiring surface information. An important means. It can be seen that the processing, characterization and function of the surface are interrelated: on the one hand, each processing stage and processing of the surface formation determines the macroscopic and microscopic geometric properties of the surface; on the other hand, the geometrical properties and physics of the surface of the workpiece The chemical properties, etc., determine the final function of the surface of the product to a considerable extent. The relationship between processing, characterization and function of the surface can be illustrated by the following figure. For specific application functions, the geometric, physical and chemical properties of the corresponding surface should be considered. Only the corresponding machining control and quality control can achieve the desired surface design function.

Surface processing

Advanced processing technology is an important prerequisite and guarantee for obtaining high quality surfaces. Ultra-precision machining technology with nano-scale processing as the development goal is one of the foundations of today's and tomorrow's manufacturing technology. Ultra-precision cutting is an important part of ultra-precision machining. Its key technology is extremely sharp diamond single point cutting (SPDT), which uses a cutting edge with nano-scale sharpness. The cutting edge can be copied on the machined surface during cutting. A single crystal diamond tool with high wear resistance is processed. This technology has evolved into a sophisticated processing technology for the manufacture of cutting-edge, precision components that can produce workpieces with micron to submicron accuracy and surface roughness up to the nanometer range. Due to the high quality, high precision machining surface available, Diamond Single Point Cutting (SPDT) technology has been widely used in the processing of precision components and optical components such as scanning mirrors and injection molding lens molds. In addition, high-quality surfaces with special functional requirements are completed by a variety of processing processes, and the resulting surface features are also the result of a combination of multiple processes. For example, the planar grinding of the cylinder bore is a multi-machining process that produces a special type of surface feature, consisting of deep grooves (facilitating oil retention) and a fine surface between the grooves (ensuring high support) Ability) composition. The formation of the surface is the result of the comprehensive action of the whole process, so there are many processing factors that affect the surface quality. For cutting, forming, grinding and etching, laser, electron beam and other processing techniques, the formation of surface geometry is mainly affected by factors such as machine tools, tools, workpieces and machining environments, as shown in Table 1.

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