TOOL MIMIC APPROACH FOR THE FABRICATION OF FUNCTIONAL SURFACES

Abstract

The increasing demand for micro-sized products in various fields, such as biomedical testing, micro-fluidics, micro-reactors, automotive and aerospace industries, has led to the development of innovative manufacturing methods. However, manufacturing micro-sized products with high precision is a complex task, and the tool's characteristics play a crucial role in determining the manufactured product's surface texture, geometric accuracy, and precision. Various tool fabrication techniques have been developed, but producing accurate and precise micro-sized features is challenging with other machining processes such as grinding, milling, CNC, and conventional machining. Besides the typical conventional and non-conventional machining processes, chemical etching is a low-cost method that produces burr-free edges, processes thin materials, and is fast, making it an alluring method for producing patterned tools. Research is continuously refining the chemical etching process to make it more accessible for cost-effective and precise tool fabrication. The fabricated patterned tool can be used further to create functional surfaces with surface textures. Surface texturing of the substrate surface is one method used to improve surface properties and control the adverse effects caused by the mating surfaces. Textured surfaces have become popular in various fields, such as biomedicine, electronics, optics, metrology, and tribological improvement. Titanium and its alloys are popular biocompatible materials used in biomedical applications due to their superior properties, such as high strength-to-weight ratio, low density, relatively low Young's modulus, and corrosion resistance. However, the Ti-6Al-4V alloy possesses limited biomedical applications due to its weak shear strength, inability to control substrate wear, low work hardening, and high friction coefficient. Surface modification techniques such as nitriding, physical vapor deposition, anodizing, surface coatings, and laser and electrochemical application have improved the biocompatibility of Titanium and its alloys. Surface modification in creating textures has gained popularity, with micro-dimples being one of the popular methods to improve surface characteristics, including the change in friction coefficient under lubrication conditions. Nevertheless, it can be hard to identify a possible surface modification method that may generate the required surface characteristics. The high energy requirements, burr formation, and investment cost are limitations on the fabrication of micro-dimples employing competent methods of machining such laser, mechanical, micro-milling and micro-drilling, and electrochemical machining. An approach used to generate textured surfaces is electric discharge machining (EDM). It is a non-contact machining technology that creates stress-free cavities in conducting and semi-conducting materials that require low specific energy. In conclusion, innovative surface modification methods and manufacturing techniques provide the potential to generate precise and cost-effective instruments and substrates for a wide range of applications. In modern manufacturing, micromachining is essential for producing small, precise parts with complex geometries. However, conventional machining processes such as turning, milling, grinding, and drilling are insufficient for achieving the high levels of precision and complexity required in micromachining. Therefore, combining chemical and non-traditional machining provides better feature size and shape manufacturing solutions. One of the main challenges in micromachining is the tool-making process, which involves individual research and analysis to get the appropriate micro tool for obtaining the desired output in terms of shape, size, and surface roughness. The selection of a specific process and material for tooling depends on the required characteristics of the tool in terms of feature size, aspect ratio, precision, and durability. Research in this field has led to advanced processes such as micro-milling, which can create intricate 3D geometries out of various materials with relatively high material removal rates. Due to the miniaturization of the parts, tools, and processes, there are challenges with microfabrication, such as small vibrations and excessive pressures that may influence the longevity of the tools and component tolerance control. To overcome these obstacles and achieve costeffective micromachining, innovative methods are therefore required. A few examples include using a low-cost printing technique or photolithography and etching. Overall, micromachining is an encouraging technique for creating miniature, accurate parts with complicated geometries, but additional research is required to address the issues that emerge. This thesis primarily focuses on developing a patterned tool using chemical etching techniques and its utilization to create functional surfaces for tribological applications. In order to develop functional surfaces with superior tribological properties, a patterned tool with a chemical machining design is crucial. Chemical etching is a method that is employed to generate a patterned tool. This method of subtractive manufacturing uses a chemical solution to remove material from the surface of the work material. This technique renders it possible to accurately and precisely produce intricate patterns and shapes. The second objective of this thesis is to employ the generated patterned tool to create desirable surfaces for tribological applications. Functional surfaces can be created utilizing electrical discharge machining (EDM). EDM can be used to create micro-surface features that will improve the tribological characteristics of functioning surfaces. All things considered, the development of the patterned tool and its use in the production of useful surfaces mark a significant step forward in the field of tribology research. This research work focuses on the utilization of both chemical etching and EDM processes for the fabrication of the precise tools and their implementation to fabricate the functional surfaces. With the flexibility to create the desired surfaces over the substrate material, the tribological properties can be enhanced and the research can be utilised for the broad range of industrial applications.