Development of innovative waste utilization methodologies for material removal processes

Abstract

Sustainable manufacturing is the need of the hour globally. In this regard, there is a dire need to find appropriate technological and managerial solutions to deal with the waste/scrap arising out of various manufacturing processes. The focus of the current research is directed towards the development and investigation of some technologies to tackle the problem of such scrap. In the first approach, the concept of modulation-assisted machining (MAM) is used, in which low frequency (< 1000 Hz) and high amplitude (< 150 μm) vibrations are superimposed to the cutting tool; for example, to the drill bit in the feed direction during a drilling operation. At the initial stage of research work, a preliminary study has been performed to confirm the possibility of modulation-assisted machining (MAM) technology to drill one of the aerospace alloys, Inconel-718. The effect of low-frequency vibrations on the hole quality during MAD of Inconel-718 superalloy has been investigated. Comparison between the quality of conventional and modulation-assisted drilled (MAD) holes has been discussed on the basis of positional error, form error, tool wear, generated thrust force, torque, and surface roughness characteristics. A tribo-MAM tool holder (Patented tool-M4 Sciences) has been retrofitted on a computer-controlled lathe for providing sinusoidal vibrations to the drill bit. Flank wear has been directly measured by the tool condition monitoring method. The maximum flank wear has been measured with a tool maker’s microscope. The used carbide drills have been inspected under the scanning electron microscope (SEM) to establish the probable wear mechanism. The results of the study showed that the tool flank wear (VBmax), thrust force and surface roughness got reduced significantly during MAD in comparison with that during the conventional drilling (CD). Moreover, the ii viability of MAM technology for the production of controllable (specific characteristics) discrete micro-meter sized chips of Inconel-718 has been confirmed. Accordingly, the suitable modulation conditions for the production of Inconel-718 micro-chips are suggested using a triplet-U curve model. This results in the production of discrete chips, even for the ductile materials, along with advantages such as better surface finish and lubrication conditions. For in-depth investigation of the chip powder analysis, various characterization techniques viz. scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), X-ray diffraction (XRD) and mechanical testing including microhardness were used. The study shows that MAD is a promising process for the production of discrete micro-chips of difficult-to-cut materials that can be used as feedstock materials in thermal spraying, powder metallurgy applications. Inconel-718 micro-chips find a variety of applications in powder metallurgy and metal-matrix composites. Apart from the conventional powder production methods, this technique can provide an economic way of producing microchips with a better uniform size distribution. Consequently, it has been decided to use MAM technology and hence optimize the process parameters and their responses for drilling of Inconel-718 and Ti6Al4V aerospace alloys. The multi-variable optimization has been performed using response surface methodology (RSM), considering input variables such as drill diameter (DD), feed rate (FR), and spindle speed (SS). Comparative analysis of MAD and CD has been done based on tool wear (TW), surface roughness (ASR), and thrust force (TF). The characterization of the machined surface and tool wear has been done using SEM and EDS analysis. In the second approach, a novel metal swarf coating technology has been developed. The invention provides an innovative method for metal coating, which has been designated as the Grind-Coating (GC) process. The proposed sustainable technology deposits a metal coating onto a metal, ceramic and polymeric surfaces. In this invention, iii the grinding process is retrofitted to deposit coatings onto substrates that range from both soft (e.g. Polymers and Aluminium) to hard (e.g., Glass Ceramic) materials. High speed of the grinding wheel transfers the material removed from the workpiece (referred to as “swarf”) onto a target surface as a coating. GC is a unique and flexible process that establishes a metal coating without the use of costly and complex conventional surface coating techniques. The deposited coatings have been characterized to evaluate their quality. Apart from the grind coating (GC) technology, another novel portable equipment named as “angle-grind coating technology” (AGCT), is also developed for swarf deposition on various metallic and non-metallic substrates. In the third approach, another novel technology has been reported for additive manufacturing (AM), which has been named as “Chop Saw Printing” (CSP) process. CSP can be used to print metal and non-metal materials and produce a 3D-printed product. This technology prints the metal and non-metal onto a die cavity to produce different geometries. In this invention, the material removed by a chop saw can be used to print 3D metal and non-metal structures directly. This technology also presents a possibility to deposit waste material from a cutting/sawing process; therefore, CSP is regarded as a sustainable manufacturing technology. This unique, sustainable technology can also deposit a non-metal (e.g., polymer) coating onto polymeric surfaces. The high speed of a cutting wheel transfers the material removed from a workpiece (referred to as scrap chip segments or “swarf”) onto a required die cavity surface. In this process, the waste swarf (that is., discrete metal and non-metal segments) is used for additive manufacturing (AM). The particle size distribution of molten and semi-molten swarf augments the printing process. The cutting/sawing of low carbon steel (metal) or nylon (non-metal) by a cutting wheel produces a stream of hot swarf that consists of micrometre-sized particles of the steel or nylon. CSP is a unique and flexible process that establishes printing of a standalone iv product with swarf without the use of costly, sophisticated and complicated traditional metal and polymer printing technologies. Overall, the machining waste/scrap utilization-based development of technologies is an important social need. Moreover, the proposed approaches are suitable for tackling waste and significantly enhancing the machining performance with an improved product quality. The technologies that recycle scrap during its in-situ manufacture have potential for application in various industrial sectors.