Mushtaq Khan

Selective Laser Melting (SLM) of pure gold

This work presents an investigation into the Selective Laser Melting (SLM) of 24 carat gold (Au) powder with a mean particle size of 24μm. An SLM 100 system was used which is intended for production of highly detailed and intricate parts. Gold powder was tested for its properties such as tap density, Particle Size distribution (PSD) and reflectance etc. A suitable processing window was identified and gold cubes were produced using these parameters. Gold cubes were also checked for their internal porosity and mechanical properties.

Selective Laser Melting (SLM) of gold (Au)

Purpose – Different metals have been processed using laser‐based solid freeform fabrication (SFF) processes but very little work has been published on the selective laser melting (SLM) of gold (Au). The purpose of this paper is to check the properties of gold powder and identify suitable processing parameters for SLM of 24 carat gold powder.Design/methodology/approach – A full factorial approach was used to vary the processing parameters and identify suitable processing region for gold powder. The effects of laser processing parameters on the internal porosity of the multi‐layer parts were examined.Findings – The gold powder was found to be cohesive in nature with apparent and tap densities of 9.3 and 10.36 g/cm3, respectively. The reflectance of gold powder was found to be 85 per cent in the infrared range. A very narrow good melting region was identified for gold powder. The balling phenomenon was observed at both low and high scan speeds. The size of droplets in the balling region tended to increase wi...

Statistical analysis of process parameters in micromachining of Ti-6Al-4V alloy

The demand for miniaturized components is on the rise, especially from the biomedical and aerospace industry. As a result, there is a strong research potential towards the micro-manufacturing of biomedical and aerospace components. Titanium-based alloys are known for their biocompatibility and high strength-to-weight ratio, making them most suitable for such applications. In this research, flank wear progression, surface roughness and side burrs, the basic performance parameters of a typical micromachining operation, are presented and analysed through analysis of variance in order to determine the key process parameters. It was found that micromachining can be classified into two categories: micromachining with undeformed chip thickness below the tool edge radius and micromachining keeping the undeformed chip thickness above the tool edge radius. The results showed that when machining with undeformed chip thickness above edge radius, the feedrate remains the most significant parameter affecting tool wear (41% contribution ratio), surface roughness (83%) and burr width (80%). This result places this type of machining closer to macro-machining where feed contribution was found to be 69%, 92% and 75% as against micromachining below edge radius, where contributions stood at 17%, 53% and 52% on tool wear, surface roughness and burr width, respectively. The results underscored the importance of considering the tool edge radius in micromachining.

Wear mechanism analysis in milling of Ti-6Al-4V alloy

This article presents an investigation into the wear of cutting tool during milling operation of Ti-6Al-4V using H13A carbide inserts. Wear tests were conducted using machining parameters (feed, speed, and depth of cut) falling in the permissible range recommended by the supplier of the inserts. A wear map was created to identify different regions that characterize the tool wear intensity. The wear map revealed a region of avoidance characterized by higher wear for cutting speed of around 55 m/min and feedrate of 0.15 mm/tooth. The Ti:Al ratio reached values between 4:1 and 6:1 for the cutting parameters that resulted in lower–tool wear rate. However, for higher wear rates, the ratio of Ti:Al did not exhibit any stability across the flank wear land. Scanning electron microscope and energy-dispersive x-ray analysis were performed on the worn inserts to identify the high–tool wear regions and material composition at different locations. Titanium aluminides (TiAl and TiAlN) were found just in the low–tool wear regions, and titanium nitride was found across the avoidance region in the wear map. Microscope and x-ray analysis of inserts in the safety zone clearly revealed a built-up edge on the cutting edge of the tools.

RRT*-SMART: A Rapid Convergence Implementation of RRT*

Many sampling based algorithms have been introduced recently. Among them Rapidly Exploring Random Tree (RRT) is one of the quickest and the most efficient obstacle free path finding algorithm. Although it ensures probabilistic completeness, it cannot guarantee finding the most optimal path. Rapidly Exploring Random Tree Star (RRT*), a recently proposed extension of RRT, claims to achieve convergence towards the optimal solution thus ensuring asymptotic optimality along with probabilistic completeness. However, it has been proven to take an infinite time to do so and with a slow convergence rate. In this paper an extension of RRT*, called as RRT*-Smart, has been prposed to overcome the limitaions of RRT*. The goal of the proposecd method is to accelerate the rate of convergence, in order to reach an optimum or near optimum solution at a much faster rate, thus reducing the execution time. The novel approach of the proposed algorithm makes use of two new techniques in RRT*–Path Optimization and Intelligent Sampling. Simulation results presented in various obstacle cluttered environments along with statistical and mathematical analysis confirm the efficiency of the proposed RRT*-Smart algorithm.

Turbine Blade Manufacturing Through Rapid Tooling (RT) Process and Its Quality Inspection

Rapid prototyping (RP) technologies have played vital role in product development and validation. Another aspect of RP is rapid tooling (RT). The development and manufacturing of conventional tools (die and molds) take considerable amount of time. RP technologies could be used to shorten the development time of these tools for shorten the time to production. This investigation focuses on the development of turbine blade through RT technique with quality inspection at three different stages, i.e., after manufacturing of master patterns, wax patterns, and casting in metal. Three different materials were considered for RT techniques, i.e., Room temperature vulcanization (RTV) silicon, polyurethane, and plaster of Paris. Master patterns were developed using stereolithography(SLA) and fused deposition modeling (FDM) process. Both master patterns were analyzed for surface roughness and dimensional accuracy. SLA pattern showed better results for surface finish and dimensional accuracy, and it was used for mold manufacturing. Wax patterns were produced from RTV silicon, polyurethane (PU), and plaster of Paris molds,and used for metal casting. Dimensional quality inspection was performed for both wax and metallic parts using noncontact three-dimensional (3D)digitizer. RTV silicon and SLA process were selected as the suitable mold material and process respectively for RT of turbine blade.

Analysis of forces in conventional and ultrasonically assisted plane cutting of cortical bone

Bone cutting is a well accepted but technically demanding surgical procedure in orthopaedics. A level of tool penetration force during cutting of bones has been the prime concern to surgeons, since it can produce unnecessary mechanical damage to surrounding tissues. Research in this area has been undertaken for many decades to find ways to minimise the cutting force. Cutting of bone with ultrasonic tools is a relatively new technique replacing conventional procedures in neuro-, dental and orthopaedic surgeries, due to its precision and safety. In this article, the level of forces produced during a chisel-like tool penetration in a fresh cortical bone is studied. The obtained force data are analysed for both conventional cutting and ultrasonically assisted cutting. Through a series of experiments, it was demonstrated that the depth of cut and parameters of ultrasonic oscillations affected the level of cutting force, the former being the main factor in both types of cutting. It was found that the tool penetration force was decreased with an increase in the ultrasonic frequency or amplitude and was not affected by the cutting speed. The rise in bone temperature was measured and was found to be insensitive to the level of cutting speed within the range used in this study.

Selective laser melting (SLM) of pure gold for manufacturing dental crowns

Purpose This paper aims to present the application aspect of the work to manufacturing premolar and molar dental crowns by selective laser melting (SLM) of pure gold. Over the years different metals have been processed using laser-based Additive Manufacturing processes, but very little work has been published on the SLM of gold (Au). Previously published work presented suitable processing parameters for SLM of pure gold. Design/methodology/approach Suitable processing parameters were used to manufacture premolar and molar dental crowns using SLM system. Different layer thickness was used to analyse the effect on surface quality of crowns. Mechanical properties are checked using nanoindentation and micro Computerized Tomography scanning. Findings Dental crowns were successfully manufacturing using new build platform and suitable processing parameters. Parts were manufacturing using minimal supports which prevented parts from damaging during removal. A bed temperature of 100°C was found suitable for reducing warpage in the layers. Layer thickness of 50μm was found to have better surface quality and structural integrity as compared to 75μm. Porosity was found to be predominantly inter-layer. Small difference in mechanical properties of dental crowns is associated with the laser processing. Originality/value This research is the first of its kind which presents dental crown manufacturing using SLM of pure gold.

Optimization of process parameters for plasma arc welding of austenitic stainless steel (304 L) with low carbon steel (A-36):

This research aims to optimize the process parameters of plasma arc welding for welding of dissimilar metals: austenitic stainless steel SS-304 L and low carbon steel A-36. It investigates the effect of welding current and welding speed on the quality of the welded joints. The quality characteristics like bead geometry, microstructure, hardness, ferrite measurement and tensile test are considered for qualification of the welded samples. Welded specimens were prepared both with and without filler material. These specimens were mechanically tested and analyzed using metallographic techniques. Based on the results, suitable welding parameters were found to be 45 A and 2 mm/s for samples prepared with and without filler wire. An all-martensitic weld zone structure was obtained for direct fusion. However, a complex heterogeneous microstructure was obtained by using austenitic stainless steel filler wire E 309 L. Hardness of directly fused sample was observed to be significantly higher compared to filler wire sample.

Improvement in the Mechanical Properties of High Temperature Shape Memory Alloy (Ti50Ni25Pd25) by Copper Addition

High temperature shape memory alloys Ti50Ni25Pd25 and Ti50Ni20Pd25Cu5 were developed, characterized, and tensile tested in both martensite ( − 50°C) and austenite (