Carbon dioxide (CO2) laser cutting finds one of its most relevant applications in the processing of a wide variety of polymeric materials like thermoplastics and thermosetting plastics. Different types of polymeric materials like polypropylene (PP), polymethyl methacrylate (PMMA), low- and high-density polyethylene (LDPE, HDPE), are processed by laser for different household as well as commercial products in the industry. The reason is their easy availability and economical aspect in the market. The problems associated with laser cutting include heat-affected zone (HAZ) generated on the cut surface, kerf width (KW), surface roughness (SR), dross formation, and striations formation. Furthermore, other related problems include taper cutting for deep parts and high-power consumption. The primary purpose of this work is a comprehensive literature review in CO2 laser cutting of polymeric materials. The influence of parametric variation on the cut quality is also explained. Cut quality in terms of KW, SR, HAZ, dross formation, and striations formation is analyzed by optimizing cutting variables like laser power (PL), cutting speed (CS), assist gas pressure (Pg), pulse frequency, nozzle type and its diameter, and stand-off distance (SOD). The effects of the laser cutting on the properties of different thermoplastics/thermosetting materials are also reported. However, this topic requires further studies on exploring the range of polymeric materials, and their optimal parameters selection to improve the cut quality. Therefore, the research gaps and future research directions are also highlighted in the context of CO2 laser cutting for polymeric materials.

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Additively manufactured nano-MEH systems are widely used to harvest energy from renewable and sustainable energy sources such as wind, ocean, sunlight, raindrops, and ambient vibrations. A comprehensive study focusing on in-depth technology evolution, applications, problems, and future trends of specifically 3D printed nano-MEH systems with an energy point of view is rarely conducted. Therefore, this paper looks into the state-of-the-art technologies, energy harvesting sources/methods, performance, implementations, emerging applications, potential challenges, and future perspectives of additively manufactured nano-mechanical energy harvesting (3DP-NMEH) systems. The prevailing challenges concerning renewable energy harvesting capacities, optimal energy scavenging, power management, material functionalization, sustainable prototyping strategies, new materials, commercialization, and hybridization are discussed. A novel solution is proposed for renewable energy generation and medicinal purposes based on the sustainable utilization of recyclable municipal and medical waste generated during the COVID-19 pandemic. Finally, recommendations for future research are presented concerning the cutting-edge issues hurdling the optimal exploitation of renewable energy resources through NMEHs. China and the USA are the most significant leading forces in enhancing 3DP-NMEH technology, with more than 75% contributions collectively. The reported output energy capacities of additively manufactured nano-MEH systems were 0.5–32 mW, 0.0002–45.6 mW, and 0.3–4.67 mW for electromagnetic, piezoelectric, and triboelectric nanogenerators, respectively. The optimal strategies and techniques to enhance these energy capacities are compiled in this paper. Graphical Abstract

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Purpose Human aging is becoming a common issue these days as it results in orthopaedic-related issues such as joints disorderness, bone-fracture. People with age = 60 years suffer more from these aforesaid issues. It is expected that these issues in human beings will ultimately reach 2.1 billion by 2050 worldwide. Furthermore, the increase in traffic accidents in young people throughout the world has significantly emerged the need for artificial implants. Their implantation can act as a substitute for fractured bones or disordered joints. Therefore, this study aims to focus on electron beam melted titanium (Ti)-based orthopaedic implants along with their recent trends in the field. Design/methodology/approach The main contents of this work include the basic theme and background of the metal-based additive manufacturing, different implant materials specifically Ti alloys and their classification based on crystallographic transus temperature (including α, metastable β, β and α + β phases), details of electron beam melting (EBM) concerning its process physics, various control variables and performance characteristics of EBMed Ti alloys in orthopaedic and orthodontic implants, applications of EBMed Ti alloys in various load-bearing implants, different challenges associated with the EBMed Ti-based implants along with their possible solutions. Recent trends and shortfalls have also been described at the end. Findings EBM is getting significant attention in medical implants because of its minor issues as compared to conventional fabrication practices such as Ti casting and possesses a significant research potential to fabricate various medical implants. The elastic modulus and strength of EBMed ß Ti-alloys such as 24Nb-4Zr-8Sn and Ti-33Nb-4Sn are superior compared to conventional Ti for orthopaedic implants. Beta Ti alloys processed by EBM have near bone elastic modulus (approximately 35–50 GPa) along with improved tribo-mechanical performance involving mechanical strength, wear and corrosion resistance, along with biocompatibility for implants. Originality/value Advances in EBM have opened the gateway Ti alloys in the biomedical field explicitly ß-alloys because of their unique biocompatibility, bioactivity along with improved tribo-mechanical performance. Less significant work is available on the EBM of Ti alloys in orthopaedic and orthodontic implants. This study is directed solely on the EBM of medical Ti alloys in medical sectors to explore their different aspects for future research opportunities.

Recently, DC53 die steel was introduced to the die and mold industry because of its excellent characteristics i.e., very good machinability and better engineering properties. DC53 demonstrates a strong capability to retain a near-net shape profile of the die, which is a very challenging process with materials. To produce complex and accurate die features, the use of the wire electric discharge machining (WEDM) process takes the lead in the manufacturing industry. However, the challenge is to understand the physical science of the process to improve surface features and service properties. In this study, a detailed yet systematic evaluation of process parameters investigation is made on the influence of a wire feed, pulse on duration, open voltage, and servo voltage on the productivity (material removal rate) and material quality (surface roughness, recast layer thickness, kerf width) against the requirements of mechanical-tooling industry. Based on parametric exploration, wire feed was found the most influential parameter on kerf width: KW (45.64%), pulse on time on surface roughness: SR (84.83%), open voltage on material removal rate: MRR (49.07%) and recast layer thickness: RLT (52.06%). Also, the optimized process parameters resulted in 1.710 µm SR, 10.367 mm3/min MRR, 0.327 mm KW, and 10.443 µm RLT. Moreover, the evolution of surface features and process complexities are thoroughly discussed based on the involved physical science. The recast layer, often considered as a process limitation, was explored with the aim of minimizing the layers’ depth, as well as the recast layer and heat-affected zone. The research provides regression models based on thorough investigation to support machinists for achieving required features.

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