Well-established Manufacturing Process Research Articles

Opportunities and Challenges in the Application of Bioplastics: Perspectives from Formulation, Processing, and Performance.

Tremendously negative effects have been generated in recent decades by the continuously increasing production of conventional plastics and the inadequate management of their waste products. This demands the production of materials within a circular economy, easy to recycle and to biodegrade, minimizing the environmental impact and increasing cost competitiveness. Bioplastics represent a sustainable alternative in this scenario. However, the replacement of plastics must be addressed considering several aspects along their lifecycle, from bioplastic processing to the final application of the product. In this review, the effects of using different additives, biomass sources, and processing techniques on the mechanical and thermal behavior, as well as on the biodegradability, of bioplastics is discussed. The importance of using bioplasticizers is highlighted, besides studying the role of surfactants, compatibilizers, cross-linkers, coupling agents, and chain extenders. Cellulose, lignin, starch, chitosan, and composites are analyzed as part of the non-synthetic bioplastics considered. Throughout the study, the emphasis is on the use of well-established manufacturing processes, such as extrusion, injection, compression, or blow molding, since these are the ones that satisfy the quality, productivity, and cost requirements for large-scale industrial production. Particular attention is also given to fused deposition modeling, since this additive manufacturing technique is nowadays not only used for making prototypes, but it is being integrated into the development of parts for a wide variety of biomedical and industrial applications. Finally, recyclability and the commercial requirements for bioplastics are discussed, and some future perspectives and challenges for the development of bio-based plastics are discussed, with the conclusion that technological innovations, economic incentives, and policy changes could be coupled with individually driven solutions to mitigate the negative environmental impacts associated with conventional plastics.

On the use of slurry as an alternative to dry powder for laser powder bed fusion of 316L stainless steel

Laser powder bed fusion (LPBF) is a well-established additive manufacturing process for producing high-quality metal components with unparallelled design freedom. However, LPBF also has its limitations, including a limited materials palette, low productivity and high costs, mainly due to the expensive feedstock powders. These powders must meet highly stringent requirements regarding particle size (15–45μm), particle size distribution (mono-modal) and morphology (spherical), which is achievable only through expensive gas- and plasma-atomised powders. This paper investigates slurry-LPBF as an alternative to conventional dry powder LPBF. The use of slurry removes some of the stringent powder requirements by allowing deposition of smaller particles with a variety of particle morphologies. Slurry-LPBF can therefore increase the useful yield of the atomisation process and expand the materials palette for LPBF, by enabling the use of powders for which atomised variants are not commercially available. This study used 316L stainless steel powder with an average particle size <18μm. An existing slurry-LPBF machine was re-designed and re-built, allowing successful slurry processing. Two optimal parameter sets were obtained, resulting in component density of 99.4%. Tensile testing revealed an ultimate tensile strength (UTS) of 622 ± 2 MPa and an elongation at break of 66 ± 2%. These results are consistent, and fall within the range of reported values in literature for dry-powder LPBF, with the UTS being on the lower side of the range, whilst elongation at break being on the higher side.

Synthesis of Poly-Lactic Acid by Ring Open Polymerization from Beer Spent Grain for Drug Delivery.

Poly-lactic acid (PLA) is a synthetic polymer that has gained popularity as a scaffold due to well-established manufacturing processes, predictable biomaterial properties, and sustained therapeutic release rates. However, its drawbacks include weak mechanical parameters and reduced medicinal delivery efficacy after PLA degradation. The development of synthetic polymers that can release antibiotics and other medicines remains a top research priority. This study proposes a novel approach to produce PLA by converting Brewer's spent grain (BSG) into lactic acid by bacterial fermentation followed by lactide ring polymerization with a metal catalyst. The elution properties of the PLA polymer are evaluated using modified Kirby-Bauer assays involving the antimicrobial chemotherapeutical, trimethoprim (TMP). Molded PLA polymer disks are impregnated with a known killing concentration of TMP, and the PLA is evaluated as a drug vehicle against TMP-sensitive Escherichia coli. This approach provides a practical means of assessing the polymer's ability to release antimicrobials, which could be beneficial in exploring new drug-eluting synthetic polymer strategies. Overall, this study highlights the potential of using BSG waste materials to produce valuable biomaterials of medical value with the promise of expanded versatility of synthetic PLA polymers in the field of drug-impregnated tissue grafts.

Evaluating the effect of solid lubricant inclusion on the friction and wear properties of Laser Sintered Polyamide-12 components

The processing of Polyamide-12 (PA12) by Laser Sintering is one of the most well-established Additive Manufacturing (AM) processes for producing functional components for end-use applications. However, its further adoption within industry remains hindered by an incomplete understanding of resultant part quality and the impact this has on component wear. The scope of this research was to investigate the dry sliding behaviour of Laser Sintered Polyamide-12, as well as evaluate whether the inclusion of solid lubricant fillers effect the friction and wear properties of parts produced. Polytetrafluoroethylene (PTFE), Graphite and Molybdenum disulphide (MoS2) were added to Polyamide-12 powder in 1 : 100 mass ratios, respectively, to create three different polymeric composites. Mechanical blending and Laser Sintering then ensued; the latter was performed using identical processing parameters throughout. Tribological performance was evaluated by ball-on-flat uni-directional wear testing. Tensile testing was also carried out to help elucidate what wear mechanisms were active during sliding, as well as identify whether solid lubricant inclusion impacted mechanical performance. Results showed that in all instances solid lubricant inclusion significantly influenced the friction and wear properties of resultant composites, without compromising their mechanical performance when compared with neat-PA12. More specifically, it was demonstrated that the individual additions of PTFE and MoS2 could reduce the coefficient of friction and specific wear rate of Laser Sintered PA12 components by as much as 50% and 78%, respectively.

Experimental analysis on the influence of the tool micro geometry on the wear behavior in gear hobbing

Gear hobbing is a well-established manufacturing process for cylindrical spur gears. The cutting edge of a hobbing tool is, among others, characterized by the cutting edge radius and the form-factor K. The magnitude of these parameters is ideally chosen based on the machining conditions given by the workpiece and cutting material and the cutting parameters as well as the gear and tool geometry. However, the influence of the cutting edge geometry on tool life and wear behavior is hardly known, which complicates an optimized tool design. Furthermore, the preparation process regarding the coating thickness distribution on the wear behavior is equally relevant. Therefore, the objective was to identify the influence of the cutting edge radius, the form-factor K, and the preparation process on the wear behavior of gear hobbing tools made of powder metallurgical high-speed steel (PM-HSS). Fly-cutting trials were performed as an analogy process for gear hobbing in order to study the wear behavior and identify the respective tool lives. The trials indicated that the form-factor K influences the wear behavior, while a variation of the cutting edge radius did not have a significant effect. A homogenous coating thickness could extend the tool life significantly.

Optimization of material and process parameters for plasma transferred arc hard facing for high temperature applications

The authors in this research paper have investigated the process of hardfacing, which is a well-established manufacturing process for increasing the durability of industrial components, which are subjected to extreme wear, erosion, abrasion. The objective of this study is to establish a scientific methodology to select the most suitable combinations of materials as base-deposition materials for hardfacing, specifically focusing on Nickel-based and Cobalt-based materials. In order to make an informed decision, multi-criteria decision-making method known as “Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS)” is used. This technique permits to deal with wide range of important factors, such as the materials' high-temperature resistance, wear resistance, and corrosion resistance, among others. The paper discusses a step-by-step approach to selecting the best alternative material for hardfacing by considering eight different criteria and assigning preferences to each of the available materials. The results of this methodology suggested that Stellite-6 based cobalt-based alloy is best suitable for AISI 304 grade austenitic stainless steel materials used for high temperature applications.In addition, the paper also studies the effects of various welding parameters on the hardfacing process. This includes parameters such as welding current, welding speed, powder feed rate and the type of shielding gas used. The significance of each parameter is also studied, and the results of these investigations are discussed in detail. Overall, this research paper provides a comprehensive overview of the hardfacing process and the materials and techniques that are best suited for it, making it valuable resource for professionals and researchers in the field.

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Design and Manufacturing of a Modular Low-Voltage Multimegawatt High-Speed Solid-Rotor Induction Motor

High-speed solid-rotor induction machines (HSIMs) are popular within high-speed (HS) applications because of their high rotor structural integrity and their fairly well-established manufacturing process guaranteeing high quality series products. Designing a new HS electric machine requires a multidisciplinary team to accomplish the machine performance desired. In case of a HS machine design, the components and applied materials often reach their physical limits at the rated operating condition. Therefore, the design process is highly iterative and, thus, a systematic approach has a high potential to reduce the time of the design phase significantly. In this article, a systematic design process is proposed for a modular, multimegawatt (MMW) HSIM with three radial active magnetic bearings. The process includes a traditional multidisciplinary design flow with extra critical aspects of MMW HS machines: manufacturability, bearing system, housing, and operating unit. In addition, the manufactured machine is reported. The proposed systematic design process is described, including several multidisciplinary critical design aspects of HS machinery.

Effect of AlSi10Mg0.4 long-term reused powder in PBF-LB/M on the mechanical properties

Laser-based powder bed fusion (PBF-LB/M) is a well-established additive manufacturing (AM) process capable of producing high quality parts with excellent mechanical properties. Industrial applications of additively manufactured parts require the usage of fresh powder which makes the process expensive, especially in case of AM machines with enlarged build envelopes. Processing long-term reused powder fits to economic yields with the drawback of increased porosity and incorporated oxides.In this study, a detailed analysis of components made of virgin and long-term reused AlSi10Mg0.4 powder is provided. The experiments reveal that process parameters qualified for the virgin powder are not working offhand for the reused powder, as an increase of porosity from less than 1% up to 3% and a decline of tensile strength as well as yield strength of about 15% are observed. The results indicate that powder degradation, which is based on the formation of hydroxides and oxides, has a significant impact on as-built microstructure as well as mechanical properties of additively manufactured parts. The amount of hydrogen and oxygen is measured for different powder conditions and the powder ageing process of AlSi10Mg0.4 is discussed in detail.

Improving surface quality in selective laser melting based tool making

In the last years, Additive Manufacturing, thanks to its capability of continuous improvements in performance and cost-efficiency, was able to partly replace and redefine well-established manufacturing processes. This research is based on the idea to achieve great cost and operational benefits especially in the field of tool making for injection molding by combining traditional and additive manufacturing in one process chain. Special attention is given to the surface quality in terms of surface roughness and its optimization directly in the Selective Laser Melting process. This article presents the possibility for a remelting process of the SLM parts as a way to optimize the surfaces of the produced parts. The influence of laser remelting on the surface roughness of the parts is analyzed while varying machine parameters like laser power and scan settings. Laser remelting with optimized parameter settings considerably improves the surface quality of SLM parts and is a great starting point for further post-processing techniques, which require a low initial value of surface roughness.

Heat Transfer and Solidification Methodology Involved in the Simulation of Steelmaking

The research work done in the last three decades has made continuous casting an advanced and sophisticated technology. The continuous casting process comprises many complicated phenomena in terms of fluid flow, heat transfer and structural deformation. The important numerical modeling method of the continuous casting process has been discussed in reference in this work. The present work describes molten steel flow, heat transfer, solidification, formation of the shell by solidification and coupling, etc. Continuous casting process is presently a well-established manufacturing process for steel production. The continuous casting process comprises many complicated phenomena in terms of fluid flow, heat transfer, and structural deformation. To achieve efficient and effective production, the manufacturers of steel keep on searching for new methods which increase productivity. One such kind of method has become more popular to use optimizing using numerical modeling. It describes molten steel flow, formation of the shell by solidification. With the recent advancement in metallurgical methods, the continuous casting process now becomes the main method for steel production. To achieve efficient and effective production, the manufacturers of steel keep on searching for new methods which increase productivity. In this work, we have studied and reviewed the literature to provide current information on the numerical modeling of continuous casting processes.

Porosity Reducing Processing Stages of Additive Manufactured Molding (AMM) for Closed-Mold Composite Fabrication.

This article aims to merge two evolving technologies, namely additive manufacturing and composite manufacturing, to achieve the production of high-quality and low-cost composite structures utilizing additive manufacturing molding technology. This work studied additive manufacturing processing parameters at various processing stages on final printed part performance, specifically how altering featured wall thickness and layer height combine to affect final porosity. Results showed that reducing the layer height yielded a 90% improvement in pristine porosity reduction. Optimal processing parameters were combined and utilized to design and print a closed additive manufacturing molding tool to demonstrate flexible composite manufacturing by fabricating a composite laminate. Non-destructive and destructive methods were used to analyze the composite structures. Compared to the well-established composite manufacturing processes of hand lay-up and vacuum-assisted resin transfer molding methods, additive manufacturing molding composites were shown to have comparable material strength properties.

An integrated analysis of productivity, hole quality and cost estimation of single-pulse laser drilling process

Laser drilling is a well-established manufacturing process utilised to produce holes in various aeroengine components. This research presents an experimental investigation on the effects of laser drilling process parameters on productivity (material removal rate), hole quality (hole taper) and drilling cost. Single-pulse drilling was employed to drill a thin-walled Inconel 718 superalloy plate of 1 mm thickness using pulsed Nd:YAG laser. The experiments were designed using Box-Behnken statistical approach to investigate the impacts of pulse energy, pulse duration, gas pressure and gas flow rate on the selected responses. Multi-objective optimisation was performed using response surface methodology (RSM) based grey rational analysis (GRA) to identify optimal drilling conditions aiming to maximise the MRR and minimise hole taper and drilling cost. The optimal combination of drilling parameters was found as pulse energy of 20 J, pulse duration of 6 ms, gas pressure of 100 psi and gas flow rate of 40 mm3/s. A detailed cost analysis identified labour cost, gas consumption and machine costs as the major cost elements of the laser drilling process.

Investigation on EDM Plasmas Using Time and Spatially-Resolved Optical Emission Spectroscopy

Electrical discharge machining (EDM) is a well-established non-conventional manufacturing process. The underlying working principles of EDM relay on interactions of electric discharge plasmas with the electrodes material and dielectric in micrometer gaps. Key aspects of the process, such as material removal mechanisms, are strongly related to this complex interaction. Therefore, observation of small gaps plasma-material interactions can help to better understand this particular EDM process, supply new boundary conditions for existing models, and lead to more sophisticated processing. Different methods of analysis have been used to study and explain the physics of EDM discharges. In the present work, spatially-resolved high-speed optical emission spectroscopy is used to analyze emission spectra from small gap discharges under different conditions. Results on the plasma expansion in function of time as well as time resolved profiles of plasma components and of different plasma parameters are obtained and interpreted. Optical emission spectra supported by emission spectra simulations suggest that the center of the micro discharge is dominated by highly ionized species, whereas single ionized and atomic species are more uniformly distributed over the whole plasma. Furthermore, the spatially-resolved measurements shows that the center of the plasma is not in thermodynamic equilibrium, probably field emission leads to an ion-enhanced FE driven Townsend discharge in the small gaps.

Electroporation of a nanoparticle-associated DNA vaccine induces higher inflammation and immunity compared to its delivery with microneedle patches in pigs

DNA vaccination is an attractive technology, based on its well-established manufacturing process, safety profile, adaptability to rapidly combat pandemic pathogens, and stability at ambient temperature; however an optimal delivery method of DNA remains to be determined. As pigs are a relevant model for humans, we comparatively evaluated the efficiency of vaccine DNA delivery in vivo to pigs using dissolvable microneedle patches, intradermal inoculation with needle (ID), surface electroporation (EP), with DNA associated or not to cationic poly-lactic-co-glycolic acid nanoparticles (NPs). We used a luciferase encoding plasmid (pLuc) as a reporter and vaccine plasmids encoding antigens from the Porcine Reproductive and Respiratory Syndrome Virus (PRRSV), a clinically-significant swine arterivirus. Patches were successful at inducing luciferase expression in skin although at lower level than EP. EP induced the cutaneaous recruitment of granulocytes, of MHC2posCD172Apos myeloid cells and type 1 conventional dendritic cells, in association with local production of IL-1β, IL-8 and IL-17; these local responses were more limited with ID and undetectable with patches. The addition of NP to EP especially promoted the recruitment of the MHC2posCD172Apos CD163int and CD163neg myeloid subsets. Notably we obtained the strongest and broadest IFNγ T-cell response against a panel of PRRSV antigens with DNA + NPs delivered by EP, whereas patches and ID were ineffective. The anti-PRRSV IgG responses were the highest with EP administration independently of NPs, mild with ID, and undetectable with patches. These results contrast with the immunogenicity and efficacy previously induced in mice with patches. This study concludes that successful DNA vaccine administration in skin can be achieved in pigs with electroporation and patches, but only the former induces local inflammation, humoral and cellular immunity, with the highest potency when NPs were used. This finding shows the importance of evaluating the delivery and immunogenicity of DNA vaccines beyond the mouse model in a preclinical model relevant to human such as pig and reveals that EP with DNA combined to NP induces strong immunogenicity.

3D Printing Methods for Pharmaceutical Manufacturing: Opportunity and Challenges.

A recently FDA approved 3D printed drug is paving a path for new pharmaceutical manufacturing era. The 3D printing is a novel approach of producing 3D pharmaceuticals from digital designs, in a layer-by-layer fashion. However, traditional manufacturing of drug products is being carried out from decades with well-established manufacturing processes and with well approved regulatory guidelines but these processes are too obsolete in concern of process aptitude and manufacturing flexibility. On the other hand, 3D printing provides a competitive flexibility in terms of personalized drug dosage forms with complex geometries that will be made on-demand with desired drug release kinetics, hence providing the formulator a substantial provision of improvising the safety and efficacy of the drugs. Furthermore, this novel 3D technology allows tailoring of composite tissue scaffolds and sample models for characterization that closely mimic in-vivo simulations. Nevertheless, certain limitations are there in terms of regulatory aspects hindering the launch of 3DP products in the market. Exhaustive search were made on Google Scholar and PubMed databases concerning 3-D printing methods, drug delivery applications, and past to present evolution of personalized medicine. Although a high magnitude of progress have been made on 3-D printing techniques in a short span of time, still inkjet, nozzle-based deposition, stereolithography and selective laser sintering techniques are the most popular ones. Their application is adapted in the fabrication of tablets, implants, polypills and nanoparticles. 3D printing is revolutionizing the pharma expectations towards customized medicines but still there is a need to explore the aspects of cost, flexibility and bioequivalence. The present review provides a comprehensive account of various 3D printing technologies and highlights the opportunities and key challenges of 3D printing relevant to pharmaceuticals.

Approach Towards Surface Improvement in Additively Manufactured Tools

Abstract Additive Manufacturing has arisen as a ground-breaking set of technologies that, thanks to their capability of continuous improvements in performance and cost-efficiency, was able in the last years to replace well-established manufacturing processes. Proficiency in the fabrication of highly complex parts forced this astonishing development. This research is based on the idea that through the integration of additive and conventional manufacturing technologies it is possible to achieve great cost and operational benefits especially in the field of tool making for injection molding. Such an integrated manufacturing solution could overcome the limitations of independent additive, subtractive, and post-processing procedures by strengthening their potentialities. The present study highlights the opportunities of a synergy between the above-mentioned manufacturing technologies for the optimized fabrication of injection molds. An additive manufacturing process chain is presented, and special attention is given to the surface quality and its optimization directly in the Selective Laser Melting process. The potentialities of the Laser Surface Re-melting technique are analyzed, and the process optimization leads to a reduction of 45% of the average roughness directly in the SLM process.

Process characterization of powder based laser metal deposition on thin substrates

Powder-based laser metal deposition is a well-established generative manufacturing process in the field of tool and mould building to produce or repair components. Conventionally manufactured tools are often completely constructed of a high-alloyed, hardened-tempered, and expensive tool steel. An alternative way to manufacture tools and moulds is the combination of a cost-efficient, mild steel, and a functional coating. Such specific, locally adapted coating can be generated by laser metal deposition. The functional coating is just located in the area of the interaction zone of the tool. Consequently, costs and resources can be saved. Such coatings are created by positioning multiple individual weld tracks next to and on top of each other in an overlapping manner. It is therefore useful to characterize und optimize the individual weld track. Thermal processing methods, like a laser metal deposition, are always characterized by thermal distortion. The resistance against the thermal distortion of the work piece is decreasing with the reduction of the material thickness. Thus, there is a special process management for the laser based coating of thin-walled parts or tools with a small material thickness needed to reduce thermal distortion. The experimental approach in the present paper is to keep the energy and the mass per unit length constant by varying the laser power, the feed rate, and the powder mass flow. The typical seam parameters (such as width, height and depth, cross-sectional area, and angular distortion) are measured in order to characterize the cladding process, define process limits, and evaluate the process efficiency of an individual weld track. Ways to optimize dilution, angular distortion, and clad height are presented. After the characterization of individual weld tracks, optimized process parameters are deduced from the process window and used to create functional, two-dimensional coatings on thin substrates. Different scanning strategies are compared with each other to reduce processing time and thermal distortion.

Porous Nanocrystalline Silicon Supported Bimetallic Pd-Au Catalysts: Preparation, Characterization, and Direct Hydrogen Peroxide Synthesis.

Bimetallic Pd-Au catalysts were prepared on the porous nanocrystalline silicon (PSi) for the first time. The catalysts were tested in the reaction of direct hydrogen peroxide synthesis and characterized by standard structural and chemical techniques. It was shown that the Pd-Au/PSi catalyst prepared from conventional H2[PdCl4] and H[AuCl4] precursors contains monometallic Pd and a range of different Pd-Au alloy nanoparticles over the oxidized PSi surface. The PdAu2/PSi catalyst prepared from the [Pd(NH3)4][AuCl4]2 double complex salt (DCS) single-source precursor predominantly contains bimetallic Pd-Au alloy nanoparticles. For both catalysts the surface of bimetallic nanoparticles is Pd-enriched and contains palladium in Pd0 and Pd2+ states. Among the catalysts studied, the PdAu2/PSi catalyst was the most active and selective in the direct H2O2 synthesis with H2O2 productivity of 0.5 at selectivity of 50% and H2O2 concentration of 0.023 M in 0.03 M H2SO4-methanol solution after 5 h on stream at −10°C and atmospheric pressure. This performance is due to high activity in the H2O2 synthesis reaction and low activities in the undesirable H2O2 decomposition and hydrogenation reactions. Good performance of the PdAu2/PSi catalyst was associated with the major part of Pd in the catalyst being in the form of the bimetallic Pd-Au nanoparticles. Porous silicon was concluded to be a promising catalytic support for direct hydrogen peroxide synthesis due to its inertness with respect to undesirable side reactions, high thermal stability, and conductivity, possibility of safe operation at high temperatures and pressures and a well-established manufacturing process.

163 - The Bone: Implant Interface in Loaded and Unloaded Models

BACKGROUND CONTEXT: PEEK cages have a long clinical history for successful fusion and well-established manufacturing processes. There does however remain a concern with the hydrophobic nature of this semi-crystalline thermoplastic and the nonreactive fibrous tissue layer reported in preclinical and clinical studies. Bulk incorporation of a hydroxyapatite (HA), an osteoconductive material, is a potential solution to address the fibrous tissue interface and encourage direct bone apposition.