Determination Of Process Parameters Research Articles

On the Heuristic Procedure to Determine Processing Parameters in Additive Manufacturing Based on Materials Extrusion.

We present a heuristic procedure for determining key processing parameters (PPs) in materials-extrusion-based additive manufacturing processes. The concept relies on a design-of-experiment approach and consists of eleven “test objects” to determine the optimal combinations of key PPs values, starting with the PPs for printing the first layer and progressing to more complex geometric features, e.g., “bridges”. In each of the test objects, several combinations of the known PPs’ values are used, and only the values resulting in the best printed-part quality are selected for the following tests. The concept is intrinsically insensitive to different artefacts of the additive manufacturing machine (e.g., discrepancies between the nominal and actual nozzle diameters, and improper calibration of the feeding screws) and the optimal values of key PPs for manufacturing defect-free parts under the actual processing conditions can be determined. We validated the proposed procedure for two common commercial polymer feedstock materials, and we show that, by using the proposed procedure, it is possible to reduce the optimization time down to several hours, as well as to reduce the amount of consumed feedstock material. Tensile tests revealed a strong effect of amorphous and semi-crystalline nature of the polymer on the results of optimization. To the best of our knowledge, this is the first attempt to describe a systematic approach for optimizing PPs for materials extrusion-based additive manufacturing processes without relying on statistical data analysis or virtual simulations. The concept was implemented as a web-tool 3DOptimizer®.

Process Characterization by Definitive Screening Design Approach on DNA Vaccine Production.

Plasmid DNA is a vital biological tool for molecular cloning and transgene expression of recombinant proteins; however, decades ago, it has become an exceptionally appealing as a potential biopharmaceutical product as genetic immunization for animal and human use. The demand for large-quantity production of DNA vaccines also increases. Thus, we, herein, presented a systematic approach for process characterization of fed-batch Escherichia coli DH5α fermentation producing a porcine DNA vaccine. Design of Experiments (DoE) was employed to determine process parameters that have impacts on a critical quality attribute of the product, which is the active form of plasmid DNA referred as supercoiled plasmid DNA content, as well as the performance attributes, which are volumetric yield and specific yield from fermentation. The parameters of interest were temperature, pH, dissolved oxygen, cultivation time, and feed rate. Using the definitive-screening design, there were 16 runs, including 3 additional center points to create the predictive model, which then was used to simulate the operational ranges for capability analysis.

Thermal Hazards for Autocatalysis and Stability in CSTR: Decomposition of Solution from Nitrolysis of Hexamethylenetetramine

AbstractNitrolysis solution is a kind of spent acid, obtained after the nitration and ripening of hexamethylenetetramine (HA). Its decomposition is generally spontaneous and hazardous. Therefore, the thermal hazards of a real nitrolysis solution were studied here. The prepared nitrolysis solution was analysed by isoperibolic experiments, differential thermal analysis (DTA), accelerating rate calorimetry (ARC), and a bursting point test. We employed non‐linear regression and ordinary differential equation (ODE) fitting methods to obtain kinetic parameters, such as 120.73 kJ mol−1 of the activation energy (E), 36.388 s−1 of the natural logarithm of the pre‐exponential factor (lnA), 1.155 of the reaction order, and 0.6615 of the catalytic index. Based on these kinetic parameters, thermal safety parameters were obtained to evaluate the hazards of a real nitrolysis solution from four aspects: severity, thermal stability, process hazards, and thermal sensitivity. The results indicate critical severity, high process hazards and thermal sensitivity, and very low thermal stability. The hazards due to real nitrolysis solution are higher than those of nitric ester explosives and azos. Further, the value of the initial mass ratio between the concentrated nitric acid and HA could severely pose safety risks during the nitration process. Additionally, the sensitivity analyses of the four process parameters (space‐time of CSTR, τCSTR; feeding temperature, T0; ambient temperature, Ta; specific cooling capacity, hS/V) were performed under the critical conditions for thermal stability in a continuous stirred tank reactor (CSTR). The suited margin of Ta could be 333.15–342.81 K with other determined process parameters.

Optimizing multi-requirements of surface finishing in magnetic abrasive cutting process using grey relational analysis

Mechanical machining inevitably generates undesirable parts on the surface of workpieces. It brings adverse effects in terms of manufacturing cost, surface fineness, malfunction, and lifetime. In order to achieve precise surface with high geometric accuracy, this study proposes a magnetic abrasive cutting (MAC) process to improve surface roughness and make burr-free on the surface of STD-11. All the experiments were conducted by Taguchi’s orthogonal array method with four determined process parameters and three levels. The results analyzed by signal-to-noise (S/N) ratio and analysis of variance (ANOVA) showed that the working gap was the most contribution to the fine surface with 69.9 %, and viscosity of silicone oil affected high geometric precision with 54.1 %. In addition, to satisfy multiple requirements for improving burr removal and surface roughness simultaneously, grey relational analysis (GRA) was employed. From the analysis, the best configuration was at 1.0 mm of the working gap, 600 rpm of spindle speed, 150000 cs of silicone oil, and 1:3 of mixing ratio of abrasive grains and ferromagnetic particles. This study clearly showed that the MAC process assisted by magnetic force was useful to satisfy multi-objective optimization for surface roughness reduction and burr removal.

Crystallization process modifications to address polymorphic and particle size challenges in early stage development of an API salt

A case study highlighting the risk of generating undesired hydrate polymorph following seeded distillative crystallization of an active pharmaceutical ingredient (API) from aqueous alcoholic solution and a strategy to overcome the issue is presented. The API salt had two known crystalline forms, the desired anhydrate Form A, and hydrate Form B. Importance of water content at the time of seeding to minimize the risk of precipitation of From B is emphasized. A novel approach termed distillative pathway diagram (DPD) was developed to assess the risk of generation of Form B at larger scales. The application of this diagram to determine process parameters to address form issues during distillative crystallization is explained. Given the likely risk of Form B precipitation predicted by DPD, an alternate non-aqueous antisolvent crystallization process was developed that provided both form and particle size control.

CFD modelling of air staged combustion in a wood pellet boiler using the coupled modelling approach

Optimal geometric and process parameters related to air staging, which ultimately lead to lower pollutant formation and a higher thermal efficiency, can be found by utilisation of the CFD simulation method. Simplified and computationally efficient methods for the simulation of complex phenomena which occur in a biomass boiler can, therefore, be of great use, provided they offer reliable and reasonably accurate predictions. A previously developed and validated Computational Fluid Dynamics combustion simulation methodology for large-scale waste to energy grate-fired boilers is modified and implemented for the case of a commercial 32 kW wood pellet hot water boiler. An experimental investigation is performed in order to determine process parameters used in the fuel conversion modelling, case setup and, finally, to enable the validation of the numerical modelling approach. The solid fuel conversion is modelled by a coupled empirical 1D bed model which predicts the composition of the combustible gas mixture released from the fuel bed into the freeboard. Compared to the originally proposed fuel bed conversion model, the modified model includes partial char and volatile oxidation, and relies on gas temperatures measured above the fuel bed. Using the modified fuel bed conversion model, several cases were simulated in order to find the most appropriate parameters of the combined finite rate – eddy dissipation combustion model. Results show that by implementing the modified fuel bed conversion model that relies on measurements, reasonably accurate predictions can be achieved of the gas temperature in the combustion chamber and CO concentration at the flue gas outlet.

Influence of Selective Laser Melting Process Parameters on Densification Behavior, Surface Quality and Hardness of 18Ni300 Steel

This study investigated the effect of laser power (P), scan speed (v) and hatch space (h) on densification behavior, surface quality and hardness of 18Ni300 maraging steel fabricated by selective laser melting (SLM). The results indicated that the relative density of the SLMed samples has a shape increase from 73% to 97% with the laser energy density increasing from 0.5 to 2.2 J/mm2. The relative density ≥ 99% was achieved at the energy density in the range of 2.2~5.9 J/mm2. The optimum process parameters were found to be laser power of 150~200 W, scan speed of 600mm/s and hatch space of 0.105mm. In addition, it was found that the hardness increased initially with the increasing relative density up to relative density of 90% and then little relationship, but finally increase again significantly. This work provides reference for determining process parameters for SLMed maraging steel and the development of 3D printing of die steels.

Generic method of printing window adjustment for extrusion-based 3D-bioprinting to maintain high viability of mesenchymal stem cells in an alginate-gelatin hydrogel

Over the last decade, bioprinting of artificial tissues has been developed into a significant field of research. With an increasing number of printing technologies and bioinks used in bioprinting, its complexity increases as both the printing technology and the properties of the bioink influence the cell biological functionality and printing accuracy of the printed tissue. Therefore, optimization of bioprinting processes often remains a challenge, which could be solved by a smart fine-tuning of the process parameters. We present a novel method to adjust the printing window for extrusion-based bioprinting on the basis of a two-step assessment to determine process parameters such as nozzle size, extrusion flow rate, and printing temperature. First, a suitable printing temperature is deduced from the bioink properties and second nozzle size and extrusion flow rate is selected in a way that the immediate cell damage after printing is reduced. For both steps only basic rheological properties of the bioinks need to be known as well as detailed knowledge of the cell survival in the bioink for different shear stresses.This method is applied to an exemplary alginate-gelatin hydrogel to show how the printing temperature affects the achievable printing accuracy. For this bioink, viability of immortalized mesenchymal stem cells (iMSC) decreases with about 4% per thousand Pascal increase in maximum shear stress. For different combinations of flow rate, nozzle size and nozzle shape it is shown, that only the maximum shear stress experienced by the iMSCs influences average cell viability. Factors like flow rate, nozzle size and shape only play an indirect role by influencing the maximum shear stress and individually have no significant influence on cell viability.The experimental results allow a direct adjustment of printing parameters for the presented combination of hydrogel and cell type but are not limited to it. For other bioinks, the described generic method can be easily used to systematically adjust the printing parameters. For this purpose, only the basic rheological properties and the influence of shear stress on cell survival need to be known and process parameters can be set concerning the respective application.

MAG Welding of Structures Used in Means of Transport and Made of Steel DOCOL 1200M

Steels of the DOCOL group, characterised by high tensile strength and yield point, play an important role in the manufacturing of means of transport. However, the above-named steels are difficult to weld and joints made in them do not guarantee comparable mechanical properties. The research work discussed in the article aimed to determine process parameters suitable for the welding of a moving platform made of steel DOCOL 1200M as well as to assess the effect of welding parameters on the quality of obtained joints. The tests also involved analysing the effect of shielding gases, preheating and interpass temperature on the quality of an 8 mm thick MAG welded moving platform structure.

Improving the technological process of restoring the tillage machine working parts

An analysis of the wear of machine parts has made it possible to establish characteristic requirements for the technological process of restoring worn surfaces. Experimental studies on hardening the working surfaces of plowshares have made it possible to determine processing parameters: oscillation frequency of the processing tool of 1,400 min -1 , the oscillation amplitude of 0.5 mm and processing time of 20 s. Studies of the influence of conventional and vibration working on strength characteristics were carried out first on models and then on actual parts. New shares served as models. Experimental studies of these shares provided the identity of the nature of the cutting element wear. The sameness of the model and the actual part deformation degree was provided by the same conditions of the passage of the hardening processes. The trustworthiness of the results of experimental studies was assessed in accordance with the law of theoretical distribution at a given value of confidence probability α=0.95. The studies have established that the share width of 116–117.5 mm which has a certain effect on the share efficiency corresponds to the highest probability of 0.39. It has been experimentally established that the degree of hardening of the shares made of L-53 steel and surfaced with sormite and vibration hardened is 1.85 times greater than in conventional processing. The studies have made it possible to determine the nature of change in the share shape and thickness of the cutting edge and choose a more efficient process of its restoration by vibration hardening. A method of recovering shares by welding strips of 45 steel with automatic hard surfacing and vibration hardening was proposed

Prediction of initial transient behavior with stationary heating during laser powder bed fusion processes

Laser powder bed fusion (L-PBF) has become a popular additive manufacturing process. To minimize the need to perform experimental trial-and-error based searching, physical models can be used to determine process parameters to achieve desirable process conditions. In this paper, a physics-based predictive model is presented to describe the underlying physics of L-PBF during the initial highly transient process of molten pool and keyhole formation during spot heating, i.e., zero-velocity, finite-duration laser energy addition to a Ti-6Al-4V/Ti-6Al-4V powder bed system. The simulation presented herein uses a computationally-efficient volumetric energy addition method to describe energy transfer to the particles during melting and ray-tracing to account for attenuated beam energy reaching the substrate through the powder bed. Validation of the model was performed against imagery captured from synchrotron measurements of a static L-PBF process which showed a keyhole welding mode for each of two power settings. The model presented herein was able to describe the laser energy absorption, molten bead formation, keyhole welding mode, and showed excellent correlation of keyhole and molten bead dimensions for each of the cases presented.

Методика определения технологических параметров ремонта трубопровода с ненормативной кривизной

Pipe sections with curvatures exceeding the required specified values are often found during the pigging of major pipelines. Process parameters for repairs have to be defined in order to develop a maintenance project that also includes works to restore the specified status of the section found. A corresponding method is known for cases of relocation of an initially straight pipeline. The authors developed a method for determining process parameters for repairing pipelines with out-of-project axis curvature. The method is based on modeling the deformation of a pipeline with initial axis curvature; it takes into account the actual operating conditions of the pipeline and in-line inspection data. Examples of calculating process parameters for repairs and stress-deformed state of pipeline sections with out-of-specs curvature have been presented. The modeling results confirm the possibility of using the method for evaluating the repair process parameters, the length of the required trench exposure, and the magnitude and boundaries of additional digging-in or the need to lift the pipeline in order to determine the stress–strain state of the pipeline section to be repaired during execution and after the completion of repairs.

Removal of Cu2+, Zn2+ and Pb2+ ions using a graphene-containing nanocomposite: a kinetic study

In the present paper, the urgent issue of removing heavy metal ions from aqueous solutions is considered by the example of extraction of Cu2+, Zn2+ and Pb2+ ions using an innovative sorbent - polyhydroquinone/graphene nanocomposite. Kinetics of the metal sorption on this material was studied. Moreover, the effect of solution pH on the sorption capacity of the nanocomposite was estimated. Besides, to elucidate mechanisms of kinetic removal and determine process parameters, experimental data were fitted to kinetic (pseudo-first- and pseudo-second-order, and Elovich) and diffusion (intraparticle and Boyd) models. The kinetic experiments showed that equilibrium is reached within 60 min. The effective diffusion coefficient values calculated according to the Boyd model were found to increase in the following sequence: Pb2+ (1.26 10-13 m2 s-1) < Zn2+ (3.74 10-13m2 s-1) < Cu2+ (4.24 10-13 m2 s-1). Finally, it was established that the metal sorption process is controlled by the internal diffusion of the sorbate into the bulk (volume) of the sorbent.

Kesan Proses Pembentukan Tuangan Reo terhadap Sifat Mikrostruktur dan Mekanikal Aloi Al-5.7Si-2Cu-0.3Mg

This study shows the results of an experimental investigation of semisolid rheocasting of Al-5.7Si-2Cu-0.3Mg alloy using a cooling slope (CS) casting technique. However, the challenge is to determine process parameters of the CS process to get a desirable microstructure in the semisolid feedstock material. cooling slope technique was employed to create feedstock material for thixoforming under an argon gas atmosphere, where on an inclined plate that was fixed at a 60° slope angle, molten alloy is poured at different temperatures of 640°C, 650°C and 660°C at lengths 300, 400 and 500 mm. Examination the microstructure with optical microscope observed that the microstructure of conventionally cast alloy presented coarse and dendritic primary α-Al phase, whereas rheocast alloy included fine and nondendritic primary α-Al phase with homogeneous distribution of eutectic phase. The best CS processing condition has been identified for optimum pouring temperature of 650°C and the slope length of 400 mm as average globular grain size of around 31.67 ± 3 μm and a shape factor of about 0.66 ± 0.09 were obtained. The mechanical properties of conventional cast alloy were enhanced by the CS casting process. The ultimate tensile strength, the yield strength and elongation of the rheocast alloy were increased by 10%, 12% and 22% respectively compared to the conventional cast alloy. due to a reduction in shrinkage and porosity of the microstructure of the CS alloy.

Techno-economic analysis of producing liquid fuels from biomass via anaerobic digestion and thermochemical conversion

This paper discusses a preliminary design and a techno-economic analysis of a process that produces liquid hydrocarbon fuels from biomass through a combined biochemical and thermochemical process. The biochemical component involves anaerobic digestion (AD) of the biomass's biodegradable portion to produce biogas. Biogas is purified by removing contaminants and upgraded to liquid hydrocarbon fuel in a biogas to liquid facility (BGTL) via thermochemical conversion route. The BGTL process involves two major steps: tri-reforming to produce syngas (a mixture of CO and H2), and, Fischer-Tropsch Synthesis (FTS) to convert the syngas to a spectrum of hydrocarbons (synthetic crude). Separation and upgrading of the produced hydrocarbon mixture allows production of transportation fuels such as gasoline, jet fuel, and diesel.In order to evaluate the economics of the combined process a detailed process modelling was carried out using Aspen Plus® software. Bench-scale experimental results served as the basis of modelling the BGTL section of the plant, while the AD portion of the plant is based on empirical models selected from the literature validated by comparison with experimental results. Recent bench scale tests in our lab were used to determine processing parameters (yield, temperature, and pressure) for the reforming and FTS conversion.A plant capable of processing 90,000 tonne year−1 of wet biomass feed was designed and analyzed using the model. Results of the economic analysis estimate that a breakeven cost of diesel of $1.30 L-1 is achievable without the consideration of charging tipping fees to accept the biomass feedstock. Sensitivity study shows that the economics are significantly affected by the fixed capital investment (FCI) and less so by the operating expenses and interest rate. In addition, tipping fees and biomass feedstock cost have a substantial effect on the breakeven price of diesel.

Parameter optimization of aluminum alloy thin structures obtained by Selective Laser Melting

ABSTRACTSelective Laser Melting (SLM) involves numerous fabrication parameters, the interaction between those parameters determine the final characteristics of the resulting part and because of the latter, it is considered a complex process. Low-density components is one of the main issues of the SLM process, due to the incorrect selection of process parameters. These defects are undesired in high specialized applications (i.e. aerospace, aeronautic and medical industries). Therefore, the characterization of the defects (pores) found in aluminum parts manufacture by SLM and the relationship with fabrication parameters was performed. A robust orthogonal design of experiments was implemented to determine process parameters, and then parts were manufactured in SLM. Relative density of the samples was then characterized using the Archimedes principle and microscopy; the data was then statistically analyzed in order to determine the optimal process parameters. The main purpose of the present research was to establish the best processing parameters of an in-house SLM system, as well as to characterize the pore geometry in order to fully eliminate pores in a future research.

Study of Rheological Properties of Modified Concrete Mixtures at Vibration

Study of rheological properties of concrete mixtures based on modified cement systems in order to determine process parameters. Methodology. To study structural-mechanical properties of modified concrete mixtures of different consistency at their horizontal vibrating displacement an oscillatory viscometer was designed. Results. The optimization of the process of vibration displacement of concrete mixtures with the specification of parameters of vibration impacts taking into account structural-mechanical properties of the mixture is performed. It has been established that the viscosity of the modified cement system of the concrete mixture is a variable quantity, which depends on the parameters of the vibration impacts. Scientific novelty. The mechanism of interaction of the modified concrete mixture with the form and the table vibrator during its vibration compaction is determined. On the basis of this, a model of concrete laying process control is proposed, that allows to predict the ability to form a dense concrete structure. Practical significance. Disclosed physical nature of the process of vibrating displacement of modified concrete mixtures using the principles of physical-chemical mechanics of concrete allows reasonably choose the best options for vibration impacts.

Picosecond pulsed laser ablation of dielectric rods: Angle-dependent ablation process model for laser micromachining

The ablation of fused silica and sapphire is investigated from the perspective of laser micromachining. In this study, dielectric rods are machined using a 12 ps pulsed laser at 1064 nm wavelength. The machining of the rods is a calibration method to determine process parameters for an analytical ablation model. More specifically, the ablation threshold fluence and effective penetration depth are determined under process-relevant conditions due to the removal of macroscopic volumes, which leads to a higher accordance. The introduced ablation model predicts macroscopic ablation volumes and ablation efficiencies of dielectric materials as a function of the angle of incidence. Originally, the ablation process model was developed for metals under the normal incidence, but this work extends its applicability to dielectrics. In contrast to metals, the optical penetration depth should be independent of the angle of incidence. Altogether, the presented model is universally applicable and can be seen as a first step toward computer-aided 3D-manufacturing using ultrashort pulsed lasers. The ability to predict ablation volumes and machine heat-sensitive tool materials with high accuracy and precision is demonstrated by the fabrication of end mills made of fused silica and sapphire with a diameter of 1 mm. This shows that picosecond lasers are well suited for the fabrication of such microcutting tools. In particular, the ability of ultrashort pulses to ablate materials independent of their hardness and without any wear makes this technology highly promising for the tooling industry.

Leaching of lead and copper from flash smelting slag by citric acid

As a direct-to-blister copper flash smelting slag contains important levels of copper (14%) and lead (2–4%) it is subjected to a process of high temperature reduction. To recover copper as well as lead the slag is subjected then to a process of decopperization by reducing the oxide metal compounds in an electric furnace. This study presents an alternative to the above process by recovering Pb and Cu from the slag by a hydrometallurgical route using citric acid solutions. The objective of this study was to determine process parameters at which the effectiveness of the lead leaching process is greatest with the minimum transfer of copper to the solution. This paper presents the results of laboratory tests on flash smelting slag leaching with citric acid solutions. Process parameters (time, temperature, citric acid concentration, l/s ratio) at which the Pb concentration decreases from the initial value (3.05%) to the value of 0.41–0.6% in the post-leaching sediment were determined. Analogous values for copper were 12.44% (before leaching) and 11.5–11.8% (after). The lead and copper content was determined by atomic absorption spectrometry (AAS). The hydrometallurgical method could successfully replace the existing treatment of slag in an electric furnace and converter.

Determining process parameters for successful material reclamation of lead-free brass chips using hot forging operations: Lubrication

When small and hollow components are being manufactured, it is not uncommon that a majority of the workpiece material is removed by machining. A demand for parts made with lead-free brass alloys can potentially increase the manufacturing cost and therefore it is necessary to investigate ways to increase the material utilization. As part of a more resource efficient production, a method for reusing chips from metal cutting in brass using hot forging operations is investigated.In this study, the brass alloy CW724R is used. Different lubrication agents are used, including mineral oil and vegetable oil with and without addition of nano-sized graphite platelets, GnP, in the production of green compacts. Material properties of the green compacts and the finished products are analyzed using mechanical testing and microscopy. Quality of the finished product is evaluated using multi-variable regression analysis. The results of the statistical analysis indicate the best mechanical properties when using 0.2 – 0.25 vol. % GnP suspension in oil and 0.15 – 0.2 wt. % oil mixed with the chips before compaction. Microscopy shows diffusion bonding between the chips after forging, yet some porosities is still observed. This indicates potential for the investigated material reclamation method.