Relevant Process Parameters Research Articles

An outcome-based process optimization model using fuzzy-based association rules

PurposeThe purpose of this paper is to propose an outcome-based process optimization model which can be deployed in companies to enhance their business operations, strengthening their competitiveness in the current industrial environment. To validate the approach, a case example has been included to assess the practicality and validity of this approach to be applied in actual environment.Design/methodology/approachThis model embraces two approaches including: fuzzy logic for mimicking the human thinking and decision making mechanism; and data mining association rules approach for optimizing the analyzed knowledge for future decision-making as well as providing a mechanism to apply the obtained knowledge to support the improvement of different types of processes.FindingsThe new methodology of the proposed algorithm has been evaluated in a case study and the algorithm shows its potential to determine the primary factors that have a great effect upon the final result of the entire operation comprising a number of processes. In this case example, relevant process parameters have been identified as the important factors causing significant impact on the result of final outcome.Research limitations/implicationsThe proposed methodology requires the dependence on human knowledge and personal experience to determine the various fuzzy regions of the processes. This can be fairly subjective and even biased. As such, it is advisable that the development of artificial intelligence techniques to support automatic machine learning to derive the fuzzy sets should be promoted to provide more reliable results.Originality/valueRecent study on the relevant topics indicates that an intelligent process optimization approach, which is able to interact seamlessly with the knowledge-based system and extract useful information for process improvement, is still seen as an area that requires more study and investigation. In this research, the process optimization system with an effective process mining algorithm embedded for supporting knowledge discovery is proposed for use to achieve better quality control.

Process parameters tuning and online re-slicing for robotized additive manufacturing of big plastic objects

Abstract Complex parts can be successfully manufactured by means of Additive Manufacturing (AM) techniques based on thermoplastic polymer extrusion, whose use for mass production is restricted by their slow printing speed. To address this limitation, a flexible AM platform for big plastic objects has been realized mounting an industrial screw-based extruder on an anthropomorphic robot. An experimental campaign has been performed to set a suitable range of relevant process parameters, with the aim of ensuring a regular deposited layer geometry. Moreover, a closed-loop control strategy has been developed to correct the robot height based on data measured during the material deposition, thus further improving the process parameter setting and compensating the material shrinkage or other unexpected defects. Eventually, an online re-slicing algorithm has been implemented to preserve the desired height of the manufactured object, despite the layer height changes. The proposed approach allows a deposition flow rate up to 1250 cm3/h within a building volume limited only by the robot workspace.

Biofabrication of glass scaffolds by 3D printing for tissue engineering

This paper reports a study on the development of bioactive glass powders for biofabrication of scaffolds by an additive manufacturing technique, three-dimensional printing (3DP). Several formulations of the glass were developed from the CaO·P2O5·TiO2 system and prepared on the basis of the results for the commercial powder characterization (average particle size, particle size distribution, microstructural and crystallographic analysis). For printing the glass models in the prototyping machine, a virtual model defined as the “standard model” was produced in commercial powder, and a systematic study of the relevant processing parameters (binder composition, formulation of powder, saturation level in the shell and core, bleed compensation, and printed layer thickness) was carried out in order to determine the most suitable conditions for the fabrication of porous structures for tissue engineering applications. The printed glass models were sintered through specific thermal programs and then characterized in terms of dimensions, structure, morphological features, and mechanical properties. Finally, the sintered models were submitted to mineralization tests in simulated physiological media. In this work, it was demonstrated that it is possible to use a printing machine to manufacture 3DP glassy porous structures with suitable features for tissue engineering applications as temporary scaffolds. The mechanical properties of the produced structures and its mineralization capability in physiological fluids suggest that they have potential to be used in bone tissue regeneration under low load-bearing situations.

Indirect Microwave Curing Process Design for Manufacturing Thick Multidirectional Carbon Fiber Reinforced Thermoset Composite Materials

Recently, indirect microwave curing technology was developed to process multidirectional carbon fiber reinforced composite materials with high efficient and energy saving purpose. The aim of this paper is to solve the problem of large mid-plane heat generation in manufacturing this kind of materials with large thickness. The difference between the traditional thermal curing and indirect microwave curing processes was analyzed. A Multiphysics model was constructed to reflect the composite curing behavior in a cost-effective manner, which agreed well with the experimental results. On this basis, a new indirect microwave curing cycle was designed, and relevant process parameters were determined. Compared with the manufacturer’s recommended cycle, the degree of mid-plane heat generation was greatly relieved, and a reduction of 34.6% in composite residual strains was achieved. Moreover, the curing cycle was reduced by 38%, while the interlaminar shear strength of the composite was improved by 1.38 times. Corresponding reinforcement mechanisms were explored through the observation of composite cross-sections with optical microscopes.

Roll-to-Roll Mechanical Peeling for Dry Transfer of Chemical Vapor Deposition Graphene

Scaling up graphene fabrication is a critical step for realizing industrial applications of chemical vapor deposition (CVD) graphene, such as large-area flexible displays and solar cells. In this study, a roll-to-roll (R2R) graphene transfer system using mechanical peeling is proposed. No etching of graphene growth substrate is involved; thus, the process is economical and environmentally benign. A prototype R2R graphene transfer machine was developed. Experiments were conducted to test the effects of relevant process parameters, including linear film speed, separation angle, and the guiding roller diameter. The linear film speed was found to have the highest impact on the transferred graphene coverage, followed by the roller diameter, while the effect of separation angle was statistically insignificant. Furthermore, there was an interaction effect between the film speed and roller diameter, which can be attributed to the competing effects of tensile strain and strain rate. Overall, the experimental results showed that larger than 98% graphene coverage could be achieved with high linear film speed and large guiding roller diameter, demonstrating that a large-scale dry graphene transfer process is possible with R2R mechanical peeling.

Development of ciprofloxacin-loaded poly(vinyl alcohol) dry powder formulations for lung delivery

Polymeric microparticles are micro carriers for the sustained drug delivery of drugs in the lungs, used as alternatives to the use of established excipients. This study aims to develop and characterize inhalable ciprofloxacin (CPx)-loaded poly(vinyl alcohol) (PVA) microparticles by a single-step spray-drying procedure. The optimization of the processing parameters was achieved by an orthogonal design of the most relevant processing parameters (polymer concentration, feed rate and inlet temperature). The obtained spray-dried particles showed a drug encapsulation efficiency higher than 90%. Furthermore, PVA-CPx formulations, with drug contents up to 10 wt%, showed a morphology and size suitable for inhalation, with a sustained release profile over 24 h. Data from Fourier transformed infra-red spectroscopy and differential scanning calorimetry indicated absence of interaction between the polymer matrix and the drug. Aerodynamic assessment of PVA-CPx 10 wt% was determined by the next generation impactor (NGI), using spray-dried CPx as a control. The results showed improved values of mass median aerodynamic diameter (5.06±0.10μm) and a fine particle fraction (39.78±0.98%) when comparing with the CPx alone (5.33±0.39μm and 30.43±1.38%). This study highlights the potential of spray-dried PVA microparticles as drug carriers for lung local delivery of antibiotics.

Application of the oxidation reduction potential (ORP) for process control and monitoring nitrite in a Coupled Aerobic-anoxic Nitrous Decomposition Operation (CANDO)

Energy recovery from nitrogen via nitrous oxide by applying e.g., the Coupled Aerobic-anoxic Nitrous Decomposition Operation (CANDO), is a potential key to more sustainable and energy-efficient wastewater treatment facilities. In this study, laboratory-scale investigations were conducted for the second stage of a continuously operated CANDO process over 84 cycles to test and validate the oxidation reduction potential (ORP) as operational control variable. The ORP was investigated to optimize effluent nitrite (NO2−) concentrations, nitrous oxide (N2O) yields and overall process conditions under real feed-stream conditions. Characteristic deviations for stable operational conditions, underload and overload could be derived based on representative cycles. The results revealed that continuously increasing ORP deviations are correlated to the abundance of nitrite in anoxic reaction periods and that the depletion of nitrite and nitrous oxide correlates with switching from a positive to negative ORP gradient. These observations were supported by investigating the dynamics of relevant process parameters of a single cycle. Ultimately, the reactor was successfully operated under dynamic conditions i.e., different chemical oxygen demand to nitrite ratios (COD/N) ratios, and automatically controlled by applying an ORP gradient of −1 mV/min over 20 min as termination criterion for anoxic reaction periods. This operation resulted in stable and reliable NO2− elimination. Additionally, previous observations concerning the necessity of a COD/N ratio of 4 could be confirmed concerning optimal N2O yields. A COD/N ratio of 5 compromised the N2O yield to a higher nitrogen removal rate.

Experimental Study on Optimal Parameters of Stem Wetting Procedure

The fluctuation of the moisture content of tobacco stem after storage is the most common problem in the process of tobacco stem treatment. After relevant process parameters analysis on stem wetting procedure by multi-factor orthogonal test and multiple regression analysis, it was found that the water temperature of stem washing is the significant reason for moisture content of the stems after storage, and the fitted model equation shows that the moisture content of tobacco stem after storage reaches the optimum value when the water temperature of the stem washing is 59.7i.

A combined model of heat and mass transfer for the in situ extraction of volatile water from lunar regolith

Chemical analysis of lunar soil samples often involves thermal processing to extract their volatile constituents, such as loosely adsorbed water. For the characterization of volatiles and their bonding mechanisms it is important to determine their desorption temperature. However, due to the low thermal diffusivity of lunar regolith, it might be difficult to reach a uniform heat distribution in a sample that is larger than only a few particles. Furthermore, the mass transport through such a sample is restricted, which might lead to a significant delay between actual desorption and measurable outgassing of volatiles from the sample. The entire volatiles extraction process depends on the dynamically changing heat and mass transfer within the sample, and is influenced by physical parameters such as porosity, tortuosity, gas density, temperature and pressure. To correctly interpret measurements of the extracted volatiles, it is important to understand the interaction between heat transfer, sorption, and gas transfer through the sample. The present paper discusses the molecular kinetics and mechanisms that are involved in the thermal extraction process and presents a combined parametrical computation model to simulate this process. The influence of water content on the gas diffusivity and thermal diffusivity is discussed and the issue of possible resorption of desorbed molecules within the sample is addressed. Based on the multi-physical computation model, a case study for the ProSPA instrument for in situ analysis of lunar volatiles is presented, which predicts relevant dynamic process parameters, such as gas pressure and process duration.

Studies on glycerol conversion to tricaproin over sulfate promoted iron oxide as catalyst using response surface methodology

Novel and pioneering insight towards the synthesis of remarkable tricaproin was endeavored by aqueous phase esterification of caproic acid with glycerol over sulfate promoted iron oxide catalyst. Tricaproin has good solubility with paclitaxel, an anticancer compound for nanoemulsion formation. Catalyst has also displayed tunable selectivity towards tricaproin over variable reaction parameters. The catalyst was characterized using a range of physicochemical methods such as SEM, XRD and FT-IR. Resourceful appliance of central composite design (CCD) from response surface methodology (RSM) scrutinized the interactive effects between relevant process parameters in model system portraying three dimensional surface plots. In this demeanor, caproic acid and glycerol is esterified subsequently to tricaproin with foremost selectivity of 71.6%. Detailed kinetic study was established for scaling up purposes.

Mechanical performance of wall structures in 3D printing processes: Theory, design tools and experiments

In the current contribution for the first time a mechanistic model is presented that can be used for analysing and optimising the mechanical performance of straight wall structures in 3D printing processes. The two failure mechanisms considered are elastic buckling and plastic collapse. The model incorporates the most relevant process parameters, which are the printing velocity, the curing characteristics of the printing material, the geometrical features of the printed object, the heterogeneous strength and stiffness properties, the presence of imperfections, and the non-uniform dead weight loading. The sensitivity to elastic buckling and plastic collapse is first explored for three basic configurations, namely i) a free wall, ii) a simply-supported wall and iii) a fully-clamped wall, which are printed under linear or exponentially-decaying curing processes. As demonstrated for the specific case of a rectangular wall lay-out, the design graphs and failure mechanism maps constructed for these basic configurations provide a convenient practical tool for analysing arbitrary wall structures under a broad range of possible printing process parameters. Here, the simply-supported wall results in a lower bound for the wall buckling length, corresponding to global buckling of the complete wall structure, while the fully-clamped wall gives an upper bound, reflecting local buckling of an individual wall. The range of critical buckling lengths defined by these bounds may be further narrowed by the critical wall length for plastic collapse. For an arbitrary wall configuration the critical buckling length and corresponding buckling mode can be accurately predicted by deriving an expression for the non-uniform rotational stiffness provided by the support structure of a buckling wall. This has been elaborated for the specific case of a wall structure characterised by a rectangular lay-out. It is further shown that under the presence of imperfections the buckling response at growing deflection correctly asymptotes towards the bifurcation buckling length of an ideally straight wall. The buckling responses computed for a free wall and a wall structure with a rectangular lay-out turn out to be in good agreement with experimental results of 3D printed concrete wall structures. Hence, the model can be applied to systematically explore the influence of individual printing process parameters on the mechanical performance of particular wall structures, which should lead to clear directions for the optimisation on printing time and material usage. The model may be further utilised as a validation tool for finite element models of wall structures printed under specific process conditions.

Hybrid modelling of MTO/ETO manufacturing environments for performance assessment

Performance assessment is critical in today’s competitive environments, where companies need to establish trade-offs between key competitive dimensions. The complexity of these environments calls for new approaches to performance assessment. Thus, in this work, we propose a novel conceptual framework for performance assessment in manufacturing environments combining different production strategies. Focus is laid on MTO/ETO combined environments and a three-stage problem analysis is considered. Firstly, a hybrid SD-DES-ABS model approach addresses the needs of a system that handles different types of orders, processes and workforce allocation requirements; secondly, the model results for different demand scenarios are assessed using a one-way ANOVA analysis followed by a Tukey – Kramer’s test, with pairwise comparisons for assessment of significant performance variations under different system operating policies. A full factorial Design of Experiments (DOE) analysis follows, for determining the relevant process parameters influencing the system performance. As an example of application of the proposed framework, we consider the case of an advanced manufacturing company, whose manufacturing environment encompasses combined MTO/ETO production strategies.

Friction stir welding parameters optimization for tailored welded blank sheets of AA1100 with AA6061 dissimilar alloy using response surface methodology

Presently, tailored welded blank (TWB) sheets have found various applications in automotive, aeronautical and many other industries. The most popular method for production of TWB sheets is friction stir welding (FSW) process. In this investigation, an attempt has been made to develop an empirical relationship between FSW parameters and tensile strength of the friction stir welded AA1100 with AA6061 aluminum alloys. To obtain the desired strength, it is essential to have a complete control over the relevant process parameters to maximize the tensile strength for forming of TWB on which the quality of a weldment is based. Therefore, it is very important to select and control the welding process parameter for obtaining maximum strength. To achieve this statistical tool such as response surface method (RSM), analysis of variance (ANOVA), Students t-test, coefficient of determination, etc., can be applied to define the desired response through developing mathematical model s to specify the relationship between the output response and input variables. Four factors, five levels central composite design have been used to minimize number of experimental conditions. The developed mathematical relationship can be effectively used to predict the tensile strength of FSW joint s of AA1100/ AA6061 aluminum alloy at 95% confidence level.

Retention of Acholeplasma laidlawii by Sterile Filtration Membranes: Effect of Cultivation Medium and Filtration Temperature.

ALCM: A. laidlawii culture medium; ASTM: American Society for Testing and Materials; ATCC: American Type Culture Collection; CFU/mL: colony-forming units per milliliter; DLS: Dynamic light scattering; LRV: Log reduction value; PES: Polyethersulfone; PFU/mL: Plaque-forming units per milliliter; PSD: Particle size distribution; PVP: Polyvinylpyrrolidone; SDS: Sodium dodecyl sulfate; SEM: Scanning electron microscopy; SLB: Saline lactose broth; TMP: Transmembrane pressure; TSB: Tryptic soy broth.

Additive manufacturing of metal components with the ARBURG plastic freeforming process

Using the ARBURG freeformer in the metal injection molding (MIM) process chain instead of an injection molding machine for molding the parts constitutes a new approach for the additive production of sintered metal components. Its main benefits are toolless manufacturing and using the conventional MIM feedstock. This paper presents this kind of approach with a carbonyl iron feedstock. The investigation includes the determination of the influences of the relevant printing process parameters on the mechanical properties of the sintered parts and the comparison with MIM. Experimental results are discussed, including an analysis of microsections, density, tensile strength Rm and shrinkage.

Smart Manufacturing of Thermoplastic CFRP Skins

High performance aerospace structures often require a combination of innovative materials and new production technologies. Carbon fiber reinforced thermoplastics (CFRTP) have shown their potentials over the last decades especially due to their competitive production rates. Thermoplastic matrix systems allow joining by welding, which is a major advantage for assembly. Production systems for flat thermoplastic organic sheets are readily available on the market, as well as advanced fiber placement and tape laying machines (AFP/ATL). But there is a lack of systems capable of fabricating 3D-curved, near net shaped patch preforms that may serve for mass-customization of standard parts, e.g. for future aerospace panel production. With the composite prepregs being stacked within the mold the fibers will undergo less reshaping during consolidation (i.e. debulking) thus giving a better control over fiber angles. We describe an autonomous smart manufacturing system that is capable of handling unique parts by means of a complete digital workflow from part design over automated cut-piece fabrication, generation of system related meta-information, virtual planning of grip and drop up to the final layup. The system consists of a preprocessing and production planning apps, an industrial robot, a gripper with an ultrasonic welder, a storage system for cut-piece supply, a computer vision system, a collision avoidance app and a logging system for process relevant production parameters for inline quality control. The described system was successfully used for the production of four thermoplastic CFRP skin segments each consisting of 104 cut-pieces.

Thermally Conductive Composite Material With Percolating Microparticles Applied as Underfill

Efficient thermal management of large vertically stacked integrated circuits (ICs) requires a material with high thermal conductivity inside the micrometer-sized gaps between the IC dies. Such an underfill material can be obtained by adding thermally conductive filler particles at high loadings to the adhesive matrix material. However, viscosity requirements for the state-of-the-art capillary-driven filling of particle-loaded adhesives limit the particle fill fraction to values lower than those necessary to reach true percolation. Accordingly, heat transfer through the composite material is dominated by conduction through the adhesive matrix material. We propose using an alternative, sequential filling method to achieve percolation with particles down to $1~\mu \text{m}$ in diameter. The percolating thermal underfill (PTU) can be achieved by a centrifuge-assisted filling of micrometer-sized particles, followed by a backfilling of a low-viscosity epoxy with long open time acting as matrix material, and a final thermal curing step. In this paper, we present and discuss the fabrication and relevant process parameters of the PTU composite material in chip stacks with critical dimensions below $30~\mu \text{m}$ . The wet dispensing of alumina particles with a diameter distribution of 1– $15~\mu \text{m}$ is proposed for overcoming the agglomeration observed for dry particle filling. Thermal conductivities of up to 3 W/( $\hbox {m}\cdot \hbox {K}$ ) for the underfill system with a particle fill fraction of 61% were achieved, which is three times higher than those of commercially available capillary thermal underfills. Critical parameters in the formation of the percolating composite, such as the choice of filler material and its refinement, as well as the properties of the particle bed and the process parameters for the centrifugal filling, epoxy capillary backfilling, and composite curing are addressed.

Manufacturing and crashworthiness of fabric-reinforced thermoplastic composites

In the present paper, the crashworthiness of fabric-reinforced thermoplastic composites is experimentally and numerically investigated under axial impact loading. Main aim of this article is the qualification of large-scale producible structures for energy absorbing applications. For this reason, the considerable steps of thermo-forming as well as relevant process parameters are identified. This includes the development of an appropriate handling system for production on lab-scale. Formed three-dimensional profiles are tested under axial impact loading in a drop tower to initiate a continuous progressive crushing mode. Experimental results are analysed and evaluated regarding specific energy absorption (SEA). Numerical analysis by the explicit finite element code LS-Dyna is based on the orthotropic material model MAT54 and a four-layered shell model to implement crushing failure. Investigations show, that energy absorbing structures made of bidirectional organic sheets are suitable for automotive lightweight design.

Hybrid heating system for increased energy efficiency and flexible control of low temperature heat

This study presents the evaluation of functionality and potential of a hybrid heating system (H2S) prototype. This technology is designed for retrofitting thermal treatment plants to use hot water (HW) and steam in controlled ratios. In the food industry, steam with a temperature above 140 °C usually indirectly supplies the thermal production processes, but most of them only require temperatures below 100 °C. Total site heat integration is applied on a cheese and whey powder plant to show the potential for low-temperature heat (below 100 °C) that could be supplied more appropriately by hot water cogeneration, heat recovery and heat pumps. These low-temperature heat sources can only be combined with the rigid steam system if the demand structure is changed to a hybrid use of HW and steam. The H2S increases the energy efficiency and flexibility by integrating low-temperature heat and responding to sudden changes in the demand and supply structure, like demand response strategies on intermittent renewable energies and the changing availability of HW and steam. The technical implementation is realised by a hydraulic interconnection of heat exchangers and valves. A smart control algorithm acutely determines the share of HW and steam. Prerequisite for functional verification on a laboratory scale is a hardware-in-the-loop (HIL) testbed, in which load profiles and relevant process parameters are passed in real time between hardware components and simulation. The results show that the H2S is a feasible solution for maintaining product quality and safety while also increasing energy efficiency and energy flexibility.

One-dimensional model of a closed low-pressure adsorber for thermal energy storage

The energy transition from fossil to renewable energy requires the development and integration of efficient energy storages. For thermal energy storage, concepts based on adsorption are promising. One key challenge is to overcome limitations of the storage performance by the heat and mass transfer. Against this background, a closed low-pressure adsorber with zeolite 13X honeycomb adsorbent is studied numerically to identify the limiting factors. The focus of the study is on the adsorption process with the heat extraction limited to the end of the zeolite honeycomb arrangement. A detailed model which takes effects of rarefied gas flow (e.g. slip) as well as cooling effects by the inflowing vapour into account is derived. The model is applied to study the mass transport, heat transport and adsorption over a broad range of relevant geometry and process parameters. The simulations demonstrate that the adsorption process is not limited by the mass transport and isobaric conditions can be assumed in most of the studied cases. In addition, special effects of rarefied gas flow are found to be negligible. Regarding the heat transport, the convective cooling by the vapour is found only to be significant for a very short initial time period. Further analysis show that the process is mainly limited by the heat transport. Only for short channels and wide channel diameters the process becomes limited by the adsorption.