Relevant Process Parameters Research Articles

Investigations into side gap in wire electrochemical micromachining (wire-ECMM)

Electrochemical machining (ECM) process is now in application in various industries like maritime, automobile, and aerospace. Wire-ECM, a variant of ECM, is now under investigation, for its applications in electronics industries for the fabrication of PCB on conductive metals like copper and in medical industries for the fabrication of micro needles with textures on its surface for the painless delivery of drugs. One of the most important parameters in wire-ECM is side gap. This paper aims at obtaining minimum side gap for the given machining conditions. In order to achieve this, three different workpieces of Al, Cu, and stainless steel are examined. Effects of different electrolytes on the side gap are also examined. Later on, different electrolytes at different temperatures are used to study their effect on the side gap. Finally, optimum parameters are determined in order to keep the side gap to a minimum level. In order to keep the findings significant for industrial applications, machining rate is kept as high as 5 μm/s. Other relevant process parameters are so derived that the machining process can attain stability at high feed rate. To realize this, regulated DC power supply is used. Average side gap was finally reduced to 26.8 μm using a commercially available copper wire of diameter 90 μm.

Influence of process pressures on filling behavior of tubular fabrics in bladder-assisted resin transfer molding

Among the family of liquid composite molding techniques, bladder-assisted resin transfer molding (BARTM) enables efficient manufacturing of hollow composite parts based on tubular reinforcing textiles. However, resin injection under certain processing conditions can result in high filling times or improper parts and finding the optimal process parameters is often a difficult task. This paper studies the impregnation behavior of a biaxial braided fabric in pressure-driven BARTM under a wide range of injection and bladder pressures. Saturation experiments were accomplished by means of a specifically developed injection test rig comprising an under-sized elastomeric bladder and a monolithic transparent mold. The results obtained show significant influence of the relevant process parameters on local preform compaction, apparent global permeability and filling time. Based on the experiments, a universal moldability diagram was derived that enables identification of admissible and critical operating conditions in BARTM, which supports the finding of optimal part filling settings.

A qualitative, process-parameter-based model for the release agent transfer during CFRP-part production: an approach to increase the initial bondability

Adhesive bonding shows a high potential to join carbon fiber reinforced plastics (CFRP), if the adhesion between adhesive and part surface is verified. Unfortunately, this adhesion is often reduced in case of the mold-based part production and its unavoidable application of release agents. Due to the resulting presence of release agent residues on the surface of the cured CFRP-parts the adhesion is lowered. To increase the bondability and correlating production efficiency, the amount of release agent transfer should be as small as possible, to reduce the effort in terms of bonding pre-treatment. To achieve this goal, a theoretical, qualitative model about the influence of the relevant processing parameters for a thermoset CFRP-production was developed focusing the (diffusion-based) transfer reduction based on an adapted processing. Indicating the time in which the diffusion is possible, as the main criteria.

Electrospinning of polyimide nanofibres – effects of working parameters on morphology

Abstract The use of the electrospinning technique is a promising and versatile method for producing fibrous nonwovens from various polymers. Here we present fibre formation via direct electrospinning of a soluble polyimide, a class of polymers that is typically insoluble. In this study solution parameters as the solvent and the polymer concentration are investigated. Furthermore relevant process parameters are varied for optimization of the performance. The presented data indicate polyimide as a promising material for the fabrication of nanofibrous nonwovens via direct electrospinning.

High-pressure foaming properties of carbon dioxide-saturated emulsions

The aeration of emulsions with tailored properties and structure is of widespread importance in processing of foods and cosmetics. This report addresses the micro-cellular foam formation of carbon dioxide-saturated oil-in-water emulsions triggered by the application of a controlled pressure drop. The experimental setup combines a stirred pressure vessel with a pressure cell-equipped rheometer and pneumatic expansion valves. This allows to systematically study the process of gas dissolution, bubble nucleation, and growth under defined pressure, temperature, and flow conditions. Investigations on the impact of relevant process parameters show that dissolved gas fraction, emulsion viscosity, and shear rate have a major influence on foam formation. Dissolution of carbon dioxide leads to a viscosity reduction of the emulsion which and is described by a viscosity reduction factor. The point of bubble nucleation is derived from rheological patterns during depressurization. Experiments show that lower emulsion viscosity and higher shear rate favor bubble nucleation upon pressure release. Rheological results are supported by video analysis as the setup allows capturing nucleation, growth, and destabilization of bubbles as a function of pressure, supersaturation, and time. The results of this work yield the understanding of the high-pressure foaming mechanism from a rheological perspective and foster the design of such processes.

Analysis of mesoscale effects in high-shear granulation through a computational fluid dynamics–population balance coupled compartment model

There is a need for mesoscale resolution and coupling between flow-field information and the evolution of particle properties in high-shear granulation. We have developed a modelling framework that compartmentalizes the high-shear granulation process based on relevant process parameters in time and space. The model comprises a coupled-flow-field and population-balance solver and is used to resolve and analyze the effects of mesoscales on the evolution of particle properties. A Diosna high-shear mixer was modelled with microcrystalline cellulose powder as the granulation material. An analysis of the flow-field solution and compartmentalization allows for a resolution of the stress and collision peak at the impeller blades. Different compartmentalizations showed the importance of resolving the impeller region, for aggregating systems and systems with breakage. An independent study investigated the time evolution of the flow field by changing the particle properties in three discrete steps that represent powder mixing, the initial granulation stage mixing and the late stage granular mixing. The results of the temporal resolution study show clear changes in collision behavior, especially from powder to granular mixing, which indicates the importance of resolving mesoscale phenomena in time and space.

Productive and environmental performance indicators analysis by a combined LCA hybrid model and real-time manufacturing process monitoring: A grinding unit process application

Among machining processes, grinding has been used to achieve high dimensional tolerances and surface quality on workpieces. Yet, high levels of energy expenditure per volume of removed material and the need for cutting fluids make grinding one of the most environmentally impactful machining processes. Furthermore, changes in parameters such as grain and bond specifications of the grinding wheel, cutting speed, and specific material removal rate can lead to different productive and environmental results. Thus, the analysis of grinding processes should not be aggregated and leveraged into a single and broad output parameter. Instead, comprehensive study should be performed, in which the most relevant process parameters, inputs and outputs are considered. This paper presents a detailed study of grinding process, including the characterization of machine subunits and production modes, along with the use of a combined life cycle assessment hybrid model and real-time monitoring system to evaluate the consumption of energy, tooling, cutting fluid and compressed air. A detailed cradle-to-gate life cycle assessment study using eleven different impact categories and a productive performance assessment were performed to evaluate the effects on varying specific material removal rate and wheel type. For equal values of specific material removal rate, the change from a conventional wheel to a cubic boron nitride represented a power requirement increase of 19–24%. Cubic boron nitride wheel achieved remarkably better results on the wheel wear and part roughness indicators for all tested conditions. The environmental performance assessment showed a strict relation between the process environmental impacts and the consumption of electric energy and cutting fluid. To conclude, despite the higher power requirements, the combination of cubic boron nitride wheel with high values of specific material removal rate optimizes both the productive and the environmental results.

Continuous noninvasive monitoring of cell growth in disposable bioreactors

To ensure high quality output of biotechnological processes, relevant process parameters need to be monitored. As bioprocesses are increasingly executed in single use bioreactors, there is an increasing demand for new sensors applicable to these processes. In this work, we investigate different approaches for continuous non-invasive cell growth monitoring, especially for single use bioreactor applications. Therefore, the permittivity of the cell culture is used as a measure for the biomass. In a first step, a measuring procedure based on the transmission measurement of an electromagnetic wave is investigated. It appears that the penetration depth of this sensor is not sufficient for a noninvasive measurement through the polymer wall of a single use bioreactor. Therefore, alternative setups based on magnetic induction are investigated. The initial setup is very simple. It consists of a planar coil connected to an impedance analyzer. The coil is attached to the outside of the polymer foil of the single use bioreactor and an impedance spectrum is measured. To evaluate the sensor, E. coli cultivations are performed in a modified cultivation setup, which enables measurements through the polymer foil of a Sartorius BIOSTAT® CultiBag RM, and additionally allows sampling of culture medium for optical density reference measurements. The resonance peak of the coil in the impedance spectrum, is observed as measure for the optical density. Regardless of the simple sensor construction, we found a good correlation between optical density and the damping ratio of the resonance peak. However, the sensor signal shows saturation towards high optical densities. Therefore, an LTCC coil producing a higher magnetic flux density in the culture medium is investigated subsequently. This sensor shows a linear response up to high optical densities, but the sensitivity is reduced compared to the former used coil and therefore scattering of the data is increased. However, to increase the sensitivity, a linear variable differential transformer is realized. Using this setup, the influence of the primary magnetic flux is eliminated from the measuring voltage. This approach delivers the most promising results, as the sensor response is linear up to high optical densities and data scattering is low.

Improving docosahexaenoic acid production by Schizochytrium sp. using a newly designed high‐oxygen‐supply bioreactor

A sufficiently high oxygen supply is crucial for high‐cell‐density cultivation of aerobic microorganisms, including Schizochytrium sp. We, therefore, designed a novel bioreactor enabling high‐level oxygen supply, and its relevant process parameters and fermentation‐stage characteristics were investigated. The real‐time changes of pH and nonoil biomass were monitored as proxies for the consumption of nitrogen and lipid accumulation status, which was first applied to divided fermentation process with three stages. The experimental results showed that the biomass in this porous‐membrane‐impeller bioreactor was higher than in conventional bioreactor, while docosahexaenoic acid (DHA) percentage in total lipids was lower than in conventional bioreactor. A multistage control strategy is subsequently implemented for the porous‐membrane‐impeller bioreactor, and the maximum biomass, DHA concentration, DHA percentage in biomass and DHA productivity reached 151.0 g/L, 44.3 g/L, 29.33%, 369.08 mg/(L·h), respectively. This study thus provides a highly efficient and economic bioreactor for the production of DHA by Schizochytrium sp. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4278–4286, 2017

Water and Oil Repellent Finishing of Textiles by UV Curing: Evaluation of the Influence of Scaled-Up Process Parameters

In this work, various textile fabrics were coated with silicone and fluorocarbon-based resins by photo-curing using ultraviolet irradiation. A great number of large fabric samples were impregnated by padding with commercial finishing agents and then irradiated in air with a high power, semi-industrial UV source. The add-on of various finishing agents was kept low to reduce the treatment cost. White and dyed samples of different textile composition were treated and evaluated in terms of conferred repellency, yellowing, or color changes. Most relevant process parameters were investigated, utilizing the thermal process normally adopted at industrial level as reference. The results were statistically evaluated by ANOVA using Minitab 16 software, in order to identify the most influential parameters and to evaluate the real possibility of replacing the thermal treatment with UV curing.

Challenges in Rheological Characterization of Highly Concentrated Suspensions — A Case Study for Screen-printing Silver Pastes

A comprehensive rheological characterization of highly concentrated suspensions or pastes is mandatory for a targeted product development meeting the manifold requirements during processing and application of such complex fluids. In this investigation, measuring protocols for a conclusive assessment of different process relevant rheological parameters have been evaluated. This includes the determination of yield stress, viscosity, wall slip velocity, structural recovery after large deformation and elongation at break as well as tensile force during filament stretching. The importance of concomitant video recordings during parallel-plate rotational rheometry for a significant determination of rheological quantities is demonstrated. The deformation profile and flow field at the sample edge can be determined using appropriate markers. Thus, measurement parameter settings and plate roughness values can be identified for which yield stress and viscosity measurements are possible. Slip velocity can be measured directly and measuring conditions at which plug flow, shear banding or sample spillover occur can be identified clearly. Video recordings further confirm that the change in shear moduli observed during three stage oscillatory shear tests with small deformation amplitude in stage I and III but large oscillation amplitude in stage II can be directly attributed to structural break down and recovery. For the pastes investigated here, the degree of irreversible, shear-induced structural change increases with increasing deformation amplitude in stage II until a saturation is reached at deformations corresponding to the crossover of G' and G'', but the irreversible damage is independent of the duration of large amplitude shear. A capillary breakup elongational rheometer and a tensile tester have been used to characterize deformation and breakup behavior of highly filled pastes in uniaxial elongation. Significant differences were observed in all experiments described above for two commercial screen-printing silver pastes used for front side metallization of Si-solar cells.

Challenges in Rheological Characterization of Highly Concentrated Suspensions - A Case Study for Screen-printing Silver Pastes.

A comprehensive rheological characterization of highly concentrated suspensions or pastes is mandatory for a targeted product development meeting the manifold requirements during processing and application of such complex fluids. In this investigation, measuring protocols for a conclusive assessment of different process relevant rheological parameters have been evaluated. This includes the determination of yield stress, viscosity, wall slip velocity, structural recovery after large deformation and elongation at break as well as tensile force during filament stretching.The importance of concomitant video recordings during parallel-plate rotational rheometry for a significant determination of rheological quantities is demonstrated. The deformation profile and flow field at the sample edge can be determined using appropriate markers. Thus, measurement parameter settings and plate roughness values can be identified for which yield stress and viscosity measurements are possible. Slip velocity can be measured directly and measuring conditions at which plug flow, shear banding or sample spillover occur can be identified clearly. Video recordings further confirm that the change in shear moduli observed during three stage oscillatory shear tests with small deformation amplitude in stage I and III but large oscillation amplitude in stage II can be directly attributed to structural break down and recovery. For the pastes investigated here, the degree of irreversible, shear-induced structural change increases with increasing deformation amplitude in stage II until a saturation is reached at deformations corresponding to the crossover of G' and G'', but the irreversible damage is independent of the duration of large amplitude shear. A capillary breakup elongational rheometer and a tensile tester have been used to characterize deformation and breakup behavior of highly filled pastes in uniaxial elongation. Significant differences were observed in all experiments described above for two commercial screen-printing silver pastes used for front side metallization of Si-solar cells.

Local characterisation of variances for the planning and configuration of process chains in micro manufacturing

During the last decades, a continuous trend towards miniaturisation leads to an increasing demand of metallic micromechanical components. To achieve an economic production on an industrial scale, the planning and configuration of process chains has become a key success factor. Thereby, the occurrence of so-called size-effects renders the planning and particularly the configuration of process chains complicated. While process planners have to ensure very small tolerances, these size-effects lead to comparably strong variances within the behaviour of processes. To cope with these, this article proposes an extension to the μ-ProPlAn methodology. While μ-ProPlAn, in its current state, provides tools to characterise and utilise interdependencies between production relevant parameters, it lacks the capabilities to quantify and use variances for the prediction of process results. In this article, we propose an extension to this methodology, enabling a local estimation of variance of relevant process parameters using sample data. As a result, the planning quality can be increased as additional goals and methods for optimisation become available.

Recent findings in pulsed light disinfection.

Nonthermal disinfection technologies are gaining increasing interest in the field of minimally processed food in order to improve the microbial safety or to extend the shelf life. Especially fresh-cut produce or meat and fish products are vulnerable to microbial spoilage, but, due to their sensitivity, they require gentle preservation measures. The application of intense light pulses of a broad spectral range comprising ultraviolet, visible and near infrared irradiation is currently investigated as a potentially suitable technology to reduce microbial loads on different food surfaces or in beverages. Considerable research has been performed within the last two decades, in which the impact of various process parameters or microbial responses as well as the suitability of pulsed light (PL) for food applications has been examined. This review summarizes the outcome of the latest studies dealing with the treatment of various foods including the impact of PL on food properties as well as recent findings about the microbicidal action and relevant process parameters.

Towards Controlled Fermentation of Table Olives: LAB Starter Driven Process in an Automatic Pilot Processing Plant

The results of an experimental trial, carried out using a specifically prepared microbial starter, in an automated pilot plant, are presented. The microbial starter was composed by Lb. pentosus strains. The automatized process was compared with natural fermentation in plastic vats, as control. Relevant process parameters, chemico-physical determinations, instrumental texture, and microbiological analyses were carried out to monitor the fermentation process. Driving the process in controlled conditions resulted in a more rapid acidification, pH reaching lower values than the control. In controlled conditions, inoculated lactobacilli carried out a fast colonization supplanting more rapidly spoilage microflora. In started samples, yeasts number increased until reaching 5 log at 60 days, keeping this value constant until the end of the trials, while, in control batches, their growth was more rapid, reaching 5 log from 15 to 30 days, but their number decreased to 3 log at 90 days. The two processes produced olives with comparable texture profile. However, olives coming from the controlled process resulted debittered in 3 months (descriptive sensory analyses and oleuropein quantification in HPLC), while naturally fermented olives resulted not yet debittered at the end of the trial (180 days). Slight differences were found in few other sensory descriptors. Our results showed that, along with the use of effective autochthonous microbial starters, the innovation of processing plants is the next step towards the shortening of the processing time and the safety assurance of the product, while retaining the sensory quality of naturally fermented olives, using an environmentally friendly technology.

Numerical investigation of warpage in insert injection-molded lightweight hybrid products

In this study, a numerical investigation of warpage found within insert injection-molded frame parts was carried out based on the Taguchi method in conjunction with a response surface methodology. An integrated mold frame unit was recently developed by integrating a conventional mold frame, metal reflector, and bezel together, to be used in a back light unit system of a liquid crystal display. Such an integrated plastic-metal hybrid part could be successfully manufactured through the insert injection molding process. However, minimization or even elimination of warpage, one of the severe defects found in injection-molded products, is required for reliable mass production. Therefore, a numerical analysis was performed to reveal the effects of the relevant processing parameters, showing that packing pressure played the most significant role, originated from temperature difference between corners of the final product. Furthermore, a double optimization process combining the Taguchi method and the response surface methodology was employed to determine accurate and optimal processing conditions. The results clearly verified that the current combination technique can overcome the Taguchi method’s limitation, resulted from a discrete optimization nature, and also effectively give more accurate optimum solutions without complicated algorithms and software.

Analysis of Electrical Energy Demands in Friction Stir Welding of Aluminum Alloys

Manufacturing processes, as used for discrete part manufacturing, are responsible for a substantial part of the environmental impact of products. Despite that, most of metalworking processes are still poorly documented in terms of environmental footprint. To be more specific, the scientific research has well covered conventional machining processes, concerning the other processes there is a lack of knowledge in terms of environmental load characterization instead. The present paper aims to contribute to fill this knowledge gap and an energetic analysis of Friction Stir welding (FSW) is presented. Following the CO2PE! methodological approach, power studies and a preliminary time study have been performed in order to comply with the In-Depth approach. The influence of the most relevant process parameters is analyzed regarding the required FSW energy. Finally, a few potential improvement strategies to reduce FSW energy consumption are reported.

Life Cycle Management of Cutting Tools: Comprehensive Acquisition and Aggregation of Tool Life Data

The complexity and number of variants of today's cutting tools is constantly growing due to the customer-specific requirements.These requirements and constantly changing circumstances in manufacturing environment can result in complications for the tool management since conventional tool histories and tool management systems are not pursuing a comprehensive approach to collect all necessary data along the tool life cycle. To identify and evolve dependencies of all relevant processes and process parameters, support tool manufacturers and their development departments as well as end users wanting to extend tool life to its fullest, tool history data must be distributed.Once tools have an individual tool ID, the acquisition of tool usage data via installation of process monitoring devices, together with tracking data and information of individual tools enable a holistic knowledge base and the adaption of tool concepts to fit the steadily changing circumstances in manufacturing environment. The objective of this research project is to support optimisation procedures in early stages of the tool life cycle by developing a generic tool history data pool. A methodical approach was developed for defining tool history data to support the information flow by using a life cycle process model. The intention is to detect and track relevant data and their sources such as MES, ERP, NC control, identification technology and sensors in stations located in the tool life cycle and allocate and distribute the history data from the shop floor to suitable process owners. The approach supports tool life cycle management and can lead to enhancing tool performance.

Compression testing of martensitic stainless steel with superimposed ultrasonic vibration

Abstract The expanding use of materials with high strength in cold forging and the associated force increases as well as the limited formability present a major challenge for conventional process technology. One method to respond to this challenge is the use of high frequently oscillating forming tools which lead to a decrease of the required forces. Previous research on this topic has focused on fairly soft materials, such as aluminum. Materials with higher strength have only been analyzed to a very limited extent. This study addresses the ultrasonic-assisted compression testing of high strength martensitic stainless steel with 20 kHz oscillation frequency aiming at the identification of relevant process parameters and the partial separation of occurring effects. Experimental investigations are carried out to analyze the effect of ultrasonic-assistance during compression testing with varying oscillation duration and amplitude on the maximum forming force and on specimen heating. To isolate the proportional force reduction due to material heating from other oscillation induced causes, a comparison with conventional warm compression tests is performed. Finally, a simplified numerical simulation which is able to model the ultrasonic-assisted compression test is proposed. The experimental results reveal a strong influence of the oscillation amplitude on the reduction of maximum forces and on specimen heating. The oscillation duration presents a minor influence on the maximum forces, but strongly affects the heat generation. The developed simulation model is in good accordance with experimental force displacement curves and allows the separation between stress superposition and other ultrasonic-induced effects.

Detection and Prediction of Corrosion-Affecting Parameters in Cold Flat Rolling Processes

Cold flat rolling of DC04 is a widespread manufacturing process. A defined state can only be reached by careful consideration of relevant processing parameters. Characterizing suitable parameters numerically by means of forming simulation allows a prediction of corrosion-affecting parameters. The experimental methods applied are X-ray diffraction and immersions tests. Numerical analyses of flat rolling processes were performed using finite element simulations, which were created with simufact.forming. The numerical results show that the variation of relevant parameters (e.g., friction, shape of the elements, and mesh size) has a great impact on the simulation results. These influences are systematically studied and the results are compared with the real cold-rolling process. Based on this comparison, it could be concluded that the macromechanic results of the simulation and the experiments (plastic strain and residual stresses) can be correlated with the corrosion rates of the specimens. Thus, the susceptibility of the sheet metal to corrosion can be predicted. Therefore, it is possible to adapt the chosen process parameters and processing routes to the real process in order to control the corrosion resistance.