Single Process Parameter Research Articles

Multi-Factors Interaction Effects of Process Parameters on the Joint Strength of Laser Transmission Joining between PC and PA66

This paper presents a laser transmission joining (LTJ) experiment between thermoplastic Polycarbonate (PC) and glass reinforced nylon (PA66GF) using diode laser equipment. Laser transmission joining experimental design and experiment are carried out according to a single process parameters window. Response surface methodology (RSM) in Design-Expert v7 software is employed to develop mathematical models between LTJ process parameters and joint strength. The interaction effects of joining process parameters (line energy, spot diameter, clamp pressure) on the joint strength are investigated using analysis-of-variance (ANOVA), the result shows that the interaction effect of line energy and spot diameter has maximum influence on the joint quality. Finally, the predicted values from mathematical models developed by RSM are compared with the experimental values and it is found that they are nearly agreed with each other. The purpose of predicting joint strength based on reasonable process parameters is achieved.

Simulation of a real-time process adaptation in the manufacture of high-density fibreboards using multivariate regression analysis and feedforward control

The industrial manufacturing of wood-based panels has become a highly technological process, where all parameters have to be perfectly adjusted to manufacture products of high quality. However, variations caused by differing wood characteristics as well as variations of single process parameters can cause out-of-control events. These undesirable events can be diminished by monitoring and controlling the entire manufacturing process using multivariate statistical techniques. Hence, a real-time process adaptation of an industrial scale fibreboard manufacturing process was simulated. Regression results revealed a mean normalised root mean squared error of prediction of 4.6 %, when predicting the internal bond strength of fibreboards. The regression model is regularly validated and, if necessary, recalibrated using the offline determined board properties (feedback control). Consequently, the process can immediately be adapted as soon as the board is produced (feedforward control). The investigations resulted in reliable models and revealed high potential for permanent industrial implementation.

Influence of Process Parameters on Surface Hardening in Hammer Peening and Deep Rolling

This paper focusses on the statistical evaluation of process parameters in the mechanical surface treatments deep rolling (DR) and machine hammer peening (MHP) on the hardness increase. In MHP process a spherical hard metal tool is repeatedly accelerated onto the material surface. Just as the shot peening process MHP is an impact treatment although in MHP the impact area can be controlled, leading to the desired impact density. In DR the contact between spherical tool and work piece is quite different to MHP as the spherical is in sliding contact as it is moved along the surface. Although the material loading of both surface treatments vary, the resulting surface structure is the same. Both lead to a cold worked, smooth surface including compressive residual. Technically DR and MHP parameters have been part of researches but there still is a lack of statistical validation of every single process parameter leading to a hardened surface. This paper tries to close this gap. DR and MHP are conducted on different materials, containing tool steel 1.2379 and grey cast iron EN-JS-2070. Using a fractional factorial test design an experimental matrix was created able to examine the influence of every single process parameter. Which were for DR: rolling pressure, line spacing between hammer traces, diameter of roller ball and the travelling speed. For MHP the influence of the following process parameters was investigated: angle between hammering direction and surface normal, line spacing between hammering traces, diameter of hammering ball, hammering energy, travelling speed and hammering frequency. On every single sample ten Brinell hardness indents are made which give the statistical coverage needed to calculate the effect of every single process parameter within a confidence interval of at least 95 %. For all mentioned materials the effect of every single process parameter has been calculated with respect to hardening. It could be shown that especially the loading of the cast iron is quiet complex as a high amount of impact energy (MHP) or contact pressure (DR) can lead to overloading of the material leading to a degradation of the surface. At least an explanatory approach which describes the different influence of the tool diameter on the surface hardness is given using FEM simulations. These FEM simulations contain an advanced material model in which the Bauschinger-effect of 1.2379 is implemented. It can be clearly shown that a larger tool diameter in DR produces a higher amount of cold working in the material surface leading to harder surfaces compared to the smaller tool diameter. In contrast to DR the contact pressure in MHP is determined by the Hertzian pressure distribution. Here smaller tool diameters create larger Hertzian pressure and therefore a higher amount of cold working.

An influence of a gas velocity on morphology of molybdenum oxide nanoparticles generated by a glowing wire generator

In this paper we report the results of investigation of a gas carrier velocity influence on morphology and structure of molybdenum oxide nanoparticles, produced by a glowing wire generator. The device operational principle is based on electrical resistance related heating of a metal wire and placement it into relatively cool and not ionized gas carrier for rapid solidification of vapour released from the wire surface. The results show that the suggested system is capable of producing a variety of nanostructures by changing a single process parameter—velocity of the gas carrier.

Scanning velocity influence on microstructure, microhardness and wear resistance performance of laser deposited Ti6Al4V/TiC composite

Ti6Al4V is the most widely used titanium alloy in the aerospace industry because of its excellent properties. However, the wear resistance behaviour of this material is not very impressive and surface damage occurs in applications involving contact loadings. Laser material deposition process, an additive manufacturing technology offers lots of advantages in surface modification of components, repair of existing worn out parts, as well as building new components from the scratch, most especially complex components. A good control of the process parameters is inevitable to achieve the desired properties. It is easier to control a single process parameter to achieve the desired property than to control a number of the processing parameters. In this study, the influence of the scanning velocity on the evolving physical properties, the microstructure, the microhardness and the wear resistance behaviour of Ti6Al4V/TiC composite is thoroughly investigated towards achieving an effective properties control. The results showed that controlling only the scanning velocity, the physical, mechanical, metallurgical and the tribological properties of the Ti6Al4V/TiC composite can be effectively controlled. It was found that as the scanning velocity was increased, the wear resistance performance also increased, until the scanning velocity of 0.065m/s, after which the wear resistance performance began to experience a decrease. At low scanning velocity, there were less Unmelted Carbide particles in the microstructure due to more melting of the TiC powder taking place, hence the low wear resistance performance obtained.

Prioritization of Process Parameters for an Efficient Optimisation of Additive Manufacturing by Means of a Finite Element Method

At present, several tendencies like market globalisation induce an increasing usage of additive manufacturing technologies in dif- ferent branches (e. g. mould and tool making, medical devices, aerospace and automotive industry). A resource efficient application of these processes requires a high process stability and reproducibility. Currently, these target figures are reached by numerous test rigs at the manufacturing system which cause high resource consumption and an uneconomic application of these processes.A virtual process design prior to the building phase is an opportunity to enhance the process efficiency of metal-based, additive processes. Previously developed technology specific simulation models enable users to examine and optimise different process parameter compositions. Though, whilst planning the design of experiments study for the simulation based optimisation, it should be considered, that with every single additional process parameter which is thereby taken into account the calculation time increases significantly. Regarding this fact, the presented research works in this publication are including procedure models for an efficient and target figure dependent analysis of a high amount of different process parameter constellations by means of the developed sim- ulation models. Methods and procedures for the identification, categorisation and prioritisation of influencing parameters and their interdependencies amongst each other are shown for the target figure “dimensional accuracy” and with utilising the alloy AlSi12. The results of these investigations are summarised in a process-specific prioritisation and correlation matrix.

Optimisation of Micro Injection Moulding Process through Design of Experiments

The paper presents the optimisation of Micro Injection Moulding (MIM) process through Design of Experiments (DoE). MIM is a relatively new technology which is used for the rapid manufacture of micro components. In order to meet the quality and reliability constraints it is important to reduce variability during its operation due to changes in process parameters. In this study, an understanding of the MIM process and consequently its optimisation is carried out by DoE based on six parameters which influence the surface quality, flow length and the aspect ratio. Significant single process parameters and interactions between them were determined through statistical analysis. For the 2-level test, an aspect ratio of 20, 21, and 20 were achieved respectively for Polypropylene (PP), Acrylonitrile-Butadiene-Styrene (ABS) and Polyoxymethylene (POM).

Decomposing attention-deficit/hyperactivity disorder (ADHD)-related effects in response speed and variability.

Slow and variable reaction times (RTs) on fast tasks are such a prominent feature of attention-deficit/hyperactivity disorder (ADHD) that any theory must account for them. However, this has proven difficult because the cognitive mechanisms responsible for this effect remain unexplained. Although speed and variability are typically correlated, it is unclear whether single or multiple mechanisms are responsible for group differences in each. RTs are a result of several semi-independent processes, including stimulus encoding, rate of information processing, speed-accuracy trade-offs, and motor response, which have not been previously well characterized. A diffusion model was applied to RTs from a forced-choice RT paradigm in two large, independent case-control samples (NCohort 1 = 214 and NCohort 2 = 172). The decomposition measured three validated parameters that account for the full RT distribution and assessed reproducibility of ADHD effects. In both samples, group differences in traditional RT variables were explained by slow information processing speed, and unrelated to speed-accuracy trade-offs or nondecisional processes (e.g., encoding, motor response). RT speed and variability in ADHD may be explained by a single information processing parameter, potentially simplifying explanations that assume different mechanisms are required to account for group differences in the mean and variability of RTs.

Saccharification of Lignocellulosic Biomass for Biofuel and Biorefinery Applications – A Renaissance for the Concentrated Acid Hydrolysis?

Hydrolysis of lignocelluloses using concentrated acids achieves near-theoretical sugar yields, and with fewer degradation products than the more commonly employed dilute acid hydrolysis process. In this paper, the dependence of sugar yield and the production of fermentation inhibitors on central process parameters is investigated, and the “severity factor” concept of one single process parameter characterizing the extent of the reaction is applied for the first time to concentrated acid hydrolysis of lignocellulosic biomass. Selected hydrolyzates have been fermented in the laboratory to investigate the effect of analyzed and unknown fermentation inhibitors in the hydrolyzates on fermentation performance. The concentrated acid hydrolysis process appears to be an interesting process for saccharification of lignocellulosic biomass for biofuel and biorefinery applications, with high sugar yields, low levels of fermentation inhibitors, good fermentability and good robustness towards changes in raw material quality.

Application of Taguchi method to selection of optimal lubrication and cutting conditions in face milling of AlMg 3

This paper outlines the Taguchi optimization methodology, which is applied to optimize the cutting parameters in face milling when machining AlMg 3 (EN AW 5754) with HSS (high speed steel) tool under semi-finishing conditions in order to get the best surface roughness and the minimum power consumption. Beside the conventional flood lubrication, the investigations include the minimal quantity lubrication and the dry milling. These environment-friendly cutting techniques are considered two practical ways to the cleaner manufacturing in the context of the sustainable production. The parameters evaluated are the cutting speed, the depth of cut, the feed rate and the cooling lubrication techniques (cutting fluid flow). The appropriate orthogonal array, signal to noise (S/N) ratio and Pareto analysis of variance (ANOVA) are employed to analyze the effect of the mentioned parameters on the good surface finish (surface roughness). This paper illustrates the application of the techniques for single performance characteristics optimization, which employs the weighting factors to each of the S/N ration of the responses to obtain a multi-response S/N ratio for each trial of the orthogonal array and, finally, a single optimal process parameters setting. Using Taguchi method for the design of experiments (DOE), it is investigated the significant influence and the parameters interaction effect with minimum number of trials as compared with a full factorial design.

Optimization of reactive ion etching processes using desirability

This work discusses the potential of process optimization of reactive ion etching processes by the help of desirability. The idea is a model based approach due to the complexity of the chemical and physical operational sequence within the plasma during the etching. The whole etching process is considered as black box with input and output factors. Instead of searching for local optimums concerning the single process parameters during the conventional optimization a response surface methodology describes the black box by the help of an appropriate model with a desirability index which is afterwards optimized by the help of nonlinear optimization algorithms. The method is introduced and evaluated by using the example of a polysilicon etch process with the gases sulfur hexafluoride and oxygen.

Manufacturing challenges in obtaining tailor-made closed-cell structures in metallic foams

The evolution of closed-cell aluminum foam synthesized by titanium hydride decomposition is explained on the basis of foam stability and gravity-induced drainage of liquid. While the average pore size progressively increases due to TiH2 decomposition, the aspect ratio shows a sudden transition during the holding period. The sudden increase in aspect ratio with the major axis transverse to the growth direction is explained on the basis of the loss of elasticity of the cell wall due to drainage and subsequent cell wall collapse due to the weight of the overlying foam. Intermetallic particles with a high aspect ratio distributed in the cell wall matrix significantly improve the stability of the liquid foam. It is demonstrated that by varying a single process parameter, such as the holding time, foams with a wide range of structural parameters are accessed. The Gibson and Ashby model showed good correlation with the plateau stress and Young’s modulus results presented in this work.

Modelling the effects of constraints and single axis welding process parameters on angular distortions in one-sided fillet welds

Welding process parameters and joint fit-ups significantly affect angular distortion patterns. By using constraints at proper positions the angular distortion can be minimized. In the present work the effect of constraints in the form of tack welds to minimize angular distortion in one-sided fillet welds has been analysed. It has been observed that proper positioning of tacks plays an important role in controlling angular distortion. The process was modelled using the three-dimensional finite element technique. Three-dimensional transient thermal analyses were done for predicting temperature distributions by considering a moving heat source. The element birth and death technique was used for simulating filler material deposition. The fillet welds were sectioned and microstructure zones were measured. The thermal model was verified by comparing the temperatures obtained from the thermal analysis with experimental results. Transient thermal and non-linear structural analyses were carried out in order to predict angular distortions.

Thick Co-based coating on cast iron by side laser cladding: Analysis of processing conditions and coating properties

The objective of this work was to create Co-based coatings (compositionally close to Stellite 6) on compacted graphite and gray cast iron substrates with a high power laser (2 kW continuous Nd:YAG) cladding process. The relationships between the relevant laser cladding parameters (i.e. laser beam scanning speed, laser power and powder feeding rate) and the main geometrical characteristics of a single laser track (height, width, dilution, etc.) were examined. A gradual variation of a single processing parameter was used for an appropriate experimental analysis and statistical correlations study between main processing parameters and geometrical characteristics of an individual laser track. These relations lead to the design of a laser cladding processing map that can be used as a guideline for the selection and further tuning of proper processing parameters for laser cladding of extensive layer. The coatings with thickness from 1.0 to 3.3 mm were created on flat substrates without cracks and other major defects. The microstructural features of these coatings were studied using optical microscopy, scanning electron microscopy (Philips XL30 FEG), EDS (EDAX) and XRD. Mechanical properties were determined using microhardness measurement, scratch test (CSM Revetest) analysis at room temperature and using the tribotesting (CSM HT Tribometer) at room and elevated (up to 525 °C) temperatures.

Four-Quadrant-Input Linear Transconductor Employing Source and Sink Currents Pair for Analog Multiplier

A four-quadrant-input linear transconductor generating a product or a product sum current is proposed. The proposed circuit eliminates the influence of channel length modulation and expands a dynamic input voltage range. As an application of the proposed circuit, the four-quadrant analog multiplier is designed. The four-quadrant analog multiplier consists of the proposed circuit, an input circuit and a class AB current buffer. HSPICE simulation results with 0.35 μm n-well single CMOS process parameter are shown in order to evaluate the proposed circuit.

Laser surface treatment of grey cast iron for automotive applications

The surface of pearlitic grey cast iron was treated using a 2 kW Nd:YAG laser beam with the final aim to improve its surface properties, mainly for automotive applications. Two kinds of laser surface treatments were experimentally applied. In the laser surface hardening approach the surface of cast iron was hardened simply by passing a laser beam at travel speeds 1-50 mm/s keeping the surface temperature constant in the irradiated area. Detailed structural analysis of the layer modified by the laser treatment was performed by optical and scanning electron microscopy, EDS and orientation imaging microscopy with the electron back scattered diffraction and microhardness profiles were measured. Conclusions concerning the mechanism and kinetics of pearlite-austenite transformation during the laser surface hardening were drawn. The size of the transformed zone was calculated using a three dimensional model for a Gaussian beam distribution in accordance with direct observations of laser beam energy densities. In the laser surface cladding experiments a thick Co-based alloy coating was created on the cast iron surface using so-called side-cladding set-up when the powder of additional material is locally molten together with a small amount of substrate and then rapidly solidified creating a coating with the metallurgical bond to the substrate. A gradual change of a single processing parameter was used for an appropriate experimental analysis and statistical correlation study between main processing parameters and geometrical characteristics of an individual laser track.

Analysis of coaxial laser cladding processing conditions

The formation of thick Ni-based coating on a steel substrate by coaxial laser cladding using the Nd:YAG 2 kW continuous laser was studied both from a theoretical and experimental point of view. The theoretical analysis concentrated on the transfer of laser irradiation and powder particles using a simple model of heat transfer to the substrate. This approach provides predictions of the laser power required for melting powder particles and substrate, respectively. For an appropriate experimental analysis of the main process parameters involved, a method based on a gradual change of a single processing parameter was examined. Correlations between the main processing parameters and geometrical characteristics of an individual laser track have been found and are discussed.

The PIL (Not PID?) Controller as Eigenvalue Assigner and Optimum Stabiliser

For reasons of saturation avoidance and limitation of high frequency noise, the classical PID controller is usually implemented with a lowpass filter on the derivative channel. As pointed out by the author some years ago, this has profound implications for the stability of digital control systems based on discretised analog designs. However, it then ceases to be a PID controller and might be better described as PIL, where L normally stands for phase “lead,” but might in exceptional circumstances be phase “lag.” Such controllers are investigated as eigenvalue assigners for an inherently unstable magnetic levitation (maglev) system and for a first order lag with pure time delay, where the time delay is approximated by a first order Padé approximation for design purposes and then simulated exactly for performance evaluation. Explicit controller designs are derived with all closed loop eigenvalues placed at the same location. It is demonstrated, using root locus arguments, that this gives an optimally stable system in the sense that as any single controller or process parameter is varied with respect to its nominal value, the rightmost eigenvalue, on passage through the nominal parameter setting, is as deep in the left half plane as possible.

Composition control in the direct laser-deposition process

Laser-engineered net shaping (LENS) is a solid freeform fabrication process that has the capability of producing functionally graded material (FGM) components by selectively depositing different powder materials in the melt pool at specific locations in the structure during part buildup. The composition in each layer of an FGM is dependent upon the degree of dilution between the substrate (or previous layer) and powder material. A study on the effects of LENS processing parameters (laser power, travel speed, and powder mass flow rate) on dilution was conducted for deposits of H-13 tool steel and copper powder on H-13 tool steel substrates. When varying a single processing parameter while holding all others constant, the dilution was found to increase with increasing laser input power and travel speed and decrease with increasing powder mass additions into the melt pool. A method for estimating dilution in LENS deposits was developed from knowledge of LENS process efficiencies and material thermophysical properties. A reasonable correlation was shown to exist between the experimentally measured dilution and the dilution calculated from the model.

A methodology for monitoring system performance

Monitoring and improving manufacturing processes involves identifying, investigating and eliminating problems responsible for inefficiencies in production operations. While statistical process control tools, such as control charts, are available for process monitoring at the operational level, methods for evaluating system performance from more strategic and tactical levels are limited. The traditional control charts that monitor a single process parameter at a time may not be appropriate in situations where interrelationships among various system measures exist. Although multivariate process control techniques allow for simultaneous monitoring of several process parameters, they require assumptions of independence and multivariate normality of data. In addition, their application has mostly been at an operational level. In order to assist managers in monitoring and improving manufacturing system performance, this paper proposes an individual control chart that monitors an integrated performance index generated from a non-parametric method, which effectively considers multiple performance measures and the relationships between them. The primary advantages of this method are that a single integrated measure can be monitored, does not require assumptions of independence and multivariate normality of data, and allows for the integration of decision-maker's input when the system measures that are monitored have unequal importance.