Selective Inhibition Sintering Process Research Articles

Parametric Optimization on Impact Strength of Selective Inhibition Sintering Fabricated PA-12 Parts Based on Evolutionary Optimization Algorithms

Selective inhibition sintering (SIS) is one of the novel additive manufacturing techniques to fabricate complex three-dimensional (3D) functional parts in short span. The quality of SIS processed parts can be achieved through appropriate selection of various SIS process variables such as infrared (IR) sintering temperature, part bed temperature, IR heater scanning distance, IR heater feed rate and layer thickness. The higher impact resistance is always preferred so that the materials absorb more energy during the collision. However, additively manufactured parts have experienced low impact strength. The effect of SIS process variables on the impact strength characteristics of SIS-processed parts has not yet studied. Hence, the present investigation emphasizes on the optimization of these variables on enhancing the impact strength of polyamide parts through using metaheuristic techniques, namely genetic and simulated annealing algorithms. The SIS experiments were planned and performed based on three-level five-factor Box-Behnken design (BBD). An empirical model was developed to correlate the impact strength and input process variables. The cogency of the developed model was validated using analysis of variance (ANOVA) at 95% confidence levels. The optimization results show that the genetic algorithm provides optimal SIS parameters with minimized computational efforts compared to that of simulated annealing algorithm. The maximum impact strength of 44.26 J/m was found with optimal IR heater temperature of 240 °C, sintering bed temperature of 176 °C, IR heater feed rate of 3.46 mm/s, IR heater scanning distance of 10 mm and layer thickness of 0.6 mm. Further, the validation experiments were conducted based on the attained optimal SIS process variables for evaluating the effectiveness of both the optimization methods.

SIS Parameters Optimization and Reliable Analysis to Achieve Reduced roughness of PA12 Parts

Selective inhibition sintering (SIS) results in easy, flexible, fast and cost-efficient fabrication of functional parts by using powder material for various applications. The functional part is important for operational examination by fabricating the part unswervingly from CAD data. However, poor surface quality is the major disadvantage in SIS procedure. Selection procedure of optimal operating parameters plays a major role in the fabrication of end products. The present study discusses the effect of key contributing operating parameters on the surface quality of the Polyamide parts fabricated by the SIS process. The parameters like heater power (HP), layer thickness (LT), heater feed rate (HFR), machine feed rate (MFR) and bed temperature (BT) were considered in this study. Face-Centered Central (FCC) design was employed as a statistical technique to set the optimal inhibition sintering parameters. Different mathematical models had also been generated in order to develop a relationship between influencing parameters. Further, adequacies of generated models were validated by analysis of variance (ANOVA) approach. Moreover, to decide the survival rate of the SIS parts for industrial applications, the surface roughness reliability with higher error ([Formula: see text]%) was tested by using Weibull statistics. It was observed that HP, LT and HFR are contributing more to increase surface roughness.

Study on compressive strength characteristics of selective inhibition sintered UHMWPE specimens based on ANN and RSM approach

Selective inhibition sintering (SIS) is an evolving additive manufacturing (AM) technology that enables to build functional parts from various polymers, metals and ceramics materials in reasonable cost and time. SIS parts are significantly influenced through their process parameters. Further, due to the brittleness and anisotropic characteristics of functional parts, optimization of SIS process variables is necessary to improve the compressive loading capacity. In this study, the effect of five main SIS process parameters such as infrared (IR) heater power, bed temperature, IR heater feedrate, layer thickness and IR heater scanning distance on the compressive strength (CS) of selective inhibition sintered ultra-high molecular weight poly ethylene (UHMWPE) test specimens was examined. Firstly, experimentations were conducted based on Box–Behnken design (BBD) scheme by considering three levels for each process parameters. Subsequently, the CS of SIS test specimens were predicted using response surface methodology (RSM) based on developed quadratic regression model. Finally, the predicted CS using RSM model were compared with that of artificial neural network (ANN) model. Further, the influence of SIS parameters on CS was studied through performing analysis of variance (ANOVA) and sensitivity analysis. The results show that the power and feed rate of the infrared heater have a significant influence on CS. Furthermore, an optimization was performed using the desirability approach to identify the optimal levels of the SIS process parameters and was validated through experimental result.

Optimization of fatigue strength of selective inhibition sintered polyamide 12 parts using RSM

Selective inhibition sintering (SIS) is a powder based that fabricate functional parts through fusion of powder bed on a layer by layer basis. Being a new fabrication method, the correlation between process variables and part properties are not fully comprehended. Polyamide 12 (nylon 12) is one of the widely used materials in powder based AM processes including SIS. Therefore, in this work, the effect of critical SIS process parameters on the fatigue behavior of polyamide 12 parts was experimentally investigated, and the parameter settings were optimized to maximize fatigue strength. The number of experimental runs was determined based on Box-Behnken design, and specimens were fabricated as per ASTM D7791. Specimens were tested by subjected them to fluctuating loading at a frequency of 3 Hz. The test results were analyzed using Minitab statistical analysis software. From the ANOVA result, it was identified that the fatigue life of SIS parts is significantly influenced by layer thickness, heater temperature, and heater feed rate. Optimization of process variables settings was performed using the Minitab response optimizer and maximum fatigue strength of 17.43 MPa was obtained. The verification experiment resulted in 17.93 MPa fatigue strength which is comparable to the predicted value and with the result from the literatures.

The Effects of Sintering Conditions on Selective Inhibition Sintering Process for Bronze

Selective inhibition sintering (SIS) process is a relatively new additive manufacturing technology that builds parts on a layer-by-layer basis. This new process has been of high interest in recent years. The principal idea of the SIS process for metallic parts is based on the retardation of selected segments of each powder layer from sintering. In this process, the inhibitor, which is an inorganic salt solution or a carbohydrate solution (sucrose), is printed on the boundary of each metal powder layer cross-section to form the green part. During bulk sintering, the inhibitor decomposes to second-phase particles. The decomposed solid particles cover the surface of affected metal powder particles and exert a retarding force on the surface movement, which results in sintering retardation in the printed sections. In this article, the effects of inhibitor and sintering conditions on the SIS process for bronze were investigated. Retardation from sintering was studied for bronze inhibited by sucrose through the SIS process. The mechanical properties of the printed and nonprinted sections under different sintering conditions were characterized by the aid of design of experiments methodology. The characterizations were conducted by measuring the mechanical properties of metallic parts under different sintering temperature and sintering time. Scanning electron microscopy and energy-dispersive X-ray spectroscopy techniques were used to study the printed sections after sintering.

Effect of Various Infrared Heaters on Sintering Behavior of UHMWPE in Selective Inhibition Sintering Process

Selective inhibition sintering (SIS) is an emerging powder-based additive manufacturing technology that creates polymer or metal based parts through adhesion of layer-by-layer from three-dimensional computer-aided design model. Replacement of costly laser system in selective laser sintering tremendously reduces the cost of manufacturing. SIS attempts to incorporate low cost heaters to achieve efficient sintering for production of high quality parts. However, SIS demands uniform heating of each layer for effective sintering. The present study focused on examining the heating characteristics of three different types of infrared heaters with respect to various layer thickness and determining the optimal distance between the heating surface and the powder bed. Experiments are conducted using the low-cost heaters to obtain uniform distribution of heat energy across the ultra-high molecular weight polyethylene (UHMWPE) powder surface. The thermal and optical images are captured to observe the temperature distribution on the powder and the surface roughness. Tensile and compressive specimens were fabricated and their corresponding strength was determined and surface roughness was measured to study the surface characteristics of the parts.

Investigation of parameters influencing mechanical properties in SIS by using RSM

The key challenge of selective inhibition sintering process is to select optimal process parameters to fabricate parts with desired dimensions. Heater power, layer thickness, heater feed rate, roller feed rate, and bed temperature are considered as candidate factors to optimise by using RSM. Face centred composite was employed to plan the experimental design with five factors-three levels. The experiments are performed on polyamide (PA12) material through by a novel SIS process. ANOVA was used to verify the adequacy of the developed models. Experimental results revealed that mechanical properties of fabricated parts increased with the decrease in heater power, layer thickness and with the increase in heater feed rate, roller feed rate. The microstructure evaluation was also performed to justify the surface morphology. Comparative study like sensitivity analysis is carried out to measure the impact of process parameters on mechanical properties and the obtained results are validated to select optimal parameters.

Prediction and analysis of surface roughness in selective inhibition sintered high-density polyethylene parts: A parametric approach using response surface methodology–grey relational analysis

Selective inhibition sintering (SIS) process intends to produce near-net-shape components through sintering of specific region of powder particles. The prediction of surface quality in SIS parts is a challenging task due to its complex part building mechanism and influence of abundant process parameters. Therefore, this study investigates the key contributing parameters such as layer thickness, heater energy, heater feedrate and printer feedrate on the surface quality characteristics ( Ra, Rz and Rq) of high-density polyethylene specimens fabricated through selective inhibition sintering process. The SIS system is custom built and experiments are conducted based on four-factor, three-level Box–Behnken design. The empirical models have been developed for predicting the influence of selected parameters on surface quality. The optimal process parameters such as the layer thickness of 0.1 mm, heater energy of 28.48 J/mm2, heater feedrate of 3.25 mm/s and printer feedrate of 110 mm/min are attained using grey relational multi-criteria decision-making approach. Furthermore, response surface analysis revealed that surface quality of sintered components is influenced significantly with heater energy and heater feedrate, followed by layer thickness. The confirmation experiments based on optimal process variables validate the developed grey relational analysis strategy.

Experimental Investigations and Parametric Optimization of Process Parameters on Shrinkage Characteristics of Selective Inhibition Sintered High Density Polyethylene Parts

Fabrication of functional prototypes from computer-aided design data through joining polymer powders particles is accomplished using selective inhibition sintering (SIS) process. The dimensional accuracy of sintered specimens in SIS process is significantly affected for the materials such as polymer and inhibitor, complex geometry and process parameters. Increasing dimensional accuracy in SIS process improves the quality and functional ability of end-use components. The present work investigates the shrinkage characteristics of SIS parts with reference to various process parameters such as thickness of layer, heater energy and its feedrate, and inhibitor nozzle feedrate. The test specimens are fabricated using the developed SIS system. Experimental study and mathematical modelling is accomplished based on statistical box-behnken response surface methodology. The result of analysis of variance (ANOVA) revealed that the layer thickness followed by printer feedrate and heater feedrate are the dominating variables on shrinkage. The optimal operating conditions of selected process variables to reduce shrinkage is presumed using desirability approach. The results revealed that the settings of low layer thickness and high heater energy with medium heater feedrate and medium printer feedrate is beneficial for improving dimensional stability of sintered specimen. Furthermore, the effect of these parameters on shrinkage are evaluated by conducting sensitivity analysis.

A study on influence of process parameters on the SIS processability and mechanical properties of a HDPE

Selective Inhibition Sintering (SIS) is emergent rapid prototyping technology that builds the solid parts by fusing the powder particles layer by layer with heat, directly from CAD model.The SIS process has many processing parameters of which some have a direct effect on the mechanical properties of the parts fabricated.The HDPE powder particle size was characterized by scanning electron microscopy, differential scanning calorimetry and particle size analysis. This work shows feasibility of processing an HDPE by SIS process. The effects of SIS process parameters like layer thickness, heater power and heater feed rate on tensile properties of HDPE samples are investigated. To obtain the mechanical properties, the samples were submitted to tensile testing. A thermal consequence on the mechanical properties of HDPE parts fabricated by inhibition sintering process is also discussed

An Intelligent Modeling System to Predict Mechanical Strength Characteristics of Selective Inhibition Sintered Parts using Fuzzy Logic Approach

Selective inhibition sintering (SIS) is a powder-based additive manufacturing technique that produces near net shape components through prevention of selected regions of powder particles from sintering. In SIS, due to its non-linear phenomenon, predicting functional relationship between input process parameters and output responses are cumbersome. Therefore, in the present work, an effort has been made to build an intelligent fuzzy-logic expert system for analyzing the mechanical strength characteristics includes tensile and flexural strengths of SIS processed high strength polyethylene (HDPE) parts. The experiments are conducted using response surface methodology based four-factor, three-level box-behnken design through considering SIS process variables such as layer thickness, heater energy, heater feedrate, and printer feedrate. A mamdani based fuzzy rule model is developed to predict the responses. Comparative studies of experimental and fuzzy results suggested that the obtained average error of mechanical strength characteristics using fuzzy system is in good agreement with experimental results. Thus, the developed fuzzy model can be effectively used to model SIS process to predict part strength characteristics in automated manufacturing environments to reduce the complexity of process planning activities.

A Study On Dimensional Accuracy Of Selective Inhibition Sintered HDPE Parts Using Fuzzy Logic

Selective Inhibition Sintering (SIS) is a novel additive manufacturing technology that can built functional parts through sintering of selected powder particles with least human intervention. The process parameters such as layer thickness, heat energy, heater federate, and printer federate largely influence on dimensional accuracy of built parts. The present work is to predict the dimensional accuracy on SIS fabricated high density polyethylene (HDPE) parts using mamdani based fuzzy and regression modeling techniques. The experiments are conducted using response surface methodology based box-behnken design method. A fuzzy rule based models are developed to predict the dimensional variations. Comparative evaluation of fuzzy results with experimental data indicated that the average error of fuzzy logic approach is least. It has been concluded that the fuzzy logic modeling technique can be effectively used for prediction of dimensional shrinkage in selective inhibition sintering process.

Artificial Neural Network and Regression Modeling of SIS Process for Predicting Dynamic Mechanical Properties

Selective inhibition sintering (SIS) is a novel rapid prototyping technique that produces parts of high quality with low cost. The present study focuses on predicting the dynamic mechanical properties of selective inhibition sintered high density polyethylene part. Experiments are designed based on RSM-BBD design approach through considering various SIS process parameters such as layer thickness, heater energy, heater feedrate and printer feedrate. Regression and artificial neural network (ANN) modeling are formulated and employed to evaluate the relationship between input parameters and output responses of SIS process. The trained model using ANN has attained better prediction of loss and storage modulus in comparison with regression analysis. Hence, the developed ANN network can be incorporated in manufacturing systems to predict nonlinear mechanical characteristics of SIS parts.

Fuzzy Logic-Based Expert System for Prediction of Wear Rate in Selective Inhibition Sintered HDPE Parts

Selective inhibition sintering (SIS) is a novel additive manufacturing process to build parts with least human effort and cost. The SIS made high density polyethylene (HDPE) parts undergo wear, which is robustly influenced by the SIS process parameters like layer thickness, heat energy, heater feed rate and printer feed rate. Predicting the wear rate being a complex phenomenon, a fuzzy logic based expert system is proposed to evaluate the wear characteristics of SIS made HDPE specimens. Experiments are conducted using pin-on-disc wear testing apparatus to examine the wear rate. Comparative evaluation of experiments and fuzzy approach suggested that the obtained average error of wear rate using fuzzy system is concord with experimental results. Hence, the developed fuzzy rules can be effectively utilized to predict the wear rate of SIS polymer parts in automated manufacturing environments.

Modeling and prediction of optimal process parameters in wear behaviour of selective inhibition sintered high density polyethylene parts

Owing to the dependency of multiple process parameters in additive manufacturing (AM) techniques, it is tedious to determine optimal processing conditions for improving quality characteristics of fabricated functional pats. The present study focuses on optimization of four key contributing parameters such as layer thickness, heater energy, heater feedrate, and printer feedrate on dry sliding wear behaviour of high-density polyethylene (HDPE) parts fabricated through a novel selective inhibition sintering (SIS) process. The experiments are conducted on the basis of response surface methodology (RSM) and four factor-three level box-behnken design. The significance of the developed models and contribution of each process parameters on wear rate are estimated through analysis of variance (ANOVA). The results suggested that wear rate is influenced principally by the layer thickness and heater energy. The quadratic regression model of RSM associated with the desirability approach is employed to determine optimum levels of process parameters. The morphologies of worn surfaces are observed using scanning electron microscope. Sensitivity analysis has been performed to measure the relative impact of SIS process parameters on wear rate.

Examining Mechanical Strength Characteristics of Selective Inhibition Sintered HDPE Specimens Using RSM and Desirability Approach

Selective inhibition sintering (SIS) is a powder based additive manufacturing (AM) technique to produce functional parts with an inexpensive system compared with other AM processes. Mechanical properties of SIS fabricated parts are of high dependence on various process parameters importantly layer thickness, heat energy, heater feedrate, and printer feedrate. In this paper, examining the influence of these process parameters on evaluating mechanical properties such as tensile and flexural strength using Response Surface Methodology (RSM) is carried out. The test specimens are fabricated using high density polyethylene (HDPE) and mathematical models are developed to correlate the control factors to the respective experimental design response. Further, optimal SIS process parameters are determined using desirability approach to enhance the mechanical properties of HDPE specimens. Optimization studies reveal that, combination of high heat energy, low layer thickness, medium heater feedrate and printer feedrate yielded superior mechanical strength characteristics.

Comparative Study of High Performance Polymers in Selective Inhibition Sintering Process through Finite Element Analysis

Selective Inhibition Sintering (SIS) is a novel additive manufacturing process which uses indigenously available polymers and the high cost laser system is avoided that makes the system cost-effective. Finite Element Analysis (FEA) is carried out to evaluate the performance of SIS process. The effect of temperature on the polymer structure is examined through coupled field transient thermo-structural analysis of various high performance polymer particles such as Polysulfone (PSU), Polybenzimidazole (PBI), Polyimide (PI), Polyethersulfone (PES), Perfluoroalkoxy alkanes (PFA), Ethylene tetrafluoroethylene (ETFE) and KCl is used as the inhibitor material. The structured finite element mesh model is created and heat flux is applied in equivalent time intervals to study the transient characteristics. Simulation results are presented with displacement, temperature and thermal stress for each polymer materials and their characteristics performance is evaluated.

Investigation on multi-layer selective inhibition sintering process using finite element analysis

Recently, Additive Layer Manufacturing (ALM) has attracted a lot of attention to produce complex parts in short time, without the usage of fixtures, molds, dies or additional tools. One of the cost effective ALM technique in utilizing the indigenous polymers is Selective Inhibition Sintering Process (SISP). This article examines the effect on thermal loading to polymers structure with respect to part dimensional stability. The multiple layers of polymers with inhibitors at its periphery are modelled using Finite Element Method. The birth and death finite element behaviour is incorporated to achieve layer by layer sintering phenomenon. Coupled transient thermo - structural analysis is performed through sequential coupling method to evaluate the heat distribution and structural displacement of the three dimensional part. The simulation results reveal that parts with good dimensional accuracy with less residual stress is attainableusing SISP.

Coupled Field Transient Thermo - Structural Analysis of Inhibited Sintering Process

Proliferation in the use of digital data in manufacturing led to a new industrial revolution by virtue of which user groups and researchers from multiple industrial enterprises have introduced Rapid Prototyping (RP) into their product development processes. This paper presents a coupled field thermos-structural analysis of new RP process namely, Selective Inhibition Sintering Process (SISP) for the evaluation on the effect of temperature in various polymer materials. The present study provides information of the requirement of heat source to achieve effective sintering phenomenon. The structured Finite Element (FE) model with a dimension of 30 X 30 X 1.5 mm is considered for the analysis where in different heat quantity is applied in an iterative manner to examine the sintering temperature. Based on the simulation results, for each polymer, required amount of heat to observe sintering characteristics is evaluated. The effect of applied heat on the examination of structural aspects of polymer materials including thermal stress, distortion and displacement is carried out. The simulation results affirms that the polymer materials are within in the safe structural and thermal limit and the selection of low cost heat source will be useful for the development of cost-effective SISP system.

A new heater design by radiation modeling and a new polymer waste‐saving mechanism design for the SIS process

PurposeThe purpose of this paper is to describe a heating system for the selective inhibition sintering (SIS) process that will produce uniform heat and minimize the polymer powder waste.Design/methodology/approachThis research was conducted in two areas: the first was the production of uniform heat distribution. For this task, a lighting design software was used for the initial heater design. The result was then validated by thermal images, point‐by‐point temperature measurement, and physical part fabrication. The second area was the minimization of polymer powder waste. For this task, a finger‐based masking mechanism was designed, prototyped, and tested.FindingsThe lighting design software output illustrates that the square, crossed, and parallel patterns have very low variation and seem to be acceptable alternatives for the heating system pattern. Also, results show that the temperature variation for the ceramic heater is lower (therefore better) than the wire heater. Also, the study reveals that a finger‐based masking system design and prototype is very promising from the polymer powder waste‐saving standpoint.Research limitations/implicationsOwing to the software limitation, radiation is the only source of heat transfer in this research (convection and conduction were not considered). Also, a limited number of patterns were examined for the heater design; this number can be expanded in future research.Originality/valueA new design and development method has been proposed for the heating system for the SIS process that could lead to better heaters and waste‐reducing mechanisms for the SIS process and similar applications.