Experimental Investigations and Multi-Objective Optimization of Selective Inhibition Sintering Process Using the Dragonfly Algorithm

The chapter focuses on utilizing a hybrid approach of response surface methodology and dragonfly algorithm for investigations and optimization of the selective inhibition sintering (SIS) process to improve the mechanical strengths such as tensile and flexural of fabricated high density polyethylene parts. The layer thickness (LT), heater energy (HE), heater and printer feedrate (HFR & PFR) are considered as the independent variables for the investigation. The SIS experiments are planned and conducted through a response surface methodology-based box-Behnken design approach to fabricate the test specimens. The optimal SIS parameters are obtained through a swarm intelligence metaheuristic technique namely dragonfly algorithm (DFA). The optimal parameter settings of LT of 0.102 mm, HE of 28.46 J/mm2, HFR of 3.22 mm/sec, and PFR of 110.49 mm/min are achieved through DFA for improved tensile and flexural strengths of 26.21 MPa and 65.71 MPa, respectively. Further, the prediction ability of DFA was compared with particle swarm optimization algorithm.

DEVELOPMENT OF LOW-COST ADDITIVE MANUFACTURING SYSTEM THROUGH SELECTIVE INHIBITION SINTERING (SIS) PROCESS AND EVALUATION OF MECHANICAL CHARACTERISTICS OF FABRICATED PARTS

Additive manufacturing (AM) is widely being used in today’s contemporary industry; however, products fabricated by the existing AM techniques are costly due to the high machine cost and low production rate. Therefore, the focus of this work is to design and fabricate a cost-effective and novel powder based selective inhibition sintering (SIS) system. Various subsystems of the machine such as the infrared heater assembly, inhibition deposition mechanism, build and feed tank assemblies, powder deposition, and the compaction system have been indigenously designed and fabricated. An electronic control system is also established through integrating sensors, linear and rotary actuators, belt and pulley mechanism, and temperature feedback control unit. The customized SIS system is developed by integrating the assembly of all the subsystems, and the electronic modules with an open-source platform to generate the necessary motion characteristics. Besides, an open source RepRap user interface firmware has been used to control the machine. Thermo-structural finite element analysis has been used to study the sintering behaviour of powder material. Inhibitor material selection and preparation have been carried out by performing an experimental investigation on the inhibition effects of various materials. The machine has been tested through fabricating parts from HDPE polymer powder. Finally, the performance of the produced parts has been evaluated by conducting an experimental investigation. The results of the investigation indicated that the fabricated parts have attained sufficient mechanical strength and, hence, the developed SIS system can be utilized to manufacture functional parts. ABSTRAK: Industri pembuatan bahan tambahan (AM) banyak digunakan dalam industri kontemporari semasa; walau bagaimanapun, produk yang terhasil daripada teknik sedia ada AM adalah mahal disebabkan harga mesin yang mahal dan kadar penghasilan yang rendah. Oleh itu, tujuan kajian ini adalah bagi mereka cipta serbuk baharu dengan harga berpatutan berdasarkan sistem pensinteran rencatan pilihan (SIS). Pelbagai mesin subsistem seperti pemasangan pemanas inframerah, mekanisme pemendapan rencatan, binaan dan pemasangan tangki suapan, deposisi serbuk, dan sistem pemadatan telah direka cipta secara alami dan dipasang siap. Sistem kawalan elektronik juga diadakan melalui integrasi sensor, lelurus dan penggerak putaran, jaluran dan mekanisme takal dan suhu unit kawalan suap balik. Sistem SIS yang dibuat mengikut pesanan ini dihasilkan dengan mengintegrasi pemasangan kesemua subsistem, dan modul elektronik melalui platfom sumber terbuka bagi menghasilkan ciri-ciri pergerakan bersesuaian. Selain itu, sumber terbuka RepRap perisian tegar antara muka telah digunakan bagi mengawal mesin. Analisis unsur terhingga struktur-terma digunakan bagi mempelajari perihal pensinteran bahan serbuk. Pilihan bahan perencat dan persediaan telah dijalankan dengan menjalankan siasatan eksperimen pada kesan perencat pelbagai bahan. Mesin diuji melalui pemasangan bahagian daripada HDPE serbuk polimer. Akhirnya, bahagian yang terhasil diuji melalui ujian eksperimen. Hasil kajian menunjukkan pemasangan bahagian telah mencapai kekuatan mekanikal mencukupi, dengan itu sistem SIS yang dibina boleh digunakan bagi mengilang bahagian berkaitan.

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.

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.

Effects of heat energy on morphology and properties of selective inhibition sintered high density polyethylene

This study provides an account of comprehensive experimentation and mechanical characterisation of high density polyethylene (HDPE) parts that are fabricated through an additive manufacturing process called selective inhibition sintering (SIS). In this study, test specimens are fabricated by selective fusing of HDPE particles through controlled heating. Morphological studies and mechanical property evaluation of these specimens are carried out to assess the impact of energy on sintering of HDPE particles and structural integrity. Results indicate that, heat energy up to a threshold level of 28.48 J/mm2 results in superior fusion of the HDPE particles, and further increase causes degradation of the structure. Surface roughness, tensile and flexural properties of SIS parts are compared with those of injection moulded parts for assessing their suitability to engineering applications.

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.