Fractional relaxation model of materials obtained with selective laser sintering technology

2019 ◽  
Vol 25 (1) ◽  
pp. 76-86 ◽  
Author(s):  
Jerzy Bochnia ◽  
Slawomir Blasiak
Keyword(s):  
Differential Calculus ◽  
Selective Laser Sintering ◽  
Laser Sintering ◽  
Content Type ◽  
Relaxation Properties ◽  
Viscosity Coefficients ◽  
Functional Models ◽  
Depth Study ◽  
Relaxation Curves ◽  
Polyamide Powder

Purpose The purpose of this paper was to verify the possibility of applying differential calculus of incomplete order to describe relaxation of the material obtained using selective laser sintering (SLS) technology. Design/methodology/approach The samples were made using the incremental technology for three print directions. Relaxation tests were conducted. The theoretical curves, which are the solution of the equation describing the five-parameter Maxwell-Wiechert model for derivatives in relation to the total time of complete order and fractional order, were adjusted to the obtained experimental curves. Findings The SLS technology creates new possibilities regarding modelling polymeric elements which might be applied as functional models (products). Therefore, it is necessary to conduct an in-depth study of their properties, including relaxation properties, which is associated with the necessity to use proper mathematical tools to describe those properties. The differential calculus of incomplete order was applied herein to describe the anisotropy of relaxation properties because of the print direction in relation to the relaxation curves adjusted with the five-parameter Maxwell-Wiechert model. Research limitations/implications As a result of the conducted considerations, the authors obtained the dependencies describing the anisotropy of relaxation properties with the use of coefficients alpha and beta, which stand for the derivative order of the differential equation, whereas coefficient kappa stands for the translation coefficient which is an innovative application of this type of mathematical apparatus. Practical implications The developed method might be applied to describe the anisotropy of a broader group of materials manufactured with the use of incremental technologies. Originality/value The application of the differential calculus of incomplete order to describe the anisotropy of the materials manufactured from polyamide powder using the SLS technology is a distinctive feature of this paper. A crucial cognitive element of the conducted research is the fact which confirms that the dynamic viscosity coefficients have the greatest impact on the anisotropy of material properties depending on the print directions.

Study in performance and morphology of polyamide 12 produced by selective laser sintering technology

2018 ◽  
Vol 24 (5) ◽  
pp. 813-820 ◽  
Author(s):  
Junjie Wu ◽  
Xiang Xu ◽  
Zhihao Zhao ◽  
Minjie Wang ◽  
Jie Zhang
Keyword(s):  
Selective Laser Sintering ◽  
Polarized Light ◽  
Chain Scission ◽  
High Energy ◽  
Laser Sintering ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Content Type ◽  
X Ray ◽  
Polyamide 12

Purpose The purpose of this paper is to investigate the effect of selective laser sintering (SLS) method on morphology and performance of polyamide 12. Design/methodology/approach Crystallization behavior is critical to the properties of semi-crystalline polymers. The crystallization condition of SLS process is much different from others. The morphology of polyamide 12 produced by SLS technology was investigated using scanning electron microscopy, polarized light microscopy, differential scanning calorimetry, X-ray diffraction and wide-angle X-ray diffraction. Findings Too low fill laser power brought about bad fusion of powders, while too high energy input resulted in bad performance due to chain scission of macromolecules. There were three types of crystal in the raw powder material, denoted as overgrowth crystal, ring-banded spherulite and normal spherulite. Originality/value In this work, SLS samples with different sintering parameters, as well as compression molding sample for the purpose of comparison, were made to study the morphology and crystal structure of sintered PA12 in detail.

Selection of selective laser sintering materials for different applications

2015 ◽  
Vol 21 (6) ◽  
pp. 630-648 ◽  
Author(s):  
Sunil Kumar Tiwari ◽  
Sarang Pande ◽  
Sanat Agrawal ◽  
Santosh M. Bobade
Keyword(s):  
Process Parameters ◽  
High Performance ◽  
Material Selection ◽  
Selective Laser Sintering ◽  
Laser Sintering ◽  
Optimal Process ◽  
Content Type ◽  
Volume Production ◽  
High Performance Application ◽  
Selection Of

Purpose – The purpose of this paper is to propose and evaluate the selection of materials for the selective laser sintering (SLS) process, which is used for low-volume production in the engineering (e.g. light weight machines, architectural modelling, high performance application, manufacturing of fuel cell, etc.), medical and many others (e.g. art and hobbies, etc.) with a keen focus on meeting customer requirements. Design/methodology/approach – The work starts with understanding the optimal process parameters, an appropriate consolidation mechanism to control microstructure, and selection of appropriate materials satisfying the property requirement for specific application area that leads to optimization of materials. Findings – Fabricating the parts using optimal process parameters, appropriate consolidation mechanism and selecting the appropriate material considering the property requirement of applications can improve part characteristics, increase acceptability, sustainability, life cycle and reliability of the SLS-fabricated parts. Originality/value – The newly proposed material selection system based on properties requirement of applications has been proven, especially in cases where non-experts or student need to select SLS process materials according to the property requirement of applications. The selection of materials based on property requirement of application may be used by practitioners from not only the engineering field, medical field and many others like art and hobbies but also academics who wish to select materials of SLS process for different applications.

Numerical modeling and experimental verification of the composite material of PA12/HA with parameterized random distribution in selective laser sintering

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Junchao Li ◽  
Yanan Yang ◽  
Ze Zhao ◽  
Ran Yan
Keyword(s):  
Composite Material ◽  
Random Distribution ◽  
Mechanical Performance ◽  
Selective Laser Sintering ◽  
Laser Sintering ◽  
Vital Role ◽  
Physical Parameters ◽  
Fe Model ◽  
Content Type ◽  
Stress Changes

Purpose The purpose of this study is to establish a finite element (FE) model with the random distribution of the Nylon12/hydroxyapatite (PA12/HA) composite material in selective laser sintering (SLS) process for considering the material anisotropy, which aims to obtain the law of temperature and stress changes in PA12/HA sintering. Design/methodology/approach By using python script in Abaqus, the FE model is established in which the two materials are randomly distributed and are assigned to their intrinsic temperature-dependent physical parameters. Molten pool sizes at various process parameters were evaluated in terms of numerical simulation and scanning electron microscope analysis, identifying a good agreement between them. Evaluation of temperature and stress distribution under the condition of different HA contents was also conducted. Findings It shows that the uneven distribution and quantity of HA powder play a vital role in stress concentration and temperature increase. Additionally, the influence of HA addition on the mechanical performance of SLS-fabricated parts shows that it is conducive to improve compressive strength when the HA ratio is less than 5% because an excess of HA powder tends to bring about a certain amount of microspores resulting in a decrease in part density. Originality/value The FE model of the PA12/HA composite material with parameterized random distribution in SLS can be applied in other similar additive manufacturing technologies. It provides a feasible guideline for the numerical analysis of properties of composite materials.

Study of the complementary usages of selective laser sintering during the high volume production of plastic parts

2016 ◽  
Vol 22 (4) ◽  
pp. 735-742 ◽  
Author(s):  
Tomaz Brajlih ◽  
Matej Paulic ◽  
Tomaz Irgolic ◽  
Ziga Kadivnik ◽  
Joze Balic ◽  
...  
Keyword(s):  
Selective Laser Sintering ◽  
High Volume ◽  
Laser Sintering ◽  
Time Cost ◽  
Content Type ◽  
Manufacturing Method ◽  
Product Availability ◽  
High Volume Production ◽  
The Times ◽  
Plastic Parts

Purpose This paper aims to present a comparison between selective laser sintering and injection moulding technology for the production of small batches of plastic products. Design/methodology/approach The comparison is based on analysing the time–cost efficiencies of each manufacturing process regarding the size of the series for the selected product sample. Both technologies are described and the times and costs of those individual processes needed to create a final product are assessed when using each of the manufacturing processes. Findings The study shows that the time-cost efficiency of the selected laser sintering technology increases according to the complexity of the product and decreases with increasing series size and product volume. Research limitations/implications The study and absolute values of the presented results are limited to a selected plastic product, but the series size-focused efficiency analysis could be expanded to general cases. Originality/value The presented analysis could be used as a general guideline for a decision-making process regarding the more efficient manufacturing method. In addition, the results show the viability of using selective laser sintering during the early stages of production when fast product availability is required, regardless of the series size. Also, some complementary effects of using both technologies in the serial production of the same part are discussed.

scholarly journals Shaping ceramics through indirect selective laser sintering

2016 ◽  
Vol 22 (3) ◽  
pp. 544-558 ◽  
Author(s):  
Jan Patrick Deckers ◽  
Khuram Shahzad ◽  
Ludwig Cardon ◽  
Marleen Rombouts ◽  
Jozef Vleugels ◽  
...  
Keyword(s):  
Design Methodology ◽  
Dispersion Polymerization ◽  
Selective Laser Sintering ◽  
Laser Sintering ◽  
Powder Synthesis ◽  
Composite Powders ◽  
Content Type ◽  
Production Methods ◽  
Nylon 12 ◽  
Furnace Sintering

Purpose The purpose of this paper is to compare different powder metallurgy (PM) processes to produce ceramic parts through additive manufacturing (AM). This creates the potential to rapidly shape ceramic parts with an almost unlimited shape freedom. In this paper, alumina (Al2O3) parts are produced, as Al2O3 is currently the most commonly used ceramic material for technical applications. Design/methodology/approach Variants of the following PM route, with indirect selective laser sintering (indirect SLS) as the AM shaping step, are explored to produce ceramic parts: powder synthesis, indirect SLS, binder removal and furnace sintering and alternative densification steps. Findings Freeform-shaped Al2O3 parts with densities up to approximately 90 per cent are obtained. Research limitations/implications The resulting Al2O3 parts contain inter-agglomerate pores. To produce higher-quality ceramic parts through indirect SLS, these pores should be avoided or eliminated. Originality/value The research is innovative in many ways. First, composite powders are produced using different powder production methods, such as temperature-induced phase separation and dispersion polymerization. Second, four different binder materials are investigated: polyamide (nylon-12), polystyrene, polypropylene and a carnauba wax – low-density polyethylene combination. Further, to produce ceramic parts with increased density, the following densification techniques are investigated as additional steps of the PM process: laser remelting, isostatic pressing and infiltration.

scholarly journals Environmental impact modeling of selective laser sintering processes

2014 ◽  
Vol 20 (6) ◽  
pp. 459-470 ◽  
Author(s):  
Karel Kellens ◽  
Renaldi Renaldi ◽  
Wim Dewulf ◽  
Jean-pierre Kruth ◽  
Joost R. Duflou
Keyword(s):  
Environmental Impact ◽  
Selective Laser Sintering ◽  
Laser Sintering ◽  
Resource Consumption ◽  
Parametric Models ◽  
Process Models ◽  
Environmental Footprint ◽  
Design Features ◽  
Content Type ◽  
Impact Reduction

Purpose – This paper aims to present parametric models to estimate the environmental footprint of the selective laser sintering (SLS)’ production phase, covering energy and resource consumption as well as process emissions. Additive manufacturing processes such as (SLS) are often considered to be more sustainable then conventional manufacturing methods. However, quantitative analyses of the environmental impact of these processes are still limited and mainly focus on energy consumption. Design/methodology/approach – The required Life Cycle Inventory data are collected using the CO2PE! – Methodology, including time, power, consumables and emission studies. Multiple linear regression analyses have been applied to investigate the interrelationships between product design features on the one hand and production time (energy and resource consumption) on the other hand. Findings – The proposed parametric process models provide accurate estimations of the environmental footprint of SLS processes based on two design features, build height and volume, and help to identify and quantify measures for significant impact reduction of both involved products and the supporting machine tools. Practical implications – The gained environmental insight can be used as input for ecodesign activities, as well as environmental comparison of alternative manufacturing process plans. Originality/value – This article aims to overcome the current lack of environmental impact models, covering energy and resource consumption as well as process emissions for SLS processes.

Investigating the stress relaxation of photopolymer O-ring seal models

2014 ◽  
Vol 20 (6) ◽  
pp. 533-540 ◽  
Author(s):  
Czesław Kundera ◽  
Jerzy Bochnia
Keyword(s):  
Stress Relaxation ◽  
Test Results ◽  
Content Type ◽  
Relaxation Properties ◽  
Ring Model ◽  
Relaxation Functions ◽  
Elastomeric Materials ◽  
Ring Seal ◽  
Relaxation Curves ◽  
Practical Implications

Purpose – This paper aims to investigate the suitability of additive manufacturing to produce O-ring seals. Design/methodology/approach – The O-rings were made by the PolyJet-Matrix technology using four different digital materials and then tested for relaxation properties under static and dynamic (sliding) conditions. The approximation of the relaxation curves involved modelling with a Prony series. Findings – The PolyJet-Matrix technology offers new opportunities to model elastomeric elements, with examples being the O-rings produced and tested for their relaxation properties. Describing the behaviour of the particular materials fabricated with this technology by using relaxation functions will extend the knowledge base on digital materials. Research limitations/implications – The four types of photopolymers used in the experiment differed in viscoelastic properties. The analysis of the stress relaxation of the O-ring models was performed at four different step displacements of the loading element. Practical implications – The test results may be useful for the design of O-ring seals made of new elastomeric materials. The relaxation properties of the O-rings made of such materials can be applied to analyse the dynamics of seals, for instance, face seals. Originality/value – The originality of the work lies in the use of digital materials to design and produce elastomeric elements with different relaxation properties, which was confirmed by the test results. This paper presents results of a relaxation analysis for a ring model and the material that the ring is made of. It also discusses how 3D printing and digital materials can be applied in practice.

Investigation on selective laser sintering of PA12: dimensional accuracy and mechanical performance

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Achille Gazzerro ◽  
Wilma Polini ◽  
Luca Sorrentino
Keyword(s):  
Mechanical Performance ◽  
Selective Laser Sintering ◽  
Central Zone ◽  
Dimensional Accuracy ◽  
Laser Sintering ◽  
Point Of View ◽  
Content Type ◽  
Mechanical Performances ◽  
The Many ◽  
Additional Support

Purpose Selective laser sintering (SLS) has passed other techniques, thanks to its high print resolution, its ability to print microscale geometries without any additional support, its surface quality and its long-term thermal stability. However, despite the many advantages of SLS compared to fusion deposition modelling, there are still today some limitations on the materials to be printed. A limit critical from an industrial point of view is the aging of PA12 powder, i.e. the degradation of its physical and chemical performances, due to the high temperatures and the long printing cycles, thus involving a decrease of the mechanical properties of the printed parts. The purpose of this study was to charaterize mechanically and dimensionally specimens printed in PA12 through SLS by means of virgin or aged powder, i.e. powder just used for five printing cycles. Design/methodology/approach To achieve this aim, a set of specimens were designed, built, measured and mechanically tested; the obtained results were put into relationship with the values of the process parameters used to print them. Statistical tools to design the experiments and to analyse the obtained results were used. Findings The results show that the SLS process carried out through a Sintratec machine on PA12 powder has a good repeatability. To obtain the best dimensional and mechanical performances, it is needed to use virgin powder and place the part in the central zone of the printing area. Originality/value There are no scientific articles dealing with the influence of both the aging of the powder and the manufacturing parameters on the dimensional and mechanical characterization of specimens printed with SLS technique in PA12.

Selective Laser Sintering of Tissue Engineering Scaffolds Using Poly(L-Lactide) Microspheres

2007 ◽  
Vol 334-335 ◽  
pp. 1225-1228 ◽  
Author(s):  
Wen You Zhou ◽  
S.H. Lee ◽  
Min Wang ◽  
W.L. Cheung
Keyword(s):  
Tissue Engineering ◽  
Porous Scaffold ◽  
Selective Laser Sintering ◽  
Laser Sintering ◽  
Porous Scaffolds ◽  
Tissue Engineering Scaffolds ◽  
Water Emulsion ◽  
Bed Temperature ◽  
Oil In Water Emulsion ◽  
Polyamide Powder

This paper reports a study on the modification of a commercial selective laser sintering (SLS) machine for the fabrication of tissue engineering scaffolds from small quantities of poly(L-lactide) (PLLA) microspheres. A miniature build platform was designed, fabricated and installed in the build cylinder of a Sinterstation 2000 system. Porous scaffolds in the form of rectangular prism, 12.7×12.7×25.4 mm3, with interconnected square and round channels were designed using SolidWorks. For initial trials, DuraFormTM polyamide powder was used to build scaffolds with a designed porosity of ~70%. The actual porosity was found to be ~83%, which indicated that the sintered regions were not fully dense. PLLA microspheres in the size range of 5-30 μm were made using an oil-in-water emulsion solvent evaporation procedure and they were suitable for the SLS process. A porous scaffold was sintered from the PLLA microspheres with a laser power of 15W and a part bed temperature of 60oC. SEM examination showed that the PLLA microspheres were partially melted to form the scaffold. This study has demonstrated that it is feasible to build tissue engineering scaffolds from small amounts of biomaterials using a commercial SLS machine with suitable modifications.

Fabrication of three dimensional open porous regular structure of PA-2200 for enhanced strength of scaffold using selective laser sintering

2016 ◽  
Vol 22 (4) ◽  
pp. 752-765 ◽  
Author(s):  
Jatender Pal Singh ◽  
Pulak M. Pandey ◽  
Anita Kamra Verma
Keyword(s):  
Porous Structure ◽  
Pore Size ◽  
Process Parameters ◽  
Cell Structure ◽  
Selective Laser Sintering ◽  
Three Dimensional ◽  
Laser Sintering ◽  
Open Cell ◽  
Content Type ◽  
Open Porous Structure

Purpose Scaffolds are essentially required to have open porous structure for facilitating bone to grow. They are generally placed on those bone defective/fractured sites which are more prone to compressive loading. Open porous structure lacks in strength in comparison to solid. Selective laser sintering (SLS) process is prominently used for fabrication of polymer/composite scaffolds. So, this paper aims to study for fabrication of three-dimensional open porous scaffolds with enhanced strength, process parameters of SLS of a biocompatible material are required to be optimized. Design/methodology/approach Regular open porous structures with suitable pore size as per computer-aided design models were fabricated using SLS. Polyamide (PA-2200) was used to fabricate the specimen/scaffold. To optimize the strength of the designed structure, response surface methodology was used to design the experiments. Specimens as per ASTM D695 were fabricated using SLS and compressive testing was carried out. Analysis of variance was done for estimating contribution of individual process parameters. Optimized process parameters were obtained using a trust region algorithm and correlated with experimental results. Accuracy of the fabricated specimen/scaffold was also assessed in terms of IT grades. In vitro cell culture on the fabricated structures confirmed the biocompatibility of polyamide (PA-2200). Findings Optimized process parameters for open cell process structures were obtained and confirmed experimentally. Laser power, hatch spacing and layer thickness have contributed more in the porous part’s strength than scan speed. The accuracy of the order of IT16 has been found for all functional dimensions. Cell growth and proliferation confirmed biocompatibility of polyamide (PA-2200) for scaffold applications. Originality/value This paper demonstrates the biocompatibility of PA-2200 for scaffold applications. The optimized process parameters of SLS process for open cell structure having pore size 1.2 × 1.2 mm2 with strut diameter of 1 mm have been obtained. The accuracy of the order of IT16 was obtained at the optimized process factors.

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