DMLS Research Papers - Academia.edu (original) (raw)

Direct metal laser sintering (DMLS) process used to make three-dimensional product or joining two elements without any tooling or human intervention from computer aided data (CAD) file. CL50WS material is hot work tool steel which widely... more

Direct metal laser sintering (DMLS) process used to make three-dimensional product or joining two elements without any tooling or human intervention from computer aided data (CAD) file. CL50WS material is hot work tool steel which widely used to make die and mould in tooling industries. DMLS widely accepted to manufactured die, mould and tooling insert in tooling industries. It can be made customized tooling insert, die and mould with cooling channel which is also known as conformal cooling. Die, mould or tooling insert are widely used in injection moulding industries which manufacture mass production of discrete parts for assembly or as final product. Thus, worse dimensional accuracy and surface roughness of die and mould affect number of parts or products that make huge losses to industries. Thus, dimensional accuracy and surface roughness of die or mould is very significant parameter for injection moulding industries. Hence, this study carried out for the same. In this study, the relationship between input parameters of DMLS (laser power, layer thickness, scan speed and hatch distance) and performance characteristic (Dimensional accuracy and Surface roughness) have been discussed. From study, it can be seen that Layer thickness and laser power are most affective parameter for mentioned characteristic. Empirical model for both characteristics have been developed for future prediction of DA and SR at outside range of process parameter. Optimum result has been determined by Response Surface methodology (RSM). The obtained result was validated and that optimum result have good agreement with performed regression result.

The powder bed fusion additive manufacturing process enables fabrication of metal parts with complex geometry and elaborate internal features, the simplification of the assembly process, and the reduction of development time; however, its... more

The powder bed fusion additive manufacturing process enables fabrication of metal parts with complex geometry and elaborate internal features, the simplification of the assembly process, and the reduction of development time; however, its tremendous potential for widespread application in industry is hampered by the lack of consistent quality. This limits its ability as a viable manufacturing process particularly in the aerospace and medical industries where high quality and repeatability are critical. A variety of defects, which may be initiated during powder bed fusion additive manufacturing, compromise the repeatability, precision, and resulting mechanical properties of the final part. One approach that has been more recently proposed to try to control the process by detecting, avoiding, and/or eliminating defects is online monitoring. In order to support the design and implementation of effective monitoring and control strategies, this paper identifies, analyzes, and classifies the common defects and their contributing parameters reported in the literature, and defines the relationship between the two. Next, both defects and contributing parameters are categorized under an umbrella of manufacturing features for monitoring and control purposes. The quintuple set of manufacturing features presented here is meant to be employed for online monitoring and control in order to ultimately achieve a defect-free part. This categorization is established based on three criteria: (1) covering all the defects generated during the process, (2) including the essential contributing parameters for the majority of defects, and (3) the defects need to be detectable by existing monitoring approaches as well as controllable through standard process parameters. Finally, the monitoring of signatures instead of actual defects is presented as an alternative approach to controlling the process " indirectly."

Metalni materijali koji se koriste u procesima brze izrade proizvoda, alata i prototipa.

Direct metal laser sintering is an additive manufacturing method which allows manufacturing of complex parts without using dies in short time. In the present study, direct metal laser sintering of steel 316 powder has been studied.... more

Direct metal laser sintering is an additive manufacturing method which allows manufacturing of
complex parts without using dies in short time. In the present study, direct metal laser sintering
of steel 316 powder has been studied. Response surface methodology has been used for the
design and analysis of experiments. Nd:YAG laser with a maximum power of 75 W has used to
sinter the powder. The effect of current, scan speed and laser frequency has been investigated
on layer thickness and density of fabricated samples. In addition, by using multi response
optimisation; appropriate setting to maximise layer thickness and density and also minimise
applied energy was suggested. It can be seen that increases in current and frequency lead to
increases in thickness and density of samples. Also increasing scan speed decreases layer
thickness and density of samples.

Powder bed fusion is an additive manufacturing method which allows production of complex parts, in a shorter time compared to the conventional fabrication methods. During the last 60 years, Fe–Cu powders were widely used because of their... more

Powder bed fusion is an additive manufacturing
method which allows production of complex parts, in a
shorter time compared to the conventional fabrication
methods. During the last 60 years, Fe–Cu powders were
widely used because of their anti-friction behavior and
superior mechanical properties. Therefore, Fe–Cu powder
has been selected as the basic material for the powder bed
fusion process. In the present study, laser-assisted powder
bed fusion of Fe–Cu powder mixture has been studied
experimentally. Nd:YAG laser with a maximum power of
75 W has been used to melt the powder. The effects of
volume fraction of the Cu powder in the mixture and
applied energy density on thickness, surface concavity and
geometrical accuracy of manufactured parts have been
investigated. Results show that higher values of energy
density lead to lower geometrical accuracy, higher thickness and surface concavity.

—There is a general interest today to explore the potential of layered manufacturing as an alternative to conventional subtractive manufacturing for functional application. Direct Metal laser Sintering (DMLS) is one of the promising... more

—There is a general interest today to explore the potential of layered manufacturing as an alternative to conventional subtractive manufacturing for functional application. Direct Metal laser Sintering (DMLS) is one of the promising technologies in this regard, which is generally used to built prototypes and tooling applications. This work presents the results of a study to determine the wear behaviour of DMLS components. Wear is an important issue in using layer manufactured parts for functional application. An automotive bush was manufactured by DMLS and was tested for the wear behaviour and compared with the bushes manufactured by conventional manufacturing methods. Process parameters like sintering speed, scan spacing and hatch type were used for manufacturing the components. A comparative study for the wear behaviour was carried out and the results are discussed.

A multi-objective optimisation study is carried out for direct metal laser sintering process (DMLS). In order to optimise the individual process parameters and mechanical properties, analysis of variance (ANOVA) methods were used.... more

A multi-objective optimisation study is carried out for direct metal laser sintering process (DMLS). In order to optimise the individual process parameters and mechanical properties, analysis of variance (ANOVA) methods were used. Experiments were conducted by varying the process parameters using Taguchi's modified L8 orthogonal array method. Mechanical properties such as fatigue cycles to failure, tensile strength, compressive strength, hardness and wear rate of components have been ascertained and a mathematical model has been developed using multi-variable linear regression analysis. Genetic algorithm (GA) was used to carry out final multi-objective optimisation studies. Optimal process parameters for better mechanical properties were observed by initiating multi-objective optimisation using genetic algorithm. By selecting better process parameters, components could be manufactured in the near future with improved mechanical properties. Results obtained will be useful to manufacturing components for functional application so that DMLS technology can be brought to the mainstream manufacturing process.

Implementing additive manufacturing in an industry, particularly for critical applications of lightweight aluminum (AlSi10Mg), requires part properties that are both accurate and precise to conform to the intent of a robust design. In... more

Implementing additive manufacturing in an industry, particularly for critical applications of lightweight aluminum (AlSi10Mg), requires part properties that are both accurate and precise to conform to the intent of a robust design. In this experimental study, the objective was to evaluate anisotropy in part properties (i.e., flatness, surface roughness, surface porosity, surface hardness, pre-hole shrinkage, drilling thrust force, and thread-stripping force) when the part orientation (i.e., print inclination and recoater angle) was independently changed. This study developed and investigated an innovative procedure for determining anisotropy in part properties. The part properties were evaluated by designing specific features on a tailor-made flat plate. The replicas of the aluminum plate were additively manufactured at varying orientations using two commercial EOS parameter sets for the laser-based powder bed fusion technique. Conventional measurement equipment was used to analyze all the part properties, except the thread-stripping force, which was measured using a custom-made setup. All the part properties indicated a considerable degree of anisotropy, excluding the drilling thrust force. The printing parameters dictate the significance of the anisotropy. The anisotropy in flatness and pre-hole shrinkage decreases with an increased substrate temperature and a decrease in energy input and thermal gradient. The presence of surface overlapping contours in the scan strategy and an increased energy input can reduce anisotropy in surface roughness and hardness. No significant anisotropy was detected when the recoater angle was changed. This study helps designers establish and substantiate design for additive manufacturing that is within the limits of appropriate anisotropy for a robust design.

This work presents the results of a study to determine the wear behavior of components manufactured by direct metal laser sintering (DMLS). Wear is an important issue in using layer manufactured parts for functional application. Two... more

This work presents the results of a study to determine the wear behavior of components manufactured by direct metal laser sintering (DMLS). Wear is an important issue in using layer manufactured parts for functional application. Two different bushes were selected for the functional testing for wear behavior studies. Specimens (bushes) were manufactured by DMLS technology and was tested for wear behavior and compared with bushes manufactured by conventional manufacturing methods. Components were manufactured by using the process parameters like sintering speed, hatch spacing, post contouring speed, hatch type and infiltration with an optimized value. Testing was carried out for bushes, used for an automobile engine starter motor. A
comparative study for the wear behavior was carried out and results are discussed.

This work presents the results of a study to determine the reliability of components manufactured by direct metal laser sintering (DMLS) for fatigue strength. A standard procedure and specimen according to IS 5075-1986 had been used in... more

This work presents the results of a study to determine the reliability of components manufactured by direct metal laser sintering (DMLS) for fatigue strength. A standard procedure and specimen according to IS 5075-1986 had been used in the experiment. Using Taguchi's experimental design techniques, an orthogonal array of L4 experiments had been developed. Fatigue testing was carried out and analysis of variance (ANOVA) technique was employed to investigate the process parameters in order to identify the main process parameter that affects the performance of the fatigue component. It has been found that scan spacing had more influence on fatigue strength as compared to sintering speed and hatch type. The two-parameter Weibull distribution was adopted to find the reliability of the manufactured components. The Weibull shape parameter and scale parameter was estimated and found approximately by a normal distribution. Micro structural analysis shows that there is a better bonding between the materials when the sintering speed is reduced. Reference to this paper should be made as follows: Naiju, C.D., Adithan, M. and Radhakrishnan, P. (2010) 'Evaluation of fatigue strength for the reliability of parts produced by direct metal laser sintering (DMLS)', Int.

This work presents the results of a study carried out to determine the reciprocating wear behavior and its effect on the process parameters of components manufactured by direct metal laser sintering (DMLS). A standard... more

This work presents the results of a study carried out to determine the reciprocating wear behavior and its effect on the process parameters of components manufactured by direct metal laser
sintering (DMLS). A standard procedure and specimen had been used
in the present study to find the wear behavior. Using Taguchi’s
experimental technique, an orthogonal array of modified L8 had been
developed. Reciprocating wear testing was carried out and analysis of
variance (ANOVA) technique was used to investigate the effect of
process parameters and to identify the main process parameter that
influences the properties of wear behavior on the DMLS components.
It has been found that sintering speed had more influence on wear as
compared to other selected process parameters. Micro-structural
analysis shows that there is a better bonding between the materials
when the sintering speed is reduced and gives better wear rate.

Direct Metal Laser Sintering(DMLS) is a sequential layered manufacturing method to produce any desired three dimensional parts with simple or complex shapes with no or minimum post-processing. In this study Bronze-Nickel powder was used... more

Direct Metal Laser Sintering(DMLS) is a sequential layered manufacturing method to produce any desired three dimensional parts with simple or complex shapes with no or minimum post-processing. In this study Bronze-Nickel powder was used to make the samples. The samples were produced with the optimized set of parameters such as sintering speed, scan spacing, hatch type, hatch distance and infiltration based on previous studies. To investigate the tribological behavior of the sintered components for functional applications, reciprocating wear tests under lubricated condition were carried out. A ball-on-flat configuration was chosen for the tests. Using Design of Experiments, Taguchi's modified L9 orthogonal Table has been implemented to carry out the experiments. Hardness, load and temperature were the three parameters considered and three levels were chosen for each to create the orthogonal array. Wear tests were carried out with the set parameters and wear rates of the DMLS samples were found out. ANOVA statistical method was used to find the influence of major parameter and the contribution of each parameter on the wear rate of the samples. It has been found that the applied load, one of the selected test parameters had more influence on lubricated wear as compared to other parameters.

This work presents the results of a study to determine the direct metal laser sintering (DMLS) manufactured tooling insert for injection molding application. Surface roughness of insert as well as the part produced is important issue in... more

This work presents the results of a study to determine the direct metal laser sintering (DMLS) manufactured tooling insert for injection molding application. Surface roughness of insert as well as the part produced is important issue in using layer manufactured parts for functional application. The tool inserts were manufactured by DMLS technology
and was tested for surface roughness as well as dimensional accuracy and compared with the parts manufactured by conventional manufacturing methods. Inserts were manufactured by using process parameters like sintering speed, scan spacing, post contouring speed, hatch type and infiltration with an optimized value. Testing was carried out for inserts used for an injection molding machine used for manufacturing washers. Results of the comparative study are comparable with industrial application.

A study was carried out to find the reliability of components manufactured by Direct Metal Laser Sintering (DMLS) for tensile strength. An orthogonal array of modified L8 experimental design using Taguchi's experimental design techniques... more

A study was carried out to find the reliability of components manufactured by Direct Metal Laser Sintering (DMLS) for tensile strength. An orthogonal array of modified L8 experimental design using Taguchi's experimental design techniques was developed and used. Test results were analysed using analysis of variance (ANOVA) technique to identify the main process parameter that influences the tensile strength. It has been found that sintering speed had more influence on tensile strength as compared to other process parameters. Regression analysis shows that regression model for tensile strength is within the significance level and adequate within 90%. Detailed investigations on reliability using Weibull analysis shows that the distribution plot considered as a good Weibull design. Results show that the Weibull distribution method can be used for describing the distribution of failure times for tensile strength of DMLS components for functional applications.

A study was carried out to find the reliability of components manufactured by direct metal laser sintering (DMLS) for compressive strength. An orthogonal array of modified L8 experimental design using Taguchi's experimental design... more

A study was carried out to find the reliability of components manufactured by direct metal laser sintering (DMLS) for compressive strength. An orthogonal array of modified L8 experimental design using Taguchi's experimental design techniques was developed and used. Test results were analysed using analysis of variance (ANOVA) technique to identify the main process parameter that influences the compressive strength. It has been found that infiltration had more influence on compressive strength as compared to other process parameters. Regression analysis shows that regression model for compressive strength is within the significance level and adequate within 90%. Detailed investigations on reliability using Weibull analysis shows that the distribution plot and were considered as a good design for Weibull analysis. The Weibull distribution method can be used for describing the distribution of times to compressive strength of rapid prototyped components using DMLS for functional applications.

This work presents the results of a study carried out to determine the topology of lateral surface and its effect on the process parameters of components manufactured by direct metal laser sintering (DMLS). Using Taguchi's experimental... more

This work presents the results of a study carried out to determine the topology of lateral surface and its effect on the process parameters of components manufactured by direct metal laser sintering (DMLS). Using Taguchi's experimental technique, an orthogonal array of L4 had been developed. Surface roughness was measured along built direction and analysis of variance (ANOVA) technique was used to investigate the effect of process parameters and to identify main process parameter that influences surface roughness on DMLS components. It has been found that post contouring speed and sintering speed had more influence on surface roughness as compared to scan spacing. Microstructure of the sintered specimen along the build direction was studied using Scanning Electron Microscope (SEM). It was observed that variations in post contouring speed and sintering speed affect surface topology of DMLS components.

Production of bronze–nickel parts was undertaken by solid freeform fabrication method involving direct metal laser sintering (DMLS). Sintering speed, scan spacing and hatch pattern were considered as effective process variables governing... more

Production of bronze–nickel parts was undertaken by solid freeform fabrication method involving direct metal laser sintering (DMLS). Sintering speed, scan spacing and hatch pattern were considered as effective process variables governing the quality of parts manufactured. Two values were chosen for each of these process variables and tests for studying their effect on fatigue cycles failure using Taguchi technique. To understand the, generally, observed scatter in mechanical properties of DMLS parts, specimens produced under different processing conditions were also subjected to microstructural examination by optical microscopy and scanning electron microscopy. Microstructural defects include regions containing micro-as well as macro-segregation of bronze which cause the observed scatter in mechanical properties of DMLS parts. The likely physical reasons for the occurrence of these microstructural defects have been explained. From the analysis of results of fatigue test, it has been concluded by contribution of different processing parameters. Effect of processing parameters and microstructural defects 151 Reference to this paper should be made as follows: Naiju, C.D., Adithan, M. and Radhakrishnan, P. (2011) 'Effect of processing parameters and microstructural defects on fatigue properties of direct metal laser sintered bronze–nickel parts', Int.

Implementing additive manufacturing in an industry, particularly for critical applications of lightweight aluminum (AlSi10Mg), requires part properties that are both accurate and precise to conform to the intent of a robust design. In... more

Implementing additive manufacturing in an industry, particularly for critical applications of lightweight aluminum (AlSi10Mg), requires part properties that are both accurate and precise to conform to the intent of a robust design. In this experimental study, the objective was to evaluate anisotropy in part properties (i.e., flatness, surface roughness, surface porosity, surface hardness, pre-hole shrinkage, drilling thrust force, and thread-stripping force) when the part orientation (i.e., print inclination and recoater angle) was independently changed. This study developed and investigated an innovative procedure for determining anisotropy in part properties. The part properties were evaluated by designing specific features on a tailor-made flat plate. The replicas of the aluminum plate were additively manufactured at varying orientations using two commercial EOS parameter sets for the laser-based powder bed fusion technique. Conventional measurement equipment was used to analyze ...

The functionally graded material (FGM) is referred as the material which is non-uniform and has changing structure and material composition. FGMs are now being used in different types of areas that are different from the initial area of... more

The functionally graded material (FGM) is referred as the material which is non-uniform and has changing structure and material composition. FGMs are now being used in different types of areas that are different from the initial area of application. A functional gradient porous structure is designed and modelled as prototype to validate for the mechanical and biomedical applications. In this work, gradient porous structure of Gyroid shape is used to design a model. Gradient porous structure is entirely different from the homogenous porous structure but like homogenous porous structure, it reduces material consumption with maintenance of similar strength. To fabricate the model, stainless steel 316L is used, which is a biomaterial. The effect of functional gradient on the compressive strength of the structures by considering nine different porosities (porosities = 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%) both experimentally and numerically, is studied. The initial stage involved the development of mathematical model of functionally gradient porous structure based on governing equation of Gyroid, which is a triply periodic minimal surface. CAD models of normal porous and gradient porous structures are generated using K3DSurf and Rhinoceros software. Developed structures are manufactured by Direct Metal Laser Sintering (DMLS) Additive manufacturing method with stainless steel 316L as the build material and experimentally tested under quasi static compressive loading conditions. These models are analyzed in ANSYS software. The CAD model is validated by comparing the experimental and numerical results and the Deviation between yield stress from experimental and numerical results obtained was 3.5%.

Direct Metal Laser Sintering (DMLS) is one of the methods in layered manufacturing technologies by which metal powder can be directly used to produce both prototype and production tools. Fatigue strength is one of the important mechanical... more

Direct Metal Laser Sintering (DMLS) is one of the methods in layered manufacturing technologies by which metal powder can be directly used to produce both prototype and production tools. Fatigue strength is one of the important mechanical properties for the functional application of DMLS parts. This study was carried out to determine the optimum process parameters influencing the fatigue cycles to failure of DMLS components. Sintering speed, scan spacing, post-contouring speed, infiltration and hatch type are the process parameters taken up for the study. Statistical design of experiments using Taguchi's orthogonal array was employed for this study. Experimental data obtained were analysed using analysis of variance (ANOVA). From the results, it is found that one of the process parameters, sintering speed affects the fatigue properties of parts produced by this technology to a significant extent.