Special Issue "Metal Injection Moulding"

A special issue of Metals (ISSN 2075-4701).

Deadline for manuscript submissions: closed (31 March 2016)

Special Issue Editors

Guest Editor
Prof. Dr. Hideshi Miura

Department of Mechanical Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, 819-0395, Japan
Website | E-Mail
Interests: Metal injection molding; Microprosessing; Evaluate technology of properties; Micro forming; Microgrooves; Coining; Rolling; Fluid dynamic spindle
Guest Editor
Dr. Seong Jin Park

Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), San 31, Hyoja dong, Nam-gu, Pohang, Gyunguk, 790-784, Korea
Website | E-Mail
Interests: polymer assisted powder processing such as powder injection molding and its modeling and simulation with different scales

Special Issue Information

Dear Colleagues,

MIM (Metal Injection Molding) is an advanced manufacturing technology for the production of complex, high volume net-shape components with a high production rate. This technology combines the advantages of plastic injection molding and conventional powder metallurgy. A MIM process consists of four steps: mixing, injection molding, debinding, and sintering. In the mixing step, a small quantity of a polymer with metal powder forms a feedstock that can be molded. After shaping, the polymeric binder system is extracted and the powder in sintered, often to near-theoretical densities. MIM technology has been applied in various industries, such as the automobile, electronic, medical, aerospace, and defense industries.

MIM is faced with a number of issues related to materials, process, modeling, and simulations. Powder characteristics have a significant effect on the overall process of MIM. Development and optimization of the binder system is one of the most essential topics in MIM technology. The development of appropriate process conditions is required to achieve desired properties. Simulations for feedstock behavior during molding and sintering need to be investigated. Powder-binder separation, double insert injection molding, porosity control using polymeric beads, and powder orientation simulations are also recent topics of MIM. Papers regarding fundamental MIM processes and the development of novel techniques and technologies in MIM processes, as well as review articles, are invited for inclusion in this Special Issue on "MIM".

Prof. Dr. Hideshi Miura
Dr. Seong Jin Park
Guest Editors

Manuscript Submission Information

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Keywords

  • Metal Injection Molding
  • metal powder
  • binder
  • feedstock
  • feedstock rheology
  • debinding
  • sintering
  • modeling

Published Papers (7 papers)

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Research

Open AccessArticle Models to Predict the Viscosity of Metal Injection Molding Feedstock Materials as Function of Their Formulation
Metals 2016, 6(6), 129; doi:10.3390/met6060129
Received: 30 March 2016 / Revised: 19 May 2016 / Accepted: 23 May 2016 / Published: 28 May 2016
Cited by 3 | PDF Full-text (2674 KB) | HTML Full-text | XML Full-text
Abstract
The viscosity of feedstock materials is directly related to its processability during injection molding; therefore, being able to predict the viscosity of feedstock materials based on the individual properties of their components can greatly facilitate the formulation of these materials to tailor properties
[...] Read more.
The viscosity of feedstock materials is directly related to its processability during injection molding; therefore, being able to predict the viscosity of feedstock materials based on the individual properties of their components can greatly facilitate the formulation of these materials to tailor properties to improve their processability. Many empirical and semi-empirical models are available in the literature that can be used to predict the viscosity of polymeric blends and concentrated suspensions as a function of their formulation; these models can partly be used also for metal injection molding binders and feedstock materials. Among all available models, we made a narrow selection and used only simple models that do not require knowledge of molecular weight or density and have parameters with physical background. In this paper, we investigated the applicability of several of these models for two types of feedstock materials each one with different binder composition and powder loading. For each material, an optimal model was found, but each model was different; therefore, there is not a universal model that fits both materials investigated, which puts under question the underlying physical meaning of these models. Full article
(This article belongs to the Special Issue Metal Injection Moulding)
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Open AccessArticle Algorithm for Improvement of a Wrongly Adverted Filling Profile in Injection Flow
Metals 2016, 6(6), 124; doi:10.3390/met6060124
Received: 17 March 2016 / Revised: 7 May 2016 / Accepted: 18 May 2016 / Published: 24 May 2016
PDF Full-text (5854 KB) | HTML Full-text | XML Full-text
Abstract
As Eulerian description is generally used for the simulation of filling flow problems in the powder injection molding process, and the governing equation of the filling state takes the form of an advection equation, the distortion can be easily produced when dealing with
[...] Read more.
As Eulerian description is generally used for the simulation of filling flow problems in the powder injection molding process, and the governing equation of the filling state takes the form of an advection equation, the distortion can be easily produced when dealing with the filling process in complex cavities, such as the similar channels in shapes of and L, inside which the phenomena of opposite joining and bypass are involved. In order to improve the precision, causes of the unrealistic results were analyzed in the present paper. A notion similar to the upwind method was introduced and a corresponding correction method was proposed to settle this problem. Based on the efficient explicit algorithm for PIM simulation, and by means of systematic operation to modify the fluid velocity field, the untrue impact of air flow, represented by the velocity field in front of the filling fronts, can be weakened. Then, the advection of the filling state can be mainly affected by the flow field behind the filling front. The simulation results show that the correction algorithm can effectively inhibit the distortion. The simulation of the filling processes in the complex cavities, inside which the flow directions will be subject to the sudden changes, can be realized correctly. Full article
(This article belongs to the Special Issue Metal Injection Moulding)
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Open AccessArticle Metal Injection Molding (MIM) of Magnesium and Its Alloys
Metals 2016, 6(5), 118; doi:10.3390/met6050118
Received: 24 March 2016 / Revised: 12 May 2016 / Accepted: 13 May 2016 / Published: 20 May 2016
Cited by 2 | PDF Full-text (4283 KB) | HTML Full-text | XML Full-text
Abstract
Current research has highlighted that magnesium and its alloys as biodegradable material are highly suitable for biomedical applications. The new material fully degrades into nontoxic elements and offers material properties matching those of human bone tissue. As biomedical implants are rather small and
[...] Read more.
Current research has highlighted that magnesium and its alloys as biodegradable material are highly suitable for biomedical applications. The new material fully degrades into nontoxic elements and offers material properties matching those of human bone tissue. As biomedical implants are rather small and complex in shape, the metal injection molding (MIM) technique seems to be well suited for the near net shape mass production of such parts. Furthermore, MIM of Mg-alloys is of high interest in further technical fields. This study focusses on the performance of MIM-processing of magnesium alloy powders. It includes Mg-specific development of powder blending, feedstock preparation, injection molding, solvent and thermal debinding and final sintering. Even though Mg is a highly oxygen-affine material forming a stable oxide layer on each particle surface, the material can be sintered to nearly dense parts, providing mechanical properties matching those of as cast material. An ultimate tensile strength of 142 MPa, yield strength of 67 MPa, elastic modulus of 40 GPa and 8% elongation at fracture could be achieved using novel organic polymer binders for the feedstock preparation. Thus, first implant demonstrator parts could be successfully produced by the MIM technique. Full article
(This article belongs to the Special Issue Metal Injection Moulding)
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Open AccessArticle Development and Characterization of a Metal Injection Molding Bio Sourced Inconel 718 Feedstock Based on Polyhydroxyalkanoates
Metals 2016, 6(4), 89; doi:10.3390/met6040089
Received: 31 March 2016 / Revised: 11 April 2016 / Accepted: 14 April 2016 / Published: 18 April 2016
Cited by 1 | PDF Full-text (2955 KB) | HTML Full-text | XML Full-text
Abstract
The binder plays the most important role in the metal injection molding (MIM) process. It provides fluidity of the feedstock mixture and adhesion of the powder to keep the molded shape during injection molding. The binder must provide strength and cohesion for the
[...] Read more.
The binder plays the most important role in the metal injection molding (MIM) process. It provides fluidity of the feedstock mixture and adhesion of the powder to keep the molded shape during injection molding. The binder must provide strength and cohesion for the molded part and must be easy to remove from the molded part. Moreover, it must be recyclable, environmentally friendly and economical. Also, the miscibility between polymers affects the homogeneity of the injected parts. The goal of this study is to develop a feedstock of superalloy Inconel 718 that is environmentally friendly. For these different binders, formulations based on polyethylene glycol (PEG), because of his water solubility property, and bio sourced polymers were studied. Polyhydroxyalkanoates (PHA) were investigated as a bio sourced polymer due to its miscibility with the PEG. The result is compared to a standard formulation using polypropylene (PP). The chemical and rheological behavior of the binder formulation during mixing, injection and debinding process were investigated. The feedstock was characterized in the same way as the binders and the interactions between the powder and the binders were also studied. The results show the well adapted formulation of polymer binder to produce a superalloy Inconel 718 feedstock. Full article
(This article belongs to the Special Issue Metal Injection Moulding)
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Open AccessArticle Influencing Factors for the Microstructure and Mechanical Properties of Micro Porous Titanium Manufactured by Metal Injection Molding
Metals 2016, 6(4), 83; doi:10.3390/met6040083
Received: 16 March 2016 / Revised: 30 March 2016 / Accepted: 31 March 2016 / Published: 9 April 2016
Cited by 1 | PDF Full-text (18288 KB) | HTML Full-text | XML Full-text
Abstract
Porous titanium is a new structural and functional material. It is widely used in many fields since it integrates the properties of biomaterials with those of metallic foam. A new technology that combines both the preparation and forming of porous materials has been
[...] Read more.
Porous titanium is a new structural and functional material. It is widely used in many fields since it integrates the properties of biomaterials with those of metallic foam. A new technology that combines both the preparation and forming of porous materials has been proposed in this paper. Moreover, a new solder was developed that could be employed in the joining of porous materials. Influencing factors for microstructure and mechanical properties of the parent material and joint interface are identified. Metal injection molding (MIM) technology was used for fabricating porous materials. The feedstock for injection molding of porous titanium powders was prepared from titanium powders and a polymer-based binder system. In addition, the proportion of powder loading and binders was optimized. Through MIM technology, a porous titanium filter cartridge was prepared. For the purpose of investigating the thermal debinding technology of the filter cartridge, effects of the sintering temperature on the porosity, morphology of micropores and mechanical properties were analyzed. It could be found that when the sintering temperature increased, the relative density, bending and compression strength of the components also increased. Moreover, the porosity reached 32.28% when the sintering temperature was 1000 °C. The microstructure morphology indicated that micropores connected with each other. Meanwhile, the strength of the components was relatively high, i.e., the bending and compression strength was 65 and 60 MPa, respectively. By investigating the joining technology of porous filter cartridges, the ideal components of the solder and pressure were determined. Further research revealed that the micropore structure of the joint interface is the same as that of the parent material, and that the bending strength of the joint interface is 40 MPa. Full article
(This article belongs to the Special Issue Metal Injection Moulding)
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Open AccessArticle Influences of Restaurant Waste Fats and Oils (RWFO) from Grease Trap as Binder on Rheological and Solvent Extraction Behavior in SS316L Metal Injection Molding
Metals 2016, 6(2), 19; doi:10.3390/met6020019
Received: 4 November 2015 / Revised: 14 December 2015 / Accepted: 18 December 2015 / Published: 2 February 2016
Cited by 2 | PDF Full-text (2833 KB) | HTML Full-text | XML Full-text
Abstract
This article deals with rheological and solvent extraction behavior of stainless steel 316L feedstocks using Restaurant Waste Fats and Oils (RWFO) from grease traps as binder components along with Polypropylene (PP) copolymer as a backbone binder. Optimal binder formulation and effect of solvent
[...] Read more.
This article deals with rheological and solvent extraction behavior of stainless steel 316L feedstocks using Restaurant Waste Fats and Oils (RWFO) from grease traps as binder components along with Polypropylene (PP) copolymer as a backbone binder. Optimal binder formulation and effect of solvent extraction variables on green compacts are being analyzed. Four binder formulations based on volumetric ratio/weight fraction between PP and RWFO being mixed with 60% volumetric powder loading of SS316L powder each as feedstock. The rheological analysis are based on viscosity, shear rate, temperature, activation energy, flow behavior index, and moldability index. The optimal feedstock formulation will be injected to form green compact to undergo the solvent extraction process. Solvent extraction variables are based on solvent temperature which are 40 °C, 50 °C, and 60 °C with different organic solvents of n-hexane and n-heptane. Analysis of the weight loss percentage and diffusion coefficient is done on the green compact during the solvent extraction process. Differential Scanning Calorimeter (DSC) is used to confirm the extraction of the RWFO in green compacts. It is found that all binder fractions exhibit pseudoplastic behavior or shear thinning where the viscosity decreases with increasing shear rate. After considering the factors that affect the rheological characteristic of the binder formulation, feedstock with binder formulation of 20/20 volumetric ratio between PP and RWFO rise as the optimal binder. It is found that the n-hexane solvent requires less time for extracting the RWFO at the temperature of 60 °C as proved by its diffusion coefficient. Full article
(This article belongs to the Special Issue Metal Injection Moulding)
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Open AccessArticle Control of the Nano-Particle Weight Ratio in Stainless Steel Micro and Nano Powders by Radio Frequency Plasma Treatment
Metals 2015, 5(4), 2058-2069; doi:10.3390/met5042058
Received: 14 October 2015 / Revised: 2 November 2015 / Accepted: 2 November 2015 / Published: 6 November 2015
Cited by 2 | PDF Full-text (637 KB) | HTML Full-text | XML Full-text
Abstract
This study describes how to make stainless steel hybrid micro-nano-powders (a mixture of micro-powder and nano-powder) using an in situ one-step process via radio frequency (RF) thermal plasma treatment. Nano-particles attached to micro-powders were successfully prepared by RF thermal plasma treatment of stainless
[...] Read more.
This study describes how to make stainless steel hybrid micro-nano-powders (a mixture of micro-powder and nano-powder) using an in situ one-step process via radio frequency (RF) thermal plasma treatment. Nano-particles attached to micro-powders were successfully prepared by RF thermal plasma treatment of stainless steel powder with an average size of 35 μm. The ratio of nano-powders is estimated with a two-dimensional fluid simulation that calculates the temperature profile influencing the rate of surface evaporation. The simulation is conducted to determine the variation of the input power and the distance from the plasma torch to the feeding nozzle. It was demonstrated experimentally that the nano-powder ratio in the micro-nano-powder mixture can be controlled by adjusting the feeding rate, plasma power, feeding position and quenching effect during plasma treatment. The ratio of nano-particles in the micro-nano-powder mixture was controlled in a range from 0.1 (wt. %) to 30.7 (wt. %). Full article
(This article belongs to the Special Issue Metal Injection Moulding)
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