Sintering Simulation and Automatic Shape Compensation for Shrinkage during Binder Jet Sintering Process
Pavan Suri, HP Inc.
Additive Manufacturing (AM) techniques are being adopted in the commercial production of parts and are becoming the future of the manufacturing industry. These processes differ based on the material type, material feedstock, the state of fusion, the energy source of fusion, and the AM principle. Among these methods, metal Binder Jet Sintering (BJS) is finding a prominent role due to its energy efficiency and low operation cost. However, it comes with significant challenges, such as meeting the dimensional tolerance requirements, density variation of the printed part, and potential cracking during the debinding stage. Part designers have to design the green part to meet the desired dimensional tolerances after shrinkage during the sintering process. Since this shrinkage is a nonlinear phenomenon, correcting it requires a trial-and-error approach. The local relative density increase is also driven by the same process mechanism and predicting this variation in the part geometry is critical for the part quality. These challenges require accurate numerical simulation of the BJS process to predict the final part dimensions, density distribution, and other part quality issues. This becomes the basis for the shape correction of the green part to meet the final dimensional requirements.
A transient finite element solution to model the BJS process accurately is presented in this work. The laws of conservation mass, momentum, and energy are solved with the models for material behavior and sintering stress. The sintering process is driven by the reduction of free energy by forces associated with the curvature of the particle surface, any applied external pressure, and chemical reactions. The governing equations are written in terms of relative density, and we consider the effects of thermal, elastic, viscoplastic, and sintering stress. Two different material models – the powder Skorohold-Olevsky Viscous Sintering model and the two-phase densification models are studied in this work. For improving computational efficiency, the method developed can model the entire or partial oven curve, and in addition, it can be done either by imposing the temperature or by computing it using the energy equation. The numerical simulation includes grain growth prediction using Arrhenius models. The computed transient results include relative density, temperature, sinter deviation, shrinkage, and grain size. The predicted results presented are validated using experimental data to enable its use for compensation analysis.
The shape compensation analysis is achieved through an iterative solution methodology. It starts with a sintering analysis of the part under the specified conditions using the initially designed geometry, based on the predicted shrinkage and distortion the green part geometry is automatically adjusted and solved again. This process is repeated until the desired tolerance is achieved. The results and validations are presented to demonstrate the accuracy and practical utility of the solution presented in designing and manufacturing parts using 3D printing with a binder jet sintering process.
Sintering Studies Inspired by RMG
T S Shivashankar, INDO-MIM LIMITED
Hybrid Manufacturing (SLA + MIM) of Copper Alloy for Fanless Heatsink Applications
Krishna Sai Aparna Munjuluri, University of Louisville
Additive manufacturing (AM) methods like Selective Laser Melting (SLM) have demonstrated the capability to produce high-density parts (achieving >99.8% relative density) for metals such as steels, copper, and titanium alloys. However, significant challenges remain for large-scale industrial adoption, including high surface roughness, the need for extensive post-processing, high energy consumption, and elevated production costs. In contrast, Metal Injection Molding (MIM) presents an established, cost-effective solution for large-volume production. In this study, we propose a novel hybrid manufacturing approach that combines Stereolithography (SLA) 3D printing with Metal Injection Molding to fabricate fanless copper heatsinks for power electronics. The use of SLA enables the creation of high-resolution, complex sacrificial mold inserts, facilitating the production of intricate geometries not achievable through conventional MIM processes. These designs are further optimized using Fusion360 for lattice structures, followed by flow simulations in Moldex3D to ensure proper mold filling and manufacturability.
For the final part production, a copper-based feedstock specifically tailored for MEX (Material Extrusion) 3D printing is utilized during the injection molding phase. The manufactured heatsinks are characterized in terms of microstructure, mechanical properties, and surface roughness. A comparative analysis is presented against SLM-printed copper parts, highlighting improvements in design flexibility, surface finish, and potential reductions in post-processing steps. This hybrid approach demonstrates a promising pathway toward cost-effective, large-scale manufacturing of high-performance copper components, offering potential benefits in applications where thermal management is critical.
Sintering Simulation by Integrating Results from Injection Molding in Metal Injection Molding
Cristoph Hinse, SimpaTec Inc.
Simulation tools play a crucial role in enhancing the Metal Injection Molding (MIM) process, particularly in the modeling of feedstock flow behavior during the injection molding phase. These tools allow for the prediction and identification of potential defects such as incomplete filling, weld lines, voids, and even powder-binder segregation. By simulating these aspects, manufacturers can optimize critical process parameters such as injection speed, pressure, and temperature to ensure the production of high-quality "green parts" with minimal defects.
Beyond optimizing processing conditions, simulations are invaluable for refining the geometry of both the part and the mold. By predicting issues early in the design phase, manufacturers can reduce trial-and-error approaches and achieve better outcomes with more complex part geometries. Feedstock behavior simulations allow for the identification of stress points, flow imbalances, or geometrical inconsistencies, helping to ensure uniform feedstock distribution and enhance part strength.
In the next step, integrating the results from injection molding simulations into sintering simulations provides a comprehensive understanding of material behavior throughout the MIM process. Sintering simulations can predict part shrinkage, densification, and the development of defects such as deformation, giving manufacturers insight into final part quality and dimensional accuracy. Combining both sets of simulations helps achieve a highly optimized process, geometries and even more important – time to market.
This integrated simulation approach not only reduces lead times but also ensures higher part quality and improved efficiency. By refining process parameters and geometries before production begins, manufacturers can significantly reduce waste, minimize post-production alterations, and enhance overall part performance.
A Synergy Approach Integrating Master Alloy Design and Powder Injection Moulding for High-performance Interconnectors Leveraging SOFCs Industry
Elena de Lamo Riuz, University of Castilla La Mancha
Solid oxide fuel cells and electrolyzers are promising systems to address the challenges of electrical energy storage. However, the components of these systems must meet specific requirements due to the extreme conditions to which they are subjected. Interconnectors, in particular, require high corrosion resistance, as well as excellent thermal and electrical conductivity. Currently, they are manufactured using commercial alloys and conventional methods, resulting in simple geometries that often fail to meet performance demands such as durability and efficiency. To address these limitations, our group has developed a master alloy with superior material properties compared to commercial alternatives. This alloy is optimized for metal injection molding (MIM), aiming to enhance the industrial production of these components. Additionally, we leverage 3D printing techniques using filaments and pellets (material extrusion) for prototyping, developing new alloys, and designing advanced geometries, demonstrating the synergy between powder injection molding (PIM) and additive manufacturing.
Use of Sinter-Based Additive Manufacturing as a Bridge to Production for Metal Injection Molding Production
David Smith, APG-MIM
Metal injection molding (MIM) is a widely accepted sinter-based forming technology capable of producing intricate net-shape or near net-shape metal components. Unfortunately, the tooling investment for injection molding can be high, and because MIM is a net-shape forming process, any late design changes in the launch phase will likely require additional investment. For entrepreneurs and inventors trying to bring their new products to market, these up-front MIM costs can be a major hurdle, especially if the designs are still in a state of flux. Alpha Precision Group’s MIM operation (APG MIM) is leveraging sinter-based metal additive manufacturing (MAM) to minimize the up-front costs and optimize the part design to mitigate any risk for the eventual switch-over to the MIM process. This presentation and case study will detail how sinter-based MAM can be a cost-effective bridge between an early design concept and MIM production.
Use of Finite Element Analysis to Mitigate MIM Sintering Distortion
Joe Taylor, APG-MIM
Metal injection molding (MIM) is an efficient, sinter-based metal forming technology that allows intricate metal components to be formed without relying on the flow of molten metal to fill the mold, making it a great process for metals with high melting points. Although the sintering of MIM components does not reach the melting point of the metal, the heat and subsequent consolidation of material is sufficient to induce unwanted distortion. Un-supported and cantilevered part features can “droop”, and the consolidation of the material can cause drag between the parts and the sintering fixtures. The use of simulation software to predict the behavior of a MIM component during sintering can be used as an aid in the design of ceramic sintering fixtures to compensate for material shrinkage and minimize distortion. This case study outlined in this paper will show how simulation software improved the net-shape dimensional capability of a MIM component.
Powder Injection Molding of Thermal Management Materials
John L. Johnson, FAPMI, Novamet/Ultra Fine Specialty Products
Dissipation of heat from microelectronic devices as their size decreases and their power increases is an on-going challenge. Powder injection molding (PIM) enables fabrication of unique geometric features for heat transfer from materials with high thermal conductivity, such as W-Cu, Mo-Cu, Cu, Al, and AlN. The development of PIM processing of these thermal management materials will be traced from early work in the early 1990s, to growing commercial applications in the 2000s, to current prospects for PIM and additive manufacturing. The links between particle size and impurity contents on densification, microstructure, and thermal properties of sintered or infiltrated PIM components will be highlighted.
Additive Manufacturing of 6061 Aluminum Alloy by Material Extrusion (MEX)
Kunal Kate, University of Louisville
This research studies additive manufacturing of 6061 aluminum alloy via Material Extrusion (MEX). Feedstock was prepared by mixing Al-6061 powder and polymer binder and then extruded using a capillary rheometer to form a filament. The filament was used to print green parts with varying extrusion multipliers of 0.9, 0.95, and 1 with standard MEX 3D printers to achieve 100% dense green parts. Additionally, tensile geometries with ASTM-E8M standards were 3D printed and sintered. The green parts were subjected to solvent debinding, thermal debinding, and finally, sintered to reach 97±0.9%. Additionally, the sintered tensile bars were tested for their mechanical properties and it was found that the parts reached an ultimate tensile strength (UTS) of 153±3 MPa, elongation of 28±3%, and yield strength 28±11 MPa. These mechanical properties were found to be comparable to annealed Al-6061. The microstructure of the sintered specimens was also characterized. The main objective is to apply the MEX process to aluminum alloys and optimize the process parameters for better mechanical properties.
Development of Innovative Ti Alloy through MIM
Hideshi Miura, FAPMI, Kyushu University
Ti-6Al-4V is the most common Ti alloy and has been used in various industrial fields such as aerospace and power plant because of their high tensile strength, high fatigue strength and light weight. However, their low thermal conductivity, high hardness and low Young’s modulus make them difficult to produce the complicated shapes via machining. On the other hand, metal injection molding process offers net shape production, high design flexibility, and high cost efficiency, which is useful for forming the materials with poor workability such as Ti alloys.
In our previous studies, the injection molded Ti-6Al-4V alloy compacts were improved the properties by addition of third elements such as Cr and Mo, and they showed high tensile strength and high elongation comparable to wrought materials. However, the fatigue strength was significantly lower than that of wrought materials. In order to improve the fatigue strength of injection molded Ti-6Al-4V alloy compacts, refining of microstructure was treated by addition of 3rd & 4th elements including TiB2 powders and also heat treatment. Eventually, we obtained the same fatigue strength as that of wrought materials. In addition, the relationship of grain size and fatigue strength showed good agreement with Hall-Petch relations
Sinterability of Hydroxyapatite/Zirconia Micro-Parts Fabricated by Two-Component Micro-Powder Injection Molding Process
Muhammad Mohamed Amin, Universiti Kebangsaan Malaysia
In the present study, we investigated the effect of the sintering temperature on the physical properties of bi-material micro-components of hydroxyapatite (HA) and 3 mol% yttria-stabilized zirconia (3YSZ) fabricated utilizing a two-component micro-powder injection molding (2C-µPIM) technique. Firstly, HA and 3YSZ powders were individually mixed with binders to prepare the feedstocks. Following micro-injection molding of the HA and 3YSZ feedstocks into the dumbbell shape, the debinding procedure was carried out. The debound samples were sintered at temperatures ranging from 1200 ◦C to 1400 ◦C. According to field emission scanning electron microscopy (FESEM) analysis of the microstructures, sintering resulted in the formation of a bonding between two different types of ceramic in micro-sized HA/3YSZ components. The highest relative density of 98% was achieved after sintering. The sintered HA/3YSZ micro-parts demonstrated a linear shrinkage between11% and 19% after the sintering process.
Microstructural Evolution of WC/Co Alloys with V Additions
Joseph Strauss, FAPMI, HJE Company, Inc.
The microstructural development of a WC/Co (tungsten carbide/cobalt) alloy has been investigated in order to determine the mechanism through which vanadium acts as a grain growth inhibitor. A novel method of characterizing the microstructure was employed. This entailed the measurement of the specific surface area of the composite microstructure. This allowed the tracking of individual microstructural attributes and their contribution to the development of the overall microstructure. This susequently led to innovations in MIM. This paper is a summary of select portions of a Ph.D. thesis initially published in 1991.
Elevating Aerospace Materials: Powder Injection Molding of Graphene-Reinforced Components
Álvaro Garcia Juarez, University of Castilla La Mancha
The aerospace industry continually pushes the boundaries of innovation, demanding components with exceptional mechanical and functional properties. Powder Injection Molding (PIM) offers the precision and geometric tolerances required for these advanced applications. Graphene has emerged as a promising reinforcement material, enhancing both mechanical strength and functional performance. However, cost-effective integration of graphene into feedstocks, ensuring uniform dispersion within the microstructure, remains a significant challenge. This study investigates the incorporation of reduced graphene oxide into two feedstocks: a cordierite ceramic and an Inconel 718 alloy. Cordierites, known for their exceptional thermal shock resistance, offer potential in high-temperature applications, while Inconel 718 can extend beyond aerospace to aeronautical uses. By analyzing the effects of graphene on processing and composite properties, this work highlights its transformative potential in developing stronger, more efficient materials for demanding sectors, paving the way for next-generation components.
Pressed-and-Sintered Parts with MIM Powders
Kuen-Shyang Hwang, National Taiwan University
Owing to the use of coarse powders, it is a big challenge to produce pressed-and-sintered parts with a high density, homogeneous microstructure, and good mechanical properties. The MIM process, on the other hand, can solve these problems but with a higher tooling and manufacturing costs. This talk presents a high-density high-performance PM (HPM) process that combines PM and MIM technologies. Using spray-dried MIM powders, parts are processed using the press-and-sinter technology. The microstructure, density, and sintered properties thus obtained are the same as those of MIM parts. Production parts including low-alloyed steels and 17-4PH stainless steels are used to demonstrate the advantages of the HPM process. The challenges will also be discussed.
Hot Disk Thermal Characterization of Copper Powder and AM Copper Parts
Artem A. Trofimov, The Edward Orton Jr. Ceramic Foundation
Thermal characterization (thermal conductivity; specific heat capacity, etc.) of metal and ceramic additively manufactured (AM) parts is critical for modeling and simulations, optimization of the processing parameters, and can be used for quality evaluation of components at different steps of manufacturing. Such characterization is especially vital for materials, whose applications are directly related to their thermal properties; a great example is pure copper with an excellent combination of both thermal and electrical conductivity.
In this work, Hot Disk Transient Plane Source (TPS) technique is demonstrated as a suitable and convenient tool for thermal characterization of raw copper powder as well as green and sintered AM copper products. The investigation demonstrates how the Hot Disk method allows evaluation of most pivotal thermal properties, thermal conductivity and heat capacity, and the applicability of the technique to both powders and solid samples. Flexibility of the sample size requirements (from a few millimeters and larger) is also discussed.
The Magic of Cleaning with Dry Ice in MIM
Anthony Valenta, Cold Jet
One of the coolest things about dry ice is the fact that it simply disappears before your eyes as it cleans molds. Not only do the dry ice particles disappear, but so do extended downtimes and the need for cleaning agents that could be contributing to your greenhouse gas emissions score.
No matter how large or small a MIM molder is, there is a great demand for improving productivity and quality (Quality and Availability OEE Scores). This can be a balancing act between using the most effective technology while working within a budget. This presentation discusses the advantages of cleaning molds, in-situ, with dry ice. This presentation will demonstrate how various contaminants, namely binders, can be cleaned from tooling in an efficient, sustainable and non-abrasive manner. We will also discuss how IIoT smart technology now allows the machine and the entire cleaning process to be remotely monitored.
Supporting research from several independent mechanical and thermal studies including statements from both the EPA & CARB will be presented to demonstrate that cleaning with dry ice can extend the asset life of tooling and is sustainable. The attendee will also achieve an understanding of the science behind how the process works, and how to implement the process in their facilities. Prepare to believe in magic for dry ice is too good to not believe!