Additive manufacturing (AM) is the fabrication of real three-dimensional objects from metals, ceramics, or plastics by adding material, usually as layers. There are several variants of AM; among them material extrusion (ME) is one of the most versatile and widely used. In MEAM, molten or viscous materials are pushed through an orifice and are selectively deposited as strands to form stacked layers and subsequently a three-dimensional object. The commonly used materials for MEAM are thermoplastic polymers and particulate composites; however, recently innovative formulations of highly-filled polymers (HP) with metals or ceramics have also been made available. MEAM with HP is an indirect process, which uses sacrificial polymeric binders to shape metallic and ceramic components. After removing the binder, the powder particles are fused together in a conventional sintering step. In this review the different types of MEAM techniques and relevant industrial approaches for the fabrication of metallic and ceramic components are described. The composition of certain HP binder systems and powders are presented; the methods of compounding and filament making HP are explained; the stages of shaping, debinding, and sintering are discussed; and finally a comparison of the parts produced via MEAM-HP with those produced via other manufacturing techniques is presented.

https://pure.unileoben.ac.at/portal/files/2455715/materials_11_00840.pdf

Additive Manufacturing of Metallic and Ceramic Components by the Material Extrusion of Highly-Filled Polymers: A Review and Future Perspectives

Micro-powder injection moulding (µPIM) is a fast-developing micro-manufacturing technique for the production of metal and ceramic components. Shape complexity, dimensional accuracy, replication fidelity, material variety combined with high-volume capabilities are some of the key advantages of the technology. This review assesses the capabilities and limitations of µPIM as a micro-manufacturing technique by reviewing the latest developments in the area and by considering potential improvements. The basic elements of the process chain, variant processes and simulation attempts are discussed and evaluated. Challenges and research gaps are highlighted, and potential areas for improvement are presented.

/pdf/a-review-of-micro-powder-injection-moulding-as-a-40bufy7nhq.pdf

A review of micro-powder injection moulding as a microfabrication technique

A review of biocompatible metal injection moulding process parameters for biomedical applications

The metal injection moulding (MIM) process combines the well-known thermoplastic injection and powder metallurgy technologies to manufacture small and intricate parts to nearly net shape. The design of injection moulds is a very important stage in such a technology as the mixture of metallic powder and thermoplastic binder is injected in the mould with a viscous behaviour strongly different from the pure polymer injection. To improve the mould design by an efficient numerical tool, an explicit 3D software has been developed to perform efficiently the injection simulation. Taking into account the special behaviour of feedstock in MIM injection, a bi-phasic model is used to describe the flows of metallic powder and plastic binder so as to predict accurately the powder segregation in injection. The volume fractions of metallic powder and plastic binder give directly the evolution of segregation during the injection course. The numerical results are compared with experiments, in which a multi-cavity mould specially designed and realised in our laboratory is used. The segregation zones are well predicted. This specially developed software permits to optimise the mould design and processing parameters to get required components.

Improving mould design and injection parameters in metal injection moulding by accurate 3D finite element simulation

Investigation of the rheological behavior of 316L stainless steel micro-nano powder feedstock for micro powder injection molding

Determination of critical and optimal powder loadings for 316L fine stainless steel feedstocks for micro-powder injection molding

Superior mechanical properties and deformation mechanisms of a 304 stainless steel plate with gradient nanostructure

Manufacturing of 3D micro‐components by powder injection molding process consists of four main stages: preparation of the feedstock of metal powders and binders, injection of powder/binder feedstock using micro‐injection molding equipment, thermal or solvent debinding and sintering by solid state diffusion. For our research pruposes, the feedstocks have been realized with stainless steel 316L powders of 3.4 μm (D50) and polymer binders. Finite element method has been used for the simulation in order to estimate shrinkage, relative density and evolution of the shapes of the micro‐components, the parameters used in the sintering model have been identified in using Matlab® procedures before to be used in the simulation with Abaqus®.

Micro powder injection moulding of 316l stainless steel feedstock and numerical simulation of the sintering stage

Research tasks at ENSMM/LMA are focused on the development of mixtures of very fine powders (5μm size) associated to polymer binders dedicated to the micro powder injection moulding (μPIM) in accordance with many works already carried out with different feedstock suppliers dedicated to the macro-components.

Mixing and Characterisation of stainless steel 316L feedstock

The powder injection moulding (PIM) process satisfies the increasing demand to manufacture smaller parts with complex shapes. The related researches in this area have been carried out at FEMTO-ST Institute since a few years. An injectable feedstock formulation composed of polymers and metallic powders has been tested. Micro injection and bi-material injection tests have been carried out. During the bi-material injection test with a three-plate mould configuration, the interface between the two different feedstocks has been well defined. After thermal debinding stage, the correctly debinded components are sintered with different sintering cycles, the resulted components have been successfully realized.

http://documents.irevues.inist.fr/bitstream/handle/2042/46841/cfm2011_991.pdf;sequence=1

X. Kong

Papers

Determination of critical and optimal powder loadings for 316L fine stainless steel feedstocks for micro-powder injection molding

Superior mechanical properties and deformation mechanisms of a 304 stainless steel plate with gradient nanostructure

Micro powder injection moulding of 316l stainless steel feedstock and numerical simulation of the sintering stage

Mixing and Characterisation of stainless steel 316L feedstock

Manufacturing of micro-components by powder injection moulding process