Mass Production Of Microcomponents Research Articles

Analysis of the Downscaling Effect and Definition of the Process Fingerprints in Micro Injection of Spiral Geometries.

Microinjection moulding has been developed to fulfil the needs of mass production of micro components in different fields. A challenge of this technology lies in the downscaling of micro components, which leads to faster solidification of the polymeric material and a narrower process window. Moreover, the small cavity dimensions represent a limit for process monitoring due to the inability to install in-cavity sensors. Therefore, new solutions must be found. In this study, the downscaling effect was investigated by means of three spiral geometries with different cross sections, considering the achievable flow length as a response variable. Process indicators, called “process fingerprints”, were defined to monitor the process in-line. In the first stage, a relationship between the achievable flow length and the process parameters, as well as between the process fingerprints and the process parameters, was established. Subsequently, a correlation analysis was carried out to find the process indicators that are mostly related to the achievable flow length.

Investigation and modeling of binder removal process in nano/micro bimodal powder injection molding

Nano powder injection molding is an appropriate technique for the mass production of micro components. However, the large surface area of nano powder increases the processing challenges, and as a result, nano/micro bimodal powder has been introduced into the process to reduce the problems. Although the understanding of the debinding behavior directly contributes to a fabrication of defect-free parts with a high production rate, most studies for the bimodal powder injection molding focused on the feedstock rheology and properties of sintered samples. In this study, nano powder effects on both of solvent and thermal debinding processes have been investigated with nano/micro bimodal feedstocks, and the master decomposition curve was developed. To prepare the bimodal feedstocks, premixed Fe nano/micro bimodal powders were blended with a wax-based binder system as the optimal volume ratios. Solvent and thermal debinding behaviors were analyzed by observing the weight change of the samples depending on the process time and temperature, respectively. The result indicated nano powder increased immersing time required in the solvent and the amount of the residual binder. It also narrowed the decomposition temperature range of the binder system by affecting the decomposition activation energy. From the result, the master decomposition curves of each bimodal feedstock were constructed and verified.

The effect of nano-sized stainless steel powder addition on mechanical and physical properties of micropowder injection molded part

Micropowder injection molding (μPIM) is a new technology that has potential in the mass production of microcomponents. A bulk material of nanoparticles possesses completely different properties from those of large-sized particles. The main objective of this study is to study the effects of nano-sized powder addition on the μPIM process of powder-polymer mixtures for the fabrication of miniature parts. The binder systems consist of polyethylene glycol (PEG), polymethyl methacrylate (PMMA), and stearic acid (SA) with different powder loading blended with powders. The results indicate that increasing the nanopowder content to 30wt.% increased the powder loading and decreased the injection and sintering temperatures. The sintered parts had densities of 96% of the theoretical value. High physical and mechanical properties of the sintered specimen were achieved with the 30wt.% nano-sized powder sintered at 1200°C at a heating rate of 5°C/min under vacuum atmosphere. A significant reduction of the surface roughness of the sintered parts using the nano–microhybrid powder (Sa=0.365μm) was observed compared with the sintered parts with only micropowder (Sa=1.002μm). Using nanopowders, the hardness also increased from 182HV to 221HV with a linear shrinkage of approximately 9%, which is less than that of the micropowders (18%).

Investigation on Micro Components Fabricated by Micro Powder Injection Molding

The development of microsystems and related products has caused an upsurge in the mass production of micro components. In the paper, fabrication of zirconia micro gears of 700μm, 800μm, 900μm based on water-soluble binder were investigated. The water-soluble binder system consists of 30%PEG-4000+10%SA+30%PVB+30%EVA components. Experimental results show that zirconia micro gears are successfully fabricated using the in-house feedstock. And the decrease of the molecular weight of water-soluble component is beneficial to the quality of the molded part.

Injection molding and debinding of micro gears fabricated by micro powder injection molding

Micro powder injection molding (μPIM) was investigated for possible mass production of micro-components at relatively low cost. However, scaling down to such a level produces challenges in injection molding and debinding. Micro gears were fabricated by μPIM from in-house feedstock. The effect of injection speed and injection pressure on the replication of the micro gear cavity was investigated. Solvent debinding and thermal debinding processes were discussed. The results show that micro gears can be successfully fabricated under the injection pressure of 70 MPa and the 60% injection speed. Either too low or too high injection speed can cause incomplete filling of micro gears. The same is the case with too low injection pressure. Too high injection pressure can bring cracks. Solvent debinding of micro gears was performed in a mixture of petroleum ether and ethanol. Subsequently, micro gears were successfully debound by a multistep heating schedule.

Investigation of final-stage sintering of various microsize structures prepared by micro powder injection molding

Micro powder injection molding (μPIM) has been developed as a potential technique for mass production of microcomponents in microsystems due to its shaping complexity at low cost, in which sintering is a crucial step to dictate the final properties of the microcomponents. In this paper, final-stage sintering behavior of 316L stainless steel microsize structures prepared by μPIM, φ100 μm and φ60 μm, respectively, was studied. The effect of size reduction in the regime of micrometers on the density of various microsize structures was investigated. Sintering kinetics of the microsize structures of φ100 μm and φ60 μm were studied based on particle level sintering models. It is found that the microsize structures of φ60 μm had higher density than the microsize structures of φ100 μm given the same sintering condition. The results indicate that size reduction in the regime of micrometers facilitated densification of microsize structures. The grain growth mechanism of microsize structures varied with size. Whereas the grain growth of the microsize structures of φ100 μm is governed by surface-diffusion-controlled pore drag, the grain growth of the microsize structures of φ60 μm is controlled by boundary diffusion. During densification, the microsize structures, φ100 μm and φ60 μm, are both controlled by lattice diffusion. The corresponding activation energies are reported in the paper.