微结构模芯的精密磨削及其在微注塑成形中应用

针对微结构聚合物元器件的批量化生产与制造效率低等问题,采用精密修整成V形尖端的金刚石砂轮,在自润滑性和脱模性良好的钛硅碳陶瓷模芯表面加工制造出形状精度可控的V沟槽阵列结构,然后利用微注塑成形工艺将模芯表面的V沟槽阵列结构一次成形复制到聚合物表面,高效注塑成形制造出倒V形阵列结构的聚合物工件。分析了微模芯的表面加工质量与形状精度,研究了熔体温度、注射速度、保压压力、保压时间等微注塑成形工艺参数对微结构聚合物注塑成形角度偏差和填充率的影响。实验结果表明：通过微细磨削加工技术和微注塑成形工艺可以高效率、高精度地制造出规则整齐的微结构注塑工件,注射速度对微成形角度偏差的影响最大,保压压力对微成形填充率的影响最大,微结构模芯的微细磨削形状精度值为4.05 μm,微成形的最小角度偏差和最大填充率分别为1.47°和99.30%。     

Micro-injection moulding: Factors affecting the achievable aspect ratios

Micro-injection moulding is one of the key technologies for micro-manufacture because of its mass-production capability and relatively low component cost. The aspect ratios achievable in replicating micro features are one of the most important process characteristics and constitute a major manufacturing constraint in applying injection moulding in a range of micro-engineering applications. This research studies the effects of five process and one size factors on the achievable aspect ratios, and the role they play in producing micro components in different polymer materials. In particular, the following factors are considered: barrel temperature, mould temperature, injection speed, holding pressure, the existence of air evacuation and the sizes of micro features. The study revealed that the barrel temperature and the injection speed are the key factors affecting the aspect ratios of micro features replicated in PP and ABS. In case of POM, in addition to these two factors, the mould temperature is also an important factor for improving the replication capabilities of the micro-injection moulding process. For all three materials, an increase of feature sizes improves the melt flow. However, the melt fill of micro features does not increase linearly with the increase of their sizes.     

Characterization and analysis of weld lines on micro-injection moulded parts using atomic force microscopy (AFM)

In recent years plastic moulding techniques, such as injection moulding, have been developed to fulfil the needs of micro-components fabrication. Micro-injection moulding (μIM) is the process which enables the mass production of polymer micro-systems such as micro-mechanical parts, micro-fluidic systems, micro-optics, micro-components for medical devices, etc. A key factor in micro-polymer based systems is the possibility of designing and therefore replicating very complex geometries, allowing an increasing number of applications and micro-products.Complex geometries bring challenges during the filling stage of the process. Many features cause melt front separation: through holes, presence of pins and cores, changes of thickness, multi-gating systems, existence of micro-inserts, two component injection moulding, etc. When two or more melt flows join each other after separation, a layer between the two original flows will generate and a weld line is formed on the surface of the micro-moulded part. This phenomenon has to be avoided or at least reduced, since in the weld line area the mechanical properties are poorer than in the bulk part, creating strength problems on the final part. Although weld lines are unavoidable, the micro-injection moulding process can indeed be optimized in order to on one hand obtain a good filling of the cavity and on the other hand decrease the size of the weld lines. In this paper, an investigation devoted to the determination of the influence of typical injection moulding parameters on the weld lines’ dimensions is presented, using an atomic force microscope (AFM). Depth and width of weld lines were chosen as parameters to be optimized.     

Manufacturing of multi-functional micro parts by two-component metal injection moulding

Several metals and alloys can be used to enhance the mechanical and physical properties of micro parts and components for micromechanical, micro-chemical or sensor applications. Such parts can be produced in series by the powder metallurgical process of micro metal injection moulding (μ-MIM). This paper describes a novel manufacturing route for metallic multi-material micro components, two-component micro metal injection moulding (2C-μ-MIM). Similar to “two-colour” injection moulding of plastics, the process allows the integration of multiple functions in a micro part by simultaneously injecting and joining two materials in one mould. Net-shape parts with solid material interfaces are obtained. In this paper, the 2C-μ-MIM process is exemplified for the combination of a non-magnetic and a ferromagnetic stainless steel (316 L and 17-4PH). It is shown that intact material interfaces of less than 500×500 μm² can be achieved by careful selection and tailoring of metal powders, injection moulding and co-sintering parameters.     

Investigation of polymer inserts as prototyping tooling for micro injection moulding

An increasing number of microfluidic applications linked with a strong demand for low-cost solutions has pushed research activities towards the development of polymer-based microfluidic systems. This requires the use of micro injection moulding technology to accurately replicate polymer micro parts; however, the tooling cost associated with this manufacturing route remains relatively high. The purpose of this paper is to investigate the feasibility of utilising polymer inserts for prototype tooling in micro injection moulding that can reduce product development time and cost associated with the design and testing of microfluidic systems prior to mass fabrication.     

Additive manufacturing tooling for the automotive industry

Micro injection moulding is a mass production of micro optics that offers the possibility of a high functional integration within a single micro part by insert moulding. Since the functionality of the micro parts depends on the homogeneity of the overmoulded polymer layer, a robust, accurate and fast metrology system is needed for a quantitative quality assessment. Here, we demonstrate an in-line metrology approach for the optical inspection of insert molded micro parts. In contrast to standard interferometers, the proposed system has low demands regarding the coherence of illumination. Thus, an LED light source can be used instead of a laser, reducing the cost and increasing the safety of the production platform. In addition, the system is robust against mechanical distortions, since it is based on a common path approach. These advantages make the system a good candidate that fulfills the needs in regard to the in-line inspection of insert molded micro parts. As an example of application, the proposed system is used to inspect a cannula with overmolded thermoplastic as a light sleeve providing illumination over a specific area of surgery.     

Experimental investigation of the factors influencing the polymer–polymer bond strength during two-component injection moulding

Two-component injection moulding is a commercially important manufacturing process and a key technology for combining different material properties in a single plastic product. It is also one of most industrially adaptive process chain for manufacturing so-called moulded interconnect devices (MIDs). Many fascinating applications of two-component or multi-component polymer parts are restricted due to the weak interfacial adhesion of the polymers. A thorough understanding of the factors that influence the bond strength of polymers is necessary for multi-component polymer processing. This paper investigates the effects of the process conditions and geometrical factors on the bond strength of two-component polymer parts and identifies the factors which can effectively control the adhesion between two polymers. The effects of environmental conditions on the bond strength are also investigated. Investigation shows that melt and mould temperatures are vital process parameters that influence the bond strength. Besides this, surface roughness of the first-shot part and environmental factors like moisture have profound influence on the bonding of the two materials. The selections of materials and environmental conditions were done based on the suitability of MID production, but the results could be useful for two-component polymer processing for a wide range of industrial applications. The results and discussion presented in this paper are only valid for the two-component plastic parts moulded by over moulding in cavity-transfer process.     

Study of process parameters effect on the filling phase of micro-injection moulding using weld lines as flow markers

Micro-injection moulding (micro-moulding) is a process which enables the mass production of polymer micro-products. In order to produce high-quality injection moulded micro-parts, a crucial aspect to be fully understood and optimised is the filling of the cavity by the molten polymer. As a result, the relationships between the filling pattern and the different process parameter settings have to be established. In this paper, a novel approach based on the use of weld lines as flow markers to trace the development of the flow front during the filling is proposed. The effects on the filling stage of process parameters such as temperature of the melt, temperature of the mould, injection speed and packing pressure have been investigated. An optical coordinate measuring machine has been employed for the investigation. The micro-cavity, which presents micro-features ranging from 600 μm down to 150 μm, has been manufactured by micro-electrodischarge machining. A commercially available polystyrene grade polymer has been moulded using a high-speed injection moulding machine. The design of experiment technique was employed to determine the effect of the process parameters on the filling phase of the micro-cavity. In addition, extensive measuring uncertainty analysis was performed to validate the experimental plan. Results show that the temperature of the mould and the injection speed are the most influencing process parameters during the injection moulding of a micro-component.     

Optimising process conditions for multiple quality criteria in micro-injection moulding

This paper presents a statistical technique to optimise process conditions for multiple quality criteria in micro-injection moulding. A sample hierarchical component with micro-features was replicated where it was required to improve the process conditions for both complete mould filling and variability in mass. A design-of-experiments approach was used to investigate the effect of five processing parameters on both criteria. It was found that holding pressure, melt temperature and injection velocity were statistically significant for part mass, whereas injection velocity alone was significant for mass variation. Desirability functions were used to predict processing conditions that improved both requirements within pre-set conditions. The technique was validated by experiment and it was shown to be applicable for process parameters for multiple criteria.     

Injection moulding parameters influence on weight quality of complex parts by means of DOE application: Case study

Injection moulding is a very popular plastic transformation process to produce complex parts, since a mould is capable to reproduce different shapes, and also due to its economic advantages for large series. However, defects can appear into the pieces, leading to reject them in the quality control.In order to control these defects, it is necessary to know the influence of the injection parameters on the quality of the part. Several researchers applied Design of Experiments (DOE) methods to injection process, with good results for test or lab specimens, but many industrial parts usually have more complex geometries or singularities.This paper introduces a case study focused on the application of DOE in a complex part because it has an integrated hinge. In this case study, the weight and pressure curves (hydraulic and specific) are analysed depending on the variation of process parameters. The authors would show that the analysis has found a strong influence of the geometry on the results which sometimes are different to the expected ones.In authors’ opinion, the use of this procedure it still is a challenge, and this example could assist future attempts to create new expert systems in injection moulding.     

Advances in micro assembly injection moulding for use in medical systems

In micro systems technology, the process of micro assembly injection moulding is used for the generation of hybrid micro systems. With this process, more functions are integrated in less space. In the field of medical technology, miniaturisation also means new methods of treatment with fewer side effects on the patient. New cures are developed by the miniaturisation of medical instruments, such as keyhole surgery. For detailed investigations a specific demonstration was developed to display the potential of micro assembly injection moulding in medical science. This part consists of a carbon-fibre reinforced PEEK puncture needle, which incorporates three lumens. The selected materials allow use of the needle during magnetic resonance imaging. In order to attach additional equipment a plastic connector needs to be overmoulded on the needle. The investigations focus on the injection moulding process by characterising the influences of temperature, moulding parameters and material combinations on the resulting bond strength between needle and connector.     

Process chain development for the rapid prototyping of microstructured polymer, ceramic and metal parts: composite flow behaviour optimisation, replication via reaction moulding and thermal postprocessing

Different variants of reaction moulding techniques exploiting the rapid light-induced photopolymerisation of reactive resins are widely used in microsystem technologies for the fabrication of plastic components or for rapid prototyping (RP) purposes. In this paper, the further development of micro reaction moulding with respect to a rapid prototyping of ceramic and metal parts will be described. As in powder injection moulding, the process sequence binder–filler–formulation, replication, debinding and sintering has to be passed. The mould filling and, hence, the accurate reproduction of surface details depend strongly on the composite’s viscosity, which is a function of the filler load. Especially, an improved process control of the composite formation prior to moulding and the thermal debinding is crucial for the realisation of microstructured ceramic or metal parts. The development of the whole process chain and some examples will be presented. This paper was originally presented at the International Conference on Multi-Material Micro Manufacture (4M), Karlsruhe, Germany, 29 June 2005 to 1st July 2005, and is extended for publication in this journal.     

Conformal cooling channel design and CAE simulation for rapid blow mould

Blow moulding is one of the most important polymer processing technologies to produce hollow-shaped parts at a short time. The cooling stage takes up approximately two thirds of the complete blow moulding cycle. It becomes the major factor to determine the productivity and the quality of the blow-moulded part. The cooling time and the quality part are controlled by an adequate cooling channel design inside the blow mould. Inappropriate cooling channel design will increase the cooling time after part ejection. Recently, the success of integrating conformal cooling channel (CCC) design in the injection moulding process has been proven by different research publications and practices. The merit of the applications of CCC can also be extended to the existing blow moulding process. In this study, an effective design method is proposed for integrating CCC into the blow mould with the aid of computer-aided design and analysis tools. The fabrication of integrating CCC into the blow mould by rapid tooling technology is explored. Computer-aided engineering simulation is employed to verify the cooling performance of the CCC corresponding to the blow mould surface geometry. The analysed results are compared with those using the traditional straight line-drilled cooling channel (SLDCC) used in the blow moulding process. The results indicated that the cooling time and temperature uniformity of the blow-moulded part can be effectively improved. The proposed CCC design has a shorter cooling time and a lower part temperature than the SLDCC one.     

Effects of machined cavity texture on ejection force in micro injection molding

The friction force developed in the demolding phase of the micro injection molding process is mainly determined by mold surface finish, which affects the tribological phenomena occurring at the polymer–tool interface. In this work, the effects on the ejection force of two cavity surfaces machined with different technologies (viz. micro milling and micro electro discharge machining), but with similar value of Ra, were investigated. The relations between different surface topography parameters and the ejection force were then analyzed, in order to identify the parameters that most appropriately describe the friction at the polymer–tool interface. The experimental results showed the strong interactions between the mold surface texture and the micro injection molding process parameters that promote the replication, such as mold temperature and holding pressure. The different machining technologies generated two mold textures that have a similar value of Ra, but their influence on friction can be properly described only using several other surface topography parameters.     

三维注射模CAD系统的开发

作者在新近开发的三维注射模结构CAD系统中.以AutoCAD12.O作为图形平台,利用其高级三维实体造型功能及ADS开发语言.实现了对AutoCAD的注射模专业化改造.使得注射件尺寸向型芯、型腔尺寸的转换可自动进行,建立了注射模标准零件库及抽芯机构结构图库,开发了标准模架组合装配程序.实现了模架装配及其在注射成型过程中的运动模拟.并能形成二维工程图.     

Mold surface roughness effects on cavity filling of polymer melt in micro injection molding

Micro injection molding presents many challenges in the injection-molding community. When the dimensions of the part (and thus the cavity of the mold) are small, micro-scale factors such as mold surface roughness may play an important role in the filling of polymer melt. This paper investigates the effects of mold surface roughness on cavity filling of polymer melt in micro injection molding. A disk insert, which has two halves with different surface roughness but with the same roughness mean lines, was used in the investigations. The ratio of flow area of the rougher half with the total flow area of the molded part is used to evaluate the significance of surface roughness effect. The experimental results revealed that mold surface roughness does resist the cavity filling of polymer melt in micro injection molding. For the limited range of injection rate investigated, it is not significant on the surface roughness effects. The increase of mold temperature will decrease surface roughness effects. The change of melt temperature within the range allowed by the process is insignificant for surface roughness effects.     

多孔复杂型腔塑件注塑模具CAD/CAE数字化研究

在UG中建立了塑件的三维数据图,借助模流分析(Moldflow)软件对塑件注射压力、时间、温度、浇注系统进行计算机辅助工程分析(CAE),确定最优的注射压力、注射时间、模具温度、熔体温度、浇口位置及流道等。优化了注塑工艺参数、注塑模具的设计,确定了最佳的注塑工艺方案,快速成型出优质的塑料制品,提高了模具的质量,缩短了模具的开发周期。     

注射成型工艺参数对微结构零件复制度的影响

为改善微结构零件的复制度,以具有广泛应用前景的精细微结构零件——微透镜阵列为案例,将制品成型重量作为制品复制度的量化衡量指标,运用单因素实验方法实验研究了注射成型工艺参数（熔体温度、模具温度、注射时间、保压压力、保压时间）对微结构零件制品重量的影响规律。实验结果表明,增加熔体温度和模具温度能使保压压力更有效地通过浇注系统传递到微型腔,增加制品重量;成型重量大的制品,微结构的填充要好于重量轻的制品,微结构零件复制度与成型重量存在对应关系。制品重量可初步评价微结构零件的复制度,研究各工艺参数对制品重量的影响规律对提高微结构零件的复制度有重要意义。     

微注射成型技术的最新进展与展望

简述了微注射成型技术的产生背景、应用范围和最新进展,详细介绍了微注射成型机、微注射工艺的发展现状,分析了微型腔和微型芯的制造技术及存在的问题,归纳总结了微注射常用的材料及模具成型零件能够达到的最大纵横比和最小结构壁厚,展望了微注射成型的发展趋势.     

Moulage par injection de poudres métalliques. Expérimentation,modélisation et simulation

Metal injection moulding. Experiment, modelling and simulation. The metal injection moulding process is used to produce small and complex metallic components. The first step is the injection of a mixture composed by a metallic powder and a thermoplastic binder. The binder is eliminated by a thermal or catalytic debinding. The last step is the sintering in order to obtain a part with the correct size and required mechanical properties. The metal injection moulding process is analysed using both experiments and computational modelling. A numerical approach for biphasic mixtures has been developed to analyse the flow of the feedstock during injection. The solution of the Navier–Stokes equations is made by an implicit finite element method. The mould filling simulation uses an Eulerian formulation with a VOF method. The simulation gives the density field in order to detect the segregation zones leading to an anisotropic shrinkage. The modelling of the solid state sintering is based on a viscoplastic model. The results obtained by experiments and numerical simulations are compared and reveal a good agreement. Furthermore, the components obtained after injection, debinding and sintering have the correct size and required mechanical properties.