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Understanding the relationship between injection molding parameters and the acoustic properties of polymers is crucial for optimizing the design and performance of acoustic-based polymer devices. In this work, the impact of injection molding parameters, such as the injection velocity and packing pressure, on the acoustic parameters of polymers, namely the elastic moduli, is studied. The measurements lead to calculating material parameters, such as the Young's modulus and Poisson's ratio, that can be swiftly measured and determined thanks to this method. Polymethyl methacrylate (PMMA) was used as the molding material, and using PMMA LG IG 840, the parts were simulated and injection molded, applying a 'design of experiment' (DOE) statistical method. The results indicated a correlation between the injection molding process parameters and the acoustic characteristics, such as the elastic moduli, and a specifically decreasing trend with increase in the injection velocity. Notably, a relative decrease in the Young's modulus by 1 % was observed when increasing the packing pressure from 90 MPa to 120 MPa . Similarly, a decrease in the Poisson's ratio of 2.9 % was observed when the injection velocity was increased from 16 mm / s to 40 mm / s . This method can be used to fine-tune the material properties according to the needs of a given application and to facilitate the characterization of different polymer acoustic properties essential for acoustic-based polymer devices. [ABSTRACT FROM AUTHOR]

Injection molding is one of the most important processes for the mass production of plastic parts. In recent years, many researchers have focused on predicting the occurrence and intensity of defects in injected molded parts, as well as the optimization of process parameters to avoid such defects. One of the most frequent defects of manufactured parts is blush, which usually occurs around the gate location. In this study, to identify the effective parameters on blush formation, eight design parameters with effect probability on the influence of this defect have been investigated. Using a combination of design of experiments (DOE), finite element analysis (FEA), and ANOVA, the most significant parameters have been identified (runner diameter, holding pressure, flow rate, and melt temperature). Furthermore, to provide an efficient predictive model, machine learning methods such as basic artificial neural networks, their combination with genetic algorithms, and particle swarm optimization have been applied and their performance analyzed. It was found that the basic artificial neural network (ANN), with an average accuracy error of 1.3%, provides the closest predictions to the FEA results. Additionally, the process parameters were optimized using ANOVA and a genetic algorithm, which resulted in a significant reduction in the blush defect area. [ABSTRACT FROM AUTHOR]

Micro and nano molding technologies are continuously being developed due to enduring trends such as increasing miniaturization and the higher functional integration of products, devices and systems. Calaon et al. [[1]] analyzed and compared the process capability and design of conventional injection molding and of micro injection molding machines; Wöhner et al. [[2]] characterized the formation of blisters in film micro insert molding; Loaldi et al. [[3]] integrated direct ink writing with injection molding to generate micro conductive tracks in polymer devices. Weng et al. [[4]] modeled the demolding phase in nano scale molding by using molecular dynamic simulations; Loaldi et al. [[5]] simulated the micro injection molding process of both three-dimensional micro parts and micro structured components by applying multi-scale meshing and virtual design of experiment techniques. [Extracted from the article]

Powder injection molding is like the process of plastics injection molding capable of the mass production of highly functional complex 3D parts, just in ceramics and metals. The market for products made by powder injection molding is constantly growing. With this growth, the need for reliable process simulations arises. Simulation tools are widely used in the development of new products and are applied in powder and polymer injection molding to support the product design, shorten the development time, avoid errors, and help to optimize the mold and process design. However, material data for feedstocks and thus simulations of the powder injection molding process are hardly available yet. The present work introduces the necessary material data for establishing a material model for simulations. An extensive material characterization of ceramic feedstocks was conducted. The material investigations comprised the determination of basic, thermal, and rheological material properties to collect a comprehensive data set. The necessary measurements and tools are outlined and their results are discussed in detail with regard to powder content and in comparison to pure plastics. The gained data enabled to successfully create a material model for mold filling simulations. Powder injection molding experiments were carried out with a spiral test geometry. The mold was equipped with a sensor array for the process monitoring during injection. Furthermore, a simulation model of the test geometry was established. Finally, the results of the experiments and simulations are discussed and are compared to validate the performance of the simulations. The results showed the potential and limitations of process simulations and standard software applied in conventional and micro powder injection molding. [ABSTRACT FROM AUTHOR]

There is a growing interest for integrating additive manufacturing (AM) technology in different manufacturing processes such as injection moulding (IM) due to the possibility of achieving shorter manufacturing times and increased cost effectiveness. This paper evaluates IM inserts fabricated by the AM vat photopolymerisation method. The inserts are directly manufactured with a photopolymer material, integrated on an injection moulding tool and subsequently used for IM. Therefore, particular attention has to be paid in order to develop the soft tooling process chain and the IM experimental procedure as detailed in this study. Different combinations of IM parameters are investigated in this work in order to determine the influence of the various process settings on the inserts' performance (lifetime, crack propagation, consistency of the mould surface features). The mould inserts were analysed by three-dimensional optical metrology and evaluated with regard to the different surface features that were affected by the IM process. A three-dimensional thermo-mechanical with phase change model for the analysis of the effects of the IM process on the additive manufactured tools was accomplished in the FE software COMSOL Multiphysics. The potential causes for the insert failure are identified both by means of the IM experiments and the numerical model. The developed model could also predict the thermally induced deformations produced in the mould and identify where this phenomenon would eventually lead to defects in the shape of the parts. The influence of three different temperatures of the insert at 25 °C, 50 °C and 100 °C on the failure of the insert was investigated. Also a detailed discussion about the solidification and temperature changes is given. [ABSTRACT FROM AUTHOR]

This paper reports an investigation of the effects of process parameters on the quality characteristics of polymeric parts produced by micro injection moulding (μIM) with two different materials. Four injection moulding process parameters (injection velocity, holding pressure, melt temperature and mould temperature) were investigated using Polypropylene (PP) and Acrylonitrile Butadiene Styrene (ABS). Three key characteristics of the mouldings were evaluated with respect to process settings and the material employed: part mass, flow length and flash formation. The experimentation employs a test part with four micro fingers with different aspect ratios (from 21 up to 150) and was carried out according to the Design of Experiments (DOE) statistical technique. The results show that holding pressure and injection velocity are the most influential parameters on part mass with a direct effect for both materials. Both parameters have a similar effect on flow length for both PP and ABS at all aspect ratios and have higher effects as the feature thickness decreased below 300 μm. The study shows that for the investigated materials the injection speed and packing pressure were the most influential parameters for increasing the amount of flash formation, with relative effects consistent for both materials. Higher melt and mould temperatures settings were less influential parameters for increasing the flash amount when moulding with both materials. Of the two investigated materials, PP was the one exhibiting more flash formation as compared with ABS, when corresponding injection moulding parameters settings for both materials were considered. [ABSTRACT FROM AUTHOR]

To directly compare experimental moldings from an injection molding machine with simulations, a special mold has been produced with a glass window. The injection plane is perpendicular to the opening and closing planes, in order for the 55 mm thick glass window to be easily visible from the side. A high speed camera recording 500 frames per second was employed, and the mold had three thermocouples and two pressure sensors installed. The molded part is a 2 mm thick plate with a 0.5 mm thin section, which creates a characteristic V-shaped flow pattern. Two different materials were employed, namely ABS and a high viscosity PC. Simulations were performed using the actual machine data as input, including the injection screw acceleration. Furthermore, the nozzle and barrel geometries were included as a hot runner to capture the effect of compressibility of the material in front of the screw. These two had significant effects on the filling times and injection pressure calculated by the simulations. Other effects investigated included transient thermal management of the mold, pressure dependent viscosity and wall slip, but their effect were not remarkably large in this work. The obtained simulation results showed deviations within 10–30 ms (relative deviation in the order of 5–10%) for the ABS and slightly more for the high viscosity PC in the range of 100–500 ms (relative deviation in the order of 20–30%) on timings between different sections during filling. [ABSTRACT FROM AUTHOR]

The manufacturing of inserts for micro injection moulding made of mortar material is presented in this work. The fabrication of the mortar insert described in this publication relied on a versatile and relatively fast rapid prototyping process based on soft tooling. The mortar insert has a QR code with micro features on its surface, which was replicated in acrylonitrile butadiene styrene (ABS) polymer by the micro injection moulding process. With this approach, it is possible to fabricate hard inserts for micro injection moulding purposes that are able to compete with conventional-made inserts made of tool steel. [ABSTRACT FROM AUTHOR]

Micro polymer parts can be usually manufactured either by conventional injection moulding (IM) or by micro-injection moulding (µIM). In this paper, functional analysis was used as a tool to investigate the performances of IM and µIM used to manufacture the selected industrial component. The methodology decomposed the production cycle phases of the two processes and attributed functions to parts features of the two investigated machines. The output of the analysis was aimed to determine casual chains leading to the final outcome of the process. Experimental validation of the functional analysis was carried out moulding the same micro medical part in thermoplastic elastomer (TPE) material using the two processes by means of multi-cavity moulds. The produced batches were assessed using a precision scale and a high accuracy optical instrument. The measurement results were compared using capability indexes. The data-driven comparison identified and quantified the correlations between machine design and part quality, demonstrating that the µIM machine technology better meets the accuracy and precision requirements typical of micro manufacturing productions. [ABSTRACT FROM AUTHOR]

The increasing demand for micro-injection molding process technology and the corresponding micro-molded products have materialized in the need for models and simulation capabilities for the establishment of a digital twin of the manufacturing process. The opportunities enabled by the correct process simulation include the possibility of forecasting the part quality and finding optimal process conditions for a given product. The present work displays further use of micro-injection molding process simulation for the prediction of feature dimensions and its optimization and microfeature replication behavior due to geometrical boundary effects. The current work focused on the micro-injection molding of three-dimensional microparts and of single components featuring microstructures. First, two virtual a studies were performed to predict the outer diameter of a micro-ring within an accuracy of 10 µm and the flash formation on a micro-component with mass a 0.1 mg. In the second part of the study, the influence of microstructure orientation on the filling time of a microcavity design section was investigated for a component featuring micro grooves with a 15 µm nominal height. Multiscale meshing was employed to model the replication of microfeatures in a range of 17–346 µm in a Fresnel lens product, allowing the prediction of the replication behavior of a microfeature at 91% accuracy. The simulations were performed using 3D modeling and generalized Navier–Stokes equations using a single multi-scale simulation approach. The current work shows the current potential and limitations in the use of micro-injection molding process simulations for the optimization of micro 3D-part and microstructured components. [ABSTRACT FROM AUTHOR]

The integration of additive manufacturing direct-writing technologies with injection molding provides a novel method to combine functional features into plastic products, and could enable mass-manufacturing of custom-molded plastic parts. In this work, direct-write technology is used to deposit conductive ink traces on the surface of an injection mold. After curing on the mold surface, the printed trace is transferred into the plastic part by exploiting the high temperature and pressure of a thermoplastic polymer melt flow. The transfer of the traces is controlled by interlocking with the polymer system, which creates strong plastic/ink interfacial bonding. The hybrid process chain uses designed mold/ink surface interactions to manufacture stable ink/polymer interfaces. Here, the process chain is proposed and validated through systematic interfacial analysis including feature fidelity, mechanical properties, adhesion, mold topography, surface energy, and hot polymer contact angle. [ABSTRACT FROM AUTHOR]

Highlights from the article: The continuous trend towards miniaturization and multi-functionality embedded in products and processes calls for an ever-increasing research and innovation effort in the development of micro components and related micro manufacturing technologies. It is of critical importance to reduce metrology and optimization efforts, since process and product quality control can take a significant portion of total production time and cost in micro manufacturing. By integrating both Product and Process Manufacturing Fingerprint concepts, metrology and optimization efforts are highly reduced and the micro product quality increased, with an obvious improvement of the production yield. The Special Issue consists of 16 original research papers, which cover both fundamental process technology developments, as well as their application, combined with the definition and the validation of Product and Process Manufacturing Fingerprints.

Injection molding is increasingly gaining favor in the manufacturing of polymer components since it can ensure a cost-efficient production with short cycle times. To ensure the quality of the finished parts and the stability of the process, it is essential to perform frequent metrological inspections. In contrast to the short cycle time of injection molding itself, a metrological quality control can require a significant amount of time and the late detection of a problem may then result in increased wastage. This paper presents an alternative approach to process monitoring and the quality control of injection molded parts with the concept of "Product and Process Fingerprints" that use direct and indirect quality indicators extracted from part quality data in-mold and machine processed data. The proposed approach is based on the concept of product and process fingerprints in the form of calculated indices that are correlated to the quality of the molded parts. A statistically designed set of experiments was undertaken to map the experimental space and quantify the replication of micro-features depending on their position and on combinations of processing parameters with their main effects to discover to what extent the effects of process variation were dependent on feature shape, size, and position. The results show that a number of product and process fingerprints correlate well with the quality of the micro features of the manufactured part depending on their geometry and location and can be used as indirect indicators of part quality. The concept can, thus, support the creation of a rapid quality monitoring system that has the potential to decrease the use of off-line, time-consuming, and detailed metrology for part approval and can thus act as an early warning system during manufacturing. [ABSTRACT FROM AUTHOR]

Injection compression molding (ICM) provides enhanced optical performances of molded polymer optics in terms of birefringence and transmission of light compared to Injection molding (IM). Nevertheless, ICM requires case-dedicated process optimization to ensure that the required high accuracy geometrical replication is achieved, particularly especially in the case of surface micro-features. In this study, two factorial designs of experiments (DOE) were carried out to investigate the replication capability of IM and ICM on a micro structured Fresnel lens. A laser scanning confocal microscope was employed for the quality control of the optical components. Thus, a detailed uncertainty budget was established for the dimensional measurements of the replicated Fresnel lenses, considering specifically peak-to-valley (PV) step height and the pitch of the grooves. Additional monitoring of injection pressure allowed for the definition of a manufacturing signature, namely, the process fingerprint for the evaluation of the replication fidelity under different process conditions. Moreover, considerations on the warpage of parts were related to a manufacturing signature of the molding processes. At last, the global part mass average and standard deviation were measured to correlate local geometrical replication performances with global part quality trends. [ABSTRACT FROM AUTHOR]

Micro-injection moulding (μIM) is a replication-based process enabling the cost-effective production of complex and net-shaped miniaturized plastic components. The micro-scaled size of such parts poses great challenges in assessing their dimensional quality and often leads to time-consuming and unprofitable off-line measurement procedures. In this work, the authors proposed a novel method to verify the quality of a three-dimensional micro moulded component (nominal volume equal to 0.07 mm3) based on the combination of optical micro metrology and injection moulding process monitoring. The most significant dimensional features of the micro part were measured using a focus variation microscope. Their dependency on the variation of µIM process parameters was studied with a Design of Experiments (DoE) statistical approach. A correlation study allowed the identification of the product fingerprint, i.e., the dimensional characteristic that was most linked to the overall part quality and critical for product functionality. Injection pressure and velocity curves were recorded during each moulding cycle to identify the process fingerprint, i.e., the most sensitive and quality-related process indicator. The results of the study showed that the dimensional quality of the micro component could be effectively controlled in-line by combining the two fingerprints, thus opening the door for future µIM in-line process optimization and quality assessment. [ABSTRACT FROM AUTHOR]

Optics is one of the most important applications of functional surfaces enabled by micro-/Nano-structuring. Mass production of optical functional surfaces mainly relies on replication technologies. In optical applications, structural consistency is essential for the precise control of functions such as micro-mirror/lens arrays. A big challenge from the design phase when fabricating functional surfaces is the geometrical constraint, e.g. patterning orient-consistent micromirrors on three-dimensional surfaces. This present paper demonstrates a voxel-based method to indirectly pattern consistently oriented microstructures onto 3D surfaces by creating a hierarchical structure, consisting of the substrate level of a "Minecraft"-like voxel structure and the feature level of micro features machined on the voxels. As a study case, RSA905 injection moulding inserts with 3D functional surfaces for optical encoding are fabricated with diamond machining: a spherical and a sinusoidal sample with a data matrix as an optical ID on each. The encoding is based on the optical contrast generated by the surfaces' directional reflection, which is led by the bevel surfaces of the micro ridge arrays. With the quantified evaluation of the resultant surface quality and functionality, the feasibility of the "Minecraft" method is validated, the surface quality is correlated with its complexity and the process optimization routine is determined. Moreover, by over 15,000 injection moulding cycles, the method is also proved suitable for batch production of 3D functional surfaces by micro injection moulding. • A novel voxel-based hierarchically µ-structuring method for optical functionality of 3D surfaces is proposed and validated. • The Minecraft method is especially suitable for fabricating uniformly oriented microstructure arrays on 3D surfaces. • The surface optical functionality is quantitatively evaluated and correlated with the geometrical quality of microstructures • This method is proven stable and robust in the batch-scale injection moulding of parts with complex functional surfaces [ABSTRACT FROM AUTHOR]

The production of polymeric components with functional structures in the micrometer and sub-micrometer range is a complex challenge for the injection molding process, since it suffers the use of low cavity surface temperatures that induce the fast formation of a frozen layer, thus preventing accurate replication of micro and nano-features. In this work, a thin heating device allowed reaching and maintaining the desired temperature on the cavity surface, by joule effect. A nickel insert with micro and nano-features in relief was located on the cavity surface, and the replication by isotactic polypropylene of the features was analyzed, by Atomic Force Microscopy, under several process parameters. The increase of holding pressure enhanced the replication, but accurate replication was achieved only increasing the cavity surface temperature. A heating time comparable with cavity filling time was sufficient to obtain accurate replication, with adequate surface temperatures. In the case of nano-features, the replication accuracy was affected by the morphology developed on the molding surface, that is aligned along the flow direction with dimensions comparable with the dimension of the nano-features. Therefore, their formation on the surface reduced the accuracy of replication in the direction orthogonal to the flow front. [ABSTRACT FROM AUTHOR]

• Fabrication of the components with injection molding (IM), soft tooling method. • Influence of thermal ageing on the fracture and lifetime behavior of polymer printed inserts. • The surface roughness of the unaged, aged before IM and aged after IM experiments were evaluated. • Measurement and comparison of the IM unaged and aged parts components. • Thermal ageing leads to crack formations in different areas in the mold inserts. Due to the significant technical benefits of additive manufacturing (AM), its application has grown considerably in recent years. In this respect, the integration of AM in the injection molding (IM) process chain for tooling purposes is an ongoing research topic. In the current study, the design, fabrication and use of a tool inserts for injection molding process fabricated by a vat photopolymerisation technique. Since molds during the injection molding process are subjected to cyclic thermal variation, accelerated thermal ageing was applied on the AM mold inserts to emulate the effect of continuous production on the tool lifetime. The additively manufactured mold inserts were exposed to thermal cycling loading in the range between room temperature up to 100 °C, and then, they were used in the actual injection molding process. According to the obtained results, effects of thermal ageing on behavior of the mold inserts are demonstrated. Moreover, fractographic analysis is performed on the fractured surfaces to determine crack initiation and propagation on the mold inserts. The current study provides insight about ageing and fracture of IM mold inserts produced by vat photopolymerisation , and these results can be used for the development of computational models, future material design and load-carrying capabilities of additively manufactured mold inserts to expand the use of AM for tooling purposes. [ABSTRACT FROM AUTHOR]