Plastic syringes often rely on silicone oil lubrication to reduce plunger-barrel friction, leading to potential issues like oil droplet release and drug aggregation. This study explored an ...alternative approach combining two-photon polymerization, laser machining, and microinjection molding to manufacture micro-dimpled structures for low friction. Plastic microdimples with high area density and low aspect ratio significantly reduced the coefficient of friction against rubber, while the dimple profile proved crucial in facilitating replication and demolding. The results of this study provide valuable insights into reducing friction between rubber and plastic, particularly in applications like syringes.
The quality control of plastic products is an essential aspect of the plastic injection molding (PIM) process. However, the warpage and shrinkage deformations continue to exist because the PIM ...process is easily interfered with by several related or independent process parameters. Thus, great efforts have been devoted to optimizing process parameters to minimize the warpage and shrinkage deformations of products during the last decades. In this review, we begin by introducing the manufacturing process in PIM and the cause of warpage and shrinkage deformations, followed by the mechanism about how process parameters, like mold temperature, melt temperature, injection rate, injection pressure, holding pressure, holding and cooling duration, affect those defects. Then, we summarize the recent progress of the design of experiments and four advanced methods (artificial neural networks, genetic algorithm, response surface methodology, and Kriging model) on optimizing process parameters to minimize the warpage and shrinkage deformations. In the end, future perspectives of quality control in injection molding machines are discussed.
•Precision plastic biaspheric lens having high and uneven thickness was developed using injection molding process.•A hybrid ANN and PSO technique was employed to predict the optimal process ...parameters.•Mould with aspheric profiles was prepared using single point diamond turning machine.•Surface characterisation like form, waveiness and surface roughness of mould and moulded bi-aspheric lens are measured.•Aberrations in the injection molded lens were studied using Shack-Hartmann Wavefront Sensor.
Injection molding of bi-aspheric lens using polycarbonate material with minimum variation in volumetric shrinkage is crucial for optical quality and is more challenging task among the researchers. In this paper, a hybrid artificial neural networks (ANN) and particle swarm optimization (PSO) technique is used to predict the optimal process parameters of injection molding process of the bi-aspheric lens. The developed ANN network (7-13-6) was trained as well as tested with experimental data sampled from statistical methods. The well trained and tested ANN network was coupled with improved PSO algorithm as a hybrid ANN-PSO to optimize the injection molding process parameters. The optimized injection molding process parameters obtained from hybrid ANN-PSO algorithm are validated with experiments using J. S. W injection molding machine. It is observed from the lens quality parameters that the proposed hybrid ANN-PSO method optimized the injection molding process of the bi-aspheric lens with an optical power of 27.73 Diopter and the lens posses seventh order spherical aberrations.
Double‐injection molding involves the use of two injection units, A and B, which can combine two different plastics into one part in a single injection molding process. Double‐injection molding can ...promote the recycling of plastic waste as well as improve the performance and dull appearance of plastic products made from recycled materials. However, the warpage of parts is a significant challenge in double‐injection molding. Warpage is significantly affected by the properties of the recycled material and injection molding process. In this study, the relationship between the warpage of double‐injection‐molded parts using raw and recycled materials was studied through uniform design experiments. To investigate the processes and warpage, the material was recycled several times, and its properties were tested. A regression model was established to describe the quantitative relationship between the important parameters and warpage. The number‐average molecular weight and weight‐average molecular weight exhibited the largest decrease after the first recycling cycle with a 21.11% and 41.11% decrease, respectively. The melting temperature decreased from 164.61 to 159.35°C, and the crystallinity did not change significantly. The processing parameters varied with the change in the properties of PP recycled materials, with the melt temperature decreased from 225 to 210°C. In addition, the number of recycling cycles and holding time for B were the most important factors influencing the warpage of double‐injection‐molded parts, followed by holding time for A and melt temperature for A. Warpage can be reduced by increasing holding times B and A. The experimental results provide important data for reducing the warpage of double‐injection‐molded parts with recycled materials.
Highlights
Double‐injection‐molded parts containing recycled materials were prepared.
Recycling enhanced the filling capacity of polypropylene.
The regression model of warpage with variables was established.
Warpage can be improved by adjusting processes and materials.
The effects of recycled materials and injection molding process on warpage in double‐injection molding.
Based on the self‐assisted injection experimental platform, experimental studies on gas‐assisted injection molding (GAIM), and water‐assisted injection molding (WAIM) of 2 curved pipe fittings by ...adopting short‐shot method were carried out. UDF model was constructed for numerical simulation analysis. The influence rules of auxiliary medium and bending angle on the terminal morphology, inner wall surface quality at bending angle, medial and lateral residual wall thickness, variation range, and residual wall thickness deviation rate of short‐shot fluid assisted injection molding (SSFAIM) bending samples were compared. Meanwhile, the influence mechanism was investigated. The following experimental findings were obtained. SSFAIM had secondary penetration, while water produced multiple penetrations. There are multiple vacuum shrinkage pores in the unpenetrated area at the end of the SSWAIM sample, as well as serious shrinkage depressions on the surface. The shape of the penetration front of water is arc‐shaped with many penetration holes. The shape of the penetration front of the gas at the end of the SSGAIM sample is “pointy.” Compared with the SSWAIM sample, the residual wall thickness of SSGAIM has a narrow distribution range when the bending angle is 0°. With the increase of the bending angle, the “foaming” phenomenon of the inner wall surface quality at the bending angle of the SSGAIM sample becomes less and less obvious. Moreover, the deviation of the inner and outer residual wall thickness of SSGAIM is more obvious than that of SSWAIM due to the increase of bending angle.
Through the comparative analysis of the quality and residual wall thickness distribution characteristics of SSGAIM specimen and SSWAIM specimen, the influence law and mechanism would be explored, aiming to provide theoretical basis and guideline recommendations for the development of SSFAIM process.
•Presents a survey of manufacturing oriented topology optimization methods.•Investigates the length scale control and geometric feature based design for machining oriented topology ...optimization.•Investigates the part ejection and rib thickness control for injection molding/casting oriented topology optimization.•Proposes the future research direction for additive manufacturing oriented topology optimization.
Topology optimization is developing rapidly in all kinds of directions; and increasingly more extensions are oriented towards manufacturability of the optimized designs. Therefore, this survey of manufacturing oriented topology optimization methods is intended to provide useful insight classification and expert comments for the community.
First, the traditional manufacturing methods of machining and injection molding/casting are reviewed, because the majority of engineering parts are manufactured through these methods and complex design requirements are associated. Next, the challenges and opportunities related to the emerging additive manufacturing (AM) are highlighted. SIMP (Solid Isotropic Material with Penalization) and level set are the concerned topology optimization methods because the majority of manufacturing oriented extensions have been made based on these two methods.
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•25-fold low-density BPP foam was fabricated using foam injection molding.•The BPP foam can have a thermal conductivity of as low as 32.4 mW·m−1·K−1.•In-situ fibrillated nano PTFE can ...refine the cellular structure significantly.•The compression strength of BPP foam was improved by the refined cellular structure.
Polymer foam has become an important thermal insulation material due to its outstanding features, while its fabrication is still very challenging by foaming injection molding technology. Herein, we reported the successful fabrication of low-density branched polypropylene (BPP) foam with an expansion ratio of up to 25-fold and fine cellular structures using mold-opening foam injection molding (MOFIM) technology. To improve foaming ability, polytetrafluoroethylene (PTFE) nanofiber reinforced BPP composite was prepared in an in-situ way through a simple twin-screw blending technology. The DSC results show that PTFE nanofibers can promote crystallization of BPP effectively, while the rheological measurements demonstrate that PTFE fibers can improve the viscoelastic behavior of BPP. Furthermore, the MOFIM experimental results show that the cell size is reduced by one order of magnitude while the cell density is increased by four orders of magnitude. Interestingly, PTFE nanofibers endow BPP/PTFE foams a unique cell wall structure with plenty of micro-holes and micro/nano fibrils. Moreover, BPP/PTFE foams show markedly improved thermal insulation and compressive mechanical performance with a thermal conductivity of as low as 32.4 mW·m−1·K−1. Thus, this unique low-density BPP/PTFE foam shows a promising future in high-performance thermal insulation applications, particularly considering the used scalable, versatile, facile and cost-saving processing technology.
In this paper, cooling performance of conformal cooling channel in plastic injection molding (PIM) is numerically and experimentally examined. To examine the cooling performance, cycle time and ...warpage are considered. Melt temperature, injection time, packing pressure, packing time, cooling time, and cooling temperature are taken as the design variables. A multi-objective optimization of the process parameters is then performed. First, the process parameters of conformal cooling channel are optimized. Numerical simulation in the PIM is so intensive that a sequential approximate optimization using a radial basis function network is used to identify a pareto-frontier. It is found from the numerical result that the cooling performance of conformal cooling channel is much improved, compared to the conventional cooling channel. Based on the numerical result, the conformal cooling channel is developed by using additive manufacturing technology. The experiment is then carried out to examine the validity of the conformal cooling channel. Through numerical and experimental result, it is confirmed that the conformal cooling channel is effective to the short cycle time and the warpage reduction.
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