Micro‐injection molding of thermoplastic polymers: Proposal of a constitutive law as function of the aspect ratios

Mélé, P.; Giboz, Julien

doi:10.1002/app.45719

Cited by 14 publications

(7 citation statements)

References 19 publications

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“…Typical products from μIM include microgears, microneedles, microfilters, and microfluidic devices . The common feature for these microparts is the very high surface‐area‐to‐volume ratio (up to 10 3 –10 6 /m) , which poses certain challenges for the mold filling process due to the very high cooling rate effects in μIM . To avoid premature solidification of polymer melts, certain processing parameters in μIM (such as melt and mold temperatures as well as injection velocities) are typically higher than those in CIM .…”

Section: Introductionmentioning

confidence: 99%

Properties of microinjection‐molded polypropylene/graphite composites

Zhou

Hrymak

Kamal

et al. 2019

Polymer Engineering & Sci

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In this study, polypropylene (PP) composites filled with two different types of graphite particles, that is, flake‐shaped synthetic graphite (SG) and low‐temperature expandable graphite (LTEG), were prepared by melt blending, followed by microinjection molding (μIM). The microparts had three consecutive zones with decreasing thickness along the flow direction (FD). Results showed that, in addition to the larger particle size, the in situ exfoliation of LTEG during melt processing is crucial to the overall enhancement of electrical conductivity when compared with their SG‐containing counterparts, as corroborated by morphology observations. Moreover, the preferential alignment of conductive particles favors the construction of conductive pathways along the FD. The melting and crystallization behavior for PP, PP/LTEG, and PP/SG materials, and samples from each section of the corresponding microparts were evaluated by differential scanning calorimetry. Results indicated that both the addition of graphite particles and the typical thermomechanical history of μIM (i.e., high shearing and cooling rates) experienced in different sections of the three‐step microparts influence the melting and crystallization behavior of the composites. POLYM. ENG. SCI., 59:1560–1569 2019. © 2019 Society of Plastics Engineers

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Section: Introductionmentioning

confidence: 99%

Properties of microinjection‐molded polypropylene/graphite composites

Zhou

Hrymak

Kamal

et al. 2019

Polymer Engineering & Sci

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“…gives the flow length of the plastic from the start of the gate to the end of the flow using the particle tracking technique, where the maximum flow length is 372.5679 mm. Because product thickness and flow length both affect flow capacity, product design is usually checked for good design by the value of "Flow length ratio" [43], which is defined as equation (9). So based on the data given in Fig.…”

Section: Model Informationmentioning

confidence: 99%

A research method to improve the quality of box-type thin-walled parts by combining parameter optimization and i nverse-deformation design

Zhai

Chang²,

Li³

et al. 2022

Preprint

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In this paper, a five-part study on the molding quality of box-type thin-walled injection molded parts with volume shrinkage and warpage deformation was conducted. In the first part, the molding parameters: filling time, plastic temperature, mold temperature (C), holding time (D), maximum holding pressure (E), and cooling time (F) were selected, and a six-factor, five-level L25 (5 6 ) orthogonal experimental design (OED) was designed. Then, the optimal combination of molding parameters was optimized by using gray correlation (GC) theory analysis. In the second part, the six molding parameters from the first part were further optimized based on the Box Behnken Design (BBD) response surface method (RSM) and BP neural network (BPNN) training, and the results showed that the fitted regression model after BPNN training had a smaller prediction error. In the third part, the regression models fitted with BBD and BPNN-BBD are further optimized globally. The optimization search method uses the NSGA-II genetic optimization algorithm. And comparing the above four optimization methods found that BPNN-BBD-NSGA-II prediction error < BPNN-BBD prediction error < BBD-NSGA-II prediction error < BBD prediction error. The fourth part is based on the anti-deformation design (ADD) theory. The NX/Moldex3D global optimization platform is created to finally almost completely eliminate warpage deformation of box-type thin-walled injection molded parts. In the last part, a trial mold verification analysis was performed, and the molding quality data was obtained by using optical scanning instruments, and the GOM software was used to compare and analyze the deviation values of each appearance surface and the flatness values.

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“…Moreover, the sharp decrease of melt temperature more easily brings about the formation of the frozen layer at the interface where the polymer melt contacts with the surface of micro cavity, which causes the short shots, and thus the molding qualities of micro polymer parts are deteriorated. [6][7][8] The researchers mainly increased the filling capability of polymer melt in the micro cavity and improved the mold filling quality by optimizing the parameters of micro-injection molding such as mold temperature, melt temperature, injection speed, and holding pressure, and so on. [9][10][11][12][13] But the excessively high-injection molding parameters made enormous demands on injection machine performance, and mold design and manufacturing, which increased the cost of micro-injection molding and might cause some molding defects, such as oxidation degradation, air traps, and warping deformation, and so on.…”

Section: Introductionmentioning

confidence: 99%

Theoretical analysis and numerical modeling of the evolution mechanism of polymer melt unstable flow in two‐dimensional ultrasonic‐assisted micro‐injection molding

Qiu

Wang

2021

J of Applied Polymer Sci

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Micro polymer parts are usually fabricated by ultrasonic-assisted micro-injection molding which is an effective and low-cost method. This method solves some injection molding defects such as short shot by reducing the melt viscosity, and the clarification of its mechanism is a challenge. This article is aimed at studying the evolution mechanism of two-dimensional ultrasonic vibration on the polymer melt unstable flow. A two-dimensional ultrasonic vibration, whose displacements components in the x-and y-directions are large, is applied to the polymer melt. The unstable flow is a flow field with perturbations. The formulas of perturbation stream function and velocity perturbations are established based on the theories of absolute instability and convective instability. The established formulas are verified by numerical analysis. The results show that the flow of

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Micro‐injection molding of thermoplastic polymers: Proposal of a constitutive law as function of the aspect ratios

Cited by 14 publications

References 19 publications

Properties of microinjection‐molded polypropylene/graphite composites

Properties of microinjection‐molded polypropylene/graphite composites

A research method to improve the quality of box-type thin-walled parts by combining parameter optimization and i nverse-deformation design

Theoretical analysis and numerical modeling of the evolution mechanism of polymer melt unstable flow in two‐dimensional ultrasonic‐assisted micro‐injection molding

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