Non-conventional injection molding of poly(lactide) and poly(ε-caprolactone) intended for orthopedic applications

Molding is one of the most versatile and important processes for manufacturing complex plastic parts. It is a method of fabricating plastic parts by utilizing a mold or cavity that has a shape and size similar to the part being produced. Molten polymer is injected into the cavity, resulting in the desired part upon solidification. The injection-molded parts typically have excellent dimensional tolerance and require almost no finishing and assembly operations. But new variations and emerging innovations of conventional injection molding have been continuously developed to offer special features and benefits that cannot be accomplished by the conventional injection molding process. This study aims to improving the life of stereolithography injection mold.

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Comparison of Mechanical Properties of Polymeric Materials Produced by Vented and Conventional Injection Molding Processes

10.4271/961041 ◽

1996 ◽

Cited By ~ 1

Author(s):

Iqbal Shareef ◽

William M. Hammond ◽

John A. Meek

Keyword(s):

Mechanical Properties ◽

Injection Molding ◽

Polymeric Materials ◽

Conventional Injection Molding

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Reducing the Burn Marks on Injection-Molded Parts by External Gas-Assisted Injection Molding

Polymers ◽

10.3390/polym13234087 ◽

2021 ◽

Vol 13 (23) ◽

pp. 4087

Author(s):

Jiquan Li ◽

Wenyong Liu ◽

Xinxin Xia ◽

Hangchao Zhou ◽

Liting Jing ◽

...

Keyword(s):

Image Processing ◽

Injection Molding ◽

Delay Time ◽

Quantitative Method ◽

Surface Defect ◽

Processing Method ◽

Traditional Methods ◽

Molded Parts ◽

Injection Molded ◽

Conventional Injection Molding

A burn mark is a sort of serious surface defect on injection-molded parts. In some cases, it can be difficult to reduce the burn marks by traditional methods. In this study, external gas-assisted injection molding (EGAIM) was introduced to reduce the burn marks, as EGAIM has been reported to reduce the holding pressure. The parts with different severities of burn marks were produced by EGAIM and conventional injection molding (CIM) with the same molding parameters but different gas parameters. The burn marks were quantified by an image processing method and the quantitative method was introduced to discuss the influence of the gas parameters on burn marks. The results show that the burn marks can be eliminated by EGAIM without changing the structure of the part or the mold, and the severity of the burn marks changed from 4.98% with CIM to 0% with EGAIM. Additionally, the gas delay time is the most important gas parameter affecting the burn marks.

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Dual-Scale Modeling and Simulation of Skin Layer Thickness in Injection Molding with Variable Mold Temperatures

Journal of Computational and Theoretical Nanoscience ◽

10.1166/jctn.2016.5681 ◽

2016 ◽

Vol 13 (10) ◽

pp. 7125-7136

Author(s):

Bei Su ◽

Ying-Guo Zhou ◽

Lih-Sheng Turng

Keyword(s):

Injection Molding ◽

Layer Thickness ◽

Mold Temperature ◽

Optical Microscope ◽

Skin Layer ◽

Injection Flow ◽

Scale Modeling ◽

Molded Parts ◽

Dual Scale ◽

Conventional Injection Molding

Compared with the constant mold temperature in conventional injection molding (CIM), injection molded parts with variable mold temperatures undergo a different thermomechanical history. As a result, the microstructure—for example, the skin–core structure found often in CIM—can be changed. However, unlike conventional injection molding, there have been few studies on the microstructure of injection molding with variable mold temperatures (IMVMT), possibly because the experimental control of variable mold temperatures remains difficult. In this paper, the skin layer thickness of CIM and IMVMT under different mold temperatures was carefully investigated by optical microscope. The higher mold temperatures and longer holding times during the injection flow stage caused a thinning of the highly oriented skin layer, and vice-versa. A dual-scale modeling was then proposed based on the prediction of crystal dimensions, and it was further used to predict the thickness of the skin layer. The predicted results were in agreement with the experimental observations under the different mold temperatures during IMVMT processing, and the proposed model proved to be effective.

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Banded spherulites of HDPE molded by gas-assisted and conventional injection molding

Polymer ◽

10.1016/j.polymer.2008.07.005 ◽

2008 ◽

Vol 49 (19) ◽

pp. 4051-4056 ◽

Cited By ~ 37

Author(s):

Li Huang ◽

Wei Yang ◽

Bin Yang ◽

Mingbo Yang ◽

Guoqiang Zheng ◽

...

Keyword(s):

Injection Molding ◽

Banded Spherulites ◽

Conventional Injection Molding

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Influence of Packing Phase Parameters in the Optimization of Mechanical, Weight Reduction and Dimensional Properties of Microcellular Foaming Injection Molding of Polypropilene

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.445.319 ◽

2012 ◽

Vol 445 ◽

pp. 319-324 ◽

Cited By ~ 1

Author(s):

Angel Fernandez ◽

Manuel Muniesa

Keyword(s):

Mechanical Properties ◽

Injection Molding ◽

Weight Reduction ◽

Mechanical Performance ◽

Process Window ◽

Foam Density ◽

Microcellular Foam ◽

Molded Part ◽

Microcellular Foaming ◽

Conventional Injection Molding

Microcellular foaming of injected plastics offers the possibility to manufacture parts with reductions in costs and weight if compared with conventional injection molding. For this reason there is an increasing interest in challenging applications such as HEV (hybrid and electrical vehicles) and lightweight material applications in general. Complexity of microcellular injection molding is very high because the final properties of the material obtained depend largely on the processing conditions and these in turn unalterable factors such as mold design and manufacturing. The shrinkage of the molded part must be applied as an oversize of the mold cavity in the design phase. Shrinkage of a microcellular foam depends on the reduction of foam density. Moreover, the piece is designed to get a mechanical performance and meet the dimensional tolerances. Knowing that the reduction of foam density implies a reduction of the mechanical properties and influences the final piece dimensions the conclusion is that the microcellular injection process has a very small process window to fit all these factors. This research focuses on two objectives. First is the variation of post-molding shrinkage in terms of reduction of weight to determine the process window. Second is the determination of mechanical properties which do not show a proportional reduction but exponentially with weight reduction components. The results obtained with a 750 Tons. injection moulding machine equipped with a MuCell plastication unit and a large spiral mold have shown small variations in the dimensions for a predetermined process window and smaller reduction of mechanical properties with weight reductions for 20% talc filled polypropylene. The goal of this applied research is that all experiments have been developed with scaled-industry tools (large injection molding machine, Mucell unit and mold and test parts) comparing with conventional injection molding.

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An Investigation into the Influencing Factors for Polymer Melt at the Filling Stage in Micro Injection Molding

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.562-565.1380 ◽

2013 ◽

Vol 562-565 ◽

pp. 1380-1386

Author(s):

Jian Zhuang ◽

Da Ming Wu ◽

Ya Jun Zhang ◽

Lin Wang ◽

Xiong Wei Wang ◽

...

Keyword(s):

Injection Molding ◽

Influencing Factors ◽

Polymer Melt ◽

Theoretical Models ◽

Injection Molding Process ◽

Melt Flow ◽

Molding Process ◽

Micro Injection Molding ◽

Filling Stage ◽

Conventional Injection Molding

The flow behaviors for polymer melt at the filling stage in micro injection molding are different from those in conventional injection molding due to the miniaturization of plastic parts. This paper focuses on the study of the effects of three main influencing factors, including the microscale viscosity and wall slip, on melt filling flow in microscale neglected those in conventional injection molding process. The theoretical models and the interrelation of these factors in microscale channels were constructed by means of the model correction method. Then, the micro melt flow behaviors were investigated with comparisons of the available experimental data. The results indicate that the dimensions affect the shear rates and viscous dissipation, which in turn affects the apparent viscosity. Finally, the conclusion is that the melt flow behaviors in microchannels are different from those in macrochannels owing to these significant influencing factors.

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Comparative study of crystallization and lamellae orientation of isotactic polypropylene by rapid heat cycle molding and conventional injection molding

e-Polymers ◽

10.1515/epoly-2016-0251 ◽

2017 ◽

Vol 17 (1) ◽

pp. 71-81 ◽

Cited By ~ 2

Author(s):

Jiquan Li ◽

Shaoguang Yang ◽

Lih-Sheng Turng ◽

Wei Zheng ◽

Shaofei Jiang

Keyword(s):

Injection Molding ◽

Isotactic Polypropylene ◽

Heated Surface ◽

Skin Layer ◽

Multilayered Structure ◽

X Ray Diffraction ◽

Heat Cycle ◽

Molded Parts ◽

Part Thickness ◽

Conventional Injection Molding

AbstractThe crystallization and orientation of isotactic polypropylene (iPP) molded by rapid heat cycle molding (RHCM) and conventional injection molding (CIM) were studied. Due to the varying cooling rates and shearing, the molded parts exhibited a multilayered structure (skin, shear and core) across the part thickness, reflecting different degrees of crystallization and lamellae orientation of iPP. The morphology evolution of RHCM products was discussed based on the comparative research of morphology and structure at multiple sites on the RHCM and CIM specimens. Scanning electron microscopy (SEM) and wide angle X-ray diffraction (WAXD) were used to analyze the thickness, crystallinity and lamellae orientation of these three distinct layers. The crystallization and lamellae orientation of iPP correlated strongly with the multilayered structure. In the RHCM process, one side of the mold is equipped with the rapid heat cycle function. The thickness and lamellae orientation next to the heated surface were less than that of the opposite skin layer without heating. Meanwhile, the crystallinity was greater than that of the opposite skin layer.

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