Multi-Scale Simulation of Injection Molding Process with Micro–Features Replication: Relevance of Rheological Behaviour and Crystallization

The possibility of tailoring key surface properties through the injection molding process makes it intriguing from the perspective of sustainability enhancement. The surface properties depend on the replication accuracy of micro and nanostructures on moldings; such an accuracy is enhanced with cavity temperature. The simulation of the injection molding process is very challenging in the presence of micro and nanostructures on the cavity surface; this does not allow for the neglect of phenomena generally considered not to influence the overall process. In this paper, a multiscale approach was proposed: in the first step, the simulation of the overall process was conducted without considering the presence of the microstructure; in the second step the outputs of the first step were used as an input to simulate the replication of the microfeature. To this purpose, a lubrication approximation was adopted, and the contribution of the trapped air, which slows down the polymer advancement, was accounted for. A modification of the viscosity equation was also proposed to describe the rheological behavior of isotactic polypropylene at very low temperatures. Concerning the microcavity filling simulation, the modification of the viscosity description at low temperatures consistently describes the process, in terms of polymer solidification. Concerning the replication accuracy, it increases with the cavity surface temperature, consistently with the experimental observations.

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Replication of Micro- and Nanofeatures in Injection Molding of Two PLA Grades with Rapid Surface-Temperature Modulation

Materials ◽

10.3390/ma11081442 ◽

2018 ◽

Vol 11 (8) ◽

pp. 1442 ◽

Cited By ~ 6

Author(s):

Sara Liparoti ◽

Vito Speranza ◽

Roberto Pantani

Keyword(s):

Injection Molding ◽

Surface Temperature ◽

Mold Temperature ◽

Cavity Surface ◽

Injection Molding Process ◽

Temperature Modulation ◽

Molding Process ◽

Fast Heating ◽

Crystallinity Degree ◽

Replication Accuracy

The production by injection molding of polymeric components having micro- and nanometrical surfaces is a complex task. Generally, the accurate replication of micro- and nanometrical features on the polymeric surface during the injection-molding process is prevented by of the low mold temperature adopted to reduce cooling time. In this work, we adopt a system that allows fast heating of the cavity surface during the time the melt reaches the cavity, and fast cooling after heater deactivation. A nickel insert with micro- and nanofeatures in relief is located on the cavity surface. Replication accuracy is analyzed by Atomic Force Microscopy under different injection-molding conditions. Two grades of polylactic acid with different viscosity have been adopted. The results indicate that the higher the cavity surface temperature is, the higher the replication accuracy is. The viscosity has a significant effect only in the replication of the microfeatures, whereas its effect results are negligible in the replication of nanofeatures, thus suggesting that the interfacial phenomena are more important for replication at a nanometric scale. The evolution of the crystallinity degree on the surface also results in a key factor on the replication of nanofeatures.

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The Feasibility of an Internal Gas-Assisted Heating Method for Improving the Melt Filling Ability of Polyamide 6 Thermoplastic Composites in a Thin Wall Injection Molding Process

Polymers ◽

10.3390/polym13071004 ◽

2021 ◽

Vol 13 (7) ◽

pp. 1004 ◽

Cited By ~ 1

Author(s):

Thanh Trung Do ◽

Tran Minh The Uyen ◽

Pham Son Minh

Keyword(s):

Injection Molding ◽

Heating Rate ◽

Temperature Control ◽

Cavity Surface ◽

Heating Process ◽

Injection Molding Process ◽

Thin Wall ◽

Molding Process ◽

Filling Ability ◽

Wall Injection

In thin wall injection molding, the filling of plastic material into the cavity will be restricted by the frozen layer due to the quick cooling of the hot melt when it contacts with the lower temperature surface of the cavity. This problem is heightened in composite material, which has a higher viscosity than pure plastic. In this paper, to reduce the frozen layer as well as improve the filling ability of polyamide 6 reinforced with 30 wt.% glass fiber (PA6/GF30%) in the thin wall injection molding process, a preheating step with the internal gas heating method was applied to heat the cavity surface to a high temperature, and then, the filling step was commenced. In this study, the filling ability of PA6/GF30% was studied with a melt flow thickness varying from 0.1 to 0.5 mm. To improve the filling ability, the mold temperature control technique was applied. In this study, an internal gas-assisted mold temperature control (In-GMTC) using different levels of mold insert thickness and gas temperatures to achieve rapid mold surface temperature control was established. The heating process was observed using an infrared camera and estimated by the temperature distribution and the heating rate. Then, the In-GMTC was employed to produce a thin product by an injection molding process with the In-GMTC system. The simulation results show that with agas temperature of 300 °C, the cavity surface could be heated under a heating rate that varied from 23.5 to 24.5 °C/s in the first 2 s. Then, the heating rate decreased. After the heating process was completed, the cavity temperature was varied from 83.8 to about 164.5 °C. In-GMTC was also used for the injection molding process with a part thickness that varied from 0.1 to 0.5 mm. The results show that with In-GMTC, the filling ability of composite material clearly increased from 2.8 to 18.6 mm with a flow thickness of 0.1 mm.

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Influence of Technological Parameters on Material Flow

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1120-1121.1194 ◽

2015 ◽

Vol 1120-1121 ◽

pp. 1194-1197 ◽

Cited By ~ 2

Author(s):

Michal Stanek ◽

David Manas ◽

Miroslav Manas ◽

Vojtech Senkerik ◽

Adam Skrobak ◽

...

Keyword(s):

Injection Molding ◽

Injection Pressure ◽

Polymer Processing ◽

Injection Rate ◽

Cavity Surface ◽

Injection Molding Process ◽

Technological Parameters ◽

Molding Process ◽

Processing Technologies

Injection molding is one of the most extended polymer processing technologies. It enables the manufacture of final products, which do not require any further operations. The tools used for their production – the injection molds – are very complicated assemblies that are made using several technologies and materials. Delivery of polymer melts into the mold cavity is the most important stage of the injection molding process. The fluidity of polymers is affected by many parameters Inc. mold design. Evaluation of set of data obtained by experiments in which the testing conditions were widely changed shows that the quality of cavity surface and technological parameters (injection rate, injection pressure and gate size) has substantial influence on the length of flow.

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Design and Experimental Validation of a Process Chain for Thin Components Manufacturing by Micro Injection Molding Process

Journal of Micro and Nano-Manufacturing ◽

10.1115/1.4051485 ◽

2021 ◽

Author(s):

Vincenzo Bellantone ◽

Fulvio Lavecchia ◽

Rossella Surace ◽

Onofrio Spadavecchia ◽

Francesco Modica ◽

...

Keyword(s):

Injection Molding ◽

Rapid Development ◽

Micro Milling ◽

Surface Finishing ◽

Injection Molding Process ◽

Manufacturing Cost ◽

Process Chain ◽

Molding Process ◽

Micro Injection Molding ◽

Micro Features

Abstract Micro applications, especially in biomedical and optical sectors, require the fabrication of thin polymeric parts which can be commonly realized by micro injection molding process. However, this process is characterized by a relevant constraint regarding the tooling. Indeed, the design and manufacturing of molds could be a very time-consuming step and so, a significant limitation for the rapid development of new products. Moreover, if the design displays challenging micro-features, their realization could involve the use of more than one mold for the fabrication of a single thin part. Therefore, a proper integration of different manufacturing micro technologies may represent an advantageous method to realise such polymeric thin micro features. In this work, a micro-manufacturing process chain including stereolithography, micro milling and micro injection molding is reported. The mold for the micro injection molding process was fabricated by means of stereolithography and micro milling, which allowed to produce low-cost reconfigurable modular mold, composed by an insert support and a removable insert. The assessment of the proposed process chain was carried out by evaluating the dimensions and the surface finishing and texturing of the milled mold cavities and molded components. Finally, a brief economic analysis compares three process chains for fabricating the micro mold showing that proposed one reduces manufacturing cost of almost 61% with the same production time.

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Micro-injection Molded Polymeric Surfaces for the Maintenance of Human Mesenchymal Stem Cells (hMSCs)

MRS Proceedings ◽

10.1557/opl.2013.441 ◽

2013 ◽

Vol 1499 ◽

Author(s):

Meghan E. Casey ◽

John W. Rodgers ◽

Courtney E. LeBlon ◽

John P. Coulter ◽

Sabrina S. Jedlicka

Keyword(s):

Stem Cells ◽

Mesenchymal Stem Cells ◽

Injection Molding ◽

Silicon Wafer ◽

Human Mesenchymal Stem Cells ◽

Mold Insert ◽

High Volume ◽

Injection Molding Process ◽

Molding Process ◽

Micro Features

ABSTRACTIn this work, we take advantage of injection molding as a high volume and repeatable method to create surface areas for the growth of human mesenchymal stem cells (hMSCs). Ultraviolet lithography, combined with deep reactive ion etching, was used to generate micro-features over a relatively large surface area of a silicon wafer. The micro-featured silicon wafer was used as a mold insert for the micro-injection molding process to create polystyrene and low density polyethylene surfaces. Micro-geometry was used to alter the effective surface stiffness of the polymer substrate. Created samples were characterized via scanning electron microscopy and tensile testing. hMSCs were seeded onto samples for initial studies. Actin and vinculin were visualized through ICC to compare cytoskeletal elements. Changes in cell morphology were examined using ICC. Results indicate that injection molding of microfeatured substrates is a viable technique to produce surfaces amenable to stem cell growth.

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Hierarchical Structure of iPP During Injection Molding Process with Fast Mold Temperature Evolution

Materials ◽

10.3390/ma12030424 ◽

2019 ◽

Vol 12 (3) ◽

pp. 424 ◽

Cited By ~ 11

Author(s):

Vito Speranza ◽

Sara Liparoti ◽

Roberto Pantani ◽

Giuseppe Titomanlio

Keyword(s):

Injection Molding ◽

Surface Temperature ◽

Hierarchical Structure ◽

Flow Fields ◽

Electrical Heating ◽

Cavity Surface ◽

Injection Molding Process ◽

Mold Surface ◽

Molding Process ◽

Injection Molded

Mold surface temperature strongly influences the molecular orientation and morphology developed in injection molded samples. In this work, an isotactic polypropylene was injected into a rectangular mold, in which the cavity surface temperature was properly modulated during the process by an electrical heating device. The induced thermo-mechanical histories strongly influenced the morphology developed in the injection molded parts. Polarized optical microscope and atomic force microscope were adopted for morphological investigations. The combination of flow field and cooling rate experienced by the polymer determined the hierarchical structure. Under strong flow fields and high temperatures, a tightly packed structure, called shish-kebab, aligned along the flow direction, was observed. Under weak flow fields, the formation of β-phase, as cylindrites form, was observed. The formation of each morphological structure was analyzed and discussed on the bases of the flow and temperature fields, experienced by the polymer during each stage of the injection molding process.

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Injection Molding of Rubber Compound Influenced by Injection Mold Surface Roughness

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1025-1026.283 ◽

2014 ◽

Vol 1025-1026 ◽

pp. 283-287 ◽

Cited By ~ 1

Author(s):

Michal Stanek ◽

David Manas ◽

Miroslav Manas ◽

Martin Ovsik ◽

Vojtech Senkerik ◽

...

Keyword(s):

Surface Roughness ◽

Injection Molding ◽

Flow Characteristics ◽

Mold Cavity ◽

Cavity Surface ◽

Injection Molding Process ◽

Mold Surface ◽

Technological Parameters ◽

Molding Process ◽

Melt Temperature

Delivery of polymer melts into the mold cavity is the most important stage of the injection molding process. This paper shows the influence of cavity surface roughness and technological parameters on the flow length of rubber into mold cavity. The fluidity of polymers is affected by many parameters (mold design, melt temperature, injection rate and pressures) and by the flow properties of polymers. Results of the experiments carried out with selected types of rubber compounds proved a minimal influence of surface roughness of the runners on the polymer melt flow. This considers excluding (if the conditions allow it) the very complex and expensive finishing operations from the technological process as the influence of the surface roughness on the flow characteristics does not seem to play as important role as was previously thought. Application of the measurement results may have significant influence on the production of shaping parts of the injection molds especially in changing the so far used processes and substituting them by less costly production processes which might increase the competitiveness of the tool producers and shorten the time between product plan and its implementation.

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Effect of Micro-Injection Molding Process Parameters for Various Micro-Channels

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.483.53 ◽

2011 ◽

Vol 483 ◽

pp. 53-57 ◽

Cited By ~ 3

Author(s):

Duo Yang ◽

Chong Liu ◽

Zheng Xu ◽

Ji Zhang Wang ◽

Li Ding Wang

Keyword(s):

Injection Molding ◽

Process Parameters ◽

Mold Temperature ◽

Injection Molding Process ◽

Molding Process ◽

Injection Process ◽

Orthogonal Experiments ◽

Micro Channels ◽

Principal Factors ◽

Replication Accuracy

Micro-channels were the main microstructures in most micro-fluidic devices. In this paper, the effects of injection molding process parameters on the replicability of micro-channels profile are studied. Orthogonal experiments (Taguchi method) are carried out to establish the relationship between injection process parameters and replication accuracy for various micro-channels. Experimental results show that mold temperature and packing pressure are the principal factors in molding process. The replication accuracy depends strongly on the processing conditions. The replication accuracy reached about 99.84% using the optimum parameters.

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