The effect of flow on cavity surface temperatures in thermoset and thermoplastic injection molding

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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Multi-Objective Optimization of the Heating Rods Layout for Rapid Electrical Heating Cycle Injection Mold

Journal of Mechanical Design ◽

10.1115/1.4001529 ◽

2010 ◽

Vol 132 (6) ◽

Cited By ~ 2

Author(s):

Guoqun Zhao ◽

Xiping Li ◽

Yanjin Guan

Keyword(s):

Temperature Distribution ◽

Injection Molding ◽

Mold Cavity ◽

Electrical Heating ◽

Cavity Surface ◽

Heating Cycle ◽

Multi Objective Optimization ◽

Heating Efficiency ◽

Multi Objective ◽

Distribution Uniformity

Rapid electrical heating cycle injection molding (ERHCM) technology is a promising green manufacturing technology for plastic parts. By using this technology, the defects that usually appear on the surface of conventionally injected parts, such as weld and flow marks, can be avoided effectively. This paper studies rapid electrical heating cycle injection molding technology and its mold structure design techniques. Temperature distribution uniformity and heating efficiency on the mold cavity surface are considered as the major influencing factors on product quality and production efficiency. A multi-objective optimization model for the heating rods layout in the mold cavity plate is formulated to optimize temperature distribution uniformity and heating efficiency with respect to the heating rods layout. An application to a liquid crystal display TV panel is implemented successfully using a genetic algorithm.

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Optimization and application of temperature field in rapid heat cycling molding

Thermal Science ◽

10.2298/tsci210606291h ◽

2021 ◽

pp. 291-291

Author(s):

Mingliang Hao ◽

Haimei Li

Keyword(s):

Injection Molding ◽

Electric Heating ◽

Heating System ◽

Mold Temperature ◽

Temperature Control System ◽

Cavity Surface ◽

Injection Mold ◽

Molding Process ◽

Molded Parts ◽

Automotive Part

The rapid thermal cycle molding (RHCM) belongs to the injection mold temperature control system which is helpful to improve mold ability and enhance part quality. Despite many available literatures, RHCM does not represent a well-developed area of practice. The challenge is the uneven distribution of temperature in the cavity after heating, which mostly leads to defects on the surface of the products. In order to obtain uniform cavity surface temperature distribution of RHCM, the power of heating rods of the electric-heating system in an injection mold was optimized by the response surface method(RSM) in this work. The proposed optimization result was applied to design a complex RHCM injection mold with side core-pulling, holes and different thickness of an automotive part to verify its effectiveness by injection molding. Compared with initial design, the mold temperature uniformity was remarkably improvedby79%. Based on the optimization and injection molding numerical simulation results, the workable molding process to weaken the weld-lines effects on the quality was suggested and the practical injection molded parts were well produced.

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Fast cavity surface temperature evolution in injection molding: control of cooling stage and final morphology analysis

RSC Advances ◽

10.1039/c6ra22968a ◽

2016 ◽

Vol 6 (101) ◽

pp. 99274-99281 ◽

Cited By ~ 20

Author(s):

Sara Liparoti ◽

Andrea Sorrentino ◽

Giuseppe Titomanlio

Keyword(s):

Injection Molding ◽

Surface Temperature ◽

Temperature Evolution ◽

Cavity Surface ◽

Cooling Stage ◽

Morphology Analysis

New isotropic morphologies are obtained by controlling pressure and temperature evolution.

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Thermal Modeling of Solar Central Receiver Cavities

Journal of Solar Energy Engineering ◽

10.1115/1.3268296 ◽

1989 ◽

Vol 111 (2) ◽

pp. 117-123 ◽

Cited By ~ 12

Author(s):

R. D. Skocypec ◽

V. Romero

Keyword(s):

Energy Transfer ◽

Steady State ◽

Radiative Transfer ◽

Molten Salt ◽

Front Surface ◽

Cavity Surface ◽

Outlet Temperature ◽

Incident Flux ◽

Loss Mechanism ◽

Surface Temperatures

Results are presented from a numerical model of the steady-state energy transfer in molten-salt-in-tube solar cavity receivers that includes convective energy transfer at a local (spatially resolved) level. Molten salt energy absorption and gray radiative transfer between all cavity surfaces are also included. This model is applied to the Molten Salt Subsystem Component Test Experiment (MSS/CTE) cavity receiver. Results for this receiver indicate the global (entire cavity) receiver thermal efficiency is invariant within a few percent to most parameters investigated, although front surface temperatures of the nonabsorbing walls vary considerably, and are particularly sensitive to the type of convective submodel used. Absorption efficiencies indicate the effects of the cavity enclosure environment. For all conditions investigated, tube inner wall temperatures remain under 855 K, ensuring that the salt remains chemically stable. Global results for the receiver indicate thermal conditions in the receiver are temporally constant within an hour of solar noon, and solar panel temperatures are governed by the temperature of the flowing salt (the outlet temperature is maintained at 839 K by varying the salt mass flow rate). The dominant loss mechanism is radiative transfer, although convective loss predictions are of the same order of magnitude. The absorbing panel front surface temperatures and the panel thermal losses are somewhat invariant with incident flux. Losses from the nonabsorbing surfaces (comprising over 60 percent of the cavity surface area), however, do vary with incident flux levels. These results suggest that a correction for nonconstant losses in the Barron flux-on loss method is necessary. Global predictions compare well with data obtained in the MSS/CTE experiment. Predicted salt flow rates and absorbed powers were within one percent of values measured during steady-state tests. Predicted global loss values compare well with current loss estimates from measured data.

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Replication of micro and nano-features on iPP by injection molding with fast cavity surface temperature evolution

Materials & Design ◽

10.1016/j.matdes.2017.08.016 ◽

2017 ◽

Vol 133 ◽

pp. 559-569 ◽

Cited By ~ 18

Author(s):

Vito Speranza ◽

Sara Liparoti ◽

Matteo Calaon ◽

Guido Tosello ◽

Roberto Pantani ◽

...

Keyword(s):

Injection Molding ◽

Surface Temperature ◽

Temperature Evolution ◽

Cavity Surface

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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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The feasibility of external gas-assisted mold-temperature control for thin-wall injection molding

Advances in Mechanical Engineering ◽

10.1177/1687814018806102 ◽

2018 ◽

Vol 10 (10) ◽

pp. 168781401880610 ◽

Cited By ~ 1

Author(s):

Pham Son Minh ◽

Thanh Trung Do ◽

Tran Minh The Uyen

Keyword(s):

Temperature Distribution ◽

Injection Molding ◽

Heating Rate ◽

Temperature Control ◽

Mold Temperature ◽

Cavity Surface ◽

Thin Wall ◽

Mold Surface ◽

Hot Gas ◽

Wall Injection

Simulation and experimental testing were conducted on an external gas-assisted mold-temperature control combined with a pulsed cooling system used for thin-wall injection molding to determine its effect on the heating rate and temperature distribution of a mold surface. For mold heating via external gas-assisted mold-temperature control, a hot gas was directly discharged on the cavity surface. Based on the heat convection between the hot gas and the cavity surface, the cavity temperature rose to the target value. Practically, the gap between the heating surface and the gas gate is an important parameter as it strongly influences the heating process. Therefore, this parameter was analyzed under different values of plate-insert thickness herein. Heating was elucidated by the temperature distribution and heating-rate data detected by the infrared camera and sensors. Then, external gas-assisted mold-temperature control was applied for the thin-wall injection-molding part of 0.5 mm thickness with the local-gate-temperature control. The results show that with 300°C gas temperature, the heating rate could reach 9°C/s with a 0.5-mm stamp thickness and a 4-mm gas gap. The results show that with local heating at the melt-entrance area of the mold plate, the cavity was filled with a 20-s heating cycle.

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