Selective induction heating to eliminate the fundamental defects of thin‐walled moldings used in electrical industry

Mrozek, Krzysztof; Chen, Shia‐Chung

doi:10.1002/app.44992

Cited by 23 publications

(22 citation statements)

References 32 publications

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“…They are therefore forced to look for new technological solutions. A certain solution to the problem of weld lines in parts is the use of unconventional injection molding methods, such as push–pull injection molding , cascade , vibration , and injection molding with variable temperature . However, each of these methods involves higher costs of moldings production, associated with a more complicated mold design and the need to ensure proper control of the injection molding machine.…”

Section: Introductionmentioning

confidence: 99%

The influence of the type of polypropylene and the length of the flow path on the structure and properties of injection molded parts with the weld lines

Bociąga

Kaptacz

Duda

et al. 2019

Polymer Engineering & Sci

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Weld lines, created in the areas of collision of two flow fronts of plastic in the injection mold cavity, are the reason of lower mechanical properties and a worse surface condition of molded parts. In the weld line area, the V‐shaped notch is formed and its shape and size depend on injection molding conditions and properties of processed polymer. Addition of the foaming agent to the polymer can be one of the way to improve conditions of melt streams welding due to the higher velocity of the colliding streams of unfilled polypropylene (PP) and PP filled with talc. The examinations of mechanical properties showed, however, lower tensile strength of porous parts compared to solid ones, but in the microscopic observation and measurements of the geometric structure of moldings, in the weld lines area, better surface conditions were achieved for samples made of the foamed polypropylene. The size of V‐notch, determined by the total height of the raw profile Pt, depends also on the length of polymer flow path from the gate to the weld line area. The values of Pt parameter increase with the length of the flow path, but this increase is smaller for foamed polypropylene. POLYM. ENG. SCI., 59:1710–1718 2019. © 2019 Society of Plastics Engineers

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Section: Introductionmentioning

confidence: 99%

The influence of the type of polypropylene and the length of the flow path on the structure and properties of injection molded parts with the weld lines

Bociąga

Kaptacz

Duda

et al. 2019

Polymer Engineering & Sci

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show abstract

“…A solution to the problem of visible traces of the joining of plastic streams in molded parts there is a cyclic change in mold temperature (heating/cooling) during the injection cycle, e.g. induction heating in the areas where they occur and then cooling with water in the cooling channels system [28,[30][31][32][33][34]. In the injection phase at a higher temperature, the polymer macromolecules are easier to combine with each other, and as a result, a bonding with a higher strength and a part with a better surface condition is obtained.…”

Section: Injection Methodsmentioning

confidence: 99%

Characteristics of injection molded parts with the areas of weld lines

Bociąga

Skoneczny

2020

Polimery

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The weld lines in injection molded parts arise as a result of the collision of two fronts of the flowing material, which fills the mold cavity and are sometimes unavoidable. They decrease the mechanical properties and surface state of the moldings, due to insufficient connection of the fronts of melted polymer streams. The paper discusses the reasons for the occurrence of weld lines in molded parts, which have been divided into ones related to the design of the injection molded part, properties of the injected material, injection mold construction and injection parameters. The design of the molded parts should ensure even, smooth flow of the material in the cavity, but in the case of parts with many injection points, holes, varied wall thickness, complicated and irregular structure the weld lines can not be avoided. The type of material processed significantly influences the strength of the weld line area. Too high viscosity of the material, fillers and large particles of the coloring agent highly oriented in the weld line area, are the factors lowering properties of the molded part. Considering the design of the injection mold, the most important aspects in forming proper parts with weld lines are correct venting of the mold, small differences in the material temperature in all cavity areas, correctly selected injection points, avoiding jet filling of the cavity. The quality of such parts can be improved by changing the injection conditions, mainly by increasing the mold and melt temperature, also increasing the holding pressure and the injection speed. The possibilities of preventing the weld lines creation or reducing the negative effects of their occurrence have been presented, e.g. by changing the design and location of gates in injection molds, changing processing conditions or using unconventional methods of injection molding, like cascade cavity filling, push-pull and multiple live-feed injection molding, vibration process. Further examinations in the range of cyclic heating/cooling of the injection mold are suggested as the most promising regarding the quality of parts in the area of weld line, their strength and surface state.

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“…The numerical simulations were validated with the experimental setup that contained: induction generator EFD Minac 6/10, a coil with a magnetic concentrator, thermal imaging camera FLIR T620, temperature regulation system PSG, and injection mold block with changeable inserts. The precise description of the experiment can be found at [ 7 ], while Figure 3 shows a scheme and a photograph of the test stand.…”

Section: Methodsmentioning

confidence: 99%

“…Reducing wall thickness results in increased injection pressure, due to the reduction in the cross-section of the mold’s cavity of the flow path of the plastic [ 6 ]. A thin layer of polymer melt cools down rapidly, increasing the resistance of the flow and leads to freezing of the material before the complete filling of the cavity [ 7 ]. The increase of the surface temperature above the transition temperature of the polymer melt allows the manufacturing of long thin-walled parts.…”

Section: Introductionmentioning

confidence: 99%

Application of Magnetic Concentrator for Improvement in Rapid Temperature Cycling Technology

2020

Self Cite

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The main method to improve the filling of the cavity by the polymer melt is to increase the mold temperature. Rapid temperature cycling (RTC) technologies have been used around the world for several years, improving the quality of injection molded parts with a slight extension of production time. The present work focuses on the application of induction heating technology in the injection molding process since it is the most effective and most intensively developing method of heating in modern RTC technologies. In this research, the application of the induction heating process for selected surfaces was investigated with particular emphasis on the dynamics of the process. The numerical simulations were used to study the influence of the number of coils, the distance between coils and cavity surface and the mold material was examined with and without the presence of a magnetic concentrator. According to the obtained results, several crucial conclusions were made: the efficiency of heating is directly correlated with the distance between the inductor and the mold surface, the presence of magnetic flux concentrator significantly improves the homogeneity of temperature distribution and heating efficiency, application of aluminum mold lowers the obtained surface temperature.

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Selective induction heating to eliminate the fundamental defects of thin‐walled moldings used in electrical industry

Cited by 23 publications

References 32 publications

The influence of the type of polypropylene and the length of the flow path on the structure and properties of injection molded parts with the weld lines

The influence of the type of polypropylene and the length of the flow path on the structure and properties of injection molded parts with the weld lines

Characteristics of injection molded parts with the areas of weld lines

Application of Magnetic Concentrator for Improvement in Rapid Temperature Cycling Technology

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