Runner System Research Articles

Study of the Structural Characteristics of Mold for Precise Injection Molding

With the improvement of accuracy requirements for industrial products, the precise injection molding is replacing the traditional injection molding quickly and widely. Many factors influence the quality of injection-molded parts greatly, such as the property of the plastics, mold structure and the manufacturing accuracy, injecting machine and the injecting process parameters. In this paper, the work is emphasized for the influence of mold structure on the quality of injection-molded parts. Eight portions of injection mold are analyzed, including the cavities and cores, the guide components, the runner system, the ejection system, the side-core pulling mechanism, the temperature balance system, the venting system and the supporting parts. The structural characteristics of the above eight portions are presented.

Multi-Objective Runner Optimization for Injection Mold of Combinational Cavities Based on Kriging Model

Aiming at the runner design feature of injection mold of combinational cavities laid in non-natural balance, the design method of multi-objective runner optimization is put forward based on Kriging model. At fist, the basic theory of Kriging approximate model is proposed, and aiming at the feature of combinational cavities, the multi-objective optimum model of runner system is proposed also. In the solving multi-objective optimum model, the multi-objective ant colonies algorithm with crossover and mutation based on Pareto optimization is proposed. The given method is testified by a runner design instance of top and down cover of mouse, and it has a good application in engineering. The optimum result shows that the multi-objective ant colonies algorithm with crossover and mutation has good algorithmic performance.

다수 캐비티 사출금형에서의 균형 충전을 위한 러너 시스템 연구

사출성형은 열가소성 수지의 가공법으로 정밀도나 고품질의 제품을 효과적으로 생산하는데 널리 이용되는 기술이다. 다수 캐비티 사출성형에서 캐비티 충전 불균형이 발생하는데 이러한 현상은 사출성형품의 치수 및 중량의 편차 뿐 아니라 물리적 특성에 영향을 미치고 있다. 충전 불균형은 충전 단계에서 러너 내에서 발생되는 불균일한 전단분포에 기인하여 발생되므로 점도 변화에 영향을 주는 수지의 물성, 사출조건 등 성형공정 조건 요인에 의해 충전 불균형의 양상이 다르게 된다. 본 논문에서는 점도 및 물성이 다른 PC, PP 수지에 대하여 성형조건에 따른 충전 현상을 관찰하고 원인을 분석하였고 사출속도에 따른 충전 불균형 현상의 원인을 고찰하기 위해 사출성형실험과 CAE 해석을 수행하였다. CAE 해석을 수행하여 각 수지마다 사출속도에 따른 충전 패턴 경향과 온도분포를 예측하고 캐비티 간 충전 균형을 위해 새로운 볼륨 러너 시스템을 제시하였고 캐비티 간 충전 균형을 확인 할 수 있었다. In this study, flow characteristics in a multi-cavity injection molding process were investigated. One of main problems occurred in the multi-cavity molding is a flow imbalance among cavities since it affects physical properties and quality of products. Charge imbalance is caused by the uneven shear stress. Therefore, changes in viscosity affect the physical properties of resin and injection conditions differ in the filling imbalance phenomenon. Through, this study focus on experimental studies of flow imbalance for PC and PP resin occurring in a balanced delivery system. Experimental results were compared with CAE results. By experimental and CAE analysis, main cause for the flow imbalance is temperature distribution in cross section of runner. New runner system with a simple change of runner shape was suggested to avoid the flow imbalance. A series of simulation to confirm feasibility of Volume Runner's effects was conducted using injection molding CAE.

Design and fabrication of miniature compliant hinges for multi-material compliant mechanisms

Multi-material molding (MMM) enables the creation of multi-material mechanisms that combine compliant hinges, serving as revolute joints, and rigid links in a single part. There are three important challenges in creating these structures: (1) bonding between the materials used, (2) the ability of the hinge to transfer the required loads in the mechanism while allowing for the prescribed degree(s) of freedom, and (3) incorporating the process-specific requirements in the design stage. This paper presents the approach for design and fabrication of miniature compliant hinges in multi-material compliant mechanisms. The methodology described in this paper allows for the concurrent design of the part and the manufacturing process. For the first challenge, mechanical interlocking strategies are presented. For the second challenge, the development of a simulation-based optimization model of the hinge is presented, involving functional and manufacturing constrains. For the third challenge, the development of hinge positioning features and gate positioning constraints is presented. The developed MMM process is described, along with the main constraints and performance measures. This includes the process sequence, the mold cavity design, gate selection, and runner system development. A case study is presented to demonstrate the feasibility of creating multi-material mechanisms with miniature hinges serving as joints through MMM process. The approach described in this paper was utilized to design a drive mechanism for a flapping wing micro air vehicle. The methods described in this paper are applicable to any lightweight, load-bearing compliant mechanism manufactured using multi-material injection molding.

Application of computer simulation of thermoset resins casting in rapid prototyping techniques

Summary — The article presents a methodology of the technological process to manufacture technical cast profile models based on the example of gear wheels in silicone molds produced with the vacuum casting (VC) method. In this process, designing of the model manufacturing begins with the preparation of the silicone mold structure. At this stage the properties of the material to be cast into the silicone mold should be taken into account. The properties, including the viscosity, density, reactivity and crosslinking thermal effect of the material should be build into designing of the prototype. They determine also the geometry of the runner system supplying mold cavity and its vents.

The Applied Study on Hot Runner Technology and Design of Injection Molds

The hot runner technology is an advanced & applied technology in process of forming of an injection mold. As soon as the hot runner technology is applied in injection molds, it will obtain the aim for optimization of product quality, increasing efficiency of production, saving raw materials, saving energy, decreasing cost of products and so on. The article will mainly discusses the applied study of hot runner technology in injection mold, and has a detailed explanation for the design instances of hot runner technology in injection mold, the suitability of hot runner system and the technological & economical analyses of hot runner molds.

Computer Simulation of Melt Flow in Different Gate System for Metal Injection Molding Connecting Shaft

On the basis of continuous medium theory, computer simulation analysis of metal-powder injection molding was carried out with the help of FLOTRAN hydro-analysis module of ANSYS software. The effects of the gates with different dimension and location were testified. The impact of gate system on the filling process is discussed. The dynamic display of the flow leading edge in the cavity, and temperature field of the melt were researched. A result was obtained that we can modify the design of runner system if we make a full use of existing equipment resource.

High-quality aluminum turbocharger impellers produced by thixocasting

The thixocasting process was chosen to produce the impellers as it is capable of producing castings with extremely high internal quality. Slugs cut from the DC cast bars are re-heated to the semi-solid casting temperature, and a specially-designed runner and gating system is used to prevent oxide from the surface of the slugs from becoming incorporated into the impeller. The technology used to produce the semi-solid impellers is described in detail. The semi-solid cast impellers, produced from an Al-Si-Mg-Cu alloy, are heat treated to the T6 temper. Results from testing are presented demonstrating that the impellers are free of porosity and other internal defects. Both mechanical property and fatigue data are presented showing that the semi-solid impellers have better properties than impellers produced by conventional casting and similar properties to forged and machined impellers. A short study is also described which identified suitable processing parameters to minimize hot tearing in the complex-shaped turbocharger impellers semi-solid cast from alloy 201. The surfaces of the impellers were examined using penetrant testing, and the results of modifying processing parameters on the propensity for surface cracking are presented. An aging study was performed to identify optimum mechanical strength.

The Influence of the Solidification Process to the Dimensional Accuracy of Castings

The real system under consideration comprises of a solidifying casting with the casting mould, environment and other external influences. The process observed begins with the introduction of liquid metal to the channels of the runner system and filling of the mould cavity. This is connected with the contact of liquid metal with the atmosphere and also, with the walls of the mould. During the filling of the mould cavity heat transfer between the metal surface and the walls of the mould takes place (by radiation and conduction), which in practice can lead to mould cracking, and next to the formation of casting surface defects. In this stage of the process of great significance are the hydrodynamic conditions. These are dependent on the metal itself (its viscosity), and also on the runner system (rate of flow, resistances). During this time in the volume of the casting and mould, a pseudo-initial temperature fields is generated which is significant for the filling of the mould cavity and also for further cooling and solidification of the casting.

BOEHLER UDDEHOLM ALLOY BeCu172

Abstract Boehler Uddeholm alloy BeCu172 is a high-strength beryllium copper mold with high thermal conductivity. BeCu Alloy 172 can be supplied in the high-hard (HH) condition at approximately 40 HRC and in the low-hard (LH) condition at approximately 30 HRC. This alloy is used for applications such as pinch-offs and neck rings for blow molds, cores, and inserts in injection molds and injection nozzles and manifolds for hot runner systems. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on forming, heat treating, machining, joining, and surface treatment. Filing Code: CU-781. Producer or source: Böhler-Uddeholm Corporation.

Inclusion Characteristics of Bearing Steel in a Runner after Ingot Casting

AbstractIn the uphill teaming method of ingot casting molten metal from the ladle goes into the runner system, which feeds one or several ingot moulds. This method is still important for production of bearing steel. In order to make clean steel, which has a controlled amount of inclusions, good understanding of inclusions characteristics is necessary. In this work non‐metallic inclusions of steel left in the runner part of an ingot casting system were studied. Inclusion type, size, and morphology were the main focus of this study. A scanning electron microscope (SEM) was used to assess inclusion size and morphology. The chemical composition of inclusions was determined by SEM equipped with EDS. An automated program called ‘INCAFeature’ was used to collect statistics of inclusion characteristics. Based on the statistical analysis of inclusion composition, four types of inclusions including oxides, sulfides, carbonitrides and complex inclusions were defined. The inclusion characteristics in the runner were also compared to literature data of inclusions found in ladle and mould samples.

Strategic steps towards longer and reliable blast furnace trough campaign – Tata Steel experience

At Tata Steel, Jamshedpur works the hot metal production capacity was enhanced from 3·57 mT in 1997–1998 to 5·51 mT in 2007–2008 with the same number of cast houses, thereby, increasing the thermal load on the runner system. Maximising trough availability and ensuring zero breakouts were the means to fulfill the objective of handling the increased furnace production. Significant changes in trough refractory design and introduction of new materials like prefabricated shapes helped to improve reliability of the troughs. The paper presents the design and mode of operation of main troughs of different blast furnaces (BFs) operated at Jamshedpur works, modification of trough design in the upgraded G-BF and its performance and details of improvements made in the trough back-up refractory lining, its wear monitoring and cooling systems.

The Optimal Structure Design of Mold in Powder Injection Molding Based on the Numerical Simulation

The quality of the green and the shaping efficiency are affected by the mold structure during the course of powder injection molding (PIM). Based on the numerical simulation, the mathematic model for the optimal design of the gating and runner system in PIM mould is constructed. The method is testified by the Moldflow software and the experiment. From the result, it is suggested that the clamp force and the shape cycle are clearly decreased, the green is densified and the samples’ density error of the green is decreased after the optimal design of the mold structure. Furthermore, the number of trial mold is reduced and the shape efficiency is improved.

A Diffusing Runner for Gravity Casting

In gravity casting, the quality of an aluminum alloy casting relies on, among other things, the design of the runner system in which the ingate velocity into the mold cavity should be controlled to stay under a critical velocity (close to 0.5 m/s). In this study, a diffuser was proposed to reduce the velocity of liquid metal to below this critical value, while the flow rate remained almost unchanged. Flow separation and dead zones in the diffuser design were avoided. A computational modeling package and a real casting experiment (water analogy method) were employed for exploring and verifying the new design. The efficiency of the diffuser was quantified by the measurement of coefficient of discharge Cd. For this new diffuser, the pressure recovery coefficient C p and the loss coefficient K L were also estimated.

A multiple-gate runner system for gravity casting

The L-shaped junctions in running and gating systems used in aluminum gravity casting have been investigated. Using computational modeling, a guideline for constructing two geometries of L-junctions was developed. The sequential filling profile of liquid metal along L-junction was confirmed by real-time X-ray video of an aluminum alloy sand casting. The change of flow direction through L-junctions can yield a high coefficient of discharge Cd, without entrapping detrimental oxide film defects because of the smooth flow, minimizing surface turbulence. A short “clear-up” time, the duration of filling a component, of L-shaped junction is also achieved. For the necessary of future application of this junction, its dimensionless equivalent lengths ( L E / D) and loss coefficient K were estimated. The main aim of this work was to eliminate the trial and error approach as designing a multiple-gate system. From the guideline of L-junction, the two junctions can be assembled into a complex multiple-gate runner system. In this novel design of multiple-gate system, uniform distribution of flow through each gate into a mould cavity has been demonstrated. A high Cd value was also predicted.

사출금형에서 균형충전을 위한 새로운 러너시스템 멜트버퍼

The injection mold with multi-cavity is essential for mass production of plastic products. Multi-cavity molds are designed to geometrically balanced runner system to uniformly fill to each cavity. However, despite geometrical balanced runner system, filling imbalances between cavity to cavity have always been observed in injection molding. To solve these problems, many studies such as Melt Flipper, RC Pin, and others have been presented. The results of these studies have been an effect on filling balances in multi-cavity molds. But, those have had a limitation that additional insert parts must have existed in the mold. In this study, a new runner system is suggested for filling balance between cavity to cavity using "Melt-Buffer" with simple change of runner shape. A series of simulation to confirm feasibility of Melt-Buffer's effects was conducted using injection molding CAE program. Also, a series of injection molding experiment was conducted using plastic materials such as ABS and PP. As results of this study, feasibilities of filling balances by Melt-Buffer were confirmed.

Runner sizing in multiple cavity injection mould by non-dominated sorting genetic algorithm

Runner system is important in the plastic injection moulding as it affects the part quality and the material costs. The layout of the runners for a multiple non-identical cavity mould is geometrically imbalance. Even for a multiple identical cavity mould, the layout can be imbalance due to various reasons. This paper presents an approach to balance the flow by adjusting the runner sizes. Runner size determination is a multiobjective optimisation problem. The non-dominated sorting genetic algorithm is adopted for determining the runner sizes. Multiple objective functions including runner balancing, part quality in terms of warpage and runner volume are incorporated into the algorithm. The moulding conditions affecting the mould cavity filling are also determined due to their sensitivity to runner sizes. This runner sizing approach is suitable for the geometric imbalance mouldings and family mouldings.

플라스틱 DVD-Tray의 박막 사출성형을 위한 최적화 설계 Simulation에 관한 연구

사출성형은 다양한 형태의 제품을 대량 생산할 수 있는 플라스틱 성형 공법중의 하나이다. 플라스틱 제품을 만들기 위해서는 고상의 재료를 액상으로 녹인 후 다시 고상으로 굳히는 과정을 거치는 데, 이 과정 중에 많은 문제점들이 발생을 하게 된다. 과거에는 이러한 문제를 해결하기 위해서 성형 후 금형 설계 변경 등의 시행착오적 방법을 사용하였으나, 성형과정에 대한 사출성형 CAE(Computer Aided Engineering)를 적용함으로써, 사전에 문제점을 파악하는 기술이 도입되었다. 플라스틱 제품의 큰 문제점 중 하나가 치수안정성이다. 특히 박막사출성형품은 게이트의 위치, 냉각채널과 온도에 따라서 변형량이 크게 달라진다. 본 연구에서는 현재 Stackmold방식으로 4개의 Cavity에 4개의 Hot-Runner가 설치된 금형을 통해 생산중인 DVD Tray 박막사출제품의 생산 원가 절감을 위해서 Cavity하나에 한 개의 Hot-Runner를 설계하기 위해서 CAE 해석을 통해 게이트의 위치, 냉각채널과 온도에 따라 비교하여 해석해 최적의 제품 설계를 하였다. CAE 해석에는 상업화된 CAE 프로그램인 Moldflow를 사용하였고, 수지는 PC+ABS를 사용하였다. 【Injection molding is one of plastic forming technology which can easily mass-produce plastic parts with various and even complex shape. The technology has lots of difficulties in making a good part due to phase change of material, high applied pressure, and fast melt flow speed in the cavity. To overcome the problems, they had to make trial and error method until the CAE(Computer Aided Engineering) could be a tool for concurrent engineering. In this paper, we investigate the optimal design for a plastic DVD tray part by systematic approach of the commercial CAE program. In design, we should consider two objectives which are both dimensional stability and cost-down. The dimension of the part is crucial because the tray should carry a DVD correctly, but the part is too thin to injection-mold easily. In order to improve the moldability, the mold is designed in the form of stack mold which is a kind of 4 hot runner system. In first, we changed the stack-mold system with one hot-runner to cost down, and decided the optimal position of the gate. After that, we investigate the effect of both the layout of cooling channels and the cooling temperature on the shrinkage of the DVD tray. A optimal simulation approach, the gate design is 2Gate#3 and the layout is Case2 cooling line as the optimal temperature of $70^{\circ}C$ . The Moldflow and PC+ABS are used for the CAE program and material respectively.】

Improving Flow Balance during Filling a Multi-cavity Mold with Modified Runner Systems

Abstract Multi-cavity injection molding has been regarded as low cost mass-production method for producing plastic products such as optical elements. However, the flow imbalance during filling a multi-cavity mold using symmetrical runner system is a serious problem. This paper is devoted to improving the flow balance by modifying the runner system design. For this purpose, four eight-cavity molds with four modified symmetrical runner systems are designed, constructed and tested. They are tapering H-type runners, pinned H-type runners, curved A runners, and curved B runners. The flow imbalance in each runner system is observed and measured with the aid of short-shot experiments. The experimental results indicate that the tapering H-type runner system can improve flow balance. The pinned H-type runner system fails to improve flow balance. The curved A and B runner system can reverse the imbalance trend, but the stability of the curved systems is poor at high melt temperature.

Microinjection moulding: The influence of runner systems on flow behaviour and melt fill of multiple microcavities

To increase productivity and thus reduce the unit cost, often micro moulding tools incorporate multiple cavities and the selected runner design and applied pressure are very important for achieving satisfactory moulding results. The main function of the runner system is to facilitate the flow of molten material from the injection nozzle into the mould cavity. Therefore, the microinjection filling process depends on the optimum design of runner systems and this is an important prerequisite for the production of high quality parts. In this context, the paper reports on an experimental study that investigates the flow behaviour of the polymer melts in microcavities with a particular focus on the relationship between the filling of micro parts and the size of the runner system. In particular, the runner size effects on the microinjection moulding process were investigated by focusing the research on only the filling stage of the process. The filling performance of spiral-like micro cavities was studied as a function of runner size in combination with melt temperature, mould temperature, injection speed, and holding pressure time employing the design of the experiment approach. In addition, the results were analysed further with melt flow simulation to identify the effects of the runner size together with flow properties of the polymers, PP and ABS, on the behaviour of the microinjection moulding process.