【机械类毕业论文中英文对照文献翻译】转子系统在注塑模具设计中的椭圆截面形状
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【机械类毕业论文中英文对照文献翻译】转子系统在注塑模具设计中的椭圆截面形状,机械类毕业论文中英文对照文献翻译,机械类,毕业论文,中英文,对照,文献,翻译,转子,系统,注塑,模具设计,中的,椭圆,截面,形状
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转子系统在注塑模具设计中的椭圆截面形状摘要本文介绍了注射成型工艺模具设计中流道系统的一种新的横截面形状。新几何结构的目标是减少废料，缩短周期时间，并减轻模具工具的流道系统弹出。针对两个厚度为1mm的圆形平板，提出了具有不同比例的椭圆横截面形状。 SolidWorks Plastic采用有限元法（FEM）来模拟注塑零件。 SolidWorks Plastic分析了注塑成型过程中塑料零件的短缺缺陷，以验证新建议的几何结构。对新的几何结构进行了聚丙烯圆形平板注射成型工艺的实验研究。所选择的输入机器参数是填充时间，熔体温度，模具温度，压力保持时间和纯冷却时间。研究结果显示，与新的几何形状相比，没有短路缺陷，与圆形截面相比，废钢和冷却时间分别显着减少25和2.5。流道系统与模具壁的接触表面的减少也改善了流道系统从模腔排出的容易性。这项研究的贡献是设计冷流道系统的新几何结构，以减少废料，循环时间，并提供注射成型中流道系统的简单排出。关键词 注塑工艺；模具设计；浇道几何形状；短缺缺陷介绍在过去的一个世纪里，塑料的迅速增长及其在所有市场的扩散。根据世界原料重量的消耗，塑料是最高的与其他旧材料，如铝，钢，橡胶，铜和锌相比。它是由塑料的特殊性能和较低的生产成本造成的1,2。注塑是制造塑料制品最重要的工艺之一，大约三分之一的塑料通过注塑成型转化为零件3。注塑成型工艺在包装，航空航天，建筑，汽车零部件，家居用品等行业的应用越来越广泛1，3，4。注塑件的质量取决于材料特性，模具设计和工艺条件4-7。注塑成型的三个基本操作是：（1）将塑料颗粒转化为熔体; （2）将熔融塑料通过浇口，流道和浇口系统注入模具型腔或型腔中，（3）打开模具将部件推出模腔1，8，9。决定注入部件最终质量的因素之一是浇口系统，它是浇口和浇口之间的连接线10。转轮系统的主要目的是将熔融塑料从浇口转移到浇口11,12。在冷流道系统中，废钢的主要来源是去水后来自浇道和浇口系统的废料。因此，评估跑步者系统设计的不同规则以证明跑步者系统在注射中的重要性（a）较小的转轮尺寸以最小化废品; （b）容易从模具中取出并从模制部件上取下; （c）用最小的凹痕和焊缝快速填充模腔13-16。转轮系统设计的三个基本因素是横截面形状，直径和腔体布局13。七种类型的横截面形状可用于不同应用的转轮系统13,14,17（图1）。根据要求，选择不同类型的转轮横截面18。图1不同的流道横截面形状本文的贡献在于为转轮系统定义椭圆形或半椭圆形几何形状作为一种有效的横截面形状，针对较小的转轮尺寸将废料与圆形相比减少到最小，从而减少注射的总周期时间和喷射来自模具的零件更容易。此外，在这项研究中，已经检测到与转轮系统的过程参数和新几何形状有关的显着现象，这将在另一篇论文中提出。本文介绍了转轮系统的椭圆形横截面形状的设计标准，并考虑了转轮系统的圆形和半椭圆形之间的比较。对作者而言，有许多论文研究了注射成型的工艺参数和材料特性，其中一些包括浇道，浇口和浇口，但就作者的最佳知识而言，没有参考分析和模拟椭圆转轮系统的横截面形状。根据注入部件的尺寸和几何形状进行流道和浇口系统的设计。然后，通过SolidWorks设计带浇道和浇口系统的注塑零件。为了准确模拟结果，采用了SolidWorks Plastic中的有限元法（FEM）。最后，为了验证模型，对两个圆形注射板进行了实验方法。转轮系统的横截面形状浇道系统的主要目的是通过浇口将熔融塑料从浇道转移到所有模腔。流道系统有不同的横截面形状，每个都有不同的应用11,17（图1）。设计师应该评估不同的因素，为特定产品选择合适的浇道系统几何形状。用于双板模具的最流行的形状也是最高效率的圆形。对于三板模具工具，如果浇道仅在模具的一半中制造，则梯形和改型梯形是最佳选择，但仍然不能接受，因为浇口不能与中心线一致流动流14。由于尖角，从矩形，正方形和多边形形状的腔体中弹出流道系统是具有挑战性的。如果设计人员无法确定所需流道系统的适当横截面形状及其尺寸，则会导致压力下降，导致模腔不完全填充以及高度向模具壁传递热量13,17,19。因此，可以考虑流道系统的各种横截面积来调节通向更好注入部分的流动。最后，形状以及通道的长度对于实现最佳流动是重要的，因此具有较少缺陷的最佳产品20。具有椭圆横截面形状的流道系统在注射成型中，流道系统最常见的横截面形状是圆形。在选择特定零件设计的圆形时，三个主要因素是（a）较小的流道尺寸以最小化废料；（b）容易从模具中弹出；（c）以最小凹痕，焊缝和短射线快速填充模腔13-15。这里的目的是研究一种新的几何形状的流道系统，这种流道系统可以产生最少的废料，与浇口的中心流动流线对齐，适当填充模腔，并且便于将模具从模具中弹出。为此目的，正在研究椭圆形或半椭圆形横截面形状，并与圆形横截面形状的流道系统进行了精确比较。为了证明跑步者的椭圆横截面形状的重要性，对跑步者系统的其他几何形状的评估是必要的。这两者的最佳现有比较是矩形和方形。矩形是一种宽度不同的正方形。在宽度方面，矩形浇道系统的尺寸与正方形浇道系统的尺寸相比有三种不同的比率17（图2）。根据不同的应用，选择不同宽度比的矩形流道系统。长方形形状的优点是减少了转轮系统的废料，并且更容易从模具中取出。压降是通过减小方形宽度而发生的这种几何形状的缺点之一17。圆和椭圆之间的比较与正方形和矩形的比较相似。如图3所示，D是圆的直径，a是长轴长度，b是椭圆的短轴长度。根据不同的工业应用，主轴长度是固定的，短轴长度是不同的速率（图3）。因为这会导致废料的进一步减少，更容易将部件从模腔中排出，并进一步减少循环时间。对于不同的部分，这个因素将会改变。因此，提出不同的b比例取决于零件设计的诸多因素，如尺寸和厚度。图2 转轮系统的正方形和矩形形状之间的比较图3转轮系统的圆形和椭圆形状之间的比较椭圆形转轮系统的优点如下：1.废品减量：转轮和门系统的大小和体积是产品废品的根本原因。 因此，与圆跑者相比，椭圆跑步者导致更少的报废。2.从模腔：椭圆形流道系统中，部分射出更加容易，冷却后与圆形相比，与模具壁接触的表面更少，从而更容易将注射部件从模腔中排出。3.缩短循环时间：椭圆流道所需熔融塑料量较少; 因此包括注入和冷却阶段时间的循环时间将减少。与亚军系统的门的中央流程流。 椭圆流道具有中心流动流，其中大部分浇口设计减少了熔融塑料至腔体的湍流。模拟在为这个应用程序设计两个圆形零件作为两个样品之后，下一步是通过SolidWorks Plastic来模拟零件。对于模拟，需要定义注射系统。因此，应考虑考虑事先计算来设计浇道，浇道和浇口系统（图4）。设计椭圆截面形状的比例为0.7b。为确保分析结果的准确性，FEM将在模拟中发挥重要作用。根据样品的几何形状，将选择有限元的三角形形状（图5）。用于此模拟的选定材料是聚丙烯（PP）。对表面网格和表面网格的不同三角形尺寸评估不同的尺寸，为注入部分选择1毫米的三角形尺寸。对于包括浇口，流道和浇口的注射系统，考虑更小的尺寸。它是由注射系统的灵敏度作为此模拟的关键区域而产生的。因此，浇道和浇道的三角形尺寸分别为0.3mm和浇口的三角形尺寸分别为椭圆形和圆形横截面形状。网格的精度通过网格细化研究来确定。对于直径为100毫米的两个圆形部件，浇道和浇口总长度为28毫米。此外，浇道的长度为60毫米，拔模角度为1.5。图4浇口，流道和浇口系统的注射样品图5 转轮椭圆横截面形状的FEA图6 用椭圆交叉容易填充注射部分下一步是设置适当的工艺参数。根据所选用的材料和注塑机进行该模拟，填充时间为0.59秒，熔体温度为230，模具温度为50，保压时间为2.04秒，纯冷却时间3.9秒。如前所述，包括浇道，浇道和浇口的注射系统的几何形状和尺寸对操作循环时间，冷却时间以及不同的缺陷（如凹痕，短射等）具有显着影响25。在运行模拟之后，根据新的几何形状和尺寸检查新的流道系统的可接受性。检查的主要因素包括易于填充，填充时间分析和汇痕分析;并在注射结束时注射压力。如图6所示，椭圆形横截面的容易填充是处于最可接受水平的绿色区域。注塑成型中的一个常见缺陷是如果流动距离较长，将发生在薄壁或远离浇口的短射26。根据模拟结果，该部分可以成功填充，甚至如图7a所示的椭圆截面的填充时间低于流道的圆形截面形状的填充时间（图7b）。图7 a椭圆形横截面的填充时间，b圆形横截面的填充时间图8 a椭圆截面的流动前沿中心温度，b圆形截面的流动前沿中心温度防止喷射部件短射的另一个因素是评估流动前沿中心温度，该温度代表注入部件每个区域的流动前沿温度。根据模拟结果，注射部件的每个区域的流动前端中心温度对于转轮的椭圆横截面形状为230.15C（图8a）。流道的圆形横截面形状的模拟结果是相同的（图8b）。这意味着椭圆形横截面形状的转子在腔内短射的可能性很低。评估浇道和浇口系统合适尺寸所需的最重要因素之一是注射压力。根据模拟，这部分可以成功注入压力42.1MPa。注射压力小于满足最大注射压力极限的66（图9）。圆形截面的注射压力为39.6 MPa，接近椭圆形截面。实验装置使用商用注塑颗粒聚丙烯（PP）制造两个圆形板，其具有100mm直径和1mm厚度。 所选材料的聚合物材料参数列于表2中。用于制造模具的机器有钻孔机，数控铣床和磨床。 实验采用全电动卧式注塑机-Poolad-Bch系列。图9 浇道系统的圆形和椭圆形横截面形状的注射压力表2 材料属性PP熔体温度230最高熔化温度280最低熔融温度200Mod温度50熔体流动速率20厘米3/10分钟最大剪切应力250,000 pa模具设计模具制造有不同的设计概念。在这项研究中，选择了双板模具，该模具具有一个带有双腔的分模线和一个供料系统并且没有顶针。模具由碳钢CK45制成，表面硬度为56 HRC。磨削后的椭圆形横浇道，浇口系统和浇口衬套分配到模腔板中（图10a）。还展示了磨削前带有导杆的型腔板（图10b）。在设计模具时，另一个要素是导致塑料部件固化的冷却系统。基于塑料部件的几何形状，冷却系统的设计是不同的。因此，选择腔板冷却系统的圆形几何形状（图11）。制造模具时要考虑的另一个因素是通风孔。它们的功能是在关闭模具之后从模腔中释放空气；否则如果空气被困在模具内，会发生短射击。两个腔体在腔板的左侧和右侧具有单独的通气孔（图12）。图10磨削后具有椭圆横截面的空腔板，b磨削之前具有椭圆横截面的空腔盘图11模腔板内的冷却系统，用于注入部件的凝固图12 通风孔避免注入部件的空气陷阱实验结果根据不同的工艺参数设置模具和注塑机后，从制造过程的不同角度评估流道系统新的横截面形状是本实验的目标。为了确保本研究椭圆截面转轮的有效性，需要实施基于不同工艺参数的填充腔体和注射过程的显着性测试。短射击分析的结果（图13）显示，具有新的流道横截面形状的两个腔体被适当地填充。当注入压力高于最大入口压力并且注入时间高于注入机器的输入时，会发生短射击。这些实验中最重要的部分是，与图14所示的模拟结果相比，即使在较低的入口压力和填充时间下，腔体也能够正确填充。模拟和实验结果的比较显示在表4中。表4中的百分比变化预测和实际的入口压力和填充时间结果分别为7.36和3.38，这证明了转轮系统的新几何结构的稳健性。通过定义转轮系统的新几何形状，这项研究的新颖之处在于减少废料和冷却时间，并且实现从腔体中最终注射部件的更容易的喷射。因此，就废品率和冷却时间而言，需要在圆形和椭圆形横截面之间进行比较。表5显示了对于100,000个注射部件的流道系统的圆形和椭圆形横截面的废料率和冷却时间。圆形横截面的冷却时间为每次注射4 s，椭圆截面每次注射3.9 s。与圆形横截面相比，椭圆形横截面的废钢和铝合金减少了25，注入部件的冷却时间为2.5。图13 最后注射部分具有椭圆形流道横截面形状图14 椭圆跑步者的每个因素水平较低的注射部位结论冷流道系统注塑废料的主要原因是由浇口，流道和浇口系统组成的供料系统。跑步者对于不同的应用具有不同的横截面。本文介绍了椭圆形横截面与圆形横截面比较的流道系统新几何的成功开发。这种几何形状是通过模拟和实验开发的，以生产两个1mm厚的圆形板。工艺参数为填充时间，熔体温度，模具温度，压力保持时间和纯冷却时间。为了验证模型，进行了实验测试。预测和实际结果的入口压力和填充时间的百分比变化分别为7.36和3.38。结果证明了转轮系统的新几何结构的稳健性。与圆形横截面相比，椭圆形横截面对于注射部件具有25的废料减少和2.5的冷却时间。模拟和实验测试的结果表明，椭圆形截面形状是一种有效的几何形状，可以减少废料和总循环时间，并且还可以使模制件更容易从模腔中弹出。模具设计的进一步研究将为设计师和模具制造商创造更具包容性和适当的指导方针。参考文献1 Zhou H (2013) Computer modeling for injection molding. 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Longman Scientific & Technical, Harlow12Int J Plast Technol (December 2016) 20(2):249264263DOI 10.1007/s12588-016-9153-4Elliptical cross sectional shape of runner system in injection mold designMehdi Moayyedian1 Kazem Abhary1 Romeo Marian1Received: 3 June 2015 / Accepted: 21 July 2016 / Published online: 27 July 2016 Central Institute of Plastics Engineering & Technology 2016Abstract This paper presents a new cross sectional shape of the runner system in the mold design of the injection molding process. The aim of the new geometry is to reduce scrap, cycle time and ease the ejection of runner system from mold tools. An elliptical cross sectional shape of runner with different ratios was proposed for two circular flat plates with thickness 1 mm. Finite element method (FEM) is employed in SolidWorks Plastic for simulation of the injected part. Short shot defect in the plastic part during the injection molding process is analyzed by SolidWorks Plastic to validate the new proposed geometry. An experimental study of the injection molding process of polypropylene circular flat plates is conducted for the new geometry. The input machine parameters selected are filling time, melt temperature, mold temperature, pressure holding time, and pure cooling time. The research outcomes show no short shot defect associated with the new geometry and also significant 25 and 2.5 % reduction in scrap and cooling time respectively compared to round cross sections. Reduction in contact surface of the runner system with mold walls improved the ease of ejection of runner system out of the cavity as well. The contribution of this study is to design a new geometry of a cold runner system to reduce scrap, cycle time and also provide easy ejection of runner system in the injection molding.Keywords Injection molding process Mold design Runner geometry Short shot defects& Mehdi Moayyedian .au1School of Engineering, University of South Australia, Mawson Lakes Campus, Adelaide, SA 5095, AustraliaIntroductionThe past century has observed the rapid increase of plastics and their proliferation into all markets. According to world consumption of raw materials by weight, plastic is the highest in comparison with other old materials such as aluminum, steel, rubber, copper, and zinc. It has resulted from specific properties and lower production cost of plastics 1, 2. Injection molding is one of the most significant processes for manufacturing of plastic products and approximately one-third of all plastics are converted into parts via injection molding 3. The application of the injection molding process is increasing significantly in many industries like packaging, aerospace and aviation, building and construction, automotive parts, household articles and so on 1, 3, 4. The quality of the injection moldings depends on material characteristics, mold design and process conditions 47. Three fundamental operations in injection molding are: (1) plastic granules are converted into a melt; (2) molten plastic is injected into the mold cavity or cavities under pressure via sprue, runner and gate systems and (3) mold tools are opened to eject the part out of cavity 1, 8, 9.One of the factors which will determine the final quality of injected part is the runner system which is a connection line between sprue and gates 10. The main purpose of the runner system is to transfer molten plastic from sprue to gates 11, 12. In the cold runner system, the main source of scrap is the scrap from runner and gate system after de-gating. Hence, different rules are evaluated for runner system design to demonstrate the significance of runner systems in injectionroundsemicircularsquarerectangularTrapezoidalModied TrapezoidalPolygonFig. 1 Different runner cross sectional shapesmolding such as (a) smaller runner size to minimize the scrap; (b) easy ejection from mold tools and removal from molded part; (c) filling the cavity quickly with minimum sink mark and weld lines 1316. Three fundamental factors in the runner system design are cross sectional shape, diameter and cavity layout 13. Seven types of cross sectional shapes are available for the runner system for different applications 13, 14, 17 (Fig. 1). Depending on the requirements, different types of runner cross sections are selected 18.The contribution of this paper is to define elliptical or semi-elliptical geometry for runner systems as an effective cross sectional shape aiming at smaller runner size to minimize the scrap, in comparison with round shape, to reduce the total cycle time of injection and to eject the part from mold tools more easily. Furthermore, in this research remarkable phenomena related to process parameters and new geometry of runner systems have been detected that will be presented in another paper.The design criteria of elliptical cross sectional shape for runner systems are introduced herein, and a comparison between round shape and semi-elliptical shape of runner system is considered. To the authors best of knowledge, there are many papers studying process parameters and material characteristics of injection molding a few of which include runner, gate, and sprue but, to the authors best of knowledge, there is no reference analyzing and simulating the elliptical cross sectional shape of runner system.The design of runner and gate systems is conducted herein based on the size and geometry of injected parts. Then, the injected part with runner and gate system is designed via SolidWorks. For accurate result of simulation, finite element method (FEM) in SolidWorks Plastic is employed. Finally, to validate the model, experimental method is conducted for two circular injected platesCross sectional shape of runner systemThe main purpose of a runner system is to transfer the molten plastic from sprue to all cavities via the gate. There are different cross sectional shapes for runner systems and each of them have different applications 11, 17 (Fig. 1). The designer should evaluate different factors for selecting the right geometry of the runner system for a specific product. The most popular shape of runner systems for two-plate mold tools, which is also of the highest efficiency, is round shape. For three-plate mold tools, the trapezoidal and modified trapezoidal are the best options if the runner is to be manufactured only in one half of the mold, but still they are not acceptable be- cause the gate cannot be positioned in line with the central flow stream 14. Ejecting a runner system out of cavity with rectangular, square, and polygon shape is challenging due to sharp corners. If a designer cannot determine the appropriate cross sectional shape of the required runner system and their dimensions, pressure drops and leads to incomplete filling of cavities and high level of heat transfer to mold walls 13, 17, 19. Hence, various cross-sectional area of a runner system can be considered to regulate the flow leading to a better injected part. Finally, the shape and the length of the channel are significant for achieving the optimal flow and consequently the best product with less defects 20.Runner systems with elliptical cross sectional shapeIn injection molding, the most common cross sectional shape for runner system is round shape. In selecting the round shape for specific part design, three main elements are (a) smaller runner size to minimize the scrap; (b) easy ejection from mold tools; (c) filling the cavity quickly with minimum sink mark, weld lines and no short shot 1315. The aim herein is to investigate a runner system of new geometry which can lead to minimal scrap, be positioned in line with the central flow stream of gate, properly fill the cavities, and facilitate the easy eject the part from mold tools. For this purpose elliptical or semi-elliptical cross sectional shape has been taken under investigation and accurately compared with runner systems of round cross sectional shape.To demonstrate the significance of elliptical cross sectional shape of runners, the evaluation of other geometries of runner systems is necessary. The best existing comparison of these two is rectangular and square shape. Rectangle is a kind of square with different width. There are three different ratios in designing the dimension of rectangular runner system in comparison with square ones in terms of width 17 (Fig. 2). According to different applications, rectangular runner system with different ratios of width is chosen. The advantages of rectangular shape over square ones are less scrap of runner system and easier ejection from mold tools. Pressure drop is one of the disadvantages of this geometry which happens by decreasing the width of the square 17.The comparison between circle and ellipse is similar to that of square and rectangle. As shown in Fig. 3, D is the diameter of circle, a is major axis length, and b is minor axis length of ellipse. Major axis length is fixed and the minor axis length is of different rates depending on different industrial applications (Fig. 3). As it leads to further reduction in scrap, easier ejection of part out of cavity, and further reduction in cycle time. For different parts, this factor will be changed. Hence,square shaperectangular shape with width ratio 1/2rectangular shape with width ratio 1/4rectangular shape with width ratio 1/6Fig. 2 Comparison between square and rectangular shape of runner systemcircular shapeelliptical shape with b=0.9aelliptical shape with b=0.8aelliptical shape with b=0.7aFig. 3 Comparison between round and elliptical shape of runner systemproposing different ratio of b depends on many factors of part design such as size and thickness.Advantages of an elliptical runner system over a round one are as follows:1. Reduction in scrap: the size and volume of runner and gate system are the root cause of product scrap. Hence an elliptical runner leads to less scrap compared to the round runner.2. Easier ejection of part from cavity: elliptical runner system, after cooling process compared to round shape has less contact surface with mold walls which leads to easier ejection of the injected part from the cavity.3. Cycle time reduction: the elliptical runner requires less amount of molten plastic; hence the cycle time which includes the injection and cooling phase time will be reduced.4. Central flow stream of gate with runner system. Elliptical runner has central flow stream with most of the gate designs which decrease the turbulences of molten plastic to the cavities.SimulationAfter designing two circular parts as two samples for this application, the next step is to simulate the part via SolidWorks Plastic. For the simulation, defining the injection system is needed. Hence, designing the sprue, runner and gate system with consideration of prior calculations should be considered (Fig. 4). The ratio for designing elliptical cross sectional shape is 0.7b.To make sure that the analysis results are sufficiently accurate, FEM will play a significant role in simulation. According to the geometry of samples, the triangle shape for FEM will be selected (Fig. 5). The selected material for this simulation is polypropylene (PP). Different sizes were evaluated for the surface mesh and from different triangle size of surface mesh, the triangle size of 1 mm is chosen for the injected part. For the injection system which includes sprue, runner and gate, smaller sizes are considered. It has resulted from the sensitivity of the injection system as a critical area of this simulation. Hence, triangle sizes of 0.3 mm for sprue and runner and triangle 0.2 mm for gate are selected for both elliptical and round cross sectional shape of runner. The accuracy of the mesh is determined through a mesh refinement study. The runner and gate length in total is 28 mm for two circular parts with diameter of 100 mm. Also, the sprue has 60 mm length with draft angle 1.5.Fig. 4 Samples of injection with sprue, runner and gate systemFig. 5 FEA for elliptical cross sectional shape of runnerFig. 6 Easy filling of injected part with elliptical crossThe next stage is to set up appropriate process parameters. According to the selected material and injection machine for this simulation, filling time is 0.59 s, melt temperature is 230 C, mold temperature is 50 C, pressure holding time is2.04 s, and pure cooling time is 3.9 s. As mentioned before, the geometry and size of the injection system which includes sprue, runner and gate, have significant effects on operation cycle time, cooling time, and different defects such as sink marks, short shot etc. 25. After running the simulation, the new runner system is checked for acceptability in terms of new geometry and size. The main factors checked are ease of fill, filling time analysis, sink mark analysis; and injection pressure at the end of injection. As shown in Fig. 6, ease of fill for the elliptical cross section is the green area which is in the most acceptable level.One common defect in injection molding is short shot which will happen on thin walls or far from the gate if there are long flow distances 26. According to the simulation results, this part can be successfully filled and even the filling time for an elliptical cross section as shown in Fig. 7a is lower than that of for a round cross sectional shape of runner (Fig. 7b).Fig. 7 a Filling time for elliptical cross section, b Filling time for round cross sectionFig. 8 a Flow front central temperature for elliptical cross section, b Flow front central temperature for round cross sectionAnother factor to prevent short shot for the injected part is to evaluate the flow front central temperature which represents the flow front temperature at every region of the injected part. Based on the simulation results, the flow front central temperature in every region of the injected part is 230.15 C for the elliptical cross sectional shape of runner (Fig. 8a). The simulation result for a round cross sectional shape of runner is the same (Fig. 8b). It means that the possibility of short shot in the cavities for an elliptical cross section shape of runner is low.One of the most significant factors which are necessary to evaluate for the determination of the right size of the runner and gate system is the injection pressure. According to the simulation, this part can be successfully filled with injection pressure42.1 MPa. The injection pressure is less than 66 % of the maximum injection pressure limit which is satisfactory (Fig. 9). The injection pressure for a round cross section is39.6 MPa which is close to an elliptical cross section.Experimental set-upA commercial injection molding granule polypropylene (PP) is employed to produce two circular plates which have 100 mm diameter and 1 mm thickness. The polymer-material parameters of selected material are listed in Table 2. Fig. 9 Injection pressure for both round and elliptical cross section shape of runner systemTable 2 Material properties ofPPMelt temperature230 CMax melt temperature280 CMin melt temperature200 CMod temperature50 CMelt flow rate20 cm3/10 minMax shear stress250,000 pa The machines used to fabricate the mold tools are drilling machine, CNC milling machine and grinding machine. Fully electric horizontal-plastic-injection machinePoolad-Bch seriesis employed for the experimentsMold designThere are different design concepts in fabrication of mold tools. In this study, a two-plate mold which has one parting line with double cavities with a feeding system and without an ejector pin is selected. The mold tools are made of steel CK45with surface hardness 56 HRC. The runner with an elliptical cross section, gate system, and sprue bush are allocated in the cavity plate after grinding (Fig. 10a). Also the cavity plate with guide bars before grinding is demonstrated (Fig. 10b).In designing the mold tools, another element is the cooling system which leads to the solidification of plastic part. Based on the geometry of plastic part, the design for the cooling system is vary. Hence, the circular geometry for the cooling system of cavity plate is selected (Fig. 11).Another factor to consider in fabrication of mold tools is the air vents. Their function is to release the air from the cavity after closing the mold tools; otherwise short shot will happen if air is trapped inside the mold. Both cavities have separate air vents at the left and right side of the cavity plate (Fig. 12).Fig. 10 a Cavity plate with elliptical cross section of runner after grinding, b Cavity plate with elliptical cross section of runner before grindingFig. 11 Cooling system in cavity plate for solidification of injected partFig. 12 Air vents to avoid the air trap in injected partsExperimental resultsAfter setting up the mold tools and injection machine based on different process parameters, the evaluation of the new cross sectional shape of the runner system from different aspects in the manufacturing process is the target of this experiment. To ensure the effectiveness of an elliptical cross section of runner in this study, the test for significance of filling the cavities and injection process based on the different process parameters need to be implemented. The result of short shot analysis (Fig. 13) shows that two cavities with the new cross sectional shape of runner are filled properly.When the injection pressure is higher than the maximum inlet pressure and filling time is higher than the input of the injection machine, short shot will happen. The most significant part of these experiments is that the cavities filled properly even with lower inlet pressure and filling time in comparison with simulation results as shown in Fig. 14. The comparison of the simulation and experimental result is shown in Table 4. Percentage change for predicted and actual results of inlet pressure and filling time are 7.36 and 3.38 % respectively which demonstrates the robustness of new geometry of runner system.The novelty of this research by defining the new geometry of the runner system is to reduce scrap and cooling time and achieve easier ejection of final injected part from the cavity. Hence, the comparison between a round and an elliptical cross section in terms of scrap rate and cooling time is necessary. Table 5 demonstrates the scrap rate and cooling time of a round and an elliptical cross section of runner system for 100,000 injected parts. The cooling time for a round cross section is 4 s per injection and for an elliptical cross section 3.9 s per injection. An elliptical cross section in comparison with round cross section has 25 % reduction in scrap and 2.5 % in cooling time for the injected parts.Fig. 13 Final injected part with elliptical cross sectional shape of runnerFig. 14 Injected part with lower level of each factor for an elliptical runnerTable 4 Comparison of simulation and experimental result based on process parametersProcess parameterSimulation resultExperimental resultInlet pressure42.1 MPa39 MPaFilling time0.59 s0.57 sTable 5 Scrap rate and cycle time for the round and elliptical cross sectionFactorRoundEllipticalScrap rate of runner (g)80006000Cooling time (h)111.11108.33ConclusionThe main reason for scrap in injection molding for cold runner system is the feeding system which consists of sprue, runner and gate system. The runner has different cross sections for different applications. This paper presents the successful development of a new geometry of a runner system with an elliptical cross section in comparison with a round cross section. This geometry was developed via simulation and experiments to produce two circular plates with a 1 mm thickness. The process parameters were filling time, melt temperature, mold temperature, pressure holding time and pure cooling time.To validate the model, an experimental test was carried out. Percentage change for predicted and actual results of inlet pressure and fill
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