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AbstractIn this paper, the structural feature and forming technology of two automobile engine covers are analyzed. The mould structure with two cavities is designed and the working process of the injection mould is discussed. The mould structure is complicated. Ten core-pulling mechanisms are designed reasonably in one mould and demoulding of the plastic parts is realized. Many inserts and standard parts are used in the injection mould, so the economical efficiency of the injection mould is well and the injection mould can be maintained conveniently. The injection mould is already in mass production. Industrial practice proves that the action of the core-pulling mechanisms, ejector mechanisms and resetting mechanisms is stable and reliable. The plastic parts produced can meet the customers technical requirements. Keywords- injection mould; core-pulling mechanism; slide;demouldingI. INTRODUCTIONTwo automobile engine covers are shown in figure 1.The plastic parts are in mass production and the two plasticparts are asked to be moulded in one mould. The plastic parts are made of polypropylene (PP). The molding shrinkage is 0.95%. The outline dimensions of two plastic parts are 124.26mm219.16mm78.6mm and 174.58mm221.67mm146.32mm. The basic wall thickness of the two plastic parts is 1.8mm. The appearance of the plastic parts should maintain perfect. The mark of pouring and ejecting is not allowable to appear on the plastic part.The disfigurement of injection such as weld lines, sink mark, flashing, splay, etc. is not allowable to appear either. Design of the parting surface of the two plastic parts is difficult. The parting surface is complicated curved surface and it has uneven step shape. The side gate is adopted. There are two reentrant structures in the area of A and B of the plastic part 1, the draft angle is zero in the area of C of the plastic part 1and there are six reentrant structures within the limit of Dand E of the plastic part 1. The corresponding core-pulling mechanisms should be designed in the five places. There are three reentrant structures in the area of F, G and H of the plastic 2 and there are six reentrant structures within the limit of I and J of the plastic part 2. The corresponding cor-pulling mechanisms should be designed in the five places also. Thenten core-pulling mechanisms will be placed in one mould. Sothe reasonable design of the core-pulling mechanisms is the most important in the course of designing the injection mould.II. DESIGN OF ANGLE PIN CORE-PULLING MECHANISMS According to the structure feature of the plastic parts, sixangle pin core-pulling mechanisms are designed in the area of A, B and C of the plastic part 1 and in the area of F, G and H of the plastic part 2. The mechanisms are distributed inFigure 2. Fig.2 Distribution of the angle pin core-pulling mechanisms Taking the angle pin core-pulling mechanism 1 shown in Fig.2 for example, the mechanism is mostly composed ofslide 1, angle pin 4, positioning screw 6, slide wedge 8, wear plate 5 and wear plate 7. The mechanism is shown in figure 3 When the mould is opened, the angle pin fixed in the fixed half of the mould guides the slide in the moving half of the mould. The slide moves outward along the slide way. The inclined plane of the cavity plate which is mated with the slide can ensure wedging the slide when the mould is closed. Considering the mould structure and process parameters, the inclined angle of the angle pin is 13and the inclined angle in the cavity plate is 15. The slide and thecomponents which are in touch with the slide are easy to wear because the slide moves frequently. In order topostpone wearing the components, the two steps are adopted as follow: The slide is made of 718H and is quenched to 50HRC around. The wear plates are laid on the bottom of the slide and on the back of the slide. The wear plates are madeof GS2510 and are quenched to 60HRC around. The slide way is formed by the slide wedge and the core plate. The slide way is easy to machine and to maintain.1. slide 2. fixed block 3. locking block 4. angle pin 5. wearplate 6. positioning screw 7.wear plate 8. slide wedge 9.spring rodFigure 3. Angle pin core-pulling mechanism III. DESIGN OF ANGLE EJECTOR ROD CORE-PULLINGMECHANISMSFour angle ejector rod core-pulling mechanisms are designed in the area of D and E of the plastic part 1 and inthe area of I and J of the plastic part 2. The mechanisms are distributed in figure 4.Fig.4 Distribution of angle ejector rod core-pullingmechanismsTaking the angle ejector rod core-pulling mechanism 1 shown in figure 4 for example, the mechanism is mostlycomposed of angle ejector block 1, angle ejector rod 9, angle ejector guide block 4, angle ejector guide block 6, angle pin 5, angle ejector slide 7 and wear plate 8. The mechanism is shown in figure 51. angle ejector block 2. straight guide bush 3. headed guidebush 4. angle ejector guide block 5. angle pin 6. angleejector guide block 7. angle ejector slide 8. wear plate 9.angle ejector rod 10. pinFigure 5. Angle ejector rod core-pulling mechanismThe angle ejector rod is made of SUJ2 which is premium alloy material and the surface is in nitrogen treatment. The wear resistance of the angle ejector rod is well. By analyzing and computing, the Inclined angle of the angle ejector rod is 20which ensures the realization of the core-pulling and the better power distribution. The angle ejector guide block is made of nickel bronze and is fixed in the core plate. The mould is easily maintained and the precision of the angle ejector rod is ensured by using the angle ejector guide block. The angle ejector rod is fixed in the angle ejector slide which moves along the slide way of the ejector retainer plate. Whenthe mould is opened, the angle ejector rod moves with theejector retainer plate. The angle ejector block moves ahead with the angle ejector rod and moves in the side direction. So the core-pulling is achieved. The angle ejector block returns to its original position in virtue of the angle ejector rod which is driven by the ejector retainer plate.IV. OVERALL STRUCTURE AND WORKING PROCESS OF THEINJECTION MOULDThe mould structure is shown in figure 6. The layout of two cavities in one mould and side gate are adopted. The ten core-pulling mechanisms shown in figure 6 is reasonably designed and compact in terms of structure.Figure 6. Mould structureThe whole working process of the mould is as follow:The melt plastic flows into the cavity of the mould throughthe feed system and the mould is opened after full packing and cooling. The moving plate of the injection machine moves back together with the moving half of the injection mould and the mould opened between the parting face of the mould. The plastic parts are pulled from the cavities of mould and stay with the moving half of the mould. The angle pins fixed in the cavity plate guide the six slides in the moving half of the mould to finish core-pulling. When the mould is opened for a fixed distance, the moving half of the mould stops moving back. The ejector rods of the injection machine move ahead and push forward the ejector plate of the mould with the ejector rods, angle ejector rods. Then the plastic parts are pushed out of the injection mould and corepullingis accomplished during the ejecting. When ejector rods of the injection machine move just for 120mm, theejector mechanism stops moving and the plastic parts are taken out. The action of demoulding is completed. When the mould is closed, the ejector rods of the injection machine move back. The mould components return to their original position in virtue of the return pins and the angle pins. The second working cycle begins after the mould is closed. V. CONCLUSIONThe mould structure is complicated. Ten core-pulling mechanisms are designed reasonably in one mould anddemoulding of the plastic parts is realized. Many inserts and standard parts are used in the injection mould, so the economical efficiency of the injection mould is well and the injection mould can be maintained conveniently. The injection mould is already in mass production. Industrial practice proves that the action of the core-pullingmechanisms, ejector mechanisms and resetting mechanisms is stable and reliable. The plastic parts produced can meet the customers technical requirements.REFERENCES1 AUSTIN C. Computer aided engineering in injection molding.Application of Computer Aided Engineering in Injection MoldingM,New York : Hanser Publishers ,1987.2 WANG K K, Khullar P , Wang W P. Designing injection molds bycomputerJ . Plastics Engineering ,1981(11) : 25-27.3 F. Shi, Z. L. Lou, J. G. Lu, Y. Q. Zhang. Optimisation of plasticinjection moulding process with soft computing. Int. J. Adv. Manuf.Technol.2003;21: 656661.4 L. S. Turng, M. Peic. Computer-aided process and designoptimization for injection moulding. IMechE. 2002;216: 1523 1532.5 G.PBtch and W.Michaeli. “Injection Molding. An Introduction”. Ed.Hanser, Munich, 19956 D.M.Bryce. Plastic Injection Molding. Manufacturing ProcessFundamentals”. Society of Manufacturing Engineers. Dearbonr,Michigan, 1996484Authorized licensed.抽芯机构在注塑模具设计的应用摘 要： 对两个汽车发动机构造特征、形成进行了分析。对注塑模具的结构设计与两腔和工作过程的进行了探讨。模具结构比较复杂。10抽芯机构被合理设计在一个模具及脱模的塑料配件的实现。许多的插入和标准的部分用于注塑模具, 这样注塑模具、注塑模具的经济效益好，而且维护方便。注射模具已经是在大规模生产，工业实践证明, 这个行动的抽芯机制, 弹射机制和复位机制,稳定可靠。塑料部件能满足客户的技术要求。关键词-注塑模具、抽芯机构;幻灯片，脱模一.简介以下是两个汽车发动机的表面，如图，1。塑料配件开始被大规模生产成两个塑料的部件，而且是要被塑造成一个模子。塑料配件是由聚丙烯(PP)做的。该配件成型后会缩0.95%。两个塑料部件的提纲维度分别是124.26mm219.16mm 78.6mm,和174.58mm221.67mm 146.32mm。这两个塑料部件的基本的壁厚是1.8毫米。而且，这个塑料部件的外观要保持完美，浇注的标志，不允许出现在塑料部件表面上。注射的缺陷，如焊接线、沉马克,、闪光、变色等，也不允许出现, 两个塑料部件的分隔表面制作起来是非常困难的，两个塑料部件的分隔表面和复杂曲面具都有着凹凸不平的步骤的形状。于是，就采用侧浇扣，那里有2种构造在A和B的塑料第一部分，在C的塑料第一部分的区域，其拔模角的角度为零，并且，在六个凹进去的结构里，C和D的塑料第一部分被限制。相应的抽芯机制设计应在5个地方。在F,H,G的塑料第二部分区域里，有三种构造，I和J的塑料第二部分在这三种构造里有六个凹进去的限制，在五个地方，相应的cor-pulling机制也应设计成一样。然后十个抽芯机制将放置在一个模子。所以合理的设计机制并且注入模具是抽芯设计过程中最重要的环节。塑料第一部分塑料第二部分图1。塑料部件二斜导柱抽芯机构的设计根据塑料配件结构特的特点，6个斜导柱抽芯机机构被设计在A、B、C的塑料第一部分以及F、G和H的塑料的第二部分，这个机制是分布在图2。如下：图2分布的斜导柱抽芯机构，以上是斜导柱抽芯机构1中在图2中的显示，例如,该机制的主要由滑块1、斜导柱4、定位螺丝钉6，滑动楔板8、耐磨护板5和耐磨护板7组成，该机制如图3所示。当模具打开的时候, 斜顶柱被固定在固定的模具中间，引导下滑到模具的一半，运动沿着下滑道滑动，与其配对的斜面腔板能够确保劈滑动作用，当模具关闭的时候。考虑到模具结构及工艺参数的问题, 这个倾斜角的角度被定为13度，斜板的角度被定为15。由于滑动频繁，在接触的滑动部件就容易磨损。为了减少部件的磨损，于是采用了以下两个步骤，首先，滑动部件是由718H和淬火50HRC做的。耐磨护板被放置在滑动部件的底部和后面，其次，耐磨护板是由GS2510和60HRC组成，滑道是由滑动锲板和铁芯片组成，而且，滑道很容易机和维护。 图3 顶针板抽芯机构1. 滑块 2.固定件 3.压块. 4.斜导柱 5.耐磨护板 6.定位螺丝 7.耐磨护板8.滑动锲板 9弹簧杆 三、弹射杆设计的角度抽芯机制四个斜顶杆抽芯机构被设计在D和E的塑料第一部分，I和J的塑料第二部分。这个机构被分布在图4。如下：图4斜顶杆抽芯机械的分布以在图4显示的斜顶杆抽芯机构1为例, 该机制的主要是由斜顶块1、斜顶杆9、斜顶导向板4、斜顶导向板6、斜导柱5、斜顶滑动杆7和耐磨护板8组成的. 这个机制是显示在图5，如下：图5斜顶杆抽芯机械1. 斜顶块 2.直线导套 3.带头导套 4.斜顶导块 5斜导柱 6. 斜顶导块 7.斜顶板 8 耐磨护板 9斜顶赶 10销斜顶杆机构是由SUJ2制作的，SUJ2是一种由优质铝合金材料，而且他的表面经过氮处理。斜顶杆的耐磨性能非常的好，通过分析和计算，斜导杆的倾斜角度是20，这样的角度可以确保实现抽芯和的受力分布。斜顶导向块是有镍铜和被固定的铁芯片组成，这类模具的维护是很容易的，其次，斜顶杆的精密度由斜顶导向块来确保。斜顶杆机构被固定在斜顶块上，这个斜顶块是沿着面针板的滑动而移动的。当模具大块的时候，斜顶杆随着面针板移动，斜顶块在侧向提前随着斜顶杆的移动而移动。就这样，这个抽芯的目的得到了实现。如果执行失败，斜顶杆受到面针板的推动，斜顶块由于斜顶杆而返回到起始位置的坐标。五、注塑模具的整体结构和工作过程模具结构如图6。是一个模具的两腔和侧浇口的布局，10个抽芯机制如图的的设计，是合理的，机构紧凑的。图6如下：图6.模具结构整个模具工作过程如下：融化塑料流入型腔模具通过浇注系统，在全部填充满后，模具才打开。注射成型机的移动板块由于杠杆原理一起向后移动，在模具的表面分段加工中模具被打开。塑料部件从模具的凹陷孔里被拿出，与塑料动模保持一致，斜导柱被插入到母模的导向板中，机构的抽芯步骤由塑料动模的6个滑动块来完成。当模具打开的时候，必须要有一个固定的距离。塑料动模停止向后移动。注塑成型机的顶出杆向前移动，并且向顶出杆模具的顶针板前推，斜顶杆。然后那个塑料件被挤出模具，并且在对喷射抽芯完成。注塑成型机的顶出杆只需要移动120毫米。当脱模器停止运动后，塑料零件就会被取出来。这样，脱模这个动作就完成了，那时候，模具就被封闭起来。注塑成型机的顶出杆向后移动。由于回位销和斜导柱的关系，模具部件将回到他们原来的位置。在模具封闭后，第二个工作周期就开始了。六、结论 模具的结构是比较复杂的。10个抽芯机构被合理的设计在一个模具内及塑料部件脱模过程的实现。很多的镶嵌件和标准零件被用于注塑模具。所以，注塑模具的经济效率非常的好,而且注塑模具的维修比较的容易。注塑模具已经开始批量的生产，工业实践证明，抽芯机构、弹射机制和复位机制的功能是相当的稳定和可靠的。塑料部件已经可以满足客户各方面的技术要求参考1奥斯汀c计算机辅助工程塑料注塑成型，应用计算机辅助工程塑料注塑成型M,纽约出版社1987年出版。2王K.K、Khullar王建民W .由电脑注塑模具的设计J。塑料工程,1981年1月1日(11):25-27。3史、柯正龙”,国立中山大学电机,问陆g。注塑工艺的优化和软计算。智力。Adv.之日Manuf.Technol.2003;656-661。4,m. Turng Peic 。电脑辅助设计和优化过程中注入成型。IMechE。2002;于216:1523年。5。PBtch和W.Michaeli。“注塑成型。介绍”。艾德。Hanser,慕尼黑,19956D.M.Bryce。塑料注塑成型。生产工艺原理”。制造工程师学会。1996年,密西根州,Dearbonr授权许可484
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