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组合式排插外观结构创新与注塑模具设计

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编号: 毕业设计(论文)任务书题 目: 组合式排插外观结构 创新与注塑模具设计 学院: 机电工程学院 专 业: 机械制造及其自动化 学生姓名: 曾骁杨 学 号: 1000110133 指导教师单位: 桂林电子科技大学 姓 名: 彭晓楠 职 称: 副教授 题目类型:理论研究 实验研究 工程设计 工程技术研究 软件开发 2013年12月13日一、毕业设计(论文)的内容 在工业生产中,采用模具生产零部件,具有生产效率高、质量好、成本低等一系列优点,使得模具的使用范围日益广泛,特别是发展最快的注塑模具,已经成为现代工业生产中重要的工艺设备和发展方向。模具作为工业生产的基础工艺装备,对提升我国制造业水平及增强我国制造业的国际竞争力具有越来越大的作用,其技术水平的高低已成为衡量一个国家制造业水平的重要标志。 本课题以组合式排插为载体,完成组合式排插注塑模具设计。从而进一步提升专业技能,为踏上工作岗位做好准备。本课题的主要工作内容有以下几点:1、收集关于注塑模具设计及组合式排插的相关知识,了解现有组合式排插产品的结构;2、熟悉注塑模具设计的原理及过程;3、查阅相关资料,熟悉塑料产品设计、机械设计基础、注塑模具设计、塑料产品成型工艺、工程力学、工程制图等与本毕业设计课题相关的知识;4、熟练掌握计算机辅助设计软件;5、对设计方案进行详细规划及分析,反复对方案进行论证,逐步进行修改及优化;5、利于相关专业软件完成组合式排插外观结构结构创新设计;6、利于相关专业软件完成组合式排插注塑模具的设计;7、利于相关专业软件完成模具加工工艺及注塑工艺相关项目的计算和分析;8、利于相关专业软件完成产品零件、模具零件及装配2D工程图的绘制;9、利于相关专业软件完成模具开、合模及零件拆、装过程视频动画的制作;二、毕业设计(论文)的要求与数据 本毕业设计课题需要掌握塑料产品设计、机械设计基础、注塑模具设计、塑料产品成型工艺、工程力学、工程制图等相关知识及计算机辅助设计技能。本课题需要提交的数据及资料主要有以下方面:1、设计方案的规划及分析对比必须在毕业设计说明书中体现出来;2、外观结构创新设计要实用合理;3、模具分型面及浇口的设计要合理,且容易脱模;4、模具的型腔布局要规范合理;5、模具零部件装配正确合理,对模具进行校核计算及填充分析,并提供结果;6、2D工程图要整洁规范,必须符合国家标准;7、模具开、合模及零件拆、装过程视频动画分辨率不小于720*480 px;7、外文资料翻译和毕业设计说明书(论文)的内容及字符要符合“毕业设计任务书”的要求;8、毕业设计说明书的格式必须符合 “2014年毕业设计说明书统一格式”的要求;9、各个文件资料所需填写的时间必须符合“2014年毕业设计(论文)管理办法”的要求;10、答辩PPT课件能清晰体现毕业设计课题的设计思路,版面生动、简洁;三、毕业设计(论文)应完成的工作1、完成开题报告及进度计划表的撰写;2、完成中期检查表的填写;3、完成二万字左右的毕业设计说明书(论文);在毕业设计说明书(论文)中必须包括详细的300-500个单词的英文摘要;4、独立完成与课题相关,不少于四万字符的指定英文资料翻译(附英文原文);5、完成产品零件、模具零件及装配2D工程图的绘制;6、完成工作量折合A0图纸3张以上,其中必须包含两张A3以上的计算机绘制图纸;7、完成模具开、合模及零件拆、装过程视频动画的制作;8、完成答辩PPT课件的制作;四、应收集的资料及主要参考文献1 吴生绪.塑料成形模具设计技术手册M. 机械工业出版社,20082 屈华昌.塑料成型工艺与模具设计.北京:高等教育出版社.20013 陈万林.实用塑料注射模设计与制造,机械工业出版社2000.104 吴梦陵.塑料成型CAE:Moldflow应用基础M. 北京:电子工业出版社,20105 蒋继宏,王效岳.注塑摸具典型结构100例M.北京:中国轻工业出版社.20006 CAHN, R.W. The Coming of Materials Science The_Coming_of_Materials _ScienceM,2001五、试验、测试、试制加工所需主要仪器设备及条件所需主要仪器设备及条件如下:1、计算机一台2、CAD设计软件(UG或Solidworks)任务下达时间:2013年12月17日毕业设计开始与完成时间:2013年12月17日至 2014年05 月26日组织实施单位:桂林电子科技大学机电工程学院教研室主任意见:签字: 2013年12月14日院领导小组意见:签字: 2013 年12月16日编号: 毕业设计(论文)开题报告题 目: 组合式排插外观结构 创新与注塑模具设计 学院: 机电工程学院 专 业: 机械制造及其自动化 学生姓名: 曾骁杨 学 号: 1000110133 指导教师单位: 桂林电子科技大学 姓 名: 彭晓楠 职 称: 副教授 题目类型:理论研究 实验研究 工程设计 工程技术研究 软件开发 2013年12月13日1本课题的研究内容、重点及难点本次毕业设计课题为组合式排插外观结构创新与注塑模具设计。近年来,我国模具工业有了很大的发展,模具与生活越来越贴近,给我们的生活带来了很打的方便。在未来的模具市场中,塑料模具发展的速度将高于其它模具,在模具行业中的比例将逐步提高。排插在我们生活中十分常见,模具的使用能降低排插的生产成本并提高生产效率。此次设计中有许多地方需要仔细研究,1.主要内容:1、查阅资料。结合本次课题查阅相关资料;2、 撰写开题报告;3、通过对产品的性能分析,完成相关的模具结构与零件设计;4、设计的模具结构要求完整、合理;5、合理选择尺寸、公差、表面粗糙度和制件材料,绘制的产品图样完整;6、认真分析制件图,确定模具型腔、模具结构、分型面和进料口形式,计算含 收缩率的相关尺寸和模具的强度和刚度;7、 翻译专业外语文献。8、 撰写毕业设计(论文)说明书;9、 绘制模具装配图和零件图;2.重点:1、脱模推出机构和侧抽芯机构的设计;2、塑件的结构及工艺分析;3、材料选择及相关参数的计算;4、模具型腔数的确定,模具结构、分型面和进料口形式的选择;5、绘制模具总装图、零件图及尺寸标注。3.难点注射模具的设计以及加工工艺设计。2 准备情况(查阅过的文献资料及调研情况、现有设备、实验条件等)1、调研情况:21世纪,塑料工业以前所谓有的速度高速发展,在各个领域乃至国名经济中已拥有举足轻重的地位。目前,我国塑料工业的高速发展对模具工业提出了越来越高的要求。在2010年,塑料模具在整个模具行业中所占的比例已上升到50%左右,未来几年中,所料模具还将保持高速度发展。模具是工业生产中使用极为广泛的重要装备,采用模具生产制品及零件,具有生产效率高,节约原材料,陈本低廉,保证质量等一系列优点,是现代工业生产中的重要手段和主要发展方向。 注塑成型所用的模具即为注塑模(也称为注射模),注塑成型的原理(以螺杆式注射机为例)。首先将颗粒或粉状的塑料加入料斗,然后输送到侧装有电加热的料筒中塑化。螺杆在料筒前端原地转动,使被加热预塑的塑料在螺杆的转动作用下通过螺旋槽输送至料筒前端的喷嘴附近。螺杆的转动使塑料进一步化,料温在剪切摩擦热的作用下进一步提高并得以均匀化。当料筒前端堆积的体对螺杆产生一定的压力时(称为螺杆的背压),螺杆将转动后退,直至整好的行程开关接触,从而使螺母与螺杆锁紧。具有模具一次注射量的塑料预塑和储过程结束。这时,马达带动气缸前进,与液压缸活塞相连接的螺杆以一定的速度和压力将熔料通过料筒前端的喷嘴注入温度较低的闭合模具型腔中。熔体通过喷嘴注入闭合模具腔后,必须经过一定时间的保压,熔融塑料才能冷却固化,保持模具型腔所赋予形状和尺寸。当合模机构打开时,在推出机构的作用下,即可顶出注塑成型的塑料制品。2、现有设备:电脑及机械设计专业软件。3、试验条件:电脑机房4、参考查阅的文献资料1 吴生绪.塑料成形模具设计技术手册M. 机械工业出版社,20082 屈华昌.塑料成型工艺与模具设计.北京:高等教育出版社.20013 陈万林.实用塑料注射模设计与制造,机械工业出版社2000.104 吴梦陵.塑料成型CAE:Moldflow应用基础M. 北京:电子工业出版社,20105 蒋继宏,王效岳.注塑摸具典型结构100例M.北京:中国轻工业出版社.20006 CAHN, R.W. The Coming of Materials Science The_Coming_of_Materials ScienceM,20013、实施方案、进度实施计划及预期提交的毕业设计资料1、 实施方案(1)通过查阅资料文献和相关手册了解设计背景、现状及工作原理;(2)制定出详细的设计方案及设计过程规划,反复对设计方案进行论证;(3)学习三维绘图软件;(4)使用三维绘图软件完成结构设计;(5)使用软件完成相关参数的计算及结构、受力等分析;(6)使用软件完成零件及装配二维图的绘制;(7)使用软件完成机构运动仿真;(8)完成毕业设计说明书的撰写;2、 进度计划1. 2013年12月17日至2013年12月23日,理解消化毕设任务书要求并收集、分析、消化资料文献.2. 2013年12月24日至2013年12月30日,开展调研,了解塑件结构,对原材料进行分析,考虑塑件的成型工艺性、模具的总体结构的形式,3. 2013年12月31日至2014年1月6日,根据毕设内容完成并交开题报告;4. 2014年1月7日至2014年1月13日,完成部分英文摘要翻译。5. 2014年3月4日至2014年3月10日,查阅资料,熟悉注射模的结构及有关计算.6. 2014年3月11日至2014年3月17日,拟定模具的方案设计、总体设计及主要零件设计,拟定成型工艺过程.7. 2014年3月18日至2014年3月24日,查阅有关手册确定适宜的工艺参数,注射机的选择及确定注射设备及型号规格;8. 2014年3月25日至2014年3月31日,完成设计计算任务,9. 2014年4月1日至2014年4月7日,总体结构的设计和完成总装配图及零件图的设计;10. 2014年4月8日至2014年4月14日,完成设计,图纸绘制任务11. 2014年4月15日至2014年4月21日,工艺规程说明书的编写;12. 2014年4月22日至2014年4月28日,完善设计并完成论文的撰写;13. 2014年4月29日至2014年5月日,修改并打印毕业论文及整理相关资料14. 2014年5月6日至2014年5月12日,交导老师评阅,准备论文答辩。15. 2014年5月13日至2014年5月19日,修改完善论文准备答辩16. 2014年5月20日至2014年5月26日,完成毕业设计,提交论文3、 预期提交的毕业设计资料:1. 开题报告(电子档和纸质材料各一份);2. 进度计划表(电子档和纸质材料各一份);3. 二万字以上的毕业设计论文;在毕业设计论文中必须包括详细的300-500个单词的英文摘要4. 不少于四万字符的指定英文资料翻译(附英文原文;电子档和纸质材料各一份);5. 零件及装配三维数字模型(电子档一份);6. 零件及装配二维图纸(电子档和纸质材料各一份);7. 运动仿真视频文件(电子档一份);8. 刻录光盘(一张,包含所有毕业设计资料电子文档)指导教师意见 指导教师:年 月 日开题小组意见 开题小组成员签字: 年 月 日院系审核意见院系主管领导签字:年 月 日编号: 毕业设计(论文)外文翻译(原文)院 (系): 机电工程学院 专 业: 机械设计制造及其自动化 学生姓名: 曾骁杨 学 号: 1000110133 指导教师单位: 机电工程学院 姓 名: 彭晓楠 职 称: 副教授 2013年 3 月 1 日The Injection MoldingThe Introduction of MoldsThe mold is at the core of a plastic manufacturing process because its cavity gives a part its shape. This makes the mold at least as critical-and many cases more so-for the quality of the end product as, for example, the plasticiting unit or other components of the processing equipment.Mold MaterialDepending on the processing parameters for the various processing methods as well as the length of the production run, the number of finished products to be produced, molds for plastics processing must satisfy a great variety of requirements. It is therefore not surprising that molds can be made from a very broad spectrum of materials, including-from a technical standpoint-such exotic materials as paper matched and plaster. However, because most processes require high pressures, often combined with high temperatures, metals still represent by far the most important material group, with steel being the predominant metal. It is interesting in this regard that, in many cases, the selection of the mold material is not only a question of material properties and an optimum price-to-performance ratio but also that the methods used to produce the mold, and thus the entire design, can be influenced.A typical example can be seen in the choice between cast metal molds, with their very different cooling systems, compared to machined molds. In addition, the production technique can also have an effect; for instance, it is often reported that, for the sake of simplicity, a prototype mold is frequently machined from solid stock with the aid of the latest technology such as computer-aided (CAD) and computer-integrated manufacturing (CIMS). In contrast to the previously used methods based on the use of patterns, the use of CAD and CAM often represents the more economical solution today, not only because this production capability is available pin-house but also because with any other technique an order would have to be placed with an outside supplier.Overall, although high-grade materials are often used, as a rule standard materials are used in mold making. New, state-of-the art (high-performance) materials, such as ceramics, for instance, are almost completely absent. This may be related to the fact that their desirable characteristics, such as constant properties up to very high temperatures, are not required on molds, whereas their negative characteristics, e. g. low tensile strength and poor thermal conductivity, have a clearly related to ceramics, such as sintered material, is found in mild making only to a limited degree. This refers less to the modern materials and components produced by powder metallurgy, and possibly by hot isocratic pressing, than to sintered metals in the sense of porous, air-permeable materials.Removal of air from the cavity of a mold is necessary with many different processing methods, and it has been proposed many times that this can be accomplished using porous metallic materials. The advantages over specially fabricated venting devices, particularly in areas where melt flow fronts meet, I, e, at weld lines, are as obvious as the potential problem areas: on one hand, preventing the texture of such surfaces from becoming visible on the finished product, and on the other hand, preventing the microspores from quickly becoming clogged with residues (broken off flash, deposits from the molding material, so-called plate out, etc.). It is also interesting in this case that completely new possibilities with regard to mold design and processing technique result from the use of such materials. A. Design rules There are many rules for designing molds. These rules and standard practices are based on logic, past experience, convenience, and economy. For designing, mold making, and molding, it is usually of advantage to follow the rules. But occasionally, it may work out better if a rule is ignored and an alternative way is selected. In this text, the most common rules are noted, but the designer will learn only from experience which way to go. The designer must ever be open to new ideas and methods, to new molding and mold materials that may affect these rules.B. The basic mold1. Mold cavity space The mold cavity space is a shape inside the mold, “excavated” in such a manner that when the molding material is forced into this space it will take on the shape of the cavity space and, therefore, the desired product. The principle of a mold is almost as old as human civilization. Molds have metals into sand forms. Such molds, which are still used today in foundries, can be used only once because the mold is destroyed to release the product after it has solidified. Today, we are looking for permanent molds that can be used over and over. Now molds are made from strong, durable materials, such as steel, or from softer aluminum or metal alloys and even from certain plastics where a long mold life is not required because the planned production is small. In injection molding the plastic is injected into the cavity space with high pressure, so the mold must be strong enough to resist the injection pressure without deforming.2. Number of cavities Many molds, particularly molds for larger products, are built for only cavity space, but many molds, especially large production molds, are built with 2 or more cavities. The reason for this is purely economical. It takes only little more time to inject several cavities than to inject one. For example, a 4-cavity mold requires only one-fourth of the machine time of a single-cavity mold. Conversely, the production increases in proportion to the number of cavities. A mold with more cavities is more expensive to build than a single-cavity mold, but not necessarily 4 times as much as a single-cavity mold. But it may also require a larger machine with larger platen area and more clamping capacity, and because it will use 4 times the amount of plastic, it may need a large injection unit, so the machine hour cost will be higher than for a machine large enough for the smaller mold.3. Cavity shape and shrinkage The shape of the cavity is essentially the “negative” of the shape of the desired product, with dimensional allowance added to allow for shrinking of the plastic. The shape of the cavity is usually created with chip-removing machine tools, or with electric discharge machining, with chemical etching, or by any new method that may be available to remove metal or build it up, such as galvanic processes. It may also be created by casting certain metals in plaster molds created from models of the product to be made, or by casting some suitable hard plastics. The cavity shape can be either cut directly into the mold plates or formed by putting inserts into the plates.C. Cavity and core By convention, the hollow portion of the cavity space is called the cavity. The matching, often raised portion of the cavity space is called the core. Most plastic products are cup-shaped. This does not mean that they look like a cup, but they do have an inside and an outside. The outside of the product is formed by the cavity, the inside by the core. The alternative to the cup shape is the flat shape. In this case, there is no specific convex portion, and sometimes, the core looks like a mirror image of the cavity. Typical examples for this are plastic knives, game chips, or round disks such as records. While these items are simple in appearance, they often present serious molding problems for ejection of the product. The reason for this is that all injection molding machines provide an ejection mechanism on the moving platen and the products tend to shrink onto and cling to the core, from where they are then ejected. Most injection molding machines do not provide ejection mechanisms on the injection side.Polymer Processing Polymer processing, in its most general context, involves the transformation of a solid (sometimes liquid) polymeric resin, which is in a random form (e.g., powder, pellets, beads), to a solid plastics product of specified shape, dimensions, and properties. This is achieved by means of a transformation process: extrusion, molding, calendaring, coating, thermoforming, etc. The process, in order to achieve the above objective, usually involves the following operations: solid transport, compression, heating, melting, mixing, shaping, cooling, solidification, and finishing. Obviously, these operations do not necessarily occur in sequence, and many of them take place simultaneously. Shaping is required in order to impart to the material the desired geometry and dimensions. It involves combinations of viscoelastic deformations and heat transfer, which are generally associated with solidification of the product from the melt. Shaping includes: two-dimensional operations, e.g. die forming, calendaring and coating; three-dimensional molding and forming operations. Two-dimensional processes are either of the continuous, steady state type (e.g. film and sheet extrusion, wire coating, paper and sheet coating, calendaring, fiber spinning, pipe and profile extrusion, etc.) or intermittent as in the case of extrusions associated with intermittent extrusion blow molding. Generally, molding operations are intermittent, and, thus, they tend to involve unsteady state conditions. Thermoforming, vacuum forming, and similar processes may be considered as secondary shaping operations, since they usually involve the reshaping of an already shaped form. In some cases, like blow molding, the process involves primary shaping (pair-son formation) and secondary shaping (pair son inflation). Shaping operations involve simultaneous or staggered fluid flow and heat transfer. In two-dimensional processes, solidification usually follows the shaping process, whereas solidification and shaping tend to take place simultaneously inside the mold in three dimensional processes. Flow regimes, depending on the nature of the material, the equipment, and the processing conditions, usually involve combinations of shear, extensional, and squeezing flows in conjunction with enclosed (contained) or free surface flows. The thermo-mechanical history experienced by the polymer during flow and solidification results in the development of microstructure (morphology, crystallinity, and orientation distributions) in the manufactured article. The ultimate properties of the article are closely related to the microstructure. Therefore, the control of the process and product quality must be based on an understanding of the interactions between resin properties, equipment design, operating conditions, thermo-mechanical history, microstructure, and ultimate product properties. Mathematical modeling and computer simulation have been employed to obtain an understanding of these interactions. Such an approach has gained more importance in view of the expanding utilization of computer design/computer assisted manufacturing/computer aided engineering (CAD/CAM/CAE) systems in conjunction with plastics processing. It will emphasize recent developments relating to the analysis and simulation of some important commercial process, with due consideration to elucidation of both thermo-mechanical history and microstructure development. As mentioned above, shaping operations involve combinations of fluid flow and heat transfer, with phase change, of a visco-elastic polymer melt. Both steady and unsteady state processes are encountered. A scientific analysis of operations of this type requires solving the relevant equations of continuity, motion, and energy (I. e. conservation equations).Injection Molding Many different processes are used to transform plastic granules, powders, and liquids into final product. The plastic material is in moldable form, and is adaptable to various forming methods. In most cases thermoplastic materials are suitable for certain processes while thermosetting materials require other methods of forming. This is recognized by the fact that thermoplastics are usually heated to a soft state and then reshaped before cooling. Theromosets, on the other hand have not yet been polymerized before processing, and the chemical reaction takes place during the process, usually through heat, a catalyst, or pressure. It is important to remember this concept while studying the plastics manufacturing processes and the polymers used. Injection molding is by far the most widely used process of forming thermoplastic materials. It is also one of the oldest. Currently injection molding accounts for 30% of all plastics resin consumption. Since raw material can be converted by a single procedure, injection molding is suitable for mass production of plastics articles and automated one-step production of complex geometries. In most cases, finishing is not necessary. Typical products include toys, automotive parts, household articles, and consumer electronics goods, Since injection molding has a number of interdependent variables, it is a process of considerable complexity. The success of the injection molding operation is dependent not only in the proper setup of the machine variables, but also on eliminating shot-to-shot variations that are caused by the machine hydraulics, barrel temperature variations, and changes in material viscosity. Increasing shot-to-shot repeatability of machine variables helps produce parts with tighter tolerance, lowers the level of rejects, and increases product quality ( i.e., appearance and serviceability). The principal objective of any molding operation is the manufacture of products: to a specific quality level, in the shortest time, and using a repeatable and fully automatic cycle. Molders strive to reduce or eliminate rejected parts, or parts with a high added value such as appliance cases, the payoff of reduced rejects is high. A typical injection molding cycle or sequence consists of five phases:1 Injection or mold filling2 Packing or compression3 Holding4 Cooling5 Part ejectionInjection Molding OverviewProcessInjection molding is a cyclic process of forming plastic into a desired shape by forcingthe material under pressure into a cavity. The shaping is achieved by cooling(thermoplastics) or by a chemical reaction (thermosets). It is one of the most commonand versatile operations for mass production of complex plastics parts with excellentdimensional tolerance. It requires minimal or no finishing or assembly operations. Inaddition to thermoplastics and thermosets, the process is being extended to suchmaterials as fibers, ceramics, and powdered metals, with polymers as binders.ApplicationsApproximately 32 percent by weight of all plastics processed go through injection moldingmachines. Historically, the major milestones of injection molding include the invention of thereciprocating screw machine and various new alternative processes, and the application of computersimulation to the design and manufacture of plastics parts.Development of the injection molding machineSince its introduction in the early 1870s, the injection molding machine has undergone significantmodifications and improvements. In particular, the invention of the reciprocating screw machine hasrevolutionized the versatility and productivity of the thermoplastic injection molding process.Benefits of the reciprocating screwApart from obvious improvements in machine control and machine functions, the majordevelopment for the injection molding machine is the change from a plunger mechanism to areciprocating screw. Although the plunger-type machine is inherently simple, its popularity waslimited due to the slow heating rate through pure conduction only. The reciprocating screw canplasticize the material more quickly and uniformly with its rotating motion, as shown in Figure 1. Inaddition, it is able to inject the molten polymer in a forward direction, as a plunger.Development of the injection molding processThe injection molding process was first used only with thermoplastic polymers. Advances in theunderstanding of materials, improvements in molding equipment, and the needs of specific industrysegments have expanded the use of the process to areas beyond its original scope.Alternative injection molding processesDuring the past two decades, numerous attempts have been made to develop injection moldingprocesses to produce parts with special design features and properties. Alternative processes derivedfrom conventional injection molding have created a new era for additional applications, more designfreedom, and special structural features. These efforts have resulted in a number of processes,including: Co-injection (sandwich) molding Fusible core injection molding) Gas-assisted injection molding Injection-compression molding Lamellar (microlayer) injection moldin Live-feed injection molding Low-pressure injection molding Push-pull injection molding Reactive molding Structural foam injection molding Thin-wall moldingComputer simulation of injection molding processesBecause of these extensions and their promising future, computer simulation of the process has alsoexpanded beyond the early lay-flat, empirical cavity-filling estimates. Now, complex programs simulate post-filling behavior, reaction kinetics, and the use of two materials with different properties, or two distinct phases, during the process.The Simulation section provides information on using C-MOLD products.Among the Design topicsare several examples that illustrate how you can use CAE tools to improve your part and molddesign and optimize processing conditions.Co-injection (sandwich) moldingOverviewCo-injection molding involves sequential or concurrent injection of two different butcompatible polymer melts into a cavity. The materials laminate and solidify. This processproduces parts that have a laminated structure, with the core material embedded betweenthe layers of the skin material. This innovative process offers the inherent flexibility ofusing the optimal properties of each material or modifying the properties of the moldedpart.FIGURE 1. Four stages of co-injection molding. (a) Short shot of skin polymer melt (shown in dark green)is injected into the mold. (b) Injection of core polymer melt until cavity is nearly filled, as shown in (c). (d)Skin polymer is injected again, to purge the core polymer away from the sprue.Fusible core injection moldingOverviewThe fusible (lost, soluble) core injection molding process illustrated below producessingle-piece, hollow parts with complex internal geometry. This process molds a coreinside the plastic part. After the molding, the core will be physically melted or chemicallydissolved, leaving its outer geometry as the internal shape of the plastic part.FIGURE 1. Fusible (lost, soluble) core injection moldingGas-assisted injection moldingGas-assisted processThe gas-assisted injection molding process begins with a partial or full injection ofpolymer melt into the mold cavity. Compressed gas is then injected into the core of thepolymer melt to help fill and pack the mold. This process is illustrated below.FIGURE 1. Gas-assisted injection molding: (a) the electrical system, (b) the hydraulic system, (c) the control panel, and (d) the gas cylinder.Injection-compression moldingOverviewThe injection-compression molding process is an extension of conventional injectionmolding. After a pre-set amount of polymer melt is fed into an open cavity, it iscompressed, as shown below. The compression can also take place when the polymer isto be injected. The primary advantage of this process is the ability to producedimensionally stable, relatively stress-free parts, at a low clamp tonnage (typically 20 to50 percent lower).Lamellar (microlayer) injection moldingOverviewThis process uses a feedblock and layer multipliers to combine melt streams from dualinjection cylinders. It produces parts from multiple resins in distinct microlayers, asshown in Figure 1 below. Combining different resins in a layered structure enhances anumber of properties, such as the gas barrier property, dimensional stability, heatresistance, and optical clarity.Live-feed injection moldingOverviewThe live-feed injection molding process applies oscillating pressure at multiple polymerentrances to cause the melt to oscillate, as shown in the illustration below. The action ofthe pistons keeps the material in the gates molten while different layers of molecular orfiber orientation are being built up in the mold due to solidification. This process providesa means of making simple or complex parts that are free from voids, cracks, sink marks,and weld-line defects.Low-pressure injection moldingOverviewLow-pressure injection molding is essentially an optimized extension of conventionalinjection molding (see Figure 1). Low pressure can be achieved by properly programmingthe screw revolutions per minute, hydraulic back pressure, and screw speed to controlthe melt temperature and the injection speed. It also makes use of a generous gate size ora n reduce umber of valve gates that open and close sequentially to reduce the flow length. Thepacking stage is eliminated with a generally slow and controlled injection speed. Thebenefits of low-pressure injection molding include a reduction of the clamp force tonnagerequirement, less costly molds and presses, and lower stress in the molded parts.Push-pull injection moldingOverviewThe push-pull injection molding process uses a conventional twin-component injectionsystem and a two-gate mold to force material to flow back and forth between a masterinjection unit and a secondary injection unit, as shown below. This process eliminatesweld lines, voids, and cracks, and controls the fiber orientation.Reactive molding ProcessingMajor reactive molding processes include reactive injection molding (RIM), and compositesprocessing, such as resin transfer molding (RTM) and structural reactive injection molding (SRIM).The typically low viscosity of the reactive materials permits large and complex parts to be moldedwith relatively lower pressure and clamp tonnage than required for thermoplastics molding.relatively For example, to make high-strength and low-volume large parts, RTM and SRIM can be used to include a preform made of long fibers. Another area that is receiving more attention than ever before is the encapsulation of microelectronic IC chips.The adaptation of injection molding to these materials includes only a small increase in temperature in the feed mechanism (barrel) to avoid pre-curing. The cavity, however, is usually hot enough to initiate chemical cross-linking. As the warm pre-polymer is forced into the cavity, heat is added from the cavity wall, from viscous (frictional) heating of the flow, and from the heat released by the reacting components. The temperature of the part often exceeds the temperature of the mold. When the reaction is sufficiently advanced for the part to be rigid (even at a high temperature) the cycle is complete and the part is ejected.Design considerationsThe mold and process design for injection molding of reactive materials is much more complexbecause of the chemical reaction that takes place during the filling and post-filling stages. Forinstance, slow filling often causes premature gelling and a resultant short shot, while fast fillingcould induce turbulent flow that creates internal porosity. Improper control of mold-walltemperature and/or inadequate part thickness will either give rise to moldability problems duringinjection, or cause scorching of the materials. Computer simulation is generally recognized as amore cost-effective tool than the conventional, time-consuming trial-and-error method for tool andprocess debugging.Structural foam injection moldingOverviewStructural foam molding produces parts consisting of solid external skin surfacessurrounding an inner cellular (or foam) core, as illustrated in Figure 1 below. This processis suitable for large, thick parts that are subject to bending loads in their end-use application. Structural foam parts can be produced with both low and high pressure, withnitrogen gas or chemical blowing agents.Thin-wall moldingOverviewThe term thin-wall is relative. Conventional plastic parts are typically 2 to 4 mm thick.Thin-wall designs are called advanced when thicknesses range from 1.2 to 2 mm, andleading-edge when the dimension is below 1.2 mm. Another definition of thin-wallmolding is based on the flow-length-to-wall-thickness ratios. Typical ratios for thesethin-wall applications range from 100:1 to 150:1 or more.Typical applicationsThin-wall molding is more popular in portable communication and computing equipment, whichdemand plastic shells that are much thinner yet still provide the same mechanical strength asconventional parts.ProcessingBecause thin-wall parts freeze off quickly, they require high melt temperatures, high injectiospeeds, and very high injection pressures if multiple gates or sequential valve gating are not an optimized ram-speed profile helps to reduce the pressure requirement.Due to the high velocity and shear rate in thin-wall molding, orientation occurs more readilyhelp minimize anisotropic shrinkage in thin-wall parts, it is important to pack the part adequately while the core is still molten.Injection molding machineComponentsFor thermoplastics, the injection molding machine converts granular or pelleted rawplastic into final molded parts via a melt, inject, pack, and cool cycle. A typical injectionmolding machine consists of the following major components, as illustrated in Figure 1below.Machine functionInjection molding machines can be generally classified into three categories, based on machinefunction:General-purpose machinesPrecision, tight-tolerance machinesHigh-speed, thin-wall machinesAuxiliary equipmentThe major equipment auxiliary to an injection molding machine includes resin dryers,materials-handling equipment, granulators, mold-temperature controllers and chillers, part-removal robots, and part-handling equipment.Automated surface nishing of plastic injection mold steel with spherical grinding and ball burnishing processesAbstractThis study investigates the possibilities of automated spherical grinding and ball burnishing surface nishing processes in a freeform surface plastic injection mold steel PDS5 on a CNC machining center. The design and manufacture of a grinding tool holder has been accomplished in this study.The optimal surface grinding parameters were determined usingTaguchis orthogonal array method for plastic injection moldingsteel PDS5 on a machining center. The optimal surface grinding parameters for the plastic injection mold steel PDS5 werethe combination of an abrasive material of PA Al2O3, a grinding speed of 18 000 rpm, a grinding depth of 20 m, and a feed of 50 mm/min. The surface roughness Raof the specimen can be improved from about 1.60 m to 0.35 m by using the optimal parameters for surface grinding. Surface roughness Ra can befurther improved from about 0.343 m to 0.06 m by using the ball burnishing process with the optimal burnishing parameters.Applying the optimal surface grinding and burnishing parame-ters sequentially to a ne-milled freeform surface mold insert,the surface roughness Raof freeform surface region on the tested part can be improved from about 2.15 m to 0.07 m.KeywordsAutomated surface nishing Ball burnishing process Grinding process Surface roughness Taguchis method1 IntroductionPlastics are important engineering materials due to their specic characteristics, such as corrosion resistance, resistance to chemicals, low density, and ease of manufacture, and have increasingly replaced metallic components in industrial applications. Injection molding is one of the important forming processes for plastic products. The surface nish quality of the plastic injection mold is an essential requirement due to its direct effects on the appearance of the plastic product. Finishing processes such as grinding, polishing and lapping are commonly used to improve the surface nish. The mounted grinding tools (wheels) have been widely used in conventional mold and die nishing industries. The geometric model of mounted grinding tools for automated surface nishing processes was introduced in 1. A nishing process model of spherical grinding tools for automated surface nishing systems was developed in 2. Grinding speed, depth of cut, feed rate, and wheel properties such as abrasive material and abrasive grain size, are the dominant parameters for the spherical grinding process, as shown in Fig. 1. The optimal spherical grinding parameters for the injection mold steel have not yet been investigated based in the literature.In recent years, some research has been carried out in determining the optimal parameters of the ball burnishing process (Fig. 2). For instance, it has been found that plastic deformation on the workpiece surface can be reduced by using a tungsten carbide ball or a roller, thus improving the surface roughness, surface hardness, and fatigue resistance 36. The burnishing process is accomplished by machining centers 3, 4 and lathes 5, 6. The main burnishing parameters having signicant effects on the surface roughness are ball or roller material,burnishing force, feed rate, burnishing speed, lubrication, and number of burnishing passes, among others 3. The optimal surface burnishing parameters for the plastic injection mold steel PDS5 were a combination of grease lubricant, the tungsten carbide ball, a burnishing speed of 200 mm/min, a burnishing force of 300 N, and a feed of 40 m 7. The depth of penetration of the burnished surface using the optimal ball burnishing parameters was about 2.5 microns. The improvement of the surface roughness through burnishing process generally ranged between 40% and 90% 37.The aim of this study was to develop spherical grinding and ball burnishing surface nish processes of a freeform surface plastic injection mold on a machining center. The owchart of automated surface nish using spherical grinding and ball burnishing processes is shown in Fig. 3. We began by designing and manufacturing the spherical grinding tool and its alignment device for use on a machining center. The optimal surface spherical grinding parameters were determined by utilizing a Taguchis orthogonal array method. Four factors and three corresponding levels were then chosen for the Taguchis L18matrix experiment.The optimal mounted spherical grinding parameters for surface grinding were then applied to the surface nish of a freeform surface carrier. To improve the surface roughness, the ground surface was further burnished, using the optimal ball burnishing parameters.Fig. 1. Schematic diagram of the spherical grinding process Fig. 2. Schematic diagram of the ball-burnishing processFig. 3. Flowchart of automated surface nish using spherical grinding and ball burnishing processes2 Design of the spherical grinding tool and its alignment deviceTo carry out the possible spherical grinding process of a freeform surface, the center of the ball grinder should coincide with the z-axis of the machining center. The mounted spherical grinding tool and its adjustment device was designed, as shown in Fig. 4. The electric grinder was mounted in a tool holder with two adjustable pivot screws. The center of the grinder ball was well aligned with the help of the conic groove of the alignment components. Having aligned the grinder ball, two adjustable pivot screws were tightened; after which, the alignment components could be removed. The deviation between the center coordinates of the ball grinder and that of the shank was about 5 m, which was measured by a CNC coordinate measuring machine. The force induced by the vibration of the machine bed is absorbed by a helical spring. The manufactured spherical grinding tool and ball-burnishing tool were mounted, as shown in Fig. 5. The spindle was locked for both the spherical grinding process and the ball burnishing process by a spindle-locking mechanism.3 Planning of the matrix experiment3.1 Conguration of Taguchis orthogonal arrayThe effects of several parameters can be determined efciently by conducting matrix experiments using Taguchis orthogonal array 8. To match the aforementioned spherical grinding parameters, the abrasive material of the grinder ball (with the diameter of 10 mm), the feed rate, the depth of grinding, and the revolution of the electric grinder were selected as the four experimental factors (parameters) and designated as factor A to D (see Table 1) in this research. Three levels (settings) for each factor were congured to cover the range of interest, and were identied by the digits 1, 2, and 3. Three types of abrasive materials, namely silicon carbide (SiC), white aluminum oxide (Al2O3, WA), and pink aluminum oxide (Al2O3, PA), were selected and studied. Three numerical values of each factor were determined based on the pre-study results. The L18 orthogonal array was selected to conduct the matrix experiment for four 3-level factors of the spherical grinding process.Fig. 4. Schematic illustration of the spherical grinding tool and its adjustment deviceFig. 5. a Photo of the spherical grinding tool b Photo of the ball burnishing tool3.2 Denition of the data analysisEngineering design problems can be divided into smaller-the-better types, nominal-the-best types, larger-the-better types, signed-target types, among others 8. The signal-to-noise (S/N) ratio is used as the objective function for optimizing a product or process design. The surface roughness value of the ground surface via an adequate combination of grinding parameters should be smaller than that of the original surface. Consequently, the spherical grinding process is an example of a smaller-the-better type problem. The S/N ratio, is dened by the following equation 8: =10 log (mean square quality characteristic)=10 logwhere:yi: observations of the quality characteristic under different noise conditionsn: number of experimentAfter the S/N ratio from the experimental data of each L18 orthogonal array is calculated, the main effect of each factor was determined by using an analysis of variance (ANOVA) technique and an F-ratio test 8. The optimization strategy of the smaller-the better problem is to maximize , as dened by Eq. 1. Levels that maximize will be selected for the factors that have a signicant effect on. The optimal conditions for spherical grinding can then be determined.Table 1. The experimental factors and their levels4 Experimental work and resultsThe material used in this study was PDS5 tool steel (equivalent to AISI P20) 9, which is commonly used for the molds of large plastic injection products in the eld of automobile components and domestic appliances. The hardness of this material is about HRC33 (HS46) 9. One specic advantage of this material is that after machining, the mold can be directly used for further nishing processes without heat treatment due to its special pre-treatment. The specimens were designed and manufactured so that they could be mounted on a dynamometer to measure the reaction force. The PDS5 specimen was roughly machined and then mounted on the dynamometer to carry out the ne milling on a three-axis machining center made by YangIron Company (type MV-3A), equipped with a FUNUC Company NC-controller (type 0M) 10. The pre-machined surface roughness was measured, using Hommelwerke T4000 equipment, to be about 1.6 m. Figure 6 shows the experimental set-up of the spherical grinding process. A MP10 touch-trigger probe made by the Renishaw Company was also integrated with the machining center tool magazine to measure and determine the coordinated origin of the specimen to be ground. The NCcodes needed for the ball-burnishing path were generated by PowerMILL CAM software. These codes can be transmitted to the CNC controller of the machining center via RS232 serial interface.Table 2 summarizes the measured ground surface roughness value Raand the calculated S/N ratio of each L18orthogonal array using Eq. 1, after having executed the 18 matrix experiments. The average S/N ratio for each level of the four factors can be obtained, as listed in Table 3, by taking the numerical values provided in Table 2. The average S/N ratio for each level of the four factors is shown graphically in Fig. 7.Table 2. Ground surface roughness of PDS5 specimenFig. 6. Experimental set-up to determine the optimal spherical grinding parametersTable 3. Average S/N ratios by factor levels (dB)Fig. 7. Plots of control factor effectsThe goal in the spherical grinding process is to minimize the surface roughness value of the ground specimen by determining the op
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