油窗端盖注塑模具设计
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Intelligence and Automation CAD Soft WaresWith advancement of technology and high一speed development of world,Upgrade and innovation of Products are speeded up. No matter what industrial Products and appliance,are mostly molded by mold. Therefore,Plastic Parts design advances higher demands for periods and Precision of mold design and Manufacture . Because mold design depends on designers experience and Knowledge completely by traditional CAD soft wares ,50 efficiency and quality cant completely satisfy the demands of mold development. So intelligence and automation are very important in mold design .This issue Has joined the expert system to mold design,and developed an intelligentzed Injection mold design system .Basing on the Plastic Parts information,the System can implement automatically reasoning and analysis by the interrelatedknowledge,and select an relevant model from the model base,then rebuild the model by Parameterized technology,finally finish the design Process of injection mold .The entire design Process is completed by computer automatically without the calculation of designers,which decreases flaws caused by lack of experience of mold designers,and helps to avoid mistakes and improve efficiency and quality of mold design .This Paper summarized the design knowledge of injection molds side action; Then builds knowledge base suing the hybrid representation of framerepresentation and ruler representation :and introduces the Principles ,Processed method of compute automatic design system for side action in detail :Taking the best quality of Plastic Parts and highest efficiency as main purpose ,this paper finally develops side action :and also builds the graph library of side action using Parameterized technology based on Solid works .In information management system,Plastic Parts are decaled with in aspect of shrinkage and draft,which will make model、more Precision for the next design .An actual Process of the mold design for atypical Plastic Part has been demonstrated,which shows that the idea of system is feasible and this system can be used expediently to satisfy the demands of mold design. This paper also investigates menu and interface of this software,and finally Designs a laconic ,intuitive and manipulated friendly interface for injection mold design in order to make this software more acceptable to users.Mold Cavities and CoresThe cavity and core give the molding its external and internal shapes respectively, the impression imparting the whole of the form to the molding.We then proceeded to indicate alternate ways by which the cavity and core could be incorporated into the mold and we found that these alternatives fell under two main headings,namelythe integer method and the insert method.Another method by which the cavity can be incorporated is by means of split inserts or splits.When the cavity or core is machined from a large plate or block of steel,or is cast in one piece,and used without bolstering as one of the mod plates ,it is termed an integer cavity plate or integer core plate. This design is preferred for single-impression molds because of characteristics of the strength,smaller size and lower cost. It is not used as mush for multi-impression molds as there are other factors such as alignment which must be taken into consideration.Of the many manufacting processes available for preparing molds only two are normally used in this case. There are a direct machining operation on a rough steel forging or blank using the conventional machine tools, or the precision invstment casting technique in which a master pattern is made of the cavity and core. The pattern is then used to prepare a casting of the cavity or core by a special process.A 4.25%nickel-chrome-molybdenum steel(BS 970-835 M30) is normally specified for integer mold plates which are to be made by the direct machining method.The precision investment casting method usually utilizes a high-chrome steel.For molds containting intricate impressions, and for multi-impression molds, it is not satisfactory to attempt to machine the cavity and core plates from single blocks of steel as with integer molds. The machining sequences and operation would be altogether too complicated and costly. The insert-bloster assembly method is therefore used instead.The method consists in machining the impression out of small blocks of steel.These small blocks of steel are known,after machininf, as inserts, and the one which forms the male part is termed the core insert and, conversely, the one which forms the female part the cavity insert. These are the inserted and securely fitted into holes in a substantial block or plate of steel called a bloster. These holes are either sunk part way or are machined right through the bolster plate. In the latter case there will be a plate fastened behind the bolster and this secures the inserts in position.Both the integer and the insert-bolster methods have their advantages depending upon the size, the shape of the molding, the complexity of the mold, whether a single impression or a multi-impression ;old is desired,the cost of making the mold, ect. It can therefore be said that in general, once the characteristics of the mold reqired to do a particular job which have been weighed up, the decision as to which design to adopt can be made. Some of these considerations have already been discussed under various broad headings, such as cost, but to enable the reader to weigh them up more easily, when faced with a particular problem, the comparison of the relative advantages of each system is discussed under a number of headings. Unquestionably for single impression molds the integer design is ti be preferred irrespective of whether the component form is a simple or a complex one. The resulting mold will be stronger, smaller, less costly, and generally incorporate a less elaborate colling system than the insert-bolster design. It should be borne in mind that local inserts can be judiciously used to simplify the general manufactureof the mold impression.For multi-impression molds the choices is not so clear-cut. In the majority of cases the insert-bolster method of construction is used, the case of manufacture, mold alignment, and resulting lower mold costs being the overriding factors affecting the choices. For compenents of very simple form it is often advantangeous to use one design for one of the mold plates and the alternative design for the other. For example, consider a multi-impression mold for a box-type compenent. The cavity plate could be of the integer design to gain the advantages of strength, thereby allowing a smaller mold plate, while the core plate couls be of the insert-bolster design which will simplify machining of the plate and allow for adjustments for mold alignment.The Injection MoldingInjection molding ( British Engish : Molding ) is a manufacturing process for producing parts form both thermoplastic and thermosetting plastic materials.Material is fed into a heated brarel, mixed, and forced into a mold cavity where it cools and hardens to configuration of the mold cavity. After a product is designed, usually by an industrial designer or an engineer, molds aer made by a moldmaker ( or a toolmaker ) from metal, usually either steel or aluminium, and precision-machined to form the features of the desired part. Injection molding is widely used for manufacturing a varitey of parts, from the smallest compenent to entire body panels of cars.Injection molding machines consist of a material hopper, an injection ram of screw-type plunger, and a heating unit. They are also known as presses. They hold the molds in which the compenents are shaped. Presses are rated by tonnage, which expresses the amount of clamping force that the machine can exert. This force keeps the mold closed during the injection process. Tonnage can vary from less than 5 tons to 6000 tons, with the higher figures used in determined by the projected area of the part being molded.This projected area is multiplied by a champ force of 2 to 8 tons for each square inch of the projected area. As a rule of thumb, 4 or 5 t/in can be used for most products. If the plastic material is very stiff, it will require more injection pressure to fill the mold, thus more clamp tonnage to hold the mold closed. The required force can also be determined by the material used and the size of the part, larger parts require higher clamping force. Mold or die are the common terms used to describe the tooling used to produce plastic parts in molding.Traditionally, molds have been expensive to manufacture. They were usually only used in mass production where thousands of parts were being produced. Molds are typically constructed from hardened steel, pre-hardened steel, aluminium, and/or beryllium-copper alloy. The chioce of material to build a mold from is primarily one of economics. Steel molds generally cost more to construct, but their longer number of parts made before wearing out. Pre-hardened steel molds are less wear resistant and are used for lower volume requirements or large compenents. The steel hardness is tyoically 38-45 on the Rockwell-C scale ( HRC). Hardened steel molds are heat treated after machining. These are by far the superior in terms of wear resistance and lifespan. Typical hardness ranges between 50 to 60 Rockwell scale. Aluminium molds can cost substantially less , and when designed and machined with morden computerized equipment, can be economical for molding tens or even hundreds of thousands of parts. Beryllium copper is used in areas of the mold which require fast removal or area that see the most shear heat generated. The molds can be manufactured by either CNC or by using Electrical Discharge Machining processes.Standard two plates tooling: core and cavity are inserts in a mold base “Family mold ” of 5 different parts.The mold consists of two primary compenents, the injection mold ( A plate ) and the ejector mold ( B plate ). Plastic resin enters the mold through a sprue in the injection mold, the sprue bush is to seal tightly against the nozzle of the injection barrel of the molding machine and allow molten plastic to flow from the barrel into the mold , also known as cavity. The sprue bush directs the molten plastic to the cavity images through channels that are machined into the faces of the A or B plates. These channels allow plastic to run along them, so they are referred to as runners. The molten plastic flows through the runner and enters one or more specialized gates and into the cavity geometry to form the desired part.The amount of resin required to fill the sprue, runner and cavities of a mold is a shot. Trapped air in the mold can escape through air vents that are grinded into the parting line of the mold. If the trapped air is not allowed to escape , it is compressed by the pressure of the incoming material and is squeezed into the corners of the cavity , where it prevents filling and causes other defects as well . The air can become so compressed that it ignites and burns the surrounding plastic material. To allow for removal of the molded part from the mold , the mold features must not overhang one another in the direction that the mold opens , unless parts of the mold are designed to move from between such overhangs when the mold opens ( utilizing composnents called Lifters ).外文资料翻译智能型模具CAD系统随着科学技术的不断进步和社会的高速发展,产品更新换代越来越快。无论是工业产品还是家电产品,大多数应用模具成型。因此,对模具的设计和制造提出了更高的要求。传统的模具CAD软件完全依赖于设计人员的经验和知识,设计效率和设计质量很难满足模具发展的要求。因此在模具设计的过程中,使用智能型模具CAD系统显得尤为重要。本课题将专家系统技术引入到模具设计中,开发了智能注塑模具设计系统。该系统利用塑件产品信息,通过推理机对知识库中的相关知识进行自动推理、分析、决策,得出模具结构总体方案以及相关尺寸,从模型库中选出相应模型,通过参数化驱动重新建模,最终自动完成注塑模具设计过程。本文在前面几届研究生开发的基础上,总结了注塑模具斜销侧向分型与抽芯机构设计知识,结合模具设计知识的特点,利用框架/规则混合表示方法建立了注塑模具侧向分型与抽芯机构设计知识库;详细介绍了斜销侧向分型与抽芯机构的设计理论、过程和方法:系统以成型制品质量最优、效率最高为目标,最终形成了斜销侧向分型与抽芯机构的计算机自动设计系统。以Solid works为平台,采用参数化技术建立了侧向分型与抽芯机构的实体模型库。系统通过推理机对知识的推理,模型的调入,参数的驱动,实现侧向分型与抽芯机构的自动化设计。系统还对塑件模型进行了收缩率和脱模斜度的处理,实现了从塑件模型到模具模型的转化,使设计结果更加准确、严谨。通过典型制品的模具设计实例,演示了系统的设计过程。结果表明,系统设计思路正确,操作方便简单,运行可靠,适合模具设计要求。同时,本文在系统软件菜单、界面、设计思路等方面也做了大量的工作,使本系统软件更加人性化,具备了良好的实用性。型腔和型芯模具的型腔和型芯分别形成塑件内部和外部形状,型腔形状决定了塑件形状,接下来我们简要说明选择那种型腔和型芯安装在模具中。这些方式可以归纳为两大类,即整体形式和镶拼形式。另一种组成型腔的方式是加入拼块或滑块。当型腔或型芯由一块大的钢板或钢块加工而成,或是铸成一体,不需要使用支承件而形成一块模板时,就构成整体式模腔板或型芯板。这种设计因具有强度高,尺寸小和成本低的特性,而主要应用在单型腔模具中。整体式型腔和型芯一般不用在多型腔模具中,因为多型腔模具设计时必须考虑一些其他因素,例如安装组合镶件等。在模具制造的众多方法中,用于加工整体式型腔板或型芯板的方法主要有两种:使用传统机床对粗锻钢材料直接加工,或是利用精确的熔模铸造技术将坯料加工成型腔和型芯。用于制造型腔和型芯的坯料经常需要特殊工艺的处理。通常,4.25%的镍镉钼合金钢是生产整体式模板的指定材料,选用这种材料时采用直接的机加工方式。精确的熔模铸造常常用来加工高铬钢。对于成型部位复杂的模具和多腔模具,也像整体式模具那样用一块钢材加工型腔和型芯并不容易。如果采用整体式结构,则加工顺序和操作过程将变得非常复杂,成本也高,因此镶拼式装配方式替代了整体式。镶拼式型腔由小钢块加工而成。加工后的小钢块作为镶件,形成型芯部分的称为型芯嵌件,相反地,形成型腔部分的成为型腔嵌件。然后,把这些镶件牢固地安装在被称为垫板的孔中,垫板由实心钢板或钢块加工而成。这些安装孔有的是由垫板的局部凹陷形成,有的是在垫板上直接加工而成。在后一种方式中,垫板后部还要增加一块模板,起加固作用,确保镶件安装到位。整体式和镶拼式结构均有优点,这取决于塑件尺寸和形状,模具的复杂程度,所需的是单型腔模具还是多型腔模具以及模具制造成本等。通常,塑件的形状,尺寸等特性确定后,采用哪种形式的型腔和型芯就已经确定了。在不同的章节中,我们已经讨论过型腔和型芯的安装方式所涉及的问题,例如成本等,但为使读者在处理特殊问题时更容易知道重点所在,我们将用一定的章节再次讨论每种结构优缺点的对比。毫无疑问,对于单型腔模具,无论是简单还是复杂,整体式型腔是首选方式。若选择整体式,则模具的强度高,体积小,成本低,而冷却系统的设计却比镶拼式简单,方便。设计时需要常记于心的是,适当地使用镶件可以简化模具型腔的加工制造难度。对于多型腔模具,选择哪种方式不是很明显。大多数型腔模具采用镶拼式结构,这种结构加工简单,装配容易,模具成本低,这些是影响选择哪种结构形式的重要因素。一种非常简单且具有很多优点的设计是采用一种形式设计模板,而采用另一种形式设计模具的其他部分。例如,采用箱形组件设计多型腔模具。型腔板设计成小型整体式模板,以满足模具高强度的要求;型芯板则设计成镶拼式,可因简化模板加工过程,并且能根据模具需要进行调整。注塑成型注塑成型是将热塑性和热固性塑料加工成零件的制造过程。材料被入加热筒中,混合后压入模腔,冷却硬化成它们的形状。通常工业设计师或工程师设计完一个产品后,模具制造师(或工人)就会用金属,通常为刚或铝,制造模具,且精加工以达到理想效果。从最小的部件到整个汽车的面板,注塑成型广泛应用于各种零部件的制造。 模具注塑机由一个料斗、注射活塞或螺旋式活塞以及一个加热装置构成。他们也被称为压力机,内含零部件形成的模具。压力机以吨位来衡量,表示机器可以施加的锁模力。锁模力保障模具在注塑的过程中是封闭的。吨位可以从少于5t到6000t,较高的吨位应用于相对少量的生产中。需要多少锁模力取决于零件的投影面积。每平方英寸的投影面积要乘以2-8t的锁模力。根据经验法则,每平方英寸的投影面积对应4-5t的锁模力,即可应用于大部分产品。如果塑料很硬,它需要更多的压力来填充模具,因此需要更多的锁模力来保障模具的封闭性。所需的压力也取决于使用的材料及零件的大小,越大的零件需要的锁模力越大。实际的注塑模具如所示。注塑或冲模是描述注塑中用于制造塑料零件的工具的常用术语。传统上,模具制造一直很昂贵。它们通常只使用于成千上万的大批量零件的生产。模具通常由淬火钢、预硬钢、铝或铍铜合金制成。选择制造模具的原料首先要考虑经济因素,钢模具成本较高,但使用寿命较长。在用完之前,钢模能制造更多的零件,这会抵消最初的高成本投入。预硬钢模具不耐磨,适用于小批量生产或制造较大的零件。钢的硬度通常是38-45HRC,淬硬钢模具加工后要进行热处理。这类模具在耐磨性和使用寿命方面具有较强的优势,其典型的硬度范围介于50-60HRC之间。铝模具成本大幅度减少,利用现代计算机设备设计与加工,对于注塑成千上万个零件来说是经济的。铍-铜合金使用于制造需快速去热或消除产生的热能的模具。这类模具可利用数控加工或电火花加工来生产。标准的两板模具包括:型芯和型腔所在的模具内部,其余的则为五个不同的典型模具结构。模具有两个主要部分构成:合模(A板)和出模(B板)。塑料树脂通过注塑模具浇道进入模具,浇口套密封紧接在注塑机注射料筒的喷嘴处,让熔化的塑料从料筒流到模具,也就是型腔。浇口套通常加工成A、B板的管道引导熔化的塑料流向型腔。这些管道使塑料沿着他们流动,进入几何形状的型腔,形成所需的零件。填充模具浇口套、流道和型腔的大量树脂是一瞬间。模具里积存的空气可以通过模具分型线的通风口排出。如果积存的空气不能排出,进料的压力会把它们挤压到型腔的角落,这会妨碍填充并导致其他问题。空气压缩到一定程度会被引燃,导致周围的塑料燃烧。为了消除成型模具某个部分,模具不能彼此悬垂于模具打开的方向,除非该模具部分设计成模具打开时悬空一定(所用的组件称为侧抽芯)。油窗端盖注塑模具设计摘 要塑料工业是当今世界上增长最快的工业门类之一,而注塑模具是其中发展较快的种类,因此,研究注塑模具对了解塑料产品的生产过程和提高产品质量有很大意义。注射模技术的不断发展需要越来越多的工艺流程。注射成型过程中最重要的问题是模具的正确设计。从根本上说,注射模具包括浇口和浇注系统,另一部分是放置顶出系统。模具零件是在分型面被定位的。注射模具型腔选择等设计计算要求掌握加工材料、注射机和模具等方面的准确知识。模具的制造成本随着型腔数目的增加而增加,而相关的加工费用减少了。一个给定的模具零件的生产周期取决于壁厚、注射速度、收缩率、模内材料的冷却时间、冷却的效能及必要的辅助时间,如压力持续时间、排气时间及延迟时间等。本设计介绍了注射成型的基本原理,特别是单分型面注射模具的结构与工作原理,对注塑产品提出了基本的设计原则;详细介绍了冷流道注射模具浇注系统、温度调节系统和顶出系统的设计过程,通过本设计,可以对注塑模具有一个初步的认识,注意到设计中的某些细节问题,了解模具结构及工作原理。关键词:塑料模具,参数化,分型面,浇注系统,模具型腔。THE PLASTIC INJECT MODLE DESIGNABSTRACTplastic industry is in the world grows now one of quickest industry classes, but casts the mould is development quick type, therefore, the research casts the mold to understand the plastic product the production process and improves the product quality to have the very big significance. The continuing development of injection mold technology demands more and more of the processes. The most important problem in the process of injection molding is undoubtedly the correct design of injection mold . Basically the injection mold consists of two halves.One mold half contains the sprue bushing and runner system, the other half houses the ejection system. The molded part is located at the parting line.To set up a calculation conceiving the choice of cavities in an injection mold requires accurate knowledge of the matrrial to be processed, of the injection-molding machine and of the molds. The mold costs increase with the rising number of cavities and the relative machine costs decrease. The production time required for a given molded part depends on the wall thicknes, the injection speed, the recovery rate, the time required to coll the molded material, the cooling capacity of the mold and the necessary incidental time such as duration of pressure holding time, ejection time, delay time, ect.This design introduced the injection takes shape the basic principle, specially single is divided the profile to inject the mold the structure and the principle of eork, to cast the product to propose the basic principle of design; Introducted in detail the cold flod channel injection evil spirit mold pours the system, the temperature contral system and goes against the system the design process, and has given the explanation to the mold intensity request; Through this design, may to cast the mold to have a preliminary understanding, notes in the design certain detail question, understands the mold structure and the principle of work; Through to the PROGRAM study, may establish the simple components the components storehouse, thus effective enhancement eorking efficiency.KEY WORDS: The plastic mold, the parameterization, inlays, divides the profile43目录前言1第一章:制件的结构与工艺性分析21.1制件相关信息21.2材料的相关性质31.2.1 基本特性31.2.2 主要用途31.2.3 成型特点31.3塑件的脱模斜度41.4塑件的尺寸精度及表面质量要求4第二章:初选注射机62.1 计算塑件体积和最大投影面积62.2选择压力机62.3确定型腔数目7第三章 模具设计93.1 型腔的分布设置93.2 分型面的确定93.3 浇口的确定原则103.4 浇注系统的确定113.4.1 主流道的设计113.4.2 分流道的设计123.4.3 冷料穴的设计133.4.4浇口的相关参数选择143.5成型零部件的结构设计143.5.1 型腔的结构设计143.5.2 型芯的结构设计153.6 模具成型零部件尺寸计算153.5.1 计算成型零部件尺寸要考虑的因素163.5.2 制件尺寸的公差转换163.5.3成型零部件尺寸计算173.7 模架的选用203.7.1 模架型号的确定203.7.2 模架具体尺寸的确定213.8 结构零部件的设计223.8.1 支承板的设计223.8.2 垫块的设计223.8.3 定模座板和动模座板的设计223.8.4 导柱的设计233.8.5 导套的设计243.8.6 设计导柱导套需要注意的事项243.9推出机构的设计243.9.1 推杆的设计25第四章 冷却系统的设计284.1 冷却水孔直径的确定284.2 冷却水回路的布置原则28第五章 注射机的相关校核295.1 注射机额定注射量的校核295.2注射压力的校核295.3锁模力的校核295.4模具安装尺寸的校核305.41喷嘴尺寸校核305.4.2模具厚度校核305.5 开模行程的校核31结论32谢 辞33参考文献34外文资料翻译41前言 塑料工业是新兴的工业,是随着石油工业的发展因应运而生的,目前塑料制件几乎已经进入一切工业部门以及人民日常生活的各个领域。塑料工业又是一个飞速发展的工业领域。塑料作为一种新的工程材料,其不断被开发与应用,加之成型工艺的不断成熟,完善和发展,极大的促进了塑料成型方法的研究与运用和塑料模具的开发与制造。随着工业塑料制件和日用塑料之间的品种和需求量日益增加,这些产品的更新换代的周期越来越短。因此对塑料的品种、产量和质量都提出了越来越高的要求。对塑料制件提出高要求的同时意味着对塑料模具提出了很高的要求。因为模具是塑料工业生产中重要的工艺设备,因此模具设计显得越来越重要。塑料模具的设计是模具制造中的关键工作。通过合理设计制造出来的模具不仅能顺利的成型高质量的塑件,还能简化模具的加工过程和实施塑件的高效率生产,从而达到降低生产成本和提高附加价值的目的。近几年来塑料成型工艺迅速发展,塑料模具种类不断增加。结构也更为复杂,在该套模具的设计中采用的是一模四腔的模具结构。该套模具的浇口采用的是侧浇口。侧浇口又称标准浇口,这种浇口一般开设在分型面上,塑料熔体内侧或外侧注入型腔,其截面形状多为矩形,改变浇口的宽度与厚度可以调节熔体的剪切速率及浇口的冻结时间。这类浇口可以根据塑件的形状特征选择其位置,加工和修正方便,普遍用于中小型塑件的多型腔模具,且对各种塑料的成型适应性均较强。其浇口截面小,减少了浇注系统塑料的消耗量,同时去除浇口容易,且不留明显痕迹。因此塑件的表面不受损伤,不致因浇口痕迹而影响塑件的表面质量与美观效果。该套模具的工作原理是当注射结束时,模具在开模力的作用下从D-D分型面分型,当动模向后移动一定距离后推出机构开始工作,推杆推动推件板把塑件从型芯上推下,完成整个开模过程 。 第一章:制件的结构与工艺性分析1.1 制件相关信息名称:端盖 材料:PS;精度:一般,零件直观图如图1-1所示:图1-1 制件立体图生产批量:中批生产; 粗超度要求:Ra=0.6um;用途:利用PS透明度高的特点,制造仪器端盖,一方面防尘,阻挡异物进入仪器;另一方面可从顶部区域,观察仪器内部油面,以便随时掌握油量,及时添加。侧壁上长条形孔洞,用于扣紧端盖,保证端盖与仪器牢固结合。表面质量要求:要求顶面必须光滑平整,无浇口痕迹及顶出痕迹;四壁光滑,无明显痕迹。1.2材料的相关性质 1.2.1 基本特性PS(聚苯乙烯)是无色透明并有金属光泽的非结晶型线性结构的高聚物,落地式发出类似金属的声音,密度为1.054g/cm3。聚苯乙烯的透明度好,透光率高,在塑料中期光学性能仅次于有机玻璃。聚苯乙烯有优良的电性能,尤其是高频绝缘性能,并具有一定的化学稳定性。聚苯乙烯能耐除硝酸以外的酸及碱、醇、油、水等,但对与氧化剂、苯、四氯化碳、酮类、酯类等的抵抗力较差。聚苯乙烯的着色性能优良,能染成各种鲜艳的颜色。但其耐热性低,热变形温度一般在70-90,所以只能用在不高的温度下。聚苯乙烯质地硬而脆,有较高的热膨胀系数,塑件易产生内应力易开裂,因此限制了它在工程上的应用。近几十年来,由于有了改性聚苯乙烯和以聚苯乙烯为基体的共聚物,从而扩大了它的用途。1.2.2 主要用途 聚苯乙烯是仅次于聚乙烯和聚氯乙烯的第三大塑料品种。在工业上可用作制作仪表外壳、灯罩、化学仪器零件、透明模型等。在电器方面用于制作良好的绝缘材料,如电视机的结构零件、接线盒和电池盒等。在日用品方面则广泛用于制作包装材料、各种容器和玩具等。1.2.3 成型特点聚苯乙烯成型性能优良,吸水性小,可不进行干燥处理。由于热膨胀系数较高,故而塑件中不宜含有嵌件,否则会因两者的热膨胀系数相差太大而导致开裂。宜采用高料温,高模具温度,低注射压力成型并延长注射时间,以防止缩孔和变形,降低内应力。由于聚苯乙烯流动性很好,故而在模具设计中大多采用点浇口进料。聚苯乙烯可采用注射,挤出,真空等多种方法成型。 1.3塑件的脱模斜度由于塑件成型冷却过程中产生收缩,使其紧箍在凸模或型芯上,为了便于脱模,防止因脱模力过大而拉坏塑件或使其表面受损,与脱模方向平行的塑件内、外表面都应具有合理的斜度。以下是 PS的脱模斜度推荐值:型腔:35-130型芯:30-40对于本制件而言,型腔取1脱模斜度,型芯取30脱模斜度。1.4塑件的尺寸精度及表面质量要求该制件为简单的壳类零件,侧面有一成型孔。表面粗糙度为0.6.属于一般的粗糙度要求。由于上表面要求不能出现任何形式的不光整现象,侧面也要求尽量平整,故而最初大致确定,制件注塑成型时,从底部耳边处进料,即浇口开在耳边,同时刚好开在最大分型面处。制件的详细尺寸见零件图,如下图1-2所示:图1-2 制品零件图制件各个尺寸的相关要求如下:制件内轮廓径向尺寸44和侧壁成型孔尺寸18、4为MT3,其余尺寸,为一般精度MT5。第二章:初选注射机2.1 计算塑件体积和最大投影面积考虑到制件形状简单,体积较小,批量不大,故而初定模具生产为一模两腔。一次开模,耗费塑料的总体积,可以分两部分:制件部分的体积V1和料把的体积V2。V1KPCA=248.1kN (公式 5-2)故注塑机的额定锁模力符合要求。5.4模具安装尺寸的校核5.41喷嘴尺寸校核 注塑模浇口套始端凹坑的球面半R2应大于注塑机喷嘴球头半径R1,以利用同心和紧密接触,本设计按半径R2= R1+(0.52)计算,故符合要求;主流道的始端直径d1应大于注塑机喷嘴孔直径d2,本设计按d1=d2+(0.51)mm关系计算,亦符合要求。5.4.2模具厚度校核模具厚度(闭合高度)必须满足下式: 式中所设计的模具高度(mm); 注塑机所允许的最小模具厚度(mm); 注塑机所允许的最大模具厚度(mm)。结合注塑机的参数,模具总高度为235mm,XS-Z125型号注射机的装模高度介于200mm与300mm之间,因此本设计符合要求。5.5 开模行程的校核注塑机模座间距是指注塑机动模座和定模座之间的间距,对于所选用的注塑机,模具的闭模高度必须满足 开模取出塑件所需的开模距离必须小于注塑机的最大开模行程。本设计选用注塑机为液压-机械式锁模机构,液压-机械式锁模机构的最大开模行程由屈肘机构的最大行程决定,与模具厚度决定无关。
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