外文翻译-模具类注塑机模具设计.doc

外 文 翻 译毕业设计题目：操纵机构及其面板凸轮机构模具设计原文1：Plastic Material Molding译文1：塑料成型 原文2：The Injection-molding Maching译文2：注塑机1Plastic Material MoldingPlastic objects are formed by comperssion,transfer,and injection molding.Other processes are casting, extrusion and laminating, filament winding, sheet forming, jointing, foaming, and maching. Some of these and still otherrs are used for rubber. A reason for a variety of processes is that different materials must be worked in differentways. Also, each methods is advantageous for certain kind of product(Table 1)Table 1 Characteristics of Forming and Shaping Processes for Plastics and Composite Materials processCharacteristicsExtrusionLong, uniform, solid or hollow complex cross-sections; high production rates; low tooling costs; wide tolerrances.Injection moldingComplex shapes of various sizes, eliminating assembly; high production rates; costly tooling; good dimensional accurancy.Structural foam moldingLarge parts with high stiffness-to-weight ratio; less expensive tooling than in injection molding; low production rates.Blow moldingHollow thin-walled parts of various sizes; high production rates and low cost for making containers.Rotational moldingLarge hollow shapes of relatively simple shape; low tooling cost; low production rates.ThermoformingShallow or relatively deep cavities; low tooling costs; medium production rates.Compression moldingParts similar to impression-die forging; relatively inpensive tooling; medium production rates.Transfer moldingMore complex parts than compression molding and higher production rates; some scrap loss; medium tooling cost.CastingSimple or intricate shapes made with flexible molds; low production rates.Processing of composite materialsLong cycle time; tolerances and tooling cost depend on process.There are two main steps in the manufacture of plastic products. The first is a chemical process to create the resin. The second is to mix and shape all the material into the finished article or product.1.1 Compression MoldingIn compression molding, a preshaped charge of material, a premeasured volume of powder, or a viscous mixture of liquid redin and filler material is placed directly into a heated mold cavity. Forming is done under pressure from a plug or from the upper half of the die (Figer 1). Compression molding results in the formation of flash (if additional plastic is forced between the mold halves, because of a poor mold fit or wear, it is called flash.), which is subsequently removed by trimming or other means.Typical parts made are dishes, handles, container caps, fittings, electrical and electronic components, washing-machine agitators, and housings. Fiber-reinforced parts with long chopped fibers are formed by this process exclusively.Compression molding is used mainly with thermosetting plastics, with the original material being in a partially ploymerized state. Cross-linking (in these ploymers, additional element link one chain to another. The best example is the use of sulfur to cross-link elastomers to create automobile tires) is completed in the heated die; curing times rang from 0.5 to 5 minutes, depending on the material and on part thickness and geometry. The thicker the material is, the longer it will take to cure. Elastomers are also shaped by compression molding.Three types of compression molds are available as follows:Figuer 1 Typres of compression moldinga. flash-type, for shallow or flat parts,b. positive, for high density parts,c. semipositive, for quality production.1.2 Transfer Molding Transfer molding represents a further development of compression molding. The uncured thermosetting material is placed in a heated transfer pot or chamber （Figer 2）. After the material is heated, it is injected into heated closed molds. A ram, a plunger, or a rotating-screw feeder (depending on the type of machine used) forces the material to flow through the narrow channels into the mold cavity. Typical parts made by transfer molding are electrical and electronic components and rubber and silicone parts. This process is particularly suitable for intricate parts with varying wall thickness.1.3 Injection Molding Injection molding (injection of plastic into a catity of desired shape. The plastic is then cooled and ejected in its final form. Most consumer productions such as telephones, computer casings, and CD players are injection molded. ) is principally used for the production of thermoplastic parts, although some process has been made in developing a method for injection molding some thermosetting materials. Figure 2 Sequence of operations in transfer molding for thermosetting plasticsThe problem of injection a melted plastic into a mold cavity from a reservoir melted material has been extremely difficult to solve for thermosetting plastics which cure and harden such conditions within a few minutes. The principle of injection molding is quite similar to that of die-casting. Plastic powder is loaded into the feed hopper and a certain amount feeds into the heating chamber when the plunger draws back. The plastic powder under heat and pressures in the heating chamber becomes a fluid. After the mold is closed, the plunger moves forward, forcing some of the fluid plastic into the mold cavity under pressures. Since the mold in cooled by circulating cold water, the plastic hardens and the part may be ejected when the plunger draws back and the mold opens. Injection-molding machines can be arranged for manual operation, automatic single-cycle operation, and ful automatic operation. Typical machines produce molded parts weighing up to 22 ounces at the rate of four shots per minute, and it is possible on molded parts machines to obtain a rate of six shots per minute. The molds used are similar to the dies of a die-casting machine. The advantages of injection molding are as follows:1. A high molding speed adapted for mass production is possible,2. There is a wide choice of thermoplastic materials providing a variety of useful properties,3. It is possible to mold threads,(“sideways” racesses or projections of the molded part that prevent its removal from the mold along the parting direction. They can accommodated by specialized mold design such as sliders.), side holes, and large thin sections.1.4 Thermoplastic Mold Design Basically, there are two types of transfer mold: the conventional sprue type and the positive plunger type. In the sprue type the plastic performs are placed in a separate loading chamber above the mold cavity. One or more sprues (the runway between the injection machines nozzle and the runners or the gate) lead down to the parting surface of the mold where they connect with gates to the mold cavity or cavities (Figer 3). Special press with a floating intermediate platen are especially useful for accommodating the two parting surface molds. The plunger acts directly on the plastic material, forcing it through the sprues and gates into the mold cavities. Heat and pressure must be maintained for a definite time for curing. When the part is cured the press is opened, breaking the sprues from the gates. The cull and sprues and raised upward, being held by a tapered, dovetailed projection machine on the end of Figure 3 Schematic illustration of transfer moldingthe plunger. They can easily be removed from the dovetail by pushing horizontally. In a positive plunger-type transfer mold the sprue is eliminated so that the loading chamber extends through to the mold parting surface and connects directly with the gates (the entrance to the mold cavity). The positive plunger type is preferred, because the mold is less complicated, and less material is wasted. Parts made by transfer molding have greater strength, more uniform densities, closer dimensional tolerances, and the parting plane (the separation plane of the two mold halves) requires less cleaning as compression molding.The following figure shows a typical two-plate mold and indicates the structure of mold and the arrangement of all parts in mold (Figure 4).Figure 4 The typical structure of two-plate mold作者：Yijun Huang国籍：china出处：Qinghua university press塑料成型塑料制品一般是由压缩，传递和注塑成型等方法形成的。其他形成过程比如铸造，挤塑和层压，纤维缠绕，板料成形，焊接和发泡等, 其中还存在一些塑料制品是用橡胶制成的，导致这些各种各样繁杂成型过程的一个原因是，各种不同的材料必须在不同的工作方法下进行。此外，每个方法适用于某种制品，比如（如表1）表一 特征的形成和塑料及复合材料成型过程成型方法使用的特征挤塑长，均匀，制品一般具有实心或空心复杂的横截面，高生产效率低，加工成本，公差要求不高。注塑适用于复杂的形状大小不同，不用装配，高生产效率，成本较高的工具，良好的立体准确度。结构发泡成型高刚度大部件的重量比;较便宜注塑模具，低生产率。吹塑适用于空心薄壁件，高生产率和低成本制造的容器。滚塑适用于大型空心形状比较简单的形状，低模具成本低，生产速度。热成型适用于浅或深腔比较低，加工成本;中型生产速度。压铸成型部分类似于模锻;相对便宜的模具;中型生产速度。传递模塑成型应用于更加复杂的零件，比压缩成型和生产效率有所提高，减少损失;中型模具成本。铸造简单灵活的模具或作出复杂的形状，低生产率。复合材料加工周期时间长;公差和模具成本依赖性较高的加工过程。其中塑料制品的生产主要有两类生产步骤。第一个是化学过程创建树脂来形成制品。第二是将产品的所有材料混合化成成品。1.1压缩成型在压缩成型中，压缩成型是将塑料直接加入到具有一定温度的敞开的模具型腔内，然后闭合模具，在热与压力作用下塑料熔融变成流动状态。由于物理及化学作用，而使塑料硬化成为具有一定形状和尺寸的常温保持不变的塑件（图1）。压缩成型，在急速压缩的作用下，被迫压在塑料模具型腔之间，因为容易导致模具的磨损，这是后来为什么删除此种方法的原因。比如典型零件的部件，碗碟，拉手，容器盖，配件，电器及电子元件，洗衣机搅拌器，和外壳的制造。压缩成型主要是用于热固性塑料的成型，原始材料是处在一种部分聚合状态。交叉连接（在这些聚合物，以链的形式一个连接到另一个。最好的例子是使用硫磺交联橡胶汽车轮胎的制造）是在激烈的模具冲击下完成，固化时间由0.5至5分钟，根据材料和零件的厚度和几何，越厚，材料的成型时间越长，弹性也决定了压缩成型的效果。三种类型的压缩模具可如下： 图1压缩成型种类a. 不溢料式压缩型，适用于浅或平面塑件，b. 溢料式压缩型，使用与成型高密度塑件，c. 半溢料式压缩型，适用于高质量的生产。1.2转移成型 转移成型是压缩成型方法的进一步延伸。热固性材料的固化是放置在一个加热型腔内的(图2).。转移成型采用注射设备将专用注射热固性塑料体系注入闭合模具。模具内预先铺放好增强材料预成型体。然后，模具被紧固和密封，塑料被注入摸具。摸具上事先设计有注射及排气孔系统，以保证塑料顺畅流动和模具内气体的顺利排出。栓或柱塞，或旋转螺杆即螺旋给料机（具体取决于所用机器的类型）控制塑料穿过进入模腔狭窄的通道。一般典型零件的电气和电子元件的橡胶和有机硅的部分都是有传递塑模法制造的。这个过程是特别适合与不同壁厚的复杂部件的制造。 图2 热固性塑料转移塑模的注塑流程1.3注射成型注塑成型（将塑料注射进所需形状的空腔，然后冷却并在其最后以顶出的形式顶出。如电话部件的制作，电脑外壳和CD播放机的注射成型等。）主要用于生产使用热塑性塑料部件，虽然有些地方注射成型方法已发展为可用于一些热固性材料的成型。在注射期间，塑料经加热变成了熔化的塑料进入型腔，然而热固性塑料却很难在以流体形式在几分钟之内被填充而后不失去其材料特性。塑料粉末装入进料斗和一定量色母被送入加热室时，柱塞退。在高温下和加热室压力塑料粉末变成液体。模具关闭后，柱塞向前推进，迫使在压力下，模腔流体的塑料部分在型腔内定型。自通过循环冷水冷却模具，塑料变硬，柱塞退和模具打开。注塑机，可进行手动操作，自动单周期操作安排，并可以实现自动操作。在一般典型的注塑机每分钟可以注射四次，每次可以生产处重达22盎司左右的成型件，然有些特别的注塑机每分钟可以注射6次。该模具采用类似压铸机采用的模具。注射成型的优点如下：1. 速度适应大规模生产， 2. 给特性热塑性材料提供了一个广泛的应用选择， 3. 使模具结构性更强（对成型零件把握性更强，对于沿模具脱模方向的抽芯可以通过滑块机构模具设计形式。），如方孔，大薄片。1.4热塑性塑料模具设计基本上，有两种类型的转让型模具：常规浇口类型和积极的柱塞式类型。在浇口类型中，熔融的塑胶流至于一个以上的分开的模腔内。一个或多个浇注（之间由多个分流道和注塑机的喷嘴连接在一起），流道缩小到了模具分型面，他们与模具型腔或腔门连接（图3）。中间的模具板为专用压力机作用用于容纳模具的两个分型面。柱塞直接作用于塑料材料，迫使通过浇注和流体入模腔了。热和压力，必须保持了一定的保压时间。保压一段时候后，浇注停住。在浇注结束时，柱塞移出并向上提，此时柱塞移动结束。这样，操作人员可以很容易地拿出塑件。在积极的柱塞式转移模具浇口是，相浇套延伸至模具分型面，直接（向模腔入口）注塑。一般积极柱塞式是首选，因为往往模具不太复杂，以及较少材料的浪费。通过转移成型的零部件需要更大的压力，因而制品更均匀密度和尺寸公差。图3传递模塑示意图下图显示了一个典型的二板模，并说明了模具结构和在模具各部分的安排（图4）。 图4两板模具典型结构作者：黄易俊国籍：中国出处：清华大学出版社The Injection-molding Maching The injection-molding machines are usually horizontal(Figure 1). Vertical machines are used for making small close-tolerance parts and for insert molding. The clamping force on the molds is generally supplied by hydraulic means.Figure 1 The injection-molding machine The injection-molding machines are rated according to the capacity of the mold and the clamping force. In most machines, this force rangs from 100 to 250 tons. The largest machines in operation has a capacity of 5000 tons, and it can produce parts weighting 25kg (most parts weigh from 100g to 600g). The tonnage is the force applied to keep the molds closed during injection of molten plastics into the mold cavities.There are two basic units to an injection-molding machine, one for injecting the heated plastic and one for opening and closing the mold. The first unit includes a feed hopper, heated injection cylinder, and an injection plunger or reciprocating-screw system. The second unit comprises a hydraulic operated moving platen and a stationary platen on which the halves of the mold are mounted. Injection-molding machines are also available in vertical models.There are many variations in injection-molding machine design (Figure 2), or plunger injection system (Figure 3). The main difference between these system is the method in which the plastic material is delivered from the hopper to the nozzle of the machine. Machines of the reciprocating-screw system are used more because of faster cycles, lower melting temperatures, and better mixing of the material.The most commonly used systems in the larger machines is the in-line reciprocating screw, as shown in Figure 2. Figure 2 The reciprocating-screw injection systemFigure 3 The plunger injection systemThe screw acts as a combination injection and plasticizing unit. As the plastic is fed to the rotating screw, it passes through three zones as shown: feed, compression, and metering. After feed zone , the screw-flight depth is gradully reduced, forcing the plastic to compress. The work is converted to heat by shearing the plastic, making it a semifluid mass. In the metering zone, additional heat is applied by conduction from the barrel surface. As the chamber in front of the screw becomes filled, it forces the screw forward and injects the fluid plastic into the closed mold. An antiflowback valve precents plastic under pressure from escaping back into the screw flights.The clamping force that a machine is capable of exerting is part of the size designation and is measured in tons. A rule-of-thumb can be used to determine the tonnage required for a particular job. It is based on two tons of clamp force per square inch of projected area. If the flow pattern is difficult and the parts are thin, this have to go to three or four tons.Many reciprocating-screw machines are capable of handing thermosetting plastic materials. Previously these materials were handled by compression or transfer molding. Thermosetting materials cure or ploymerize in the mold and are ejected hot in the rang of 190-210. Thermoplastic parts must be allowed to cool in the mold in order to remove them without distortion. Thus thermosetting cycles are can be faster. Of course the mold muse be heated rather chilled, as with thermoplastics.The process consists of feeding a plastic compound or granular form to a hopper through metering and melting stages ang then injecting it into a mold. Ways of injection molding plastic material are shown in Figure 3. The oldest is the single-stage plunger method. When the plunger is drawn back, raw material through the heating cylinder where it is softened and squired under pressure into mold. The single-stage reciprocating screw system has hopper into the heating cylinder. When enough material has been prepared, the screw stops turning and is driven forward as a plunger to ram the change into the die. In a two-stage, the material is plasticized in one cylinder, and a definite amount transferred by a plunger or screw into a shot chamber from which a plunger injects it into the mold.An injection molding machine heats to soften, molds, and cools to harden a thermoplastic material. Operation-temperature is generally between 150 and 380with full pressure usnally over 35 and up to 350Mpa (5000 to 50,000psi). The mold is water cooled. The molded piece and sprue are withdrawn from the injection side and ejected from the other side when the mold is opened. The mold is then closed and clamped to start another cycle. Thermosetting plastic can be injection molded but have to be polymerized and molded before they set in the machine. This may be done in a reciprocating