压缩和转移模具外文文献翻译、中英文翻译

外文资料翻译资料来源：书籍文章名：Compression and Transfer Molds书刊名：English for Die & Mould Design and Manufacturing作 者：JianXiong Liu 出版社：北京大学出版社，2006章 节：2.4 Compression and Transfer Molds页 码：P43P49Compression and Transfer Molds外文原文：Compression Molding Compression molding is the basic forming process where an appropriate amount of material is introduced into a heated mold, which is subsequently closed under pressure. The molding material, softened by heat, is formed into a continuous mass having the geometrical configuration of the mold cavity. Further heating (thermosetting plastics) results in hardening of the molding material. If thermoplastics are the molding material, hardening is accomplished by cooling the mold. Fig. 2-6 illustrates types of compression molding. Here the molding compound is placed in the heated mold. After the plastic compound softens and becomes plastic, the punch moves down and compresses the material to the required density by a pressure. Some excess material will flow (vertical flash) from the mold as the mold closes to its final position. Continued heat and pressure produce the chemical reaction which hardens the compound. The time required for polymerization or curing depends principally upon the largest cross section of the product and the type of molding compound. The time may be less than a minute, or it may take several minutes before the part is ejected from the cavity. Since the plastic material is placed directly into the mold cavity, the mold itself can be simpler than those used for other molding processes. Gates and sprues are unnecessary. This also results in a saving in material, because trimmed-off gates and sprues would be a complete loss of the thermosetting plastic. The press used for compression molding is usually a vertical hydraulic press. Large presses may require the full attention of one operator. However, several smaller presses can be operated by one operator. The presses are conveniently located so the operator can easily move from one to the next. By the time he gets around to a particular press again, that mold will be ready to open. The thermosetting plastics which harden under heat and pressure are suitable for compression molding and transfer molding. It is not practical to mold thermoplastic materials by these methods, since the molds would have to be alternately heated and cooled. In order to harden and eject thermoplastic parts from the mold, cooling would be necessary.Transfer Molding The transfer molding process consists of placing a charge of material (extrudate or preheated preform) into the chamber, referred to as the pot. The press is activated and travels upward making contact with the floating plate, which closes the two halves of the mold. Further travel of both plates causes contact of the plunger with the material in the pot. Material is then forced through a sprue or sprues directly into the closed cavity. When the cavity is completely filled, the excess material forms a cull in the pot (excess waste material). After the part is cured, the press is opened and the floating plate and bottom plate separate from the top plate, exposing the plunger and cull. As the press travel continues, the floating plate motion is stopped by straps fastened to the top plate. This separates the two halves of the mold, and the part remains in the lower half until knockout pins extract it. Since the process requires that the single charge (shot) of material be transferred from the pot to the cavities, it is known as pot-type transfer (Fig. 2-7). An operator is needed to remove the cull from the pot plunger, remove the part or parts, clean the mold, charge a single shot of preheated material into the pot area, and activate the press. A relatively short time after the patenting of the transfer mold; transfer presses were developed. These consist of a main clamping ram located at either the top or the bottom of the press, with one or more auxiliary rams mounted opposite the clamping ram. The clamping rams activate the movable platen. The auxiliary rams are fastened to the stationary platen and are used to activate a plunger, which moves within a transfer sleeve or cylinder. For the plunger in the bottom half of the mold, the process consists of placing preheated preforms or extrudates in the transfer sleeve or cylinder, closing the two halves of the mold, and activating the plunger, which forces material out through channels, known as runners, and through the restricted gate area into the mold halves. When the cavities are completely filled, the excess material remains as a cull at the face of the plunger. After the material is cured, the press is opened at the parting line, parts are removed and the gate, runner and cull. This molding process is commonly called the plun- ger-transfer method. A typical mold construction is shown in Fig. 2-8. If the bottom plunger- transfer mold is constructed, the operation may be automated, since auxiliary devices may load the preheated preforms, and unloading trays may be utilized to receive and separate the parts, runner, gates, and plunger culls. In all other cases an operator is required for each press. The two-stage plunger transfer process requires a conventionally designed hydraulic or toggle top clamp press, with a bottom transfer cylinder and plunger. A reciprocal screw within a heated barrel is mounted horizontally next to the press. The granular material charge is preheated in the barrel and is discharged into the transfer cylinder or sleeve through an opening in its side. The material flow from the same way as described in the plunger-transfer molding process. The two-stage plunger-transfer molds are similar in construction to the plunger transfer, except that a special transfer cylinder or sleeve and plunger are required.Compression Molds Thermosetting compression-molding compounds can be molded into articles of excellent rigidity and shape retention by supplying heat and pressure. Apart from the molding material, the mold itself is of great importance. Compression molds nowadays are heated electrically exclusively. The mold is loaded with molding compound, by hand, with the aid of a filling device, or with pellets. A construction drawing should be mandatory for every mold to be newly produced. Any new ideas concerning the mold, such as stability of the mold construction, optimum heating, aids to demolding and ejection, e.g., slides, split cavities, cores, etc., can be included in advance and given due consideration. The cost of such drawings will be more than justified as a rule by the ensuing efficient mold production and by fewer alterations and less finishing work on the completed mold. The more accurately details are incorporated in the design, the more finishing work is avoided, e.g., specification of the draft angle required and dimensional tolerances. Because alterations to compression molds are always very expensive, it is of particular importance that the detail drawings be completely clear. The mold must be of sufficiently solid and rigid construction to enable it to withstand the high pressures required with compression molding. The outer walls should be only slightly flexible. If the mold is too flexible, the result could be jamming of the two mold halves on opening, or troublesome ejection. High-walled parts may well exert the total compression a pressure on the side walls. The bottom of the mold must be well supported to absorb the pressure exerted on it and to avoid deflection. As the material costs are comparatively low compared to wages, one can afford to have the mold solidly constructed without incurring any significant increase in cost. The higher steel content ensures a more uniform temperature distribution and temperature control, apart from the greater rigidity. A good polish of the molding areas is absolutely essential for trouble-free ejection and to give a satisfactory surface to the molded article. The mold surface should be glass-hard so that it can withstand the wearing effect the molding material exerts when flowing under pressure and so that it retains its polish. On the other hand, the tool steel needs to possess a tough core, as a slight distortion of the mold walls and the ribs is unavoidable. It is recommended to use a carburizing steel for the shape-giving mold parts. This has already proved itself in the construction of molds for the plastics-processing industry. The mold surface must be resistant to constant attack by chemicals, which is particularly prevalent with certain types of compression-molding compounds. A mold can be protected from chemical attack and frictional wear by chrome plating of the molding surfaces. A further important requirement is that the mold consists of as few interlocking parts as possible. The fitting of several parts into each other is always fraught with danger because of the possible distortion caused by the high compression pressures employed. Should it not be possible to avoid working with inserts, it is then essential that the inserts always be fitted into the compression mold in line with the pressure and never across it. A compression mold basically consists of an upper and a lower part. In normal cases the lower half is fitted to the table of the press and the upper half to the ram. Both mold halves are guided by hardened dowels. Asymmetrical parts cause large one-sided pressure loads to be exerted on the mold. They require compensation through special guides. Ejection usually calls for special equipment. Parts such as flat dishes or plates are easily ejected by compressed air, which is already available on the machine for cleaning flash and material residue from the molds. In all other cases, ejection by ejector pins or ribs is feasible. For parts with a multitude of fibs and openings, ejector pins are essential because of the material shrinkage.Transfer Molds Thermosetting molding compounds can be processed by the transfer molding process. The hot injection cylinder, however, should not contain material reserves for several parts since the material would, only cure in the heat. Thermosets can only be transfer molded if the material volume corresponds to the volume of the part to be produced plus the sprue. It would be expedient to mold with material that has been predried in a high-frequency oven, to be taken out of the oven only just before it is metered into the transfer cylinder. The most favorable and most accurate type of metering in this caseas with conventional compression moldingisalso achieved with precompressed pellets. As they are already of a certain density, greater leeway can be given to the dimensions of the injection cylinder, which has a decisive influence on the injection pressure required. Because the material is injected through a small nozzle bore very uniform heat permeation is achieved. Whereas in compression molding-even with well prewarmed pelletsthe material does not flow very easily, thoroughly plasticized material enters the cavities in transfer molding. The material is additionally warmed by the heated mold walls. Heat permeation is therefore better than with compression molding. A considerably shorter cure time is needed for the transfer molding process than for the compression molding method. The transfer molding process also is of particular advantage when long cores have to be employed due to the nature of the parts. In this instance, their guidance and support against unilateral pressure is considerably easier to design than for compression molding. This is also the reason why injection around sensitive metal parts is possible. The cores and the inserts must be advantageously positioned in the flow path of the material by arranging the runners accordingly. The requirements to be met by a transfer mold are basically the same as those for a compression mold. Due to the injection pressure required, which lays around 1,000 to 1,800 bar in the injection cylinder but is somewhat lower inside the mold cavity, although still higher than with ordinary compression molding, the mold must be more solidly constructed. Particular care must be taken with the venting of the shape-giving cavities as the mold is already fully clamped during injection. If this is not observed, voids and incomplete parts will result in the same manner as can be experienced when injection molding thermoplastics material. However, as venting of the mold is not possible in the same way as it is done on standard compression molds, air vents have to be positioned and dimensioned so that they permit the gases to escape from the material without allowing the latter to clog up the venting channels. The construction of a transfer mold differs from that of a compression mold in that the charging chamber does not exist. This has been replaced by an injection cylinder and piston positioned in the center of the mold. One differentiates between the two basic types of transfer mold as follows: transfer mold with top injection cylinder and piston. These molds can be operated on standard presses, in which case the restriction in the opening stroke has of course to be taken into consideration. Transfer mold with bottom injection cylinder and piston. For molds of this type of construction a press with a separate injection unit is compulsory. This is usually a press with a hydraulic cylinder mounted centrally underneath the mold table to operate the injection piston, which is interlocked with the timers on the machine (transfer molding). The shape-forming mold parts and cavities are executed in the same manner as those on standard compression molds.压缩和转移模具外文原文:压缩成型 压缩成型是一种基本的成型过程，在加热的模具中加入适量的材料，然后在压力下关闭。成型材料经热软化后，形成具有模腔几何结构的连续质量。进一步加热(热固性塑料)会导致模塑材料硬化。如果热塑性塑料是成型材料，则通过冷却模具来实现硬化。 图2-6说明了压缩成型的类型。在这里，模塑化合物被放置在加热的模具中。当塑料混合物变软成为塑料后，冲头向下移动，通过压力将材料压缩到要求的密度。当模具接近最终位置时，一些多余的材料会从模具中流出(垂直闪光)。 持续的热和压力产生化学反应，使化合物变硬。聚合或固化所需的时间主要取决于产品的最大横截面和成型化合物的类型。时间可能少于一分钟，或者可能需要几分钟才能将零件从空腔中喷射出来。 由于塑料材料直接放置在模具型腔中，因此模具本身可以比其他成型工艺更简单。盖茨和云杉是不必要的。这也节省了材料，因为修剪过的门和云杉将完全失去热固性塑料。用于压缩成型的压力机通常是立式液压压力机。大型印刷机可能需要一个操作员的全力关注。然而，一些较小的印刷机可以由一个操作员操作。冲压机位置方便，操作人员可以很容易地从一个冲压机移动到另一个冲压机。当他再次来到一个特定的出版社时，那个模子就可以打开了。 热固性塑料在高温和高压下变硬，适用于压缩成型和传递成型。用这些方法制作热塑性材料是不实用的，因为模具必须交替加热和冷却。为了从模具中硬化和喷射热塑性部件，需要冷却。传递模塑法 转移成型过程包括将材料(挤出或预热的预成型)放入被称为“锅”的腔内，按压被激活并向上移动，与浮动板接触，浮动板关闭模具的两个部分。 两个板块的进一步移动导致柱塞与锅内材料的接触，然后材料通过浇口或云杉直接进入封闭的腔内。当空腔被完全填满时，多余的材料就会在锅中形成一个挑出物(多余的废料)。固化后，打开压力机，将浮板和底板与顶板分开，露出柱塞和挑刀。当印刷机继续前进时，浮板运动被固定在顶部板上的皮带停止。 这将模具的两个部分分开，部分保持在下半部分，直到敲除针将其取出。由于这一过程要求材料的单个电荷(镜头)从罐子转移到空腔，因此被称为波特型转移(图2-7)。需要操作人员从柱塞中取出cull，取出部分或部件，清洗模具，将一针预热过的材料装入罐区，并激活压力机。 在较短的时间内对转移模进行专利申请;按开发转移。这些包括位于压力机顶部或底部的主夹紧闸板，以及安装在夹紧闸板对面的一个或多个辅助闸板。夹紧公羊激活可移动的压板。辅助公羊被固定在固定的压板上，用来启动一个活塞，它在一个传递套筒或气缸内移动。柱塞的底部一半的模具,将预热的过程由预先形成或挤出物转让套筒或圆柱,关闭的两半模具,并激活柱塞,这迫使材料通过通道,称为跑步者,并通过限制成模具半门区域。当空腔被完全填满时，多余的物质会在柱塞的表面形成一个挑口。材料固化后，在分割线处打开压力机，拆下零件和浇口，浇口和切刀。这种成型过程通常被称为plun- go -transfer方法。典型的模具结构如图2-8所示。如果建立了下柱塞-转移模，操作可能是自动化的，因为辅助装置可以装入预热过的预制件，卸载托盘可以用来接收和分离零件、浇口、浇口和柱塞。在所有其他情况下，每个压力机都需要一个操作员。 两个阶段的柱塞传递过程需要一个常规设计的液压或切换顶部夹紧压力机，底部输送气缸和柱塞。加热桶内的一个反向螺丝水平安装在压力机旁。颗粒物质电荷在筒体中预热，通过筒体侧面的开口排放到传递筒或套筒中。在柱塞传递成型过程中，材料的流动方式与描述的相同。 两级柱塞-转移模在结构上与柱塞转移模相似，只是需要一个特殊的转移筒或套筒和柱塞。压缩模具 通过提供热量和压力，热固性压缩成型化合物可以被模塑成具有极好的硬度和形状保持性的物品。除了模具材料外，模具本身也很重要。 现在的压缩模只有电加热。模具是用手工，在填充装置的帮助下，或用微丸填充。 每一个新生产的模具都必须有施工图。任何关于模具的新想法，如模具结构的稳定性，最佳的加热，辅助脱模和顶出，如滑梯，开孔，芯等，都可以预先包含并给予适当的考虑。这类图纸的成本将被证明是合理的，作为一个规则，后续有效的模具生产，减少对已完成的模具的改造和完成工作。在设计中加入的细节越精确，就越避免了精加工工作，例如要求的牵伸角的规格和尺寸公