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资料来源：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：P43P49文 章 译 名： 压缩和转移模具 模具设计及制造英语 Compression 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.压缩和转移模具译文：压缩成型 压缩成型是基本的成型过程，其中将适量的材料引入加热的模具中，随后在 压力下将其关闭。 通过加热软化的模制材料形成具有模腔几何构型的连续物质。进一步加热（热固性塑料）导致模塑材料硬化。如果热塑性塑料是模塑材料，则通过冷却模具来完成硬化。 图 2-6 显示了压缩成型的类型。这里将模塑料放置在加热的模具中。塑料复合物软化并变成塑料后，冲头向下移动并通过压力将材料压缩到所需密度。当 模具接近其最终位置时，一些多余的材料将从模具流出（垂直闪光）。 持续的热量和压力产生使化合物硬化的化学反应。聚合或固化所需的时间主要取决于产物的最大横截面和模塑料的类型。时间可能不到一分钟，或者可能需要几分钟时间才能将零件从腔体中弹出。 由于塑料材料直接放入模腔内，所以模具本身可以比用于其他模塑工艺的模 具更简单。Gates和sprues是不必要的。这也节省了材料，因为修剪的浇口和浇口会完全损失热固性塑料。用于压缩成型的压机通常是立式液压机。大型印刷机可能需要一位操作员的全面关注。但是，一个操作员可以操作几台较小的印刷机。 这些印刷机位置便利，因此操作员可以轻松地从一个移动到另一个。当他再次接触特定媒体时，该模具将准备打开。 在热和压力下硬化的热固性塑料适用于压缩成型和传递模塑。用这些方法模塑热塑性材料是不实际的，因为模具必须交替加热和冷却。为了硬化并从模具中排出热塑性部件，需要冷却。 传递模塑 传递模塑工艺包括将一定量的材料（挤出物或预热的预成型件）放入称为锅 的腔室中。压机启动并向上移动，与浮动板接触，从而关闭模具的两半。 两个板的进一步行程导致柱塞与罐中的材料接触。然后材料被迫直接通过浇口或浇口进入封闭的空腔。当空腔被完全填满时，多余的材料在罐中形成剔除（多余的废料）。部件固化后，打开压机，浮板和底板与顶板分离，露出柱塞并剔除。随着印刷机行程的继续，浮板运动通过固定在顶板上的带子停止。 这将模具的两个半部分分开，并且该部分保持在下半部分，直到挖空销拔出。由于该工艺要求材料的单次装料（喷丸）从罐转移到腔，所以称为罐式转移（图 2-7）。操作人员需要从痰壶柱塞上取下剔除器，取下零件或部件，清洁模具，将预热材料注入罐区并启动压机。 在转移模具申请专利之后相对较短的时间; 转印机开发。 它们包括一个位于压力机顶部或底部的主夹紧滑块，一个或多个辅助滑块安装在夹紧滑块对面。夹紧顶杆激活可移动压板。辅助压头固定在固定压板上，用于启动一个柱塞，该柱塞在传输套筒或气缸内移动。对于模具下半部的柱塞，该过程包括将预热的预成型件或挤出物放置在传送套筒或圆筒中，关闭模具的两半，并启动柱塞，该柱塞迫使材料通过通道被称为流道，并通过限制的门区进入半模。当空腔完全填充时，多余的材料在柱塞的表面保持为剔除状态。材料固化后，压机在分模线处打开，零件被移除，浇口，浇道和剔除。这种成型工艺通常被称为浸入式转移法。 典型的模具结构如图 2-8 所示。如果底部柱塞传递模具被构造，则操作可以是自动的，因为辅助装置可以装载预热的预成型件，并且卸载盘可以用于接收和分离部件，流道，闸门和柱塞剔除。在所有其他情况下，每台印刷机都需要操作员。 两级柱塞传送过程需要传统设计的液压或肘节顶部夹钳压力机，带有底部传 送滚筒和柱塞。加热桶内的往复螺丝水平安装在印刷机旁边。颗粒物料在料筒中被预热，并通过其侧面的开口排入转移圆筒或套筒。材料以与柱塞传递模塑工艺中所述相同的方式流动。 两级柱塞传输模具的结构与柱塞传输相似，只是需要特殊的传输圆柱体或套 筒和柱塞。 图2-7热固器的罐型或浇口型传热成型 图2-8热固性塑料柱塞传递成型压缩模具 通过提供热量和压力，热固性压缩模制化合物可以模制成具有优异刚性和形 状保持的制品。除了成型材料外，模具本身也非常重要。 当今的压缩模具仅通过电加热。手工借助填充装置或颗粒将模具装载模塑 料。 对于每个新生产的模具都应该强制施工图纸。可以预先考虑关于模具的任 何新观点，例如模具结构的稳定性，最佳加热，辅助脱模和喷射，例如载玻片， 分裂腔，型芯等。通过高效的模具生产以及对完成的模具进行更少的改造和更少的精加工工作，这些图纸的成本将超过合理程度。 更精确的细节被纳入设计中，避免了更多的精加工工作，例如规定所需的拔模角度和尺寸公差。 由于对压缩模具的改造总是非常昂贵，因此细节图完全清晰是特别重要的。 模具必须具有足够坚固和刚性的结构，以使其能承受压缩成型所需的高压。外墙应该只是稍微有些弹性。如果模具过于柔软，则结果可能是两个半模在打开时卡住，或者弹出很麻烦。高壁部件可能在侧壁上施加总压缩压力。模具的底部必须很好地支撑以吸收施加在其上的压力并避免挠曲。 由于材料成本与工资相比相对较低，因此可以使模具结构坚固而不会导致成 本显着增加。除了更高的刚性外，更高的钢材含量确保更均匀的温度分布和温度控制。模塑区域的良好抛光对于无故障排出以及为模制品提供令人满意的表面是绝对必要的。模具表面应该是玻璃坚硬的，以便它能够承受模压材料在压力下流动时施加的磨损效应并且因此保持其抛光。另一方面，由于模具壁和肋条的轻微变形是不可避免的，所以工具钢需要具有坚韧的芯。建议使用渗碳钢作为赋形模具零件。这已经在塑料加工行业的模具制造中得到了证明。模具表面必须耐受化学物质的不断侵袭，这对于某些类型的压缩模塑化合物尤其普遍。模具可以通过成型表面的铬镀层来防止化学侵蚀和摩擦磨损。 另一个重要的要求是模具由尽可能少的互锁部件组成。由于所采用的高压 缩压力可能导致变形，因此将多个部件相互配合总是充满危险。如果不能避免使用刀片，那么插入件必须始终与压力一致地安装到压模中，并且永远不会穿过它。 压缩模具基本上由上部和下部组成。在正常情况下，下半部分安装在压机的工作台上，上半部分安装在冲压机上。两个半模均由硬化销钉引导。非对称部件会在模具上产生较大的单侧压力负载。他们需要通过特别指南进行赔偿。 弹射通常需要特殊设备。平盘或盘子等部件很容易通过压缩空气排出，机器上已有该压缩空气用于清洁模具上的闪蒸和材料残留物。在所有其他情况下，可以通过顶针或肋条进行喷射。对于具有多个纤维和开口的零件，由于材料收缩，顶针是必不可少的。 转移模具 热固性模塑料可以通过传递模塑工艺加工。然而，热注射筒不应该含有多个部件的材料储备，因为材料只能在热量中固化。如果材料体积与待生产零件的体积以及浇口相匹配，则热固性塑料只能进行传递模塑。用已经在高频炉中预干燥的材料进行模制将是有利的，仅在其被计量到传送滚筒中之前才从烘箱中取出。 在这种情况下，最有利和最准确的计量类型与传统压缩成型一样也 可通过预压缩颗粒实现。由于它们已经具有一定的密度，所以可以给注射缸的尺寸带来更大的余地，这对注塑压力具有决定性的影响。由于材料通过小喷嘴孔注入，所以可以实现非常均匀的热渗透。而在压缩成型中即使预热好的丸粒材料也不易流动，完全塑化的材料在传递模塑中进入腔体。材料另外被加热的模具壁加热。因此，热渗透优于压缩成型。传递模塑工艺所需的固化时间要比压缩模塑法短得多。由于部件的性质，必须使用长芯时，传递模塑工艺也是特别有利的。在这种情况下，他们对单向压力的指导和支持比压塑更容易设计。这也是为什么可能在敏感金属部件周围注射的原因。通过相应地布置滑道，芯和插入件必须有利地定位在材料的流动路径中。 传递模具所要满足的要求与压缩模具的要求基本相同。由于所需的注塑压 力在注塑缸中的压力约为1,000至1,800 巴，但在模腔内稍低，虽然仍高于普通压缩成型，但模具的结构必须更牢固。由于模具在注射过程中已经被完全夹紧， 因此必须特别注意形状赋予腔的排气。如果没有观察到，空隙和不完整的部件将导致与注塑热塑性塑料材料时所经历的相同的方式。但是，由于不能像在标准压缩模具上那样进行模具的排气，所以必须定位和确定通风孔的尺寸，使得气体能够从材料中逸出而不会使材料堵塞通风管道。 传送模具的构造与压缩模具的构造的不同之处在于不存在填充室。这已被 位于模具中心的注射缸和活塞所取代。一种是根据以下两种基本类型的传递模 具进行区分：用顶部注射缸和活塞传递模具。这些模具可以在标准压力机上操作，在这种情况下，打开冲程的限制当然要考虑在内。 用底部注射缸和活塞传输模具。对于这种结构的模具，必须使用带有单独注射装置的压力机。这通常是一台带有液压缸的压力机，液压缸安装在模具台下方的中央，用于操作与机器上的定时器（传递模塑）互锁的注射活塞。成型模具部件和模腔的加工方式与标准加压模具相同。 14
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