外文資料翻譯 Mold Cooling One fundamental principle of injection molding is that hot material enters the mold, where is cools rapidly to a temperature at which it solidifies sufficiently to retain the shape of the impression. The temperature of the mold is therefore important as it governs a portion of the overall molding cycle. While the meld flows more freely in a hot mold, a greater cooling period is required before the solidified molding can be ejected. Alternatively, while the meld solidifies quickly in a cold mold it may not reach the extremities of impression. A compromise between the two extremes must therefore be accepted to obtain the optimum molding cycle. The operating temperature for a particular mold will depend on a number of factors which include the following: type and grade of material to be molded; length of flow within the impression; wall section of the molding; length of the feed system, etc. It is often found advantageous to use a slightly higher temperature than is required just to fill the impression, as this tends to improve the surface finish of the molding by minimizing weld lines, flow marks and other blemishes. To maintain the required temperature differential between the mold and plastic material, water (or other fluid) is circulated through holes or channels within the mold. These holes or channels are termed flow-ways and the complete system of flow ways is termed the circuit. During the impression filling stage the hottest material will be in the vicinity of the entry point, i.e. the gate, the coolest material will be at the point farthest from the entry. The temperature of the coolant fluid, however, increases as it passes through the mold. Therefore to achieve an even cooling rate over the molding surface it is necessary to locate the incoming coolant fluid adjacent to hot molding surface and to locate the channels containing heated coolant fluid adjacent to cool molding surface. However as will be seen from the following discussion, it is not always practicable to adopt the idealized approach and the designer must use a fair amount of common sense when laying out coolant circuits if unnecessarily expensive molds are to be avoided. Units for the circulation of water (or other fluid) are commercially available. These units are simply connected to the mold via flexible hoses, with these units the mold’s temperature can be maintained within close limits. Close temperature control is not possible for using the alternative system in which the mold is connect to a cold water supply. It is the mold designer’s responsibility to provide an adequate circulating system within the mold. In general, the simplest systems are those in which holes are bored longitudinally through the mold plates. However, this is not necessarily the most efficient method for a particular mold. When using drillings for the circulation of the coolant, however, these must not be positioned too close to the impression (say closer than 16mm) as this is likely to cause a marked temperature variation across the impression, with resultant molding problems. The layout of a circuit is often complicated by the fact that flow ways must not be drilled too close to any other holes in the same mold plate. It will be recalled that the mold plate has a large number of holes or recesses, to accommodate ejector pins, guide pillars, guide bushes, sprue bush, inserts, etc. How close it is safe to position in a flow way adjacent to another hole depends to a large extent on the depth of the flow way drilling required. When drilling deep flow ways there is a tendency for the drill to wander off its prescribed course. A rule which is often applied is that for drillings up to 150mm deep the flow way should not be closer than 3mm to any other hole. For deeper flow ways this allowance is increased to 5mm. To obtain the best possible position for a circuit it is good practice to lay the circuit in at the earliest opportunity in the design. The other mold items such as ejector pins, guide bushes, etc. can then be positioned accordingly. Mold Cavities and Cores The cavity and core give the molding its external shapes respectively, the impression imparting the whole of the form to the molding. When then proceeded to indicate alternative ways by which the cavity and core could be incorporated into the mold and we found that these alternatives fell under two main headings, namely the 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 mold 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 much for multi-impression molds as there are other factors such as alignment which must be taken into consideration. Of the many manufacturing 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 tool, or the precision investment 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 or 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 containing 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 inset-bolster 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 machining, 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 inserts. These are then inserted and securely fitted into holes in a substantial block or plate of steel called a bolster. 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 insert 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 the single impression or a multi-impression mold is desire, the cost of making the mold, etc. It can therefore be said that in general, once the characteristics of the mold required 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 integer design is to 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 cooling system than the insert-bolster design. It should be borne in mind that local inserts can be judiciously used to simplify the general manufacture of the mold impression. For multi-impression molds the choice is not so clear-cut. In the majority of cases the insert-bolster method of construction is used, the ease of manufacture, mold alignment, and resulting lower mold costs being he overriding factors affecting the choice. For components of very simple form it is often advantageous to use one design for one of the mold plate and the alternative design for the other. For example, consider a multi-impression mold for a box-type component. 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 could be of insert-bolster design which will simplify machining of the plate and allow for adjustments for mold alignment. Feed System It is necessary to provide a flow-way in the injection mold to connect the nozzle (of the injection machine) to each impression. This flow-way is termed the feed system. Normally the feed system comprises a sprue runner and gate. These terms apply equally to the flow-way itself, and to the molded material which is removed from the flow-way itself in the process of extracting the molding. A typical feed system for a four-impression, it is seen that material passes through the sprue, main runner, branch runners and gate before entering the impression. As the temperature of molten plastic is lowered while going through the sprue and runner, the viscosity will rise; therefore, the viscosity is lowered by shear heat generated when going through the gate to fill the cavity. It is desirable to keep the distance that the material has to travel down to a minimum to reduce pressure and heat losses. It is for this reason that careful consideration must be given to the impression layout and gate’s design. 1. Sprue A spru is a channel through to transfer molten plastic injected from the nozzle of the in injector into the mold. 2. Runner A runner is a channel that guides molten plastic into the cavity of a mold. 3. Gate A gate is an entrance through which molten plastic enters the cavity. The gate has the following functions: restricts the flow and the direction of molten plastic; simplifies cutting of a runner and molding to simplify finishing of parts; quickly cools and solidifies to avoid backflow after molten plastic has filled up in the cavity. 4. Cold Slug Well The purpose of the cold slug well, shown opposite the sprue, is theoretically to receive the material that has chilled at the front of the nozzle during the cooling and ejection phase. Perhaps of greater importance is the fact that it provides positive means whereby the sprue can be pulled from the sprue bush for ejection purposes. The sprue, the runner, and the gate will be discarded after a part is complete. However, the runner and the gate are important items that affect the quality or the cost of pats. 模具冷卻系統(tǒng) 注塑生產(chǎn)的基本原理是把高溫熔體注入模具型腔，熔體在型腔內(nèi)迅速冷卻到固化溫度，并保持一定形狀。由于模具溫度在一定程度上控制塑件的整個成型周期，因此在生產(chǎn)中非常重要。熔體在高溫模具內(nèi)流動順暢，但固化塑件推出前，一定的冷卻階段是比不可少的，另一方面，熔體在溫度較低額模具中固化較快，又可能造成塑件末端填充不滿。因此必須在這兩種對立的條件中選擇一個平衡點，以獲得最佳的生產(chǎn)循環(huán)。 模具的工作溫度與幾種因素有關(guān)，包括成型材料的等級與分類、熔體在型腔內(nèi)的流動路線、塑件壁厚以及澆注系統(tǒng)長度等。使用比充模要求稍高的溫度注塑比較有利，這樣生產(chǎn)的塑件熔接痕少、流痕不明顯，其他缺陷也較少，因此可提高塑件表面質(zhì)量。 為保持模具和塑料熔體之間所需的溫差，水（或其他液體）在模具上的通道或通孔中循環(huán)。這些通道或通孔稱為流道或水道，整個水道系統(tǒng)稱為冷卻循環(huán)系統(tǒng)。 在充模階段，溫度最高的熔體位于進入口，即澆口附近；溫度最低的熔體位于距進入口最遠的地方。冷卻介質(zhì)在模具內(nèi)循環(huán)時，介質(zhì)溫度將升高。因此，為使塑料表面獲得均勻的冷卻速率，冷卻通道的入口應(yīng)開設(shè)在高溫塑件附近，受熱后冷卻介質(zhì)溫度升高，出口開設(shè)在低溫塑件附近，設(shè)計者往往憑借經(jīng)驗設(shè)計冷卻水道。 冷卻水（或其他冷卻介質(zhì)）回路所需的部件在市場上就可以買到。這些部件通過軟管與模具直接連在一起，通過這些部件形成的冷卻回路，模具溫度便控制在要求的范圍內(nèi)。但是，使用這種直接與冷水相連的冷卻回路是不可能精確的控制模具的溫度的。 為模具提供合適的冷卻系統(tǒng)是設(shè)計者的責任。通常，最簡單的冷卻系統(tǒng)是在模板上縱向鉆出通孔。然而對于精密模具，這不是最有效的冷卻方法。 使用鉆孔的方法加工冷卻水道時，冷卻通道與塑件距離一定不能太近（即距離小于16mm），如果距離太近，有可能引起整個型腔的溫度發(fā)生顯著的變化，使塑件出現(xiàn)問題。 冷卻水道不能距離同一模板上任何其他的孔道太近，這使得冷卻回路的布局通常比較復雜。，模板上存在大量的孔道或凹陷，用來安裝推桿、導柱、導套、澆口套以及鑲件等。冷卻水道與其他孔道之間的安全距離在很大程度上取決于所需冷卻水道的鉆入深度。流道深度較深時， 鉆頭有偏離預定加工路線的趨勢。常用的規(guī)則是鉆入深度達到150mm的冷卻水道與其他孔道距離不小于3mm，比這更深的流道所需的距離增加到5mm。 為獲得最佳的冷卻回路，設(shè)計初期就考慮冷卻回路的位置不失為一種好方法。其他模具零件，如推桿、導套等，可相應(yīng)的確定安裝位置。 型腔和型芯 模具的型腔和型芯分別形成塑件內(nèi)部和外部形狀，型腔形狀決定了塑件外部形狀，接下來我們簡要說明選擇哪種方式把型腔和型芯安裝在模具中，這些方式可歸納為兩大類，即整體式和鑲拼式。另一種組成型腔的方式是加入拼塊或滑塊。 當型腔或型芯由一塊大的鋼板或剛塊加工而成，或者鑄成一體，不需使用支承板件而形成一塊模板時，就構(gòu)成整體式型腔板或型芯板。這種設(shè)計因具有強度高、尺寸小和成本低的特性，而主要應(yīng)用在單型腔模具中。整體式型腔和型芯一般不用在多用于多型腔模具中，因為多型腔模具設(shè)計時必須考慮一些其他因素，例如安裝組合鑲件等。 在模具制造的眾多方法中，用于加工整體式型腔板或型芯板的方法主要有兩種：使用傳統(tǒng)機床對粗鍛鋼胚料直接加工，或利用精確的熔模鑄造技術(shù)將胚料加工成型腔和型芯。用于制造型腔和型芯的胚料經(jīng)常需要特殊工藝的處理。 通常，4.25%的鎳鉻鉬合金鋼（BS970-835M30）是生產(chǎn)整體模板的制定材料，選用這種材料時采用直接的機加工方式。 精確的熔模鑄造常常用來加工高鉻鋼。 對于成型部模具和位復雜的多腔模，也像整體式模具那樣用一塊鋼材加工型腔和型芯并不容易。如果采用整體式結(jié)構(gòu)，則加工順序和操作過程將變得非常復雜，成本也高，因此鑲拼式裝配方式替代了整體式。 鑲拼式型腔由小鋼塊加工而成。加工后的小鋼塊作為鑲件，形成型芯部分的稱為型芯嵌塊，相反的，形成型腔部分的稱為型腔嵌件。然后，把這些嵌件牢固的安裝在被稱為墊板的孔中，墊板有實心鋼板或鋼塊加工而成。這些安裝孔有的是由墊塊的局部凹陷形成，有的是在墊板上直接加工而成的。在后一種方式中，墊板后部還要加一塊模板，起加固作用，確保鑲件安裝到位。 整體式和鑲拼式結(jié)構(gòu)均有優(yōu)點，這取決于塑件尺寸和形狀、模具的復雜程度、所需的是單型腔模具還是多型腔模具以及模具的制造成本等。通常，塑件的形狀、尺寸等特性確定后，采用哪種形式的型腔和型芯就已經(jīng)確定了。 在不同的章節(jié)中，我已經(jīng)討論過型腔和型芯的安裝方式所涉及的問題，例如成本等。但為使讀者在處理特殊問題時更容易知道重點所在，我們將用一定的章節(jié)再次討論每種結(jié)構(gòu)優(yōu)缺點的對比。 毫無疑問，對于單型腔模具，無論是簡單還是復雜，整體式型腔是首選方式。若選擇整體式，則模具的強度高、體積小、成本低，而冷卻系統(tǒng)的設(shè)計卻比鑲拼式簡單、方便。設(shè)計時需要常記于心的是，適當?shù)氖褂描偧梢院唵位＞咝颓坏募庸ぶ圃祀y度。 對于多型腔模具選擇哪種方式不是很明顯。大多數(shù)多型腔模具采用鑲拼式結(jié)構(gòu)，這種結(jié)構(gòu)加工簡單、裝配容易、模具成本低，這些是影響選擇哪種結(jié)構(gòu)形式的最重要因素。一種非常簡單且具有很多優(yōu)點的設(shè)計形式是采用一種形式設(shè)計模板，而采用另一種形式設(shè)計模具的其他部分。例如，采用箱型組件設(shè)計多型腔模具。型腔板設(shè)計成小型整體式模板，以滿足模具高強度的要求；型芯板則設(shè)計成鑲拼式，可以簡化模板加工過程，并且能根據(jù)模具需要進行調(diào)整。 澆注系統(tǒng) 在注塑模具中，連接注塑機噴嘴和各個分流道型腔的流動通常是非常必要的，這種進料通道稱為澆注系統(tǒng)。 通常，澆注系統(tǒng)由主流道、分流道和澆口組成。這些術(shù)語應(yīng)用在相應(yīng)的進料通道本身，以及取出塑件時從進一同取出的料通道中澆注系統(tǒng)凝料。 可以看出，原料通過主流道、第一分流道、第二分流道和澆口注入型腔中。熔融塑料通過主流道和分流道時溫度降低而使熔體粘度升高，然而當熔體通過澆口填入型腔時，由于剪切作用產(chǎn)生的熱量又使粘度降低。澆注系統(tǒng)要保持適當長度，使熔體的壓力減少且熱量損失降到最低。因此，設(shè)計時必須充分考慮型腔分布和澆口形式。 1、 主流道 主流道是將熔融塑料從注塑機噴嘴傳遞到模具型腔的通道。主流道是澆口套的一部分，澆口套是獨立于模具的單獨零件。 2、 分流道 分流道是引導熔融塑料進入模具型腔的通道。 3、 澆口 澆口是熔融塑料進入型腔的入口。澆口有以下作用：約束熔體流動；引導熔體的流動方向；使分流道和塑件末端易于分離；快速冷卻固化以防止熔融塑料充滿型腔后倒流。 4、 冷料井 冷料井正對著主流道。理論上，冷料井的作用是用來儲存在塑件冷卻和推出過程中注塑機噴嘴處形成的熔體前鋒冷料。也許冷料井更重要的作用是開模時幫助澆道凝料脫出澆口套。 塑件成型后，主流道、分流道和澆口部分凝料將被遺棄。然而，分流道和澆口是影響塑件質(zhì)量和成本的重要因素。 外文資料翻譯 The Injection Molding Injection 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. As shown in Fig.2-1, 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. Actual injection molding is shown in Fig 2-2. 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 ) , as shown in Fig. 2-3. 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 ). Three-plate Mold A simple mold of this type is shown in Fig .2-5,and a descripsion of the design and of theopening sequence follows.The mold consists of three basic prats ,namely :the moving half ,the floating cavity plate and the feed plate ,respectively. The moving half consists of the moving mold plate assembly,support blocks,backing plate,ejector assembly and the pin ejection system .Thus the moving half in this design is identical with the moving half of basic molds . The floating cavity plate ,which may be of the integer or insert-bolster design, is located on substantial guide pillars (not shown)fitted in the feed plate . These guide pillars must be of sufficient to perform the function of alignment between the cavity and core when the mold is being closed .Guide bushes are fitted into the moving mold plate and the floating cavity plate respectively . The maximum movement of the floating cavity plate is controlled by stop bolt assembly .The moving mold plate is suitably bored to provide a clearance for the stop bolt assembly . The stop bolts must be long enough to provide sufficlient space between the feed plate and the floating cavity plate for easy removal of the feeding system .The minimum space provided for should be 65 mm, just sufficient for an operator to remove the feed system by hand if necessary . The desired operating sequenc is for the first daylight to occur between the floating cavity plate and the feedi