注射成型外文文獻(xiàn)翻譯@塑料模具類外文翻譯@中英文翻譯

2.3 注射成型 2.31 注射成型 注塑主要用于生產(chǎn)熱塑性塑料零件，也是最原始的方法之一。目前注塑占所有塑料樹脂消費(fèi)量的 30%。典型的注塑成型產(chǎn)品“塑料杯、容器、外殼、工具手柄、旋鈕、電氣和通信組件 (如電話接收器 )、玩具、和水暖配件。 聚合物熔體由于其分子量具有很高的粘度；它們不能像金屬液在重力的條件下倒進(jìn)模 ,必須在高壓力下注入模具。因此 ,金屬鑄造的力學(xué)性能是由模具壁傳熱的速度決定，同時(shí)也決定了在最終鑄件的晶粒尺寸和晶粒取向 , 高壓注射成型過程中熔體的注射剪切力產(chǎn)生的主要原因是材料最后的分子取向。力學(xué)性能影 響成品都是因?yàn)樵谀＞呃锏淖⑺軛l件很冷卻條件。 注塑已應(yīng)用于熱塑性塑料和熱固性材料 ,發(fā)泡部分 ,也已被修改過用于展現(xiàn)注射成型（ RIM）反應(yīng)過程，其中有兩個(gè)部分組成，一種是熱固性樹脂體系，另一種是聚合物快速注射模具。然而大多數(shù)注射成型是熱塑性塑料 ,后面的討論集中于這樣的模型。 一個(gè)典型的注塑周期或序列由五個(gè)階段組成 (見圖 2 - 1): 注射或模具填充 ； (2) 包裝或壓縮 ； (3) 保持 ； (4) 冷卻 ； (5)部分排除物 圖 2 - 1 注射成型過程 塑料顆粒（或粉末）被裝入進(jìn)料斗并通過注塑缸上的 開口在那里它們被旋轉(zhuǎn)螺桿結(jié)轉(zhuǎn)。螺桿的旋轉(zhuǎn)使顆粒處于高壓下加上受熱缸壁使它們?nèi)诨?。加熱溫度范圍?265 到 500 F。隨著壓力的增大 ,旋轉(zhuǎn)螺絲被迫向后 ,直到積累了足夠的塑料可以進(jìn)行注射。注射活塞 (或螺釘 )迫使熔融塑料從料桶通過噴嘴、澆口和流道系統(tǒng) ,最后進(jìn)入模腔。在注射過程中 ,熔融塑料充滿模具型腔。當(dāng)塑料接觸冷模具表面 ,它迅速凝固 (凍結(jié) )產(chǎn)生皮膚層。由于核心仍在熔融狀態(tài) ,塑料流經(jīng)核心來完成填充。一般的，該空腔被注入期間填充到 95 ?98。 然后成型工藝轉(zhuǎn)向了填充的階段。型腔填充后，熔融塑料開始冷卻。由于冷卻塑料 會(huì)收縮產(chǎn)生缺陷，如縮孔、氣泡，而且空間存在不穩(wěn)定性。所以被迫實(shí)行空穴用來補(bǔ)償收縮、添加塑料。一旦模腔被填充，壓力應(yīng)用熔體防止腔內(nèi)熔融塑料會(huì)流進(jìn)澆口。壓力必持續(xù)到澆口部分就凝固了。該過程可以分成兩個(gè)步驟（填充和保持）或者可能在一個(gè)步驟中（保持或第二級(jí)）所涵蓋。在填充過程中，熔體被用于收縮的填充壓力補(bǔ)償壓入型腔中。保持過程中，壓力只是防止聚合物熔體的倒流。 保持階段結(jié)束后冷卻階段開始。在冷卻過程中，部分在模具持有指定期間。冷卻階段的持續(xù)時(shí)間主要取決于材料的性質(zhì)和厚度。通常，該部分的溫度必須冷卻到低于材料的脫模溫 度。 在冷卻部件，這臺(tái)機(jī)器塑性熔化在下一個(gè)周期。聚合物受剪切作用以及電熱絲的能量。一旦開槍，塑化停止。這應(yīng)該是在冷卻階段結(jié)束之前。然后將模具開啟，一部分被排出。 2.3.2注塑模具 注塑模具的多種多樣的設(shè)計(jì)、復(fù)雜程度和大小作為它們的生產(chǎn)部分。功能熱塑性塑料模具，基本上是傳授理想的形狀，然后進(jìn)行聚合物注射件的冷卻。 一種模具是由兩組部件組成：（ 1）型腔和型芯（ 2）空腔和型芯的安裝。模塑部件的尺寸和重量限制了模腔的數(shù)量并且還決定了所要求的設(shè)備的能力?？紤]成型工藝，模具必須設(shè)計(jì)的安全地吸收由于夾緊。注塑。脫模帶來 的力。同時(shí)，澆口和流道的設(shè)計(jì)必須允許有效流動(dòng)和統(tǒng)一的模具型腔填充。 圖 2-2 示出了一個(gè)典型的注塑模具。模具主要由兩部分組成：一個(gè)部分精止不動(dòng)的（模腔板），在那邊熔融聚合物被注入，另一部分可以移動(dòng)（型心板）在截止面上或噴射器的注塑設(shè)備上。兩個(gè)半模之間的分離線被稱為分型線。注射的材料是通過中央進(jìn)料通道，稱為澆口。物料位于錐形流道，便于套管在打開的模具中釋放模具材料。在多數(shù)模具、物料聚合物熔體助長(zhǎng)了流道系統(tǒng)，通過一個(gè)澆口流向每個(gè)模具型腔。 核心板的主要核心。主要的核心的目的是建立內(nèi)部部分的配置。核心目的是建立內(nèi)部 結(jié)構(gòu)。核心板具有備份或支撐板，支撐板是由支柱所支撐的，這個(gè)支柱是作為噴射器殼體的 u 型結(jié)構(gòu)為人所知，它由后部夾持板和隔塊組成。此 U 形結(jié)構(gòu)是用螺栓固定在核心板，它為起模行程也就是脫模行程提供了空間。在凝固過程中該部分圍繞主芯收縮，使模具打開時(shí)，第二部分和澆道一起被移動(dòng)的半模進(jìn)行。隨后，中央噴射器被激活時(shí)，使頂出板向前移動(dòng)，導(dǎo)致頂出桿可以推動(dòng)這部分遠(yuǎn)離核心。兩個(gè)半模設(shè)置有冷卻通道，通過該冷卻通道，水被循環(huán)以吸收由熱塑性聚合物熔體輸送到模具的熱量。模腔還采用精細(xì)的通風(fēng)口（ 0.02?0.08 毫米 5毫米）的，以確保填 充過程中沒有空氣殘留。 注塑模具現(xiàn)在在使用中有六種基本類型。它們是：（ 1）雙板模具，（ 2）三板模，（ 3）熱澆道模，（ 4）絕緣熱澆道模，（ 5）熱歧管模具，以及層疊模具。圖。 2-3 和圖 2-4 說明了這六種基本類型的注塑模具。 圖 2 - 2 注塑模具 1 - 頂桿 2 - 推板 3 - 導(dǎo)套 4 - 導(dǎo)柱 5 - 頂桿底板 6 鉤料桿銷 7 推回針 8 針限制 9 導(dǎo)柱 10 - 導(dǎo)柱 11 腔板 12 - 澆口套 13 塑料工件 14 芯 圖 2-3 這說明三者的六種基本類型的注塑模具 (1) 兩板注射模具（ 2）三板注塑模（ 3）熱流道模具 見圖 . 2-4 其他三種型。 圖 2-4 這說明三者的六種基本類型的注塑模具 （ 1）絕緣熱流道注塑模具（ 2）熱歧管注塑模具（ 3）堆疊式注塑模具 見圖 .2-3 對(duì)于其他三種類型。 1兩板模 一種雙板模具由兩個(gè)板與腔和型芯安裝在任一模版上 .板被固定到壓板上。移動(dòng)一半的模具通常含有推出結(jié)構(gòu)和澆道系統(tǒng)。所有注塑模具的基本設(shè)計(jì)有這樣的設(shè)計(jì)理念。兩板模具是最合乎邏輯的類型對(duì)于一些需要使用那些需要很大澆口零件的工具來說。 2三板模具 這種類型的模具是由三塊板組成：（ 1）固定或流道板是連接到靜止的滾筒，通 常包含澆道和半流道，（ 2）中間板或模腔板，包含一半道和澆口，允許在開模時(shí)浮動(dòng)，（ 3）移動(dòng)板或受力板塑造和推出系統(tǒng)部分切除塑造的部分。當(dāng)通道開始打開，中間板和可動(dòng)板一起移動(dòng)，從而釋放澆道和流道系統(tǒng)和去澆口的成型部件。這種類型的模具的設(shè)計(jì)能夠分隔流道系統(tǒng)和部件當(dāng)模具打開時(shí)。這種模具的設(shè)計(jì)可以使用點(diǎn)澆口澆注系統(tǒng)。 3 .熱流道模具 在注射成型的過程中，流道保持熱量以保證熔融塑料是流體狀態(tài)，在任何時(shí)候。實(shí)際上這是一個(gè) 無澆道 成型工藝而且有時(shí)被稱為是相同的。在無流道模具中，流道包含在一個(gè)獨(dú)立的板上。熱流道模具類似三 板注塑模具，除了模具流道的部分在成型周期打不開。加熱流道板與其余的冷模隔熱。除了加熱板是為了流道設(shè)計(jì)，模具剩余部分是一個(gè)標(biāo)準(zhǔn)兩板模。 無流道成型較傳統(tǒng)澆道式成型有很多優(yōu)點(diǎn)。沒有成型的副產(chǎn)物（澆口，流道，或主流道）被處理掉或循環(huán)再使用，沒有從主流到分離。周期時(shí)間是成型部分被冷卻，從模具中頂出。在這個(gè)系統(tǒng)中，一個(gè)均勻的熔體溫度可以從注射模具型腔的汽缸達(dá)到的。 4絕緣熱流道模具 這是一個(gè)變化的保溫模具。在這種類型的模具中，流道的外表面材料是絕緣體的優(yōu)質(zhì)材料。在絕熱模具中，成型材料鑄造成型仍然通過保持熱量。有時(shí) 一個(gè)分料梭和熱探測(cè)器需要更多的靈活性。這種類型的模具多腔中心澆口部分是理想的。、 5.熱流道模具 這是一個(gè)變化的保溫流道模具。在熱流道模具中，流道是加熱的而不是流道板。這是通過使用一個(gè)電子嵌入探針完成的。 6.堆疊模具 堆疊注塑模具，顧名思義就是多個(gè)兩板模具放置一起。這種結(jié)構(gòu)也可以用于三板模具和保溫流道模具。堆疊兩模板的構(gòu)造重點(diǎn)提出一個(gè)單一通道要求比同樣數(shù)量的模具減少一般夾緊壓力。這個(gè)方法有時(shí)候被稱為“二級(jí)成型”。 2.3.3 成型機(jī) 1.傳統(tǒng)注塑機(jī) 在這個(gè)過程中 ,塑料顆?；蝾w粒注入機(jī)料斗并注入加熱缸腔內(nèi) 。然后柱塞壓縮材料 ,迫使它逐步通過加熱缸的溫度區(qū)域 ,在那里它被分料梭分散的很薄。分料梭安裝在缸的中心，目的是為了加快塑料中心的加熱質(zhì)量。分料梭也可從內(nèi)部加熱處理使塑料內(nèi)外都加熱。 材料從加熱缸流動(dòng)通過一個(gè)管口進(jìn)入模具。這個(gè)管口是缸和和模具的分割點(diǎn) ,它是用來防止產(chǎn)生壓力導(dǎo)致物質(zhì)泄漏。模具是關(guān)閉了有夾鉗一端的機(jī)器。對(duì)于聚苯乙烯 ,夾鉗上兩到三噸的壓力要用于材料和系統(tǒng)的每一寸空間。傳統(tǒng)的柱塞機(jī)是唯一可以產(chǎn)生雜色部件的注塑機(jī) ,其他類型的完全將塑料材料融合在一起 ,只會(huì)產(chǎn)生一種顏色。 2.柱塞式預(yù)塑機(jī) 這臺(tái)機(jī)器使用一個(gè)分 料梭加熱器來預(yù)塑塑料顆粒。融化階段后 ,液體塑料是被排入一個(gè)存放腔內(nèi)，直到可以進(jìn)入模具。這種類型的機(jī)器生產(chǎn)速度比傳統(tǒng)的機(jī)器快 ,由于成型室是在冷卻時(shí)不斷釋放能量。由于注射柱塞作用于流體材料 ,在顆粒壓縮時(shí)沒有壓力損失。這允許更大的部件有更大的投影面積。它其余的特性與傳統(tǒng)單活塞注射機(jī)相同。圖 2 - 5 演示了一個(gè)柱塞式預(yù)塑機(jī)。 3.螺桿式預(yù)塑機(jī) 這種注射機(jī)用擠出機(jī)塑化塑料材料。車削螺桿向擠壓機(jī)內(nèi)表面供料。將擠出機(jī)熔融、塑化的材料移動(dòng)到另一個(gè)存放腔 ,然后從那里被注射柱塞擠入模具。使用螺旋有以下優(yōu)點(diǎn) :(1)塑性材料 能更好的融合和受力 ；(2)流動(dòng)材料更硬，熱敏感材料能流動(dòng) ；(3)顏色變化可以在更短的時(shí)間內(nèi)處理 (4)模制品受更小的壓力。 4.往復(fù)式螺桿注塑機(jī) 這種類型的注塑機(jī)在加熱室處采用臥式擠壓機(jī)。塑料材料由于螺桿的旋轉(zhuǎn)被推進(jìn)擠壓機(jī)管道。隨著材料通過加熱筒與螺桿時(shí) ,它正在從顆粒變成塑料熔融狀態(tài)。在往復(fù)式螺桿注塑機(jī)中 ,熱量傳遞到模塑料的熱量是由螺桿之間的摩擦傳導(dǎo)和擠壓機(jī)管道壁。材料移動(dòng)時(shí) ,螺桿又回到極限狀態(tài) ,這種狀態(tài)是決定材料在壓力機(jī)管道前的體積的。這時(shí) ,與典型壓力機(jī)的相似之處結(jié)束了。在材料注入模具時(shí) ,螺桿向前移動(dòng)，重新 塑造管道中的材料。在這臺(tái)機(jī)器中，螺桿的角色既是一個(gè)柱塞又是一個(gè)螺桿。在模型澆口部分已經(jīng)凝固不能回流時(shí)，螺桿開始旋轉(zhuǎn)回程，走下一圈。圖 2-5 是一個(gè)往復(fù)式螺桿注塑機(jī)。 這種注塑方法有幾個(gè)優(yōu)點(diǎn)。它能使熱敏材料更有效地塑化，使顏色融合更快 ,材料的溫度通常更低，整個(gè)循環(huán)時(shí)間也更短。 2.3 Injection Molds 2.3.1 Injection Molding Injection molding is principally used for the production of thermoplastic parts, and it is also one of the oldest. Currently injection-molding accounts for 30% of all plastics resin consumption.Typical injection-molded products are cups, containers, housings, tool handles, knobs, electrical and communication components (such as telephone receivers), toys, and plumbing fittings. Polymer melts have very high viscosities due to their high molecular weights； they cannot be poured directly into a mold under gravity flow as metals can, but must be forced into the moldunder high pressure. Therefore while the mechanical properties of a metal casting are predominantly determined by the rate of heat transfer from the mold walls, which determines the grain size and grain orientation in the final casting, in injection molding the high pressure during the injection of the melt produces shear forces that are the primary cause of the final molecularorientation in the material. The mechanical properties of the finished product are therefore affected by both the injection conditions and the cooling conditions within the mold. Injection molding has been applied to thermoplastics and thermosets, foamed parts, and has been modified to yield the reaction injection molding (RIM) process, in which the twocomponents of a thermosetting resin system are simultaneously injected and polymerize rapidly within the mold. Most injection molding is however performed on thermoplastics, and the discussion that follows concentrates on such moldings.Chapter 2 Plastics Molds A typical injection molding cycle or sequence consists of five phases (see Fig. 2-1): （ 1） Injection or mold filling； (2) Packing or compression； (3) Holding； (4) Cooling； (5) Part ejection. Plastic pellets (or powder) are loaded into the feed hopper and through an opening in the injection cylinder where they are carried forward by the rotating screw. The rotation of the screw forces the pellets under high pressure against the heated walls of the cylinder causing them to melt. Heating temperatures range from 265 to 500 F. As the pressure builds up, the rotating screw is forced backward until enough plastic has accumulated to make the shot. The injection ram (or screw) forces molten plastic from the barrel, through the nozzle, sprue and runner system,and finally into the mold cavities. During injection, the mold cavity is filled volumetrically.When the plastic contacts the cold mold surfaces, it solidifies (freezes) rapidly to produce the skin layer. Since the core remains in the molten state, plastic flows through the core to complete mold filling. Typically, the cavity is filled to 95%98% during injection. Then the molding process is switched over to the packing phase. Even as the cavity is filled,the molten plastic begins to cool. Since the cooling plastic contracts or shrinks, it gives rise to defects such as sink marks, voids, and dimensional instabilities. To compensate for shrinkage,addition plastic is forced into the cavity. Once the cavity is packed, pressure applied to the melt prevents molten plastic inside the cavity from back flowing out through the gate. The pressure must be applied until the gate solidifies. The process can be divided into two steps (packing and holding) or may be encompassed in one step (holding or second stage). During packing, melt forced into the cavity by the packing pressure compensates for shrinkage. With holding, the pressure merely prevents back flow of the polymer melt. After the holding stage is completed, the cooling phase starts. During cooling, the part is held in the mold for specified period. The duration of the cooling phase depends primarily on the material properties and the part thickness. Typically, the part temperature must cool below the materials ejection temperature. While cooling the part, the machine plasticates melt for the next cycle. The polymer is subjected to shearing action as well as the condition of the energy from the heater bands. Once the shot is made, plastication ceases. This should occur immediately before the end of the cooling phase. Then the mold opens and the part is ejected. 2.3.2 Injection Molds Molds for injection molding are as varied in design, degree of complexity, and size as are the parts produced from them. The functions of a mold for thermoplastics are basically to impart the desired shape to the plasticized polymer and then to cool the molded part. A mold is made up of two sets of components: (1) the cavities and cores, and (2) the base in which the cavities and cores are mounted. The size and weight of the molded parts limit the number of cavities in the mold and also determine the equipment capacity required. From consideration of the molding process, a mold has to be designed to safely absorb the forces of clamping, injection, and ejection. Also, the design of the gates and runners must allow for efficient flow and uniform filling of the mold cavities. Fig.2-2 illustrates the parts in a typical injection mold. The mold basically consists of two parts: a stationary half (cavity plate), on the side where molten polymer is injected, and a moving half (core plate) on the closing or ejector side of the injection molding equipment. The separating line between the two mold halves is called the parting line. The injected material is transferred through a central feed channel, called the sprue. The sprue is located on the sprue bushing and is tapered to facilitate release of the sprue material from the mold during mold opening. In multicavity molds, the sprue feeds the polymer melt to a runner system, which leads into each mold cavity through a gate. The core plate holds the main core. The purpose of the main core is to establish the inside configuration of the part. The core plate has a backup or support plate. The support plate in turn is supported by pillars against the U-shaped structure known as the ejector housing, which consists of the rear clamping plate and spacer blocks. This U-shaped structure, which is bolted to the core plate, provides the space for the ejection stroke also known as the stripper stroke. During solidification the part shrinks around the main core so that when the mold opens, part and sprue are carried along with the moving mold half. Subsequently, the central ejector is activated,the ejector plates to move forward so that the ejector pins can push the part off the core.Both mold halves are provided with cooling channels through which cooled water is circulated to absorb the heat delivered to the mold by the hot thermoplastic polymer melt. The mold cavities also incorporate fine vents (0.02 to 0.08 mm by 5 mm) to ensure that no air is trapped during filling. There are six basic types of injection molds in use today. They are: (1) two-plate mold； (2)three-plate mold, (3) hot-runner mold； (4) insulated hot-runner mold； (5) hot-manifold mold； and（ 6） stacked mold. Fig. 2-3 and Fig. 2-4 illustrate these six basic types of injection molds. 1. Two-Plate Mold A two-plate mold consists of two plates with the cavity and cores mounted in either plate.The plates are fastened to the press platens. The moving half of the mold usually contains the ejector mechanism and the runner system. All basic designs for injection molds have this design concept. A two-plate mold is the most logical type of tool to use for parts that require large gates. 2. Three-Plate Mold This type of mold is made up of three plates: (1) the stationary or runner plate is attached to the stationary platen, and usually contains the sprue and half of the runner； (2) the middle plate or cavity plate, which contains half of the runner and gate, is allowed to float when the mold is open； and (3) the movable plate or force plate contains the molded part and the ejector system for the removal of the molded part. When the press starts to open, the middle plate and the movable plate move together, thus releasing the sprue and runner system and degating the molded part.This type of mold design makes it possible to segregate the runner system and the part when the mold opens. The die design makes it possible to use center-pin-point gating. 3. Hot-Runner Mold In this process of injection molding, the runners are kept hot in order to keep the molten plastic in a fluid state at all times. In effect this is a runnerless molding process and is sometimes called the same. In runnerless molds, the runner is contained in a plate of its own. Hot runner molds are similar to three-plate injection molds, except that the runner section of the mold is not opened during the molding cycle. The heated runner plate is insulated from the rest of the cooled mold. Other than the heated plate for the runner, the remainder of the mold is a standard two-plate die. Runnerless molding has several advantages over conventional sprue runner-type molding.There are no molded side products (gates, runners, or sprues) to be disposed of or reused, and there is no separating of the gate from the part. The cycle time is only as long as is required for the molded part to be cooled and ejected from the mold. In this system, a uniform melt temperature can be attained from the injection cylinder to the mold cavities. 4. Insulated Hot-Runner Mold This is a variation of the hot-runner mold. In this type of molding, the outer surface of the material in the runner acts like an insulator for the melten material to pass through. In the insulated mold, the molding material remains molten by retaining its own heat. Sometimes a torpedo and a hot probe are added for more flexibility. This type of mold is ideal for multicavity center-gated parts. 5. Hot-Manifold This is a variation of the hot-runner mold. In the hot-manifold die, the runner and not the runner plate is heated. This is done by using an electric-cartridge-insert probe. 6. Stacked Mold The stacked injection mold is just what the name implies. A multiple two-plate mold is placed one on top of the other. This construction can also be used with three-plate molds and hot-runner molds. A stacked two-mold construction doubles the output from a single press and reduces the clamping pressure required to one half, as compared to a mold of the same number of cavities in a two-plate mold. This method is sometimes called “two-level molding”. 2.3.3 Mold Machine 1. Conventional Injection-Molding Machine In this process, the plastic granules or pellets are poured into a machine hopper and fed into the chamber of the heating cylinder. A plunger then compresses the material, forcing it through progressively hotter zones of the heating cylinder, where it is spread thin by a torpedo. The torpedo is installed in the center of the cylinder in order to accelerate the heating of the center of the plastic mass. The torpedo may also be heated so that the plastic is heated from the inside as well as from the outside. The material flows from the heating cylinder through a nozzle into the mold. The nozzle is the seal between the cylinder and the mold； it is used to prevent leaking of material caused by the pressure used. The mold is held shut by the clamp end of the machine. For polystyrene, two to three tons of pressure on the clamp end of the machine is generally used for each inch of projected area of the part and runner system. The conventional plunger machine is the only type of machine that can produce a mottle-colored part. The other types of injection machines mix the plastic material so thoroughly that only one color will be produced. 2. Piston-Type Preplastifying Machine This machine employs a torpedo ram heater to preplastify the plastic granules. After the melt stage, the fluid plastic is pushed into a holding chamber until it is ready to be forced into the die. This type of machine produces pieces faster than a conventional machine, because the molding chamber is filled to shot capacity during the cooling time of the part. Due to the fact that the injection plunger is acting on fluid material, no pressure loss is encountered in compacting the granules. This allows for larger parts with more projected area. The remaining features of a piston-type preplastifying machine are identical to the conventional single-plunger injection machine. Fig. 2-5 illustrates a piston or plunger preplastifying injection molding machine. 3. Screw-Type Preplastifying Machine In this injection-molding machine, an extruder is used to plasticize the plastic material. The Chapter 2 Plastics Molds 41turning screw feeds the pellets forward to the heated interior surface of the extruder barrel. The molten, plasticized material moves from the extruder into a holding chamber, and from there is forced into the die by the injection plunger. The use of a screw gives the following advantages:(1) better mixing and shear action of the plastic melt； (2) a broader range of stiffer flow and heatsensitive materials can be run； (3) color changes can be handled in a shorter time, and (4)fewer stresses are obtained in the molded part. 4. Reciprocating-Screw Injection Machine This type of injection molding machine employs a horizontal extruder in place of the heating chamber. The plastic material is moved forward through the extruder barrel by the rotation of a screw. As the material progresses through the heated barrel with the screw, it is changing from the granular condition to the plastic molten state. In the reciprocating screw, the heat delivered to the molding compound is caused by both friction and conduction between the screw and the walls of the barrel of the extruder. As the material moves forward, the screw backs up to a limit switch that determines the volume of material in the front of the extruder barrel. It is at this point that the re- semblance to a typical extruder ends. On the injection of the material into the die, the screw moves forward to displace the material in the barrel. In this machine, the screw performs as a ram as well as a screw. After the gate sections in the mold have frozen to prevent backflow, the screw begins to rotate and moves backward for the next cycle. Fig.2-5 shows a reciprocating-screw injection machine. There are several advantages to this method of injection molding. It more efficiently plasticizes the heat-sensitive materials and blends colors more rapidly, due to the mixing action of the screw. The material heat is usually lower and the overall cycle time is shorter. 2.1 計(jì)算機(jī)輔助設(shè)計(jì)和計(jì)算機(jī)輔助 CAD/CAM 縱觀人類工業(yè)社會(huì)的歷史 ,許多發(fā)明獲得了專利，整個(gè)新技術(shù)也逐漸形成?；萏啬岬耐ㄓ昧慵乃悸?,瓦特的蒸汽機(jī)和福特的流水線不僅是幾個(gè)少數(shù)的發(fā)展階段而且是人類工業(yè)的幾個(gè)重要的發(fā)展階段。正如我們所知的任何一個(gè)這樣的發(fā)展都影響了制造業(yè)并且在歷史的掛鉤中贏得了這些個(gè)體應(yīng)得的承認(rèn)?；蛟S單個(gè)的發(fā)展影響制造業(yè)更快，而影響比先前技術(shù)更大的是數(shù)字電腦。 自從電腦技術(shù) 出現(xiàn)以來 ,制造業(yè)人員一直希望自動(dòng)化設(shè)計(jì)過程和使用數(shù)據(jù)庫(kù)開發(fā)自動(dòng)制造過程。計(jì)算機(jī)輔助設(shè)計(jì) /計(jì)算機(jī)輔助制造 (CAD/CAM),當(dāng)成功執(zhí)行 ,應(yīng)該消除存在于設(shè)計(jì)和生產(chǎn)部件之間的傳統(tǒng)屏障。 CAD/CAM 意味著用電腦進(jìn)行設(shè)計(jì)和制造過程。因?yàn)?CAD/CAM 的出現(xiàn)其他方面也 發(fā)展起來： 計(jì)算機(jī)圖形 CG 電腦輔助工程 CAE 電腦輔助設(shè)計(jì)和繪圖設(shè)計(jì) CADD 計(jì)算機(jī)輔助工藝規(guī)劃 CAPP 這些附帶條件是指包括解答 11 項(xiàng)具體方面的 CAD / CAM 的概念而 CAD / CAM 本身就是一個(gè)更廣泛平臺(tái) ,它是在生產(chǎn)的自動(dòng)化和集成的核心。 CAD/CAM 成功的一個(gè)關(guān)鍵目標(biāo)是創(chuàng)建可以用來產(chǎn)品的數(shù)據(jù)當(dāng)成功實(shí)施的產(chǎn)品設(shè)計(jì)的發(fā)展數(shù)據(jù)庫(kù)。 CAD/CAM 致力于一個(gè)在設(shè)計(jì)和生產(chǎn)部件分享通用的數(shù)據(jù)庫(kù)的公司。 交 互 式 計(jì) 算 機(jī) 圖 形 學(xué) (ICG) 在 CAD/CAM 扮演一個(gè)重要角色，雖然 ICG 用途上 ,設(shè)計(jì)師沖洗被設(shè)計(jì)的產(chǎn)品的一個(gè)圖表圖象 ,當(dāng)存放電子上組成圖表圖象的數(shù)據(jù)。圖表圖象在二維可以被提出二維 (2-D)三維 (3-D)或者固體格式化。 ICG 圖象被修建使用這樣基本的幾何字符象點(diǎn)、線、圈子和曲線。一旦生成 ,這些圖象可以容易地 被編輯和被操作用各種各樣的方式包括擴(kuò)大、減少、自轉(zhuǎn)和運(yùn)動(dòng)。 lCG 系統(tǒng)有三個(gè)主要成份 ,1)硬件 ,包括計(jì)算機(jī)和各種各樣的外圍設(shè)備 ； 2)軟件 ,包括系統(tǒng)的計(jì)算機(jī)程序和技術(shù)指南 ； 3)設(shè)計(jì)師 ,最重要三個(gè)組分。 ICG 系統(tǒng)的典型的硬件構(gòu)造包括一個(gè)電腦 ,一個(gè)顯示終端、磁盤的一個(gè)驅(qū)動(dòng)器單位，一個(gè)硬盤或者兩個(gè) ； 并且輸入 -輸出設(shè)備例如鍵盤，繪圖器和打印機(jī)。這些設(shè)備 ,與軟件一起，是現(xiàn)代工具設(shè)計(jì)師用以開發(fā)和提供他們的設(shè)計(jì)的。 ICG 系統(tǒng)能通過允許人的設(shè)計(jì)師集中提高設(shè)計(jì)過程于設(shè)計(jì)過程的智力方面，例如概 念化 和做出基于評(píng)斷的決定。計(jì)算機(jī)執(zhí)行它更好地適合，例如數(shù)據(jù)的各種各樣的反復(fù)操 作數(shù)學(xué)演算、存貯與檢索，和各種各樣的反復(fù)操作比如交叉涂畫。 2.11CAD/CAM 的基本原理 CAD/CAM 的基本原理類似于制造業(yè)以前證明技術(shù)為基礎(chǔ)的提高。它來源于一個(gè)需要不斷提高生產(chǎn)率，質(zhì)量和反過來的競(jìng)爭(zhēng)力。還有其他原因，可能使公司從手工流程轉(zhuǎn)換為 CAD / CAM 的。 提高生產(chǎn)力 質(zhì)量更好 更好的溝通 共同的數(shù)據(jù)庫(kù)與制造 降低建造成本原型 更快的響應(yīng)客戶 2.12 CAD/CAM 的歷史發(fā)展 CAD/CAM 的歷史發(fā)展在計(jì)算機(jī)科技的發(fā)展之后緊密跟隨了和對(duì)應(yīng)了 ICG 技術(shù)的發(fā)展。使得 CAD/CAM 的重大發(fā)展在 20 世紀(jì) 50 年代和 60 年代初期末期開始了。最先發(fā)展的是在麻省理工學(xué)院 (MIT)進(jìn)行的刀具控制程序自動(dòng)編制系統(tǒng) (APT)計(jì)算機(jī)程式語(yǔ)言。 APT 的目的是將數(shù)字控制器部分方案的開發(fā)進(jìn)行簡(jiǎn)化。它是為此計(jì)劃被使用的第一 種計(jì)算機(jī)語(yǔ)言。 APT 語(yǔ)言代表了主要步往制造過程的自動(dòng)化。 在 CAD/CAM 的歷史中的另一重大發(fā)展在 APT 之后 緊密跟隨了，也被開發(fā)在 MIT，一個(gè)項(xiàng)目被稱之為草圖項(xiàng)目。這個(gè)項(xiàng)目， Ivan Sutherland 誕生了 ICG 的概念。草圖項(xiàng)目是第一個(gè)計(jì)算機(jī)在實(shí)時(shí)中被用于生成和操作在 CRT 中顯示的圖表圖象。 在 20 世紀(jì) 60 年代和 70 年代的剩下的人中， CAD 繼續(xù)被開發(fā)，多家廠商提出了自己的名字生產(chǎn)和銷售生產(chǎn)全套 CAD 系統(tǒng)。這是一個(gè)完整的系統(tǒng)方案包括硬，軟件，銷售和維修培訓(xùn)。這些早期的系統(tǒng)被大型機(jī)和小型機(jī)左右。因此 ,它們太昂貴一直不能實(shí)現(xiàn)大規(guī)模被中小型制造業(yè)接受。 在 20 世紀(jì) 70 年代末之前 微型計(jì)算機(jī)在 CAD/CAM 的更加一步的發(fā)展中最終將扮演一個(gè)重要角色變得日益清晰。然而早期的微型計(jì)算機(jī)沒有配置為 ICG 需要的處理能 力、記憶能力或者圖表能力。結(jié)果 ,早期嘗試在微型計(jì)算機(jī)附近配置 CAD/CAM 系統(tǒng)的嘗試失敗了。 在 1983 IBM 介紹了 IBM PC 第一個(gè)有處理能力、記憶能力和圖表能力可被用于 CAD/CAM 的微型計(jì)算機(jī)。這使得了 CAD/CAM 供營(yíng)商的數(shù)量的迅速增量。截止到 l989 安裝 CAD/CAM 設(shè)施的數(shù)量的微型計(jì)算機(jī)等于安裝在大型機(jī)和小型機(jī)上的數(shù)量 。 2.13 CAD 到 CAM 接口 使用 CAD/CAM，設(shè)計(jì)和制造之間的真正的接，是他們分享的共同的數(shù)據(jù)庫(kù)。這是 CAD/CAM 精華。 手工設(shè)計(jì)和制造，工程師審閱在設(shè)計(jì)，起草生產(chǎn)圖紙和其他文件傳達(dá)設(shè)計(jì)的每步，生產(chǎn)人員使用圖畫開發(fā)處理計(jì)劃，車間人員負(fù)責(zé)實(shí)際上的生產(chǎn)。 與舊方法相比 ,直到設(shè)計(jì)和起草人員完成他們的工作，生產(chǎn)人員都沒有看到它。設(shè)計(jì)和起草部門做他們的工作，把計(jì)劃再扔過墻再讓制造部門做他們的工作。這種做法導(dǎo)致溝通的不暢通以及制造部分與設(shè)計(jì)部分的脆弱關(guān)系。其結(jié)果是生產(chǎn)力 的損失。 使用 CAD/CAM,生產(chǎn)人員可以盡快進(jìn)入創(chuàng)建的數(shù)據(jù)的設(shè)計(jì)階段。在任何一點(diǎn)在設(shè)計(jì)過程中，他們可以調(diào)用數(shù)據(jù)庫(kù)中的信息并使用它。因?yàn)閿?shù)據(jù)分享從開始到結(jié)束，所以當(dāng)設(shè)計(jì)成到準(zhǔn)備生產(chǎn)時(shí)沒有一點(diǎn)吃驚。 當(dāng)設(shè)計(jì)師創(chuàng)造時(shí)數(shù)據(jù)庫(kù)和起草者提供的設(shè)計(jì)，使生產(chǎn)人員也成為項(xiàng)目的一部分。生產(chǎn)人員生產(chǎn)產(chǎn)品的任何需要都被包含在一個(gè)共同的數(shù)據(jù)庫(kù)里。數(shù)學(xué)模型，圖形圖像，用料清單，零件清單，尺寸，從區(qū)位尺寸到公差規(guī)格和原材料明細(xì)表都包含數(shù)據(jù)庫(kù) 。 2.1 Computer-aided Design and Computer-aided Manufacturing(CAD/CAM) Throughout the history of our industrial society ,many invention have been patented and whole new technologies have evolved .Whitney is concept of interchangeable parts ,Watts steam engine,and Ford is assembly line are but a few developments that are most noteworthy during our industrial period . Each of these developments has impacted manufacturing as we know it,and has earned these individuals deserved recognition in 0ur history hooks. Perhaps the single development that has impacted manufacturing more quickly and significantly than any previous technology is the digital computer. Since the advent 0f computer technology, manufacturing professionals have wanted to automate the design process and use the database developed therein for automating manufacturing processes. Computeraided design,computer-aided manufacturing (CAD/CAM),when successfully implemented, should remove the “wall” that has traditionally existed between the design and manufacturing components . CAD/CAM means using computers in the design and manufacturing processes. Since the advent of CAD/CAM other terms have developed: Computer graphics(CG) Computeraided engineering(CAE) Computer-aided design and drafting(CADD) Computer aided process planning(CAPP) These spin-off terms a11 refer to specific aspects of the CAD/CAM concept CAD/CAM itself is a broader,more inclusive term. It is at the heart of automated and integrated manufacturing. A key goal of CAD/CAM is to produce data that can be used in manufacturing a product while developing the database for the design of that product When successfully implemented, CAD/CAM involves the sharing of a common database between the design and manufacturing components of a company, Interactive computer graphics (ICG) plays an important role in CAD/CAM, Though the use of ICG, designers develop a graphic image of the product being designed while storing the data that electronically make up the graphic image. The graphic image can be presented in a two-dimensional (2-D) , three-dimensional(3-D),or solids format. ICG image are constructed using such basic geometric characters as points, lines, circles, and curves. Once created, these images can be easily edited and manipulated in a variety of ways including enlargements,reductions, rotations, and movements. An lCG system has three main components :1 ) hardware, which consists of the computer and various peripheral devices； 2) software, which consists of the computer programs and technical manuals for the system ； and 3) the human designer, the most important of the three components. A typical hardware configuration for an ICG System include a computer,a display terminal, a disk drive unit for floppy diskettes, a hard disk, or both； and input/output devices such as a keyboard,plotter, and printer. These devices, along with the software, are the tools modern designers use to develop and document their designs. The ICG systems could enhance the design process by allowing the human designer to focus on the intellectual aspects of the design process, such as conceptualization and making judgment-based decisions. The computer performs tasks for which it is better suited, such as mathematical calculations, storage and retrieval of data and various repetitive operations such as crosshatching. 2.1.1 Rationale for CAD/CAM The rationale CAD/CAM is similar to that used to justify any technology-based improvement in manufacturing . It grows out of a need to continually improve productivity,Quality and in turn competitiveness. There are also other reasons why a company might make a conversion from manual processes to CAD/CAM: increased productivity better quality better communication common database with manufacturing reduced prototype construction costs faster response to customers 2.12 Historical Development of CAD/CAM The historical development of CAD/CAM has followed close behind the development of computer technology and has paralleled the development of ICG technology. The significant developments leading to CAD/CAM began in the late 1950s and early 1960s. The first of these was the development, at Massachusetts Institute of Technology (MIT),of the Automatically Programmed Tools (APT) computer programming language. The purpose of APT was to simplify the development of parts programs for numerical control machines. It was the first computer language to be used for this purpose. The APT language represented a major step toward automation of manufacturing processes. Another significant development in the history of CAD/CAM followed close behind APT, also developed at MIT, was called the Sketchpad project. With this project, Ivan Sutherland gave birth to the concept of ICG.