外文文獻(xiàn)及翻譯-TheintrodutionoftheInjectionMold

1、- -注射模具的介紹模具基本知識1.1引言我們?nèi)粘Ｉa(chǎn)、生活中所使用到的各種工具和產(chǎn)品，大到機(jī)床的底座、機(jī)身外殼， 小到一個胚頭螺絲、紐扣以及各種家用電器的外殼，無不與模具有著密切的關(guān)系。模具 的形狀決定著這些產(chǎn)品的外形，模具的加工質(zhì)量與精度也就決定著這些產(chǎn)品的質(zhì)量。因 為各種產(chǎn)品的材質(zhì)、外觀、規(guī)格及用途的不同，模具分為了鑄造模、鍛造模、壓鑄模、 沖壓模等非射膠模具，以及射膠模具。近年來，隨著射料工業(yè)的飛速發(fā)展和通用與工程 射料在強(qiáng)度和精度等方面的不斷提高，射料制品的應(yīng)用范圍也在不斷擴(kuò)大，如：家用電 器、儀器儀表，建筑器材，汽車工業(yè)、日用五金等眾多領(lǐng)域，射料制品所占的比例正迅 猛增加。一個設(shè)計

2、合理的射料件往往能代替多個傳統(tǒng)金屬件。工業(yè)產(chǎn)品和日用產(chǎn)品射料 化的趨勢不斷上升。1.2模具的一般定義在工業(yè)生產(chǎn)中，用各種壓力機(jī)和裝在壓力機(jī)上的專用工具，通過壓力把金屬或非金 屬材料制出所需形狀的零件或制品，這種專用工具統(tǒng)稱為模具。1.3模具的一般分類可分為射膠模具及非射膠模具：（1）非射膠模具有：鑄造模、鍛造模、沖壓模、壓鑄模等。A 鑄造模一一水龍頭、生鐵平臺B.鍛造模一一汽車身C沖壓模一一計算機(jī)面板D.壓鑄模一一超合金，汽缸體（2）射膠模具根據(jù)生產(chǎn)工藝和生產(chǎn)產(chǎn)品的不同又分為：A.注射成型模一一電視機(jī)外殼、鍵盤按鈕（應(yīng)用最普遍）B 吹 氣模一一飲料瓶C 壓縮成型模一一電木開關(guān)、科學(xué)瓷碗碟D.轉(zhuǎn)

3、移成型模一一集成電路制品E.擠壓成型模膠水管、射膠袋F.熱成型模透明成型包裝外殼G .旋轉(zhuǎn)成型模軟膠洋娃娃玩具注射成型是射料加工中最普遍采用的方法。該方法適用于全部熱射性射料和部分熱 固性射料，制得的射料制品數(shù)量之大是其它成型方法望塵莫及的，作為注射成型加工的 主要工具之一的注射模具，在質(zhì)量精度、制造周期以及注射成型過程中的生產(chǎn)效率等方 面水平高低，直接影響產(chǎn)品的質(zhì)量、產(chǎn)量、成本及產(chǎn)品的更新，同時也決定著企業(yè)在市 場競爭中的反應(yīng)能力和速度。注射模具是由若干塊鋼板配合各種零件組成的，基本分為：A成型裝置（凹模，凸模） B定位裝置（導(dǎo)柱，導(dǎo)套）C固定裝置（工字板，碼?？樱〥冷卻系統(tǒng)（運水孔）E恒溫

4、系統(tǒng)（加熱管，發(fā)熱線） F流道系統(tǒng)（唧咀孔，流道槽，流道孔） G頂出系統(tǒng)（頂針，頂棍）1.4模具的類型根據(jù)澆注系統(tǒng)型制的不同可將模具分為三類：（1）大水口模具：流道及澆口在分模 線上，與產(chǎn)品在開模時一起脫模，設(shè)計最簡單，容易加工，成本較低，所以較多人采用 大水口系統(tǒng)作業(yè)。（2）細(xì)水口模具：流道及澆口不在分模線上，一般直接在產(chǎn)品上， 所以要設(shè)計多一組水口分模線，設(shè)計較為復(fù)雜，加工較困難，一般要視產(chǎn)品要求而選用 細(xì)水口系統(tǒng)。（3）熱流道模具：主要由熱澆口套，熱澆道板，溫控電箱構(gòu)成。熱流道 模具是在一個半模有流道加熱系統(tǒng)的兩板式模具。熱流道系統(tǒng)分成兩個部分：分流板和 噴嘴。分流板的通道將射料傳送到一

5、個和分型線平行平面，這個平面在型腔的上面。噴 嘴垂直于分流板安裝，把射料從分流板送進(jìn)行腔。熱流道系統(tǒng)的優(yōu)勢：（1）無水口料，不需要后加工，使整個成型過程完全自動化，節(jié)省工作時間，提高工作效率。（2）壓力損耗小。注射模設(shè)計模具有很多的規(guī)則。這些規(guī)則和標(biāo)準(zhǔn)的做法，都是基于邏輯，過往的經(jīng)驗，方 便性，經(jīng)濟(jì)性。設(shè)計，模具制造，和成型，它通常的優(yōu)勢就是遵循規(guī)則。但有時候，它 可能會做出更好的，如果一項方法是被忽視和另一種方法被選擇。在一些書中，最普通的規(guī)則都會一一列出，而設(shè)計者設(shè)計的東西也僅僅是跟著以往的經(jīng)驗走而已。設(shè)計者應(yīng) 該研究出新的想法和方法，來進(jìn)行新的成型和選擇模具材料。注射工藝過程就是從給料斗

6、送進(jìn)粉狀或粒狀的射料混合物，經(jīng)過定量區(qū)和熔化區(qū)， 然后將其注射到模具型腔中。注射過程說明：模具是一種生產(chǎn)射料制品的工具。它由幾 組零件部分構(gòu)成，這個組合內(nèi)有成型模腔。注射時，模具裝夾在注射機(jī)上，熔融射料被 注入成型模腔內(nèi)，并在腔內(nèi)冷卻定型，然后上下模分開，經(jīng)由頂出系統(tǒng)將制品從模腔頂 出離開模具，最后模具再閉合進(jìn)行下一次注射，整個注射過程是循環(huán)進(jìn)行的。注射模至少是由裝在注射機(jī)的兩個壓板上的兩部分組成，以便可以開模和合模。在 合模的時候，模具的兩半部分形成的產(chǎn)品成型表面是由射料熔體通過澆口和熱流道系統(tǒng) 注入模具型腔形成的。模具中冷卻的原則是產(chǎn)品要在模具中冷卻和凝固，以便隨后可以脫模。隨著產(chǎn)品注射的

7、完成，模具就必須開模。產(chǎn)品的形狀決定著它是否由模具兩部份簡 單地開?；蛴捎袀?cè)向分型來開模。模具的設(shè)計是由產(chǎn)品的形狀和產(chǎn)品開模的方式?jīng)Q定 的。注射成型的產(chǎn)品可以分為以下幾類：無側(cè)抽芯的產(chǎn)品；有側(cè)向開口的外側(cè)抽芯的產(chǎn)品；有內(nèi)側(cè)抽芯的產(chǎn)品；有外側(cè)抽芯和內(nèi)側(cè)抽芯的產(chǎn)品。注射模具的組成3.1型腔空間型腔空間是在模具中的一個形狀，當(dāng)注射的材料充滿這個空間的時候，它就會呈現(xiàn) 出和型腔空間一樣的形狀。在注射成型時，射料是通過很高的壓力注射入型腔空間的，所 以模具必須要足夠的堅固來抵抗注射的壓力，以防變形。3.2型腔的數(shù)量許多的模具，特別是較大產(chǎn)品的模具，僅僅只有一個模具型腔，但是也有許多的模 具，特別是比較大

8、型的模具，都會有 2個或更多的型。究其原因就是它純粹的經(jīng)濟(jì)性。 它僅僅是注入多個型腔比注入一個型腔多花了一點的時間。今天，大多數(shù)的模具型腔數(shù)量都是以這些數(shù)字為參考的：2,4,6,8,12,16,24,32,48,64,96,128。選擇這些數(shù)字（偶數(shù)）的原因是為了在長方形區(qū)域內(nèi)布置型腔方便，這樣就有利于設(shè)計、定尺寸、加工制 造和圍繞機(jī)器中心對稱，這種對稱分布對于保證每個型腔分配到相同的鎖模力非常重 要。3.3型腔和型芯按照習(xí)慣，腔空間的中空部分稱為型腔。與型腔空間所匹配的部分稱為型芯。大部分射膠制品是杯形的。但這并不意味著它們看起來就像是一個杯，只是它們有一個內(nèi)部和外部。產(chǎn)品的外部是由型腔形成

9、的，而內(nèi)部是有由型芯形成的。通常情況下，型腔 是位于注射一邊的那半模具上，而型芯是位于可以移動的那半模具上的。這樣安排的原 因是注射機(jī)上的移動板有一個彈射裝置 ，而產(chǎn)品是收縮和包緊在型芯上的，然后產(chǎn)品就 可以通過此來彈射出來。大部分的注射機(jī)在注射的一邊都不會安裝彈射裝置。對于模具包含復(fù)雜型腔和多型腔模具，試圖象整體模具那樣在一塊鋼板加工型腔和 型芯是不讓人滿意的。型腔和型芯分別決定著成型的外部和內(nèi)部的形狀，而它們的整體決定著整個成型的方式。3.4分模線為了能夠生產(chǎn)出一個模具，我們必需具備有兩個分半的模具，一半裝型腔一半裝型 芯。這兩個板分離時的部分叫做分模線，簡稱P/L。其實,這是一個分離的區(qū)

10、域或面，但是 為了方便,我們習(xí)慣叫它成一條線。模具的分型面是兩模板接近型腔的那些部分，它們對接一起形成油封并且避免型腔里射性材料的損失。分模線可以是任何形狀的，許多的注射成型都是要求分模線是不在同一平面或是曲面的，但是為了便于模具制造，最好設(shè)計在同一個平面上。為了能夠在模具上脫出產(chǎn)品，分模線總是在分布在產(chǎn)品最寬的圓周區(qū)域。對一些形狀來說，設(shè)置分模線或其角度是非常有必要的，但是在任何情況下，都 要有目的地讓它容易加工，以確保當(dāng)注射的時候模具能夠緊緊地合在一起。如果分模線 設(shè)計不好，射料將會溢出來，那樣產(chǎn)品就會有一個非常大的凹陷，那樣的產(chǎn)品肯定會被拆 除,否則那樣的產(chǎn)品是不能夠使用的。甚至更危險的

11、是，射料噴射進(jìn)模具的時候，它會飛濺出傷害到人本身。3.5流道和澆口現(xiàn)在,增加介紹的是把射料從外面帶到型腔空間的裝置。在射料冷卻之前（也就是射料冷卻后不能在流動之前）,它必需有足夠的壓力以便使射料能夠充滿型腔。 流動的通道 就是流道，它把注射機(jī)的噴嘴和模具連接了起來，流道是一個獨立的型腔，流道本身要 光滑,以便可以阻止射料自由流動。同時，型腔被充滿后，澆口處先凝固，注射機(jī)螺桿 抽回時可防止成型中的回流。澆口是一個小型的開口，它引導(dǎo)著流道到型腔空間。澆口是一個渠道，是連接與流道相通的小口。與其他的進(jìn)料系統(tǒng)相比，它有一個很小的橫截面 積。在射料充滿型腔后，澆口很快就會冷卻，注射的噴嘴往后退，在模具退

12、后的時候射料 還是留有在噴嘴中的。注射機(jī)的工作過程注射模具是安裝在注射機(jī)上的，它的注射成型過程是由注射機(jī)來完成的。以下是注 射機(jī)的工作過程：注射成型機(jī)通過抽真空把射料原料從干燥機(jī)吸到料斗里面。料斗實際 上是一個小的漏斗，它被安裝在機(jī)臺料筒的后面。開始起實際作用的地方是料筒，料筒 實質(zhì)上是四周都是加熱器的一個很大的螺桿安放室，它把原料送向模具。隨著螺桿的旋 轉(zhuǎn)，原料在料筒里前進(jìn)并成為熔融狀態(tài)。只有完全熔融后，原料才會在螺桿高速旋轉(zhuǎn)產(chǎn) 生的擠壓力下射進(jìn)模腔。當(dāng)螺桿前端壓室注滿射料時，螺桿被迫后退，斷開限位開關(guān)而 開動液壓缸，從而向前推動螺桿，將熔融射料注射到閉合的模具型腔中。 型腔被充滿后， 澆口

13、處先凝固，注射機(jī)螺桿抽回時可防止成型中的回流。螺桿端部稱為噴嘴，從這里開 始直到模具型腔這段空間內(nèi)，熔融材料沒有被加熱，并且一直處于被冷卻的狀態(tài)。流道 水口料就是在噴嘴到模腔之間冷卻固化的射料，屬于工藝廢料。實際上，在噴嘴到模腔 之間的冷卻射料是“主流道”，但它和流道是連在一塊的。有一些關(guān)于處理水口料的方 法，但這不是我們這里要討論的。大多數(shù)人以前都見過流道，但卻沒有認(rèn)出。最容易見 到他們的地方是由單獨零件構(gòu)成的飛機(jī)和汽車模型上，在這些零件上面一般都附著著流 道系統(tǒng)。一般地，水口料被頂出，落進(jìn)安放在模具下面的落料裝置（通過一個斜坡傳送 通道），或者被機(jī)械手取出，然后投入粉料機(jī)。粉料機(jī)把水口料絞

14、成碎料并送回干燥機(jī)。盡管塑料一旦被加熱就會發(fā)生降解，而且有些成型工藝不允許碎材混入原材料里 面，因為這樣會導(dǎo)致成品的缺陷。這種情況下水口料可以用到其他地方或者干脆不用。 收縮在成型中影響深遠(yuǎn)，大部分塑料冷卻后會收縮 20%為了在重點（關(guān)鍵）塑料零件 上-當(dāng)然不只是玩具克服這種現(xiàn)象，模具設(shè)計者必須把這個要素考慮到設(shè)計里面去， 那樣成型出來的產(chǎn)品才能滿足設(shè)計規(guī)格。頂針是模具本身的零件，用來在模具打開的時候頂出產(chǎn)品。整個過程都有注射成型機(jī)控制。一個成型周期實際上就是合模-注射-開模-頂出。模具被鎖緊在機(jī)臺上，前模固定不動（在機(jī)臺的料筒側(cè)），后模則可以移 動。上面說的頂針就是后模側(cè)。當(dāng)模具打開，產(chǎn)品吸

15、附在后模側(cè)以被頂出。以上就是關(guān)于注射模具的相關(guān)介紹。The in troduti on of the Injectio n MoldMold basic kno wledgeIn troducti onThere is a close relati on ship with all kinds of mold,which are refered to our daily product ion, and life in the use of the various tools and products, the large base of the machi ne tool, the body

16、 shell, the first embryo to a small screws, buttons, as well as various home appliances shell. Mold s shape determ ine the shape of these products, mold s precisi on and machi ning quality determ ine the quality of these products,too. Because of a variety of products, appearanee, specifications and

17、the different uses,mold devide into Die Casting into the mould, die forging, die-casting mould, Die, and so on other non - plastic molds, as well as plastic mold. In rece nt years, with the rapid developme nt of the plastics industry, and GMand engineering plastics in areas such as strength and accu

18、racy of the continu ous enhan ceme nt , the scope of the applicati on of plastic products have also constantlyexpanded, such as: household appliances,in strume ntati on, con structi on equipme nt, automotive, daily hardware, and many other fields, the proportionof plastic products is rapidly increas

19、ing. Arati onal desig n of plastic parts ofte n can replace much more traditi onal metal pieces. The trend of in dustrial products and daily products plasticed is rising day after day.Mold general defin itionIn the in dustrial producti on , with the variouspress and the specialin strume nts which in

20、 stalled in the press,it produces the required shape parts or products through pressure on the metal or non-metallicmaterials, this specialin strume nts collectively call as the mold.Mold gen eral classificati onMold can be divided into plastic and non - plastic mould: (1) Non-plastic mould: Die Cas

21、ting, forging Die, Die, die-casting mould and so on. A. Die Casting -taps, pig iron platformB. Forgi ng Die - car body C. Die - computer panel D.Die Cast ing Die - superalloy, cyli nder body (2) For the producti on tech no logy and product ion, the plastic mold are divided into differe nt products:

22、A. Injectio n moldi ng die - TV cas ing, keyboard butt on (the most commorapplicati on) B. In flatable module - drink bottles C. Compressi on moldi ng die - bakeliteswitches,scientificCiwan dish D. Transfermolding die - IC products E.Extrusi on die - of glue, plastic bags F. Hot forming die - tran s

23、pare nt shell moldi ng packag ing G. Rotomouldi ng mode - Flexible toy doll. In jecti on Moldi ng is the most popurlar method in plastics produc ing process. The method can be applied to all parts of thermoplastic and some of thermosett ing plastics, the quantityof plasticproductionis much more than

24、 any other formingmethod .I nject ionmold as one of the ma in toolsofinjectio nmoldi ngprocess in g,whosh product ion efficie ncy is low or high in the quality of precision 、manufacturing cycle and the process of injection molding and so on,directly affect the quality of products, production,cost an

25、d product updates,at the same time it also determ ines the competitive ness of en terprises in the markets resp onse capacity and speed. Inject ion Mold con sists of a nu mber of plate which mass with the various comp onent parts. It divided in to: A mold ing device (Die, punch)B positioning system

26、(I. column I. sets) C fixtures (the word board, code-pit) D cooli ng system (carry ing water hole) E thermostat system (heating tubes, the hotline) F-Road System (jack Tsui hole, flow slot, streaming Road Hole) G ejectio n system (Din gzhe n, top stick).Type of moldIt can be divided in to three cate

27、gories accordi ng to gati ng system with the differe nt type of mold :(1) in take die: Runner and gate at the partig lin e,it will strip together with products whe n in the ope n mode,it is the most simple of design, easy processing and lower costing.So more people operations by using large in take

28、system. (2) small in let die:It gen eral stay in the products directly,but runner and gate are not at the partig lin e.Therefore,it should be design a multi-outlet parting line.And then it is more complex in the designing, more difficult in process ing, gen erally chos ing the small inlet die is dep

29、e nding on the product s requirements. (3) hot runner die:It consists of heat gate, heat runner plate, temperature control box. Hot runner molds are two plate molds with a heated runner system in side one half of the mold. A hot runner system is divided into two parts: the manifold and the drops. Th

30、e manifold has channels that convey the plastic on a sin gle pla ne, parallel to the part ing line, to a point above the cavity. The drops, situated perpendicular to the manifold, convey the plastic from the manifold to the part. The advantages of hot runner system : (1) No outlet expected, no n eed

31、 process ing, the whole process fully automated, save time and enhance the efficie ncy of the work. (2) small pressure loss.2、Injection MoldThere are manyrules for designing molds.These rules and standard practices are based on logic,pastexperie nce,c onvenien ce,a ndeconomy .For desig nin g,moldmak

32、in g,a nd moldi ng,itis usuallyof adva ntage to follow the rules.Butoccasi on ally,itmaywork out better if a rule is ignored and an alter nativewayis selected .Insometexts,the most commorrules are no ted,but the desig ner willlearn only from experie nee which way to go.The desig ner must ever be ope

33、 n to new ideas and methods,to new mold ing and mold material that may affect these rules.The process consists of feeding a plastic compoundin powdered or granular form from a hopper through meteri ng and melt ing stages and the n injecting it into a mold .I njectio n mold ing process: Mold is a pro

34、ducti on of plastic tool.It con sists of several parts and this group contains formi ng cavities. When it injects molding, mold clamping in the injectionmolding machine, melting plasticis Injected formi ng cavities and cooli ng stereotypes in it, the n it separate upper and lower die,it will push th

35、e product ion from the cavity in order to leave the mold through ejectio n system, fin ally mold close aga in and prepared the n ext injectio n. The en tire process of injectio n is carried out of the cycle.An injectio n mold con sists of at least two halves that are faste ned to the two plate ns of

36、 the injectio n moldi ng machi ne so that can be ope ned and closed .In the closed positi on ,theproduct-form ing surfaces of the two mold halves defi nethe mold cavity into which the plastic melt is injected via the runner system and the gate.Cooling provisions in the mold provide forcoolingandsoli

37、dificati on of the molded product so that it can be subseque ntly ejected.For product ejection to occur,the mold must ope n. The shape of the molded product determines whether it can be ejected simply by opening the two mold halves or whether undercuts must be present.The design of a mold is dictate

38、d primarily by the shape of the product to be molded and the provisions necessary for product ejectio n.l njectio n-m olded products can be classified as:.Products without un ducts with exter nal un dercuts of lateral ope nin ducts with internal un ducts with exter nal an

39、d internal un dercuts.The compositi on of injecti on moldMold Cavity SpaceThe mold cavity space is a shape in side the mold,whe n the mold ing material is forced into this space it will take on the shape of the cavity space .In injectio n moldi ng the plastic is injected into the cavity space with h

40、igh pressures。the mold must be strong eno ugh to resist the in jecti on pressure without deform ing.Number of CavitiesMany molds,particularly molds for larger products,ate built for only 1 cavity space,but many molds,especially large product ion molds,are built with 2 or more cavities.The reason for

41、 this is purely economical.lttakes only littlemore time to inject several cavities tha n to inject on e.Today,most multicavity molds are built with a preferred nu mber of cavities:2,4,6,8,12,16,24,32,48,64,96,128.These numbers are selected because the cavities can be easily arra nged in a recta ngul

42、ar patter n, which is easier for desig ning and dime nsio nin g,for manu facturi ng,a nd for symmetry around the center of the machine ,which is highly desirable to ensure equal clamping force for each cavity.Cavity and CoreBy convention,thehollow portionof the cavity space is called thecavity.The m

43、atchi ng,ofte n raised porti on of the cavity space is called the core.Most plastic products are cup-shaped.This does not mean that they look like a cup,but they do have an in side and an outside.The outside of the product is formed by the cavity, the in side by the core.Usually,the cavities are pla

44、ced in the mold half that is mounted on the injection side,while the cores are placed in the moving half of the mold.The reason for this is that all injection molding mach ines provide an ejectio n mecha nism on the movi ng plate n and the products tend to shri nk on to and cli ng to the core,from w

45、here they are the n ejected.Most injection moldingmachines do not provide ejection mechanisms on theinjectionside.For moulds containing intricateimpressions,and for multi-impression moulds,it is n ot satisfactory to attempt to machi ne the cavity and core plates from sin gle blocks of steel as with

46、in teger moulds. The cavity and core give the molding its external and internal shapes respectively, the impression imparting the whole of the form to the mold ing.The Parti ng LineTo be able to produce a mold,we must have ta least two separate mold halves,with the cavity in one side and the core in

47、 the other.The separatio n between these plates is called the parting line,and designated P/L.Actually,this is a part ing area or pla ne,but,by cinven ti on ,i n this in text it is referred to as a line. The parting surfaces of a mould are those portion of both mould plates, adjace nt to the impress

48、i ons, which butt together to form a seal and preve nt the loss of plastic material from the impression.The parting line can have any shape, many moldings are required which have a parting line which lies on a non-planar or curved surface,but for ease of mold manu facturi ng,it is preferable to have

49、 it in one pla ne.The parting line is always at the widest circumfere nee of the product,to makeejectionof the product from the mold possible.With someshapesit may be n ecessary to offset the P/L,or to have it at an an gle,but in any eve nt it is best to have is so that itan be easily machined,and o

50、ften ground, to ensure that it shuts off tightly whenthe mold is clamped during injection.lf the parting line is poorly fini shed the plastic will escape,which shows up on the product as an unsightlysharp projection,whichmust then be removed;otherwise,theproduct could be unu sable.There is eve n a d

51、an ger that the plastic could squirt out of the mold and do pers onal dan ger.Runners and GatesNow,we must add provisi ons for bringing the plastic into these cavity spaces.This must be done with eno ugh pressure so that the cavity spaces are filled completely before the plastic freezes(that is,cool

52、s so muchthat the plasticcannot flow anym ore).The flow passages are the sprue,from wherethe mach ine nozzle contactss the mold,the runners,whichdistribute the plastic to thein dividual cavities, the wall of the runner cha nnel must be smooth to preve nt any restrictionto flow. Also, as the runner h

53、as to be removed with the molding,there must be no mach ine marks left which would tend to retain the runner in the mould plate.A nd the gates which are small ope nings leadi ng from the runner into the cavity space. The gate is a cha nnel or orifice connecting the runner with the impression. It has

54、 a small cross-sectional area when compared with the rest of the feed system. The gate freezes soon after the impressi on is filled so that the inject ion plun ger can be withdraw n without the probability of void being created in the mold ing by suck-back.The injectio n moldi ng mach ine processInj

55、ectio n Mold is in stalled in the injectio n moldi ng mach ine, and its injection molding process is completed by the injection molding machine. Follow ing is the injectio n moldi ng mach ine process.The mold ing mach ine uses a vacuum to move the plastic from the dryer to its initial holding chambe

56、r. This chamber is actually a small hopper on the back of the barrel of the mach ine。The barrel is where all the real work is done and its essentially a large screw housed in a heater which movesthe plastic closer to the mold. As the screw turns, the plastic traverses the barrel and reaches a molten

57、 state. Only whenitsmoltencan it be injected in to the mold with a rapid turn of the screw. As the chamber in front of the screw becomesfilled, it forces the screw back, trippinga limitswitch that activates a hydraulic cyli nder that forces the screw forward and injects the fluid plastic in to the c

58、losed mold. The gate freezes soon after the impression is filled so that the injectionplunger can be withdrawn without theprobability of void being created in the mold ing by suck-back. The tip of the barrel is called theno zzle and from this point to the cavity in the mold thematerial is not heated

59、 and is constantly cooling. The runner is the cooled/set plastic that extends from the nozzle to the cavity and is process scrap. Actually, the cooled material from the nozzle to the mold is the sprue but its connected to the runner. There are ways around having sprues and runners, but itsbeyondthe

60、scope of what were talking about here. Most people have probably seen runners before and not realized it. The most likely place to see them are in model airpla ne/car kits as the in dividual comp onents are left attached to the runner system. Typically the runners are ejected in to a chute below the