玩具小車(chē)上蓋注塑模具設(shè)計(jì)
以上為資料預(yù)覽概圖,下載文件后為壓縮包資料文件。【清晰,無(wú)水印,可編輯】dwg后綴為cad圖,doc后綴為word格式,需要請(qǐng)自助下載即可,有疑問(wèn)可以咨詢(xún)QQ 197216396 或 11970985
編號(hào): 畢業(yè)設(shè)計(jì)外文翻譯(譯文)題目: 注塑成型指南 院(系): 機(jī)電工程學(xué)院 專(zhuān)業(yè): 機(jī)械設(shè)計(jì)制造及其自動(dòng)化 學(xué)生姓名:學(xué)號(hào):指導(dǎo)教師單位:姓名:職稱(chēng): 2014年5月26日 桂林電子科技大學(xué)畢業(yè)設(shè)計(jì)(論文)報(bào)告用紙 第 26 頁(yè) 共 26 頁(yè)注塑成型指南引言目標(biāo)本文檔提供了零件設(shè)計(jì),模具設(shè)計(jì)和苯乙烯嵌段共聚物(SBC),熱塑性彈性體的處理準(zhǔn)則。 GLS的產(chǎn)品系列,其中包括苯乙烯類(lèi)熱塑性彈性體等科騰化合物,DYNAFLEX熱塑性彈性體化合物和的Versaflex TPE合金。SBC流變性SBC的一個(gè)主要特點(diǎn)是,它們都依賴(lài)剪切,是剪切依賴(lài)性的材料,其粘度是在低剪切速率(如擠出)較高,在高剪切速率下(如在注射成型)較低。因此,SBC化合物在高剪切速率會(huì)更容易地流入模具的薄的區(qū)域。SBC的高剪切速率粘度降低的性能應(yīng)在設(shè)計(jì)精密注塑模具時(shí)和設(shè)置加工模具的條件過(guò)程中予以考慮。圖1:苯乙烯類(lèi)熱塑性彈性體化合物受GLS的粘度剪切速率的影響 (在390F(200C)測(cè)定)。要獲得關(guān)于單個(gè)等級(jí)的粘度信息,請(qǐng)參閱產(chǎn)品技術(shù)數(shù)據(jù)表,可在www.glscorporation.com或聯(lián)系您的GLS代表。零件設(shè)計(jì)一般零件設(shè)計(jì)概念當(dāng)設(shè)計(jì)一個(gè)TPE零件,應(yīng)遵循的幾個(gè)基本原則:零件壁厚應(yīng)盡可能均勻。從厚到薄的區(qū)域的過(guò)渡應(yīng)循序漸進(jìn),以防止流通的問(wèn)題而產(chǎn)生的填充缺陷。 厚部分應(yīng)挖出來(lái)減少收縮,降低零件重量(和循環(huán)時(shí)間)。 半徑/圓角所有的尖角,促進(jìn)流動(dòng),盡量減少無(wú)填充區(qū)域。 應(yīng)避免深盲孔或肋板。 避免壁薄,防止排氣時(shí)產(chǎn)生破裂。 過(guò)小的斜度會(huì)難以脫模。流動(dòng)長(zhǎng)度與壁厚可達(dá)到的最大流動(dòng)長(zhǎng)度是依賴(lài)于所選擇的特定材料,該零件的厚度,和加工條件。一般來(lái)說(shuō),吉力士化合物會(huì)比其他類(lèi)型的熱塑性彈性體流入更遠(yuǎn)更薄的壁。流向厚度比最大應(yīng)為200;然而,這是依賴(lài)于材料和部件的設(shè)計(jì)。高流動(dòng)GLS熱塑性彈性體化合物(如VERSALLOY)已成功地用于通流比高達(dá)400的填充。材料的填補(bǔ)零件的能力可以通過(guò)螺旋線(xiàn)流的測(cè)量進(jìn)行比較分析。螺旋流動(dòng)試驗(yàn)是通過(guò)將材料注射到一個(gè)螺旋模具(類(lèi)似于形成為螺旋形帶狀)上進(jìn)行。該材料流動(dòng)的距離的單位是英寸。在這種情況下,螺旋流動(dòng)試驗(yàn)中采用兩種不同的注射速度(3英寸/秒和5英寸/秒)進(jìn)行。各種GLS產(chǎn)品系列的典型的螺旋線(xiàn)流動(dòng)長(zhǎng)度概述于表1中。隨著具體的化合物,高達(dá)40英寸的流動(dòng)長(zhǎng)度(以5英寸/秒注射速度)是可能的。表1 GLS化合物典型的螺旋流動(dòng)長(zhǎng)度為系列流動(dòng)長(zhǎng)度3英寸/秒5英寸/秒Dynaflex D13-1518-20Dynaflex G12-2218-30Versaflex 9-1613-26*螺旋流動(dòng)試驗(yàn),寬通道使用0.0625的厚度和0.375,在400F進(jìn)行如需有關(guān)螺旋流的特定等級(jí)或其他詳細(xì)信息螺旋流信息測(cè)試程序,請(qǐng)參閱GLS公司TPE提示表7,可在 www.glscorporation.com或聯(lián)系您的GLS代表。倒扣熱塑性彈性體的柔軟性和彈性性質(zhì)允許有倒扣的零件結(jié)構(gòu)。由于其優(yōu)異的復(fù)原特性,GLS的化合物是能夠被拉伸和變形,從而允許它們倒扣深拉(圖2)。如果內(nèi)部和外部的倒扣存在于相同的部分,滑塊和型芯分割可能是必要的。部件與內(nèi)部倒扣(例如燈泡形部件)可以是通過(guò)利用核心的提升閥的從型芯中彈出。由于變形脫模時(shí)可能會(huì)產(chǎn)生輕微的永久伸長(zhǎng)率(3 - 8)。圖2 TPE零件倒扣的例子。澆口與熔接痕位置產(chǎn)品工程師應(yīng)該指出零件的表面那些是影響功能的,并在圖紙上表明這些信息。這將幫助模具設(shè)計(jì)人員,以確定允許的澆口和熔接痕位置。各向異性具有在流動(dòng)方向與橫流方向不同的性質(zhì)的熱塑性材料(90垂直于流動(dòng)方向)被定性為“各向異性”材料??赡苁苡绊懙膶傩允鞘湛s和拉伸性能。當(dāng)聚合物鏈取向的流動(dòng),從而導(dǎo)致在流動(dòng)方向上較高的物理性質(zhì)的各向異性的方向發(fā)生。壁厚,注射速度,熔體溫度和模具溫度是影響各向異性的幾個(gè)變量。根據(jù)不同的工藝條件和模具設(shè)計(jì),吉力士苯乙烯類(lèi)TPE復(fù)合材料表現(xiàn)出一定程度的各向異性。收縮由于它們的各向異性的性質(zhì),GLS的苯乙烯類(lèi)熱塑性彈性體化合物的收縮在流動(dòng)方向上比在交叉流動(dòng)方向更多。通常,SEBS化合物具有更高的收縮率,并且比SBS化合物更多的各向異性。SEBS類(lèi)化合物的典型收縮值是1.3 - 2.5,而對(duì)于SBS系化合物是0.3 - 0.5。較軟的SEBS化合物(低于30邵氏A)收縮率比較硬的材料大。一些材料,如DYNAFLEX G7700,G7800,G7900和系列含有填充物,從而降低其收縮率。通常GLS的收縮率是按0.125倍壁厚確定的。但應(yīng)注意的是,收縮率不是一個(gè)確切的數(shù)字,而是一個(gè)范圍值。這個(gè)范圍會(huì)受到零件的壁厚,熔體溫度,模具溫度,注射速度,填充和保壓的壓力的影響,也受成型時(shí)間的影響。因此,零件必須設(shè)置一定的公差,以更好地量化材料在特定應(yīng)用中的特定等級(jí)的實(shí)際收縮率。有關(guān)特定牌號(hào)收縮率,請(qǐng)參閱產(chǎn)品技術(shù)數(shù)據(jù)表,可在www.glscorporation.com或聯(lián)系您的GLS代表。模具設(shè)計(jì)模具的類(lèi)型吉力士SBC化合物可使用在二板和三板模具。常規(guī)和熱流道模具設(shè)計(jì)已使用GLS化合物。推薦自絕緣熱流道模具的設(shè)計(jì)是由于在滯流區(qū)的材料存在降解的可能。雙射模具和插入件的模具也可以被使用。如果時(shí)同一家廠(chǎng)商生產(chǎn)的模具,腔體體積應(yīng)該是相似的,否則可能會(huì)產(chǎn)生過(guò)度填充或填充不滿(mǎn)。鋼材的選擇吉力士熱塑性彈性體苯乙烯一般都是非研磨性和非腐蝕性。模具鋼的選擇將取決于零件的要生產(chǎn)的數(shù)量和質(zhì)量。對(duì)于大批量的生產(chǎn),提高模具的初始費(fèi)用是一個(gè)明智的投資。 各種各樣的模具鋼可用于注塑模結(jié)構(gòu)。表2列出了常見(jiàn)的模具鋼用于制造的典型模具零件的屬性,包括軟金屬,如鋁和銅鈹合金,可用于樣機(jī)零件或多達(dá)10000份的小批量生產(chǎn)。表2 典型模具鋼注塑模結(jié)構(gòu)鋼種類(lèi)鋼材特性模具組件P-20硬度高,機(jī)械性能良好,高碳鋼,一般用途的鋼。缺點(diǎn):如果儲(chǔ)存不當(dāng)可能會(huì)生銹。模架,頂出板,和一些模腔(如果鍍鎳或鍍鉻,以防止生銹)。H-13良好的通用工具鋼??梢?huà)伖饣蜻M(jìn)行熱處理。更好的耐腐蝕性。腔板和芯板。S-7高硬度,較高韌性,一般用途工具鋼。 機(jī)械性能良好,耐沖擊,耐磨。缺點(diǎn):成本高。型腔板,芯板和層壓板,以及薄壁部分。A-2良好的高韌性工具鋼。熱處理和耐磨性好。頂針,推管,頂桿和葉片。D-2高強(qiáng)度,高耐磨特性,高釩含量,有點(diǎn)脆。缺點(diǎn):難加工。耐磨墊板,耐磨滑塊。420 SS堅(jiān)韌的耐腐蝕材料,熱處理和耐磨性好。 缺點(diǎn):成本高。腔體塊,頂針,套筒等。某些零件的設(shè)計(jì)可能會(huì)受益于使用較高的熱導(dǎo)率的材料如銅鈹合金。這種材料比鋼輕耐用,如果用在分型面可能磨損比鋼更快。鈹銅合金可用于插入,滑塊或型芯,以增加傳熱速率和減少循環(huán)時(shí)間。在有很長(zhǎng)的型芯結(jié)構(gòu)的情況下,高熱導(dǎo)率的零件是很有益的。模具表面處理,整理和紋理大多數(shù)GLS材料注塑成型表面相當(dāng)好。為產(chǎn)生有光澤的表面,在填充成型前拋光模具是必需的。高度拋光模具和透明材料,可以生產(chǎn)出具有良好的清晰度的零件。如果需要類(lèi)似于熱固性橡膠的亞光,則應(yīng)該使用一個(gè)粗糙的模具(或GLS產(chǎn)品,如GLS VERSALLOY TPV合金,這自然產(chǎn)生了磨砂表面)。在一般情況下,一個(gè)電火花加工表面會(huì)產(chǎn)生良好的手感,并可能使零件脫模過(guò)程中從模具釋放更加容易。磨砂表面也可以掩飾任何流痕或其他表面缺陷。蒸汽珩磨,噴砂或噴丸和化學(xué)蝕刻也可以用來(lái)產(chǎn)生表面紋理具有不同程度的光澤度和外觀(guān)的零件。為了幫助脫模,在噴砂或電火花加工后型腔或型芯可涂覆剝離涂層如PTFE浸漬鎳。澆口和澆道拉料桿設(shè)計(jì)澆道應(yīng)有足夠的錐度,從1度到3度,以減少阻力和防止?jié)驳辣徽匙?。長(zhǎng)直澆道可能需要更多的錐度(3 - 5),如圖3,主流道的直徑應(yīng)比噴嘴直徑稍大。在電火花加工完成后是可以適應(yīng)的大多數(shù)苯乙烯熱塑性彈性體材料的。永久性脫模劑處理也已成功地使用。 拉料桿的設(shè)計(jì)變化與材料的硬度。不同的澆道尺寸設(shè)計(jì)見(jiàn)圖4到圖7。此外,表3示出了用于一個(gè)典型澆道設(shè)計(jì)的適用錐度范圍。表3 各種用于典型澆口設(shè)計(jì)的硬度值典型的熱塑性彈性體硬度 范圍最常見(jiàn)的澆口拉料桿類(lèi)型數(shù)值 50邵氏A錐形,針,Z型3,4和640-70邵氏A底切55-40邵氏A松樹(shù)7熱澆道襯套和擴(kuò)展的噴嘴,也可以使用與GLS的化合物。在許多模具,澆口一般設(shè)在在模具中最厚的壁部,這樣需要最小的冷卻時(shí)間。使用一個(gè)熱澆道,其可以被看作是在機(jī)器噴嘴的延伸,有時(shí)可以減少周期時(shí)間。延伸機(jī)器的噴嘴也可用于降低澆道長(zhǎng)度和大小。當(dāng)使用熱澆道使用時(shí),機(jī)器的噴嘴端頭應(yīng)是自由運(yùn)動(dòng)的噴嘴,而不是相反的固定流道。圖3 圓錐拉料桿 圖4 Z-針拉料桿 圖5 倒扣拉料桿圖6 箘形拉料桿圖7 松樹(shù)拉料桿常規(guī)的流道的結(jié)構(gòu)與設(shè)計(jì)設(shè)計(jì)腔內(nèi)平衡流道是得到統(tǒng)一質(zhì)量的零件的關(guān)鍵。在平衡的流道系統(tǒng)中,熔體以相等的時(shí)間和壓力流入各個(gè)模腔。澆道平衡可以通過(guò)使用計(jì)算機(jī)模流分析程序進(jìn)行設(shè)計(jì),并通過(guò)執(zhí)行短射的研究證實(shí)。不平衡的流道,可能會(huì)導(dǎo)致不一致的零件重量和尺寸的變化。最接近澆道的型腔可能過(guò)填充而溢料。由于在注射成型后,零件也可能產(chǎn)生較高的內(nèi)應(yīng)力,從而導(dǎo)致翹曲。平衡流道系統(tǒng)的例子示于圖8和圖9。圖8 平衡式蜘蛛流道 圖9 平衡剖面流道圖10顯示了不同的澆道橫截面和它們相關(guān)的效率。圓形流道具有減少流動(dòng)阻力和表面面積,使材料保持熔融更長(zhǎng)。第二個(gè)最有效的澆道橫截面是梯形截面。U形流道的結(jié)構(gòu)與梯形流道的截面形狀和性能接近,只需要加工在分型面一側(cè)。圖11顯示了典型的流道截面形狀和相應(yīng)的尺寸。圖12示出了典型澆道的尺寸。圖10。典型的流道橫截面 圖11 普通流道的截面形狀圖12 典型澆道的尺寸冷料穴是澆注系統(tǒng)的結(jié)構(gòu)。冷料穴的作用是接收熔體的前鋒冷料。與澆道連接的位置結(jié)構(gòu)應(yīng)該足夠大,以接收模具注塑成型循環(huán)過(guò)程中在機(jī)器噴嘴中形成的冷料。典型冷料穴尺寸為約流道的1.5到2.0倍的直徑或?qū)挾?。分流道在分型面下分流道和型芯底部存在倒扣,料流通過(guò)分澆道不應(yīng)該受到限制。圖8和圖9顯示了分流道和拉料桿的典型位置。圖13顯示了一個(gè)分流道的設(shè)計(jì)實(shí)例。 圖13分流道的設(shè)計(jì)實(shí)例澆口的設(shè)計(jì)與位置大多數(shù)傳統(tǒng)的澆口類(lèi)型都適合加工吉力士苯乙烯類(lèi)熱塑性彈性體化合物。澆口的形式和位置,相對(duì)于該零件的類(lèi)型,可能會(huì)影響到以下內(nèi)容: 零件的填料 澆口拆除或去除痕跡 部分化妝品的外觀(guān) 零件尺寸(包括翹曲)澆口所選的類(lèi)型取決于零件和模具設(shè)計(jì)。而澆口的位置同樣重要的。為了防止噴射產(chǎn)生,找到一個(gè)區(qū)域的設(shè)置澆口防止熔體直接撞擊腔壁。較軟的熱塑性彈性體的彈性特性使得潛伏式澆口設(shè)計(jì)的自動(dòng)去除澆口模具或三板模具自動(dòng)去除澆口痕跡更加困難。更高的硬度和填充級(jí)通常具有較低的極限伸長(zhǎng)率,因此更容易去除澆口痕跡。為了保證澆口會(huì)打破在特定位置,它們應(yīng)具有短的長(zhǎng)度以創(chuàng)建高應(yīng)力集中。側(cè)澆口 側(cè)澆口(圖14)是冷熱流道系統(tǒng)中最常見(jiàn)的傳統(tǒng)的澆口。它們位于塑件的分型面上。一個(gè)小切口即可,放在那里的澆口符合零件減少去除澆口痕跡的難度的要求。側(cè)澆口的優(yōu)點(diǎn)是便于制造,改裝及維修。澆口深度(D)應(yīng)為壁厚的15%,在澆口入口為30。常見(jiàn)做法是啟動(dòng)“安全”。 一個(gè)很好的起點(diǎn)澆口寬度應(yīng)為1.0 - 1.5倍的澆口深度。澆口寬度應(yīng)等于或大于澆口深度略長(zhǎng)。澆口的大小也取決于該零件大小。可以被插入到流道區(qū)方便澆口維修或改裝。圖14 側(cè)澆口 圖15 潛伏式澆口潛伏式澆口是自去澆口。在零件脫模時(shí),自動(dòng)分離零件和澆口。圖15顯示了一個(gè)潛伏式澆口的典型設(shè)計(jì)。潛伏式澆口不應(yīng)該被用于中軟硬度,高摩擦和高伸長(zhǎng)率的化合物。扇形澆口扇形澆口是一個(gè)側(cè)澆口的流線(xiàn)型變化(圖16) 扇形澆口所分銷(xiāo)材料到型腔中更均勻;因此,它通常是使用在高平直度和不存在的曲面的零件中。它也最大限度地減少澆口引起皺褶或零件翹曲的可能性。 圖16 扇形澆口 直接澆口或中心澆口直接澆口或中心常用于原型部件,因?yàn)樗鼉r(jià)格低廉。不建議使用,因?yàn)檫@種澆口類(lèi)型適用于類(lèi)似吉力士苯乙烯類(lèi)化合物的高伸長(zhǎng)率塑料。此外,直澆口需要修整,而且塑件的外觀(guān)質(zhì)量部分通常較差。如果使用直澆口,應(yīng)注意保持雙方的澆口長(zhǎng)度和直徑盡可能短,并盡可能小。環(huán)形澆口環(huán)形澆口用于保證的圓形部分的同心度。它甚至可以讓流入模腔,并最大限度地減少熔接痕。由于各向異性收縮,扁圓形部件采用中心或環(huán)形澆口可能無(wú)法平衡。環(huán)形澆口也可以使用在圓形部分的外側(cè)。表4所討論的各種澆口類(lèi)型的優(yōu)點(diǎn)和缺點(diǎn)比較在這一節(jié)。表4 各種澆口形式的優(yōu)缺點(diǎn)澆口類(lèi)型優(yōu)點(diǎn)缺點(diǎn)側(cè)家口/平縫/扇形適合平板零件易于修改脫模澆口難分離澆口痕跡明顯側(cè)澆口 自動(dòng)分離澆口痕跡最小較難加工環(huán)形澆口同心度高無(wú)熔接痕廢料多澆口難去除點(diǎn)澆口自動(dòng)分離澆口痕跡小充??煨枰“甯鄰U料更高的加工成本閥式澆口(熱流道系統(tǒng))澆口痕跡小強(qiáng)制截流后處理簡(jiǎn)單更高的加工成本更高的維護(hù)成本僅適用于熱流道系統(tǒng)澆口位置苯乙烯類(lèi)熱塑性彈性體化合物是各向異性的,因此它們具有不同的物理特性的流動(dòng)方向與橫流方向。這些屬性的差異對(duì)最后零件的使用性能至關(guān)重要。因此,需要考慮的苯乙烯熱塑性彈性體的各向異性性質(zhì)確定零件上的澆口位置。熔體料流充模過(guò)程可以通過(guò)模流分析軟件進(jìn)行仿真。如果收縮率過(guò)高,零件在澆口位置可能會(huì)收縮嚴(yán)重,這會(huì)導(dǎo)致“澆口皺褶”,如果澆口附近產(chǎn)生較高內(nèi)應(yīng)力,零件形狀可能會(huì)彎曲翹曲。在零件頂部設(shè)置澆口能最大限度地減少這種問(wèn)題。在零件的兩側(cè)使用兩個(gè)澆口也可以解決這個(gè)問(wèn)題,但它會(huì)導(dǎo)致兩個(gè)熔接痕。如果在薄壁件存在填充問(wèn)題,增加流量壓力或在壁厚小的變化可以改變的流動(dòng)。在某些情況下,有必要增加一個(gè)澆口來(lái)填充零件。澆口位置的設(shè)置應(yīng)使流道盡可能短。澆口應(yīng)設(shè)在流道截面最大的位置,以提高熔體充模性能和排除氣體。如果可能的話(huà),澆口的位置應(yīng)以避免障礙物(在流道的中心或側(cè)面)。熔體流道應(yīng)盡量避免形成熔接痕。在注射時(shí),盡量避免塑料熔體沖擊型腔側(cè)壁,以減少?lài)娚涞目赡苄?。為了盡量減少模具內(nèi)應(yīng)力(在澆口上)對(duì)零性能件的影響,澆口應(yīng)設(shè)在該零件的非關(guān)鍵區(qū)域。此外,澆口痕跡應(yīng)能夠易于手動(dòng)或自動(dòng)去。模具排氣模具排氣是對(duì)成品零件的質(zhì)量和一致性的關(guān)鍵。排氣是要求當(dāng)熔融流體填充型腔時(shí)空氣在直澆道,流道和空腔中排出模具外。排氣不良可能會(huì)導(dǎo)致填充不滿(mǎn),表面外觀(guān)差,或熔接痕跡明顯。模具的排氣設(shè)計(jì)可以通過(guò)模流分析軟件設(shè)計(jì)。一旦該模具已經(jīng)加工完成,短射的研究可以被用來(lái)找到臨界排氣的位置。排氣口應(yīng)放在填充最后的地方,在熔接痕發(fā)生的區(qū)域。典型GLS化合物的排氣孔尺寸為“0.0005 - 0.0010”(0.0010毫米- 0.025毫米)與 “0.040 - 0.060”(10毫米- 15毫米)的結(jié)構(gòu)。 一般的結(jié)構(gòu),排氣槽的深度應(yīng)增加 “0.005 - 0.010”(0.12毫米- 0.25mm)的,提供暢通無(wú)阻的通道將空氣排出模具(圖17)。排氣在下面的分型面的區(qū)域可以通過(guò)頂銷(xiāo)的配合間隙排氣(圖18)。頂桿和內(nèi)孔的配合間隙可以排出空氣,一般在多孔模具中使用。如果使用推桿縫隙排氣,需要對(duì)其進(jìn)行清理,每天一次,以去除積聚起來(lái)的廢料。排氣塞需要更換,或者拆卸和清洗,以免堵塞。圖17 模具排氣槽設(shè)計(jì) 圖18 通過(guò)頂銷(xiāo)排氣 零件的推出側(cè)面接觸面積大的零件脫模較困難,建議設(shè)計(jì)35的脫模斜度。推桿應(yīng)位于流道過(guò)渡和零件外觀(guān)并不重要的地方。頂桿的直徑應(yīng)盡可能大,以盡量減少推出的痕跡。較大的直徑也允許推出溫度高的零件,它可以縮短周期時(shí)間。噴射器葉片,推管和汽提器的環(huán)可用于零件推出??諝鈬娚浜陀锰嵘y幫助推出大倒扣,對(duì)于具有室溫變形時(shí)性能的材料適用。模具表面紋理和專(zhuān)用模具的表面處理也可以幫助推出零件。退出大的內(nèi)部結(jié)構(gòu)時(shí),推出機(jī)構(gòu)通常用側(cè)向抽芯。模具冷卻模具應(yīng)該有足夠的冷卻,以?xún)?yōu)化循環(huán)時(shí)間。使用模具材料應(yīng)具有高的熱傳遞,如銅鈹合金,可用于冷卻管道或插入。市售的噴泉型鼓泡也可能有助于減少冷卻時(shí)間。建議設(shè)計(jì)單獨(dú)的可移動(dòng)冷水系統(tǒng)固定在模具兩側(cè)。這允許處理器使用差分冷卻,以安裝在可移動(dòng)的(“B”)的動(dòng)模。應(yīng)避免從一種連接冷卻管到B板。特殊的冷卻組件和管道也是一個(gè)選項(xiàng),以提高冷卻效率。熱流道系統(tǒng)熱流道系統(tǒng)之間的差異; 冷流道和熱流道的區(qū)別見(jiàn)表5。GLS SEBS化合物的熱穩(wěn)定性相當(dāng)好,并成功地用當(dāng)今的熱流道模具。選擇特定類(lèi)型的熱流道系統(tǒng)是由產(chǎn)品設(shè)計(jì)和生產(chǎn)要求確定的。有許多熱流道元件和模具制造商可用。如果可能的話(huà),利用系統(tǒng)或元件供應(yīng)商與苯乙烯的經(jīng)驗(yàn)熱塑性彈性體,如果保持在高溫度過(guò)長(zhǎng)的一段時(shí)間SBS 化合物可交聯(lián)(形成凝膠),因此熱流道工具不建議使用這些材料流道設(shè)計(jì)表5 熱流道系統(tǒng)的比較評(píng)估系統(tǒng)類(lèi)型優(yōu)點(diǎn)缺點(diǎn)冷流道 降低模具成本 輕松修改 允許使用機(jī)器人 成型周期長(zhǎng) 存在冷料 可能粘住澆口 廢料(雖然重磨)擴(kuò)展噴嘴熱流道 更快的周期 最大限度地減少?gòu)U料 易于維護(hù) 更好的溫度控制 更高的模具成本 SBS的化合物可能熱降解熱流道 無(wú)廢流道 更快的周期時(shí)間 精確的溫度控制 最高的模具成本 難清理 材料降解 難維護(hù)外部加熱系統(tǒng)是最好的。內(nèi)部加熱的流道不適合于熱塑性彈性體。這些系統(tǒng)通常有熱點(diǎn)和滯流區(qū),導(dǎo)致部分凝固的材料固守冷卻器流道墻壁。為了獲得最大的靈活性,該設(shè)計(jì)應(yīng)該是自然的或幾何的平衡。流變學(xué)平衡是可能的,但僅為特定等級(jí)或流變曲線(xiàn)。 內(nèi)部加熱的流道不適合于熱塑性彈性體-這些系統(tǒng)通常有熱點(diǎn)和滯流區(qū),導(dǎo)致部分凝固的材料固守冷卻器歧管墻壁。所有通道應(yīng)高度輕輕彎曲拋光圓形橫截面,以盡量減少停滯的可能性區(qū)。為了保持高剪切,減少停留時(shí)間,促進(jìn)流動(dòng),在通道直徑應(yīng)為為“0.250至0.375”。對(duì)于個(gè)性化的區(qū)域控制熱流道被推薦并允許操作者稍微調(diào)整平衡,以使零部件更加均勻。熱流道系統(tǒng)澆口閥式澆口閥式澆口提供了大批量生產(chǎn)對(duì)表面質(zhì)量高要求的零部件的最好解決方案,例如醫(yī)療和美容產(chǎn)品。由于閥式澆口只留下一個(gè)輕微的響動(dòng)上的部分,澆口痕跡減至最小。進(jìn)一步的改進(jìn)可以獲得高質(zhì)量表面的零件,例如在分型面下方的設(shè)置閥式澆口或隱藏澆口的注塑成型細(xì)節(jié)美感的零件產(chǎn)品。熱流道系統(tǒng)的閥門(mén)的一個(gè)例子是在圖19中所示圖片由馬斯特模具有限公司提供,杜拉是Mold-Masters公司有限公司的注冊(cè)商標(biāo)。圖19。使用閥式澆口熱流道系統(tǒng)一個(gè)閥澆口的澆口直徑應(yīng)為約“0.030到0.125”,這取決于部件的尺寸和厚度。閥門(mén)不要求該材料中的零件在閥門(mén)關(guān)閉前凍結(jié),保持壓力被釋放。因此,螺桿恢復(fù)為下一個(gè)周期可以提前,總循環(huán)時(shí)間可以減少。對(duì)于非常厚的壁部與內(nèi)應(yīng)力或收縮空隙,閥式澆口可保持打開(kāi)一個(gè)較長(zhǎng)的時(shí)間提供注射材料,消除空隙和下沉。閥門(mén)元件需要與模具板隔絕,以維持適當(dāng)?shù)臏囟瓤刂?。只有閥門(mén)可以用于多模腔模制泡沫或級(jí)聯(lián)成型,填補(bǔ)長(zhǎng)的細(xì)流無(wú)熔接痕。由于一些低粘度GLS的成績(jī),保養(yǎng)得當(dāng)緊閥式澆口才能防止?jié)B漏或溢料。閥式澆口可氣動(dòng)或液壓激活。加熱器在每個(gè)門(mén)的控制將允許精確控制熔體粘度和灌裝熱管式熱流道熱管式熱流道適用于SBC化合物,但會(huì)留下一些澆口痕跡(這可高達(dá)50至75的澆口直徑)。亦可以通過(guò)以下方式減少零件表面的澆口痕跡。注射機(jī)噴嘴的直徑應(yīng)小于澆口的直徑。熱管式的零件應(yīng)該從模具板和模腔進(jìn)行絕緣處理。為了實(shí)現(xiàn)這一點(diǎn),該噴嘴的長(zhǎng)度可能需要加長(zhǎng),噴嘴應(yīng)作為零件型腔的一部分。尖端之內(nèi)的所有通道應(yīng)高度拋光和精簡(jiǎn),盡量減少停滯和退化區(qū)。該設(shè)計(jì)的效率可能會(huì)通過(guò)記錄所花費(fèi)的時(shí)間,使一個(gè)完整的驗(yàn)證顏色的變化而產(chǎn)生的零件。這表明是否有任何剩余死區(qū)的材料,繼續(xù)進(jìn)入熔體流對(duì)于熱管式流道系統(tǒng),在開(kāi)始下一個(gè)注射成型周期開(kāi)始之前應(yīng)該有一個(gè)足夠長(zhǎng)保壓時(shí)間。沒(méi)有延遲,部件可能填充不滿(mǎn)。這對(duì)低硬度,高流動(dòng)性的材料特別重要。為了減少對(duì)厚壁零件填充時(shí)間,使用大澆口減少注射壓力。由于熱塑性彈性體化合物在熔融狀態(tài)下是微可壓縮性的,大保壓壓力可能引起熱管式模具打開(kāi)后溢料。為了防止溢料,熱流道系統(tǒng)應(yīng)盡量減少保壓壓力在模具打開(kāi)之前。熱管式流道可以用于填充次級(jí)冷澆道供給材料到多個(gè)零件。每個(gè)熱管應(yīng)使用單獨(dú)的溫度控制器。如果選擇的熱管制造商不具有SBC化合物的使用經(jīng)驗(yàn),則應(yīng)該通過(guò)實(shí)驗(yàn)確定通過(guò)最佳澆口類(lèi)型和幾何原型設(shè)計(jì)。二次注塑成型其中增長(zhǎng)熱塑性彈性體的最大領(lǐng)域是二次注塑。許多產(chǎn)品設(shè)計(jì)師利用熱塑彈性體,以一個(gè)“軟接觸”添加到一個(gè)剛性的材料。GLS的化合物可以是包覆模制到許多不同基材,以改變表面的觸感,改善美觀(guān)性,和緩沖防振-的可能性是無(wú)限的。大多數(shù)DYNAFLEX 以及科騰化合物(和VERSALLOY TPV合金)適于兩桿或嵌件成型到聚丙烯(和在某些情況下,PE)的襯底。該的Versaflex OM品位已專(zhuān)門(mén)制定粘接PC,ABS,尼龍6/6,PC / ABS,和 PPO。新VERSOLLAN OM系列的基礎(chǔ)上,巴斯夫高性能聚氨酯(TPU),是專(zhuān)門(mén)為薄壁包覆成型設(shè)計(jì)的TPU合金(包括插入和雙射成型)PC,ABS和PC / ABS基材。隨著新的創(chuàng)新技術(shù),GLS的不斷發(fā)展熱塑性彈性體的粘結(jié)各種襯底。有關(guān)標(biāo)準(zhǔn)的Versaflex OM系列及其他信息 新型熱塑性彈性體的國(guó)債,以不尋常的基板開(kāi)發(fā),請(qǐng)聯(lián)系您的GLS 代表。有關(guān)二次注塑零件設(shè)計(jì),模具設(shè)計(jì)和加工,歡迎更多信息參考GLS出版的“二次注塑成型指南”,可在 www.glscorporation.com或 通過(guò)聯(lián)系GLS代表。注射機(jī)的選擇機(jī)器類(lèi)型推薦往復(fù)式螺桿機(jī)。然而,RAM或柱塞設(shè)備已被用于生產(chǎn)SBS塑件。與計(jì)算機(jī)接口提供較新的機(jī)器改進(jìn)的工藝控制和優(yōu)先選用于多腔模具工具和高生產(chǎn)應(yīng)用程序。注射機(jī)的可編程注射速度和壓力的能力可以生產(chǎn)出更優(yōu)質(zhì)的部件。即通過(guò)控制位置的控制注射量的成型機(jī)是最好的機(jī)器,其能通過(guò)壓力或時(shí)間控制。立式壓機(jī)用旋轉(zhuǎn)式或滑臺(tái)非常適用于嵌件成型。多工位輪轉(zhuǎn)注射機(jī)能減少冷卻時(shí)間,提高部件成型效率。注射能力GLS苯乙烯化合物注射量容量一般比大多數(shù)熱塑性彈性體低。注射容量可以計(jì)算由下面的公式: t注射量計(jì)算示例如圖20圖20 估算注射量桶容量如果可能的話(huà),使用一臺(tái)機(jī)器,每桶的注射量的利用率大小為25%到75%。這使得該材料的最佳溫度控制并在高溫下減少物料的停留時(shí)間。SEBS化合物的停留時(shí)間為應(yīng)該是不超過(guò)10分鐘。SBS的化合物的停留時(shí)間為應(yīng)該沒(méi)有最大超過(guò)8分鐘。如果材料的利用率更高,桶容量應(yīng)減少。噴嘴的選擇建議使用較小的噴嘴直徑,因?yàn)樗麄冊(cè)诖龠M(jìn)剪切熱注射,產(chǎn)生較少的冷料的材料。建議噴嘴直徑為“0.0625 0.1875“(1.59毫米- 4.76毫米)。靜態(tài)混合噴嘴已被用于改善具有很高的摻合比的顏色分散體的濃縮物。擴(kuò)展的噴嘴也已用于降低澆道(導(dǎo)致廢品更少)的長(zhǎng)度。如果需要發(fā)泡劑(以產(chǎn)生泡沫份),必須被用機(jī)械關(guān)閉噴嘴來(lái)控制發(fā)泡活性,以防止泄露。螺釘?shù)倪x擇通用螺絲適用于苯乙烯類(lèi)熱塑性彈性體。 2:1到3:1的壓縮比通常用于SEBS和SBS的化合物。材料處理和編制烘干通常力士苯乙烯類(lèi)熱塑性彈性體化合物的需要干燥。某些專(zhuān)業(yè)產(chǎn)品,如的Versaflex和VERSOLLAN重疊模塑的產(chǎn)品,有吸濕性;因此從而他們需要在成型前要進(jìn)行干燥。干燥吸濕材料建議設(shè)置吸附式干燥器溫度為40。每個(gè)產(chǎn)品都有特定的干燥溫度和時(shí)間,其可以在技術(shù)數(shù)據(jù)表中找到。染色SBC化合物具有天生優(yōu)越的色彩比其他大多數(shù)熱塑性彈性體。因此,他們比其他熱塑性彈性體需要較少的彩色濃縮物中以獲得特定的顏色。通常,彩色濃縮物應(yīng)該是低粘度(具有更高的熔融指數(shù))比基化合物。這將促進(jìn)緩解分散。 推薦用于SBS苯乙烯類(lèi)化合物的顏色載體。 推薦用于較硬的SEBS化合物,聚丙烯(PP)的運(yùn)營(yíng)商。 對(duì)于軟的SEBS化合物,低密度聚乙烯(LDPE)或乙烯-乙烯酯共聚物(EVA)已被使用。PP的載體是不建議較軟的等級(jí),作為化合物的硬度會(huì)受到影響。液體的顏色可以使用,但載體應(yīng)該是石蠟型礦物。聚乙酸乙烯聚氯乙烯(PVC)增塑劑,如二辛酯(DOP),不應(yīng)該被用來(lái)作為載體。干的顏色也被使用,但可能需要更多的材料和時(shí)間執(zhí)行顏色變化。使用聚乙烯(PE)的載體可能不利地影響對(duì)基材的附著力對(duì)一些重疊模塑應(yīng)用。如果使用的是特殊包覆成型級(jí),按照著色的建議對(duì)個(gè)別產(chǎn)品技術(shù)數(shù)據(jù)表給出。詳細(xì)著色的建議總結(jié)在 TPE提示3光澤度和透明度GLS的化合物可分為不透明,半透明和透明等級(jí)。該VERSAFLEXCL系列是制定高清晰度。清晰的等級(jí)可以產(chǎn)生最佳金屬或珠光色。高光澤透明牌號(hào)有更高的摩擦系數(shù)和更多親密模具接觸,因此更難以噴出。填充不透明的化合物更難的顏色深強(qiáng)烈的色彩,但會(huì)產(chǎn)生良好的柔和色彩。再生料高達(dá)80的回用料可用于SEBS化合物。高水平的回用料的更好容忍黑色材料。自然,淺色或透明的化合物會(huì)更容易顯示污染或變色。用于產(chǎn)生黃色,紅色,藍(lán)色有機(jī)顏料和綠色的顏色更容易后變色延長(zhǎng)停留時(shí)間或高回收料的水平。對(duì)于SBS的化合物,回用料應(yīng)保持低于25。DYNAFLEX化合物具有高的伸長(zhǎng)率和良好的撕裂強(qiáng)度,因此需要采用了高品質(zhì)的研磨機(jī)用鋒利的刀。對(duì)于較低的硬度苯乙烯化合物的間隙應(yīng)設(shè)置為0.003“的最大值。只有高磨床質(zhì)量支撐軸承和一個(gè)剛性框架可以保持必要的公差實(shí)現(xiàn)必要的轉(zhuǎn)子刀刀床間隙。使用少量的隔離劑,如滑石或碳酸鈣可以在最小化的結(jié)塊磨削過(guò)程。喂少量零件的進(jìn)入粉碎機(jī)在同一時(shí)間,以盡量減少熱量積聚,從而導(dǎo)致結(jié)塊。 為了使回收料的最佳摻入新料,屏幕尺寸應(yīng)選擇得到的粒子是大致相同的尺寸原生顆粒。清洗如果按下跌超過(guò)10分鐘,重新啟動(dòng)生產(chǎn)之前清除。至防止泄露,降低使用的注射量重新啟動(dòng)計(jì)算機(jī)并逐漸增加其回到原來(lái)的注射量。這將有助于防止閃爍的發(fā)生背后幻燈片或插入。對(duì)于SBS的化合物 - 如果一臺(tái)機(jī)器是在溫度要留給更長(zhǎng)超過(guò)一小時(shí),清除使用低密度聚乙烯或聚苯乙烯之前關(guān)閉。對(duì)于SEBS化合物- 如果計(jì)算機(jī)已關(guān)閉周末,清除具有很高的分子量(或低分?jǐn)?shù)熔體流動(dòng))的LDPE在低溫下才關(guān)閉。在啟動(dòng)時(shí),收回試圖填補(bǔ)了之前的模具擠出機(jī)和空氣凈化它做好。工藝條件介紹本節(jié)介紹的苯乙烯類(lèi)熱塑性彈性體的一般處理準(zhǔn)則。具體對(duì)于每個(gè)單獨(dú)的產(chǎn)品開(kāi)始條件均位于產(chǎn)品技術(shù)數(shù)據(jù)表。設(shè)定溫度桶圖21顯示了典型的起始筒溫度。機(jī)筒溫度應(yīng)設(shè)置逐步。進(jìn)料區(qū)的溫度應(yīng)設(shè)定得相當(dāng)?shù)屯ǔ?50F -300F(120-150),以避免進(jìn)料口橋接,并允許夾帶的空氣逸出。在過(guò)渡區(qū)較低的溫度允許的適當(dāng)?shù)膲嚎s和剪切復(fù)合才完全融化。為了提高使用色母料混合時(shí),設(shè)置過(guò)渡區(qū)的溫度高于所述濃縮物的熔融溫度。區(qū)域最靠近噴嘴應(yīng)設(shè)置接近所需的熔體溫度。經(jīng)過(guò)這個(gè)過(guò)程已經(jīng)穩(wěn)定,實(shí)際料筒溫度應(yīng)比設(shè)定點(diǎn)低。如果實(shí)際溫度超過(guò)設(shè)定溫度時(shí),則剪切熱造成過(guò)熱的材料。如果好的部分正在制作中,溫度設(shè)置應(yīng)該被重置為相同的實(shí)際溫度。加熱器應(yīng)要求功率25至50的時(shí)間。如果加熱器上連續(xù),沒(méi)有足夠的熱量從剪切正在生產(chǎn)。為了提高剪切加熱,提高螺桿轉(zhuǎn)速和背壓。圖21 建議初始啟動(dòng)條件的注塑成型。設(shè)置模具溫度模具溫度應(yīng)高于露點(diǎn)溫度在成型區(qū)域中設(shè)置。這可以防止在腔模和可能的污染水的出汗。水污染通常會(huì)出現(xiàn)在零件條紋。模具溫度可以提高如果存在已經(jīng)被證明是難以填充的部分的長(zhǎng)或薄的部分。更高模具溫度通常會(huì)導(dǎo)致更高的循環(huán)時(shí)間,但可以提高焊接線(xiàn)的完整性和部分外觀(guān)。表6 產(chǎn)品和溫度產(chǎn)品模熔體噴嘴3區(qū)2區(qū)1區(qū)塑料SBS 化合物75-90F (25-32C)370-390F(190 - 200C)370-390F(190 - 200C)360-380F (185 - 195C)340-360F (170 - 182C)300-330F (150 - 165C)100-150F (40-65C)SEBS 化合物110-130F (43-55C)370-430F(190 - 220C)390-430F(200 - 220C)390-430F (200 - 220C)370-390F (190 - 200C)350-370F (175 - 190C)100-170F (40-75C)超柔化合物110-130F (43-55C)340-390F(170 - 200C)360-390F (180 - 200C)360-390F (180 - 200C)335-375F (170 - 190C)300-330F (150 - 165C)100-120F (40-50C)設(shè)定注射量當(dāng)啟動(dòng)了全新的模具,開(kāi)始短的鏡頭,然后逐漸增加出手大小,直到所有的部分型腔80-90填滿(mǎn)。這個(gè)程序可以最小化潛在的過(guò)填充,防止閃光燈通風(fēng)口。螺桿位置應(yīng)當(dāng)指出,并用于設(shè)置轉(zhuǎn)換點(diǎn)。監(jiān)視墊,以確保它被包在維持并保持階段。如果沒(méi)有墊,包裝壓力不能保持和沒(méi)有控制部分致密化。后柵極凍結(jié),任何附加的材料體積或壓力將只包澆道和澆口系統(tǒng),這會(huì)導(dǎo)致困難的部分脫模時(shí)澆口切除。螺桿轉(zhuǎn)速,背壓和螺桿延遲時(shí)間螺桿轉(zhuǎn)速應(yīng)設(shè)置以使螺釘完全恢復(fù)為下一桿,在模具打開(kāi)之前,通常2至3秒。典型的螺桿轉(zhuǎn)速為50轉(zhuǎn)150轉(zhuǎn)。如果螺釘恢復(fù)過(guò)快,并且該機(jī)配備有螺旋延遲定時(shí)器,設(shè)定的延遲時(shí)間,以便有最小的延遲后的螺桿是完全恢復(fù)和模具打開(kāi)。這將減少物料停留時(shí)間,溫度和死區(qū)時(shí)間在槍管。增加背壓增加了材料的剪切熱。正常設(shè)置背壓為50-150磅。當(dāng)混合色母料,高背壓優(yōu)選的,以實(shí)現(xiàn)最佳的分散性。注射速度如果可能的話(huà),配置文件的注射速度,迅速填補(bǔ)了熱流道系統(tǒng),然后慢下來(lái)該材料開(kāi)始流過(guò)柵極和進(jìn)入型腔后。保持這個(gè)速度直到部分是90滿(mǎn),然后進(jìn)一步降低它完全填滿(mǎn)模腔無(wú)閃爍的一部分。如前所述,GLS的化合物是剪切響應(yīng)。如果零件有難度填充,增加溫度升高之前的注射速度。該注射時(shí)間,以填補(bǔ)部分應(yīng)該是一至兩秒之間。慢填充率如果表面流發(fā)生瑕疵,可能需要。注入和傳輸壓力如果機(jī)器是不能夠被填充速度被控制,設(shè)定注射壓力高到足以填充流道系統(tǒng)和模腔中大約1至5秒。調(diào)整初始的壓力傳遞到所需的注射壓力的約50,以填補(bǔ)部 腔。這有助于最小化電池組時(shí)的壓力和保持噴射的相位。當(dāng)設(shè)定注射量,監(jiān)測(cè)墊,以確保它是在包期間保持按住階段。增壓加速注射較新的模塑設(shè)備為從注射增壓傳輸?shù)母郊舆x項(xiàng)(第一級(jí)噴射),以群雄并保持階段。最準(zhǔn)確的方法來(lái)傳輸從刺激包壓力是螺絲的位置。使用螺釘位置允許處理器材料的特定體積一致地注入到模腔中。它也提供精確控制部分包裝和致密化的,它可以幫助防止水槽和空隙中的一部分。時(shí)間是另一種方法,用于控制傳輸,但不推薦。使用模腔壓力的轉(zhuǎn)移是昂貴的,因?yàn)樗婕暗桨惭b壓力換能器在部分腔。這個(gè)過(guò)程是用來(lái)當(dāng)高度精確的模塑公差要求。減少來(lái)自增壓輸送壓力收拾按住意志幫助在套管尖端控制流口水。如果注射單元配備一個(gè)異形打包和保持相位,它可以用來(lái)降低速度和壓力向奔跑。注射時(shí)間最佳的時(shí)間來(lái)填充流道系統(tǒng)是約0.5 - 1.5秒。它應(yīng)該采取另一種1 - 5秒鐘以充滿(mǎn)模腔。如果可能的話(huà),最好是控制填充時(shí)間通過(guò)控制注射速度。保持時(shí)間保持時(shí)間應(yīng)設(shè)置為實(shí)現(xiàn)澆口凝固。通常,柵極尺寸是確定保持時(shí)間的因素。較大的柵極的不再需要的保持時(shí)間實(shí)現(xiàn)門(mén)凍結(jié)。冷卻時(shí)間冷卻時(shí)間主要取決于熔體的溫度,壁厚的部分和冷卻效率。此外,該材料的硬度是一個(gè)因素。哈德等級(jí)( 50邵氏A)將成立快于模具相比,非常柔軟成績(jī)(20邵氏A)。對(duì)于一個(gè)普通組成部分,中等硬度SEBS復(fù)合冷卻時(shí)間將是大約15到20秒,每0.100壁厚“,提供有從兩側(cè)冷卻可用。超模壓部件將需要更長(zhǎng)的時(shí)間來(lái)冷卻因?yàn)樗鼈兛梢杂行У乩鋮s在較小的表面面積。冷卻時(shí)間為包覆成型部分將是大約35到40秒,每0.100英寸壁厚度。保持坐墊膠墊應(yīng)保持或?qū)](méi)有控制部分致密化或補(bǔ)償材料的收縮。不足坐墊和保持壓力將導(dǎo)致底部填充零件空隙或水槽和物理性能差。蓋茨說(shuō)凍掉太快(作為過(guò)小或過(guò)涼的模具溫度下的結(jié)果)也可能引起上述這些問(wèn)題。磨損或污染的止逆環(huán)可以限制本機(jī)的能力,保持壓力和保持一個(gè)氣墊。吉力士化合物具有較低的粘度(高流量)比傳統(tǒng)的熱塑性塑料和會(huì)泄漏回比其他材料更容易。的密封能力檢查環(huán)應(yīng)通過(guò)觀(guān)察機(jī)器的能力,保持緩沖進(jìn)行驗(yàn)證位置。熱澆口套或延長(zhǎng)噴嘴的工藝條件熱澆道襯套應(yīng)被看作是本機(jī)的噴嘴的延伸。外熱澆道襯套與熱塑性彈性體的正常工作。熱澆道和擴(kuò)展的噴嘴通常設(shè)置5- 10F比前區(qū)溫度高。避免使用自耦變壓器或可變電阻控制器,這些控制器趨向于過(guò)熱在很短的停機(jī)材料。成型條件的影響如果某個(gè)部件被模制在過(guò)低的溫度下,這將需要過(guò)大的壓力,以填補(bǔ)腔。這將導(dǎo)致高的模內(nèi)應(yīng)力。這反過(guò)來(lái)又可以導(dǎo)致部分翹曲在噴射或在當(dāng)它被暴露于升高的溫度以后的時(shí)間。那里也可以大于正常交成型收縮率,并在最終的減少伸長(zhǎng)率。過(guò)填充的零件的影響可能包括: 澆口墜脹 密度增加,從而提高零件重量 硬度增加過(guò)填充的零件的作用可以包括: 澆口皺褶 空隙和/或表面匯 減少物理性能 比正常低硬度監(jiān)視部分權(quán)重已經(jīng)被成功地用于驗(yàn)證過(guò)程的穩(wěn)定性和一致性。 應(yīng)當(dāng)指出的是,澆口尺寸/位置,流道尺寸和其他模具設(shè)計(jì)方面也可能會(huì)影響到部分的性能。對(duì)于明確的化合物,已處理在過(guò)低的溫度下部分會(huì)有一個(gè)冷若冰霜的表面外觀(guān)。SBS基化合物將開(kāi)發(fā)一個(gè)黃色或橙色顏色而當(dāng)他們已經(jīng)處理在過(guò)高的溫度或獨(dú)特的氣味在溫度太久舉行。顏色和氣味都很強(qiáng)的跡象表明,材料已降級(jí)。退化結(jié)果在外觀(guān)差,減少物理屬性。已處理在太高的溫度SEBS化合物會(huì)有焦臭(降解),在最壞的情況下,變得發(fā)粘和油滲出。成型軟的化合物( 20邵氏A)柔軟的化合物具有很低的粘度(高流動(dòng));因此,他們需要最少的注射壓力。注射壓力的典型值是150磅 - 450磅。大多數(shù)GLS軟苯乙烯熱塑性彈性體化合物或者是無(wú)色透明或半透明。清晰的模制部件可以通過(guò)增加模具被輕微改善和熔融溫度。這些產(chǎn)品通常需要高拋光模具表面光潔度,因?yàn)樗鼈儚?fù)制模具表面相當(dāng)不錯(cuò)。 較軟的材料表現(xiàn)出一些俗氣的行為。成型區(qū)的清潔是非常重要的。因?yàn)檩^軟的材料吸引并留住灰塵和污染物。這種粘性也使得零件脫模更加困難。在這些情況下,機(jī)械手澆道拾取器,轉(zhuǎn)輪飼養(yǎng),或空氣噴射可能需要。增加了一個(gè)輕微的表面紋理的模具可以幫助掩蓋可能的表面瑕疵的模塑制品。成型硬質(zhì)化合物( 50邵氏A)較硬的化合物通常具有較高的粘度,并且可能需要略微較高的注射壓力(400磅 - 800磅),以填充型腔。由于其較高的模量,化合物難以從流道流過(guò)。它們也傾向于建立更快,更容易被排出,并且可以從模具中頂出在較高溫度下。此外,化合物越軟循環(huán)時(shí)間就越難減少。故障排除故障排除方法正確的故障排除應(yīng)使用一種系統(tǒng)的方法來(lái)解決問(wèn)題。有兩種類(lèi)型的問(wèn)題:涉及“質(zhì)量控制”和那些在啟動(dòng)過(guò)程中遇到的問(wèn)題。 當(dāng)零件已經(jīng)在過(guò)去已經(jīng)成功生產(chǎn),但現(xiàn)在“質(zhì)量控制”的問(wèn)題出現(xiàn),已經(jīng)超出規(guī)定范圍。這些問(wèn)題是在零件生產(chǎn)過(guò)程中不斷變化的結(jié)果。要解決這些問(wèn)題,必須確定發(fā)生了什么變化和過(guò)程恢復(fù)到適當(dāng)?shù)钠胶?。期間推出的一個(gè)新的模具或機(jī)器出現(xiàn)啟動(dòng)問(wèn)題。質(zhì)量控制問(wèn)題大多數(shù)質(zhì)量控制問(wèn)題是由工藝條件,材料,或注射機(jī)和模具的維護(hù)造成的。如果在材料批號(hào)的改變后發(fā)生的問(wèn)題,嘗試不同的大量的材料。明智的做法是保留了以前使用過(guò)的材料。 如果模具的設(shè)定成功的制造過(guò)零件,檢查原有的設(shè)置條件。如果模具是用在不同的機(jī)器上,細(xì)微的調(diào)整,只用新設(shè)備可能是必要的。如果模具是它的停工期間被修改,則可能需要進(jìn)行調(diào)整。啟動(dòng)問(wèn)題要解決啟動(dòng)問(wèn)題,必須確定該材料的工藝條件,確保有足夠的條件,可以生產(chǎn)出好的零件。開(kāi)始的工藝條件設(shè)定為材料的處理范圍的中間位置,然后調(diào)整過(guò)程,以修復(fù)任何觀(guān)察到的問(wèn)題。如果成功的零件是不可能的,確定的什么變量組合必須改變,以解決問(wèn)題。這些變化包括材料選擇,注射機(jī)選擇或者模具的重新設(shè)計(jì)。編號(hào): 畢業(yè)設(shè)計(jì)外文翻譯 (原文)題 目: Injection Molding Guide 學(xué)院: 機(jī)電工程學(xué)院 專(zhuān) 業(yè): 機(jī)械設(shè)計(jì)制造及其自動(dòng)化 學(xué)生姓名:學(xué) 號(hào): 指導(dǎo)教師單位 姓 名:職 稱(chēng):2014年5月26日桂林電子科技大學(xué)畢業(yè)設(shè)計(jì)(論文)說(shuō)明書(shū)用紙 第26頁(yè) 共25頁(yè)Injection Molding GuideINTRODUCTIONObjectiveThis document provides guidelines for part design, mold design and processing of styrenic block copolymer (SBC) TPEs. The GLS product families that include styrenic TPEs are Kraton compounds, Dynaflex TPE compounds and Versaflex TPE alloys.SBC RheologyOne major characteristic of SBCs is that they are shearing dependent. A material is shear dependent when its viscosity is higher at low shear rates (such as extrusion) and lower at high shear rates (as in injection molding). Therefore, SBC compounds will flow more easily into thin areas of the mold at high shear rates. The shear thinning behavior of SBCs should be considered when designing injection molds and also when setting mold conditions during processing.Figure 1.The effect of shear rate on the viscosity of GLSstyrenic TPE compounds (measured at 390F (200C).To obtain information regarding the viscosity of an individual grade, refer to the Product Technical Data Sheet, available at www.glscorporation.com or contact your GLS representative.PART DESIGNGeneral Part Design ConceptsWhen designing a TPE part, there are a few general rules to follow: The part wall thickness should be as uniform as possible. Transitions from thick to thin areas should be gradual to prevent flow problems, back fills, and gas traps. Thick sections should be cored out to minimize shrinkage and reduce part weight (and cycle time). Radius / fillet all sharp corners to promote flow and minimize no-fill areas. Deep unventable blind pockets or ribs should be avoided. Avoid thin walls that cannot be blown off the cores by air-assist ejection. Long draws with minimum draft may affect ease of ejection.Flow Length and Wall ThicknessThe maximum achievable flow length is dependent on the specific material selected, the thickness of the part, and processing conditions. Generally, GLS compounds will flow much further in thinner walls than other types of TPEs. The flow to thickness ratio should be 200 maximum; however this is dependent on the material and the part design. High flow GLS TPE compounds (such as Versalloy) have been used successfully to fill flow ratios up to 400.The measurement of spiral flow offers a comparative analysis of a materials ability to fill a part. The spiral flow test is performed by injecting a material into a spiral mold (similar to a ribbon formed into a spiral). The distance the material flows is measured in inches. In this case, the spiral flow test was conducted using two different injection speeds (3 in/sec and 5 in/sec). The typical spiral flow lengths for the various GLS product families are summarized in Table 1. With specific compounds, flow lengths of up to 40 inches (at 5 in/sec injection speed) are possible.Table 1. Typical Spiral Flow Lengths for GLS Compounds*SeriesFlow length, in3 in/sec5 in/secDynaflex D13-1518-20Dynaflex G12-2218-30Versaflex 9-1613-26*Spiral flow tests performed using 0.0625 in thickness and 0.375 in width channel at 400F.For spiral flow information about a specific grade or additional details about the spiral flow test procedure, please refer to the GLS Corporation TPE Tips Sheet #7, available at www.glscorporation.com or by contacting your GLS representative.UndercutsThe flexibility and elastic nature of TPEs allows for the incorporation of undercuts into the part design. Because of their excellent recovery characteristics, GLS compounds are capable of being stretched and deformed, allowing them to be pulled from deep undercuts (Figure 2). If both internal and external undercuts are present on the same part, slides or core splits may be necessary. Parts with internal undercuts (e.g. bulb shaped parts) may be air ejected from the core by use of a poppet valve in the core. Minor permanent elongation (3% - 8%) due to deformation may occur during ejection.Figure 2. An example of TPE parts with large undercuts.Gate and Knit Line LocationsThe product engineer should indicate the areas of the part that are cosmetic and those that are functional and include this information on the drawing. This will help the mold designer to determine the allowable gate and knit line locations.AnisotropyThermoplastic materials that have different properties in the flow direction versus the cross-flow direction (90 perpendicular to the flow direction) are characterized as “anisotropic” materials. Properties that may be affected are shrinkage and tensile properties. Anisotropy is caused when the polymer chains orient in the direction of flow, which leads to higher physical properties in the flow direction. Wall thickness, injection speed, melt temperature and mold temperature are a few variables that affect anisotropy. Depending on the processing conditions and mold design, most GLS styrenic TPE compounds exhibit a degree of anisotropy.ShrinkageDue to their anisotropic nature, GLS styrenic TPE compounds shrink more in the flow direction than in the cross-flow direction. Generally, SEBS compounds have higher shrinkage and are more anisotropic than SBS compounds. Typical shrinkage values for SEBS-based compounds are 1.3% - 2.5%, whereas those for SBS based compounds are 0.3% - 0.5 %. Softer SEBS compounds (below 30 Shore A) will shrink more than harder 6 materials. Some grades, such as Dynaflex G7700, G7800, and G7900 Series contain filler, which reduces their shrinkage.The shrinkage values reported by GLS are determined using a 0.125” thick plaque. It should be noted that shrinkage is not an exact number, but a range value. This range can be affected by the part wall thickness, melt temperature, mold temperature, injection speed, hold/pack pressures and also the time between molding and measuring. As a result, prototyping is strongly recommended for parts with close tolerances to better quantify the realistic shrinkage of a specific grade of material in a specific application.For shrinkage values for specific grades, please refer to the product Technical Data Sheet, available at www.glscorporation.com or by contacting your GLS representative.MOLD DESIGNTypes of MoldsGLS SBC compounds can be molded in two- and three-plate molds. Both conventional and hot runner tool designs have been used with GLS compounds. Self-insulating hot runner tool designs are not recommended due to the potential for material degradation in the stagnation zones. Two-shot molds and insert molds can also be used. If a family mold is required, the cavity volumes should be similar, otherwise over packing and flashing of the smaller cavity may occur.Steel SelectionGLS styrenic TPEs are generally non-abrasive and non-corrosive. The selection of tool steel will depend on the quantity and quality of parts to be produced. For high volume production, the initial expense of quality tooling is a sound investment.A wide variety of tool steels are available for injection mold construction. Table 2 lists the properties of common tool steels and the typical mold components for which they are used. Soft metals, such as aluminum and beryllium copper, can be used for prototype parts or short production runs up to 10,000 parts.Table 2. Typical Tool Steel for Injection Mold ConstructionSteel TypeSteel PropertiesMold ComponentP-20Pre-hardened, machines well, high carbon, general-purpose steel. Disadvantage: May rust if improperly stored.Mold bases, ejector plates, and some cavities (if nickel or chrome plated to prevent rust).H-13Good general purpose tool steel. Can be polished or heat-treated. Better corrosion resistance.Cavity plates and core plates.S-7Good high hardness, improved toughness, general-purpose tool steel. Machines well, shock resistant, polishes well. Disadvantage: Higher cost.Cavity plates, core plates and laminates, as well as thin wall sections.A-2Good high toughness tool steel. Heat-treats and polishes well.Ejector pins, ejector sleeves, and ejector blades.D-2Very hard, high wear characteristics, high vanadium content, somewhat brittle. Disadvantage: Difficult to machine.Gate blocks, gibe plates to prevent galling, gate blocks to prevent wear.420 SSTough corrosion resistant material.Heat-treats and polishes well.Disadvantage: High cost.Cavity blocks, ejector pins, sleeves, etc.Some part designs may benefit from the use of higher thermal conductivity materials such as beryllium copper. This material is less durable than steel and may hob or wear faster than steel if used at the parting-line. Beryllium copper can be used for inserts, slides or cores to increase heat transfer rates and reduce cycle times. In cases where there is a long draw core, a fountain-type bubbler may be beneficial.Mold Surface Treatment, Finishing and TexturingMost GLS materials replicate the mold surface fairly well. To produce a glossy surface, a polished mold is required and an unfilled grade should be used. A highly polished tool and a transparent material are required to produce a part with good clarity. If a matte finish similar to that of a thermoset rubber is required, a rougher mold texture should be used (or a GLS product such as GLS Versalloy TPV alloys, which naturally produce a matte surface). In general, an EDM surface will produce a good texture and may improve release from the tool during part ejection. Matte surfaces can also help to hide any flow marks or other surface defects. Vapor honing, sand or bead blasting and chemical etching are also used to produce textured surfaces with varying degrees of gloss and appearance. To aid in release, the cavity or core may be coated with a release coating such as PTFE impregnated nickel after it has been given a sandblast or EDM finish.Sprue and Sprue Puller DesignThe sprue should have sufficient draft, from 1 to 3 to minimize drag and sprue sticking. Longer sprues may require more taper (3 - 5), as shown in Figure 3. Typically, the sprue diameter should be slightly larger than the nozzle diameter. An EDM finish is acceptable for most styrenic TPE materials. Permanent surface lubricant treatments have also been used successfully.Sprue puller designs vary with the hardness of the material. The different sprue designs possible and their relative dimensions are shown in Figures 4 through 7. In addition, Table 3 shows the typical hardness range for which a particular sprue design is applicable.Table 3. Typical Sprue Designs for Various Hardness ValuesTypical TPE Hardness RangeMost Common Sprue Puller TypesFigure50 Shore ATapered, Pin, Z-Type3, 4 and 640-70 Shore AUndercut55-40 Shore APine Tree7Hot sprue bushings and extended nozzles may also be used with GLS compounds. In many molds, the sprue is the thickest wall section in the mold and will control the minimum cooling time. The use of a hot sprue, which may be viewed as an extension of the machine nozzle, can sometimes reduce cycle time. Extended machine nozzles may also be used to reduce sprue length and size. When hot sprues are used, the machine nozzle tip should be a free-flow nozzle rather than a reverse tip.Figure 3. Tapered Sprue Puller Figure 4. Z-Pin Sprue PullerFigure 5. Undercut Sprue PullerFigure 6. Sucker Pin Sprue Puller Figure 7. Pine Tree Sprue PullerConventional Runner Configuration and DesignA balanced runner configuration is critical to achieve uniform part quality from cavity to cavity. In a balanced runner system, the melt flows into each cavity at equal times and pressure. The runner balance can be designed by using computer mold-flow analysis programs and verified by performing short-shot studies.An unbalanced runner may result in inconsistent part weights and dimensional variability. The cavity closest to the sprue may be over packed and flashing may occur. As a result of over packing, parts may also develop high molded-in stresses, which lead to warpage. Examples of balanced runner systems are shown in Figures 8 and 9.Figure 8. Example of Balanced Spider Runner Figure 9. Example of Balanced Cross-RunnerFigure 10 shows different runner cross-sections and their associated efficiency. Full round runners have the least resistance to flow and surface area, allowing the material to stay molten longer. The second most efficient runner cross-section is the modified trapezoid. This runner geometry most closely simulates a full round runner but only requires machining in only one plate. Figure 11 shows typical ball cutter dimensions and the corresponding modified trapezoid runner sizes. Figure 12 illustrates typical runner dimensions.Figure 10. Typical Runner Cross-SectionsFigure 11. Modified Trapezoid Runner SizesFigure 12. Runner Design and DimensionsCold slug wells should be used at each runner transition (turn). Cold slug wells serve to remove the leading edge of the melt. The slug well associated with the sprue should be large enough to trap the cold material formed in the machine nozzle during the mold-open cycle. Typical slug well dimensions are approximately 1.5 to 2.0 times the diameter or width of the feed runner.Runner KeepersRunner keepers or sucker pins provide undercuts to keep the runner on the desired plate but should not restrict material flow through the runner. Figures 8 and 9 show typical locations for runner keepers and sucker pins. Figure 13 illustrates an example design of a runner keeper.Figure 13. Runner Keeper designGate Design and LocationMost conventional gating types are suitable for processing GLS styrenic TPE compounds.The type of gate and the location, relative to the part, may affect the following: Part packing Gate removal or vestige Part cosmetic appearance Part dimensions (including warpage)The type of gate selected is dependent on both part and tool design. The gate location is equally important. To prevent the chances of jetting, locate the gate entrance in an area where the flow will impinge on a cavity wall. For automatically degating tools, the highly elastic nature of softer TPEs makes submarine gate designs or three plate tools with selfdegating drops more difficult. Higher hardness and filled grades usually have lower ultimate elongation and therefore are more easily degated. To assure the gates will break at a specific location, they should have a short land length to create a high stress concentration.Tab/Edge GatesTab or edge gates (Figure 14) most commonly utilize a conventional sprue and cold runner system. They are located along the tool parting line. A small undercut can be placed where the gate meets the part to minimize gate vestige caused by degating. Advantages of edge gates are ease of fabrication, modification and maintenance. The 14 gate depth (D) should be 15% - 30% of the wall thickness at the gate entrance. Common practice is to start “steel safe”. A good starting point for the gate width should be 1.0 - 1.5 times the gate depth. The gate land should be equal to or slightly longer than gate depth. The gate size may also depend on the part volume. The gate area may be inserted to facilitate gate maintenance or modification.Figure 14. Tab or edge gate Figure 15. Submarine GateSubmarine or tunnel gates are self-degating. During part ejection, the tool steel separates the part and the runner. Figure 15 shows a typical design of a submarine gate. Cashew type submarine gates should not be used for medium to soft hardness compounds due to their high coefficient of friction and high elongation.Fan GatesA fan gate is a streamlined variation of a tab gate (Figure 16). The fan gate distributes material into the cavity more evenly; thus it is normally used in parts that require a high degree of flatness and absence of flow lines. It also minimizes the possibility of gate pucker or part warpage.Figure 16. Fan gateSprue or Direct GateThe sprue or direct gate is often used on prototype parts because it is inexpensive. This type of gating is not recommended for GLS styrenic compounds because of their high elongation. In addition, the sprue will need to be trimmed thus appearance quality of the part is usually poor. If sprue gating is selected, care should be taken to keep both the sprue length and diameter as short and small as possible.Diaphragm GateThe diaphragm gate is used to maintain the concentricity of round parts. It allows even flow into the cavity and minimizes the potential for knit lines. Due to anisotropic shrinkage, flat round parts using center or diaphragm gating may not lay flat. A ring gate may also be used on the outside of a circular part.Table 4 compares the advantages and disadvantages of the various gate types discussed in this section.Table 4. Advantages and Disadvantages of Various Gate TypesGate TypeAdvantageDisadvantageEdge/Tab/Fan Gate Appropriate for flat parts Easy to modify Post-mold gate/runner removal is difficult Poor gate vestigeSubmarine Gate Automatic gate removal Minimal gate vestige More difficult to machineDiaphragm Gate Concentricity Appropriate for round parts No knit lines Scrap Post-molding gate removalPin gate (3-plate) Automatic gate removal Minimal gate vestige Localized cooling Requires floater plate More scrap Higher tool costValve gate (Hot runner systems) Minimal gate vestige Positive shut-off Minimizes post pack Higher tool cost Higher maintenance Only for hot runner systemsGate LocationStyrenic TPE compounds are anisotropic, thus they have different physical properties in the flow direction versus the cross-flow direction. Depending on the products intended usage, these property differences could be critical to the performance of the final part. As a result, the anisotropic nature of the styrenic TPE needs to be taken into consideration when determining the gate location on the part.The material flow may be estimated by eye or by using flow analysis programs. For higher shrinkage grades, the part may shrink near the gate, which causes “gate pucker” if there is a high molded-in stress at the gate. Parts shaped like a handle grip may warp toward the gate side of the part. Locating the gate at the top of the part minimizes this problem. Using two gates on opposite sides of the part can also address the issue, but it will result in two knit lines. If filling problems exist in thin walled parts, adding flow channels or minor changes in wall thickness can alter the flow. In some cases, it may be necessary to add a second gate to properly fill the parts.The gate should be placed so that the flow path is as short as possible. Locating the gate at the heaviest cross section of the part can improve packing and minimize voids or sinks. If possible, the gate should be positioned so as to avoid obstructions (flowing around cores or pins) in the flow path.The flow path of the material should minimize the possibility of formation of knit lines and flow marks. Upon injection, the material should impinge off the cavity wall to reduce the possibility of jetting. To minimize the effect of molded-in stress (at the gate) on part performance,
收藏