洗衣機注水盒注塑模設(shè)計【CAD】
洗衣機注水盒注塑模設(shè)計【CAD】,CAD,洗衣機注水盒注塑模設(shè)計【CAD】,洗衣機,注水,注塑,設(shè)計
任 務(wù) 書
1． 背景：
注塑成型具有成型周期短、尺寸精確、生產(chǎn)率高等優(yōu)點，易實現(xiàn)自動化生產(chǎn)。目前生活中90%以上的塑料制品是通過注射成型的。市場前景好、容量大，應(yīng)用廣。我國的注塑模具起步比較晚，與國外相比有相當(dāng)大的差距。注射模的基本組成：定模機構(gòu)、動模機構(gòu)、澆注系統(tǒng)、導(dǎo)向裝置、頂出機構(gòu)、冷卻和加熱裝置、排氣系統(tǒng)等。
2． 內(nèi)容和要求：
1）與課題有關(guān)的外文文獻翻譯不少于4000漢字；
2）設(shè)計說明書的字?jǐn)?shù)不少于20000字；
3）畢業(yè)答辯圖紙總量不少于3張A0圖紙；
4）主要參考文獻不少于15篇。
3．主要參考文獻：
[1] 夏江梅主編. 塑料成型模具與設(shè)備.機械工業(yè)出版社，2005.
[2] 張維合主編. 注塑模具設(shè)計實用手冊.化學(xué)工業(yè)出版社，2011.
[3] 張孝民主編. 塑料模具技術(shù).機械工業(yè)出版社，2003.
[4] 付偉主編. 注塑模具設(shè)計原則、要點及實例解析.機械工業(yè)出版社，2010.
[5] 葉久新. 王群主編, 塑料成型工藝及模具設(shè)計.機械工業(yè)出版社，2008.
[6] 陳萬林等編著.實用塑料注射模設(shè)計與制造[M].機械工業(yè)出版社，2004.
[7] 伍先明等編著.塑料模具設(shè)計指導(dǎo)[M].國防工業(yè)出版社,2006.
[8] 張學(xué)文、鄭午編著.注塑模設(shè)計，化學(xué)工業(yè)出版社，2007.
[9] 黃銳編主編.塑料成型工藝學(xué)，中國輕工業(yè)出版社，2005.
[10] 齊曉杰主編.塑料成型工藝與模具設(shè)計，機械工業(yè)出版社，2005.
[11] 鄒強主編.塑料模具設(shè)計參考資料匯編,清華大學(xué)出版社，2005.
[12] 張洪峰主編.塑料模具設(shè)計與制造[M].北京：高等教育出版社，2008.
[13] 孫建民主編.基于Pro/E的塑料模具設(shè)計研究[J].現(xiàn)代塑料加工應(yīng)用，2006.
[14] 蔡于紅.塑料轉(zhuǎn)葉零件模具設(shè)計與制造[J].模具技術(shù)，2007.
[15] S.H.Tang.The use of Taguchi method in the design of plastic injection mould for reducing warpage[J].Journal of materials processing technology ,2007.
[16] Tsan Jou.A Web-based model for developing:A mold base design system[J].Expert Systems with applications,2009.
4． 進度計劃(以周為單位)：
第1、2周 調(diào)研實習(xí)，查閱文獻，整理收集資料。明確課題任務(wù)，完成開題報告和外文翻譯；
第3、4周 對塑件進行工藝性分析、選擇注塑機、理解注射工藝參數(shù)，確定分型面、型腔的數(shù)目、型腔型芯的確定，選擇合適的模架、設(shè)計澆注系統(tǒng)，確定脫模方式，確定冷卻系統(tǒng)；
第5-10周 繪制裝配圖和零件圖；
第11、12周 編寫設(shè)計說明書，撰寫畢業(yè)論文；
第13周整理設(shè)計資料，完善并提交設(shè)計成果，準(zhǔn)備答辯。
教研室審查意見：
室主任簽名： 年 月 日
學(xué)院審查意見：
教學(xué)院長簽名： 年 月 日
開題報告
課題名稱
洗衣機注水盒注塑模設(shè)計
課題來源
社會生產(chǎn)實踐
課題類型
B..工程設(shè)計類
1．選題的背景及意義：
注塑成型具有成型周期短、尺寸精確、生產(chǎn)率高等優(yōu)點，易實現(xiàn)自動化生產(chǎn)。目前生活中90%以上的塑料制品是通過注射成型的。市場前景好、容量大，應(yīng)用廣。我國的注塑模具起步比較晚，與國外相比有相當(dāng)大的差距。注射模的基本組成：定模機構(gòu)、動模機構(gòu)、澆注系統(tǒng)、導(dǎo)向裝置、頂出機構(gòu)、冷卻和加熱裝置、排氣系統(tǒng)等。
另外中國作為發(fā)展中國家，具有生產(chǎn)發(fā)展水平較低，勞動力資源豐富，生產(chǎn)成本低廉及市場前景廣闊等一般發(fā)展中國家同樣的一些特點，但中國人均GDP己超過2000美元，同時還具有相當(dāng)雄厚的技術(shù)和工業(yè)基礎(chǔ)，人們聰慧、勤勞、靈巧和改革開放良好環(huán)境等一些特殊的特點，這些特點很適合發(fā)展模具工業(yè)，可以預(yù)設(shè)，不遠(yuǎn)的將來，我國將成為世界最大的制造中心，這給我國的模具行業(yè)提供了前所未有的發(fā)展機遇。因此，加快高技術(shù)設(shè)備如數(shù)控加工、快速制模特種加工在模具行業(yè)的應(yīng)用，加大新興CAM/CAM技術(shù)在模具設(shè)計與制造中的應(yīng)用比例，加速模具新結(jié)構(gòu)、新工藝、性材料的研究和強化模具高級技術(shù)人員的培養(yǎng)，已成為我國模具行業(yè)再上一個新臺階的關(guān)鍵。
當(dāng)然對于我本身，選擇注射模具作為畢業(yè)設(shè)計題目，也有很多積極的意義。首先模具設(shè)計還是屬于機械學(xué)科領(lǐng)域，完成一整套的注射模具設(shè)計必然能夠鞏固并且拓展自己的專業(yè)知識。第二的話，對于熟練應(yīng)用各類工程軟件有著莫大的幫助，例如AUTOCAD和PROE等。第三，畢業(yè)設(shè)計是相對獨立的一次任務(wù)，對于自我各個方面都會有所提高。第四，畢業(yè)之際，也就是事業(yè)生涯的開始，有利于開闊工作視野，了解生產(chǎn)實情。
2．研究內(nèi)容擬解決的主要問題：
畢業(yè)設(shè)計的主要內(nèi)容：
分析塑料制品的工藝性，選擇注塑機并校核，確定分型面及型腔數(shù)目，設(shè)計型腔型芯的形狀并計算模板的厚度，設(shè)計流道系統(tǒng)和推出機構(gòu)，設(shè)計模具的冷卻系統(tǒng)，選擇模架、模具零件的制造。
畢業(yè)設(shè)計的要求：
1）與課題有關(guān)的外文文獻翻譯不少于4000漢字；
2）設(shè)計說明書的字?jǐn)?shù)不少于20000字；
3）畢業(yè)答辯圖紙總量不少于3張A0圖紙，其中包括計算機輔助繪圖的工作量；
4）主要參考文獻不少于15篇（包括2篇以上外文文獻）。
3．研究方法技術(shù)路線：
1. 明確塑件設(shè)計要求
仔細(xì)閱讀塑件制品零件圖，從制品的塑料品種，塑件形狀，尺寸精度，表面粗糙度等各方面考慮注塑成型工藝的可行性和經(jīng)濟性。
2. 運用PROE及CAD軟件完成模具設(shè)計。
分型面應(yīng)選在塑件外形最大輪廓處。滿足塑件的外觀質(zhì)量要求:注塑時分型面處不可避免地要在塑件上留下溢料或拼合縫的痕跡，因此分型面最好不要選在塑件光亮的外表面或帶圓弧的轉(zhuǎn)角處。其中分模是最重要的一環(huán)。
3. 模具總體尺寸的確定，選購模架
模架已逐漸標(biāo)準(zhǔn)化，根據(jù)生產(chǎn)廠家提供的模架圖冊，選定模架，在以上模具零部件設(shè)計基礎(chǔ)上初步繪出模具的完整結(jié)構(gòu)圖。
4. 模具結(jié)構(gòu)總裝圖和零件工作圖的繪制
模具總圖繪制必須符合機械制圖國家標(biāo)準(zhǔn)，其畫法與一般機械圖畫法原則上沒有區(qū)別，只是為了更清楚地表達模具中成型制品的形狀，澆口位置的設(shè)置，在模具總圖的俯視圖上，可將定模拿掉，而只畫動模部分的俯視圖。
模具總裝圖應(yīng)該包括必要尺寸，如模具閉合尺寸，外形尺寸，特征尺寸（與注塑機配合的定位環(huán)尺寸），裝配尺寸，極限尺寸（活動零件移動起止點）及技術(shù)條件，編寫零件明細(xì)表等。
通常主要工作零件加工周期較長，加工精度較高，因此應(yīng)首先認(rèn)真繪制，而其余零部件應(yīng)盡量采用標(biāo)準(zhǔn)件。
4．研究的總體安排和進度計劃：
第1、2周 調(diào)研實習(xí)，查閱文獻，整理收集資料。明確課題任務(wù)，完成開題報告和外文翻譯；
第3、4周 對塑件進行工藝性分析、選擇注塑機、理解注射工藝參數(shù)，確定分型面、型腔的數(shù)目、型腔型芯的確定，選擇合適的模架、設(shè)計澆注系統(tǒng)，確定脫模方式，確定冷卻系統(tǒng)；
第5-10周 繪制裝配圖和零件圖；
第11、12周 編寫設(shè)計說明書，撰寫畢業(yè)論文；
第13周整理設(shè)計資料，完善并提交設(shè)計成果，準(zhǔn)備答辯。
5．主要參考文獻：
[1] 夏江梅主編. 塑料成型模具與設(shè)備.機械工業(yè)出版社，2005.
[2] 張維合主編. 注塑模具設(shè)計實用手冊.化學(xué)工業(yè)出版社，2011.
[3] 張孝民主編. 塑料模具技術(shù).機械工業(yè)出版社，2003.
[4] 付偉主編. 注塑模具設(shè)計原則、要點及實例解析.機械工業(yè)出版社，2010.
[5] 葉久新. 王群主編, 塑料成型工藝及模具設(shè)計.機械工業(yè)出版社，2008.
[6] 陳萬林等編著.實用塑料注射模設(shè)計與制造[M].機械工業(yè)出版社，2004.
[7] 伍先明等編著.塑料模具設(shè)計指導(dǎo)[M].國防工業(yè)出版社,2006.
[8] 張學(xué)文、鄭午編著.注塑模設(shè)計，化學(xué)工業(yè)出版社，2007.
[9] 黃銳編主編.塑料成型工藝學(xué)，中國輕工業(yè)出版社，2005.
[10] 齊曉杰主編.塑料成型工藝與模具設(shè)計，機械工業(yè)出版社，2005.
[11] 鄒強主編.塑料模具設(shè)計參考資料匯編,清華大學(xué)出版社，2005.
[12] 張洪峰主編.塑料模具設(shè)計與制造[M].北京：高等教育出版社，2008.
[13] 孫建民主編.基于Pro/E的塑料模具設(shè)計研究[J].現(xiàn)代塑料加工應(yīng)用，2006.
[14] 蔡于紅.塑料轉(zhuǎn)葉零件模具設(shè)計與制造[J].模具技術(shù)，2007.
[15] S.H.Tang.The use of Taguchi method in the design of plastic injection mould for reducing warpage[J].Journal of materials processing technology ,2007.
[16] Tsan Jou.A Web-based model for developing:A mold base design system[J].Expert Systems with applications,2009.
指導(dǎo)教師意見：
對“文獻綜述”的評語： 內(nèi)容豐富
對總體安排和進度計劃的評語： 進度合理
指導(dǎo)教師簽名： 2018年 3 月 16 日
教研室意見：
通過，同意開題
教研室主任簽名： 2018 年 3 月 19 日
學(xué)院意見：
教學(xué)院長簽名： 年 月 日
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徐州工程學(xué)院 班級：班級：姓名：姓名：學(xué)號：學(xué)號：指導(dǎo)老師：指導(dǎo)老師：2018-5-29123 研究背景研究目標(biāo)研究問題4成型方法中最常采用的是注塑模設(shè)計。在工業(yè)成型方法中最常采用的是注塑模設(shè)計。在工業(yè)生產(chǎn)中，占很重要的地位。生產(chǎn)中，占很重要的地位。解決以往模具設(shè)計中遇到的問題；對注塑模解決以往模具設(shè)計中遇到的問題；對注塑模有關(guān)知識做更深入研究。有關(guān)知識做更深入研究。注塑機校核、分型面的選擇以及型芯，型腔注塑機校核、分型面的選擇以及型芯，型腔的形狀等。的形狀等。2018-5-29 研究意義研究注塑模具，對了解塑料產(chǎn)品的生產(chǎn)過程和研究注塑模具，對了解塑料產(chǎn)品的生產(chǎn)過程和提高產(chǎn)品質(zhì)量有很大的意義。提高產(chǎn)品質(zhì)量有很大的意義。1塑件的工藝性分析名稱：洗衣機注水盒名稱：洗衣機注水盒材料：聚丙烯（材料：聚丙烯（PPPP）技術(shù)要求：塑件不得有影響外觀技術(shù)要求：塑件不得有影響外觀的缺陷飛邊、毛刺、縮影等熔接的缺陷飛邊、毛刺、縮影等熔接痕，表面粗糙度痕，表面粗糙度RaRa均在均在0.02m0.02m，拔模斜度為拔模斜度為1 1。結(jié)構(gòu)工藝性：為了便于產(chǎn)品從注結(jié)構(gòu)工藝性：為了便于產(chǎn)品從注射機中順利的開?；蛎撃?，才會射機中順利的開模或脫模，才會將產(chǎn)品制成了一個具有斜度的零將產(chǎn)品制成了一個具有斜度的零件，拔模斜度為件，拔模斜度為1 1。10/11/2022塑件三維圖2模具結(jié)構(gòu)設(shè)計分型面的選擇原則：1、為了脫模方便，塑件在開模后要留在動模上；2、選擇在塑件的最大輪廓處；3、分型面的痕跡不影響塑件的外觀；4、分型面選擇要有利于排氣。型腔數(shù)目的確定：塑件的投影面積不大，但是具有較復(fù)雜的三側(cè)邊抽芯機構(gòu)，所以采用一模一腔的結(jié)構(gòu)。模架的選擇：標(biāo)準(zhǔn)模架 注水盒分型面的選擇 10/11/2022上模板上模板下模板下模板導(dǎo)導(dǎo)柱柱導(dǎo)導(dǎo)套套300 x290 x30300 x290 x2522x18226x116模具外型尺寸模具外型尺寸300 x290 x357mm 模架的尺寸3注塑機型號的選擇注塑機它是將熱塑性塑料或熱固性塑料利用塑料成型模具制成各種形狀的塑料制品的主要成型設(shè)備。它的主要結(jié)構(gòu)：由注射裝置、合模結(jié)構(gòu)、頂出裝置、機械和液壓傳動以及電氣控制系統(tǒng)等組成。10/11/2022F(3010628 mm)/1000=625.7KN鎖模力鎖模力注塑機的最大開模行程注塑機的最大開模行程單個分型面的下模具開模長度單個分型面的下模具開模長度根據(jù)綜合評定，根據(jù)綜合評定，選用的是選用的是HTF150XHTF150X系列的注塑機系列的注塑機.4設(shè)計澆注系統(tǒng) 按照常規(guī)來說，澆口的截面尺寸宜小不宜大，可先確定的小一些，然后在試模時，根據(jù)對型腔的充填情況再進行修正。主澆道為直接與注射機的連接部分。主澆道截面為圓形，整體為圓錐體。主澆道為一圓錐孔，其小頭正對注射機的噴嘴。因噴嘴外形為球面，所以主澆道小頭孔端的外形應(yīng)為一凹球面。選用的是直接澆口。其結(jié)構(gòu)形式如下圖所示：10/11/20225型芯和型腔的形成確定工件的尺寸是：確定工件的尺寸是：，接著依據(jù)分型面的位置來分模?？冀又罁?jù)分型面的位置來分模?？紤]到產(chǎn)品的一些結(jié)構(gòu)問題，將型芯做成了鑲嵌式，而型腔則做成了整體式的型腔。慮到產(chǎn)品的一些結(jié)構(gòu)問題，將型芯做成了鑲嵌式，而型腔則做成了整體式的型腔。凹模的大小是凹模的大小是 ，凸模的尺寸是凸模的尺寸是 。10/11/2022上模（型腔）實體分模圖下模（型芯）實體分模圖6導(dǎo)向機構(gòu)設(shè)計1.1.導(dǎo)柱、導(dǎo)套的設(shè)計導(dǎo)柱、導(dǎo)套的設(shè)計在定模板、動模板之間，上、下頂板在定模板、動模板之間，上、下頂板之間各設(shè)置之間各設(shè)置4 4根導(dǎo)柱，各有導(dǎo)套與之配根導(dǎo)柱，各有導(dǎo)套與之配合。合。2.2.導(dǎo)柱與導(dǎo)套均使用常用的形式導(dǎo)柱與導(dǎo)套均使用常用的形式3.3.導(dǎo)柱和導(dǎo)套使用的是導(dǎo)柱和導(dǎo)套使用的是H7/f6H7/f6的配合，的配合，屬于間隙配合；導(dǎo)柱和安裝孔之間使屬于間隙配合；導(dǎo)柱和安裝孔之間使用的是用的是H7/m6H7/m6配合，屬于過渡配合。配合，屬于過渡配合。10/11/2022導(dǎo)柱結(jié)構(gòu)導(dǎo)柱結(jié)構(gòu)導(dǎo)套結(jié)構(gòu)導(dǎo)套結(jié)構(gòu)7冷卻系統(tǒng)的設(shè)計10/11/20221.冷卻水孔的直徑可以根據(jù)經(jīng)驗得到，由模具寬度及塑件厚度。我選擇冷卻水道的直徑D=6mm。2.本次設(shè)計使用的是串聯(lián)方式的水道，而且是外接直通型的。這種類型的水道結(jié)構(gòu)簡單便捷，而且可以在第一時間發(fā)現(xiàn)水道是否被堵塞。3.冷卻水道的布局見右圖。由于塑料的不同，它們的性能和成型工藝也不同，模具溫度要求也不同，設(shè)計冷卻系統(tǒng)的時候就是要保證塑件的表面質(zhì)量，盡量不讓塑件變形，把工藝時間縮短?？偨Y(jié)PPT模板下載： 通過這次畢業(yè)設(shè)計，讓我正確的認(rèn)識到模具的每個零件的結(jié)構(gòu)和作用，設(shè)計出一套完整的模具。（1）利用UG軟件畫出三維立體圖；（2）分析塑件，選擇合適的材料，分型面以及型芯型腔等建立；（3）選擇適合的模架，增加澆注和冷卻系統(tǒng)等；（4）在各個板塊上加上螺釘?shù)裙潭瓿裳b配圖和零件圖。10/11/202210/11/2022
轉(zhuǎn)子系統(tǒng)在注塑模具設(shè)計中的橢圓截面形狀
摘要
本文介紹了注射成型工藝模具設(shè)計中流道系統(tǒng)的一種新的橫截面形狀。新幾何結(jié)構(gòu)的目標(biāo)是減少廢料，縮短周期時間，并減輕模具工具的流道系統(tǒng)彈出。針對兩個厚度為1mm的圓形平板，提出了具有不同比例的橢圓橫截面形狀。 SolidWorks Plastic采用有限元法（FEM）來模擬注塑零件。 SolidWorks Plastic分析了注塑成型過程中塑料零件的短缺缺陷，以驗證新建議的幾何結(jié)構(gòu)。對新的幾何結(jié)構(gòu)進行了聚丙烯圓形平板注射成型工藝的實驗研究。所選擇的輸入機器參數(shù)是填充時間，熔體溫度，模具溫度，壓力保持時間和純冷卻時間。研究結(jié)果顯示，與新的幾何形狀相比，沒有短路缺陷，與圓形截面相比，廢鋼和冷卻時間分別顯著減少25％和2.5％。流道系統(tǒng)與模具壁的接觸表面的減少也改善了流道系統(tǒng)從模腔排出的容易性。這項研究的貢獻是設(shè)計冷流道系統(tǒng)的新幾何結(jié)構(gòu)，以減少廢料，循環(huán)時間，并提供注射成型中流道系統(tǒng)的簡單排出。
關(guān)鍵詞 注塑工藝；模具設(shè)計；澆道幾何形狀；短缺缺陷
介紹
在過去的一個世紀(jì)里，塑料的迅速增長及其在所有市場的擴散。根據(jù)世界原料重量的消耗，塑料是最高的與其他舊材料，如鋁，鋼，橡膠，銅和鋅相比。它是由塑料的特殊性能和較低的生產(chǎn)成本造成的[1,2]。注塑是制造塑料制品最重要的工藝之一，大約三分之一的塑料通過注塑成型轉(zhuǎn)化為零件[3]。注塑成型工藝在包裝，航空航天，建筑，汽車零部件，家居用品等行業(yè)的應(yīng)用越來越廣泛[1，3，4]。注塑件的質(zhì)量取決于材料特性，模具設(shè)計和工藝條件[4-7]。注塑成型的三個基本操作是：（1）將塑料顆粒轉(zhuǎn)化為熔體; （2）將熔融塑料通過澆口，流道和澆口系統(tǒng)注入模具型腔或型腔中，（3）打開模具將部件推出模腔[1，8，9]。
決定注入部件最終質(zhì)量的因素之一是澆口系統(tǒng)，它是澆口和澆口之間的連接線[10]。轉(zhuǎn)輪系統(tǒng)的主要目的是將熔融塑料從澆口轉(zhuǎn)移到澆口[11,12]。在冷流道系統(tǒng)中，廢鋼的主要來源是去水后來自澆道和澆口系統(tǒng)的廢料。因此，評估跑步者系統(tǒng)設(shè)計的不同規(guī)則以證明跑步者系統(tǒng)在注射中的重要性（a）較小的轉(zhuǎn)輪尺寸以最小化廢品; （b）容易從模具中取出并從模制部件上取下; （c）用最小的凹痕和焊縫快速填充模腔[13-16]。轉(zhuǎn)輪系統(tǒng)設(shè)計的三個基本因素是橫截面形狀，直徑和腔體布局[13]。七種類型的橫截面形狀可用于不同應(yīng)用的轉(zhuǎn)輪系統(tǒng)[13,14,17]（圖1）。根據(jù)要求，選擇不同類型的轉(zhuǎn)輪橫截面[18]。
圖1不同的流道橫截面形狀
本文的貢獻在于為轉(zhuǎn)輪系統(tǒng)定義橢圓形或半橢圓形幾何形狀作為一種有效的橫截面形狀，針對較小的轉(zhuǎn)輪尺寸將廢料與圓形相比減少到最小，從而減少注射的總周期時間和噴射來自模具的零件更容易。此外，在這項研究中，已經(jīng)檢測到與轉(zhuǎn)輪系統(tǒng)的過程參數(shù)和新幾何形狀有關(guān)的顯著現(xiàn)象，這將在另一篇論文中提出。
本文介紹了轉(zhuǎn)輪系統(tǒng)的橢圓形橫截面形狀的設(shè)計標(biāo)準(zhǔn)，并考慮了轉(zhuǎn)輪系統(tǒng)的圓形和半橢圓形之間的比較。對作者而言，有許多論文研究了注射成型的工藝參數(shù)和材料特性，其中一些包括澆道，澆口和澆口，但就作者的最佳知識而言，沒有參考分析和模擬橢圓轉(zhuǎn)輪系統(tǒng)的橫截面形狀。
根據(jù)注入部件的尺寸和幾何形狀進行流道和澆口系統(tǒng)的設(shè)計。然后，通過SolidWorks設(shè)計帶澆道和澆口系統(tǒng)的注塑零件。為了準(zhǔn)確模擬結(jié)果，采用了SolidWorks Plastic中的有限元法（FEM）。最后，為了驗證模型，對兩個圓形注射板進行了實驗方法。
轉(zhuǎn)輪系統(tǒng)的橫截面形狀澆道系統(tǒng)的主要目的是通過澆口將熔融塑料從澆道轉(zhuǎn)移到所有模腔。流道系統(tǒng)有不同的橫截面形狀，每個都有不同的應(yīng)用[11,17]（圖1）。設(shè)計師應(yīng)該評估不同的因素，為特定產(chǎn)品選擇合適的澆道系統(tǒng)幾何形狀。用于雙板模具的最流行的形狀也是最高效率的圓形。對于三板模具工具，如果澆道僅在模具的一半中制造，則梯形和改型梯形是最佳選擇，但仍然不能接受，因為澆口不能與中心線一致流動流[14]。由于尖角，從矩形，正方形和多邊形形狀的腔體中彈出流道系統(tǒng)是具有挑戰(zhàn)性的。如果設(shè)計人員無法確定所需流道系統(tǒng)的適當(dāng)橫截面形狀及其尺寸，則會導(dǎo)致壓力下降，導(dǎo)致模腔不完全填充以及高度向模具壁傳遞熱量[13,17,19]。因此，可以考慮流道系統(tǒng)的各種橫截面積來調(diào)節(jié)通向更好注入部分的流動。最后，形狀以及通道的長度對于實現(xiàn)最佳流動是重要的，因此具有較少缺陷的最佳產(chǎn)品[20]。
具有橢圓橫截面形狀的流道系統(tǒng)
在注射成型中，流道系統(tǒng)最常見的橫截面形狀是圓形。在選擇特定零件設(shè)計的圓形時，三個主要因素是（a）較小的流道尺寸以最小化廢料；（b）容易從模具中彈出；（c）以最小凹痕，焊縫和短射線快速填充模腔[13-15]。這里的目的是研究一種新的幾何形狀的流道系統(tǒng)，這種流道系統(tǒng)可以產(chǎn)生最少的廢料，與澆口的中心流動流線對齊，適當(dāng)填充模腔，并且便于將模具從模具中彈出。為此目的，正在研究橢圓形或半橢圓形橫截面形狀，并與圓形橫截面形狀的流道系統(tǒng)進行了精確比較。
為了證明跑步者的橢圓橫截面形狀的重要性，對跑步者系統(tǒng)的其他幾何形狀的評估是必要的。這兩者的最佳現(xiàn)有比較是矩形和方形。矩形是一種寬度不同的正方形。在寬度方面，矩形澆道系統(tǒng)的尺寸與正方形澆道系統(tǒng)的尺寸相比有三種不同的比率[17]（圖2）。根據(jù)不同的應(yīng)用，選擇不同寬度比的矩形流道系統(tǒng)。長方形形狀的優(yōu)點是減少了轉(zhuǎn)輪系統(tǒng)的廢料，并且更容易從模具中取出。壓降是通過減小方形寬度而發(fā)生的這種幾何形狀的缺點之一[17]。
圓和橢圓之間的比較與正方形和矩形的比較相似。如圖3所示，D是圓的直徑，a是長軸長度，b是橢圓的短軸長度。根據(jù)不同的工業(yè)應(yīng)用，主軸長度是固定的，短軸長度是不同的速率（圖3）。因為這會導(dǎo)致廢料的進一步減少，更容易將部件從模腔中排出，并進一步減少循環(huán)時間。對于不同的部分，這個因素將會改變。因此，提出不同的b比例取決于零件設(shè)計的諸多因素，如尺寸和厚度。
圖2 轉(zhuǎn)輪系統(tǒng)的正方形和矩形形狀之間的比較
圖3轉(zhuǎn)輪系統(tǒng)的圓形和橢圓形狀之間的比較
橢圓形轉(zhuǎn)輪系統(tǒng)的優(yōu)點如下：
1.廢品減量：轉(zhuǎn)輪和門系統(tǒng)的大小和體積是產(chǎn)品廢品的根本原因。 因此，與圓跑者相比，橢圓跑步者導(dǎo)致更少的報廢。
2.從模腔：橢圓形流道系統(tǒng)中，部分射出更加容易，冷卻后與圓形相比，與模具壁接觸的表面更少，從而更容易將注射部件從模腔中排出。
3.縮短循環(huán)時間：橢圓流道所需熔融塑料量較少; 因此包括注入和冷卻階段時間的循環(huán)時間將減少。
與亞軍系統(tǒng)的門的中央流程流。 橢圓流道具有中心流動流，其中大部分澆口設(shè)計減少了熔融塑料至腔體的湍流。
模擬
在為這個應(yīng)用程序設(shè)計兩個圓形零件作為兩個樣品之后，下一步是通過SolidWorks Plastic來模擬零件。對于模擬，需要定義注射系統(tǒng)。因此，應(yīng)考慮考慮事先計算來設(shè)計澆道，澆道和澆口系統(tǒng)（圖4）。設(shè)計橢圓截面形狀的比例為0.7b。
為確保分析結(jié)果的準(zhǔn)確性，F(xiàn)EM將在模擬中發(fā)揮重要作用。根據(jù)樣品的幾何形狀，將選擇有限元的三角形形狀（圖5）。用于此模擬的選定材料是聚丙烯（PP）。對表面網(wǎng)格和表面網(wǎng)格的不同三角形尺寸評估不同的尺寸，為注入部分選擇1毫米的三角形尺寸。對于包括澆口，流道和澆口的注射系統(tǒng)，考慮更小的尺寸。它是由注射系統(tǒng)的靈敏度作為此模擬的關(guān)鍵區(qū)域而產(chǎn)生的。因此，澆道和澆道的三角形尺寸分別為0.3mm和澆口的三角形尺寸分別為橢圓形和圓形橫截面形狀。網(wǎng)格的精度通過網(wǎng)格細(xì)化研究來確定。對于直徑為100毫米的兩個圓形部件，澆道和澆口總長度為28毫米。此外，澆道的長度為60毫米，拔模角度為1.5°。
圖4澆口，流道和澆口系統(tǒng)的注射樣品
圖5 轉(zhuǎn)輪橢圓橫截面形狀的FEA
圖6 用橢圓交叉容易填充注射部分
下一步是設(shè)置適當(dāng)?shù)墓に噮?shù)。根據(jù)所選用的材料和注塑機進行該模擬，填充時間為0.59秒，熔體溫度為230℃，模具溫度為50℃，保壓時間為2.04秒，純冷卻時間3.9秒。如前所述，包括澆道，澆道和澆口的注射系統(tǒng)的幾何形狀和尺寸對操作循環(huán)時間，冷卻時間以及不同的缺陷（如凹痕，短射等）具有顯著影響[25]。在運行模擬之后，根據(jù)新的幾何形狀和尺寸檢查新的流道系統(tǒng)的可接受性。檢查的主要因素包括易于填充，填充時間分析和匯痕分析;并在注射結(jié)束時注射壓力。如圖6所示，橢圓形橫截面的容易填充是處于最可接受水平的綠色區(qū)域。
注塑成型中的一個常見缺陷是如果流動距離較長，將發(fā)生在薄壁或遠(yuǎn)離澆口的短射[26]。根據(jù)模擬結(jié)果，該部分可以成功填充，甚至如圖7a所示的橢圓截面的填充時間低于流道的圓形截面形狀的填充時間（圖7b）。
圖7 a橢圓形橫截面的填充時間，b圓形橫截面的填充時間
圖8 a橢圓截面的流動前沿中心溫度，b圓形截面的流動前沿中心溫度
防止噴射部件短射的另一個因素是評估流動前沿中心溫度，該溫度代表注入部件每個區(qū)域的流動前沿溫度。根據(jù)模擬結(jié)果，注射部件的每個區(qū)域的流動前端中心溫度對于轉(zhuǎn)輪的橢圓橫截面形狀為230.15°C（圖8a）。流道的圓形橫截面形狀的模擬結(jié)果是相同的（圖8b）。這意味著橢圓形橫截面形狀的轉(zhuǎn)子在腔內(nèi)短射的可能性很低。
評估澆道和澆口系統(tǒng)合適尺寸所需的最重要因素之一是注射壓力。根據(jù)模擬，這部分可以成功注入壓力42.1MPa。注射壓力小于滿足最大注射壓力極限的66％（圖9）。圓形截面的注射壓力為39.6 MPa，接近橢圓形截面。
實驗裝置
使用商用注塑顆粒聚丙烯（PP）制造兩個圓形板，其具有100mm直徑和1mm厚度。 所選材料的聚合物材料參數(shù)列于表2中。用于制造模具的機器有鉆孔機，數(shù)控銑床和磨床。 實驗采用全電動臥式注塑機-Poolad-Bch系列。
圖9 澆道系統(tǒng)的圓形和橢圓形橫截面形狀的注射壓力
表2 材料屬性PP
熔體溫度
230℃
最高熔化溫度
280℃
最低熔融溫度
200℃
Mod溫度
50℃
熔體流動速率
20厘米3/10分鐘
最大剪切應(yīng)力
250,000 pa
模具設(shè)計
模具制造有不同的設(shè)計概念。在這項研究中，選擇了雙板模具，該模具具有一個帶有雙腔的分模線和一個供料系統(tǒng)并且沒有頂針。模具由碳鋼CK45制成，表面硬度為56 HRC。磨削后的橢圓形橫澆道，澆口系統(tǒng)和澆口襯套分配到模腔板中（圖10a）。還展示了磨削前帶有導(dǎo)桿的型腔板（圖10b）。
在設(shè)計模具時，另一個要素是導(dǎo)致塑料部件固化的冷卻系統(tǒng)?；谒芰喜考膸缀涡螤?，冷卻系統(tǒng)的設(shè)計是不同的。因此，選擇腔板冷卻系統(tǒng)的圓形幾何形狀（圖11）。
制造模具時要考慮的另一個因素是通風(fēng)孔。它們的功能是在關(guān)閉模具之后從模腔中釋放空氣；否則如果空氣被困在模具內(nèi)，會發(fā)生短射擊。兩個腔體在腔板的左側(cè)和右側(cè)具有單獨的通氣孔（圖12）。
圖10磨削后具有橢圓橫截面的空腔板，b磨削之前具有橢圓橫截面的空腔盤
圖11模腔板內(nèi)的冷卻系統(tǒng)，用于注入部件的凝固
圖12 通風(fēng)孔避免注入部件的空氣陷阱
實驗結(jié)果
根據(jù)不同的工藝參數(shù)設(shè)置模具和注塑機后，從制造過程的不同角度評估流道系統(tǒng)新的橫截面形狀是本實驗的目標(biāo)。為了確保本研究橢圓截面轉(zhuǎn)輪的有效性，需要實施基于不同工藝參數(shù)的填充腔體和注射過程的顯著性測試。短射擊分析的結(jié)果（圖13）顯示，具有新的流道橫截面形狀的兩個腔體被適當(dāng)?shù)靥畛洹?
當(dāng)注入壓力高于最大入口壓力并且注入時間高于注入機器的輸入時，會發(fā)生短射擊。這些實驗中最重要的部分是，與圖14所示的模擬結(jié)果相比，即使在較低的入口壓力和填充時間下，腔體也能夠正確填充。模擬和實驗結(jié)果的比較顯示在表4中。表4中的百分比變化預(yù)測和實際的入口壓力和填充時間結(jié)果分別為7.36和3.38％，這證明了轉(zhuǎn)輪系統(tǒng)的新幾何結(jié)構(gòu)的穩(wěn)健性。
通過定義轉(zhuǎn)輪系統(tǒng)的新幾何形狀，這項研究的新穎之處在于減少廢料和冷卻時間，并且實現(xiàn)從腔體中最終注射部件的更容易的噴射。因此，就廢品率和冷卻時間而言，需要在圓形和橢圓形橫截面之間進行比較。表5顯示了對于100,000個注射部件的流道系統(tǒng)的圓形和橢圓形橫截面的廢料率和冷卻時間。圓形橫截面的冷卻時間為每次注射4 s，橢圓截面每次注射3.9 s。與圓形橫截面相比，橢圓形橫截面的廢鋼和鋁合金減少了25％，注入部件的冷卻時間為2.5％。
圖13 最后注射部分具有橢圓形流道橫截面形狀
圖14 橢圓跑步者的每個因素水平較低的注射部位
結(jié)論
冷流道系統(tǒng)注塑廢料的主要原因是由澆口，流道和澆口系統(tǒng)組成的供料系統(tǒng)。跑步者對于不同的應(yīng)用具有不同的橫截面。本文介紹了橢圓形橫截面與圓形橫截面比較的流道系統(tǒng)新幾何的成功開發(fā)。這種幾何形狀是通過模擬和實驗開發(fā)的，以生產(chǎn)兩個1mm厚的圓形板。工藝參數(shù)為填充時間，熔體溫度，模具溫度，壓力保持時間和純冷卻時間。
為了驗證模型，進行了實驗測試。預(yù)測和實際結(jié)果的入口壓力和填充時間的百分比變化分別為7.36和3.38％。結(jié)果證明了轉(zhuǎn)輪系統(tǒng)的新幾何結(jié)構(gòu)的穩(wěn)健性。與圓形橫截面相比，橢圓形橫截面對于注射部件具有25％的廢料減少和2.5％的冷卻時間。模擬和實驗測試的結(jié)果表明，橢圓形截面形狀是一種有效的幾何形狀，可以減少廢料和總循環(huán)時間，并且還可以使模制件更容易從模腔中彈出。模具設(shè)計的進一步研究將為設(shè)計師和模具制造商創(chuàng)造更具包容性和適當(dāng)?shù)闹笇?dǎo)方針。
參考文獻
[1] Zhou H (2013) Computer modeling for injection molding. Wiley, Hoboken
[2] Salimi A, Subas?? M, Buldu L, Karatas? C? (2013) Prediction of flow length in injection molding for engineering plastics by fuzzy logic under different processing conditions. Iran Polym J 22(1):33–41
[3] Tang SH, Kong YM, Sapuan SM, Samin R, Sulaiman S (2006) Design and thermal analysis of plasticinjection mould. J Mater Process Technol 171(2):259–267
[4] Altan M (2010) Reducing shrinkage in injection moldings via the Taguchi, ANOVA and neural network methods. Mater Des 31(1):599–604
[5]Khoshooee N, Coates PD (1998) Application of the Taguchi method for consistent polymer melt production in injection moulding. Proc Inst Mech Eng Part B J Eng Manuf 212(8):611–620
[6]Ni S (2002) Reducing shrinkage and warpage for printer parts by injection molding simulation analysis. J Inject Molding Technol 6(3):177–186
[7]Mok CK, Chin KS, Ho JKL (2001) An interactive knowledge-based CAD system for mould design in injection moulding processes. Int J Adv Manuf Technol 17:27–38
[8]Dai W, Liu P, Wang X (2002) An improved mold pin gate and its flow pattern in the cavity. J Inject Molding Technol 6(2):115
[9]Hassan H, Regnier N, Pujos C, Arquis E, Defaye G (2010) Modeling the effect of cooling system on the shrinkage and temperature of the polymer by injection molding. Appl Therm Eng 30(13):1547–1557
[10] Tsai KM (2013) Runner design to improve quality of plastic optical lens. Int J Adv Manuf Technol 66(1–4):523–536
[11]Zhen-Yong Z, Zheng-Chao G, Jiao-Ying S (2000) Research on integrated design techniques for injection mold runner system. J Comput Aided Des Comput Graph 12(1):6–10
[12] Bejgerowski W, Gupta SK (2011) Runner optimization for in-mold assembly of multi-material compliant mechanisms. In: Proceedings of the ASME Design Engineering Technical Conference.
[13] Jones P (2008) The mould design guide. Smithers Rapra Technology
[14] Goodship V (ed) (2004) ARBURG practical guide to injection moulding. iSmithers Rapra Publishing
[15] Calhoun DAR, Golmanavich J (2002) Plastics technicians toolbox-extrusion-fundamental skills and polymerscience. Ron Jon, Addison
[16] Zhang Y, Deng YM, Sun BS (2009) Injection molding warpage optimization based on a mode- pursuing sampling method. Polym-Plast Technol Eng 48(7):767–774
[17]Pye RGWte (1989) Injection mould design: a textbook for the novice and a design manual for the thermoplastice industry. Longman Scientific & Technical, Harlow
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Int J Plast Technol (December 2016) 20(2):249–264
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DOI 10.1007/s12588-016-9153-4
Elliptical cross sectional shape of runner system in injection mold design
Mehdi Moayyedian1 ? Kazem Abhary1 ?
Romeo Marian1
Received: 3 June 2015 / Accepted: 21 July 2016 / Published online: 27 July 2016
? Central Institute of Plastics Engineering & Technology 2016
Abstract This paper presents a new cross sectional shape of the runner system in the mold design of the injection molding process. The aim of the new geometry is to reduce scrap, cycle time and ease the ejection of runner system from mold tools. An elliptical cross sectional shape of runner with different ratios was proposed for two circular flat plates with thickness 1 mm. Finite element method (FEM) is employed in SolidWorks Plastic for simulation of the injected part. Short shot defect in the plastic part during the injection molding process is analyzed by SolidWorks Plastic to validate the new proposed geometry. An experimental study of the injection molding process of polypropylene circular flat plates is conducted for the new geometry. The input machine parameters selected are filling time, melt temperature, mold temperature, pressure holding time, and pure cooling time. The research outcomes show no short shot defect associated with the new geometry and also significant 25 and 2.5 % reduction in scrap and cooling time respectively compared to round cross sections. Reduction in contact surface of the runner system with mold walls improved the ease of ejection of runner system out of the cavity as well. The contribution of this study is to design a new geometry of a cold runner system to reduce scrap, cycle time and also provide easy ejection of runner system in the injection molding.
Keywords Injection molding process · Mold design · Runner geometry · Short shot defects
& Mehdi Moayyedian mehdi.moayyedian@unisa.edu.au
1 School of Engineering, University of South Australia, Mawson Lakes Campus, Adelaide, SA 5095, Australia
Introduction
The past century has observed the rapid increase of plastics and their proliferation into all markets. According to world consumption of raw materials by weight, plastic is the highest in comparison with other old materials such as aluminum, steel, rubber, copper, and zinc. It has resulted from specific properties and lower production cost of plastics [1, 2]. Injection molding is one of the most significant processes for manufacturing of plastic products and approximately one-third of all plastics are converted into parts via injection molding [3]. The application of the injection molding process is increasing significantly in many industries like packaging, aerospace and aviation, building and construction, automotive parts, household articles and so on [1, 3, 4]. The quality of the injection moldings depends on material characteristics, mold design and process conditions [4–7]. Three fundamental operations in injection molding are: (1) plastic granules are converted into a melt; (2) molten plastic is injected into the mold cavity or cavities under pressure via sprue, runner and gate systems and (3) mold tools are opened to eject the part out of cavity [1, 8, 9].
One of the factors which will determine the final quality of injected part is the runner system which is a connection line between sprue and gates [10]. The main purpose of the runner system is to transfer molten plastic from sprue to gates [11, 12]. In the cold runner system, the main source of scrap is the scrap from runner and gate system after de-gating. Hence, different rules are evaluated for runner system design to demonstrate the significance of runner systems in injection
round semicircular square
rectangular Trapezoidal Modi?ed Trapezoidal
Polygon
Fig. 1 Different runner cross sectional shapes
molding such as (a) smaller runner size to minimize the scrap; (b) easy ejection from mold tools and removal from molded part; (c) filling the cavity quickly with minimum sink mark and weld lines [13–16]. Three fundamental factors in the runner system design are cross sectional shape, diameter and cavity layout [13]. Seven types of cross sectional shapes are available for the runner system for different applications [13, 14, 17] (Fig. 1). Depending on the requirements, different types of runner cross sections are selected [18].
The contribution of this paper is to define elliptical or semi-elliptical geometry for runner systems as an effective cross sectional shape aiming at smaller runner size to minimize the scrap, in comparison with round shape, to reduce the total cycle time of injection and to eject the part from mold tools more easily. Furthermore, in this research remarkable phenomena related to process parameters and new geometry of runner systems have been detected that will be presented in another paper.
The design criteria of elliptical cross sectional shape for runner systems are introduced herein, and a comparison between round shape and semi-elliptical shape of runner system is considered. To the authors best of knowledge, there are many papers studying process parameters and material characteristics of injection molding a few of which include runner, gate, and sprue but, to the authors’ best of knowledge, there is no reference analyzing and simulating the elliptical cross sectional shape of runner system.
The design of runner and gate systems is conducted herein based on the size and geometry of injected parts. Then, the injected part with runner and gate system is designed via SolidWorks. For accurate result of simulation, finite element method (FEM) in SolidWorks Plastic is employed. Finally, to validate the model, experimental method is conducted for two circular injected plates
Cross sectional shape of runner system
The main purpose of a runner system is to transfer the molten plastic from sprue to all cavities via the gate. There are different cross sectional shapes for runner systems and each of them have different applications [11, 17] (Fig. 1). The designer should evaluate different factors for selecting the right geometry of the runner system for a specific product. The most popular shape of runner systems for two-plate mold tools, which is also of the highest efficiency, is round shape. For three-plate mold tools, the trapezoidal and modified trapezoidal are the best options if the runner is to be manufactured only in one half of the mold, but still they are not acceptable be- cause the gate cannot be positioned in line with the central flow stream [14]. Ejecting a runner system out of cavity with rectangular, square, and polygon shape is challenging due to sharp corners. If a designer cannot determine the appropriate cross sectional shape of the required runner system and their dimensions, pressure drops and leads to incomplete filling of cavities and high level of heat transfer to mold walls [13, 17, 19]. Hence, various cross-sectional area of a runner system can be considered to regulate the flow leading to a better injected part. Finally, the shape and the length of the channel are significant for achieving the optimal flow and consequently the best product with less defects [20].
Runner systems with elliptical cross sectional shape
In injection molding, the most common cross sectional shape for runner system is round shape. In selecting the round shape for specific part design, three main elements are (a) smaller runner size to minimize the scrap; (b) easy ejection from mold tools; (c) filling the cavity quickly with minimum sink mark, weld lines and no short shot [13–15]. The aim herein is to investigate a runner system of new geometry which can lead to minimal scrap, be positioned in line with the central flow stream of gate, properly fill the cavities, and facilitate the easy eject the part from mold tools. For this purpose elliptical or semi-elliptical cross sectional shape has been taken under investigation and accurately compared with runner systems of round cross sectional shape.
To demonstrate the significance of elliptical cross sectional shape of runners, the evaluation of other geometries of runner systems is necessary. The best existing comparison of these two is rectangular and square shape. Rectangle is a kind of square with different width. There are three different ratios in designing the dimension of rectangular runner system in comparison with square ones in terms of width [17] (Fig. 2). According to different applications, rectangular runner system with different ratios of width is chosen. The advantages of rectangular shape over square ones are less scrap of runner system and easier ejection from mold tools. Pressure drop is one of the disadvantages of this geometry which happens by decreasing the width of the square [17].
The comparison between circle and ellipse is similar to that of square and rectangle. As shown in Fig. 3, D is the diameter of circle, a is major axis length, and b is minor axis length of ellipse. Major axis length is fixed and the minor axis length is of different rates depending on different industrial applications (Fig. 3). As it leads to further reduction in scrap, easier ejection of part out of cavity, and further reduction in cycle time. For different parts, this factor will be changed. Hence,
square shape rectangular shape with width ratio 1/2
rectangular shape with width ratio 1/4 rectangular shape with width ratio 1/6
Fig. 2 Comparison between square and rectangular shape of runner system
circular shape elliptical shape with b=0.9a
elliptical shape with b=0.8a elliptical shape with b=0.7a
Fig. 3 Comparison between round and elliptical shape of runner system
proposing different ratio of b depends on many factors of part design such as size and thickness.
Advantages of an elliptical runner system over a round one are as follows:
1. Reduction in scrap: the size and volume of runner and gate system are the root cause of product scrap. Hence an elliptical runner leads to less scrap compared to the round runner.
2. Easier ejection of part from cavity: elliptical runner system, after cooling process compared to round shape has less contact surface with mold walls which leads to easier ejection of the injected part from the cavity.
3. Cycle time reduction: the elliptical runner requires less amount of molten plastic; hence the cycle time which includes the injection and cooling phase time will be reduced.
4. Central flow stream of gate with runner system. Elliptical runner has central flow stream with most of the gate designs which decrease the turbulences of molten plastic to the cavities.
Simulation
After designing two circular parts as two samples for this application, the next step is to simulate the part via SolidWorks Plastic. For the simulation, defining the injection system is needed. Hence, designing the sprue, runner and gate system with consideration of prior calculations should be considered (Fig. 4). The ratio for designing elliptical cross sectional shape is 0.7b.
To make sure that the analysis results are sufficiently accurate, FEM will play a significant role in simulation. According to the geometry of samples, the triangle shape for FEM will be selected (Fig. 5). The selected material for this simulation is polypropylene (PP). Different sizes were evaluated for the surface mesh and from different triangle size of surface mesh, the triangle size of 1 mm is chosen for the injected part. For the injection system which includes sprue, runner and gate, smaller sizes are considered. It has resulted from the sensitivity of the injection system as a critical area of this simulation. Hence, triangle sizes of 0.3 mm for sprue and runner and triangle 0.2 mm for gate are selected for both elliptical and round cross sectional shape of runner. The accuracy of the mesh is determined through a mesh refinement
study. The runner and gate length in total is 28 mm for two circular parts with diameter of 100 mm. Also, the sprue has 60 mm length with draft angle 1.5°.
Fig. 4 Samples of injection with sprue, runner and gate system
Fig. 5 FEA for elliptical cross sectional shape of runner
Fig. 6 Easy filling of injected part with elliptical cross
The next stage is to set up appropriate process parameters. According to the selected material and injection machine for this simulation, filling time is 0.59 s, melt temperature is 230 °C, mold temperature is 50 °C, pressure holding time is
2.04 s, and pure cooling time is 3.9 s. As mentioned before, the geometry and size of the injection system which includes sprue, runner and gate, have significant effects on operation cycle time, cooling time, and different defects such as sink marks, short shot etc. [25]. After running the simulation, the new runner system is checked for acceptability in terms of new geometry and size. The main factors checked are ease of fill, filling time analysis, sink mark analysis; and injection pressure at the end of injection. As shown in Fig. 6, ease of fill for the elliptical cross section is the green area which is in the most acceptable level.
One common defect in injection molding is short shot which will happen on thin walls or far from the gate if there are long flow distances [26]. According to the simulation results, this part can be successfully filled and even the filling time for an elliptical cross section as shown in Fig. 7a is lower than that of for a round cross sectional shape of runner (Fig. 7b).
Fig. 7 a Filling time for elliptical cross section, b Filling time for round cross section
Fig. 8 a Flow front central temperature for elliptical cross section, b Flow front central temperature for round cross section
Another factor to prevent short shot for the injected part is to evaluate the flow front central temperature which represents the flow front temperature at every region of the injected part. Based on the simulation results, the flow front central temperature in every region of the injected part is 230.15 °C for the elliptical cross sectional shape of runner (Fig. 8a). The simulation result for a round cross sectional shape of runner is the same (Fig. 8b). It means that the possibility of short shot in the cavities for an elliptical cross section shape of runner is low.
One of the most significant factors which are necessary to evaluate for the determination of the right size of the runner and gate system is the injection pressure. According to the simulation, this part can be successfully filled with injection pressure
42.1 MPa. The injection pressure is less than 66 % of the maximum injection pressure limit which is satisfactory (Fig. 9). The injection pressure for a round cross section is
39.6 MPa which is close to an elliptical cross section.
Experimental set-up
A commercial injection molding granule polypropylene (PP) is employed to produce two circular plates which have 100 mm diameter and 1 mm thickness. The polymer-material parameters of selected material are listed in Table 2.
Fig. 9 Injection pressure for both round and elliptical cross section shape of runner system
Table 2 Material properties of
PP Melt temperature 230 ○C
Max melt temperature 280 ○C
Min melt temperature 200 ○C
Mod temperature 50 ○C
Melt flow rate 20 cm3/10 min
Max shear stress 250,000 pa
The machines used to fabricate the mold tools are drilling machine, CNC milling machine and grinding machine. Fully electric horizontal-plastic-injection machine—Poolad-Bch series—is employed for the experiments
Mold design
There are different design concepts in fabrication of mold tools. In this study, a two-plate mold which has one parting line with double cavities with a feeding system and without an ejector pin is selected. The mold tools are made of steel— CK45—with surface hardness 56 HRC. The runner with an elliptical cross section, gate system, and sprue bush are allocated in the cavity plate after grinding (Fig. 10a). Also the cavity plate with guide bars before grinding is demonstrated (Fig. 10b).
In designing the mold tools, another element is the cooling system which leads to the solidification of plastic part. Based on the geometry of plastic part, the design for the cooling system is vary. Hence, the circular geometry for the cooling system of cavity plate is selected (Fig. 11).
Another factor to consider in fabrication of mold tools is the air vents. Their function is to release the air from the cavity after closing the mold tools; otherwise short shot will happen if air is trapped inside the mold. Both cavities have separate air vents at the left and right side of the cavity plate (Fig. 12).
Fig. 10 a Cavity plate with elliptical cross section of runner after grinding, b Cavity plate with elliptical cross section of runner before grinding
Fig. 11 Cooling system in cavity plate for solidification of injected part
Fig. 12 Air vents to avoid the air trap in injected parts
Experimental results
After setting up the mold tools and injection machine based on different process parameters, the evaluation of the new cross sectional shape of the runner system from different aspects in the manufacturing process is the target of this experiment. To ensure the effectiveness of an elliptical cross section of runner in this study, the test for significance of filling the cavities and injection process based on the different process parameters need to be implemented. The result of short shot analysis (Fig. 13) shows that two cavities with the new cross sectional shape of runner are filled properly.
When the injection pressure is higher than the maximum inlet pressure and filling time is higher than the input of the injection machine, short shot will happen. The most significant part of these experiments is that the cavities filled properly even with lower inlet pressure and filling time in comparison with simulation results as shown in Fig. 14. The comparison of the simulation and experimental result is shown in Table 4. Percentage change for predicted and actual results of inlet pressure and filling time are 7.36 and 3.38 % respectively which demonstrates the robustness of new geometry of runner system.
The novelty of this research by defining the new geometry of the runner system is to reduce scrap and cooling time and achieve easier ejection of final injected part from the cavity. Hence, the comparison between a round and an elliptical cross section in terms of scrap rate and cooling time is necessary. Table 5 demonstrates the scrap rate and cooling time of a round and an elliptical cross section of runner system for 100,000 injected parts. The cooling time for a round cross section is 4 s per injection and for an elliptical cross section 3.9 s per injection. An elliptical cross section in comparison with round cross section has 25 % reduction in scrap and 2.5 % in cooling time for the injected parts.
Fig. 13 Final injected part with elliptical cross sectional shape of runner
Fig. 14 Injected part with lower level of each factor for an elliptical runner
Table 4 Comparison of simulation and experimental result based on process parameters
Process parameter
Simulation result
Experimental result
Inlet pressure
42.1 MPa
39 MPa
Filling time
0.59 s
0.57 s
Table 5 Scrap rate and cycle time for the round and elliptical cross section
Factor
Round
Elliptical
Scrap rate of runner (g)
8000
6000
Cooling time (h)
111.11
108.33
Conclusion
The main reason for scrap in injection molding for cold runner system is the feeding system which consists of sprue, runner and gate system. The runner has different cross sections for different applications. This paper presents the successful development of a new geometry of a runner sys
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