塑料殼體注塑模具設(shè)計(jì)【一模兩腔】
塑料殼體注塑模具設(shè)計(jì)【一模兩腔】,一模兩腔,塑料,殼體,注塑,模具設(shè)計(jì)
塑料模具設(shè)計(jì)說(shuō)明書(shū)設(shè) 計(jì) 題 目 :設(shè) 計(jì) 者:班 級(jí):指 導(dǎo) 教 師:摘 要論文根據(jù)工程實(shí)際的需要完成塑料殼體的注射模設(shè)計(jì)。在設(shè)計(jì)中采用塑料注射成型論文中具體分析了產(chǎn)品的工藝性,確定了所采用塑料的工藝參數(shù)和所采用的成型設(shè)備,確定了模具制作的總體方案,分析并解決了模具的總體結(jié)構(gòu)和各工作部分的具體結(jié)構(gòu),并進(jìn)行了一些必要的尺寸計(jì)算和強(qiáng)度的校核。論文中還對(duì)分型面、澆注系統(tǒng)、脫模機(jī)構(gòu)和溫度調(diào)節(jié)系統(tǒng)進(jìn)行了分析設(shè)計(jì),完成了工件工程圖設(shè)計(jì),圓滿完成了模具設(shè)計(jì)所要求的各項(xiàng)工作。本文中針對(duì)塑料殼體注射模具制定出合理的設(shè)計(jì)結(jié)構(gòu),其中包括成型部分及其零部件設(shè)計(jì),澆注系統(tǒng)設(shè)計(jì),脫模機(jī)構(gòu)設(shè)計(jì),冷卻系統(tǒng)設(shè)計(jì)等。根據(jù)分析,設(shè)計(jì)了一套塑料注射模具,并對(duì)模具以及主要零件進(jìn)行了CAD繪圖。關(guān)鍵字:注射模具,澆注系統(tǒng),脫模機(jī)構(gòu),冷卻系統(tǒng)目 錄摘 要II目 錄III第1章 前言1第2章 塑件的工藝分析22.1塑件的工藝性分析22.2塑件的結(jié)構(gòu)和尺寸精度及表面質(zhì)量分析32.2.1結(jié)構(gòu)分析32.2.2尺寸精度分析32.2.3表面質(zhì)量分析32.3 計(jì)算塑件的體積和質(zhì)量32.4 注射機(jī)的初選4第3章 分型面選擇和澆注系統(tǒng)設(shè)計(jì)53.1 注射模具分型面的選擇53.1.1 分型面的基本形式53.1.2 分型面選擇的基本原則53.1.3 分型面的選擇53.2 澆注系統(tǒng)的設(shè)計(jì)63.2.1 澆注系統(tǒng)的組成63.2.2 注射模具流道的設(shè)計(jì)7第4章 成型零件的設(shè)計(jì)144.1 模具型腔的結(jié)構(gòu)設(shè)計(jì)144.2 型芯的結(jié)構(gòu)設(shè)計(jì)154.3 成型零件的尺寸確定16第5章 頂出機(jī)構(gòu)的設(shè)計(jì)22第6章 冷卻系統(tǒng)的設(shè)計(jì)25第7章 排氣系統(tǒng)26第8章 成型設(shè)備有關(guān)參數(shù)校核26第9章 模具特點(diǎn)和工作原理28總 結(jié)28參考文獻(xiàn)30第1章 前言模具工業(yè)是現(xiàn)代工業(yè)的基礎(chǔ),它的技術(shù)水平很大程度上決定了產(chǎn)品的質(zhì)量和市場(chǎng)的競(jìng)爭(zhēng)能力。隨著我國(guó)加入“WTO”步伐的日益加快?!叭胧馈睂?duì)我國(guó)模具工業(yè)產(chǎn)生重大而深遠(yuǎn)的影響,經(jīng)濟(jì)全球化的趨勢(shì)日益明顯,同時(shí)世界眾多知名公司不斷進(jìn)行構(gòu)調(diào)整,國(guó)內(nèi)市場(chǎng)的國(guó)際性進(jìn)一步現(xiàn),該行業(yè)將經(jīng)受更大的沖擊,競(jìng)爭(zhēng)也會(huì)更加激烈。在如此嚴(yán)峻的行業(yè)背景下,我國(guó)的技術(shù)人員經(jīng)過(guò)不斷的改革和創(chuàng)新使得我國(guó)模具水平有了較大的提高,大型,復(fù)雜,精密,高效和長(zhǎng)壽命模具有上了新的臺(tái)階。塑料制品的成型是塑料成為具有實(shí)用價(jià)值制品的重要環(huán)節(jié)。塑料成型方法已達(dá)40多種。其中最重要的是注射,擠出,吹塑和壓制等。它們幾乎占了整個(gè)塑料成型的85%;其中注射尤為突出,占塑料成型的30%以上。注射模具成形是熱塑性塑料成型的一種方法,幾乎所有的熱塑性塑料都可以用此方法成型,有些熱固性塑料也可以用注射模塑成型。先進(jìn)制造技術(shù)的發(fā)展使人們不再單純地依賴產(chǎn)品圖或產(chǎn)品樣件來(lái)設(shè)計(jì)制作模具,逆向工程技術(shù)的應(yīng)用使產(chǎn)品的圖片、照片或影像資料,甚至產(chǎn)品模具本身,都可以作為模具的設(shè)計(jì)依據(jù)。逆向工程技術(shù)特別在消化、吸收國(guó)外先進(jìn)模具技術(shù)方面具有突出的優(yōu)勢(shì), 由此還帶來(lái)設(shè)計(jì)思路上的變化,有時(shí)可以先設(shè)計(jì)模具型腔,然后據(jù)此再完善產(chǎn)品設(shè)計(jì)圖樣1。31第2章 塑件的工藝分析第2章 塑件的工藝分析該塑件是塑料殼體產(chǎn)品,其零件圖如圖所示。本塑件的材料采用ABS,生產(chǎn)類型為大批量生產(chǎn)。圖2.1 塑料殼體圖2.1塑件的工藝性分析該材料為ABS,一般聚苯乙烯強(qiáng)度不高,質(zhì)硬而脆,有易破碎和耐熱性低性等缺點(diǎn)。分析塑件的結(jié)構(gòu)工藝性塑件尺寸較小,內(nèi)部結(jié)構(gòu)簡(jiǎn)單,對(duì)塑件的測(cè)量和計(jì)算沒(méi)較大影響,符合塑件的設(shè)計(jì)要求。塑件精度要求,塑件工作要求不高,故選普通精度:級(jí)2.2塑件的結(jié)構(gòu)和尺寸精度及表面質(zhì)量分析2.2.1結(jié)構(gòu)分析該塑料件是一殼體,塑件壁屬厚壁塑件,生產(chǎn)批量大,材料選ABS,考慮到主流道應(yīng)盡可能短,一般小于60mm,過(guò)長(zhǎng)則會(huì)影響熔體的順利充型,因此采用下例數(shù)據(jù):2.2.2尺寸精度分析從塑件的壁厚上來(lái)看,壁厚最大處為3mm,壁厚均勻,在制件的轉(zhuǎn)角處設(shè)計(jì)圓角,防止在此處出現(xiàn)缺陷,由于制件的尺尺寸中等。2.2.3表面質(zhì)量分析該零件的表面除要求沒(méi)有缺陷毛刺,內(nèi)部不得有雜質(zhì)外,沒(méi)有什么特別的表面質(zhì)量要求,故比較容易實(shí)現(xiàn)。綜上分析可以看出,注塑時(shí)在工藝控制得較好的情況下,零件的成型要求可以得到保證.2.3 計(jì)算塑件的體積和質(zhì)量計(jì)算塑件的質(zhì)量是為了選用注塑機(jī)及確定模具型腔數(shù)。1.通過(guò)Pro/E建模分析,塑件為m1=26.5g,v1=m1/, =1.05V1=25.2cm3,流道凝料的質(zhì)量m2=0.6m1 m=1.6nm12.塑件和流道凝料在分型面上的投影面積及所需的鎖模力. 流道凝料(包括澆口)在分型面上的投影面積A2,A2可用0.35nA1來(lái)進(jìn)行估算,所以 A=nA1+A2=1.35A1 n=1.354A1=25920mm2 式中A1=8060=4800mm2查表2-2取P型=25MpaFm=AP型=2592025=648000N聚苯乙烯的密度為1.058克每立方厘米2.4 注射機(jī)的初選根據(jù)每一生產(chǎn)周期的注射量和鎖模力的計(jì)算值可選用SZ-250/1250理論注射量/cm3_270_ 鎖模力/ KN 1250_螺桿直徑/mm _45_ 拉桿內(nèi)間距/mm_415415注射壓力/ MPa 160_ 移模行程/mm_360_注射速率/g/s_110_ 最大模厚/mm_塑化能力/_18.9 最小模厚/mm150螺桿轉(zhuǎn)速/10200_ 定位孔直徑/mm160噴嘴半徑/mm15 鎖模方式/雙曲肘第3章 分型面選擇和澆注系統(tǒng)設(shè)計(jì)3.1 注射模具分型面的選擇3.1.1 分型面的基本形式分型面的形式由塑料的具體情況而定,但大體上有平面式分型面、階梯式分型面、斜面式分型面、曲面式分型面、綜合式分型面。3.1.2 分型面選擇的基本原則選擇分型面的基本原則:(1)保持塑料外觀整潔;(2)分型面應(yīng)有利于排氣;(3)應(yīng)考慮開(kāi)模是塑料留在動(dòng)模一側(cè);(4)應(yīng)容易保證塑件的精度要求;(5)分型面應(yīng)力求簡(jiǎn)單適用并易于加工;(6)考慮側(cè)向分型面與主分型面的協(xié)調(diào);(7)分型面應(yīng)與成型設(shè)備的參數(shù)相適應(yīng);(8)考慮脫模斜度的影響11。3.1.3 分型面的選擇1、確定成型位置由于塑件結(jié)構(gòu)簡(jiǎn)單,所以不用設(shè)計(jì)小型心,型腔直接開(kāi)設(shè)在定模板和中間板上.采用兩排各8個(gè)型腔分布.2、確定分型面采用單分型面注射模,從AA分型面一次分型,如下圖所示:圖3.1 分型面3.2 澆注系統(tǒng)的設(shè)計(jì)3.2.1 澆注系統(tǒng)的組成澆注系統(tǒng)是將熔融的塑料從成型設(shè)備噴嘴進(jìn)入模具型腔所經(jīng)的通道,它包括主流道、分流道、澆口及冷料。在設(shè)計(jì)注射模具的澆注系統(tǒng)應(yīng)注意以下幾項(xiàng)原則12。(1)根據(jù)所確定的塑件型腔數(shù)設(shè)計(jì)合理的澆注系統(tǒng)布局。(2)根據(jù)塑件的形狀和大小以及壁厚等諸多因素,并結(jié)合選擇分型面的形式選擇澆注系統(tǒng)的形式及位置。(3)應(yīng)盡量的縮短物料的流程和便于清除料把,以節(jié)省原料,提升注射效率。(4)應(yīng)根據(jù)所選用塑件的成型性能,特別是它的流動(dòng)性能,選擇澆注系統(tǒng)的截面積和長(zhǎng)度,并使其圓滑過(guò)渡以利于物流的流動(dòng)。3.2.2 注射模具流道的設(shè)計(jì)1. 主流道設(shè)計(jì)1)主流道尺寸設(shè)計(jì) 根據(jù)所選注射機(jī),則主流道小端尺寸為 d=注射機(jī)噴嘴尺寸+(0.51) =3.5+0.5=42) 主流道球面半徑為 SR=噴嘴球面半徑+(12)=15+(12)=16mm3) 球面配合高度 h=3mm5mm,取h=3mm4) 主流道長(zhǎng)度,盡量小于60,由標(biāo)準(zhǔn)模架結(jié)合該模具的結(jié)構(gòu),取L=25+20=45mm5) 主流道大端直徑 D=d+2Ltan=6.54mm(半錐角為1- 2,取= 2)取D=6.5mm.6) 澆口套總長(zhǎng) L0=25+20+h+2=502. 主流道襯套的形式 主流道小端入口處與注射機(jī)噴嘴反復(fù)接觸屬易損件,對(duì)材料要求嚴(yán)格,因而模具主流道部分常設(shè)計(jì)可拆卸更換的主流道襯套形式即澆口套,以便常用碳素工具鋼如T8A,T10A等,熱處理硬度為50HRC-55HRC.如圖示3.主流道襯套的固定4.冷料穴的設(shè)計(jì)1)主流道冷料穴的設(shè)計(jì) 開(kāi)模時(shí)應(yīng)將主流道中的凝料拉出,所以冷料穴直徑稍大于主流道大端直徑.采用Z形頭冷料穴,很容易將主流道凝料拉離定模,如圖所示1;定模座板 2;冷料穴 3;動(dòng)模板 4;推桿主流道凝料體積Q主= h/12(D2+Dd+d2)=40/12(6.52+6.53.5+3.52) =809mm2=0.8cm3主流道剪切速率校核 由經(jīng)驗(yàn)公式 v=3.3qv/Rqv=q主+q分+q塑件=0.8+425.28+0.58=102.5cm2Rn=(3.5+6.5)/2/2=0.25cm 主流道剪切速率偏小主要是注射量小,噴嘴尺寸偏大,使主流道尺寸偏大所致。5 分流道設(shè)計(jì)分流道布置形式 分流道布置有多種形式,但是需要循兩方面原則:一方面排列緊湊,縮小模具版面尺寸;另一方面流程盡量短,鎖模力力求平衡。應(yīng)采用平衡式分流道。分流道長(zhǎng)度第一級(jí)分流道 L1=50mm第二級(jí)分流道 L2=15mm分流道的形式.截面尺寸以及凝料體積為了便于加工及凝料脫模,分流道大多設(shè)置在分型面上。工程設(shè)計(jì)中常用梯形截面,加工工藝性好,且塑料熔體的熱量散失.流動(dòng)阻力均不大,一般采用下面的經(jīng)驗(yàn)公式可確定其截面尺寸,即 B=0.2654式中,B-梯形大底邊的寬度 m-塑件的質(zhì)量(g),為26.5g根據(jù)塑料模具設(shè)計(jì)手冊(cè)表4-9,取B=4 H=2/3B=2.67mm 取H=3mm 從理論上L2,L3分流道可以L1截面小1/10,但為了刀具的統(tǒng)一和加工方便,在分型面上的分流道采用一樣的截面.分流道的表面粗糙度由于分流道中與模具接觸的外層塑料迅速冷卻,只有中心部位的塑料熔體的流動(dòng)狀態(tài)較理想,因此分流道的內(nèi)表面粗糙度Ra并不要求很低,一般取0.63m-1.6m,這樣表面稍不光滑,有助于增大塑料熔體的外層流動(dòng)阻力,避免熔體表面滑移,使中心層具有較高的剪切速率。此處Ra=0.8m。 凝料體積分流道長(zhǎng)度 L=(50+82+12)2=136mm分流道截面積 A=(3+4)/23=10.5mm2凝料體積 q分=13610.5=1428mm3=1.428cm3分流道剪切速率校核采用經(jīng)驗(yàn)公式 r =3.3q/R 3=3.3101.12/(3.140.253)=6801式中 q=1/t=425.28=101.126澆口的設(shè)計(jì) 澆口截面積通常為分流道截面積的0.07倍0.09倍,澆口截面積形狀多為矩形和圓形兩種,澆口長(zhǎng)度為0.5mm2mm。澆口具體尺寸一般根據(jù)經(jīng)驗(yàn)確定,取其下限值,然后在試模時(shí)逐漸修正。1 澆口類型及位置確定該模具是中小型塑件的多型腔模具,設(shè)置側(cè)澆口比較合適。側(cè)澆口開(kāi)設(shè)在垂直分型面上,從型腔(塑件)外側(cè)面進(jìn)料,側(cè)澆口是典型的矩形截面澆口,能很方便的調(diào)整充模時(shí)的剪切速率和澆口封閉時(shí)間,因而又被稱為標(biāo)準(zhǔn)澆口。這類澆口加工容易,修正方便,并且可以根據(jù)塑件的形狀特征靈活地選擇進(jìn)料位置,因此它是廣泛使用的一種澆口形式,普遍使用于中小型塑件的多型腔模具。2 澆口結(jié)構(gòu)尺寸的經(jīng)驗(yàn)公式側(cè)澆口深度和寬度經(jīng)驗(yàn)計(jì)算:經(jīng)驗(yàn)公式為 h=nt=1mm w=2.3式中,h-側(cè)澆口深度(mm); W-澆口寬度(mm); A-塑件外表面積; t-塑件厚度(約為3mm ) n-塑料系數(shù),查表得 n=0.67 澆注系統(tǒng)的平衡對(duì)于該模具,從主流道到各個(gè)型腔的分流道的長(zhǎng)度相等,形狀及截面尺寸對(duì)應(yīng)相同,各個(gè)澆口也相同,澆注是平衡的。8 澆注系統(tǒng)凝料體積計(jì)算 主流道與主流道冷料井凝料體積 V主=v錐v冷=h/12(D2+Dd+d2)+/4(D2h)=15919.8mm39 普通澆注系統(tǒng)截面尺的計(jì)算與校核確定適當(dāng)?shù)募羟兴俾蕆根據(jù)經(jīng)驗(yàn)澆注系統(tǒng)各段的r取以下值,所成型塑件質(zhì)量較好。 主流道 rs=5102s-15103s-1 分流道 R=5102s-1 點(diǎn)澆口 rG=105s-1 其他澆口 rG=5103s-15104s-1 確定體積流率q1). 主流道體積流率qs 因塑件小,即使是一模四腔的模具結(jié)構(gòu),所需注射塑料熔體的體積也還是比較小的,而主流道尺寸并不小,因此主流道體積流率并不大,取rs=1103s-1代入得 qs=/4R3=/41030.33=21.9cm3/s2). 澆口體積流率qG 側(cè)(矩形)澆口用適當(dāng)?shù)募羟兴俾蕆G=1104s-1代入得 qG=Wh2/6=2.30.12104/6=38cm3/s. 注射時(shí)間(充模時(shí)間)的計(jì)算 1).模具充模時(shí)間 ts=vs/qs=25.28/21.9=1.15s 式中 qs-主流道體積流率; ts-注射時(shí)間,s; Vs-模具成型時(shí)所需塑料熔體的體積,cm32). 單個(gè)型腔充模時(shí)間 tG=VG/qG=25.25/38=0.66s3). 注射時(shí)間 根據(jù)經(jīng)驗(yàn)公式5求得注射時(shí)間 t=ts/3+2tG/3=0.82s4 校核各處剪切速率1).澆口剪切速率 rG=6V3/Wh2=625.25/2.30.12=6.59103s-12).分流道剪切速率由經(jīng)驗(yàn)公式 =3.3q/R3=3.3101.12/3.140.253 =6.8103s-1第4章 成型零件的設(shè)計(jì)4.1 模具型腔的結(jié)構(gòu)設(shè)計(jì)型腔大體有以下幾種結(jié)構(gòu)形式:整體式、整體組合式、局部組合式和完全組合式。型腔由整塊材料制成,用臺(tái)肩或螺栓固定在模板上。它的主要優(yōu)點(diǎn)是便于加工,特別是在多型腔模具中,型腔單個(gè)加工后,在分別裝入模板,這樣容易保證各型腔的同心度以及尺寸精度要求,并且便于部分成型件進(jìn)行處理等。型腔由整塊材料制成,但局部鑲有成型嵌件的局部組合式型腔。局部組合式型腔多于型腔較深或形狀較為復(fù)雜,整體加工比較困難或局部需要淬硬的模具。完全組合式是由多個(gè)螺栓拼塊組合而成的型腔。它的特點(diǎn)是,便于機(jī)加工,便于拋光研磨和局部熱處理。節(jié)約優(yōu)質(zhì)鋼材。這種形式多用于不容易加工的型腔或成型大面積塑件的大型型腔上。這里選擇整體式型腔。在塑料注射模具的注射過(guò)程中,型腔從合模到注射保證過(guò)程中受到高壓的沖擊力,因此模具型腔應(yīng)該有足夠的硬度和剛度,總的來(lái)說(shuō),型腔所承受的力大體有合模時(shí)的壓應(yīng)力、注射過(guò)程中塑料流動(dòng)的注射壓力、澆口封閉前一瞬間的壓力保證和開(kāi)模時(shí)的壓應(yīng)力,但型腔所承受的力主要是注射壓力和保證壓力,并在注射過(guò)程中總是在變化。在這些壓力作用下,當(dāng)型腔的剛度不足時(shí),往往會(huì)產(chǎn)生彈性變形,導(dǎo)致型腔向外膨脹,它將直接影響塑件的質(zhì)量和尺寸精度。所以在模具設(shè)計(jì)時(shí)要首先考慮使型腔的壁厚和底板厚度都有足夠的強(qiáng)度和剛度,以保證型腔在注射過(guò)程中產(chǎn)生超過(guò)規(guī)定限度的彈性變形。因此型腔壁厚和底板的計(jì)算和選擇是十分重要的。(1)型腔側(cè)壁厚度的計(jì)算按強(qiáng)度計(jì)算其壁厚S按下列公式計(jì)算 式中 型腔材料的許用應(yīng)力,=156.8MPa p型腔內(nèi)單位平均壓力,P=38.4MPar型腔內(nèi)半徑,r=10mm代入公式得:S=4mm(2)底板厚度的計(jì)算按強(qiáng)度計(jì)算其壁厚H按下面公式計(jì)算 式中 型腔材料的許用應(yīng)力,=156.8MPa p型腔內(nèi)單位平均壓力,P=38.4MPar型腔內(nèi)半徑,r=10mm代入公式得:H=5.5mm4.2 型芯的結(jié)構(gòu)設(shè)計(jì)型芯的結(jié)構(gòu)形式大體有:整體式、整體復(fù)合式、局部組合式、完全組合式。4.3 成型零件的尺寸確定(1)型腔尺寸計(jì)算型腔的各部分尺寸一般都是趨于增大尺寸,因此應(yīng)選擇塑件公差的1/2,取負(fù)偏差,再加上-1/4的磨損量,而型芯深度則再加上-1/6的磨損量,這樣的型芯的計(jì)算尺寸的表述如下。(a)型腔的徑向尺寸的計(jì)算式: 式中 D0型芯的最小基本尺寸; 塑件的最大基本尺寸;S塑件的平均收縮率,S=0.02;塑件的公差,取八級(jí)精度;模具制造公差,按1/4選?。唬╞)型腔的深度根據(jù)尺寸的計(jì)算公式 式中 型腔深度的最小尺寸; 塑件的最大基本小尺寸;S塑件的平均收縮率;塑件的公差,取八級(jí)精度;模具制造公差,按1/4選??;(2)型芯尺寸的計(jì)算型芯的各部尺寸除特殊情況外都是趨于縮小尺寸,因此應(yīng)選擇塑件公差的1/2,取正偏差,再加上+1/4的磨損量,而型芯高度則加上+1/6的磨損量.型芯的計(jì)算尺寸表達(dá)如下。(a)型芯的徑向尺寸的計(jì)算式: 式中 型芯的最大基本尺寸; 塑件的最小基本尺寸;S塑件的平均收縮率;塑件的公差,取八級(jí)精度;模具制造公差,按1/4選?。桓鶕?jù)公式計(jì)算得型芯的徑向尺寸: (b)型芯的高度尺寸的計(jì)算: 式中 型芯高度的最大尺寸; 塑件內(nèi)形深度的最小尺寸;S塑件的平均收縮率;塑件的公差,取八級(jí)精度;模具制造公差,按1/4選取;根據(jù)公式計(jì)算得型芯的高度尺寸:4.6確定主要零件結(jié)構(gòu)及尺寸塑料模具型腔在成型過(guò)程中受到塑料熔體的高壓作用應(yīng)具有足夠的強(qiáng)度和剛度,如果型腔側(cè)壁和底版厚度過(guò)小,可能因強(qiáng)度不夠而產(chǎn)生塑性變形甚至破壞,也可能因剛度不足而產(chǎn)生撓曲變形,導(dǎo)致溢料飛邊,降低塑件尺寸精度并影響順利脫模。1.模部分的型芯為了便于加工設(shè)置一個(gè)定模型芯,它的配合可以采用過(guò)盈配合。 2.成型零件鋼材的選用 零件是大批量生產(chǎn),成型零件所選用鋼材耐磨性和抗疲勞性能應(yīng)該良好,機(jī)械加工性能和拋光性能也應(yīng)該良好,因此構(gòu)成型腔的嵌入式凹模鋼材選用SMI3.成型零件工作尺寸的計(jì)算 塑件尺寸公差按SJ137278標(biāo)準(zhǔn)中的6級(jí)精度選取1).型腔徑向尺寸Lm1=(1+s)Ls1-x+20=(1+s)80-0.580.70+0.120 =80.28+0.120Lm2=(1+s)Ls2- x+20=1.003594-0.580.7+0.120 =93.79+0.120式中, S塑件平均收縮率S=(0.006+0.008)=0.0035X修正系數(shù)(取0.58) 塑件公差值(查塑件公差表取0.70)2制造公差,(取/5) 參考塑料模具設(shè)計(jì)手冊(cè)P49型腔深度尺寸 Hm=(1+s)h-x0+=24.7+0.120 式中,h塑件厚度最大尺寸(取25)x修正系數(shù)(取0.56) 塑件公差值(取0.40)參考塑料模具設(shè)計(jì)手冊(cè)P47型芯高度尺寸hm=(1+s)H+x0-2=3.130-0.04式中,h塑件厚度最小尺寸(取3) X修正系數(shù)(取0.58) 塑件公差值(查塑件公差表取0.20)模架的確定和標(biāo)準(zhǔn)件的選用 模架尺寸確定后,對(duì)模具有關(guān)零件要進(jìn)行必要的強(qiáng)度或剛度的計(jì)算,以校核所選模架是否適當(dāng),尤其對(duì)大型模具。 由前面型腔的布局以及相互的位置尺寸,再根據(jù)成型零件尺寸結(jié)合標(biāo)準(zhǔn)模架,選用模架尺寸為710mm745mm的標(biāo)準(zhǔn)模架,可符合要求。 模具上所有的螺釘盡量采用內(nèi)六角螺釘,模具外表盡量不要有突出部分,模具外表面應(yīng)光潔,加涂防銹油。兩模板之間應(yīng)用分模間隙,即在裝配,調(diào)試,維修過(guò)程中,可以方便地分開(kāi)兩塊模板。八.合模導(dǎo)向機(jī)構(gòu)的設(shè)計(jì) 1.導(dǎo)向機(jī)構(gòu)的總體設(shè)計(jì)1. )導(dǎo)向零件應(yīng)合理地均勻分布在模具的周圍或靠近邊緣的部分。2. )該模具采用4根導(dǎo)柱,其分布為等直徑導(dǎo)柱不對(duì)稱裝置3. )該模具導(dǎo)柱安裝在支撐板和模套上,導(dǎo)套安裝在定模固定板上。4. )為了保證分型面很好的接觸,采用在導(dǎo)套的孔口倒角。5. )在合模時(shí),應(yīng)保證到向零件首先接觸。6. )動(dòng)定模板采用合并加工時(shí),可確保同軸度要求。2.到導(dǎo)柱的設(shè)計(jì) 該模具采用帶頭導(dǎo)柱,不加油槽,如下圖示導(dǎo)柱的長(zhǎng)度必須比凸模端面高度高出,6mm8mm.1.) 為使導(dǎo)柱能順利地進(jìn)入導(dǎo)向孔,導(dǎo)柱的端部常做成錐形或球形的先導(dǎo)部分.2.) 導(dǎo)柱的直徑應(yīng)根據(jù)模具尺寸來(lái)確定,應(yīng)保證具有足夠的抗彎強(qiáng)度,該導(dǎo)柱直徑由標(biāo)準(zhǔn)模架可知為mm.3.) 導(dǎo)柱的安裝形式,導(dǎo)柱固定部分與模架按H7/f6配合,導(dǎo)柱的滑動(dòng)部分按H7/f7或H8f7的間隙配合.4.) 導(dǎo)柱工作部分的表面粗糙度為Ra=0.4mm5.) 導(dǎo)柱應(yīng)具有堅(jiān)硬耐磨的表面,堅(jiān)韌而不易折斷的內(nèi)芯.多采用低碳鋼經(jīng)滲碳淬火處理或碳素工具鋼T8A.T10A,經(jīng)淬火處理,硬度為50HRC以上或45鋼經(jīng)調(diào)質(zhì)表面淬火,低溫回火,硬度為50HRC以上.3.導(dǎo)套設(shè)計(jì) 導(dǎo)套與安裝在另一半模上的導(dǎo)柱相配合,用一確定運(yùn)動(dòng)定模的相對(duì)位置,保證模具運(yùn)動(dòng)導(dǎo)柱相配合,用以確定運(yùn)動(dòng)定模的相對(duì)位置,保證模具運(yùn)動(dòng)導(dǎo)向精度的圓套形零件.導(dǎo)套常用的結(jié)構(gòu)形式有兩種:直導(dǎo)套(GB/T41692.2-1984(帶頭導(dǎo)套(GB/T4169.31984).1.) 結(jié)構(gòu)形式,采用帶頭導(dǎo)套(型)如圖所示2.) 導(dǎo)套的端面應(yīng)倒角,導(dǎo)柱孔最好做成面孔,利于排出孔內(nèi)剩余空氣.3.) 導(dǎo)套孔的滑動(dòng)部分按H8/f7或H7/f7的間隙配合,表面粗糙度為0.4mm.導(dǎo)套外徑與模板一端采用H7/k6配合;另一端采用H7/e7配合 入模板.4.) 導(dǎo)套材料可用,淬火鋼或青銅合金等耐磨材料制造該模具中采用T8A.4.推板導(dǎo)柱與導(dǎo)套設(shè)計(jì)推板導(dǎo)柱除了起導(dǎo)向作用外,還支撐著支撐板,從而改善了支撐板的受力情況,大大提高了支撐板的剛性,該模具設(shè)置了4套推板導(dǎo)柱與導(dǎo)套,它們之間采用H8/f7配合其形狀與尺寸配合如圖所示第5章 頂出機(jī)構(gòu)的設(shè)計(jì)頂出機(jī)構(gòu)的分類:按驅(qū)動(dòng)方式分類可分為:手動(dòng)頂出、機(jī)動(dòng)頂出、啟動(dòng)頂出。按模具結(jié)構(gòu)分類可分為:一次頂出、二次頂出、螺紋頂出、特殊頂出。(1)推出機(jī)構(gòu)的結(jié)構(gòu)組成 在注射成形的每個(gè)周期中,將塑料制品及澆注系統(tǒng)凝料從模具巾脫出的機(jī)構(gòu)稱為推出機(jī)構(gòu),也叫頂出機(jī)構(gòu)或脫模機(jī)構(gòu)。推出機(jī)構(gòu)的動(dòng)作通常是由安裝在成型設(shè)備上的機(jī)械頂桿或液壓缸的活塞桿來(lái)完成的。結(jié)構(gòu)組成:由推出、復(fù)位和導(dǎo)向零件組成。(2)結(jié)構(gòu)分類手動(dòng)推出、機(jī)動(dòng)推出、液壓或氣動(dòng)推出。(3)結(jié)構(gòu)設(shè)計(jì)要求塑件留在動(dòng)模,塑件在推出過(guò)程中不變形、不損壞,不損壞塑件的外觀質(zhì)量,合模時(shí)應(yīng)使推出機(jī)構(gòu)正確復(fù)位,動(dòng)作可靠。(4)結(jié)構(gòu)設(shè)計(jì)(a)推桿推出機(jī)構(gòu)推桿推出機(jī)構(gòu)是整個(gè)推出機(jī)構(gòu)中最簡(jiǎn)單、最常見(jiàn)的一種形式。由于設(shè)置推桿的自由度較大,而且推桿截面大部分為圓形,容易達(dá)到推桿與模板或型芯上推桿孔的配合精度推桿推出時(shí)運(yùn)動(dòng)阻力小,推出動(dòng)作靈活可靠,因此在生產(chǎn)中廣泛應(yīng)用。 但是因?yàn)橥茥U的推出面積一般比較小,易引起較大局部應(yīng)力而頂穿塑件或使塑件變形,所以很少用于脫模斜度小和脫模阻力大的管類或箱類塑件。(b)推管推出機(jī)構(gòu)推管推出機(jī)構(gòu)是用來(lái)推出圓筒形、環(huán)形塑件或帶有孔的塑件的一種特殊結(jié)構(gòu)形式,其脫模運(yùn)動(dòng)方式和推桿相同。由于推管是一種空心推桿,故整個(gè)周邊接觸塑件,推出塑件的力量均勻,塑件不易變形,也不會(huì)留下明顯的推出痕跡。(c)推件板的推出機(jī)構(gòu)凡是薄壁容器、殼形塑件以及表面不允許有推出痕跡的塑料制品,可采用推件板推出推件板推出機(jī)構(gòu)義稱頂板頂出機(jī)構(gòu),它由一塊與型芯按一定配合精度相配合的模板和推桿組成。 特點(diǎn):推件板推出的特點(diǎn)是頂出力均勻,運(yùn)動(dòng)平穩(wěn),且推出力大。但是對(duì)于截面為非圓形的塑件,其配合部分加工比較困難。 (d)活動(dòng)嵌件及凹模推出機(jī)構(gòu)有一些塑件由于結(jié)構(gòu)形狀和所用材料的關(guān)系,不能采用推桿、推管、推件板等簡(jiǎn)單推出機(jī)構(gòu)脫模時(shí),可用成形嵌件或型腔帶出塑件。(5)頂出機(jī)構(gòu)的設(shè)計(jì)原則: 塑件在成型頂出后,一般都留有頂出痕跡,但應(yīng)盡量使頂出的殘留痕跡不影響塑件的外觀,這是在選擇頂出形式和頂出位置時(shí)必須考慮到的問(wèn)題。一般頂出機(jī)構(gòu)應(yīng)設(shè)在塑件的內(nèi)表面以及不顯眼的位置。注射設(shè)備的頂出裝置都設(shè)計(jì)在動(dòng)模一側(cè),因此,在一般情況下開(kāi)模時(shí),盡量設(shè)計(jì)使塑件留在動(dòng)模一側(cè),以便于頂出塑件。這在分型面的選擇時(shí)就應(yīng)充分考慮。在實(shí)踐中如果出現(xiàn)塑件并沒(méi)有留在動(dòng)模側(cè)的情況時(shí),可設(shè)法增加動(dòng)默一側(cè)的阻力,一是將型芯的脫模斜度變小,或增加型芯的表面粗糙度,或者在不影響塑件使用的前提下,在型芯側(cè)面人為的開(kāi)設(shè)橫凹槽、凹窩等脫模障礙,以增大動(dòng)模的阻力。在特殊情況下必須使塑件留在定模時(shí)可采用定模頂出機(jī)構(gòu)。 塑件在成型頂出后,一般都留有頂出痕跡,但應(yīng)盡量使頂出的殘留痕跡不影響塑件的外觀,這是在選擇頂出形式和頂出位置時(shí)必須考慮到的問(wèn)題。一般頂出機(jī)構(gòu)應(yīng)設(shè)在塑件的內(nèi)表面以及不顯眼的位置。頂出零件應(yīng)有足夠的機(jī)械強(qiáng)度和耐磨性能,使其在相當(dāng)長(zhǎng)的運(yùn)作周期內(nèi)平穩(wěn)順暢,無(wú)卡滯現(xiàn)象,并力求制造方便,容易維修。 頂出裝置力求均勻分布,頂出力作用點(diǎn)應(yīng)在塑件承受頂出力最大的部件,盡量避免頂出力作用于最薄的部位,防止塑件在頂出過(guò)程中的變形和損傷。頂出零件應(yīng)有足夠的機(jī)械強(qiáng)度和耐磨性能,使其在相當(dāng)長(zhǎng)的運(yùn)作周期內(nèi)平穩(wěn)順暢,無(wú)卡滯現(xiàn)象,并力求制造方便,容易維修。第6章 冷卻系統(tǒng)的設(shè)計(jì)塑料注射成型是將熔融狀態(tài)的塑料向模腔高壓注射,其后這些熔料在摸腔中冷卻到塑料變形溫度以下固化成型。在塑料固化成型過(guò)程中,由熔融狀態(tài)冷卻到固化狀態(tài)是由熔料溫度和模具的溫差來(lái)實(shí)現(xiàn)的,而且一般說(shuō)來(lái),模具溫度應(yīng)在塑料熱變形溫度以下才能達(dá)到迅速固化成型的目的。但是模具的溫度既不能過(guò)高也不能過(guò)低。模具溫度過(guò)高會(huì)造成溢料,脫模困難,并使塑件固化時(shí)間延長(zhǎng),延長(zhǎng)注射成型周期,降低生產(chǎn)效率;模溫過(guò)低則會(huì)影響注射熔料的流動(dòng)性,使塑料應(yīng)力增大,并可能出現(xiàn)熔接痕及缺料等制品缺陷,影響塑件質(zhì)量。模具溫度不均勻會(huì)使塑件變形,以及收縮率偏差等諸多問(wèn)題影響塑件的質(zhì)量。為此,控制模具溫度是塑件注射成型中的重要環(huán)節(jié)。第7章 排氣系統(tǒng)在注塑模具的設(shè)計(jì)過(guò)程中,必須考慮排氣結(jié)構(gòu)的設(shè)計(jì),否則,熔融的塑料流體進(jìn)入模具型腔內(nèi),在填充模具的型腔過(guò)程中同時(shí)要排出型強(qiáng)及流道原有的空氣,氣體如不能及時(shí)排出會(huì)使制件的內(nèi)部有氣泡, 除此以外,塑料熔體會(huì)產(chǎn)生微量的分解氣體。這些氣體必須及時(shí)排出。否則,被壓縮的空氣產(chǎn)生高溫,會(huì)引起塑件局部碳化燒焦,或塑件產(chǎn)生氣泡,或使塑件熔接不良引起強(qiáng)度下降,甚至充模不滿甚至?xí)a(chǎn)生很高的溫度使塑料燒焦,從而出現(xiàn)廢品。排氣方式有兩種:開(kāi)排氣槽排氣和利用合模間隙排氣。由于塑料殼體注塑模是小型鑲拼式模具,可直接利用分型面和鑲拼間隙進(jìn)行排氣,而不需在模具上開(kāi)設(shè)排氣槽。第8章 成型設(shè)備有關(guān)參數(shù)校核4.注射機(jī)有關(guān)參數(shù)的校核n(KMt/3600-m2)/m1=(0.810.530/3600)-m2/m2 =(0.8*18.9*3600*30/3600-0.6*4*26.5)/26.5 =14.74型腔數(shù)校核合格.式中,K注射機(jī)最大注射量的利用系數(shù)一般取0.8 m-注射機(jī)的額定塑化量(10.5g/s) t成型周期取30s1)注射壓力的校核 PekP0=1.3150=195Mpa K-注射壓力的安全系數(shù),一般取K=1.25-1.4 P0-取130Mpa,中等壁厚件2)鎖模力校核 FKAP型=1.2648=777.6KN.而F=1250 KN K0鎖模力安全系數(shù),一般取K0=1.1-1.2 其他安裝尺寸的校核要待模架的選定,結(jié)構(gòu)尺寸確定后才可進(jìn)行.8.3、模具厚度H與成型設(shè)備閉合高度成型設(shè)備開(kāi)模行程應(yīng)大于模具開(kāi)模時(shí)取出塑件(包括澆注系統(tǒng))所需的開(kāi)模距,即滿足下式: SH1+H2+a+(510)mm 式中 S成型設(shè)備最大開(kāi)模行程,180mm; H1推出距離(脫模距離),mm; H2塑料高度,mm; a定模板與中間板之間的分開(kāi)距離。 則:H1+H2+a+(510)=5+3.5+60+10=78.5mm180mm 所以,能滿足要求。第9章 模具特點(diǎn)和工作原理1、模具的特點(diǎn):該模具是兩板模,設(shè)計(jì)了1 個(gè)水平分型面。設(shè)計(jì)了定距拉桿, A 分型面是為了取出制件。該模具一模2件,節(jié)省了成本,降低了制造周期,提高了生產(chǎn)效率。2、模具的工作過(guò)程模具裝配試模完畢后,模具進(jìn)入正式工作狀態(tài),其基本工作過(guò)程如下。(1)對(duì)塑料進(jìn)行烘干,并裝入料斗。(2)清理模具型芯、型腔,并噴上脫模劑,進(jìn)行適當(dāng)?shù)念A(yù)熱。(3)合模、鎖緊模具。(4)對(duì)塑料進(jìn)行預(yù)塑化,注射裝置準(zhǔn)備注射。(5)注射過(guò)程包括充模、保壓、倒流、澆口凍結(jié)后的冷卻和脫模。(6)脫模過(guò)程。制件的推出同一般注塑模具推出方式相同,即由注塑機(jī)推桿推動(dòng)模具推板,從而推動(dòng)推件桿將之間頂出。總 結(jié)課程設(shè)計(jì)從CAD造型設(shè)計(jì);完成塑件注射模具方案設(shè)計(jì)和相關(guān)設(shè)計(jì)計(jì)算;模具成型零件CAD造型設(shè)計(jì);最后完成模具加工,掌握了完整的工程設(shè)計(jì)過(guò)程,工程設(shè)計(jì)應(yīng)用能力得到了鍛煉和提高。這次課程設(shè)計(jì),歷時(shí)3個(gè)月。在此期間,針對(duì)設(shè)計(jì)內(nèi)容進(jìn)行了大量的工作,順利完成了課程設(shè)計(jì)中所提出的各項(xiàng)任務(wù),達(dá)到了課程設(shè)計(jì)的目的。通過(guò)此課程設(shè)計(jì),掌握了模具設(shè)計(jì)的方法和步驟,并結(jié)合具體的零件進(jìn)行了具體的設(shè)計(jì)工作,包括確定型腔的數(shù)目、選擇分型面、確定澆注系統(tǒng)、脫模方式、溫度調(diào)節(jié)系統(tǒng)的設(shè)計(jì)、注射模成型零件尺寸的計(jì)算等。課程設(shè)計(jì)從測(cè)繪塑件,進(jìn)行三維造型繪制;完成塑件注射模具方案設(shè)計(jì)和相關(guān)設(shè)計(jì)計(jì)算;最后完成模具加工,掌握了完整的工程設(shè)計(jì)過(guò)程,工程設(shè)計(jì)應(yīng)用能力得到了鍛煉和提高。完成了注射模具的制造工藝設(shè)計(jì),但由于缺乏實(shí)際工作經(jīng)驗(yàn),在這些設(shè)計(jì)過(guò)程中也遇到了很多困難,但在老師的指導(dǎo)下,問(wèn)題都迎刃而解??傊?,通過(guò)本次課程設(shè)計(jì),加強(qiáng)了我對(duì)各項(xiàng)知識(shí)的學(xué)習(xí)深度,更培養(yǎng)了分析問(wèn)題和解決問(wèn)題的能力,教會(huì)我怎樣才能按步驟有條不紊地進(jìn)行工作。這些為我走上工作崗位奠定了堅(jiān)實(shí)的基礎(chǔ)。參考文獻(xiàn)1 王國(guó)中,申長(zhǎng)雨注塑模具CAD/CAE/CAM技術(shù)M北京:中國(guó)標(biāo)準(zhǔn)出版社, 1998.2王文廣等塑料注射模具設(shè)計(jì)技巧與實(shí)例M北京:化工工業(yè)出版社,2003.3日村上宗雄最新塑料模具手冊(cè)S上海:上??茖W(xué)技術(shù)文獻(xiàn)出版社, 1985.4德K.斯托克海特注塑成型模具102例M北京:中國(guó)輕工業(yè)出版社, 1991.5王文廣塑料材料的選用M北京:化工工業(yè)出版社,2001.6成都科技大學(xué)塑料成型工藝M北京:中國(guó)輕工業(yè)出版社,1983.7歐陽(yáng)國(guó)思實(shí)用塑料材料學(xué)M長(zhǎng)沙:國(guó)防科技大學(xué)出版社,1991.8唐志玉大型注塑模設(shè)計(jì)基礎(chǔ)M 成都:成都科技大學(xué)出版社,1987.9馬金俊塑料模具設(shè)計(jì)M北京:中國(guó)科學(xué)科技出版社,199410 曹宏深,趙仲冶塑料成型工藝與模具設(shè)計(jì)M北京:機(jī)械工業(yè)出版社,1993.11 肖景容模具計(jì)算機(jī)輔助設(shè)計(jì)和制造M北京:國(guó)防工業(yè)出版社,1990.12 李志剛等.模具計(jì)算機(jī)輔助設(shè)計(jì)M武漢:華中理工大學(xué)出版社,1990.Single gate optimization for plastic injection mold Journal of Zhejiang University - Science A Volume 8, Number 7 (2007), 1077-1083, DOI: 10.1631/jzus.2007.A1077 Ji-quan Li, De-qun Li, Zhi-ying Guo and Hai-yuan LvAbstract:Abstract: This paper deals with a methodology for single gate location optimization for plastic injection mold. The objective of the gate optimization is to minimize the warpage of injection molded parts, because warpage is a crucial quality issue for most injection molded parts while it is influenced greatly by the gate location. Feature warpage is defined as the ratio of maximum displacement on the feature surface to the projected length of the feature surface to describe part warpage. The optimization is combined with the numerical simulation technology to find the optimal gate location, in which the simulated annealing algorithm is used to search for the optimum. Finally, an example is discussed in the paper and it can be concluded that the proposed method is effective.Key words: Injection mold, Gate location, Optimization, Feature warpage.INTRODUCTIONPlastic injection molding is a widely used, com- plex but highly efficient technique for producing a large variety of plastic products, particularly those with high production requirement, tight tolerance, and complex shapes. The quality of injection molded parts is a function of plastic material, part geometry, mold structure and process conditions. The most important part of an injection mold basically is the following three sets of components: cavities, gates and runners, and cooling system.Lam and Seow (2000) and Jin and Lam (2002) achieved cavity balancing by varying the wall thick- ness of the part. A balance filling process within the cavity gives an evenly distributed pressure and tem- perature which can drastically reduce the warpage of the part. But the cavity balancing is only one of the important influencing factors of part qualities. Espe- cially, the part has its functional requirements, and its thicknesses should not be varied usually.From the pointview of the injection mold design, a gate is characterized by its size and location, and the runner system by the size and layout. The gate size and runner layout are usually determined as constants. Relatively, gate locations and runner sizes are more flexible, which can be varied to influence the quality of the part. As a result, they are often the design pa- rameters for optimization.Lee and Kim (1996a) optimized the sizes of runners and gates to balance runner system for mul- tiple injection cavities. The runner balancing was described as the differences of entrance pressures for a multi-cavity mold with identical cavities, and as differences of pressures at the end of the melt flow path in each cavity for a family mold with different cavity volumes and geometries. The methodology has shown uniform pressure distributions among the cavities during the entire molding cycle of multiple cavities mold.Zhai et al.(2005a) presented the two gate loca- tion optimization of one molding cavity by an effi- cient search method based on pressure gradient (PGSS), and subsequently positioned weld lines to the desired locations by varying runner sizes for multi-gate parts (Zhai et al., 2006). As large-volume part, multiple gates are needed to shorten the maxi- mum flow path, with a corresponding decrease in injection pressure. The method is promising for de- sign of gates and runners for a single cavity with multiple gates.Many of injection molded parts are produced with one gate, whether in single cavity mold or in multiple cavities mold. Therefore, the gate location of a single gate is the most common design parameter for optimization. A shape analysis approach was pre- sented by Courbebaisse and Garcia (2002), by which the best gate location of injection molding was esti- mated. Subsequently, they developed this methodol- ogy further and applied it to single gate location op- timization of an L shape example,(Courbebaisse,2005). It is easy to use and not time-consuming, while it only serves the turning of simple flat parts with uniform thickness.Pandelidis and Zou (1990) presented the opti- mization of gate location, by indirect quality measures relevant to warpage and material degradation, which is represented as weighted sum of a temperature dif- ferential term, an over-pack term, and a frictional overheating term. Warpage is influenced by the above factors, but the relationship between them is not clear. Therefore, the optimization effect is restricted by the determination of the weighting factors.Lee and Kim (1996b) developed an automated selection method of gate location, in which a set of initial gate locations were proposed by a designer and then the optimal gate was located by the adjacent node evaluation method. The conclusion to a great extent depends much on the human designers intuition, because the first step of the method is based on the designers proposition. So the result is to a large ex- tent limited to the designers experience.Lam and Jin (2001) developed a gate location optimization method based on the minimization of the Standard Deviation of Flow Path Length (SDL) and Standard Deviation of Filling Time (SDT) during the molding filling process. Subsequently, Shen et al.(2004a; 2004b) optimized the gate location design by minimizing the weighted sum of filling pressure, filling time difference between different flow paths, temperature difference, and over-pack percentage. Zhai et al.(2005b) investigated optimal gate location with evaluation criteria of injection pressure at the end of filling. These researchers presented the objec- tive functions as performances of injection molding filling operation, which are correlated with product qualities. But the correlation between the perform- ances and qualities is very complicated and no clear relationship has been observed between them yet. It is also difficult to select appropriate weighting factors for each term. A new objective function is presented here to evaluate the warpage of injection molded parts to optimize gate location. To measure part quality di- rectly, this investigation defines feature warpage to evaluate part warpage, which is evaluated from the “flow plus warpage” simulation outputs of Moldflow Plastics Insight (MPI) software. The objective func- tion is minimized to achieve minimum deformation in gate location optimization. Simulated annealing al- gorithm is employed to search for the optimal gate location. An example is given to illustrate the effec- tivity of the proposed optimization procedure. QUALITY MEASURES: FEATURE WARPGEDefinition of feature warpageTo apply optimization theory to the gate design, quality measures of the part must be specified in the first instance. The term “quality” may be referred to many product properties, such as mechanical, thermal, electrical, optical, ergonomical or geometrical prop- erties. There are two types of part quality measures: direct and indirect. A model that predicts the proper- ties from numerical simulation results would be characterized as a direct quality measure. In contrast, an indirect measure of part quality is correlated with target quality, but it cannot provide a direct estimate of that quality.For warpage, the indirect quality measures in related works are one of performances of injection molding flowing behavior or weighted sum of those. The performances are presented as filling time dif- ferential along different flow paths, temperature dif- ferential, over-pack percentage, and so on. It is ob- vious that warpage is influenced by these perform- ances, but the relationship between warpage and these performances is not clear and the determination of these weighting factors is rather difficult. Therefore, the optimization with the above objective function probably will not minimize part warpage even with perfect optimization technique. Sometimes, improper weighting factors will result in absolutely wrong re- sults.Some statistical quantities calculated from the nodal displacements were characterized as direct quality measures to achieve minimum deformation in related optimization studies. The statistical quantities are usually a maximum nodal displacement, an av- erage of top 10 percentile nodal displacements, and an overall average nodal displacement (Lee and Kim,1995; 1996b). These nodal displacements are easy to obtain from the simulation results, the statistical val- ues, to some extents, representing the deformation. But the statistical displacement cannot effectively describe the deformation of the injection molded parts.In industry, designers and manufacturers usually pay more attention to the degree of part warpage on some specific features than the whole deformation of the injection molded parts. In this study, feature warpage is defined to describe the deformation of the injection parts. The feature warpage is the ratio of the maximum displacement of the feature surface to the projected length of the feature surface (Fig.1):where is the feature warpage, h is the maximum displacement on the feature surface deviating from the reference platform, and L is the projected length of the feature surface on a reference direction paralleling the reference platform.For complicated features (only plane feature discussed here), the feature warpage is usually separated into two constituents on the reference plane, which are represented on a 2D coordinate system:where x, y are the constituent feature warpages in the X, Y direction, and Lx, Ly are the projected lengths of the feature surface on X, Y component.Evaluation of feature warpageAfter the determination of target feature com- bined with corresponding reference plane and pro- jection direction, the value of L can be calculated immediately from the part with the calculating method of analytic geometry (Fig.2). L is a constant for any part on the specified feature surface and pro- jected direction. But the evaluation of h is more com- plicated than that of L.Simulation of injection molding process is a common technique to forecast the quality of part de- sign, mold design and process settings. The results of warpage simulation are expressed as the nodal de- flections on X, Y, Z component (Wx, Wy, Wz), and the nodal displacement W. W is the vector length of vector sum of Wxi, Wyj, and Wzk, where i, j, k are the unit vectors on X, Y, Z component. The h is the maximum displacement of the nodes on the feature surface, which is correlated with the normal orientation of the reference plane, and can be derived from the results of warpage simulation.To calculate h, the deflection of its node is evaluated firstly as follows:where Wi is the deflection in the normal direction of the reference plane of ith node; Wix, Wiy, Wiz are the deflections on X, Y, Z component of ith node; , , are the angles of normal vector of the reference; A and B are the terminal nodes of the feature to projectingdirection (Fig.2); WA and WB are the deflections of nodes A and B:where WAx, WAy, WAz are the deflections on X, Y, Zcomponent of node A; WBx, WBy and WBz are the de- flections on X, Y, Z component of node B; iA and iB are the weighting factors of the terminal node deflections calculated as follows:where LiA is the projector distance between ith node and node A. Ultimately, h is the maximum of the absolute value of Wi:In industry, the inspection of the warpage is carried out with the help of a feeler gauge, while the measured part should be placed on a reference plat- form. The value of h is the maximum numerical reading of the space between the measured part surface and the reference platform.GATE LOCATION OPTIMIZATION PROBLEM FORMATIONThe quality term “warpage” means the perma- nent deformation of the part, which is not caused by an applied load. It is caused by differential shrinkage throughout the part, due to the imbalance of polymer flow, packing, cooling, and crystallization.The placement of a gate in an injection mold is one of the most important variables of the total mold design. The quality of the molded part is greatly af- fected by the gate location, because it influences the manner that the plastic flows into the mold cavity. Therefore, different gate locations introduce inho- mogeneity in orientation, density, pressure, and temperature distribution, accordingly introducing different value and distribution of warpage. Therefore, gate location is a valuable design variable to minimize the injection molded part warpage. Because the correlation between gate location and warpage distribu- tion is to a large extent independent of the melt and mold temperature, it is assumed that the moldingconditions are kept constant in this investigation. The injection molded part warpage is quantified by the feature warpage which was discussed in the previous section.The single gate location optimization can thus be formulated as follows:Minimize:Subject to: where is the feature warpage; p is the injection pressure at the gate position; p0 is the allowable in- jection pressure of injection molding machine or the allowable injection pressure specified by the designer or manufacturer; X is the coordinate vector of the candidate gate locations; Xi is the node on the finite element mesh model of the part for injection molding process simulation; N is the total number of nodes. In the finite element mesh model of the part, every node is a possible candidate for a gate. There- fore, the total number of the possible gate location Np is a function of the total number of nodes N and the total number of gate locations to be optimized n:In this study, only the single-gate location problem is investigated. SIMULATED ANNEALING ALGORITHMThe simulated annealing algorithm is one of the most powerful and popular meta-heuristics to solve optimization problems because of the provision of good global solutions to real-world problems. The algorithm is based upon that of Metropolis et al. (1953), which was originally proposed as a means to find an equilibrium configuration of a collection of atoms at a given temperature. The connection between this algorithm and mathematical minimization was first noted by Pincus (1970), but it was Kirkpatrick et al.(1983) who proposed that it formed the basis of an optimization technique for combinational (and other) problems.To apply the simulated annealing method to op timization problems, the objective function f is used as an energy function E. Instead of finding a low energy configuration, the problem becomes to seek an approximate global optimal solution. The configura- tions of the values of design variables are substituted for the energy configurations of the body, and the control parameter for the process is substituted for temperature. A random number generator is used as a way of generating new values for the design variables. It is obvious that this algorithm just takes the mini- mization problems into account. Hence, while per- forming a maximization problem the objective func- tion is multiplied by (1) to obtain a capable form.The major advantage of simulated annealing algorithm over other methods is the ability to avoid being trapped at local minima. This algorithm employs a random search, which not only accepts changes that decrease objective function f, but also accepts some changes that increase it. The latter are accepted with a probability pwhere f is the increase of f, k is Boltzmans constant, and T is a control parameter which by analogy with the original application is known as the system “temperature” irrespective of the objective function involved.In the case of gate location optimization, the implementation of this algorithm is illustrated in Fig.3, and this algorithm is detailed as follows:(1) SA algorithm starts from an initial gate loca- tion Xold with an assigned value Tk of the “temperature” parameter T (the “temperature” counter k is initially set to zero). Proper control parameter c (0c1) in annealing process and Markov chain Ngenerateare given.(2) SA algorithm generates a new gate location Xnew in the neighborhood of Xold and the value of the objective function f(X) is calculated.(3) The new gate location will be accepted with probability determined by the acceptance functionFig.3 The flow chart of the simulated annealing algorithmAPPLICATION AND DISCUSSIONThe application to a complex industrial part is presented in this section to illustrate the proposed quality measure and optimization methodology. The part is provided by a manufacturer, as shown in Fig.4. In this part, the flatness of basal surface is the most important profile precision requirement. Therefore, the feature warpage is discussed on basal surface, in which reference platform is specified as a horizontal plane attached to the basal surface, and the longitudinal direction is specified as projected reference direction. The parameter h is the maximum basal surface deflection on the normal direction, namely the vertical direction, and the parameter L is the projected length of the basal surface to the longitudinal direction.Fig.4 Industrial part provided by the manufacturerThe material of the part is Nylon Zytel 101L (30% EGF, DuPont Engineering Polymer). The molding conditions in the simulation are listed in Table 1. Fig.5 shows the finite element mesh model of the part employed in the numerical simulation. It has1469 nodes and 2492 elements. The objective func- tion, namely feature warpage, is evaluated by Eqs.(1), (3)(6). The h is evaluated from the results of “Flow+Warp” Analysis Sequence in MPI by Eq.(1), and the L is measured on the industrial part immediately, L=20.50 mm.MPI is the most extensive software for the in- jection molding simulation, which can recommend the best gate location based on balanced flow. Gate location analysis is an effective tool for gate location design besides empirical method. For this part, the gate location analysis of MPI recommends that the best gate location is near node N7459, as shown in Fig.5. The part warpage is simulated based on this recommended gate and thus the feature warpage is evaluated: =5.15%, which is a great value. In trial manufacturing, part warpage is visible on the sample work piece. This is unacceptable for the manufacturer.The great warpage on basal surface is caused by the uneven orientation distribution of the glass fiber, as shown in Fig.6a. Fig.6a shows that the glass fiber orientation changes from negative direction to positive direction because of the location of the gate, particularly the greatest change of the fiber orientation appears near the gate. The great diversification of fiber orientation caused by gate location introduces serious differential shrinkage. Accordingly, the feature warpage is notable and the gate location must be optimized to reduce part warpageTo optimize the gate location, the simulated annealing searching discussed in the section “Simulated annealing algorithm” is applied to this part. The maximum number of iterations is chosen as 30 to ensure the precision of the optimization, and the maximum number of random trials allowed for each iteration is chosen as 10 to decrease the probability of null iteration without an iterative solution. Node N7379 (Fig.5) is found to be the optimum gate loca- tion. The feature warpage is evaluated from the war- page simulation results f(X)=0.97%, which is less than that of the recommended gate by MPI. And the part warpage meets the manufacturers requirements in trial manufacturing. Fig.6b shows the fiber orientation in the simulation. It is seen that the optimal gate location results in the even glass fiber orientation, and thus introduces great reduction o
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