薄壁PE桶氣動(dòng)脫模的注射模具設(shè)計(jì)【說(shuō)明書(shū)+CAD+SOLIDWORKS+仿真】
薄壁PE桶氣動(dòng)脫模的注射模具設(shè)計(jì)【說(shuō)明書(shū)+CAD+SOLIDWORKS+仿真】,說(shuō)明書(shū)+CAD+SOLIDWORKS+仿真,薄壁PE桶氣動(dòng)脫模的注射模具設(shè)計(jì)【說(shuō)明書(shū)+CAD+SOLIDWORKS+仿真】,薄壁,pe,氣動(dòng),脫模,注射,模具設(shè)計(jì),說(shuō)明書(shū),仿單,cad,solidworks
模具與設(shè)計(jì)制造項(xiàng)目
設(shè)計(jì)說(shuō)明書(shū)
題目：薄壁PE桶氣動(dòng)脫模的注射模具設(shè)計(jì)
班 級(jí)
姓 名
學(xué) 號(hào)
成 績(jī)
2006年 1月 25 日
目錄
封面……………………………………………………………1
目錄……………………………………………………………2
（一） 設(shè)計(jì)指導(dǎo)…………………………………………….4
（二）進(jìn)度表………………………………………………..5
（三）說(shuō)明書(shū)正文……………………………………………6
1、塑料零件工藝的分析……………………………….6
2、分型面的選擇……………………………………..9
3、澆注位置的確定…………………………………..9
4、抽芯機(jī)構(gòu)的確定…………………………………..9
5、脫模機(jī)構(gòu)的確定…………………………………..9
6、成型零件的工作尺寸的計(jì)算………………………10
7、模具側(cè)壁厚與底板厚的確定………………………10
8、模架的選擇……………………………………….12
9、注射機(jī)參數(shù)的選擇………………………………..12
10、體會(huì)………………………………………………14
11、參考資料…………………………………………14
12、附圖……………………………………………..14
（一）設(shè)計(jì)指導(dǎo)
1. 課程目的和意義：
《模具設(shè)計(jì)與制造項(xiàng)目》課程是作為《成型技術(shù)與模具》理論課之外的一門(mén)重要補(bǔ)充課程，由于模具結(jié)構(gòu)的多樣性、復(fù)雜性及其巧妙性，走馬觀花式的結(jié)構(gòu)介紹顯然難以達(dá)到對(duì)該門(mén)課程真正的理解和掌握。如結(jié)構(gòu)也許可行，但是否合理；結(jié)構(gòu)雖然巧妙，但能否更佳？結(jié)構(gòu)即使科學(xué)，但是否經(jīng)濟(jì)等等，這些單憑書(shū)本知識(shí)是難以做出直觀判斷的。作為社會(huì)需求量極大的熱門(mén)技術(shù)，必須真正地全面領(lǐng)會(huì)其基本結(jié)構(gòu)原理，并對(duì)各類(lèi)變形、延伸結(jié)構(gòu)的科學(xué)性、合理性融會(huì)貫通，才能真正做到舉一反三，完全掌握，滿足社會(huì)的需要。
正是基于上述目的，開(kāi)設(shè)了《模具設(shè)計(jì)與制造項(xiàng)目》課程，期望學(xué)生們能在創(chuàng)新設(shè)計(jì)中，將書(shū)本內(nèi)容與工程實(shí)踐有機(jī)結(jié)合，鞏固和加深對(duì)理論知識(shí)的理解，并充分發(fā)揮同學(xué)們的想象力、創(chuàng)造力，形成一種科學(xué)的發(fā)散性思維。舉一反三，靈活運(yùn)用所學(xué)知識(shí)，進(jìn)行模具結(jié)構(gòu)設(shè)計(jì)。
2. 實(shí)驗(yàn)的內(nèi)容和方法：
本課程的開(kāi)設(shè)是一種新的嘗試，是適應(yīng)當(dāng)前本科教學(xué)改革而進(jìn)行的一項(xiàng)前沿性探索。課程學(xué)習(xí)過(guò)程中，同學(xué)們可以從網(wǎng)上、期刊上、工廠搜集一些實(shí)際模具的設(shè)計(jì)實(shí)例，對(duì)其結(jié)構(gòu)進(jìn)行分析、研究并吸收消化。完全了解其結(jié)構(gòu)，掌握其工作原理，同時(shí)如有可能的話，給出更佳的替代機(jī)構(gòu)，完成模具設(shè)計(jì)。
課程學(xué)習(xí)中學(xué)生一人一題 。學(xué)生在規(guī)定的學(xué)時(shí)內(nèi)完成對(duì)某一模具機(jī)構(gòu)的分析。首先分析塑料制品結(jié)構(gòu)特點(diǎn)，確定自己的模具方案，如二板?；蛉迥?，強(qiáng)脫或旋脫等等；其次對(duì)照實(shí)物或平面圖，研究他人模具結(jié)構(gòu)特點(diǎn)；最后對(duì)比分析二者差異，從中獲得感性的設(shè)計(jì)知識(shí)。
3. 完成步驟：
1) 搜集模具資料，現(xiàn)場(chǎng)觀看模具實(shí)物、搜集模具設(shè)計(jì)圖紙；
2) 分析塑料制品結(jié)構(gòu)特點(diǎn)，擬定自己的模具方案；
3) 分析研究他人模具設(shè)計(jì)結(jié)構(gòu)，與自己方案對(duì)比，從中細(xì)細(xì)體會(huì)他人模具設(shè)計(jì)的科學(xué)性合理性，或提出自己的不同見(jiàn)解；
4) 進(jìn)行模具設(shè)計(jì)，包括模具三維結(jié)構(gòu)設(shè)計(jì)，演示模具工作過(guò)程；
5) 老師定期為學(xué)生進(jìn)行輔導(dǎo)和答疑工作；
6) 撰寫(xiě)實(shí)驗(yàn)報(bào)告；
7) 打印報(bào)告書(shū)，提交電子文檔。若干個(gè)同學(xué)合一個(gè)光碟，以姓名為文件夾的名稱(chēng)。應(yīng)交材料：
①報(bào)告書(shū)；②塑料產(chǎn)品三維圖電子文檔；③模具三維圖電子文檔；④模具動(dòng)作Flash動(dòng)畫(huà)電子文檔。
8) 進(jìn)行答辯和評(píng)定成績(jī)。
4. 撰寫(xiě)報(bào)告內(nèi)容包括驟：
①塑料制品結(jié)構(gòu)分析；
②模具結(jié)構(gòu)分析、模具各部件功能和用途；
③以圖文形式論述，附塑料制品、模具三維圖和工作原理動(dòng)畫(huà)圖等。
（二）進(jìn)度表
學(xué)年度 專(zhuān)業(yè) 班級(jí)： 學(xué)生人數(shù)：
課程名稱(chēng)：模具設(shè)計(jì)與制造項(xiàng)目 總學(xué)時(shí)：72 共 1 頁(yè) 第 1 頁(yè)
周次
講授主要內(nèi)容
學(xué)時(shí)分配
備注
講課
實(shí)驗(yàn)
上機(jī)
19
布置任務(wù)，提出設(shè)計(jì)要求，明確設(shè)計(jì)任務(wù)
分發(fā)資料，閱參考書(shū)、查資料；
2
2
19
制品工藝分析、模具的方案分析、模具結(jié)構(gòu)分析；
模架選型、成型設(shè)備選定，基本尺寸參數(shù)確定、繪二維草圖。
20
設(shè)計(jì)指導(dǎo)
20
模具的方案確定、模具結(jié)構(gòu)確定；
確定模架及模具結(jié)構(gòu)尺寸和參數(shù)、繪制模具三維圖。
24
設(shè)計(jì)指導(dǎo)
21
模具三維圖繪制。
檢查設(shè)計(jì)質(zhì)量，撰寫(xiě)報(bào)告
16
設(shè)計(jì)指導(dǎo)
21
模具動(dòng)畫(huà)繪制
整理材料。
準(zhǔn)備答辯
8
說(shuō)明：1、本表由主講教師編制，經(jīng)教研室主任審閱，系主任批準(zhǔn)執(zhí)行；
2、本表須在該課程開(kāi)課后第一周內(nèi)送交教務(wù)科一份，本院系(部)一份和發(fā)給學(xué)生班一份。
教學(xué)主管： 教研室主任： 主講教師：
（三）說(shuō)明書(shū)正文
一、 塑料零件工藝的分析
目前,市場(chǎng)上采用薄壁塑料桶進(jìn)行食品包裝十分廣泛,如盛放0.5kg、1kg家庭裝冰淇淋的包裝桶。一般材料為較軟的高壓聚乙烯(LDPE) ,壁厚在0. 6～1 mm 之間,所選用的工藝為注射成型,雖然制品形狀簡(jiǎn)單,但由于側(cè)面積大,壁薄,料軟,塑件和型芯之間易形成真空,脫模較困難,下面以某廠家生產(chǎn)的1 kg 裝冰淇淋包裝桶為例,來(lái)進(jìn)行模具設(shè)計(jì)。其結(jié)構(gòu)如下所示：
（一）、材料的選擇:由于高壓聚乙烯具有如下這些特性所以非常適合用于制造薄壁塑料桶。因?yàn)榫垡蚁┯⑽拿麨镻olythylene或Pdythene,簡(jiǎn)稱(chēng)PE，所以此塑料桶又稱(chēng)為PE桶。
A聚乙烯英文名為Polythylene或Pdythene,簡(jiǎn)稱(chēng)PE.PE為乳白色半透明至不透明的熱塑性樹(shù)脂.
B以密度的大小分為:低密度聚乙烯LDPE,高密度聚乙烯HDPE,線性低密度聚乙烯LLDPE,中密度聚乙烯MDPE,超高分子量聚乙烯HMW-HDPE,甚低密度聚乙烯VLDPE等
LDPE密度為0.910-0.925,因其為高壓法(ICI)聚合所得的聚乙烯,也稱(chēng)為高壓聚乙烯.
LDPE是一種具有蠟感的白色樹(shù)脂,其結(jié)構(gòu)特點(diǎn)是非線型的,分子量一般為100000~500000.因此,與中密度,高密度聚乙烯相比,它具有較低的結(jié)晶度和軟化點(diǎn),有較好的柔軟性,伸長(zhǎng)率,電絕緣性,透明性以及較高的耐沖擊強(qiáng)度.LDPE機(jī)械強(qiáng)度差,耐熱性低,此外一個(gè)明顯的弱點(diǎn)是耐環(huán)境應(yīng)力開(kāi)烈性較差.
低密度聚乙烯可與其它聚合物共混以改進(jìn)性能,通過(guò)共混可以改善性能的聚合物有PC.PA,PP,HDPE和LLDPE.
特性
1.??? 物理、機(jī)械特性:PE拉伸強(qiáng)度隨結(jié)晶地的增大而提高,其值為7-40MPa.伸長(zhǎng)率隨結(jié)晶度的增大而減小,其值為800%-50%.沖擊強(qiáng)度隨結(jié)晶地增加而增大,其值為0.02-1KJ/m.軟而柔韌的PE不易被破壞,沖擊時(shí)呈彎曲狀.PE的硬度隨結(jié)晶度增加而增高,其值為洛氏D41-65.
交聯(lián)PE拉伸強(qiáng)度與拉伸彈性模量均較中密度聚乙烯為大,伸長(zhǎng)率下降.
2.??? 溫度特性、熱性能:PE結(jié)晶度不同,熱變形溫度也有差異.低密度聚乙烯在0.46MPa的負(fù)荷下為40-50℃,中密度與高密度可達(dá)88℃.交聯(lián)聚乙烯耐熱性較未交聯(lián)聚乙烯為好.
PE耐熱性能良好,在-20℃時(shí),其性能仍無(wú)顯著變化.
PE遇火易燃,產(chǎn)生石蠟味并產(chǎn)生低級(jí)碳?xì)浠衔?
3.??? 電氣特性:PE因?yàn)椴缓瑯O性基團(tuán),電氣特性極為良好,具有低介電系數(shù),在較寬的頻率下,介電損耗低,尤其是高頻電氣絕緣性?xún)?yōu)注射成型異.
4.????? 化學(xué)特性:耐藥品性良好,在常溫下幾乎不受有機(jī)藥品的侵蝕
吸水性:吸濕率幾乎等于零,耐水性別極好.濕氣、空氣、碳酸氣幾乎不透過(guò),較能透過(guò)氧氣.
在紫外光、太陽(yáng)光線的影響下,漸漸老化,出現(xiàn)變色與產(chǎn)生裂紋
粘接性與印刷性很差,當(dāng)需要印刷時(shí),需要進(jìn)行表面處理,使印刷油墨對(duì)PE的親和性提高.
應(yīng)用
低密度聚乙烯LDPE,主要的用途是用于薄膜產(chǎn)品.
1.??? 農(nóng)業(yè)用薄膜,地面覆蓋膜,農(nóng)膜,蔬菜大篷膜
2.??? 包裝用膜:如糖果,蔬菜冷凍食品等包裝
3.??? 液體包裝用:如吹塑薄膜,重包裝袋,收縮包裝袋等
4.??? 還可用于注塑制品,擠塑管材,電線電纜,吹塑中空容器.
中密度聚乙烯MDPE,用途不如低密度聚乙烯LDPE和高密度聚乙烯HDPE廣泛,適合擠塑管材,蒸煮袋的內(nèi)襯薄膜和包裝等制品.
成型
PE加熱后,形成粘度適中的熔融體,加工容易,能成型各種尺寸的制品.但超高分子量PE的熔融粘度太高,樹(shù)脂的流動(dòng)性極差,當(dāng)MFR值在0.01以下時(shí),采用注射成型很困難.
PE注射成型的概要如下:
1.選用標(biāo)準(zhǔn)注射成型機(jī)為宜,不需特殊的成型機(jī).
2.收縮率大,在注射方向?yàn)?%-4%,垂直于注射方向?yàn)?.5%-2%,制品易產(chǎn)生形變,特別是薄壁制件.
3.由于吸濕性極小,幾乎不必干燥.當(dāng)表面附著水分時(shí),可進(jìn)行熱風(fēng)干燥.
4.可采用干混著色或擠壓發(fā)法著色.
（二）、塑料桶結(jié)構(gòu)的分析：如下圖所示塑件,桶壁為0.8mm ,材料為低壓聚乙烯,塑件要求圓度好,并且要有一定的剛度,為了桶的穩(wěn)定性,底部中心設(shè)計(jì)成內(nèi)凹。
二、 分型面的選擇
為了減少模具的加工難度很增加模具的精度，避免在桶口產(chǎn)生飛邊和側(cè)向分型抽芯。應(yīng)把分型面設(shè)在桶頂部的桶口面上，且與桶口面平行。
三、 澆注位置的確定
澆口位置選擇的一般原則是：澆口位置應(yīng)盡量選擇在分型面上，以便于模具加工及使用時(shí)澆口的清理；澆口位置距型腔各個(gè)部位的距離應(yīng)盡量一致，并使其流程為最短；澆口的位置應(yīng)保證塑料流入型腔時(shí)，對(duì)著型腔中寬敞、壁厚位置，以便于塑料的流入;避免塑料在流入型腔時(shí)直沖型腔壁,型芯或嵌件,使塑料能盡快的流入到型腔各部位,并避免型芯或嵌件變形;盡量避免使制件產(chǎn)生熔接痕,或使其熔接痕產(chǎn)生在之間不重要的位置;澆口位置及其塑料流入方向,應(yīng)使塑料在流入型腔時(shí),能沿著型腔平行方向均勻的流入,并有利于型腔內(nèi)氣體的排出。
而對(duì)于此注塑模具，由于制品是一個(gè)薄壁深腔的結(jié)構(gòu)，其為繞中心軸線旋轉(zhuǎn)的旋轉(zhuǎn)體，所以要把澆注口設(shè)在桶底的中心位置上。這樣設(shè)置的有點(diǎn)有：1、能使熔料均勻的流向桶的各個(gè)位置，不易產(chǎn)生注塑不完全。2、能沿著型腔平行方向均勻的流入,并有利于型腔內(nèi)氣體的排出。3、使其熔接痕產(chǎn)生在之間不重要的位置即桶底位置，不會(huì)影響精度和美觀。
四、 抽芯機(jī)構(gòu)的確定
由于分型面與桶的脫模方向垂直，所以此模具不用設(shè)置側(cè)向分型抽型機(jī)構(gòu)。
五、 脫模機(jī)構(gòu)的確定
由于桶口的壁較薄,而且也不希望產(chǎn)品在桶口有飛邊,因此不適宜采用推件板脫模,本設(shè)計(jì)采用氣動(dòng)脫模推出塑件,模具簡(jiǎn)單,脫模力大,塑件受力平穩(wěn),變形小,氣動(dòng)脫模機(jī)構(gòu)非常適用于深腔、薄壁、軟材塑件的脫模。
脫模力的計(jì)算
將制品從包緊的型芯上脫出時(shí)所需克服的阻力稱(chēng)為脫模力。如果塑件為不帶通孔的殼體,脫模力主要是由塑料成型收縮而產(chǎn)生的對(duì)型芯包緊力和克服大氣壓力兩部分組成。塑件脫模時(shí),由塑料成型收縮而產(chǎn)生的對(duì)型芯包緊力,型芯的受力分析如圖3 所示。
圖3 型芯受力分析
根據(jù)平衡原理,可列出平衡方程為:
ΣFx = 0
F′t + Fbsinα= Fcosα
式中:F′t —塑件由成型收縮對(duì)型芯的包緊力;
F —脫模時(shí)型芯由于成型收縮所受的摩擦阻力;
Fb —脫模力;
α—型芯的脫模斜度。
又F = Fbμ
所以F′t = Fb (μcosα- sinα)= Ap (μcosα- sinα)
式中:μ—塑料對(duì)鋼的摩擦系數(shù),LDPE 為0. 23 ;
A —塑件包容型芯的面積,A =πd ;
p —塑件對(duì)型芯的單位面積上的包緊力,一般模內(nèi)冷卻的塑件p 約取0. 8～1. 2 Mpa 。
總的脫模力應(yīng)為:Ft = F′t + Fk
式中:Ft —塑件對(duì)型芯的包緊力;
Fk —脫模時(shí)型芯由于大氣壓所受的摩擦阻力,據(jù)經(jīng)驗(yàn),一般取0. 1A1 (A1為塑件的底面積) 。
將塑件尺寸代入后,得:Ft = 3305Mpa
閥桿的直徑
閥桿的直徑可按下式計(jì)算:
d′=4Ftπp′
(由 Ft = p′(л/ 4) d′2得出
式中:p′—壓縮空氣的氣壓;d′—閥桿頭部的直徑。)
按壓縮空氣的氣壓為0. 6 MPa ,并將塑件尺寸代入后,得:d′= 83 mm。
六、 成型零件的工作尺寸的計(jì)算
七、 模具側(cè)壁厚與底板厚的確定（強(qiáng)度和剛度的校核）
（1）、側(cè)壁厚度的計(jì)算 當(dāng)型腔側(cè)壁受高壓塑料熔體作用時(shí)，其內(nèi)徑增長(zhǎng)量為δ，因此在側(cè)壁和底之間產(chǎn)生一縱向間隙，間隙過(guò)大將輝發(fā)生溢料，其最大值為：
式中 P—型腔內(nèi)壓力，MPa
E—彈性模量，炭鋼為2.1*10^5MPa
r—內(nèi)半徑，mm
R—外半徑，mm
μ—泊松比，碳鋼取0.25
所以
或壁厚：
（1）
作強(qiáng)度計(jì)算時(shí)，按第三強(qiáng)度理論計(jì)算，其計(jì)算公式為：
(2)
查得：高壓聚乙烯得注射壓力為600～1500bar。取900bar，即90MPa。所以其塑料壓力p=90MPa/3=30MPa.取允許變形量為δ＝0.005mm.
所以，作剛度計(jì)算時(shí)，將上述數(shù)據(jù)代入（1）式得側(cè)壁厚S=15.15mm.
作強(qiáng)度計(jì)算時(shí)，將上述數(shù)據(jù)代入（2）式得側(cè)壁厚S=17.75mm.
取其中大者S=17.75mm.
（2）、底板厚的計(jì)算
底板固定在中空的園環(huán)形支座上，設(shè)計(jì)時(shí)取支座上的內(nèi)圓直徑近似等于型腔內(nèi)徑。這時(shí)該底板可視為周邊簡(jiǎn)支的圓板最大撓度發(fā)生在圓板的中心，其值為：
式中 S-----底板厚度，mm
R―――圓環(huán)形支座內(nèi)半徑，mm
設(shè)允許變形為，可得
（3）
按最大應(yīng)力作強(qiáng)度計(jì)算，最大應(yīng)力也發(fā)生在圓板中心，其值為：
故：
（4）
所以，作剛度計(jì)算時(shí)，將數(shù)據(jù)代入（3）式得底板厚S=29.93mm.
作強(qiáng)度計(jì)算時(shí)，將數(shù)據(jù)代入（4）式得底板厚S=27.44mm.
取其中大者S=29.93mm.
八、 模架的選擇
如下圖所示：選用單腔模具，定模由兩塊模板組成，其中無(wú)可移動(dòng)模板，動(dòng)模也可由兩塊模板組成。
由制品的投影面積S=(134/2)^2*3.14=14095mmXmm
得：動(dòng)定模座尺寸B1XL=250mmX200mm
動(dòng)定模板尺寸BXL=200mmX200mm
九、 注射機(jī)參數(shù)的選擇
1．塑件的體積計(jì)算
在solidworks軟件中繪制零件三維圖，在菜單欄點(diǎn)擊：工具――質(zhì)量特性。跳出的對(duì)話框中顯示零件的體積=44021.94立方 毫米
2．計(jì)算塑件的質(zhì)量
根據(jù)“塑料模具設(shè)計(jì)手冊(cè)”查得LDPE的密度為：ρ=0.92g/cm3，根據(jù)塑件形狀及尺寸，采用一模一腔的模具結(jié)構(gòu),
塑件和澆注系統(tǒng)的質(zhì)量:W總=ρ（Vz件+Vj）
=0.92×(4.4022+1)
=5.062g
g
3.注塑機(jī)的選擇
查手冊(cè),由塑料特性以及零件要求,取注塑壓力P=90MPa,
（1） 塑件投影面積計(jì)算A’=π×6.72=140.95cm2
（2） 澆注系統(tǒng)投影面積計(jì)算A’’=8.5 cm2
(3) 型腔壓力計(jì)算p腔=30Mpa
（4）鎖模力計(jì)算F=0.1p腔×A=0.1×30×（140.95＋8.5）=448.35KN
查手冊(cè),選擇SYS-30（立式）注塑機(jī)
SYS-30（立式）型注射機(jī)的主要參數(shù)
注射容量
30g
定位孔直徑
Φ55mm
最大開(kāi)模行程S′
80mm
噴嘴球頭直徑
Φ12mm
最大裝模高度Hmax
200mm
噴嘴孔直徑
Φ3mm
最小裝模高度Hmin
70mm
頂出中心孔徑
Φ50
注射壓力
150 Mpa
鎖模力
500KN
十、 體會(huì)
模具課程設(shè)計(jì)是塑料成型模具課程以后第一次對(duì)模具知識(shí)的綜合運(yùn)用，在設(shè)計(jì)的過(guò)程中涉及多方面的知識(shí)，是對(duì)以往學(xué)習(xí)成果的綜合檢驗(yàn)，也是對(duì)知識(shí)的深化，使我對(duì)模具方面的知識(shí)有了進(jìn)一步的體會(huì)和掌握。
本次設(shè)計(jì)因?yàn)槌醮卧O(shè)計(jì)較復(fù)雜的模具，在設(shè)計(jì)中有不少錯(cuò)誤，但是我覺(jué)得更多的是收獲，聯(lián)系了計(jì)算機(jī)輔助繪圖，扎實(shí)了基本功.也練習(xí)了資料、圖冊(cè)等的查閱. 通過(guò)本次設(shè)計(jì)我覺(jué)得我們的設(shè)計(jì)功底有了更進(jìn)一步的提高，為即將進(jìn)入工作崗位的我們打下了堅(jiān)實(shí)的基礎(chǔ)。
十一、參考資料：
1、塑料成型模具 . 申開(kāi)智主編 .第二版 . 北京：中國(guó)輕工業(yè)出版社 . 2006
2、SolidWorks2005 .胡仁喜編著 .北京：機(jī)械工業(yè)出版社 . 2003
3、塑料模具設(shè)計(jì)手冊(cè) .《塑料模具設(shè)計(jì)手冊(cè)》編寫(xiě)組編著.機(jī)械工業(yè)出版社 。1982
4、模具設(shè)計(jì)與制造簡(jiǎn)明手冊(cè)（第二版） （電子版）
5、模具標(biāo)準(zhǔn)（電子版）
十二、附圖：
模具圖（1）
模具圖（2）
模具爆炸圖
16
Microsystem Technologies 10 (2004) 531–535 _ Springer-Verlag 2004
DOI 10.1007/s00542-004-0387-2
Replication of microlens arrays by injection molding
B.-K. Lee, D. S. Kim, T. H. Kwon
B.-K. Lee, D. S. Kim, T. H. Kwon (&)
Department of Mechanical Engineering,
Pohang University of Science and Technology (POSTECH),
San 31, Hyoja-Dong, Nam-Gu, Pohang, 790-784, Korea
e-mail: thkwon@postech.ac.kr
Abstract Injection molding could be used as a mass production technology for microlens arrays. It is of importance, and thus of our concern in the present study, to understand the injection molding processing condition effects on the replicability of microlens array profile. Extensive experiments were performed by varyingprocessing conditions such as flow rate, packing pressure and packing time for three different polymeric materials (PS, PMMA and PC). The nickel mold insert of microlens arrays was made by electroplating a microstructure master fabricated by a modified LIGA process. Effects of processing conditions on the replicability were investigated with the help of the surface profile measurements. Experimental results showed that a packing pressure and a flow rate significantly affects a final surface profile of the injection molded product. Atomic force microscope measurement indicated that the averaged surface roughness value of injection molded microlens arrays is smaller than that of mold insert and is comparable with that of fine optical components in practical use.
1
Introduction
Microoptical products such as microlenses or microlens arrays have been used widely in various fields of microoptics, optical data storages, bio-medical applications, display devices and so on. Microlenses and microlens arrays are essential elements not only for the practical applications but also for the fundamental studies in the microoptics. There have been several fabrication methods for microlenses or microlens arryas such as a modified LIGA process [1], photoresist reflow process [2], UV laser illumination [3], etc. And the replication techniques, such as injection molding, compression molding [4] and hot embossing [5], are getting more important for a mass production of microoptical products due to the cost-effectiveness. As long as the injection molding can replicate subtle microstructures well, it is surely the most cost-effective method in the mass production stage due to its excellent reproducibility and productivity.
In this regard, it is of utmost importance to check the injection moldability and to determine the molding processing condition window for proper injection molding of microstructures. In this study, we investigated the effects of processing conditions on the replication of microlens arrays by the injection molding. The microlens arrays were fabricated by a modified LIGA process, which was previously reported in [6, 7]. Injection molding experiments were performed with an electroplated nickel mold insert so as to investigate the effects of some processing conditions. The surface profiles of molded microlens arrays were measured, and were used to analyze effects of processing conditions. Finally, a surface roughness of microlens arrays was measured by an atomic force microscope (AFM).
2
Mold insert fabrication
Microlens arrays having several different diameters were fabricated on a PMMA sheet by a modified LIGA process [6]. This modified LIGA process is composed of an X-ray irradiation on the PMMA sheet and a subsequent thermal treatment. The X-ray irradiation causes the decrease of molecular weight of PMMA, which in turn decreases the glass transition temperature and consequently causes a net volume increase during the thermal cycle resulting in a swollen microlens [7]. The shapes of microlenses fabricated by the modified LIGA process can be predicted by a method suggested in [7].
The microlens arrays used in the experiments were composed of 500μm -(a 2 × 2 array), 300μm -(2 × 2) and 200μm (5 × 5) diameter arrays, and their heights were 20.81, 17.21 and 8.06 μm, respectively. Using the microlens arrays fabricated by the modified LIGA process as a master, a metallic mold insert was fabricated by a nickel electroplating for the injection molding. Typical materials used in a microfabrication process, such as silicon, photoresists or polymeric materials, cannot be directly used as the mold or the mold insert due to their weak strength or thermal properties. It is desirable to use metallic materials which have appropriate mechanical and thermal properties to endure both a high pressure and a large temperature variation during the replication process. Therefore, a metallic mold insert is being used rather than the PMMA master on silicon wafer for mass production with such replication techniques. Otherwise special techniques should be adopted as a replication method, e.g. a low pressure injection molding [8].
The size of final electroplated mold insert was 30 × 30 × 3 mm. The electroplated nickel mold insert having microlens
arrays is shown in Fig. 1.
Fig.1.Moldinsert fabricated by a nickel electroplating (a) Real view of the mold insert (b) SEM image of 200 μm diameter microlens array (c) SEM image of 300 μmdiameter microlens array
3
Injection molding experiments
A conventional injection molding machine (Allrounders 220 M, Arburg) was used in the experiments. A mold base for the injection molding was designed to fix the electroplated nickel mold insert firmly with the help of a frametype bolster plate (Fig. 2). Shape of aperture of the bolster plate (in this study, a rectangular one) defines the outer geometry of the molded part on which the profiles of microlens arrays are to be transcribed. The mold base itself has delivery systems such as sprue, runner and gate which lead the molten polymer to the cavity formed by the bolster plate, the mold insert and amoving mold surface. The mold base was designed such that mold insert replacement is simple and easy. Of course, one may introduce an appropriate bolster plate with a specific aperture shape.
Fig. 2. Mold base and mold insert used in the injection molding experiment
The injection molding experiments were carried out with three general polymeric materials – PS (615APR, Dow Chemical), PMMA (IF870, LG MMA) and PC (Lexan 141R, GE Plastics). These materials are quite commonly used for optical applications. They have different refractive indices (1.600, 1.490 and 1.586 for PS, PMMA and PC, respectively), giving rise to different optical properties in final products, e.g. different foci with the same geometry.
The injectionmolding experiments were performed for seven processing conditions by changing flow rate, packing pressure and packing time for each polymeric material. Furthermore, same experiments were repeated three times for checking the reproducibility. It may be mentioned that the mold temperature effect was not considered in this study since the temperature effect is relatively less important for these microlens arrays due to their large radius of curvature than other microstructures of high aspect ratio. For high aspect ratio microstructures, we are currently investigating the temperature effect more closely and plan to report separately in the future. Therefore, flow rate, packing pressure and packing time were varied to investigate their effects more thoroughly with the mold temperature unchanged in this study. Table 1 shows the detailed processing conditions for three polymeric materials. Other processing conditions were kept unchanged during the experiment. The mold temperatures were set to 80, 70 and 60 _C for PC, PMMA and PS, respectively.
It might be mentioned that we carried out the experiments without a vacuum condition in the mold cavity considering that the large radius of curvature of the microlens arrays in the present study will not entrap air in the microlens cavity during the filling stage.
Table 1. Detailed processing conditions used in the injection molding experiments
Case
Flow rate (cc/sec)
Packing time (sec)
Packing pressure(MPa)
1
12.0
5.0
10.0
2
12.0
5.0
15.0
3
12.0
5.0
20.0
PS
4
12.0
2.0
10.0
5
12.0
10.0
10.0
6
18.0
5.0
10.0
7
24.0
5.0
10.0
PMMA
1
6.0
10.0
10.0
2
6.0
10.0
15.0
3
6.0
10.0
20.0
4
6.0
5.0
10.0
5
6
7
6.0
9.0
12.0
15.0
10.0
10.0
10.0
10.0
10.0
PC
1
6.0
5.0
5.0
2
6.0
5.0
10.0
3
5
6.0
6.0
9.0
5.0
10.0
15.0
5.0
6
5.0
5.0
7
12.0
5.0
5.0
4
Results and discussion
Before detailed discussion of the experimental results, it might be helpful to summarize why flow rate, packing
pressure and packing time (which were chosen as processing conditions to be varied in this study) affect thereplication quality. As far as the flow rate is concerned, there may exist an optimal flow rate in the sense that too small flow rate makes too much cooling before a complete filling and thus possibly results in so-called short shot phenomena whereas too high flow rate increases pressure fields which is undesirable.
The packing stage is generally required to compensate for the volume shrinkage of hot molten polymer when
cooled down, so that enough material should flow into a mold cavity during this stage to control the dimensional
accuracy. The higher the packing pressure, the longer the packing time, more material tends to flow in. However, too much packing pressure sometimes may cause uneven distribution of density, thereby resulting in poor optical
quality. And too long packing time does not help at all since gate will be frozen and prevent material from flowing into the cavity. In this regard, one needs to investigate the effects of packing pressure and packing time.
4.1
Surface profiles
Figure 3 shows typical scanning electron microscope (SEM) images of the injection molded microlens arrays for different diameters for PMMA (a) and different materials (b). Cross-sectional surface profiles of the mold insert and all the injection molded microlens arrays were measured by a 3D profile measuring system (NH-3N, Mitaka).
Fig. 3. SEM images of the
injection molded microlens
arrays and microlenses (a)
Injection molded microlens
arrays (PMMA) (b) Injection
molded microlenses of 300 μmdiameter for different materials
As a measure of replicability, we have defined a relative deviation of profile as the height difference between the molded one and the corresponding mold insert for each microlens divided by the mold insert one. The computed relative deviations for all the microlenses are listed in Table 2.
Diameter ( μm)
Relative deviation (%)
1
2
3
4
5
6
7
PS
200
300
500
-7.62
5.86
2.38
-7.59
2.03
-0.38
2.08
2.86
0.51
-
5.61
1.47
-8.66
6016
1.47
-11.44
4.29
1.47
-
5.73
1.95
PMMA
200
300
500
7.20
5.77
-0.66
1.31
5.60
-1.62
-3.88
6.45
3.98
-5.80
5.95
2.80
-0.97
5.95
-0.72
-8.53
6.68
-0.90
4.86
-2.62
-0.72
PC
200
300
500
23.02
6.20
-0.93
16.05
4.96
5.09
16.87
2.66
-1.86
19.66
4.53
1.88
33.97
4.78
6.96
18.67
1.79
2.43
-2.94
4.15
-1.55
It may be mentioned that the moldability of polymeric materials affects the replicability. Therefore, the overall relative deviation differs for three polymeric materials used in this study. It may be noted that PC is the most difficult material for injection molding amongst the three polymers. The largest relative deviation can be found in PC for the smallest diameter case, as expected. In that specific case, the largest value is corresponding to the low flow rate and low packing pressure. Packing time in this case does not significantly affect the deviation. The relative deviation for PS and PMMA with the smallest diameter is far better than PC case.
Table 2 indicates that the larger the diameter, the smaller the relative deviation. The larger diameter microlens is, of course, easier to be filled than smaller diameter during the filling stage and packing stage. Microlenses of larger diameters were generally replicated well regardless of processing conditions and regardless of materials. The best replicability is found for the case of PS with 500 μm diameter. Generally, PS has a good moldability in comparison with PMMA and PC.
It may be mentioned that some negative values of relative deviation were observed mostly in the smallest diameter case for PS and PMMA according to Table 2. In these cases, however, the absolute deviation is an order of 0.1 μm in height, which is within the measurement error of the system. Therefore, the negative values could be ignored in interpreting the experimental data of replicability.
Surface profiles of microlens of 300 μm diameter are shown in Figs. 4 and 5 for PC and PMMA, respectively. As shown in Fig. 4, the higher packing pressure or the higher flow rate results in the better replication of microlens for the case of PC, as mentioned above. Packing time has little effect on the replication for these cases. For the case of PMMA, the packing pressure and packing time have insignificant effect as shown in Fig. 5; however, flow rate has the similar effect to PC. It might be reminded that packing time does not affect the replicability if a gate is frozen since frozen gate prevents material from flowing
into the cavity. Therefore, the effect of packing time disappears after a certain time depending on the processing conditions.
Fig.4a–c(leftside).Surface profiles of microlens (PC with diameter (/) of 300 μm). a effect of packing pressure, b effect of flow rate, c effectof packing time
Fig.5a–c.(rightside)Surface profiles of microlens (PMMA with diameter(/) of 300 μm). a effect of packing pressure, b effect of flow rate,c effect of packing time
4.2
Surface roughness
Averaged surface roughness, Ra, values of 300 μm diameter microlenses and the mold insert were measured by an atomic force microscope (Bioscope AFM, Digital Instruments). The measurements were performed around the top of each microlens and the measuring area was 5 μm · 5 μm. Figure 6 shows AFM images and measured Ra values of microlenses. PMMA replicas of microlens have the lowest Ra value, 1.606 nm. It may be noted that AFM measurement indicated that Ra value of injection molded microlens arrays is smaller than the corresponding one of the mold insert. The reason for the improved surface roughness in the replicated microlens arrays is not clear at this moment, but might be attributed to the reflow caused by surface tension during a cooling process. It may be further noted that the Ra value of injection molded microlens arrays is comparable with that of fine optical components in practical use.
Fig. 6. AFM images and averaged surface roughness, Ra, values of the mold insert and injection molded 300 μm diameter microlenses. a Nickel mold insert, b PS, c PMMA, d PC
4.3
Focal length
The focal length of lenses can be calculated by a wellknown equation as follows:
where f, nl, R1 and R2 are focal length, refractive index of lens material, two principal radii of curvature, respectively.For instance, focal lengths of the molded microlenses were approximately calculated as 1.065 mm (with R1 0.624 mm and R2 11 ￥) for 200 μm diameter microlens, 1.130 mm (with R1= 0.662 mm and R2=∞) for 300 μm microlens and 2.580 mm (with R1=1.512 mm and R2=∞) for 500 μm microlens according to Eq. (1). These calculations were based on an assumption that microlenses are replicated with PC (nl= 1.586) and have the identical shape of the mold insert. It might be mentioned that the geometry of the molded microlens might be inversely deduced from an experimental measurement of the focal length.
5
Conclusion
The replication of microlens arrays was carried out by the injection molding process with the nickel mold insert which was electroplated from the microlens arrays master fabricated via a modified LIGA process.
The effects of processing conditions were investigated through extensive experiments conducted with various processing conditions. The results showed that the higher packing pressure or the higher flow rate is, the better replicability is achieved. In comparison, the packing time was found to have little effect on the replication of microlens arrays.
The injection molded microlens arrays had a smaller averaged surface roughness values than the mold insert, which might be attributed to the reflow induced by surface tension during the cooling stage. And PMMA replicas of microlens arrays had the best surface quality (i.e. the lowest roughness value of Ra =1.606 nm). The surface roughness of injection molded microlens arrays is comparable with that of fine optical components in practical use. In this regard, injection molding might be a useful manufacturing tool for mass production of microlensarrays.
References
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微透鏡陣列注塑成型的復(fù)制
B.-K. Lee, D. S. Kim, T. H. Kwon
樸航科技大學(xué)(POSTECH) 機(jī)械工程學(xué)院
San 31, Hyoja-Dong, Nam-Gu, Pohang, 790-784, Korea
電子郵箱l: thkwon@postech.ac.kr
摘要 微透鏡陣列注塑成型，可作為一種非常重要的大量生產(chǎn)技術(shù)。因此我們?cè)诮鼇?lái)的研究中非常關(guān)注， 為了進(jìn)一步了解注塑成型在不同的加工條件下對(duì)可復(fù)制的微透鏡陣列剖面的影響，如流量、填料壓力和填料時(shí)間，對(duì)3種不同的高分子材料(PS，PMMA和PC)進(jìn)行了大量的試驗(yàn)。 鎳金屬模具嵌件微陣列就是利用改良的LIGA技術(shù)電鍍主裝配的顯微結(jié)構(gòu)制造的。在表面輪廓得到測(cè)量的前提下，研究工藝條件對(duì)可復(fù)制的微透鏡陣列的影響。實(shí)驗(yàn)結(jié)果表明， 填料壓力和流速對(duì)注射模塑的終產(chǎn)品的表面輪廓有重要的影響。 原子力顯微鏡測(cè)量表明， 微透鏡陣列注塑成型的平均表面粗糙度值小于模具嵌件成型， 并在實(shí)際運(yùn)用中，能與精細(xì)的光學(xué)元件相媲美。
1 說(shuō)明
微型光學(xué)產(chǎn)品，如微透鏡或微透鏡陣列已廣泛應(yīng)用于光學(xué)數(shù)據(jù)存儲(chǔ)、生物醫(yī)學(xué)、顯示裝置等各個(gè)光學(xué)領(lǐng)域。微透鏡和微透鏡陣列不僅在實(shí)踐應(yīng)用上，而且在微型光學(xué)的基礎(chǔ)研究上都是非常重要的。有幾種微透鏡或微透鏡陣列的制作方法，如改良的LIGA技術(shù)[1] ，光阻回流進(jìn)程[2]，紫外激光照射[3]等。還有復(fù)制技術(shù)，如注塑模壓成型[4]和熱壓[5]技術(shù) ，這種方法對(duì)于減少大規(guī)模生產(chǎn)的微型光學(xué)產(chǎn)品的成本尤為重要。由于其優(yōu)越的生產(chǎn)和再生產(chǎn)能力，只要注塑成型過(guò)程中能很好的復(fù)制微觀結(jié)構(gòu)，那么肯定是最適合于降低大量生產(chǎn)成本的方法。
基于這點(diǎn)，檢查注塑成型能力并確定成型加工條件是注塑成型微觀結(jié)構(gòu)過(guò)程中最重要的步驟。在本次研究中，我們考察了工藝條件對(duì)可復(fù)制的微透鏡陣列的注射成型的影響。微透鏡陣列是用之前介紹過(guò)[6，7]的改良的LIGA技術(shù)來(lái)編制的。注塑成型實(shí)驗(yàn)采用的是一種鍍鎳金屬模具，來(lái)探討了幾種不同工藝條件對(duì)成型的影響。通過(guò)對(duì)微透鏡陣列的表面輪廓測(cè)量，用來(lái)分析工藝條件產(chǎn)生的影響。最后，利用原子力顯微鏡(AFM)測(cè)量微透鏡的表面粗糙度值的大小。
2 模具嵌件的制造
利用改良的LIGA技術(shù)[6]，在一個(gè)有機(jī)玻璃板上制造出具有幾種不同直徑微透鏡陣列。此種技術(shù)是先用X光照射有機(jī)玻璃板，然后再進(jìn)行熱處理兩部分構(gòu)成的。X-射線照射引起有機(jī)玻璃分子質(zhì)量的減少，同時(shí)降低了玻璃化轉(zhuǎn)變溫度，并因此導(dǎo)致凈含量的增加，在熱循環(huán)的作用下，微透鏡發(fā)生微膨脹[7]。利用[7]中提出的方法，結(jié)合改良的LIGA技術(shù)可以預(yù)測(cè)微透鏡形狀的變化過(guò)程。
在試驗(yàn)中使用的微透鏡陣列，有500μm (2×2陣列)，300μm (2×2)和200μm (5×5)的直徑陣列，高分別是20.81μm，17.21μm和8.06μm。采用改良的LIGA技術(shù)制造微透鏡陣列作為一個(gè)主要的技術(shù)，用來(lái)制作鍍鎳的金屬模具的注塑成型。另一些特殊材料，因?yàn)樗鼈兊膹?qiáng)度不夠或熱性能差而不能直接進(jìn)行微細(xì)加工，當(dāng)作模具或金屬模具使用，如硅、光阻劑或高分子材料。盡量使用具有良好機(jī)械性能和熱性能的金屬材料，因?yàn)樗鼈兡茉诳蓮?fù)型加工過(guò)程中經(jīng)受高壓力和不斷變化的溫度。因此，為了利用這種復(fù)制技術(shù)進(jìn)行大批量生產(chǎn)，我們選擇使用金屬模具材料而不是有機(jī)玻璃硅晶體。一些特殊技術(shù)，如低壓注塑成型[8]技術(shù)，應(yīng)該作為良好的復(fù)制加工方法被采納。
電鍍模具的最終大小為30 mm×30 mm×3mm。鍍鎳金屬模具所具有的微透鏡陣列如圖1所示。
圖1 鍍鎳模具嵌件的制造 （a）直接觀察；（b）直徑為200μm
的微透鏡陣列電子顯微鏡圖像；（c）直徑為300μm的微透鏡陣列電子顯微鏡圖像
3 注塑成型實(shí)驗(yàn)
傳統(tǒng)注塑機(jī)(Allrounders 220 M，Arburg)多用做實(shí)驗(yàn)機(jī)。注塑模具設(shè)計(jì)的模架就是利用一塊框形支撐板固定鍍鎳模具(如圖2所示)。
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