模具畢業(yè)論文剃須刀蓋塑料模具的設(shè)計(jì)

1、 摘 要時(shí)代的變化，社會(huì)的進(jìn)步，人們對物質(zhì)的需求越來越高，模具的地位在當(dāng)今社會(huì)越來越重要。所以我這次的畢業(yè)設(shè)計(jì)就選擇了設(shè)計(jì)一副模具，希望通過這次的設(shè)計(jì)能夠使我的理論知識得到檢驗(yàn)和實(shí)踐。本論文是剃須刀蓋塑料模具的設(shè)計(jì)，采用abs材料進(jìn)行對模具的零件結(jié)構(gòu)工藝分析的過程。在選擇注塑機(jī)的時(shí)候要考慮模具的型腔數(shù)量和最大注射量以及注射壓力等。利用ug、autocad繪圖軟件繪制出模具的裝配圖和零件圖。并利用ug對模具的仿真加工，制定相應(yīng)加工工藝的過程。關(guān)鍵詞：剃須刀后蓋； ug；點(diǎn)澆口； abs；注塑模具；目 錄 引言1一、塑件成型工藝性分析2（一）塑件（剃須刀后蓋）分析21.塑件結(jié)構(gòu)分析22.成型工藝分

2、析如下2（二）abs 的成型過程、工藝的參數(shù)31.注射成型過程32.abs 的注射工藝參數(shù)33.abs 化學(xué)和物理特性3（三）注塑模工藝條件3二、擬定模具結(jié)構(gòu)形式4（一）分型面的選擇41.分型面的選擇原則42.分型面的確定4（二） 型腔數(shù)目的確定5三、注塑機(jī)型號的確定5（一）所需注射量的計(jì)算5（二）選擇注射機(jī)5四、澆注系統(tǒng)設(shè)計(jì)6（一）主流道的設(shè)計(jì)61.主流道設(shè)計(jì)要點(diǎn)62.主流道澆口套的形式6（二） 分流道的布置形式61.分流道的長度62.分流道的形狀、尺寸63.分流道的表面粗糙度6（三）澆口的設(shè)計(jì)71.澆口類型及位置的確定72.澆口結(jié)構(gòu)尺寸的經(jīng)驗(yàn)計(jì)算7五、成型零件的結(jié)構(gòu)設(shè)計(jì)、計(jì)算7（一）成型零

3、件的結(jié)構(gòu)設(shè)計(jì)7（二）工作尺寸的校核81.型腔尺寸8型腔徑向尺寸8型腔深度尺寸82.型芯尺寸8六、模架確定、標(biāo)準(zhǔn)件選用9七、脫模推出機(jī)構(gòu)的設(shè)計(jì)10(一) 推出機(jī)構(gòu)的設(shè)計(jì)原則：10（二）脫模機(jī)構(gòu)的結(jié)構(gòu)設(shè)計(jì)10八、設(shè)計(jì)側(cè)向的抽芯機(jī)構(gòu)10（一）斜頂?shù)脑O(shè)計(jì)10（二）抽芯距的確定10九、排氣系統(tǒng)的設(shè)定11十、冷卻系統(tǒng)設(shè)計(jì)12 總 結(jié)13 參考文獻(xiàn)14 致 謝15 引 言目前，我國的經(jīng)濟(jì)在經(jīng)濟(jì)全球化下得到了高速發(fā)展。這樣一來為中國的模具產(chǎn)業(yè)提供了具有良好的條件和機(jī)遇。不但國內(nèi)的模具市場在市場經(jīng)濟(jì)中所占的份額越來越多，而且有許多的國外公司向國內(nèi)的模具制造企業(yè)采購。因此，展望未來，在良好的市場環(huán)境下我國的模具產(chǎn)

4、業(yè)會(huì)逐步邁進(jìn)模具制造強(qiáng)國的行列。然而在國民經(jīng)濟(jì)的快速發(fā)展下，國內(nèi)的模具產(chǎn)量達(dá)到了一定的規(guī)模，但發(fā)展重點(diǎn)沒有放在模具產(chǎn)品水平上。致使我國的模具在模具的精度要求和結(jié)構(gòu)以及壽命上遠(yuǎn)遠(yuǎn)地低于國際水平。不但如此模具標(biāo)準(zhǔn)件的種類以及水平對整個(gè)模具行業(yè)的發(fā)展有重大影響。所以要不斷地提高標(biāo)準(zhǔn)件水平，才能不斷地提高我國模具的總體水平。綜合看來提高模具工業(yè)水平是在國民經(jīng)濟(jì)發(fā)展中占有至關(guān)重要的地位。 一、塑件成型工藝性分析 （一）塑件（剃須刀后蓋）成型分析塑件的視圖如圖所示:圖1-1 xxxxx1 塑件結(jié)構(gòu)分析該塑件結(jié)構(gòu)較簡單，復(fù)雜程度不高。保證塑件的壁厚盡可能均勻，以此減少氣泡、縮孔等不良現(xiàn)象。又因?yàn)樯a(chǎn)批量不是

5、很多，還要保證生產(chǎn)成本低，所以考慮材料為abs。塑件的表面不允許有明顯的熔接痕、飛邊等工藝痕跡，要求表面光滑，對模具表面進(jìn)行拋光處理。2成型工藝分析如下（1）精度等級有許多影響塑件精度因素，塑料的收縮率、注塑條件、模具結(jié)構(gòu)、斜度、模具的磨損等都直接影響精度。根據(jù)sj13721978標(biāo)準(zhǔn)，abs塑料零件的精度分八個(gè)等級。查詢可知，abs塑料零件盡可能選用一般精度m5級。（2）脫模斜度為了避免在塑件冷卻收縮的時(shí)候緊緊卡在型腔部分，強(qiáng)行取出損壞塑件的表面質(zhì)量。設(shè)計(jì)塑料零件時(shí)須考慮脫模方向于內(nèi)外表面，使之平行，并盡量加大脫模斜度，為了容易脫模。 （二）abs 的成型過程、工藝的參數(shù)1注射成型過程（1）

6、成型前的準(zhǔn)備 對abs 的色澤、細(xì)度和均勻度等進(jìn)行檢驗(yàn)。（2）塑料顆粒在注射機(jī)料筒內(nèi)先進(jìn)行加熱，達(dá)到熔融狀態(tài)后，填充模具再經(jīng)過壓實(shí)和保持壓力不變以及回流和冷卻這五個(gè)階段完成成型過程。2. abs 的注射工藝參數(shù)（1）注射機(jī)： 螺桿式（2）螺桿轉(zhuǎn)速(r/min)： 30（3）料筒溫度() ： 150170(后段)、165180(中段)、180200(前段)（4）噴嘴溫度()： 170180（5）模具溫度()： 4060（6）注射壓力(mpa)： 100130（7）成型時(shí)間(s)：2s注射 ； 25s保壓 ； 20s冷卻 ；成型總周期 473. abs 化學(xué)和物理特性 abs為黃色無毒無味的不透明

7、狀的可塑性樹脂。abs 特性很大程度上取決于三種單體和兩相分子結(jié)構(gòu)的比例，所以abs 材料具有良好的光澤度、流動(dòng)性、耐化學(xué)藥品性和電絕緣性。（三）注塑模工藝條件abs 容易吸水，建議加工前在80的條件下進(jìn)行兩個(gè)小時(shí)的干燥。熔化溫度：210280；建議溫度：245。注射速度：中高速度。abs 塑料的主要技術(shù)指標(biāo):密度（kg/dm3） 1.021.16 抗拉屈服強(qiáng)度(mpa) 50,比體積（dm3/ kg） 0.860.96 拉伸彈性模量(mpa) 1.8103,吸水率（pc100） 0.20.4 抗彎強(qiáng)度(mpa) 80收縮率(%) 0.40.8 沖擊韌度( kj/m2) 261(無缺口)/11

8、(缺口)熔點(diǎn)() 130160 硬度(hb) 9.7熱變形溫度() 90108(0.46 mpa) 83103(0.185mpa)體積電阻系數(shù)(cm) 6.910167 二、擬定模具結(jié)構(gòu)形式 （一）分型面的選擇在模具設(shè)計(jì)階段，首先要確定模具分離的位置，然后才選擇模具結(jié)構(gòu)。分型面的合理設(shè)計(jì)，影響著塑件質(zhì)量和工藝操作的難易程度。1分型面的選擇原則：（1）要便于塑件脫模；（2）要保證塑件的質(zhì)量；（3）要防止熔料從分型面處滲出；（4）要便于氣體的排出；（5）要盡量便于加工成型零件；2分型面的確定在進(jìn)行該塑件模具設(shè)計(jì)時(shí)，對上述原則已經(jīng)充分的考慮，同時(shí)從塑件樣圖可看出該塑件具有明顯的一個(gè)平面，再結(jié)合塑件形

9、狀，考慮其具有抽芯機(jī)構(gòu)，所以選擇采用該平面作為分型面，如圖21所示：21 分型面示意圖 （二）型腔數(shù)目的確定根據(jù)塑件的表面精度高，和模具加工以及產(chǎn)品的生產(chǎn)成本考慮，所以設(shè)定一模兩腔。 三、注塑機(jī)型號的確定 所需注射量的計(jì)算1塑件質(zhì)量、體積計(jì)算通過ug 建模查詢可知一個(gè)塑件的體積v13.166cm3，兩個(gè)約為6.322 cm3，按公式計(jì)算得注射量為：1.6 x 6.3cm3 = 10.08 cm3查得abs的密度為1.06g/ cm3 。故所需塑料為的質(zhì)量1.06g/ cm310.08 cm3=10.68g2. 模具中冷凝料體積的估算本模具采用一模兩腔，并按照體積的0.6倍估算凝料體積為：v2=

10、v10.6=3.1660.6x23.799cm33. 該模具一次注射所需塑料abs體積 v0= v1+ v2=6.965 cm3 質(zhì)量 m0=v0=1.06x6.9657.4g （二）鎖模力的計(jì)算根據(jù)ug 建模分析，分型面上的單一投影面積a1約為1133.54 mm2，那么兩個(gè)就約為2267 mm2。根據(jù)經(jīng)驗(yàn)公式計(jì)算得施壓面積為：1.35 x2267 mm2 =3060.6 mm2。查資料得：在abs成型時(shí)型腔內(nèi)所產(chǎn)生的平均壓力為34.3mpa,故所需鎖模力為：3060.6 mm2 x 34.3mpa =104.98kn 取105kn （三）選擇注射機(jī)通過分析，根據(jù)每一生產(chǎn)周期的注塑量和所需壓

11、力，查閱參考書，可選用xs-zy-125a 臥式注塑機(jī)比較合理，其主要技術(shù)參數(shù):額定注射 125 注射壓力 150螺桿直徑 42鎖模力 900kn注射時(shí)間 1.6s最大開合模行程 325mm模具最大厚度 350mm 模具最小厚度 220mm噴嘴圓弧半徑 12mm噴嘴孔直徑 4mm動(dòng)、定模板尺寸 428mm458mm拉桿內(nèi)間距 360 mm360mm頂出形式 模具兩側(cè)裝有頂桿，離中心的距離分別為240mm 四、澆注系統(tǒng)設(shè)計(jì) （一）主流道的設(shè)計(jì)1主流道設(shè)計(jì)要點(diǎn) （1）設(shè)計(jì)圓錐形主流道，便于凝料脫離。(2）錐角度數(shù)=26。內(nèi)壁表面粗糙度一般為ra=0.4。(3）設(shè)定主流道進(jìn)口直徑d=8mm的半球形凹

12、坑。(4) 主流道末端與分流道連接處采用圓角銜接。其圓角半徑r=13mm。(5) 為了減少流道內(nèi)的凝料，盡量縮短主流道長度l，取值l=95mm。2主流道澆口套的形式為了避免損傷主流道的小端入口處，通常采用碳素工具鋼，如t8a、t10a 等。本模具材料采用t8a,熱處理硬度為50hrc55hrc，如圖4-1示:4-1澆口套示意圖 （二）分流道的布置形式本模具采用一模兩腔平衡式分流道的結(jié)構(gòu)形式，使塑料熔體由中心向四周分散而出。1分流道的長度兩級分流道對稱布局。一級管道長度取值44.5mm,二級管道長度取值57mm。2分流道的形狀、尺寸一級管采用半圓形，二級管采用圓錐形。根據(jù)經(jīng)驗(yàn)，要保證比主流道的大

13、端小1-2mm，本模具的一級管直徑6mm。圓錐形二極管的大端直徑取4mm,小端和澆口的大小同取1.2mm。3分流道的表面粗糙度分流道表面粗糙度為：ra=1.6m。 （三）澆口的設(shè)計(jì)為了避免引起塑件的缺陷，要考慮澆口的形狀、位置和大小等。應(yīng)盡可能設(shè)在澆口壁比較厚的地方。1澆口類型及位置的確定由于該模具是中小型塑件的多腔模具，塑件外形為圓形，結(jié)構(gòu)簡單，故采用點(diǎn)澆口。2澆口結(jié)構(gòu)尺寸的經(jīng)驗(yàn)計(jì)算根據(jù)塑件的結(jié)構(gòu)尺寸，本模具點(diǎn)澆口的進(jìn)料口直徑取1.2mm，澆口長度取1.6mm。 五、成型零件的結(jié)構(gòu)設(shè)計(jì)、計(jì)算 （一）成型零件的結(jié)構(gòu)設(shè)計(jì)1根據(jù)塑件輪廓，采用整體式凹模結(jié)構(gòu)。該結(jié)構(gòu)是由一塊金屬材料直接加工出來的。因

14、為有良好的強(qiáng)度，不容易發(fā)生變形，表面光滑平整，不會(huì)又銜接的痕跡。但是加工精度要求很高，所以只適用于簡單形狀比較小的塑件。而本塑件分型面設(shè)置于沒有突出的光滑頂面，凹模深度比較淺且形狀簡單的小型模具。故可采用整體凹模結(jié)構(gòu)，如5-1 圖示。5-1凹模結(jié)構(gòu)圖2因?yàn)樵撍芗膬?nèi)部形狀也簡單，所以采用整體式凸模,如圖5-2所示。5-2凸模示意圖 （二）工作尺寸的校核經(jīng)查詢知：abs塑料的收縮率為0.3%0.8%。平均收縮率 s=(0.4%+0.8%)/2=0.6%模具的制造公差取 查塑料模塑成型技術(shù)書 國家標(biāo)準(zhǔn)模塑件公差數(shù)值表310，由樣件知該塑件取公差等級為mt5級。1型腔尺寸型腔徑向尺寸d1(max)

15、=（d1+ d1scp% 3/4）+0=（38+38*0.0063*0.32/4）+00.18mm=37.98+0018mm型腔深度尺寸h1 (max)= (h+h scp% 2/3) +0 = (10+100.00620.2/3) +0006mm=9.93 +00.06 mm 2型芯尺寸型芯徑向尺寸 d1(min)= (d1+d1scp%+3/4)0 = (36+360.006+30.32/4) 0-0.18mm=36.430-0.18 mm 型芯深度尺寸h2（min） = (h2+ h2scp%+2/3) 0 = (8+80.006+20.2/3) 00.06mm=8.1700.06mm

16、六、模架確定、標(biāo)準(zhǔn)件選擇由前型腔的布局以及相互的位置大小，然后根據(jù)成型部件的尺寸與標(biāo)準(zhǔn)模架相結(jié)合，選用結(jié)構(gòu)形式為a1-2730-z2.的標(biāo)準(zhǔn)模架，即可滿足要求。 （一）定模座板（350mmx300mm、厚30mm）材料選用45鋼。 （二）定模板（型腔固定板）（3000mmx300mm 厚60mm）用于固定型腔部分。一般選擇45 鋼，調(diào)質(zhì)230hb270hb。 （三）動(dòng)模型芯固定板（300mmx300mm 厚70mm）一般材料選用45 鋼，進(jìn)行回火和淬火。 （四）墊塊（300mmx58mm 厚度90mm）1主要作用:適應(yīng)注射機(jī)的模具安裝厚度。2結(jié)構(gòu)形式:該模具采用的墊塊是平行的。3墊塊材料: 該

17、模具墊塊采用q235a 制造。也可用ht200、球墨鑄鐵等。4支承板（300mmx300mm 厚45mm）作用是防止凸模、凹模、導(dǎo)柱、導(dǎo)套等零件脫出。5墊塊的高度h 校核h =h1 +h2 +h3 +s=0+25+20+45=90mm, 符合要求。式中 h1頂出板限位釘?shù)母叨龋驗(yàn)楸驹O(shè)計(jì)未采用，故其值為0；h2推板的厚度，為25 mm；h3推桿固定板厚度，為20mm；s推出行程，為45mm；6推板（300mmx120mm、厚25mm），材料為45 鋼。7推板固定板（300mmx120mm、厚20mm），材料為45 鋼。 七、脫模推出機(jī)構(gòu)的設(shè)計(jì) （一）推出機(jī)構(gòu)的設(shè)計(jì)原則：（1） 應(yīng)盡量設(shè)置在動(dòng)模

18、一側(cè)。（2） 機(jī)構(gòu)簡單，推出動(dòng)作可靠。 （3） 使脫模后的制品有良好的外觀。（4） 合模時(shí)能準(zhǔn)確復(fù)位。 （二）脫模機(jī)構(gòu)的結(jié)構(gòu)設(shè)計(jì)由該塑件的外形特征及內(nèi)部型芯的情況，設(shè)置脫模機(jī)構(gòu)為標(biāo)準(zhǔn)推桿及利用斜頂頂出。如圖7-1所示：7-1結(jié)構(gòu)示意圖 八、設(shè)計(jì)側(cè)向的抽芯機(jī)構(gòu)根據(jù)設(shè)計(jì)要求采用斜頂頂出。 （一）斜頂?shù)脑O(shè)計(jì)斜頂結(jié)構(gòu)簡單，制造方便，穩(wěn)定性好，普遍用于內(nèi)抽心距較小的模具。 （二）抽芯距的確定抽芯距應(yīng)大于制品凸臺高度2mm。設(shè)凸臺高度為h，因此s=h(13)mm=22=4mm分析產(chǎn)品，根據(jù)查詢得斜頂斜角5度。 九、排氣系統(tǒng)的設(shè)定在成型過程中，除了有空氣外還有在成型時(shí)產(chǎn)生的低揮發(fā)氣體存在于模具型腔中。如果不

19、能將這些氣體排出模具外會(huì)在內(nèi)部產(chǎn)生很大的壓力，阻礙塑料熔體的快速填充。同時(shí)在高壓下，氣體壓縮產(chǎn)生高溫，可能會(huì)燒焦損傷塑件。甚至氣體在一定的壓縮下會(huì)滲入塑件內(nèi)部，導(dǎo)致產(chǎn)品有氣孔、疏松等缺陷。通常一般的模具是靠分型面的間隙排出氣體，很少開設(shè)排氣槽。而一般在凹模的分型面上開設(shè)排氣槽，尺寸一為寬1.56mm，深0.020.05mm，要小于塑料的溢料間隙規(guī)格，避免熔料從排氣槽溢出。根據(jù)本設(shè)計(jì)結(jié)構(gòu)，利用分型面之間的間隙自然排氣就可以了，不需要開設(shè)排氣槽。 十、 冷卻系統(tǒng)設(shè)計(jì)模具的溫度過高會(huì)直接影響塑件的成型收縮，容易導(dǎo)致塑件脫模時(shí)變形，甚至還容易造成熔料溢出和粘在模具上。而溫度過低時(shí)，將導(dǎo)致熔體流動(dòng)性變差

20、，從而使塑料零件的輪廓不清晰，表面有明顯的缺陷，例如銀絲和流紋狀。本設(shè)計(jì)塑件材料為abs，流動(dòng)性好，要求模具溫度（一般低于80）較低，只需要調(diào)節(jié)水的流量就可以對模具進(jìn)行冷卻。 （一）冷卻系統(tǒng)的設(shè)計(jì)原則：（1） 盡可能地增大冷卻管直徑和增加冷卻管數(shù)量；（2） 冷卻通道的布置應(yīng)合理；（3） 結(jié)構(gòu)應(yīng)便于清理、加工； （二）冷卻管道直徑d查模具設(shè)計(jì)基礎(chǔ)及模具cad表9-4知,為了使冷卻水在冷卻管內(nèi)處于急流狀態(tài)，取d=8mm,布局如圖10-1所示：10-1冷卻系統(tǒng)布局圖請您刪除一下內(nèi)容，o(_)o謝謝！many people have the same mixed feelings when plann

21、ing a trip during golden week. with heaps of time, the seven-day chinese請您刪除一下內(nèi)容，o(_)o謝謝！national day holiday could be the best occasion to enjoy a destination. however, it can also be the easiest way to ruin how you feel about a place and you may become more fatigued after the holiday, due to battl

22、ing the large crowds. during peak season, a dream about a place can turn to nightmare without careful planning, especially if you travel with children and older people. as most chinese people will take the holiday to visit domestic tourist destinations, crowds and busy traffic are inevitable at most

23、 places. also to be expected are increasing transport and accommodation prices, with the possibility that there will be no rooms available. it is also common that youllwait in the line for one hour to get a ticket, and another two hours at the site, to only see a tiny bit of the place due to the cro

24、wds. last year, 428 million tourists traveled in china over the week-long holiday in october. traveling during this period is a matter that needs thorough preparation. if you are short on time to plan the upcoming golden week it may not be a bad idea to avoid some of the most crowded places for now.

25、 there is always a place so fascinating that everyone yearns for. arxan is a place like this. the beauty of arxan is everlasting regardless of the changing of four seasons. bestowed by nature, its spectacular seasonal landscape and mountains are just beyond word. arxan is a crucial destination for t

26、he recommended travelling route, china inner mongolia arxan hailar manzhouli. it is also the joint of the four prairies across the sino-mongolian border, where people gravitate towards the exotic atmosphere mixed with chinese, russian, and mongolia elements. as a historic site for the yitian battle,

27、 arxan still embodies the spirit of genghis khan. walking into arxan, you will be amazed by a kaleidoscope of gorgeous colors all the year round - the spring azaleas blooming red in the snow, the summer sea wavering blue in the breeze, the autumn leaves painted in yellow covering volcanic traces, an

28、d the winter woods shining white on the vast alpine snowscape. hinggan league arxan city is situated in the far eastern area of inner mongolia autonomous region. its full name haren arxan means hot holy water in the mongolian language. arxan is a tourism city in the northern frontier with a blend of

29、 large forest, grand prairies, vast snowfield, heaven lake cluster, thermium, as well as volcanic cluster. it is a rare and unique ecotourism base filled with healthy sunshine, clean air and unspoiled green. nestled close to the countrys largest virgin forest, and known for its spring and ecological

30、 environment, arxan is marveled at by many tourists as the purest land on earth. you cannot miss out the autumn of arxan. it is definitely the best with brightly-colored scenery full of emotions. autumn in the northern part of the country comes earlier than the south. a september rain followed by th

31、e footprints of autumn brings more colors to the once emerald green mountain and blooming grassland. shutterbugs flock to see for themselves the marvel of splendid colors around the mountains and waters, many of whom have travel a long distance and even camp here only to capture a moment of the natu

32、re wonder. the silver birch turns golden, while the larch is still proudly green. you will find yourself drowned in the intoxicating red of the wild fruits as well as the glamour of flowers in full blown. and your heart will be lingering on the woods as its time for the wild fruits to ripe. the pict

33、uresque arxan in autumn is indeed a fairyland only exists in a dream that satisfies all your fantasies. if itrains heavily on saturday night, some elderly chinese will say it is because zhinu, or the weaving maid, is crying on the day she met her husband niulang, or the cowherd, on the milky way. mo

34、st chinese remember being told this romantic tragedy when they were children on qixi, or the seventh night festival, which falls on the seventh day of the seventh lunar month, which is usually in early august. this year it falls on saturday, august 2. folklore story as the story goes, once there was

35、 a cowherd, niulang, who lived with his elder brother and sister-in-law. but she disliked and abused him, and the boy was forced to leave home with only an old cow for company. the cow, however, was a former god who had violated imperial rules and was sent to earth in bovine form. one day the cow le

36、d niulang to a lake where fairies took a bath on earth. among them was zhinu, the most beautiful fairy and a skilled seamstress. the two fell in love at first sight and were soon married. they had a son and daughter and their happy life was held up as an example for hundreds of years in china. yet i

37、n the eyes of the jade emperor, the supreme deity in taoism, marriage between a mortal and fairy was strictly forbidden. he ordered the heaven troop to catch zhinu back. niulang grew desperate when he discovered zhinu had been taken back to heaven. driven by niulangs misery, the cow told him to turn

38、 its hide into a pair of shoes after it died. the magic shoes whisked niulang, who carried his two children in baskets strung from a shoulder pole, off on a chase after the empress. the pursuit enraged the empress, who took her hairpin and slashed it across the sky creating the milky way which separ

39、ated husband from wife. but all was not lost as magpies, moved by their love and devotion, formed a bridge across the milky way to reunite the family. even the jade emperor was touched, and allowed niulang and zhinu to meet once a year on the seventh night of the seventh month. this is how qixi came

40、 to be. the festival can be traced back to the han dynasty (206 bc-ad 220). traditionally, people would look up at the sky and find a bright star in the constellation aquila as well as the star vega, which are identified as niulang and zhinu. the two stars shine on opposite sides of the milky way. customs in bygone days, qixi was not only a special day for lovers, but also for girls. it is also known as the begging for skills festival or daughters festival. in this day, girls will throw a sewing needle into a b