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[摘要]塑料保險杠取代金屬保險扛是汽車行業(yè)的發(fā)展趨勢，但是塑料保險杠的設計目前仍采用傳統(tǒng)的模具設計方法。因此本文針對轎車前保險杠的制品結構，采用華塑CAE(HSCAE)軟件對轎車保險杠注射模的型腔壓力、熔體溫度及流動前沿進了優(yōu)化分析及模擬，同時對保險杠注射模的主要參數(shù)進行了校核。研究結果表明本文采用的設計方法可以極大提高保險杠注射模設計開發(fā)的效率。
關鍵詞保險杠 注射模 熱流道 CAE
1 前言
??? 隨著汽車上業(yè)的發(fā)展，全金屬保險杠越來越不適應現(xiàn)代汽車在輕量化、高機能化以及與車體造型一體化等方面的要求，尤其在轎車、輕型車上，有用塑料保險杠取代全金屬保險杠的趨勢。作為鋼鐵件的替代產品，汽車塑料保險杠以其造型美觀，重量輕，易于成型，耐腐蝕，成本低，綜合機械性能良好，且容易實現(xiàn)規(guī)?；a等優(yōu)點在汽車行業(yè)占據(jù)了一席之地。目前，我國轎車。微型車、輕型車等生產廠家正在逐步實現(xiàn)該產品的更新?lián)Q代。
2 轎車前保險杠幾何結構分析
??? 圖1所示零件為馬自達轎車前保險杠，零件壁厚3.5mm，通常要求制件表面光滑無缺陷，對其外形精度沒有過高要求。如圖1所示，保險杠形狀為馬鞍形，長1925mm，寬715mm，高538mm，平均壁厚為3.5mm。橢圓形燈孔左右各一，中間為通風柵格，內側加強筋若干。尾部有內側卷曲，因此，需要采用內側抽芯。
1 前言???
隨著汽車上業(yè)的發(fā)展，全金屬保險杠越來越不適應現(xiàn)代汽車在輕量化、高機能化以及與車體造型一體化等方面的要求，尤其在轎車、輕型車上，有用塑料保險杠取代全金屬保險杠的趨勢。作為鋼鐵件的替代產品，汽車塑料保險杠以其造型美觀，重量輕，易于成型，耐腐蝕，成本低，綜合機械性能良好，且容易實現(xiàn)規(guī)?；a等優(yōu)點在汽車行業(yè)占據(jù)了一席之地。目前，我國轎車。微型車、輕型車等生產廠家正在逐步實現(xiàn)該產品的更新?lián)Q代。
2 轎車前保險杠幾何結構分析
???圖1所示零件為馬自達轎車前保險杠，零件壁厚3.5mm，通常要求制件表面光滑無缺陷，對其外形精度沒有過高要求。如圖1所示，保險杠形狀為馬鞍形，長1925mm，寬715mm，高538mm，平均壁厚為3.5mm。橢圓形燈孔左右各一，中間為通風柵格，內側加強筋若干。尾部有內側卷曲，因此，需要采用內側抽芯。
保險杠材料要求在較寬的溫度范圍內剛性好，耐沖擊性能好，尺寸穩(wěn)定性好，耐溶劑性好，涂裝性能好。丙烯綜合什能較好，故在此選用聚丙烯(改性)作為保險杠材料。
?所設計保險杠模具特點為：模具外形尺寸大(2400mm×700mm×11OOmm)、體積重(25~40t)，結構復雜，類似為一個中等程度的工作母機；模具澆注系統(tǒng)為熱流道，需要電加熱；型腔、型芯冷卻系統(tǒng)復雜，型腔與澆注系統(tǒng)的熱流道相互矛盾；制品頂出系統(tǒng)復雜，常用液壓、機械聯(lián)合頂出，并采用機械手自動取出制品；制品尺寸大，澆注系統(tǒng)常為冷，熱流道相結合。
3 CAE優(yōu)化分析
在對轎車前保險杠注射模的總體結構、使用功能控制及模具結構的具體設計(包括澆注系統(tǒng)成型零件和導向裝置、測向分型抽芯機構、模溫控制裝置等的設計)進行全面設定的基礎上，采用華中科技大學國家模具重點實驗室開發(fā)的HSCAE(華塑CAE)軟件進行優(yōu)化及動態(tài)模擬分析，從而改變了過去那種單靠人為經驗來設計模具澆口位置及尺寸，需要多次試模．反復修改，才能最后設計定型和制造模具的落后方法。該課題的開展，將會極大地減少設計人員反復估算饒口尺寸的繁雜勞動，加速我國對大型轎車注射模設計、制造及產品牛產系列化的進程。
? 塑料注射成型時，塑料在型腔中的流動和成型，與材料的性能、塑件的形狀尺寸、成型溫度、成型速度．成型壓力、成型時間、模腔表面情況和模具設計等一系列因素有關。CAE優(yōu)化分析就是利用計算機高速運算功能，綜合考慮各種因數(shù)，得出流動場、溫度場、壓力場、剪切應力場等模擬結果，從而評定所用方案的優(yōu)劣。這里使用華中科技大學模具國家重點實驗室開發(fā)的HSCAE5.0軟件進行優(yōu)化分析。
流動場分析結果如圖2所示，其流動是平衡的，結合后面熔結痕分析結果說明澆口開設是合理的。
溫度場分結果如圖3所示，結束時溫差比較大，可能原因是此模具采用熱流道技術，而CAE分析結果按冷流道汁算得出。若出現(xiàn)注射結束時不同位置的溫差太大，就很難獲得均勻的冷卻，不同的溫度將導致聚合體的密度和性能都發(fā)生著改變，這樣會產生翹曲。同時可能會產生較大的因溫差引起的殘余應力。
壓力場結果如圖4所示，因為熱流道原因，出現(xiàn)輕度壓力不是現(xiàn)象。若出現(xiàn)壓力不足現(xiàn)象應考慮以下因素：①材判流動性不夠；②制品過大而零件壁厚很?。虎哿鞯篱L度過長；④需要分級注射。
剪切應力場結果如圖畫所示，應力場均勻，不會產生噴現(xiàn)象。
CAE優(yōu)化分析時必須考慮到分析時所用STL，文件沒有坐標，不能精確定位，會人為引入流動不平衡因數(shù)。大型注射模常用熱流道或冷、熱流道結合技術與CAE分析假定的冷流道有很大區(qū)別，這也給分析帶來很大誤差。
4 保險杠大型注射模熱流道設計
在設計大型塑件模具澆注系統(tǒng)時，既要保證型腔充滿，又要減少因系統(tǒng)設計不當給制品帶來的缺陷。特大型塑件常采用多級分流道。多點同時澆注方案。復雜的澆注系統(tǒng)在提高塑件質量的同時也使設計的難度增加。因此，澆注系統(tǒng)的設計是設計大型注射橫的關鍵之一。
??? 本次沒計采用熱流道技術，這項新技術的開發(fā)乃是注射模的一次重大改革。它的應用不僅縮短了成型周期、提高了生產效率，同時也節(jié)省了原料。在大型模具設計中，熱流道系統(tǒng)設計應用愈來愈廣，特別是熱流道模具，它是大型模具的發(fā)展方向。
??? 下面就熱流道模具加以討淪。熱流道模貝之所以得到廣泛應用，是因為它具有以下獨特優(yōu)點：縮短成型周期，一般可達30％-40％；避免回收大量回頭料．從而節(jié)省原料，降低成本；由于嚴格控制溫度，因此提高了制品質量，保證了制品的尺寸精度和強度；熱流道有利于壓力傳遞，從而可以降低注射壓力；縮短開模行程，有利于保護模具，延長模具使用壽命；無需修剪料把，節(jié)省工時和人力；縮短制模周期，制品成本降低，在一般情況下生產成本降低16％。
??? 根據(jù)CAE分析結果，采用AutoCAD軟件進行二維模具設計，本模具設計為單型腔，熱流道、9點進澆、內側抽芯等技術。合模過程由兩矩形導滑塊導向，最后由錐面定位鎖緊。模具總長2000mm，寬1200mm，高1440mm，模具結構總圖如圖6所示。
二維模具設計的基本步驟如下：
(1) 繪制制品二維結構圖，確定好分型面，澆口的位置及尺寸大小。
(2) 采用金屬零件包圍制品內外表面。
(3) ?設置澆注系統(tǒng)、合模導向機構、頂出系統(tǒng)、加熱冷卻系統(tǒng)。
(4) 按動、定模分型面繪制左右動定模的方位圖。
(5) 在動、定模視圖中分別表示出相關零件的裝配坐標位置。
(6) ?采用另一個視圖表達未完整主視圖的相關內容。
(7) ?在主視圖下方繪出制品圖，并標注產品的尺寸。
(8) ?標注零件序號，并列出零件明細表中的材料、件數(shù)、熱處理等技術要求。
(9) 在總裝圖中寫山技術要求及模具的動作原理.
5 大型注射模主要參數(shù)校核
(1)加熱流道板的熱功率計算。熱流道板相當于延伸了注塑機噴嘴，使得熔料流程大為縮短，有利于熔料的填充。但是采用熱流道澆注系統(tǒng)需配備精碗的模具溫度控制器，以防止熔料溫度過高而燒焦。加熱管功率一般憑經驗按每kg熱流道板需0.1-O.15kW估算，也叫按下式進行計算
(2)型芯、型腔的加熱冷卻系統(tǒng)。
??? 模溫是影響制品質量及成型效率的一個重要因素。在使用了熱流道的模具中，一方面熱流道需要加熱而另一方面模具需要冷卻。且由于此模具體積巨大模具開始工作時模溫低，需要預熱，工作一段時間后模溫上升超過規(guī)定溫度時又需要冷卻。聚丙烯(PP)的成型溫度在160℃-260℃，其模具溫度應控制在55℃~65℃。大型注射模最好用自來水冷卻，比較經濟，冷卻水孔直徑一般在φ8-φ12mm。
??? 大型注射模加熱裝置一般為電加熱棒加熱，它有方便、易控制等優(yōu)點，但必須防止局部過熱。
(3)型腔側壁厚度計算。
???理論分析與實踐證明，大型模具的剛度是中要問題，而強度足次要問題。故成型件尺寸應以滿足剛度條件為前提，聚丙烯所允許撓曲量在0.03-0.04mm。將側壁看作是受均布載荷的固定梁模型，由撓度公式可推出允許最小側壁厚度：
對于此保險杠模具:
(4)動模墊板問受力變形計算，方法原理同側壁校核，允許最大撓曲量一般取0.05mm。
一般對大型注射模還需進行制品對型芯包緊力的計算及頂出力的校核；連接螺釘頂出杠強度校核等。可參見注時模設計手冊。
6 結束語
??? 設計保險杠大型注射模應注意的問題：
? (1)應認真分析產品幾何結構，選擇好分型面；CAE優(yōu)化分析選擇澆口形式、大小、數(shù)目及進澆位置。
? (2)確定產品所用原材料常需要流動性好(即熔體流動指數(shù)大的塑料)、有利充模；好的機械力學特性，能保證轎車在沖擊下不變形、有彈性回復；耐惡劣環(huán)境氣候變化而不變形(翹曲)。
???(3)大型或特大型注射模設計應考慮使用熱流道或冷、熱流道相結合的澆注系統(tǒng)。
???(4)加熱、冷卻是大型注射模設計需要解決的一對矛盾。
???(5)大型注射模頂出系統(tǒng)一般很復雜，常需要機械液壓聯(lián)合頂出。
[Abstract] that the plastic safety bar substitutes metal being sure shouldering is that automobileindustry developing trend, but plastic safety bar design adopt the tradition design for die and mould method at present still. Therefore the main body of a book type cavity pressure , the forward position melting experiencing and observing the temperature and being on the move adopt China tomould the CAE (HSCAE) software injecting a model to saloon safety bar have entered the mainparameter optimizing analysis and the simulation , injecting a model at the same time to the safety bar specifically for saloon front safety bar products structure, having carried out the core ofschool. Study result indicates the main body of a book the design procedures adopting can beimmense raising a safety bar injecting a model designing development efficiency.
[Keyword] safety bar injection model heat current says CAE
1 preface
mounts development of job with the automobile, entire the more and more unadaptable metal safety bar Hyundai Motor request in the field of make light of quantization , high enginery-rization and unifying with car body model and so on, the plastic safety bar especially useful on the saloon , light vehicle, substitutes entire metal safety bar trend. And as iron and steel piece of replacement product, the plastic safety bar makes light of an automobile with whose attractive appearance , weight , molding , be able to bear corrosion , cost low , synthetical mechanical performance are easily fine, scale-rization childbirth easy to come true waits for merit to have occupied a space for one person in automobile industry. At present, our country saloon. That minitype vehicle , light vehicle etc. produces a manufacturer is realizing the renovation and upgrade being a product's turn step by step.
2 saloon front safety bars geometries structural analysis
Picture what 1 shows a part is a Mazda saloon front safety bar, part wall thickness 3.5 mms, generally, had demanded a request to make piece of surface nothing defect glossy , do not had to it's external form accuracy. 715 mms, are 538 mms taller than if picture what 1 shows , the safety bar form are shape of a saddle , 1925 long mms , width, average wall thickness is 3.5 mms. The ellipse light hole controls every one, centre is the grid being ventilated , reinforce a tendon on the inner side some. The tail assembly has inner side to curl , needs to adopt inner side to take a core out therefore.
Safety bar material requires that stiffness is easy to be able to bear within broader temperature range, pounding a function well , the dimension stability is able to bear the function of menstruum easy to spread dress well,well. The miscellaneous energy propylene is synthesized is fairly good , is safety bar material therefore selecting and using polypropylene (change nature) here.
Designed that the safety bar mould characteristic is: Mould external form dimension big (2400 mms X 700 mms X 11 OOmm) , volume duplicate each other (25 ~ 40 ts) , structure is complicated , are similar with for a medium degree machine tool; Mould teeming system is that heat current says , needs an electrical heating; The type cavity , core cooling system are complicated , the type cavity and systematic heat current of teeming contradict mutually; And take place products top system is complicated , hydraulic pressure in common use , machinery unity support out, adopt machine hand to take out products voluntarily; The products dimension is big , teeming system is often cold, heat current combines each other.
3 CAE optimize analysis
On injecting model population structure to saloon front safety bar , using a function to control (the design reaching architectural designing including pouring the system molding part and the guiding device , measuring to being allotted a type taking core organization , the model temperature out a control device) concretely and so on of mould carrying out the basis setting up all round, has adopt the development country of Huazhong University of Science an Technology mould priority laboratory HSCAE (China moulds CAE) software to carry out the optimization and the development simulation analysis , has changed thereby that depended solely on the location and dimension coming to design the mould running gate artificial experience in the past, Require that many times tries a modelRelapse revises , ability designs finally the method getting into form and making the mould falling behind. Should the problem carrying out, with course that can cut down the seriation designing that the personnel estimates that complication giving a mouth extra a dimension works , acceleration our country designs that to large-scale saloon injection model , fabrication and the product cattle produce again and again tremendously.
Plastic form dimension , the molding temperature , molding speed molding pressure , molding time , model cavity moulding a piece with the material function in flow and molding , in type cavity, surface a series of factor such as condition and design for die and mould is relevant when plastic injection molding. CAE optimizes analysis being to make use of the computer high speed arithmetic function , to consider the various factor synthetically , reach field , the temperature , pressure being on the move , shear strain waiting to simulate result, appraise what be used a scheme superior or inferior rank thereby. Use the development HSCAE5.0 of Huazhong University of Science an Technology mould country priority laboratory software to carry out optimization analysis here。
The field being on the move analyses result if pursuing what 2 shows , that the running gate establishes it's the explanation being on the move being balanced , forming trace analysing result combining with melting later is rational.
The temperature is allotted if result pursuing what 3 shows, the difference in temperature is comparatively big when being over , possibility cause is that this mould adopt heat current to say technology, but analytical result of CAE finally reaches according to cold runner juice. Inject the very big , right away very difficult to gain homogeneous difference in temperature cooling being unlike location when being over if appearing, the different temperature the density and function leading to the polymerization body is changed being happening , this may produce buckling. May possibly produce remains strain that bigger reason difference in temperature arouses at the same time.
Pressure bears fruit if pursuing what 4 shows , making light of degree pressure because of heat current says that cause, appears is not phenomenon. If pressure appears, the insufficient phenomenon should consider the following factor: (1) material be sentenced to flowability insufficient; (2) products is too big but part wall thickness is very infertile; The runner length is too long (3) The runner length is too long; (4) require that classification gets a shot.
Shear strain finally gushing phenomenon if what picture shows , strain come into being homogeneous incapable。
CAE optimization analytical now and then must think arrive at analytical now and then used STL, document not coordinate, unable accurate fix position, meeting artificial introduction be on the move unbalance factor. Large-scale injection model heat current in common use is say or cold, heat current says that the cold runner linking technology with CAE analysing assumption has very big differences , this to bring very big error to very big error analysis also.
4 Heat current designs large-scale safety bar injection models
During the period of the system designing that heavy section moulds piece of mould teeming, now that want the guarantee type cavity be full of, will fall off again designing the defect not should be brought about by products because of system. The super-huge type moulds a document often adopt multistep to shunt saying. The multiple spot pours a scheme at the same time. That complicated teeming system moulds piece of mass simultaneous in rise also makes the degree of difficulty designing that increase by. Therefore, pouring systematic design is one of the horizontal key designing that heavy section gets a shot.
Have not been a significant reformation adopt heat current to say that the technology , this new technique exploitation are indeed to be to inject a model originally time. Not only, its application has shortened the molding period , has improved an efficacy, have economized at the same time also raw material. In large-scale design for die and mould, heat current says that system designs that application is broader and broader , heat current says that mould , it are large-scale mould development direction especially.
With regard to heat current, the mould gets men at the lower levels additionally fall to. Heat current says that model cowry gets extensive use , is unique merit because of it has the following: Shorten the molding period , the sort but amount to 30%- 40%; Avoid reclaiming a great quantity turning about to expect economizing raw material , cost reduction thereby; Products dimension accuracy and intensity having controlled the temperature since strict , having improved the products mass, guarantee therefore; Pressure beneficial to saying transfers heat current to, can reduce injection pressure thereby; Shorten the model route or distance of travel , life time beneficial to protecting a mould , prolonging a mould open; Need not trim material with economizing the working hour and manpower,; Shorten the moulding period , products cost reducing , produce Cheng under ordinary circumstances。
Analyse result according to CAE , adopt the AutoCAD software to carry out two-dimensional design for die and mould, design for die and mould is a Shan type cavity , heat current says that 9 o'clock enters technologies such as irrigating , taking a core out on the inner side. Agree well with model process leading smooth piece guiding from two rectangles, locking fixing position finally from the conic surface. Mould cabinet minister 2000 mms , width 1200 mms , 1440 high mms, if mould structure general view pursuing what 6 shows.
Fundamental two-dimensional design for die and mould step as follows：
(1)Draw two-dimensional structural drawing of products, ascertain location and dimension size easy to be allotted type face , the running gate.
(2) adopt the metal part to surround products inside and outside outside.
(3) sets up teeming system , closes model guiding organization , is equivalent to system out , heats cooling system.
(4) draws a retinue moving bearing picture fixing a model face to face according to moving , fixing a model be allotted a type.
(5) expresses out relevance part assembling coordinate location respectively in moving , fixing model view.
(6)adopt another view to express not entire front view relevance content.
7) dimensions drawing out products picture, and marking a product on the down part in front view.
(8) marks the part serial number , standing side by side out specification such as material ,numbers heat treatment in part detail list.
(9) write mountain specification and the mould action principle in general dress picture.
5 The main large-scale injection model parameter is proofreaded
(1) heats the unnatural thermal power of Liudao secretly scheming against. Heat current says that board has been equal to extending injection machine spray nozzle , will do melt expecting that technological process shortens extremely , beneficial to melting material filling. But adopt heat current to say that teeming system needs allocating the mould temperature controller being skill in a bowl, to prevent from melting expecting that the temperature is excessive but charring. Like heating pipe power, heat current says that board needs 0.1-O let experience push down every kg. Estimate , also call 15 kW to press down style being in progress secretly scheming against
(2) cores , type cavity warmup cooling system.
The model temperature is a key factor affecting products mass and molding efficiency. In the mould having used heat current to say, on one hand, heat current needs to heat but the another aspect mould needs to cool down. And when exceeding the regulation temperature since the model temperature requires that the period of time queen model temperature preheating , working rises low when this enormous mould volume mould begins to work, need to cool down. The polypropylene (PP) molding temperature is in 160 ~C- 260 ~C, whose mould temperature should be in 55 ~C ~ under the control of 65 ~C. Use running water to cool down , parallel large-scale best injection model economy, the chilled water hole diameter is just like in phi8-phi12mm.
The large-scale injection model heats the device sort for the electrical heating stick heats , it has merit such as convenient , easy to control, but guards against part be obliged to hotness.
(3) type cavity oblique tones wall thickness secretly schemes against.
Theoretical analysis and practice are testified, large-scale mould stiffness is middle want problem, but the intensity is fully secondary questions. Therefore the molding document dimension responds to satisfy stiffness, condition are allowed bend amounts by the premise , polypropylene in 0.03-0.04mm. Oblique tones wall look upon as being to accept the fixed beam model spreading loading equally , to may debut allowable minimal oblique tones wall thickness from deflection formula:
To this safety bar mould:
(4) moves model backing board asking that deformation is calculated by the force , method principle and oblique tones wall are proofreaded , allows maximal bend to take 0.05 mm like the amounts.
To large-scale injection, the model requires the parcel carrying out products on the core to tighten the force calculation and the core of school supporting to make efforts in general; The screw linking up is equivalent to the thick stick intensity core of school in waiting out. When may consult notes, the model designs a handbook.
6 concluding remark
The model designing that safety bar heavy section gets a shot responds to the problem paying attention to:
(1) should conscientious analyse face of product geometry structure, choice easy to be allotted a type; The CAE optimization analyses the form , size , number choosing a running gate and moves forward irrigating location.
(2) ascertains what product uses raw material to require that flowability is good (be to melt experiencing and observing big exponent plastic) being on the move often, help charge a model; Good mechanics of machinery characteristic property, can ensure that the saloon not becoming deformed , has elastic property replying to under pounding; Be able to bear adverse circumstances climate change but not becoming deformed (buckling).
(3) large-scale or very large-scale injection models design that heat current says or cools down should consider usage , heat current says that the teeming being tied in wedlock each other is systematic.
(4) heats , the model cooling down being that heavy section gets a shot designs that needing a pair of contradiction solving. Take place
(5) large-scale injection model tops system is in general very complicated , often requires that machinery hydraulic pressure supports out combinedly.