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附錄
DEVELOPMENT AND APPLICATION OF PLASTICS MOLDING CAD/CAM/CAE SYSTEM
ABSTRACT: this paper describes features of plastics molding CAD/CAM/CAE integrated system and process of applying the system to practice. Development and application of I-DEAS (integrated design engineering software) were performed in view of actual plastics molding. The results show that plastics molding CAD/CAM/CAE system is a practical and efficient technique which is worth spreading.
KEY WORDS: plastics molding CAD/CAM/CAE; integrated; I-DEAS
1. introduction
Plastics molding is the main method of producing plastics product. It develops in high speed but its history is short. Plastics molding is also used extensively. According to the statistics, the quantity of plastics molding is about 28% of that of all molding, but the traditional design of plastics molding is low efficient, long periodic and wasteful. It contradicts with the development of plastics industry. With the development of technique in computer, numerical control and plastics fluid, plastics molding CAD/CAM/CAE has been applied extensively at present
2. plastics Molding CAD/CAM/CAE system
2.1 process of plastics molding CAD/CAM/CAE
The integration of CAD/CAM/CAE changes the traditional mode of producing molding. Fig.1 show the integrated process.
In traditional design, it is required to produce actual solid molding to evaluate the appearance and test the function of product when the product construction is finished. By contrast, in CAD/CAM/CAE system, by using solid geometry modeling users can display the picture of product vividly on graphic terminal, evaluate the appearance and modeling technology through observing the screen, and need not produce actual solid modeling. By using finite
Fig1 process of plastics molding CAD/CAM/CAE
Element method analysis software, users can also test the mechanical functions of product. The main feature of CAD/CAM system is the generation of a common database which is used for all design and manufacturing activities, so another function of geometry modeling is to provide geometry data for the families of plastics analysis and graphic numerical control, hence the redundant data is avoided, and the efficiency and prevision are improved. Three dimensional geometry solids can also be converted into two dimensional engineering drawing, so designer would be relaxed from drafting and calculating, concentrated on creative work..
When finishing the preliminary design, users could check the molding technology and the extent of molding construction by using CAE software, that is to say, users should simulate the process of plastics injection before the molding is manufactured. Through the analysis of CAE software, all kinds of results are gotten in each phase of plastics injection, such as temperature, pressure, stress, filling time, cooling time, warp age and shrinkage, etc. these results are also shown with abundant modes of post process. Users can perform a quantitative or qualitative analysis. If there are some problem, the design could be correct in computer. the interaction is operated between CAD and CAE until the reasonable results are gotten. Not as the traditional process, the molding would be modified when it has been manufactured if something is wrong, so process period i shorten dramatically, and efficiency and prevision are improved. When injecting simulation is finished, if the results are reasonable, it shows the design is applicable. The next step is to finish detail design and manufacturing technology, prepare to manufacture.
Recently, the technique of numerical control (NC) makes a great progress. The automatically programmed tool (APT) appeared in 1960’s promoted the development of NC technology dramatically. APT is also used widely at present, but it also has some defects, such as low efficiency, etc. at present, the development orientation of NC is to merge CAD and CAM into an organic whole, so CAD/CAM is a unified software system, in which the CAD portion is interfaced inside the computer with the CAM system. Therefore the track of cutting tool is created with the mode of man-machine interaction by using the geometry data fully which is created in the phase of CAD. Now a new programming technique has been come into using—graphic numerical control (GNC) based on graphic. In the system, cutting tool, workpiece and fixture are displayed on computer screen by generating animation, so the track of tool is optimum and safety. In sum, GNC system is very efficient and convenient.
2.2 application of I-DEAS software in practice
Our advanced manufacturing technology center (AMMTEC) of harbin institute of technology makes an effort to develop integrated system of CAD/CAM/CAE. AMTEC was founded in 1992. it imported many NC machines and large style engineering software IDEAS (integrated-design engineering analysis software) with which equips IBM-RISC 6000 work station, so we have the condition to apply plastics molding CAD/CAM/CAE system to design, analysis and manufacturing of plastics molding .
I-DEAS is a type of synthetically automatic software. It integrates the functions of design, drawing, engineering analysis, digital simulation of plastics molding, numerical control programming and test. The families of geometry modeling, plastics analysis and graphic numerical control constitute a plastics molding CAD/CAM/CAE system. We would design and manufacture a set of molding which produces the plastic pedal of “jetta” car (product material is nylon-66) for the first Automobile Work of city of changchun. It is difficulty to design and manufacture the molding because the shape of pedal is very complicated, so we decided to apply the families of I-DEAS to design, analysis and NC programming.
I-DEAS solid modeling is an important component of I-DEAS. It supplies a set of functional tool for geometry modeling and detail mechanical design. The method of solid modeling is constructive solid geometry (CSG). The steps are in following:
(1) creating basic elements, such as cubic, cylinder, sphere, etc.
(2) disposing the basic elements by using Boolean operation. So the complicated geometry can be created.
Using these steps, the three dimensional geometry modeling of pedal can be created. computer graphics enable the designer to study the object by rotating it on screen, enlarging a specific portion of the object to observe it in detail.
Finishing the preliminary design of molding, we can perform an injecting simulation to evaluate the design by using the family of plastics analysis which uses finite element method. I-DEAS provides three methods of creating the geometry shape of finite element.
from the family of solid modeling.
From the family of itself.
From other CAD system.
Because the product modeling has been created in the family of solid modeling, we can use the first method to avoid reconstructing. After selecting elements, creating elements, creating mesh and checking modeling, we can create the finite element model used to perform plastics analysis.
In this design, it is difficulty to decide where to set the gate. we can see that the pedal is slender. According to common concepts, the gate should be set in the middle of product. Welding line would come into being if this design is adopted. Therefore mechanical strength of product will be reduced. In practice using, the middle of product would bear heavy force, so it is not safety to set the gate in the middle of product. Finally we set the gate at the top of product to ensure the mechanical functions of product. In this design the fluid orientation would be consistent in the molding, and the mechanical function could be ensured, but the temperature of tip fluid will drop much more because of the long route of flowing, the fluidity of fluid becomes bad. It is necessary to raise the pressure of entrance to fill the impression, but the raising is limited in certain range, so it is possible that the impression could not be filled fully. When we simulated the process of injection, the initial result was always unreasonable that the pressures of impression exceed that of injecting jet supplying. after analyzing, we modified the injection parameters. The temperature of molding and plastics fluid are raised so that the fluidity of fluid became good. Though the correcting, the results are very satisfied. The filling time is shown is Fig.3. we can see that the filling time is 4.81 second at which is the furthest from the gate. The pressure and temperature of analysis results are also in normal range. In actual molding, we adopted corresponding steps according to the analysis results, so the qualified products were produced.
DEAS GNC is a new kind of NC programming tool based on graphic. GNC system has the function of creating and operating of complicated surface elements. We could also use the method as same as that is used in plastics analysis, namely, the geometry model was gotten from the family of solid geometry modeling. Thereafter we use a set of describing instructions to define the machining process and parameter, such as cutting tool, manufacturing orientation and step, etc. the system would display the manufacturing process. At the same time the cutter location (CL) file comes into being which includes all manufacturing information but cannot be discriminated by NC machine directly, so the post-process is necessary. The post-process of GNC is different from that of normal. Normal post-process user the special principle. At present, with the rapid developing of NC technology, the number of NC system become more and more. It couldn’t meet the present needs that post-process is only consistent to special machines. GNC system uses the common principle. It supplies a functional tool—text macro processor (TMP) with which user can program post-process procedure suit for all kinds of machine easily. According to the specialty of manufacturing molding and the FANUC 11system that we own, we programmed the post-process procedure of three axes that is used to operate the standard cutting location file. The result is the ISO machining codes which can be directly fed into the control computer of CNC machines, and the effect of actual machining is very good.
3. conclusions
(1) the integration of CAD/CAM/CAE changes the traditional production of plastics molding. User can modify and optimize the product, molding and manufacturing at the aid of computer. The efficiency is improved and the error is cut.
(2) by adopting the technique of CAD/CAM/CAE, the period of design and manufacturing of molding is shorten dramatically. The cost is cut and the quality of product is improved.
(3) I-DEAS software is a CAD/CAM/CAE software system includ ̄ing geometry modeling, plastics analysis and graphic numerical control whose function are strong and practical value is high.
References
Li Dequn and Xiao Jinrong. CAD technology of plastics injection molding, Molding industry. 1989.NO.12
Yoram Koren computer control of manufacturing systems. McGraw-Hill Book company 1983
Ulrich Rembold. Computer integrated manufacturing technology and system. Marcel dekker inc,1984
CAD/CAM/CAE系統(tǒng)得發(fā)展和應(yīng)用
摘要:
本章主要講述塑料制品成型CAD/CAM/CAE綜合系統(tǒng)的特點和他在實際生產(chǎn)系統(tǒng)中的應(yīng)用。I-DEAS——(綜合工程設(shè)計軟件)的發(fā)展和應(yīng)用是綜合考慮了塑料制品成型的現(xiàn)狀。結(jié)果表明塑料制品成型CAD/CAM/CAE系統(tǒng)是一個值得推廣的實用有效的技術(shù)。
關(guān)鍵字:塑料制品CAD/CAM/CAE; 綜合; I-DEAS
緒論
塑料制品成型是生產(chǎn)塑料制品的主要方法,他的發(fā)展很快但是歷史卻不長。塑料制品成型的應(yīng)用也是很廣闊的。據(jù)統(tǒng)計:在所有的成型中塑料制品成型的數(shù)量占28% 但是傳統(tǒng)的塑料制品設(shè)計的效率很低,周期長而且很浪費。這與目前計算機技術(shù),數(shù)控 ,和流體塑料,塑料制品成型CAD/CAM/CAE綜合系統(tǒng)廣泛應(yīng)用的塑料工業(yè)的發(fā)展相矛盾。
塑料制品成型CAD/CAM/CAE系統(tǒng)
2.1 塑料制品成型CAD/CAM/CAE系統(tǒng)的過程。
CAD/CAM/CAE的集成改變了傳統(tǒng)生產(chǎn)成型的方法。圖1表示了完整的過程。
在傳統(tǒng)的設(shè)計中, 要求對產(chǎn)品實際的整體模作出外觀的評價并且當(dāng)產(chǎn)品構(gòu)建完成以后進行功能的測試,在CAD/CAM/CAE系統(tǒng)中,通過幾何建模的方法,用戶可以在繪圖終端上做出產(chǎn)品的生動圖片。通過圖形來評估外形和形體的工藝性,而不需要生產(chǎn)出實際的產(chǎn)品。通過有限元軟件的分析,用戶可以測試產(chǎn)品的機械性能。CAD/CAM/CAE系統(tǒng)得主要特點是有一個能夠用于設(shè)計和制造活動的通用數(shù)據(jù)庫。因此幾何建模的另一個功能就是為外形分析和圖形數(shù)字控制家族提供數(shù)據(jù)基礎(chǔ)。因而避免了多余的數(shù)據(jù),而且提高了效率和預(yù)見力,三維的幾何實體也可以被畫成二維的工程圖。因此設(shè)計者可以減輕起草和計算的工作,而把精力放在創(chuàng)新設(shè)計上面。當(dāng)完成初步設(shè)計時,用戶能檢查成型的技術(shù)和通過使用CAE軟件檢查成型變形的范圍, 那就是說,在模型被生產(chǎn)之前,用戶應(yīng)該模擬塑料注射的過程。 通過CAE軟件的分析, 各種結(jié)果進入到塑料制品注射的每階段, 例如溫度,壓力,形變,填飽時間,冷卻時間,變形時間和收縮過程等等,這些結(jié)果也被后置處理以豐富的模式顯示出來。
圖1 可塑性成型工藝過程CAD/CAM/CAE
如果這里存在問題,設(shè)計就可以在電腦上修改。CAD和CAE之間的交互作用一直持續(xù)到得出合理的結(jié)果。
不同于傳統(tǒng)的過程, 模型被制造出來后如果有錯誤才進行修改,因此處理時間被急劇縮短,并且效率和預(yù)見力被提高。 當(dāng)注入模擬被完成時,如果結(jié)果是合理的,它表明設(shè)計是適用的。 下一步是完成詳細(xì)設(shè)計和生產(chǎn)技術(shù),準(zhǔn)備生產(chǎn)。
最近,數(shù)控(NC)技術(shù)取得大的進步。 大大的促進NC 技術(shù)的發(fā)展,自動編程的工具(ATP) 在20世紀(jì)60年代出現(xiàn)。 ATP目前也被廣泛的使用, 但是它也有一些缺陷, 例如效率低, 等等。目前, NC的發(fā)展定向是把計算機輔助設(shè)計和計算機輔助制造合并成有機的整體, 使其成為一個統(tǒng)一的軟件系統(tǒng),其中計算機輔助設(shè)計部分在計算機中與計算機輔助制造系統(tǒng)形成內(nèi)部聯(lián)系。 因此切割工具的軌跡通過使用人機交互的方式被計算機輔助設(shè)計階段過程中創(chuàng)造的幾何學(xué)數(shù)據(jù)創(chuàng)建。 現(xiàn)在,一種新的編程技術(shù)開始使用——基于圖表的圖表數(shù)值控制(GNC)。 在系統(tǒng)內(nèi),切割工具,工件和固定設(shè)備通過產(chǎn)生生動的動畫顯示在計算機屏幕上,因此工具的軌跡是最佳的和安全的。 總之,GNC系統(tǒng)非常便利和有效。
I-DEAS軟件在實際中的應(yīng)用
哈爾濱工業(yè)大學(xué)的先進生產(chǎn)技術(shù)中心(AMMTEC) 努力開發(fā)CAD/CAM/CAE的綜合系統(tǒng)。 AMTEC在1992年建立。 它進口很多數(shù)控機器和大風(fēng)格的工程軟件想用其——(綜合設(shè)計工程分析軟件)裝備IBM -RISC6000工作站, 我們有條件使用塑料制品成型CAD/CAM/ CAE系統(tǒng)來設(shè)計,分析和制造塑料制品。
DEAS 是一種綜合的自動機械軟件。 它將設(shè)計,開發(fā),工程分析,塑料制品的數(shù)學(xué)仿真,數(shù)字控制程序的數(shù)字模擬功能和測試集于一體。由幾何建模,可塑性分析和圖表數(shù)值控制庫形成塑造塑料制品的CAD/CAM/CAE系統(tǒng)。 我們將設(shè)計和生產(chǎn)一套產(chǎn)品, 為長春第一汽車工作生產(chǎn)"jetta" 小汽車(產(chǎn)品材料是尼龍-66)的塑料踏板。 因為踏板的形狀錯綜復(fù)雜所以設(shè)計和制造模型是困難得, 因此我們決定對設(shè)計,分析和NC編程使用I-DEAS。
I-DEAS固定模型是I-DEAS重要的零部件。 它為幾何建模和詳細(xì)機械設(shè)計提供一套功能強大的工具。實體幾何學(xué)模型(CSG)的建立方法是有建設(shè)性的。 她的過程如下:
基本元素,例如體,腔,球,等等。
通過使用一元布爾運算安排基本要素。 因此可能建立錯綜復(fù)雜的幾何體。 使用這些步驟,踏板的三維幾何學(xué)模型可能被建立。計算機圖形使設(shè)計者能夠通過在屏幕上旋轉(zhuǎn)對象而研究它,放大物體的細(xì)節(jié)而詳細(xì)觀察它。
完成塑造的初步設(shè)計, 我們能進行一次注入的模擬通過使用有限元法的可塑性分析的家庭評價設(shè)計。I-DEAS提供創(chuàng)建有限元的幾何學(xué)形狀的3 種方法。
(1)從固定模型庫創(chuàng)建。
(2)從庫自行創(chuàng)建。
(3)從其他計算機輔助設(shè)計系統(tǒng)創(chuàng)建。
因為產(chǎn)品模型化已經(jīng)創(chuàng)建在固態(tài)模型的庫里,我們能使用這種優(yōu)先的方法避免重建。 在選擇要素,建立要素,建立澆口并且檢查模型之后,我們能創(chuàng)建用來進行可塑性分析的有限元模型。 在這種設(shè)計過程中,決定在哪里確定澆口是困難。我們能看見這塊踏板是細(xì)長的。 根據(jù)普通概念,澆口應(yīng)該在產(chǎn)品的中間確定。 如果這種設(shè)計被采用,焊接線將形成。因此產(chǎn)品的機械力量將被降低。在實際使用中,產(chǎn)品中間將承擔(dān)很重的力,因此在產(chǎn)品的中間確定澆口是不安全。 最后我們在產(chǎn)品頂上確定澆口保證產(chǎn)品的機械功能。 在這種設(shè)計過程中流動的方向?qū)⒃谒茉爝^程中一致, 并且機械性能可能得到保證, 但是因為流動的路線很長使流體的溫度下降的很多,流體的流動性將變壞。 因此提高入口的壓力充滿型腔是必要的,但是提高在一定范圍內(nèi)受限制,因此型腔不能被完全充滿是可能的。 當(dāng)我們模擬注射的過程時,最初結(jié)果總不合理:即型腔的壓力超過注入噴射提供的壓力。在分析之后,我們修改注射參數(shù)。 注射的溫度和塑料流動性被提高,因此流體的流動性變好。 通過修改,結(jié)果非常令人滿意。我們看見從澆口到最遠的流動時間是4.81秒。 分析結(jié)果的壓力和溫度也在正常范圍里。 在實際塑造過程中,我們根據(jù)分析結(jié)果采用相應(yīng)步驟,因此合格的產(chǎn)品被生產(chǎn)出來。I-DEASGNC是一種新的基于圖表的數(shù)控編程工具。 GNC系統(tǒng)有建立和操作復(fù)雜表面要素的函數(shù)的功能。 我們也能使用在可塑性分析過程中使用的同一事物的方法 即:幾何學(xué)模型從立體幾何學(xué)模型化庫里得到。 此后我們使用一套詳細(xì)的參考書確定機器加工的過程和參數(shù), 像切割工具,生產(chǎn)方向和生產(chǎn)步驟等等,系統(tǒng)將展示生產(chǎn)過程。 同時,產(chǎn)生包括全部生產(chǎn)信息但是不能被NC機器直接區(qū)別的刀具坐標(biāo)文件, 因此后置處理是必要的。GNC的后置處理不同于正常得后置處理。 正常的后置處理使用特別的原則。 目前,隨著NC 技術(shù)的迅速發(fā)展, NC系統(tǒng)的數(shù)量變得越來越多。傳統(tǒng)后置處理只適用于專用機床,這不能滿足目前的需要。 GNC 體制使用普遍原則。 通過職能工具文本宏觀處理器(TMP),用戶能輕易的安排適合各種機器用行的程序。 根據(jù)生產(chǎn)成型和我們擁有的FANUCⅡ系統(tǒng)的特點, 我們編制3軸的后置處理程序用來確定刀具標(biāo)準(zhǔn)切削位置文件。 結(jié)果作為標(biāo)準(zhǔn)ISO代碼被直接反饋到數(shù)控機床的計算機上, 并且實際機器加工的效果非常好。
結(jié)論
(1)CAD/CAM/CAE的綜合改變了傳統(tǒng)生產(chǎn)塑料制品的方法。 用戶能利用計算機修改并且優(yōu)化這種產(chǎn)品的造型和生產(chǎn)。 從而提高了效率,減少了錯誤。
(2)通過采用CAD/CAM/CAE,設(shè)計和生產(chǎn)模型的時間被急劇的縮短。 費用也減少了,產(chǎn)品的質(zhì)量得到改進。
(3)I-DEAS軟件是包括幾何學(xué)模型化的CAD/CAM/CAE軟件系統(tǒng), 包括可塑性分析和圖表數(shù)值控制,功能強大而且實際使用價值很高。
引用
1. 李德清 肖景榮。 塑料注入成型的計算機輔助設(shè)計技術(shù),塑造工業(yè)。 1989年第十二期。
2. 科倫計算機控制制造系統(tǒng)。麥格勞-希爾伯克公司 1983年
3. 烏爾里-克萊伯 計算機集成制造技術(shù)和系統(tǒng)。 馬賽洛德克有限公司, 1984年。
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