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Intelligence and Automation CAD Soft Wares
With advancement of technology and high一speed development of world,Upgrade and innovation of Products are speeded up. No matter what industrial Products and appliance,are mostly molded by mold. Therefore,Plastic Parts’ design advances higher demands for periods and Precision of mold design and Manufacture . Because mold design depends on designers’ experience and Knowledge completely by traditional CAD soft wares ,50 efficiency and quality can’t completely satisfy the demands of mold development. So intelligence and automation are very important in mold design .This issue Has joined the expert system to mold design,and developed an intelligentzed Injection mold design system .Basing on the Plastic Parts’ information,the System can implement automatically reasoning and analysis by the interrelated
knowledge,and select an relevant model from the model base,then rebuild the model by Parameterized technology,finally finish the design Process of injection mold .The entire design Process is completed by computer automatically without the calculation of designers,which decreases flaws caused by lack of experience of mold designers,and helps to avoid mistakes and improve efficiency and quality of mold design .This Paper summarized the design knowledge of injection mold’s side action; Then builds knowledge base suing the hybrid representation of frame
representation and ruler representation :and introduces the Principles ,Processed method of compute automatic design system for side action in detail :Taking the best quality of Plastic Parts and highest efficiency as main purpose ,this paper finally develops side action :and also builds the graph library of side action using Parameterized technology based on Solid works .In information management system,Plastic Parts are decaled with in aspect of shrinkage and draft,which will make model、more Precision for the next design .An actual Process of the mold design for atypical Plastic Part has been demonstrated,which shows that the idea of system is feasible and this system can be used expediently to satisfy the demands of mold design. This paper also investigates menu and interface of this software,and finally Designs a laconic ,intuitive and manipulated friendly interface for injection mold design in order to make this software more acceptable to users.
Mold Cavities and Cores
The cavity and core give the molding its external and internal shapes respectively, the impression imparting the whole of the form to the molding.We then proceeded to indicate alternate ways by which the cavity and core could be incorporated into the mold and we found that these alternatives fell under two main headings,namelythe integer method and the insert method.Another method by which the cavity can be incorporated is by means of split inserts or splits.
When the cavity or core is machined from a large plate or block of steel,or is cast in one piece,and used without bolstering as one of the mod plates ,it is termed an integer cavity plate or integer core plate. This design is preferred for single-impression molds because of characteristics of the strength,smaller size and lower cost. It is not used as mush for multi-impression molds as there are other factors such as alignment which must be taken into consideration.
Of the many manufacting processes available for preparing molds only two are normally used in this case. There are a direct machining operation on a rough steel forging or blank using the conventional machine tools, or the precision invstment casting technique in which a master pattern is made of the cavity and core. The pattern is then used to prepare a casting of the cavity or core by a special process.
A 4.25%nickel-chrome-molybdenum steel(BS 970-835 M30) is normally specified for integer mold plates which are to be made by the direct machining method.
The precision investment casting method usually utilizes a high-chrome steel.
For molds containting intricate impressions, and for multi-impression molds, it is not satisfactory to attempt to machine the cavity and core plates from single blocks of steel as with integer molds. The machining sequences and operation would be altogether too complicated and costly. The insert-bloster assembly method is therefore used instead.
The method consists in machining the impression out of small blocks of steel.These small blocks of steel are known,after machininf, as inserts, and the one which forms the male part is termed the core insert and, conversely, the one which forms the female part the cavity insert. These are the inserted and securely fitted into holes in a substantial block or plate of steel called a bloster. These holes are either sunk part way or are machined right through the bolster plate. In the latter case there will be a plate fastened behind the bolster and this secures the inserts in position.
Both the integer and the insert-bolster methods have their advantages depending upon the size, the shape of the molding, the complexity of the mold, whether a single impression or a multi-impression ;old is desired,the cost of making the mold, ect. It can therefore be said that in general, once the characteristics of the mold reqired to do a particular job which have been weighed up, the decision as to which design to adopt can be made.
Some of these considerations have already been discussed under various broad headings, such as cost, but to enable the reader to weigh them up more easily, when faced with a particular problem, the comparison of the relative advantages of each system is discussed under a number of headings.
Unquestionably for single impression molds the integer design is ti be preferred irrespective of whether the component form is a simple or a complex one. The resulting mold will be stronger, smaller, less costly, and generally incorporate a less elaborate colling system than the insert-bolster design. It should be borne in mind that local inserts can be judiciously used to simplify the general manufactureof the mold impression.
For multi-impression molds the choices is not so clear-cut. In the majority of cases the insert-bolster method of construction is used, the case of manufacture, mold alignment, and resulting lower mold costs being the overriding factors affecting the choices. For compenents of very simple form it is often advantangeous to use one design for one of the mold plates and the alternative design for the other. For example, consider a multi-impression mold for a box-type compenent. The cavity plate could be of the integer design to gain the advantages of strength, thereby allowing a smaller mold plate, while the core plate couls be of the insert-bolster design which will simplify machining of the plate and allow for adjustments for mold alignment.
The Injection Molding
Injection molding ( British Engish : Molding ) is a manufacturing process for producing parts form both thermoplastic and thermosetting plastic materials.Material is fed into a heated brarel, mixed, and forced into a mold cavity where it cools and hardens to configuration of the mold cavity. After a product is designed, usually by an industrial designer or an engineer, molds aer made by a moldmaker ( or a toolmaker ) from metal, usually either steel or aluminium, and precision-machined to form the features of the desired part. Injection molding is widely used for manufacturing a varitey of parts, from the smallest compenent to entire body panels of cars.
Injection molding machines consist of a material hopper, an injection ram of screw-type plunger, and a heating unit. They are also known as presses. They hold the molds in which the compenents are shaped. Presses are rated by tonnage, which expresses the amount of clamping force that the machine can exert. This force keeps the mold closed during the injection process. Tonnage can vary from less than 5 tons to 6000 tons, with the higher figures used in determined by the projected area of the part being molded.This projected area is multiplied by a champ force of 2 to 8 tons for each square inch of the projected area. As a rule of thumb, 4 or 5 t/in can be used for most products. If the plastic material is very stiff, it will require more injection pressure to fill the mold, thus more clamp tonnage to hold the mold closed. The required force can also be determined by the material used and the size of the part, larger parts require higher clamping force.
Mold or die are the common terms used to describe the tooling used to produce plastic parts in molding.
Traditionally, molds have been expensive to manufacture. They were usually only used in mass production where thousands of parts were being produced. Molds are typically constructed from hardened steel, pre-hardened steel, aluminium, and/or beryllium-copper alloy. The chioce of material to build a mold from is primarily one of economics. Steel molds generally cost more to construct, but their longer number of parts made before wearing out. Pre-hardened steel molds are less wear resistant and are used for lower volume requirements or large compenents. The steel hardness is tyoically 38-45 on the Rockwell-C scale ( HRC). Hardened steel molds are heat treated after machining. These are by far the superior in terms of wear resistance and lifespan. Typical hardness ranges between 50 to 60 Rockwell scale. Aluminium molds can cost substantially less , and when designed and machined with morden computerized equipment, can be economical for molding tens or even hundreds of thousands of parts. Beryllium copper is used in areas of the mold which require fast removal or area that see the most shear heat generated. The molds can be manufactured by either CNC or by using Electrical Discharge Machining processes.
Standard two plates tooling: core and cavity are inserts in a mold base – “Family mold ” of 5 different parts.
The mold consists of two primary compenents, the injection mold ( A plate ) and the ejector mold ( B plate ). Plastic resin enters the mold through a sprue in the injection mold, the sprue bush is to seal tightly against the nozzle of the injection barrel of the molding machine and allow molten plastic to flow from the barrel into the mold , also known as cavity. The sprue bush directs the molten plastic to the cavity images through channels that are machined into the faces of the A or B plates. These channels allow plastic to run along them, so they are referred to as runners. The molten plastic flows through the runner and enters one or more specialized gates and into the cavity geometry to form the desired part.
The amount of resin required to fill the sprue, runner and cavities of a mold is a shot. Trapped air in the mold can escape through air vents that are grinded into the parting line of the mold. If the trapped air is not allowed to escape , it is compressed by the pressure of the incoming material and is squeezed into the corners of the cavity , where it prevents filling and causes other defects as well . The air can become so compressed that it ignites and burns the surrounding plastic material. To allow for removal of the molded part from the mold , the mold features must not overhang one another in the direction that the mold opens , unless parts of the mold are designed to move from between such overhangs when the mold opens ( utilizing composnents called Lifters ).
外文資料翻譯
智能型模具CAD系統(tǒng)
隨著科學技術(shù)的不斷進步和社會的高速發(fā)展,產(chǎn)品更新?lián)Q代越來越快。無論是工業(yè)產(chǎn)品還是家電產(chǎn)品,大多數(shù)應(yīng)用模具成型。因此,對模具的設(shè)計和制造提出了更高的要求。傳統(tǒng)的模具CAD軟件完全依賴于設(shè)計人員的經(jīng)驗和知識,設(shè)計效率和設(shè)計質(zhì)量很難滿足模具發(fā)展的要求。因此在模具設(shè)計的過程中,使用智能型模具CAD系統(tǒng)顯得尤為重要。本課題將專家系統(tǒng)技術(shù)引入到模具設(shè)計中,開發(fā)了智能注塑模具設(shè)計系統(tǒng)。該系統(tǒng)利用塑件產(chǎn)品信息,通過推理機對知識庫中的相關(guān)知識進行自動推理、分析、決策,得出模具結(jié)構(gòu)總體方案以及相關(guān)尺寸,從模型庫中選出相應(yīng)模型,通過參數(shù)化驅(qū)動重新建模,最終自動完成注塑模具設(shè)計過程。本文在前面幾屆研究生開發(fā)的基礎(chǔ)上,總結(jié)了注塑模具斜銷側(cè)向分型與抽芯機構(gòu)設(shè)計知識,結(jié)合模具設(shè)計知識的特點,利用框架/規(guī)則混合表示方法建立了注塑模具側(cè)向分型與抽芯機構(gòu)設(shè)計知識庫;詳細介紹了斜銷側(cè)向分型與抽芯機構(gòu)的設(shè)計理論、過程和方法:系統(tǒng)以成型制品質(zhì)量最優(yōu)、效率最高為目標,最終形成了斜銷側(cè)向分型與抽芯機構(gòu)的計算機自動設(shè)計系統(tǒng)。以Solid works為平臺,采用參數(shù)化技術(shù)建立了側(cè)向分型與抽芯機構(gòu)的實體模型庫。系統(tǒng)通過推理機對知識的推理,模型的調(diào)入,參數(shù)的驅(qū)動,實現(xiàn)側(cè)向分型與抽芯機構(gòu)的自動化設(shè)計。系統(tǒng)還對塑件模型進行了收縮率和脫模斜度的處理,實現(xiàn)了從塑件模型到模具模型的轉(zhuǎn)化,使設(shè)計結(jié)果更加準確、嚴謹。通過典型制品的模具設(shè)計實例,演示了系統(tǒng)的設(shè)計過程。結(jié)果表明,系統(tǒng)設(shè)計思路正確,操作方便簡單,運行可靠,適合模具設(shè)計要求。同時,本文在系統(tǒng)軟件菜單、界面、設(shè)計思路等方面也做了大量的工作,使本系統(tǒng)軟件更加人性化,具備了良好的實用性。
型腔和型芯
模具的型腔和型芯分別形成塑件內(nèi)部和外部形狀,型腔形狀決定了塑件形狀,接下來我們簡要說明選擇那種型腔和型芯安裝在模具中。這些方式可以歸納為兩大類,即整體形式和鑲拼形式。另一種組成型腔的方式是加入拼塊或滑塊。
當型腔或型芯由一塊大的鋼板或鋼塊加工而成,或是鑄成一體,不需要使用支承件而形成一塊模板時,就構(gòu)成整體式模腔板或型芯板。這種設(shè)計因具有強度高,尺寸小和成本低的特性,而主要應(yīng)用在單型腔模具中。整體式型腔和型芯一般不用在多型腔模具中,因為多型腔模具設(shè)計時必須考慮一些其他因素,例如安裝組合鑲件等。
在模具制造的眾多方法中,用于加工整體式型腔板或型芯板的方法主要有兩種:使用傳統(tǒng)機床對粗鍛鋼材料直接加工,或是利用精確的熔模鑄造技術(shù)將坯料加工成型腔和型芯。用于制造型腔和型芯的坯料經(jīng)常需要特殊工藝的處理。
通常,4.25%的鎳鎘鉬合金鋼是生產(chǎn)整體式模板的指定材料,選用這種材料時采用直接的機加工方式。
精確的熔模鑄造常常用來加工高鉻鋼。
對于成型部位復雜的模具和多腔模具,也像整體式模具那樣用一塊鋼材加工型腔和型芯并不容易。如果采用整體式結(jié)構(gòu),則加工順序和操作過程將變得非常復雜,成本也高,因此鑲拼式裝配方式替代了整體式。
鑲拼式型腔由小鋼塊加工而成。加工后的小鋼塊作為鑲件,形成型芯部分的稱為型芯嵌件,相反地,形成型腔部分的成為型腔嵌件。然后,把這些鑲件牢固地安裝在被稱為墊板的孔中,墊板由實心鋼板或鋼塊加工而成。這些安裝孔有的是由墊板的局部凹陷形成,有的是在墊板上直接加工而成。在后一種方式中,墊板后部還要增加一塊模板,起加固作用,確保鑲件安裝到位。 整體式和鑲拼式結(jié)構(gòu)均有優(yōu)點,這取決于塑件尺寸和形狀,模具的復雜程度,所需的是單型腔模具還是多型腔模具以及模具制造成本等。通常,塑件的形狀,尺寸等特性確定后,采用哪種形式的型腔和型芯就已經(jīng)確定了。
在不同的章節(jié)中,我們已經(jīng)討論過型腔和型芯的安裝方式所涉及的問題,例如成本等,但為使讀者在處理特殊問題時更容易知道重點所在,我們將用一定的章節(jié)再次討論每種結(jié)構(gòu)優(yōu)缺點的對比。
毫無疑問,對于單型腔模具,無論是簡單還是復雜,整體式型腔是首選方式。若選擇整體式,則模具的強度高,體積小,成本低,而冷卻系統(tǒng)的設(shè)計卻比鑲拼式簡單,方便。設(shè)計時需要常記于心的是,適當?shù)厥褂描偧梢院喕>咝颓坏募庸ぶ圃祀y度。
對于多型腔模具,選擇哪種方式不是很明顯。大多數(shù)型腔模具采用鑲拼式結(jié)構(gòu),這種結(jié)構(gòu)加工簡單,裝配容易,模具成本低,這些是影響選擇哪種結(jié)構(gòu)形式的重要因素。一種非常簡單且具有很多優(yōu)點的設(shè)計是采用一種形式設(shè)計模板,而采用另一種形式設(shè)計模具的其他部分。例如,采用箱形組件設(shè)計多型腔模具。型腔板設(shè)計成小型整體式模板,以滿足模具高強度的要求;型芯板則設(shè)計成鑲拼式,可因簡化模板加工過程,并且能根據(jù)模具需要進行調(diào)整。
注塑成型
注塑成型是將熱塑性和熱固性塑料加工成零件的制造過程。材料被入加熱筒中,混合后壓入模腔,冷卻硬化成它們的形狀。通常工業(yè)設(shè)計師或工程師設(shè)計完一個產(chǎn)品后,模具制造師(或工人)就會用金屬,通常為剛或鋁,制造模具,且精加工以達到理想效果。從最小的部件到整個汽車的面板,注塑成型廣泛應(yīng)用于各種零部件的制造。
模具注塑機由一個料斗、注射活塞或螺旋式活塞以及一個加熱裝置構(gòu)成。他們也被稱為壓力機,內(nèi)含零部件形成的模具。壓力機以噸位來衡量,表示機器可以施加的鎖模力。鎖模力保障模具在注塑的過程中是封閉的。噸位可以從少于5t到6000t,較高的噸位應(yīng)用于相對少量的生產(chǎn)中。需要多少鎖模力取決于零件的投影面積。每平方英寸的投影面積要乘以2-8t的鎖模力。根據(jù)經(jīng)驗法則,每平方英寸的投影面積對應(yīng)4-5t的鎖模力,即可應(yīng)用于大部分產(chǎn)品。如果塑料很硬,它需要更多的壓力來填充模具,因此需要更多的鎖模力來保障模具的封閉性。所需的壓力也取決于使用的材料及零件的大小,越大的零件需要的鎖模力越大。實際的注塑模具如所示。
注塑或沖模是描述注塑中用于制造塑料零件的工具的常用術(shù)語。
傳統(tǒng)上,模具制造一直很昂貴。它們通常只使用于成千上萬的大批量零件的生產(chǎn)。模具通常由淬火鋼、預硬鋼、鋁或鈹銅合金制成。選擇制造模具的原料首先要考慮經(jīng)濟因素,鋼模具成本較高,但使用壽命較長。在用完之前,鋼模能制造更多的零件,這會抵消最初的高成本投入。預硬鋼模具不耐磨,適用于小批量生產(chǎn)或制造較大的零件。鋼的硬度通常是38-45HRC,淬硬鋼模具加工后要進行熱處理。這類模具在耐磨性和使用壽命方面具有較強的優(yōu)勢,其典型的硬度范圍介于50-60HRC之間。鋁模具成本大幅度減少,利用現(xiàn)代計算機設(shè)備設(shè)計與加工,對于注塑成千上萬個零件來說是經(jīng)濟的。鈹-銅合金使用于制造需快速去熱或消除產(chǎn)生的熱能的模具。這類模具可利用數(shù)控加工或電火花加工來生產(chǎn)。
標準的兩板模具包括:型芯和型腔所在的模具內(nèi)部,其余的則為五個不同的典型模具結(jié)構(gòu)。
模具有兩個主要部分構(gòu)成:合模(A板)和出模(B板)。塑料樹脂通過注塑模具澆道進入模具,澆口套密封緊接在注塑機注射料筒的噴嘴處,讓熔化的塑料從料筒流到模具,也就是型腔。澆口套通常加工成A、B板的管道引導熔化的塑料流向型腔。這些管道使塑料沿著他們流動,進入幾何形狀的型腔,形成所需的零件。
填充模具澆口套、流道和型腔的大量樹脂是一瞬間。模具里積存的空氣可以通過模具分型線的通風口排出。如果積存的空氣不能排出,進料的壓力會把它們擠壓到型腔的角落,這會妨礙填充并導致其他問題。空氣壓縮到一定程度會被引燃,導致周圍的塑料燃燒。為了消除成型模具某個部分,模具不能彼此懸垂于模具打開的方向,除非該模具部分設(shè)計成模具打開時懸空一定(所用的組件稱為側(cè)抽芯)。