型星齿轮的注塑模具设计【一模四腔】【说明书+CAD】
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图书分类号：密 级：毕业设计附件外文及翻译学生姓名学院名称专业名称机械设计制造及其自动化指导教师年5月18日 新一代注塑技术 外文出处 University Hospital Zurich, Zurich, Switzerland 摘要:本文介绍新一代瓶坯注塑技术的特点以及通过一个循环所实现的瓶性能。这一循环使瓶胚冷却不再需要机械手和引出板,而是瓶胚直接在模芯上冷却,在进一步通过2.5 注射循环冷却之后被顶出。这使制件的冷却得以改进,从而大大提高了每个阴模的产量。从工作单元去掉机械手减少了空间需求,并大大简化了系统。 关键词: 注塑模具设计 循环速度 1、概述 转位瓶胚注塑技术是在Husky 注塑系统双压板机器设计发展起来的。该系统有一个四面动压板绕横轴旋转。每一面配一个典型的半冷塑模。原模系统是一个48 阴模,从而提供192 个模芯。定压板上装有一个标准的热流道和半阴模。 本系统配备一个标准两级注塑装置,该装置有一个120 毫米挤塑机和120 毫米注射压料塞,注射压料塞上有一个机筒头和分配阀连接两级。用目前的瓶胚设计,目标重量是47.3 克瓶胚,从而注射量为2270 克。两42 个不同的聚对苯二甲酸乙二醇酯螺杆用于本系统,每个都取得了可以接受的效果。 当机器循环时,塑料首先注射到A 面。由于瓶胚要留在模芯上,瓶胚在开模不需要象在传统系统上那么硬。因此,循环的绝大部分冷却可以在随后的机器循环期间从闭模转到在模芯上冷却。然后循环需要一个非常短的冷却期间以允许模具释压,注射和保压也是如此。当开模时,这一面转位到压板的顶部表面,然后塑料在B 面注射。当D 面到达前端时,此时A 面在压板的底部位置,顶杆在这里被启动,瓶胚被从机器卸到制件引出传送器上。注射行程对循环时间没有影响,因而可以较慢地完成。重力帮助确保制件脱离模具落下。制件落在其格端头的传送器上,造成表面擦伤的可能性较小。 在顶部、背部和底部位置,气冲成型系统对瓶胚提供表面冷却。由于瓶胚保持在模具的模芯上,它们还容易在内表面得到传导冷却。总体上讲,瓶胚的整体温度比它在传统模塑系统和冷却引出板中呆类似的时间要冷。 2、瓶性能 我们分析转位系统的一个重要方面是拿这种系统生产的瓶胚制造出来的瓶的性能与传统工作单元上生产的类似瓶胚制造出来的瓶相比较。表1 给出从进行的试验中得出的比较数据。 转位瓶胚的性能在强度测试中一直较好,这是因为改进的浇口质量允许材料在瓶内较好地分布,没有迹象表明使用这种系统在瓶的任何地方结晶度升高。生产的转位样品可能平均较轻,因为它们的重量分布要紧密得多。 3、系统的特点 这种托坯最明显的好处是需要的模内冷却时间减少了,从而减少了整个循环的时间长度。目前,这种系统用最大壁厚为4 毫米的47.3 克瓶胚工作。这种瓶胚加工循环时间测定为22.5 秒,对于一个阴模系统来说是最佳的了。转位48 阴模系统实现14.2 秒的循环,能取得较好的商业质量结果。图2 给出循环细分的比较情况。 旋转塔台不再需要机械手。这样,就减少了由传统系统上机械手故障造成的干扰告警和服务停机时间。制件顶出现在不是机械循环时间的一个因素。随着消除机械手需要的开模间隙减少了,随着模具行程的减少还提高了空循环速度。 系统的另一个好处是需要的地板面积减少,以及由于没有机械手和引出板冷却系统,系统的可靠性得以提高的潜力。预计不发生机械手故障的整个系统可靠性可允许系统可用性提高30%。转位系统的地板面积只有传统48 阴模系统所需面积的55%。与之相伴的还有每英尺地板面积的产量进一步提高。 使用转位系统使瓶胚的浇口质量得到改进。在阀浇口区冷冻之后,瓶胚在较短时间内与阀杆的热点接触,因为瓶胚在阴模内的冷却时间被大大减少。去掉这一热源就消除一个结晶源。除了较好的视觉效果,还导致浇口区更结实,从而使得整个瓶侧壁区更好,及有更多的机会减轻基础区瓶胚的重量。 瓶胚留在模芯较长时间。与标准瓶胚注塑系统相比,整个瓶胚冷却得到改进。在一个传统的机械手冷却板内,制件遇到被冷却的管表面就会收缩,这样热传递就不完美。在转位系统中,制作在模芯上收缩,从而保持热传递,在被顶出时,转位瓶胚的全面整体温度比瓶胚从传统系统的引出位置取出时要低。还有,对于目前的瓶胚设计来说,不向颈模圈区供应冷却水,在顶出时仍比标准系统要冷得多。对于一个典型的成型系统来说,冷却该区能限制循环。 转位系统用几种不同材料及测试的两种不同材料和两种不同的聚对苯二甲酸乙二醇酯螺杆设计,可以看到乙醛(AA)量一直较低。与注射量相比这一循环时间对注射装置提出非常高的要求,注射装置连续不断地冲刷没有一点滞留时间的螺杆。 由于模具内的峰值阴模与两个不同的螺杆相符,并与不同的加工设置一致,乙醛量到底有多低主要原因在于模具集料管。用目前的模具可以看到的第二个好处是有非常好的重量分布,从而允许在目前制件规格的允差内把整个制件的重量降到最低程度。 4、介绍IKB-MOULD设计的基础注塑模组成的分析处理分为两部份：设计的首字母和详细的设计，初期的设计决定模具的组成，例如模具类型、型腔数、流道的类型、浇口类型等。详细设计是型芯型腔的组成、浇注系统的设计、冷却和排气系统的设计、集成分析和最后的草图。他们需要什么,分析什么是好的CAIMDS的发展方向。 他们所拥有的客户对产品的要求。包括产品外形和详细的尺寸。 一个已经设计好的模具方案这个方案包括模具设计的初级部分和标准部分举例来说模具设计的基础动模和定模的一部分填充和顶出的一部分。注塑模具设计的行业知识等。 设计者从专业知识中得出模具设计的设计计划和详细步骤这些知识包括原材料的选择型腔型芯分型面的规划和其他相关细节的介绍。 他们所想要得一个先进的交互式模具设计环境。模具设计是由一系列细小的环节组成的设计程序。这些程序通常需要将已有的模块和制作好的模件装配好。这些模具设计系统不需要自动完成尤其是对切口部分特征比较复杂的产品。先进的交互式程序善于整合自动化运算法则和有经验的设计者的在线知识交流。 标准件/早期设计部分/组装/产品管理。一个注塑模具在其它注塑模里相同的形状尺寸分别有型腔型芯。这些部分与注塑模产品无关。他们使用在不同模具中重复使用的大概标准。 有用的工具包括实体设计和分析计算在模具型腔型芯中的设计。型芯和型腔的外形和大小直接影响模具产品。这些部分也是模具设计中相当重要的环节。他们的几何形状要求可能相当苛刻。因此一些模芯设计工具的发展方向基于自动生成模具型芯交互作用是相当有用的。 组装设计在传统的CAD/CAM设计系统中模具的实体形状被当作几何图形储存模型在一个三维空间以边和面的形式生成。象这样的一个以严密的几何计算表现的视觉外形可以完成工程分析和模拟。但是这种工作方式不适合设计高层数据和产 品的几何实体外形的关系。 模具设计者更喜欢装配环境的设计而不是一种简单的固体模型环境。这个方案被 Ye et al 提出。 5、循环速度的限制因素 在整个循环期间对转位循环的影响因素可以分为五个组成部分: (1)机器空循环时间(这是完成开模、旋转塔台90 度,闭模和为注射做准备的循环的时间); (2)阴模充料时间; (3)为避免正冷却的制件形成凹陷的保压要求; (4)模内冷却以使模具从保压期间要求的合模力吨数中释压; (5)在顶出时瓶胚的大量热造成的表面热以及热再生,以避免后续处理期间制件被刮伤或有粘性。 系统的机器空循环时间被优化。模具不必开那么多,以允许转位旋转,象传统系统为允许机械手进入模具区所要求的那样,从而减少了开模和闭模时间。转位速度也比机械手进去,转移制件和机械手再出去快。目前4.3秒的机器空循环已经充分优化,改进的余地很小。 如果注射装置尺寸过小,生成熔体可能是一个限制因素。已经在循环速度低达11.6 秒,用2280 克注射量的0.82IV 树脂测试过目前120 毫米的螺杆可接受的塑炼能力。这时没有剩余的滞留时间,这样循环将受螺杆性能限制。 充料和保压时间大约为9 秒。现正在做试验以量化最佳的充料速度和保压外形。 冷却0.5 秒可以实现模具释压,但目前的工艺需要冷却1.3 秒,循环目前受到在制件上形成凹陷限制。这受到包装数量、保压压力和开模的速度的影响。由于转位循环的冷却时间非常短,瓶胚遇到阴模壁收缩的时间非常少。正在研究改进这方面的循环性能的机会。 目前出模时的瓶胚温度将允许循环时间远远少于13 秒,如果仅这一方面是循环的限制因素的话。 6、瓶胚设计的考虑因素 根据最初比较原型系统中使用的瓶胚以及为促进使用转位方法减少转位循环而对各种瓶胚设计做的试验。因此,实施一种转位系统而非较传统的成型方法的决定是由于其他许多考虑因素)转位系统要求四套制件模芯,这样模芯的复杂性以及由此导致的整个模具成本是选择的一个因素。其他因素包括生产能力要求、可用的地板面积、资本成本。 The Fresh Generation Injection Mould TechniqueAbstract : The original is introduced fresh generation vase earthen brick mould plastics technique distinguishing feature along with by means of the vase performance that the cycle was achieved That this cycles causes an a jar of embryo become cool not needing manipulator and the lead-out plank again , but is an a jar of embryo directly is living that the standard becomes cool on the rush pith , and is living further by means of 2.5 to inject after the cycle cooling being come out by the peak This causes the finished piece cooling may improve , thereby lift every one the overcast standard yield enormously Decreased the demand in room through the work cell gets rid of the manipulator , and simplify the system enormously Keyword : Injection mould design Cycle velocity 1、Summary The indexing vase embryo mould plastics technique is designed the development at twin teeterboard machinerys of Huskys mould plastics system Ought to systematically there be an all sides to stir the teeterboard to coil the cross axle to circle Each one section is matched somebody with somebody a type semi to cool to mold the standard The master stamper systematically is 48 an overcast standard , thereby supplys 192 standard rushs pith Fiing teeterboard jacket possess criterion heat flux a road and semi an overcast standard Standardized two steps of moulds plastics units are equipd to this system , and that unit possessone 120 millimeters to pack the engine molding and 120 millimeters to inject the pressure stuff to squeeze in , and injecting along the Great Wall the pressure stuff possess engine a thick tube-shaped head and a distribution valve to join two grades Designing in the way of the vase embryo at the moment , target weight is the 47.3 grams vase embryos , thereby injecting amount is 2270 grams Two 42 differences is gatherd being used a system to the benzol two methanoic acid glycol ester studs , and every one wholly acquireed the effect that may be receiveed When the machinery cycles , the plastic material first of all injects up A Since the fact that the vase embryo will remain the standard rush pith on , the vase embryo is living to turn on the standard not necessaries , and that traditional system goes up such as being living is stiff in that way Hence , the machinery cycle that the overwhelming majority cooling may be living soon afterwards perioc through shuts the standard revolves up to become cool on the rush pith at the standard Afterwards the cycle needs an extraordinary brief cooling perioc in order to permit the pattern to elucidate the pressure , injects and defends and to be getting near also is such in this way Afterwards the plastic material are living Bs surface is injected on this peak ministry face that the teeterboard was reachd in the indexing on one section when turning on the standard As D before arrival when the extremity , now A is living teeterboard base place , and the push rod is switched on here , and the vase embryo is unloaded the finished piece through the machinery and leads to on the conveying utensil Injecting the stroke adjust the cycle time not effect , as a result may complete more slowly Gravitational force help is guarranteed that the finished piece breaks away from that the pattern drops secondly The finished piece drops such the curtain squares formed by crossed lines tip conveying utensil on , and the probability that creates the surperficial gall is littleer A ministry is living 、Gas dashing systematic twin vase embryo of forming supplys the face and becomes cool the place of back and base Since the fact that the vase embryo maintains the pattern standard rush pith on , the face obtains the conduction cooling included they are still convenient Says in the total , the entire temperature of vase embryo than it is living traditional compression molding system and cooling leads to in the plank to stay analogous time will cool 2、The Bottle Function Significant respect that we analyse the indexing system analogous a of jar of vase that the embryo was manufacture out that to be the performance takeing this kind of vase that the vase embryo that the system was gived birth to was manufacture out against traditional work gived birth to on the cell one another contrasts The comparand that obtaines in the eperiment that the table 1 is give out through is underway is depenied on The indexing vase embryo performance is living and is better always in the intensity quiz , and this is better distributing for the runner quality which improved permits the stuff to be living inner place the vase , and does not there is the indication to make known that use this kind of system is living whatever space crystallinity of vase and ascendes The indexing specimen gived birth to is probably equally light , for their weight distributions is to be much inseparable .、This kind of system distinguishing feature Inner place the standard that to support with the hand the obviousest advantage of earthen brick is needs the cooling time decreased , thereby decreased entire time length that cycles At the moment , this kind of system employ the largesttest breastwork thickly act as 4 millimeters the 47.3 grams vase embryos do This kind of vase embryo process cycle time ascertains by measuring to 22.5 seconds , was optimum as to the overcast standard system Overcast standard system implementation 14.2 seconds of indexing 48 cycle be able to be acquireed the better trade quality killing The picture 2 is give out the cycle subdivided comparing situation Circling the control tower does not need the manipulator again Like this , therefore decreased from the tradition system to go up the jam that the manipulator block created is giveed an alarm and the service ceases engine time The finished piece peak has ariseed to be living not to be the inflexible cycle time the element Decreased in the standard the turning on gap that needs in the wake of removing the manipulator , in the wake of decreasing of pattern stroke still lift empties cycle velocity Systematic another advantage is the floor area that needs decreases , along with thanks to does not there is manipulator and lead-out plank cooling system , latent capacity that the dependability of system may be liftd Calculate in advance entire systematic dependability that therefore the manipulator obstructs does not happen permit the systematic usability to lift 30% Merely traditional 48 55% of overcast areas that the standard system requires of indexing system floor area Against the person who one another accompanies the yield that still possess per foot of floor area lifts further.Employ the indexing systematically to cause an a jar of embryo runner quality obtain the modification Being living , the valve runner district is freezed afterwards , the vase embryo is living brieflyer time inner place the heatpoint contact against the valve staff , for the cooling that the vase embryo is living inner place the overcast standard time by enormously decreases Geing rid of this heat source removes a crystal source Except for better vision effect , still causes that the runner district is more sturdy , thereby causes entire a of jar of side wall district better , and possess the weight that even more opportunitys ease the vase embryo in base district The vase embryo to remain at the standard rush pith elderer time Systematically being contrastd against a criterion a jar of embryo mould plastics , entire a of jar of embryo becomes cool obtainning the modification Being living , tradition manipulator becomes cool inner place the plank , and the finished piece is encounter and be able to be shrinked by the tube face becoming cool , and such heat transfer is imconsummate In being living the indexing system manufactures at the standard shrinking on the rush pith , thereby maintain heat transfer , and is living when being come out , and will let drop when comprehensive entirety temperature of indexing vase embryo contrasts the a jar of embryo lead-out place through traditional system brings out by the peak .Still possesing , and designs as to the vase embryo at the moment , not to the throat standard ring district supply cooling water , being living , the peak when comeing out yet systematically will be cooled far more than the criterion Become cool that district threshold energy system cycling as to the forming system of type The distinct stuffs of indexing system in the way of some kinds reaches the difference of two kinds of distinct stuffs testing with two kinds to gather designing to the benzol two methanoic acid glycol ester studs , and may catch sight of that the acetaldehyde ( AA ) amount lets drop always against injecting amount is contrastd this cycle time adjust injects the unit proposes the very much tall demand , injects the unit constinuously scousrs not to there is a few is held up time the stud . Since the overcast standard of peak value inner place the pattern tallys with against the two differences studs , and against the difference process installation unanimously , the acetaldehyde is measured ever to possess to let drop that the main reason rests with that the pattern gathers materials the tube more Second advantage may catch sight ofin the way of the pattern at the moment is possesing the very much good weight distributions , thereby permits to be living at the moment finished piece standard allows bad inside entire finished piece weight to drop the thest least degree 4 、The injection mould design process requirementanalysis An injection mould design is composed of two steps: theinitial design and the detailed design. The initial design iscomposed of decisions made at the early stage of themould design, such as the type of mould configuration,the number of cavities, the type of runner, the type of gate and the type of mould base. The detailed design iscomposed of the insert (core/cavity) design, the ejectionsystem design, the cooling and venting component design,the assembly analysis and the final drafting. To develop a good CAIMDS, an analysis of whatthey have and what they want needs to be performed.What they have: The customers requirements for the product. Thisincludes the detailed geometry anddimension requirementsof the product. An existing mould design library. This library coversthe standard or previously designedcomponents andassemblies of the mould design, for example, themould base (the fixed half and the moving half) andthe pocket (the fixed half and the moving half). An expert knowledge in injection mould design. Expertknowledge of both initial and detailed designs forthe injection mould is obtained mainly from experiencedmould designers. Such knowledge includesmaterial selection, shrinkage suggestion, cavity layoutsuggestion and others. What they want: An intelligent and interactive mould design environment.Mould design is often composed of a series ofdesign procedures. These procedures usually requirecertain mould parts to be created and existing mouldparts to be assembled. Such a mould design environmentneed not be fully automatic, especially forcomplicated products with many undercuts. Anintelligent and interactive environment will be a goodchoice to integrate some useful automation algorithms,heuristic knowledge and on-lineinteraction by the experienced mould designer. Standard/previous designed components/assemblies(product-independent parts) management. Apart from the core and cavity, an injection mould hasmany other parts that are similar in structure and geometrical shape that can be used in other injectionmould designs. These parts are independent of the plastic mould products. They are mostly standardcomponents that can be reused in different mould designs and mould sets. Useful tools (including solid design and analysiscalculation) in the core and the cavity (productdependentparts) design. Geometrical shapes and thesizes of the core and cavity system are determineddirectly by the mould product. All components insuch a system are product dependent. Also, theseparts are the critical components in the mould design Their geometrical requirements may be complicated.Thus, some tools developed to design the core and thecavity based on partial automation and partialinteraction can be quite useful. Design for assembly. In conventional CAD/CAMsystems, moulds are represented and stored as a complete geometric and topological solid model. Thismodel is composed of faces, edges and vertices in athree dimensional (3D) Euclidean space. Such a representationis suitable for visual display and performinggeometrically computation-intensive taskssuch as engineering analysis and simulation. However,this form is not appropriate for tasks thatrequire decision-making based on high-level informationabout product geometric entities and theirrelationships. Mould designers prefer a design forassembly environment instead of a simple solid modelenvironment. This idea is also presented in Ye et al.s work 24. A design for manufacture. A complete injectionmould design development cycle can be composed ofthe mould design and mould manufacturing process.To integrate CAD/CAM into the mould design, themanufacturing features on the mould should be abstracteand analysed for the specific NC machine. Both the process plan and the NC code should beautomatically generated to enable the final designed mould to be manufactured. A design for engineering drawings. For manycompanies, the injection mould design has to be represented in the form of engineering drawingswith detailed dimensions. CAD/CAM tools that are able to automatically generate these engineeringdrawings from the final injection mould design will be useful.Based on the above analysis, our research focus is todevelop techniques to represent what they have andwhat they want.Representing what they want is actually the representationof the knowledge and injection mould object.Developing what they want means to integrate the representation with intelligent and interactive tools forthe injection mould design into a completed designenvironment. Therefore, an IKB-MOULD is proposedfor mould designers to realise the above two requirements 5、 Limitational factor of cycle velocity Is living the entire cycle perioc to the indexing what cycles the effect element may be divided into five component part : (1)Machinery emptying cycle time ( this is completeing turning on the standard 、Circles the control tower 90 degrees , shuts standard and in the interest of injects acting the ready cycle time ) ; (2)The overcast standard charges to anticipate time ; (3)The demand is getting near in the interest of averting the finished piece that becomes cool to take shape sunken guarantor ; (4)Becomes cool the pattern inner place the standard in order to cause through guarantor to be getting near perioc in the person who requires the standard the shuing force tonne figure elucidates the pressure ; (5)The vase embryo greats quantity of peak when comeing out being living warm that the face creating warms up along with warm up regeneration , in order to avert the follow-up handle perioc finished piece is fleeced the injury either is possess viscosity Systematic machinery the emptying cycle time is optimized The pattern need not turned on so manyly ,in order to permit the indexing to circle , such as the tradition systematically by permits themanipulator gos into the pattern district demand , thereby decreases turns on the standard with shuts the standard time Indexing velocity is also get in than the manipulator , and transfers finished piece and manipulator geting out quickly again The machinery of 4.3 seconds at the moment empties to cycle sufficiently to optimize , and the margin of modification is very little Unduly little in case injecting the unit dimensions , the part of the body is melted in the formation probably is a limitational factor The cycle velocity being living is leted drop to attain 11.6 seconds , in the way of 2280 be able to injecting amount 0.82IVs resin has tested at the moment 120 millimeters stud the person who may receive the plasticate capability At this moment does not there is remainder is held up time , cycles like this to accept the stud performance limit Charges the stuff with guarantors pressure time about act as 9 seconds Acting the eperiment current optimum with the quantification charges to anticipate that the velocity is getting near the external form with guarantor . Becoming cool to achieve the pattern in 0.5 second to elucidate the pressure , yet the technology at the moment need to be become cool 1.3 seconds , and the cycle is subjected to the finished piece on takeing shape the sunken limit at the moment This is subjected to packageing amount 、Guarantors pressure and effect turning on standard velocity Since indexing cycle cooling time very much brief , the vase embryo encounters the overcast standard breastwork what shrinks time very much little .Research to improve this the respect cycle performance opportunity . The vase embryo temperature when comeing out the standard at the moment shall permit cycles time far away a moment to 13 seconds , in case merely on the one hand this is the limitational factor that cycles . 6 、Element considering that the vase embryo is designed Vase embryo which on the basis of the initial comparing model employd in the system along with cycling and designs the eperiment which do to different as of jar of embryos in the interest of accelerating the use indexing means to decrease the indexing .Hence the indexing system requires that four suits of finished piece standard rushs pith , such standard rush pith complexity along with entire pattern cost that thus causes are the selection elements .Else element consists of the production capacity demand 、Usable floor area 、Capital cost .注塑模具自动装配造型X. G. Ye, J. Y. H. Fuh and K. S. Lee机械和生产工程部，新加坡国立大学，新加坡注射模是一种由与塑料制品有关的和与制品无关的零部件两大部分组成的机械装置。本文提出了（有关）注射模装配造型的两个主要观点，即描述了在计算机上进行注射模装配以及确定装配中与制品无关的零部件的方向和位置的方法，提出了一个基于特征和面向对象的表达式以描述注射模等级装配关系，该论述要求并允许设计者除了考虑零部件的外观形状和位置外，还要明确知道什么部份最重要和为什么。因此，它为设计者进行装配设计（DFA）提供了一个机会。同样地，为了根据装配状态推断出装配体中装配对象的结构，一种简化的特征几何学方法也诞生了。在提出的表达式和简化特征几何学的基础上，进一步深入探讨了自动装配造型的方法。关键字：装配造型；基于特征；注射模；面向对象。1、简介注射成型是生产塑料模具产品最重要的工艺。需要用到的两种装备是：注射成型机和注射模。现在常用的注射成型机即所谓的通用机，在一定尺寸范围内，可以用于不同形状的各种塑料模型中，但注射模的设计就必须随塑料制品的变化而变化。模型的几何因素不同，它们的构造也就不同。注射模的主要任务是把塑料熔体制成塑料制品的最终形状，这个过程是由型芯、型腔、镶件、滑块等与塑料制品有关的零部件完成的，它们是直接构成塑料件形状及尺寸的各种零件，因此，这些零件称为成型零件。（在下文，制品指塑料模具制品，部件指注射模的零部件。）除了注射成型外，注射模还必须完成分配熔体、冷却，开模，传输、引导运动等任务，而完成这些任务的注射模组件在结构和形状上往往都是相似的，它们的结构和形状并不取决于塑料模具，而是取决于塑料制品。图1显示了注射模的结构组成。 成型零件的设计从塑料制品中分离了出来。近几年，CAD/CAM技术已经成功的应用到成型零件的设计上。成型零件的形状的自动化生成也引起了很多研究者的兴趣，不过很少有人在其上付诸实践，虽然它也象结构零件一样重要。现在，模具工业在应用计算机辅助设计系统设计成型零件和注射成型机时，遇到了两个主要困难。第一，在一个模具装置中，通常都包括有一百多个成型零部件，而这些零部件又相互联系，相互限制。对于设计者来说，确定好这些零部件的正确位置是很费时间的。第二，在很多时候，模具设计者已想象出工件的真实形状，例如螺丝，转盘和销钉，但是CAD系统只能用于另一种信息的操作。这就需要设计者将他们的想法转化成CAD系统能接受的信息(例如线，面或者实体等)。因此，为了解决这两个问题，很有必要发展一种用于注射模的自动装配成型系统。在此篇文章里，主要讲述了两个观点：即成型零部件和模具在计算机上的防真装配以及确定零部件在模具中的结构和位置。这篇文章概括了关于注塑成型的相关研究，并对注射成型机有一个完整的阐述。通过举例一个注射模的自动装配造型，提出一种简化的几何学符号法，用于确定注射模具零部件的结构和位置。2、相关研究在各种领域的研究中，装配造型已成为一门学科，就像运动学、人工智能学、模拟几何学一样。Libardi作了一个关于装配造型的调查。据称，很多研究人员已经开始用图表分析模型会议拓扑。在这个图里，各个元件由节点组成的，再将这些点依次连接成线段。然而这些变化矩阵并没有紧紧的连在一起，这将严重影响整体的结构，即，当其中某一部分移动了，其他部分并不能做出相应的移动。Lee and Gossard开发了一种新的系统，支持包含更多的关于零部件的基本信息的一种分级的装配数据结构，就像在各元件间的“装配特征”。变化矩阵自动从实际的线段间的联系得到，但是这个分级的拓扑模型只能有效地代表“部分”的关系。自动判别装配组件的结构意味着设计者可避免直接指定变化的矩阵，而且，当它的参考零部件的尺寸和位置被修改的时候，它的位置也将随之改变。现在有三种技术可以推断组件在模具中的位置和结构：反复数值技术,象征代数学技术，以及象征几何学技术。Lee and Gossard提出一项从空间关系计算每个组成元件的位置和方向的反复数值技术。他们的理论由三步组成：产生条件方程式，降低方程式数量，解答方程式。方程式有：16个满足未知条件的方程式，18个满足已知条件的方程式，6个满足各个矩阵的方程式以及另外的两个满足旋转元件的方程式。通常方程式的数量超过变量的数量时，应该想办法去除多余的方程式。牛顿迭代法常用来解决这种方程式。不过这种方法存在两种缺点：第一，它太依赖初始解；第二：反复的数值技术在解决空间内不能分清不同的根。因此，在一个完全的空间关系问题上，有可能解出来的结果在数学理论上有效，但实际上却是行不通的。Ambler和Popplestone提议分别计算每个零部件的旋转量和转变量以确定它们之间的空间关系，而解出的每个零部件的6个变量(3个转变量和3旋转量)要和它们的空间关系一致。这种方法要求大量的编程和计算，才能用可解的形式重写有关的方程式。此外，它不能保证每次都能求出结果，特别是当方程式不能被以可解答的形式重写时。为了能确定出满足一套几何学限制条件的刚体的位置与方向，Kramer开发了一种特征几何学方法。通过产生一连串满足逐渐增长的限制条件的动作推断其几何特征，这样将减少物体的自由度数。Kramer使用的基本参考实体称为一个标识，由一个点和两正交轴构成。标识间的7个限制条件（coincident, in-line, in-plane, parallelFz,offsetFz, offsetFx and helical)都被定了义。对于一个包括独立元件、相互约束的标识和不变的标识的问题来说，可以用动作分析法来解决问题，它将一步一步地最后求出物体的最终的几何构造。在确定物体构造的每一个阶段，自由度分析将决定什么动作能提供满足限制物体未加限制部位的自由度。然后计算该动作怎样能进一步降低物体的自由度数。在每个阶段的最后，给隐喻的装配计划加上合适的一步。根据Shah和Rogers的分析，Kramer的理论代表了注射模具最显著的发展，他的特征几何学方法能解出全部的限制条件。和反复的数值技术相比，他的这种方法更具吸引力。不过要实行这种方法，需要大量的编程。现在虽然已有很多研究者开始研究注射成型机，但仍很少有学者将注意力放在注射模设计上。Kruth开发了一个注射模的设计支援系统。这个系统通过高级的模具对象(零部件和特征)支持注射模的成型设计。因为系统是在AUTOCAD的基础上设计的，因此它只适于线和简单的实体模型操作。3、注射模装配概述主要讲述了关于注射模自动装配造型的两个方面：注射模在电脑上的防真装配和确定结构零件在装配中的位置和方向。在这个部分，我们基于特征和面向对象论述了注射模装配。注射模在电脑上的防真装配包含着注射模零部件在结构上和空间上的联系。这种防真必须支持所有给定零部件的装配、在相互关联的零部件间进行变动以及整体上的操作。而且防真装配也必须满足设计者的下列要求： 1）支持能表达出模具设计者实体造型想象的高级对象。2）成型防真应该有象现实一样的操作功能，就如装入和干扰检查。为了满足这些要求，可用一个基于特征和面向对象的分级模型来代替注射模。这样便将模型分成许多部分，反过来由多段模型和独立部分组成。因此，一个分级的模型最适合于描述各组成部分之间的结构关系。一级表明一个装配顺序，另外，一个分级的模型还能说明一个部分相对于另一个部分的确定位置。与直观的固体模型操作相比，面向特征设计允许设计者在抽象上进行操作。它可以通过一最小套参数快速列出模型的特征、尺寸以及其方位。此外，由于特征模型的数据结构在几何实体上的联系，设计者更容易更改设计。如果没有这些特征，设计者在构造固体模型几何特征时就必须考虑到所有需要的细节。而且面向特征的防真为设计者提供了更高级的成型对象。例如，模具设计者想象出一个浇口的实体形状，电脑就能将这个浇口造型出来。面向对象造型法是一种参照实物的概念去设计模型的新思维方式。基本的图素是能够将数据库和单一图素的动作联系起来的对象。面向对象的造型对理解问题并且设计程序和数据库是很有用的。此外，面向对象的装配体呈现方式使得“子”对象能继承其“父”对象的信息变得更容易。Automated Assembly Modelling for Plastic Injection MouldsX. G. Ye, J. Y. H. Fuh and K. S. LeeDepartment of Mechanical and Production Engineering, National University of Singapore, SingaporeAn injection mould is a mechanical assembly that consists of product-dependent parts and product-independent parts. Thispaper addresses the two key issues of assembly modellingfor injection moulds, namely, representing an injection mouldassembly in a computer and determining the position andorientation of a product-independent part in an assembly. Afeature-based and object-oriented representation is proposedto represent the hierarchical assembly of injection moulds.This representation requires and permits a designer to thinkbeyond the mere shape of a part and state explicitly whatportions of a part are important and why. Thus, it providesan opportunity for designers to design for assembly (DFA). Asimplified symbolic geometric approach is also presented toinfer the configurations of assembly objects in an assemblyaccording to the mating conditions. Based on the proposedrepresentation and the simplified symbolic geometric approach,automatic assembly modelling is further discussed.Keywords: Assembly modelling; Feature-based; Injectionmoulds; Object-oriented1. IntroductionInjection moulding is the most important process for manufacturingplastic moulded products. The necessary equipment consistsof two main elements, the injection moulding machineand the injection mould. The injection moulding machines usedtoday are so-called universal machines, onto which variousmoulds for plastic parts with different geometries can bemounted, within certain dimension limits, but the injectionmould design has to change with plastic products. For differentmoulding geometries, different mould configurations are usuallynecessary. The primary task of an injection mould is to shapethe molten material into the final shape of the plastic product.This task is fulfilled by the cavity system that consists of core,cavity, inserts, and slider/lifter heads. The geometrical shapes and sizes of a cavity system are determined directly by theplastic moulded product, so all components of a cavity systemare called product-dependent parts. (Hereinafter, product refersto a plastic moulded product, part refers to the component ofan injection mould.) Besides the primary task of shaping theproduct, an injection mould has also to fulfil a number oftasks such as the distribution of melt, cooling the moltenmaterial, ejection of the moulded product, transmitting motion,guiding, and aligning the mould halves. The functional partsto fulfil these tasks are usually similar in structure and geometricalshape for different injection moulds. Their structuresand geometrical shapes are independent of the plastic mouldedproducts, but their sizes can be changed according to theplastic products. Therefore, it can be concluded that an injectionmould is actually a mechanical assembly that consists ofproduct-dependent parts and product-independent parts. Figure1 shows the assembly structure of an injection mould.The design of a product-dependent part is based on extractingthe geometry from the plastic product. In recent years,CAD/CAM technology has been successfully used to helpmould designers to design the product-dependent parts. The automatic generation of the geometrical shape for a productdependentpart from the plastic product has also attracted alot of research interest 1,2. However, little work has beencarried out on the assembly modelling of injection moulds,although it is as important as the design of product-dependentparts. The mould industry is facing the following two difficultieswhen use a CAD system to design product-independentparts and the whole assembly of an injection mould. First,there are usually around one hundred product-independent partsin a mould set, and these parts are associated with each otherwith different kinds of constraints. It is time-consuming forthe designer to orient and position the components in anassembly. Secondly, while mould designers, most of the time,think on the level of real-world objects, such as screws, plates,and pins, the CAD system uses a totally different level ofgeometrical objects. As a result, high-level object-oriented ideashave to be translated to low-level CAD entities such as lines,surfaces, or solids. Therefore, it is necessary to develop anautomatic assembly modelling system for injection moulds tosolve these two problems. In this paper, we address the followingtwo key issues for automatic assembly modelling: representinga product-independent part and a mould assembly ina computer; and determining the position and orientation of acomponent part in an assembly.This paper gives a brief review of related research inassembly modelling, and presents an integrated representationfor the injection mould assembly. A simplified geometric symbolicmethod is proposed to determine the position and orientationof a part in the mould assembly. An example of automaticassembly modelling of an injection mould is illustrated. 2. Related ResearchAssembly modelling has been the subject of research in diversefields, such as, kinematics, AI, and geometric modelling. Libardiet al. 3 compiled a research review of assembly modelling.They reported that many researchers had used graphstructures to model assembly topology. In this graph scheme,the components are represented by nodes, and transformationmatrices are attached to arcs. However, the transformation matrices are not coupled together, which seriously affects the transformation procedure, i.e. if a subassembly is moved, all its constituent parts do not move correspondingly. Lee and Gossard 4 developed a system that supported a hierarchical assembly data structure containing more basic information about assemblies such as “mating feature” between the components. The transformation matrices are derived automatically from the associations of virtual links, but this hierarchical topology model represents only “part-of” relations effectively.Automatically inferring the configuration of components in an assembly means that designers can avoid specifying the transformation matrices directly. Moreover, the position of a component will change whenever the size and position of its reference component are modified. There exist three techniques to infer the position and orientation of a component in theassembly: iterative numerical technique, symbolic algebraic technique, and symbolic geometric technique. Lee and Gossard 5 proposed an iterative numerical technique to compute the location and orientation of each component from the spatial relationships. Their method consists of three steps: generation of the constraint equations, reducing the number of equations, and solving the equations. There are 16 equations for “against” condition, 18 equations for “fit” condition, 6 property equations for each matrix, and 2 additional equations for a rotational part. Usually the number of equations exceeds the number of variables, so a method must be devised to remove the redundant equations. The NewtonRaphson iteration algorithm is used to solve the equations. This technique has two disadvantages: first, the solution is heavily dependent on the initial solution; secondly, the iterative numerical technique cannot distinguish between different roots in the solution space. Therefore, it is possible, in a purely spatial relationship problem, that a mathematically valid, but physically unfeasible, solution can be obtained. Ambler and Popplestone 6 suggested a method of computing the required rotation and translation for each component to satisfy the spatial relationships between the components in an assembly. Six variables (three translations and three rotations) for each component are solved to be consistent with the spatial relationships. This method requires a vast amount of programming and computation to rewrite related equations in a solvable format. Also, it does not guarantee a solution every time, especially when the equation cannot be rewritten in solvable forms.Kramer 7 developed a symbolic geometric approach for determining the positions and orientations of rigid bodies that satisfy a set of geometric constraints. Reasoning about the geometric bodies is performed symbolically by generating a sequence of actions to satisfy each constraint incrementally, which results in the reduction of the objects available degrees of freedom (DOF). The fundamental reference entity used by Kramer is called a “marker”, that is a point and two orthogonal axes. Seven constraints (coincident, in-line, in-plane, parallelFz, offsetFz, offsetFx and helical) between markers are defined. For a problem involving a single object and constraints between markers on that body, and markers which have invariant attributes, action analysis 7 is used to obtain a solution. Action analysis decides the final configuration of a geometric object, step by step. At each step in solving the object configuration, degrees of freedom analysis decides what action will satisfy one of the bodys as yet unsatisfied constraints, given the available degrees of freedom. It then calculates how that action further reduces the bodys degrees of freedom. At the end of each step, one appropriate action is added to the metaphorical assembly plan. According to Shah and Rogers 8, Kramers work represents the most significant development for assembly modelling. This symbolic geometric approach can locate all solutions to constraint conditions, and is computationally attractive compared to an iterative technique, but to implement this method, a large amount of programming is required.Although many researchers have been actively involved in assembly modelling, little literature has been reported on feature based assembly modelling for injection mould design.Kruth et al. 9 developed a design support system for an injection mould. Their system supported the assembly design for injection moulds through high-level functional mouldobjects (components and features). Because their system was based on AutoCAD, it could only accommodate wire-frame and simple solid models.3. Representation of Injection Mould AssembliesThe two key issues of automated assembly modelling for injection moulds are, representing a mould assembly in computers, and determining the position and orientation of a product- independent part in the assembly. In this section, we present an object-oriented and feature-based representation for assemblies of injection moulds.The representation of assemblies in a computer involves structural and spatial relationships between individual parts. Such a representation must support the construction of an assembly from all the given parts, changes in the relative positioning of parts, and manipulation of the assembly as a whole. Moreover, the representations of assemblies must meet the following requirements from designers:1. It should be possible to have high-level objects ready to use while mould designers think on the level of realworld objects.2. The representation of assemblies should encapsulate operational functions to automate routine processes such as pocketing and interference checks. To meet these requirements, a feature-
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