壳体零件的工艺与工装夹具设计【柴油机油泵调速器外壳】【说明书+CAD】
壳体零件的工艺与工装夹具设计【柴油机油泵调速器外壳】【说明书+CAD】,柴油机油泵调速器外壳,说明书+CAD,壳体零件的工艺与工装夹具设计【柴油机油泵调速器外壳】【说明书+CAD】,壳体,零件,工艺,工装,夹具,设计,柴油机,油泵,调速器,外壳,说明书,CAD
英文原文
Application and development
Of case based reasoning in fixture design
Abstract: Based on the case based designing (CBD) methodology, the fixture similarity is in two respects: the function and the structure information. Then, the computer aided fixture design system is created on case based reasoning (CBR),in which the attributes of the main features of workpiece and structure of fixture as case index code are designed for the retrieve of the similar cases, and the structure and hierarchical relation of case library are set up for store. Meanwhile, the algorithm based on the knowledge guided in the retrieve of the similar cases, the strategy of case adapt at ion and case storage in which the case ident if cat ion number is used to distinguish from similar cases are presented. The application of the system in some projects improves the design efficiency and gets a good result .
Keywords: case based reasoning ;fixture design; computer aided design(CAD)
Fixtures are devices that serve as the purpose of holding the workpiece securely and accurately, and maintaining a consistent relationship with respect to the tools while machining. Because the fixture structure depends on the feature of the product and the status of the process planning in the enterprise, its design is the bottleneck during manufacturing, which restrains to improve the efficiency and leadtime. And fixture design is a complicated process, based on experience that needs comprehensive qualitative knowledge about a number of design issues including workpiece configuration, manufacturing processes involved, and machining environment. This is also a very time consuming work when using traditional CAD tools (such as Unigraphics, CATIA or Pro/E), which are good at performing detailed design tasks, but provide few benefits for taking advantage of the previous design experience and resources, which are precisely the key factors in improving the efficiency. The methodology of case based reasoning (CBR) adapts the solution of a previously solved case to build a solution for a new problem with the following four steps: retrieve, reuse, revise, and retain [1]. This is a more useful method than the use of an expert system to simulate human thought because proposing a similar case and applying a few modifications seems to be self explanatory and more intuitive to humans .So various case based design support tools have been developed for numerous areas[2-4], such as in injection molding and design, architectural design, die casting die design, process planning, and also in fixture design. Sun used six digitals to compose the index code that included workpiece shape, machine portion, bushing, the 1st locating device, the 2nd locating device and clamping device[5]. But the system cannot be used for other fixture types except for drill fixtures, and cannot solve the problem of storage of the same index code that needs to be retained, which is very important in CBR[6].
1 Construction of a Case Index and Case Library
1.1 Case index
The case index should be composed of all features of the workpiece, which are distinguished from different fixtures. Using all of them would make the operation in convenient. Because the forms of the parts are diverse, and the technology requirements of manufacture in the enterprise also develop continuously, lots of features used as the case index will make the search rate slow, and the main feature unimportant, for the reason that the relative weight which is allotted to every feature must diminish. And on the other hand, it is hard to include all the features in the case index.
Therefore, considering the practicality and the demand of rapid design, the case index includes both the major feature of the workpiece and the structure of fixture. The case index code is made up of 16 digits: 13 digits for case features and 3 digits for case identification number.
The first 13 digits represent 13 features. Each digit is corresponding to an attribute of the feature, which may be one of“*”, “？”, “1”, “2”,…,“A”,“B”,…, “Z”,…, etc. In which, “*” means anyone, “?” uncertain, “0” nothing.
The system rules: fixture type, workpiece shape, locating model cannot be “*”or“?”. When the system is designed, the attribute information of the three items does not have these options, which means the certain attribute must be selected.
The last three digits are the case identification number, which means the 13 digits of the case feature are the same, and the number of these three digits is used for distinguishing them.
The system also rules: “000” is a prototype case, which is used for retrieval, and other cases are “001”,“002”,…, which are used for reference cases to be searched by designers. If occasionally one of them needs to be changed as the prototype case, first it must be required to apply to change the one to “000”, and the former is changed to referential case automatically.
The construction of the case index code is shown in Fig.1.
1.2 Case library
The case library consists of lots of predefined cases. Case representation is one of the most important issues in case based reasoning. So compounding with the index code,.
1.3 Hierarchical form of Case
The structure similarity of the fixture is represented as the whole fixture similarity, components similarity and component similarity. So the whole fixture case library, components case library, component case library of fixture are formed correspondingly. Usually design information of the whole fixture is composed of workpiece information and workpiece procedure information, which represent the fixture satisfying the specifically designing function demand. The whole fixture case is made up of function components, which are described by the function components’ names and numbers. The components case represents the members. (function component and other structure components， main driven parameter, the number, and their constrain relations.) The component case (the lowest layer of the fixture) is the structure of function component and other components. In the modern fixture design there are lots of parametric standard parts and common non standard parts. So the component case library should record the specification parameter and the way in which it keeps them.
2 Strategy of Case Retrieval
In the case based design of fixtures ,the most important thing is the retrieval of the similarity, which can help to obtain the most similar case, and to cut down the time of adaptation. According to the requirement of fixture design, the strategy of case retrieval combines the way of the nearest neighbor and knowledge guided. That is, first search on depth, then on breadth; the knowledge guided strategy means to search on the knowledge rule from root to the object, which is firstly searched by the fixture type, then by the shape of the workpiece, thirdly by the locating method. For example, if the case index code includes the milling fixture of fixture type, the search is just for all milling fixtures, then for box of workpiece shape, the third for 1plane+ 2pine of locating method. If there is no match of it, then the search stops on depth, and returns to the upper layer, and retrieves all the relative cases on breadth.
Retrieval algorithms:
1)According to the case index information of fixture case library, search the relevant case library;
2)Match the case index code with the code of each case of the case library, and calculate the value of the similarity measure;
3)Sort the order of similarity measure, the biggest value, which is the most analogical case.
Similarity between two cases is based on the similarity between the two cases. features. The calculation of similarity measure depends on the type of the feature. The value of similarity can be calculated for numerical values, for example, compareWorkpiece with the weight of 50kg and 20kg. The value can also be calculated between non numerical values, for example, now the first 13 digits index code is all non numerical values. The similarity measure of a fixture is calculated as follows:
where S is the similarity measure of current fixture, n is the number of the index feature, is the weight of each feature, is the similarity measure of the attribute of the i2th feature with the attributeof relative feature of the j-th case in the case library. At the same time, , the value counts as follows:
.
Where is the value of the index attribute of the i-th feature, and is the value of attribute of the relative i-th feature of the j-th case in case library.
So there are two methods to select the analogical fixture. One is to set the value. If the values of similarity measure of current cases were less than a given value, those cases would not be selected as analogical cases. When the case library is initially set up, and there are only a few cases, the value can be set smaller. If there are lots of analogical cases, the value should get larger. The other is just to set the number of the analogical cases (such as10), which is the largest value of similarity measure from the sorted order.
3 Case adaptation and Case Storage
3.1 Case adaptation
The modification of the analogical case in the fixture design includes the following three cases:
1) The substitution of components and the component;
2) Adjusting the dimension of components and the component while the form remains;
3) The redesign of the model.
If the components and component of the fixture are common objects, they can be edited, substituted and deleted with tools, which have been designed.
3.2 Case storage
Before saving a new fixture case in the case library, the designer must consider whether the saving is valuable. If the case does not increase the knowledge of the system, it is not necessary to store it in the case library. If it is valuable, then the designer must analyze it before saving it to see whether the case is stored as a prototype case or as reference case. A prototype case is a representation that can describe the main features of a case family. A case family consists of those cases whose index codes have the same first 13 digits and different last three digits in the case library. The last three digits of a prototype case are always “000”. A reference case belongs to the same family as the prototype case and is distinguished by the different last three digits.
From the concept that has been explained, the following strategies are adopted:
1) If a new case matches any existing case family, it has the same first 13 digits as an existing prototype case, so the case is not saved because it is represented well by the prototype case. Or is just saved as a reference case (the last 3 digits are not “000”, and not the same with others) in the case library.
2) If a new case matches any existing case family and is thought to be better at representing this case family than the previous prototype case, then the prototype case is substituted by this new case, and the previous prototype case is saved as a reference case.
3) If a new case does not match any existing case family, a new case family will be generated automatically and the case is stored as the prototype case in the case library.
4 Process of CBR in Fixture Design
According to the characteristics of fixture design, the basic information of the fixture design such as the name of fixture, part, product and the designer, etc. must be input first. Then the fixture file is set up automatically, in which all components of the fixture are put together. Then the model of the workpiece is input or designed. The detailed information about the workpiece is input, the case index code is set up, and then the CBR begins to search the analogical cases, relying on the similarity measure, and the most analogical case is selected out. If needed, the case is adapted to satisfy the current design, and restored into the case library. The flowchart of the process is shown in Fig.3.
5 Illustrating for Fixture Design by CBR
This is a workpiece (seeFig.4). Its material is 45# steel. Its name is seat. Its shape is block, and the product batch size is middle, etc. A fixture is turning fixture that serves to turn the hole, which needs to be designed.
The value of feature, attribute, case index code and weight of the workpiece is show n in Tab.2.
Through searching, and calculating the similarity, the case index code of the most similar case is 19325513321402000, and the detailed information is show n in Tab. 3.
The similarity is calculated as follows:
So the value of similarity measure of the fixture which needs to be designed with the most analogical case in case library is 0.806, and the structure of the most analogical case is shown in Fig.5.
After having been substituted the component, modified the locating model and clamp model, and adjusted the relative dimension, the new fixture is designed, and the figure is show n in Fig.6.
As there is not the analogical fixture in the case library, the new fixture is restored in to the case library. The case index code is 19325513311402000.
6 Conclusion
CBR, as a problem solving methodology, is a more efficient method than an expert system to simulate human thought, and has been developed in many domains where knowledge is difficult to acquire. The advantages of the CBR are as follows: it resembles human thought more closely; the building of a case library which has self learning ability by saving new cases is easier and faster than the building of a rule library; and it supports a better transfer and explanation of new knowledge that is more different than the rule library. A proposed fixture design framework on the CBR has been implemented by using Visual C ++, UG/Open API in U n graphics with Oracle as database support, which also has been integrated with the 32D parametric common component library, common components library and typical fixture library. The prototype system, developed here, is used for the aviation project, and aids the fixture designers to improve the design efficiency and reuse previous design resources.
中文
应用和发展
基于实例推理的夹具设计
摘要：基于案例的设计（CBD）方法，夹具相似性体现在两个方面:功能和结构信息。然后，计算机辅助夹具设计系统是建立在基于案例的推理（CBR），并对工件和夹具结构的主要特征属性作为案例索引代码用于检索类似的情况，并且结构和案例库的层次关系建立商店，同时，算法在检索相似案例知识的引导，案例策略适应在离子和案例库中案例验证如果猫离子数是用来区分相似的案例，该系统在某工程中的应用提高了设计效率，取得了良好的效果。
关键词：基于案例的推理；夹具设计；计算机辅助设计（CAD）
夹具装置，作为夹持工件的安全的目的地，并且维护方面的工具的一致性关系，而加工。因为夹具的结构取决于产品的特点以及在企业中的地位的计划，它的设计制造过程中的瓶颈，制约提高效率和交货期。夹具的设计是一个复杂的过程，根据经验，需要一系列的设计问题包括工件的结构综合定性知识，制造过程与加工环境。这也是一个使用传统的CAD工具时，非常耗费时间的工作（如词素文字，CATIA、PRO/E），在进行详细设计的任务是好的，但提供很少的利益利用以往设计经验和资源，这正是提高效率的关键因素。基于案例的推理（CBR）方法适应以前解决的情况下为以下四个步骤建立一个新的问题的解决方案：检索，重用，修改，并保留[ 1 ]。这是一个比一个专家系统模拟人类思维的运用更有用的方法，因为提出类似的案例和应用了一些修改似乎是自我解释和更直观的人类。于是各种基于案例的设计支持工具已经开发了众多的地区[ 2-4 ]，如在注射成型设计，建筑设计，压铸模的设计，工艺规划，并在夹具设计。太阳用六个数字组成，包括工件形状，机械部分，该索引编码套管，第一定位装置，定位装置和夹紧装置第二[ 5 ]。但是该系统不能用于除钻夹具其他灯具类型，并不能解决同一索引的代码存储问题需要被保留，而CBR [ 6 ]是很重要的。
1 一个案例检索和案例库的建设
1.1例指数
案例索引应该由工件的所有特征，是区别于不同的夹具。使用所有这些会使操作方便。因为地区的形式是多种多样的，并在企业的制造技术的要求也不断发展，作为案例索引的许多功能将使搜索速度慢，和主要特点不重要，因为相对权重分配给每个特征，必须减少。另一方面，它是很难包括案例索引的所有功能。
因此，从实用化、快速的设计需求，案例索引包括工件的主要特征和夹具结构。案例索引代码由16位数：13位数的情况下识别号案件的特点和3个数字。
前13个数字代表13个特点。每个数字对应的特征的属性，这可能是一个“*”，“？”，“1”，“2”，……，“A”，“B”，……，“Z”，……，等等。其中，“*”是指任何人，”？“不，”0“没有什么。
系统规则：夹具，工件形状，定位模型不能“*”或“？“。当系统的设计，该三个项目的属性信息，没有这些选项，这意味着一定的属性必须选择。
最后三位数字是如此的识别号码，即案例特征的13位数字是相同的，和这三个数字的位数是用来区分。
该系统还规定：“000”是一个原型的情况下，这是用于检索，和其他案件的“001”，“002”，……，这是用于要搜索的设计者参考案例。如果偶尔他们当中的一个需要改变为原型的情况下，首先必须将改变一个“000”，和前改为自动参考案例。
的情况下，指数代码结构如图1所示。
1.2例库
案例库包含预定义的众多案例。案例的表示是基于案例推理的最重要的问题。所以复合指标代码，。
1.3个层次的案例
夹具的结构相似性表示作为整个夹具的相似性，相似性和相似性成分组成。所以整个夹具实例库，组件的案例库，案例库的夹具元件形成相应。通常整个夹具设计信息是由工件信息和工件程序的信息，这是专门设计满足功能需求的夹具。整个夹具实例是由功能部件，这是由功能部件的名称和编号描述。组件的情况下代表成员。（功能组件和其他结构部件，主要驱动参数，数量，和他们的约束关系。）的组件的情况下（夹具的最低层）的功能组件和其他组件的结构。在现代灯具设计有参数化标准件和常用的非标准件的大量。这样的组件的情况下，图书馆应记录，它使他们这样的规格参数。
2.案例检索策略
基于案例的夹具设计，最重要的是相似性检索，以获得最相似的情况下，和降低的时间适应。根据夹具的设计要求，案例检索策略相结合的方式，最近的邻居和知识引导。那是，深度优先搜索，然后在广度；知识引导策略意味着对从根到对象的知识规则的搜索，这是由夹具类型首先搜索，然后通过工件的形状，然后通过定位方法。例如，如果指数代码包括夹具式铣床夹具，搜索是为所有的铣削夹具，然后箱工件形状，对1plane + 2pine定位方法第三。如果没有匹配的话，那么对深度搜索停止，并返回上一层，和检索所有相关案件的广度。
检索算法：
1）根据夹具的案例库的案例索引信息，搜索相关案例库；
2）的情况下，指数代码与每个案例的案例库代码匹配，并计算出的值的相似性度量；
3）的相似性度量的顺序，最大的价值，这是最相似实例。
两起案件之间的相似性是基于两个案例之间的相似性。特征。相似性度量的计算取决于类型的特征。相似的值可以计算出的数值，例如，与50公斤的重量compareworkpiece 20公斤。值也可以计算非数值之间，例如，现在第一个13位数代码都是非数值索引。一个夹具的相似性度量的计算如下：
其中S是当前夹具的相似性度量，n是指数的特征数量，是每个特征的重量，是用在案例库中案例属性的第j个相对特征的i2th特征属性的相似性度量。同时，，价值数如下：
的第i个特征指标属性的价值在哪里，是在案例库的第j下相对i特征属性的值。
所以选择类比夹具的两种方法。一是要设置的值。如果目前的情况下，相似度量值均小于给定值，这些案件将不被选择作为类比案例。当案例库的初步建立，只有少数情况下，该值可设定较小。如果有相似事例很多，应该得到更大的价值。另一个是建立类推的案件数量（如10），这是最大的值的排序顺序的相似性度量。
3.例适应和案例存储
3.1例适应
在夹具设计的相似实例的修改包括以下三例：
1）组件的替代和组件；
2）调整组件的尺寸和成分而形成仍然；
3）模型的设计。
如果零件和夹具组件是常见的对象，他们可以编辑和删除，替换工具，已被设计。
3.2例存储
在案例库中保存新的夹具实例之前，设计者必须考虑的是节约宝贵的。如果不增加系统的知识，不需要存储在案例库。如果它是有价值的，那么设计师就必须分析它，拯救它是否是存储为原型的情况下，或作为参考的情况下在。一个原型是一个表示可以描述个案家庭的主要特点。一例家族是指那些案件指标代码库中的情况下，具有相同的前13个数字和不同的最后三位数字。一个原型的情况下，最后三位数字是“000”。参考的情况下，属于同一家族的原型的情况下，由不同的最后三位杰出的。
从已解释的概念，采用以下策略：
1）如果一个新的案例匹配任何存在的情况下，家庭，它具有相同的前13个数字作为一个现有的原型实例，所以并不是因为它是由原型的情况下，很好的体现。或只是作为一个参考案例（最后3位数字是不是“000”，并与别人不一样）在案例库。
2）如果一个新的案例匹配任何存在的情况下，家庭和被认为是更好的代表这种情况下的家庭比以前的原型实例，然后原型以新案子取代，和以前的原型的情况下被保存作为参考的情况下。
3）如果一个新的案件不符合任何现有情况的家庭，一个新的案例的家庭将自动生成和案例存储在案例库的原型实例。
4 CBR的夹具设计过程
根据夹具设计的特点，对夹具设计如夹具，部分的名称的基本信息，产品设计师，必须先输入等。然后夹文件自动设置，其中所有的夹具组件放在一起。然后对工件的模型输入或设计。输入的工件的详细信息的情况下，指数代码设置，然后开始搜寻相似案例推理，依靠的相似性度量，并筛选出最相似实例。如果需要的话，情况来满足当前的设计，并恢复到案例库。该过程的流程图如图3所示。
5CBR的夹具设计说明
这是一个工件（seefig。4）。材料为45 #钢。它的名字是座。它的形状是块，和产品的批量大小中等，等。一个夹具，夹具，用于把车孔，需要设计。
特征，属性值，指数代码和工件的重量在选项卡显示2 N。
通过搜索，计算相似度，最相似的案例的情况下，指数代码为19325513321402000，和详细信息显示在标签3
相似度的计算方法如下：
因此，需要设计的最为相似的案例案例库的夹具相似性度量的值是0.806，和最相似实例的结构如图5所示。
经取代的组件，修改了定位模型和夹具模型，和调整的相对尺寸，设计新的夹具，和图显示在图6。
因为没有在案例库中相似的夹具，夹具的新恢复的案例库。的情况下，指数代码为19325513311402000。
6 结论
CBR，作为一个解决问题的方法，是一种比模拟人类思维的专家系统更有效的方法，并已在许多领域的知识是很难获得的开发。案例推理方法的优点如下：它类似于人类的思想更加紧密；一个案例库，通过节约新病例的自我学习能力更容易，比一个规则库的建设速度更快的建设；并支持更好的转移和新知识的解释，比规则库的不同。提出了一种对CBR的夹具设计框架已用Visual C++实现，在U N图形以Oracle为数据库支持UG/Open API，也已与三维参数化通用组件库集成，通用组件库和典型夹具库。这里开发的原型系统，，用于航空项目，和艾滋病的夹具设计人员提高设计效率和重用以前的设计资源。
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