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解决金属切削问题的智能专家系统的开发乌鲁达大学，机械工程系，Gorukle16059，布尔萨，土耳其于2004年9月8日收稿，于2005年1月31日接受2005年3月21日可在线摘 要 在金属切削方面，这些问题需要有良好的分析，以便遇到任何意外的结果之前，可以采取有效的防范措施。这一过程在实现产品质量稳定和控制生产总成本方面起很重要的作用。但是，需要一个拥有在金属切削方面有大量经验和知识的专家是一项艰巨的任务。在本文，智能专家系统（COROSolve）调查并解决了在金属切削领域遇到的三个主要问题：车削，铣削和钻孔。许多金属切削方面的问题都被考虑在内，如在车削过程中的工件内部插入转折点，铝件车削，沟槽车削，螺纹车削等工序; 在铣削方面面铣，方肩铣，端铣，多用途铣和侧铣等工序；在和钻孔作业，使用固定或可转位钻头钻孔等。COROSolve可以给出建议的切削参数而且能及时更新在切削问题，产生原因和补救措施等方面的数据库，因此系统能够处理的问题数量在增加。关键词：金属切削问题 专家系统 KBS 刀具磨损1、引言 现代制造业的目标是，在组织设施能够进行有效控制，以便能以在较短生产周期内以较低的生产价格制造出高质量的产品 。为了实现能以较低的价格获得更优质的产品，制造部门格关注采用更好的刀具和高精密的机械等1。然而，在大多数情况下对于生产要求这是不够的。专业的工作选择正确的工具是重要的，但是为了更高效的制造，刀具磨损也应考虑在内。在文献中，许多出版物上对于不同材料制造的刀具的磨损的确做了很多研究2。金属切削是切削碎片的形成过程。虽然切削过程是把金属切削成所规定的形状和大小，但这必须通过定义切削碎片工作来完成。切削碎片的形成意味着一个新的金属界面不断形成并沿刀具材料承受着非常高的压力和温度3。所产生的区域成为发生金属扩散和化学反应的理想场所。所有刀具在加工过程中不断变得破旧，并继续这样工作直到它们报废。刀具磨损是不可避免的，如果能了解刀具磨损的时间，程度，类型时，刀具磨损就不再是一个消极的进程。在不同的金属切削过程中存在着几种不同的磨损机理，相近不同类型的问题由于这些机制作用的结果而联系交织在一起。如果这些问题能够得到很好的分析，我们就有可能找到其中每一种问题的正确的解决方案。在分析金属切削问题时这个问题应当明确界定，而且其可能的原因也应该得到确认。找一个拥有知识和大量金属切削经验的专家是一项艰巨的任务。今天在金属切削领域，关于解决切削碎片问题的专业设施主要由切削刀具生产企业提供。由于在这一领域工作的人是有限的，因此并不总是能够找到真正需要的专家。在现有专家聘用费用昂贵而且人员稀缺的领域中专家系统一直特别受欢迎。对于解决金属切削问题专家系统将是非常有益的。2、专家系统在协助发展制造工艺上的应用基于知识的系统或专家系统是一个体现狭窄领域的知识并解决该领域相关问题的计算机程序。专家系统通常包括两个主要内容，知识基础和推理机制（图1）。基础知识包含一个可以表述为由IF - THEN规则、事实说明、框架、对象、程序和案件组合而成的知识领域。推理机制，是专家系统操纵存储的知识并对遇到的生产问题提出解决方案的一个组成部分4。一个人类专家利用知识和推理最终得出的结论，专家系统也是如此。推理在专家系统试图模仿结合人类专家的知识的过程中进行。因此，专家系统的结构或架构有些类似于人类专家的执行情况。因此，专家系统可以比喻成专家。一个比较明显的问题是规则的收集。人类专家聘用费用高昂，而且并不想要坐下来写关于他们是怎样得出他们结论的那些大量的规则。更重要的一点，他们可能也无法做到。虽然他们通常会遵循逻辑的路径来得到他们的结论，但是把那些规则放入一套标准之中实际上是非常困难的，并且也许是不可能的。对于许多人类专家下面这种情况是很可能的。虽然他们开始时有着自己的专业规则，但是在工作中通过自己的工作经验知识来开展自己的工作，并且通过直觉得出正确的解决方案。它们可能都跟随逻辑路径，但是在沿着这逻辑的路径上，他们精神上已经跳过许多步骤。专家系统不能做到这一点，它需要很清楚的知道各种规则。专家系统的一个很突出的好处是能够广泛把知识分发给每一个专家，或者可以同时汇总的几个远远相隔的几个专家的知识。当偶尔的执行任务时专家系统特别有用，而专家每次执行任务时则需要重新学习工作程序。专家系统是用来规范操作的。如果你有三个机器操作员（或工程师）来执行相同的任务，但是每个人都会做的不同。而专家系统则每次都可以用同样的方式来工作。这些系统可用于培训员工，指导他们，或进行实际执行如计算任务。专家系统的另一个用途是作为专家辅助您的工作。他们将使您能更准确，更一致，更快，从而为专家能更创意的完成任务而节省了时间。当处理乏味、重复的任务时这是特别有用的。因此，一旦领域知识被专家系统提取，建设此系统的过程比较简单。能被发展的专家系统的易用性，导致了刀具广泛应用。在工程，可以找到在各种任务上的应用，包括选料，机械零件，刀具，设备和工艺，信号解释，状态监测，故障诊断，机器和过程控制，机械设计，工艺规划，生产调度和系统配置。最近专家系统所执行的一些具体任务的例子如下：(1)确定和规划离岸结构重要组成部分的检查时间表5;(2)在设计和评价能源热电厂方面培训技术人员6;(3)配置输纸机构 7;(4)在有限元分析锻造变形时自动重新啮合8;(5)存储，检索和修改平面连杆机构设计9;(6)应用于发动机油产品的添加剂配方设计10;(7)选择刀具和切削参数11-13； 有几个潜在的研究领域肯定了专家系统在制造业方面价值14，15 Kojiyama et al 16在其文章中讨论了关于加工操作规划的系统框架。在此框架中从电子刀具目录和网络环境下的加工实例数据库中提取和组织的加工技术诀窍了发挥了主要作用。在有参考的情况下可以构成加工数据，这些加工数据来自翻查的刀具目录，相关的国际标准，参考教材和手册。在一般车削和铣削时，Mookherjee 和Bhattacharyya 11在专家系统的应用对于解决制造工程师目前所面临的CAD和各类数控加工中心一体化过程中遇到的一些挑战性问题是非常有用的。Jiang et al. 17开发了一种优化棱镜组件加工业务的专家系统。他们描述了一种新的GT编码方案用于代表待加工得棱镜组件表面。Limsombutanan 18在可以作为霍隆的5轴曲面加工过程中提出了一个用来选择刀尺寸和工具方向的算法。铣削表面分为三个阶段，即粗加工，半粗加工和精加工。该算法在曲率分析的基础上选择最佳的刀具并且在立方（凹-凸）表面上自主的计划刀具路径。本文的主要目的是建立这种涵盖了主要的金属切削问题的系统，并帮助那些参与金属切削工作的人们提高产品质量。3、专家系统在解决金属切削问题上的应用3.1解决金属切削问题时应考虑的因素 在金属切削过程中大部分问题是磨损的结果。所有刀具在加工过程中不断变得破旧，并继续这样工作直到它们报废。刀具磨损是不可避免的，如果能了解刀具磨损的时间，程度，类型时，刀具磨损就不再是一个消极的进程。因此，如果对刀具磨损所导致的问题以及其他不利于机械加工业务的有害因素进行了分析，我们就有可能找到其中个个问题的正确解决方案。这将减少非生产性故障的检查时间，因此，减少了加工时间、非生产性停工时间、加工费用并且提高生产效率。在解决金属切削加工问题时所使用的专家系统的结构图如图1。通过软件需要考虑的输入列于图2。3.2 COROSolve的特点 该软件已开发利用Delphi可视化编程语言。而建立一个咨询系统的主要困难在获取和研究在解决方案中使用的要素。根据目前在解决金属切削问题上的设计，一旦选中操作类型，对于每个类型的操作的四个主要阶段已经确定：(1)切削数据的建议。 (2)问题的定义。(3)切割数据评价。(4)问题的汇总。3.2.1、切削数据的建议 在加工过程中刀具的正确选择是实现最大的生产力的关键。但是，虽然工具是正确的，如果加工条件不符合标准，特别是在切削参数一般稳定，问题将会出现而且刀具的最佳寿命将无法达成。切削参数不正确，刀柄、夹紧的振动和缺乏刚性这些都是金属切削的主要问题。除了解决问题该软件对每个操作类型（业务类型如前所述）、每个材料组(ISO P, M or K), 每个应用类型（粗，中，完成）、每加工条件类型（好，一般，困难）提供切削数据的建议并且显示如图4的可用插入列表。在这里不是为了找到应用程序的最合适的插入点但是监测金属切削中使用的插入的初始值和切削参数的工作范围（即切削速度，进给量和切削深度）。在这个阶段决定的合适的等级与所选操作，材料组，应用程序等有关。此外，个个材料组的材料清单能够清楚的看到。推荐切削参数值取自Sandvik Coromant20，其他厂商的刀具切削参数可作为建议的值。切削数据显示值是在一定的材料硬度和一定的刀具寿命下得到的。对于任何工件材料跟指定的值相比具有不同的硬度值而且如果刀具寿命超过15分钟，提供的切削数据应乘以修正系数（见表1）。3.2.2、分析金属切削问题目前有在金属切削过程中存在多种不同/类似的问题。表面上看这些问题有些是相同的，但是很难相区分开来。问题类型的分类已经形成评估加工操作的重要基础，它通过获取刀具等级以及适合切削类型材料类型的正确的加工条件而优化了生产力。正确的工具，良好的出发切削数据，专家的支持下，自己的经验，工件的材料和优质的设备条件是加工成功的重要因素。对各种工具制造商问题清单的聚合进行归类形成了可由软件使用的KBS。用户分析金属切削问题时要么在一个或两个阶段之一：从菜单中直截了当的挑选出定义的问题或者首先检查金属切削过程中使用的切削数据，之后访问定义的问题。问题定义模块显示问题的清单，包括其可能的原因及补救措施。一旦选定一个问题（例如，后刀面磨损的转折点或在钻深孔是的转头的跳动），一张图片，清楚的提供了问题的界定和其可能原因的列表。因此一旦选择了可能的原因就确定了相应的补救措施。更多与该问题有关的信息通过点击 “？”获得（图5）。3.2.3、切削数据评估 在金属切削过程中，大部分的问题是切削数据不合适应用程序的结果。因此，在这些问题直接列出之前，用户被建议检查操作，应用程序和加工条件的切削参数以确定是否切削速度，进给量和切削深度是否与事先插入的长度，厚度和圆角半径相符。切削数据模块检查在运行中的切削参数是否与插入的相符而且这项工作基本上是与理想的切削数据值进行比较，理想的切削数据值是目录值和校正因子的乘积。如果不相符（这意味着切削参数的值不在范围内），用户应修正切削参数。在铣削和钻孔只有切削速度和进给速度值被考虑，在钻孔时钻头直径和钻头中心或周边的等级被考虑在内（图6）。在图中对中型钢（L代表轻型，M代表中型，H代表中型铣削操作）面铣的切削参数被评估，由于使用价值远低于由给定硬度和刀具寿命计算的理想值，则就会显示警告。一旦切削数据被审查（和纠正），下一个步骤就是访问这个问题的定义模块。由于切削数据被修正，原因列表和补救措施将会不同而且“切削速度过高”或者“进给量太低” 将不会是有关问题产生的根源。 该软件能够在各种业务类型中分析超过100多种问题，并对近200个问题原因提供补救措施（340补救措施）。他系统中包含的知识有两个主要来源：从事金属切削领域的专家或者来自于技术文件，目录和各种刀具生产公司的手册21，22，23，24和25。3.2.4、问题编辑系统中包含的知识有两个主要来源：从事金属切削领域的专家或者来自于技术文件，目录和各种刀具生产公司的手册。一个专家系统的成功之处隐藏在像人类专家一样的扩展结构当中。人类专家遇到每一次新的解决方案时都增加了他的知识并且在未来分析时能再利用这些知识。因此，COROSolve有一个可扩展增长的数据库结构，它能处理每天越来越多的问题。由于系统有单独的和模块化的知识基础，只要进入到数据库编辑获得知识文件就可以很容易的更新系统。系统包含的信息越多，它能够处理的金属切削方面的问题就越多。 知识库是系统的核心，因此，负责生产、添加、删除或修改是那些少数人的任务。因此，用户需要知道密码才能进入的知识库。问题编辑允许和问题，原因和补救措施相关的问题，图片和资料档案添加到知识库。此外，还有可能增加新的问题原因或原本已存在知识库中的问题原因的新的补救办法（图7）。该系统是多语言，因此它能够处理无论是土耳其文还是英文的金属切削的问题。一旦确定语言被确定，所有程序菜单和问题，原因及补救措施清单都用所选择的语言显示出来。4、结论本文介绍了一种为解决各种加工操作任务中金属切削问题的专家系统。由于在许多文献中没有很多关于此主题的工作也因为这种类型的系统可以实现多种金属切削业的要求，这里所描述的工作可以认为是一件有益的工作。在制造业，特别是在小型或中型加工车间，切削数据是不正确是问题的主要原因。工具一般以较低的切削数据运行来使他们在频繁的启动中能维持较长的寿命。这就显然是低效率的利用金属切削时间。由于系统提供的便利之一便是评估的切削参数，这将帮助用户为应用程序选择合适的速度，进给量或切削深度。如果切削数据是正确的而且金属切削问题也得到解决，由于发生故障而引起的停顿将缩短，良好的利用发电能力的目的将可以达到而且金属得切削时间将会有所减少。这就意味着生产成本将会下降很多。该系统开发也为了培训从事金属切削业的人。这些照片和有关问题的资料将会帮助用户更多的认识了解他们。这些图片和信息收集于应用于工业的各种手册和研究报告。参考文献1 Modern metal cutting. 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Cemal Cakir*, Kadir Cavdar1Uludag University, Mechanical Engineering Department, Gorukle 16059, Bursa, TurkeyReceived 8 September 2004; accepted 31 January 2005Available online 21 March 2005AbstractIn metal cutting, the problems need to be well analyzed in order to take precautions before any unexpected results are encoun-tered. This process plays a significant role in achieving consistent quality and in controlling the overall cost of manufacturing. How-ever, it is a difficult task that needs an expert who has a great deal of information and experience in metal cutting. In the presentpaper, a knowledge-based expert system (COROSolve) that investigates problems that are encountered in three main metal cuttingareas: turning, milling and drilling is developed. A great deal of metal cutting operations such as external/internal turning with neg-ative/positive inserts, aluminum turning, parting bars/tubes, grooving, profiling, recessing and threading operations in turning; facemilling, square shoulder milling, end milling, multi-purpose milling and side and face milling operations in milling; and drilling oper-ations that use solid drills or drills with indexable inserts in drilling are taken into consideration. COROSolve gives recommenda-tions for the cutting data (i.e., cutting speed, depth of cut, and feed) and updates the problem, cause and remedy database, thus thenumber of problems that the system can handle is increased.? 2005 Elsevier Ltd. All rights reserved.Keywords: Metal cutting problems; Expert systems; KBS; Tool wear1. IntroductionThe objective of modern manufacturing is to haveefficient control over the organizational facilities in or-der to produce high quality products at lower priceswithin a shorter time period. To achieve better qualityat a lesser price, every attention has to be paid in themanufacturing division by employing better cuttingtools, inserts and high precision machines, etc. 1. How-ever, this is not sufficient for productivity in most of thecases. Choosing the right tool for the right job is impor-tant, but tool wear should also be considered for moreefficient manufacturing. In the literature, many publica-tions do exist on the tool wear in manufacturing of var-ious materials 2.Metal cutting is a chip forming process. Although theprocess is directed at cutting metal to shape and size, thishas to be done by creating defined chips. The chip-form-ing process means that a fresh metal interface is contin-ually produced and forced at very high pressure andtemperature along the tool material 3. The zones pro-duced make it an attractive environment for diffusionand chemical reactions of metal. All cutting tools areworn during machining and continue to do so until theycome to the end of their tool-life. Tool wear is inevitableandas such not a negative process if the answers of when,how much and what type is known. There are certaintypes of wear mechanisms on different types of metal cut-ting processes and similar/different types of problems areencountered as a result of these mechanisms. If these0261-3069/$ - see front matter ? 2005 Elsevier Ltd. All rights reserved.doi:10.1016/j.matdes.2005.01.022*Corresponding author. Tel.: +90 224 4428176; fax: +90 2244428021.E-mail addresses: cemal.tr (M.C. Cakir), cavdar.tr (K. Cavdar).1Tel.: +90 224 4428176; fax: +90 224 4428021./locate/matdesMaterials and Design 27 (2006) 10271034Materials& Designproblems are well analyzed, it could be possible to findthe right solutions to each of them.To analyze a problem in metal cutting, the problemshould be defined precisely and its possible causesshould be well determined. This is a difficult task thatneeds an expert who has a great deal of informationand experience in metal cutting. Today in metal cutting,the expertise facilities about the problems in chip form-ing are mainly provided by the cutting tool producingcompanies. Since the number of people working in thisarea is limited, it is not always possible to find an expertwhen he/she is really needed. Since expert systems havebeen particularly welcome in fields where existing ex-perts are expensive and in short supply, an expert systemthat solves metal cutting problems will be very useful.2. Expert systems for aiding manufacturing processesKnowledge-based systems, or expert systems, arecomputer programs embodying knowledge about anarrow domain for solving problems related to thatdomain. An expert system usually comprises two mainelements,aknowledgebaseandaninferencemechanism (Fig. 1). The knowledge base containsdomain knowledge which may be expressed as anycombination of ?IF-THEN? rules, factual statements,frames, objects, procedures and cases. The inferencemechanism is that part of an expert system thatmanipulates the stored knowledge to produce solu-tions to problems 4.A human expert uses knowledge and reasoning toarrive at conclusions, so does an expert system. Thereasoning carried out in an expert system attemptstomimichumanexpertsincombiningpiecesofknowledge. Thus, the structure or architecture of anexpert system partially resembles how a human expertperforms. Thus, there is an analogy between an expertand an expert system.A more obvious problem is that of gathering therules. Human experts are expensive and are not extre-mely likely to want to sit down and write out a largenumber of rules as to how they come to their conclu-sions. More to the point, they may not be able to.Although they will usually follow a logical path to theirconclusions, putting these into a set of IF . THENrulesmayactuallybeverydifficultandmaybeimpossible.It is quite possible that many human experts, thoughstarting offin their professions with a set of rules, learnto do their job through experiential knowledge and ?justknow? what the correct solution is. Again they may havefollowed a logical path, but mentally they may have?skipped some steps? along the way to get there. An Ex-pert System cannot do this and needs to know the rulesvery clearly.A very strong benefit of expert systems is being ableto widely distribute the knowledge of a single expert,or being able to accumulate the knowledge of severalwidely separated experts in one place. Expert systemsare especially helpful when a task is performed onlyoccasionally and the expert has to relearn the procedureeach time it is performed.Expert systems are used to standardize operations.If you have three machine operators (or engineers) thatperform the same task but each does it differently, anexpert system will do it the same way everytime. Thesesystems can be used to train employees, advise them, orcan actually perform a task such as a calculation. An-other use for expert systems is as job aids for your ex-perts.Theywillallowthemtoperformmoreaccurately, more consistently, and faster, freeing uptime for the expert to be more creative performingthe task. This is especially helpful when dealing with te-dious, repetitious tasks.Consequently, once the domain knowledge to beincorporated in an expert system has been extracted,the process of building the system is relatively simple.Fig. 1. Knowledge based expert system.1028M.C. Cakir, K. Cavdar / Materials and Design 27 (2006) 10271034The ease with which expert systems can be developed hasled to a large number of applications of the tool. In engi-neering, applications can be found for a variety of tasksincluding selection of materials, machine elements, tools,equipment and processes, signal interpreting, conditionmonitoring, fault diagnosis, machine and process con-trol, machine design, process planning, productionscheduling and system configuring. Some recent exam-ples of specific tasks undertaken by expert systems are: identifying and planning inspection schedules for crit-ical components of an offshore structure 5; training technical personnel in the design and evalua-tion of energy cogeneration plants 6; configuring paper feeding mechanisms 7; carrying out automatic re-meshing during a finite-elements analysis of forging deformation 8; storing,retrievingandadaptingplanarlinkagedesigns 9; designing additive formulae for engine oil products10; selecting cutting tools or cutting data 1113.Several potential research areas were identified withrespect to expert systems in manufacturing 14,15.Kojiyama et al. 16 have discussed in their articles thata framework for machining operation planning systems,in which machining know-how extracted and organizedfrom electronic tool catalogs and machining instancedatabases available in the Internet environment plays aprincipal role. On the use of reference machining datacan be constitute, which is derived from the investiga-tion of tool catalogs, related international standards,reference textbooks, and handbooks.Fig. 2. Inputs of the software.M.C. Cakir, K. Cavdar / Materials and Design 27 (2006) 102710341029The application of Mookherjee and Bhattacharyya11 on expert system in the general turning and mill-ing operation is very useful for solving some of thechallenging problems presently faced by manufactur-ing engineers during the integration of CAD and var-ious CNC machining centers. Jiang et al. 17 havedeveloped an expert system to optimize the millingoperationsforprismaticcomponents.Theyhavedescribed a new GT based coding scheme that repre-sentsthesurfacestobemachinedofprismaticcomponents.Limsombutanan 18 has presented an algorithm toselect the cutter size and tool orientation in 5-axis sur-face machining that can act as a holon. Milling the sur-face is divided in to three phases, namely, roughing,semi-roughing and finishing. This algorithm selects thebest tool and plans the tool path autonomously for abicubic (convexconcave) surface based on analysis ofthe curvature.The main objective of the present paper is to buildsuch system that covers most of the major metal cuttingproblems and helps the people who are involved in metalcutting to improve the quality.3. A knowledge-based expert system for metal cuttingproblems3.1. Factors considered in solving metal cutting problemsMost of the problems in metal cutting are the resultof wear mechanisms. All cutting tools wear duringmachining and continue to do so until they come tothe end of their tool-life. Tool wear is inevitable andFig. 3. Flowchart of COROSolve.1030M.C. Cakir, K. Cavdar / Materials and Design 27 (2006) 10271034as such not a negative process if the answers of when,how much and what type is known. Thus, if the prob-lems resulted from tool wear as well as the other harmfulfactors effecting the machining operations are well ana-lyzed, it could be possible to find the right solutions toeach of them. This would reduce the unproductive faultsearching time, therefore reduce machining time, unpro-ductive stoppage times of machine tools, machining costand therefore increase the efficiency of the process.Architecture of the expert system used in solving metalcutting problems is given in Fig. 1. Inputs that are takeninto consideration by the software are given in Fig. 2.3.2. Features of COROSolveThe software has been developed using DELPHI Vi-sual programming language. A major difficulty in build-ingaconsultationsystemwasincapturingandexamining the knowledge elements used in the solutionof the problem. Based upon the design for solving prob-lems in metal cutting study, once the operation type isselected, four major stages have been identified for eachtype of operation: Cutting data recommendations. Problem definition. Cutting data evaluation. Problem editor.The flowchart of the software is given in Fig. . Cutting data recommendationsThe selection of the right cutting tool is critical forachieving maximum productivity during machining.But although the tooling is right, if the machining con-ditions are not up to standard, especially as regards cut-ting data and general stability, problems arise andoptimum tool-life will not be reached. Incorrect cuttingdata, vibrations and lack of rigidity in tool holders andclamping are the main reasons of the metal cuttingproblems.Apart from being a problem solver, the softwareprovides cutting data recommendations for each typeof operation (types of operations were mentionedpreviously), for each type of material group (ISO P,M or K), for each type of application (rough, mediumor finish), for each type of machining condition (good,average,difficult)anddisplays thelistofinsertsavailable (Fig. 4). Here, it is not intended to findthe most suitable insert for the application, but tomonitor the starting values and the working rangesof cutting data (i.e., the cutting speed, feed rate andthe depth of cut) for the insert used in metal cutting.At this stage, it is possible to see the suitable gradethat was determined due to the selected operation,material group, application, etc. Besides, the list ofmaterials that each material group consist of can alsobe observed.Recommended cutting data values were acquiredfrom Sandvik Coromant 20, the cutting data fromthe other cutting tool vendors can be used as the rec-ommended values as well. Cutting data values dis-played are for a certain material hardness and for acertain tool-life. For any workpiece material havingdifferent hardness values than the specified values,and the tool-life different than 15 min, the cutting dataprovided should be multiplied by the correction factors(see Table 1).Fig. 4. Cutting data recommendations.M.C. Cakir, K. Cavdar / Materials and Design 27 (2006) 1027103410313.2.2. Analysing the metal cutting problemsThere are various different/similar types of problemsin metal cutting processes. In appearance some of theseproblems are identical and very hard to be distinguishedfrom each other. The classification of problem types hasbeen developed to form an important basis for assessingthe machining operation and to optimize productivityby getting the tool grade and machining conditions rightfor the type of cut and material. The right tool, goodstarting values for cutting data, expert support, ownexperience, good quality of workpiece materials and ma-chine conditions are important ingredients for success inmachining. Aggregation of problem lists from varioustool manufacturers is classified to form KBS used bythe software.The user analyses the metal cutting problems either inone or two stages: by straightforwardly picking outProblem Definition option from the menu or by checkingout the cutting data used in the metal cutting processfirst and accessing to the problem definition sectionafterwards. Problem Definition section displays the listof problems, their possible causes and the remedies withrespect to the causes. Once a problem is selected (i.e.,flank wear in turning or chip jamming in drill flutes indrilling), a picture that provides a clear definition tothe problem and the list of possible causes are displayed.Consequently once a possible cause is selected, the rem-edies are determined. More information about the prob-lem is obtained by clicking on ? (Fig. 5).3.2.3. Cutting data evaluationIn metal cutting, most of the problems are the resultof unsuitable cutting data for the application. Thus,before straightforward listing of the problems, the useris advised to check the cutting data for the operation,for the application and for the machining conditionsto find out whether the cutting speed, feed rate andthe cutting depth are correct for the length, thicknessand nose radius of the insert used. The Cutting Dataoption checks if the cutting data in the operation areright for the insert in use and this task is basically theFig. 5. Problems, causes and remedies.Fig. 6. Checking the cutting data.Table 1Material hardness and tool life considerations 19ISO/ANSIHBReduced hardnessIncreased hardness?60?40?200+20+40+60+80+100P1801.441.251.1110.910.840.770.720.67M1801.421.241.1110.910.840.780.730.68K260610.950.90.860.820.79Tool life (min)10152025304560Correction factor1.111.00.930.880.840.750.701032M.C. Cakir, K. Cavdar / Materials and Design 27 (2006) 10271034comparison of the cutting data with the ideal values cal-culated from the multiplication of the catalogue valuesand the correction factors. If there is no match (thismeans the values of cutting data are not in the range)the user is advised to correct the cutting data. In millingand drilling only cutting speed and feed rate values areconsidered, in drilling this consideration takes the drilldiameter and the grade of the centre/periphery insertinto account (Fig. 6). In the figure, cutting data for facemilling of steel for medium feed rates (L for light, M formedium, H for heavy milling operations) are evaluatedand since the feed value is lower than the ideal valuescalculated for given hardness and tool life, a warningis displayed.Once the cutting data are reviewed (and corrected),accessing to the problem definition section is the nextstep.Sincethecuttingdataarecorrected,thelistofcausesand the remedies will now be different and no such causesasCuttingspeedistoohighorFeedrateistoolowwillnot be amongst the causes of the related problem.The software is capable of analysing more than 100types of problems in various types of operations andproviding remedies to the nearly 200 causes (340 reme-dies). The knowledge contained in the system has beencompiled from two main sources: from human expertsworking in the field of metal cutting and from thetechnical documents, catalogues or handbooks of vari-ous cutting tool producing companies 2. Problem editorThe knowledge contained in the system has beencompiled from two main sources: from human expertsworking in the field of manufacturing and from the tech-nical documents, catalogues or handbooks of variouscutting tool producing companies. The success of an ex-pert system is hidden in its expandable structure like ahuman expert who adds every new solution he comesacross to his knowledge and uses this knowledge in hisfuture analyses. Thus, COROSolve has an expandabledatabase structure that grows to handle more and moreproblems everyday.Since the system has a separate and modular knowl-edge base, it is very easy indeed to update the system bysimply getting into the database and editing the knowl-edge files. The more information the system contains,the more problems it can handle in metal cutting.Knowledge base is the heart of the system, therefore itis the task of a few people who are responsible fromthe production to add, delete or modify it. Thus, theuser needs to know the password to access to the knowl-edge base.Problem edit allows the new problems, picture andinformation files related to the problems, causes andthe remedies of the problems to be added to the knowl-edge base. Besides, it is possible to add new causes to theproblems, or new remedies to the causes that are alreadyexist in the knowledge base (Fig. 7).The system is multi-linguistic, therefore it is capableof handling the metal cutting problems both in Turkishand English. Once the language is determined, all theprogram menus and problem, cause and remedy listsare displayed in the language chosen.4. ConclusionsThis paper introduces an expert system approach forthe task of solving metal cutting problems in variousmachining operations. Since there are not many workexist in the literature about this subject and since thistype of system can mostly fulfil the requirements in me-tal cutting industry, the work described here can beFig. 7. Adding a new remedy.M.C. Cakir, K. Cavdar / Materials and Design 27 (2006) 102710341033considered as a useful piece of work. In manufacturingindustry, especially in small or medium-volume machineshops, incorrect cutting data are the main reason of theproblems. Tools were generally run at lower cutting datato make them last longer for less frequent changes. Thisthen obviously meant poor utilization of the metal cut-ting time. Since one of facilities that the system provideis the evaluation of the cutting data, it will help the userto choose the right speed, feed or the depth of cut for theapplication. If the cutting data are correct and the metalcutting problems are solved, the stoppages due to thebreakdowns will be shorten, good utilization of powercapacity will be achieved and the metal cutting time willtherefore be reduced. This means a great deal of reduc-tion in production cost.The system developed intends to educate the peoplein metal cutting industry as well. The pictures and theinformation about the problems help the users to recog-nize and learn more about them. These pictures and theinformatio