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CAD CAM技术在摩托 护片锻模设计中的应用 CAM 技术 摩托 锻模 设计 中的 应用

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南昌航空大学科技学院学士学位论文计算机辅助设计与制造CAD/CAM是表示计算机辅助设计和计算机辅助制造的专业术语。它是一种使用计算机完成某些设计和生成功能的技术。在生产企业里，人们通常把设计和制造是为两项有着明显不同职能的分工，而这项技术正朝着设计与制造的更大程度一体化方向发展。最终，CAD/CAM将会为未来的计算机集成工厂提供技术基础。计算机辅助设计（CAD）可定义为运用计算机系统对设计的创意、修改、分析或优化予以辅助。这些由硬件和软件构成的计算机系统，用于完成用户公司要求的特定设计功能。CAD硬件通常包括：一台计算机，一个或多个图形显示终端，键盘和其他外围设备。CAD软件包括各种计算机制图程序，这些程序便于用户公司完成设计职能，如：零部件的应变分析，机构的动态响应，热传输计算和数控零件编程。由于用户的生产流程、制造工艺和销售市场方面的差异，应用程序的配置也将因用户而异。这些因素均导致对CAD系统要求的差异性。计算机辅助制造（CAM）可定义为通过直接或间接与厂家生产资源相适应的计算机界面，使用计算机系统来规划、管理和控制制造工厂的运行。正如定义所表示的那样，CAM应用程序可分为两大类：1. 计算机监控程序；2. 制造程序。二者之间的区别是理解计算机辅助制造的基础。计算机辅助制造的应用程序，除了为监控制造过程而直接使用计算机界面的应用程序之外，还包括在工厂生产运行过程中由计算机提供支持的间接应用程序。在这些应用程序中，计算机并不直接与制造过程相联接。相反，在脱机状态下，计算机可用来提供计划书、进度表、预报、指令和使厂家生产资源管理更加有效的信息资料。计算机和制造过程间的关系如下图所示。图中虚线用来说明交流和控制处于脱即状态下，需要人来完善界面。目前，CAM的应用需要由人来为计算机输入程序，解释计算机的输出，并采取所要求的措施。生产操作 计算机 处理数据 控制信号 CAM用于生产支持Notes:1. CAD(computer-aided design) 计算机辅助设计2. CAM(computer-aided manufacturing) 计算机辅助制造3. computer monitoring and control 计算机监控4. manufacturing support applications 生成支持应用软件5. peripheral equipment 外围设备（外设）6. computer graphics 电脑制图什么是CAD/CAM软件？许多刀具轨迹是简单的但太复杂和昂贵以致于人们很难制造，对于这种情况，我们需要在计算机的帮助下来作数控部分程序。CAD/CAM最基础的概念是，我们可以用计算机辅助设计系统在计算机上画出工件的几何形状。几何形状一旦完成，我们就可以用计算机辅助制造系统根据CAD的几何形状，生成数控机床的刀具轨迹。利用CAD绘制所有路径对数控加工的路径如下：第一步：利用CAD绘制几何图形已被定义这种工件包括型腔加工。对于这种型腔加工很可能将花几个小时去制造代码。然而，我们能够利用CAM程序去创造NC代码在每分钟内。第二步：接着，这个模型就被输入到CAM模块中。然后，我们就选择合适的几何形状并定义要生成的刀具轨迹类型，在这个例子中就是一个型腔。我们一定也能够让CAM系统如刀具的使用，材料的类型，进给量，切屑深度等信息。第三步：CAM模型证实保证刀具轨迹的正确性。如果发现了一些错误，最简单就是在某个位置上加以改正。第四步：CAD/CAM模块最终产生的是NC代码。通过模型的后处理则可以生成适用于特定CNC控制器的NC代码。我们取字体的首字母即CAPP，它代表了计算机辅助程序。CAPP是使用计算机辅助在数控刀具轨迹中的应用。然而，CAPP从来就没有真正获得广泛的流传和接受，而且至今我们很少听到这个项目。取而代之的是在更多的市场上使用CAD/CAM，使用计算机的思维来帮助生产NC程序。不幸的是，因为CAM是一个整体技术与制造技术和自动化技术有着关联的不仅是软件，而且使用CNC机器工具。描述CAD/CAM组成及功能CAD系统包括CAD设备及CAM设备每个都有许多功能元件。它们将在短时间内扫描这些元件目的是为了了解其工作的整个过程。1. CAD模型系统的CAD部分用于生成可作为CAD模型的几何形状。CAD模型是工件几何形状的电子描述，她在数学上是十分精确的。不论是独立的CAD系统还是作为CAD/CAM软件包的一部分的CAD系统，往往都可以在几个不同的层次上混合使用。两维线条图 几何图形被体现出两个方向，就象一张清单，Z轴深度将不得不与CAM相关。三维线框模型通过将代表边界的元素连接早一起，就可以在三维空间中表现几何形状。虽然线框图难以想象,但可以得到CAM所需的所有的Z向信息。三维表面模型 它与线框模型十分相似，所不同的是，在线框模型间覆盖了一层薄薄的外皮，从而使模型更形象。另外，模型型腔是空的，完成表面模型即可。三维实体模型这种当前高科技市场形式被使用必须通过所有的高端科技软件。几何形状被看作是一个实体特征其包括许多方面。实体模型可以被切开以展示内部特征，而不仅仅是拥有一层表皮。2. CAM模型根据CAD模型提供的几何形状，CAM模块用于创建加工工艺模型。例如，CAD模型可能包括一些特征，即凹槽型腔。我们可能应用其加工路线来加工几何图形，然后，所有的刀具路径将是自动的产生凹槽行程。同样，CAD模型也可包括几何图形应该产生钻的操作。我们能够选择简单的几何图形和按照CAM系统的说明在适当的位置上进行钻孔。CAM系统将生成描述加工操作的普通中间代码，这些代码以后可被用来生成G和M代码或会话式程序。在它们合适的环境下，有些系统产生中间代码。而其他使用较标准代码例如APT就是他们的中间文件。CAM模块也有多种类型和层次。首先，通常有些不同模型功能如铣、钻、以及装配，每一步工艺是唯一的，典型的模型有附加软件。每一个模型也可能使用不同的设备。例如，开始用简单的设备，到后来用复杂的、多方向的刀具轨迹路线，CAM模型中铣床加工通常加工的过程如下： 21/2-方向的机床 3个方向的机床 加工表面的机床 5个方向混合的机床每种体现出高精度的设备不可能在所有的坏镜下制造，一个工序很可能只要求三个方向的设备，而一个模型工序很可能需要全部的表面加工设备，而且可能需要五个方向的CAM软件包混合这样就有可能完成其加工表面。这种一流的软件安装很可能需要花费￥5000，但是许多复杂模型将花费￥15000甚至更多。因此，我们没有必要购买这种高水准的软件，因为我们不能完全发挥他们的潜能。3. 几何图形及刀具轨迹我们必须理解一个重要的概念，即CAD所绘制的几何形状并不一定与CNC机床加工出的几何形状完全一致。只要刀具轨迹是直线或圆弧，CNC机车就可以加工出非常精确的刀具轨迹。CAD系统也可能加工高精度几何图形如直线及圆弧，但是也可能加工许多不同层次的曲面，同样许多这种曲面被认为是非均匀有理B样条曲线。事实上，NURBS曲线可以描绘出从直线或圆弧到复杂的表面的任何几何形状。例如，就象几何图形为椭圆形，椭圆有一系列曲线，有着不同的环形弧，椭圆在CAD系统利用鼠标单击很容易产生。然而，一个标准的CNC加工刀具不能够直接使用产生一个椭圆它只能产生直线和圆弧。CAM系统将顺从于这种问题，通过估算用直线段代替曲线。CNC机床刀具通常只能识别圆弧或直线。因此，CAM系统必须估计直线段代替曲线之间的公差带。在这种情况下，就像椭圆刀具轨迹产生包含着用直线段代替曲线之间的公差带。CAM系统会在真正的曲线两侧各生成一个几何边界，从而形成一个公差带。它将生成一道刀具轨迹线包含着少量的公差带，结果这刀具轨迹将在数学理论上不正确CAM系统只能估算表面，使用它最基本的方法是为了估算刀具轨迹包括两维曲线及三维表面曲线。有些CAM系统也有可能直接绘制直线段为圆弧曲线。这可能在程序中产生许多模块导致表面的光滑。这种出现能够控制公差带的大小，其目的是使的刀具轨迹更加精确，这是有必要的。较小的公差带可以生成细致的刀具轨迹以及大量的直线段，而较大的公差带将会产生较少的直线段，刀具轨迹也比较粗糙。每一个直线段将要求在NC程序有模块代码。因此，当使用这种技术时，NC程序能够扩大范围。在加工表面时我们一定要细心，依靠计算机生成正确的刀具很容易，但在用球状端铣刀进行曲面的精加工是须进一步估价。如果我们没能注意到这种技术的局限性，那么精加工后工件的精度就会大打折扣。4. 刀具库和材料库为了创建机械加工工艺，CAM系统需要了解切割刀具的利用以及机械材料。CAM注意的是通过提供可定制的刀具型号及类型。材料库包括的信息是最优化的切削速度以及进给量。CAM使用这种信息聚在一起创建正确的刀具轨迹以及机床参数。这类刀具和材料库的格式经常是独有的，这一点带来了一些兼容问题。专用的工具库及材料库不容易修改或不容易使用其他的系统。进步的CAM开发者趋向于将刀具和材料库生成数据库文件，这样就可以为其他的应用者进行修改和定制提供方便。5. 检验及后置处理CAM系统通常提供检验刀具轨迹是否正确性的功能。这可以通过加工操作的刀具中心线的简单绘制或通过复杂的实体模型来实现。实体验证通常是CAD/CAM软件公司已经获得许可的第三方软件。然而，它可能是作为一个独立的软件包。后置处理器是一个软件程序，他将通过的中间代码格式化为使用于每个特定机床控制器的NC代码。后置处理器通常可以通过模板和变量被定制为需要的样式。6. 便捷性电子数据的便捷性是CAD/CAM系统唯一致命的弱点，这个问题任就是一件十分耗时的事情。CAD文件创建了许多格式以及它们之间有许多步同的组成。利用CAD系统创建一个复杂的模型是比较昂贵的。因此，我们希望使模型的便捷性最大化，而使在不同系统中重新生成几何模型的需求最小化。CAM模型与手提式的CAD模型不同，我们通常不能够发展一个CAM模型以及把它转换成其他格式。唯一被广泛接受的CAM模型交换版本就是自动编程工具（APT）。自动编程工具是一种利用描述机床操作的程序语言工具，自动编程工具是一种标准的、有着好的文件能够通过三个方向软件的发展的促进。许多CAD/CAM系统可以按照这种标准输出文件，而（由此生成的）CAM文件以后也可以被后置处理程序和校验软件使用。有时会有这样的情况，即特定的CAD/CAM系统生成的特有的中间文件不经任何额外的后置处理就可以直接输入到机床之中。这是理想的解决方案，然而目前尚无任何标准管理这种交换。CAD/CAM模型交换的另一种方法是利用逆向后置处理器。逆向后置处理器可以从数控G&M代码程序生成CAD/CAM模型。这种程序确实有些作用，但是，程序员必须花相当多的时间去搞清楚模型的设计意图，而且还要将刀具路径从几何形状中分离出来。总体来说，后置处理器的应用具有一定的局限性。软件的组成及发展趋势在整个工业上，许多软件包利用CAD或CAD/CAM。纯CAD系统被应用于所有的设计领域，实际上今天所有的产品都是用CAD软件设计出来的用纸笔绘的日子已经一去不复返了。另一方面，CAD/CAM软件包有着更多专利。CAD/CAM虽然小，但地位十分重要，它的应用通常限制在加工和装配业，其数量要比CAD小得多。CAD/CAM系统包括CAD软件设计以及CAM软件去创建刀具轨迹和NC代码。然而，普通的CAD模型相比于纯CAD软件比较弱及不精炼。这种不匹配造成了CAD设计者与CAD/CAM程序员之间一直以来的争论，其主题是如何使CAD/CAM能够融合。如果先在业界一流的CAD系统上生成所有几何形状，然后再图形输入到某个CAD/CAM系统中，就会产生很大的争论。工程师创建CAD模型逐步形成一种模式，商业就会更加充裕。几何形状能够输入到CAD/CAM软件包中产生处理模型。因此，工业引导CAD软件包走向不正式的标准。标准的接受度越高，拥有该软件的公司的投资回报率就会越高。反对意见来自于小的组织，他们没有必要或者没有资源同时拥有昂贵的符合工业标准的CAD软件包以及CAD/CAM软件包。他们往往需要根据纸上工程图重画几何图形，或者用并不完善的翻译设备输入模型。任何起源模型将结束走向于更高的正式的CAD/CAM文件。这类模型很可能在将来又被翻译成更为标准的版本。不论选择什么样的方法，各种组织和个人往往都会竭尽保护某种技术。如果他们检查发现有巨大的效果，花时间去学习它以及吸收科学知识。然而，他将转变成一种新的技术是很困难的事，即使它们体现出具有无法抵抗的证据来证实更好的方法。这是一次十分痛苦的转变，当然如果我们能够看见我们的将来，这是不可能发生的事情。但是事实上，我们不可能总是预测支配的科学技术将在几年内走下坡路。结果形成了技术壕沟，要从脚下消除这种壕沟将会十分困难和昂贵。大约只能保证，我们能够发现去选择技术出现最标准，即使不完美也要留住它.然而，如果发现走下坡路，我们将也更加适应这位置。Modern design and manufacturing CAD/CAMCAD/CAM is a term which means computer-aided design and computer-aided manufacturing. It is the technology concerned with the use of digital computers to perform certain functions in design and production. This technology is moving in the direction of greater integration（一体化）of design and manufacturing, two activities which have traditionally been treated as distinct（清楚的）and separate functions in a production firm. Ultimately, CAD/CAM will provide the technology base for the computer-integrated factory of the future.Computer-aided design (CAD) can be defined as the use of computer systems to assist in the creation, modification, analysis, or optimization（最优化）of a design. The computer systems consist of the hardware and software to perform the specialized design functions required by the particular user firm. The CAD hardware typically includes the computer, one or more graphics display terminals, keyboards, and other peripheral equipment. The CAD software consists of the computer programs to implement（实现，执行）computer graphics to facilitate the engineering functions of the user company. Examples of these application programs include stress-strain（压力-应变）analysis of components（部件）, dynamic（动态的）response of mechanisms, heat-transfer calculations, and numerical control part programming. The collection of application programs will vary from one user firm to the next because their product lines, manufacturing processes, and customer markets are different these factors give rise to differences in CAD system requirements.Computer-aided manufacturing (CAM) can be defined as the use of computer systems to plan, manage, and control the operations of a manufacturing plant through either direct or indirect computer interface with the plants production resources. As indicated by the definition, the applications of computer-aided manufacturing fall into two broad categories: 1.computer monitoring and control. 2.manufacturing support applications.The distinction between the two categories is fundamental to an understanding of computer-aided manufacturing.In addition to the applications involving a direct computer-process interface（界面，接口）for the purpose of process monitoring and control, compute-aided manufacturing also includes indirect applications in which the computer serves a support role in the manufacturing operations of the plant. In these applications, the computer is not linked directly to the manufacturing process. Instead, the computer is used “off-line”（脱机）to provide plans, schedules, forecasts, instructions, and information by which the firms production resources can be managed more effectively. The form of the relationship between the computer and the process is represented symbolically in the figure given below. Dashed lines（虚线）are used to indicate that the communication and control link is an off-line connection, with human beings often required to consummate（使圆满）the interface. However, human beings are presently required in the application either to provide input to the computer programs or to interpret the computer output and implement the required action.Manufacturing operations computer Process data Control signals CAM for manufacturing supportWhat is CAD/CAM software? Many toolpaths are simply too difficult and expensive to program manually. For these situations, we need the help of a computer to write an NC part program.The fundamental concept of CAD/CAM is that we can use a Computer-Aided Drafting (CAD) system to draw the geometry of a workpiece on a computer. Once the geometry is completed, then we can use a computer-Aided Manufacturing (CAM) system to generate an NC toolpath based on the CAD geometry. The progression（行进，级数 ）from a CAD drawing all the way to the working NC code is illustrated as follows:Step 1: The geometry is defined in a CAD drawing. This workpiece contains a pocket to be machined. It might take several hours to manually write the code for this pocket（凹槽，型腔）. However, we can use a CAM program to create the NC code in a matter of minutes. Step 2: The model is next imported into the CAM module. We can then select the proper geometry and define the style of toolpath to create, which in this case is a pocket. We must also tell the CAM system which tools to use, the type of material, feed, and depth of cut information.Step 3: The CAM model is then verified to ensure that the toolpaths are correct. If any mistakes are found, it is simple to make changes at this point. Step 4: The final product of CAD/CAM process is the NC code. The NC code is produced by post-processing（后处理）the model, the code is customized（定制，用户化）to accommodate the particular variety of CNC control. Another acronym that we may run into is CAPP, which stands for Computer-Aided Part Programming. CAPP is the process of using computers to aid in the programming of NC toolpaths. However, the acronym CAPP never really gained widespread acceptance, and today we seldom hear this term. Instead, the more marketable CAD/CAM is used to express the idea of using computers to help generate NC part programs. This is unfortunate because CAM is an entire group of technologies related to manufacturing design and automation-not just the software that is used to program CNC machine tools.Description of CAD/CAM Components and FunctionsCAD/CAM systems contain both CAD and CAM capabilities each of which has a number of functional elements. It will help to take a short look at some of these elements in order to understand the entire process.1. CAD ModuleThe CAD portion of the system is used to create the geometry as a CAD model. The CAD model is an electronic description of the workpiece geometry that is mathematically precise. The CAD system, whether stand alone or as part of a CAD/CAM package, tends to be available in several different levels of sophistication. （强词夺理，混合）2-D line drawings 两维线条图Geometry is represented in two axes, much like drawing on a sheet of paper. Z-level depths will have to be added on the CAM end.3-D wireframe models 三维线框模型Geometry is represented in three-dimensional space by connecting elements that represent edges and boundaries. Wiregrames can be difficult to visualize（想象，形象化，显现）, but all Z axis information is available for the CAM operations. 3-D surface models 三维表面模型These are similar to wireframes except that a thin skin has been stretched over the wireframe model to aid in visualization. Inside, the model is empty. Complex contoured Surfaces are possible with surface models.3-D solid modeling 三维实体模型This is the current state of the market technology that is used by all high-end software. The geometry is represented as a solid feature that contains mass. Solid models can be sliced（切片，部分 ，片段）open to reveal internal features and not just a thin skin. 2. CAM ModuleThe CAM module is used to create the machining process model based upon the geometry supplied in the CAD model. For example, the CAD model may contain a feature that we recognize as a pocket .We could apply a pocketing routine to the geometry, and then all of the toolpaths would be automatically created to produce the pocket. Likewise, the CAD model（模子，铸型）may contain geometry that should be produced with drilling operations. We can simply select the geometry and instruct the CAM system to drill holes at the selected locations.The CAM system will generate a generic（一般的，普通的 ）intermediate（中间的，媒介）code that describes the machining operations, which can later be used to produce G & M code or conversational programs. Some systems create intermediate code in their own proprietary（所有的，私人拥有的 ） language, which others use open standards such as APT for their intermediate files.The CAM modules also come in several classes and levels of sophistication. First, there is usually a different module available for milling, turning, wire EDM, and fabrication（装配）. Each of the processes is unique enough that the modules are typically sold as add-ins（附加软件）. Each module may also be available with different levels of capability. For example, CAM modules for milling are often broken into stages as follows, starting with very simple capabilities and ending with complex, multi-axis toolpaths : 21/2-axis machining Three-axis machining with fourth-axis positioning Surface machining Simultaneous five-axis machiningEach of these represents a higher level of capability that may not be needed in all manufacturing environments. A job shop might only require 3-axis capability. An aerospace contractor might need a sophisticated 5-axis CAM package that is capable of complex machining. This class of software might start at $5,000 per installation, but the most sophisticated modules can cost $15,000 or more. Therefore, there is no need to buy software at such a high level that we will not be able to use it to its full potential.3.Geometry vs. toolpathOne important concept we must understand is that the geometry represented by the CAD drawing may not be exactly the same geometry that is produced on the CNC machine tool. CNC machine tools are equipped to produce very accurate toolpaths as long as the toolpaths are either straight lines or circular arcs. CAD systems are also capable of producing highly accurate geometry of straight line and circular arcs, but they can also produce a number of other classes of curves. Most often these curves are represented as Non-Uniform（不均匀的，不一致的）Rational Bezier Splines (NURBS) （非均匀有理B样条）. NURBS curves can represent virtually any geometry, ranging from a straight line or circular arc to complex surfaces. Take, for example, the geometric entity that we call an ellipse（椭圆形）. An ellipse is a class of curve that is mathematically different from a circular arc. An ellipse is easily produced on a CAD system with the click of the mouse. However, a standard CNC machine tool cannot be use to directly problem an ellipse it can only create lines and circular arcs. The CAM system will reconcile（使和解，使顺从）this problem by estimating the curve with line segments.CNC machine tools usually only understand circular arcs or straight lines. Therefore, the CAM system must estimate curved surfaces with line segments. The curve in this illustration is that of an ellipse, and the toolpath generated consists of tangent line segments that are contained within a tolerance zone.The CAM system will generate a bounding geometry on either side of the true curve to form a tolerance zone. It will then produce a toolpath from the line segment that stays contained within the tolerance zone. The resulting toolpath will not be mathematically correct the CAM system will only be able to estimate the surface. This basic method is used to produce estimated toolpaths for both 2-D curves and 3-D surface curves.Some CAM programs also have the ability to convert the line segments into arc segments. This can reduce the number of blocks in the program and lead to smoother surfaces.The programmer can control the size of the tolerance zone to create a toolpath that is as accurate as is needed. Smaller tolerance zones will produce finer toolpaths and more numerous line segments, while larger tolerance zones will produce fewer line segments and coarser（粗糙的） toolpaths. Each line segment will require a block of code in the NC program, so the NC part program can grow very large when using this technique.We must use caution when machining surfaces. It is easy to rely on the computer to generate the correct tooolpath, but finished surfaces are further estimated during machining with ball end mills. If we do not pay attention to the limitations of these techniques, then the accuracy of the finished workpiece may be compromised（妥协，折衷）.4.Tool and material librariesTo create the machining operations, the CAM system will need to know which cutting tools are available and what material we are machining. CAM systems take care of this by providing customizable （可定制的 ）libraries of cutting tools and materials. Tool libraries contain information about the shape and style of the tool. Material libraries contain information that is used to optimize（使最优化）the cutting speeds and feeds. The CAM system uses this information together to create the correct toolpaths and machining parameters.（参数）The format of these tool and material libraries is often proprietary（专利的，独占的，私有的）and can present some portability issues. Proprietary（轻便，移动）tool and material files cannot be easily modified or used on another system. More progressive （ 改革论者，进步论者，前进的）CAM developers tend to produce their tool and material libraries as database files that can be easily modified and customized for other applications. 5.Verification and post-processorCAM systems usually provide the ability to verify that the proposed toolpaths are correct. This can be via a simple backplot（背景绘制） of the tool centerline or via a sophisticated solid model of the machining operations. The solids verifications（确认，查证）is often a third-party software that the CAD/CAM software company has licensed.（得到许可的 ） However, it may be available as a standalone package.The post-processor is a software program that takes a generic intermediate code and formats the NC code for each particular machine tool control. The post-processor（后置处理器） can often be customized through templates（模板）and variables to provide the required customization. （用户化，专用化，定制）6.Portability 轻便，可带的Portability of electronic data is the Achilles heel(唯一致命的弱点)of CAD/CAM systems and continues to be a time-consuming concern. CAD files are created in a number of formats and have to be shared between many organizations. It is very expensive to create a complex model on a CAD system; therefore, we want to maximize the portability of our models and minimize the need for recreating the geometry on another system. DXF, DWG, IGES, SAT, STL and parasolids are a few of the common formats for CAD data exchange.CAM process models are not nearly as portable as CAD models. We cannot usually take a CAM model developed in one system and transfer it to another platform. The only widely accepted standard for CAM model interchange is a version of Automatically Programmed Tool (APT). APT is a programming language used to describe machining operations. APT is an open standard that is well documented and can be accessed by third-party software developers. A number of CAD/CAM systems can export to this standard, and the CAM file can later be used by post-processors and verification software. There are some circumstances when the proprietary intermediate files created by certain CAD/CAM systems can be fed directly into a machine tool without any additional post-processing. This is an ideal solution, but there is not currently any standard governing this exchange.One other option for XAD/CAM model exchange is to use a reverse post-processor. A reverse post-processor can create a CAD/CAM model from a G &M-code of NC part program. These programs do work; however, the programmer must spend a considerable amount of time determining the design intent of the model and to separate the toolpaths from the geometry. Overall, reverse post-processing has very limited applications.Software issues and trendsThroughout industry, numerous software packages are used for CAD and CAD/CAM. Pure CAD systems are used in all areas of design, and virtually any product today is designed With CAD software-gone are the days of pencil and paper drawings.CAD/CAM software, on the other hand, is more specialized. CAD/CAM is a small but important niche（适当的位置）confined to machining and fabrication organizations, and it is found in much smaller numbers than its CAD big brother.CAD/CAM systems contain both the software for CAD d