(论文翻译 页数:9 字数:3885)如果从事数控机床工作，很可能会从事数控编程和CAD/CAM系统的工作。
CAD（计算机辅助设计）常指各种能够用几何模型、曲面模型或实体模型描述机械零件的软件。CAM（计算机辅助制造）是用于开发数控程序的软件。
三个不同的用途
工程设计和制造使用CAD/CAM软件有三个截然不同的用途：
1．设计建模
机械设计工程师使用CAD软件来设计零件。最初设计出来的零件被称为“模型”。模型可用图纸或CAD数据文件表示。
2．制造模型
•制造工程师或数控程序员使用CAD软件；
•创建有图纸定义的零件的计算机模型；
•评估和修正CAD设计数据，以符合制造公差要求。这是最为常见的工作；
•由原始设计建立适于制造的零件新模型，这些工作包括加入拔模角度或者开发多工序制造中不同工步的零件模型；
•设计夹具、模腔、模芯、模架和其他加工所需的模型。在零件加工之完成所要制造的模型的准备工作。
3．数控编程
为了加工上述定义的制造模型，制造工程师或数控编程员使用CAM软件选择刀具、加工方法和加工工序。注意：建立制造模型的人员就是进行数控编程的人员。
刚开始，只有CAD系统，工程师用CAD系统进行零件绘图。早期的CAM系统协助数控编程员/机械师/制造工程师根据这些CAD图纸进行编程。这种制图方法以及根据零件图纸编程的方法仍然是十分费时的，并且受到人为错误因素的影响。有人就有了消除这种重复的绘图步骤的聪明想法，于是诞生了集成的CAD/CAM系统。
加工方法
可用两种方法加工输入的CAD模型：一种是运用曲面边界保护，由曲面和刀具几何形状生成刀具轨迹；另一种是运用布尔运算，计算刀具的扫掠体，直接由实体模型生成刀具轨迹。
第二种方法需要大量的计算，因为刀具的移动需要连续的基于实体相交点的计算值。由于所用的数学算法非常复杂，产生错误的可能性很大，并且加工时产生过切的可能性也较大。通过生成10000~100000次单独的刀具轨迹移动，只要有一次出错，就会中断了整个实体加工，这都会影响表面粗糙度。
如果CAM系统使用效率很低的技术生成刀具轨迹，任何软件或硬件向导都不能提高数控编程的速度。最好的方法是将零件分成由无数三角形（小平面或平面）组成的多面体，用户指定的精度决定了小平面的数目。成品件的精度通常在0.0005~0.0001英寸之间，因此用数学求解刀尖形状和小平面的交点比用公式直接由实体生成刀具轨迹更加快速，更加可靠。
CAD/CAM and CNC
From CNC Engraving And Milling Machine
If you are involved with CNC machines, you are probably involved with CNC programming and CAD/CAM systems.
CAD(Computer Aided Design) is widely used to describe any software capable of defining a mechanical component with geometry, surfaces, or solid models. CAM(Computer Aided Manufacturing) is software used to develop NC programs.
Three different purposes
Engineering design and manufacturing uses CAD/CAM software for three distinctly different purposes:
Design modeling
A mechanical design engineer uses CAD software to create a part. This definition of the part can be called its model. This model can be represented as a drawing or a CAD data file.
Manufacturing modeling
•A manufacturing engineer or NC programmer, uses CAD software to:
•Develop a computer model of a part that was defined by a drawing.
•Evaluate and repair the design CAD data to manufacturing tolerances. This is a surprisingly common task.
•Create new part model from the original design to allow for manufacturability. This would include adding draft angles or developing models of the part for different steps in multi-process manufacturing.
•Design models of fixtures, mold cavities, mold cores, mold bases, and other tooling. An example of what manufacturing modeling needs to be done before a part can be machined is shown.。
NC programming
A manufacturing engineer or NC programmer uses CAM software to select tools, methods, and procedures to machine the models defined in the manufacturing modeling section described above. Note that the user that performs manufacturing modeling is usually the same user that performs NC programming.
In the beginning, there were only CAD systems. Engineers used CAD systems to draw pictures of parts. The first CAM systems helped an NC programmer/machinist/manufacturing engineer program from these drawings. This making of drawings, and programming parts from drawings, was (and still is) time consuming and subject to a lot of human error. Someone got the bright idea to eliminate this to-and-from drawing step, and integrated CAD/CAM was born.
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