关于 CNC 路由器你应该知道什么？

简介

CNC路由器是一种机床套件，其刀具路径可以通过计算机数控进行控制。它是一种计算机控制的机器，用于切割各种硬质材料，如木材、复合材料、铝、钢、塑料和泡沫。它是具有 CNC 变体的多种工具之一。 CNC雕刻机在概念上与CNC铣床非常相似。

CNC 路由器有多种配置，从小型家用“台式”CNC 路由器到用于造船设施的大型“龙门”CNC 路由器。虽然有很多配置，但大多数 CNC 路由器都有几个特定的​​部分：一个专用的 CNC 控制器、一个或多个主轴电机、交流逆变器和一个工作台。

CNC 路由器一般有 3 轴和 5 轴 CNC 格式。

CNC 路由器由计算机运行。坐标从单独的程序上传到机器控制器。 CNC 路由器所有者通常有两个软件应用程序——一个用于设计 (CAD) 的程序，另一个用于将这些设计转换为机器指令程序 (CAM)。与 CNC 铣床一样，CNC 路由器可以通过手动编程直接控制，但 CAD/CAM 为轮廓加工开辟了更广泛的可能性，加快了编程过程，并且在某些情况下创建了手动编程即使不是真的不可能的程序，当然商业上不切实际。

CNC 路由器在执行相同的重复性工作时非常有用。 CNC 路由器通常会产生一致和高质量的工作，并提高工厂的生产力。

CNC 路由器可以减少浪费、错误频率和成品上市所需的时间。

CNC 路由器为制造过程提供了更大的灵活性。它可用于生产许多不同的物品，如门雕、室内外装饰、木板、招牌、木框、线条、乐器、家具等。此外，CNC 铣刀通过自动化修边过程使塑料的热成型变得更容易。 CNC 路由器有助于确保零件的可重复性和足够的工厂产量。

数控

今天所知的数控技术出现于 20 世纪中叶。可以追溯到1952年，美国空军，以及美国马萨诸塞州剑桥市的约翰·帕森斯和麻省理工学院的名字。它直到 1960 年代初才应用于生产制造。真正的繁荣以 CNC 的形式出现，大约在 1972 年，十年后随着价格合理的微型计算机的推出。这项迷人技术的历史和发展已在许多出版物中得到详细记录。

在制造领域，特别是在金属加工领域，数控技术引起了一些革命。甚至在计算机成为每个公司和许多家庭的标准装置之前的每一天，配备数控系统的机床在机加工车间中占有特殊的地位。微电子的最新发展和计算机的不断发展，包括其对数控的影响，给整个制造业，特别是金属加工行业带来了重大变化。

数控定义

在各种出版物和文章中，多年来使用了许多描述来定义数字控制是什么。许多这些定义共享相同的思想，相同的基本概念，只是使用了不同的措辞。

大多数已知的定义可以总结为相对简单的陈述：

数控可以定义为通过向机器控制系统发出特定编码指令对机床进行的操作。

指令是字母、数字和选定符号的组合，例如小数点、百分号或括号符号。所有指令都是按照逻辑顺序和预定形式编写的。加工零件所需的所有指令的集合称为 NC 程序、CNC 程序或零件程序。这样的程序可以存储以备将来使用并重复使用以随时获得相同的加工结果。

数控与数控技术

在严格遵守术语的情况下，缩写 NC 和 CNC 的含义有所不同。 NC 代表订单和原始数控技术，其中缩写 CNC 代表较新的计算机数字控制技术，它是其较旧的亲戚的现代衍生产品。然而，在实践中，CNC 是首选的缩写。为了阐明每个术语的正确用法，请查看 NC 和 CNC 系统之间的主要区别。

这两个系统执行相同的任务，即为了加工零件而操作数据。在这两种情况下，控制系统的内部设计都包含处理数据的逻辑指令。至此，相似结束。

NC 系统（与 CNC 系统相反）使用固定的逻辑功能，这些功能是内置的并永久连接在控制单元内。程序员或机器操作员不能更改这些功能。由于控制逻辑的固定编写，NC 控制系统可以解释零件程序，但它不允许必须在控制之外进行任何更改，通常是在办公环境中。另外，数控系统需要强制使用穿孔带来输入程序信息。

现代 CNC 系统，而不是旧的 NC 系统，使用内部微处理器（即计算机）。这台计算机包含内存寄存器，用于存储能够处理逻辑功能的各种例程。这意味着零件程序员或机器操作员可以更改控制本身（在机器上）的程序，并获得即时结果。这种灵活性是 CNC 系统的最大优势，也可能是该技术在现代制造中得到如此广泛应用的关键因素。 CNC 程序和逻辑功能存储在特殊的计算机芯片上，作为软件指令。而不是由控制逻辑功能的硬件连接（例如电线）使用。与数控系统相比，数控系统是“软接线”一词的同义词。

在描述与数控技术相关的特定主题时，习惯上使用术语 NC 或 CNC。请记住，在日常谈话中，NC 也可以表示 CNC，但 CNC 永远不能指代订单技术，这里以 NC 的缩写进行描述。字母“C”代表计算机化，不适用于硬接线系统。今天制造的所有控制系统都采用 CNC 设计。诸如 C&C 或 C'n'C 之类的缩写词是不正确的，并且对使用它们的任何人都有不良影响。

术语

绝对零

这是指所有轴位于传感器可以物理检测到它们的位置时的位置。执行原点命令后，通常会到达绝对零位。

轴

对象平移或旋转的固定参考线。

滚珠丝杠

滚珠丝杠是一种将旋转运动转化为直线运动的机械装置。它由一个在精密螺纹中运行的循环滚珠轴承螺母组成。

CAD

计算机辅助设计 (CAD) 是使用各种基于计算机的工具来协助工程师、建筑师和其他设计专业人员进行设计活动。

摄像头

计算机辅助制造 (CAM) 是使用各种基于计算机的软件工具来协助工程师和 CNC 机械师制造或制作产品组件原型。

数控

缩写CNC代表计算机数控，特指读取g代码指令并驱动机床的计算机“控制器”。

控制器

控制系统是管理、命令、指导或调节其他设备或系统行为的一个或一组设备。

日光

这是刀具最低部分与机床工作台表面之间的距离。最大日光是指从工作台到工具所能达到的最高点的距离。

钻井库

也称为多钻头，这些钻头通常以 32 毫米的增量间隔开。

进给速度

或切削速度是切削刀具与其所操作零件表面的速度差。

夹具偏移

这是一个表示给定夹具参考零的值。对应于绝对零点与夹具零点在所有轴上的距离。

G 代码

G-code是控制数控机床和数控机床的编程语言的通用名称。

首页

这是编程参考点，也称为 0,0,0，表示为绝对机器零或夹具偏移零。

线性和圆形插值是一种从一组离散的已知数据点构建新数据点的方法。换句话说，这就是程序在只知道圆心和半径的情况下计算一个完整圆的切割路径的方式。

机器首页

这是机器上所有轴的默认位置。执行归位命令时，所有驱动器都会向默认位置移动，直到它们到达告诉它们停止的开关或传感器。

嵌套

它是指从板材高效制造零件的过程。套料软件使用复杂的算法确定如何以最大限度地利用可用库存的方式布置零件。

偏移量

是指CAM软件测得的距中心线的距离。

搭载工具

该术语用于指安装在主轴旁边的气动工具。

后处理器

对数据进行一些最终处理的软件，例如将其格式化以进行显示、打印或加工。

程序零

这是程序中指定的参考点 0,0。在大多数情况下，它与机器零不同。

齿轮齿条

齿条和小齿轮是将旋转运动转化为直线运动的一对齿轮。

主轴

主轴是装有刀具夹持装置的高频电机。

扰流板

它也被称为牺牲板，它是用作被切割材料的基础的材料。它可以由许多不同的材料制成，其中最常见的是中密度纤维板和刨花板。

工具加载

这是指刀具切割材料时施加在刀具上的压力。

刀具速度

也称为主轴转速，这是机器主轴的旋转频率，以每分钟转数 (RPM) 为单位。

工具

令人惊讶的是，工具通常是 CNC 设备中最不为人知的方面。考虑到它是影响切割质量和切割速度的最大因素，操作者应该花更多的时间探索这个主题。

切削工具通常有三种不同的材料；高速钢、硬质合金、金刚石。

高速钢（HSS）

HSS 是三种材料中最锋利的，也是最便宜的，但它磨损最快，只能用于非研磨材料。它需要经常更改和锐化，因此它主要用于操作员需要在内部切割自定义轮廓以进行特殊工作的情况。

整体硬质合金

硬质合金刀具有不同的形式：硬质合金刀头、硬质合金刀片和整体硬质合金刀具。请记住，并非所有碳化物都相同，因为这些工具的制造商之间的晶体结构差异很大。因此，这些工具对热、振动、冲击和切割载荷的反应各不相同。一般来说，低成本的通用硬质合金刀具比价格较高的名牌刀具磨损和碎屑更快。

碳化硅晶体嵌入钴粘合剂中以形成工具。当工具被加热时，钴粘合剂失去了保持碳化物晶体的能力，它变得暗淡。同时，缺失的碳化物留下的中空空间被切割材料中的污染物填满，加剧了钝化过程。

金刚石工具

在过去几年中，此类工具的价格有所下降。其卓越的耐磨性使其成为切割高压层压板或 Mdf 等材料的理想选择。有些人声称它比碳化物寿命长 100 倍。如果钻石尖头工具碰到嵌入的钉子或硬结，它们很容易碎裂或破裂。一些制造商使用金刚石工具粗切削磨料，然后改用硬质合金或刀片工具进行精加工。

刀具几何形状

柄

刀柄是由刀架固定的刀具部分。它是工具中没有加工迹象的部分。刀柄必须保持无污染、无氧化和无划痕。

切割直径

这是刀具将产生的切割直径或宽度。

切割长度

这是刀具的有效切削深度或刀具可以切入材料的深度。

长笛

这是钻出切割材料的工具部分。刀具上的排屑槽数量对于确定切屑负载很重要。

工具简介

此类别中有许多工具配置文件。主要考虑的是上切和下切螺旋，压缩螺旋，

粗加工、精加工、低螺旋和直切削刀具。所有这些都由一到四个长笛组合而成。

上切螺旋将导致切屑向上飞出切口。这在进行盲切或直接向下钻孔时非常有用。然而，这种工具的几何形状会促进提升并倾向于撕裂被切割材料的顶部边缘。

下切螺旋刀具会将切屑向下推入切削中，这有助于提高零件夹持力，但在某些情况下会导致堵塞和过热。这个工具也容易撕裂被切割材料的底部边缘。

上切和下切螺旋刀具都带有粗加工、断屑槽或精加工刃。

压缩螺旋是上切槽和下切槽的组合。

压缩工具将切屑从边缘推向材料的中心，在切割双面层压板或边缘撕裂成为问题时使用。

当切割塑料和泡沫等较软的材料时，焊接和排屑至关重要时，使用低螺旋或高螺旋螺旋钻头。

芯片负载

延长刀具寿命的最重要因素是散发刀具吸收的热量。最快的方法是切割更多的材料而不是减慢速度。切屑从工具中吸收的热量比灰尘多。同样，将工具与材料摩擦会引起摩擦，从而转化为热量。

在寻求延长刀具寿命的过程中需要考虑的另一个因素是保持刀具、夹头和刀架的清洁，没有沉积物或腐蚀，从而减少因刀具不平衡引起的振动。

刀具每个齿去除材料的厚度称为切屑负载。

芯片负载计算公式如下：

切屑负载 =进给率 / RPM / # 槽数

当切屑负载增加时，刀具寿命增加，同时减少循环时间。此外，广泛的切屑负载范围将实现良好的边缘光洁度。最好参考工具制造商的芯片负载图表，找到最佳使用数量。推荐的芯片负载范围通常在 0.003" 到 0.03" 或 0.07 mm 到 0.7 mm 之间。

配件

标签打印

这是一种在行业中越来越受欢迎的选择，尤其是因为 CNC 机器越来越多地融入整个业务模式。控制器可以连接到销售或调度软件，一旦零件加工完成，就会打印零件标签。一些供应商使用标签来识别剩余材料，以便日后轻松检索。

光学阅读器

也称为条形码棒，它们可以集成到控制器中，以便可以通过扫描工作时间表上的条形码来调用程序。此选项通过自动执行程序加载过程来节省宝贵的时间。

探针

这些测量设备有多种形式并执行许多不同的功能。一些探头仅测量表面高度以确保在高度敏感的应用中正确对准。其他探头可以自动扫描三维物体的表面，以备后用。

刀具长度传感器

刀具长度传感器的作用就像一个探针，它测量日光或刀具末端与工作区表面之间的距离，并将此数字输入到控件的刀具参数中。这个小小的添加将使操作员免于每次更换刀具所需的冗长过程。

激光投影仪

这些设备首先出现在家具行业的 CNC 皮革切割机中。安装在 CNC 工作台上方的激光投影仪会投射出将要切割的零件的图像。这大大简化了在工作台上放置坯料的过程，以避免出现缺陷和其他问题。

乙烯基切割机

乙烯基刀具附件经常出现在标牌行业。这是一种刀具，可以连接到主轴上，也可以安装在带有自由转动刀的侧面，其压力可以通过旋钮调节。此附件允许用户将他的 CNC 路由器变成绘图仪，以制作用于喷砂的乙烯基面具或用于卡车和标志的乙烯基字母和徽标。

冷却液分配器

冷气枪或切割液喷雾器与木刨机一起使用，以切割铝或其他有色金属。这些附件在刀具附近喷射冷空气或切削液雾，以确保刀具在工作时保持凉爽。

雕刻师

雕刻机安装在主轴上，由一个浮动头组成，上面装有一个小直径雕刻刀，转速在 20,000 到 40,000 RPM 之间。浮动头确保即使材料厚度发生变化，雕刻深度也将保持不变。尽管奖杯制造商、制琴师和木制品店将其用于镶嵌工艺，但此选项最常用于标牌制作行业。

旋转轴

沿 x 或 y 轴设置的旋转轴可以将路由器变成 CNC 车床。其中一些旋转轴只是一个旋转主轴，而另一些则是可转位的，这意味着它们可以用于雕刻复杂的零件。

浮动刀头

浮动刀头将使刀具保持在距离被切割材料顶面的特定高度。当在可能不呈现平坦表面的零件的顶面上切割特征时，这一点很重要。一个例子是在餐桌顶部切割 V 形槽。

等离子切割机

等离子切割机是一些机器的附件，允许用户切割不同厚度的钣金零件。

聚合工具

集料刀具可用于许多直线刀具无法完成的操作。

传统和数控加工

是什么让CNC加工优于传统方法？它完全优越吗？主要好处在哪里？如果将 CNC 与传统加工工艺进行比较，就会出现一种通用的零件加工方法：

1.获取并学习图纸

2.选择最合适的加工方法

3. 确定设置方法（工件保持）

4. 选择刀具

5. 建立速度和进给

6. 加工零件

两种加工的基本方法相同。主要区别在于各种数据的输入方式。进给速度为每分钟 10 英寸（10 英寸/分钟）与手动相同

或数控应用，但应用它的方法不是。冷却液也是如此——它可以通过转动旋钮、按下开关或编程特殊代码来激活。所有这些动作都会导致冷却液从喷嘴中喷出。在这两种加工中，用户都需要一定的知识。毕竟，金属加工，尤其是金属切削，主要是一门技能，但在很大程度上，它也是一门艺术，也是一门人多的职业。计算机数控的应用也是如此。像任何技能、艺术或职业一样，要成功就必须将其掌握到最后的细节。成为 CNC 机械师或 CNC 程序员需要的不仅仅是技术知识。工作经验、直觉和有时被称为“直觉”的东西是任何技能都非常需要的补充。

在传统加工中，机器操作员设置机器并使用一只手或两只手移动每个切削刀具，以生产所需的零件。手动机床的设计提供了许多有助于加工零件杠杆、手柄、齿轮和刻度盘的功能，仅举几例。操作员对批次中的每个零件重复相同的身体运动。但是，在这种情况下，“相同”一词实际上意味着“相似”而不是“相同”。人类无法始终完全相同地重复每个过程——这是机器的工作。人们不可能一直以相同的绩效水平工作而不休息。我们每个人都有一些好的和一些不好的时刻。当应用于零件加工时，这些力矩的结果很难预测。每批零件内都会有一些差异和不一致。零件不会总是完全相同。保持尺寸公差和表面光洁度质量是传统加工中最典型的问题。个别机械师可能有他们的同事。这些因素和其他因素的结合造成了大量的不一致。

数控加工消除了大部分不一致。它不需要与加工相同的物理参与。数值

受控加工不需要任何杠杆、刻度盘或手柄，至少与传统机械加工的意义不同。零件程序经过验证后，可以多次使用，始终返回一致的结果。这并不意味着没有限制因素。刀具确实磨损了，一个批次的材料毛坯与另一批次的毛坯材料不同，设置可能会有所不同等。这些因素都需要考虑并在必要时进行补偿。

数控技术的出现并不意味着所有手动机器的瞬间甚至长期消亡。有时，传统的加工方法比计算机化的方法更可取。例如，一个简单的一次性工作在手动机器上可能比在 CNC 机器上更有效地完成。某些类型的加工作业将受益于手动或半自动加工，而不是数控加工。数控机床并不是要取代每一台手动机床，而是要对其进行补充。

在许多情况下，决定是否在 CNC 机床上进行某些加工取决于所需零件的数量，而不是其他任何因素。虽然批量加工零件的数量一直是重要的标准，但它绝不应该是唯一的因素。

还要考虑零件的复杂性、公差、表面光洁度要求等，往往一个复杂的零件会受益于CNC加工，而五十个相对简单的零件则不会。

请记住，数控系统从未单独加工过单个零件。数控只是使机床能够以高效、准确和一致的方式使用的过程或方法。

数控优势

数控的主要优点是什么？

重要的是要知道哪些加工领域将受益于它，哪些加工可以通过传统方式更好地完成。认为一台两马力的 CNC 铣床会胜过目前由功率大 20 倍的手动铣床完成的工作是荒谬的。同样不合理的是，期望比传统机床大幅提高切削速度和进给率。如果加工和刀具条件相同，两种情况下的切削时间将非常接近。

CNC 用户可以并且应该期望改进的一些主要领域：

1. 减少设置时间

2. 缩短交货期

3. 准确性和重复性

4. 复杂形状的轮廓

5. 简化工具和工件夹持

6.一致的切割时间

7. 生产力普遍提升

每个领域都只提供一个潜在的改进。根据现场制造的产品、使用的数控机床、设置方法、夹具的复杂程度、刀具质量、管理理念和工程设计、员工的经验水平、个人态度等

减少设置时间

在许多情况下，CNC 机床的设置时间可以减少，有时甚至会显着减少。重要的是要认识到设置是手动操作，很大程度上取决于 CNC 操作员的性能、夹具类型和机械车间的一般做法。设置时间是非生产性的，但却是必要的——它是开展业务的间接成本的一部分。将设置时间保持在最短应该是任何机加工车间主管、程序员和操作员的主要考虑因素之一。

由于数控机床的设计，设置时间应该不是主要问题。模块化夹具、标准工具、固定定位器、自动换刀、托盘和其他高级功能，使设置时间比传统机器的可比设置更高效。熟悉现代制造业，可以显着提高生产力。

在一次设置下加工的零件数量对于评估设置时间成本也很重要。如果在一次设置中加工大量零件，则每个零件的设置成本可能非常微不足道。将几个不同的操作分组到一个设置中可以实现非常相似的减少。即使设置时间更长，但与设置几台常规机器所需的时间相比，这可能是合理的。

缩短交货时间

编写并验证零件程序后，即使在很短的时间内，它也可以在将来再次使用。虽然第一次运行的提前期通常更长，但对于任何后续运行几乎为零。即使零件设计的工程变更需要修改程序，通常也可以很快完成，从而缩短交付周期。

通常可以通过准备零件程序和使用简化的夹具来缩短为传统机器设计和制造几种特殊夹具所需的较长交货时间。

准确性和可重复性

现代 CNC 机床的高度准确性和可重复性一直是许多用户的主要优势。无论零件程序是存储在磁盘上还是计算机内存中，甚至在磁带上（原始方法），它始终保持不变。任何程序都可以随意更改，但一旦得到证实，通常就不再需要更改了。一个给定的程序可以根据需要多次重复使用，而不会丢失它包含的任何数据。诚然，程序必须遵循诸如刀具磨损和操作温度等可变因素，必须安全存储，但通常很少需要 CNC 程序员或操作员的干预，CNC 机器的高精度及其可重复性允许高一次又一次地生产出高质量的零件。

复杂形状的轮廓

CNC车床和加工中心能够加工各种形状的轮廓。许多 CNC 用户购买他们的机器只是为了能够处理复杂的零件。很好的例子是飞机和汽车行业的 CNC 应用。任何三维刀具路径生成实际上都必须使用某种形式的计算机编程。

可以制造复杂的形状，例如模具，而无需制作用于追踪的模型的额外费用。直接切换按钮、模板、木模等制版工具即可实现镜像零件。

简化的工具和工作保持

通过使用专为数控应用而设计的标准工具，无法消除使传统机器周围的工作台和抽屉杂乱无章的标准和自制工具。多步工具，例如导向钻、阶梯钻、组合工具、埋头钻等，已被多个单独的标准工具所取代。与特殊和非标准工具相比，这些工具通常更便宜且更容易更换。成本削减措施迫使许多工具供应商保持低价甚至不存在。标准的、现成的工具通常比非标准工具的获得速度更快。

CNC 机床的夹具和工件夹持只有一个主要目的 - 将零件牢固地固定在同一批次中的所有零件上。专为 CNC 工作设计的夹具通常不需要夹具、导孔和其他孔定位辅助工具。

切割时间和生产率提高

CNC机床上的切削时间俗称循环时间，始终保持一致。与传统加工不同，操作者的技能、经验和个人疲劳会发生变化，CNC加工是在计算机控制下进行的。少量的手动工作仅限于设置和装卸零件。对于大批量运行，非生产时间的高成本分散在许多零件中，使其不那么重要。一致的切削时间的主要好处是对于重复性工作，可以非常准确地完成生产计划和单个机床的工作分配。

The main reason companies often purchase CNC machines is strictly economic – it is a serious investment. Also, having a competitive edge is always on the mind of every plant manager. The numerical control technology offers excellent means to achieve a significant improvement in the manufacturing productivity and increasing the overall quality of the manufactured parts. Like any means, it has to be used wisely and knowledgeably. When more and more companies use the CNC technology, just having a CNC machine does not offer the extra edge anymore. The companies that get forward are those who know to use the technology efficiently and practice it to be competitive in the global economy.

To reach the goal of major increase in productivity, it is essential that users understand the fundamental principles on which CNC technology is based. These principles take many forms, for example, understanding the electronic circuitry, complex ladders diagrams, computer logic, metrology, machine design, machine principles and practices and many others. Each one has to be studied and mastered by the person in charge. In this handbook, the emphasis is on the topics that relate directly to the CNC programming and understanding the most common CNC machine tools, the machining centers and the lathes (sometimes also called the turning centers). The part quality consideration should be very important to every programmer and machine tool operator and this goal is also reflected in the handbook approach as well as in numerous examples.

TYPES OF CNC MACHINE TOOLS

Different kinds of CNC machines cover an extremely large variety. Their numbers are rapidly increasing, as the technology development advances. It is impossible to identify all the applications; they would make a long list. Here is a brief list of some of the groups CNC machines can be part of:

1. Mills and machining centres

2. Lathes and turning centres

3. Drilling machines

4. Boring mills and profilers

5. EDM machines

6. Punch presses and shears

7. Flame cutting machines

8. Routers

9. Water jet and laser profilers

10. Cylindrical grinders

11. Welding machines

12. Benders, winding and spinning machines, etc.

CNC machining centres and lathes dominate the number of installations in industry. These two groups share the market just about equally. Some industries may give a higher need for one group of machines, depending on their needs. One must remember that there are many different kinds of lathes and equally many different kinds of ma-chining centres. However, the programming process for a vertical machine is similar to the one for a horizontal ma-chine or a simple CNC mill. Even between different ma-chine groups, there is a great amount of general applications and the programming process is generally the same For example, a contour milled with an end mill has a lot in common with a contour cut with a wire.

Mills and Machining Centres

Standard number of axes on a milling machine is three-the X, Y and Z axes. The part set on a milling system is al-cutting tool rotates, it can move up and down (or in and out), but it does not physically follow the tool path.

CNC mills sometimes called CNC milling machines are usually small, simple machines, without a tool changer or other automatic features. Their power rating is often quite low. In industry, they are used tool room work, maintenance purposes, or small part production. They are usually designed for contouring, unlike CNC drills.

CNC machining centres are for more popular and efficient that drills and mills, mainly for their flexibility. The main benefit user gets out of a CNC machining centre is the ability to group

several diverse operations into a single setup. For example, drilling, boring, counter boring, tapping, spot facing and contour milling can be incorporated into a single CNC program. In addition, the flexibility is enhanced by automatic tool changing using pallets to minimize idle time, indexing to a different side of the part, using a rotary movement of additional axes, and a number of other features, CNC machining centres can be equipped with special software that controls the speeds and feeds, the life of the cutting tool, automatic in-process gauging and offset adjustment and other production enhancing and time saving devices.

There are two basic designs of a typical CNC machining centre. There are the vertical and the horizontal machining centres. The major difference between the two types is the nature of work that can be done on them efficiently. For a vertical CNC machining centre, the most suitable type of work are flat parts, either mounted to the fixture on the table, or help in a vise or a chuck. The work that requires machining on two or more faces in a single setup is more desirable to be done on a CNC horizontal machining centre. A good example is pump housing and other cubic-like shapes. Some multi-face machining of small parts can also be done on a CNC vertical machining center equipped with a rotary table.

The programming process is the same for both designs, but an additional axis (usually a B axis) is added to the horizontal design. This axis is either a simple positioning axis (indexing axis) for the table, or a fully rotary axis for simultaneous contouring.

This handbook concentrates on the CNC vertical machining centres applications, with a special section dealing with the horizontal setup and machining. The programming methods are also applicable to the small CNC mills or drilling and/or tapping machines, but the programmer has to conceder their restrictions.

Lathes and Turning Centres

A CNC lathe is usually a machine tool with two axes, the vertical X axis and the horizontal Z axis. The main future of the lathe that distinguishes it from a mill is that the part is rotating about the machine center line. In addition, the cutting tool is normally stationary, mounted in a sliding turret. The cutting tool follows the contour of the programmed tool path. For the CNC lathe with a milling attachment, so called live tooling, the milling tool has its own motor and rotates while the spindle is stationary.

The modern lathe design can be horizontal or vertical. Horizontal type is far more common than the vertical type, but both designs exist for either group. For example, a typical CNC lathe of the horizontal group can be designed with a flat bed or a slant bed, as a bar type, chucker type or universal type. Added to these combinations or many accessories that make a CNC lathe is an extremely flexible machine tool. Typically, accessories such as a tailstock, steady rests or followup rests, part catchers, pullout-fingers and even a third axis milling attachment are popular components of the CNC lathe. A CNC lathe can be very versatile so versatile in fact, that it is often called a CNC turning centre. All text and program examples in this handbook use the more traditional term CNC lathe, yet still recognizing all its modern functions.

PERSONNEL FOR CNC

Computers and machine tools have no intelligence. They cannot think, they cannot evaluate a station in a rational way. Only people with certain skills and knowledge can do that. In the field of numerical control, the skills are usually in the hands of two key peopleone doing the programming, the other doing the machining. Their respective numbers and duties typically depend on the company preference, its size, as well as the product manufactured there. However, each position is a quite distinct, although many companies combine the two functions into a one, often called a CNC programmer/operator.

CNC Programmer

The CNC programmer is usually the person who has the most responsible in the CNC machine shop. This person is often responsible for the success of numerical control technology in the plant. Equally this person is held responsible for problems related to the CNC operations.

Although duties may vary, the programmer is also responsible for a variety of tasks relating to the effective usage of the CNC machines. In fact, this person is often accountable for the production and quality of all CNC operations.

Many CNC programmers are experienced machinists, who have had a practical, hands-on experience as machine tool operations they know how to read technical drawings and they can comprehend the engineering intent behind the design. This practical experience is the foundation for the ability to ‘machine’ a part in an office environment. A good CNC programmer must be able to visualize all the tool motions and recognize all restricting factories that may be involved. The programmer must be able to collect, analyze process and logically integrate all the collected data into a signal, cohesive program. In simple terms, the CNC programmer must be able to decide upon the best manufacturing methodology in all respects.

In addition to the machining skills, the CNC programmer has to have an understanding of mathematical principles, mainly application of equations, solutions of arcs and angles. Equally important is the knowledge of trigonometry. Even with computerized programming, the knowledge of manual programming methods is absolutely essential to the through understanding of the computer output and the control of this output.

The last important quality of a truly professional CNC programmer is his or her ability to listen to the other people – the engineers, the CNC operators, the managers. Good listing skills are the first prerequisites to become flexible. A good CNC programmer must be flexible in order to offer high programming quality.

CNC Machine Operator

The CNC machine tool operator is a complementary position to the CNC programmer. The programmer and the operator may exist in a single person, as is the case in many small shops. Although the majority of duties performed by conventional machine operator has been transferred to the CNC program, the CNC operator has many unique responsibilities. In typical cases, the operator is responsible for the tool and machine setup, for the changing of the parts, often even for some in-process inspection. Many companies expect quality control at the machine – and the operator of any machine tool, manual or computerized, is also responsible for the quality of the work done on that machine. One of the very important responsibilities of the CNC machine operator is to report findings about each program to the programmer. Even with the best knowledge, skills, attitudes and intentions, the "final" program can always be improved. The CNC operator being the one, who is the closest to the actual machining, knows precisely what extent such improvements can be.

Justifying the Cost of CNC

The cost of a CNC machine might make most manufacturers nervous but the benefits of owning a CNC router will most likely justify the cost in very little time.

The first cost to take into consideration is the machine cost. Some vendors offer bundled deals that include installation, software training and shipping charges. But in most cases, everything is sold separately to allow for customization of the CNC router.

Light duty

Low-end machines cost from $2,000 to $10,000. they are usually bolt-it yourself kits made of bent sheet metal and use stepper motors. They come with a training video and an instruction manual. These machines are meant for do-it-yourself use, for the signage industry and other very light duty operations. they will usually come with an adapter for a conventional plunge router. accessories such as a spindle and vacuum work holding are options. These machines can be very successfully integrated into a high production environment as a dedicated process or as part of a manufacturing cell. for instance, one of these CNC’s can be programmed to drill hardware holes on drawer fronts before assembly.

Medium duty

Mid-range CNC machines will cost between $10,000 and $100,000. these machines are built of heavier gauge steel or aluminium. They might use stepper motors and sometimes servos; and use rack and pinion drives or belt drives. they will have a separate controller and offer a good range of options such as automatic tool changers and vacuum plenum tables. these machines are meant for heavier duty use in the signage industry and for light panel processing applications.

These are a good option for start-ups with limited resources or manpower. They can perform most operations needed in cabinet making although not with the same degree of sophistication or with the same efficiency.

Industrial strength

High-end routers cost upward of $100,000. This includes a whole range of machines with 3 to 5 axes suited for a broad range of applications. these machines will be built out of heavy gauge welded steel and come fully loaded with automatic tool changer, vacuum table and other accessories depending on the application. these machines are usually installed by the manufacturer and training is often included.

Shipping

Transporting a CNC router carries a considerable cost. With routers weighing anywhere from a few hundred pounds to several tons, freight costs can range from $200 to $5,000 or more, depending on location. remember that unless the machine was built nearby, the hidden cost of moving it from europe or asia to the dealer’s showroom is likely included. additional costs may also be incurred just to get the machine inside once it is delivered as it is always a good idea to use professional riggers to deal with this kind of operation.

Installation and training

CNC vendors typically charge from $300 to $1,000 per day for installation costs. It can take anywhere from a half day to a full week to install and test the router. This cost could be included in the price of buying the machine. some vendors will provide free training on how to use the hardware and software, usually on-site, while others will charge $300 to $1,000 per day for this service.

SAFETY RELATED TO CNC WORK

One the wall of many companies is a safety poster with a simple, yet powerful message:

The first rule of safety is to follow all safety rules.

The heading of this section does not indicate whether the safety is oriented at the programming or the machining level. The season is that the safety is totally independent. It stands on its own and it governs behaviour of everybody in a machine shop and outside of it. At first sight, it may appear that safety is something related to the machining and the machine operation, perhaps to the setup as well. That is definitely true but hardly presents a complete picture.

Safety is the most important element in programming, setup, machining, tooling, fixturing, inspection, chipping, and-you-name it operation within a typical machine shop daily work. Safety can never be overemphasized. Companies talk about safety, conduct safety meeting, display posters, make speeches, call experts. This mass of information and instructions is presented to all of us for some very good reasons. Quite a few are passed on past tragic occurrences – many laws, rules and regulations have been written as a result of inquests and inquire into serious accidence.

At first sight, it may seem that in CNC work, the safety is a secondary issue. There is a lot of automation; a part program that runs over and over again, tooling that has been used in the past, a simple setup, etc. All this can lead to complacency and false assumption that safety is taken care of. This is a view that can have serious consequences.

Safety is a large subject but a few points that relate to the CNC work are important. Every machinist should know the hazards of mechanical and electrical devices. The first step towards a safe work place is with a clean work area, where no chips, oil spills and other debris are allowed to accumulate on the floor. Taking care of personal safety is equally important. Loose clothing, jewellery, ties, scarves, unprotected long hair, improper use of gloves and similar infraction, is dangerous in machining environment. Protection of eyes, ears, hands and feet is strongly recommended.

While a machine is operating, protective devices should be in place and no moving parts should be exposed. Special care should be taken around rotating spindles and automatic tool changers. Other devices that could pose a hazard are pallet changers, chip conveyors, high voltage areas, hoists, etc. disconnecting any interlocks or other safety features is dangers – and also illegal, without appropriate skills and authorization.

In programming, observation of safety rules is also important. A tool motion can be programmed in many ways. Speeds and feeds have to be realistic, not just mathematically "correct". Depth of cut, width of cut, the tool characteristics, all have a profound effect on overall safety.

All these ideas are just a very short summery and a reminder that safety should always be taken seriously.