0420-SSCK20A数控车床主轴及主轴箱的数控加工工艺及数控编程【含5张CAD图】
0420-SSCK20A数控车床主轴及主轴箱的数控加工工艺及数控编程【含5张CAD图】,含5张CAD图,ssck20a,数控车床,主轴,数控,加工,工艺,编程,cad
第1页共2页机械加工工艺卡片产品型号零件图号产品名称SSCK20A零件名称主轴序号工序工 序 内 容车间设备工 艺 装 备工等工时单件备注夹具刃具量具辅具0备料10精锻立式精锻机20热处理正火30锯头40铣端面专用机床50粗车车各外圆面卧式车床60热处理调质220240HBS70车大端面卧式车床80粗车仿形车小端各部仿形车床90钻钻打断各孔摇臂钻床第2页共2页机械加工工艺卡片产品型号零件图号产品名称SSCK20A零件名称主轴序号工序工 序 内 容车间设备工 艺 装 备工等工时单件备注夹具刃具量具辅具100热处理高频感应加热淬火110数车精车各外圆并车槽数控车床120粗磨粗磨个外圆万能外圆磨床130精铣铣键槽铣床140精车加工三段螺纹卧式车床150粗精磨粗精磨各外圆万能外圆磨床第1页共6页机械加工工艺卡片产品型号零件图号产品名称SSCK20A零件名称主轴箱体序号工序工 序 内 容车间设备工 艺 装 备工等工时单件备注夹具刃具量具辅具0铸造正火10划线照顾毛坯各部划立车加工线20立车车4650.2两面,各面均留量3mm30划线划镗序加工线40卧镗镗铣A面,B面留量3mm以A面为基面,B面为导向粗镗150(-0.008,+0.002)140(-0.007,+0.003)各孔留量半径3mm过孔留量半径3mm050二次正火060划线划车序加工线第2页共6页机械加工工艺卡片产品型号零件图号产品名称SSCK20A零件名称主轴箱序号工序工 序 内 容车间设备工 艺 装 备工等工时单件备注夹具刃具量具辅具070立车车4650.2尺寸两面,至4650.1mm,两面平行0.1mm080划线划刨、镗序加工线090卧镗1)镗铣A面、B面各留量0.50.6mm铣30尺寸下面达图铣5尺寸空刀至尺寸2)按线铣右视图上部两处135度斜面达图铣:1500.2尺寸上面留量0.5mm钻:2M12底孔 X8(起吊孔)钻:2M12底孔(右上图局部剖)按线钻攻:左、右视图4M16(装配起吊孔)3)以A面为基面、 B面导向粗镗150(-0.008,+0.002)140(-0.007,+0.003)各孔留量半径11.2 mm过孔留量半径 11.2 mm第3页共6页机械加工工艺卡片产品型号零件图号产品名称SSCK20A零件名称主轴箱序号工序工 序 内 容车间设备工 艺 装 备工等工时单件备注夹具刃具量具辅具100数镗以465尺寸左面为基面; 工件压在工作台一角位置, 找正A面在0.1以内, 精铣A、B面(B面精加工用30立铣刀侧刃加工,不许有接刀痕,吃刀深度0.2mm)粗糙度达Ra3.2,平面度达0.05mm110卧镗 1)以465尺寸左面为基面;工件压在工作台一角位置找正A面在0.1以内,铣3X2空刀(根据刀具情况可加工至5X3)2)工作太转90度,包拯350尺寸,铣350尺寸左面达 Ra6.3。3)铣320尺寸两面:左面粗糙度达Ra3.2。4)铣380尺寸右6.3 面。5)钻4M6、2M8底孔。120卧镗以A面为基面,B面导向,上等高垫铁、位置公差军达图纸要求第4页共6页机械加工工艺卡片产品型号零件图号产品名称SSCK20A零件名称 主轴箱序号工序工 序 内 容车间设备工 艺 装 备工等工时单件备注夹具刃具量具辅具半精镗:150(-0.008,+0.002)140(-0.007,+0.003)、141.5孔留量,半径0.50.6mm。半精划:底面留量0.2mm精铣:280范围内,240范围内达Ra1.64650.2至465(+0.2,+0.3)130卧镗1、以465尺寸左面为基面,找正A面。在0.05以内实测140孔尺寸,按实际尺寸计算;精铣 1500.2尺寸上面。要求上面与C、D平行0.03mm。钻4M10底孔2、保证250.2,80尺寸自划线,钻划622X36140装配钳刮研A、B面。25MMX25MM范围内不少于8个点。B A达0.02MM150数镗以A面为基面、B面导向、第5页共6页机械加工工艺卡片产品型号零件图号产品名称SSCK20A零件名称主轴箱序号工序工 序 内 容车间设备工 艺 装 备工等工时单件备注夹具刃具量具辅具保证B面与主轴孔平行0.02上等高垫铁,300(0,+0.1)至300(0,+0.05)。500.1尺寸达500.05mm。保证深度尺寸115(-0.2,-0.1)。精镗141.5过孔至尺寸,精镗:140、150孔。孔径公差按轴承尺寸配镗;160卧镗1)精划Ra1.6底面。精铣:280、240(检查范围)。2)引窝:左视:6M8。 右视:6M10。在右视图125度左侧斜面打编号3) 三坐标检测:按图纸技术要求检测, 孔径用比较仪测量。170钻按窝钻攻:6M8、6M10180钳工各锐角倒钝、去刺第6页共6页机械加工工艺卡片产品型号零件图号产品名称SSCK20A零件名称主轴箱序号工序工 序 内 容车间设备工 艺 装 备工等工时单件备注夹具刃具量具辅具攻丝:4M6、4M12、2M84M10。190喷漆附录1专题部分数控五轴技术及数控编程随着科学技术的发展,制造技术的进步,以及社会对产品质量和品种多样化的要求越来越加强烈。中、小批量生产的比重明显增加,要求现代数控机床成为一种高效率、高质量、高柔性和低成本的新一代制造设备。同时,为了满足制造业向更高层次发展,为柔性制造单元,柔性制造系统,以及计算机集成制造系统提供基础设备,也要求数控机床向更高水平发展。这些要求主要由数字控制技术的发展来实现。数控技术体现在数控装置、伺服驱动系统、程序编制、机床主机和检测监控系统等方面。一、数控加工技术近代,大工业生产大量采用了刚性自动化。在汽车工业、拖拉机以及轻工业消费品生产方面。采用了大量的组合机床自动线、流水线;在标准件生产中采用了凸轮控制的专用机床和自动机床。这类机床适合于大批量生产,但是建立制造过程很难,所以更换产品,修改工艺要较长的时间和比较多的费用。由于产品多样化和产品更新,解决单件,小批量生产自动化迫在眉睫。航空、宇航、造船、电子等工艺对解决复杂型零件加工和高精度零件加工要求越来越高。这就使刚性自动化不能满足要求,柔性加工和柔性自动化也就迅速发展起来。数控机床是新型的自动化机床,它具有广泛通用性和很高的自动化程度。数控机床是实现柔性自动化最重要的装置,是发展柔性生产的基础。数控机床在下面一些零件的加工中,更能显示出它的优越性。它们是:1)批量小而又多次生产的零件;2)几何形状复杂的零件;3)在加工过程中必须进行多种加工零件;4)切削余量大的零件;5)必须控制公差(即公差带范围小)的零件;6)工艺设计会变化的零件;7)加工过程中的错误回造成严重浪费的贵重零件;8)需全部检测的零件,等等。数控加工技术的特点:1、提高生产率。数控机床能缩短生产准备时间,增加切削加工时间的比较。采用最佳切削参数和最佳走刀路线能缩短加工时间,从而提高生产率。2、稳定产品质量。采用数控机床可以提高零件的加工精度,稳定产品质量。它是按照程序自动加工不需要人工干预,而且加工精度还利用软件进行校正及补偿,因此,可以获得比机床本身精度还要高的加工精度及重复精度。3、有广泛的适应性和较大的灵活性。通过改变程序,就可以加工新品种的零件。能够完成很多普通机床难以完成,或者根本不能加工的复杂型面的零件的加工。4、可以实现一机多用。一些数控机床,例如加工中心,可以自动换刀。一次装卡后,几乎能完成零件的全部加工部位的加工,节省了设备和厂房面积。5、提高经济效益。可以进行精确的成本计算和生产进度安排,减少在制品,加速资金周转,提高经济效益。6、不需要专用夹具。采用普通的通用夹具就能满足数控加工的要求,节省了专用夹具设计制造和存放的费用。7、大大地减轻了工人的劳动强度。数控机床是具有广泛的通用性而又具有很高自动化程度的全新型机床。它的控制系统不仅能控制机床各种动作的先后顺序,还能控制机床运动部件的运动速度,以及刀具相对工件的运动轨迹。数控机床是计算机辅助设计和制造,群控,柔性制造系统,计算机集成制造系统等柔性加工和柔性制造系统的基础。但是,数控机床的初投资及维修技术等费用较高,要求管理及操作人员的素质也较高。合理地选择及使用数控机床,可以降低企业的生产成本,提高经济效益和竞争能力。二、五轴加工技术五轴加工是在数控镗或数控铣的基础上,增加了自动换刀装置,使工件在一次装夹后,可以连续对工件自动进行钻孔、扩控、铰孔、攻螺纹、铣削等多加工的机床。加工中心一般带有自动分度回转工作台或主轴箱可自动改变角度,从而使工件一次装夹后,自动完成多个平面或多个角度位置的多工序加工,工序高度集中;加工中心能自动改变主轴转速、进给量和刀具相对工件的运动轨迹;加工中心如果带有交换工作台,工件在工作位置的工作台上进行加工的同时,可在装卸位置的工作台上装卸工件,工作效率高。五轴数控加工技术可以在一次装夹中完成工件的全部机械加工工序,满足从粗加工到精加工的全部加工要求,即适用于单件小批量生产也适用于大批量生产,减少了加工时间和生产费用,提高了数控设备的生产能力和经济性。 目前国际上五轴高速切削加工技术主要应用于汽车工业、模具行业、航空航天行业,尤其是在加工复杂曲面的领域、工件本身或刀具系统刚性要求较高的加工领域,显示了强大的功能。国内五轴高速切削加工技术的研究与应用始于20世纪90年代,应用于模具、航空航天和汽车工业。但采用的高速切削CNC机床、高速切削刀具和CAD/CAM软件等以进口为主。数控五轴高速切削加工作为模具制造中最为重要的一项先进制造技术,是集高效、优质、低耗于一身的先进制造技术。在常规切削加工中备受困惑的一系列问题通过五轴高速切削加工的应用得到了解决。其切削速度和进给速度比传统的切削加工速度高,切削机理发生了根本的变化。与传统切削加工相比,切削加工发生了本质的飞跃。其单位功率的金属切除率提高了30%40%、切削力降低了30%、刀具的切削寿命提高了70%、留于工件的切削热大幅度降低、低阶切削振动几乎消失。随着切削速度的提高,单位时间毛坯材料的去除率增加,切削时间减少,加工效率提高。缩短了产品的制造周期,增加了产品的市场竞争力。同时高速加工的小量快进使切削力减少,切屑的高速排除,减少了工件的切削力和热应力变形,提高了刚性差和薄壁零件切削加工的可能性。另外,由于切削力的降低,转速的提高使切削系统的工作频率远离机床的低阶固有频率,而工件的表面粗糙度对低阶频率最为敏感,由此降低了表面粗糙度。在模具的高淬硬刚件(4565HRC)的加工过程中,采用高速切削可以取代电加工和磨削抛光的工序。避免了电极的制造和费时的电加工时间,大幅度减少了钳工的打磨与抛光量。一些市场上越来越需要的薄壁模具工件,高速铣削可顺利完成。而且在高速铣削CNC加工中心上,模具一次装夹可完成多工步加工。1、五轴高速加工切削的优点五轴高速加工切削系统主要由高速加工中心、高性能的刀具夹持系统、高速切削刀具、安全可靠的高速切削CAM软件系统,因此五轴高速加工是一项大的系统工程。随着切削刀具技术的进步,高速加工已应用于加工合金钢(硬度大于30HRC),广泛地应用在汽车和电子元件产品中的冲压模,注射模零件。高速加工的定义依赖于被加工的工件材料的类型。例如,高速加工合金钢采用的切削速度为500m/min,而这一速度在加工铝合金是常采用顺铣。2、五轴高速铣削加工机床五轴超高速切削技术是切削技术是切削加工的方向,也是时代发展的产物。高速切削技术是切削加工技术的主要发展方向之一,它随着CNC技术、微电子技术、新材料和新结构等基础技术的发展而迈尚更高的台阶。然而高速切削技术自身也存在着一些急待解决的问题,如高硬度材料的切削机理、刀具在载荷变化过程中的破损、建立高速切削数据库、开发适用于高速切削加工状态的监控技术和绿色制造技术等等。同时高速切削所用的CNC机床,车、铣、钻等刀具,CAD/CAM软件等技术含量高,价格昂贵,使得高速切削投资大,这在一定程度上制约了高速切削技术的推广应用。高速切削的高效应用要求机床系统中的部件都必须先进,主要表现在以下几个方面:a、机床结构的刚性。提供高速进给的驱动器(快进速度约40m/min,3D轮廓加工速度为10m/min),能够0.410m/s的加速度和减速度。b、主轴和刀柄的刚性。1000050000转/min的转速,通过主轴压缩空气或冷却系统控制刀柄和主轴间的轴向间隙不大于0.005mm。c、控制单元2和4位并行处理器,高的数据传输率,能够自动加减速。d、可靠性与加工工艺。提高机床的利用率和无人操作的可靠性,工艺模型有助于对切削条件和刀具寿命之间关系的理解。常见国内外五轴高速加工中心与传统普通数控机床相比,其机床结构、加工速度和性能更优秀,如德国的DMC85高速加工中心,采用直线电机和电主轴,其主轴转速达到30000转/min,进给速度达到120m/min,加速度超过1g(重力加速度)。五轴高速机床要求高的主轴单元和冷却系统、高刚性的机床结构、安全装置和监控系统、以及优良的静动力特性等,其技术含量高,机床制造难度大等特点。目前国内的高速机床其性能与国外相比还存在一定的差距。三、数控编程数控机床是按照事先编制好的工程序自动对工件进行加工的高效自动化设备。在数控机床上加工零件时,要把加工零件的全部工艺过程、工艺参数和位移数据,以信息的形式记率在控制介质上,用控制介质上的信息来控制机床,实现零件的全部加工过程。这里,我们把从零件图纸到获得数控机床所需控制介质的全部过程,称为程序编制。程序编制是数控加工的一项重要、工作,理想的加工程序不仅应保证加工出符合图纸要求的合格工件,同时应该能使数控机床的功能得到合理的应用与充分的发挥,以使数控机床安全可靠及高效地工作。数控机床程序编制的内容主要包括:分析零件图纸、工艺处理、数学处理、编写程序单、制备控制介质及程序校验。其具体步骤与要求如下:1、分析零件图纸首先要分析零件图纸。根据零件的材料、形状、尺寸、精度、毛坯形状和热处理要求等确定加工方案,选择合适的数控机床。2、工艺处理工艺处理涉及问题较多,需要考虑如下几点:1)确定加工方案 此时应按照能充分发挥数控机床功能的原则,使用合适的数控机床,确定合理的加工方法。2)刀具工夹具的设计和选择 数控加工用刀具由加工方法、切削用量及其它与加工有关的因素来确定。数控机床具有刀具补偿功能和自动换刀功能。数控加工一般不需要专用的复杂的夹具。在设计和选择夹具时,应特别注意要迅速完成工件的定位和夹紧过程,以减少辅助时间。使用组合夹具,生产准备周期短,夹具零件可以反复使用,经济效益好。此外,所用夹具应便于安装,便于协调工件和机床坐标系的尺寸关系。3)选择对刀点 程序编制时正确地选择对刀点是很重要的。“对刀点”是程序执行的起点,也称“程序原点”。对刀点的选择原则是:所选对刀点,应使程序编制简单;对刀点应选择在容易找正、并在加工过程中便于检查的位置;引起的加工误差小。对刀点可以设置在被加工零件上,也可以设置在夹具或机床上。为了提高零件的加工精度,对刀点应尽量设置在零件的设计基础或工艺基准上。4)确定加工路线 加工路线的选择主要应该考虑:尽量缩短走刀路线,减少空走刀行程,提高生产率;保证加工零件的精度和表面粗糙度的要求;有利于简化数值计算,减少程序段的数目和编程工作量。5)确定切削用量 切削用量即切削深度和宽度,主轴转速及进给速度等。切削用量的具体数值应根据数控机床使用说明书的规定,被加工工件材料,加工工序以及其它工艺要求,并结合实际经验来确定。3、数学处理在工艺处理工作完成后,根据零件的几何尺寸,加工路线,计算数控机床所需的输入数据。一般数控系统都具有直线插补、圆弧插补和刀具补偿功能。对于加工由直线和圆弧组成的较简单的平面零件,只需计算出零件轮廓的相邻几何元素的交点或切点(称为基点)的坐标值。对于较复杂的零件或零件的集合形状与数控系统的插补功能不一致时,就需要进行较复杂的数值计算。4、编写零件加工程序单在完成工艺处理和数值计算工作后,可以编写零件加工程序单,编写人员根据所使用数控系统的指令、程序段格式,逐段编写零件加工程序。编程人员要了解数控机床的性能、程序指令代码以及数控机床加工零件的过程,才能编写出正确的加工程序。5、制备控制介质及程序检验程序编好后,需制作控制介质。控制介质有穿孔纸带、穿孔卡、磁带、软磁盘和硬磁盘等。早期为穿孔纸带,现在已被磁盘所代替。但是,规定的穿孔纸带代码标准没有变。在单件和多品种小批量产品生产模式下,产品品种复杂多样,个性化要求高,没有统一的流程。数控加工技术在这种生产模式中日益发挥巨大作用人。数控加工技术不仅可以提高产品的加工精度和品质,而且可以大大缩短产品的生产周期。一般来讲,数控加工技术中包括了数控加工机床、数控编程软件和数控设备管理软件。数控编程软件( 软件)在提高机床加工精度和加工效率方面起着至关重要的作用。从目前数控加工设备的普及和发 展情况来看,数控编程软件要具有如下特性。 软件要操作简单,易学易用 随着国内企业数控设备使用的不断普及,对数控编程人员的需求量也不断增加。那种需要长时间培训才能要输入或设置很多选项,过多的操作会给编程人员带来很大的压力,也带 来了更多的出错几率。因此,操作简单、易学易用是数控编程软件普及的关键。要做到操作简单,易学易用不仅仅是软件界面的问题,更多涉及到的是软件的智能化处理算法。软件产生的刀具轨迹要保证高速、高精度和高效率 数控加工技术是提高产品生产效率,缩短生产周期的关键手段。高速不仅仅是要求编程软件支持高速加工机床,也要求编程软件产生的刀具轨迹能够发挥普通数控机床的最高切削速度。在保证高精度的前提下尽量减少空走刀和重复走刀。这样才能缩短加工时间。毕竟在中国市场上普通数控机床还占绝大多数,让这些机床充分发挥加工能力是关键。 软件要匹配各种数控系统 在中国市场上,存在着各种各样的数控机床。因此,机床控制系统也是五花八门的,这就要求数控编程软件要能够匹配各种机床控制系统。 软件要能与整个生产流程集成 随着中国企业的信息化程度不断加深,数控编程已经不再是一个独立的信息化孤岛,而是整个企业生产流程中的一个环节和数据源。对数控编程软件的要求也不仅仅是生成数控代码,而是要求数控编程软件要能够与集成以快速得到设计数据,能够产生工艺数据并与工艺管理系统集成,能够与数控设备管理系统集成使数控设备能够得到加工所需要的信息,这样才能在某种程度上做到设计、工艺和制造过程的并行,缩短制造周期。数控五轴加工技术及数控编程是数控机床应用的基础,机加工工艺是数控五轴加工技术和数控编程的基础,要充分发挥数控机床的能力,需要刀具、材料、计算机、高等数学等多学科知识,还应不断进行编程实践,总结经验教训,在实践中不断得到提高。附录2 外文翻译(外文部分)ADVANCED MACHINING PROCESSES As the hardware of an advanced technology becomes more complex, new and visionary approaches to the processing of materials into useful products come into common use. This has been the trend in machining processes in recent years. Advanced methods of machine control as well as completely different methods of shaping materials have permitted the mechanical designer to proceed in directions that would have been totally impossible only a few years ago. Parallel development in other technologies such as electronics and computers have made available to the machine tool designer methods and processes that can permit a machine tool to far exceed the capabilities of the most experienced machinist. In this section we will look at CNC machining using chip-making cutting tools. CNC controllers are used to drive and control a great variety of machines and mechanisms, Some examples would be routers in wood working; lasers, plasma-arc, flame cutting, and waterjets for cutting of steel plate; and controlling of robots in manufacturing and assembly. This section is only an overview and cannot take the place of a programming manual for a specific machine tool. Because of the tremendous growth in numbers and capability of computers ,changes in machine controls are rapidly and constantly taking place. The exciting part of this evolution in machine controls is that programming becomeseasier with each new advanced in this technology.Advantages of Numerical Control A manually operated machine tool may have the same physical characteristics as a CNC machine, such as size and horsepower. The principles of metal removal are the same. The big gain comes from the computer controlling the machining axes movements. CNC-controlled machine tools can be as simple as a 2-axis drilling machining center (Figure O-1). With a dual spindle machining center, the low RPM, high horsepower spindle gives high metal removal rates. The high RPM spindle allows the efficient use of high cutting speed tools such as diamonds and small diameter cutters (Figure O-2). The cutting tools that remove materials are standard tools such as milling cutters, drills, boring tools, or lathe tools depending on the type of machine used. Cutting speeds and feeds need to be correct as in any other machining operation. The greatest advantage in CNC machining comes from the unerring and rapid positioning movements possible. A CNC machine does dot stop at the end of a cut to plan its next move; it does not get fatigued; it is capable of uninterrupted machining error free, hour after hour. A machine tool is productive only while it is making chips. Since the chip-making process is controlled by the proper feeds and speeds, time savings can be achieved by faster rapid feed rates. Rapid feeds have increased from 60 to 200 to 400 and are now often approaching 1000 inches per minute (IPM). These high feed rates can pose a safety hazard to anyone within the working envelope of the machine tool. Complex contoured shapes were extremely difficult to product prior to CNC machining .CNC has made the machining of these shapes economically feasible. Design changes on a part are relatively easy to make by changing the program that directs the machine tool. A CNC machine produces parts with high dimensional accuracy and close tolerances without taking extra time or special precautions, CNC machines generally need less complex work-holding fixtures, which saves time by getting the parts machined sooner. Once a program is ready and production parts, each part will take exactly the same amount of time as the previous one. This repeatability allows for a very precise control of production costs. Another advantage of CNC machining is the elimination of large inventories; parts can be machined as needs .In conventional production often a great number of parts must be made at the same time to be cost effective. With CNC even one piece can be machined economically .In many instances, a CNC machine can perform in one setup the same operations that would require several conventional machines. With modern CNC machine tools a trained machinist can program and product even a single part economically .CNC machine tools are used in small and large machining facilities and range in size from tabletop models to huge machining centers. In a facility with many CNC tools, programming is usually done by CNC programmers away from the CNC tools. The machine control unit (MCU) on the machine is then used mostly for small program changes or corrections. Manufacturing with CNC tools usually requires three categories of persons. The first is the programmer, who is responsible for developing machine-ready code. The next person involved is the setup person, who loads the raw stork into the MCU, checks that the correct tools are loaded, and makes the first part. The third person is the machine and unloads the finished parts. In a small company, one person is expected to perform all three of these tasks. CNC controls are generally divided into two basic categories. One uses a ward address format with coded inputs such as G and M codes. The other users a conversational input; conversational input is also called user-friendly or prompted input. Later in this section examples of each of these programming formats in machining applications will be describes.CAM and CNC CAM systems have changed the job of the CNC programmer from one manually producing CNC code to one maximizing the output of CNC machines. Since CNC machine tools are made by a great number of manufacturers, many different CNC control units are in use. Control units from different manufacturers use a variety of program formats and codes. Many CNC code words are identical for different controllers, but a great number vary from one to another. To produce an identical part on CNC machine tools with different controllers such as one by FANCU, OKUMA or DYNAPATH, would require completely different CNC codes. Each manufacturer is constantly improving and updating its CNC controllers. These improvements often include additional code words plus changes in how the existing code works. A CAM systems allows the CNC programmer to concentrate on the creation of an efficient machining process, rather then relearning changed code formats. A CNC programmer looks at the print of a part and then plans the sequence of machining operations necessary to make it (Figure O-3). This plan includes everything, from the selection of possible CNC machine tools, to which tooling to use, to how the part is held while machining takes place. The CNC programmer has to have a thorough understanding of all the capacities and limitations of the CNC machine tools that a program is to be made for. Machine specifications such as horsepower, maximum spindle speeds, workpiece weight and size limitations, and tool changer capacity are just some of the considerations that affect programming. Another area of major importance to the programmer is the knowledge of machining processes. An example would be the selection of the surface finish requirement specified in the part print. The sequence of machining processes is critical to obtain acceptable results. Cutting tool limitations have to be considered and this requires knowledge of cutting tool materials, tool types, and application recommendations. A good programmer will spend a considerable amount of time in researching the rapidly growing volume of new and improved tools and tool materials. Often the tool that was on the cutting edge of technology just two years ago is now obsolete. Information on new tools can come from catalogs or tool manufacturers tooling engineers. Help in tool selection or optimum tool working conditions can also be obtained from tool manufacturer software. Examples would be Kennametals TOOLPRO, software designed to help select the best tool grade, speed, and feed rates for different work materials in turning application. Another very important feature of TOOLPRO is the display of the horsepower requirement for each machining selection. This allow the programmer to select a combination of cutting speed, feed rate, and depth of cut that equals the machines maximum horsepower for roughing cuts. For a finishing cut, the smallest diameter of the part being machined is selected and then the cutting speed varied until the RPM is equal to the maximum RPM of the machine. This helps in maximizing machining efficiency. Knowing the horsepower requirement for a cut is critical if more than one tool is cutting at the same time. Software for a machining center application would be Ingersoll Tool Companys Actual Chip Thickness, a program used to calculate the chip thickness in relation to feed-per-tooth for a milling cutter, especially during a shallow finishing cut. Ingersolls Rigidity Analysis software ealculates tool deflection for end mills as a function of tool stiffness and tool force. To this point we looked at some general qualifications that a programmer should possess. Now we examine how a CAM system works. Point Control Companys SmartCam system uses the following approach. First, the programmer makes a mental model of the part to be machined. This includes the kind of machining to be performed-turning or milling. Then the part print is studied to develop a machining sequence, roughing and finishing cuts, drilling, tapping, and boring operations. What work-holding device is to be used, a vise or fixture or clamps? After these considerations, computer input can be started. First comes the creation of a JOBPLAN. This JOBPLAN consists of entries such as inch or metric units, machine type, part ID, type of workpiece material, setup notes, and a description of the required tools. This line of information describes the tool by number, type, and size and includes the appropriate cutting speed and feed rate. After all the selected tools are entered, the file is saved. The second programming step is the making of the part. This represents a graphic modeling of the projected machining operation. After selecting a tool from the prepared JOBPLAN, parameters for the cutting operation are entered. For a drill, once the coordinate location of the hole and the depth are given, a circle appears on that spot. If the location is incorrect, the UNDO command erases this entry and allows you to give new values for this operation. When an end mill is being used, cutting movements (toolpath) are usually defined as lines and arcs. As a line is programmed, the toolpath is graphically displayed and errors can be corrected instantly. At any time during programming, the command SHOWPATH will show the actual toolpath for each of the programmed tools. The tools will be displayed in the sequence in which they will be used during actual machining. If the sequence of a tool movement needs to be changed, a few keystrokes will to that. Sometimes in CAM the programming sequence is different from the actual machining order. An example would be the machining of a pocket in a part. With CAM, the finished pocket outline is programmed first, then this outline is used to define the roughing cuts to machine the pocket. The roughing cuts are computer generated from inputs such as depth and width of cut and how much material to leave for the finish cut. Different roughing patterns can be tried out to allow the programmer to select the most efllcient one for the actual machining cuts. Since each tool is represented by a different color, it is easy to observe the toolpath made by each one. A CAM system lets the programmer view the graphics model from varying angles, such as a top, front, side, or isometric view. A toolpath that looks correct from a top view, may show from a front view that the depth of the cutting tool is incorrect. Changes can easily be made and seen immediately. When the toolpath and the sequence of operations are satisfactory, machine ready code has to be made. This is as easy as specifying the CNC machine that is to be used to machine the part. The code generator for that specific CNC machine during processing accesses four different files. The JOBPLAN file for the tool information and the GRAPHICE file for the toolpath and cutting sequence. It also uses the MACHINE DEFINE file which defines the CNC code words for that specific machine. This file also supplies data for maximum feed rates, RPM, toolchange times, and so on. The fourth file taking part in the code generating process is the TEMPLATE file. This file acts like a ruler that produces the CNC code with all of its parts in the right place and sequence. When the code generation is complete, a projected machining time is displayed. This time is calculated from values such as feed rates and distances traveled, noncutting movements at maximum feed rates between points, tool change times, and so on. The projected machining time can be revised by changing tooling to allow for higher metal removal rates or creating a more efficient toolpath. This display of total time required can also be used to estimate production costs. If more then one CNC machine tool is available to machine this part, making code and comparing the machining time may show that one machine is more efficient than the others.CAD/CAM Another method of creating toolpath is with the use of a Computer-aided Drafting (CAD) file. Most machine drawings are created using computers with the description and part geometry stored in the computer database. SmartCAM, though its CAM CONNECTION, will read a CAD file and transfer its geometry represents the part profile, holes, and so on. The programmer still needs to prepare a JOBPLAN with all the necessary tools, but instead of programming a profile line by line, now only a tool has to be assigned to an existing profile. Again, using the SHOWPATH function will display the toolpath for each tool and their sequence. Constant research and developments in CAD/CAM interaction will change how they work with each
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