1、为满足精度公差，需要从工件上去掉小量的材料。通常机床就是用于这种加工的设备。通过切削工具使工件成型达到所需的尺寸，机床通过其基础构件的功能作用，以控制相互关系，支持、夹紧工具和工件，基本部件列举如下：a） 床身. 这是个主要部件，它为主轴、拖板箱等提供了一个基础和连接中介，在负载作用下，它必须使形变和振动保持最小。 b） 拖板箱和导轨. 机床部件（如拖板箱）的移动，通常是在精确的导轨面约束下靠直线运动来实现。 c） 主轴和轴承. 角位移是围绕一个旋转轴线发生的。该轴线的位置必须在机床中极端精确的限度内保持恒定，而且是靠精密的主轴和轴承来提供保证。 d） 动力装置. 电机是为机床普遍采用的动力装
2、置，通过对各个电机的合适定位，使皮带和齿轮传动装置减少到最少。 e） 传动连杆机构. 连杆机构是个通用术语，用来代表机械、液压、气动或电动机构，这些机构与确定的角位移和线位移相互关联。加工工艺主要由两部分组成: a） 粗加工工艺. 粗加工，金属切除率高，因而切削力也较大，但其所要求的精度较低。 b） 精加工工艺. 精加工，金属切除率低，因而切削力较小，但其要求的尺寸精度和表面光洁度都比较高。由此可见，静载荷和动载荷，例如由不平衡的砂轮引起的动载荷，在精加工中比粗加工中有着更为重要的意义，任何加工过程所获得的精度通常将受到由于力的作用而引起形变量的影响。机床机架一般是用铸铁制造的，然而有些也有可
3、能用铸钢或中碳钢来制造。选用铸铁是因为它便宜，刚性好，抗压强度高，并有减弱机床在操作过程中产生振动的作用。为了避免机床铸件出现大的断面，精心地设计筋条构架以便提供最大的抗弯曲和抗扭转应力的能力。筋条的两种基本类型是：箱型结构和片状斜支撑式。箱型结构便于生产，箱壁上有空口，便于型芯定位和取出。片状斜支撑筋条有较大的抗扭刚度亦能使截面上的碎屑掉落。它通常用于机床床身。机床的拖板箱和导轨是支撑和引导彼此相对运动的零部件，通常是改变刀具相对于工件的位置。运动一般以直线方式运动，但有时是转动。例如，对应于工件螺纹上的螺旋角方向而使万能螺纹磨床上的砂轮头转动一个角度。拖板箱构件的基本几何结构形状是平的、V
4、型槽形、燕尾槽形和圆柱形的。这些构件可以根据用途，以各种方式分别使用和结合使用。导轨的特性如下：a） 运动精确. 因为拖板是要按直线移动的，所以这直线必须是由两个互相垂直的平面形成而且拖板不能存在转动。机床导轨的直线度公差是每米00.02毫米，在水平面这个公差可以进行推理，以得到凸形表面，这样就可以抵消导轨下凹的作用。b） 调整手段. 为了便于装配、维护精度和在发生磨损后便于限制移动构件之间的“窜动”，有时拖板内装入扁条，此扁条叫做“斜铁”。通常该斜铁用穿过长孔的沉头螺钉固定，而用平头螺钉调整好后用紧锁螺母上紧。c） 润滑. 导轨可以用以下两种装置进行润滑：间隙润滑，通过润滑油、脂嘴或油嘴进行
5、，这是一种适合于运动速度低而不频繁场合的方法。连续润滑，例如通过计量阀和管道将润滑油送到润滑点。用这种方法引入两表面的油膜必定是很薄的，目的是避免使拖板“浮起”。如果滑移表面似镜面平滑，油就会被挤出而导致表面粘贴。因而在实践上，拖板滑移是凹面砂轮的刃进行刮研。两种工艺都可以产生微小的表面凹痕，相互配合的零件就不会处处因“浮起“而发生分离，这样使得拖板确定保持接触导轨。d） 防护. 为了使导轨处于良好状态，必须满足以下条件：防止外部物质，如碎屑的进入，具有某一形状的导轨那是所期望的，在这种场合，是不可能进入杂物的，例如V形导轨，那就不可能保存碎屑杂物在导轨表面上。必须保存润滑油。在垂直或倾斜的导
6、轨面上使用的润滑油要有粘性，那很重要，为了满足这种使用要求，已经研制出多种有用的润滑油，油的粘性也要保护，以免被切削液冲毁。必须使用防护罩来防止以外损坏。钻床各种规格和类型的立式钻床或摇臂钻床是很有用的，并配以有足够的宽范围的主轴变速级，并且能够自动进给以满足大多数工业的需求，典型钻床的变速级从76转/min到2025转/min。钻头的进给速度为：主轴每转从0.002英寸0.020英寸。摇臂钻床是用来钻削那种很笨重以至于不能搬动的工件。具有速度调节和进给调节机构的主轴被装在摇臂上，通过将转臂绕立柱的转动同主轴组件沿摇臂的移动相结合，可以使得主轴和钻头对准机床可以达到范围内的任何位置。对于太大而
7、不便于放在钻床工作台上的工件，可以把主轴组件摆放到机床旁边地面上的工件上方。普通摇臂钻床只能使主轴作垂直运动，而万能摇臂钻床允许主轴围绕垂直于摇臂的轴线旋转，而摇臂可绕着水平轴线旋转，这样就可以在任何角度方位下钻削。多轴钻床具有一个或多个通过万向接头和可伸缩的花键轴来驱动主轴的装置。所有的主轴通常都是由一部电机驱动并同时进给以便钻削出所需的孔数。在大多数钻床中，每跟主轴都被装夹在一可调节盘中，以便它能够相对于其他主轴而移动，相邻主轴所对准的区域部分交叠，使钻床可以在其范围内的任何一个位置钻孔。表面精整加工机理对已加工表面进行精整加工机理，基本有以下五个方面，它们是：a） 切削过程的几何形状.
8、例如在工件每转一周，单点车刀将轴向前进一个等距，当垂直对着走刀运动方向观察时，结果在工件表面上有一系列形状基本一样，类似切割刀具到尖形状复制而成的三角槽纹。b） 切削加工的效率. 带不稳定切削瘤的切削加工将产生含有硬切削瘤碎屑的表面，这些碎屑将导致表面光洁度的破坏，已经证明，在采用进给量大，前角小，切削速度低的不利情况下，除了产生不稳定的切削瘤之外，切削过程也会不稳定。同时，在切削区里进行的也不再是切削，而是撕裂，从而导致厚度不均匀，不连续的切削，加工出的表面质量差。当加工可塑性大的材料，如铝、铜，这种情况会更突出。c） 机床的稳定性. 在各种切削条件（如工件尺寸装夹的方法、刀具对于毛坯的刚度
9、）相结合的情况下，刀具的不稳定性可能会产生，那将引起振动，在某些情况下这振动将达到维持稳定而在另一种情况下，这振动将加重，直至停止切削，否则可能使刀具和工件发生相当严重的损坏。这种现象称之为“刀振“，而且在轴向车削中是以工件表面上长间距螺纹带状和已加工表面瞬间短距波纹为特征的。d） 金属切削的有效性。 断续产生切削的机械加工中，像铣削或脆性材料车削中，切削或者是由于重力作用或者是由于切削运动而引起的切削辅助喷射作用而离开切削区，那都是希望得到的。同样它们也将不会以任何方式影响已切削表面。然而当切削的产生明显是连续不断的，除非采取措施控制切削外，否则它将冲击伤害已加工表面，并会在表面留下划痕，除
10、了看起来会另人厌恶之外，还经常导致较差的光洁度。e） 刀具上的有效排屑角. 对于主切削刃的卸荷，排屑角的某种几何结构形状，以主切削刃进行切削并且以主切刃磨光，那都是可能的，这样可以产生一个良好的表面光洁度，当然，那是一种金属切削和金属成形严密结合的加工，但这种切削方法并不建议在实际中使用。然而，由于刀具的磨损，这些状况可能偶尔发生并导致在工件表面特性上有明显的变化。Constitute machine tool and its automation assembly lineSummary: Modular machine and its automatic assembly line are
11、 the completed set of automatic equipment with combination of mechanism and electricity. It features high efficiency, high quality and economy, so it is widely used in the industries such as engineering, traffic, energy, war industry, light industry and electric appliances etc. This special-purpose
12、modular machine is designed for efficiently making the guiding rollers of high-speed wire rolling machine. This article introduces the technique scheme, whole planning。Pivotal Words : Modular machine; Automatic control;In many cases products from the primary forming processes must undergo further re
13、finements in size and surface finish to meet their design specifications. To meet such precise tolerances the removal of small amounts of material is need. Usually machine tools are used for such operation.A machine tool provides the means for cutting tools to shape a workpiece to required dimension
14、s; the machine supports the tool and the workpiece in a controlled relationship through the functioning of its basic members which are as follows:a） Bed, Structure or Frame. This is the main member which provides a basis for, and a connection between, the spindles and slides; the distortion and vibr
15、ation under load must be kept to a minimum.b） Slides and Slideways. The translations of a machine element （e.g. the slide） is normally achieved by straight-line motion under the constraint of accurate guiding surface （the slideway）c） Spindles and Bearings. Angular displacements take place about an a
16、xis of rotation; the position of this axis must be constant within extremely fine limits in machine tools, and is ensured by the provision of precision spindles and bearings.d） Power Unit. The electric motor is the universally adopted power unit for machine tools. By suitably positioning individual
17、motors, belt and gear transmissions are reduced to a minimum.e） Transmission Linkage. Linkage is the general term used to denote the mechanical; hydraulic, pneumatic or electric mechanisms which connect angular and linear displacement in defined relationship.There are two broad divisions of which op
18、erations:a） Roughing, for which the mental removal rate, and consequently the cutting force, is high, but the required dimensional accuracy relatively low.b） Finishing, for which the mental removal rate, and consequently the cutting force, is low, but the required dimensional accuracy relatively hig
19、h.It follows that static loads and dynamic loads, such as result from an unbalanced grindingwheel, are more significant in finishing operations than in roughing operations. The degree of precision achieved in any machining process will usually be influenced by the magnitude of the deflections, which
20、 occur as result of the force acting.Machine tool frames are generally made in cast iron, although some may be steel casting or mild-steel fabrications. Cast iron is chosen because of its cheapness, rigidity, compressive strength and capacity for damping the vibrations set-up in machine operations.
21、To avoid massive sections in castings, carefully designed systems of ribbing are used to offer the maximum resistance to bending and torsional stresses. Two basic types of ribbing are box and diagonal. The box formation is convenient to produce, apertures in walls permitting the positions and extrac
22、tion of cores. Diagonal ribbing provides greater torsional stiffness and yet permits swarf to fall between the sections; it is frequently used for lathe beds.The slides and slideways of a machine tool locate and guide members which move relative to each other, usually changing the position of the to
23、ol relative to workpiece. The movement generally takes the form of translation in a straight line, but is something angular rotation, e.g. tilting the wheel-head of a universal thread-grinding machine to an angle corresponding with the helix angle of the workpiece thread. The basic geometric element
24、s of slides are flat, vee, dovetail and cylinder. These elements may be used separately or combined in various ways according to the applications. Features of slideways are as follows:a） Accuracy of Movement. Where a slide is to displaced in s straight line, this line must lie in two mutually perpen
25、dicular planes and there must be no side rotation. The general tolerance for straightness of machine tool slideways is 00.02mm per 1000mm; on horizontal surfaces this tolerance may be disposed so that a cinvex surface results, thus countering the effect of “sag” of the slideway.b） Means of Adjustmen
26、t. To facilitate assembly, maintain accuracy and eliminate “play” between sliding members after wear has taken place, a strip is something inserted in the slides. This is called a gib-strip. Usually the gib is retained by socket-head screws passing though elongated slots; and is adjusted by grub-scr
27、ews secured by lock nuts.c） Lubrication. Slideways may be lubricated by either of following systems: Intermittently though grease or oil nipples, a method suitable where movements are infrequent and speed low. Continuously, e.g. by pumping though a metering value and pipe-work to the point of applic
28、ation; the film of oil introduced between surface by these means must be extremely thin to avoid the slide “floating”. If sliding surfaces were optically flat oil would be squeezed out, resulting in the surfaces sticking. Hence in practice slide surface are either ground using the edge of a cup whee
29、l, or scraped. Both processes produce minute surface depressions, which retain “pocket” of oil, and complete separation of the parts may not occur at all points; positive location of the slides is thus retained.d） Protection. To maintain slideways in good order, the following conditions must be met:
30、 Ingress of foreign matter, e.g. swarf, must be prevented. Where this is no possible, it is desirable to have a form of slideway, which dose not retain swarf, e.g. the inverted vee. Lubricating oil must be retained. The adhesive property of oil for use on vertical or inclined slide surface is import
31、ant; oils are available which have been specially developed for this purpose. The adhesiveness of oil also prevents it being washed away by cutting fluids. Accidental damage must be prevented by protective guards.Drilling Machine Upright drilling machines and drill presser are available in a variety
32、 of size and types, and are equipped with a sufficient range of spindle speeds and automatic feeds to fit the needs of most industries. Speed ranges on a typical machine are from 76 to 2025 rpm, with drill feed form 0.002 to 0.020 in. per revolution of the spindle. Radial drilling machine are used to drill workpiece that are t
