毕业设计（论文）万向节滑动叉工艺设计

南通职业大学毕业设计 万向滑动叉工艺设计摘 要万向节滑动叉位于传动轴的端部。它的主要作用：一是传递扭矩，使汽车获得前进的动力；二是当汽车后桥钢板弹簧处在不同的状态时，由本零件可以调整传动轴的长短及其位置。零件的两个叉头部位上有两个孔，用以安装滚针轴承并与十字轴相连，起万向联轴节的作用。零件上的花键孔与传动轴端部的花键轴相配合，用于传递动力之用。此次设计是在学完机械制造工艺学及机床夹具设计课程，并进行了生产实习的基础上完成的。本设计主要编制该零件的机械加工工艺规程，并设计其中一道工序的专用夹具，并撰写设计说明书。此次设计培养了我熟悉并运用有关手册、规范、图表等技术资料的能力。进一步锻炼了我识图、制图、运算、编写技术文件和操作CAD等基本能力。关键字：万向节滑动叉、工艺、专用夹具AbstractUniversal joint glide fork is located the drive shaft the nose.Its main function: One, the transmission torque, causes the automobile to obtain the advance the power; Two is when the automobile rear axle of car spring occupies the different condition, may adjust the drive shaft by this components the length and the position. In the components two jaw spot has two holes, with installs the needle bearing and is connected with the cross axle, plays the rotary shaft coupling role. On the components colored key hole and the drive shaft nose spline shaft coordinates, to use in transmitting using of the power.This design is in study the machine manufacture technology and the engine bed jig design curriculum, and carried on in the production practice foundation to complete. This design mainly establishes this components the machine-finishing technological process, and designs working procedure the unit clamp, and composes the design instruction booklet.This design trained me to be familiar with and to utilize related technical data and so on the handbook, standard, graph abilities.Further exercised me to know the chart, the charting, the operation, the compilation technology document and operates CAD and so on the basic capability.Keyword: Universal joint glide fork, craft, unit clamp.31第一章零件的分析1零件的作用放牌汽车底盘传动轴上的万向节滑动叉，它位于传动轴的端部。主要作用一是传递扭 矩，使汽车获得前进的动力；二是当汽车后桥钢板弹簧处在不同的状态时，由本零件可以调整传动轴的长短及其 位置。零件的两个叉头部位上有两个39mm的孔，用以安装该针轴承并与十字轴相连，起万向联轴节的作用。零 件65mm外圆内为50mm花键孔与传动轴端部的花键轴相配合，用于传递动力之用。2零件的工艺分析万向节滑动叉共有两组加工表面，它们之间有一定的位置要求。现分述如下：(1)以39mm孔为中心的加工表面这一组加工表面包括：两个39mm的孔及其倒角，尺寸为118mm的与两个孔39mm相垂直的平面，还有在平面上的四个M8螺孔。其中，主要加工表面为39mm的两个孔。(2)以50mm花键孔为中心的加工表面 这一组加工表面包括：50mm十六齿方齿花键孔，55mm阶梯孔，以及65mm的外圆表面和M60X16mm的外螺纹表面。 这两组加工表面之间有着一定的位置要求，主要是： 1)50mm花键孔与39二孔中心联线的垂直度公差为100：0.2； 2)39mm二孔外端面对公39孔垂直度公差为0.1mm； 3)50花键槽宽中心线与39mm中心线偏转角度公差为2。由以上分析可知，对于这两组加工表面而言，可以先加工其中一组表面，然后借助于专用夹具加工另一组表面，并且保证它们之间的位置精度要求。第二章确定毛坯，画毛坯-零件合图1.确定毛坯的制造形式零件材料为45钢。考虑到汽车在运行中要经常加速及正、反向行驶，零件在工作过程中则经常承受交变载荷及冲击性载荷，因此应该选用锻件，以使金属纤维尽量不被切断，保证零件工作可靠。由于零件年产量为4000件，已达大批生产的水平，而且零件的轮廓尺寸不大，故可采用模锻成型。这从提高生产率、保证加工精度上考虑，也是应该的。2.机械加工余量、工序尺寸及毛坯尺寸的确定 根据零件材料、硬度、毛坯重量及生产类型、锻造方法等原始资料和加工工艺，分别确定各加工表面的机械加工余量、工序尺寸及毛坯尺寸。(1) 外圆表面(62mm及M60X1mm) 考虑其加工长度为90mm，与其联结的非加工外圆表面直径为65mm，为简化模锻毛坯的外形，现直接取其外圆表面直径为65mm。62mm表面为自由尺寸公差，表面粗糙度值要求为Rz200m，只要求相加工，此时直径余量2z3mm已能满足加工要求。(2)外圆表面沿轴线长度方向的加工余量及公差(M60X1mm端面) 查机械制造工艺设计简明手册(以下简称工艺手册)表2.2l 4，其中锻件重量为6kg，锻件复杂形状系数为S1，锻件材质系数取M1，锻件轮廓尺寸(长度方向)180315mm。长度方向的余量查工艺手册表2.22.5，其余量值规定为2.0一2.5mm，现取2.0mm。(3)两内孔毛坯为实心，不冲出孔。两内孔精度要求界于IT7一IT8之间，参照工艺手册表2.3-9及表2.312确定工序尺寸及余量为： 钻孔：25mm 钻孔：37mm 2z12mm 扩钻：38.7mm 2z1.7mm 精镗；38.9mm 2Z0.2mm 细镗：39mm 2z0.1mm(4)花键孔 要求花键孔为外径定心，故采用拉削加工。参照工艺手册表2.39确定孔的加工余量分配： 钻孔25mm 钻孔41mm 扩钻42mm 拉花键孔(1650mm*43mm*5mm) 花键孔要求外径定心，拉削时的加工余量参照工艺手册表2.319取2z1mm。(5)39mm 二孔外端面的加工余量（加工与量的计算长度为118mm） 1) 按照工艺手册表2.225，取加工精度F2，锻件复杂系数S3，锻件重6kg，则二孔外端面的单边加工余量为2.0一3.0mm，取Z2mm。锻件的公差按工艺手册表2.214，材质系数取M1，复杂系数S3， 则锻件的偏差。 2) 磨削余量：单边0.2mm，(见二艺手册表2.321)，磨削公差及零件公差一0.07mm。 3) 铣削余量：铣削的公称余量(单边)为：Z2.0一0.21.8(mm) 铣削公差：现规定本工序(粗铣)的加工精度为ITll级，因此可知本工序的加工公差为-22M(入体方)。 由于毛坯及以后各道二序(或工步)的加工都有加工公差，因此所规定的加工余量其实只是名义上的加工余量。 实际上，加工余量有最大加工余量及最小加工余量之分。出于本设计规定的零件为大批生产，应该采用调整法加工，因此在计算最大、最小加工余量时， 应按调整法加工方式予以确定。 39mm二孔外端面尺寸加工余量和工序间余量及公差分布图见图7： 由图可知：毛坯名义尺寸：118十22122(mm) 毛坯最大尺寸：122十1.32124.6(mm) 毛坯最小尺寸：1220.72120.6(mm) 粗铣后最大尺寸：118十O.22118.4(mm) 粗铣后最小尺寸：118.40.22ll8.18(mm) 最后，将上述计算的工序间尺寸及公差整理成表3：第三章工艺规程设计1.基面的选择基面选择是工艺规程设计中的重要工作之一。基面选择得正确与合理，可以使加工质量得到保证，生产率得以提高。否则，加工工艺过程中会问题百出，更有甚者，还会造成零件大批报废，使生产无法正常进行。(1)粗基准的选择 对于一般的轴类零件而言，以外圆作为粗基准是完全合理的。但对于本零件来说，如果以65mm外圆(或62mm外圆)表面作基准(四点定位)，则可能造成这一组内外圆柱表面与零件的叉部外形不对称。按照有关粗基准的选择原则(即当零件有不加工表面时，应以这些不加工表面作粗基准；若零件有若干个不加工表面时，则应以与加工表面要求相对位置精度较高的不加工表面作为粗基准)，现选取叉部两个39mm孔的不加工外轮廓表面作为粗基准，利用一组共两个短形块支承这两个39mm的外轮廓作主要定位面，以消除、四个自由度，再用一对自动定心的窄口卡爪，夹持在65mm外圆柱面上，用以消除、两个自由度，达到完全定位。 (2)精基准的选择 主要应该考虑基准重合的问题。当设计基准与工序基准不重合时，应该进行尺寸换算，这在以后还要专门计算 ，此处不再重复。2.制定工艺路线制订工艺路线的出发点，应当是使零件的几何形状、尺寸精度及位置精度等技术要求能得到合理的保证。在生产纲领已确定为大批生产的条件下，可以考虑采用万能性机床配以专用工夹具，并尽量使工序集中来提高生产率。除此以外，还应当考虑经济效果，以便使生产成本尽量下降。(1)工艺路线方案一工序一：车外圆62mm，60mm，车螺纹M60X1mm；工序二：两次钻孔并扩钻花键底孔43mm，淴沉头孔55mm；工序三：倒角5X30；工序四：钻Rc1/8底孔；工序五：拉花键孔；工序六：粗铣39mm二孔端面；工序七：精铣39mm二孔端面；工序八：钻、扩、粗铰、精铰两个39mm孔至图样尺寸并淴倒角2X45；工序九：钻M8mm底孔6.7mm，倒角120；工序十：攻螺纹M8mm，Rc1/8；工序十一：冲箭头；工序十二：检查。(2)工艺路线方案二工序一：粗铣39mm二孔端面；工序二：精铣39mm二孔端面；工序三：钻39mm二孔；工序四：镗39mm二孔；工序五：精镗39mm二孔；工序六：车外圆62mm，60mm，车螺纹M60X1mm；工序七：钻、镗孔43mm，并淴沉头孔55mm；工序八：倒角5X30；工序九：钻Rc1/8底孔；工序十：拉花键孔。工序十一：钻M8mm螺纹的底孔6.7mm孔，倒角120；工序十二：攻螺纹M8mm，Rc1/8；工序十三：冲箭头；工序十四：检查。上述两个工艺方案的特点在于：方案一是先加工以花键孔为中心的一组表面，然后以此为基面加工39mm二孔，而方案二则与此相反，先是加工39mm孔，然后再以此二孔为基准加工花键孔及其外表面。两相比较可以看出，先加工花键孔后再以花键孔定位加工39二孔，这时的位置精度较易保证，并且定位及装夹等都比较方便。但方案一中的工序八虽然代替了方案二中的工序三、四、五，减少了装夹次数，但在一道工序中要完成这么多工作，除了选用专门设计的组合机床(但在成批生产时，在能保证加工精度的情况下，应尽量不选用专用组合机床)外，只能选用转塔车床，利用转塔头进行加工。而转塔车床目前大多适用于粗加工，用来在此处加工39mm二孔是不合适的，因此决定将方案二中的工序三、四、五移入方案一，改为两道工序加工。具体工艺过程如下：工序一：车外圆62mm，60mm，车螺纹M60X1mm；工序二：两次钻孔并扩钻花键底孔43mm，淴沉头孔55mm，以62mm外圆为定位基准；工序三：倒角5X30；工序四：钻Rc1/8底孔；工序五：拉花键孔；工序六：粗铣39mm二孔端面，以花键孔及其端面为基准；工序七：精铣39mm二孔端面；工序八：钻孔两次并扩孔39mm；工序九：精镗并细镗39mm二孔，倒角2X45；工序十：钻M8mm底孔6.7mm，倒角120；工序十一：攻螺纹M8mm，Rc1/8；工序十二：冲箭头；工序十三：检查；以上加工方案大致看来还是合理的.但通过仔细考虑零件的技术要求以及可能采取的加工手段之后，就会发现仍有问题，主要表现在39mm两个孔及其端面加工要求上。图样规定39mm二孔中心线应与55mm花键孔垂直，垂直度公差为100：0.2;39mm二孔与其外端面应垂直，垂直度公差为0.1mm。由此可以看出；因为39mm二孔的中心线要求与花键孔中心线相垂直，因此，加工及测量39mm孔时应以花键孔为基准。这样做，能保证设计基准与工艺基 准相重合。在上述工艺路线制订中也是这样做了的。同理，39mm二孔与其外端面的垂直度(0.1mm)的技术要求在加工与测量时也应遵循上述原则。但在已制订的工艺路线中却没有这样做：39mm孔加工时，以55mm花键孔定位(这是正确的)；而孔的外端面加工时，也是以55mm花键孔定位。这样做，从装夹上看似乎比较方便，但却违反了基准重合的原则，造成了不必要的基准不重合误差。具体来说，当39mm二孔的外端面以花键孔为基准加工时，如果两个端面与花键孔中心线已保证绝对平行的话(这是很难的)，那么由于39mm二孔中心线与花键孔仍有100：0.2的垂直度公差，则39mm孔与其外端面的垂直度误差就会很大，甚至会造成超差而报废。这就是由于基被不重合而造成的恶果。为了解决这个问题，原有的加工路线可仍大致保持不变，只是在39mm二孔加工完了以后，再增加一道工序以39mm孔为基准，磨39mm二孔外端面。这样做，可以修正由于基准不重合造成的加工误差，同时也照顾了原有的加工路线中装夹较方便的特点。因此，最后的加工路线确定如下：工序一：车端面及外圆62mm，60mm，车螺纹M60X1mm。以两个叉耳外轮廓及65mm外圆为粗基准，选用C6201卧式车床并加专用夹具；工序二：钻、扩花键底孔43mm，淴沉头孔55mm，以62mm外圆为定位基准，选用c365L转塔车床；工序三：内花键孔5X30倒角。选用c620-1车床加专用夹具；工序四：钻锥螺纹Rc1/8底孔。选用z525立式钻床及专用钻模。这里安排钻Rcl8底孔主要是为了下道工序拉花键孔时为消除回转自由度面设置的一个定位基准。本工序以花键内底孔定位，并利用叉部外轮廓消除回转自由度；工序五：拉花键孔。利用花键内底孔。55mm端面及Rcl8锥螺纹底孔定位，选用L6120卧式拉床加工；工序六：粗铣39mm二孔端面，以花键孔及其端面为基准。选用x63卧式铣床加工；工序七：钻、扩39mm二孔及倒角。以花键孔及端面定位，选用z535立式钻床加工；工序八：精镗并细镗39mm二孔。 选用T740型卧式金刚镗床及专用夹具加工，以花键内孔及其端面定位；工序九：磨39mm二孔端面，保证尺寸，以39mm孔及花键孔定位，选用M7l30平面磨床及专用夹具加工；工序十：钻叉部四个M8mm螺纹底孔并倒角。选用z525立式钻床及专用夹具加工，以花键孔及39mm孔定位；工序十一：攻螺纹4-M8mm，Rc1/8；工序十二：冲箭头；工序十三：检查。以上工艺过程详见“机械加工工艺过程综合卡片”4.确定切削用量及基本工时工序1：车削端面、外圆及螺纹。本工序采用计算法确定切削用量；工序2：钻、扩花键底孔43mm，及淴沉头孔55mm，选用机床C365L；工序3：43mm内孔50*30倒角，选用卧式车床C620-1。由于最后的切削宽度很大，故按成形车削制定进给量；工序4：钻锥螺纹Rc1/8底孔(8.8mm)；工序5：拉花键孔；工序6：粗铣39mm二孔端面，保证尺寸；工序7：钻、扩39mm二孔及倒角；工序8：精、细镗38.9mm二孔，选用机床：T740金刚镗床；工序9：磨39mm二孔端面，保证尺寸；工序10：钻螺纹底孔4-6.7mm，并倒角120；工序11：攻螺纹4M8mm及Rc1/8。 需用到的典型夹具机构 最后，将以上各工序切削用量、工时定额的计算结果，连同其它加工数据，一并填入机械加工工艺过程综合卡。 6.机械加工工艺过程综合卡片（见附图）第四章夹具设计1.问题的提出 本夹具主要用来粗铣39mm二孔的两个端面，这两个端面对39mm孔及花键孔都有一定的技术要求。但加工本道工序时，39mm孔尚未加工，而且这两个端面在工序还要进行磨加工。因此，在本道工序加工时，主要应考虑如何提高劳动生产率，降低劳动强度，面精度则不是主要问题。2.夹具设计(1)定位基准的选择 由零件图可知，39mm二孔端面应对花键孔中心线有平行度及对称度要求，其设计基准为花键孔中心线。为了使定位误差为零，应该选择以花键孔定位的自动定心夹具。但这种自动定心夹具在结构上将过于复杂，因此这里只选用以花键孔为主要定位基面。 为了提高加工效率，现决定用两把镶齿三面刃铣刀对两个孔端面同时进行加工。同时，为了缩短辅助时间，准备采用气动夹紧。(2)切削力及夹紧力计算 刀具：高速钢镶齿三面刃铣刀， z20 (见切削手册表3.28) 其中：Cr65050，a=3.1mm，x1.0，f=0.08mm，y0.72，a40mm(在加工面上侧量的近似值)O.86，d=225mm，qO.86，w=0，z20所以 当用两把刀铣削时，F2F2912(N) 水平分力：Fe1.1 F3203(N) 垂直分力：Fv=0.3F873(N) 在计算切削力时，必须把安全系数考虑在内。安全系数KK1K2K3K4。 （参见常用设计资料） 其中：K1为基本安全系数1.5； K2为加工性质系数1.1； K3为刀具钝化系数1.1； K4为断续切削系数1.1。 所以F=KH1.51.11.11.13203=6395(N) 选用气缸一斜楔夹紧机构，楔角=10，其结构形式选用w型，则扩力比i3.42。 为克服水平切削力，实际夹紧力N应为： N(f1十f2)KH 所以 其中f1及f2为夹具定位面及夹紧面上的摩擦系数，f1=f20.25。则 气缸选用100mm。当压缩空气单位压力p0.5MPa时，气缸推力为3900N。由于己知新楔机构的扩力比i3.42，故由气缸产生的实际夹紧力为 Nq3900i39003.4213338(N) 此时Nq已大于所需的12790N的夹紧力，故本夹具可安全工作。3.定位误差分析 (1)定位元件尺寸及公差的确定。夹具的主要定位元件为一花键轴，该定位花键轴的尺寸与公差现规定为与本零件在工作时与其相配花键轴的尺寸与公差相同，即16x43H1150H85H10mm。(2)零件图样规定50mm花键孔键槽宽中心线与39mm两孔中心线转角公差为2。由于39mm孔中心线应与其外端面垂直，故要求39mm二孔端面之垂线应与50mm。花键孔键槽宽中心线转角公差为2。此项技术要求主要应由花键槽宽配合中的侧向间隙保证。 已知花键孔键槽宽为5mm，夹具中定位花键轴键宽为5mm，因此当零件安装在夹具中时，键槽处的最大侧向间隙为： 0.048-(-0.065)=0.113(mm) 由此而引起的零件最大转角为： 所以 =0.258 即最大侧隙能满足零件的精度要求。(3)计算39mm二孔外端面铣加工后与花键孔中心线的最大平行度误差。 零件花键孔与定位心轴外径的最大间隙为： 0.048-(-0.083)=0.131(mm) 当定位花键轴的长度取l00mm时，则由上述间隙引起的最大倾角为0.131100。此即为由于定位问题而引起的孔端面对花键孔中心线的最大平行度误差。由于39mm孔外端面以后还要进行磨削加工，故上述平行度误差值可以允许。4.夹具设计及操作的简要说明 如前所述，在设计夹具时，应该注意提高劳动生产率。为此，应首先着眼机动夹紧而不采用手动夹紧。因为这是提高劳动生产率的重要途径。本道工序的铣床夹具就选择了气动夹紧方式。本工序由于是粗加工，切削力较大，为了夹紧工件，势必要增大气缸直径，而这样将使整个夹具过于庞大。因此，应首先设法降低切削力。目前采取的措施有三：一是提高毛坯的制造精度，使最大切削深度降低，以降低切削力；二是选择一种比较理想的斜楔夹紧机构，尽量增加该夹紧机构的扩力比，三是在可能的情况下，适当提高压缩空气的工作压力(由0.4MPa增至0.5MPa)，以增加气缸推力。结果，本夹具总的感觉还比较紧凑。夹具上装有对刀块，可使夹具在一批零件的加工之前很好地对刀(与塞尺配合使用)；同时，夹具体底面上的一对定位键可使整个夹具在机床工作台上有一正确的安装位置，以利于铣削加工。5.铣床夹具的装配图及夹具体零件图见附录致 谢这篇毕业设计论文是我大学学习生活的小结，三年的大学生活将随着论文的完成而告一段落。同时我也将开始新的工作和生活。通过三年的在校的理论学习和近三个月的在岗实习。再加上对毕业论文的编写，我不仅对所学的专业课程有了全面和系统的了解和掌握，也初步懂得了完成一项设计的步骤、方法，为以后的继续学习积累了宝贵的实践经验。本课题是在指导老师季老师的亲切关怀和悉心指导下完成的，季老师以渊博的学识和严谨的治学态度，为学生开阔了研究视野，丰富了专业知识。她谦逊无私的高尚品质和朴实真诚的做人准则，一丝不苟的敬业精神，对学生将是永远的鞭策。在本课题的设计过程中，季老师在学习与生活中给予了热情的帮助，付出了大量的心血，在此表示衷心的感谢。同时，感谢答辩组的评审老师们，感谢你们给我提出的宝贵意见和建议，你们的辛苦了！另外，非常感谢在我论文完成期间关心和帮助过我的同学、朋友们，是你们让我的工作更顺畅。还有要感谢的是我的父母，虽说平时您没有说什么，但您的行动让我知道在外不论是成功还是失败，我都有一个避风的港湾。最后，我要感谢我的母校南通职业大学，是你给我了成长的空间，是你给了我梦想的舞台，是你给了我腾飞的翅膀，在此预祝母校在今后的越办越好！Common difference and surface roughnessThe modern technology is more and more strict to the components sizeprecision request. Moreover, at present many components have spread ineach place different factory production, therefore must makes thestrict stipulation to these components sizes and the production,guaranteed they have the interchangeability.Causes it for the components sign note size to change in a stipulationsector, guaranteed they have the interchangeable technology to becalled the common difference technology. Allows each size certainly tohave in the stipulation scope changes the momentum, is called thecommon difference. For example, a components size may express for200.5, its common difference (size changes momentum) is 1.00mm.In does not affect the components performance in the situation, mustgive the size as far as possible big common difference, by falls theproduction cost to is lowest. The production cost reduces along withthe common difference elevates.Some three expressions size common difference way: Unidirectional,bidirectional and limit way. When uses the positive and negativecommon difference, adds to the common difference is been called thebasic size the theory size to come up. When only allows the size tohave (or changes in a big way to the basic size sole direction, orchanges slightly) when change, is the unilateral tolerance. May(change in the size when the basic size two directions big or changesslightly) all may change, the common difference is bidirectional. Thecommon difference also may use the limit form to produce, theexpression components contour is biggest and most light-sized.Some and common difference related terminology and definition asfollows: Common difference: Upper limit and lower limit bad value stipulatedwhich for some size. Basic size: The theory size, is calculates the extreme dimension andthe deviation outset size. Deviation The hole size or the axis size subtracts the basic sizeobtained bad value.The components biggest extreme dimension subtracts itsbasic size obtained bad value. The components smallest extreme dimension subtracts itsbasic size obtained bad value. Actual size: After processing components actual size. Coordination: Two assemble in between together components degree. May divide into the coordination three kinds: Gapcoordination, excessively full coordination, transition fit. Gap coordination: Two assemble in between the together fitting has thegap the coordination.Excessively full coordination: Two assemble in between the togethercomponents has the full coordinate - axis to be bigger than the hole,needs to make an effort the coordination which or the pressure carrieson, has is similar to two components welds in together effect. Transition fit: In two assembles in between the together components orexists excessively full, or has the gap the coordinate - axis to beallowed to be smaller than or to be bigger than the hole, but still instipulation common difference. Selective assembly: Through manually tries to match chooses and theunit method. Through this method, may assemble common differencebigger components which makes under a lower cost. It may take the highmanufacture precision and is easy between the components onecompromise method which assembles. Uses the smallest hole size to take the computation commondifference and the processing remainder basic size. When uses thestandard the drill bit, the engine bed carries on theprecision processing to the hole,the system is extremelyeffective. Uses the smallest hole the size to take the basic size isbecause the hole size may change in a big way through themachine-finishing, but cannot reduce.May defer to when the unusual high accuracy the standard sizeprovides, uses the basic shaft system is suitable. When computationcommon difference and remainder, uses the axis most large diameter totake the basic size. This is because the axis may turn a smaller sizethrough the processing, but the basic size cannot increase. International common difference (IT) rank: A series of along withbasic size change, also provides the even precision in the stipulationrank the common difference. Altogether has 18 IT rank: IT01, IT0,IT1. IT16. Common difference mark: The mark has produced the commondifference and the coordinate specification, the basic size is anumeral, behind and expresses the IT rank numeral with the expressionbasic deviation letter. They decide the tolerance zone together thesize and the position. The capital letter represents the hole thebasic deviation, the lowercase letter represents the axis the basicdeviation. Because the superficial appearance (namely fineness) canaffect the components the performance, therefore must preciselyperform to its size to stipulate, the superficial appearance is on thesuperficial difference, including roughness, waviness, processingtexture direction and flaw. Roughness: Useful causes slightest which the work piece surface brightand clean processing craft creates surface irregularity. The surfaceroughness highly uses micron and the microinch carries on the survey. Waviness: Is surpasses roughness width the boundary big gap deviation,uses inch and a millimeter survey. May regard as roughness tosuperimpose on waviness surface surface irregularity. Processing texture direction: The superficial design directionwhich by which uses the processing method produces. Flaw: Not frequently appears or the surface defect which can appear inthe very big sector talent, it including the crack, the blowhole, thetiny crack, delimits the mark and so on. The flaw influence usually isneglected in roughness levelling.The project pattern is makes the machine part the basis. Therefore, isengaged in the manufacturing industry the staff all want the correctunderstanding to apply to the entire production process patternmeaning. Must face this kind of fact in enterprise work engineer, namely anytwo machine part all cannot make the quite same not less than. He knewin the design must consider the repetition lives the small sizedifference which mid-production produces, in the pattern superscriptnote appropriate common difference, limits the size change in thepermission scope. After the processing components outline must belocated the common difference stipulation in the region. Uses thesuitable common difference to be allowed to guarantee the product thefunction and the service life aspect all can achieve the anticipatedgoal.Each design personnel extremely are all clear, if the components allprocess the manufacture by a smaller common difference, then theproduct cost can rapidly increase. Therefore, engineers unceasinglyobtain the advice, must use as far as possible the big commondifference. However, sometimes possibly appears between each kind ofcommon difference reciprocity which needs to the function request notto conduct the full research the situation. In this kind of situation,in order to guarantee components when assembly does not give rise to aquestion or problem, not not appropriately designs the personnelusually to stipulate the common difference too strictly. Is oppositeearnestly to, is thorough carries on to the common difference analyzessaid that, this obviously is a price expensive substitution way. If the product is produced by a lower price and the satisfiedmurderous intention request, stipulated the suitable processing commondifference is the most important work. The common difference size isby designs, it which the personnel determined is decided by many withthe design related condition as well as in the past when the designsimilar product obtains experience (if has this aspect experience). Ifstipulated the common difference too is small, when uses present theprocessing equipment processing work piece cannot achieve the designrequest, needs to design carries on the change. In the project pattern the place can cause many ischaotic and the economic loss. When drafts the common difference,designs the personnel to have fully to realize, must completelyachieve its design goal, in the pattern must contain the informationwhich needs. Thus, in the pattern must produce the completeinformation, and as far as possible simple was bright. In pattern eachpart all should be able to understand by everybody. In the patternexpressed the meaning regarding all uses it the personnel (design,purchase, cutting tool design, production, examination, assembly andservice department) said all should be only. The common difference may select the different sign note method in thepattern. In the unidirectional system, a limit deviation is zero,another limit deviation is the size permission completely changes themomentum. In the bidirectional system in the size sign note, uses theintermediate size and changes the momentum in its positive andnegative two directions to express. When when all sizes all occupy the material which the permissioncomponents includes for most limiting condition, called thiscomponents are at the biggest entity condition (MMC). Regarding anaxis or external dimensions, its basic size for the biggest extremedimension, it changes when the tolerance zone, only can causeminification. Regarding a hole or the internal size, its basic sizefor the smallest extreme dimension, in the tolerance zone change, onlycan cause the size to increase.Each design personnel extremely are all clear, if the components allprocess the manufacture by a smaller common difference, then theproduct cost can rapidly increase. Therefore, engineers unceasinglyobtain the advice, must use as far as possible the big commondifference. However, sometimes possibly appears between e