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附表附表12：理工类论文格式模板：理工类论文格式模板（斜体字均作为格式说明用斜体字均作为格式说明用）本科毕业论文（设计）本科毕业论文（设计） 青饲料切割机设计青饲料切割机设计 学 院专 业学 号学生姓名指导教师提交日期年 月 日2015-JXLW商商 丘丘 工学院工学院专业代码专业代码- -编号编号II诚诚信信承承 诺诺 书书本人郑重承诺和声明:我承诺在毕业论文撰写过程中遵守学校有关规定,恪守学术规范,此毕业论文(设计)中均系本人在指导教师指导下独立完成,没有剽窃、抄袭他人的学术观点、思想和成果,没有篡改研究数据,凡涉及其他作者的观点和材料,均作了注释,如有违规行为发生,我愿承担一切责任,接受学校的处理,并承担相应的法律责任。毕业论文（设计）作者签名：年月日I摘 要青饲料切割机主要用于青饲料原料切割，主要由电机、传动装置、进料装置、切割装置、出料装置、机架等组成。本次设计主要针对青饲料切割机进行设计。首先，通过对青饲料切割机结构及原理进行分析，在此分析基础上提出了总体结构方案；接着，对主要技术参数进行了计算选择；然后，对各主要零部件进行了设计与校核；最后，通过 AutoCAD 制图软件绘制了青饲料切割机总装图及主要零部件图。通过本次设计，巩固了大学所学专业知识，如：机械原理、机械设计、材料力学、公差与互换性理论、机械制图等；掌握了普通机械产品的设计方法并能够熟练使用 AutoCAD 制图软件，对今后的工作于生活具有极大意义。关键词：青饲料，切割，绞龙，设计IIABSTRACTThe green fodder cutting machine is mainly used for cutting the green fodder raw material, which is mainly composed of a motor, a transmission device, a feeding device, a cutting device, a discharging device, a machine frame, etc.This design mainly aims at the design of the green feed cutting machine. Firstly, through to green fodder cutting machine structure and principle were analyzed. This analysis is proposed based on the overall structure of the program; then, the main technical parameters were calculated to select; then, of the main parts were designed and checked. Finally, through the AutoCAD drawing software drawn green fodder cutting machine assembly and major parts of the map.Through the design, the consolidation of the University of the professional knowledge, such as: mechanical principles, mechanical design, mechanics of materials, tolerance and interchangeability theories, mechanical drawing; master the design method of general machinery products and be able to skillfully use AutoCAD drawing software, for the future work in life is of great significance.Key Words：Green feed, Cutting, Auger, Design目 录摘 要.IABSTRACT .II1 引 言.11.1 研究背景及意义.11.2 青饲料切割机类型.11.3 市场前景分析.22 系统设计.42.1 方案设计.42.2 工作原理分析.43 进料及切割装置设计.53.1 电机的选择.53.2 总体动力参数计算.53.2.1 传动比计算.53.2.2 各轴的转速.53.2.3 各轴的输入功率.63.2.4 各轴的输入转矩.63.3 V 带传动的设计.63.3.1 V 带的基本参数计算.63.3.2 带轮结构的设计.83.4 齿轮传动设计.83.4.1 选精度等级、材料和齿数.83.4.2 按齿面接触疲劳强度设计.93.4.3 按齿根弯曲强度设计.103.4.4 几何尺寸计算.113.4.5 验算.113.5 轴及轴承、键的设计.123.5.1 尺寸与结构设计计算.123.5.2 强度校核计算.123.6 切割刀的设计.133.6.1 切割刀的基本结构尺寸设计.133.6.2 刀的安装.163.7 进料螺旋搅龙设计.174 出料装置及机架的设计.19IV4.1 蜗杆减速机的选择.194.2 V 带传动设计.194.2.1 V 带的基本参数计算.194.2.2 带轮结构的设计.214.3 出料螺旋搅龙设计.214.4 机架设计.22结 论.24致 谢.25参考文献.26附 录.271 引言11 引 言1.1 研究背景及意义近两年来，饲料加工机械形势看好，国产机型如割草机、搂草机、捡拾打捆机、青饲收获机、铡草机、揉搓机以及乳品机械等的销量大幅增加，特别是青贮切碎机在去年出现了供不应求的局面。我国现阶段农机市场上产品繁多、货源充足，农机购机热情空前高涨。然而，据专家分析，我国农机产品还远不能满足当前农村市场的需求。当前的主要障碍不是农机产品的数量，而是技术性障碍。饲料加工机械是建设现代农业的重要物质基础，是先进生产力的代表，是提高农业劳动生产率的主要手段。随着国家惠农政策的不断出台，我国现阶段农机市场上产品繁多、货源充足，农机购机热情空前高涨。国产机型如割草机、搂草机、捡拾打捆机、青饲收获机、铡草机、揉搓机以及乳品机械等的销量大幅增加，特别是青贮切碎机在去年出现了供不应求的局面。然而，据专家分析，我国农机产品还远不能满足当前农村市场的需求。当前的主要问题不是农机产品的数量，而是技术性与实用性的问题。在此基础上结合生产生活实际设计一个小型家用青饲料切割机，其结构简单，操作方便，经济实惠，能够满足大多数个体户的需要。1.2 青饲料切割机类型通过查阅资料，目前青饲料切割机主要如下四类：（1）卧式切割机图 1-1 所示是最常见的卧室切割机，砍刀片装在电动机的主轴上，通过电动机提供给刀片的旋转运动来切割青饲料，但是缺点是不能切割块茎类饲料，同时刀片为直刃砍刀，消耗功率大，振动也大。（2）立式切割机图 1-2 所示是立式切割机，优点是结构紧凑，占用空间小，缺点与方案一一样，对能切割饲料的种类有限。商丘工学院本科毕业设计（论文）2 图 1-1 卧式切割机 图 1-2 立式切割机（3）卧式辊筒切碎机图 1-3 所示是卧式辊筒破碎机，有点是能很好切割块茎，辊筒上的刀片拆卸也很方便，缺点是不能切割藤蔓类青饲料，所以他的使用也受到了很大的限制。（4）卧式多功能切割机图 1-4 所示是卧式多功能切割机，优点是即能切割藤蔓类，又能切割块茎类，缺点是，该设计在为了完成切割块茎的目的是，过多装入转动刀片，在拆卸刀片时，非常不便，并且过多的刀片也增加产品的成本。 图 1-3 卧式辊筒切碎机 图 1-4 卧式多功能切割机1.3 市场前景分析经过市场调研发现。很少有适合小型养殖场、专业户和个体农户要求的小型青饲料切割机。并且这些青饮料切割机还具有以下缺点：1 引言3（1）大多数青饲料切割机只能单独切割块状饲料或茎杆类物料；（2）切割刀刃为直刃、切割刚度低、对多纤维茎杆的切割性能差；（3）用手喂入茎杆娄物料安全性差；（4）块料切碎时切碎均匀度差；故我们设计一种能满足小型养殖场、专业户和个体农户要求。切割性能好，操作安全的小型青饲料切割机。商丘工学院本科毕业设计（论文）42 系统设计2.1 方案设计根据上述青饲料切割机类型，本次设计的青饲料切割机采用如下结构：图 2-1 青饲料切割机方案简图2.2 工作原理分析工作时，青饲料从料斗投入后，首先在输送螺旋的推动下向右进入切割滚筒进行切割。切碎的青饲料落入出料斗在输送螺旋的推动下送出出料斗。3 进料及切割装置设计53 进料及切割装置设计3.1 电机的选择电动机是标准部件。因为室内工作，运动载荷平稳，所以选择 Y 系列一般用途的全封闭自扇冷鼠笼型三相异步电动机。调查市场上现有青饲料切割机本次选用电机为 Y100L1-4，其额定功率为 2.2KW，满载转速为 1420r/min。3.2 总体动力参数计算3.2.1 传动比计算满载转速min/1420rnm取除梗轴转速为：min/600550rnw故 V 带传动比为：58. 237. 26005501420nnwmvi为使传动装置尺寸协调、结构匀称、不发生干涉现象，选 V 带传动比：；5 . 2带i选取滚筒转速为：min/120rng83.111201420nnwmgi考虑结构因素取两级齿轮传动比分别为： 85. 01i则：；2 . 433.133 . 13 . 11ii；6 . 585. 05 . 283.1183.1112iiiv3.2.2 各轴的转速1 轴 min/5685 . 214201rinnm带2 轴 min/2 .66885. 0568112rinn滚筒 min/33.1196 . 52 .668223rinn3.2.3 各轴的输入功率1 轴 kwPP112. 296. 02 . 2101商丘工学院本科毕业设计（论文）62 轴 kwPP028. 298. 098. 0112. 23212滚筒 kwPP948. 198. 098. 0028. 232233.2.4 各轴的输入转矩电机轴 mNnPT8.1414202.2955095500001 轴 mNnPT51.35568112.2955095501112 轴 mNnPT99.282.668028.295509550222滚筒 mNnPT9.15533.119948.195509550333整理列表轴名功率kwP/转矩mNT/转速min)/( rn传动比电机轴2.214.814201 轴2.11235.515682.52 轴2.02828.99668.20.853 轴1.948155.9119.335.63.3 V 带传动的设计3.3.1 V 带的基本参数计算1）确定计算功率：cP已知：；kwP2 . 2min/1420rnm查机械设计基础表 13-8 得工况系数：；2 . 1AK则：kwkwPKPAc64. 22 . 22 . 12）选取 V 带型号：根据、查机械设计基础图 13-15 选用 A 型 V 带,cPmn3）确定大、小带轮的基准直径dd（1）初选小带轮的基准直径：；mmdd801（2）计算大带轮基准直径：；mmdiddd200805 . 202. 0112）（带3 进料及切割装置设计7圆整取，误差小于 5%，是允许的。mmdd20024）验算带速：smsmndvmd/)25, 5(/32. 5100060142010614. 31000601带的速度合适。5）确定 V 带的基准长度和传动中心距：中心距：)(2)(7 . 021021ddddddadd初选中心距mma700（2）基准长度：mmaddddaLddddd15535004)80200()20080(214. 350024)()(22202122100对于 A 型带选用mmLd1600（3）实际中心距：mmLLaadd5 .7232155316007002006）验算主动轮上的包角：1由adddd3 .57)(180121得1209 .1535 .7233 .57)80200(1801主动轮上的包角合适。7）计算 V 带的根数：zLArKKPPPKPPzc)(00，查机械设计基础表 13-3 得：min/142rnmmmdd801；kwP05. 10（2），查表得：；3min/1420带，irnmkwP11. 00（3）由查表得，包角修正系数9 .153193. 0K（4）由，与 V 带型号 A 型查表得： mmLd160099. 0lK综上数据，得01. 299. 093. 0)11. 005. 1 (2 . 22 . 1z取合适。102 z商丘工学院本科毕业设计（论文）88）计算预紧力（初拉力）：0F根据带型 A 型查机械设计基础表 13-1 得：mkgq/1 . 0NqvkzvPFc11.24632. 51 . 0193. 05 . 232. 53152. 450015 . 25002209）计算作用在轴上的压轴力：QFNZFFQ54.239729 .153sin11.246522sin210其中为小带轮的包角。110）V 带传动的主要参数整理并列表：带型带轮基准直径(mm)传动比基准长度(mm)A801dd2002dd2.51600中心距（mm）根数初拉力(N)压轴力(N)723.52246.112397.543.3.2 带轮结构的设计1）带轮的材料：采用铸铁带轮（常用材料 HT200）2）带轮的结构形式：V 带轮的结构形式与 V 带的基准直径有关。小带轮接电动机，较小，所以mmdd801采用实心式结构带轮。3.4 齿轮传动设计3.4.1 选精度等级、材料和齿数采用 7 级精度由表 6.1 选择小齿轮材料为 45（调质） ，硬度为 280HBS，大齿轮材料为45 钢（调质） ，硬度为 240HBS。选小齿轮齿数，201Z大齿轮齿数，取112206 . 5122ZiZ1122Z3 进料及切割装置设计9则实际传动比：6 . 520112122ZZi传动误差小于 5，合适。3.4.2 按齿面接触疲劳强度设计由设计计算公式进行试算，即3211)(132. 2HEdttZuuTkd1） 确定公式各计算数值（a）试选载荷系数3 . 1tK（b）计算小齿轮传递的转矩mNT99.281（c）小齿轮相对两支承非对称分布，选取齿宽系数8 . 0d（d）由表 6.3 查得材料的弹性影响系数2/18 .189 MPaZE（e）由图 6.14 按齿面硬度查得小齿轮的接触疲劳强度极限MPaH6001lim大齿轮的接触疲劳强度极限MPaH5502lim（f）由式 6.11 计算应力循环次数9111002. 1) 1830010(12 .6686060hjLnN8921082. 16 . 51002. 1N（g）由图 6.16 查得接触疲劳强度寿命系数 88. 01NZ92. 02NZ（h）计算接触疲劳强度许用应力取失效概率为 1，安全系数为 S=1，由式 10-12 得MPaMPaSZHNH52860088. 01lim11MPaMPaSZHNH50655092. 02lim22（i）计算试算小齿轮分度圆直径，代入中的较小值td1Hmmdt3 .54)5068 .189(346 . 01029. 73 . 132. 23231计算圆周速度 vsmndvt/97. 06000002 .6683 .5414. 310006011计算齿宽 bmmdbtd6 .323 .546 . 01商丘工学院本科毕业设计（论文）10计算齿宽与齿高之比 b/h模数mmZdmtnt72. 2203 .5411齿高37. 6453. 2/63.15/453. 209. 125. 225. 2hbmmmhnt计算载荷系数 K根据，7 级精度，查得动载荷系数smv/97. 005. 1VK假设，由表查得mmNbFKtA/100/0 . 1FHKK由表 5.2 查得使用系数25. 1AK由表查得查得287. 1FK故载荷系数689. 1287. 10 . 105. 125. 1HHVAKKKKK（j）按实际的载荷系数校正所算得的分度圆直径，由式可得mmKKddtt25.593 . 1/689. 13 .54/3311（k）计算模数mmZdm96. 220/25.59/113.4.3 按齿根弯曲强度设计弯曲强度的设计公式为32112FSFdnYYZKTm1）确定公式内的计算数值由图 6.15 查得小齿轮的弯曲疲劳强度极限MPaFE5001大齿轮的弯曲疲劳强度极限MPaFE3802由图 6.16 查得弯曲疲劳寿命系数 85. 01NZ88. 02NZ计算弯曲疲劳许用应力取失效概率为 1，安全系数为 S=1.3，由式得MPaSZFENF9 .3263 . 150085. 0111MPaSZFENF2 .2573 . 138088. 0222计算载荷系数382. 128. 10 . 108. 10 . 1FFVAKKKKK2）查取齿形系数由表 6.4 查得91. 21FaY22. 22FaY3 进料及切割装置设计113）查取应力校正系数 由表 6.4 查得53. 11SaY77. 12SaY4）计算大小齿轮的，并比较FSaFaYY01494. 01 .26377. 122. 201362. 09 .32653. 191. 2222111FSaFaFSaFaYYYY 大齿轮的数据大5）设计计算mmm62. 201494. 0241102 .28382. 12323对比计算结果，由齿面接触疲劳强度计算的模数 m 大于由齿根弯曲疲劳强度计算的模数，可取有弯曲强度算得的模数 2.62，并圆整为标准值 m3mm，按接触强度算得的分度圆直径mmd25.591算出小齿轮齿数取75.193/25.59/11mdZ201Z大齿轮齿数取112206 . 5122ZiZ1122Z3.4.4 几何尺寸计算1）计算分度圆直径mmmZdmmmZd33631126032022112）计算中心距 mmdda1982/ )33660(2/ )(213）计算齿宽宽度取 35mmmmdbd36606 . 013.4.5 验算NdTFt4863072902211 合适mmNmmNbFKtA/100/38.302048625. 1序号名称符号计算公式及参数选择1齿数Z20，1122模数m3mm3分度圆直径21ddmmmm 336,604齿顶高ahmm35齿根高fhmm75. 36全齿高hmm75. 67顶隙cmm75. 0商丘工学院本科毕业设计（论文）128齿顶圆直径21ddmmmm 342,669齿根圆直径43ffddmmmm5 .328,5 .5210中心距amm1983.5 轴及轴承、键的设计3.5.1 尺寸与结构设计计算1）轴上的功率 P1,转速 n1 和转矩 T1，kwP112. 21min/5681rn mmNT51.3512）初步确定轴的最小直径先按式初步估算轴的最小直径。选取轴的材料 45 钢，调质处理。根据机械3PdCn设计表 11.3，取，于是得：112C mmd35.17568112. 211231该处开有键槽故轴径加大 510，且高速轴的最小直径显然是安装大带轮处的直径。取；。1dmmd361mmL3013）根据轴向定位的要求确定轴的各段直径和长度（a）为了满足大带轮的轴向定位的要求 2 轴段左端需制出轴肩，轴肩高度轴肩高度，取故取 2 段的直径，长度。dh07. 0mmh1mmd382mmL302（b）初步选择滚动轴承。因轴承只受径向力的作用，故选用深沟球轴承。根据，查机械设计手册选取 0 基本游隙组，标准精度级的深沟球轴承 6208，故mmd382，轴承采用轴肩进行轴向定位，轴肩高度轴肩高度，取，mmdd4073dh07. 0mmh2因此，取。mmdd4664（c）齿轮处由于齿轮分度圆直径，故采用齿轮轴形式，齿轮宽度mmd1801B=20mm。另考虑到齿轮端面与箱体间距 10mm 以及两级齿轮间位置配比，取，mml774。mml664）轴上零件的周向定位查机械设计表，联接大带轮的平键截面。mmmmmmlhb328103.5.2 强度校核计算1）求作用在轴上的力已知大齿轮的分度圆直径为，根据机械设计 （轴的设计计算部分未作说mmd180明皆查此书）式(10-14)，则3 进料及切割装置设计13NtgFFNdTFntrt75.6852007.1884tan07.1884103078.20223NFp5 .10952）求轴上的载荷首先根据轴的结构图作出轴的计算简图。在确定轴承支点位置时，从手册中查取 a 值。对于 6208 型深沟球轴承，由手册中查得 a=15mm。因此，轴的支撑跨距为 L1=72mm。根据轴的计算简图作出轴的弯矩图和扭矩图。从轴的结构图以及弯矩和扭矩图可以看出截面 C 是轴的危险截面。先计算出截面 C 处的 MH、MV 及 M 的值列于下表。载荷水平面 H垂直面 V支反力F，NFNH11431NFNH12622，NFNV22371NFNV15162C 截面弯矩 MmmNLFMNHH8518532mmNMLFMaNVV14555132总弯矩mmNMMMVH168646145551851852222max扭矩mmNT 208703）按弯扭合成应力校核轴的强度根据式(15-5)及上表中的数据，以及轴单向旋转，扭转切应力，取，轴的计算应6 . 0商丘工学院本科毕业设计（论文）14力MpaMpaWTMca61.28401 . 0508706 . 0168646)(32222已选定轴的材料为 45Cr，调质处理。由表 15-1 查得。因此，故70MPa1 -1 -ca安全。4）键的选择采用圆头普通平键 A 型（GB/T 10961979）连接，联接大带轮的平键截面，。齿轮与轴的配合为，滚动轴承与轴的周mmmmmmlhb32810Mpap11076Hr向定位是过渡配合保证的，此外选轴的直径尺寸公差为。6m3.6 切割刀的设计3.6.1 切割刀的基本结构尺寸设计所谓切割，是指通过机械的方法克服物料内部的凝聚力，并将其分裂成规格划一的块、片、丝、粒及酱状产品的操作过程。满足切割运动的机器必须具备两个关键条件，一是切割刀具，另一个是物料的“进给”运动。进给运动系指物料与刀具的相对接触运动。（1）切刀材料 一般采用经过热处理的 T9 碳素工具钢或锰钢。在此选 T9 工具钢（2）对切刀的要求良好的切刀（或称切碎器）应满足下列要求：切割质量高，耗用动力小，结构紧凑，工作平稳，安全可靠，便于刃磨，使用维修方便。（3）选用或设计刀片时应满足的要求刀片在设计和选用时应满足下列三个方面的要求，即 钳住物料，保证切割； 切割功率要小； 切割阻力矩均匀。（4）刀片刃口几何形状及常用刀片形状切刀的刀刃有直线型与曲线型几何形状，如图 3-1 所示。图 3-1 各几何形状刀刃在本次设计中选用（c）外曲线刃口刀 进行滑切。（5）刀的滑切与正切分析切割机械工作时，功耗的大小与切刀的工作方式以及刀片的特性参数有关，切刀的工作3 进料及切割装置设计15方式有滑切与正切之分。当按滑切工作时，切割阻力小，容易切割，切割时省力，功率消耗也小。当切刀按正切方式工作时，切割阻力大，切割困难，功率消耗也大。下面仅讨论本刀具用到的滑切原理。图 3-2 为切刀滑切示意图。图 3-2 切刀滑切示意图图中 BC 为回转曲线刃口刀的刀刃，O 为刃口曲线的圆心，A 点为切割工作点，切刀的回转半径为 r。当切刀在传动系统作用下绕刀轴中心 P 以一定角速度做定轴回转切割运动时，刀刃上工作点 A 的切割速度为 V，显然，VOA，将 V 分解为过点 A 切线和法线方向的两个分速度，则称为滑切速度，称为正切（砍切）速度。zVHVzV与 V 之间的夹角及为滑切角。当滑切速度不为零时的切割及称为有滑切的切割，zV简称滑切；当滑切速度为零的切割称为正切或砍切。和和的关系为 HVzV /=tanHVzV由图 3-2 分析可知，滑切角显然不为零，最大为，能实现滑切。660下面用一直刃切刀来进一步阐述滑切省力原理，如图 5-3 所示。图 3-3 滑切省力原理图若切刀的楔角为，则正切时，切割速度 V 就在 A 点的法线方向，即 V 垂直于刀刃，切刀正好是以角的楔子楔入物料。滑切时，因切割速度 V 偏离了刀刃的法线方向，与法线方向产生了一个滑切角，这时切刀的楔入角度由减小到。从上图的几何关系可知 tan=BC/AB商丘工学院本科毕业设计（论文）16 tan= tancos即滑切角越大时，刀刃切入物料的实际楔入角就越小（即实际切割时只是刀刃口在切割） ，这是大小，切刀受到的法向阻力越小，易于切入，切割省力。因此，要使切HVzV割省力，除保证刃口锋利以降低刃口比压（比压为刃口单位面积的压力，与刀刃锋利程度有关）外，还须使切割为滑切，这正是利用了滑切省力的原理。此外，刀刃口的表面即使看起来光滑，但由于刀片在加工时的精度问题，在显微镜下观察，刃口也呈现锯齿状的“微观齿” 。滑切时，这些尖锐的“微观齿”就像锯子一样将物料纤维切断，这是滑切较正切省力的另一原因。（6）钳住物料的条件分析滑切也可以分为有滑移的滑切和无滑移的滑切两种。切割时当动刀片与静刀片之间的夹角达一定值时，物料就会产生沿刃口向外推移的现象，这叫有滑移的滑切。出现这种情况对稳定切割是不利的，所以应当尽可能的避免此种情况的出现。下面以两种不同钳住角切割物料的受力情况来分析钳住物料，保证稳定的切割条件。下图 3-4 表示了不同钳住角切割物料时物料的受力情况。图 3-4 不同钳住角的物料受力分析图图 3-4 中 AB 为动刀片刃口，CD 为定刀片刃口，夹角为动、定刀片对物料的钳住角，也称推挤角。假定以两种钳住角切割时的摩擦角均为。21 和AB 为动刀片刃口；CD 为定刀片刃口；为动、定刀片对物料的钳住角，又称推挤角；为动刀片对物料产生的正压力；为定刀片（或支撑面）对物料产生的正压力；、1N2N1T为动、静刀片与物料在切割点处的摩擦力；为两种钳住角切割时物料与动、静2T21 和刀片间的摩擦角。由图 3-4(a)知，由于此时,两个支撑反力的合力的合力 F 将把被切物料2121FF与沿刃口向外推出，即在切割时产生滑移，不能保证稳定切割。由图 3-4(b)知，由于此时。的合力 F 指向刃口里面，即切割时合力 F2121FF与将把被切物料沿刃口向里面推，切割时不会产生滑移，能保证稳定切割，提高效率。由此可知，保证钳住物料稳定切割的条件是：钳住角须小于物料与定刀片之间摩擦角之和，21在本设计中刀与料的相对位置图如图 3-5 所示，进行钳住物料条件的分析3 进料及切割装置设计17图 3-5 刀与料的相对位置图由图 5-5 可知，切刀在旋转过程中，的最大值为，同时由经验可知，通常381，所以只要小于就可以了，显然以上设计是满足要求的，刀的安装3221850也是合理的。3.6.2 刀的安装曲线动刀片 A、B 通过螺栓 1、2、3、4 安装在刀盘 P 上，通过调节螺栓 1、2、3、4 来调整动刀片与定刀片的间隙。具体如下图 5-6 所示。图 3-6 切刀简图1、4六角螺栓 2、3。 沉头螺栓3.7 进料螺旋搅龙设计根据连续输送机生产率的公式； 3600QF 式中：F被输送青饲料层的横断面积m2； 被输送青饲料的堆积密度kg/m3； 被输送物材的轴向输送速度m/s。料层横断面面为：商丘工学院本科毕业设计（论文）1824DFc式中：D螺旋直径m； 充填系数，其值与物材的特性有关，见下表中的 、K 及 A 的值； c倾斜修正系数，见表 45。在料槽中，青饲料的充填系数影响输送过程和能量的消耗。当充填系数较小(即 =5%)时，青饲料堆积的高度低矮且大部分青饲料靠近槽壁并且具有较低的圆周速度，运动的滑移面几乎平行于输送方向(图 410a)。青饲料颗粒沿轴向的运动要较圆周方向显著得多。所以，这时垂直于输送方向的附加青饲料流不严重，单位能量消耗也较小。但是，当充填系数提高(即 =13%或 40%)时，则青饲料运动的滑移面将变陡(图 410b、c)。此时，在圆周方向的运动将比输送方向的运动强，导致输送速度的降低和附加能量的消耗。因而，对于水平立式混料机来说，青饲料的充填系数并非越大越好，相反取小值有利，一般取 50%。各种微粒青饲料的充填系数 值可参考表 44。青饲料的轴向输送速度 按下式计算：60shn式中：h-螺旋节距m；ns-螺旋转速r/min；螺距 h 通常为：h1=k1D式中：k1-螺旋节距与螺旋直径的比值，与青饲料性质有关，通常取 k1=0.71，对于摩擦系数大的青饲料，取小值（k1=0.70.8） ；对于流动性较好，易流散的青饲料，可取k1=1。表 45 倾斜修正系数 c倾斜角 05101520c1.000.900.800.700.65将上式结合起来，则有：Q=47ck1D3ns，即：3147sQck D n（1）螺旋直径根据设计要求该搅龙直径选用 280mm，即：D=280mm（2）螺距3 进料及切割装置设计19取 h1=（0.50.6）D=140168mm，所以螺距为 160mm。（3）轴径d=(0.20.35)D，取 d=0.2D=0.15280=42mm，所以轴径为 42mm。（3）筛筒设计筛筒为圆筒形，筛孔直径为 1520mm。材料用薄不锈钢板制造。商丘工学院本科毕业设计（论文）204 出料装置及机架的设计4.1 蜗杆减速机的选择出料搅龙转速不宜过高，本次取 25r/min，因此选用传动比为：29，中心距为 80 的蜗杆减速器。4.2 V 带传动设计4.2.1 V 带的基本参数计算1）确定计算功率：cP已知：；kwP2 . 2min/1420rnm查机械设计基础表 13-8 得工况系数：；2 . 1AK则：kwkwPKPAc64. 22 . 22 . 12）选取 V 带型号：根据、查机械设计基础图 13-15 选用 A 型 V 带,cPmn3）确定大、小带轮的基准直径dd（1）初选小带轮的基准直径：；mmdd801（2）计算大带轮基准直径：；mmdiddd16080202. 0112）（带圆整取，误差小于 5%，是允许的。mmdd16024）验算带速：smsmndvmd/)25, 5(/32. 5100060142016014. 31000601带的速度合适。5）确定 V 带的基准长度和传动中心距：中心距：)(2)(7 . 021021ddddddadd初选中心距mma200（2）基准长度：4 出料装置及机架设计21mmaddddaLddddd9765004)80160()16080(214. 320024)()(22202122100对于 A 型带选用mmLd1000（3）实际中心距：mmLLaadd212297610002002006）验算主动轮上的包角：1由adddd3 .57)(180121得1209 .1532123 .57)80160(1801主动轮上的包角合适。7）计算 V 带的根数：zLArKKPPPKPPzc)(00，查机械设计基础表 13-3 得：min/1420rnmmmdd801；kwP05. 10（2），查表得：；2min/142带，irnmkwP11. 00（3）由查表得，包角修正系数9 .153193. 0K（4）由，与 V 带型号 A 型查表得： mmLd100099. 0lK综上数据，得62. 199. 093. 0)11. 005. 1 (2 . 22 . 1z取合适。102 z8）计算预紧力（初拉力）：0F根据带型 A 型查机械设计基础表 13-1 得：mkgq/1 . 0NqvkzvPFc11.24632. 51 . 0193. 05 . 232. 53152. 450015 . 25002209）计算作用在轴上的压轴力：QF商丘工学院本科毕业设计（论文）22NZFFQ54.239729 .153sin11.246522sin210其中为小带轮的包角。110）V 带传动的主要参数整理并列表：带型带轮基准直径(mm)传动比基准长度(mm)A801dd1602dd21000中心距（mm）根数初拉力(N)压轴力(N)2122246.112397.544.2.2 带轮结构的设计1）带轮的材料：采用铸铁带轮（常用材料 HT200）2）带轮的结构形式：V 带轮的结构形式与 V 带的基准直径有关。小带轮接电动机，较小，所以mmdd801采用实心式结构带轮。4.3 出料螺旋搅龙设计根据连续输送机生产率的公式； 3600QF 式中：F被输送青饲料层的横断面积m2； 被输送青饲料的堆积密度kg/m3； 被输送物材的轴向输送速度m/s。料层横断面面为：24DFc式中：D螺旋直径m； 充填系数，其值与物材的特性有关，见下表中的 、K 及 A 的值； c倾斜修正系数，见表 45。在料槽中，青饲料的充填系数影响输送过程和能量的消耗。当充填系数较小(即 =5%)时，青饲料堆积的高度低矮且大部分青饲料靠近槽壁并且具有较低的圆周速度，运动的滑移面几乎平行于输送方向(图 410a)。青饲料颗粒沿轴向的运动要较圆周方向显著得多。所以，这时垂直于输送方向的附加青饲料流不严重，单位能量消耗也较小。但是，当充填系数提高4 出料装置及机架设计23(即 =13%或 40%)时，则青饲料运动的滑移面将变陡(图 410b、c)。此时，在圆周方向的运动将比输送方向的运动强，导致输送速度的降低和附加能量的消耗。因而，对于水平立式混料机来说，青饲料的充填系数并非越大越好，相反取小值有利，一般取 50%。各种微粒青饲料的充填系数 值可参考表 44。青饲料的轴向输送速度 按下式计算：60shn式中：h-螺旋节距m；ns-螺旋转速r/min；螺距 h 通常为：h1=k1D式中：k1-螺旋节距与螺旋直径的比值，与青饲料性质有关，通常取 k1=0.71，对于摩擦系数大的青饲料，取小值（k1=0.70.8） ；对于流动性较好，易流散的青饲料，可取k1=1。表 45 立式混料机倾斜修正系数 c倾斜角 05101520c1.000.900.800.700.65图 3-2 不同充填系数时青饲料层堆积情况及其滑移面将上式结合起来，则有：Q=47ck1D3ns即：3147sQck D n（1）螺旋直径根据设计要求该立式混合机搅龙直径选用 100mm，即：D=100mm（2）螺距h1=D，取 h1=（1.52）D=150200mm，所以螺距为 180mm。（3）轴径d=(0.20.35)D，取 d=0.24D=0.24100=24mm，所以轴径为 24mm。4.4 机架设计机架的主要作用为支承与安装其它各零件。为了节约成本，机架全件采用焊接件与螺栓连接。根据设计要求，机架焊接的主要零件包括左右机架，加强钢板，角铁梁等部分组成。商丘工学院本科毕业设计（论文）24焊接时主要保证加强铁与机架的位置要求，同时要保证焊接时不能出现焊渣，裂缝等现象。机架的材料主要是厚度为 5mm 的角钢，尺寸为 1435mm100mm，用等离子切割机切割成型后，采用冲压等方式进行加工。左右机架分别有一块加强板进行强度的加强，加强板与左右机架的连接方式是采用螺栓连接，在机架与加强板加工过程中，对其上螺栓连接孔的位置有一定的技术要求。左右机架间采用角铁梁进行固定，固定方式为焊接，因为此轴流式脱粒机作业环境为山地及丘陵地区，搬运较多，所以为保证人员搬运过程中的安全，在焊接时要保证焊接技术要求，要求焊接中不能有焊渣，不得有裂缝等缺陷出现。机架的组装完成后，机架外露表面须刷防锈漆。结论25结 论毕业设计是对大学中所学知识的回顾，是对以往所学知识的综合运用，锻炼了我们的独立思考能力、独立解决工程实际问题的能力、画图能力，更是从课本中的理论知识到生产实际的转变。在这之前，虽然经过四年的学习学到了很多知识，但是还没有机会来运用和掌握这些东西。通过这次实践，我对机械设计过程都有了全面的了解，设计、计算和绘图方面的能力都得到了全面的训练和提高，也使我对机械产生了更加浓厚的兴趣，更坚定了我从事机械行业的信心。设计初期，我去图书馆的网站内下载了许多相关的文献资料，对青饲料切割机有所了解，然后开始准备我的开题报告、任务书和文献综述。在总体结构设计的过程中，我也遇到了很多困难，经过多次的数据修改才把总体方案给确定下来，开始画图等工作。设计期间得到了我的指导老师的帮助，我觉得从与老师的沟通过程中，我能学到很多东西，老师可以从另外一个角度来启发我，给了我很多帮助、鼓励和指导。通过这段时间的设计，我已基本按照设计要求完成青饲料切割机的设计，但是由于本人知识水平有限，又没有实际工作经验，本设计中定存在不足之处，敬请老师同学批评指正，提出宝贵意见，以便及时纠正。当然，我知道整个毕业设计还没有结束，因为还需要答辩，还要有答辩老师的提问与意见，我的毕业设计才能最终画上句号。因此，我还需要继续努力，认真准备答辩，仔细检查我的论文，更好的完善，为我的大学画上一个圆满的句号。致谢26致 谢大学生活即将结束，在这短短的四年里，让我结识了许许多多热心的朋友、工作严谨教学相帮的教师。毕业设计的顺利完成也脱离不了他们的热心帮助及指导老师的精心指导，在此向所有给予我此次毕业设计指导和帮助的老师和同学表示最诚挚的感谢。首先，向本设计的指导老师表示最诚挚的谢意。在自己紧张的工作中，仍然尽量抽出时间对我们进行指导，时刻关心我们的进展状况，督促我们抓紧学习。老师给予的帮助贯穿于设计的全过程，从借阅参考资料到现场的实际操作，他都给予了指导，不仅使我学会书本中的知识，更学会了学习操作方法。其次，要向给予此次毕业设计帮助的老师们，以及同学们以诚挚的谢意，在整个设计过程中，他们也给我很多帮助和无私的关怀，更重要的是为我们提供不少技术方面的资料。另外，也向给予我帮助的所有同学表示感谢。总之，本次的设计是老师和同学共同完成的结果，在设计的一个月里，我们合作的非常愉快，教会了大我许多道理，是我人生的一笔财富，我再次向给予我帮助的老师和同学表示感谢！参考文献27参考文献1 潘树良小型爪式粉碎机常见故障J农机具之友，2007， （03）2 段长勇等.发展饲料玉米优化农牧业结构.J饲料与畜牧2010， （1）：28293 王三民机械原理与设计M北京机械工业出版社20014 机械设计手册编委会机械设计手册M北京机械工业出版社20045 食品工业与设备M中国轻工业出版社，20006 王三民主编机械原理与课程设计M北京：机械工业出版社，20047 成大先主编机械设计手册（单行本） 减（变）速器电机与电器M北京：化学工业出版社，20048 王世刚主编机械设计实践M哈尔滨：哈尔滨工程大学出版社，20039 成大先主编机械设计手册（单行本） 机械传单M北京：化学工业出版社，200410 王三民诸问俊主编机械原理与设计M北京：机械工业出版社，200011 刘品主编机械精度设计与检测基础M哈尔滨：哈尔滨工业出版社，200412 工程制图基础武汉理工大学等五院校工程制图基础编写组编M北京高等教育出版社，200313农产品加工机械M.长沙.湖南科技出版社.200214 Doughty S.mechanics of Machines.New York:Johh Wiley &Sons Inc,2010.315 Jensen P. W.Classical and Modern Mechanisms for Engineers and Inventors.New York:Marcel Dekker,2012.3附录28附 录Basic Machining Operations and Cutting TechnologyBasic Machining Operations Machine tools have evolved from the early foot-powered lathes of the Egyptians and John Wilkinsons boring mill. They are designed to provide rigid support for both the workpiece and the cutting tool and can precisely control their relative positions and the velocity of the tool with respect to the workpiece. Basically, in metal cutting, a sharpened wedge-shaped tool removes a rather narrow strip of metal from the surface of a ductile workpiece in the form of a severely deformed chip. The chip is a waste product that is considerably shorter than the workpiece from which it came but with a corresponding increase in thickness of the uncut chip. The geometrical shape of workpiece depends on the shape of the tool and its path during the machining operation. Most machining operations produce parts of differing geometry. If a rough cylindrical workpiece revolves about a central axis and the tool penetrates beneath its surface and travels parallel to the center of rotation, a surface of revolution is produced, and the operation is called turning. If a hollow tube is machined on the inside in a similar manner, the operation is called boring. Producing an external conical surface uniformly varying diameter is called taper turning, if the tool point travels in a path of varying radius, a contoured surface like that of a bowling pin can be produced; or, if the piece is short enough and the support is sufficiently rigid, a contoured surface could be produced by feeding a shaped tool normal to the axis of rotation. Short tapered or cylindrical surfaces could also be contour formed. Flat or plane surfaces are frequently required. They can be generated by radial turning or facing, in which the tool point moves normal to the axis of rotation. In other cases, it is more convenient to hold the workpiece steady and reciprocate the tool across it in a series of straight-line cuts with a crosswise feed increment before each cutting stroke. This operation is called planning and is carried out on a shaper. For larger pieces it is easier to keep the tool stationary and draw the workpiece under it as in planning. The tool is fed at each reciprocation. Contoured surfaces can be produced by using shaped tools. Multiple-edged tools can also be used. Drilling uses a twin-edged fluted tool for holes with depths up to 5 to 10 times the drill diameter. Whether the drill turns or the workpiece rotates, relative motion between the cutting edge and the workpiece is the important factor. In milling operations a rotary cutter with a number of cutting edges engages the workpiece. Which moves slowly with respect to the cutter. Plane or contoured surfaces may be produced, depending on the geometry of the cutter and the type of feed. Horizontal or vertical axes of rotation may be used, and the feed of the workpiece may be in any of the three coordinate directions. 附录29Basic Machine Tools Machine tools are used to produce a part of a specified geometrical shape and precise I size by removing metal from a ductile material in the form of chips. The latter are a waste product and vary from long continuous ribbons of a ductile material such as steel, which are undesirable from a disposal point of view, to easily handled well-broken chips resulting from cast iron. Machine tools perform five basic metal-removal processes: I turning, planning, drilling, milling, and grinding. All other metal-removal processes are modifications of these five basic processes. For example, boring is internal turning; reaming, tapping, and counter boring modify drilled holes and are related to drilling; bobbing and gear cutting are fundamentally milling operations; hack sawing and broaching are a form of planning and honing; lapping, super finishing. Polishing and buffing are variants of grinding or abrasive removal operations. Therefore, there are only four types of basic machine tools, which use cutting tools of specific controllable geometry: 1. lathes, 2. planers, 3. drilling machines, and 4. milling machines. The grinding process forms chips, but the geometry of the abrasive grain is uncontrollable. The amount and rate of material removed by the various machining processes may be I large, as in heavy turning operations, or extremely small, as in lapping or super finishing operations where only the high spots of a surface are removed. A machine tool performs three major functions: 1. it rigidly supports the workpiece or its holder and the cutting tool; 2. it provides relative motion between the workpiece and the cutting tool; 3. it provides a range of feeds and speeds usually ranging from 4 to 32 choices in each case. Speed and Feeds in Machining Speeds, feeds, and depth of cut are the three major variables for economical machining. Other variables are the work and tool materials, coolant and geometry of the cutting tool. The rate of metal removal and power required for machining depend upon these variables. The depth of cut, feed, and cutting speed are machine settings that must be established in any metal-cutting operation. They all affect the forces, the power, and the rate of metal removal. They can be defined by comparing them to the needle and record of a phonograph. The cutting speed (V) is represented by the velocity of- the record surface relative to the needle in the tone arm at any instant. Feed is represented by the advance of the needle radially inward per revolution, or is the difference in position between two adjacent grooves. The depth of cut is the penetration of the needle into the record or the depth of the grooves. Turning on Lathe Centers The basic operations performed on an engine lathe are illustrated. Those operations performed on external surfaces with a single point cutting tool are called turning. Except for drilling, reaming, and lapping, the operations on internal surfaces are also performed by a single point cutting tool. 附录30All machining operations, including turning and boring, can be classified as roughing, finishing, or semi-finishing. The objective of a roughing operation is to remove the bulk of the material as rapidly and as efficiently as possible, while leaving a small amount of material on the work-piece for the finishing operation. Finishing operations are performed to obtain the final size, shape, and surface finish on the workpiece. Sometimes a semi-finishing operation will precede the finishing operation to leave a small predetermined and uniform amount of stock on the work-piece to be removed by the finishing operation. Generally, longer workpieces are turned while supported on one or two lathe centers. Cone shaped holes, called center holes, which fit the lathe centers are drilled in the ends of the workpiece-usually along the axis of the cylindrical part. The end of the workpiece adjacent to the tailstock is always supported by a tailstock center, while the end near the headstock may be supported by a headstock center or held in a chuck. The headstock end of the workpiece may be held in a four-jaw chuck, or in a type chuck. This method holds the workpiece firmly and transfers the power to the workpiece smoothly; the additional support to the workpiece provided by the chuck lessens the tendency for chatter to occur when cutting. Precise results can be obtained with this method if care is taken to hold the workpiece accurately in the chuck. Very precise results can be obtained by supporting the workpiece between two centers. A lathe dog is clamped to the workpiece; together they are driven by a driver plate mounted on the spindle nose. One end of the Workpiece is mecained;then the workpiece can be turned around in the lathe to machine the other end. The center holes in the workpiece serve as precise locating surfaces as well as bearing surfaces to carry the weight of the workpiece and to resist the cutting forces. After the workpiece has been removed from the lathe for any reason, the center holes will accurately align the workpiece back in the lathe or in another lathe, or in a cylindrical grinding machine. The workpiece must never be held at the headstock end by both a chuck and a lathe center. While at first thought this seems like a quick method of aligning the workpiece in the chuck, this must not be done because it is not possible to press evenly with the jaws against the workpiece while it is also supported by the center. The alignment provided by the center will not be maintained and the pressure of the jaws may damage the center hole, the lathe center, and perhaps even the lathe spindle. Compensating or floating jaw chucks used almost exclusively on high production work provide an exception to the statements made above. These chucks are really work drivers and cannot be used for the same purpose as ordinary three or four-jaw chucks. While very large diameter workpieces are sometimes mounted on two centers, they are preferably held at the headstock end by faceplate jaws to obtain the smooth power transmission; moreover, large lathe dogs that are adequate to transmit the power not generally available, although they can be made as a special. Faceplate jaws are like chuck jaws except that they are mounted on a faceplate, which has less overhang from the spindle bearings than a large chuck would have. 附录31Introduction of Machining Machining as a shape-producing method is the most universally used and the most important of all manufacturing processes. Machining is a shape-producing process in which a power-driven device causes material to be removed in chip form. Most machining is done with equipment that supports both the work piece and cutting tool although in some cases portable equipment is used with unsupported workpiece. Low setup cost for small Quantities. Machining has two applications in manufacturing. For casting, forging, and press working, each specific shape to be produced, even one part, nearly always has a high tooling cost. The shapes that may he produced by welding depend to a large degree on the shapes of raw material that are available. By making use of generally high cost equipment but without special tooling, it is possible, by machining; to start with nearly any form of raw material, so tong as the exterior dimensions are great enough, and produce any desired shape from any material. Therefore .machining is usually the preferred method for producing one or a few parts, even when the design of the part would logically lead to casting, forging or press working if a high quantity were to be produced. Close accuracies, good finishes. The second application for machining is based on the high accuracies and surface finishes possible. Many of the parts machined in low quantities would be produced with lower but acceptable tolerances if produced in high quantities by some other process. On the other hand, many parts are given their general shapes by some high quantity deformation process and machined only on selected surfaces where high accuracies are needed. Internal threads, for example, are seldom produced by any means other than machining and small holes in press worked parts may be machined following the press working operations. Primary Cutting Parameters The basic tool-work relationship in cutting is adequately described by means of four factors: tool geometry, cutting speed, feed, and depth of cut. The cutting tool must be made of an appropriate material; it must be strong, tough, hard, and wear resistant. The tool s geometry characterized by planes and angles, must be correct for each cutting operation. Cutting speed is the rate at which the work surface passes by the cutting edge. It may be expressed in feet per minute. For efficient machining the cutting speed must be of a magnitude appropriate to the particular work-tool combination. In general, the harder the work material, the slower the speed. Feed is the rate at which the cutting tool advances into the workpiece. Where the workpiece or the tool rotates, feed is measured in inches per revolution. When the tool or the work reciprocates, feed is measured in inches per stroke, Generally, feed varies inversely with cutting speed for otherwise similar conditions. 附录32The depth of cut, measured inches is the distance the tool is set into the work. It is the width of the chip in turning or the thickness of the chip in a rectilinear cut. In roughing operations, the depth of cut can be larger than for finishing operations. The Effect of Changes in Cutting Parameters on Cutting Temperatures In metal cutting operations heat is generated in the primary and secondary deformation zones and these results in a complex temperature distribution throughout the tool, workpiece and chip. A typical set of isotherms is shown in figure where it can be seen that, as could be expected, there is a very large temperature gradient throughout the width of the chip as the workpiece material is sheared in primary deformation and there is a further large temperature in the chip adjacent to the face as the chip is sheared in secondary deformation. This leads to a maximum cutting temperature a short distance up the face from the cutting edge and a small distance into the chip. Since virtually all the work done in metal cutting is converted into heat, it could be expected that factors which increase the power consumed per unit volume of metal removed will increase the cutting temperature. Thus an increase in the rake angle, all other parameters remaining constant, will reduce the power per unit volume of metal removed and the cutting temperatures will reduce. When considering increase in unreformed chip thickness and cutting speed the situation is more complex. An increase in undeformed chip thickness tends to be a scale effect where the amounts of heat which pass to the workpiece, the tool and chip remain in fixed proportions and the changes in cutting temperature tend to be small. Increase in cutting speed; however, reduce the amount of heat which passes into the workpiece and this increase the temperature rise of the chip m primary deformation. Further, the secondary deformation zone tends to be smaller and this has the effect of increasing the temperatures in this zone. Other changes in cutting parameters have virtually no effect on the power consumed per unit volume of metal removed and consequently have virtually no effect on the cutting temperatures. Since it has been shown that even small changes in cutting temperature have a significant effect on tool wear rate it is appropriate to indicate how cutting temperatures can be assessed from cutting data. The most direct and accurate method for measuring temperatures in high -speed-steel cutting tools is that of Wright &. Trent which also yields detailed information on temperature distributions in high-speed-steel cutting tools. The technique is based on the metallographic examination of sectioned high-speed-steel tools which relates microstructure changes to thermal history. Trent has described measurements of cutting temperatures and temperature distributions for high-speed-steel tools when machining a wide range of workpiece materials. This technique has been further developed by using scanning electron microscopy to study fine-scale microstructure changes arising from over tempering of the tempered martens tic matrix of various high-speed-steels. This technique has also been used to study temperature distributions in both high-speed -steel single point turning tools and twist drills. 附录33Wears of Cutting Tool Discounting brittle fracture and edge chipping, which have already been dealt with, tool wear is basically of three types. Flank wear, crater wear, and notch wear. Flank wear occurs on both the major and the minor cutting edges. On the major cutting edge, which is responsible for bulk metal removal, these results in increased cutting forces and higher temperatures which if left unchecked can lead to vibration of the tool and workpiece and a condition where efficient cutting can no longer take place. On the minor cutting edge, which determines workpiece size and surface finish, flank wear can result in an oversized product which has poor surface finish. Under most practical cutting conditions, the tool will fail due to major flank wear before the minor flank wear is sufficiently large to result in the manufacture of an unacceptable component. Because of the stress distribution on the tool face, the frictional stress in the region of sliding contact between the chip and the face is at a maximum at the start of the sliding contact region and is zero at the end. Thus abrasive wear takes place in this region with more wear taking place adjacent to the seizure region than adjacent to the point at which the chip loses contact with the face. This result in localized pitting of the tool face some distance up the face which is usually referred to as catering and which normally has a section in the form of a circular arc. In many respects and for practical cutting conditions, crater wear is a less severe form of wear than flank wear and consequently flank wear is a more common tool failure criterion. However, since various authors have shown that the temperature on the face increases more rapidly with increasing cutting speed than the temperature on the flank, and since the rate of wear of any type is significantly affected by changes in temperature, crater wear usually occurs at high cutting speeds. At the end of the major flank wear land where the tool is in contact with the uncut workpiece surface it is common for the flank wear to be more pronounced than along the rest of the wear land. This is because of localised effects such as a hardened layer on the uncut surface caused by work hardening introduced by a previous cut, an oxide scale, and localised high temperatures resulting from the edge effect. This localised wear is usually referred to as notch wear and occasionally is very severe. Although the presence of the notch will not significantly affect the cutting properties of the tool, the notch is often relatively deep and if cutting were to continue there would be a good chance that the tool would fracture. If any form of progressive wear allowed to continue, dramatically and the tool would fail catastrophically, i. e. the tool would be no longer capable of cutting and, at best, the workpiece would be scrapped whilst, at worst, damage could be caused to the machine tool. For carbide cutting tools and for all types of wear, the tool is said to have reached the end of its useful life long before the onset of catastrophic failure. For high-speed-steel cutting tools, however, where the wear tends to be non-uniform it has been found that the most meaningful and reproducible results can be obtained when the wear is allowed to continue to the onset of catastrophic failure even though, of 附录34course, in practice a cutting time far less than that to failure would be used. The onset of catastrophic failure is characterized by one of several phenomena, the most common being a sudden increase in cutting force, the presence of burnished rings on the workpiece, and a significant increase in the noise level. Mechanism of Surface Finish Production There are basically five mechanisms which contribute to the production of a surface which have been machined. These are:(l) The basic geometry of the cutting process. In, for example, single point turning the tool will advance a constant distance axially per revolution of the workpiecc and the resultant surface will have on it, when viewed perpendicularly to the direction of tool feed motion, a series of cusps which will have a basic form which replicates the shape of the tool in cut. (2) The efficiency of the cutting operation. It has already been mentioned that cutting with unstable built-up-edges will produce a surface which contains hard built-up-edge fragments which will result in a degradation of the surface finish. It can also be demonstrated that cutting under adverse conditions such as apply when using large feeds small rake angles and low cutting speeds, besides producing conditions which lead to unstable built-up-edge production, the cutting process itself can become unstable and instead of continuous shear occurring in the shear zone, tearing takes place, discontinuous chips of uneven thickness are produced, and the resultant surface is poor. This situation is particularly noticeable when machining very ductile materials such as copper and aluminum. (3) The stability of the machine tool. Under some combinations of cutting conditions; workpiece size, method of clamping ,and cutting tool rigidity relative to the machine tool structure, instability can be set up in the tool which causes it to vibrate. Under some conditions this vibration will reach and maintain steady amplitude whilst under other conditions the vibration will built up and unless cutting is stopped considerable damage to both the cutting tool and workpiece may occur. This phenomenon is known as chatter and in axial turning is characterized by long pitch helical bands on the workpiece surface and short pitch undulations on the transient machined surface. (4)The effectiveness of removing swarf. In discontinuous chip production machining, such as milling or turning of brittle materials, it is expected that the chip (swarf) will leave the cutting zone either under gravity or with the assistance of a jet of cutting fluid and that they will not influence the cut surface in any way. However, when continuous chip production is evident, unless steps are taken to control the swarf it is likely that it will impinge on the cut surface and mark it. Inevitably, this marking besides looking. (5)The effective clearance angle on the cutting tool. For certain geometries of minor cutting edge relief and clearance angles it is possible to cut on the major cutting edge and burnish on the minor cutting edge. This can produce a good surface finish but, of course, it is strictly a 附录35combination of metal cutting and metal forming and is not to be recommended as a practical cutting method. However, due to cutting tool wear, these conditions occasionally arise and lead to a marked change in the surface characteristics. Limits and Tolerances Machine parts are manufactured so they are interchangeable. In other words, each part of a machine or mechanism is made to a certain size and shape so will fit into any other machine or mechanism of the same type. To make the part interchangeable, each individual part must be made to a size that will fit the mating part in the correct way. It is not only impossible, but also impractical to make many parts to an exact size. This is because machines are not perfect, and the tools become worn. A slight variation from the exact size is always allowed. The amount of this variation depends on the kind of part being manufactured. For examples part might be made 6 in. long with a variation allowed of 0.003 (three-thousandths) in. above and below this size. Therefore, the part could be 5.997 to 6.003 in. and still be the correct size. These are known as the limits. The difference between upper and lower limits is called the tolerance. A tolerance is the total permissible variation in the size of a part. The basic size is that size from which limits of size arc derived by the application of allowances and tolerances. Sometimes the limit is allowed in only one direction. This is known as unilateral tolerance.Unilateral tolerancing is a system of dimensioning where the tolerance (that is variation) is shown in only one direction from the nominal size. Unilateral tolerancing allow the changing of tolerance on a hole or shaft without seriously affecting the fit.When the tolerance is in both directions from the basic size it is known as a bilateral tolerance (plus and minus). Bilateral tolerancing is a system of dimensioning where the tolerance (that is variation) is split and is shown on either side of the nominal size. Limit dimensioning is a system of dimensioning where only the maximum and minimum dimensions arc shown. Thus, the tolerance is the difference between these two dimensions. Surface Finishing and Dimensional Control Products that have been completed to their proper shape and size frequently require some type of surface finishing to enable them to satisfactorily fulfill their function. In some cases, it is necessary to improve the physical properties of the surface material for resistance to penetration or abrasion. In many manufacturing processes, the product surface is left with dirt .chips, grease, or other harmful material upon it. Assemblies that are made of different materials, or from the same materials processed in different manners, may require some special surface treatment to provide uniformity of appearance. 附录36Surface finishing may sometimes become an intermediate step processing. For instance, cleaning and polishing are usually essential before any kind of plating process. Some of the cleaning procedures are also used for improving surface smoothness on mating parts and for removing burrs and sharp corners, which might be harmful in later use. Another important need for surface finishing is for corrosion protection in a variety of: environments. The type of protection procedure will depend largely upon the anticipated exposure, with due consideration to the material being protected and the economic factors involved. Satisfying the above objectives necessitates the use of main surface-finishing methods that involve chemical change of the surface mechanical work affecting surface properties, cleaning by a variety of methods, and the application of protective coatings, organic and metallic. In the early days of engineering, the mating of parts was achieved by machining one part as nearly as possible to the required size, machining the mating part nearly to size, and then completing its machining, continually offering the other part to it, until the desired relationship was obtained. If it was inconvenient to offer one part to the other part during machining, the final work was done at the bench by a fitter, who scraped the mating parts until the desired fit was obtained, the fitter therefore being a fitter in the literal sense. J It is obvious that the two parts would have to remain together, and m the event of one having to be replaced, the fitting would have to be done all over again. In these days, we expect to be able to purchase a replacement for a broken part, and for it to function correctly without the need for scraping and other fitting operations.When one part can be used off the shelf to replace another of the same dimension and material specification, the parts are said to be interchangeable. A system of interchangeability usually lowers the production costs as there is no need for an expensive, fiddling operation, and it benefits the customer in the event of the need to replace worn parts. Automatic Fixture Design Traditional synchronous grippers for assembly equipment move parts to the gripper centre-line, assuring that the parts will be in a known position after they arc picked from a conveyor or nest. However, in some applications, forcing the part to the centre-line may damage cither the part or equipment. When the part is delicate and a small collision can result in scrap, when its location is fixed by a machine spindle or mould, or when tolerances are tight, it is preferable to make a gripper comply with the position of the part, rather than the other way around. For these tasks, Zaytran Inc. Of Elyria, Ohio, has created the GPN series of non- synchronous, compliant grippers. Because the force and synchronizations systems of the grippers are independent, the synchronization system can be replaced by a precision slide system without affecting gripper force. Gripper sizes range from 51b gripping force and 0.2 in. stroke to 40Glb gripping force and 6in stroke. Grippers Production is characterized by batch-size becoming smaller and smaller and greater variety of products. Assembly, being the last production step, is particularly vulnerable to changes in 附录37schedules, batch-sizes, and product design. This situation is forcing many companies to put more effort into extensive rationalization and automation of assembly that was previouslyextensive rationalization and automation of assembly that was previously the case. Although the development of flexible fixtures fell quickly behind the development of flexible handling systems such as industrial robots, there are, nonetheless promising attempts to increase the flexibility of fixtures. The fact that fixtures are the essential product - specific investment of a production system intensifies the economic necessity to make the fixture system more flexible. Fixtures can be divided according to their flexibility into special fixtures, group fixtures, modular fixtures and highly flexible fixtures. Flexible fixtures are characterized by their high adaptability to different workpieces, and by low change-over time and expenditure. There are several steps required to generate a fixture, in which a workpiece is fixed for a production task. The first step is to define the necessary position of the workpiece in the fixture, based on the unmachined or base pan, and the working features. Following this, a combination of stability planes must be selected. These stability planes constitute the fixture configuration in which the workpiece is fixed in the defined position, all the forces or torques are compensated, and the necessary access to the working features is ensured. Finally, the necessary positions of moveable or modular fixture elements must be calculated- adjusted, or assembled, so that the workpiece is firmly fixed in the fixture. Through such a procedure the planning and documentation of the configuration and assembly of fixture can be automated.The configuration task is to generate a combination of stability planes, such that fixture forces in these planes will result in workpiece and fixture stability. This task can be accomplished conventionally, interactively or in a nearly fully automated manner. The advantages of an interactive or automated configuration determination are a systematic fixture design process, a reduction of necessary designers, a shortening of lead time and better match to the working conditions. In short, a significant enhancement of fixture productivity and economy can be achieved.基本加工工序和切削技术基本加工工序和切削技术附录38基本机床基本机床机床通过从塑性材料上去除屑片来产生出具有特别几何形状和精确尺寸的零件。后者是废弃物，是由塑性材料如钢的长而不断的带状物变化而来，从处理的角度来看，那是没有用处的。很容易处理不好由铸铁产生的破裂的屑片。机床执行五种基本的去除金属的过程：车削，刨削，钻孔，铣削。所有其他的去除金属的过程都是由这五个基本程序修改而来的，举例来说，镗孔是内部车削；铰孔，攻丝和扩孔是进一步加工钻过的孔；齿轮加工是基于铣削操作的。抛光和打磨是磨削和去除磨料工序的变形。因此，只有四种基本类型的机床，使用特别可控制几何形状的切削工具 1.车床，2.钻床，3.铣床，4.磨床。磨削过程形成了屑片，但磨粒的几何形状是不可控制的。通过各种加工工序去除材料的数量和速度是巨大的，正如在大型车削加工，或者是极小的如研磨和超精密加工中只有面的高点被除掉。一台机床履行三大职能：1.它支撑工件或夹具和刀具 2.它为工件和刀具提供相对运动 3.在每一种情况下提供一系列的进给量和一般可达 4-32 种的速度选择。加工速度和进给加工速度和进给速度，进给量和切削深度是经济加工的三大变量。其他的量数是攻丝和刀具材料，冷却剂和刀具的几何形状，去除金属的速度和所需要的功率依赖于这些变量。切削深度，进给量和切削速度是任何一个金属加工工序中必须建立的机械参量。它们都影响去除金属的力，功率和速度。切削速度可以定义为在旋转一周时速度记录面相对任何瞬间呈辐射状扩散的针，或是两个相邻沟槽的距离。切削深度是进入的深度和沟槽的深度。在车床中心的车削在车床中心的车削在机动车床上完成的基本操作已被介绍了。那些用单点刀具在外表面的操作称为车削。除了钻孔，铰孔，研磨内部表面的操作也是由单点刀具完成的。所有的加工工序包括车削，镗孔可以被归类为粗加工，精加工或半精加工。精加工是尽可能快而有效的去除大量材料，而工件上留下的一小部分材料用于精加工。精加工为工件获得最后尺寸，形状和表面精度。有时，半精加工为精加工留下预定的一定量的材料，它是先于精加工的。一般来说，较长的工件同时被一个或两个车床中心支撑。锥形孔，所谓的中心孔，两端被钻的工件适于车床中心-通常沿着圆柱形工件的轴线。工件接近为架的那端通常由尾架中心支撑，在靠近主轴承的那端由主轴承中心支撑或由爪盘夹紧。这种方法可以牢固的加紧工件并且能顺利地将力传给工件；由卡盘对工件提供的辅助支撑减少切削时发生的颤振趋势，如果能小心准确地采用卡盘支撑工件的方法，则可以得到精确的结果。在两个中心之间支撑工件可以得到非常精确的结果。工件的一端已被加工，那么工件便可车削了。在车床上加工另一端，中心孔充当精确定位面和承载工件重量和抵制切削力的支撑面。当工件由于任何一原因从车床上移除后，中心孔将准确地使工件回到这个车床上或另