重单螺杆干法膨化机的设计【人为地抑制茶树等顶端主枝生长优势】【说明书+CAD】
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重单螺杆干法膨化机的设计【人为地抑制茶树等顶端主枝生长优势】【说明书+CAD】,人为地抑制茶树等顶端主枝生长优势,螺杆,膨化,设计,人为地,抑制,茶树,顶端,主枝,生长,优势,说明书,CAD
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毕 业 设 计 任 务 书 200 8年2月19日 毕业设计题目单螺杆干法膨化机指导教师曾文萱职称讲师专业名称机电一体化技术班级机电50532学生姓名刘玲学号5020053212设计要求1.完成资料翻译一份（3000字以上）2.完成毕业设计调研报告一份；3.完成仿型切割机4.完成系统程序设计；5.完成毕业设计说明书一份；6.完成相关图纸。完成毕业课题的计划安排序号内容时间安排1外文资料翻译2008.2.20至2008.2.292搜集相关资料并调研，完成调研报告2008.3.1至2008.3.53进行硬件电路的设计，并完成相关程序的编写，编写说明书，绘制相关图纸。2008.3.6至2008.4.84整理毕业设计说明书并定稿，准备答辩2008.4.9至2008.4.105答辩2008.4.11答辩提交资料外文资料翻译，毕业设计调研报告，毕业设计说明书，相关图纸。计划答辩时间2008.4.11 无锡职业技术学院机电技术学院 2008 年 2 月 19日分类号 密级 无锡职业技术学院毕业设计说明书毕业设计说明书题题 目：单螺杆干法膨化机目：单螺杆干法膨化机英文并列题目英文并列题目：学 生 姓 名： 专 业：指 导 教 师： 职 称： 毕业设计说明书提交日期 2008.4.11 地址：无锡职业技术学院目录第一章 摘要 （1） 第二章 前言 （1）一、单螺杆干法膨化机的研制 （2） 二、对单螺杆干法膨化机的应用研究 （2）三、对茶树重单螺杆干法膨化机的研究 （2）第三章 设计任务 （3）第四章 设计分析 （4） 一传动路线的拟订 （4） 二膨化机的选择 （5） 三带轮的设计 （1）带的设计 （6）（2）带的设计 （9） *四轴的设计与校验 （1）轴的设计 （13）（2）轴的设计 （16） （3）轴承的选择 （18）（4）键的选用 （19）五刀片结构的设计及材料的选择 第五章 心得体会 （19）第六章 参考文献 （20）第一章 摘要 由于我国种茶历史悠久，种植地域广泛，迫切需要机械膨化器具来代替手工单螺杆干法膨化机械膨化是解决劳力不足和降低生产成本的根本途径。而普通单螺杆干法膨化机用于重膨化是属于破坏性使用，一般不宜提倡。本课题即针对成龄的深膨化、衰老的重膨化或台刈面临的问题及现有膨化设备的不足，研究出一种全新的重单螺杆干法膨化机械设备，并对整机各结构部件进行协调，对单螺杆干法膨化机所用刀片的材料、结构进行分析，研制配套的传动系统，相应的带轮，轴，机架，并进行计算和装配图的绘制。关键字：机械膨化器具，重膨化，全新的重单螺杆干法膨化机械设备，刀片的材料，传动系统，带轮，轴，机架。第二章 前言膨化是人为地抑制顶端主枝生长优势的措施，可刺激着生部位较低的芽萌发新技，增强树势，培养高产优质树冠。膨化方法主要有幼龄的定形膨化、成龄的轻膨化与深膨化，衰老的重膨化及台刈等。成龄经多年采摘和轻膨化后，采树冠摘面上会形成密集而细弱的分枝，这就是常说的“鸡爪枝”， 这时，新梢育芽能力减弱，生长乏力，茶叶产量和品质下降，为更新树冠采摘面，就得采用深膨化技术，剪去密集细弱的鸡爪枝层，使重新抽发新枝，提高育芽能力，延长高产稳产年限。一绪论 深膨化通常剪去冠面1015cm枝梢，目前的深膨化工作一般用双人抬单螺杆干法膨化机来实施，但双人抬单螺杆干法膨化机比较笨重，且工作效率低。重膨化的对象则是半衰老和未老先衰的。这种，虽然骨干枝的抽生能力仍较强，但生产枝的育芽能力已很弱，芽叶瘦小，叶张薄细，轻伸膨化根本不起作用，即使采用深膨化也不能达到目的，这时，就得采用重膨化技术。重膨化一般在离地3040cm处膨化树干。台刈则是比重膨化更为彻底的改造树冠的膨化技术，其对象是严重衰老的，但目的与重膨化相同；台刈后，从根颈部抽发的新枝能重新形成树冠。重膨化及台刈由于膨化的枝干一般较粗，现有的单螺杆干法膨化机械很难担当大任、不但效率低，而且常出现露枝现象；因此许多地方还在采用人工以砍柴刀对枝干进行砍切膨化，劳动状况恶劣、劳作水平极其落后，另外人工砍切膨化对生长是十分不利的。二国内外同类研究概况目前，国内科研人员对的膨化研究多集中于的轻膨化、中单螺杆干法膨化机械研制及应用上，而在专门用于老或未老先衰的重单螺杆干法膨化机械的研究与应用上，还基本处于空白状态。1、单螺杆干法膨化机的研制由于我国种茶历史悠久，种植地域广泛，迫切需要机械膨化器具来代替手工膨化，因此国内在单螺杆干法膨化机具的研制上，已取得了很大进步，国内已有多家单位生产出了多款单螺杆干法膨化机。如南京秦淮园林机械厂生产的单人多功能电动单螺杆干法膨化机，其主要技术参数为：主机重量：2.5kg；电压：24v；杆长：110cm；功率：100w；转速：6000转/分钟。该机具有环保节能，效率高，能耗小，对茶作物无污染等优点。浙江省生产的PSM110型单螺杆干法膨化机双人抬跨行作业机具，由两把锯齿型刀片作相对往复运动完成膨化作业。单螺杆干法膨化机的动力选用日本三菱TL33PVD型汽油机。当汽油机运转达到一定速度时，离合器先带动风机运转，继而将动力传输到减速齿轮箱，减速齿轮与偏心机构设计在同一箱体内，通过一级齿轮减速，动力传到偏心机构，偏心机构上有偏心方向为180的双凸台，带动连杆驱动刀片作往复运动，完成膨化作业。国外如日产的7-750型单人单螺杆干法膨化机配日本单缸二冲程1.03(1.4马力)汽油机，采用平刀片往复式膨化，膨化幅宽750。具有以下特点：重量轻、方便于单人操作，平形、弧形树冠均可使用，适应性很好；发动机性能好，操作简便，机身上设有停车按钮及汽油机调速控制手柄，刀片动、停、快、慢控制十分方便。目前，国内外对的轻、中单螺杆干法膨化机械的研制及应用均已成熟。并进入大面积应用的推广期。2、对单螺杆干法膨化机的应用研究人工膨化每人8小时只能剪0.02hm2，需付酬金1750元/hm2；采用单螺杆干法膨化机膨化，二人8小时可膨化0.4hm2，人均工效为手工的10倍，与人工相比费用降低了1312.5元/hm2。采用单螺杆干法膨化机进行重膨化时，人工重膨化每人8小时仅能剪0.0133hm2，每天工资需40元，需付酬金3000元/hm2；用单螺杆干法膨化机勉强凑合使用，两人用双人单螺杆干法膨化机作主膨化，另一人用单人单螺杆干法膨化机补修遗留枝与边枝，三人可膨化0.2hm2，工效是手剪的5倍，生产成本是1963元/hm2。与手工相比可降低成本1037元/hm2。1999年单临安市的深膨化工作就可节约劳力1050工，节约生产成本30580余元；重膨化工作可节约成本13820余元，节约劳力800工。通过以上研究，过婉珍等人认为：机械膨化是解决劳力不足和降低生产成本的根本途径。而普通单螺杆干法膨化机用于重膨化是属于破坏性使用，一般不宜提倡。并建议生产厂家能生产专用重单螺杆干法膨化机，以满足用户需要。华南农业大学的覃松林研究分析了单、双人单螺杆干法膨化机使用时应该注意的问题，他重点指出，单人单螺杆干法膨化机和双人单螺杆干法膨化机不准作老的深膨化和重膨化，否则机器将严重超载而遭到破坏。3对重单螺杆干法膨化机的研究 通过以上科技人员的研究结果可以看出，单螺杆干法膨化机无论是单人型还是双人型，都难以承担起老的重膨化任务，这迫切需要国内的科技工作者研究开发出一种专门用于老的重单螺杆干法膨化机械。综观国内外，目前对老重膨化方面的研究很少，而且研究领域也仅仅侧重于重膨化工作对的影响及效应分析，对重单螺杆干法膨化机械的开发和研制以及应用基本上还处于空白状态，本课题的开展将打破该领域的空白局面，属国内首创。第三章 设计任务 （一） 膨化是人为地抑制顶端主枝生长优势的措施，可刺激着生部位较低的芽萌发新技，增强树势，培养高产优质树冠。膨化方法主要有幼龄的定形膨化、成龄的轻膨化与深膨化，衰老的重膨化及台刈等。 （二）、主要技术指标：1）刀具使用寿命：720h左右；2）膨化树高：250cm；3）膨化幅宽：500cm；4）工作效率：最高0.24hm2/h；5）切口平整度：平均80； （四）、传动路线的拟定考虑到经济性及机器的整体结构和所需传动的准确性，我们拟定了整台机器的示意图 （五）、设计步骤 1.基本结构的确定 2.根据基本结构计算分析各个零部件 3.根据设计说明画出总装图4.根据计算结果及总装图，画出各个零件图 第二章设计分析一 传动路线的拟定 1.对传动方案的要求 合理的传动方案，首先应满足工作机的功能要求，其次还应满足工作可靠、传动效率高、结构简单、尺寸紧凑、重量轻、成本低、工艺性好、使用和维护方便等要求 2.拟定传动方案 任何一个方案，要满足上述所有要求是十分困难的，要统筹兼顾，满足最主要的和最基本的要求。方案一： 方案二： 考虑到经济性及机器的整体结构和传动所需要的准确性，我们分析决定采用结构比较简单的带轮传动，故我们选择第一种传动方案。 二.汽油机的选择 1、已知给定的参数如下： （1）.切削力F=200N； （2）.切削最大半径R=60mm; （3）.刀片转速n=1500r/min; 2、汽油机的选择计算：（如图）T=FR=200N0.06m=12N.m 选择2E60C型汽油机，立轴，水冷，P=7.4KW n=2500r/min,T=53N.m三.带的设计1.确定计算功率 工 况 KA空、轻载起动重载起动每天工作小时数/h1616载荷变动微小液体搅拌机，通风机，和鼓风机（7.5kW）、离心式水泵和压缩机、轻型输送机1.01.11.21.11.21.3载荷变动小带式输送机（不均匀载荷）、通风机（7.5kW）、旋转式水泵和压缩机、发电机金属切削床、旋转筛、剧木机和木工机械1.11.21.31.21.31.4载荷变动较大制砖机、斗式提升机、往复式水泵和压缩机、起重机、磨粉机、冲剪机、橡胶机械、振动筛、纺织机械、重载运送机1.21.31.41.41.51.4载荷变动很大破碎机（旋转式。颚式等）、磨碎机（球磨、棒磨、管磨）1.31.41.51.51.61.8 表8.21 工作情况系数KA由表8.21查得=1.1 由式（8.12）得=1.17.4KW=8.14KW2. 选择普通V带型号 根据=8.14KW =2500r/min 由图8.12选用B型普通V带3. 确定带轮直径 根据表8.6和图8.12选取=140mm 且=140mm125mm 大带轮直径为 =/=2500/1500140=233mm按表8.3选取标准植236mm,则实际传动比I,从动轮的转速分别为 i=/=236/140=1.69 =/i=2500/1.69=1479r/min 从动轮的转速误差为 （1479-1500）/1500100%=-1.4%在5%以内，为允许值4.验算带速VV=/601000=18m/s在5-25m/s的范围内。5.确定带的基准长度和实际中心距a 按结构设计要求初定中心距 0.7(+)a2(+) 263a 7.确定V带根数Z 由式(8.18)得Z/ 根据=140mm ，=2500r/min 查表8.10用内插法得 =3.8KW 由式(8.11)得功率增量为 = 由表8.18查得=2.6494 根据传动比i=1.69 查表8.19得=1.1202 则=2.64942500（1-）=0.7KW 由表8.4查得带长度修正系数=0.92 由表8.11查得包角系数=0.99 得普通V带的根数为 Z=8.14/(3.8+0.7)0.920.99=1.98 圆整后得Z=2跟 8.求初拉力及带轮轴上的压力 由表8.6查得B型普通V带每米质量q=0.17kg/m 根据式(8.19)得单根V带的初拉力为 = = =227.5N 由式(8.20)可得作用在轴上的压力 =2Z =22272 =904N 9. 设计结果 选择.2跟B-4000GB1171-89V带 , 中心距a=505mm ,带轮直径=140mm , =236mm ,轴上压力=904N带设计 主动轮的转速1500r/min,从动轮转速1500r/min1 确定计算功率 工 况 KA空、轻载起动重载起动每天工作小时数/h1616载荷变动微小液体搅拌机，通风机，和鼓风机（7.5kW）、离心式水泵和压缩机、轻型输送机1.01.11.21.11.21.3载荷变动小带式输送机（不均匀载荷）、通风机（7.5kW）、旋转式水泵和压缩机、发电机金属切削床、旋转筛、剧木机和木工机械1.11.21.31.21.31.4载荷变动较大制砖机、斗式提升机、往复式水泵和压缩机、起重机、磨粉机、冲剪机、橡胶机械、振动筛、纺织机械、重载运送机1.21.31.41.41.51.4载荷变动很大破碎机（旋转式。颚式等）、磨碎机（球磨、棒磨、管磨）1.31.41.51.51.61.8 表8.21 工作情况系数KA由表8.21查得=1.1 ，由式（8.12）得1.17=7.7KW2. 选择普通V带型号根据=7.7KW 由图8.12选用B型普通V带3. 确定带轮基准直径 根据表8.6和图8.12选取=125mm ,且为B型V带最小直径大带轮直径为： =125=125mm按表8.3选取标准值为125mm ,则实际传动比i ,从动轮的实际转速分别为： 从动轮的转速误差率为： 100%=0 在5%以内，为允许值。4. 验算带速V 在5-25m/s范围内5. 确定带的基准长度和实际中心距a 按结构设计要求初定中心距 0.07（）() 175500取=200mm由式(8.15)得 =792.5mm由表8.4选取基准长度=800mm a = =6. 校验小带轮包角由式(8.17)得 =7. 确定V带根数Z 根据=125mm =1500r/min ,查表8.10用内插法得 由式(8.11)得功率增量为 由表(8.18)查得 根据传动i=1 ，查表8.19得=1则 =0 由表8.4查得带长度修正系数 ，由图8.11查得包角系数 得普通V带根数 圆整得Z=28. 求初拉力及带论轴上的压力由表8.6查得B型普通V带的每米质量q=0.17kg/m ,根据式(8.19)得单根V带的初拉力为： =284N由式(8.20)可得作用在轴上的压力为： =1136N9. 计算结果 选用2根B-GB1171-89V带，中心距a=200mm ,带轮直径 ，轴上压力四轴的设计 （一）.轴的计算 1. 选择轴的材料 ，确定许用应力 因我们设计的轴对材料无特殊要求，故选用45钢并经调质处理，由表13.4查得强度极限 ，再由表13.2查得许用弯曲应力2. 按扭强度估算轴径根据表13.1得 ,又由式(13.2)得 因最小轴径处有键槽存在，故将估算增大3%5%取为19.1mm21.1mm由设计手册查得标准直径3. 设计轴的结构并绘制机构草图a.确定各轴段直径 根据设计手册公式 取h=2.5mm 初选轴承6307的直径根据轴承的内径决定取为的直径也是根据轴承来定 取为b.确定各轴段长 根据汽油机高度及整机结构，轴的总长为520mm 轴段的长度可以根据所选带轮宽螺母厚度及安装结构确定为125mm 轴段的长度根据轴承座端面和带轮的距离确定为26mm 轴段的长度轴承宽得21mm 轴段用装刀片，可根据刀片的厚度，螺母和垫片的厚度确定轴长为50mm轴段的长也为轴承宽21mm 轴段的长和轴段的一样为26mm 最后留下的长度就为轴段的长（二）.轴的校验 以B为基点 ， 在以C点为基点： 查表13.1得，满足，故轴的设计满足要求。 (三).轴承的选择 应 所以只要边的轴承可用即可 初选轴承6307 GB/T276-1994 按文献8-23，基本额定功率为 轴的预期寿命取为 查表得 故6307滚动轴承满足要求(四). 键的选用根据结构选用10110 普通A型平键轴的设计 （一）.轴的计算 4. 选择轴的材料 ，确定许用应力 因我们设计的轴对材料无特殊要求，故选用45钢并经调质处理，由表13.4查得强度极限 ，再由表13.2查得许用弯曲应力5. 按扭强度估算轴径根据表13.1得 ,又由式(13.2)得 因最小轴径处有键槽存在，故将估算增大3%5%取为18.820.06mm由设计手册查得标准直径6. 设计轴的结构并绘制机构草图a.确定各轴段直径 根据设计手册公式 取h=2.5mm 初选轴承6307的直径根据轴承的内径决定取为的直径也是根据轴承来定 取为b.确定各轴段长 根据汽油机高度及整机结构，轴的总长为470mm 轴段的长度可以根据所选带轮宽螺母厚度及安装结构确定为66mm 轴段的长度根据轴承座端面和带轮的距离确定为27mm 轴段的长度轴承宽得21mm 轴段用装刀片，可根据刀片的厚度，螺母和垫片的厚度确定轴长为50mm轴段的长也为轴承宽21mm 轴段根据轴承座端面和带轮的距离确定为26mm 最后留下的长度就为轴段的长 (二).轴的校验 以B点为基点： 在以C点为基点： 查表13.1得，满足，故轴的设计满足要求。 （三）.轴承的选择 应 所以只要边的轴承可用即可 初选轴承6307 GB/T276-1994 按文献8-23，基本额定功率为 轴的预期寿命取为 查表得 故6307滚动轴承满足要求 （四）.键的选用 根据结构选择1056的普通A型平键五刀片结构的设计及材料的选择 1.刀片的结构采用用圆盘形的刀盘，两边有装有两个对称的刀片，刀片示意图入图所视： 2.材料的选择：刀片在高速的环境下工作，且在剪切过程中，刀片会受到很大的挤压力，摩擦也会很厉害，需要的硬度也比较高。根据这些我们决定选择W18Cr4VW18Cr4V是应用最广泛的高速钢，其性能只要有：热处理硬度可达63-66HRC，抗弯强度可达3500MPa，可磨性好。其优点：通用性强，工艺成熟。热处理的主要特点：淬火加高温（1200摄氏度），以及回火时温度高（560摄氏度）左右、次数多达三次左右。采用高淬火温度是为了让难溶的特殊炭化物能充分溶入奥氏体，最终使马氏体中W、Mo、V等含量足够高，保证其热硬性足够高；回火温度心 得 体 会经过自己和小组成员的共同努力，终于将毕业设计完成了。在这次毕业设计过程中，我们遇到了许许多多的问题，一遍又一遍的计算，一遍又一遍的修改，一遍又一遍的推敲机械结构，由于一开始对结构的设计不太完美，导致我们走了很多弯路。后来，在完全没老师的指导下，我们进一步对结构进行了修改和推敲，并得到了比较完善的框架结构。尽管这次设计的时间是短暂的，但是对我来说，收获却是很大的，俗话说的好“学到用时方狠少”，以前，我们只知道学知识，但是对知识的吸收和利用并不多，这次毕业设计，让我们再次温习了以前学过的知识，并联系起来，运用在自己的设计中。同时也对知识有了进一步的巩固，不仅让我们对的生长和膨化有了进以步的了解，而且也让我们对office软件，和计算机绘图软件AutoCAD等工具软件有了熟练的掌握 参 考 文 献1机械零件设计手册，吴宗泽，机械工业出版社，2003年112互换性与测量技术基础，陈于萍，机械工业出版社，2003年103机械制图李澄，吴天生，闻百桥，高等教育出版社，1997年74机械设计基础。陈立德，高等教育出版社2000年85机械设计手册，联合编写化学工业出版社，1981年16工程力学，张定华 ，高等教育出版社， 2000年8第21页 共21页编号无锡太湖学院毕业设计（论文）相关资料题目： 反向旋转型双螺杆挤压机 及挤压部件设计 机电 系 机械工程及自动化专业学 号： 0923168学生姓名： 沈杰 指导教师： 戴宁 （职称：副教授 ） （职称： ）2013年5月25目 录一、毕业设计（论文）开题报告二、毕业设计（论文）外文资料翻译及原文三、学生“毕业论文（论文）计划、进度、检查及落实表”四、实习鉴定表无锡太湖学院毕业设计（论文）开题报告题目： 反向旋转型双螺杆挤压机 及挤压部件设计 机电 系 机械工程及自动化 专业学 号： 0923168 学生姓名： 沈杰 指导教师： 戴宁 （职称：副教授 ） （职称： ）2012年11月25日 课题来源用于食品生产的工程实践性自拟课题。科学依据（包括课题的科学意义；国内外研究概况、水平和发展趋势；应用前景等）（1）课题科学意义挤压机是挤压加工技术的关键。 挤压加工技术作为一种经济实用的新型加工方法在食品生产中得到迅速发展。 挤压加工主要由一台挤压机一步完成原料的混炼、熟化、粉碎、杀菌、预干燥、成型等工艺, 制成膨化、组织化产品或制成不膨化的产品。 只要简单地更换挤压模具, 便可以很方便地改变产品的造型。反向型螺杆挤压机用于食品生产具有工艺简单、一机多能、生产连续化、效率高、能耗低、投资少、收效快的特点。生产出来的食品口感细腻、易消化吸收、营养成份损失少、贮藏时间长、不易产生“回生”现象、食用方便. 目前，挤压技术已经发展成为最常用的膨化食品生产技术之一。反向型双螺杆挤压机的研究与开发也势在必行。（2）反向双螺杆挤压机的研究状况及其发展前景上世纪60 年代, 开始出现了双螺杆挤压机, 并用于食品加工领域. 我国从70 年代开始研究食品挤压技术和挤压加工机械. 1980 年3 月, 北京食品研究所仿制出第一台自热式PJ ) 1 型谷物膨化挤压机. 1982 年无锡轻工业大学从法国Clext ral 公司引进一台BC ) 45 型双螺杆挤压机, 开始了对挤压加工技术的研究。与此同时, 国内许多生产厂家也先后从世界各大公司引进了先进的挤压设备。国际上有代表性的挤压机生产企业除法国Clext ral 公司外，还有美国Wenger 公司，德国的WP 公司, 意大利MAP 公司，日本的恩奴比食品有限公司，瑞士的Buchcler 公司等。在引进国外设备的同时，国内的许多厂家也先后生产了不同类型的挤压设备。反向型双螺杆挤压技术在近几年得到了迅速地发展。研究表明,反向型双螺杆挤出技术具有无法比拟的优越性能, 如物料能充分、彻底混合揉捏, 并且在反向型双螺杆挤出机运转时, 由于反向双螺杆互相啮合而具有自行擦净的功能, 避免了螺杆堵塞的物料在套筒内产生表面结焦的现象。同时反向型双螺杆挤压机还具有广泛的原料适应性的优点。反向型双螺杆挤出机因其具有突出的高效工作性能, 受到了食品行业的广泛重视。根据收集的相关文献, 对反向双螺杆挤压机在食品工业中的应用、发展前景、主要组成部分，以及挤压机的各项参数等进行综合的分析和论述,希望对我国反向型双螺杆食品挤压的研究与发展有益。 研究内容 螺杆挤压机的挤压膨化原理和结构特点 反向旋转型双螺杆挤压机的工作原理 反向旋转型双螺杆挤压机主要参数计算 反向旋转型双螺杆挤压机的总体结构设计 反向旋转型双螺杆挤压机挤压部件的设计拟采取的研究方法、技术路线、实验方案及可行性分析（1）实验方案 掌握反向旋转型双螺杆挤压机的工作原理，通过对其结构及特点的研究了解挤压机的内部结构，从而进行对挤压部件的研究和设计。（2）研究方法 通过实验了解挤压机的结构参数，对挤压部件的参数进行计算及确定，按照挤压机的结构进行装配图及挤压部件零件图的绘制。研究计划及预期成果研究计划：2012年10月12日-2012年12月31日：按照任务书要求查阅论文相关参考资料，完成毕业设计开题报告书。2013年1月1日-2013年1月27日：学习并翻译一篇与毕业设计相关的英文材料。2013年1月28日-2013年3月3日：毕业实习。2013年3月4日-2013年3月17日：反向旋转型双螺杆挤压机螺杆、机筒的主要参数计算与确定。2013年3月18日-2013年4月14日：反向旋转型双螺杆挤压机总体结构设计。2013年4月15日-2013年4月28日：部件及零件图设计。2013年4月29日-2013年5月21日：毕业论文撰写和修改工作。 预期成果：了解挤压机的工作原理、内部结构以及反向旋转型双螺杆挤压机的优缺点，熟练绘制挤压机的装配图，挤压部件的零件图。特色或创新之处 双螺杆挤压机在食品工业中应用更广泛。 反向旋转型双螺杆挤压机结构简单，更适合对高粘度食品的输送加工。已具备的条件和尚需解决的问题 设计方案思路已经非常明确，已经具备机械设计的能力和图纸处理方面的知识。 结构设计的能力尚需加强。指导教师意见 指导教师签名：2012年 12 月 15 日教研室（学科组、研究所）意见 教研室主任签名： 年 月 日系意见 主管领导签名： 年 月 日A simplified twin screw co-rotating food extruder: design, fabrication and testingAbstract A simplified co-rotating twin screw food extruder was designed, fabricated and tested in England, followed by extensive testing in Sri Lanka. It was built as a model to meet the specic product and nancial constraints of less developed countries and was expected to be used in those countries to widen the production capabilities of extruded foods. The machine had an estimated delivery of 10 kg/h and was made mainly with mild steel. Two types of screw were made, one with a constant pitch of 14 mm and the other with varying pitch in segments of 14, 12 and 10 mm. The machine was powered by a 2.2 kW electric motor with electronic speed controls. The machine also had electrical heating with a temperature controller and a pressure sensing device. The cost of fabrication of the machine was estimated at 2000 with most of the parts built in a fairly simple workshop. A mixture of rice and dried banana was successfully extruded as a potential snack food and on the basis of maximum expansion the best results was obtained from a barrel temperature of 120C, screw speed 125 rpm, feed moisture 15% and with a die orice size of 3 mm. When the alternative compression screw was tested very similar results were achieved with no signicant improvement in product expansion. 1999 Elsevier Science Ltd. All rights reserved.Keywords: Twin screw extruder; Design; Low cost; Snack food; Continuous cooker; Local construction; Cereal mixturesNomenclatureA Die diameter (mm)B Channel width (mm)C Screw circumference (mm)d Screw core diameterD Outer diameter of screws (mm)H Flight depth (mm)M Moisture content (% wet basis)n Number of fight turnsN Speed angular (rev/min)p Pitch (mm)Q Delivery rate (mm3/min)S Total helical length of screws (mm)t Temperature (C)T Residence time (min) Overlap angle of screw fights (degrees) Calender gap (mm) Side clearance (mm) Product density (g/mm3 ) Helix angle (degrees)1. Introduction Extrusion cooking is finding ever increasing applications in the food process industry. Apart from providing a means of manufacturing new products, it has successfully revolutionised many conventional manufacturing processes (Harlow, 1985, Frame, 1994). Today,extruders come in a wide variety of sizes, shapes and method of operation. There are three types of food extruder found in industry: hydraulic ram, roller and screw type extruders (Frame, 1994). The screw extruders are very different to the other two having special features such as continuous processing and mixing ability. Single and twin screw types are both widely used in the food process industry. Unfortunately, most of the food extruders available in the market are either so costly that less developed countries cannot a.ord to buy them except by some form of assistance or outside investment or else are not appropriate for the wide variety of materials that need to be processed. As a result the growth of extrusion technology of food into these countries has been hindered despite its many advantages. In particular there appears not to be a suitable twin screw extruder available at suffciently low cost for use in developing countries. The high cost of these machines is largely due to the sophisticated constructional features with many controls that are not essential for many applications.The initial purchase cost is therefore a major barrier to the wider introduction of extrusion to developing countries where many raw materials are available to be processed into nutritious and palatable food items. Attempts have been made to utilise low pressure and simple extruders for baby weaning foods some of which have been very successful with programs through organizations such as Feed the Millions (Santa Monica,California, 90406, USA) and Thriposha (USDA/USAID). The need has long been recognised for simple,yet versatile machines at affordable prices which are capable of exploiting the natural food resources (Sahagun,1977), Jansen and Harper (1980), Harper and Jansen(1985). These could incorporate all the usual cereals such as rice, millet, maize and sorghum with a rich variety of nutritional and tasty additives such as fruits,vegetables and spices. The objective of this study therefore was to eliminate or simplify many of the unnecessary features of the currently available machines so that fabrication could be done in an unsophisticated workshop, while ensuring the versatility to permit the production of acceptable extruded foods especially using blends of fruits and cereals. This latter technique was developed by Gamlath (1995) using a single screw extruder to produce a range of extrudates that she adjudged to show great promise as a snack food or breakfast cereal in Sri Lanka in particular but also in many developing countries and also as a high value export. These products were largely based on mixtures of fruit and cereals such as mango, banana and tomato with maize, rice and wheat. Attractively textured and flavoured items were produced which could easily be further flavoured with spices, sugar and salt. Many developing countries use home based businesses to produce snacks and ready-to-eat meals and these product well into this well established culture. Machines made in the developing country, however, need to be low cost and relatively simple, easy to maintain and operate. In this study the particular features required were good transport characteristics for sticky materials and good mixing ability which are needed for the blended crops selected. Short residence times and low to medium pressures were acceptable.2. Design approach The design of the extruder in this study was mostly based on the results of extrusion studies done using a single screw laboratory scale extruders (Brabender,Warrington, Cheshire, UK) as part of the same programme,and supported by engineering principles and constraints applicable to a developing country. In the design process, the level of pressure likely to be developed within the extruder barrel becomes the most important factor as it determines the sizes of all the important components of the extruder such as bearings,shaft diameters and barrel dimensions. As these machines often operate under elevated temperatures, pressure tends to vary unpredictably because of complex rheological properties of food dough as related to varying temperature along the barrel. Therefore, actual measurements of extruder process variables, were made on the chosen range of food materials on the laboratory single screw extruder. This approach was reckoned to be more appropriate rather than a theoretical one, that cannot be generalised especially for materials of unknown rheology. Hence, approximate values for some of the most important parameters such as die sizes, pressures,temperatures etc. were quantified. These values were then tested again in the experiments described later for the twin screw system.2.1. Single vs twin screws Many comparisons between twin and single screw extruders have been made (Harper, 1992) (Hauck, 1985 ) (Hauck & Ben Gera, 1987) (Van Zuilichem, Stolp & Janssen, 1984) and many of the features discussed are relevant to the current application. Single screw machines meet most of the criteria for developing countries but unfortunately certain of the technical requirements can only be met by twin screws such as versatility, adequateow of feed into the screws and, particularly in this case, ow of the material down the barrel without spinning within it. This is a common problem with the rather sticky or high moisture materials that were envisaged with the incorporation of fruits and vegetables and other tropical crops and flavours and experienced by Gamlath (1995). The forward motion of the food dough relies entirely on the friction between the material and the interior surfaces of both screw and barrel. This is particularly so in a single screw but less so in a twin screw. Single screw extruders are generally cheaper than the twin screw type owing to their simpler construction, but they are more likely to block than twin screw extruders. The dilemma facing the designer, therefore, is that although the operational problems can be avoided by using twin screws their sophisticated constructional features would have to be simplified significantly to achieve the low cost objective. In twin screw extruders the screws can be made as either co-rotating or counter rotating, with differing amounts of intermesh, pitch and clearances, all of which affect the processing characteristics of the machine (Martelli, 1983). Since the flight of one screw engages the channel of the other the twin screws prevent material from sticking to the screws and rotating with the screw, hence encouraging forward motion of dough with reduced slip (Jansen, 1978). This also enhances the mixing of materials in the channels of the screws. The counter rotating type of twin screw extruder can give better material ow characteristics pushing the material positively forward towards the die but reducing the degree ofmixing of materials within the extruder. Another unfortunate feature is that separating forces between the screws can cause severe wear of the side walls. On the other hand, co-rotating, twin screw extruders give additional advantages such as pressure balance in transverse planes of the screws and a wiping action of the fights due to the opposing linear velocities at the fights of intermeshing region. Therefore, it was decided that a twin screw co-rotating extruder would provide all the versatility and characteristics required for processing the food materials envisaged in a developing country. The only problem then was to design a satisfactory machine that would also meet the cost criteria.2.2. Screws The central part of an extruder is the screw. The screws rotate in a tightly fitting barrel and convey the material from feed end to die end, mixing and com-pressing the ingredients. The capacity of the extruder is mainly determined by the screw outer and root diameters, pitch and fight width (Fig. 1). Therefore, the screw overall dimensions have to be first determined according to the desired output to initiate the design process. One other important factor is the residence time, as it determines the degree of cooking taking place in the extruder. Exploratory trials and the work of Gamlath (1995) indicated that a residence time of about 16 s would be adequate at the mean speed. It is, however, influenced by many of the design parameters including the length, diameter and pitch of the screws although it can be controlled largely by the operational screw speed of the extruder and the selected die size. The rheology of the material also has a major influence on the throughput so residence time cannot be accurately predicted. In this study several dimensions of the screws were determined in order to suit the expected output and residence time. The geometry and equations relating many of these factors are given in Fig. 1 and Eqs. (1)(3) below. The maximum output was not the rst priority but similar sized extruders and single screw trials indicated a typical delivery rate of up to 10 kg/h. The residence time was designed to be short as the novel products planned were not expected to rely on long processing times. The short residence time was particularly sought in order to maintain the vitamin C content of perishable products which could be easily destroyed if cooked too long (Seiler, 1984). The influence of screw pitch is such that low values with small helix angles lead to longer residence times because of the increased number of cycles that the material has to go through. On the other hand, large pitches would reduce the degree of mixing and uniformity of heat distribution due to the increase in volume of material contained in the screw channels. Furthermore, if the fight width is also in-creased in proportion with the pitch to avoid large gaps between engaging fights, the power consumption is in-creased due to the increased surface area of shear be-tween the fight tip and the barrel. Therefore, in order to maintain the channel volume within reasonable limits and to have a fairly short residence time the pitch was selected as 14 mm. In view of the foregoing the outer diameter of the extruder was chosen at 30 mm with a helix angle at 8.5 which is in the range recommended by Martelli (1983) for similar plastic extrusion machines. The parameter most affected by the outer diameter is the extruder throughput, which was not a critical factor in this study apart from it being a low value to suit a large numbers of experiments. Another feature affected by the outer diameter is the screw center distance which in turn determines the fight height and the amount of intermesh. The screw center distance is vital as it establishes the space available for thrust bearings. Therefore, the screw center distance, the amount of intermesh and the root diameter all have to be carefully adjusted so that a maximum space is made available for the thrust bearings. The screw length, with pitch, governs the number of fight turns and has a major influence on the residence time which was planned to be short compared to most extruders. The length of the screws had to be relatively short therefore which was fortunate as this suited the manufacturing facilities available to construct a twin screw extruder barrel. It is not easy to machine two overlapping holes to accommodate the twin screws with a simple machine tool especially when the length is large as drills tend to wander. The length of barrel and screws to give the required residence time was 224 mm. The foregoing design choices permitted calculation of the number of turns as 16 (Eq. (1) with a preliminary value of fight height of 4 mm.The residence time is dened assuming no slip as,Referring to Fig. 1, the non-intermeshing part of the screws the length of circumference, C can be written as, ,=overlap angle= (1)The channel width is a major factor affecting the volume of screw channels and hence the throughput. Since the pitch is already xed, the value of the channel width depends on the selection of the values for the width of the fight and the clearance needed between engaging fight flanks. Considering the primary dimensions of the screw profile, the fight width at the root was calculated as 5 mm, leaving a reasonable side clearance of 2 mm. This established the channel width as 9 mm. The channel height was taken as 4 mm to have an output of 10kg/h at 200 rpm. A simple volumetric determination based on no-back flow was used to estimate the delivery rate (Q) as given by Eq. (2). (2)Referring to Fig. 1, the root diameter and the center distance between two screws were calculated as 22 and 27 mm, respectively, leaving a clearance (calender gap) of 1 mm between the tip of the screw fight and the bottom of the channel of the other screw.The fight flank angle of 7 was selected to avoid possible binding of the fights in operation. The minimum angle was given by the Eq. (3) (Jansen, 1978). (3)Compression of the product in the single screw barrels can be achieved by one of several methods as described by Harper (1979). These include varying pitch with constant root and outer diameters, use of tapered screws having constant pitch and tapered root diameter with constant outer diameter. Not all these possibilities can be applied to twin screws because of their geometrical interdependency. One of the simplest way of making screws achieve compression is to change the pitch along the screw and thus change the channel volume from feed end to die end. In this study it was decided to give the screws three different pitches in equal lengths along the screw using a lathe. The pitches selected were 14, 12 and 10 mm and in equal lengths along the screw with aclearance of 7 mm between each segment allowed for machining purposes. An alternative for simple compression screw design is to increase the root diameter of the screws from feed to delivery but this was considered to be somewhat harder to make on a simple lathe than the system chosen.2.3. Barrel The extruder barrel that accommodates the screws should be mechanically strong enough to withstand the pressures developed in the barrel and to resist the wear. The exact pressures inside the barrel are not known and, therefore to estimate the barrel wall thickness as well as to design the thrust bearings a level of pressure had to be assumed. It was measured during the preliminary work in the single screw extruders and from quoted work for similar materials. Pressures in commercial extrusion machines can reach up to 17 MPa (2500 psi) (Harper,1979), depending on type of material, length of extruder and many other factors. In this study a maximum pressure of 10 MPa as design pressure was considered to be more than adequate especially with such a shortbarrel. The minimum barrel wall thickness was calculated as 6 mm from thin cylinder theory (Ryder, 1953) that would withstand a hoop stress of 100 MPa. The barrel, shown in Figs. 2 and 3, was designed to t together in two parts, each 112 mm long for ease of manufacture, as it can be dicult to retain the correct alignment of the bores otherwise. These were bolted end to end with locating pins, each portion was also split into two halves length ways for easy dismantling in theevent of a serious blockage.2.4. Dies The die of an extruder plays an important role in deciding the product physical properties such as density, expansion, surface texture and the final shape of the product. When the product emerges from the die hole,due to the rapid release of pressure flashing o. steam, the product tends to swell (Harper, 1979). Therefore the product shape is not the same as the die shape. The shape of the product depends on the ratio of length to cross sectional area of the die hole. Smith (1986) reported that swelling of the product decreases with the increase of length to diameter ratio due to the loss of memory from the entrance to the die outlet. Materials accumulated at the die entrance so ready removal of the dies was essential in order to help the cleaning up process after each run of the extruder. Die changing was an important feature in setting up randomised experiments but for a commercial machine with longer runs this would become far less frequent. In order to ensure the smooth flow of material from the screws to the dies the die plate was machined in the shape of a double cone to t the pointed end of the two screws as shown in Fig. 2. The dies were circular in shape and were made so that they could be externally screwed to the die plate.简单的双螺杆挤压设备的设计，制造和测试S.A.M.A.N.S. Senanayake a, B. Clarke摘要：简单的双螺杆食品挤压机被设计，制造和测试之后，紧接着大量的测试在斯里兰卡进行。它是用来满足一些特殊产品的的制造，而且期望能够应用于欠发达地区来扩大食品产品的生产范围。这个机器的生产能力为10Kg/h,大部分是用软钢制造而成。这个机器有两种螺杆，一种是14mm的螺距，另一种是具有14，,12和10三种变化的螺距。这个机器由2.2KW的可调电动机驱动。它还有电加热系统，拥有温度控制和压力感应功能。这款机器在一般的工厂里的制造成本约为2000英镑。大米和干香蕉的混合物被成功的挤压膨化为一种方便食品，是在机筒温度为120度，螺杆转速为125r/min，食品含有水分占15%并且挤出空的直径为3mm的时候挤出的。其它种类的螺杆在没有特别改进的情况下获得的挤压结果与此相似。 1999年Elsevier Science 有限公司的专利。关键词：双螺杆挤压机；设计；低成本；休闲食品；连续烹；地方建设；谷物混合。符号： a 挤出直径（mm） B 通道宽度（mm） C 螺杆周长（mm） d 螺杆中心距（mm） D 螺杆直径（mm） H 螺纹深度（mm） M 含水量（%） n 螺纹头数（mm） N 转速（r/min） P 螺纹高（mm） Q 生产流量（） S 螺杆长度（mm） t 温度（） T 停留时间（s） 螺纹升角（） 间隙（mm） 侧间隙（mm） 产品密度（g/ 螺旋角1简介挤压机是找到的不断为食品加工也提供应用的机器，除了提供了一系列的生产新产品之外，它已经成功的改善了许多传统制造工艺。现在也诞生了一系列不同尺寸、形状和操作方法的挤压机。工业上有三种基本的挤压机：液压挤压机、辊式挤压机和螺杆式挤压机。螺杆挤压机和其它两种类型的挤压机有着明显不同的特征，比如连续的生产能力。单、双螺杆挤压机都广泛地应用在食品加工领域，但是，市场上销售的挤压机成本太高，一般欠发达地区购买不到，除非接受援助或者有外来投资介入，或者这些机器不能适应来加工更多品种的原料，所以就导致了食品挤压机技术在这些地区的发展被阻碍，尽管它具有这些技术的优势。特别是看上去在发展中国家，存在着应用并不合适的但是成本较低的双螺杆挤压机。这种机器之所以成本高，大部分是因为其有许多的复杂结构特征，比如对其他机械来说并不必要的控制系统。初次购买最大的障碍就是却反更广泛地介绍，让欠发达地区的人们知道很多原料都可以用挤压机来加工成营养谷物食品，人们已经在尝试用低压和简单的挤压机以生产婴儿断奶食品，而且部分产品已经在某些公司取得成功，如Feed The Millions和Thriposha。这种需要一直都可以被认可，所以价格和合理多功能机可利用多种食品原料。这些机械可以混合所有常见的谷物如大米、粟、玉米和高粱以及富含营养的口感也很好的水果蔬菜和香料。之前的研究主要是为了限制和简化现在使用的机器的一些不必要结构，这样就能使制造一些不太复杂的同时又能保证多样性来生产各种挤压膨化食品，特别是和谷物的混合食品，这种技术在1995年被Gamlath应用于一个单螺杆挤压机来生产一系列的挤压膨化食品这使得她生产的休闲食品和谷物早餐不仅在许多发展中地区显得尤为特别，也可以作为一个高附加值的出口产品。这些产品大多是基于水果和谷物的混合物，比如芒果、香蕉、西红柿和玉米、大米、小麦混合，纹理美观味道好，被生产之后，能够
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