CA10B解放牌汽车第四速及第五速变速叉机械加工工艺及其M10x1螺纹孔加工夹具设计2
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机械设计制造及其自动化专业本科毕业设计(论文)开题报告书 黑龙江八一农垦大学本科毕业设计(论文)开题报告姓 名: 谢宝亭学 院: 工程学院专 业: 机械设计制造及其自动化学 号: 20064024629课 题 名 称: 设计CA10B解放牌汽车变速叉的工艺 规程及工艺装备任务书指 导 教 师: 李宝玉 研究起止日期:2010 年 3月2010年6月一、论文选题的目的和意义变速叉是一种辅助零件,通过变速叉控制滑套与旋转齿轮的接合。滑套上面有凸块,滑套的凸块插入齿轮的凹位,把滑套与齿轮固连在一起,使齿轮带动滑套,滑套带动输出轴,将动力从输入轴传送至输出轴。摆动变速叉可以控制滑套与不同齿轮的结合与分离,达到换档的目的。分析这种动力联接方式可知,车换档时要减速,这样可以减少滑套与齿轮之间的冲击,延长零件的使用寿命。机械制造工艺主要有以下几方面的目标:(1)设计结构应能够加工。在工件上应有足够的加工空间,以便刀具能够接近加工部位,如留有必要的退刀槽和越程槽等。(2)便于保证加工质量,并尽可能减少加工面积。如被加工孔的端面最好与孔加工刀具的轴线垂直;对于大的安装平面尽可能采取周边接触或四角接触的形式等。(3)要能提高劳动生产率。如加工表面尽可能地安排在同一平面或同一轴线上,以便采取多刀或多件加工的高效生产方法。(4)零件结构便于安装夹具。2、 国内外研究现状及发展趋势:工业设计是人类社会发展和科学技术进步的产物,从英国莫里斯的“工艺美术运动”,到德国的包豪斯设计革命以及美国的广泛传播与推广,工业设计经过了酝酿,探索,形成,发展百余年的历史沧桑。时至今日,工业设计已成为一门独立的专业学科,并且有一套完整的研究体系。 1980年国际工业设计协会理事会(ICSID)给工业作了明确定义:“就批量生产的工业产品而言,凭借训练,技术知识,经验及视觉感受,而预示材料、结构、构造、形态、色彩、表面加工,装饰以新的品质和规格,叫做工业设计。根据当时的具体情况,工业设计师应在上述工业产品全部侧面或其中几个方面进行工作,而且需要工业设计师对包装、宣传、展示,市场开发等问题的解决付出自己的技术知识和经验以及视觉评价能力时,这也属于工业设计的范畴。 材料、结构、工艺是产品设计的物质技术基础,一方面,技术制约着设计;另一方面,技术也推动着设计。从设计美学的观点看,技术不仅仅是物质基础还具有其本身的“功能”作用,只要善于应用材料的特性,予以相应的结构形式和适当的加工工艺,就能够创造出实用,美观,经济的产品,即在产品中发挥技术潜在的“功能”。任何设计都是时代的产物,它的不同的面貌,不同的特征反映着不同历史时期的科学技术水平。技术是产品形态发展的先导,新材料,新工艺的出现,必然给产品带来新的结构,新的形态和新的造型风格。材料,加工工艺,结构,产品形象有机地联系在一起的,某个环节的变革,便会引起整个机体的变化。三、研究的主要内容 本次设计是汽车变速箱中变速叉零件的加工工艺规程及一些工序的专用夹具设计。此变速叉零件的结构较为复杂,其加工的地方主要是孔和平面。本设计先加工孔后加工面。将孔与平面的加工明确划分成粗加工和精加工阶段以保证它们的加工精度。基准选择以变速叉右面的最大的平面作为粗基准,来加工中间的通孔,然后以此加工过的孔作为精基准。主要加工工序安排是先以中心孔定位加工出顶平面和右侧平面以及下面的大孔的两平面,再以中心孔定位加工出下端的大孔。加工时是用镗床镗孔。最后以这两个孔为基准,分别加工右侧的槽和顶面的螺纹底孔。整个加工过程选用了钻床、铣床和镗床。工件在机床上定位夹紧选用专用夹具,夹紧方式为手动夹紧,夹紧可靠,操作方便。因此生产效率较高,适用于中批量、流水线上加工。能够满足设计要求。四、研究方法及技术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的技术要求能得到合理的保证.生产纲领已确定为中批量生产的条件下,可以考虑采用万能性机床以及专用夹具,并尽量使工序集中来提高生产率.除此之外,还应当考虑经济效果,以便使生产成本尽量降低. 对于中批量生产的零件,一般总是首先加工出统一的基准。确定加工方法以后,就按生产类型、零件的结构特点、技术要求和机床设备等具体生产条件确定工艺过程的工序数。确定工序数的基本原则:(1) 工序分散原则工序内容简单,有利选择最合理的切削用量。便于采用通用设备。简单的机床工艺装备。生产准备工作量少,产品更换容易。对工人的技术要求水平不高。但需要设备和工人数量多,生产面积大,工艺路线长,生产管理复杂。(2) 工序集中原则工序数目少,工件装,夹次数少,缩短了工艺路线,相应减少了操作工人数和生产面积,也简化了生产管理,在一次装夹中同时加工数个表面易于保证这些表面间的相互位置精度。使用设备少,大量生产可采用高效率的专用机床,以提高生产率。但采用复杂的专用设备和工艺装备,使成本增高,调整维修费事,生产准备工作量大。一般情况下,单件小批生产中,为简化生产管理,多将工序适当集中。但由于不采用专用设备,工序集中程序受到限制。结构简单的专用机床和工夹具组织流水线生产。加工工序完成以后,将工件清洗干净。清洗是在的含0.4%1.1%苏打及0.25%0.5%亚硝酸钠溶液中进行的。清洗后用压缩空气吹干净。保证零件内部杂质、铁屑、毛刺、砂粒等的残留量不大于。五、课题的研究进度第一阶段(2010年3月10-2010年3月31)材料的搜集整理查阅相关资料;本阶段需要完成与课题相关的调研工作,并对相关的文章进行搜集、整理,选出与设计有关的资料备用,说明其优点所在,绘制零件图,选出最佳方案。第二阶段(2010年4.1-2010年5月10)方案设计,总体布置设计。本阶段主要清楚的表达出相关方案设计,总体布置设计.如果有不合适的地方应进行修改,计算,使之满足生产要求。第三阶段 (2010年5月11-2010年6月10) 绘制装配图 撰写设计说明书本阶段主要完成与方案相符合的文章的撰写,包括摘要、前言、设计步骤、内容、参考文献等。图纸的绘制、装配图、零件图。六、预期结论而本次对于CA10B解放牌汽车变速叉加工工艺及工艺规程的设计的主要任务是:(1) 完成变速叉零件加工工艺规程的制定;(2) 完成专用夹具的设计。通过对变速叉零件的初步分析,了解其零件的主要特点,加工难易程度,主要加工面和加工粗、精基准,从而制定出变速叉加工工艺规程;对于专用夹具的设计,首先分析零件的加工工艺,选取定位基准,然后再根据切销力的大小、批量生产情况来选取夹紧方式,从而设计专用夹具。就我个人而言,希望能通过毕业设计对自己即将从事的工作进行一次适应性训练,从中锻炼自己分析问题,解决问题的能力.由于能力有限,设计尚有诸多不足之处,恳请各位老师多多指教.七、参考文献1 傅水根。机械制造工艺基础M .第二版 北京:清华大学出版社,2004.2 王贵成.机械制造学M。北京:机械工业出版社,2001.3 邓文英。金属工艺学M。第四版。北京:高等教育出版社,2000。4 袁国定,朱洪海。机械制造技术基础M。南京:东南大学出版社,2000.5 许晓静,王宏宇。机械制造基础M.北京:化学工业出版社,2004。6 罗阳,刘胜青。现代制造系统概论M。北京:北京邮电大学出版社,2004。7 周宏甫。机械制造技术基础M.北京:高等教育出版社,2004。8 卢秉恒。机械制造技术基础M.北京:机械工业出版社,1999。9 魏康民。机械制造技术基础M.重庆:重庆大学出版社,2004。10 宋续丁。机械制造设计基础M.西安:西北工业大学出版社,2000。11 李凯岭,宋强。机械制造设计基础M.济南:山东科学技术出版社,2005。12 王先逵。机械制造工艺学M.北京:清华大学出版社,2000。13 张福润。机械制造技术基础M.武汉:华中科技大学出版社,2000。14 任家隆。机械制造技术M.北京:机械工业出版社,2000。15 袁哲俊。精密和超精密加工技术M.北京:机械工业出版社,1999.16(德)Bruno lotter。西德工业产品装配技术。付参力,刘增译。沈阳:沈阳冶金机械专科学校,1990.17(美)Paul Kenneth Wrigh著。21世纪制造。冯常学译。北京:清华大学出版社,2004指导教师意见:1对“文献综述”的评语:2对本课题的深度、广度及工作量的意见和对设计(论文)结果的预测: 指导教师: 年 月 日所在专业审查意见: 负责人: 年 月 日- 5 -CA10B解放牌汽车变速叉的工艺规程和工艺装备的设计,学生姓名:谢宝亭 指导教师:李宝玉,设计内容,1. 零件的分析 2.确定毛坯的制造形成 3.零件的工艺分析 4.基面的选择 5.工艺规程设计 6.工艺路线的拟定 7.夹具的设计,1. 零件的分析,零件是解放汽车第四速及第五速变速叉,此零件是重要零件且位于变速箱中,主要重用是拨动变速箱中的齿轮,使车达到变速的目的.,2.确定毛坯的制造形成,零件材料为20钢,零件经常拨动齿轮承受变载荷和冲击性载荷,因此应选用锻件,以使金属纤维尽量不被切断,保证零件工作可靠.,3.零件的工艺分析,变速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 mm孔为中心的加工表面 2.以 mm孔为中心的加工表面 .,4.基面的选择,1.粗基准的选择 选择粗基准时,考虑的重点是如何保证各加工表面有足够的余量,使不加工表面与加工表面间的尺寸、位置符合图纸要求。 2.精基准的选择 主要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,5. 工艺规程设计,1 加工工艺过程 该零件的主要加工表面是平面、孔系和槽系。一般来说,保证平面的加工精度要比保证孔系的加工精度容易。因此,对于变速叉来说,加工过程中的主要问题是保证孔的尺寸精度及位置精度,处理好孔和平面之间的相互关系以及槽的各尺寸精度。 2确定各表面加工方案 一个好的结构不但应该达到设计要求,而且要有好的机械加工工艺性,也就是要有加工的可能性,要便于加工,要能保证加工的质量,同时使加工的劳动量最小。设计和工艺是密切相关的,又是相辅相成的。对于我们设计变速叉的加工工艺来说,应选择能够满足平面孔系加工精度要求的加工方法及设备。除了从加工精度和加工效率两方面考虑以外,也要适当考虑经济因素。在满足精度要求及生产率的条件下,应选择价格较底的机床。,6.工艺路线的拟定, 粗铣 槽 粗铣 槽的两侧面 粗铣 孔上端两端面 槽 倒角 钻铰 孔并倒角 钻M10螺纹孔并倒角 攻螺纹M10 粗铣 孔的两端面. 粗镗 孔 精镗 孔 孔 倒角 精铣 孔的两端面 终检.,7.夹具的设计,7.1攻钻M10螺纹孔夹具的设计 利用本夹具主要用来钻攻M10 x1螺纹孔,加工时要满足粗糙度要求。为了保证技术要求,最关键是找到定位基准。 7.2 孔 的加工夹具的设计 本夹具主要用来对孔进行加工,这个孔尺寸精度要求为H7,表面粗糙度Ra1.6,钻、扩、粗铰、精铰以可满足其精度,感谢各位老师及同学,工程学院机械加工工艺过程卡片产品型号831011 产品型号 共2 页产品名称解放汽车第四及第五变速叉零件名称解放汽车第四及第五变速叉第 1页材料牌号40Cr毛坯种类铸件毛坯外型尺寸218mmx92mmx161mm每毛坯件数1每台件数1备注 工序号工序名称工 序 内 容车间工段设 备工 艺 装 备工 时准终单件00毛坯10铣粗铣16mm槽;金工XA6132型万能升降台铣床专用夹具,W18Cr4V立铣刀,游标卡尺0.29min20铣粗铣16mm槽的两侧面;金工XA6132型万能升降台铣床专用夹具,高速钢三面刃圆盘铣刀,卡板0.56min 30铣粗铣19mm孔上端两端面金工XA6132型万能升降台铣床专用夹具,高速钢镶齿三面刃铣刀,卡板0.11min40车16mm槽1.5*450倒角金工卧式车床C620-1专用夹具,高速钢车刀0.11min 50钻1、 钻孔18.5mm;2、 铰孔19mm;3、 19mm孔倒角1*450金工Z5125立式钻床专用夹具,高速钢钻头,高速钢绞刀,900锪钻0.95min 60钻钻M10螺纹孔并倒角1200金工Z5125立式钻床专用夹具,麻花钻,卡板0.24min 70攻螺纹攻螺纹M10;金工C620-1专用夹具,高速钢螺纹刀0.24min80铣粗铣82.2mm孔端面金工XA6132型万能升降台铣床专用夹具,高速钢圆柱铣刀,卡板0.75min90镗粗镗81.7mm孔;金工T740双面卧式金刚镗床专用夹具,双刃镗刀 0.96min100镗精镗82.2mm孔;金工T740双面卧式金刚镗床专用夹具,双刃镗刀0.64min110车82.2mm孔1*450倒角金工C620-1型车床专用夹具,外圆车刀0.96min120铣精铣82.2mm孔的两端面;金工XA6132型万能升降台铣床专用夹具,高速钢圆柱铣刀 1min130检验入库 标记处数更改文件号签字日期标记处数更改文件号签字 设计(日期)审核(日期)会签(日期) 谢宝亭(2010.4) 2010届本科生毕业论文(设计)中期汇报表 专 业机械设计制造及其自动化学 院工程学院姓 名谢宝亭指导教师李宝玉论文(设计)题 目设计CA10B解放牌汽车变速叉的工艺规程及工艺装备任务书毕业论文(设计)前期工作小结经过了几周的学习和认识对课题有了更加深入的认识。CA10B解放牌汽车变速叉加工工艺及工艺规程的设计的主要任务是:(1) 完成变速叉零件加工工艺规程的制定;(2) 完成专用夹具的设计。通过对变速叉零件的初步分析,了解其零件的主要特点,加工难易程度,主要加工面和加工粗、精基准,从而制定出变速叉加工工艺规程;对于专用夹具的设计,首先分析零件的加工工艺,选取定位基准,然后再根据切销力的大小、批量生产情况来选取夹紧方式,从而设计专用夹具。在设计时遇到了很多学习时没有接触过的知识,但我在老师和同学的帮助下还是一步一步克服了缺乏相关的知识。在此次设计的中期,我主要是完成CA10B解放牌汽车变速叉的工艺工序设计阶段,填写加工工艺过程卡片和工序卡片并开始进行设计夹具。为最后顺利的完成设计任务打好基础。指导教师意见指导教师签名:填表日期:2010-5-01外文原文:Machine design theory The machine design is through designs the new product or improves the old product to meet the human need the application technical science. It involves the project technology each domain, mainly studies the product the size, the shape and the detailed structure basic idea, but also must study the product the personnel which in aspect the and so on manufacture, sale and use question.Carries on each kind of machine design work to be usually called designs the personnel or machine design engineer. The machine design is a creative work. Project engineer not only must have the creativity in the work, but also must in aspect and so on mechanical drawing, kinematics, engineering material, materials mechanics and machine manufacture technology has the deep elementary knowledge. If front sues, the machine design goal is the production can meet the human need the product. The invention, the discovery and technical knowledge itself certainly not necessarily can bring the advantage to the humanity, only has when they are applied can produce on the product the benefit. Thus, should realize to carries on before the design in a specific product, must first determine whether the people do need this kind of productThe machine design must regard as the machine design personnel carries on using creative ability the product design, the system analysis and a formulation product manufacture technology good opportunity. Grasps the project elementary knowledge to have to memorize some data and the formula is more important than. The merely service data and the formula is insufficient to the completely decision which makes in a good design needs. On the other hand, should be earnest precisely carries on all operations. For example, even if places wrong a decimal point position, also can cause the correct design to turn wrongly.A good personnel design should dare to propose the new idea. moreover is willing to undertake the certain risk, when the new method is not suitable, use original method. Therefore, designs the personnel to have to have to have the patience, because spends the time and the endeavor certainly cannot guarantee brings successfully. A brand-new design, the request screen abandons absolutely many, knows very well the method for the people. Because many person of conservativeness does this certainly is not an easy matter. A mechanical designer should unceasingly explore the improvement existing product the method, should earnestly choose originally, the process confirmation principle of design in this process, with has not unified it after the confirmation new idea. Newly designs itself can have the question occurrence which many flaws and has not been able to expect, only has after these flaws and the question are solved, can manifest new goods come into the market the product superiority. Therefore, a performance superior product is born at the same time, also is following a higher risk. Should emphasize, if designs itself does not request to use the brand-new method, is not unnecessary merely for the goal which transform to use the new method. In the design preliminary stage, should allow to design the personnel fully to display the creativity, not each kind of restraint. Even if has had many impractical ideas, also can in the design early time, namely in front of the plan blueprint is corrected. Only then, only then does not send to stops up the innovation the mentality. Usually, must propose several sets of design proposals, them perform the comparison. Has the possibility very much in the plan which finally designated, has used certain not in plan some ideas which accepts. How does the psychologist frequently discuss causes the machine which the people adapts them to operated. Design personnels basic responsibility is diligently causes the machine to adapt the people. This certainly is not an easy work, because certainly does not have to all people to say in fact all is the most superior operating area and the operating process. Another important question, project engineer must be able to carry on the exchange and the consultation with other concerned personnel. In the initial stage, designs the personnel to have to carry on the exchange and the consultation on the preliminary design with the administrative personnel, and is approved. This generally is through the oral discussion, the schematic diagram and the writing material carries on. In order to carry on the effective exchange, needs to solve the following problem: (1) Designs whether this product truly does need for the people? Whether there is competitive ability (2) Does this product compare with other companies existing similar products? (3) Produces this kind of product is whether economical? (4) Product service is whether convenient? (5) Product whether there is sale? Whether may gain?Only has the time to be able to produce the correct answer to above question. But, the product design, the manufacture and the sale only can in carry on to the above question preliminary affirmation answer foundation in. Project engineer also should through the detail drawing and the assembly drawing, carries on the consultation together with the branch of manufacture to the finally design proposal usually, can have some problem in the manufacture process. Possibly can request to some components size or the common difference makes some changes, causes the components the production to change easily. But, in the project change must have to pass through designs the personnel to authorize, guaranteed cannot damage the product the function. Sometimes, when in front of product assembly or in the packing foreign shipment experiment only then discovers in the design some kind of flaw. These instances exactly showed the design is a dynamic process. Always has a better method to complete the design work, designs the personnel to be supposed unceasingly diligently, seek these better methods. Recent year, the engineering material choice already appeared importantly. In addition, the choice process should be to the material continuously the unceasing again appraisal process. The new material unceasingly appears, but some original materials can obtain the quantity possibly can reduce. The environmental pollution, material recycling aspect and so on use, workers health and security frequently can attach the new limiting condition to the choice of material. In order to reduce the weight or saves the energy, possibly can request the use different material. Comes from domestic and international competition, to product service maintenance convenience request enhancement and customers aspect the and so on feedback pressure, can urge the people to carry on to the material reappraises. Because the material does not select when created the product responsibility lawsuit, has already had the profound influence. In addition, the material and between the material processing interdependence is already known by the people clearly. Therefore, in order to can and guarantees the quality in the reasonable cost under the premise to obtain satisfaction the result, project engineer makes engineers all to have earnestly carefully to choose, the determination and the use material. Makes any product the first step of work all is designs. Designs usually may divide into several explicit stages: (a) preliminary design; (b) functional design; (c) production design. In the preliminary design stage, the designer emphatically considered the product should have function. Usually must conceive and consider several plans, then decided this kind of thought is whether feasible; If is feasible, then should makes the further improvement to or several plans. In this stage, the question which only must consider about the choice of material is: Whether has the performance to conform to the request material to be possible to supply the choice; If no, whether has a bigger assurance all permits in the cost and the time in the limit develops one kind of new material.In the functional design and the engineering design stage, needs to make a practical feasible design. Must draw up the quite complete blueprint in this stage, chooses and determines each kind of components the material. Usually must make the prototype or the working model, and carries on the experiment to it, the appraisal product function, the reliability, the outward appearance and the service maintenance and so on. Although this kind of experiment possibly can indicate, enters in the product to the production base in front of, should replace certain materials, but, absolutely cannot this point take not earnestly chooses the material the excuse. Should unify the product the function, earnestly carefully considers the product the outward appearance, the cost and the reliability. Has the achievement very much the company when manufacture all prototypes, selects the material should the material which uses with its production in be same, and uses the similar manufacture technology as far as possible. Like this has the advantage very much to the company. The function complete prototype if cannot act according to the anticipated sales volume economically to make, or is prototypical and the official production installment has in the quality and the reliable aspect is very greatly different, then this kind of prototype does not have the great value. Project engineer is best can completely complete the material in this stage the analysis, the choice and the determination work, but is not remains it to the production design stage does. Because, is carries on in the production design stage material replacement by other people, these people are inferior to project engineer to the product all functions understanding. In the production design stage, is should completely determine with the material related main question the material, causes them to adapt with the existing equipment, can use the existing equipment economically to carry on the processing, moreover the material quantity can quite be easy to guarantee the supply. In the manufacture process, inevitably can appear to uses the material to make some changes the situation. The experience indicated that, may use certain cheap materials to take the substitute. However, in the majority situation, in will carry on the production later to change the material to have in to start before the production to change the price which the material will spend to have to be higher than. Completes the choice of material work in the design stage, may avoid the most such situations. Started after the production manufacture to appear has been possible to supply the use the new material is replaces the material the most common reason. Certainly, these new materials possibly reduce the cost, the improvement product performance. But, must carry on the earnest appraisal to the new material, guarantees .its all performance all to answer the purpose. Must remember that, the new material performance and the reliable very few pictures materials on hand such understood for the people. The majority of products expiration and the product accident caused by negligence case are because in selects the new material to take in front of substitution material, not truly understood their long-term operational performance causes. The product responsibility lawsuit forces designs the personnel and the company when the choice material, uses the best procedure. In the material process, five most common questions are: (a) did not understand or cannot use about the material application aspect most newly the best information paper; (b) has not been able to foresee and to consider the dusk year possible reasonable use (for example to have the possibility, designs the personnel also to be supposed further to forecast and the consideration because product application method not when creates consequence. recent years many products responsibilities lawsuit case, because wrongly uses the plaintiff which the product receives the injury to accuse produces the factory, and wins the decision); (c) uses the material data not entire perhaps some data are indefinite, works as its long-term performance data is the like this time in particular; (d) the quality control method is not suitable and not after the confirmation; (e) the personnel which completely is not competent for the post by some chooses the material. Through to the above five questions analysis, may obtain these questions is does not have the sufficient reason existence the conclusion. May for avoid these questions to these questions research analyses the appearance indicating the direction. Although uses the best choice of material method not to be able to avoid having the product responsibility lawsuit, designs the personnel and the industry carries on the choice of material according to the suitable procedure, may greatly reduce the lawsuit the quantity. May see from the above discussion, the choice material people should to the material nature, the characteristic and the processing method have comprehensive and the basic understanding.译文:机械设计理论机械设计是一门通过设计新产品或者改进老产品来满足人类需求的应用技术科学。它涉及工程技术的各个领域,主要研究产品的尺寸、形状和详细结构的基本构思,还要研究产品在制造、销售和使用等方面的问题。进行各种机械设计工作的人员通常被称为设计人员或者机械设计工程师。机械设计是一项创造性的工作。设计工程师不仅在工作上要有创造性,还必须在机械制图、运动学、工程材料、材料力学和机械制造工艺学等方面具有深厚的基础知识。 如前所诉,机械设计的目的是生产能够满足人类需求的产品。发明、发现和科技知识本身并不一定能给人类带来好处,只有当它们被应用在产品上才能产生效益。因而,应该认识到在一个特定的产品进行设计之前,必须先确定人们是否需要这种产品。应当把机械设计看成是机械设计人员运用创造性的才能进行产品设计、系统分析和制定产品的制造工艺学的一个良机。掌握工程基础知识要比熟记一些数据和公式更为重要。仅仅使用数据和公式是不足以在一个好的设计中做出所需的全部决定的。另一方面,应该认真精确的进行所有运算。例如,即使将一个小数点的位置放错,也会使正确的设计变成错误的。一个好的设计人员应该勇于提出新的想法,而且愿意承担一定的风险,当新的方法不适用时,就使用原来的方法。因此,设计人员必须要有耐心,因为 所花费的时间和努力并不能保证带来成功。一个全新的设计,要求屏弃许多陈旧的,为人们所熟知的方法。由于许多人墨守成规,这样做并不是一件容易的事。一位机械设计师应该不断地探索改进现有的产品的方法,在此过程中应该认真选择原有的、经过验证的设计原理,将其与未经过验证的新观念结合起来。新设计本身会有许多缺陷和未能预料的问题发生,只有当这些缺陷和问题被解决之后,才能体现出新产品的优越性。因此,一个性能优越的产品诞生的同时,也伴随着较高的风险。应该强调的是,如果设计本身不要求采用全新的方法,就没有必要仅仅为了变革的目的而采用新方法。在设计的初始阶段,应该允许设计人员充分发挥创造性,不受各种约束。即使产生了许多不切实际的想法,也会在设计的早期,即绘制图纸之前被改正掉。只有这样,才不致于堵塞创新的思路。通常,要提出几套设计方案,然后加以比较。很有可能在最后选定的方案中,采用了某些未被接受的方案中的一些想法。 心理学家经常谈论如何使人们适应他们所操作的机器。设计人员的基本职责是努力使机器来适应人们。这并不是一项容易的工作,因为实际上并不存在着一个对所有人来说都是最优的操作范围和操作过程。另一个重要问题,设计工程师必须能够同其他有关人员进行交流和磋商。在开始阶段,设计人员必须就初步设计同管理人员进行交流和磋商,并得到批准。这一般是通过口头讨论,草图和文字材料进行的。为了进行有效的交流 ,需要解决下列问题:(1) 所设计的这个产品是否真正为人们所需要?(2) 此产品与其他公司的现有同类产品相比有无竞争能力?(3) 生产这种产品是否经济?(4) 产品的维修是否方便?(5) 产品有无销路?是否可以盈利? 只有时间能对上述问题给出正确答案。但是, 产品的设计、制造和销售只能在对上述问题的初步肯定答案的基础上进行。设计工程师还应该通过零件图和装配图,与制造部门一起对最终设计方案进行磋商。通常 ,在制造过程中会出现某个问题。可能会要求对某个零件尺寸或公差作一些更改,使零件的生产变得容易。但是,工程上的更改必须要经过设计人员批准,以保证不会损伤产品的功能。有时,在产品的装配时或者装箱外运前的试验中才发现设计中的某种缺陷。这些事例恰好说明了设计是一个动态过程。总是存在着更好的方法来完成设计工作,设计人员应该不断努力,寻找这些更好的方法。近些年来,工程材料的选择已经显得重要。此外,选择过程应该是一个对材料的连续不断的重新评价过程。新材料不断出现,而一些原有的材料的能够获得的数量可能会减少。环境污染、材料的回收利用、工人的健康及安全等方面经常会对材料选择附加新的限制条件。为了减轻重量或者节约能源,可能会要求使用不同的材料。来自国内和国际竞争、对产品维修保养方便性要求的提高和顾客的反馈等方面的压力,都会促使人们对材料进行重新评价。由于材料选用不当造成的产品责任诉讼,已经产生了深刻的影响。此外,材料与材料加工之间的相互依赖关系已经被人们认识得更清楚。因此,为了能在合理的成本和确保质量的前提下获得满意的结果,设计工程师的制造工程师都必须认真仔细地选择、确定和使用材料。制造任何产品的第一步工作都是设计。设计通常可以分为几个明确的阶段:(a)初步设计;(b)功能设计;(c)生产设计。在初步设计阶段,设计者着重考虑产品应该具有的功能。通常要设想和考虑几个方案,然后决定这种思想是否可行;如果可行,则应该对其中一个或几个方案作进一步的改进。在此阶段,关于材料选择唯一要考虑的问题是:是否有性能符合要求的材料可供选择;如果没有的话,是否有较大的把握在成本和时间都允许的限度内研制出一种新材料。在功能设计和工程设计阶段,要做出一个切实可行的设计。在这个阶段要绘制出相当完整的图纸,选择并确定各种零件的材料。通常要制造出样机或者实物模型,并对其进行试验,评价产品的功能、可靠性、外观和维修保养性等。虽然这种试验可能会表明,在产品进入到生产阶段之前,应该更换某些材料,但是,绝对不能将这一点作为不认真选择材料的借口。应该结合产品的功能,认真仔细地考虑产品的外观、成本和可靠性。一个很有成就的公司在制造所有的样机时,所选用的材料应该和其生产中使用的材料相同,并尽可能使用同样的制造技术。这样对公司是很有好处的。功能完备的样机如果不能根据预期的销售量经济地制造出来,或者是样机与正式生产的装置在质量和可靠性方面有很大不同,则这种样机就没有多大的价值。设计工程师最好能在这一阶段完全完成材料的分析、选择和确定工作,而不是将其留到生产设计阶段去做。因为,在生产设计阶段材料的更换是由其他人进行的,这些人对产品的所有功能的了解不如设计工程师。 在生产设计阶段中,与材料有关的主要问题是应该把材料完全确定下来,使它们与现有的设备相适应,能够利用现有设备经济地进行加工,而且材料的数量能够比较容易保证供应。在制造过程中,不可避免地会出现对使用中的材料做一些更改的情况。经验表明,可采用某些便宜材料作为替代品。然而,在大多数情况下,在进行生产以后改换材料要比在开始生产前改换材料所花费的代价要高。在设计阶段做好材料选择工作,可以避免多数这样的情况。在生产制造开始后出现了可供使用的新材料是更换材料的最常见的原因。当然,这些新材料可能降低成本、改进产品的性能。但是,必须对新材料进行认真的评价,以确保其所有性能都满足要求。应当记住,新材料的性能和可靠性很少像现有材料那样为人们所了解。大部分的产品失效和产品责任事故案件是由于在选用新材料作为替代材料之前,没有真正了解它们的长期使用性能而引起的。产品的责任诉讼迫使设计人员和公司在选择材料时,采用最好的程序。在材料过程中,五个最常见的问题为:(a)不了解或者不会使用关于材料应用方面的最新最好的信息资料;(b)未能预见和考虑擦黑年品可能的合理用途(如有可能,设计人员还应进一步预测和考虑由于产品使用方法不当造成的后果。在近年来的许多产品责任诉讼案件中,由于错误地使用产品而受到伤害的原告控告生产厂家,并且赢得判决);(c)所使用的材料的数据不全或是有些数据不确定,尤其是当其长期性能数据是如此的时候;(d)质量控制方法不适当和未经验证;(e)由一些完全不称职的人员选择材料。通过对上述五个问题的分析,可以得出这些问题是没有充分理由存在的结论。对这些问题的研究分析可以为避免这些问题的出现指明方向。尽管采用最好的材料选择方法也不能避免发生产品责任诉讼,设计人员和工业界按照适当的程序进行材料选择,可以大大减少诉讼的数量。从以上的讨论可以看出,选择材料的人们应该对材料的性质,特点和加工方法有一个全面而基本的了解.
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