3539 通用減速器機(jī)殼體側(cè)面銑削加工工藝裝備設(shè)計(jì),通用,減速器,機(jī)殼,側(cè)面,銑削,加工,工藝,裝備,設(shè)備,設(shè)計(jì) 圖號(hào) 毛坯種類 鑄件名稱 通用減速機(jī)殼體 毛坯重量被加工 零件材料 HT200 硬度 HBS160~220工序名稱 通用減速機(jī)殼體連接孔鉆削加工 工序號(hào) 工時(shí)/min序號(hào)工步名稱工作行程/mm切速/（m·min -1）進(jìn)給量/（mm·r -1）進(jìn)給量/（mm·min -1）工進(jìn)時(shí)間輔助時(shí)間1 裝卸工件 1.52 動(dòng)力部件3 滑臺(tái)快進(jìn) 47 6.3 0.00754 多軸向工進(jìn) 73 0.06 500 20.41 1.225 滑臺(tái)快退 120 6.3 0.0196789累計(jì) 1.22 1.53單件總工時(shí) 2.75機(jī)床生產(chǎn)率 17.02件/h理論生產(chǎn)率 20.966件/h備注裝卸工件時(shí)間取決于操作者熟練程度，本機(jī)計(jì)算時(shí)取1.5min負(fù)荷率 81.4%產(chǎn)品型號(hào) 零件圖號(hào) A0武漢理工大學(xué)華夏學(xué)院 機(jī)械加工工藝過程卡片 產(chǎn)品名稱 減速器 零件名稱 減速器箱體 共 4 頁 第 1 頁材 料 牌 號(hào) HT200 毛 坯 種 類 金屬模機(jī)器造 型 毛坯外形尺寸 540×250×135 每 臺(tái) 件 數(shù) 備 注工 時(shí) 工序號(hào)工 名序 稱工 序 內(nèi) 容車間工段設(shè) 備 工 藝 裝 備準(zhǔn)終 單件10 鑄造 以鑄造方式獲得工件毛坯 型腔20 時(shí)效處理30 檢驗(yàn) 檢驗(yàn)鑄件各部分尺寸 40 油漆底漆50 劃線，分 箱60 粗銑 粗銑兩箱結(jié)合面（上箱蓋以 12mm 上表面為基準(zhǔn)，下箱體以 12mm 下表面為基準(zhǔn)） X62W 游標(biāo)卡尺、硬質(zhì)合金端銑刀、專用夾具70 粗銑 粗銑上箱蓋頂面，下箱體下底面（以結(jié)合面為基準(zhǔn)） X62W 游標(biāo)卡尺、硬質(zhì)合金端銑刀、專用夾具80 人工時(shí)效90 精銑 精銑結(jié)合面（上箱蓋以頂部為基準(zhǔn)，下箱體以底面 為基準(zhǔn)） X62W 游標(biāo)卡尺、硬質(zhì)合金端銑刀、專用夾具100 半精銑 半精銑上箱蓋頂部，下箱體底面（以結(jié)合面為基準(zhǔn)） X62W 游標(biāo)卡尺、硬質(zhì)合金端銑刀、專用夾具110 合箱 按所劃線合箱120 鉆 鉆 M10 定位孔 組合鉆床 鉆頭、鉆套、專用夾具、游標(biāo)卡尺130 攻絲 對(duì) M10 定位孔攻絲至圖紙要求 組合鉆床 高速鋼機(jī)動(dòng)絲錐、專用夾具設(shè) 計(jì)（日 期） 校 對(duì)（日期） 審 核（日期） 標(biāo)準(zhǔn)化（日期） 會(huì) 簽（日期）標(biāo)記 處數(shù) 更改文件號(hào) 簽 字 日 期 標(biāo)記 處數(shù) 更改文件號(hào) 簽 字 日 期產(chǎn)品型號(hào) 零件圖號(hào) A0武漢理工大學(xué)華夏學(xué)院 機(jī)械加工工藝過程卡片 產(chǎn)品名稱 減速器 零件名稱 減速器箱蓋 共 4 頁 第 2 頁材 料 牌 號(hào) HT200 毛 坯 種 類 金屬模機(jī)器造 型 毛坯外形尺寸 540×250×135 每 臺(tái) 件 數(shù) 備 注工 時(shí) 工序號(hào)工 名序 稱工 序 內(nèi) 容車間工段設(shè) 備 工 藝 裝 備準(zhǔn)終 單件140 鉆 鉆 2×Φ8 錐銷孔 組合鉆床 高速鋼機(jī)動(dòng)絲錐、專用夾具150 擴(kuò) 擴(kuò) 2×Φ8 錐銷孔 組合鉆床 擴(kuò)孔刀、專用夾具、游標(biāo)卡尺160 定位 在錐銷孔中打入定位銷170 鉸 鉸 2×Φ8 錐銷孔 組合鉆床 機(jī)鉸刀、專用夾具、游標(biāo)卡尺180 鉆 鉆 8×Φ13 孔 組合鉆床 鉆頭、鉆套、專用夾具、游標(biāo)卡尺190 锪 將 8×Φ13 孔锪平 Φ26 組合鉆床 锪孔刀、專用夾具200 鉆 鉆 4×Φ11 孔 組合鉆床 鉆頭、鉆套、專用夾具、游標(biāo)卡尺210 锪 將 4×Φ11 孔锪平 Φ24 組合鉆床220 去毛刺230 拆箱240 清洗 清除機(jī)體結(jié)合面毛刺和切屑，重新裝配打入錐銷， 擰緊螺栓250 粗銑 粗銑軸孔端面 X62W 游標(biāo)卡尺、硬質(zhì)合金端銑刀、專用夾具260 精銑 精銑軸孔端面 X62W 游標(biāo)卡尺、硬質(zhì)合金端銑刀、專用夾具設(shè) 計(jì)（日 期） 校 對(duì)（日期） 審 核（日期） 標(biāo)準(zhǔn)化（日期） 會(huì) 簽（日期）標(biāo)記 處數(shù) 更改文件號(hào) 簽 字 日 期 標(biāo)記 處數(shù) 更改文件號(hào) 簽 字 日 期產(chǎn)品型號(hào) 零件圖號(hào) A0武漢理工大學(xué)華夏學(xué)院 機(jī)械加工工藝過程卡片 產(chǎn)品名稱 減速器 零件名稱 減速器箱蓋 共 4 頁 第 3 頁材 料 牌 號(hào) HT200 毛 坯 種 類 金屬模機(jī)器造 型 毛坯外形尺寸 540×250×135 每 臺(tái) 件 數(shù) 備 注工 時(shí) 工序號(hào)工 名序 稱工 序 內(nèi) 容車間工段設(shè) 備 工 藝 裝 備準(zhǔn)終 單件270 粗鏜 粗鏜軸孔 組合鏜床 硬質(zhì)合金鏜刀、鏜套、專用夾具、游標(biāo) 卡尺280 精鏜 精鏜軸孔 組合鏜床 硬質(zhì)合金鏜刀、鏜套、專用夾具、游標(biāo) 卡尺290 鉆 鉆軸孔端面 36×Φ8 孔 組合鉆床 鉆頭、鉆套、專用夾具、游標(biāo)卡尺300 鉸 鉸軸孔端面 36×Φ8 孔 組合鉆床 機(jī)鉸刀、專用夾具、游標(biāo)卡尺310 攻絲 對(duì)軸孔端面 36×Φ8 孔攻絲至圖紙要求 組合鉆床 高速鋼機(jī)動(dòng)絲錐、專用夾具320 鉆 鉆 2×Φ18 吊耳孔 組合鉆床 鉆頭、鉆套、專用夾具、游標(biāo)卡尺330 鉆 鉆 6×Φ20 地腳螺栓孔 組合鉆床 鉆頭、鉆套、專用夾具、游標(biāo)卡尺340 锪 將地腳螺栓孔锪平至圖紙要求 組合鉆床 锪孔刀、專用夾具350 鉆 鉆油塞、油尺孔 組合鉆床 鉆頭、鉆套、專用夾具、游標(biāo)卡尺360 攻絲 對(duì)油塞、油尺孔攻絲至圖紙要求 組合鉆床 高速鋼機(jī)動(dòng)絲錐、專用夾具370 锪 將油尺孔锪平至圖紙要求 組合鉆床 锪孔刀、專用夾具380 鉆 鉆 4×Φ6 通氣孔 組合鉆床 鉆頭、鉆套、專用夾具、游標(biāo)卡尺390 攻絲 對(duì) 4×Φ6 通氣孔攻絲 4×Φ6 通氣孔 組合鉆床 高速鋼機(jī)動(dòng)絲錐、專用夾具設(shè) 計(jì)（日 期） 校 對(duì)（日期） 審 核（日期） 標(biāo)準(zhǔn)化（日期） 會(huì) 簽（日期）標(biāo)記 處數(shù) 更改文件號(hào) 簽 字 日 期 標(biāo)記 處數(shù) 更改文件號(hào) 簽 字 日 期產(chǎn)品型號(hào) 零件圖號(hào) A0武漢理工大學(xué)華夏學(xué)院 機(jī)械加工工藝過程卡片 產(chǎn)品名稱 減速器 零件名稱 減速器箱蓋 共 4 頁 第 4 頁材 料 牌 號(hào) HT200 毛 坯 種 類 金屬模機(jī)器造 型 毛坯外形尺寸 540×250×135 每 臺(tái) 件 數(shù) 備 注工 時(shí) 工序號(hào)工 名序 稱工 序 內(nèi) 容車間工段設(shè) 備 工 藝 裝 備準(zhǔn)終 單件400去毛刺，清晰，打標(biāo)記410 檢驗(yàn)設(shè) 計(jì)（日 期） 校 對(duì)（日期） 審 核（日期） 標(biāo)準(zhǔn)化（日期） 會(huì) 簽（日期）標(biāo)記 處數(shù) 更改文件號(hào) 簽 字 日 期 標(biāo)記 處數(shù) 更改文件號(hào) 簽 字 日 期學(xué)號(hào) 10110108404英語外文翻譯教 學(xué) 系： 機(jī)械制造及其自動(dòng)化 指導(dǎo)教師： 齊洪方 專業(yè)班級(jí)： 機(jī)制 1084 學(xué)生姓名： 李笑軒 2012 年 5 月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, engineerig 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 productMust regard as the machine design is 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 design personnel 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 obsoletely 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, then 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 operate. Designs personnel''s 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, seeks these better method. Recent year, the engineerig 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, worker''s 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 customer''s 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. I n 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 is 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. ecent 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.機(jī)械設(shè)計(jì)理論機(jī)械設(shè)計(jì)是一門通過設(shè)計(jì)新產(chǎn)品或者改進(jìn)老產(chǎn)品來滿足人類需求的應(yīng)用技術(shù)科學(xué)。它涉及工程技術(shù)的各個(gè)領(lǐng)域，主要研究產(chǎn)品的尺寸、形狀和詳細(xì)結(jié)構(gòu)的基本構(gòu)思，還要研究產(chǎn)品在制造、銷售和使用等方面的問題。進(jìn)行各種機(jī)械設(shè)計(jì)工作的人員通常被稱為設(shè)計(jì)人員或者機(jī)械設(shè)計(jì)工程師。機(jī)械設(shè)計(jì)是一項(xiàng)創(chuàng)造性的工作。設(shè)計(jì)工程師不僅在工作上要有創(chuàng)造性，還必須在機(jī)械制圖、運(yùn)動(dòng)學(xué)、工程材料、材料力學(xué)和機(jī)械制造工藝學(xué)等方面具有深厚的基礎(chǔ)知識(shí)。 如前所訴，機(jī)械設(shè)計(jì)的目的是生產(chǎn)能夠滿足人類需求的產(chǎn)品。發(fā)明、發(fā)現(xiàn)和科技知識(shí)本身并不一定能給人類帶來好處，只有當(dāng)它們被應(yīng)用在產(chǎn)品上才能產(chǎn)生效益。因而，應(yīng)該認(rèn)識(shí)到在一個(gè)特定的產(chǎn)品進(jìn)行設(shè)計(jì)之前，必須先確定人們是否需要這種產(chǎn)品。應(yīng)當(dāng)把機(jī)械設(shè)計(jì)看成是機(jī)械設(shè)計(jì)人員運(yùn)用創(chuàng)造性的才能進(jìn)行產(chǎn)品設(shè)計(jì)、系統(tǒng)分析和制定產(chǎn)品的制造工藝學(xué)的一個(gè)良機(jī)。掌握工程基礎(chǔ)知識(shí)要比熟記一些數(shù)據(jù)和公式更為重要。僅僅使用數(shù)據(jù)和公式是不足以在一個(gè)好的設(shè)計(jì)中做出所需的全部決定的。另一方面，應(yīng)該認(rèn)真精確的進(jìn)行所有運(yùn)算。例如，即使將一個(gè)小數(shù)點(diǎn)的位置放錯(cuò)，也會(huì)使正確的設(shè)計(jì)變成錯(cuò)誤的。一個(gè)好的設(shè)計(jì)人員應(yīng)該勇于提出新的想法，而且愿意承擔(dān)一定的風(fēng)險(xiǎn)，當(dāng)新的方法不適用時(shí)，就使用原來的方法。因此，設(shè)計(jì)人員必須要有耐心，因?yàn)?所花費(fèi)的時(shí)間和努力并不能保證帶來成功。一個(gè)全新的設(shè)計(jì)，要求屏棄許多陳舊的，為人們所熟知的方法。由于許多人墨守成規(guī)，這樣做并不是一件容易的事。一位機(jī)械設(shè)計(jì)師應(yīng)該不斷地探索改進(jìn)現(xiàn)有的產(chǎn)品的方法，在此過程中應(yīng)該認(rèn)真選擇原有的、經(jīng)過驗(yàn)證的設(shè)計(jì)原理，將其與未經(jīng)過驗(yàn)證的新觀念結(jié)合起來。新設(shè)計(jì)本身會(huì)有許多缺陷和未能預(yù)料的問題發(fā)生，只有當(dāng)這些缺陷和問題被解決之后，才能體現(xiàn)出新產(chǎn)品的優(yōu)越性。因此，一個(gè)性能優(yōu)越的產(chǎn)品誕生的同時(shí)，也伴隨著較高的風(fēng)險(xiǎn)。應(yīng)該強(qiáng)調(diào)的是，如果設(shè)計(jì)本身不要求采用全新的方法，就沒有必要僅僅為了變革的目的而采用新方法。在設(shè)計(jì)的初始階段，應(yīng)該允許設(shè)計(jì)人員充分發(fā)揮創(chuàng)造性，不受各種約束。即使產(chǎn)生了許多不切實(shí)際的想法，也會(huì)在設(shè)計(jì)的早期，即繪制圖紙之前被改正掉。只有這樣，才不致于堵塞創(chuàng)新的思路。通常，要提出幾套設(shè)計(jì)方案，然后加以比較。很有可能在最后選定的方案中，采用了某些未被接受的方案中的一些想法。 心理學(xué)家經(jīng)常談?wù)撊绾问谷藗冞m應(yīng)他們所操作的機(jī)器。設(shè)計(jì)人員的基本職責(zé)是努力使機(jī)器來適應(yīng)人們。這并不是一項(xiàng)容易的工作，因?yàn)閷?shí)際上并不存在著一個(gè)對(duì)所有人來說都是最優(yōu)的操作范圍和操作過程。另一個(gè)重要問題，設(shè)計(jì)工程師必須能夠同其他有關(guān)人員進(jìn)行交流和磋商。在開始階段，設(shè)計(jì)人員必須就初步設(shè)計(jì)同管理人員進(jìn)行交流和磋商，并得到批準(zhǔn)。這一般是通過口頭討論，草圖和文字材料進(jìn)行的。為了進(jìn)行有效的交流 ，需要解決下列問題：（1） 所設(shè)計(jì)的這個(gè)產(chǎn)品是否真正為人們所需要？（2） 此產(chǎn)品與其他公司的現(xiàn)有同類產(chǎn)品相比有無競(jìng)爭(zhēng)能力？（3） 生產(chǎn)這種產(chǎn)品是否經(jīng)濟(jì)？（4） 產(chǎn)品的維修是否方便？（5） 產(chǎn)品有無銷路？是否可以盈利？ 只有時(shí)間能對(duì)上述問題給出正確答案。但是， 產(chǎn)品的設(shè)計(jì)、制造和銷售只能在對(duì)上述問題的初步肯定答案的基礎(chǔ)上進(jìn)行。設(shè)計(jì)工程師還應(yīng)該通過零件圖和裝配圖，與制造部門一起對(duì)最終設(shè)計(jì)方案進(jìn)行磋商。通常 ，在制造過程中會(huì)出現(xiàn)某個(gè)問題。可能會(huì)要求對(duì)某個(gè)零件尺寸或公差作一些更改，使零件的生產(chǎn)變得容易。但是，工程上的更改必須要經(jīng)過設(shè)計(jì)人員批準(zhǔn)，以保證不會(huì)損傷產(chǎn)品的功能。有時(shí)，在產(chǎn)品的裝配時(shí)或者裝箱外運(yùn)前的試驗(yàn)中才發(fā)現(xiàn)設(shè)計(jì)中的某種缺陷。這些事例恰好說明了設(shè)計(jì)是一個(gè)動(dòng)態(tài)過程。總是存在著更好的方法來完成設(shè)計(jì)工作，設(shè)計(jì)人員應(yīng)該不斷努力，尋找這些更好的方法。近些年來，工程材料的選擇已經(jīng)顯得重要。此外，選擇過程應(yīng)該是一個(gè)對(duì)材料的連續(xù)不斷的重新評(píng)價(jià)過程。新材料不斷出現(xiàn)，而一些原有的材料的能夠獲得的數(shù)量可能會(huì)減少。環(huán)境污染、材料的回收利用、工人的健康及安全等方面經(jīng)常會(huì)對(duì)材料選擇附加新的限制條件。為了減輕重量或者節(jié)約能源，可能會(huì)要求使用不同的材料。來自國(guó)內(nèi)和國(guó)際競(jìng)爭(zhēng)、對(duì)產(chǎn)品維修保養(yǎng)方便性要求的提高和顧客的反饋等方面的壓力，都會(huì)促使人們對(duì)材料進(jìn)行重新評(píng)價(jià)。由于材料選用不當(dāng)造成的產(chǎn)品責(zé)任訴訟，已經(jīng)產(chǎn)生了深刻的影響。此外，材料與材料加工之間的相互依賴關(guān)系已經(jīng)被人們認(rèn)識(shí)得更清楚。因此，為了能在合理的成本和確保質(zhì)量的前提下獲得滿意的結(jié)果，設(shè)計(jì)工程師的制造工程師都必須認(rèn)真仔細(xì)地選擇、確定和使用材料。制造任何產(chǎn)品的第一步工作都是設(shè)計(jì)。設(shè)計(jì)通常可以分為幾個(gè)明確的階段：（a）初步設(shè)計(jì)；（ b）功能設(shè)計(jì)；（ c）生產(chǎn)設(shè)計(jì)。在初步設(shè)計(jì)階段，設(shè)計(jì)者著重考慮產(chǎn)品應(yīng)該具有的功能。通常要設(shè)想和考慮幾個(gè)方案，然后決定這種思想是否可行；如果可行，則應(yīng)該對(duì)其中一個(gè)或幾個(gè)方案作進(jìn)一步的改進(jìn)。在此階段，關(guān)于材料選擇唯一要考慮的問題是：是否有性能符合要求的材料可供選擇；如果沒有的話，是否有較大的把握在成本和時(shí)間都允許的限度內(nèi)研制出一種新材料。在功能設(shè)計(jì)和工程設(shè)計(jì)階段，要做出一個(gè)切實(shí)可行的設(shè)計(jì)。在這個(gè)階段要繪制出相當(dāng)完整的圖紙，選擇并確定各種零件的材料。通常要制造出樣機(jī)或者實(shí)物模型，并對(duì)其進(jìn)行試驗(yàn)，評(píng)價(jià)產(chǎn)品的功能、可靠性、外觀和維修保養(yǎng)性等。雖然這種試驗(yàn)可能會(huì)表明，在產(chǎn)品進(jìn)入到生產(chǎn)階段之前，應(yīng)該更換某些材料，但是，絕對(duì)不能將這一點(diǎn)作為不認(rèn)真選擇材料的借口。應(yīng)該結(jié)合產(chǎn)品的功能，認(rèn)真仔細(xì)地考慮產(chǎn)品的外觀、成本和可靠性。一個(gè)很有成就的公司在制造所有的樣機(jī)時(shí)，所選用的材料應(yīng)該和其生產(chǎn)中使用的材料相同，并盡可能使用同樣的制造技術(shù)。這樣對(duì)公司是很有好處的。功能完備的樣機(jī)如果不能根據(jù)預(yù)期的銷售量經(jīng)濟(jì)地制造出來，或者是樣機(jī)與正式生產(chǎn)的裝置在質(zhì)量和可靠性方面有很大不同，則這種樣機(jī)就沒有多大的價(jià)值。設(shè)計(jì)工程師最好能在這一階段完全完成材料的分析、選擇和確定工作，而不是將其留到生產(chǎn)設(shè)計(jì)階段去做。因?yàn)椋谏a(chǎn)設(shè)計(jì)階段材料的更換是由其他人進(jìn)行的，這些人對(duì)產(chǎn)品的所有功能的了解不如設(shè)計(jì)工程師。 在生產(chǎn)設(shè)計(jì)階段中，與材料有關(guān)的主要問題是應(yīng)該把材料完全確定下來，使它們與現(xiàn)有的設(shè)備相適應(yīng)，能夠利用現(xiàn)有設(shè)備經(jīng)濟(jì)地進(jìn)行加工，而且材料的數(shù)量能夠比較容易保證供應(yīng)。在制造過程中，不可避免地會(huì)出現(xiàn)對(duì)使用中的材料做一些更改的情況。經(jīng)驗(yàn)表明，可采用某些便宜材料作為替代品。然而，在大多數(shù)情況下，在進(jìn)行生產(chǎn)以后改換材料要比在開始生產(chǎn)前改換材料所花費(fèi)的代價(jià)要高。在設(shè)計(jì)階段做好材料選擇工作，可以避免多數(shù)這樣的情況。在生產(chǎn)制造開始后出現(xiàn)了可供使用的新材料是更換材料的最常見的原因。當(dāng)然，這些新材料可能降低成本、改進(jìn)產(chǎn)品的性能。但是，必須對(duì)新材料進(jìn)行認(rèn)真的評(píng)價(jià)，以確保其所有性能都滿足要求。應(yīng)當(dāng)記住，新材料的性能和可靠性很少像現(xiàn)有材料那樣為人們所了解。大部分的產(chǎn)品失效和產(chǎn)品責(zé)任事故案件是由于在選用新材料作為替代材料之前，沒有真正了解它們的長(zhǎng)期使用性能而引起的。產(chǎn)品的責(zé)任訴訟迫使設(shè)計(jì)人員和公司在選擇材料時(shí)，采用最好的程序。在材料過程中，五個(gè)最常見的問題為：（a）不了解或者不會(huì)使用關(guān)于材料應(yīng)用方面的最新最好的信息資料；(b)未能預(yù)見和考慮擦黑年品可能的合理用途（如有可能，設(shè)計(jì)人員還應(yīng)進(jìn)一步預(yù)測(cè)和考慮由于產(chǎn)品使用方法不當(dāng)造成的后果。在近年來的許多產(chǎn)品責(zé)任訴訟案件中，由于錯(cuò)誤地使用產(chǎn)品而受到傷害的原告控告生產(chǎn)廠家，并且贏得判決）；(c)所使用的材料的數(shù)據(jù)不全或是有些數(shù)據(jù)不確定，尤其是當(dāng)其長(zhǎng)期性能數(shù)據(jù)是如此的時(shí)候；(d)質(zhì)量控制方法不適當(dāng)和未經(jīng)驗(yàn)證；(e)由一些完全不稱職的人員選擇材料。通過對(duì)上述五個(gè)問題的分析，可以得出這些問題是沒有充分理由存在的結(jié)論。對(duì)這些問題的研究分析可以為避免這些問題的出現(xiàn)指明方向。盡管采用最好的材料選擇方法也不能避免發(fā)生產(chǎn)品責(zé)任訴訟，設(shè)計(jì)人員和工業(yè)界按照適當(dāng)?shù)某绦蜻M(jìn)行材料選擇，可以大大減少訴訟的數(shù)量。從以上的討論可以看出，選擇材料的人們應(yīng)該對(duì)材料的性質(zhì)，特點(diǎn)和加工方法有一個(gè)全面而基本的了解。