外文原文：

Mechanical design

According to user requirements of special mechanical working principle, structure, movement, power and energy transmission, various parts of the material and shape size, lubrication methods for design, analysis and calculation and mechanical design

Translate them into a specific description to be made based on the workingprocess. Mechanical design is an important part of mechanical engineering, machinery is produced in the first step, is to determine the mechanical properties of the main factors. Mechanical design goal is: in various limited conditions (such as materials, processing ability, theory and calculation method of design of the best machinery ), i.e. to make optimization design. Optimization design to consider the many requirements, generally : the best performance, the minimum cost, the minimum size and weight, use the reliability, minimum consumption and the minimum environmental pollution. These requirements are often contradictory, but their relative importance for the mechanical type and use vary. The designer's task is to weigh up one thing against another according to the specific circumstance, take all factors into consideration, make the design of the mechanical optimal comprehensive technical and economic effect. In the past, optimization design depends on the designer's knowledge, experience and vision. As the base of mechanical engineering theory and the value engineering, systems analysis and other new disciplines in the development, manufacture and use of technical economy the accumulation of data, as well as computer application, optimize gradually abandon the subjective judgment and rely on scientific computing. In the service of different industry different machinery, application of different working principle, requires a different function and characteristic. Industrial machinery design, especially the whole and the entire system of mechanical design, must be attached to the relevant industrial technology to form an independent discipline. So the design of agricultural machinery, mining machinery, textile machinery, automobile design design design, ship design, design of pump, compressor, turbine design, engine design, machine design, professional mechanical design branch. However, many of these professional design and many common technologies, such as the analysis and synthesis of mechanisms, and can analysis and calculation, engineering materials, strength of materials, transmission, lubrication, sealing, and standardization, reliability, process optimization. In addition, there are research design work of the inherent law and the rationality of the design methods and steps of the new design methodology. The mechanical design of the general technology and rational design methodology brings together into an independent, comprehensive mechanical design is mechanical engineering practice and education workers are working hard.

A machine quality basically depends on the quality of design. Manufacturing process on the quality of the machine the role, essence is to realize the design required quality. Therefore, the machine's design phase is the key decision machine. Mechanical design

The discussion of the design process refers only to the narrow sense of technical design process. It is a creative process, but also a try best to use the successful experience of the job. Be well to the inheritance and innovation to combine, in order to design a high quality machine. As a complete machine, it is a complex system. To improve the design quality, must have a scientific design program. Although it is not possible for a list of valid in all cases only program, but, according to the long term experience, a machine design process basically can be as shown in Table 2- 1. 1for each stage are respectively brief description. ( a ) the planning stage in accordance with the production or life presents the need to design new machines, the planning stage is a stage of preparation. At this time, to design the machines only a vague notion. In the planning stages, to deal with the design of the machine needs to do the full investigation and analysis. Through the analysis, to further clarify the machine the function that should have, and for the subsequent decision proposed by the environmental, economic, and processing time and other aspects of the identified constraints. Based on this, clearly written assignments on the overall requirements and design details, finally forms the design task book, as the stage summary. The design task book generally should include : the machine function, economy and environmental protection estimates, manufacturing requirements with respect to roughly estimate, basic requirements, and completed the task of design is expected duration. At this point, the requirements and conditions in general can only give a reasonable range, but not the exact number. For example can be used must meet the requirements, minimum requirements, hoping to reach the requirements shall be identified.

( two) scheme design stage the stage of design play a key role. In this one phase is also fully demonstrated the design work have multiple solutions ( solution ) features. The function of the machine analysis, is to design of the proposed machine function must meet the requirements of the minimum requirements, and hope to achieve the requirements of comprehensive analysis, namely, these functions can be realized, a number of features with no contradiction, can substitute each other. Finally determines the functional parameters, as the basis for further design. In this step, want appropriate processing need and possibility, the ideal and the reality, development goals and the goals may arise between the contradictory problem. To determine the functional parameters, then propose possible solutions, which is made possible by the plan. Seek solution, according to the driving part, a transmission part and execution part are respectively discussed. , more commonly used method is to first from the operative portion began to discuss. Discuss machine execution part, the first is about the working principle of selection. For example, the design and manufacture of screw machine, its working principle can be used in the cylindrical blank by turning thread approach, can also be used in the cylindrical blanks with thread rolling die rolling thread approach. It puts forward two kinds of different working principles. Its working principle is different, of course, the design of the machine will fundamentally different. Special is to be stressed, must continue to research and development of new working principle. It is an important way of the development of design technology. According to the different working principle, can develop a variety of different execution mechanism scheme. For example, only the thread cutting, can use the workpiece can only rotate and tool for linear motion to the cutting thread ( such as in lathe cutting thread ), also can make the workpiece is fixed and the cutter to rotate and move to the cutting thread ( such as die processing thread ). That is to say, even for the same kind of work principle, also may have several different structural schemes. The original motivation scheme also can have multiple choice. Because of the power supply of the universality and the electric drive technology development, it can be said that the vast majority of the fixed mechanical is preferred choice as prime mover part of motor. The original motivation for transport, the main thermal engineering machinery and agricultural machinery. Even with the motor as the motive, there are both AC and DC selection, high speed and low speed selection. The transmission part of the scheme is more complicated and diverse. For the same transmission task, by a variety of institutions and different body combination to complete. Therefore, if the prime mover Part IV, said the number of possible schemes, N2and N3respectively representing the transmission part and the execution part number of possible schemes, then the machine the overall number of possible schemes of Ni x N2x N3. The above is only on the machine is composed of three main parts to discuss the. Sometimes, also considering the configuration assistant system, in this regard, books no longer discuss. In so many programmes, technically feasible only a few. On the several feasible solutions, from technology and economy and environmental protection and other aspects of a comprehensive evaluation. Evaluation of the method are many, now with economic evaluation for example omitted description. According to the economic evaluation, it is necessary to take into account the design and manufacture of economy, should cost taken into account when using economy. If the machine structure is more complex, its design and manufacture cost is relatively increased, but its function will be more complete, productivity is higher, so the use of economy is also good. In turn, the structure is relatively simple, the function is not complete machinery, design and manufacturing cost is less, but the use of cost will increase. Evaluation of structural scheme design and manufacturing economy, can also be used to represent the cost of unit efficiency. For example, the unit output power cost, unit cost. Machine evaluation, but also on the machine reliability analysis, the reliability as an evaluation index. From the point of view of reliability, the blind pursuit of complex structure is often not wise. Generally speaking, the system is more complex, then the system reliability is lower. In order to improve the reliability of complex systems, it is necessary to increase the parallel system, which will inevitably increase the cost of the machine. The environmental protection is also design must be carefully considered important aspects. Have a bad effect on the environment of the technical scheme, must detailed analysis, and puts forward the technical maturity of the solution. Through the evaluation, the final decision, according to determine a next step technology design of the schematic diagram or kinematic diagram of mechanism. In the program design phase, to correctly handle the relationship between reference and innovation. Similar machines ought to draw lessons from the successful precedent, originally weak and inconsistent with the current task demands of the part should be improved or changed. We should not only actively innovation, against conservative and copy the original design, but also against a novelty and reasonable original experience abandoned the two wrong tendencies.

( three) the technical design stage design goal was to generate assembly sketches and assembly sketches. The sketch design identified the components and parts of the form and basic size, including connections between components, spare, parts of the form and basic size. The final drawing parts drawing, parts and assembly drawings and assembly drawings. In order to determine the main parts of the basic size, must do the following:1) the kinematic design of machines. According to determine the structure scheme, determine the driver parameters ( power, speed, linear speed etc. ). Then do the kinematics calculation, thereby determining the motion components of movement parameters ( speed, velocity, acceleration ). 2) the machine dynamics calculation. Combined with the structure and motion parameters, calculation of the main part of the load size and characteristics. The calculated load, the part is designed, which is applied to parts of the nominal ( or nominal ) load. 3) parts of the working capability design. The known major parts by the nominal load size and characteristics, can be zero, parts of the preliminary design. The designs are based on the ability to work standards, should be zero, parts of the general failure situation, job characteristics, environmental conditions and reasonably develop, generally have the strength, stiffness, vibration, life criterion. Through calculation and comparison, then decided to spare, parts of the basic size. 4) assembly sketches and general assembly sketch design. According to the main components, the basic size, design a component assembly sketches and assembly sketches. The sketch of all parts of the shape and size of the structured design. In this step, need good coordination among the various parts of the structure and size, to consider a comprehensive design of zero, parts of the process of the structure, so that all the parts have the most reasonable configuration. 5) the main parts of the check. There are some parts, in the above third ) step due to the specific structure of undetermined, difficult to conduct detailed work capacity calculation, we can only do a preliminary calculation and design. In the draw assembly design and assembly sketches, all parts of the structure and size are known, the mutually abutting the relations between components also known as. Only then, can be more accurately determined action on the part of load, decisions affecting parts working ability detail factor. Only on this condition, it can and must be for something important or shape and stress condition of complex parts for accurate calculation of. According to the check results, repeatedly modify parts of the structure and size, until satisfied. In the technical design of the various steps in, nearly thirty or forty years with the development of the optimization design technology, more and more shows it can make the selection of structural parameters to achieve the best capacity. Some new numerical method, such as finite element method, can make previously difficult to quantitative calculation problems in obtaining excellent approximation calculation results. For a few very important, the structure is complex and expensive parts, where necessary, must use the model test method to the design, namely according to the preliminary design drawings to create a model, through the experiment, to find out the weak parts of the structure or the redundant section size, thus enhance or reduce the modification to the original design, finally achieving the perfect degree. Mechanical reliability theory for the technical design stage, according to the viewpoint of reliability design of zero, parts of structure and its parameters to make it meet the requirement of reliability evaluation, put forward the improvement design is proposed, which can further improve the quality of machine design. These new design methods and concepts, shall, should be applied in the design and promotion, make get corresponding development. Sketch design completed, according to the sketch has identified parts of basic size, design parts drawing. At this time, there are still a large number of parts structure details to be examined and determined. Design work plan, full consideration should be given to the processing of parts and assembly process, parts during machining process and processing after completion of the inspection requirements and implementation methods. Some details of the arrangement if the parts work ability was worth considering influence, must go back to check the work ability. Finally draw out in addition to the standard outside of all parts of the map. According to the final shape of the parts of the structure and size, to draw the part and assembly drawings and assembly drawings. Through this work, can check out the detail drawings may be hidden in the size and structural errors. People regard this work popularly called paper assembly.

( four) the preparation of technical documents phase technology file types, commonly used in the machine design brochures, manuals, and other standard parts list. Design calculation specification, should include the scheme selection and technical design all the conclusions of the content. Preparation for users of machine instructions, should introduce the users machine performance parameters, operation methods, daily maintenance and simple repair method, spare parts catalog. Other technical documents, such as inspection single, purchased parts list, acceptance, as needed and not be compiled. ( five) the computer application in mechanical design with the development of computer technology, the computer in the mechanical design has been increasingly widely used, and there have been many efficient design, analysis software. It can be used in the design phase of projects, can be of different includes large and complex project structural strength, stiffness and dynamic characteristics of precision analysis. At the same time, also in the computer to build virtual prototype, using virtual prototype simulation to verify the design, which realizes the design phase fully assess the feasibility of the design. Can say, the computer technology in machinery design promotion has already changed mechanical design process, it enhances the design quality and efficiency advantages is difficult to estimate. The above briefly introduced the machine design program. Broadly speaking, in the machine manufacture process, appear likely at any time due to technical reasons for modifying the design condition. If you want to modify, should follow certain procedures. Machine factory, should have planned to carry out investigation; in addition, users in the use of the process will also give the design or manufacture sector feedback problems. Design department according to these information, through the analysis, it is also possible for the original design was modified, even remodel. These work, although generalized also belong to design program components, but belongs to another level of problems, this book will not discuss its specific content. But as design worker, should have a strong sense of social responsibility, to my vision extends into the manufacture, use and waste utilization of total process, repeated constantly improve the design, in order to make the quality of the machine to continue to improve, to better meet the needs of production and life

At the beginning of the design before, must make the design task. When the design task is more complex, using three general stages of design, the preliminary design, technical design and working drawing design; when the task is relatively simple, such as the simple mechanical model design, general machinery inherited design or variant design, it will start a design to achieve technical design depth, after review, modification and approval to do working drawing design, and become two stage design. In the three stage design in the preliminary design stage, design of the main steps of : determining the working principle and basic structure, motion design, main spare parts, drawing design, preliminary master plan, the preliminary design review. In the design phase, the main steps are: according to the review comments to modify the design, design of all parts, drawing the new general plan, technical design review. In working drawing design stage, according to the review comments to modify the design, draw all the working drawings and make all technical documents. For the mass or mass production of products, but also shape design. In the design of each step, may be found in the previous step some decided not reasonable, it need to fold back in front of that step, modify the irrational decisions, redo the subsequent design work. 1, making design task it is the preparatory work of the design. Design task is based on the user orders, the market needs and the new research results. Design departments application technology and market information, to be listed options, comparing its advantages and disadvantages, and business departments and users together, formulates the reasonable design target. The new design is particularly important. The goal of the task error will be caused serious damage to the economy, even with the overall failure. 2, determine the working principle and basic structure types such as design task did not make specific provision, designed the first step is to determine the overall program, that is determined by the application of the working principle and the structure types. Such as the design of high power marine diesel engine, the first to determine the two stroke, double action, crosshead, low-speed diesel engine, or by four stroke, single function, medium speed diesel engine. Another example is designed for crushing rock crushing machinery, we must first determine the using extrusion and bending as the main role of the jaw crusher or gyratory crusher, or used to shock as the main role of the single rotor or double rotor impact crusher. 3, exercise design scheme is determined, then the need to apply the mechanism knowledge, choose appropriate institutions in order to obtain the desired motion scheme. The above mentioned jaw crusher on the movable jaw plate to swing into the crushing chamber rock by extrusion, bending and splitting the role and broken, and the swing jaw plate can adopt a double elbow board mechanism of simple swinging, or using a single elbow board mechanism of complex oscillation. In the new design, may need to be integrated with a new mechanism to obtain the required movement, this is often a difficult job. Therefore, designers commonly applied as far as possible the existing and mature mechanism is proposed for sports program. 4, structure design and draw the preliminary general motion design, designers began to carry on the structural design, calculation of the main part of the force, strength, shape, size and weight, and the mapping of the main components, sketch. Then if found out that selection of structure is not feasible, we must adjust or modify structure. At the same time also should be considered a possible cause overheating, excessive wear or vibration part. In this step, the designer through sketching will find each part of the shape, size, such as the proportion of contradiction. In order to enhance or improve certain aspects, may weaken or deterioration on the other hand. Then we must weigh up one thing against another, coordination, in order to achieve the best effect. Sketch by repeatedly revise that initial satisfaction, will be able to draw the preliminary master plan and estimated cost. A preliminary layout strictly according to scale, selection of sufficient view and section. 5, preliminary review of the initial layout drawing, the need to please the type of machinery has experience in the design, manufacture and use of personnel as well as the user or commissioned to design the delegate of the unit to conduct a preliminary examination. A review of results such as that is not designed ( such as weight, volume big, cost is too high, the reliability of structure is the doubt ), shall be to exercise design, and even to other working principle and basic structure. In most cases, to take certain measures to improve design. 6, technology design according to the preliminary examination opinions, to modify the design, and the mapping of all parts and components. On the main parts and components for accurate stress analysis, according to the analysis results of modified parts of the shape, size and other details, and the provisions of material and heat treatment. Determine the machining accuracy of the parts and components and assembly of the assembly conditions. Complete lubrication design, electrical design ( drive and control ). Redraw the map, some important and production machinery can sometimes produce model. Will complete the technical design submitted second review 7, draw working drawings according to second review comments made last modified, can draw formal part drawing, assembly drawing and assembly drawing, writing a parts list, wearing parts list, use the guide and other technical documents. Design responsible person should pay attention to coordinate the parts between the size, check the coupling between tolerance, review some parts of the strength and stiffness. Complete the parts after the start to check the drawings, it is very important work. After careful proofreading to ensure smooth processing assembly drawings. The most reliable method of proofreading is based on drawing good parts drawing heavy draw a general assembly drawing, all contradictions will be shown. In the detail drawing but also the need for two tasks: one is the process of audit, the convenient processing of the parts and the manufacturing cost is reduced the two is the standard audit, so that parts of structure, size, tolerance, heat treatment technology and standard and general parts conform to the standard. 8, trial production and designed for single or small batch production machinery, through the steps to complete the design drawings can be put into production. For batch or lot production machinery, before formal production prototype system to test, function test and identification of, by, then by batch process batch production. In batch production in the problems may also need to design corresponding modification, become available for formal production by using modular design.

The design of mechanical parts with many constraints, design criteria design should meet the constraint condition. 1, technical performance standards technical performance includes the function of products, manufacturing and operation status of all property, refers to the static performance, dynamic performance is also used to refer to. For example, the product can transfer power, efficiency, service life, strength, stiffness, friction resistance, wear resistance, thermal stability, vibration characteristics. Technical performance criterion refers to the relevant technical performance to meet the stipulated requirements. For example, the vibration will generate additional dynamic load and stress, especially when the frequency is close to the mechanical systems or parts of the natural frequency, resonance phenomenon will occur, then the amplitude will increase sharply, may lead to the parts and even whole system rapidly damage. Vibration stability criterion is limiting the mechanical systems or parts of the vibration parameters, such as frequency, amplitude, noise in the provisions of the scope of the permit. And as the machine when the fever may cause thermal stress, thermal strain, even will cause thermal damage. Thermal characteristics of guidelines is to restrict the various related thermal parameters ( such as the thermal stress, thermal strain, temperature rise ) in the specified range. 2, standardization and design of mechanical products related to the main standard generally are: the concept of Standardization: involved in the design process of the terminology, symbols, units of measurement shall be in accordance with the standard; objective form standardization: parts, raw materials, equipment and energy structure, size, performance, should be uniform choice. Methods: standardized operation method, measurement method, test method etc should be according to the relevant provisions. Standardization in the entire design process all behavior, must meet the requirements for standardization. Has been released and the design of mechanical parts related standard, from the scope of application of speaking, can be divided into national standards, industry standards and enterprise standards for three grade. From the use of mandatory, can be divided into must be performed and recommended the use of the two kind. 3: reliability, reliability standards for products or components within the prescribed conditions, the expected life to finish regulation function of theprobability of Reliability criterion refers to design products, components or parts should be able to meet the requirements of the reliability requirements in 4, the safety criterion for safety of machinery parts including: Security: defined in terms of external load and within a specified period of time, such as fracture parts not excessive deformation, excessive wear and without loss of stability and so on. Machine safety: a machine to ensure that the required conditions of trouble, can normally achieve functional requirements. Work safety: refers to the operation personnel protection guarantee the safety of humanand health of body and mind. Environmental security: refers to the machines to the surrounding environment and people do not cause the pollution and harm

Design methodology to design thinking to rational process, so that the design can follow certain logic, so that more designers can make good design. It generally includes the following content: 1, will design the stage finely, so that each stage is rule-based and reasonable thinking activity. In 2,will be successful or good design store design, establishment of database, for future reference in the design or use. In3, design work in the introduction of the concept of value engineering and method of design, the contradiction in the function and cost trade-off, to obtain good results. 4, used in the design of tribology, vibration theory, fracture mechanics, finite element method, optimization design, reliability design system engineering ergonomics and other emerging disciplines of knowledge, improve the scientific design, reduce blindness. In 5, will expand the scope of design work, extended forward to the market forecast, extends to after sale service. The application of computer aided design in order to reduce the amount of labor, improve design speed and quality of design.

译文：

机械设计

机械设计是机械工程的重要组成部分，是机械生产的第一步，是决定机械性能的最主要的因素。机械设计的努力目标是：在各种限定的条件(如材料、加工能力、理论知识和计算手段等)下设计出最好的机械，即做出优化设计。优化设计需要综合地考虑许多要求，一般有：最好工作性能、最低制造成本、最小尺寸和重量、使用中最可靠性、最低消耗和最少环境污染。这些要求常是互相矛盾的，而且它们之间的相对重要性因机械种类和用途的不同而异。设计者的任务是按具体情况权衡轻重，统筹兼顾，使设计的机械有最优的综合技术经济效果。过去，设计的优化主要依靠设计者的知识、经验和远见。随着机械工程基础理论和价值工程、系统分析等新学科的发展，制造和使用的技术经济数据资料的积累,以及计算机的推广应用,优化逐渐舍弃主观判断而依靠科学计算。

服务于不同产业的不同机械，应用不同的工作原理，要求不同的功能和特性。各产业机械的设计，特别是整体和整系统的机械设计，须依附于各有关的产业技术而难于形成独立的学科。因此出现了农业机械设计、矿山机械设计、纺织机械设计、汽车设计、船舶设计、泵设计、压缩机设计、汽轮机设计、内燃机设计、机床设计等专业性的机械设计分支学科。但是，这许多专业设计又有许多共性技术，例如机构分析和综合、力与能的分析和计算、工程材料学、材料强度学、传动、润滑、密封，以及标准化、可靠性、工艺性、优化等。此外，还有研究设计工作的内在规律和设计的合理步骤和方法的新兴的设计方法学。将机械设计的共性技术与理性化的设计方法学汇集成为一门独立的、综合性的机械设计学科是机械工程实践和教育工作者正在努力的工作。

机械设计可分为新型设计、继承设计和变型设计3类。

1、新型设计应用成熟的科学技术或经过实验证明是可行的新技术，设计过去没有过的新型机械。

2、继承设计根据使用经验和技术发展对已有的机械进行设计更新，以提高其性能、降低其制造成本或减少其运用费用。

3、变型设计为适应新的需要对已有的机械作部分的修改或增删而发展出不同于标准型的变型产品。

机械设计主要过程

1根据用户订货、市场需要和新科研成果制定设计任务。

2、初步设计。包括确定机械的工作原理和基本结构形式，进行运动设计、结构设计并绘制初步总图以及初步审查。

3、技术设计。包括修改设计（根据初审意见）、绘制全部零部件和新的总图以及第二次审查。

4、工作图设计。包括最后的修改（根据二审意见）、绘制全部工作图（如零件图、部件装配图和总装配图等）、制定全部技术文件（如零件表、易损件清单、使用说明等）。

5、定型设计。用于成批或大量生产的机械。对于某些设计任务比较简单（如简单机械的新型设计、一般机械的继承设计或变型设计等）的机械设计可省去初步设计程序。

所讨论的设计过程仅指狭义的技术性的设计过程。它是一个创造性的工作过程，同时也是一个尽可能多地利用已有的成功经验的工作。要很好地把继承与创新结合起来，才能设计出高质量的机器。作为一部完整的机器，它是一个复杂的系统。要提高设计质量，必须有一个科学的设计程序。虽然不可能列出一个在任何情况下都有效的惟一程序，但是，根据人们设计。

（一）计划阶段

在根据生产或生活的需要提出所要设计的新机器后，计划阶段只是一个预备阶段。此时，对所要设计的机器仅有一个模糊的概念。

在计划阶段中，应对所设计的机器的需求情况做充分的调查研究和分析。通过分析，进一步明确机器所应具有的功能，并为以后的决策提出由环境、经济、加工以及时限等各方面所确定的约束条件。在此基础上，明确地写出设计任务的全面要求及细节，最后形成设计任务书，作为本阶段的总结。设计任务书大体上应包括：机器的功能，经济性及环保性的估计，制造要求方面的大致估计，基本使用要求，以及完成设计任务的预计期限等。此时，对这些要求及条件一般也只能给出一个合理的范围，而不是准确的数字。例如可以用必须达到的要求、最低要求、希望达到的要求等方式予以确定。

（二）方案设计阶段

本阶段对设计的成败起关键的作用。在这一阶段中也充分地表现出设计工作有多个解（方案）的特点。

机器的功能分析，就是要对设计任务书提出的机器功能中必须达到的要求、最低要求及希望达到的要求进行综合分析，即这些功能能否实现，多项功能间有无矛盾，相互间能否替代等。最后确定出功能参数，作为进一步设计的依据。在这一步骤中，要恰当处理需要与可能、理想与现实、发展目标与当前目标等之间可能产生的矛盾问题。

确定出功能参数后，即可提出可能的解决办法，亦即提出可能采用的方案。寻求方案时，可按原动部分、传动部分及执行部分分别进行讨论。，较为常用的办法是先从执行部分开始讨论。

讨论机器的执行部分时，首先是关于工作原理的选择问题。例如，设计制造螺钉的机器时，其工作原理既可采用在圆柱形毛坯上用车刀车削螺纹的办法，也可采用在圆柱形毛坯上用滚丝模滚压螺纹的办法。这就提出了两种不同的工作原理。工作原理不同，当然所设计出的机器就会根本不同。特别应当强调的是，必须不断地研究和发展新的工作原理。这是设计技术发展的重要途径。

根据不同的工作原理，可以拟定多种不同的执行机构的具体方案。例如仅以切削螺纹来说，既可以采用工件只作旋转运动而刀具作直线运动来切削螺纹（如在普通车床上切削螺纹），也可以使工件不动而刀具作转动和移动来切削螺纹（如用板牙加工螺纹）。这就是说，即使对于同一种工作原理，也可能有几种不同的结构方案。

原动机部分的方案当然也可以有多种选择。由于电力供应的普遍性和电力拖动技术的发展，现在可以说绝大多数的固定机械都优先选择电动机作为原动机部分。热力原动机主要用于运输机、工程机械或农业机械。即使是用电动机作为原动机，也还有交流和直流的选择，高转速和低转速的选择等。

传动部分的方案就更为复杂多样了。对于同一传动任务，可以由多种机构及不同机构的组合来完成。因此，如果用Ⅳ，表示原动机部分的可能方案数，N2和N3分别代表传动部分和执行部分的可能方案数，则机器总体的可能方案数Ⅳ为Ni×N2×N3个。

以上仅是就组成机器的三个主要部分讨论的。有时，还须考虑到配置辅助系统，对此，本书不再讨论。

在如此众多的方案中，技术上可行的仅有几个。对这几个可行的方案，要从技术方面和经济及环保等方面进行综合评价。评价的方法很多，现以经济性评价为例略做说明。根据经济性进行评价时，既要考虑到设计及制造时的经济性，也要费用考虑到使用时的经济性。如果机器的结构方案比较复杂，则其设计制造成本就要相对地增大，可是其功能将更为齐全，生产率也较高，故使用经济性也较好。反过来，结构较为简单、功能不够齐全的机器，设计及制造费用虽少，但使用费用却会增多。评价结构方案的设计制造经济性时，还可以用单位功效的成本来表示。例如单位输出功率的成本、单件产品的成本等。

进行机器评价时，还必须对机器的可靠性进行分析，把可靠性作为一项评价的指标。从可靠性的观点来看，盲目地追求复杂的结构往往是不明智的。一般地讲，系统越复杂，则系统的可靠性就越低。为了提高复杂系统的可靠性，就必须增加并联备用系统，而这不可避免地会提高机器的成本。

环境保护也是设计中必须认真考虑的重要方面。对环境造成不良影响的技术方案，必须详细地进行分析，并提出技术上成熟的解决办法。

通过方案评价，最后进行决策，确定一个据以进行下步技术设计的原理图或机构运动简图。

在方案设计阶段，要正确地处理好借鉴与创新的关系。同类机器成功的先例应当借鉴，原先薄弱的环节及不符合现有任务要求的部分应当加以改进或者根本改变。既要积极创新，反对保守和照搬原有设计，也要反对一味求新而把合理的原有经验弃置不用这两种错误倾向。

（三）技术设计阶段

技术设计阶段的目标是产生总装配草图及部件装配草图。通过草图设计确定出各部件及其零件的外形及基本尺寸，包括各部件之间的连接，零、部件的外形及基本尺寸。最后绘制零件的工作图、部件装配图和总装图。

为了确定主要零件的基本尺寸，必须做以下工作：

1)机器的运动学设计。根据确定的结构方案，确定原动件的参数（功率、转速、线速度等）。然后做运动学计算，从而确定各运动构件的运动参数（转速、速度、加速度等）。

2)机器的动力学计算。结合各部分的结构及运动参数，计算各主要零件所受载荷的大小及特性。此时求出的载荷，由于零件尚未设计出来，因而只是作用于零件上的公称（或名义）载荷。

3)零件的工作能力设计。已知主要零件所受的公称载荷的大小和特性，即可做零、部件的初步设计。设计所依据的工作能力准则，须参照零、部件的一般失效情况、工作特性、环境条件等合理地拟定，一般有强度、刚度、振动稳定性、寿命等准则。通过计算或类比，即可决定零、部件的基本尺寸。

4)部件装配草图及总装配草图的设计。根据已定出的主要零、部件的基本尺寸，设计出部件装配草图及总装配草图。草图上需对所有零件的外形及尺寸进行结构化设计。在此步骤中，需要很好地协调各零件的结构及尺寸，全面地考虑所设计的零、部件的结构工艺性，使全部零件有最合理的构形。

5)主要零件的校核。有一些零件，在上述第3）步中由于具体的结构未定，难于进行详细的工作能力计算，所以只能做初步计算及设计。在绘出部件装配草图及总装配草图以后，所有零件的结构及尺寸均为已知，相互邻接的零件之间的关系也为已知。只有在这时，才可以较为精确地定出作用在零件上的载荷，决定影响零件工作能力的各个细节因素。只有在此条件下，才有可能并且必须对一些重要的或者外形及受力情况复杂的零件进行精确的校核计算。根据校核的结果，反复地修改零件的结构及尺寸，直到满意为止。

在技术设计的各个步骤中，近三四十年来发展起来的优化设计技术，越来越显示出它可使结构参数的选择达到最佳的能力。一些新的数值计算方法，如有限元法等，可使以前难以定量计算的问题获得极好的近似定量计算的结果。对于少数非常重要、结构复杂且价格昂贵的零件，在必要时还须用模型试验方法来进行设计，即按初步设计的图纸制造出模型，通过试验，找出结构上的薄弱部位或多余的截面尺寸，据此进行加强或减小来修改原设计，最后达到完善的程度。机械可靠性理论用于技术设计阶段，可以按可靠性的观点对所设计的零、部件结构及其参数做出是否满足可靠性要求的评价，提出改进设计的建议，从而进一步提高机器的设计质量。上述这些新的设计方法和概念，应当在设计中加以应用与推广，使之得到相应的发展。

草图设计完成以后，即可根据草图业已确定的零件基本尺寸，设计零件的工作图。此时，仍有大量的零件结构细节要加以推敲和确定。设计工作图时，要充分考虑到零件的加工和装配工艺性、零件在加工过程中和加工完成后的检验要求和实施方法等。有些细节安排如果对零件的工作能力有值得考虑的影响时，还须返回去重新校核工作能力。最后绘制出除标准件以外的全部零件的工作图。

按最后定型的零件工作图上的结构及尺寸，重新绘制部件装配图及总装配图。通过这一工作，可以检查出零件工作图中可能隐藏的尺寸和结构上的错误。人们把这一工作通俗地称为纸上装配。

（四）技术文件编制阶段

技术文件的种类较多，常用的有机器的设计计算说明书、使用说明书、标准件明细表等。

编制设计计算说明书时，应包括方案选择及技术设计的全部结论性的内容。

编制供用户使用的机器使用说明书时，应向用户介绍机器的性能参数范围、使用操作方法、日常保养及简单的维修方法、备用件的目录等。

其他技术文件，如检验合格单、外购件明细表、验收条件等，视需要与否另行编制。

（五）计算机在机械设计中的应用

随着计算机技术的发展，计算机在机械设计中得到了日益广泛的使用，并出现了许多高效率的设计、分析软件。利用这些软件可以在设计阶段进行多方案的对比，可以对不同的包括大型的和很复杂的方案的结构强度、刚度和动力学特性进行精确的分析。同时，还可以在计算机上构建虚拟样机，利用虚拟样机仿真对设计进行验证，从而实现在设计阶段充分地评估设计的可行性。可以说，计算机技术在机械设计中的推广使用已经并正在改变机械设计的进程，它在提高设计质量和效率方面的优势是难以预估的。

以上简要地介绍了机器的设计程序。广义地讲，在机器的制造过程中，随时都有可能出现由于工艺原因而修改设计的情况。如需修改时，则应遵循一定的审批程序。机器出厂后，应该有计划地进行跟踪调查；另外，用户在使用过程中也会给制造或设计部门反馈出现的问题。设计部门根据这些信息，经过分析，也有可能对原设计进行修改，甚至改型。这些工作，虽然广义上也属设计程序的组成部分，但是属于另一个层次的问题，本书不再讨论其具体的内容。但是作为设计工作者，应当有强烈的社会责任感，要把自己工作的视野延伸到制造、使用乃至报废利用的全过程中去，反复不断地改进设计，才能使机器的质量继续不断地提高，更好地满足生产及生活的需要。

在设计开始之前，先要制定设计任务。当设计任务比较复杂时，一般采用三阶段设计，即初步设计、技术设计和工作图设计；当任务比较简单，如简单机械的新型设计、一般机械的继承设计或变型设计，则一开始就将设计做到技术设计深度，经审查、修改和批准后做工作图设计，而成为两阶段设计。在三阶段设计中的初步设计阶段，设计的主要步骤是：确定工作原理和基本结构型式，运动设计，设计主要零、部件、绘制初步总图,初步设计审查。在技术设计阶段,主要步骤是：根据审查意见修改设计，设计全部零、部件，绘制新的总图，技术设计审查。在工作图设计阶段，根据审查意见修改设计，绘制全部工作图和制定全部技术文件。对于批量或大量生产的产品，还要进行定型设计。

在设计的每个步骤中，都可能发现前面步骤中某些决定不合理，这就需要折回到前面那个步骤，修改不合理的决定，重做随后的设计工作。

1、制定设计任务 这是设计的前期工作。设计任务的根据是用户订货、市场需要和新的科研成果。设计部门应用各种技术和市场情报，拟列可能方案，比较其利弊，与经营部门和用户共同商议，制定合理的设计任务目标。这对新型设计特别重要。任务目标的失误将造成经济上的严重损失，甚至遭到全面失败。

2、确定工作原理和基本结构型式 如设计任务未作明确规定,设计的第一个步骤就是确定总体方案,即确定所要应用的工作原理和与之相应的结构型式。例如设计大功率船用柴油机，首先要确定是用二冲程、双作用、十字头、低速柴油机，还是用四冲程、单作用、中速柴油机。又例如设计用以粗碎岩石的破碎机械，首先要确定是采用以挤压和弯折为主要破碎作用的颚式或旋回式破碎机，或者采用以冲击为主要作用的单转子或双转子冲击式破碎机。

3、运动设计 设计的总体方案确定之后，接着需要运用机构学的知识，选用合适的机构以得到所需的运动方案。上面提到的颚式破碎机依靠其动颚板的摆动使进入破碎腔的岩石受到挤压、弯折和劈裂作用而破碎，而动颚板的摆动则可以采用双肘板机构的简单摆动，或者采用单肘板机构的复杂摆动。在新型设计中，可能会需要综合一个新的机构以得到所要求的运动方案，这常是一个困难的工作。因此，设计者一般尽量应用已有的和成熟的机构所提给的运动方案。

4、结构设计和绘制初步总图 运动设计之后，设计者开始进行结构设计，计算机械各主要零件的受力、强度、形状、尺寸和重量等，并绘制主要零、部件草图。这时如发现原来选用的结构不可行，就必须调整或修改结构。同时还应考虑有无可能产生过热、过度磨损或振动的部位。

在这一步骤中，设计者通过绘制草图会发现各部分的形状、尺寸、比例等方面的矛盾。为了加强或改进某一方面，可能会削弱或恶化另一方面。这时必须权衡轻重，进行协调，以达到最佳综合效果。草图经反复修改认为初步满意后，便可绘制初步总图和估算造价。初步总图严格按比例绘制，选取足够的视图和切面图。

5、初步审查 初步总图绘制后，需要请对该类机械有经验的设计、制造和使用人员以及用户或委托设计单位的代表进行初步审查。审查结果如认为设计不适用(如重量、体积太大,造价太高,对结构的可靠性有怀疑等),则须重新进行运动设计，甚至改用别的工作原理和基本结构型式。多数情况是对设计采取某些改善措施。

6、技术设计 根据初步审查意见,对设计进行修改,并绘制所有的零件和部件图。对主要的零件和部件进行精确的应力分析，按分析结果修正零件的形状、尺寸等细节，并规定材质和热处理。确定零件加工精度以及部件和总装的装配条件。完成润滑设计、电气设计（驱动和控制）。重绘总图，某些重要的和批量生产的机械有时还要制作出模型。将完成的技术设计提交第二次审查。

7、绘制工作图 根据第二次审查的意见作最后的修改后，就可以绘制正式的零件图、部件装配图和总装配图，编写零件表、易损零件清单、使用指南等技术文件。设计负责人应注意协调零件间的尺寸，核对耦合件间的公差配合，复核某些零件的强度和刚度。零件图完成后开始图纸核对，这是非常重要的工作。经过仔细校对的图纸能保证加工后装配顺利。最可靠的校对方法是根据已绘制好的零件图重绘出一张总装配图，所有矛盾之处就会表现出来。在绘制零件图的同时还需要进行两项工作：一是工艺性审核,使零件便于加工并降低制造成本;二是标准审核，使零件结构要素、尺寸、公差配合、热处理技术条件以及标准和通用零件等符合标准的规定。

8、试生产和定型设计 对于单件或小批生产的机械,经过上述步骤完成的设计图纸可以投入正式生产。对于成批或大量生产的机械,在正式生产前要先试制样机,进行功能试验和鉴定，通过后，再按批量生产工艺进行批量试生产。在批量试生产中所出现的问题还可能需要对设计作相应的修改，方成为可供正式生产使用的定型设计。

机械零件的设计具有众多的约束条件，设计准则就是设计所应该满足的约束条件。

1、技术性能准则

技术性能包括产品功能、制造和运行状况在内的一切性能，既指静态性能，也指动态性能。例如，产品所能传递的功率、效率、使用寿命、强度、刚度、抗摩擦、磨损性能、振动稳定性、热特性等。技术性能准则是指相关的技术性能必须达到规定的要求。例如振动会产生额外的动载荷和变应力，尤其是当其频率接近机械系统或零件的固有频率时，将发生共振现象，这时振幅将急剧增大，有可能导至零件甚至整个系统的迅速损坏。振动性稳定准则就是限制机械系统或零件的相关振动参数，如固有频率、振幅、噪声等在规定的允许范围之内。又如机器工作时的发热可能会导致热应力、热应变，甚至会造成热损坏。热特性准则就是限制各种相关的热参数(如热应力、热应变、温升等)在规定范围内。

2、标准化准则

与机械产品设计有关的主要标准大致有：

概念标准化：设计过程中所涉及的名词术语、符号、计量单位等应符合标准；

实物形态标准化：零部件、原材料、设备及能源等的结构形式、尺寸、性能等，都应按统一的规定选用。

方法标准化：操作方法、测量方法、试验方法等都应按相应规定实施。

标准化准则就是在设计的全过程中的所有行为，都要满足上述标准化的要求。现已发布的与机械零件设计有关的标准，从运用范围上来讲，可以分为国家标准、行业标准和企业标准三个等级。从使用强制性来说，可分为必须执行的和推荐使用的两种。

3、可靠性准则

可靠性：产品或零部件在规定的使用条件下，在预期的寿命内能完成规定功能的概率。可靠性准则就是指所设计的产品、部件或零件应能满足规定的可靠性要求。

4、安全性准则

零件安全性：指在规定外载荷和规定时间内零件不发生如断裂、过度变形、过度磨损和不丧失稳定性等等。

整机安全性：指机器保证在规定条件下不出故障，能正常实现总功能的要求。

工作安全性：指对操作人员的保护，保证人身安全和身心健康等等。

环境安全性：指对机器周围的环境和人不造成污染和危害。

设计方法学的目的是将设计思维上升为理性过程，从而使设计能循一定的逻辑进行，使更多的设计人员能作出好的设计。它大致包括以下一些内容：

1、将设计的阶段分得很细，使每一阶段成为有章可循和有理可据的思维活动。

2、将成功的或良好的设计储存起来,建立设计资料库,以供以后设计时参考或采用。

3、在设计工作中引进价值工程的概念和方法，对设计中的矛盾进行功能与成本的权衡,以获得良好的使用效果。

4、在设计中采用摩擦学、振动学、断裂力学、有限元法、可靠性设计、优化设计、系统工程、人类工程学等新兴学科的知识，提高设计的科学性，减少盲目性。

5、将设计工作范围扩大，向前延伸到市场预测，向后延伸到售后服务。运用计算机辅助设计以减少设计劳动量、提高设计速度和设计质量。

机械设计外文文献翻译、中英文翻译、外文翻译