Lesson 19 Introduction to machine design 机械专业专业英语教学用书教学教案PPT课件下载推荐.pptx

1、Lesson 19 Introduction to machine design,Machine design is the application of science and technology to devise new or improved products for the purpose of satisfying human needs.It is a vast field of engineering technology which not only concerns itself with the original conception（最初的概念）of the prod

2、uct in terms of its size,shape and construction details,but also considers the various factors involved in the manufacture,marketing and use of the product.,Lesson 19 Introduction to machine design,People who perform the various functions of machine design are typically called designers,or design en

3、gineers.Machine design is basically a creative activity.However,inaddition to being innovative（革新的）,a design engineer must also have a solid background in the areas of mechanical drawing,kinematics,dynamics,materials engineering,strength of materials and manufacturing processes.,Lesson 19 Introducti

4、on to machine design,As stated previously,the purpose of machine design is to produce a product which will serve a need for man.Inventions,discoveries and scientific knowledge by themselves do not necessarily benefit people;#only if they are incorporated into a designed product will a benefit be der

5、ived.It should be recognized,therefore,that a human need must be identified before a particular product is designed.,Lesson 19 Introduction to machine designMachine design should be considered to be an opportunity to use innovative talents to envision a design of a product,to analyze the system and

6、then make sound judgments（合理的判断）on how the product is to be manufactured.It is important to understand the fundamentals of engineering rather than memorize mere facts and equations.There are no facts or equations which alone can be used to provide all the correct decisions required to produce a good

7、 design.On the other hand,any calculations made must be done with the utmost（极度的）care and precision.For example,if a decimal point is misplaced,an otherwise acceptable design may not function.,Lesson 19 Introduction to machine design,Good design require trying new ideas and being willing to take a c

8、ertain amount of risk,knowing that if the new idea does not work the existing method can be reinstated（使复职）.Thus a designer must have patience,since there is no assurance of success for the time and effort expended.Creating a completely new design generally requires that many old and well-establishe

9、d methods be thrust aside（推开）.,Lesson 19 Introduction to machine design,During the beginning stages of design,creativity should be allowed to flourish without a great number of constraints.Even though many impractical ideas may arise,it is usually easy to eliminate them in the early stages of design

10、 before firm details are required by manufacturing.In this way,innovative ideas are not inhibited（抑制）.Quite often,more than one design is developed,up to the point where they can be compared against each other.It is entirely possible that the design which is ultimately accepted will use ideas existi

11、ng in one of the rejected designs that did not show as much overall promise.,Lesson 19 Introduction to machine design,Psychologists frequently talk about trying to fit people to the machines they operate.It is essentially the responsibility of the design engineer to strive to fit machines to people.

12、This is not an easy task,since there is really no average person for which certain operating dimensions andprocedures are optimum（这不是一件容易的工作，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）.,Lesson 19 Introduction to machine design,Another important point which should be recognized is that a design engineer must

13、be able to communicate ideas toother people if they are to be incorporated（一起工作的的）.Initially,the designer must communicate a preliminary（预 备的）design to get management approval.This is usually done by verbal discussions in conjunction with drawing layouts（草 图）and written material.To communicate effec

14、tively,the following questions must be answered:#,Lesson 19 Introduction to machine design,Does the design really serve a human need?#Will it be competitive with existing products of rival companies?#Is it economical to produce?#（4）Can it be readily maintained?#（5）Will it sell and make a profit?#,Le

15、sson 19 Introduction to machine design,Only time will provide the true answers to the preceding questions,but the product should be designed,manufactured and marketed only with initial affirmative answers.The design engineer also must communicate the finalized design to manufacturing through the use

16、 of detail and assembly drawings.,Lesson 19 Introduction to machine design,Quite often,a problem will occur during the manufacturing cycle.It may be that a change is required in the dimensioning or tolerancing of a part so that it can be more readily produced.This falls in the category of engineering changes which must be approved by the design engineer so that the product function will not be adversely affected.,Lesson 19 Introduction to machine design,In other cases,a deficiency in the design may app