机械制造技术基础双语第3章课件

1、2022/7/24河南科技大学机电工程学院13.1 Basic concepts 3.1.1 Production course and process course of machine DefinitionProduction courseManufacturing means transformation of materials and information into goods for the satisfaction of human needs. Manufacturing means transformation of materials and information in

2、to goods for the satisfaction of human needs. Process and process course A process is simply a method or technique by which finished or semi-finished products can be manufactured from raw materials. 2022/7/24河南科技大学机电工程学院23.1 Basic concepts 3.1.1 Production course and process course of machine Defini

3、tion Process and process course Process course is one part of production course in which the shape, dimensions and performance of objects to be machined are directly changed into desired ones. It involves blank manufacturing, machining, heat treatment, assembly etc. Machining process contains the wh

4、ole process through which the dimensions, shape and surface quality of a blank are directly changed into a qualified part step by step by means of the metal cutting methods. 2022/7/24河南科技大学机电工程学院33.1 Basic concepts 3.1.2 Elements of process course Working operation (or Operation) Operation can be de

5、fined as a part of process course which is completed continuously by one operator (or a group of operators) who machine one workpiece (or several workpieces simultaneously) on a definite working place (or a definite machine tools). Four key factors: same operator(s), same workpiece(s), same working

6、place, continuous The vital sign to distinguish operations is to see whether the operation place (i.e. equipment) has been changed. 2022/7/24河南科技大学机电工程学院43.1 Basic concepts Fig.3-1 A shaft with shoulders Table 3-1 Machining process of the shaft Operation No. Operation name(工序名称)Machine tool (机床)1Fac

7、ing(车端面) , center drilling(钻中心孔)Engine lathe(车床)2Cylindrical Turning(车外圆), grooving(车槽), chamfering(倒角)Engine lathe(车床)3Keyway milling(铣键槽), deburring(去毛刺)Vertical milling machine(铣床)4Cylindrical grinding(磨外圆)Grinding machine(磨床) Fig.3-1 is a sketch map of a shaft with shoulders. The machining proce

8、ss of the shaft is shown in Tab.3-1.2022/7/24河南科技大学机电工程学院53.1 Basic concepts 3.1.2 Elements of process course Working step Working step can be defined as the part of the operation completed continuously under the condition that the machining surface, cutting tool and cutting variables (including cut

9、ting speed, feed ) are kept unchanged. Continuous working step Compound working step 2022/7/24河南科技大学机电工程学院63.1 Basic concepts 3.1.2 Elements of process course Working stroke Working stroke is the manufacturing process that is completed by cutting the surface one time with the same cutting tool and t

10、he same cutting parameters. Fig. 3-4 is a schematic diagram which shows the relationship between working step and working stroke. Fig.3-4 Working step and working stroke 2022/7/24河南科技大学机电工程学院73.1.2 Elements of process course Setting-up In order to achieve satisfying machining effects, a workpiece mu

11、st be located and clamped in a fixture before it is machined. The process to locate and clamp the workpiece on fixture or worktable is called setting-up. A working operation may have either single setting-up or several setting-ups. 3.1 Basic concepts 2022/7/24河南科技大学机电工程学院83.1.2 Elements of process c

12、ourse Working position In order to reduce the mounting times, rotary table, or rotary fixture, or movable fixture is often used to make workpiece occupy different positions successively in one setting-up. After the workpiece is clamped, each position occupied by workpiece and fixture or the movable

13、part of machine tool together relative to the cutter or the fixed part of machine tool is called one working position. 3.1 Basic concepts 2022/7/24河南科技大学机电工程学院91-Loading/unloading workpiece装卸工件；2-Drilling钻孔；3-Core drilling扩孔；4-Reaming铰孔Fig.3-5 illustrates an example of a working operation with multi

14、 working positions. A rotary table with four positions is used to fulfill loading/unloading, drilling, core drilling and reaming sequentially in an aggregate drilling machine. 3.1 Basic concepts 2022/7/24河南科技大学机电工程学院103.1.3 Production program and production typeProduction program and production type

15、 have an influencethe production organization and management, layout ofworkshop, processing method, the manufacturing equipmentsto be used and the technical requirements for operators. So itis necessary to learn something about the two terminologiesbefore set out to make process.3.1 Basic concepts 2

16、022/7/24河南科技大学机电工程学院113.1 Basic concepts 3.1.3 Production program and production type Production programProduction program N of a workpart refers to the production volume of a product per year, including spare pieces and rejected products, which can be calculated by Eq. (3-1). N = Q n(1+)(1+) (3-1)

17、where Q is the annual yield of a product; n is the number of the parts used in one product; is the average percentage of spare parts, is the average percentage of rejected parts. 2022/7/24河南科技大学机电工程学院123.1 Basic concepts 3.1.3 Production program and production type Production type and its technologi

18、cal feature Production type means the specialized classification of the production capacity of an enterprise. Based on the production program, size and complexity of a product, the production of an enterprise can be generally classified as job production, batch production, and mass production, that

19、is, three different kinds of production types. 1) Job production Low volume of production 2) Batch production Middle volume of production 3) Mass production Large volume of production 2022/7/24河南科技大学机电工程学院13 Different production types have the different manufacturing processes, machine tools, toolin

20、gs and production organization modes. The characteristics of different production types are summarized in Tab.3-2. 3.1 Basic concepts Table 3-2 Main technological characteristics of three production types Job productionBatch productionMass productionInterchangeability and assembling method No interc

21、hangeability，individual fitting method. Interchangeable for most parts.Full interchangeability, interchangeable assembly. Blank type & machining allowanceManual modeling for casting, free forgings, low precision, large machining allowance. Die casting, or die forging, moderate blank precision and ma

22、chining allowance. Blank manufacturing with high accuracy and high efficiency, low machining allowance. Equipment General purpose machine tool part of CNC machine. CNC machine, FMC, part of special purpose machine tools. Dedicated transfer line, FNL, or CNC machines. Tooling (fixture, cutter and mea

23、suring tool). Standard attachments, cutters and measuring tools.Fixtures are widely used, special-purpose cutters and measuring tools. Fixtures, cutters and measuring tools with high efficiency are widely used. Requirements for worker. Skilled workers are needed. Moderate skilled workers and program

24、mers are needed. Low-skill operators, but skilled maintenance workers are needed. Process ruleSimple process procedure sheet. process sheet, and operation sheets for key operations.Detailed process rule is provided。TypesFeatures2022/7/24河南科技大学机电工程学院143.2 Procedure of process planning 3.2.1 Process r

25、ule and its functionsOften there are several manufacturing plans which can meet the design requirements of a product or a component. But there must be a relative optimal manufacturing plan under a specific production condition. The relevant contents to the manufacturing process of a product are spec

26、ified in the forms of document expressed by charts, tables and words. This document is called process rule (also called technological document). Process rule is an essential technological document for manufacturing factories or workshops. Its functions can be summarized in the following four aspects

27、. 2022/7/24河南科技大学机电工程学院153.2.1 Process rule and its functions(1) Main technological documents used to guide production course. As a rule, process rule is formulated on the basis of process theories, necessary process tests and summarization of practical experiences. Only when the whole production pr

28、ocess is performed according to these rules, can high production quality and normal production order be guaranteed. (2) Basis of production preparation. The supply of raw materials or blanks, design and manufacturing of process equipment, the purchase of new machine tools, the planning of production

29、 schedule and the calculation of production costs are all completed on the ground of process route. 3.2 Procedure of process planning 2022/7/24河南科技大学机电工程学院163.2.1 Process rule and its functions(3) Important technical reference to build new factory or rebuild former factory. When building or rebuildi

30、ng factories or workshops, the types and numbers of machine tools required in production, workshop area, and proper operators can be determined according to the process rule. (4) Main means used to store and exchange technology. Often, the technical level of an enterprise can be reflected partly by

31、its process level. As the carrier of process level, process rule is the footstone of the development of an enterprise. It can be used to exchange and spread advanced process technologies with factories of the same industry.3.2 Procedure of process planning 2022/7/24河南科技大学机电工程学院173.2.1 Process rule a

32、nd its functionsProcess rule is composed of a series of technological files. These files are often presented in the form of sheets, such as process procedure sheet, process sheet, operation sheet, inspection sheet and so on. Generally, process procedure sheet is a kind of simplified technological fi

33、le and is often used in job or small volume production. The process sheet is often used in medium volume production. The operation sheet is used in large volume production and mass production. 3.2 Procedure of process planning 2022/7/24河南科技大学机电工程学院183.2.2 Original information required to make out pr

34、ocess rule In most cases, manufacturing process for a given part or product is not unique. The task of process planning is to find the most reasonable process route among those candidate ones. For this reason, process planning technicians must collect original materials related to this part and/or p

35、roduct as detail as possible. These materials are listed as follow: (1) Part drawings and assembly drawing of the product.(2) Production program and production type.(3) Quality standards used to inspect products.(4) Blank production situation.(5) Production condition of the factory.(6) Development o

36、f current production technology at home and abroad. 3.2 Procedure of process planning 2022/7/24河南科技大学机电工程学院193.2.3 Procedure of process planning (1) Technological analysis of the workpart to be machined. The primary tasks of this step are to analyze the structural manufacturability, technical requir

37、ements, production type, and so on.(2) Selection of blank. The types of blanks and their quality have great influence on process planning. Therefore, the fabrication method and the accuracy of blank should be specified based on the function, the production program, the mechanical properties and the

38、structural features of the part before process planning. The common used blank types in manufacturing industry are castings, forgings, sectional materials, welding parts, pressing parts, etc. Also, current production condition of the blank workshop should be taken into account when selecting blank.

39、3.2 Procedure of process planning 2022/7/24河南科技大学机电工程学院203.2.3 Procedure of process planning(3) Drawing up process route. This is a critical step in process planning. It includes selecting location datum and processing methods, dividing machining stages, arranging machining sequence of each surface,

40、 determining the degree of process concentration and process dispersal, arranging heat treatment, inspection and other auxiliary operations.(4) Determining equipment and tooling needed in each working operation. Tooling is the general name of cutting tools, fixtures, measuring instruments and auxili

41、ary tools. The production type, the structural features and the requisite machining quality of the part should be considered in selecting machine tool and tooling. Sometimes, the design task of a special purpose equipment and tooling is put forward if necessary. 3.2 Procedure of process planning 202

42、2/7/24河南科技大学机电工程学院213.2.3 Procedure of process planning(5) Specifying technical requirements and inspection means used in the key operations.(6) Determining machining allowances, calculating operation dimensions and their tolerances for each operation.(7) Specifying cutting variables for each operat

43、ion. (8) Identifying time standards.(9) Performing technical and economic analysis.(10) Filling in process sheets and other documents that would be used by operators. 3.2 Procedure of process planning 2022/7/24河南科技大学机电工程学院223.3 Selection of location datum3.3.1 Datum and its classification Points, li

44、nes, or surfaces used to determine the position of other points, lines or surfaces on the same workpiece are called datum. According to the function of datum and used situation, datums can be classified into design datum and process datum. 1. Design datum Design datum refers to the points, lines, or

45、 surfaces that are used as references by designers to mark dimensions and relative positions of other graphic elements in engineering drawings. In other words, design datum is the starting position used to label the dimensions of workpiece. Fig.3.6 shows a drawing of a spur gear. 2022/7/24河南科技大学机电工程

46、学院233.3.1 Datum and its classificationThe centerline of the gear is the design datum of cylindrical surface with diameter D and D0, and inner cylindrical surface with diameter d, while the end face A is the design datum of the surface B and C since the positions of B and C are determined by the surf

47、ace A. 3.3 Selection of location datumFig.3-6 Design datum 2022/7/24河南科技大学机电工程学院243.3.1 Datum and its classification2.Process datum Datum used in the machining or assembly process are called process datum. According to the function of process datum, process datum can be further divided into operatio

48、n datum, location datum, measuring datum and assembly datum. (1) Operation datum. The datum used in operation drawing or process file to determine the positions of surfaces to be machined in one operation are called operation datum. The dimensions marked on operation drawing are referred to as opera

49、tion dimensions. 3.3 Selection of location datum2022/7/24河南科技大学机电工程学院253.3.1 Datum and its classificationAs shown in Fig.3.7, a hole is to be machined on a sleeve. Both L1 and L2 are called operation dimension for hole drilling, but the surface A is the operation datum in Fig.3.7 a), and the surface

50、 B is the operation datum in Fig.3.7 b). 3.3 Selection of location datum Fig.3-7 Operation datum2022/7/24河南科技大学机电工程学院263.3.1 Datum and its classification2.Process datum (2) Location datum. The datum used to determine the correct position of workpiece on machine tool or fixture is called location dat

51、um. For example, when the gear teeth shown in Fig.3.6 are cut on hobbing machine, the surface A and the hole with diameter d are often the location datum (or location surface). In process files, location surfaces are often indicated with the sign “ ”.3.3 Selection of location datum2022/7/24河南科技大学机电工

52、程学院27请在这里添加章节标题3.3.1 Datum and its classificationFig.3.8 illustrates how the location sign “ ” is used, where the apex of the sign “ ” is attached directly to the location surface.Fig.3-8 Location datum 2022/7/24河南科技大学机电工程学院283.3.1 Datum and its classificationLocation datum can be further classified

53、 into rough datum and finish datum. The location surface which has not been machined is called rough datum surface or rough datum, whereas the location surface which has been machined is called finish datum surface or finish datum. Location datum used in the first machining operation must be a rough

54、 datum. Finish datums are also divided into major finish datum and auxiliary finish datum. The major finish datum is just the functional surface of workpiece, whereas the auxiliary finish datum has not any function in assembly drawing, and is machined specially for the location of workpice. For inst

55、ance, the center holes at the ends of shaft are the auxiliary finish datum. 3.3 Selection of location datum2022/7/24河南科技大学机电工程学院293.3.1 Datum and its classification2.Process datum (3) Measuring datum. The points, lines or surfaces on which the measurement of the position of machined surfaces is base

56、d are called measuring datum. Usually, design datum can be selected as the measuring datum. But when it is inconvenient or impossible for design datum to be used as measuring datum, we should choose other surface existed practically on the workpiece as measuring datum. 3.3 Selection of location datu

57、m2022/7/24河南科技大学机电工程学院303.3.1 Datum and its classificationFor example, the center O of a circle is the design datum of surface A in Fig.3-9 a) and L is a design dimension. But after surface A is machined, point C (lower generatrix of cylindrical surface B) is selected as measuring datum to measure t

58、he dimension L1, as shown in Fig.3-9 b). Fig.3-9 Measuring datum 3.3 Selection of location datum2022/7/24河南科技大学机电工程学院313.3.1 Datum and its classification2.Process datum (4) Assembly datum. The datum used to define the relative position of a part or subassembly in a product in assembling process is c

59、alled assembly datum. Assembly datum is generally consistent with the major design datum of workpart. For example, when a gear is to be coupled with a shaft, the hole of the gear is used as assembly datum. However, if the shaft is to be coupled with a box, the journal of the shaft becomes assembly d

60、atum. When the spindle box is to be installed into a bed, the base surface of the box would act as assembly datum.3.3 Selection of location datum2022/7/24河南科技大学机电工程学院323.3.2 Selection of location datum To select location datum is the first step in drawing up the machining process route. The selectio