1、2022-8-3河南科技大学机电工程学院13.1 Basic concepts nManufacturing means transformation of materials and information into goods for the satisfaction of human needs.n Manufacturing means transformation of materials and information into goods for the satisfaction of human needs.n Process and process course nA pro
2、cess is simply a method or technique by which finished or semi-finished products can be manufactured from raw materials.2022-8-3河南科技大学机电工程学院23.1 Basic concepts n Process and process course nProcess course is one part of production course in which the shape,dimensions and performance of objects to be
3、 machined are directly changed into desired ones.It involves blank manufacturing,machining,heat treatment,assembly etc.n Machining process contains the whole 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
4、the metal cutting methods.2022-8-3河南科技大学机电工程学院33.1 Basic concepts nWorking operation(or Operation)Operation can be defined 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
5、working place(or a definite machine tools).nFour key factors:same operator(s),same workpiece(s),same working place,continuousn The vital sign to distinguish operations is to see whether the operation place(i.e.equipment)has been changed.2022-8-3河南科技大学机电工程学院43.1 Basic concepts Fig.3-1 A shaft with sh
6、oulders Table 3-1 Machining process of the shaft Operation No.Operation name(工序名称)Machine tool(机床)1Facing(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 grindin
7、g(磨外圆)Grinding machine(磨床)Fig.3-1 is a sketch map of a shaft with shoulders.The machining process of the shaft is shown in Tab.3-1.2022-8-3河南科技大学机电工程学院53.1 Basic concepts nWorking step Working step can be defined as the part of the operation completed continuously under the condition that the machin
8、ing surface,cutting tool and cutting variables(including cutting speed,feed)are kept unchanged.nContinuous working step n Compound working step 2022-8-3河南科技大学机电工程学院63.1 Basic concepts nWorking stroke Working stroke is the manufacturing process that is completed by cutting the surface one time with t
9、he same cutting tool and the 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 2022-8-3河南科技大学机电工程学院7nSetting-up In order to achieve satisfying machining effects,a workpiece must be locat
10、ed 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 2022-8-3河南科技大学机电工程学院8nWorking position In order to reduce the m
11、ounting 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 part of machine tool together relative to the cutter
12、 or the fixed part of machine tool is called one working position.3.1 Basic concepts 2022-8-3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nFig.3-5 illustrates an example of a working operation with multi working positions.A rotary table with four positions
13、 is used to fulfill loading/unloading,drilling,core drilling and reaming sequentially in an aggregate drilling machine.3.1 Basic concepts 2022-8-3河南科技大学机电工程学院10Production program and production type have an influencethe production organization and management,layout ofworkshop,processing method,the m
14、anufacturing 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 2022-8-3河南科技大学机电工程学院113.1 Basic concepts nProduction program N of a workpart refers to the production volum
15、e 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)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.20
16、22-8-3河南科技大学机电工程学院123.1 Basic concepts nProduction 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
17、 mass production,that 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 2022-8-3河南科技大学机电工程学院13 Different production types have the different manufacturing processes,machin
18、e tools,toolings 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 meth
19、od No interchangeability，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 m
20、achining 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 measuring tool
21、).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 programmers are needed.Low
22、-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。TypesFeatures2022-8-3河南科技大学机电工程学院143.2 Procedure of process planning nOften there are several manufacturing p
23、lans 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 specified in the forms of document expressed by charts,tables and
24、words.This document is called process rule(also called technological document).nProcess rule is an essential technological document for manufacturing factories or workshops.Its functions can be summarized in the following four aspects.2022-8-3河南科技大学机电工程学院15n(1)Main technological documents used to gu
25、ide 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 process is performed according to these rules,can high production quality and normal production order be guara
26、nteed.n(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 schedule and the calculation of production costs are all completed on the ground of process route.3.2 Procedure o
27、f process planning 2022-8-3河南科技大学机电工程学院16n(3)Important technical reference to build new factory or rebuild former factory.When building or rebuilding factories or workshops,the types and numbers of machine tools required in production,workshop area,and proper operators can be determined according to
28、 the process rule.n(4)Main means used to store and exchange technology.Often,the technical level of an enterprise can be reflected partly by 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 advan
29、ced process technologies with factories of the same industry.3.2 Procedure of process planning 2022-8-3河南科技大学机电工程学院17nProcess 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,inspec
30、tion sheet and so on.Generally,process procedure sheet is a kind of simplified technological file 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 o
31、f process planning 2022-8-3河南科技大学机电工程学院18 nIn 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 r
32、elated to this part and/or product as detail as possible.These materials are listed as follow:n(1)Part drawings and assembly drawing of the product.n(2)Production program and production type.n(3)Quality standards used to inspect products.n(4)Blank production situation.n(5)Production condition of the
33、 factory.n(6)Development of current production technology at home and abroad.3.2 Procedure of process planning 2022-8-3河南科技大学机电工程学院19 n(1)Technological analysis of the workpart to be machined.The primary tasks of this step are to analyze the structural manufacturability,technical requirements,produc
34、tion type,and so on.n(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 structural features
35、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.3.2 Procedure of process plan
36、ning 2022-8-3河南科技大学机电工程学院20n(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,determining the degree of process concentration and process dispersal
37、,arranging heat treatment,inspection and other auxiliary operations.n(4)Determining equipment and tooling needed in each working operation.Tooling is the general name of cutting tools,fixtures,measuring instruments and auxiliary tools.The production type,the structural features and the requisite mac
38、hining 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 2022-8-3河南科技大学机电工程学院21n(5)Specifying technical requirements and inspection means us
39、ed in the key operations.n(6)Determining machining allowances,calculating operation dimensions and their tolerances for each operation.n(7)Specifying cutting variables for each operation.n(8)Identifying time standards.n(9)Performing technical and economic analysis.n(10)Filling in process sheets and
40、other documents that would be used by operators.3.2 Procedure of process planning 2022-8-3河南科技大学机电工程学院223.3 Selection of location datum Points,lines,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
41、and used situation,datums can be classified into design datum and process datum.n1.Design datum nDesign datum refers to the points,lines,or surfaces that are used as references by designers to mark dimensions and relative positions of other graphic elements in engineering drawings.In other words,des
42、ign datum is the starting position used to label the dimensions of workpiece.Fig.3.6 shows a drawing of a spur gear.2022-8-3河南科技大学机电工程学院23nThe 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 i
43、s the design datum of the surface B and C since the positions of B and C are determined by the surface A.3.3 Selection of location datumFig.3-6 Design datum 2022-8-3河南科技大学机电工程学院24n2.Process datum nDatum used in the machining or assembly process are called process datum.According to the function of p
44、rocess datum,process datum can be further divided into operation datum,location datum,measuring datum and assembly datum.n(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 dimen
45、sions marked on operation drawing are referred to as operation dimensions.3.3 Selection of location datum2022-8-3河南科技大学机电工程学院25nAs 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
46、 a),and the surface B is the operation datum in Fig.3.7 b).3.3 Selection of location datum Fig.3-7 Operation datum2022-8-3河南科技大学机电工程学院26n2.Process datum n(2)Location datum.The datum used to de-termine the correct position of workpiece on machine tool or fixture is called location datum.For example,w
47、hen 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 datum2022-8-3河南科技大学机电工程学院27请在这里添加章节标题nFig.3.8 i
48、llustrates how the location sign“”is used,where the apex of the sign“”is attached directly to the location surface.Fig.3-8 Location datum 2022-8-3河南科技大学机电工程学院28nLocation datum can be further classified into rough datum and finish datum.The location surface which has not been machined is called rough
49、 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 datum.Finish datums are also divided into major finish datum and auxiliary finish datum.The major fin
50、ish 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 instance,the center holes at the ends of shaft are the auxiliary finish datum.3.3 Selection of location datum20
