SCIENCE AND TECHNOLOGY ENGLIAH FOR MECHANICAL ENGINEERING LESSON TWO MACHINING ACCURACY Product quality is always a matter of prime importance in manufacturing. It should be given parameter the highest priority in process planning. The 参数,参量 quality of a machined part can be expressed in coordination geometrical parameters( dimension, shape,相互位置 coordination and surface finish, etc. ), physical surface finish parameters (electrical conductivity, thermal 表面光洁度 conductivity, magnetic conductivity, etc.) chemical parameters(corrosion resistance. etc. and mechanical parameters(strength, hardness, etc.). The requirements of these parameters of a part are determined by the designer, according to the condition under which the product is to function.(c)
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING LESSON TWO MACHINING ACCURACY Product quality is always a matter of prime importance in manufacturing. It should be given the highest priority in process planning. The quality of a machined part can be expressed in geometrical parameters (dimension, shape, coordination and surface finish, etc.), physical parameters (electrical conductivity, thermal conductivity, magnetic conductivity, etc.), chemical parameters (corrosion resistance. etc.) and mechanical parameters (strength, hardness, etc.). The requirements of these parameters of a part are determined by the designer, according to the condition under which the product is to function.(c) coordination 相互位置 surface finish 表面光洁度 parameter 参数，参量
SCIENCE AND TECHNOLOGY ENGLIAH FOR MECHANICAL ENGINEERING (cThe degree of coincidence of the real parameters obtained after a part is manufactured, with the parameters defined in part design, represents the manufacturing quality of the part. For the convenience of anal ysis, the degree of coincidence between the real macro-geometrical parameters(dimension, shape and coordination) of a part obtained after machining, and those specified in part design is defined as machining accuracy. The degree of coincidence between the real micro-geometrical parameters(surface finish)and the parameters of the physic-mechanical properties of part surfaces, obtained after machining a part, with those specified in part design is defined as sur face quality Other physical and chemical parameters are involved only in some special cases
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING (c)The degree of coincidence of the real parameters obtained after a part is manufactured, with the parameters defined in part design, represents the manufacturing quality of the part. For the convenience of analysis, the degree of coincidence between the real macro-geometrical parameters (dimension, shape and coordination) of a part obtained after machining, and those specified in part design is defined as machining accuracy. The degree of coincidence between the real micro-geometrical parameters (surface finish) and the parameters of the physic-mechanical properties of part surfaces, obtained after machining a part, with those specified in part design is defined as surface quality. Other physical and chemical parameters are involved only in some special cases
SCIENCE AND TECHNOLOGY ENGLIAH FOR MECHANICAL ENGINEERING Machining accuracy is expressed quantitatively by the magnitude of machining error. Machining error is defined as the difference between the parameters of a machined part and that of a perfect (absolutely accurate) part specified in the part drawing. The machining error varies from part to part even in the same batch of production. Although machining errors al ways exist in machining processes, a part can be considered acceptable, provided the magnitude of machining errors do not 公差 exceed the tolerance limits. The tolerance represents the maximum allowable machining error. The required machining accuracy of a part is specified by the designer, while the machining accuracy requirements of the part in each machining stage are determined in accordance with the needs and accuracy of the process by the process planner
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING Machining accuracy is expressed quantitatively by the magnitude of machining error. Machining error is defined as the difference between the parameters of a machined part and that of a perfect (absolutely accurate) part specified in the part drawing. The machining error varies from part to part even in the same batch of production. Although machining errors always exist in machining processes, a part can be considered acceptable, provided the magnitude of machining errors do not exceed the tolerance limits. The tolerance represents the maximum allowable machining error. The required machining accuracy of a part is specified by the designer, while the machining accuracy requirements of the part in each machining stage are determined in accordance with the needs and accuracy of the process by the process planner. 公 差
SCIENCE AND TECHNOLOGY ENGLIAH FOR MECHANICAL ENGINEERING Parameters of Machining Accuracy and Surface Quality Machining accuracy is associated with a number of macro-geometrical parameters andflatness can be classified as follows 平直度,平面度 1. Machining accuracy of part sur faces roundness Accuracy of dimensions of part sur faces(for‖圆度,球度 example. accuracy of the diameters of cylindrical surfaces, accuracy of the diameters cylindricity of spherical surfaces, and accuracy of the圆柱度 angles at the top of the cones, etc.) Accuracy of shapes of part surfaces(for example, flatness of a plane, roundness, and cylindricity of a cylindrical sur face, etc
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING Parameters of Machining Accuracy and Surface Quality Machining accuracy is associated with a number of macro-geometrical parameters and can be classified as follows: l. Machining accuracy of part surfaces. - Accuracy of dimensions of part surfaces (for example, accuracy of the diameters of cylindrical surfaces, accuracy of the diameters of spherical surfaces, and accuracy of the angles at the top of the cones, etc.). - Accuracy of shapes of part surfaces (for example, flatness of a plane, roundness, and cylindricity of a cylindrical surface, etc.). flatness 平直度,平面度 roundness 圆度，球度 cylindricity 圆柱度
SCIENCE AND TECHNOLOGY ENGLIAH FOR MECHANICAL ENGINEERING 2. Machining accuracy of relative positions between part surfaces Accuracy of dimensions between part parallelism 平行度 surfaces(for example, the distance between two parallel planes or the centers of two holes, etc.) perpendicularity 垂直度 Accuracy of positional relations between part surfaces(for example, the parallelism and surface roughness perpendicularity of two planes or two axes, etc.) 表面粗糙度 The surface quality of a part indicates the surface characteristics of the part. It includes either geometrical or physic-mechanical parameters, which are listed below D Surface roughness 2) Physic-mechanical state of surface layer
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING 2. Machining accuracy of relative positions between part surfaces. - Accuracy of dimensions between part surfaces (for example, the distance between two parallel planes or the centers of two holes, etc.). - Accuracy of positional relations between part surfaces (for example, the parallelism and perpendicularity of two planes or two axes, etc.). The surface quality of a part indicates the surface characteristics of the part. It includes either geometrical or physic-mechanical parameters, which are listed below: l) Surface roughness. 2) Physic-mechanical state of surface layer. parallelism 平行度 perpendicularity 垂直度 surface roughness 表面粗糙度