文档介绍：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, ic 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
(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.
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 tolera