机械制造技术基础课件-chapter3-section2-2012.ppt
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1、3.3 Location principle of workpiece In order to fulfill the machining requirement of a certain job, a relatively accurate position of the workpiece in a machine tool in relation to the cutting tool during the metal cutting movement must be ensured. The following three conditions must be satisfied wh
2、en fulfilling such a practical function, which are(1)The accurate position of a batch of workpieces in relation to the jigs or fixtures; (2) The accurate position of the jigs or fixtures in relation to the machine tool;(3)The accurate position of the cutting tool in relation to the jigs or fixtures.
3、 In this section, the main attention is directed to the accurate positioning of workpieces in jigs or fixtures.Relative position between workpiece, fixture and machine tool 3.3 Location principle of workpiece (1)move along axis X, denoted by (2) move along axis Y, denoted by (3) move along axis Z, d
4、enoted by (4)rotate around axis X, denoted by (5) rotate around axis Y, denoted by (6) rotate around axis Z,denoted by 3.3 Location principle of workpiece3.3,1 The 6-point location principle of the workpiece3.3 Location principle of workpiece任一物体在空间都有六种宏观运动的可能性,称为六个自由,即沿X、Y、Z轴的移动和绕此三轴的转动,欲使工件在空间取得唯一
5、位置,则必须限制六个自由度。这就是六点定位原理 There are 6 possible movements for any object in space, which is called 6-degree of freedom. If the only one position for the object is designated, the 6-degree of freedom must be limited, which is the principle of 6-point location.Principle of six-point location Question: Ho
6、w to decide the position of the object in space ? Answer: limit the 6 degrees of freedom3.3 Location principle of workpieceThe six-point location principle Fig.3-4 six degrees of freedom cancelled for a workpiece 3.3 Location principle of workpieceConcepts:Complete location(完完全全定定位位):all the six deg
7、rees of freedom have been cancelled. Incomplete location(不不完完全全定定位位):not all the 6 degrees of freedom have been cancelled, but still satisfy the requirement. Redundant location(过过定定位位): two location elements have both cancelled the same degree of freedom for a workpiece. Insufficient location(欠欠定定位位
8、):the number of location points is less than the degrees of freedom which must be cancelled, the workpiece is insufficiently located .3.3 Location principle of workpieceZYXa)ZYXb)ZYXc)Complete location and incomplete location3.3 Location principle of workpieceb)BB BInsufficient location3.3 Location
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