过定位是指工件在机床夹具中定位时,定位支承件所约束的自由度数超过了工件所必须要约束的自由度数,且这些被约束的自由度数相互发生冲突,这种情况称之为过定位。过定位具有两重性,一般来说过定位是有害的,应尽量避免。但在一些情况下又是无害的,甚至是必须的。现就过定位的两重性作一具体分析和举例,了解夹具中过定位的利与害。过定位影响定位精度由于接触点(定位点)的不稳定,增加了同批工件在夹具中位置的不同 Over positioning refers to the positioning of the workpiece in the fixture, the positioning of the degree of freedom constrained by the number of constraints than the workpiece must be constrained by the number of degrees of freedom, and the number of these constraints are free to conflict with each other, this situation is called over positioning . Positioning has a dual nature, in general, positioning is harmful, should be avoided. But in some cases it is harmless and even necessary. Now on the duality of positioning for a specific analysis and examples to understand the fixture in the positioning of the benefits and harm. Over positioning affect the positioning accuracy Due to the contact point (positioning point) instability, an increase of the same batch of workpiece in the fixture in the position of different