两种典型定位方式“过定位”问题研究

Research on“Over-positioning”of Two Typical Positioning Modes:“One side,one hole”and“Two holes,one side”

针对套筒类和箱体类零件加工分别选用“一面一孔”、“两孔一面”定位时所出现“过定位”现象,运用坐标法建立数学模型进行分析论证,得出零件中作为定位基准的基准孔和基准面之间的垂直度精度过低,夹具中限制孔的定位元件和限制面的定位元件之间的垂直度精度过低,是造成“过定位”的主要原因。在现有制造技术条件下,适当提高零件定位基准之间垂直度精度和夹具定位元件间的垂直度精度,则可避免“过定位”现象出现。

In view of the phenomenon of“Over-positioning”when two kinds of parts are machined by using“One side,one hole”and“Two holes,one side”respectively,a mathematical model is established by using the coordinate method to analyze and demonstrate,it is concluded that the verticality precision between the datum hole and the datum plane is too low,and that the verticality precision between the locating element of the limiting hole and the locating element of the limiting surface in the fixture is too low,it is the main cause of“Over-positioning”.Under the existing manufacturing technology conditions,the phenomenon of“Over-positioning”can be avoided by improving the vertical precision between parts positioning datum and between fixture positioning elements.