分析机械零件加工中变形的原因

Analysis of the causes of deformation in machining of mechanical parts

1.1 内力作用导致零件加工精度改变

1.1 internal force action leads to the change of machining precision of parts

车床加工时，通常是利用向心力的作用，用车床的三爪或者四爪卡盘，把零件卡紧，然后对机械零件进行加工。同时，为了确保零件在受力时不松动、减小内径向力的作用，必须要使夹紧力大于机械的切削力。夹紧力随着切削力的增大而增大，随之减小而减小。这样的操作才能使机械零件在加工过程中受力稳定。但是，在三爪或者四爪卡盘松开后，加工出来的机械零件就会与原来的相差甚远，有的呈现多边形，有的呈现椭圆形，出现较大偏差。

When lathe is processed, usually the centripetal force is used, and the three jaw or four jaw chuck of the lathe are used to fasten the parts and then process the mechanical parts. At the same time, in order to ensure that parts are not loose and reduce the force of internal diameter, the clamping force must be greater than the cutting force of the machine. The clamping force increases with the increase of cutting force and decreases with the increase of cutting force. Such operation can make mechanical parts stable during processing. However, after the three or four claw chuck is loosened, the machined parts that are processed will be far apart from the original ones. Some are polygons, some of them appear elliptical and large deviations appear.

1.2 热处理加工后容易产生变形问题

1.2 easy to produce deformation after heat treatment

对于薄片类的机械零件，由于其长径非常大，在对其进行热处理后容易出现草帽弯曲的状况。一方面会出现中间鼓出的现象，平面偏差增大，另一方面由于各种外界因素的影响，使零件产生弯曲现象。这些变形问题的产生不仅是由于热处理后的零件内应力发生了变化，还有操作人员的专业知识不扎实，不太了解零件的结构稳定性，从而增大了零件变形的概率。

For thin sheet mechanical parts, because of its large diameter, it is easy to appear straw hat bending after heat treatment. On the one hand, there will be a phenomenon of intermediate drum, and the plane deviation will increase. On the other hand, due to various external factors, the bending of parts will happen. These deformation problems are not only due to the changes in the internal stress of the parts after heat treatment, but also the professional knowledge of the operators is not solid, and the structural stability of the parts is not very well understood, thus the probability of the deformation of the parts is increased.

1.3 外力作用下引起的弹性变形

Elastic deformation caused by 1.3 external force

在机械加工中零件出现弹性形变的原因主要有几个方面。一是一些零件的内部构造中如果含有薄片，就会对操作方法有更高要求，否则在操作人员在对零件进行定位和装夹时，不能和图纸的设计之间进行对应，容易导致弹性形变的产生。二是车床和夹具的不平整，使零件在进行固定时两侧的受力不均匀，导致切割时受力作用小的一边在力的作用下就会出现平移出现零件变形。三是在加工过程中零件的定位不合理，使零件的刚性强度降低。四是切削力的存在也是引起零件弹性形变的原因之一。这些不同的原因导致的弹性形变，都说明外力作用对机械零件加工质量的影响。

There are several reasons for elastic deformation of parts during machining. First, if the internal structure of some parts contains thin slices, the operation method will have higher requirements. Otherwise, when the operators locate and clamp the parts, they can not correspond with the design of the drawings, which can easily lead to the production of elastic deformation. The two is the unevenness of the lathe and the fixture, so that the force on both sides of the parts is not uniform when the parts are fixed. Three, in the process of machining, the location of parts is unreasonable, so that the rigidity and strength of parts are reduced. Four, the existence of cutting force is also one of the reasons for the elastic deformation of parts. The elastic deformation caused by these different reasons indicates the influence of external force on the machining quality of machine parts.