平面尺寸链和空间尺寸链的计算方法

Calculation Methods of Planar Dimensional Chains and Spatial Dimensional Chains

当前在尺寸链计算方面存在着两个比较突出的问题:一是还没有一个简明易用并为大家所公认的既能计算直线尺寸链又能计算平面尺寸链和空间尺寸链的通用尺寸链计算方法;二是现有文献在计算尺寸的最大值和最小值时都是先算出尺寸的平均值和公差,然后使平均值和偏差结合,从而得出尺寸的最大值和最小值。用这种方法时,为了计算公差须先算出一系列的公差传递系数,而计算传递系数的工作量大,很费时间。针对上述问题,提供了一组既能计算直线尺寸链又能计算平面尺寸链和空间尺寸链的算式,其中含有专门用于计算尺寸最大值和最小值的算式。利用此算式,不用计算平均尺寸、公差和传递系数,一个算式就能算出尺寸的最大值或最小值,从而节省计算时间、提高工作效率。为了说明算式的用法,列举了几个在工作中经常遇到的具有代表性的技术问题实例,涉及工序尺寸计算、坐标尺寸换算及工艺装备设计等方面。从涉及的尺寸链类型来看,有一维、二维、三维等3种尺寸链。

At present,there are two prominent problems in dimension chain calculation:First,there is not a simple and easy-to-use general dimension chain calculation method which can calculate both linear dimension chain and plane dimension chain and spatial dimension chain.Secondly,when calculating the maximum and minimum dimensions in the existing literature,the average and tolerance of dimensions shall be calculated first,and then the average and deviation shall be combined to obtain the maximum and minimum dimensions.In this method,a series of tolerance transfer coefficients have to be calculated in order to calculate the tolerance,and the calculation of the transfer coefficients is time-consuming due to the large amount of work.In view of the above problems,this paper provides a set of formulae which can calculate both the linear dimension chain and the plane dimension chain and the space dimension chain,including the formulae specially used to calculate the maximum and minimum dimensions.With this formula,the maximum or minimum size can be calculated without calculating the average size,tolerance and transfer coefficient,thus saving calculation time and improving work efficiency.In order to explain the use of the formula,several representative technical problems encountered in the work are cited,involving process size calculation,coordinate size conversion and process equipment design.In terms of the types of dimensional chains involved,there are three types of dimensional chains such as 1D,2D and 3D.