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本文对机械工程中所用到的标准尺寸公差和形位公差作了较为详细的分析,介绍了自动获取公差值的程序设计,重点说明了程序的内部结构及实现方法,并提供了必要的流程图。 相似文献
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零件的尺寸公差、形位公差项目及精度的合理选择不仅是保证零件技术性能要求的基础,也是降低生产成本,提高产品经济性的重要因素。零件的尺寸精度、形状精度以及位置精度之间既相互联系,又相互制约,因此,弄清它们之间的相互关系,对机械零件的设计是十分重要的。 相似文献
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张统钰 《机械工业标准化与质量》1997,(1):17-19
表面粗糙度、尺寸公差及形位公差,是设计图样中应同时给出(包括技术要求中规定的未注出尺寸公差及形位公差)的基本要求。尽管它们各具不同的功能,但相互间存在着密切的联系,故取值时应互相协调。若选择不当或相互矛盾,会直接影响零件的功能和寿命,甚至无法加工。可见,正确、经济地确定表面粗糙度、尺寸公差及形位公差,是机械设计人员应熟练掌握的基本功。然而,图样中数值选用不合理、不协调的情况时有发生,如图1所示.对φ30H7同时给出了定位尺寸公差和平行度公差。定位尺寸50±0.03已经表明孔的轴线应在定位公差0.06范围内变… 相似文献
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尺寸链中形位公差的判别与解算 总被引:1,自引:1,他引:0
从零件形位公差要素所采用的公差原则入手,讨论了在尺寸链计算中,是否应该考虑形位公差的影响以及形位公差组成环性质的判别方法,并通过实例加以说明。 相似文献
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为了使公差信息更好地被计算机理解,将描述逻辑引入到对公差设计的研究中.从几何要素之间的基本空间关系出发,提出几何公差描述逻辑GTDL(Df),并给出该逻辑的Tableau判定算法.应用GTDL(Df)的刻画能力,构建几何公差的GTDL(Df)表示模型;在此基础上,借助GTDL(Df)的Tableau判定算法,设计公差类型的自动生成算法.通过工程实例验证了生成算法的有效性. 相似文献
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Tolerance charting is an effective tool to determine the optimal allocation of working dimensions and working tolerances such that the blueprint dimensions and tolerances can be achieved to accomplish the cost objectives.The selection of machining datum and allocation of tolerances are critical in any machining process planning as they directly affect any setup methods/machine tools selection and machining time.This paper mainly focuses on the selection of optimum machining datums and machining tolerances simultaneously in process planning.A dynamic tolerance charting constraint scheme is developed and implemented in the optimization procedure.An optimization model is formulated for selecting machining datum and tolerances and implemented with an algorithm namely Elitist Non-Dominated Sorting Genetic Algorithm(NSGA-II).The computational results indicate that the proposed methodology is capable and robust in finding the optimal machining datum set and tolerances. 相似文献
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Two features characterize a good inspection system: it is accurate, and compared to the manufacturing cost, it is not expensive. Unfortunately, few measuring systems posses both these characteristics, i.e. low uncertainty comes with a cost. But also high uncertainty comes with a cost, because measuring systems with high uncertainty tend to generate more inspection errors, which come with a cost. 相似文献
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计算机辅助尺寸链计算中公差设计的研究 总被引:1,自引:0,他引:1
计算机辅助尺寸链计算中一个重点和难点是工序尺寸公差的分配.由于是一个不定解问题,有很多种解决办法.本文在计算机辅助尺寸链计算中融合了多种公差分配算法.重点阐述了改进后的等精度法、基于经济公差分配法和优化分配法,并在优化模型的约束要求中提出了分级约束的概念,使优化过程更合理.文章最后结合实例对算法进行了分析比较,给出了在不同初始条件下,经济合理地分配工序尺寸公差的方法. 相似文献
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形位公差的信息模型是CAD/CAM能否有效集成的关键问题。形位公差的信息模型不仅要清楚表达它的工程语义 ,而且要便于公差信息在计算机中的表示、传递和运算。简要介绍矢量化公差数学定义标准ANSI 14 5 1M 1994及公差信息在CAD/CAM系统中的表示方法 ;分析目前该技术的研究现状 ,提出基于数学定义的三维公差模型是形位公差信息建模的发展趋势 相似文献
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文章针对设计图样上经常出现的形住公差选择不恰当问题展开了讨论。论述了尺寸公差与形住公差之间的关系;位置公差与形状公差的关系;综合公差和单项公差的关系;以及形位公差值的选用原则等。 相似文献
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Optimising tolerance allocation for mechanical components correlated by selective assembly 总被引:1,自引:0,他引:1
Selective assembly can enlarge the tolerances of mechanical components for easier manufacturing. However, the non-independent dimensions of correlated components make it difficult to optimise tolerance allocation for an assembly. This paper proposes a solution for this constrained optimisation problem consisting of tolerances and non-independent dimensions as design variables. The approach is to develop a simplified algorithm applying a Lagrange multiplier method to evaluate the optimal tolerances efficiently. The solution is shown to be a global optimum at the given correlation coefficients. The correlation coefficients are key elements in determining the optimal solution, which is demonstrated in the given examples. The results are helpful in designing tolerances for selective assembly.Notation
A
j
coefficient matrix off
j
-
B
i
coefficient of cost function
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C
total manufacturing cost function
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C
i
manufacturing cost function forx
i
-
F
j
thejth dimensional constraint function
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f
j
thejth quadratic constraint function
-
f
quadratic constraint vector
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H
j
thejth Hessian matrix
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J
kj
element ofn×m Jacobian matrix
-
L
Lagrangian
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m
number of assembly dimensions
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n
number of component dimensions
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p
number of equality dimensional constraints
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T
tolerance vector of component dimensions [mm] or [°]
-
tolerance ofx
i
[mm] or [°]
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tolerance ofZ
j
[mm] or [°]
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x
component dimension vector
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x
midpoint vector
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x
i
component dimension [mm] or [°]
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x
i
midpoint ofx
i
[mm] or [°]
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Z
j
assembly dimension [mm] or [°]
-
j
confidence coefficient forZ
j
-
i
confidence coefficient forx
i>
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j
given design value ofZ
j
[mm] or [°]
-
Lagrange multiplier vector
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j
thejth Lagrange multiplier
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*
Lagrange multiplier vector at the optimum solution
-
correlation coefficient forx
i
andx
k
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x
standard deviation vector
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x
*
standard deviation vector at the optimum solution
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x
0
candidate point satisfying the constraintsf(
x
*
)=0
-
standard deviation ofx
i
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