proe tol组装公差分析

組裝公差分析

公差分析主要是探討一個描述工件組合後，其公差變動模式，一個好的公差分析模式可以預測組件公差能吻合實際組件公差界限有多少，其預測之機率愈大愈好。組裝公差分析可分成三種模式：最壞狀況模式(Worst-case model)、統計模式(Statistical model)和蒙地卡羅模式(Monte Carlo model).

概念

Dimension chain (sometimes called tolerance chain) is a closed loop of interrelated dimensions. It consists of increasing, decreasing links and a single concluding link. In figures 2-4 and 2-5, link i is the increasing link, d is a decreasing link and c is the concluding link.

Apparently, the concluding link c is the one whose tolerance is of interest and which is produced indirectly. Increasing and decreasing links (both called contributing links) are the ones that by increasing them, concluding link increases and decreases; respectively.

Figure 1. Dimension Chain of c, 2 links, 1D Figure 2.: Dimension Chain of c, 4 links, 1The equation for evaluating the concluding link dimension is [Lin and Zhang (2001)]:

---------(1)

Where:

Σi: The summation of the increasing link dimensions.

Σd: The summation of the decreasing link dimensions.

j: increasing links index.

D

k: decreasing links index.

l: number of increasing links.

m: number of decreasing links.

For figure 1 ,c can be found as:

c = i - d ------(2)

As for chain in figure 2, c can be found as:

c = (i1 + i2)-( d1 + d2) ------(3)

1. 最壞狀況模式(Worst-case model)

最壞狀況模式又稱上下偏差模式、極限模式、完全互換模式，此模式是以工件的最大及最小狀況組合，可以滿足完全互換性、組件公差最大.

In worst-case method, the concluding dimension’s tolerance Δc can be found as following:

------(4)

Referring to figure 2 and equations (3 and 4), the deviation of the concluding link is:

Δc = Δi1 + Δi2 + Δd1 + Δd2------(5)

T0: 總公差

m: 零件之數目

Ti: 各零件之公差

2. 統計模式(Statistical model)

大量生產的產品，其零組件因為生產過程的變異所造成的公差呈統計分布，統計公差分析雖然可以估算結果尺寸公差的特性，但實際的分布情形還是無法掌握，統計模擬即是透過隨機取樣的原理