兩道關于公差簡單的題，大家可以測試一下

ValleyViews

aysuio 發表于 2015-10-6 22:50
* F; o( _) U9 a( ]5 x" d9 Q大俠可能對直線度平面度的適用范圍有點混淆，
直線度是二維的，平面度是三維的。直線度的公差帶是沒有方 ...

( n7 P, {/ r1 u6 n) b# \' @直線度是可以在某些平面上指定的。既然在平面上可以指定，就是可以應用在平面上的。ASME Y14.5 中的圖 Fig. 5-6 Specifying Straightness of a Flat Surface 恰巧指的就是本題案例相同的情況。而您13樓給出的圖示，也是在指定的平面上的。



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aysuio

ValleyViews 發表于 2015-10-7 02:44
& v( k! \9 F5 ~0 C8 b$ O直線度是可以在某些平面上指定的。既然在平面上可以指定，就是可以應用在平面上的。ASME Y14.5 中的圖 Fi ...

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- U: @' u7 D# _2 K: C* |# _0 K大俠，別用您啦，小子真擔待不起，我是小弟：D
大俠這么認真，小子自然很愿意來跟大俠說一下。
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) x, {; v& v1 d- ?6 e: I$ z; ^In Y14.5
Application:
1. Straightness tolerance specifies a tolerance zone within which the EACH (This word is not in the standard, but the following explanations indicate the "EACH" information) considered element in the surface or derived median line must lie.
2. Straightness tolerance is applied in the view where the elements to be controlled are represented by a straight line.
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These 2 sentences give us 3 information:
1. straightness tolerance controls each line elements of a surface when it is applied to the surface, or the derived median line when it is applied to the feature of size.
( W. b' J' z2 [0 y2 l2. Straightness tolerance is ONLY applied in ONE VIEW where it refers to.
3. Straightness tolerances is applied to a nominal straight line. If the line is a curve, please use profile tolerance.
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For this problem, straightness tolerance is applied to the surface, and in 2 VIEWS.
So it means 2 straightness tolerance control the straightness of each line elements of the surface in 2 VIEWS.
, A$ y) B5 E5 E( T: I3 S' b, vLine element is a 2D element, like it just has dimensions in X and Y, and NEVER think about you can measure line elements in Z axis. What you do is just to measure the line one by one according to the actual local sizes of the component (Means the straightness tolerance zone totally depends on the actual local sizes of your produced part)
" T1 X: p0 n3 \2 O; b# y% @When you talk about the flatness tolerance. This is a 3D element. I.E. it has dimesions in X,Y,Z. So when you check the tolerance, you check the whole surface at the SAME TIME where the flatness tolerance refers to.
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This is why the straightness tolerance in that figure which I posted before can be 0, but the flatness tolerance can reach 0.6
If you still have any problem about this, please read the standard again from the first sentence of form tolerance section, then I think you will understand about this problem clearly and thoroughly.
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If you are willing to talk with me about the problem, feel free to contact me I'm here with you.

aysuio

Hi, Valleyviews,
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You were saying the fig in Y14.5-2009. And yes, it is talking about this problem. I was confused by this section before, but this question just helped me to get over it! I hope that this question also let you clear some confusing theories up. Have a good day!

94371734

請解釋下為什么不是0.05。
( \* C$ x, A2 u/ t  C& `4 `機械設計手冊給直線度的定義是：在給定方向上公差帶是距離為公差值t的兩平行平面之間的區域（第三章5-271）。
" x6 _: y" h5 h1 S" u該面既要0.05又要0.2，那理所當然的可以認為平面度最大值為0.05。

類似于茴字有四種寫法，實際應用中并沒有多大的意義。

; U3 {1 t% M- v0 m補充內容 (2015-10-8 10:07):
最近智商余額不足，給定方向上這幾個字被我無視了。
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aysuio

大俠，我自以為解釋得很清楚了。。。再讓我解釋，說不過去啦吧- -！

bukeking

0.2,平面度可以限定直線度,反過來直線度也可以影響平面。4.7,只需考慮孔的尺寸和位置公差,c如果有平面度需要考慮,但是0位置度變的無意義。

bukeking

bukeking 發表于 2015-10-7 20:26
+ d7 t2 N) T7 I# z  ?7 H0.2,平面度可以限定直線度,反過來直線度也可以影響平面。4.7,只需考慮孔的尺寸和位置公差,c如果有平面度需要 ...

你好，如果直線度不能控制平面的話，這張圖的意義何在，兩向可以控制，一向足以影響，我認為沒有問題。此處大部分人都可能直接標平面度，設計者應該是在完全符合性能要求的前提下，考慮到批量件或是工件長寬相差太多，結合機床的精度，讓加工者選擇合適的走刀方向進給量速度等參數，以最經濟方式做出。

傻瓜丶

看了第一題，覺得也是0.6，第二題就不懂了

ValleyViews

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aysuio 發表于 2015-10-7 04:58
:）
大俠，別用您啦，小子真擔待不起，我是小弟：D
. b3 a* j6 a/ S6 K( S8 M# w* T大俠這么認真，小子自然很愿意來跟大俠說一下。

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四海之內皆兄弟也。

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Talking about your explanation, I think that every sentence is understandable except this one:   “Line elements is a 2D element, like it just has dimensions in X and Y, and NEVER think about you can measure line elements in Z axis.”

My understanding is that even though you measure line elements in specified view direction ( either front view or side view ), it doesn't mean the measured line element is a 2D element. Furthermore, actually it is still a 3D element. When you measure it with an indicator, what will you get? You must get some values in Z axis.

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aysuio

bukeking 發表于 2015-10-8 00:19
你好，如果直線度不能控制平面的話，這張圖的意義何在，兩向可以控制，一向足以影響，我認為沒有問題。此 ...

第一，這張圖的意義在于讓你更清楚地理解，何為平面度，何為直線度。基本概念都理解不到位，為何把題往實踐上套?

! N7 O% `* a9 d- |* A第二，你估計連直線度平面度怎么測都不大清楚吧？我相信我之前寫的解釋很全了，你有仔細看么？直線度是有 “方向”的，是分“視角的”。

第三，你說的很好，設計人員要根據現有的加工情況，實際要求，對圖紙進行標注。但這只是一點。你標注的公差，你覺得是這個意思，人家覺得是那個意思，然而事實是，公差只會表達一個意思，不會有歧義。是否看過一個大俠的文章：切莫讓感覺蒙蔽雙眼。設計公差需要的是嚴密的邏輯而不是感覺。你沒細讀過標準，沒有仔細比較過直線度和平面度之間的差別， 所以你的概念是混淆的。所我的建議是，請細讀標準，可以先讀美標，寫的嚴密，邏輯，而且較為簡單。
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讀標準這個事兒我說過好多次啦。大俠們自己斟酌吧。

PS：
8 z  o, F* i/ F$ ?0 A: F& q# r& Y, {第一題是我從老外論壇上弄下來的，每個能夠說出答案的人，都說的有理有據，不像咱們，說的理由甚至不沾邊。
雖然小弟本身水平也不咋地，但是深知基礎的重要，也知道只有說話有根據，才能說服別人，就像998大俠說的，用計算說服別人，用有根有據扎扎實實的理由說服。與君共勉。
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