机械制造作业试题答案分享 - 定位误差及其计算

Homework 6

版权声明

本内容由狂小虎原创整合，请不要售卖，为了防止爬虫以及保持免费性，设置为仅粉丝可见。另外，题目以及解释可能不完全正确，仅供参考，同时也欢迎各位在讨论区指点出内容的错误之处。

3．何谓定位误差？定位误差是由哪些因素引起的？定位误差的数值一般应控制在零件公差的什么范围内？

1. The so-called location error is referred to the positional error between the machining surface and the operational datum caused by workpiece location.
2. There two reasons that cause location error.
   The confliction between the location datum and the operational datum. It is usually called the non-superposition datum error.
   The manufacturing error of the location elements and the location datum. It is usually called the datum positional error.
3. In generally, location error should be lower than 1/3 times as dimensioning tolerance.

4．有一批图3.69所示零件，圆孔和平面均已加工合格，今在铣床上铣削宽度为b 的槽子。要求保证槽底到底面的距离为h ；槽侧面到A面的距离为a+ Δa，且与A面平行，图示定位方案是否合理？有无改进之处？试分析之。

Machining the groove should restrict 6 degrees of freedom of the workpiece. The big plane restricts $x旋,y旋,z⃗$, and cut side pin restricts $y⃗$.
Improvement: on plane A, use one more support nail to ensure complete location.

5．有一批如图3.70所示工件，采用钻模夹具钻削工件上Φ5mm和Φ8mm两孔，除保证图纸尺寸要求外，还须保证两孔的连心线通过Φ60 mm的轴线，其偏移量公差为0.08 mm。现可采用如图b、c、d三种方案，若定位误差不得大于加工允差的1/2，试问这三种定位方案是否可行（α=90˚）？

图3.70 （习题34图）
b) OK. V shape block A point as location datum.

c) NO. V shape block A point as location datum.

d) NO. Center axis of circle Φ60 as location datum.

6．有一批套类零件如图3.71a所示，欲在其上铣一键槽，试分析下述定位方案中，尺寸 、 、 的定位误差。

(a) 在可涨心轴上定位（图b）；
(b) 在处于垂直位置的刚性心轴上具有间隙的定位（图c），定位心轴直径
© 在处于水平位置的刚性心轴上具有间隙的定位（图c），定位心轴直径
(a) The datum positional error is not existed.

(b)

©