文档介绍：Fundamentals of GD&T 几何尺寸与公差
Based on ASME -1994
Edited by: 龙东飞(Mike Long)
For Internal Use Only
供内部使用
CH1 – Introduction to the GD&T Hierarchy 介绍GD&T组成层级
GOAL 目标
Understand what an engineering drawing is.
懂得什么是工程图纸
Understand why geometric tolerancing is superior to coordinate tolerance.
懂得为什么几何公差优于坐标共差
Understand the modifiers and symbols used in geometric tolerancing.
懂得几何公差修饰符和符号
Remember: Tolerances should be as large as possible to keep manufacturing cost low.
记住: 为了降低制造成本,公差应该越大越好。
CH1 – Introduction to the GD&T Hierarchy 介绍GD&T组成层级
ENGINEERING DRAWINGS 工程图纸
The Need for munications 精确交流的需要
Engineering drawings are munications tools. Engineering drawings affect many parts of anization. They have major impact on costs.
工程图纸是精确交流的工具,对机构许多部门和成本构成重大影响。
Consequences of Poor Drawings 品质差图纸后果
(Cost in four ways: Money, Time, Material, Unhappy customers)
(4 种成本:钱、时间、材料、不满意的客户)
Cost of a Drawing Error 图纸错误的成本
When discovered by the …
Design Dept. 设计 Model shop 样件 Production Group 生产 Customer 客户
$1-10
$100-500
$2,000-100,000
$50,000-$1,000,000
Figure 1-1
CH1 – Introduction to the GD&T Hierarchy 介绍GD&T组成层级
Types of Tolerances 公差的类型
- A limit tolerance 极限公差(-)
- A plus-minus tolerance 正负公差( equal bilateral tolerance)
- A unilateral tolerance 单项公差(12+)
- An unequal bilateral tolerance 双向不等公差(+- )
(Where limit or bilateral tolerancing is used, each tolerance value should have the same number of decimal places, using zeros where necessary. )
当使用极限或双向公差时,每个公差值小数点后应该有同样多位数,必要时用零)
CH1 – Introduction to the GD&T Hierarchy 介绍GD&T组成层级
Interpreting Dimensional Limits 解读尺寸极限
All dimensional limits are absolute. A dimension is considered to be followed by zeros after the last specified digit. 所有极限尺寸都是绝对精确值,其最后一个数字后面都是零。
means …0
means …0
means …0
means …0
For this dimension -
A part measuring
be rejected
And
would be rejected
GD&T