maincourseDimensioning and Tolerancing

2021年1月19日发(作者：broadcast)
Dimensioning and Tolerancing





纷纷发


术语和定义


实际局部尺寸

形体任意横截面上的任意单独距离的尺寸值。两点测量常看作实际局部尺
寸。


实际配合原则（
AME
）

对于尺寸的外形轮廓：
相似的理想的配对特征，
处于最小尺寸包络该轮廓并
接触该轮廓表面高点。

对于尺寸的内部轮廓：
相似的理想的配对特征，
处于最大尺寸包络该轮廓并
接触该轮 廓表面高点。


基本尺寸

用来描述零件特征或目标基准的理论尺 寸，
理想轮廓，
方向，
或位置的数值。
用基本尺寸定义零件特征时，
它提供了一个理想位置，
其公差由位置公差控
制。


补偿公差

几何公差的附加公差。无论特征控制框里指定
MMC
或< br>LMC
修正时，都准
许公差补偿。


基准

尺寸测量时建立的理论精确面，点或线。检测设备常用作模拟基准。


基准特征

与模拟基准关联的零件特征。


模拟基准

用来模拟基准面或轴的充分精确形体的表面（比如机轴表面）
。为 达到检测
目的，模拟基准作为基准使用。


目标基准

Terms and Definitions
Actual Local Size
The value of any individual distance at any cross-section of a feature of size. A
two- point measurement is often considered an Actual Local Size.
Actual Mating Envelope (AME)
For
an
external
feature
of
size;
a
similar
perfect
feature
counterpart
of
the
smallest size which surrounds the feature so it contacts the high points of the
surface(s). For an internal feature of size; a similar perfect feature counterpart
of the largest size which fits inside the feature so it contacts the high points of
the surface(s)
Basic Dimension
A
numerical
value
used
to
describe
the
theoretically
exact
size,
true
profile,
orientation,
of
location
of
a
part
feature
of
datum
target.
When
a
basic
dimension
is
used
to
define
part
features,
it
provides
the
location
for
which
permissible variations are established by geometric tolerances.
Bonus Tolerance
An
additional
amount
of
tolerance
for
a
geometric
tolerance.
A
bonus
tolerance is permissible whenever an MMC of LMC modifier is specified in a
tolerance portion of a feature control frame
Datum
The
theoretically
exact
plane,
point
of
axis
from
which
a
dimensional
measurement is made. Inspection equipment is often used to simulate datums.
Datum Feature
A part feature that contacts a simulated datum
Datum Feature Simulator
A
surface
of
adequately
precise
form
(such
as
a
surface
plate
of
mandrel)
which is used to simulate a datum plane or axis. A simulated datum is used as
a datum for inspection purposes.
Datum Target
Symbols that describe the shape, size, and location of gage elements that are
used to establish datum planes of axis.
描述通常用来建立基准面或轴的测量要素的形状，尺寸和位置的符号。


形体

用于零件组成部分的通用术语，比如表面，孔或槽。


FOS
一个圆柱体或球面，或两个相对要素，或相对平行表面，用尺寸联系起来。
比 如，孔的直径，轴的直径。


最小实体原则

在规定尺寸公差的范 围内，
形体所含材料最少的情形。
比如，
轴的最小直径，
孔的最大直径。

最大实体原则

在规定尺寸公差的范围内，
形体所含材料最 多的情形。
比如，
轴的最大直径，
孔的最小直径。


独立原则

不论特征尺寸在尺寸公差内如何变化，其几何公差要求不变（没有补偿）
。


规则
1
（单独形体尺寸规则）

在仅规定尺寸公差的地方，
单个特征的尺寸公差规定了特征外形及尺寸大小
的变动范围。规则
1
常解释为在
MMC
时的理想形状和包容原则。


规则
2
（所有适用的几何公差原则）

应用独立原则时，关于单独的 公差，基准体系，或两者一起，都不需要标注
修正符号。当需要时，
MMC
和
LMC
必须被定义在图纸上。


有效情况

在
M MC
或
LMC
下，
由带有形位公差的特征尺寸综合影响得到的最差边界。





























































4
Feature
A
general
term
that
applies
to
physical
portion
of
a
part,
such
as
a
surface,
hole or slot.
Feature- of-Size (FOS)
One
cylindrical
or
spherical
surface,
or
set
of
two
opposed
elements,
or
opposed parallel surfaces, associated with a size dimension. For example, the
diameter of a hole, the diameter of a shaft.
Least Material Condition (LMC)
The condition in which a feature of size contains the least amount of material
everywhere
within
the
stated
limits
of
size.
For
example,
the
smallest
shaft
diameter, the largest hole diameter.
Maximum Material Condition (MMC)
The condition in which a feature of size contains the most amount of material
everywhere
within
the
stated
limits
of
size.
For
example,
the
largest
shaft
diameter, the smallest hole diameter.
Regardless of Feature Size (RFS)
A term that indicates a geometric tolerance applies at any increment of size of
the
feature
within
its
size
tolerance
in- other-words,
a
geometric
tolerance
applies at whatever size the part feature is produced.
Rule #1 (Individual feature of size rule)
Where only a tolerance of size is specified, the limits of size of an individual
feature prescribe the extent to which variations in its form, as well as its size,
are
allowed
in
industry
Rule
#1
is
often
paraphrased
as
“
Perfect
form
at
MMC
”
or
“
The envelope rule
”

Rule #2 (All applicable geometric tolerance rule)
Regardless
of
feature
size
(RFS)
applies,
with
respect
to
the
individual
tolerance,
datum
reference(s),
or
both
,
where
no
modifying
symbol
is
specified. MMC of LMC must be specified on the drawing where desired.
Virtual Condition (VC)
A
worst-case
boundary
generated
by
the
collective
effects
of
feature
of
size
with geometric tolerances specified at MMC or LMC.

5


























































5
轮廓度公差带

轮廓公差带对轮廓控制有四种选项

默认为双边
-
等宽分布



44

PROFILE TOLERANCE ZONES
A Profile control can have four options for its tolerance zone.
Bilateral-equal distribution is the default condition.

44


最大实体原则位置度
（应用于孔）


55

POSITION MMC
（
APPLIED TO A HOLE
）

55










半径和控制半径




半径


半径是从圆心到圆弧或圆的表面的一条直线。半径的符号是
R
。符号
R

使用时，就产生了由两条圆弧（最小半径和最大半径）定义的公差带。


零件表面必需位于公差带内。












控制半径

控制半径是不准许平直和相反的半径。控制半径的符号为
CR
。当
CR
使 用时，就产生了由两条圆弧（最小半径和最大半径）定义的公差带。

零件表面位于新月型的公差带内，并且不是平直和相反圆弧。




6
Radius and Controlled Radius
Radius

A radius is a straight line extending from the center to the surface of an arc



or a circle. The symbol for a radius is
“
R
”
. When the
“
R
”
symbol is used, it

create a zone defined by two arcs(the minimum and maximum radii). The

part surface must lie within this zone.

Controlled Radius
A controlled radius is a radius with no flats of reversals allowed. The

symbol for controlled radius is
“
CR
”
. When the
“
CR
”
symbol is used, it

creates a tolerance zone defined by two arcs (the minimum and maximum

radii). The part surface must be within the crescent-shaped tolerance zone
and be an arc without flats or reversals.

6




统计公差符号


统计公差符号表示被应用的尺寸公差是由统计方法建立的
.
。当这个符号用

在图纸上时，零件形体用统计制程管制进行生产。该符号用注记标在后面，

如下图所示：











形体定义为统计公差
时，生产时用统计制程管制。



统计公差符号适用于尺寸公差或一个形位公差控制的公差值。
















7
Statistical Tolerancing Symbol
The
statistical
tolerancing
symbol
denotes
that
the
dimension
of
tolerancing to which it is applied was established by statistical methods.
When
this
symbol
is
used
on
a
drawing,
the
part
feature
should
be
manufactured
using
statistical
process
controls.
The
symbol
is
accompanied by a note as shown in the example below.


FEATURES IDENTIFIED AS STA
TISTICALLY TOLERANCED


SHALL BE PRODUCED WITH STATISTICAL PROCESS CONTROLS.
The statistical tolerance symbol may be applied to a dimensional tolerance
or to the tolerance value of a geometric control.












7



形体控制框


形体控制框包括：

1.

控制特性（几何特性）

2.

公差带尺寸

3.

公差带修正表示：

?

公差带形状

(
).

?

直径

(
)
符号表示圆柱公差带。

球径

(
)
符号表示球形公
差带

?

公差应用以下条件

(
)
4.

选用参考基准和参考基准修正

5.

参考基准修正


8
Feature Control Frame
The feature control frame consists of:
1.

Type of control (geometric characteristic)
2.

Tolerance zone size.
3.

Tolerance zone modifiers denote:
?

The tolerance zone shape (
).

?

The
diameter
(
)
symbol
denotes
a
cylindrical
tolerance
zone.
The
spherical
diameter
(
)
symbol
denotes
a
spherical
tolerance zone.
?

The conditions under which tolerance applies
(
)
4.

Datum references if applicable and any datum reference modifiers.
5.

Datum references modifiers.





8
一般规则


规则
1
：单独形体尺寸规则


常常参考为包容原则和在
MMC
时的理想形状。


规则
1
规定在仅指定尺寸公差的地方
,
尺寸界限也控制形体界限

规则
1
例子



包容原则


以上都是规则
1
的例子（或包容原则）
，详述见
a
，
b
，
c
三段


a
：形体上各表面，不得超出在 最大实体下的边界。该边界是图纸所要表达
的实际几何形状。
如果形体已达到最大实体状态尺寸 ，
那么形体形状就不
准许有任何偏差。


9
General Rules
Rule #1 Individual Feature of Size
Rule

Often referred to as the
“
envelope principle
”
or
“
perfect form at MMC
”


Rule #1 states where only a tolerance of size is specified, the limits of size


also control the limits of form.
Rule #1 Example

The Envelope Principle

The examples above are affected by Rule #1 (or the envelope principle) as

described in paragraphs a, b,& c.

a: The surface(s) of a feature shall not extend beyond a boundary (envelope)


of
perfect
from
at
MMC.
This
boundary
is
the
true
geometric
form
represented by the drawing. No variation in form is permitted if the feature



is produced at its MMC limit of size.
9
一般原则（续）


包容原则（续）


b
：
在特征实际尺寸偏离最大实体状态趋向最小实体状态的地方，
准许特征
在等于此偏 离量的范围内变动。


C
：
对在最小实体状态时的理想边界没有要 求。
因此，
当达到尺寸的最小实
体状态时，
准许特征形状至最大实体状态下所 准许的理想边界之间做变
动。





规则1
仅适应于尺寸，并不影响个特征间的位置，方向或相互关系。因
此，
单个特征间 的相互关系必须定义以避免图纸要求的不足；
通常用几
何公差来控制特征间的位置，方向和相互 关系。



如何不考虑规则
1

通过控制形体 轴（或面）的直线度，可以不考虑规则
1
。见
35
页例子。



规则
1
的例外


规则
1
有两个例外：


1,
非刚性零件


2
，原料尺寸，比如薄片，管材等


规则
2
（所有适用的几何公差规则）


独立原则应用时，对于公差状态，参考基准或两者都没有实体状态调整。





10

General Rules (Cont.)
The Envelop Principle (Cont.)
b.
where
the
actual
local
size
of
a
feature
has
departed
from
MMC
toward
LMC,
a
variation in form is allowed equal to the amount of such departure.

C. there is no requirement for a boundary of perfect from at LMC. Thus, a



feature
produced
at
its
LMC
limit
of
size
is
permitted
to
vary
from
true
form
to
the
maximum variation allowed by the boundary of perfect form at MMC

Rule
#1
only
applies
to
the
size.
Rule
#1
does
not
affect
the
location,
orientation,
or
interrelationship between features of size. Therefore, the relationship between individual
features must be defined to avoid incomplete drawing speciations; geometric tolerances
are often used to



Control the location, orientation, or interrelationship between features.

How to Override Rule #1

Rule #1
can
be
overridden
by
applying
a
straightness
control
to
an
axis
(or
plane)
of
a
feature of size. An example is shown on page 35.

Exception to Rule #1

There are two exceptions to Rule #1:
1.

Non- rigid parts
2.

Stock sizes, such as sheets, tubing. etc.

Rule #2 (All applicable geometric tolerances rule)


RFS
applies,
to
the
tolerance
condition,
datum
references,
datum
references,
or
both,
where no material condition modifier is specified.







































































10

一般原则（续）


螺纹

< br>螺纹上规定的方向，位置的公差及参考基准，都是应用在螺纹节圆轴线上
的。在例外的情形，需要 应用在螺纹上特定的特征（比如大径或小径）
上，应该放在特征控制框下方或靠近基准特征符号处，如：












齿轮和齿条


齿轮，齿条上规定的方向，位置公差及参考基准，必须指明是应用


在齿轮 或齿条上哪一个特征上的（比如大径，节径或小径）
。这些说明文
字标在特征控制框或基准特征 符号的下面，如：











11

General Rules (Cont.)
Screw Treads
Each tolerance of orientation, tolerance of position or datum reference for a
screw thread applies to the axis of the tread derived from the pitch cylinder.
Where an exception to this practice is necessary, the specific feature of the
screw thread (such as MAJOR DIA or MINOR DIA) shall be stated under the
feature control frame or adjacent to the datum feature symbol, as applicable.

Gears and Splines
Each
tolerance
of
orientation,
tolerance
of
position
or
datum
reference
specified for features, such as gears and splines, must designate the specific
feature
of
the
gear
of
spline
to
which
each
applies
(such
as
MAJOR
DIA,PITCH DIA,
(PD),
or MINOR
DIA). This
information
is
stated
under
the feature control frame or under the datum feature symbol, as applicable.



















































11

基准


参考基准坐标系


零件设计最重要的那 些基准特征，或者这些特征上指定的部分被选用来定
位零件，由此而产生的三个相互垂直的平面通称为参 考基准坐标系（看
下图）
。这个参考坐标系是理论上的，而不是零件上的。因此，建立一种方式从实际零件特征来模拟理论参考坐标系是非常必要的。














12

Datums

Datum Reference Frame
Sufficient
datum
features,
those
most
important
to
the
design
of
a
part,
or
designated
portions
of
these
features
are
chosen
to
position
the
part
in
relation to a set of three mutually perpendicular planes, jointly called datum
reference frame (see figure below). This reference frame exists in theory only
and
not
on
the
part.
Therefore,
it
is
necessary
to
establish
a
method
of
simulating the theoretical reference frame from the actual features of the part
(fig).
This
simulation
is
accomplished
by
positioning
specifically
identified
features
in
contact
with
appropriate
datum
simulators,
in
a
stated
order
of
precedence, to restrict motion of a part and to relate the part adequately to the
datum reference frame.





































































12
基准（续）


基准特征，模拟基准特征

基准面，基准轴


Datums (Cont.)
Datum Feature, Datum Feature Simulator,
Datum Plane, Datum Axis























































13







13
基准（续）


基准形体识别符号

图纸上常用下图所示符号指出基准特征。这叫做基准特征识别符号。


在基准特征上附有这种符号的方法指出了该基准是否是基准面，基准中心
面或基准轴。


特征控制框里的参考基准

特征控制框的参考基准，也指出了零件接触参考基准的顺序。这个次序

就是形体控制框中从左到右的顺序。






14

Datums (Cont.)
Datum Feature Identification Symbol
The symbol used to specify a datum feature on a drawing is shown below. It
is
called
the
datum
feature
identification
symbol.
The
method
of
attaching
this
symbol
to
a
part
feature
determines
if
it
designates
a
planar
datum,
centerplane datum or datum axis.





Referencing
Datums
in
Feature
Control Frames
When feature control frames reference datums, they also specify the sequence
for contacting the part to the datums referenced. The sequence is determined
by reading the feature control frame left to right.



























































14





基准（续）


基准识别举例


下面图形例举说明基准识别符号如何应用在指定平面，
中心面，
或基准轴。



15
Datums (Cont.)
Datum Identification Examples
The
figure
below
shows
examples
of
how
the
datum
identification
symbol
can be applied to specify a planar, centerplane, or axis datum.































































15