0 - Spesifikasi Geometrik Lanjutan 2016 - TP

8/17/2019 0 - Spesifikasi Geometrik Lanjutan 2016 - TP

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PROSES MANUFAKTUR - I

FAKULTAS TEKNIK MESIN DAN DIRGANTARA

INSTITUT TEKNOLOGI BANDUNG

By

: Dr. Ir. Tri Prakosa

, M

. Eng.

Untuk Menjamin Kualitas Produk

Spesifikasi

Geometridan

Metrologi


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Toleransi Geometrik

Geometric Tolerances


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Toleransi Geometrik

(Geometric Tolerances)

Geometric tolerances define the shape of a feature asopposed to its size.

1. Form tolerances: straightness, circularity,

flatness, cylindricity;

2. Orientation tolerances; perpendicularity,

parallelism, angularity; and

3. Position tolerances: position, symmetry,concentricity.


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Symbols for Geometric

Tolerances

Form

Orientation

Position


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Tools for Measuring Dimensions

Micrometer

Depth GaugeComparator

Surface Plate

Dial Indicator

Caliper


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Feature Control Frame

A geometric tolerance is prescribed using a feature control frame.It has three components:

1. the tolerance symbol,

2. the tolerance value,

3. the datum labels for the reference frame.


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Toleransi Bentuk

orm Tolerances


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Toleransi Bentuk

(Form Tolerances)

Form tolerances control: Straightness (kelurusan)

Flatness (kerataan)

Circularity (kebulatan) Cylindricity (kesilindrisan)

Form tolerances are applicable to single

(individual) features, elements of single

features, or features of size.


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Straightness

Straightness is a condition where an element of asurface, or derived median line, is a straight line. It

is applied in the view where the elements to be

controlled are represented by a straight line.

There are two types of straightness:

Surface Straightness

Axis Straightness


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Straightness

http://www.gdandtbasics.com/straightness/

Surface Straightness: The standard form of straightness is a 2-Dimensional

tolerance that is used to ensure that a part is uniform across a

surface or feature. Straightness can apply to either a flat feature

such as the surface of a block, or it can apply to the surface of acylinder along the axial direction. It is defined as the variance of

the surface within a specified line on that surface.


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Surface Straightness



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Axis Straightness: The form of straightness that controls the central axis of a part is

sometimes referred to as Axial Straightness. This tolerance callout

specifies how straight the axis of a part is (usually a cylinder). By

definition, axis straightness is actually a 3D tolerance that constrains the

center axis of the part preventing it from bending or twisting too far.

Axis Straightness


Axis Straightness with Maximum

Material Condition


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Axis Straightness


S f St i ht G i /


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Surface Straightness Gauging/

Measurement http://www.gdandtbasics.com/straightness/

A part is constrained

and a gauge measures

along a straight line.

In this example theheight variance is

measured to see how

flat or straight the line

is along this surface.

A i St i ht G i /


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Axis Straightness Gauging/

Measurement http://www.gdandtbasics.com/straightness/

To gauge axis straightness effectively, MMC is commonly called out.To ensure that a part or feature is axially straight, a cylinder gauge is

used to determine if the part fits in its total envelope at MMC. This is

both a control of the diameter and of the axial straightness. The ID of

the cylinder gauge represents the maximum virtual condition of the

part. Gauge Cylinder ID = Max Ø part (MMC) + Straightness Tolerance


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Surface Straightness Example


A steel bar is welded in a T pattern to another steel

bar. If you want to make sure that the surface of the

tube is always uniform, where the weld occurs, you

would need to either greatly tighten the dimensionaldiameter of the tube, (which would be very costly for

such a simple part!), or callout straightness along the

mating surface.


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Ensuring straightness without GD&T


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Controlling the surface of the tube in the weld area wi th

GD&T straightness callout.

A is Straightness ith MMC


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Axis Straightness with MMC

Examplehttp://www.gdandtbasics.com/straightness/

A boss pin on an engine housing is inserted into thechassis of a car to set the alignment before being

bolted in.

The pin is always in the correct position, however

since it is so critical the dimension of the chassis

mating hole is very tight.

To ensure that this pin is always a correct fit for the

hole, straightness is called out on the axis withmaximum material condition.



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Ensuring straightness on the drawing



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To quickly check for this a gauge was made to checkthat the pin always fits into the hole in the maximum

material condition. Using the calculation below the ID

of the cylinder gauge can be determined to check for

this during production.

Gauge Cylinder ID = MMC + Straightness

Gauge ID = Maximum Material Condition of Part +

Straightness Bonus Tolerance

Gauge ID = 10.100 + 0.050

Gauge ID = 10.150 mm



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Gauge control for axis/MMC straightness



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Flatness

Flatness is the condition of a surface or derivedmedian plane having all elements in one plane.


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Flatness

GD&T Flatness is verystraight forward. It is a

common symbol that

references how flat a surface

is, regardless of any otherdatum’s or features.

http://www.gdandtbasics.com/flatness/

It comes in useful if a feature is to be defined on a

drawing that needs to be uniformly flat

without tightening any other dimensions on the

drawing.


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Flatness

The flatness tolerance references two parallel planes(parallel to the surface that it is called out on) that

define a zone where the entire reference surface must

lie.

Flatness tolerance is always less than the dimensional

tolerance associated with it.



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Flatness, Tolerance Zone

Two Sets of Parallel Planes where the entire referenced

surface must lie.



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Flatness, Gauging/ Measurement

Flatness is can be measured using a height gauge runacross the surface of the part if only the reference

feature is held parallel.



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Flatness can be measured using a height gauge runacross the surface of the part if only the reference

feature is held parallel.

You are trying making sure that any point along the

surface does not go above or below the tolerance

zone.



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Modern CMM’s are best

for measuring the part as

they can create virtual

planes that the true surface profile can be compared to.

This is a 3D measurement

so points must be measured

across the length and widthof the part to ensure the

entire surface is in

tolerance.


http://www.coord3-cmm.com/wp-

content/uploads/2012/01/Coord3-Kronos-CMM.jpg


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Flatness cannot be measured by simply placing the part on a granite slab and running height gauge over

it.

This would be measuring parallelism instead as you

are fixing the bottom of the part as a datum.



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Circularity or Roundness

Circularity is a condition of a surface where for a feature other than a sphere, all points of the

surface intersected by any plane perpendicular to an

axis or spine (curved line) are equidistant from that

axis or spine for a sphere, all points of the surface intersected by

any plane passing through a common center are

equidistant from that center.


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Circularity

http://www.gdandtbasics.com/circularity/

Circularity Gauging/


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Measurement Examplehttp://www.gdandtbasics.com/circularity/

If you had a hole that was around a rotating shaft, Both piecesshould be circular and have a tight tolerance. Without

circularity, the diameter of the hole and shaft would have to be

very tight and more expensive to make.

Example 1: Controll ing ci rcularity w ithout GD&T Symbol



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Measurement Examplehttp://www.gdandtbasics.com/circularity/

Example 2: Control ling both features with circularity allows the diameter

tolerances of the part to be opened up much larger.


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Cylindricity

Cylindricity is a condition of a surface of revolution in which all points of the surface are

equidistant from a common axis.


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Cilindricity

http://www.gdandtbasics.com/cylindricity/

Cilindricity Gauging/


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Measurement http://www.gdandtbasics.com/cylindricity/

If you had a bushing that was to be pressed into ahousing, the bushing would take the form of the

housing bore when inserted. To ensure that the

bushing maintains its round shape, and wears evenly

along its surface, the housing bore needs to be verycylindrical.

To do this without GD&T you would need very tight

dimensions on the diameter of the bore, which may be very hard to control when being machined (and

expensive)



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Measurement http://www.gdandtbasics.com/cylindricity/


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Toleransi Orientasi

Orientation Tolerances

l f


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Tolerances of Orientation

An orientation tolerance controls parallel,perpendicular, and all other angular

relationships.

There are three orientation relationshipsand three symbols to define those

relationships.

Angularity Parallelism

Perpendicularity

l


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Angularity

Description:Angularity is the

symbol that describes

the specific orientation

of one feature to

another at a referenced

angle.

http://www.gdandtbasics.com/angularity/

It can reference a 2D line referenced to another 2Delement, but more commonly it relates the orientation

of one surface plane relative to another datum plane in

a 3-Dimensional tolerance zone.

A l i


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Angularity

Description:The tolerance does not directly control the angle

variation and should not be confused with an

angular dimension tolerance such as ± 5°. In fact

the angle for now becomes a Basic Dimension,

since it is controlled by your geometric tolerance.

The tolerance indirectly controls the angle by

controlling where the surface can lie based on the datum. See the tolerance zone below for more details.


A l i

http://www.gdandtbasics.com/datum/http://www.gdandtbasics.com/datum/http://www.gdandtbasics.com/datum/http://www.gdandtbasics.com/datum/http://www.gdandtbasics.com/datum/


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Angularity

Description:Maximum material condition or axis control can also

be called out for angularity although the use in design

and fabrication is very uncommon since gauging a

hole or pin at an angle is difficult. When angularity is

called out on an axis, the tolerance zone now

becomes a cylinder around the referenced axis at an

angle to the datum.The page on Perpendicularity goes into this type of

reference in further detail since it is more common

with perpendicularity.


Angularity, GD&T Tolerance

http://www.gdandtbasics.com/maximum-material-condition/http://www.gdandtbasics.com/maximum-material-condition/http://www.gdandtbasics.com/perpendicularity/http://www.gdandtbasics.com/perpendicularity/http://www.gdandtbasics.com/maximum-material-condition/


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Angularity, GD&T Tolerance

Zone

Two parallel planes or lines which are oriented at thespecified angle in relation to a datum. All points on the

referenced surface must fall into this tolerance zone.


Angularity, Gauging/


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Measurement http://www.gdandtbasics.com/angularity/

Angularity is measured by constraining a part, usuallywith a sine bar, tilted to the reference angle, so that

the reference surface is now parallel to the granite

slab.

By setting the part at an angle the flatness can now be

measured across the now horizontal reference surface.

The entire variation must not fall outside the

tolerance zone.



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Measurement http://www.gdandtbasics.com/angularity/

A l i E l


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Angularity, Example


Angulari ty example 1: Tightening the angle and/or the thickness are

required if angularity is not called out.

A l it E l


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Angularity, Example


Angulari ty example 2: A s imple call to angulari ty now ensures that the

stamped surface now has both proper angle and

flatness. The angle must be a basic dimension, but

now allows your part thickness to open up more.

(Note this drawing is unconstrained and would need

additional size dimensions to be accurate.)

P ll li


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Parallelism

Description:Parallelism is a fairly

common symbol that

describes a parallel

orientation of one

referenced feature to a

datum surface or line.

http://www.gdandtbasics.com/parallelism/

It can reference a 2D line referenced to anotherelement, but more commonly it relates the orientation

of one surface plane parallel to another datum plane

in a 3-Dimensional tolerance zone.

P ll li


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Parallelism

Description:The tolerance indirectly controls the 0° angle between

the parts by controlling where the surface can lie

based on the datum. See the tolerance zone below for

more details.

Note: Parallelism does not control the angle of the

referenced feature, but only creates an envelope in

which the feature must lie.


P ll li


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Parallelism

Description:It is important to determine what the reference feature

is (surface or axis) and then what is acting as the

datum (surface or axis) to determine how the

parallelism is to be controlled.


Parallelism


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Parallelism


Parallelism Gauging/


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g g/Measurement


Parallelism Example


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Parallelism Example


A gear has to maintain constant axial load on both faces. Toensure even contact one side of the gear is held parallel to the

other side. To do this without parallelism, the gear width would

have to be tightly controlled, which could be very difficult to do.

Ensuring even surfaces without GD&T

Parallelism Example


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Parallelism Example


With parallelism you can open up the dimension of the gear andcontrol the faces without rejecting good gears.

Controlling two faces with GD&T parallelism callout.

Perpendicularity


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Perpendicularity

Perpendicularity is the condition of a surface,feature’s center plane, or feature’s axis at a right

angle to a datum plane or datum axis.

Perpendicularity


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Perpendicularity

Perpendicularity in GD&T can mean two very differentthings depending which reference feature is called out.

Surface Perpendicularity and Axis Perpendicularity

http://www.gdandtbasics.com/perpendicularity/

Perpendicularity


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Perpendicularity


a tolerance that controls

Perpendicularity between

two 90° surfaces, or

features. Surface

Perpendicularity is

controlled with two

parallel planes acting as its

tolerance zone.

The normal form or Surface Perpendicularity is

Perpendicularity


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Perpendicularity


a tolerance that controls

how perpendicular a

specific axis needs to be to

a datum. Axis

Perpendicularity is

controlled by a cylinder

around a theoretical perfectly parallel axis.

Axis Perpendicularity is

Surface Perpendicularity


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f p yGauging/Measurement




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f p y Example:


Axis Perpendicularity


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p yGauging/Measurement

To ensure that a part or feature is axially perpendicular,Maximum material condition is most often called out on axis

perpendicularity to allow easy measurement with a gauge. This

allows it to be designed for either a negative (hole) or positive

(pin) feature and can take into account a bonus tolerance.*

Gauge size for an internal feature (like a hole):

Gauge Ø (pin gauge)= Min Ø of hole (MMC) –

Perpendicularity Tolerance

Gauge size for an external feature (like a pin):

Gauge Ø (hole gauge) = Max Ø of pin (MMC) +

Perpendicularity Tolerance



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Gauging/Measurement http://www.gdandtbasics.com/perpendicularity/

Axis Perpendicularity Example:


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Axis Perpendicularity Example:


Tolerances of Location


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Tolerances of Location

It Includes position, concentricity, and symmetry

SymmetrySymmetrical relationships may be controlled using

either positional, profile, or symmetry tolerances.

Symmetry


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GD&T Symmetry is a 3-Dimensional tolerance that isused to ensure that two features on a part are uniform

across a datum plane.

Symmetry

http://www.gdandtbasics.com/symmetry/

Symmetry


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An established “true” central plane is established from the datumand for the symmetry to be in tolerance, the median distance

between the every point on the two surface features need to fall

near that central plane.

Symmetry


Symmetry


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Each set of points on the reference features wouldhave a midpoint that is right between the two. If you

take all the midpoints of the entire surface, this must

lie within the tolerance zone to be in specification.

Symmetry is not a very common GD&T callout since

it has very limited functional uses (centering location

is done with Position) and the verification and

measurement of symmetry can be difficult (See: Final Notes).

Symmetry


Symmetry Gauging/ Measurement


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Symmetry Gauging/ Measurement


Symmetry, when used?


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When you want to make sure that the center plane oftwo symmetric features is always held exactly center

AND has even form along the surface of the part.

This symbol only has specific uses for mass balance

and form distribution.

However in most cases it is better to avoid using

since this is a very difficult callout to measure and

can easily be replaced with a Position tolerance.

Symmetry, when used?


Symmetry Example


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If you had a rotating U-Joint a groove that needed toalways have even balancing, you would need to make

sure that the mating part is always located to fall into

the center of the groove and that the surface form is

properly balanced.

Instead of widening the groove causing the

connection to be loose, you could constrain it with

symmetry.

Symmetry Example


Symmetry Example


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Symmetry Example


Symmetry Example 1: Call out symmetry to ensure the groove is

centered on the median plane of the latch block.

Symmetry Example


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The part would then need to be measured to ensure that all themedian points of the sides of the latch block are symmetrical

about the central axis. The part would have to be measured in

the following way:

1. Measure the width and location of both sides of the blockreference by datum A (40mm) and determine where the

exact median plane is located to establish our tolerance

zone.

2. Side 1 and Side 2 of the part are scanned for their actual

profiles

3. Using a program, the median points of the Side 1 and Side

2 scans are laid over the virtual tolerance zone planes and

determined if they are in tolerance.

Symmetry Example


Symmetry Example


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Symmetry Example



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Toleransi Posisi

Position Tolerances

Position


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Position

Position is the location of one or more features of size

relative to one another or to one or more datums.

True Position


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True center position of a hole (RFS w/ 2 Datums)

True Position


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True position of a hole under MMC (3 Datums)

True Position


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True position of a hole under MMC (3 Datums)

True Position –

Location of af t


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feature

A 2 dimensional cylindrical zone or, more commonlya 3-Dimensional cylinder, centered at the true

position location referenced by the datums.

The cylindrical tolerance zone would extend though

the thickness of the part if this is a hole. For the 3-

dimensional tolerance zone existing in a hole, the

entire hole’s axis would need to be located within this

cylinder.

http://www.gdandtbasics.com/true-position/

True Position –

Location of af t


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featurehttp://www.gdandtbasics.com/true-position/

True Position Gauging/M t


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Measurement http://www.gdandtbasics.com/true-position/

True Position –

Location of a Feature

True Position Gauging/Measurement


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Measurement

True Position Using material modifiers (MMC only)


Gauging of an Internal Feature

True Position Gauging/Measurement


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Measurement

True Position Using material modifiers (MMC only)


Gauging of an External Feature

True Position Example


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Location of Hole Example 1



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Location of Hole Example 1



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Hole size and location using MMC Example 2



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Concentricity


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Concentricity is a tolerance that controls thecentral axis of the referenced feature, to a datum

axis.

Concentricity


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ConcentricityGauging/Measurement


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Gauging/Measurement http://www.gdandtbasics.com/concentricity/

Concentricity Example


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Tolerances of Profile


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A profile tolerance may be applied to anentire part, multiple features, individual

surfaces, or to individual profiles taken at

various cross sections through a part.There are two types

Line profile

surface profile

Line profile


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Each line element tolerance zone established bythe profile of a line tolerance requirement is two-

dimensional (an area) and the tolerance zone is

normal to the true profile of the feature at each

line element.

Surface Profile


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Description:Profile of a surface

describes a 3-

Dimensional tolerance

zone around a surface,usually which is an

advanced curve or

shape.

http://www.gdandtbasics.com/profile-of-a-surface/

If it is called out on a curved surface, like a fillet on a

welded part, the entire surface where the radius is has

to fall within the tolerance zone.

Surface Profile


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Description:Profile controls all the points along the surface within

a tolerance range that directly mimics the designed

profile.

Any point on the surface would not be able to vary

inside or outside by more than the surface profile

tolerance. Usually when surface profile is required,

there are no tolerances on the dimensions thatdescribe the surface and use the GD&T callout to

give the acceptable range.

http://www.gdandtbasics.com/profile-of-a-surface/

Surface Profile


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Surface Profile Gauging/Measurement


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Measurement http://www.gdandtbasics.com/profile-of-a-surface/

Surface Profile Gauging/Measurement Example


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Measurement Examplehttp://www.gdandtbasics.com/profile-of-a-surface/

Tolerances of Runout


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Runout is a tolerance used to control thefunctional relationship of one or more

features to a datum axis established from a

datum feature specified at RMB (Regardlessof Material Boundary).

TYPES OF RUNOUT TOLERANCES

Circular Runout Total Runout

Circular Runout


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Circular runout provides control of circular

elements of a surface. The tolerance is applied

independently at each circular measuring position

as the part is rotated the full angular extent of the

surface about the simulated datum axis.

Circular Runout


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Circular RunoutGauging/Measurement


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Gauging/Measurement http://www.gdandtbasics.com/runout/

Circular RunoutGauging/Measurement Example


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Gauging/Measurement Examplehttp://www.gdandtbasics.com/runout/

Total Runout


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Total runout provides control of all surfaceelements. The tolerance is applied simultaneously

to all circular and profile measuring positions as

the part is rotated 360⁰ about the datum axis.

Total Runout


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Total Runout Gauging/ Measurement


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Total Runout Gauging/ Measurement Example


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phttp://www.gdandtbasics.com/total-runout/

True Position, description


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True position is defined as the total permissiblevariation that a feature can have from its “true”

position. Depending on how it is called out, true

position can mean several different things.

It can be used with Max Material Condition(MMC),Least Material Condition (LMC), projected

tolerances, and tangent planes.


True Position, description


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It may apply to everything from points to axes to

planes to entire features. In these examples we will

use holes, since these are the most common types of

features controlled by true position.

Keep in mind though that true position can be used onany feature.


MMC (Maximum-Material-Condition), symbol:


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), y

Definition:Maximum Material Condition or for short, MMC, is a

feature of size symbol that describes the condition of

a feature or part where the maximum amount of

material (volume/size) exists within its dimensionaltolerance.

http://www.gdandtbasics.com/maximum-material-condition/



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) y

If it is a hole or internal feature: MMC = smallesthole size




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) y

If it is a pin or external feature: MMC = largest size

of the pin




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) y

The only GD&T Symbols where Max MaterialCondition can be applied are:

Straightness (axis)

Parallelism

Perpendicularity

Angularity

True Position – very common




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y

Reason for Use:If you want to ensure that:

two parts never interfere, or

limit the amount of interference between the parts

when they are at their worst tolerances

MMC can be called out. Take a shaft that must go

through a hole with clearance between the two.




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Reason for Use:The MMC of the shaft would be the

Maximum diameter

The MMC of the hole would be its Minimum

diameter




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Reason for Use:

If you made sure that the MMC of the shaft was always

smaller than the MMC of the hole,

you guarantee there will always be clearance

between the parts.

This is important for any tolerance stack to ensurethat when the tolerances are at their least desirable

condition, the part still functions properly.


MMC (Maximum-Material-Condition), Gauging MMC


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Maximum material condition comes in handy when itcomes to making a functional gauge for the part. If

you want to limit the size of your feature, you can

specify the max material condition call out

additionally control it with GD&T.For example if you wanted to ensure that a pin always

fits into a hole when the hole is at MMC, we could

design a pin gauge that

mimics the lower limit of the hole. The gauge that

controls the Max Material Condition of a part is

called a Go-Gauge (Meaning the Part must always

Go into it)



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The Go-Gauge for a hole or internal feature wouldexist of a pin that is just a tiny bit (few microns)

smaller than the Maximum Material Condition of the

hole. The gauge pin would then be inserted into the

hole and as long as the pin Goes into the hole, the partis in spec.

(Note: The pin gauge may be made slightly smaller (a

few microns) than the MMC to account for any

straightness or tolerance issues that may be inherent

in producing the gauge)

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Remember

when no GD&T is called on the hole the envelope

principal applies –

meaning the geometric and size effects of the hole

cannot be larger or smaller than the tolerances

specified.

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MMC Combination Gauging withGD&T Symbols


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The true benefit of using the maximum materialcondition on a feature is the ability to call out GD&T

with dimensional tolerances and be able to gauge for

them at the same time.

When geometric control and material control are usedtogether, they form the true maximum envelope or

virtual condition that the part can be in and still be

to specification.

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h // d d b i / i i l di i /


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For example, you have a pin with a dimensional and perpendicularity call outs.

The pin needs to be within both perpendicular

enough and small enough so that it doesn’t get stuck

when inserted into its mating hole at a 90° angle tothe face of the part.

In this case all you really care about is the pin fits into

the hole at the worst case limits (MMC and max

perpendicularity tolerance make up the maximum

envelope of the part)

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htt // d dtb i / i t i l diti /


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The virtual condition can be controlled with a functional gauge.

Functional gauges can be a huge benefit to production environments

where measuring on the line quickly is critical.

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Gauging for MMC withGeometric tolerances:



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For the Gauging

of a hole with

perpendicularitycall out:

Gauge Ø (pin gauge) = Min Ø of hole (MMC) – GD&T

Symbol Tolerance

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Gauging for MMC withGeometric tolerances:



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For Gauging of a

pin with a

perpendicularitycallout:

Gauge Ø (hole gauge) = Max Ø of pin (MMC) + GD&T

Symbol Tolerance

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LMC (Least-Material-Condition),symbol

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Definition:Least material condition is a feature of size symbol

that describes a dimensional or size condition where

the least amount of material (volume/size) exists

within its dimensional tolerance.

http://www.gdandtbasics.com/least-material-condition/

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http // gdandtbasics com/least material condition/


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If it is a hole or internal feature: LMC =Largest hole

size (least material in part)


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http://www gdandtbasics com/least material condition/


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If it is a pin or external feature: LMC = Smallest size

of the pin


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If you want to ensure that two always have contact ora press fit Least Material condition can be called out.

It is most often the control of parts that are pressed

together to ensure that they always have a snug fit

and no clearance.If you made sure that the LMC of the shaft was

always larger than the LMC of the hole, you ensure

that there will always be a tight fit between the parts.

This creates a condition where you can use a

functional gauge to ensure that the external feature is

not too small or that the internal feature is too loose.


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LMC (Least-Material-Condition),symbol , Use in GD&T:



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Least Material Condition is fairly rare in geometricdimensioning and tolerancing.

There are only a few reasons why a LMC should be

called. The most common reason for calling it would

be that you have a hole or other internal feature that isvery close to the edge of a part.

If you call LMC with true position in figure 2 below

– you would be specifying that if the hole is at its

largest size, it can only vary by as much as the true

position tolerance.


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LMC (Least-Material-Condition),symbol , Use in GD&T:



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KK TPM http://www.gdandtbasics.com/least-material-condition/

Thin Wall Hole Example

However if the holeis smaller than its

Least Material

Condition, you can

apply a bonus

tolerance to the part,

because now the true

center of the hole can

be closer to the edge,

without minimizingthe thickness of the

material.

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Concept of LMC with No-GoGauges



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The concept of the least material condition (not theGD&T symbol) comes in handy when a functional

gauge is needed to control a part.

If you want to limit the size of your feature to insure a

proper fit, you can specify the least material conditioncallout and control it with a specific type of gauge

called a No-Go Gauge.


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http://www gdandtbasics com/least-material-condition/


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For example if you wanted to ensure that a pin alwayshas a tight fit into a hole, you could design the No-Go

hole gauge to mimic the least material condition of

the part. This would be a block with a hole of a

diameter equal to the pin’s LMC (min Ø).To check the part you would try to insert the pin into

the hole. If it doesn’t fit ( No-Go) then you know that

the pin is large enough to be a tight press fit into the

feature.


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A No-Go gauge for a hole would use a pin gauge = Hole’s Max Ø

A No-Go gauge for a pin would use a ring gauge = Pins Min Ø

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Cannot Combine Gauging withGD&T Symbols



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Here is where the weakness of LMC comes out. Inmaximum material condition you are defining that the

size cannot go past the max material size + the

geometric callout.

This works fine because you are using two tolerancesthat are positive.

However with least material condition this you cannot

create a functional gauge that controls both.


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For example if you have a perpendicularitycallout and want to also control LMC on a hole, you

can check the hole for size with a no-go gauge to

ensure it is small enough for a press fit.

However if you specify a gauge that allows for a bonus tolerance on the least material condition, you

cannot make a no-go gauge also check the

perpendicularity, because a No-Go gauge is designed

not to fit!

http://www.gdandtbasics.com/least material condition/

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The problem is that GD&T symbols always specifythe maximum amount that a part can vary and cannot

be combined when you are controlling the a least

material control of size. The only way LMC can be

called on a feature would be if the least materialcondition and the perpendicularity were measured

and calculated separately. This, however, eliminates

the benefit and speed of a gauge.


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For these reasons least material condition is seldomused as a control for geometry and size. While

gauging is always possible for least material

condition size in a production environment, you

cannot gauge for both GD&T and dimension at once.The takeaway should be that in GD&T

understanding least material condition as a

concept of size is important. The only time you

will truly see it is combined with true position onthin walled parts like in the Thin Wall Hole

Example above.


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Regardless-of-Feature-Size

http://www.gdandtbasics.com/regardless-of-feature-size/


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Definition:

Regardless of Feature Size (RFS) is the default

condition of all geometric tolerances by rule #2 of

GD&T and requires no callout.

Regardless of feature size simply means thatwhatever GD&T callout you make, is controlled

independently of the size dimension of the part.

http://www.gdandtbasics.com/regardless of feature size/

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Definition:

This rule can be overridden by Maximum Material

Condition or Least Material Condition, which specify

the GD&T conditions at the Max or Min size of the

part.LMC or MMC must be called out on the drawing

specifically though to eliminate the regardless of

feature size default.

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Definition:

For simplicity, the definitions of all the GD&T

symbols are by default, stated as Regardless of

Feature Size.

For most geometric symbols besides those that allowmaximum material condition, RFS can never be

overridden.

Regardless of feature size eliminates any potential bonus tolerance, allowing the GD&T tolerances to be

more tightly controlled.

p g g

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Reason for Use:

Since Regardless of feature size is the default

condition it is used always and ignored only when

specified.

It is applied for most part conditions.

RFS is always kept where balance is critical and

where both sides of the tolerance must be maintained

independently of the GD&T callouts.

p g g

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Reason for Use:

Regardless of Feature size requires the axis to be

measured separately from the size of the hole and

cannot be gauged easily. However, there is no bonus

tolerance allowed in this condition so the perpendicularity would be much better controlled

regardless of the size of the hole.

In the following example, no material modifiers are

called out, RFS would be implied and the control for

the parts would be like this:

p g g

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p g g


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0 - Spesifikasi Geometrik Lanjutan 2016 - TP

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