The document discusses dimensional engineering and geometric dimensioning and tolerancing (GD&T). It provides an overview of GD&T, explaining that it uses symbols, rules and definitions to define the geometry of mechanical parts. GD&T aims to improve quality, reduce costs and reduce delivery times by avoiding ambiguity. The document also discusses different GD&T controls like form controls, orientation controls and location controls. It emphasizes that GD&T defines part geometry in a standardized way so that anyone familiar with the standards understands what the design intends.
2. New product development stages
Quality assurance in product
development depends on a correct
specification that impacts directly or
indirectly in cost and time.
3. There are several ways to detail a project in order to organize it. We
consider 4 stages in product development as a proposal to show
deadlines and costs:
• Conceptual: definition of product concepts with customer
• Representative: product design definition
• Industrialization: definition and construction of equipment,
assembly line, tools, control devices etc.
• Production
New product development stages
4. Product development costs in relation to
design changes
Product development cost can be expressed as shown
in curve above. Cost are more representative in the
industrialization stage. For this reason, the so-called
representative stage is the last opportunity not to incur
high costs for the product development.
Product
Development
Design changing
5. What is a Robust
Design?
Products have their normal production
variations that influence their quality. In order
to have a product with recognized quality in
the market, a robust design is necessary.
We define here that a robust design is one
that is not sensitive to variations in production,
that is, variations inherent in the production
process do not compromise the quality of the
product.
For this, we can apply many methodologies
during development that minimize the
possibility of failures during the project or the
life of the product.
Functional analysis and FMEA are some of
these methodologies that we can use to
reduce risks and develop a robust design.
6. Sistem
CF1
Functional Analisys:
MF1 CF1 CF2 CF3
Comp 1 X
Comp 2 X
Comp 3
Comp 5 X
Comp 5 X
Comp 6 X
Comp 7 X X
MF1
Function Matrix X components:
DFMEA:
Etc…
- Methodology for organizing & structuring the analysis
of failure modes by function & by components
- Analysis of component and interface design failure
CF1: Fix component to
vehicle- Function
- Failure mode
- Components
- Update of the list of product features
- Ranking of product characteristics
Safety/ Legislative: S/R
Fit / function: F/F
Etc.
-Validation plan (virtual / prototype)
-Design evolution
-Initial control plan
Incorrect clamping:
- tube break
- bracket break etc…
- Upper bracket...
- Body...
- Interface…
DFMEA output:
Functional Analisys and FMEA
7. Functional Analisys and FMEA
- Update of the list of product features
- Ranking of product characteristics
Safety/ Legislative: S/R
Fit / function: F/F
Etc.
-Validation plan (virtual / prototype)
- Calculation, dimensioning and
tolerancing, tests etc.
- Design evolution
- Initial control plan
DFMEA output:
By FMEA analysis, we can identify the design key and
critical points and define a design that fulfills the function
and requirement from customer.
The inherent variations of the process will then be known
and properly treated in order to obtain a robust design.
Another concern in the development is to supply products
and parts that are interchangeable thinking about after-
sales.
Imagine you need to supply spare parts for a product and
ensure that it will fulfill its function and assemble at the first
time.
How can we ensure this in a competitive way?
First of all, we need to understand the evolution of the
mechanical parts dimensioning.
8. How to ensure that all these parts are
interchangeable?
9. Interchangeable parts and process variation.
The concept of the parts being interchangeable brings the
expectation of them assembling the first time and obtaining the
expected performance defined by their function. Parts can be
produced in different processes, different plants and even in
different countries and still fulfill their function and allow assembly
without rework.
All processes have their qualitative variation that influence their
assemblability and function. To fulfill part function and
assemblability, customer must clearly define part in a language
recognized by the supplier. In addition, both customer and
supplier must clearly understand the means of measurement to
ensure that what has been produced is what was defined.
Customer Supplier
Able to define Able to interpret
10. Geometric x Cartesian System
Cartesian System
Until Leonardo da Vinci (1452-1519) mechanical drawings were
more artistic than technical. They showed some dimensions for
illustrative purposes. The great evolution occurred in 1638, when
René Descartes created the analytical geometry, which started
to be used to express the dimensional requirements of
mechanical designs. Without discarding Descartes, it should be
mentioned that, by merit, the Cartesian system should be called
the Fermatian system, because it was Pierre de Fermat (1601-
1655) who discovered the equations of the straight line and the
circumference, and the simplest equations of ellipse, parabola
and hyperbola.
Geometric System
In the 1950s (some literature mentions the 1940s), the Cartesian
system was perfected by Stanley Parker, who discovered the
circular tolerance field, and called Geometric Dimensioning &
Tolerancing - GD&T. GD&T is a language resources to
communicate geometric and dimensional tolerances,
mathematical resources to define them, and statistical and
computational resources to calculate the process capacity index,
Cp.
11. What is GD&T?
GD&T means Geometric Dimensioning and Tolerancing.
It is a system of symbols, rules and definitions used to
define the geometry of mechanical parts.
GD&T is one of the most powerful tools available that can
improve quality, reduce costs and reduce delivery. GD&T
on drawing must, first of all, capture the intention of the
design. However, the best design in the world is useless
if it cannot be produced.
In summary, GD&T are:
• Symbols.
• Rules
• Vocabulary
• Mathematical definition (ASME Y14.5.1)
• Internationally recognized standards - (ASME Y14.5
and ISO 1101)
There is no other standardized way to control the
geometry of parts. The old methods are ambiguous. The
problem is that many people interpret the design
differently. GD&T is standardized and mathematicised,
which means that anyone who knows the standard
knows what the design means.
12. Target: fit the blue piece in the beige housing
Cartesian
System
Geometric
System
Example
13. Functional Dimensioning and
Geometric Tolerancing
GD&T adopts the design philosophy
in which the functional requirement
defines dimensioning and the
tolerance value for each dimension.
The purpose of the standard is that an
assebly works if all the parts that
contribute to its functioning “work”.
The geometric system avoids
ambiguity and provides the largest
tolerance without compromising the
part's function.
14. 14
What is the best tolerance?
Tight or open?Cost($)
Tolerances
Minimum
total cost
Optimal tolerance value
Development Engineering seeks the
lowest tolerance to guarantee the
fulfillment of the function and
Manufacturing seeks the highest
tolerance to have the lowest productive
cost.
The ideal tolerance is that which has
the lowest cost without compromising
the function of the product.
Production cost
regarding tolerances
Failure cost regarding
design changes
Total cost
15. Why do I need GD&T?
• Consider the gain in using the geometric system instead of
the Cartesian system.
Geometric x Cartesian System
57% gain in the
tolerance zone
ensuring the
same product
functionality
Example
Cartesian system
Tolerance zone
hole center hole center
16. Cartesian system allows ambiguity
Geometric system has a single interpretation
Why do I need GD&T?
• Consider the gain in using the geometric system instead of
the Cartesian system.
17. Lamp
Lamp base
Assembly
plate
Lamp bracket
The design requirement defines how it should be
dimensioning.
Why do I need GD&T?
• Consider the gain in using the geometric system instead of
the Cartesian system.
Define location from
assembly plate
Define orientation to have
best direction of the light.
Define form to avoid brake
of lamp base due to it’s in
porcelain material
18. Fonte: Tec-Ease
Additional 50%
gain in the
tolerance zone
50% gain in the
tolerance zone
The tolerance bonus application increases the tolerance field
allowing more parts to be approved without compromising
function and reducing the cost of the product.
Why do I need GD&T?
• Consider the gain in using the geometric system instead of
the Cartesian system.
19. Feature of size x surface
There are basically two types of elements:
feature of size (FOS) and surfaces. Feature
of size are those that have size limits, can
contain or be contained by a matching
envelope and have opposite points.
Below are some examples of feature of size
(FOS) and surfaces.
20. Feature Control Frame (FCF)
The geometric specification defines the type of
control, the measurement source and the tolerance
zone. Such frame has 3 sections:
➢ Geometric characteristics symbol;
➢ The value and shape of geometric tolerance. In
this field you can also have several modifiers;
➢ The reference frame that defines the restriction of
degrees of freedom (DOF) and the origin of the
measurement. Only through FCF we may know
the order of the datums and how the part should
be referenced.
21. Geometric tolerances
Geometric tolerances are divided into 3 types:
➢ Location controls;
➢ Orientation controls;
➢ Form controls.
Symbol Name Control type
Straightness
Form
(Never locate)
Flatness
Circularity
Cylindricity
Perpendicularity
Orientation
(Never locate) Parallelism
Angularity
Profile of a line
Location, Orientation,
Size and Form
Profile of a surface
Position
Location and
Orientation of feature of
size
Circular runout
Cylinder location
Total runout
From 2018 version of the ASME Y14.5 standard, concentricity and
symmetry are no longer used. These controls can be replaced by the
position.
22. Datums
Datums have the function of establishing the
measurement origin and only through the FCF
(feature control frame) we know which order they
have.
In the picture below, naturally datum A restrain 3 DOF
(degrees of freedom), datum B restrain 2 DOF and datum C
restrain 1 DOF.
We can apply several modifiers to represent which function
we want to “protect”. There are modifiers that allow “shift”,
others that unlock some of the degrees of freedom.
The way to define datums depends on the function of the
part and how it is assembled on a counter part.
23. Form
Form controls do not locate features and don’t have
datum.
Symbol Name Description
Straightness
Controls flat and cylindrical surfaces in
the longitudinal direction. Straightness can
also control the axis of cylindrical feature of
size. In this case, it must be placed next to
the FOS (modifier can be applied).
Flatness
Controls flat surfaces. Flatness can also
control the central plane of feature of size.
In this case, it must be placed next to the
FOS (modifier can be applied).
Circularity
Controls cross sections of cylinders
(internal or external), cones and spheres.
This control does not check for form
changes in cylinders (barrel, belt or cone
form).
Cylindricity
Controls cylindrical elements. This
control checks for changes in shape in
cylinders (barrel, belt or cone form). It also
controls circularity and straightness.
Modifier can be applied.
24. Orientation
Orientation controls do not locate features and must
have at least one datum. They are able to orient
surfaces or features of size.
Symbol Name Description
Perpendicularity
Controls flat surfaces that are
perpendicular to a datum. The entire
surface must be within the specified
tolerance zone. On feature of size it
controls the perpendicularity of the axis
or the median plane in relation to a
datum.
Parallelism
Controls flat surfaces that are parallel
to a datum. The entire surface must be
within the specified tolerance zone. On
feature of size it controls the parallelism
of the axis or the median plane in relation
to a datum.
Angularity
Controls flat surfaces that are on a
basic angle to a datum. The entire
surface must be within the specified
tolerance zone. On feature of size it
controls the angularity on a basic angle
of the axis or the median plane in relation
to a datum.
Modifiers , , and can be applied for a feature
of size and and for surfaces.
25. Location
Location controls may or may not have a datum.
Symbol Name Description
Profile of a line
Controls lines in cross sections of surfaces
that may or may not have a datum. Generally
used to refine the surface profile tolerance.
Modifiers , and can be applied.
Profile of a
surface
Controls location of any surface and may
have a datum or not. Without datum, it controls
only form. In cylindrical features you can also
control size if the size dimension is basic.
Modifiers , and can be applied.
Position
Controls location of points, axes or central
planes of feature of size. Modifiers , , and
can be applied.
Circular runout
Controls circular cross sections of features
displayed coaxial to the datum axis. It may be
applied in oblique or axially way. Modifier can
be applied.
Total runout
Controls cylindrical features displayed
coaxial to the datum axis. Controls all
characteristics except size. It may be applied in
oblique or axially way. Modifier can be
applied.
26. 26
Functional:
The part must be dimensioned attending its
function.
Cost:
Open specified tolerance, manufacturing cost will
be lower. It is important to understand how to get
the most out of GD&T resources.
Methodology:
Tec-Ease together with 2i has methods for applying
GD&T that simplify its use and maximize
tolerances.
ASME and ISO standards:
It is important to know the differences between
them for a correct interpretation in order to obtain
an adequate communication between customer
and supplier.
Dimensional Systems:
The geometric system has a clear definition for
who manufactures the part and who controls it.
Conclusion
27. Testimonials from
participants of our
courses
• “Tec-Ease training through instructor João Baker was very
aggregating for my training in GD&T. The teaching material has an
excellent quality, it’s very informative and rich in examples.”
Vinícius Eduardo (Powertrain Engineering – FCA Latam)
• “Very dynamic training with several practical discussions that
enrich students' knowledge and bring a very effective view of
knowledge in GD&T.”
Fabrício Silva (EGM Dimensional Engineering – GM)
• “The course content is very rich and very well referenced to the
standards, it fully covers all the content of the ASME Y14.5 and
ISO1101 standards. I have already participated in some courses on
GD&T, so I say that the instructor was able to provide participants
with full learning, always seeking to exhaust doubts, through a very
simple and objective didactic, not to mention the knowledge of the
standards that is of a impressive level.”
Luis Jamelli (Mechanical Development Designer – Vulkan do Brasil)
• “Excellent course, with a complete material, full of exercises
and examples. If you want to learn GD&T you need this course. A
watershed. I recommend!”
Yara Machado (Mechanical Engineer – Urthecast)
28. Coach
João Baker
Mechanical Engineer (CEFET-MG),
specialization in Innovation Management
(UFSC) and master in Mechanical Engineering
(UFMG) with 25 years of experience in the
automotive sector. Worked as Product
Engineering Supervisor at ZF Lenksysteme
managing and developing several projects.
Knowledge of the main manufacturing
processes such as stamping, machining,
welding, tube forming, plastic injection,
assemblies, surface and thermal treatment,
among others.
Coach in GD&T since 2006. Professor
at PUC, UNA and UFMG in disciplines like
Metrology, Mechanical Design among others.
