Computer Aided Design
Content
and this can be carried out in different ways in different graphics in or with s
upport softwares.
STAGES IN THE DESIGN OF COMPUTER GRAPHICS
There are three stages often followed in the design of a computer graphics. and
this stages are:
1. Modelling Stage
2. Rendering Stage
3. Display Stage
Modelling Stage: in this stage, the computer graphics artist acquires enough dat
a to represent an image in 3 dimension. the data are usually grouped into three
distinct classes according to their application.
The first class of data is geometric, the second class of data involves placing
acquired images usually from a camera or a video recorder in a 3 dimensional sta
te. The third class relates to volume data such as that acquired from a CAT scan
machine. CAT is Computerized Assisted tomographics.
Rendering Stage: This is second stage of image creation where the 2 dimensional
image is produced from a 3 dimensional input data. This method depends on the ty
pe of input data, the quality of the desired image and the amount of time needed
to render the image.
Display Stage: The display stage is the final stage in creating a computer graph
ic. it involves making the image suitable for display. During this display stage
, the computer graphic artist may change the colour representation of the image
so that the printed image may look like or the same as it does on the monitor.
GEOMETRIC MODELLING
GM is the process of generating 3 dimensional object of the real world for the p
urpose of analysis, design, drafting and manufacture. GM creates a database in t
he computer which represents the object generated. This object database is used
to display the object and to prepare drawings of the object with different views
and to prepare data for analysis and design so as to manufacture that object us
ing a CMC machine.
In general, there are three types of models used to represent physical objects a
nd this are:
1. Wireframe modelling
2. Surface Modelling
3. Solid Modelling
Wireframe Model: Wireframe modelling are generally used to create model of simpl
e objects since it does not distinguish between the inside and outside of the su
rfaces of the object. They provide sufficient information on the solid object bu
t are inadequate for generating Cutter path to drive CNC to manufacture that obj
ect. Wireframe models are generated by continuing line segments.
Surface Modelling: Surface entity are introduced to the wireframe model and are
defined as path geometric more precisely as compared to the wireframe and can be
used directly to generate path profile data for the CNC machine. Objects with c
omplex shape are generated by combining planes, ruled surfaces of resolutions, s
weep surfaces and fillet surfaces.
Solid Modelling: A cube is represented in a wireframe modelling as 12 lines and
8 points with its connectivity details. in the surface model, the cube is repres
ented as 6 surfaces with the lines defining the surfaces and the points defining
the lines. In solid model, the cube is represented by a volume and with this, i
t is easy to represent the object like cube, prism, sphere and cyclinder with so
lid modelling because they are standard and simple object and their representati
on is quite simple. Solid modelling offers many techniques to generate a model a
s real and to compute its property. two methods are generally used to construct
solid model and this are:
The use of basic shapes like cubes, prism, cylinder and sphere as primitive to b
uild the model and the use of boundary angles where the parameter at the boundar
y of the model is used to represent the solid object
ADVANTAGES OF MODELLING
Modelling with CAD system offers a number of advanages over the traditional draf
ting method that use rulers, T-squares and compasses. For example designs can be
altered without erasing and redrawing. CAD system also offers zoom features ana
logous to the camera lens where by a designer can magnify certain elements of a
model to facilitate inspection. Computer Models are typically three Dimensional
and can be rotated at any axis thus enabling the designer to gain a fuller sense
of the object. CAD system also lend themselves to modelling cut away drawings i
n which the internal shade of a part is revealed. A big advantage of CAM is that
i can be used to facilitate mass customization i.e the process of creating smal
l bashes of products that are customed designed to suit each particular clients.
AUTOMATION
Automation or automatic control is the use of various control system for the ope
ration of the equipment such as machinery, processes in the factories, boilers,
heat treatment ovens, switching in telephone networking, steering and stabilizat
ion of ships, aircrafts and other applications with minimal or reduced human int
ervention. The biggest benefit of automation is that it saves labour, however it
is also used to save energy and materials and to improve quality accuracy and p
recision. Automation has been achieved by various means including mechanincal, h
ydraulic pneumatic, electrical and electronics and recently computers and usuall
y in combination of two or more of the above means.
Complicated such as modern factories, airplane and ships typically use all this
combined techniques for its operation.
TYPES OF AUTOMATION
there are two common types of automation these are:
1. The feedback control which is usually continous and involves taking measureme
nts using sensors and making calculated adjustments to keep the measured variabl
es within a set range.
2. Sequence control: Sequence control is the one in which a programed sequence o
f discrete operations is performed offen based on system logics. Cruise control
is an example of the format (i.e the feedback control) While an elevator or an A
TM machine is an example of the sequence control.
The theoritical bases of the feedback control is the control theory which also c
overs servo-mechanism which are often part of an automated system. Feedback cont
rol is called a closed loop while non-feedback control is known as an open loop.
feedback control is accomplished with a controller and for it to function prope
rly the controller must provide correction in a manner that maintains stability,
and stability is the principle objective of the control theory.
Common applications of feedback control are the control of temperatures, pressur
e, flow and speed. Sequential control may be either a fixed sequence or a logica
l one that will perform different actions depending on various system states. An
example of an adjustable but otherwise fixed sequence is a timer. An elevator i
s an example that uses logic base on the system state to perform certain actions
in response to the operator's input.
AUTOMATION IN INDUSTRIES
Automation has also had an influence on areas of the economy other than manufact
uring. Small computers are used in system called word processor which are rapidl
y becoming standards part of the modern office. This technology combines a small
computer with a monitor screen, a keyboard and a printer. It is used to edit te
xt, to type form letters tailored to the recipient and to manipulate many list a
nd other data. it is also capable of performing many other task that increase of
fice productivity and efficiency.
Many industries are highly automated or use automation technology in some parts
of their operations. In communication for instance, and especially in the teleph
one industr
upport softwares.
STAGES IN THE DESIGN OF COMPUTER GRAPHICS
There are three stages often followed in the design of a computer graphics. and
this stages are:
1. Modelling Stage
2. Rendering Stage
3. Display Stage
Modelling Stage: in this stage, the computer graphics artist acquires enough dat
a to represent an image in 3 dimension. the data are usually grouped into three
distinct classes according to their application.
The first class of data is geometric, the second class of data involves placing
acquired images usually from a camera or a video recorder in a 3 dimensional sta
te. The third class relates to volume data such as that acquired from a CAT scan
machine. CAT is Computerized Assisted tomographics.
Rendering Stage: This is second stage of image creation where the 2 dimensional
image is produced from a 3 dimensional input data. This method depends on the ty
pe of input data, the quality of the desired image and the amount of time needed
to render the image.
Display Stage: The display stage is the final stage in creating a computer graph
ic. it involves making the image suitable for display. During this display stage
, the computer graphic artist may change the colour representation of the image
so that the printed image may look like or the same as it does on the monitor.
GEOMETRIC MODELLING
GM is the process of generating 3 dimensional object of the real world for the p
urpose of analysis, design, drafting and manufacture. GM creates a database in t
he computer which represents the object generated. This object database is used
to display the object and to prepare drawings of the object with different views
and to prepare data for analysis and design so as to manufacture that object us
ing a CMC machine.
In general, there are three types of models used to represent physical objects a
nd this are:
1. Wireframe modelling
2. Surface Modelling
3. Solid Modelling
Wireframe Model: Wireframe modelling are generally used to create model of simpl
e objects since it does not distinguish between the inside and outside of the su
rfaces of the object. They provide sufficient information on the solid object bu
t are inadequate for generating Cutter path to drive CNC to manufacture that obj
ect. Wireframe models are generated by continuing line segments.
Surface Modelling: Surface entity are introduced to the wireframe model and are
defined as path geometric more precisely as compared to the wireframe and can be
used directly to generate path profile data for the CNC machine. Objects with c
omplex shape are generated by combining planes, ruled surfaces of resolutions, s
weep surfaces and fillet surfaces.
Solid Modelling: A cube is represented in a wireframe modelling as 12 lines and
8 points with its connectivity details. in the surface model, the cube is repres
ented as 6 surfaces with the lines defining the surfaces and the points defining
the lines. In solid model, the cube is represented by a volume and with this, i
t is easy to represent the object like cube, prism, sphere and cyclinder with so
lid modelling because they are standard and simple object and their representati
on is quite simple. Solid modelling offers many techniques to generate a model a
s real and to compute its property. two methods are generally used to construct
solid model and this are:
The use of basic shapes like cubes, prism, cylinder and sphere as primitive to b
uild the model and the use of boundary angles where the parameter at the boundar
y of the model is used to represent the solid object
ADVANTAGES OF MODELLING
Modelling with CAD system offers a number of advanages over the traditional draf
ting method that use rulers, T-squares and compasses. For example designs can be
altered without erasing and redrawing. CAD system also offers zoom features ana
logous to the camera lens where by a designer can magnify certain elements of a
model to facilitate inspection. Computer Models are typically three Dimensional
and can be rotated at any axis thus enabling the designer to gain a fuller sense
of the object. CAD system also lend themselves to modelling cut away drawings i
n which the internal shade of a part is revealed. A big advantage of CAM is that
i can be used to facilitate mass customization i.e the process of creating smal
l bashes of products that are customed designed to suit each particular clients.
AUTOMATION
Automation or automatic control is the use of various control system for the ope
ration of the equipment such as machinery, processes in the factories, boilers,
heat treatment ovens, switching in telephone networking, steering and stabilizat
ion of ships, aircrafts and other applications with minimal or reduced human int
ervention. The biggest benefit of automation is that it saves labour, however it
is also used to save energy and materials and to improve quality accuracy and p
recision. Automation has been achieved by various means including mechanincal, h
ydraulic pneumatic, electrical and electronics and recently computers and usuall
y in combination of two or more of the above means.
Complicated such as modern factories, airplane and ships typically use all this
combined techniques for its operation.
TYPES OF AUTOMATION
there are two common types of automation these are:
1. The feedback control which is usually continous and involves taking measureme
nts using sensors and making calculated adjustments to keep the measured variabl
es within a set range.
2. Sequence control: Sequence control is the one in which a programed sequence o
f discrete operations is performed offen based on system logics. Cruise control
is an example of the format (i.e the feedback control) While an elevator or an A
TM machine is an example of the sequence control.
The theoritical bases of the feedback control is the control theory which also c
overs servo-mechanism which are often part of an automated system. Feedback cont
rol is called a closed loop while non-feedback control is known as an open loop.
feedback control is accomplished with a controller and for it to function prope
rly the controller must provide correction in a manner that maintains stability,
and stability is the principle objective of the control theory.
Common applications of feedback control are the control of temperatures, pressur
e, flow and speed. Sequential control may be either a fixed sequence or a logica
l one that will perform different actions depending on various system states. An
example of an adjustable but otherwise fixed sequence is a timer. An elevator i
s an example that uses logic base on the system state to perform certain actions
in response to the operator's input.
AUTOMATION IN INDUSTRIES
Automation has also had an influence on areas of the economy other than manufact
uring. Small computers are used in system called word processor which are rapidl
y becoming standards part of the modern office. This technology combines a small
computer with a monitor screen, a keyboard and a printer. It is used to edit te
xt, to type form letters tailored to the recipient and to manipulate many list a
nd other data. it is also capable of performing many other task that increase of
fice productivity and efficiency.
Many industries are highly automated or use automation technology in some parts
of their operations. In communication for instance, and especially in the teleph
one industr
