cad cam lab manual department of mechnical …

Prof.S.Sathishkumar www.vidyarthiplus.com www.kssathishkumar.blogspot.com

CAD CAM LAB MANUAL

DEPARTMENT OF MECHNICAL ENGINEERING


CAD INTRODUCTION

Computer-aided design (CAD), also known as computer-aided design and drafting

(CADD) is the use of computer technology for the process of design and design-documentation.

Computer Aided Drafting describes the process of drafting with a computer. CADD software, or

environments, provides the user with input-tools for the purpose of streamlining design

processes; drafting, documentation, and manufacturing processes. CADD output is often in the

form of electronic files for print or machining operations. The development of CADD-based

software is in direct correlation with the processes it seeks to economize; industry-based

software (construction, manufacturing, etc.) typically uses vector-based (linear) environments

whereas graphic-based software utilizes raster-based (pixelated) environments.

CAD is an important industrial art extensively used in many applications, including

automotive, shipbuilding, and aerospace industries, industrial and architectural design,

prosthetics, and many more. CAD is also widely used to produce computer animation for special

effects in movies, advertising and technical manuals. The modern ubiquity and power of

computers means that even perfume bottles and shampoo dispensers are designed using

techniques unheard of by engineers of the 1960s. Because of its enormous economic importance,

CAD has been a major driving force for research in computational geometry, computer graphics

(both hardware and software), and discrete differential geometry

The design of geometric models for object shapes, in particular, is occasionally called

computer-aided geometric design (CAGD).

Current computer-aided design software packages range from 2D vector-based drafting

systems to 3D solid and surface modellers. Modern CAD packages can also frequently allow

rotations in three dimensions, allowing viewing of a designed object from any desired angle,

even from the inside looking out. Some CAD software is capable of dynamic mathematic

modeling, in which case it may be marketed as CADD — computer-aided design and drafting.

CAD is used in the design of tools and machinery and in the drafting and design of all

types of buildings, from small residential types (houses) to the largest commercial and industrial

structures (hospitals and factories).

http://en.wikipedia.org/wiki/Computer

http://en.wikipedia.org/wiki/Industrial_arts

http://en.wikipedia.org/wiki/Prosthesis

http://en.wikipedia.org/wiki/Computer_animation

http://en.wikipedia.org/wiki/Special_effect

http://en.wikipedia.org/wiki/Special_effect

http://en.wikipedia.org/wiki/Advertising

http://en.wikipedia.org/wiki/Computational_geometry

http://en.wikipedia.org/wiki/Computer_graphics

http://en.wikipedia.org/wiki/Geometric_model

http://en.wikipedia.org/wiki/Vector_graphics

http://en.wikipedia.org/wiki/Solid_modeling

http://en.wikipedia.org/wiki/Freeform_surface_modelling


CAD is mainly used for detailed engineering of 3D models and/or 2D drawings of

physical components, but it is also used throughout the engineering process from conceptual

design and layout of products, through strength and dynamic analysis of assemblies to definition

of manufacturing methods of components. It can also be used to design objects.

GEOMETRIC MODELING

A geometric modeling is defined as the complete representation of an object that includes in both

graphical and non-graphical information. In computer-aided design, geometric modeling is

concerned with the computer compatible mathematical description of the geometry of an object.

The mathematical description of the geometry of an object to be displayed and manipulated on a

graphics terminal through signal from CPU of the CAD system. The software that provides

geometric modeling capabilities must be designed for efficient use of both by the computer and

the human designer.

To use geometric modeling, the designer construct the graphical image of the object on the CRT

screen of the IGS system by inputting three types of commands to the computer. The first type of

command generates basic geometric elements such as points, lines, and circles. The second

command types is used to accomplish scaling, rotation or other transformations of these

elements. The third type of command causes the various elements to be joined into desired shape

of the object being created on the ICG system.

During this geometric modeling process the computer converts the commands into mathematical

model, stores it in the computer data files and displays it as an image on the screen. The model

can be subsequently being called from the data files for review, analysis or alteration. The most

advanced method of geometric modeling is solid modeling in three dimensions. This method

uses solid geometry shapes called primitives to construct the object.

Basically there are three types of modeling, they are

a. Wire Frame Modeling

b. Surface Modeling

c. Solid Modeling


WIRE FRAME MODEL:-

This is the basic form of modeling; here the objects drawn will be simple but more verbose,

geometric model that can be used to represent it mathematically in the computer. It is

sometimes referred as a stick figure or an edge representation of the object. Typical CAD/CAM

system provides users with possibly three modes to input coordinates: Cartesian, Cylindrical or

Spherical. Each mode has explicit or implicit inputs. Explicit input could be absolute or

incremental coordinates. Implicit input involves user digitizes. A wire frame model consists of

points, lines, arcs, circles &curves. Early wire frame modeling techniques developed in 1960‘s

were 2-dimensional. They are not centralized &associative. Later in 1970‘s the centralized,

associative database concepts enabled modeling of 3D objects as wire frame models that can be

subject to 3-dimensional transformations.

WIRE FRAME ENTITIES

Wire frame Entities are divided into 2 types are:

a. Synthetic Entities---------- Splines & Curves

b. Analytic Entities---------- Points, lines, Circles, arcs, conics, fillet, chamfer

Applications:

1. Two-dimensional drafting.

2. Numerical control tool path generation.


Advantages:

1. It is simple to construct model.

2. Less computer memory to store the object.

3. CPU time to retrieve, edit or update a wireframe model is less.

4. Does not require extensive training.

Disadvantages:

1 .It is ambiguous representation of real object.

2 It lack in visual coherence and information to determine the object.

3. User or terminal time needed to prepare & or input data increases with complexity of object.

4. Inability to detect interference between components.

5. No facility for automatic shading.

6. Difficult in calculating Physical properties like Mass, surface area, centre of gravity etc.,

SURFACE MODEL:-

A surface model of an object is more complete and less ambiguous representation than it wire

frame model. It is also richer in associated geometric contents, which make it more suitable for

engineering and design applications. Surface model takes one step beyond wire frame models by

providing information on surfaces connecting the object edges. Creating a surface has some

quantitative data such as point & tangents & some qualitative data like desired shape &

smoothness. Choice of surface form depends on type of application.


Surface Entities:

Similar to wire frame entities, existing CAD / CAM systems provide designers with both

analytic and synthetic surface entities. Analytic entities include plane surface, ruled surface,

surface of revolution, and tabulated cylinder. Synthetic entities include the bicubic Hermite

spline surface, B – spline surface, rectangular and triangular Bezier patches, rectangular and

triangular Coons patches, and Gordon surface. The mathematical properties of some of these

entities are covered in this chapter for two purposes. First, it enables users to correctly choose the

proper surface entity for the proper application. For example, a ruled surface is a linear surface

and does not permit any twist while a B – spline surface is a general surface. Second users will

be in a position to better understand CAD/CAM documentation and the related modifiers to each

surface entity command available on a system. The following are descriptions of major surface

entities provided by CAD/CAM systems

Application:

1. Calculating mass properties.

2. Checking for interference between mating parts.

3. Generating cross-sectioned views.

4. Generating finite element mesh.

Advantages:

1. They are less ambiguous than wireframe model.

2. Surface model provides hidden line and surface algorithms to add realism to the displayed

geometry.

2. Surface model can be utilized in volume and mass property calculations, finite element

modeling, NC path generation, and cross section &interference detections.

3. Change in finite element mesh size produce more accurate results in FEA

Disadvantages:

1. Surface models are generally more complex and thus require more terminal and CPU time and

computer storage to create than wireframe models.

2. Surface models are sometimes awkward to create and may require unnecessary manipulations

of wireframe entities.


3. It requires more training to create.

4. It does not provide any topological information.

SOLID MODELING:-

A solid model of an object is more complete representation than its surface model. It is

unique from the surface model in topological information it stores which potentially permits

functional automation and integration. Defining an object with the solid model is the easiest of

the available three modeling techniques. Solid model can be quickly created without having to

define individual locations as with wire frames. The completeness and unambiguity of solid

models are attributed to the information that is related database of these models stores

(Topology--It determine the relational information between objects.)

To model an object completely we need both geometry & topological information. Geometry is

visible, whereas topological information are stored in solid model database are not visible to

user. Two or more primitives can be combined to form the desire solid. Primitives are combined

by Boolean Operations.


SOLID MODELING APPROACH

There are two basic methods used to create solid models. They are Constructive Solid

Geometry (CSG) methods, and Boundary Representation (Brep) methods. CSG uses solid primitives

(rectangular prisms, spheres, cylinders, cones, etc.) and boolean operations (unions, subtractions,

intersections) to create the solid model. Brep methods start with one or more wireframe profiles, and

create a solid model by extruding, sweeping, revolving or skinning these profiles.

The Boolean operations can also be used on the profiles themselves and the solids generated

from these profiles. Solids can also be created by combining surfaces, which often have complex

shapes, through a sewing operation. This can be used, for example, to create the body of an

aerodynamic vehicle such as an airplane, with its carefully designed wing profiles. Further details on

these two different methods can be found in Zeid [Zeid]. These two methods can often be combined

in order to create the desired parts. Each of these methods has its limitations, and parts which are

very difficult to create using just one or the other method can be created much more easily using a

combination of both methods. Thus, most commercial solid modeling systems are hybrids using both

CSG and B-rep methods.

Boundary representation models are composed of two parts: topology and geometry

(surfaces, curves and points). The main topological items are: faces, edges and vertices. A face is a

bounded portion of a surface; an edge is a bounded piece of a curve and a vertex lies at a point. Other

elements are the shell (a set of connected faces), the loop (a circuit of edges bounding a face) and

loop-edge links (also known as winged edge links or half-edges) which are used to create the edge

circuits. The edges are like the edges of a table, bounding a surface portion.

Compared to the constructive solid geometry (CSG) representation, which uses only

primitive objects and Boolean operations to combine them, boundary representation is more flexible

and has a much richer operation set. This makes boundary representation a more appropriate choice

for CAD systems. CSG was used initially by several commercial systems because it was easier to

implement. The advent of reliable commercial B-rep kernel systems like Parasolid and ACIS,

mentioned above, has led to widespread adoption of B-rep for CAD. As well as the Boolean

operations, B-rep has extrusion (or sweeping), chamfer, blending, drafting, shelling, tweaking and

other operations which make use of these.

http://en.wikipedia.org/wiki/Topology

http://en.wikipedia.org/wiki/Face_(geometry)

http://en.wikipedia.org/wiki/Edge_(geometry)

http://en.wikipedia.org/wiki/Vertex_(geometry)

http://en.wikipedia.org/wiki/Computer_representation_of_surfaces

http://en.wikipedia.org/wiki/Winged_edge

http://en.wikipedia.org/wiki/Constructive_solid_geometry

http://en.wikipedia.org/wiki/Boolean_logic

http://en.wikipedia.org/wiki/Extrusion

http://en.wikipedia.org/wiki/Chamfering


The Foundation of Pro/ENGINEER

What is Pro/ENGINEER?

Pro/ENGINEER is a computer graphics system for modeling various mechanical

designs and for performing related design and manufacturing operations.

The system uses a 3D solid modeling system as the core, and applies the feature-based,

Parametric modeling method. In short, Pro/ENGINEER is a feature-based, parametric

Solid modeling system with many extended design and manufacturing applications.

How is Pro/ENGINEER different from other CAD systems?

Pro/ENGINEER was the first CAD system entirely based upon feature-based design and

parametric modeling. Today most software producers have recognized the advantage of this

approach and shifted their product onto this platform. Nevertheless, the differences between a

feature-based, parametric solid modeling CAD system and a conventional CAD system include:

Pro/ENGINEER Conventional CAD Systems

Solid Model Wireframe and Solid Model

Parametric Model Fixed Model

Feature-Based Modeling Primitive-Based Modeling

Single Data Structure and Full Function-Oriented Data Structure

Associativity and Format Interpreters

Subject-Oriented Sub-Modeling Systems A Single Geometry-Based System

Manufacturing Information Texts Attached to Geometry Entities

Associated with Features

Generation of an Assembly by Generation of an Assembly by

Assembling Components Positioning Components

Ease of Use:

• Pro/ENGINEER was designed to begin where the design engineer begins with features

and design criteria, through cascading menus.

• Expert users employ "map keys" to combine frequently used commands along with

customized menus to exponentially increase their speed in use.

• Pro/ENGINEER provides the ability to sketch directly on the solid model, feature

Placement is thus simple and accurate.


Full Associativity: Pro/ENGINEER is based on a single data structure, with the ability to

make change built into the system. Therefore, when a change is made anywhere in the

development process, it is propagated throughout the entire design-through-manufacturing

process.

Parametric, Feature-Based Modeling:

• Pro/ENGINEER's features feature contain non-geometric information, such as

Manufacturing processes and associated costs, as well as information about location and

relationships.

• This means that features do not require coordinate systems for placement, and they

"know" how they are related to the rest of the model. As a result, changes are made quickly and

always adhere to the original design intent.

Pro/ENGINEER Functionality

The basic functionality of Pro/ENGINEER is broken into four major areas:

• Part Modeling and Design

• Assembly Modeling and Design

• Design Documentation (Drawing Generation)

• General Functionality

Part Design and Modeling

Defining Geometry - Feature-Based Design

• Create sketched features including protrusions, cuts, and slots made by extruding,

revolving, or sweeping along a 2D sketched trajectory, or blending between parallel sections

• Create pick and place features, such as holes, shafts, chamfers, rounds, shells, regular

drafts, flanges, ribs, etc.

• Sketch cosmetic features

• Reference datum planes, axes, points, curves, coordinate systems, and graphs for

creating non-solid reference datum

Manipulating Geometry and Parametric Modeling

• Modify, delete, suppress, redefine, and reorder features, as well as making

Features "read-only"

• Create table-driven parts by adding dimensions to the family table

• Capture design intent by creating relations between part dimensions and

Parameters


• Generate engineering information, including mass properties of parts, model cross

sections, and reference dimensions

• Create geometric tolerances and surface finishes on models

• Assign density, units, material properties or user-specified mass properties

to a model

• Additional functionality available through Pro/FEATURE.

Assembly Design

• Place components and subassemblies using commands like mate, align, and insert to

create full product assemblies

• Disassemble components from an assembly

• Modify assembly placement offsets

• Create and modify assembly datum planes, coordinate systems, and cross sections

• Modify part dimensions in assembly mode

• Generate engineering information, bills of materials, reference dimensions, and

assembly mass properties

• Additional functionality available through Pro/ASSEMBLY.

Design Documentation (Model Drawings)

• Create numerous types of drawing views, including general, projection, auxiliary,

detailed, exploded, partial, area cross-section, and perspective

• Perform extensive view modifications; including changing the view scale and the

boundaries of partial or detailed views, adding projection and cross-section view arrows, &

creating snapshot views

• Create drawings with multiple models, delete a model from a drawing, set and high-

light the current model of a drawing

• Use a sketch as a parametric drawing format

• Manipulate dimensions, including show, erase, switch view, flip arrows, move

dimensions, text, or attach points


• Modify dimension values and number of digits

• Create, show, move, erase, and switch view for standard notes

• Include existing geometric tolerances in drawing notes

• Update the model geometry to incorporate design changes

• Markup drawings to indicate changes to be made

• Export a drawing IGES file

• Additional functionality available through Pro/DETAIL.

General Functionality

• Database management commands

• Layer control for placing items on a layer and displaying Layers

• Measuring commands for distance, geometric information angle, clearance, and global

interference on parts and assemblies

• Viewing capabilities to pan, zoom, spin, shade, and re-orient models and drawings.

The Function Modules of Pro/ENGINEER

The core of Pro/ENGINEER is the feature-based, parametric solid modeling system for

modeling mechanical parts.

The part model created by this system can be used to form mechanical assemblies and to

produce engineering drawings.

The model can also be used to carry out many other related analyses, simulation,

planning and manufacturing activities such as the generation of CNC tool paths and Bills of

Material. These extended functions are reflected by the following example Pro/ENGINEER

modes.


MODULES OF PRO/E WILDFIRE:-


PLANE DISPLAY:-


MOUSE OPERATION:-

MODEL DISPLAY:-


Ken Youssefi Mechanical Engineering Dept., SJSU 6

Default Datum Planes in Pro/E

Three Standards Principal Orthographic Planes

Top

Right

Front


Creating Solids

Sketched Features - (extrusions, revolves, sweeps, blends,

..) These features require a two-dimensional drawing (cross

section) which is then manipulated into the third dimension.

Although they usually use existing geometry for references,

they do not specifically require this. These features will

involve the use of an important tool called Sketcher.

Select a datum plane to draw.

Create a 2D sketch.

Create a feature from the sketch

by extruding, revolving,

sweeping, ….

Revolve

Sweep

Blend

Extrude



Creating Solids

Placed Features - (holes, rounds, shells, ...) These are

features that are created directly on existing solid

geometry. Examples are placing a hole on an existing

surface, or creating a round on an existing edge of a part.

Shell

Rib

Draft

Hole

Round

Chamfer


Edit Toolbar

The final group of buttons is used for editing and

modifying existing features.

Merge

Trim

Pattern

Mirror



Implicit Constraints in Sketcher


• vertical lines

• horizontal lines

• perpendicular lines

• tangency

• equal length lines

• equal radius

• vertical alignment

Example of Implicit Constraints



Setting Sketch Orientation

Sketch plane - the plane on which you will draw and your view is always

perpendicular to the sketch plane.

The Orientation option list in the dialog window (Top, Bottom, Left, Right)

refers to directions relative to the computer screen, as in “TOP edge of the

screen” or “BOTTOM edge of the screen” and so on. This orientation must be

combined with a chosen reference plane (which must be perpendicular to the

sketch plane) so that the desired direction of view onto the sketching plane is

obtained.


Setting Sketch Orientation - Example



Sketcher


The Sketcher Toolbar



Sketcher Toolbar Flyout Buttons


Weak vs. Strong Dimensions

Sketch with weak dimensions

A dimension created by Sketcher

is called ―weak‖ and is shown in

gray. Strong dimensions, on the

other hand, are those that you

create.

You can make a strong dimension in any of three ways:

1. Modify the value of a weak dimension

2. Create a dimension from scratch by identifying entities in the sketch

and placing a new dimension on the sketch

3. Select a weak dimension and promote it to strong using the RMB

pop-up menu



Over and Under Constrained Sketch

If there is not enough information to define the drawing (it

is underconstrained), Sketcher will create the necessary

and sufficient missing dimensions.These are the weak

dimensions.

If Sketcher finds the drawing is overconstrained (too

many dimensions or constraints) it will first try to solve

the sketch by deleting one or more of the weak

dimensions (the ones it made itself earlier).

However, if Sketcher still finds the drawing

overconstrained, it will tell you what the redundant

information is (which may be dimensions or constraints),


Extrude Command in Pro/E

Extrude

The Extrude DashboardExtrude Icon

Select Placement to define the

sketch plane

Solid

Surface

Depth options

Blind depth

Thicken Sketch

Remove material (cut)

Flip direction



Extrude Command in Pro/E

Extruded surface

Extrude Dashboard

Surface

Depth Spec options

Extrude to selected point,

curve, plane or surface

Extrude on both sides of

the sketch, equal amount.

Extrude from the sketch by

a specified value

Thicken Sketch

A Thick extruded solid


Creating an Extruded Cut

1. Select a plane to sketch on, cannot

sketch on a curved surface.

2. Sketch the curve

3. Select Remove Material button

Remove Material



Creating an Extruded Cut

Common dashboard controls

Material removal arrow pointing to the right.

Material

Removal

Side

Material removal arrow pointing to the left.


Blind

Thru next

Thru all

Thru until

Depth options

Creating a Hole (placed feature)

Hole types

Straight

Sketched

Standard hole

counterbore

Standard hole

countersink



Creating a Hole (placed feature)

Hole placement:

linear or radial

The Straight hole

dashboard (default)

Standard threaded hole option


Chamfer and Fillet (Round)

Round

Chamfer

Chamfer

Dashboard

Round

Dashboard



Creating a Revolved Feature

• Sketch a 2D profile

• Revolve the sketch

around the centerline

Revolve

Extrude

• Sketch a centerline


Creating a Sweep Feature

(Protrusion)

Trajectory

Section



Creating a Sweep Feature (Cut)

Create an entity from an edge

Pick the top surface of the table top to sketch, insert the two edges

of the table into the sketch plane for reference, erase after finished.

Sketch the sweep trajectory (guide sweep)

Trajectory



select Insert → Sweep → Cut, and choose the Select Traj. option




Sketch the cut profile on the back surface f the table top

Back surface


Creating a Swept Blend Feature

Swept Blend Dashboard

Sweep type

Insert → Swept Blend



Creating a Swept Blend Feature

option keeps each of the

feature‘s cross sections normal to the trajectory of the

feature. Each section is created normal to a vertex of the

trajectory or normal to a datum point on the trajectory. It

requires the definition of a trajectory and the definition of

one or more sections

option keeps the feature‘s

cross sections normal to a selected planar pivot plane, edge,

curve, or axis. Each section of the feature is created normal

to the selected pivot plane. It requires the definition of a

trajectory a normal plane and the definition of one or more

sections.

Constant Normal Direction

option keeps the feature‘s cross

sections normal to a second trajectory. Each section of the

feature is created perpendicular to the normal trajectory. The

option requires the definition of a sweep trajectory, a normal

trajectory, and two or more sections.

The Normal to Projection

The Normal to Trajectory


Creating a Swept Blend Feature - Examples

The Normal to

Projection

The Normal to Trajectory




Sketch the

trajectory

12

3

4

5



Select Insert → Swept Blend Swept Blend dashboard

Select Normal To Trajectory (default)

Select the trajectory, if there is only one sketch,

it will be selected automatically



Swept Blend Feature - Example

Select a point and sketch the cross section

12

34

5


Select Insert when

finished with the

sketch

Follow the same steps to draw the other

sections



Creating a Variable-Section Swept FeatureUsed to create complex geometric shapes. The option sweeps a section

along one or more trajectories.


Creating a Datum Plane Tangent to a Curve at a Point

Select the curved plane

and the Tangent option

A

Select Datum Plane



Creating a Datum Plane Tangent to a Curve at a Point

Select the end point of the

line, the datum plane is

tangent to the cylinder at

point A.


Sketch on the created

datum plane

Extrude and cut


ASSEMBLY DESIGN


Top-Down Design (Modeling)

The assembly file is created first and then the components

are created in the assembly file. The parts are build relative

to other components. Useful in new designs

In practice, the combination of Top-Down and Bottom-Up

approaches is used. As you often use existing parts and

create new parts in order to meet your design needs.


Bottom-Up Design (Modeling)

The components (parts) are created first and then added to the

assembly file. This technique is particularly useful when parts

already exist from previous designs and are being re-used.



Degrees of Freedom

An object in space has six degrees of freedom.

• Translation – movement along X, Y, and Z axis (three degrees of freedom)

• Rotation – rotate about X, Y, and Z axis

(three degrees of freedom)


Fundamentals of assembly in Pro/E

In pull down menu File, select new and then choose

Assembly option.

Select



Adding Components

Or pick the Add

Component button

in the right toolbar.

Browse and open

the file for the first

component.

In the pull-down

menu, select

Insert >

Component >

Assemble


Mating ComponentsChoose constraint type

Choose Offset typeYou may Delete or Disable any

constraint by right clicking the

constraint



Informs you if the

assembly is fully or

partially constrained

Select Move to check the

relative motion of the

components (translation or

rotational motion)

Add new constraint


Assembly ConstraintsIn order to completely define the position of one part relative

to another, we must constrain all of the degrees of freedom.

Mate, Align, and Insert

Mate Offset

Two surfaces are made parallel with

a specified offset distance.

Mate

Two selected surfaces become

co-planar and face in opposite

directions. This constrains 3

degrees of freedom (two

rotations and one translation)



Assembly Constraints

Align Coincident

Two selected surfaces become co-planar

and face in the same direction. Can also

be applied to revolved surfaces. This

constrains 3 degrees of freedom (two

rotations and one translation).

When Align is used on revolved

surfaces, they become coaxial

(axes through the centers align).



Align Offset

This can be applied to planar surfaces

only, surfaces are made parallel with a

specified offset distance.

Align Orient

Two planar surfaces are made parallel,

not necessarily co-planar, and face the

same direction (similar to Align Offset

except without the specified distance).

Constrains two degrees of freedom (two rotations)



Insert

This constrain can only be applied to

two revolved surfaces in order to make

them coaxial (coincident).


Used with cylindrical surfaces


EXAMPLE ASSEMBLY DESIGN


Creating an Assembly

Part Part

Assembly


Creating an Assembly Example

The example assembly requires three mates to fully define it.

First constrain: Mate between the hollow faces as shown.

This removes

three degrees of

freedom.

Hollow faces



ExampleSecond Constrain: Align the right faces of both components.

Third Constrain: Align the top faces of both components.

top facesThe assembly is

fully defined

Right side faces One degree of

freedom left

EXAMPLE: 2


Example


COMPUTER AIDED MANUFACTURING

Programmable automation in which the mechanical actions of a ‗machine tool‘ are controlled by

a program containing coded alphanumeric data that represents relative positions between a work

head (e.g., cutting tool) and a work part

Motion Control Systems

Point-to-Point systems

Also called position systems

System moves to a location and performs an

operation at that location (e.g., drilling)

Also applicable in robotics

Continuous path systems

Also called contouring systems in machining

System performs an operation during

movement (e.g., milling and turning)


COMPUTER NUMERICAL CONTROL MACHINE

Storage of more than one part program

Various forms of program input

Program editing at the machine tool

Fixed cycles and programming subroutines

Interpolation

Acceleration and deceleration computations

Communications interface

Diagnostics

Machine Control Unit


Cost-Benefits of NC

Costs

High investment cost

High maintenance effort

Need for skilled programmers

High utilization required

Benefits

Cycle time reduction

Nonproductive time reduction

Greater accuracy and repeatability

Lower scrap rates

Reduced parts inventory and floor space

Operator skill-level reduced

NC PART PROGRAMMING

Manual part programming

Manual data input

Computer-assisted part programming

Part programming using CAD/CAM

MANUAL PART PROGRAMMING

Binary Coded Decimal System

Each of the ten digits in decimal system (0-9) is coded with four-digit binary number

The binary numbers are added to give the value

BCD is compatible with 8 bits across tape format, the original storage medium for NC

part programs

Eight bits can also be used for letters and symbols


The RS274-D is a word address format

Each line of program == 1 block

Each block is composed of several instructions, or (words)

Sequence and format of words:

N3 G2 X+1.4 Y+1.4 Z+1.4 I1.4 J1.4 K1.4 F3.2 S4 T4 M2

sequence no

preparatory function

destination coordinates dist to center of circle

feed rate spindle speed

tool

miscellaneous function

COMPUTER ASSISTED PART PROGRAMMING

Write machine instructions using natural language type statements

Statements translated into machine code of the MCU

APT (Automatically Programmed Tool) Language

Part is composed of basic geometric elements and mathematically defined surfaces

Examples of statements:

P4 = POINT/35,90,0

L1 = LINE/P1,P2

C1 = CIRCLE/CENTER,P8,RADIUS,30

Tool path is sequence of points or connected line and arc segments

Point-to-Point command: GOTO/P4

Continuous path command: GOLFT/L1,TANTO,C1


Automatic Part Programming

Software programs can automatic generation of CNC data

Make 3D model

Define Tool

CNC data

Simulate

cutting


CNC – Lathe

List of G – codes

G00 – Rapid Traverse

G01 – Linear interpolation

G02 – Circular interpolation – clockwise

G03 – Circular interpolation – counter clockwise

G21 – Dimensions are in mm

G28 – Home position

G40 – Compensation Cancel

G50 – Spindle speed clamp

G70 – Finishing cycle

G71 – Multiple turning cycle

G75 – Multiple grooving cycle

G76 – Multiple threading cycle

G90 – Box turning cycle

G98 – Feed in mm/min

List of M-codes

M03 – Spindle ON in clockwise direction

M05 – Spindle stop

M06 – Tool change

M10 – Chuck open

M11 – Chuck close

M30 – Program stop and rewind

M38 – Door open

M39 – Door close


CNC – MILLING

List of G – codes

G00 – Rapid Traverse

G01 – Linear interpolation

G02 – Circular interpolation – clockwise

G03 – Circular interpolation – counter clockwise

G21 – Dimensions are in mm

G28 – Home position

G40 – Compensation Cancel

G50 – Spindle speed clamp

G83 – Peck drilling cycle

G90 – Absolute coordinate system

G91 – Incremental coordinate system

G94 – Feed in mm/min

G170, G171 – Circular Pocketing

G172, G173 – Rectangular Pocketing

List of M-codes

M03 – Spindle ON in clockwise direction

M05 – Spindle stop

M06 – Tool change

M10 – Chuck open

M11 – Chuck close

M30 – Program stop and rewind

M38 – Door open

M39 – Door close

M70 – Mirroring ON in X-axis

M71 - Mirroring ON in Y-axis

M80 – Mirroring OFF in X-axis

M81 – Mirroring OFF in Y-axis

M98 – Sub program call statement

M99 – Sub program terminate


FACING AND TURNING

EXPT. NO :

DATE :

AIM:

To machine a given work piece for given dimension using turning and facing operations.

PROGRAM:

[BILLET X32 Z70

G21 G98

G28 U0 W0

M06 T3

M03 S1500

G00 X28 Z1

G94 X0 Z-0.5 F80

Z-1

Z-2

G00 X32 Z1

G90 X28 Z-50 F100

X27.5

X27

X26.5

X2

X25

G28 U0 W0

M05

M30


FACING AND TURNING

All dimensions are in mm

Material - Aluminum

RESULT:

Thus the given work piece was machined for the required dimensions.


STEP TURNING

EXPT. NO:

DATE :

AIM:

To machine a given work piece for given dimension using step turning operations.

PROGRAM:

[BILLET X28 Z75

N10 G21 G98

N20 G28 U0 W0

N30 M06 T1

N40 M03 S1500

N50 G00 Z2

N60 G00 X28

N70 G94 X-1 Z-.5 F1.2 FACING

Z-1

Z-1.5

Z-2

N80 G71 U0.5 R1 CANNED CYCLE

N90 G71 P100 Q140 U0.1 W0.1 F100

N100 G01 X20 Z0 CYCLE START

N110 G01 X20 Z-25

N120 G01 X25 Z-25

N130 G01 X25 Z-50

N140 G01 X28 Z-50 CYCLE END

N150 G28 U0 W0


N160 M05

N170 M30

STEP TURNING


Material - Aluminum

RESULT:

The work piece is machined as per the dimensions.


TAPER TURNING

EXPT. NO:

DATE :

AIM:

To machine a given work piece for given dimension using taper turning operations.

PROGRAM:

[BILLET X28 Z75

N10 G21 G98

N20 G28 U0 W0

N30 M06 T1

N40 M03 S1500

N50 G00 Z2

N60 G00 X28

N70 G94 X-1 Z-.5 F100 FACING

Z-1

Z-1.5

Z-2

N80 G71 U0.5 R1 CANNED CYCLE

N90 G71 P100 Q120 U0.1 W0.1 F100

N100 G01 X20 Z0

N110 G01 X20 Z-25

N120 G01 X28 Z-50

N130 G28 U0 W0

N140 M05

N150 M30


TAPER TURNING


Material - Aluminum

RESULT:

The work piece is machined as per the dimensions.


THREAD CUTTING OPERATION

EXPT. NO:

DATE

AIM:

To machine a given work piece for given dimension using step turning operation

PROGRAM:

[BILLET X28 Z75

N10 G21 G98

N20 G28 U0 W0

N30 M06 T01

N40 M03 S1200

N50 G00 X28 Z2

N60 G71 U.5 R1

N70 G71 P80 Q130 U.1 W.1 F50

N80 G00 X15 Z0

N90 G01 X15 Z-15

N120 G01 X25 Z-30

N130 G01 X28 Z-30

N140 G01 F30

N150 S1500

N160 G70 P1 Q2


N170 G28 U0 W0

N180 M06 T03

N190 M03 S600

N200 G00 X15.5 Z2

N210 G76 P021560 Q050 R.02

N220 G76 X13.774 Z-13 P613 Q100 F1

N230 G28 U0 W0

N240 M05

N250 M3

THREAD CUTTING OPERATIONS

All dimensions are in mm Material - Aluminum


RESULT

Thus the work piece is machined as per the dimensions

CONTOUR MILLING

EXPT. NO:

DATE :

AIM:

To machine a given work piece for the given dimension using contour milling

PROGRAM:

[BILLET X100 Y100 Z10

[EDGE MOVE X-50 Y-50

[TOOL DEF T1 D6

G21 G94

G91 G28 Z0


G28 X0 Y0

M06 T01

M03 S1500

G90 G00 X-25 Y-25 Z5

G01 Z-1 F30

G01 X25 Y-25

G01 X25 Y15

G03 X15 Y25 R10

G01 X-15 Y25

G02 X-25 Y15 R10

G01 X-25 Y-25

G00 Z5

G91 G28 Z0

G28 X0 Y0

M05

M30


CONTOUR MILLING


Material - Aluminum

RESULT:

Thus the work piece is machined as per the dimensions.


MIRRORING

EXPT. NO:

DATE :

AIM:

To machine a given work piece for given dimension using mirroring operations.

PROGRAM:

[BILLET X Z0


[TOOL DEF T1 D6

G21 G94

G91 G28 Z0

G28 X0 Y0

M06 T01

M03 S1500

G90 G00 X10 Y40 Z5

M98 P001 6789

M70

M98 P001 6789

M80

M71

M98 P001 6789

M81

M70

M71


M98 P001 6789

M80

M81

G91 G28 Z0

G28 X0 Y0

M05

M30

O 6789

G90 G00 X10 Y40

G01 Z-1 F40

G01 X40 Y10

G01 X10 Y10

G01 X10 Y40

G00 Z5

X0 Y0

M99


MIRRORING


Material - Aluminum

RESULT:



DRILLING

EXPT. NO:

DATE :

AIM:

To drill the four holes in the given work piece as shown in the figure.

PROGRAM CODE:

[BILLET X100 Y100 Z10


[TOOL DEF T2 D10

N10 G21 G94

N20 G28 X0 Y0

N30 G00 Z5

N40 M06 T01

N50 M03 S1500

N60 G83 X25 Y25 Z-6 R5 Q2 F100

X-25 Y25

X-25 Y-25

X25 Y-25

N70 G00 G80 G90 Z15

N80 M05


N90 M30

DRILLING


Material - Aluminum

RESULT:


cad cam lab manual department of mechnical …

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