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20ME605�COMPUTER AIDED DESIGN AND�MANUFACTURING

Department: MECHANICAL ENGINEERING�Batch/Year: 2021-2025�Created by:

Dr A.KADIRVEL

�Date: 03.01.2024

Table of Contents

COURSE OBJECTIVES

• Students completing this course are expected to:

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• Explain the advanced aspects of enabling computer aided technologies used in design, manufacturing and rapid product development

• Discuss the use of computers in mechanical component design

• Design the 3D Model of parts, assemblies and explore the features of CNC Machine tools.

• Illustrate the advances in modern techniques of rapid prototyping

• Summarize the various CAD standards in exchange of data, graphics and images

PRE REQUISITE CHART

SYLLABUS

UNIT I INTRODUCTION TO CAD AND CAM 6+6

Product cycle- Design process- sequential and concurrent engineering- Computer aided design – CAD system architecture- Computer graphics – 2D and 3D transformations - homogeneous coordinates - Line drawing -Clipping- Brief introduction to CAD and CAM – Manufacturing Planning, Manufacturing control- CAD/CAM concepts – Lean Production and Just-In-Time Production.

List of Exercise/Experiments

1.Introduction to CAD Software

2.Introduction to Fundamentals of CAM

UNIT II GEOMETRIC MODELING 6+6

Wireframe Modeling - Representation of curves - Hermite curve - Bezier curve - B-spline curves - rational curves -Techniques for surface modeling - Solid modeling techniques - CSG and B-rep- Assembly modeling- Top-down Approach – Bottom -Up Approach.

List of Exercise/Experiments

1. Creation of 3D Assembly model of Machine Elements

2. Detailing of the Assembly model of Machine Elements

UNIT III CAD STANDARDS 6+6

Standards for computer graphics - Graphical Kernel System (GKS) - standards for exchange images - Open Graphics Library (OpenGL) - Data exchange standards - IGES, STEP etc. – communication standards.

List of Exercise/Experiments

1. Export the Assembly model in IGES format.

2. Import the model in STEP & DXF format.

SYLLABUS

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UNIT IV CELLULAR MANUFACTURING AND FLEXIBLE MANUFACTURING SYSTEM 6+6

Group Technology (GT), Part Families – Parts Classification and coding – Computer Aided Process Planning (CAPP) – Production flow Analysis–Cellular Manufacturing – Composite part concept – Types of Flexibility - FMS – FMS Components – FMS Application & Benefits – FMS Planning and Control.

List of Exercise/Experiments

1. Study the Application of CAPP in machining and Turning centre

2. Post Process generation using CAM Package

UNIT V ADDITIVE MANUFACTURING 6+6

Need - Development of RP systems – RP process chain - Impact of Rapid Prototyping on Product Development. - STL file generation. Rapid Prototyping system: Stereolithography (SLA)- Fused Deposition Modeling (FDM)- laminated object manufacturing (LOM)- Selective Laser Sintering (SLS) - Working Principles, details of processes, products, materials, advantages, limitations and applications.

List of Exercise/Experiments

1. Develop a mechanical product using the 3D Printer

2. Obtain the model of the Machine Element using 3D Scanner

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COURSE OUTCOMES �

After successful completion of the course, the students should be able to

CO-PO/PSO Mapping

Lecture Plan

ACTIVITY BASED LEARNING

UNIT -I

Group Discussion: Group Discussion on Why CAD is Important in Engineering Industry?

• In engineering practice, CAD/CAM has been utilized in different ways by different people.
• Some utilize it to produce drawings and document designs.
• Others may employ it as a visual tool by generating shaded images and animated displays.
• A third group may perform engineering analysis of some sort on geometric models such as finite element analysis.
• A fourth group may use it to perform process planning an generate NC part programs. In order to establish the scope and definition of CAD/CAM in an engineering environment and identify existing and future related tools, a study of a typical product cycle is necessary

UNIT 1 : LECTURE NOTES�INTRODUCTION

PRODUCT LIFE CYCLE (PLC)

• Every product goes through a cycle from birth, followed by an initial growth stage, a relatively stable matured period, and finally into a declining stage that eventually ends in the death of the product as shown schematically in Figure.

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• Introduction stage: In this stage the product is new and the customer acceptance is low and hence the sales are low.
• Growth stage: Knowledge of the product and its capabilities reaches to a g rowing number of customers.
• Maturity stage: The product is widely acceptable and sales are now stable , and it grows with the same rate as the economy as a whole grows.
• Decline stage: At some point of time the product enters the decline stage. Its sales start decreasing because of a new and a better product has entered the market to fulfill the same customer requirements.

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PRODUCT LIFE CYCLE (PLC) FOR CONTINUOUS IMPROVEMENT

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Product Life Cycle for continuous Improvement ( Basic)

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TECHNOLOGY DEVELOPMENT CYCLE

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• The development of a new technology follows a typical S-shaped curve. In its early stage, the progress is limited by the lack of ideas. A single good idea can make several other god ideas possible, and the rate of progress is exponential. Gradually the growth becomes linear when the fundamental ideas are in place and the progress is concerned with filling the gaps between, the key ideas.

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• It is during this time when the commercial exploitation flourishes. But with time the technology begins to run dry and increased improvements come with greater difficulty. This matured technology grows slowly and approaches a limit asymptotically

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• The success of a technology based company lies in its capabilities of recognizing when the core technology on which the company‘s products are based begin to mature and through an active R&D program, transfer to another technology growth curve which offers greater possibilities.

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Engineering Design Process�

The Engineering Design Process is the formulation of a plan to help an engineer build a product with a specified performance goal. This process involves a number of steps, and parts of the process may need to be repeated many times before production of a final product can begin.

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It is a decision making process (often iterative) in which the basic sciences, mathematics, and engineering sciences are applied to convert resources optimally to meet a stated objective. Among the fundamental elements of the design process are the establishment of objectives and criteria, synthesis, analysis, construction, testing and evaluation.

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DESIGN PROCESS MODELS�

SHIGLEY MODEL

OSHUGA MODEL

�SEQUENTIAL VS CONCURRENT ENGINEERING DESIGN�

Sequential engineering is a type of engineering production method where a project is completed in a linear format. In sequential engineering, each step is worked on in a certain order. All attention is put toward completing the first step of the project until it is complete. Once the first step is complete, the engineering team will then move on to the second step of the project. Sequential engineering is sometimes referred to as "throw-it-over-the-wall" engineering, because of the linear order in which a project is completed.

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Advantages and Disadvantages of sequential engineering

+ Easy to track progress and understand the requirements of the +project and processes

It is well defined for each team member or department

Simple to understand and avoids misinterpretation

+ It is an imposed discipline approach which takes away any misunderstanding

- Increased product cycle time because of the rework during the latter stages of the NPD

- Change requests from others in the latter stages are often very expensive and difficult to manage

- Without staged feedback and specification evaluation gates, the product might creep out or fall short of the expectation

- Manufacturing and production cost might be too difficult and expensive making the final unit cost not economically viable

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Concurrent engineering is a different approach to product development within engineering and is the preferred approach. During a concurrent engineering production cycle, several teams work on different parts of the design at the same time. Flaws identifiable only in a later step using sequential engineering can be identified earlier in the process, saving both time and money.

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In addition, various life-cycle phases overlap each other, and there in no "wall" between these phases. The completion of a previous life-cycle phase is not a pre requisite for the start of the next life-cycle phase. In addition, there is a continuous feedback between these life-cycle phases so that the conflicts are detected as soon as possible.

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In concurrent engineering, different tasks are tackled at the same time, and not necessarily in the usual order. This means that info found out later in the process can be added to earlier parts, improving them, and also saving a lot of time. Concurrent engineering is a method by which several teams within an organization work simultaneously to develop new products and services and allows a more stream lined approach. The concurrent engineering is a non- linear product or project design approach during which all phases of manufacturing operate at the same time - simultaneously. Both product and process design run in parallel and occur in the same time frame.

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ROLE OF COMPUTERS IN DESIGN

Computer-aided design (CAD) is any design activity that involves the effective use of a computer to create, modify, analyze, or document an engineering design. The use of a CAD system creates huge amounts of additional data that is often stored and managed in a product data management (PDM) system.

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The use of a CAD system creates huge amounts of additional data that is often stored and managed in a product data management (PDM) system. A PDM system consists of computer software that provides links between users and a central database, where engineering design data and related documentation is stored. The PDM system manages the database by tracking the identities of users, facilitating and documenting engineering changes, recording a history of the engineering changes on each part and product, and providing documentation management functions.

Before CAD

After CAD

CAD SYSTEM ARCHITECTURE

Computer-aided drafting (CAD) is the use of computer systems to aid in the creation, modification, analysis, or optimization of a design. CAD software is used to increase the productivity of the designer, improve the quality of design, improve communications through documentation, and to create a database for manufacturing. CAD output is often in the form of electronic files for print, machining, or other manufacturing operations. The term CADD, (for Computer Aided Design and Drafting) is also used.

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Its use in designing electronic systems is known as electronic design automation, or EDA. In mechanical design it is known as mechanical design automation (MDA) or computer-aided drafting (CAD), which includes the process of creating a technical drawing with the use of computer software.

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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, often called DCC digital content creation.

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BENEFITS OF CAD

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• Productivity Improvement in Design
• Depends on Complexity of drawing,
• Degree of repetitiveness of features in the designed parts,
• Degree of symmetry in the parts,
• Extensive use of library of user defined shapes and commonly use d entities
• Shorter Lead Times
• Flexibility in Design
• Design Analysis
• Fewer Design Error
• Standardization of Design, Drafting and Documentation
• Drawings are more understandable
• Improved Procedures of Engineering Change
• Benefits in Manufacturing :
• Tool and fixture design for manufacturing
• Computer Aided process planning
• Preparation of assembly lists and bill of materials
• Computer aided inspection
• Coding and classification of components
• Production planning and control
• Preparation of numerical control programs for manufacturing the parts on CNC machines Assembly sequence planning

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REASONS FOR IMPLEMENTING CAD

• To increase the productivity of the designer
• To improve the Quality of Design
• To improve Documentation
• To create a Database for manufacturing

INTERACTIVE COMPUTER GRAPHICS� �

• Computer Graphics is defined as creation, storage, and manipulation of pictures and drawings by means of a digital computer
• It is an extremely effective medium for communication between people and computers
• Computer graphics studies the manipulation of visual and geometric information using computational techniques
• It focuses on the mathematical and computational foundations of image generation and processing rather than purely aesthetic issues

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In Interactive Computer Graphics (ICG) the user interacts with the compute and comprises the following important functions:

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Modeling, which is concerned with the description of an object in terms of its spatial coordinates, lines, areas, edges, surfaces, and volume

Storage, which is concerned with the storage of the model in the memory of the computer

Manipulation, which is used in the construction of the model from basic primitives in combination with Boolean algebra�Viewing, in the case the computer is used to look at the model from a specific angle and presents on its screen what it sees.

Typical Hardware setup of a Graphic System

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CO-ORDINATE SYSTEMS�

A coordinate system is o ne which uses one or more numbers, or coordinates, to uniquely determine the position of a point or other geometric element on a manifold such as Euclidean space.

Number line

The simplest example of a coordinate system is the identification of points on a line with real numbers using the number line. In this system, an arbitrary point O (the origin) is chosen o n a given line. The coordinate of a point P is de fined as the signed distance from O to P, where the signed distance is the distance taken as positive or negative depending on which side of the line P lies. Each point is given a unique coordinate and each real number is the coordinate of a unique point.

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Cartesian coordinate system [ (x,y) and (x,y,z) ]

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Polar coordinate system (ρ,θ)

Another common coordinate system for the plane is the polar coordinate system. A point is chosen as the pole and a ray from this point is taken as the polar axis.

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Cylindrical Coordinate systems

A cylindrical coordinate system is a three-dimensional coordinate system that specifies point positions by the distance from a chosen reference axis, the direction from the axis relative to a chosen reference direction, and the distance from a chosen reference plane perpendicular to the axis. The latter distance is given as a positive or negative number depending on which side of t he reference plane faces the point.

 The origin of the system is the point where all three coordinates can be given as zero. This is the intersection between the reference plane and the axis.

 The axis is variously called the cylindrical or longitudinal axis, to differentiate it from the polar axis, which is the ray that lies in the reference plane, starting at the origin and pointing in the reference direction.

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The distance from the axis may be called the radial distance or radius, while the angular coordinate is sometimes referred to as the angular position or as the azimuth.

θ is elevation: θ is inclination:

2D Transformation in Computer Graphics-�

In Computer graphics, Transformation is a process of modifying and re-positioning the existing graphics.

• 2D Transformations take place in a two dimensional plane.
• Transformations are helpful in changing the position, size, orientation, shape etc of the object.

Transformation Techniques

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2D Translation in Computer Graphics-

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In Computer graphics, 2D Translation is a process of moving an object from one position to another in a two dimensional plane.

Let

Initial coordinates of the object O = (Xold, Yold)

New coordinates of the object O after translation = (Xnew, Ynew)

Translation vector or Shift vector = (Tx, Ty)

 Given a Translation vector (Tx, Ty)-

Tx defines the distance the Xold coordinate has to be moved.

Ty defines the distance the Yold coordinate has to be moved.

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This translation is achieved by adding the translation coordinates to the old coordinates of the object as-�Xnew = Xold + Tx (This denotes translation towards X axis)�Ynew = Yold + Ty (This denotes translation towards Y axis)

• The homogeneous coordinates representation of (X, Y) is (X, Y, 1).
• Through this representation, all the transformations can be performed using matrix / vector multiplications.

The above translation matrix may be represented as a 3 x 3 matrix as

2D Rotation in Computer Graphics-

In Computer graphics, 2D Rotation is a process of rotating an object with respect to an angle in a two dimensional plane.

Consider a point object O has to be rotated from one angle to another in a 2D plane.

Let-

Initial coordinates of the object O = (Xold, Yold)

Initial angle of the object O with respect to origin = Φ

Rotation angle = θ

New coordinates of the object O after rotation = (Xnew, Ynew)

In Matrix form, the above rotation equations may be represented as-

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For homogeneous coordinates, the above rotation matrix may be represented as a 3 x 3 matrix as-

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2D Scaling in Computer Graphics-

In computer graphics, scaling is a process of modifying or altering the size of objects.

• Scaling may be used to increase or reduce the size of object.
• Scaling subjects the coordinate points of the original object to change.
• Scaling factor determines whether the object size is to be increased or reduced.

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• If scaling factor > 1, then the object size is increased.
• If scaling factor < 1, then the object size is reduced.

Consider a point object O has to be scaled in a 2D plane.

Let-

Initial coordinates of the object O = (Xold, Yold)

• Scaling factor for X-axis = Sx
• Scaling factor for Y-axis = Sy

New coordinates of the object O after scaling = (Xnew, Ynew)

This scaling is achieved by using the following scaling equations-

Xnew = Xold x Sx

Ynew = Yold x Sy

In Matrix form, the above scaling equations may be represented as-

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For homogeneous coordinates, the above scaling matrix may be represented as a 3 x 3 matrix as-

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2D Reflection in Computer Graphics-

 Reflection is a kind of rotation where the angle of rotation is 180 degree.

The reflected object is always formed on the other side of mirror.

The size of reflected object is same as the size of original object.

 Consider a point object O has to be reflected in a 2D plane.

Let-

Initial coordinates of the object O = (Xold, Yold)

New coordinates of the reflected object O after reflection = (Xnew, Ynew)

Reflection On X-Axis:

This reflection is achieved by using the following reflection equations-

Xnew = Xold

Ynew = -Yold

 In Matrix form, the above reflection equations may be represented as-

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For homogeneous coordinates, the above reflection matrix may be represented as a 3 x 3 matrix as-

2D Shearing in Computer Graphics-

In Computer graphics, 2D Shearing is an ideal technique to change the shape of an existing object in a two dimensional plane.

In a two dimensional plane, the object size can be changed along X direction as well as Y direction.

So, there are two versions of shearing-

• Shearing in X direction
• Shearing in Y direction

Consider a point object O has to be sheared in a 2D plane.

Let-

Initial coordinates of the object O = (Xold, Yold)

Shearing parameter towards X direction = Shx

Shearing parameter towards Y direction = Shy

New coordinates of the object O after shearing = (Xnew, Ynew)

Shearing in X Axis-

Shearing in X axis is achieved by using the following shearing equations-

Xnew = Xold + Shx x Yold

Ynew = Yold

In Matrix form, the above shearing equations may be represented as

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For homogeneous coordinates, the above shearing matrix may be represented as a 3 x 3 matrix as-

Shearing in Y Axis-

Shearing in Y axis is achieved by using the following shearing equations-

Xnew = Xold

Ynew = Yold + Shy x Xold

In Matrix form, the above shearing equations may be represented as-

Line Drawing Algorithms

In computer graphics, popular algorithms used to generate lines are-

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DDA Algorithm-

DDA Algorithm is the simplest line drawing algorithm.

Given the starting and ending coordinates of a line,

DDA Algorithm attempts to generate the points between the starting and ending coordinates.

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Procedure-

Given-

Starting coordinates = (X0, Y0)

Ending coordinates = (Xn, Yn)

The points generation using DDA Algorithm involves the following steps-

Step-01:

Calculate ΔX, ΔY and M from the given input.

These parameters are calculated as-

ΔX = Xn – X0

ΔY =Yn – Y0

M = ΔY / ΔX

Step-02:

Find the number of steps or points in between the starting and ending coordinates.

if (absolute (ΔX) > absolute (ΔY))

Steps = absolute (ΔX);

else

Steps = absolute (ΔY);

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Step-03:

Suppose the current point is (Xp, Yp) and the next point is (Xp+1, Yp+1).

Find the next point by following the below three cases-

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Step-04:

Keep repeating Step-03 until the end point is reached or the number of generated new points (including the starting and ending points) equals to the steps count.

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PRACTICE PROBLEMS BASED ON DDA ALGORITHM-

Problem-01:

Calculate the points between the starting point (5, 6) and ending point (8, 12).

Solution-

Given-

Starting coordinates = (X0, Y0) = (5, 6)

Ending coordinates = (Xn, Yn) = (8, 12)

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Step-01:

Calculate ΔX, ΔY and M from the given input.

ΔX = Xn – X0 = 8 – 5 = 3

ΔY =Yn – Y0 = 12 – 6 = 6

M = ΔY / ΔX = 6 / 3 = 2

Step-02:

Calculate the number of steps.

As |ΔX| < |ΔY| = 3 < 6, so number of steps = ΔY = 6

Step-03:

As M > 1, so case-03 is satisfied.

Now, Step-03 is executed until Step-04 is satisfied.

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Bresenham Line Drawing Algorithm-

Given the starting and ending coordinates of a line,

Bresenham Line Drawing Algorithm attempts to generate the points between the starting and ending coordinates.

Procedure-

Given-

Starting coordinates = (X0, Y0)

Ending coordinates = (Xn, Yn)

The points generation using Bresenham Line Drawing Algorithm involves the following steps-

Step-01:

Calculate ΔX and ΔY from the given input.

These parameters are calculated as-

ΔX = Xn – X0

ΔY =Yn – Y0

Step-02:

Calculate the decision parameter Pk.

It is calculated as-

Pk = 2ΔY – ΔX

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Step-03:

Suppose the current point is (Xk, Yk) and the next point is (Xk+1, Yk+1).

Find the next point depending on the value of decision parameter Pk.

Follow the below two cases-

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Step-04:

Keep repeating Step-03 until the end point is reached or number of iterations equals to (ΔX-1) times.

PRACTICE PROBLEMS BASED ON BRESENHAM LINE DRAWING ALGORITHM-

Problem-01:

Calculate the points between the starting coordinates (9, 18) and ending coordinates (14, 22).

Solution-

Given-

Starting coordinates = (X0, Y0) = (9, 18)

Ending coordinates = (Xn, Yn) = (14, 22)

Step-01:

Calculate ΔX and ΔY from the given input.

ΔX = Xn – X0 = 14 – 9 = 5

ΔY =Yn – Y0 = 22 – 18 = 4

Step-02:

Calculate the decision parameter.

Pk

= 2ΔY – ΔX

= 2 x 4 – 5

= 3

So, decision parameter Pk = 3

Step-03:

As Pk >= 0, so case-02 is satisfied.

Thus,

Pk+1 = Pk + 2ΔY – 2ΔX = 3 + (2 x 4) – (2 x 5) = 1

Xk+1 = Xk + 1 = 9 + 1 = 10

Yk+1 = Yk + 1 = 18 + 1 = 19

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Similarly, Step-03 is executed until the end point is reached or number of iterations equals to 4 times.

(Number of iterations = ΔX – 1 = 5 – 1 = 4)

Clipping & Viewing Transformation

The primary use of clipping in computer graphics is to remove objects, lines, or line segments that are outside the viewing pane. The viewing transformation is insensitive to the position of points relative to the viewing volume − especially those points behind the viewer − and it is necessary to remove these points before generating the view.

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Point Clipping

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Clipping a point from a given window is very easy. Consider the following figure, where the rectangle indicates the window. Point clipping tells us whether the given point X,YX,Y is within the given window or not; and decides whether we will use the minimum and maximum coordinates of the window.

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The X-coordinate of the given point is inside the window, if X lies in between Wx1 ≤ X ≤ Wx2. Same way, Y coordinate of the given point is inside the window, if Y lies in between Wy1 ≤ Y ≤ Wy2.

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Line Clipping

The concept of line clipping is same as point clipping. In line clipping, we will cut the portion of line which is outside of window and keep only the portion that is inside the window.

Cohen-Sutherland Line Clippings

This algorithm uses the clipping window as shown in the following figure.

The minimum coordinate for the clipping region is (XW min,YW min)(XW min,YW min) and the maximum coordinate for the clipping region is (XW max,YW max).

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We will use 4-bits to divide the entire region. These 4 bits represent the Top, Bottom, Right, and Left of the region as shown in the following figure. Here, the TOP and LEFT bit is set to 1 because it is the TOP-LEFT corner.

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Algorithm

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Step 1 − Assign a region code for each endpoints.

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Step 2 − If both endpoints have a region code 0000 then accept this line.

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Step 3 − Else, perform the logical ANDoperation for both region codes.

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Step 3.1 − If the result is not 0000, then reject the line.

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Step 3.2 − Else you need clipping.

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Step 3.2.1 − Choose an endpoint of the line that is outside the window.

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Step 3.2.2 − Find the intersection point at the window boundary base on region code.

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Step 3.2.3 − Replace endpoint with the intersection point and update the region code.

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Step 3.2.4 − Repeat step 2 until we find a clipped line either trivially accepted or trivially rejected.

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Step 4 − Repeat step 1 for other lines.

Polygon Clipping  Sutherland Hodgman Algorithm

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A polygon can also be clipped by specifying the clipping window. Sutherland Hodgeman polygon clipping algorithm is used for polygon clipping. In this algorithm, all the vertices of the polygon are clipped against each edge of the clipping window.

First the polygon is clipped against the left edge of the polygon window to get new vertices of the polygon. These new vertices are used to clip the polygon against right edge, top edge, bottom edge, of the clipping window as shown in the following figure.

While processing an edge of a polygon with clipping window, an intersection point is found if edge is not completely inside clipping window and the a partial edge from the intersection point to the outside edge is clipped. The following figures show left, right, top and bottom edge clippings

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Text Clipping

Various techniques are used to provide text clipping in a computer graphics. It depends on the methods used to generate characters and the requirements of a particular application. There are three methods for text clipping which are listed below

• All or none string clipping
• All or none character clipping
• Text clipping

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This clipping method is based on characters rather than entire string. In this method if the string is entirely inside the clipping window, then we keep it. If it is partially outside the window, then −

You reject only the portion of the string being outside

If the character is on the boundary of the clipping window, then we discard that entire character and keep the rest string.

The following figure shows text clipping −

Brief introduction to CAD and CAM

Computer-aided design (CAD) is the use of computer systems to aid in the creation, modification, analysis, or optimization of a design. Computer-aided manufacturing (CAM) is an application technology that uses computer software and machinery to facilitate and automate manufacturing processes. Many CAD vendors market fully integrated CAM systems, aptly called CAD/CAM systems. These CAD/CAM packages deliver many advantages. For starters, they feature a common user interface that allows CAD operators to quickly learn the software. Moreover, users can easily transfer CAD data to the CAM system without worrying about translation errors or other difficulties. And finally, some integrated systems provide full associatively, which means that any modification to the CAD model will prompt the associated tool path to be automatically updated. Computer Aided Design (CAD) has completely changed the drafting business and made the storage and retrieval of projects much easier. However, manual drawing is still very important and provides the basics of learning to draw.

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The first system were very expensive, the computer graphics technology was not so advanced at that time and using the system required specialized H/W and S/W which was provided mainly by the CAD vendors. The first CAD systems were mainframe computer supported systems, while today the technology is for networked but stand alone operating workstations (UNIX or WINDOWS based systems). AUTODESK was the first vendor to offer a PC based CAD system the AUTOCAD (beginning of 1980). Today WINDOWS is the main operating system for CAD systems.

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Brief introduction to CAD and CAM (Contd)

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The first applications were for 2D-Drafting and the systems were also capable of performing only 2D modeling. Even today 2D-drafting is still the main area of application (in terms of number of workplaces). Later, (mid-1980), following the progress in 3D modeling technology and the growth in the IT H/W, 3D modeling systems are becoming very popular.

3D modeling are at the beginning wire frame based. Aerospace and automotive industries were using surface modeling systems for exact representation of the body of the product. At the same time solid modeling was recognized as the only system, which could provide an unambiguous representation of the product, but it was lacking adequate support for complex part representations. Today we are experiencing a merge of solid and surface modeling technology. Most solid modeling systems are capable of modeling most of industrial products. Systems sold today (especially for mechanical applications, which are the majority of systems sold world-wide) are characterized as NURBS (Non Uniform Rational B-Spline) based systems, employing solid modeling technology, and they are parametric and feature

based systems. The use of CAD systems has also been expanded to all industrial sectors, such AEC, Electronics, Textiles, Packaging, Clothing, Leather and Shoe, etc. Today, numerous CAD systems are offered by several vendors, in various countries.

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COMPUTER AIDED MANUFACTURING

Computer-aided manufacturing (CAM) is defined as the effective use of computer technology in manufacturing planning and control. CAM is most closely associated with functions in manufacturing engineering, such as process planning and numerical control (NC) part programming.

The applications of CAM can be divided into two broad categories:

(1) Manufacturing Planning and

(2) Manufacturing Control.

CAM applications for manufacturing planning are those in which the computer is used indirectly to support the production function, but there is no direct connection between the computer and the process. The computer is used "offline" to provide information for the effective planning and management of production activities.

The following list surveys the important applications of CAM in this category:

• Computer-aided process planning (CAPP). Process planning is concerned with the preparation of route sheets that list the sequence of operations and work centers required 10 produce the product and its components. CAPP systems are available today to prepare these route sheets.
• Computer-assisted NC part programming or complex part geometries, computer assisted part programming represents a much more efficient method of generating the control Instructions for the machine tool than manual part programming is.
• Computerized machinability data systems. One of the problems in operating a metal cutting machine tool is determining the speeds and feeds that should be used to machine a given work part. Computer programs have been written to recommend the appropriate cutting conditions to use for different materials. The calculations are based on data that have been obtained either in the factory or laboratory that relate tool life to cutting conditions.

• Development of work standards. The time study department has the responsibility for setting time standards on direct labor jobs performed in the factory. Establishing standards have direct time study can be a tedious and time-consuming task. There are several commercially available computer packages for setting work standards. These computer programs 'use standard time data that have been developed for basic work elements that comprise any manual task. By summing the limes for the individual element, required to perform a new Job, the program calculates the standard lime for the job.
• Cost estimating, the task of estimating the cost of a new product has been simplified in most industries by computerizing several of the key steps required to prepare the estimate. The computer is programmed to apply the appropriate labor and overhead rates to the sequence of planned operations for the components of new products the program then sums the individual component costs from the engineering bill of materials to determine the overall product cost.
• Production and inventory planning. The computer has found widespread use in many of the functions in production and inventory planning. These functions include: maintenance of inventory records, automatic reordering of stock items when inventory is depicted, production scheduling, maintaining current priorities for the different production orders, material requirements planning, and capacity planning.
• Computer-aided line balancing. Finding the best allocation of work elements among stations on an assembly line is a large and difficult problem if the line is of significant size. Computer programs have been developed to assist in the solution of this problem.

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The second category of CAM application is concerned with developing computer systems to implement the manufacturing control function. Manufacturing control is concerned with managing and controlling the physical operations in the factory. These management and control areas include:

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• Process monitoring and control. Process monitoring and control is concerned with observing and regulating the production equipment and manufacturing processes in the plant. The applications of computer process control arc pervasive today in automated production systems. They include transfer lines, assembly systems. NC, robotics, material handling and flexible manufacturing systems.
• Quality control: Quality control includes a variety of approaches to ensure the highest possible quality levels in the manufactured product.
• Shop floor control. Shop floor control refers to production management techniques for collecting data from factory operations and using the data to help control production and inventory in the factory.
• Inventory control. Inventory control is concerned with maintaining the most appropriate levels of inventory in the face of two opposing objectives: minimizing the investment and storage costs of holding inventory and maximizing service to customers.
• Just-in-time production systems. The term just-in-time refers to a production system that is organized to deliver exactly the right number of each component to downstream workstations in the manufacturing sequence just at the lime when that component ts needed. The term applies not only to production operations but 10 supplier delivery operations as well.

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Lean Manufacturing

 Value - A capability provided to a customer at the right time at an appropriate price, as defined in each case by the customer. Features of the product or service, availability, cost and performance are dimensions of value.

Waste - Any activity that consumes resources but creates no value (waste).

What is Lean?

• Lean production focuses on eliminating waste in processes (i.e. the waste of work in progress and finished good inventories)
• Lean production is not about eliminating people
• Lean production is about expanding capacity by reducing costs and shortening cycle times between order and ship date
• Lean is about understanding what is important to the customer

Thinking Lean

• Specify value

can only be defined by the ultimate customer

• Identify the value stream

exposes the enormous amounts of waste

• Create flow

reduce batch size and WIP

• Let the customer pull product through the value stream

make only what the customer has ordered

• Seek perfection

continuously improve quality and eliminate waste

Source: From Lean Thinking by Womack and Jones

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Lean Manufacturing

Benefits:

• Lean provides tangible benefits
• Reduces costs not just selling price
• Reduces delivery time, cycle time, set-up time
• Eliminates waste
• Seeks continuous improvement
• Improves quality
• Improves customer ratings and perceptions
• Increases overall customer satisfaction
• Improves employee involvement, morale, and company culture
• Helps “transform” manufacturers

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UNIT 1: PART- A

UNIT 1: PART- A

UNIT 1: PART- A

UNIT 1: PART- A

UNIT 1: PART- B Questions

UNIT 1: PART- B Questions

Assignment Questions

Assignment Questions

SUPPORTIVE ONLINE CERTIFICATION COURSES

REAL TIME APPLICATIONS IN DAY TODAY LIFE AND TO INDUSTRY

Used by engineers, architects, and construction managers, CAD has replaced manual drafting. It helps users creating designs in either 2D or 3D so that they can visualize the construction.

CAD enables the development, modification, and optimization of the design process.

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CAD enables the development, modification, and optimization of the design process.

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Engineers can make more accurate representations and modify them easily to improve design quality. The software also takes into account how various materials interact: This is especially relevant as more details are added to drawings by subcontractors. 

Today, drawings/plans can be stored in the cloud, Thus, contractors have gained access to CAD-based drawings/plans at the worksite. Entire teams can check out plan modifications easily, including the contractor and subcontractors. This way, it is possible for relevant parties to recognize the possible impact the changes might have on construction and adapt as needed. Such ready access to plans improves communication.

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Effective utilization of all information ultimately increases productivity. CAD enables designers to consider electricity, plumbing, and other elements, helping to create a more comprehensive design. Ultimately, this translates to fewer work changes and fewer surprises during construction.

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CAD and its spinoffs, with their many features, have become a staple throughout the construction industry and through all phases of the process. Its technological impact has been a game-changer in the industry—it has transformed construction into a technology job. 

Mini project Suggestions

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1. Development of a technique for Rapid, Precise, Computer-controlled Measurement of X-V Coordinates of a product

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Objective: An experimental .r-y measurement system is described that was designed for the high-speed. high-precision measurements are required in integrated circuit manufacturing and for optical measurement applications in which a sufficiently large database is required for statistical process analysis. The technology for this experimental system differs considerably from that of conventional optical measuring systems in current use and utilizes a computer for data acquisition. manipulation and evaluation. The system, utilizing the edge detection principle, presently operates at a measuring speed of 2.5 cm/s. An analysis gives both the short-term and the long-term precision of the system. The standard deviation for the short-term precision is 0.038.

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2. Design a suitable gear for power transmission of 50 kW. Plot the profile with suitable techniques

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Mini project Suggestions

• Interactive Homogeneous Coordinate Manipulation:

Build an interactive program where users can input homogeneous coordinates and see the resulting transformation in real-time. Include options for different transformation matrices and visualize the

impact on the coordinates.

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• Line Drawing Algorithms:

Implement various line drawing algorithms such as DDA (Digital Differential Analyzer) and Bresenham & line drawing algorithm. Create a comparison of the algorithms by drawing lines with different slopes and lengths.

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• 3D Rotating Cube:

Create a 3D rotating cube using homogeneous coordinates and transformations. Users should be able to interactively rotate the cube along different axes, demonstrating the principles of 3D transformations.

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• CAD/CAM Integration for CNC Machining:

Design a simple mechanical component using CAD software and then implement the CAM process to generate toolpaths for CNC machining. Emphasize the integration between the design phase and the manufacturing phase.

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• Inventory Management System:

Create an inventory management system that incorporates Just-In-Time (JIT) principles. Implement

features for real-time monitoring of inventory levels, automated reordering, and JIT scheduling to

minimize excess stock.

Mini project Suggestions�Improve product architecture of an existing product ( anyone) to minimize the number of sub-components�Objective�To construct the product architecture of the existing product and to reduce the no of sub components involved in the assembly without compromising the level of accuracy � Methodologies (Ref: 128 (scholarsresearchlibrary.com))�This Work is performed to analyze the reduction of scrap in automotive components. The objective of the paper is to reduce the rejection of components which incurs huge costs to the company .This work aims to control the rejection occurring at the time of automotive part assembly in order to maximize the profit with reducing the scrap and it helps to increase the output as due to less vehicle hold. This work helps the companies to reduce the rejection rate with the help of quality tools.��������Figure: Pareto Analysis of component for reduction �� Expected Outcome� The no of components on assembly is calculated and the purpose have been overlooked through the inclusion of JIG�

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