mec435 chapter1 v1.1

EMD4M7A

EMD4M2B

Chapter 1 : Introduction

OBJECTIVES

Understand the various spheres of manufacturing activity where

computers are used

What is meant by product cycle with the differences between the

conventional and computer based manufacturing systems

Definitions of various computer based applications

Computer Aided Design and its applications

Various types of manufacturing organizations

Computer Aided Manufacturing and its application

Meaning of Computer Integrated Manufacturing

Nowadays, computers become very crucial to daily life

CAD/CAM are widely used in engineering practice: – Drafting

– Design

– Simulation

– Analysis

– Manufacturing

Computer-Aided Environment

The role of computer in manufacturing may be broadly classified into two groups:

1. Computer monitoring and control of the manufacturing process.

2. Manufacturing support applications, which deal essentially with the preparations for actual manufacturing and post- manufacture operations.

COMPUTERS IN INDUSTRIAL MANUFACTURING

COMPUTER AIDED PROCESSES

CAD – computer aided design.

CADD - computer aided design and drafting.

CAE - computer aided engineering.

CAM - computer aided manufacturing.

CAPP - computer aided process planning.

CATD - computer aided tool design.

CAP - computer aided planning.

1. Geometric modeling

2. Computer graphics

3. Design application

4. Manufacturing Applications

CAD/CAM Major Areas

COMPUTER AIDED ENVIRONMENT IN MANUFACTURING

Design is an activity which needs to be well organized and take into account all influences that are likely to be responsible for the success of the product under development.

The complexity of the design process increases

with the number and diversity of components

present in the final part.

COMPUTER AIDED DESIGN

Product functions

Product Specifications

Conceptual design

Ergonomics and Aesthetics

Standards

Detailed Design

Prototype development

Testing

Simulation

Analysis

Strength

Kinematics

Dynamics

Heat

Flow

Design for Manufacture

Design for Assembly

Drafting

PRODUCT ENGINEERING

DESIGN PROCESS STAGES

Is faster and more accurate than conventional methods.

A very easy task.

Editing

Never have to repeat the design or drawing of any component.

Accurately calculate the various geometric properties

Use of standard components (part libraries)

3D (3 dimensional) visualization capabilities

ADVANTAGES OF CAD

1. Mass production ─ large lots e.g. automobiles

2. Batch production ─ medium lot sizes e.g.

industrial machines, aircrafts, etc.

3. Job shop production ─ small lots or one off, e.g.

proto-types, aircrafts, etc.

COMPUTER AIDED MANUFACTURING

MANUFACTURING ENGINEERING

Process planning

Process sheets

Route sheets

Tooling

Cutting tools

Jigs and Fixtures

Dies and Moulds

Manufacturing Information

Generation

CNC Part programs

Robot Programs

Inspection (CMM) programs

Production Organization

Bill of Materials

Material Requirement

Production Planning

Shop Floor Control

Plant Simulation

Marketing and Distribution

Packaging

Distribution

Marketing

ADVANTAGES OF CAM

Greater design freedom

Increased productivity

Greater operating flexibility

Shorter lead time

Improved reliability

Reduced maintenance

Reduced scrap and rework

Better management control

COMPUTER AIDED ENGINEERING

• The use of information technology for supporting engineers in tasks such as analysis, simulation, design, manufacture, planning, diagnosis and repair.

• CAE tools are being used, for example, to analyze the robustness and performance of components and assemblies including simulation, validation and optimization of products and manufacturing tools.

AREAS OF CAE

Stress analysis on components and assemblies using FEA (Finite Element Analysis)

Thermal and fluid flow analysis - Computational fluid dynamics (CFD)

Kinematics

Mechanical event simulation (MES)

Analysis tools for process simulation for operations such as casting, molding, and die press forming.

Optimization of the product or process.

ADVANTAGES OF CAE

Reduce product development cost and time

Precise analysis and simulations

Early prediction of results

Design verification through simulation without having to

use physical prototype testing

Minimize the time for optimizing products

Parallel task can be done along the design stages

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Example of Assembly Drawing

Engineering activities

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Engineering activities

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Users of Computers Graphic

Mechanical Design

Architectural Design

Electronic Circuit Design

• Earliest CAD systems.

• Replace traditional design on drawing board.

• Engineering drawings using simple geometric and annotation entities: lines, circles, arcs, curves and points; text, dimensions, tolerances, and cross hatching.

2D Drafting tools

Provide significant productivity improvements over drawing board i.e. faster time and can easily modify old drawings.

Not a really useful design tool. Only used for documentation of finished design.

Limitation: Difficult to represent complex 3D shapes.

2D Drafting tools

• 3D extension of 2D drafting

• Allow designer to represent design in 3-dimensions, improving visualization.

• Allow user to view design from any viewpoint, and to rotate the model in real time to visualize any complex shape.

3D Wireframe

• Can be created using only lines, circles, arcs, curves and points positioned in 3D space to represent the edges and vertices of the parts.

• Limitations:

- no understanding of object properties

- cannot represent the shape of the object faces between edges

- incomplete and ambiguous

- unable to provide area or volume information

• Data is of only limited use for manufacturing.

3D Wireframe

• Completely defines external shape of an object, faces, edges and vertices.

• Each surface represented by a continuous mathematical function.

• Created by fitting smooth skin through a wireframe or sweeping a wireframe curve through 3D space.

Surface Modelling

• Created using many surface patches to define outside shape.

• Modelling complex freeform shapes e.g. car body panels, aircraft skins, and plastic injection moulded products

• Surface models provide excellent visualization of the geometry.

• Surface data from CAD is routinely used to generate tools paths to drive CNC machine tools

• Limitations:

- Only defines external shapes but not the internal shapes or topology

- unable to specify surface connectivity between surfaces (assumes rigid connections)

Surface Modelling

• The most complete and accurate CAD representation.

• Represents external and internal structure of the part.

• Generate cross-section, calculate weight, centre of gravity and moments of inertia.

• Created by combining simple solid shapes to form more complicated parts.

• Basic building blocks are simple solid shapes created using primitive parts from library or extruded/revolved from 2D wireframe

Solid Modelling

Solid Modelling

• Boolean operation: joint, subtract and intersect solid parts

• Solid models of complex freeform shapes are created using a combination of solid and surface.

• Solid modellers can directly be used for manufacturing, finite element and dynamic analyses.

• Disadvantage: can be extremely difficult to define (and modify) part geometry.

Solid Modelling

Solid Modelling

The link between a design, and the manufacture of the finished product.

Traditional manufacturing:

design intent is communicated to manufacturing using engineering drawings e.g. tolerances, surface finish, materials, standard parts.

manufacturing process plan developed based on drawings

program machine tools to manufacture the part or mould.

Computer Aided Manufacture (CAM)

In an integrated CAD/CAM:

CAD geometry is transferred to a CAM system using data exchange file and used directly for manufacturing planning.

The tool paths for computer numerically controlled (CNC) machine tools to machine parts can be generated from CAD

Computer Aided Manufacture (CAM)

Kinematics:

• analyse movement of mechanism from CAD assembly model.

• joints are applied between different parts in the assembly.

• can be used to evaluate motion of the mechanism and investigate potential locks or clashes.

Computer Aided Engineering (CAE)

Finite element Analysis (FEA): A powerful and popular technique developed for numerical solution of complex problems in

engineering mechanics. perform stress analysis to predict structural strength of a component STEPS: 1. subdivide the the geometry into small regular finite elements (finite element mesh)

2. apply loads and boundary conditions

3. perform analysis

4. results interpretation

Computer Aided Engineering (CAE)

In an integrated environment CAD geometry is transferred to the finite element pre-processor to aid building the finite element model

CAE - FEA

• Integrated CAD/CAM/CAE

• Can aid product introduction process

• Reducing cost

• Cutting lead times

Objective – to create the product geometry once and reuse it many times

Traditional product development – sequential process (design, manufacturing, stress office, logistics etc.

CAE

Sequential approach

• allows company to keep tight control over product development

• Disadvantage- disciplines later in design process do not see the design until it is well developed, when potential problem may be costly to resolve.

Concurrent Engineering and Integrated Product Development

Alternative approach to product development where a team made up from specialist disciplines are assigned to a product and have inputs to design from start of the design process.

Engineering Approach

Product development process

Concurrent Engineering

• Concurrent engineering – everyone involve in the design has access to the data as it is evolving.

• A CAD master Model containing geometry, manufacturing data, analysis and etc.

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Engineering Design Process

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Linear Engineering Design

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Sharing the 3-D CAD database

Model Centered Engineering Design

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Model Centered Engineering Design

• Sharing of 3-D CAD database

• Separation of creative design process and production process no longer necessary.

• Non-linear team approach to design that brings together input, processes and output

• May result in a better, high quality product, more satisfied customers, lesser manufacturing problems, and shorter time between initial design and final production.

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Model Centered Engineering Design