mec435 chapter1 v1.1
DESCRIPTION
catiaTRANSCRIPT
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