MT 21_CAD/CAM 3(1-2) Than Lin, Ph.D. Assistant Professor Asian Institute of Technology. Lecture: Week 1

Transcription

1 MT 21_CAD/CAM 3(1-2) Lecture: Week 1 Than Lin, Ph.D. Assistant Professor Asian Institute of Technology 1

2 Grading: Quizzes (5%) Mid-Term Exam (30%) Laboratory Exercises (10%) & Project (15%) and Final Exam (40%) 2

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4 Textbook: Kunwoo Lee Principles of CAD/CAM/CAE Systems. References: Farid M. Amirouche, Principles of Computer Aided Design and Manufacturing, 2nd Edition, Prentice-Hall, P N Rao CAD/CAM Principles and Applications 4

5 Introduction to CAD/CAM/CAE Contents Overview Definitions of CAD, CAM, and CAE Integrating the Design and Manufacturing Process through a Common Database Using CAD/CAE/CAM Systems for Product Development- Practical Example 5

6 Overview Figure: Product Cycle 6

7 Result of Synthesis A conceptual design of the prospective product in the form of sketch (layout drawing) that shows the relationships among the various product components The major financial commitments needed to realize the product idea are made The functionality of the product is determined Most of the information generated and handled is qualitative and consequently is hard to capture in the computer system 7

8 Analysis Sub-Processes 8

9 Definitions of CAD/CAM/CAE Computer Aided Design (CAD) The technology concerned with the use of computer systems to assist in the creation, modification, analysis, and optimization of a design [Groover and Zimmers 1984] Computer Aided Manufacturing (CAM)- the technology concerned with the use of computer systems to plan, manage, and control manufacturing operations through either direct or indirect computer interface with the plant s production resources Computer Aided Engineering (CAE)- The technology concerned with the use of computer systems to analyze CAD geometry, allowing the designer to simulate and study how the product will behave so that the design can be refined and optimized 9

10 Definitions of CAD/CAM/CAE CAD,CAM, and CAE- Concerned with automating specific functions of the product cycle and making more efficient Developments done separately, not fully realized the potential of integrating the design and manufacturing activities of the product cycle CIM has been introduced to solve this problem, aimed at trying the separate is lands of automation together into a smoothly running, efficient system. CIM-concerned with using the computer database as a way to run an entire enterprise more efficiently, having an impact on accounting, scheduling, shipping, and other management functions 10

11 Integrating the Design & Manufacturing Process through a common database-a Scenario To show how CAD/CAM/CAE are overla id on the product cycle to realize the goals of better quality(q), lower Cost, and Quick delivery(d) Assume [Design specification calls for the cabinet to have four spaces] -Disc player -Cassette player -Receiver -Storage compartment Figure: Audio system cabinet to be designed Designer to determine Dimensions of Ca binet, Material, thickness and considers assembly 11

12 Integration of CAD/CAM/CAE through the data-base Figure: Integration of CAD,CAM and CAE through the da tabase 12

13 Using CAD/CAM/CAE Systems for Product Development-A Practical Example -Task To design & Manufacture the front piece of cellular phone -Assume that Styling and conceptual design carried out CAD Mold Design CAM Mold Flow Mold Assembly 13

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16 A case study of CAD/CAE/CAM Four steps in the product cycle of this arm lift we ight 16

17 Step 1 Conceptual and geometric design (CAD) Design (Pg25) - Using drafting software to draw the outline curve Model (Pg26) - Using 3D modeling software to model the part as a revolution surface Database - Store the design as a file in computer Computer-aided drafting system and geometric modeling system are the two most important components of CAD. 17

18 Step 2 Analysis of CAD geometry and optimization (CAE) Simulation Analyses of stress, strain, deformation, heat transfer, kinema tics, linkage, dynamics, fluid flow, etc. Optimization Finite-element method (FEM) is the most widely used method in CAE. 18

19 Finite-Element Method Finite-element modeling Divide the CAD geometry into small pieces of required shape (Pg27) to approximate the design by a mesh. (Pg28) Finite-element analysis (Pg29) Calculate stress, strain, displacement etc. at any place in the model by solving a set of system equations and shape functio ns on the mesh. (An Example) (Pg31) 19

20 Step 3 Modify the design geometry (CAD again) Get feed back from the Finite-element analysis Modify the design geometry and other design data acc ordingly (An Example) (Pg32) 20

21 Step 4 Make it, that is, manufacture it (CAM) Manufacturing process planning Use computer technology to plan, manage, and control manufacturing process. Numerical control (NC) machining (Pg33) The technique of using programmed instructions to control a machine tool that grinds, cuts, mills, punches, bends, or turns raw stock into the finished part. Rapid prototyping (Pg35) Build a prototype of the part directly from the CAD model as a stack of layers by means of laser or other techniques. 21

22 What is made of CAD/CAM/CAE 22

23 Computer science: algorithms Your program: My program: 23

24 Math: geometry v 1 v 2 p 2 y p 1 S(u) =??? Given two points p 1 and p 2, and two vectors v 1 and v 2, x find four vectors a 0, a 1, a 2, and a 3, such that the vector function S(u) = a 0 + a 1 u + a 2 u 2 + a 3 u 3 satisfies: 1. it is a smooth function in (0 u 1), and 2. its meets the boundary conditions S(0) = p 1 and ds(u)/du u=0 = v 1 S(1) = p 2 and ds(u)/du u=1 = v 2 24

25 Design the profile using a drafting software 25

26 Modeling the part using a 3D geo metric modeling software 26

27 Basic 3D mesh elements 27

28 The triangular mesh of the model 28

29 Property analysis Finite element method (FEM) or Finite difference method (F DM) or Finite volume method For static and dynamics responses Meshing boundary condition iter ation 29

30 Property analysis 30

31 Illustration of an FEM process 31

32 New design: one arc of radius 25 now should be a curve of height 25 and width 45 that is required to smoothly connect to its two adjoining lines. 32

33 Before (without NC) Now (with NC) 33

34 NC Machining Programming To program the NC machine tool to correctly cut the part Given the CAD data: 1. How to compute the correct tool path (dotted)? 2. How to identify and determine the two phases of machining? 34

35 Rapid Prototyping Figure 1. A schematic drawing of a LOM process. Laminated Object Manufacturing 35