Masinprojekteerimine * A.Kalja * Arvutitehnika instituut Basics of CAD Ahto KALJA Department of Computer Engineering

Masinprojekteerimine * A.Kalja * Arvutitehnika instituut

Basics of CAD

Ahto KALJA

Department of Computer Engineering

Masinprojekteerimise alused * A. Kalja * Arvutitehnika instituut

CAD referencies:

1. A.Kalja, T.Tiidemann, E.Tõugu. Masin- projekteerimine. Tallinn, Valgus, 1991, 105 lk.2. A. Saxena, B. Sahay. Computer Aided Engineering Design. Springer, 2005, 394 p.3. Dean L. Taylor. Computer-Aided Design. Addison-Wesley, 1992, 492 p. 4. http://cs.ioc.ee/~nut/5. Eds. J. Gero and F. Sudweeks. Artificial Intelligence in Design ‘96. Kluwer Academic Publishers, 1996, Dordrecht, 782 p.6. Sixth International Conference on Design Computing and Cognition (DCC'14 or DCC14)7. Electronic magazine Computer-Aided Design


CAD

1. Definitions

CAD, in broadest sense, is the use of computersfor the design workCAD, in the narrower sense, is any object or process project automated preparation using a computer

CADCAD Computer Aided DesignCAMCAM Computer Aided ManufacturingCAD/CAMCAD/CAM

CAECAE Computer Aided Engineering

CATCAT C A Testing

CAPCAP C A Planning

CAIIPCAIIP


Domains of CAD



Dialog

Data base

Software

Main program

Basic software

Hardware

Computer graphics

General structure of a CAD system


A) Public CAD system

B) One user sytem

C) Local area network of a CAD system

Classification of CAD systems

. . .


Optimization

Spreadsheets Simulation

Finite ElementMethod

Geometry

Graphics

AlgebraicManipulation

calculation

recordkeeping

visualization

Relationship among CAD applicationsand aspects of computation



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2. Methods

2.1 Designing

Technical proposal

Rough plan

Technical project

Documentation



How Vasa was built

The work on Vasa was led by a Dutchman, Henrik Hybertsson, an

experienced shipwright. In this period, Dutch ships were not built

from drawings, instead the shipwright was given the overall dimensions and used proportions and rules of thumb based on his

own experience to produce a ship with good sailing qualities.


Steps of design

Designproblem

Functionaldesign

Functional schema

Schema design

Principle schema

Detailschema

Project-documentation


Design problem setting

Start

Assessment andproblem

adjustment

Modeling

Synthesis Analysis

End

Design cycle


2.2 ModelingWe take a look the concept „modeling“ in broader sence, which also includes the preparation of models

Modeling problems

static dynamic

problemsof continuousprocesses

problemsof discreteprocesses

Problems of statistical processesProblems of statistical processesAccording to the equations:- Models with functional dependencies- Models with ordinary differential equations- Models with partial derrivatives differ. equations

ExampleExample:: shaftneckneck:

d:numl:nummass:nummass=pi*7.83*d*d*l/4*106


shaft:mass:numlength:numall.mass->mass(sum)all.length->length(sum)

v: A1:neck d=28, l=30 A2:neck d=40 A3:neck d=30, l=40 copy shaft

Possible calculations:- ?A1.mass- ?A3.mass- length:=125 ?A2.L- A2.L:=55 ?A2.mass- A2.L:=55 ? length- A2.L:=55 ?mass- length:=125 ? mass

Descript. of a shaft:

Description of a shaft with 3 necks:


neck

l

shaft

A1 A2 A3

30 ? 40

?

28

40

30

d


2.3 Optimization

Let x be the set of projected object parameters.To maximize f (x), varying x-i in the domain S, where f (x) is the objective function, expresses kindness, productivity, ...To minimize g (x), varying x-i in the domain S, where g (x) is the objective function, expresses the cost of mass, consumed capacity or other.

g(x)=-f(x)restrict. inequalities hi(x)>0; i=1,2,…,n

S equalities vj(x)=0; j=1,2,…,m

ExampleExample:: rectangular cross-section of the pipeFind the maximum surface, x1 and x2 are the sides,

Restrictions x1>=c ja x2>=c i.e. none of the side should not be too short

2(x1+ x2)<=c1 i.e.circumference of the pipe should not be too big

,where c ja c1 are constances

Maximize the value of x1*x2, varying vector (x1, x2) in the domain, which has been given byx1-c>=0, x2-c>=0 ja c1-2(x1+x2)>=0


SolutionSolution:: Hyperbole, which touch to the area S, due to the symmetry of the solution is x1 = x2, so 2 (x1 + x2) = c1

x1=x2=c1/4

Finding min. material cost 2 (x1 + x2)restricting surface value x1x2>=(c1/4)2

Minimizing the x1 + x2 value, varying a vector(x1, x2) in the domain, which is given byx1-c>=0, x2-c>=0 ja x1x2-c1

2/16>=0

SolutionSolution: : is is here too : x1=x2=c1/4

x1x1

x2x2

PipePipe


Examples of the optimizations


Documents

Masinprojekteerimine * A.Kalja * Arvutitehnika instituut Basics of CAD Ahto KALJA Department of Computer Engineering