DESIGN PROCESS

CONTENTS

• INTRODUCTION

• CAD DEFINITION

• DESIGN PROCESS - SHIGLEY

• DESIGN PROCESS - PAHL AND BEITZ

• DESIGN PROCESS - OSHUGA

INTRODUCTION – WHAT IS DESIGN ?

• Design is a creative planning process that leads to useful products and systems.

• There is no perfect design.

• Requirements of a design are made up of criteria and constraints.

What is the Design

Process ?• The design process is a purposeful method of planning practical solutions to problems.

• The design process is never final; there are always multiple solutions to a problem.

• The design process is influenced by requirements called criteria and constraints.

Computer-Aided Design (CAD)

• A software system that uses computer graphics to assist in the creation, modification, and analysis of a design.

Computer-Aided Design Process

• Two types of activities: synthesis and analysis• Synthesis is largely qualitative and hard to

capture on computer• Analysis can be greatly enhanced with

computers• Once analysis is complete, then design

evaluation- rapid prototyping • Software packages for design optimization

HOW DOES IT WORK?• Geometric modeling - Uses basic lines, curves, and shapes to

generate the geometry and topology of a part– 2D -Technical drawing , General-Purpose drafting – 3D - Difficult to master , Freely rotate and zoom a model• Automated drafting and documentation -Produces

engineering drawings directly from the CAD database– More advanced documentation merges text and graphics to produce

assembly drawings, bills of material, instruction manuals and reports, parts catalogs, and sales brochures

Engineering analysis and design analysis

Advantages & Disadvantages

• Reduce the lead time for new product introduction• Products can be tested more quickly• Costly mistakes in design or production can be avoided• Time to manufacture can be reduced• Documentation can be printed in various forms for multiple

users• The quality of designs and the products manufactured from

them is improved• Incompatibility• Complex Surfaces

THE DESIGN PROCESSIn recent years there have been several attempts to provide a formal description of the stages or elementsof the design process. • The models of the design profess

1. Shighely Model2. Pahl and Beitz3. Ohsuga

Shighely ModelThe problems in the existing products

The problem in the existing product orspecification of the new product

The designer develops number ofdesigns to meet the requirement

Each design from the synthesis stages are Analysed and optimum one is selected.

A prototype of the product is developed and experimentally checked for Its performance, quality, reliability and other aspects of product

After the product design passing through the evaluation stage, drawingsdiagrams,material specification, assembly lists, bill of materials etc.

Pahl and Beitz Model

Ohsuga Model