Design Process and Engineering Drawing

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Northwestern University

ME 240

INTRODUCTION TO DESIGN ANDMANUFACTURING

DESIGN PROCESS

AND

ENGINEERING DRAWING


Steps in the Design Process

Conceptual Design

Detail Design

Preliminary Design




Preliminary (Embodiment) Design

Prel iminary design is that part of the design p rocess in which,

st ar ti ng from t he concep t o f a technical product, the design i sdeveloped, in accordance with technical and economic criteria to

the point where subsequen t detail design can lead d irectl y to

manufacturing

General objectives:

Fulfillment of technical function

Economic feasibility

Individual and environmental safety

Governing rules:

Clarity Simplicity

Safety


Preliminary (Embodiment) Design

Principles of Embodiment Design:

Principles of force transmission

Flowlines of force; Uniform strength; short force transmission path; Matched

deformations; etc.

Principle of the division of tasks

Assignment of sub-functions;

Principle of self-help

Self reinforcing solutions; Self balancing; Self protection; etc

Etc.

Methods/Guidelines for Embodiment Design:

Design for X

X = Strength; Deformation; Creep & relaxation; Corrosion; Production; Etc.




Detail Design

Steps of Detail Design:

Finalizing the definitive layout

Integration of individual components into assemblies

Completion of production documents

Detai l des ign is that par t o f the des ign process which completes the

preliminary/embodiment design with final instructions and informationabout the layout, form, dimensions and surface properties of all

individual components, the def ini tive selection of materials and a f inal

scrutiny of the manufacturing methods and costs.

The most impor tant aspect o f detai l design is the preparat ion of the

production documents and especially of detailed component drawings,

of assembly drawings and of parts l ists (BOMs).

We will focus now on the rules, techniques and methods of

developing detailed component drawings and specifications.


Example of an Engineering DrawingDimensioned according to ANSI




Projections

3-D Projections:

Multiview Projections:


Projections

Projection

Plane

Projection

Plane

View

Point

Perspective

Projection

Orthographic

Projection




Third Angle Projection


Standard Views in Third Angle Projection

Preferred

Views




First Angle Projection

Preferred

Views


First and Third Angle ProjectionSummary of standard use and symbols:




Auxiliary Views


Sections and Detail Views




Representation of Threaded Features


Sheet Layout

ANSI s izes

A 8.50” x 11.00”

B 11.00” x 17.00”

C 17.00” x 22.00”

Etc.Title block




ASSEMBLY DRAWING


PART DRAWINGS




Line Usage

EXAMPLE:

Extension (witness) line

Visible line

Hidden line

Center line

Dimension

line

25

Leader line

Outlines, edges of p lanes, etc.

Hidden lines

Center lines (axes of rotation)

Dimension lines

25

25 }

Witness and leader lines


Dimension PlacementSome impor tant rules:

Dimension lines should lie outside of the outline of the part

whenever possib le

Dimension lines should not cross one another

Dimensions should be included on a view that shows the true

length of the feature

Each feature should be dimensioned only once

Dimension lines should be aligned or grouped to promote

clarity whenever possible

The numerical dimensions and arrows should be placed

between the extension lines where space permits

Dimensions should be no closer than about 10 mm from the

object’s outline

Dimensions should be placed in clear spaces, as close as

possible to the feature they describe




Dimension Placement

Some important rules (continued):

Extension lines may cross visible lines of the object

Dimension lines and extension l ines should not cross, if

possible.

Extension lines may cross other extension lines

A center l ine may be extended to serve as an extension l ine

Centerlines should not extend from view to view

Leader lines are usually sloped at about 30, 45, or 60 degrees

and are never horizontal or vertical

There should be no redundant dimensions

Dimensions related to function or manufacturing should be

given

Numerical values of dimensions should be centered between

arrowheads Numerical values of dimensions should be standard values i f

possible


Dimension PlacementExamples of correct and incorrect use:




Dimension Placement

Examples of correct and incorrect use:






A Complete Engineering Drawing


EXAMPLE

6

8

4

3

3

3

6

2

415R

3

Incorrect Drawing




EXAMPLE

68

4

3

3

6

R15

4

6

3

Improved Drawing

(Incomplete)

6

8

4

3

3

3

6

2

415R

3

Incorrect Drawing6

8

4

3

3

3

6

2

415R

3

Incorrect Drawing

Design Process and Engineering Drawing

Documents

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