Engineering drawing 1 UniKL LDD 10303

ENGINEERING DRAWINGByNorazlina bt Abdul Nasir

CHAPTER 1 - OVERVIEW OF ENGINEERING DRAWING

A. The Purpose of Drawing in Industry

B. Types and Functions of Engineering Drawings

i. assembly ii. sub-assembly iii. detail assemblyiv. Detail

C. Producing Drawings

OVERVIEW OF ENGINEERING DRAWING i. The Purpose of Drawing in Industry

There are three main reasons for drawing in industry.

a. Communication Engineering drawing is the main method of communication between

all people concerned with the design and manufacture of components, building and constructions, and engineering projects.

b. Discussion Drawings are very useful for developing ideas and theories and

discussing them with colleagues. For instance a manufacturer might discuss the problems of a manufacturing process with an engineer.

c. Records Drawings are kept for:

1. Extra orders of components. 2. Recording previous specifications. 3. Records of current job specifications in case of faulty manufacture

or design.

TYPES AND FUNCTIONS OF ENGINEERING DRAWINGS The basic engineering drawings are:

i. assembly ii. sub-assembly iii. detail assemblyiv. detail.

Assembly drawings Assembly drawings show a general overview of

the completed job, with arrangements of parts and a list of parts. They are sometimes called general assemblies. They only show overall dimensions.

Sub-assembly drawings Sub-assembly drawings only show the

arrangement of a particular part, or a few parts, of the general assembly. Again, they do not show any fabrication details. Sub-assembly drawings show how a part of the job is assembled, not fabricated.

Detail assembly drawings Detail assembly drawings show how the job is

assembled, together with all the details you need to manufacture it.

Detail drawings Detail drawings show all the details you need to

do the job. They generally only show a part of the job, and do not show the complete assembly of the finished product

PRODUCING DRAWINGS

Drawings are done on standard size sheets, ranging from AO to A4.  

Methods of production Drawings may be made in three ways:

freehand sketching by hand using drafting equipment computer assisted (Computer Aided Design - CAD).

Copying or Reproducing Drawings Depending on the size, drawings may be reproduced by:

photocopying dyeline reproduction computer plotting

Standards Engineering drawings and other technical

drawings have to be done in ways that all engineers can recognize. These ways are called standards or conventions.

Drawings are made to standard conventions so that: they all use the same symbols, lines,

dimensioning techniques etc they can be understood in different places, eg

interstate or internationally.

Although there are several drawing standards available both nationally and internationally, for this competency all our drawings should follow the rules of:

The Australian Standard 1100 - Drawing practice The Australian Standard 1101 - Graphic symbols

for electro technology Australian Standard is usually shortened to AS.

The drawings in this competency are on standard size sheets, as stated in AS 1100.

Features There are some features, which should appear on

every drawing:

The title panel should contain the following: company name drawing name drawing number date.

Depending on the type of drawing the title panel may also include: 1. material list 2. revision panel 3. draftsman's name 4. original drawing size 5. scale of the drawing 6. general tolerances 7. projection symbol 8. drafting standard 9. surface finish 10. border.

The border is important because no information should lie outside it. If we have a copy of the drawing and the border is complete, we can be absolutely sure that we have all the information contained on the drawing.

Other useful items, which may appear near the border, are: grid referencing camera alignment marks fold lines.

Classification of Drawings As we mentioned before, our drawings can range

from the very simple, to the extremely complex - from a gee-clamp to an aircraft carrier.

There is a need then to classify our drawings according to the function, which they serve.

Assembly Drawings An Assembly Drawing may also be called an

Arrangement Drawing, General Arrangement Drawing or General Assembly Drawing.

The Assembly Drawing shows a general view of the completed job, with the arrangement of the parts and also a parts list. They show overall dimensions but do not show any manufacturing information.

The assembly drawing shows how the parts of the “Tee Wrench” fit together.

Sub-Assembly Drawings These drawings show the arrangement of a few

parts of the general assembly. Sub-assembly drawings are referenced back to an assembly drawing, and are used so that assembly drawings do not become unnecessarily complicated.

As in the assembly drawing, there is no manufacturing information on a sub- assembly drawing, only assembly information.

An example of a Sub-Assembly drawing for Exhaust Duct - Fan Support Assembly

Detail Assembly Drawings These drawings show how the parts fit together and

information necessary to manufacture the parts. Detail assembly drawings are used when both the

parts and the assembling of them are simple, and separate assembly and detail drawings are not justified.

The detail assembly drawing, Al - 428958 - 003 – AA (Vulcanising Clamp) shows the assembled parts, how they are assembled and also the sizes of each of the components.

It is different to the sub-assembly drawing, because the detail assembly drawing has manufactured information on it.

Detail Drawings Detail drawings show all the information you

need to manufacture the part and nothing else at all. The part may end up in a car, or a gantry crane, or a ship. The information relating to where the part fits is to be found on the sub-assembly or assembly drawing.

An example of a detail drawing is the Fixed Jaw drawing

Diagrams Most of the drawings that a mechanical

tradesperson would use on the job are a ‘pictorial representation’. This is the type of drawing which shows the object as it is.

Another type of drawing, which we may have to use, is the ‘diagram’. Diagrams usually consist of symbols connected by lines.

In electrical diagrams the symbols represent electrical components and the lines represent the conductors or wires.

In hydraulic and pneumatic diagrams the symbols represent the fittings and the lines represent the piping.

: END :