Engineering Drawing for Manufacture phần 2 pps

Principles of engineering drawing 11

the only one that provides a full specificatio n which allows contracts

to be issued and has the support of the law in the 'servant-master'

sense. To put it in the words of a BSI drawing manual: 'National and

international legal requirements that may place constraints on designs and

designers should be identified .... These may not only be concerned with the

aspect of health and safety of material but also the avoidance of danger to

persons and property when material is being used, stored, transported or

tested' (Parker, 1991).

1.5.2 Representation and specification

In Section 1.3, it was stated that engineering drawing was the equiv￾alent of a language. A language has to have a set of rules and regu￾lations for it to operate correctly. The same is true of engineering

drawing. In the English language, there are two basic rules. The first

is the word order that gives information on subject and object. The

second is spelling, which gives information on the words themselves

in terms of the spelling, i.e. the nouns, verbs, etc. Considering the

word order, the phrase 'the cat sat on the mat' is very different from the

phrase 'the mat sat on the cat'. All that has happened is that the words

'cat' and 'mat' have been swapped. Previously, the phrase described

a perfectly feasible situation whereas it now describes an impossible

situation. Thus, the word order gives information on which is the

subject and which is the object. The second set of rules concern

I Engineering Drawing Rules I

Drawing Layout Rules

ie how to draw the artefact

Manufacturing Details

ie how to manufacture it

* third (or first) angle ize and shape

projections * dimensions

* sections and cutting planes * tolerances

* auxiliary projections * surface finish

* views * assembly

Typical standards:

ISO128-1982, ISO128-34:2001,

ISO-44, 2001, ISO128-50:2001,

ISO7573:1983.

Typical standards:

ISO15768:2001, ISO129-1.2:2001,

ISO128-22:1999, I SO406:1987,

ISO1101:1983, ISO1302:2001.

Figure 1.8 Representation, visualization and specification