. Agriculture is the most important branch of national economy, providing a country with food-stuffs. Only full
 mechanization and automation of production processes give the possibility of getting required amount of foodstuffs and
 raw materials for light and food industries. A special branch of machine -building, complex agricultural machine building,
 is responsible for carrying out these objectives.

It has its own specificity, determined by:
-	large-scale and mass character of agricultural machinery production (notably, annually the country produces about
        70000 units of self-propelled harvesters for different branches of agriculture);
-	presence of 20 soil-climate zones, covering different conditions from Yakult tundra to subtropics of Central Asia
        (it must be noted that 19 of them are grain-seeding);
-	wide range of means for mechanization of agriculture (there were 1800 in the system of plant-growing machines;
        about 1500 articles of agricultural machines were produced during 1985-1990,700 of them will be thoroughly
        renovated, saying nothing about current routine modernization). No other branch of industry has such a wide range
        of machines. For production of such a great amount of machines, it was necessary to work out proper technical
        documents. To satisfy these demands 80 design departments were created in the branch. A typical special design
        department designs 50 machine articles simultaneously, from 30 to 60000 drawing lists (format A) and the same
        number of other design documents being produced annually. The designer's activities during designing machine
        systems and parts regulate about 500 normative technical documents.500 people work in a typical design office of
        the branch, 200"of them being designers. 10-15 estimators and 30 people from patent and technical 'information
        departments are providing service to them. The period of designing agricultural machines covers from two to eight
        years, depending on complexity, the period of putting into production - from a year to three, the period of
        satiation the stocks with new techniques is about 7-8 years. Thus a "construction life" in agricultural machine
        building is about 11-20 years. Naturally progress does stop since the adoption of the request for proposal (RFP)
        is taken, and very often the designed technics becomes obsolescent by the moment of its putting intoproduction.
        When the country's stocks are satiated with this obsolescent machinery, the losses of them count millions of 
        rubles.

The above drawbacks of the present designing methods can be overcome on the following conditions:
-	improvement of quality and technical economic level of designed objects, including the stage of their creation
        and implementation;
-	increase of labour productivity, limitation of periods, lowering of production cost and labour input of designing.
        Only due to automation of a whole number of designing process stages on the base of modern computer engineering
        techniques such problems can be solved. Complexes, carrying out such kind of work, are called Computer-Aided
        Design (CAD).

Of course, in order to master modern methods of designing, it is necessary to know classic ones. This manual describes
        the existing designing methods and CAD and their relationship. The manual is intended for the students of the
        speciality 17.06 and 17.10 "Agricultural Machine-building " for all forms of studies.

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