A machine is a mechanical device that transmits or modifies energy to an output. Usually, machines are restricted to devices having an unbending or inflexible moving part that helps in performing the valuable work. Tools, or simply devices, not machines having no rigid moving parts.

A machine design is the creation of new and ameliorates machines. A better machine is one which is more economical in the overall cost of production and performance. The process of design is a long and time consuming one. In designing a machine component, it is essential to have a good knowledge of many subjects such as mathematics, engineering mechanics, strength of materials, and most important is engineering drawing.

Classification of machine design

The machine design may be classified as follows:
1. Adaptive design
2. Development design
3. New design

Adaptive design, in this case there is no need of information or knowledge and can be created by designers of ordinary technical training. Only minor modifications or change in the existing designs of the products has to be made by the designer.

Development design, this type of designing needs extensive scientific training and design talent in order to modify the existing designs into a new idea by adopting a new material or different method of manufacture.

New design, this type of design is totally different as this design needs lot of research, technical ability and creative thinking, designers having personal qualities of sufficiently high order can take the work of new design.

The designs depending upon the methods used may be classified as follows:
a) Rational design: depend upon mathematical formulae of principle of mechanics.
b) Empirical design: depend upon empirical formulae.
c) Industrial design: depends upon the production aspects
d) System design: it is a design if any complex mechanical system like a motor car
e) Computer aided design: depends upon the use of computer systems to help in creation. Modification and optimization of a design.