Page 29 - Analysis and Design of Machine Elements

An Overview of Machine Design
possible, standard or purchasable products readily available from the market, such as 7
contact bearings, fasteners, keys, motors, pumps and so on, are the first choice. In
such cases, all designers need to do is to determine and provide preferred sizes and
specifications.
Although, the basic objective of mechanical design is to provide a machine or device
that benefits humanity, the consideration of ecological cycle or sustainable growth has
become an increasing concern [11]. In the proposed design, recyclable materials are pre-
ferred. The selected material processing should have minimal energy consumption and
reduced environmental pollution. Efficient material usage is also an important aspect
for sustainable development. Light weight design and 3D printing are examples of effec-
tive material usage. In short, environment and resource concerns during manufacture,
operation and disposal must be seriously taken into consideration.
During machine design, ergonomics or the man-machine relationship has gained
increasing attention. Its aim is to ensure that machines are designed to accommodate
operators with safety, comfort and efficiency. By incorporating human factors into
design, product efficiency and safety can be improved and potential operational
problems and product liability can be reduced.
Since designers and manufacturers are legally liable for any damage or harm from
products, they have great responsibility to ensure high quality and safe operation of
products, and should provide adequate warnings and instructions for use in the product
specifications [8].

1.2.2 Machine Design Process
Machine design aims to produce a useful product satisfying the needs of customers.
The design of a machine is inherently a complicated and delicate process, involving
interactive and iterative procedures, complex calculations and countless design deci-
sions [8]. To develop a safe, efficient and reliable product with excellent functionality and
high competitiveness, proper design procedures and approaches should be established
and followed. Figure 1.1 outlines a complete product development process currently
employed.
The development of new machine from inception through elaboration to termina-
tion can be broadly classified into four stages: planning, concept design, detailed design,
manufacturing and commercialization [8, 9]. The tasks and focus of each stage are intro-
duced next.
1. Planning
Design starts with the recognition of needs. The desire or expectation for a new prod-
uct may be acquired from a target market, from dissatisfaction with existing products
or from a particular adverse circumstance; for example, a need for a robot to work in
hostile environment.
The vague or subjective needs are then translated into detailed quantitative speci-
fications to definite the function of the expected product. These specifications are the
input and output quantities, such as power, operating speeds, expected life or safety,
space or weight limitations.
Financial investment, estimated price, cost targets, expected profits and other busi-
ness issues, together with sales operations and time schedules also need to be con-
sidered at this stage.