Machine Design Procedure lacture -2

 Design Requirement of Machine Elements

• A part of a machine that has motion relative to some other parts is called a

machine element. Some machine elements may consist several elements;

e.g., a ball bearing is a machine element and it consists an inner race,

spherical balls, a retaining cage and an outer race.

• A machine is as strong and reliable as its weakest element. Remember, a

chain breaks at its weakest, link. Same is true for machine element.

• The design requirement of a machine element is to ensure that it performs

according to the specifications during its stipulated life span. In order to

achieve the desired performance, the machine elements should satisfy the

following important requirements:

Strength, Rigidity , Wear resistance , Corrosion resistance, Ease of lubrication

Minimum dimensions, weight and power loss in friction, Safety, Reliability

Manufacturability, Maintainability, Conformance to specifications and

standards, Minimum initial and life-cycle cost, Minimum Liability and

Warranty Cost, Possibility of Recycling after its useful life.

Factors to be considered in Machine Design

• What device or mechanism to be used? This would decide 

the relative arrangement of the constituent elements.

• Material

• Forces on the elements

• Size, shape and space requirements. The final weight of the 

product is also a major concern.

• The method of manufacturing the components and their 

assembly.

• How will it operate?

• Reliability and safety aspects

• Inspectability

• Maintenance, cost and aesthetics of the designed product.