1. Introduction

Precision machinery has high requirements for its components. The differences in mechanical properties between metals and plastics determine the different roles they play in it, which is crucial for design and material selection.

2. Roles of Metal Parts

2.1 Mechanical Characteristics and Applications

Metals have high strength and stiffness. For example, steel can withstand large static forces and ensure the structural stability of key parts in precision machine tools. Take the bed of a grinding machine as an example. It is made of cast iron, which can resist deformation and maintain precision. Metals also have good fatigue properties and are suitable for rotating parts like the shafts of high-speed motors. The turbine blades of aircraft engines are a good example. Besides, metals have a small coefficient of thermal expansion and can maintain dimensional stability in temperature-sensitive equipment such as optical instruments.

2.2 Limitations and Application Scenarios

Metals have a relatively high density, so their application is limited in fields that are sensitive to weight, such as aerospace. Moreover, metals are difficult to process and have high costs, so their application in non-critical parts or areas with low cost requirements is restricted.

3. Roles of Plastic Parts

3.1 Advantage Demonstration

Plastics have a low density. They can reduce the weight and save energy in portable precision equipment like blood glucose meters. Plastics also have good elasticity. For example, the plastic cushion in the ink cartridge holder of a printer can absorb shocks and improve printing precision. In addition, plastics are easy to be molded. The plastic housing of a micro-sensor can integrate multiple functions.

3.2 Countermeasures

Plastics have relatively low strength and stiffness, but they can be reinforced with fibers. For instance, carbon fiber-reinforced plastics are used in key parts of high-performance machinery. Plastics have poor high-temperature resistance, so special plastics should be selected and heat dissipation measures should be taken in high-temperature environments.

4. Collaboration and Considerations

4.1 Structural Collaboration

In the transmission system, metal gears and plastic gears are combined, each performing its own functions. For the outer casing, a combination of a metal frame and a plastic panel is adopted.

4.2 Comprehensive Trade-off

Metal materials are selected for critical parts, while plastic materials are chosen for non-critical parts or those that are sensitive to weight and cost, so as to balance performance and cost. In addition, environmental adaptability and connection reliability should also be taken into consideration.

5. Conclusion

Metals are important in aspects such as carrying key loads in precision machinery, while plastics have advantages in lightweight design and other aspects. The collaboration between the two and comprehensive considerations can promote the progress of precision machinery. In the future, the development of materials will expand their applications.