A complete design process should start from conception and sketching. Material selection is a critical step in the design process. For selecting materials for specified components, the primary considerations are the function of the component and the material properties that determine this function. Additionally, factors such as the characteristics and prohibitions of the component, external conditions during use, critical conditions, service life, usage method, maintenance methods, product size and dimensional accuracy, molding process, production quantity, production speed, cost, raw material sources, and economic benefits must be considered. These factors can be divided into two aspects:
Environmental medium and conditions during use, including mechanical impacts such as load, self-weight, impact, and vibration; exposure to gases, liquids, solids, and chemicals; atmospheric conditions (temperature, humidity, precipitation, sunlight, snow, and harmful gases); storage conditions and long-term storage effects. Additionally, consider deformation, stress relaxation, fatigue from repeated strain, and mechanical property changes due to high strain rates.
External forces that products might encounter during handling, service processing, or operation, including accidental external forces.
Thorough consideration of these factors clarifies the required comprehensive performance.
Understanding production quantity helps economically determine the appropriate molding process. For instance, if the required quantity is a few to dozens, there's no need to manufacture molds and the products can be processed directly from sheets or rods. For quantities around a few hundred, simple molds or resin-metal molds, low melting point alloy molds, etc., may be used. For larger quantities, standard molds should be used. For example, if the designed component is urgently needed, material availability is the main concern. If designing aerospace parts, performance factors are paramount. For general products, both performance and cost must be considered. Below is a typical material selection procedure:
Component Conceptualization: Preliminary functional design, determining the component's shape and functional elements, and considering basic processing methods.
Material Selection: Screening candidate materials based on the engineering properties and processability of plastics related to the stresses applied to the component during operation.
Preliminary Design Analysis: Calculating wall thickness and other dimensions using engineering design properties. Designing the product and mold according to the characteristics of the plastic.
Prototype Testing: Testing and evaluating the sample under actual or simulated usage conditions.
Redesign and Retesting: If performance does not meet requirements, reselect materials or redesign and retest.
Final Design and Material Selection: Determining the final design and material selection based on prototype testing and component processing costs.
Specification and Inspection: Establishing the technical specifications and inspection methods for the material.
These steps can sometimes be shortened, especially when component requirements are simple or when new components differ little from old ones. However, the steps may become more complex in new applications or when plastics are subjected to complex stresses. A systematic and comprehensive analysis method is not only a reliable approach to success but also a way to save development costs. 
