First, after the designer draws the parts diagram, he must list the usage conditions and important material selection factors for the parts, and then make a reasonable material selection.
It includes the following three steps: (1) Based on the application purpose, list all functional requirements of the component (not the performance of the material) and quantify them as much as possible.
For example:
①The maximum allowable deformation under rated continuous load;
②The type and magnitude of stress experienced during use and transportation; whether it is stressed for a long time, whether it is dynamic or static stress;
③Maximum working temperature;
④ Allowable dimensional changes at operating temperature;
⑤The allowable dimensional tolerance of components;
⑥Performance requirements of parts;
⑦Whether the components require coloring, bonding, electroplating, etc.;
⑧How long is the required storage period and whether it will be used outdoors;
⑨ Whether there are flame resistance requirements, etc.
Second, according to the functional requirements of the component, consider the use of performance values (engineering performance) and design data, propose the performance values of the target material (component material), and select the material based on these performance requirements, even if these performance estimates are rough. It will greatly facilitate the screening of candidate materials and provide a useful basis for the selection of final materials.
Choosing appropriate material properties is critical and complex, because a certain function of a component often includes several properties. For example, in addition to dimensional accuracy, linear expansion coefficient, molding shrinkage, etc. must also be considered in dimensional stability requirements. Water absorption, creep properties, etc. The strength and stiffness of parts should not only be considered from the material properties, but also from the product structure design (such as thickness and reinforcement ribs, etc.). The molding processability, durability, and economy of the material are also factors that should be considered when selecting materials. Sometimes, certain usage requirements may not necessarily clarify the quantitative requirements for material performance. For example, electroplating properties often need to be screened through actual tests or existing experience. Another example is plastic cannonball belts, which require the material to withstand complex external forces such as high-speed impact, compression, twisting, and shearing, as well as the influence of high-speed, high-temperature, and high-pressure airflow. It is difficult to directly put forward quantitative performance requirements for the material. Therefore, in addition to mechanical calculations, , The stress situation can also be calculated through simulation tests and exploratory tests, and rough performance requirements can be put forward.
Third, candidate materials are finally determined by comparing component engineering performance requirements with material properties. When choosing plastics, you should pay attention to the following issues:
① It is necessary to have a comprehensive understanding of the performance of the selected plastic, and then consider the formula, process and product design according to the conditions of use.
②Plastics generally have low thermal conductivity, so please pay full attention when selecting and designing them.
③The linear expansion coefficient of plastic is generally larger than that of metal, and some are easy to absorb water, so the size changes greatly. Appropriate fit clearance and tolerance range must be considered when selecting and designing.
The above article is KFX telling customers how to choose injection molding raw materials and providing an idea for customers who need injection molding production.
