一．Choose the most suitable injection molding production material
Plastics, like metals, come in many varieties. There are more than 50 kinds of plastics commonly used in industrial production, but each type has many grades. For example, nylon plastics include nylon 3, nylon 4, nylon 6, nylon 46, nylon 66, nylon 7, nylon 8, nylon 9, and nylon 610 , nylon 1010, nylon 11, nylon 12, nylon 13, nylon 612, nylon 9T, nylon 13, MC nylon, nylon MXD6 and other varieties. Each variety can also be modified, such as adding fillers or enhancing material properties, or through co- Mixed into "alloy"; or obtain new properties through processing techniques such as directional stretching, crystallization, foaming. To meet usage requirements.
There are many varieties of plastics, and their properties are variable. Therefore, the selection of materials for plastic applications is often based on the characteristics of the plastic (including process and cost), and certain performance data such as wear and impact cannot fully predict its usability, and sometimes there is a lack of accurate and reliable design formulas. Therefore, The material selection process for most plastics is relatively complicated. In order to select materials whose performance and processing technology meet the usage requirements, a comprehensive analysis method is used to select materials. A complete design process should start with conception and sketches. Material selection is an important part of the design process. The key step is to select materials for specified components. The most important thing is to consider the function of the component and the relevant material properties that determine the function of the component. At the same time, we must also consider the characteristics and taboos of the component, the external conditions during use, critical conditions, service life and usage. Methods, maintenance methods, product size and dimensional accuracy, molding processing technology, production quantity, production speed, cost, raw material sources and economic benefits, etc. These factors include two aspects. On the one hand, the environmental medium and environmental conditions used, such as the components withstand The influence of mechanical effects such as load and dead weight, impact and vibration; contact with gases, liquids, solids and chemicals; the influence of exposed atmospheric environment (temperature, humidity, rainfall, sunlight, ice and snow, harmful gases, etc.); storage environmental conditions and the effects of long-term storage; in addition, in addition to the effects of static damage, deformation caused by friction heating, creep, molding shrinkage, fatigue caused by stress relaxation and repeated strain, changes in mechanical properties caused by high strain rates, etc. must also be considered etc. On the other hand, when handling, handling or operating, the product may be affected by external forces, or even unexpected external forces. Only by fully considering these factors can the required comprehensive performance be determined.
Understanding the production quantity is to maximize the choice of mold processing methods. If the quantity required is not large, there is no need to make molds and can be processed directly with plates or bars; or 3D proofing is used. When the quantity required is about a few hundred, simple molds or resin-metal molds or low-melting point alloys can be used as appropriate. Molds, etc.; when more quantities are needed, regular mold molding should be used. For example, if the designed parts are to be used urgently, then material supply is the main consideration; if aerospace parts are to be designed, performance factors are the most important; such as design For general-purpose products, performance and cost should be considered comprehensively.
Here is a typical material selection procedure:
(1) Concept of parts and components: Carry out preliminary functional design, that is, the shape of the component and the shape of its functional components, and consider the selection of basic processing methods.
(2) Material selection: Screen candidate materials based on the engineering properties and processability of plastics related to performance under stress. These stresses are imposed on the product when the component is working.
(3) Preliminary analysis and design: Use engineering design performance to calculate wall thickness and other dimensions of parts. And conduct product design and mold design based on the characteristics of plastics.
(4) Trial production samples: Test and evaluate under actual use conditions of components or simulated use conditions of parts.
(5) Redesign and retest: When it is found that the performance cannot meet the usage requirements, materials must be rescreened or redesigned and tested.
(6) Determine the final design and material selection based on the test results of the trial samples and the cost of processing the parts.
(7) Determine the technical specifications and inspection methods of the materials. Sometimes the above steps can be shortened, especially when the parts requirements are simple, or When the difference between new parts and old parts is very small. However, sometimes the material selection steps are more complicated, especially when developing new applications, or when the stresses endured by plastics are complex, a systematic and comprehensive analysis method is not only A reliable way to succeed, and a way to save development costs.
