1. Process analysis of plastic products
Before designing the injection mold, the designer should fully analyze and study whether the plastic product conforms to the principle of injection molding processing, and needs to negotiate carefully with the product designer to reach a consense. This includes conducting necessary discussions on the geometric shape, dimensional accuracy and appearance requirements of the product, and avoiding unnecessary complexity in mold manufacturing as much as possible.
2. Mold structure design
A set of high-quality molds not only requires good processing equipment and skilled mold manufacturing workers, but also a very important factor is to have a good mold design, especially for complex molds, the quality of the mold design accounts for 80% of the quality of the mold. %above. An excellent mold design is: under the premise of meeting the requirements of customers, the processing cost is low, the processing difficulty is small, and the processing time is short.
To do this, we must not only fully understand the customer’s requirements, but also have an understanding of the injection molding machine, mold structure, processing technology and mold factory’s own processing capabilities.
Therefore, in order to improve the level of mold design, the following points should be done:
- Understand every detail in the design of each mold and understand the purpose of each part in the mold.
- When designing, refer to the previous similar designs, and understand the situation in its mold processing and product production, and learn from the experience and lessons.
- Learn more about the working process of the injection molding machine to deepen the relationship between the mold and the injection molding machine.
- Go to the factory to understand the process of processed products, and understand the characteristics and limitations of each processing.
- Understand the mold trial results and mold modification situation of the mold designed by yourself, and learn lessons.
- Try to use the previous successful mold structure in the design.\
- Learn more about the impact of water entering the mold on the product.
- Study some special mold structures and understand the latest mold technology.
3. Determine the mold material and select standard parts
In the selection of mold materials, in addition to considering the accuracy and quality of the product, it is also necessary to make the correct choice in combination with the mold factory’s actual processing and heat treatment capabilities. In addition, in order to shorten the manufacturing cycle, the existing standard parts are used as much as possible.
4. Parts processing and mold assembly
The accuracy of the mold is not only the best structure and reasonable tolerance fit during design, but also the processing of parts and mold assembly is very important. Therefore, the choice of processing accuracy and processing method occupies an absolute dominant position in mold manufacturing.
- The dimensional error of molded products is mainly composed of the following parts:
- The manufacturing error of the mold is about 1/3
- The error caused by mold wear is about 1/6
- The error caused by uneven shrinkage of molded parts is about 1/3
- The error caused by the inconsistency between the scheduled shrinkage and the actual shrinkage is about 1/6
Therefore, in order to reduce the mold manufacturing error, the machining accuracy should be improved first. With the use of CNC machine tools, this problem has been well controlled. In addition, in order to prevent errors caused by mold wear and deformation, when processing molds with high precision requirements and large product output, key parts such as cavity and core should be quenched. In medium and large molds, in order to save materials and facilitate processing and heat treatment, mosaic structures should be used as much as possible in mold design.
In order to solve the error caused by the uneven shrinkage of the molded parts and the inconsistency between the scheduled shrinkage and the actual shrinkage, 1/3 of the product tolerance is generally selected as the manufacturing tolerance of the mold during mold manufacturing. Large adjustment leeway to solve the errors caused by the molding process.
5. Trial mold
A set of molds only completes 70%~80% of its entire manufacturing process from the beginning of design to the completion of assembly.
For the error caused by the inconsistency between the scheduled shrinkage and the actual shrinkage, whether the demoulding is smooth or not, how the cooling effect is, especially the size, position, and shape of the gate affect the accuracy and appearance of the product, etc., must be tested by mold testing. Therefore, mold trial is an indispensable step to check whether the mold is qualified and choose the best molding process.