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The design and production process of the plastic injection mold

1.Process analysis of plastic injection mold
Before the mold design, the designer shall fully analyze and study whether the plastic products comply with the injection molding processing principle. It is necessary to carefully negotiate with the product designer and reach a consensus. It includes necessary discussion on the geometric shape, dimensional accuracy and appearance requirements of products, so as to avoid unnecessary complexity in mold manufacturing as far as possible.

2.Plastic injection Mold structure design
A set of high quality molds not only needs good processing equipment and skilled mold manufacturing workers, but also a very important factor is to have good mold design, especially for complex molds, mold design quality accounts for more than 80% of the mold quality. An excellent mold design is to make the processing cost low, the processing difficulty small and the processing time short on the premise of meeting the requirements of customers.
To achieve this, we should not only fully digest the requirements of customers, but also understand the injection molding machine, mold structure, processing technology and the processing capacity of the mold factory. Therefore, to improve the mold design level, the following points should be achieved
2.1 Understand every detail of each set of mold design and the purpose of each part in the mold.
2.2 In the design, refer to the previous similar design, understand the situation in its mold processing and product production, and learn the experience and lessons.
2.3 Learn more about the working process of injection molding machine to deepen the relationship between mold and injection molding machine.
2.4 Go to the factory to understand the process of processed products and understand the characteristics and limitations of each processing.
2.5 Understand the mold test results and mold modification of the mold designed by yourself, and learn lessons.
2.6 Try to use the previously successful die structure in the design.
2.7 Learn more about the impact of mold water on products. 
2.8 Study some special die structures and understand the latest die technology.

3.Determine die material and select standard parts.
In the selection of mold materials, we should not only consider the accuracy and quality of products, but also give correct selection in combination with the actual processing and heat treatment capacity of the mold factory. In addition, in order to shorten the manufacturing cycle, use the existing standard parts as much as possible.

4.Plastic injection mold Part processing and mold assembly.

In addition to giving the best structure and reasonable tolerance fit in the design, part processing and die assembly are very important. Therefore, the choice of machining accuracy and machining method plays an absolutely dominant role in die manufacturing.
The dimensional error of formed products is mainly composed of the following parts:
4.1 The manufacturing error of the die is about 1 / 3
4.2 The error caused by die wear is about 1 / 6
4.3 The error caused by uneven shrinkage of formed parts is about 1 / 3
4.4 The error caused by the inconsistency between the predetermined shrinkage and the actual shrinkage is about 1 / 6
Total error = (1) + (2) + (3) + (4)
Therefore, in order to reduce the die manufacturing error, we should first improve the machining accuracy. With the use of NC machine tools, this problem has been well controlled. In addition, in order to prevent the error caused by die wear and deformation, when machining the die with high precision and large product output, the key parts such as cavity and core should be quenched. In order to save materials and facilitate processing and heat treatment, the mosaic structure should be adopted in the design of medium and large molds.
In order to solve the errors caused by uneven shrinkage of formed parts and the inconsistency between predetermined shrinkage and actual shrinkage, 1 / 3 of the product tolerance is generally selected as the manufacturing tolerance of the mold during mold manufacturing. Its purpose is to leave more room for adjustment in the future molding process to solve the errors caused by the molding process.
5.Plastic injection mold test
A set of molds only completes 70% ~ 80% of the whole manufacturing process from design to assembly. For the error caused by the inconsistency between the predetermined shrinkage and the actual shrinkage, whether the demoulding is smooth or not, and how the cooling effect is, especially the influence of the size, position and shape of the gate on the accuracy and appearance of the product, it must be tested through the mold test. Therefore, mold trial is an indispensable step to check whether the mold is qualified and select the best molding process.

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