The manufacturing of plastic molds can be roughly divided into the following steps:
I. Process Analysis of Plastic Products
Before designing a plastic mold, designers need to thoroughly analyze and study whether the plastic products conform to the principles of injection - molding processing. It is essential to consult carefully with the product designers to reach an agreement. This involves discussing aspects such as the geometric shape, dimensional accuracy, and appearance requirements of the plastic products, aiming to avoid unnecessary complexity in plastic mold manufacturing.
II. Plastic Mold Structure Design
A high - quality plastic mold requires not only excellent processing equipment and skilled mold - making workers but also, importantly, good plastic mold design. Especially for complex plastic molds, the quality of the design accounts for over 80% of the overall plastic mold quality. An outstanding plastic mold design aims to minimize processing costs, simplify processing difficulty, and shorten processing time while meeting the customer's requirements. To achieve this, one must not only fully understand the customer's needs but also be familiar with injection - molding machines, plastic mold structures, processing techniques, and the processing capabilities of the mold factory itself. Therefore, to enhance the level of plastic mold design, the following should be done:
Comprehend every detail in the design of each plastic mold and understand the function of every part in the plastic mold.
When designing, refer to similar previous plastic mold designs and learn about the situations during their processing and product production, drawing on the experiences and lessons.
Have a better understanding of the working process of injection - molding machines to deepen the understanding of the relationship between plastic molds and injection - molding machines.
Visit factories to understand the processing technology of plastic products and recognize the characteristics and limitations of each type of processing.
Learn about the mold - testing results and mold - modification situations of the plastic molds you design and draw lessons from them.
Try to adopt previously successful plastic mold structures in the design.
Understand the impact of plastic mold gating on products.
Research some special plastic mold structures and keep up with the latest plastic mold technologies.
III. Determination of Plastic Mold Materials and Selection of Standard Parts
When choosing plastic mold materials, aside from considering the accuracy and quality of the products, a proper selection should be made in line with the actual processing and heat - treatment capabilities of the mold factory. Moreover, to shorten the manufacturing cycle, make full use of existing standard parts as much as possible.
IV. Part Processing and Plastic Mold Assembly
Besides an optimal structure and reasonable tolerance fit in the plastic mold design, part processing and plastic mold assembly are crucial for the accuracy of the plastic mold. Thus, the selection of processing accuracy and processing methods plays a dominant role in plastic mold manufacturing.
The dimensional errors of molded plastic products mainly consist of the following parts:
The manufacturing error of the plastic mold accounts for approximately 1/3.
The error caused by plastic mold wear accounts for approximately 1/6.
The error generated by uneven shrinkage of the molded plastic parts accounts for approximately 1/3.
The error resulting from the inconsistency between the predetermined shrinkage and the actual shrinkage accounts for approximately 1/6. The total error = (1)+(2)+(3)+(4)
Therefore, to reduce the plastic mold manufacturing error, the processing accuracy should be improved first. With the use of CNC machine tools, this problem has been well - controlled. Additionally, to prevent errors caused by plastic mold wear and deformation, for plastic molds with high - precision requirements and large - volume product production, key parts such as cavities and cores should be quenched. In medium - sized and large - sized plastic molds, to save materials and facilitate processing and heat - treatment, a mosaic structure should be adopted as much as possible in the plastic mold design.
To address the errors caused by uneven shrinkage of molded plastic parts and the inconsistency between the predetermined shrinkage and the actual shrinkage, generally, 1/3 of the product tolerance is selected as the manufacturing tolerance of the plastic mold during manufacturing. The purpose is to leave a larger adjustment margin for the subsequent molding process to deal with the errors occurring during the molding process.
V. Plastic Mold Testing
From the start of plastic mold design to its assembly completion, only 70% - 80% of the entire manufacturing process is finished. Issues such as the error due to the inconsistency between the predetermined shrinkage and the actual shrinkage, the smoothness of demolding, the cooling effect, and especially the influence of the size, position, and shape of the gate on the accuracy and appearance of the plastic products must be verified through plastic mold testing. Hence, plastic mold testing is an indispensable step to check whether the plastic mold is qualified and to select the optimal molding process.
