A comprehensive guide to plastic mold design

1, Overview of mold design

Plastic mold design is an indispensable part of modern manufacturing industry, which directly affects the dimensional accuracy, surface quality, production efficiency and cost of plastic products. Mold design needs to consider product shape, material characteristics, production volume, equipment capacity and other factors, aiming at designing a reasonable structure, simple manufacturing, long service life, cost-effective mold. This guide will elaborate around the key steps of plastic mold design.

2, plastic material selection

The correct choice of plastic material is the premise of mold design. Different plastics have unique physical, chemical and processing properties, such as strength, toughness, temperature resistance, shrinkage, etc., which directly affect the mold structure design and molding process. In the selection of materials, it is necessary to consider the use of product requirements, processing difficulty, cost and environmental protection and other factors. Common plastic materials include polyethylene (PE), polypropylene (PP), polystyrene (PS), ABS, nylon (PA), polycarbonate (PC) and so on.

3, type process analysis

Molding process analysis is an important step to determine the mold design scheme. By analyzing the shape, wall thickness, dimensional tolerance of the product, choose the appropriate molding method (such as injection molding, compression molding, blow molding, etc.), and determine the best molding conditions (such as temperature, excitation, time, etc.). Injection molding has become the most commonly used plastic molding method because of its high efficiency, flexibility and adaptability. Process analysis also needs to consider the mold exhaust, filling speed, pressure holding time and other factors to ensure product quality.

4, mold structure design

Mold structure design is the core part of mold design, which directly determines the manufacturing difficulty, service life and product quality of the mold. The design should follow the principle of reasonable parting surface, compact structure, easy processing and assembly. The main structure includes cavity, core, mold frame, slide block, insert and so on. The selection of parting surfaces should ensure smooth demoulding and no obvious flash; The design of cavity and core should consider the shrinkage rate of the material, the release slope and other factors. Mold design should ensure sufficient rigidity and stability; The use of sliders and inserts can reduce the difficulty of processing and improve the flexibility and maintainability of the mold.

5, cooling system planning

The cooling system has an important effect on the molding quality and mold life of plastic parts. Reasonable cooling system design can shorten the molding cycle and reduce the deformation and warping of the product. When designing the cooling system, factors such as the type of cooling medium (such as water and oil), the location and layout of the cooling water channel, and cooling efficiency should be considered. Generally, the cooling water channel should be as close as possible to the surface of the cavity and evenly distributed to ensure that the temperature of each part of the product drops evenly.

6, foundation and release mechanism

Ejecting and demoulding mechanism is the key to ensure the smooth demoulding of plastic parts. The design should be based on the shape, size, wall thickness and other factors of the product, select the appropriate ejection method (such as thimble, push plate, gas cap, etc.), and determine the ejection position and the size of the ejection force. The ejector mechanism should be designed to ensure that the ejector force is evenly distributed to avoid damage or deformation of the product during the demoulding process.

7, mold materials and heat treatment

The choice of mold material directly affects the service life and cost of the mold. Commonly used die materials include die steel (such as P20, 718, NAK80, etc.), hard joint, etc. When selecting materials, factors such as strength, hardness, wear resistance, toughness and heat treatment performance should be considered. Heat treatment (such as quenching and tempering) is an important means to improve the performance of die materials, which can significantly improve the hardness, wear resistance and fatigue resistance of the die.

8, mold processing and assembly

Mold processing and assembly is the last link of mold manufacturing, but also the key step to ensure the accuracy of the mold. It is necessary to follow the principle of first rough and then fine, and adopt reasonable processing methods and precision control measures to ensure the dimensional accuracy and form and position tolerance of each part of the mold. During assembly, it is necessary to pay attention to the mutual cooperation of each part to ensure the smooth opening and closing of the mold and accurate positioning. At the same time, it is also necessary to carry out the necessary debugging and mold test to verify the rationality of the mold design and the molding quality of the product.

To sum up, plastic mold design is a systematic engineering, need to consider multiple aspects of factors. Through scientific design, reasonable material selection, careful processing and assembly, high quality, high efficiency and long life plastic molds can be designed, which provides a strong guarantee for the production and development of enterprises.