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Injection mold manufacturers tell you how to choose mold materials and how to control tolerances

Date: 2022-9-13

More and more enterprises choose mold manufacturing, which can be mass-produced.
How to control the tolerance of plastic molded parts?
Due to the characteristics of the material, the molded product will shrink and deform to a certain extent after cooling. In order to ensure that the product can reach the design size, the mold design should be adjusted in combination with material properties, mold structure, injection molding machine parameters, etc., and the product size should be controlled within the specified tolerance range. At present, we can start from three aspects:


1. Mold design

1 Fully consider the mold structure, mold material and hardness.

2. Setting of mold structure draft angle and parting surface.

3. A suitable ejection system.

4. Which temperature control method should be used? Which circulatory system should I choose?

5. The formation, size and location of the mold gate.



2. Forming process

Although some structural settings have been completed in mold design and manufacturing, in the actual production process, there will still be problems affecting product accuracy. How to solve them?

1. Choose the right injection molding machine.

2. Control the appropriate material temperature and mold temperature. The material temperature needs to be set within the optimum flow rate range from the physical data of the plastic material.

3. Adjustment of mold pressure and exhaust system.


3. Raw materials

A raw material is often produced by multiple suppliers, each producing a product with different properties. During the mold design stage, the molding machine needs to be adjusted according to the performance data.



Cold Runner and Hot Runner Molds

Currently, there are two different types of injection molds known as cold runner molds and hot runner molds. The runner is the most basic part of the injection mold, and it is the channel through which the molten plastic enters the cavity from the barrel. As the name suggests, it is not difficult to see that the main difference between the two molds is the structure and temperature of the mold.

1. Cold runner mold.
In the cold runner mold, the product is cooled by the cooling water of the cooling system in the mold. Compared with the hot runner mold, the biggest disadvantage of the cold runner mold is that the cold runner mold produces a lot of waste and is somewhat thin. Structural products, molten material may cool before filling the cavity.

There are two-plate molds and three-plate molds. The main difference between the two molds is the structure of the mold. The advantage of the three-plate mold is that the gate can be set at any position on the outer surface of the product, which can improve the gate selection in the design.

2. Hot runner mold
In a hot runner mold, the mold and the runner are heated by the hot runner device, and the temperature is generally higher than the melting point of the plastic material. In the hot runner mold, the product waste is less, the fluidity of the molten plastic in the cavity is good, and the structure and appearance of the product are at a high level.

The biggest disadvantage of hot runner molds is the high cost of mold manufacturing and the need for regular maintenance of hot runners. When the color needs to be changed, the molten material stuck in the runner is difficult to clean up.

Cold runner molds remain the preferred choice for some companies due to their reliability and efficiency. However, for companies with high product quality requirements, hot runners are the key to meeting their requirements.

tkb is an enterprise focusing on high-quality mold processing, we can provide customers with the best mold processing suggestions according to their needs. Welcome to consult.

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