Rubber Injection mold design

Injection mold design

(1). Rubber injection mold

It is to inject the rubber material preheated into a plastic state into the mold through the pouring system of the injection mold to shape and vulcanize.

Features: complex structure, suitable for large-scale, thick-walled, thin-walled, and complex-shaped products. The production efficiency is high, the quality is stable, and automatic production can be realized.

The injection curing temperature on the rubber injection machine is generally between 170°C and 200°C. Under high temperature and high pressure, the fluidity of the rubber is good, so the design requirements of the mold are high. The template is generally 45# steel or 40Cr, according to the size of the product And the size of the upper plate of the Hydraulic Press Machine to determine the number of mold cavities, and the number of mold cavities can also be determined through the analysis of the fluidity of the rubber compound.

According to our company's existing injection molding machine design injection mold, the design of the injection mold is similar.

(2). Rubber shrinkage rate 1. The higher the vulcanization temperature (above the positive vulcanization temperature), the greater the shrinkage rate. In general, the shrinkage rate increases by 0.1% to 0.2% for every 10°C increase in temperature.

2. The more the amount of semi-finished rubber material, the higher the density of the finished product and the smaller its shrinkage rate.

3. The greater the plasticity of the rubber, the smaller the shrinkage; the higher the hardness of the rubber, the smaller the shrinkage. (Except for high hardness. According to the experiment, the shrinkage rate of the rubber compound has a tendency of increasing if the hardness exceeds 90 degrees Shore.)

4. The more the amount of filler, the smaller the shrinkage; the higher the glue content, the greater the shrinkage.

5. In a multi-cavity mold, the shrinkage rate of the product extruded from the middle cavity is slightly smaller than that of the edge cavity product.

6. The shrinkage rate of injection method products is smaller than that of molded products.

7. The shrinkage rate of thin products (section thickness less than 3mm) is 0.2% to 0.6% larger than that of thick products (above 10mm).

5. Injection vulcanization process

The rubber injection molding process is a production method in which the rubber material is injected directly from the barrel to mold vulcanization. The characteristics of injection vulcanization are that the temperature of the rubber material is relatively uniform and the vulcanization speed is fast, and most of the molded products are engraved and processed.

The production process includes:

1. Feeding,

2. Plasticization,

3. Injection,

4. Keep pressure,

5. Vulcanization,

6. Out of the mold.

The biggest feature of injection vulcanization is that the temperature of the inner layer and the outer layer is relatively uniform, and the vulcanization speed is fast, which can process most molded products.