Reasons and solutions for wrinkles and pockmarks in the injection molding process

1.Wrinkle

Reason：

l Insufficient resin capacity: when the pressure in the cavity is insufficient or the resin fluidity is insufficient, it is easy to lead to the resin can not be fully filled with the cavity, resulting in wrinkle phenomenon.

l The exhaust effect is not good: if the mold exhaust is not smooth, it will lead to the gas in the type cavity can not be discharged smoothly, and then affect the filling of the resin, producing wrinkles.

Solution:

l Increase resin capacity: by increasing the injection. For the poor liquidity of the resin (such as polyformaldehyde, PMMA resin, polycarbonate and PP resin, etc.), more attention is needed to appropriately increase the pouring gate and appropriate injection time.

l Improve injection speed and pressure: appropriately increase injection speed and pressure to help the resin better fill the mold.

l Improve the mold temperature: appropriately increasing the mold temperature is conducive to reduce the viscosity of the resin and improve its fluidity.

l Improve the exhaust effect: by increasing the exhaust tank or adjusting the position of the exhaust rod, to ensure that the gas in the type chamber can be discharged smoothly.

2.Surface voids

Reason：

l Material: the material temperature is not consistent or too high, poor fluidity, may lead to the uneven distribution of plastic in the injection process, the formation of hemp surface.

l Mode injection: the mold cooling is not uniform, the mold exhaust is not smooth, making the resin solidified in the mold, and finally manifested as the hemp surface.

l Injection Molding Machine : improper adjustment of Injection molding machine , inaccurate temperature control, feeding mouth foreign body embedding, etc., may affect the injection of the resin injection process, resulting in hemp surface.

l Injection technology: injection process parameters are not appropriate, injection speed is too fast, may also cause anesthetic problems.

Solution:

l Adjust material: ensure uniform temperature, good fluidity and replaceable material type if necessary.

l Optimize mold design: improve the cooling system of mold to ensure uniform temperature distribution, and optimize the exhaust system of mold to avoid gas retention.

l Adjust the parameters of the injection machine: according to the characteristics of the material and the structure of the mold, adjust the temperature, pressure and speed of the injection machine to ensure that the resin can evenly fill the mold.

l Improve the injection process: optimize the injection process parameters, such as injection speed and pressure retention time, to reduce the generation of anesthetic defects.

l Cleaning the mold: clean the mold regularly to eliminate the dirt and sediment on the mold surface and reduce the production of hemp points.

Use the anesthetic agent: add the right amount of the anesthetic agent in the injection molding process, can effectively eliminate the anesthetic problem. However, attention should be paid to the use of the anesthetic agents to meet the environmental standards, and the amount of use should be correctly mastered.

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