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How to Increase the Gloss of the Injection Molding Products ? | Processes and Molds

This article shows you the ways to improve the gloss of the injection molding products from two aspects. They are respectively injection mold and injection molding process.

Injection mold

1. Make the mold cavity smooth

If the mold cavity is poorly processed, with defects like scars, micropores, wear, roughness, etc., they can be obviously seen on the plastic parts. And this will cause the the problem of poor gloss. Therefore, we must carefully process the mold to make the cavity surface less rough. And polish chrome if necessary.

2. Keep the cavity surface clean

If there are oil and water stains on the cavity surface or too much release agent, the surface of the plastic parts will be dark and dull. So we must remove the oil stains and water stains in time. And use the release agent in a limited amount.

3. Increase the draft angle

If the mold release slope is too small, it is difficult to demold. Or the force is too large during demolding, which makes the gloss of the plastic partsurface is not so good. For this, we should increase the draft angle.

4. Modify the mold exhaust system

The mold exhaust is poor, with too much gas in the model. And this also leads to poor gloss. For this, we should check and modify the mold exhaust system.

5. Increase the cross-sectional area 

The cross-sectional area of the gate or runner is too small or changes suddenly. The melt is subjected to too much shear when flowing in itin aturbulent dynamic way. And such situation will result in poor gloss. Thus, we should appropriately increase the cross-sectional area of gate and runner .


Injection molding process

1. Increase the injection speed

The injection speed is too small. Then, the surface of the plastic part is not dense, which will result in the poor gloss. So increase the injection speed appropriately.

2. Improve the cooling system

For thick-walled plastic parts, if the cooling is not sufficient, their surface will be fluffy and the gloss is dark. For this,we should improve the cooling system.

3.Increse the holding pressure and holding time

The holding pressure is insufficient with the overly short pressure holding time. Then, the density of the plastic parts is insufficient, causing the poor gloss. At this time, increase the holding pressure and the pressure holding time.

4. Increase the melt temperature

If the melt temperature is too low, the fluidity will bepoor. And it will easily cause poor gloss. So we should increase the melt temperature.

5. Improve the cooling system for plastic parts

For plastic parts made of crystalline resinlike PE, PP, POM, etc., uneven cooling will lead to poor gloss. Therefore, we should improve the cooling system to cool the plastic parts.


If the injection speed is too high, while the cross-sectional area of the gate is too small, the pouring product will be dark and have poor gloss. Thus, we should reduce the injection speed appropriately and increase the gate cross-sectional area.