Common abnormal factors and solutions in injection moulding


During the injection moulding process, some abnormal ph […]

During the injection moulding process, some abnormal phenomena are prone to occur, such as: cracks, ripples on the surface of the product, reduced brittle strength of the product, difficult demoulding, unstable product size, unstable product size, peeling and delamination of the product, weld marks, Injection dissatisfaction, etc., these phenomena will affect the specific use of the moulding die, so we need to find out related factors and solutions.


1. The mould is too cold, adjust the mould temperature.

2. The cooling time is too long, reduce the cooling time.

3. Plastic and metal inserts shrink differently, preheat the metal inserts.

4. The ejector device is tilted and unbalanced, the ejector cross-sectional area is small or the distribution is improper, adjust the ejector device or arrange the number and position of the ejector reasonably.

5. Insufficient production slope, difficult to demould, design demoulding slope correctly.

The product surface has ripples

1. The material temperature is low, and the twisting degree greatly increases the material temperature.

2. The injection pressure and the high material temperature can reduce the injection pressure, otherwise increase the injection pressure.

3. The mould temperature is low, increase the mould temperature or increase the injection pressure.

4. The injection speed is too slow to increase the injection speed.

5. The gate is too small, expand the gate appropriately.

The brittle strength of the product decreases

1. The material temperature is too high, the plastic will decompose, reduce the material temperature, and control the residence time of the material in the barrel.

2. The internal stress at the plastic and insert is too large, preheat the insert to ensure that there is a certain thickness of plastic around the insert.

3. The number of plastic recycling times is more to control the ratio of recycled materials.

4. The plastic contains water and the raw materials are preheated and dried.


Difficult to demould

1. The structure of the mould ejection device is poor, and the ejection design is improved.

2. The mould cavity demoulding angle is not enough, design the mould correctly.

3. The mould cavity temperature is inappropriate, and the mould temperature should be properly controlled.

4. There are joints or storage in the mould cavity, clean the mould.

5. The moulding cycle is too short or too long, properly control the injection cycle

6. The mould core has no air intake holes, and the mould is modified.

Unstable product size

1. The machine circuit or oil system is unstable. Correct the electrical or oil pressure system.

2. The moulding cycle is different, control the moulding cycle and make it consistent.

3. Temperature. time. Pressure changes, adjustments, and controls are basically the same.

4. Plastic particles are of different sizes, so use uniform plastic.

5. The mixing ratio of recycled leftovers and new materials is uneven, and the mixing ratio is controlled to make it even.

6. Uneven feeding control or adjustment of feeding uniformity.

Part peeling and layering

1. Different plastics are mixed, and a single type of plastic is used.

2. Different grades of the same plastic are mixed, and plastics of the same grade are used.

3. Poor plasticization, increase the moulding temperature.

4. Mix in foreign matter, clean up raw materials, and remove impurities.

Weld Line

1. The plastic temperature is too low to increase the barrel. Nozzle and mould temperature.

2. Too many gates, reduce gates or change gate positions.

3. Excessive release agent uses atomized release agent. Reduce dosage.

4. The injection speed is too slow, increase the injection speed.

5. The mould temperature is too low, increase the mould temperature.

6. The injection pressure is too small, increase the injection pressure.

7. Poor mould exhaust, increase mould exhaust holes.

Dissatisfied with injection

1. The temperature of the barrel and nozzle is low, increase the temperature of the barrel and nozzle.

2. The mould temperature is low, increase the mould temperature.

3. The feeding amount is not enough, so increase the feeding amount appropriately.

4. The part exceeds the injection volume of the injection moulding machine*, so choose an injection machine with a larger injection volume.

5. The runner and gate are too small, so increase the gate size appropriately.

6. The injection pressure is too low or the injection speed is too slow, increase the injection pressure or increase the temperature, and increase the injection speed.

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