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Solutions for air streaks, charring, wire jamming, height elevation or trapped air in molds

• 2025-08-14

Solutions for air streaks, charring, wire jamming, height elevation or trapped air in molds

The air streaks of the mold

Phenomenon: Air streaks near the glue inlet point, difficult to improve by adjusting the machine.

Analysis: The glue entry point is the submerged glue of ox horns. The glue entry point is small, and it is difficult to control the air streaks near the glue entry point during the molding process.

Characteristics of injection molding machines

Grade: DEMAG100T, Clamping force: 100t, plasticizing capacity: 61g

(2) Mold characteristics

Mold ejection number: 1×1, glue feeding method: Submerged glue feeding with ox horns, ejection method: Ejection with ejector pins and inclined ejectors, mold temperature: 115°C (constant temperature machine)

(3) Product characteristics

Material: PC HF-1023IM, Product weight (single piece) : 5.68g, nozzle weight: 9.06g

(4) Analysis of causes of defects

The glue feeding method is the submerged glue feeding with ox horns. The glue feeding port is relatively small. When the pressure is constant, the speed is too fast, causing high shear and the melt material to heat up rapidly in an instant. This leads to the decomposition of raw materials and the generation of gas. The gas is not discharged in time, resulting in gas streaks at the water outlet.

(5) Countermeasures

1. Utilize multi-level injection and position switching.

2. In the first section, fill the flow channel to the glue inlet at a relatively high speed and find the corresponding switching position. In the second section, fill the area near the glue inlet at a medium speed and a very small position to form. In the third section, fill 95% of the mold cavity at a medium speed. In the fourth section, fill the mold cavity at a slow speed to completely expel the air inside the mold cavity. Finally, switch to the pressure-holding switching position.

3. Change the glue feeding method of the product from the bull horn submerged glue to the submerged needle glue feeding.

Charring of the mold/wire clamping/top height

Phenomenon: The wire at the hole position is prone to breakage and trapped with gas, resulting in charring. There is a height increase on the product surface.

Analysis: The clamping lines left at the junctions where the plastic flows and converges in the mold due to the product's holes. The raw material used in the product is fireproof material, which has poor fluidity and causes gas entrapment and charring. When the product is being demolded, a top height appears at the dome when the product is ejected.

Auto Mould_Taizhou Jiefeng Mould Co.,Ltd. (jfmoulds.com)

Characteristics of injection molding machines

Grade: HT86T, Clamping force: 86t, plasticizing capacity: 119g

(2) Mold characteristics

Mold ejection number: 1×2, glue feeding method: large water inlet side glue feeding, ejection method: Ejection by ejector pin, mold temperature: 100°C (constant temperature machine)

(3) Product characteristics

Material: ABS+PC GN-5001RFH, product weight (single piece) : 2.60g, spout weight: 1.32g

(4) Analysis of causes of defects

1. Poor exhaust of the mold

2. The mold temperature is too low

3. The temperature of the barrel is too low

4. The injection speed is too slow and the injection pressure is too low.

5. The cross-sectional area of the ejector pin is too small.

(5) Countermeasures

1. Utilize multi-level injection and position switching.

2. In the first section, fill the flow channel to the glue inlet at a relatively fast speed and find the corresponding switching position. In the second section, fill the area near the glue inlet at a medium or small position. In the third section, fill 85% of the mold cavity at a slower speed to prevent the high-temperature molten glue from cooling. In the fourth section, fill the mold cavity at a slower speed to completely expel the air inside the mold cavity.

3. Increase the surface temperature of the mold.

4. Increase the temperature of the glue melt cylinder.

5. Add exhaust or cold material at the wire clamping position.

6. The top pin has been changed from a dome to a flat top.

Commodity Mould_Taizhou Jiefeng Mould Co.,Ltd. (jfmoulds.com)

Trapped air in the mold

Phenomenon: The product causes the bone area to turn white and lack glue due to trapped qi.

Analysis: Poor exhaust from the mold leads to trapped air. The forming pressure and speed are too high.

Characteristics of injection molding machines

Grade: HT86T, Clamping force: 86t, plasticizing capacity: 119g

(2) Mold characteristics

Mold ejection number: 1×2, glue insertion method: glue insertion by the ejection pin, ejection method: glue ejection by the ejection pin, mold temperature: 100°C (constant temperature machine)

(3) Product characteristics

Material: ABS+PC GN-5001RFH, product weight (single piece) : 2.7g, nozzle weight: 1.46g

(4) Analysis of causes of defects

Due to excessive molding pressure and speed, poor mold exhaust, excessively high mold temperature, and inconsistent glue flow between the two products, air was trapped inside the products.

(5) Countermeasures

1. Reduce the forming pressure and speed, especially the speed at the end.

2. Reduce the mold temperature.

3. Add exhaust vents at the row positions of the mold.

4. Reduce the holding pressure and duration.