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The U-shaped position of the mold is filled with water lines and trapped air, which turns white

• 2025-08-06

The U-shaped position of the mold is filled with water lines and trapped air, which turns white

U-shaped position clamping water line of the mold

Phenomenon: Water lines are clamped in the U-shaped position of the charger base.

Reason: During the formation of the base, there will be a water line at the upper position of the inverted U shape as shown in the figure.

Analysis: Both too fast and too slow injection speeds can cause water line inclusion. The surface of the mold is smooth. If the shooting speed is too fast, it is prone to high temperature and decomposition. The product has a high-gloss surface. The glue is fed into the center, and the injection speed is not very easy to control.

Characteristics of injection molding machines

Grade: Haitian (Zhejiang), clamping force: 120t, plasticizing capacity: 150g.

(2) Mold characteristics

Mold ejection number: 1×2, glue injection method: dot injection, ejection method: Ejection by ejector pin, mold temperature: 70°C for the front and 55°C for the rear (water temperature machine)

(3) Product characteristics

Material: ABS VW30, Color: Black, Product weight (single piece) : 27.9g, nozzle weight: 8.5g.

(4) Analysis of causes of defects

1.The material used in the product is VW fireproof type. The melting temperature of the glue is relatively high, and its fluidity is slightly worse than that of other similar raw materials.

2. Due to the structural limitations of the product, the molten plastic may converge during the mold filling process.

3. The temperature did not reach the optimal state, and the injection speed and stroke Settings were not accurate enough.

(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. Then, in the second section, fill the area near the glue inlet at a slow speed and a very small position. The third section is to quickly fill the U-shaped part of the mold cavity to prevent the high-temperature molten rubber from cooling and forming a fusion line. In the fourth section, fill the mold cavity slowly to completely expel the air inside the cavity, avoiding trapped air and charring and other adverse phenomena. Finally, switch to the pressure-holding switching position.

Injection molding process table

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

The trapped gas in the mold has burned white

Phenomenon: The base of the ES7115 motor is burned white due to trapped air.

Analysis: If the injection speed is too slow, there will be fusion lines; if it is too fast, it will burn white. The melting temperature of the glue needs to be 10°C higher. The position switch is too early.

Characteristics of injection molding machines

Grade: Haitian (Zhejiang), clamping force: 120t, plasticizing capacity: 150g.

(2) Mold characteristics

Mold ejection number: 1×2, glue entry method: dispensing port, ejection method: Ejection by ejector pin, mold temperature: 75°C (constant temperature machine)

(3) Product characteristics

Material: ABS-PA757 37826, Color: grey, Product weight (single piece) : 11.8g, Spout weight: 7g.

(4) Analysis of causes of defects

1. The adhesive position here is relatively thin in terms of the product structure itself.

2. The main runner of the mold is quite large, and the glue inlet method is submersible glue inlet. When the molten material reaches the vicinity of the glue inlet, due to the excessive speed, high shear occurs, causing the molten material to heat up rapidly instantly. The raw material decomposes and generates gas, which is then drawn into the mold cavity.

3. The mixed materials are not well integrated with the gas.

4. The speed and stroke adjustment of the forming process are unreasonable.

(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. Then, in the second section, fill the easily burn-white trapped air positions (U-shaped positions) of the glue inlet and the mold cavity at a slow speed and in a very small position. The third section fills 90% of the mold cavity at a relatively fast speed. In the fourth section, fill the mold cavity slowly to completely expel the air inside the cavity, avoiding trapped air and charring and other adverse phenomena. Finally, switch to the switch position.

Injection molding process table

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