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The solutions for the air marks at the arrow position in the mold direction, the black shadow lines (fusion lines) on the surface, and the trapped air and white spots at the lamp hole position

• 2025-08-13

The solutions for the air marks at the arrow position in the mold direction, the black shadow lines (fusion lines) on the surface, and the trapped air and white spots at the lamp hole position

The air pattern at the arrow position of the mold's direction

Phenomenon: Air streaks appear at the direction arrow position during the injection molding of the rotary cover.

Analysis: The technician believes that it is due to poor exhaust from the mold. The forming process was not properly adjusted.

Characteristics of injection molding machines

Grade: Haitian, Clamping force: 86t, Plasticizing capacity: 100g

(2) Mold characteristics

Mold ejection number: 1×2, glue injection method: point gate, ejection method: Ejection by ejector pin, mold temperature: 85°C (constant temperature machine)

(3) Product characteristics

Material: ABS PA757 37784, Color: black, Product weight (single piece) : 3.25g, spout weight: 2.83g

(4) Analysis of causes of defects

1. The mold's rubber feeding is single-point type, which is prone to decomposition due to high temperature generated by shearing at the rubber feeding port, and the resulting gas is drawn into the mold cavity. The mixing cylinder rotates at a relatively fast speed, and the temperature of the molten rubber at the end is relatively high.

2. The injection molding speed and stroke calibration are unreasonable.

3. The mold temperature is not stable.

(5) Countermeasures

1. By using multi-stage injection and position switching, the front and rear molds are separately connected for cooling and water supply.

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 glue inlet and the area near the arrow with a slow speed and a very small position. The third section is to quickly fill the mold cavity 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.

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

The black shadow lines (fusion lines) on the surface of the mold and the trapped gas at the lamp hole position

Phenomenon: During the molding process, a black fusion line appears at the final fusion point of the product.

Analysis: The technician believes that it is due to poor exhaust from the mold and requests an increase in exhaust. There are holes in the middle of the product. The product materials contain added silver powder, which has a certain impact on the fluidity of the melt adhesive.

Characteristics of injection molding machines

Grade: Haitian, Clamping force: 86t, Plasticizing capacity: 100g

(2) Mold characteristics

Mold output: 1×2, glue injection method: submerged glue injection, ejection method: Ejection by ejection pin, mold temperature: 90°C (constant temperature machine)

(3) Product characteristics

Material: ABS PA757 plus silver powder 060702, color: silver-black, product weight (single piece) : 3.26g, spout weight: 1.7g

(4) Analysis of causes of defects

Due to the limitations of the product structure, there is a perforation in the middle.

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 glue inlet at a slow speed and the area near the middle hole. In the third section, fill the mold cavity at a slow speed to completely expel the air inside the mold cavity, avoiding trapped air and burning and other adverse phenomena. Finally, switch to the pressure-holding switching position.

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

There is trapped air and white spots in the lamp holes of the mold

Phenomenon: During the production process of the face cover, there is often a phenomenon of trapped air and whitening at the light-transmitting lamp holes.

Analysis: Molten material shearing and high-temperature decomposition can generate gas. Under rapid injection conditions, the gas is prone to being encapsulated by the material flow, undergoing physical changes to form white spots. The surface of the mold is smooth. If the shooting speed is too fast, it is prone to high temperature and decomposition. The position switch is too early.

Characteristics of injection molding machines

Grade: Haitian 120, Clamping force: 120t, plasticizing capacity: 150g

(2) Mold characteristics

Mold ejection number: 1×2, injection method: point gate to direct injection, ejection method: Ejection by ejector pin, mold temperature: 70°C (constant temperature machine)

(3) Product characteristics

Material: ABS PA758 39225, color: semi-transparent, product weight (single piece) : 13.5g, nozzle weight: 6.34g

(4) Analysis of causes of defects

1. The mold's glue inlet changes from a large nozzle to a small one. The mold has a high-gloss surface, which is prone to generating shear gas due to high temperature. At the same time, the speed is too fast, and the glue position at the lamp hole is relatively thin, making it difficult for the gas to be discharged to the end of the glue melt.

2. The position setting is unreasonable.

(5) Countermeasures

1. Utilize multi-stage injection molding 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 glue inlet to 1/3 of the product at a slow speed. In the third section, fill the lamp hole position at a slow speed. In the fourth section, fill the mold cavity at a slow speed to completely expel the air inside the mold cavity and avoid trapped air and charring and other adverse phenomena. Finally, switch to the pressure-holding switching position.