Industry News

Solutions to the uneven surface of the mold, the whitening of the bone position due to trapped air, the air lines at the glue entry points, and the lack of glue

• 2025-08-25

Solutions to the uneven surface of the mold, the whitening of the bone position due to trapped air, the air lines at the glue entry points, and the lack of glue

The surface of the mold is uneven

Reason: The surface of the mold (front mold) is uneven, with unevenness, resulting in an uneven product surface, similar to shrinkage.

（1）Characteristics of injection molding machines

Grade: Haitian, Clamping force: 140t, Plasticizing capacity: 133g.

（2） Mold characteristics

Mold ejection number: 1x1. Injection method: Direct injection type. Gate ejection method: Push plate ejection. Mold temperature :78℃ (constant temperature machine)

（3）Product characteristics

Nozzle weight :5g

Color: Original color. Product weight (single piece) :2.5g

Material: ABS+PC

（4） Analysis of causes of defects

1.This product is a smooth electroplated one. During the early production stage, due to a mold damage on the front mold surface, the electroplated product injected out could not be completed

The mold damage was fully covered, and the quality was substandard, so the mold was repaired.

2. After mold repair, the surface of the injected product was uneven, similar to shrinkage. The technician believed that there was a problem with the machine adjustment technique

Ask the superior for assistance in handling the issue.

3. When inspecting the mold with the lower mold, it was found that during the mold repair process, due to improper mold removal, the surface of the mold had uneven surfaces

The uneven surface of the injected product, similar to shrinkage, has nothing to do with the technical aspects of machine adjustment.

（5） Countermeasures

1. Mold repair treatment: Re-polish the reduced surface of the mold to save the mold.

2. Mold repair treatment: After welding and smoothing the damaged parts of the mold, re-polish the mold.

3. After electroplating, the injection molded parts should be treated according to their actual quality conditions.

Storage box mold Manufacturer in China (jfmoulds.com)

The bone position of the mold is trapped and turns white

Reason: There is no exhaust system at the bone position of the product. If the injection speed is too fast, the gas inside the plastic cannot be discharged, resulting in trapped gas (whitening) at the bone position.

（1）Characteristics of injection molding machines

Grade: Haitian Clamping Force: 140t Plasticizing capacity :133g

（2） Mold characteristics

Mold ejection number :1x2 glue injection method: Direct injection type gate ejection method: Push plate ejection Mold temperature: 78℃(constant temperature machine)

（3）Product characteristics

Nozzle weight: 5g, color: gray. Product weight (single piece):2.5g, material: ABS +PC

（4）Analysis of causes of defects

1.This bone is located on the rear mold and no exhaust system has been made.

2. If the injection speed is too fast, the gas inside the plastic cannot be discharged from the mold cavity in time and will form trapped gas (whitening) at the dead corners of the bone position.

3. This bone position is relatively deep and it is also the last place where the gas inside the glue and plastic accumulates in the mold cavity, which is the most difficult to fill.

（5）Countermeasures

1. Use two-stage high-pressure low-speed injection. In the first stage, use low-speed injection to fill over 90% of the product at the injection position. In the second stage

The section should run at a relatively lower speed than the first section to fill the remaining amount of glue.

2. Then, use an appropriate holding pressure to ensure the appearance and size of the product.

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

Air streaks and insufficient glue at the glue entry points of the mold

Phenomenon: The surface of BIZZ lenses is prone to air streaks and lack of glue.

（1）Characteristics of injection molding machines

Grade: Haitian Clamping Force :100t Plasticizing capacity :133g

（2） Mold characteristics

Mold ejection number :2+2. Injection method: Direct injection into the gate. Ejection method: Push plate leaf ejection. Mold temperature :130℃(constant temperature machine)

（3）Product characteristics

Material: PC Color: Brown Product weight (single piece) : 4g Spout weight: 5g

（4）Analysis of causes of defects

1. The product is directly injected into the gate, and the entry point 1 is relatively small. During slow injection, the air streaks at the gate position can basically be improved, but

The product is 2+2, while the other two products are missing calibration. At high speed, the product is not short of glue but has relatively large air streaks.

2. Due to the different sizes of the product's injection ports, when the injection molding machine injects a certain amount of material into the mold cavity in parallel, the water flows through

Due to the different sizes of the glue entry points at the mouth, the direction of the glue material cannot be completed simultaneously within a certain period of time. Under the condition of different glue entry speeds, extrusion causes air marks and glue shortage.

（5）Countermeasures

1.For the product with air streaks, the glue inlet should be enlarged. This way, the glue inlet becomes larger, the injection speed slows down, and it is more conducive to water injection

Improvement of breath lines in the mouth position.

2. Add heat insulation plates to the front and rear plates of the mold to increase the mold temperature with a higher mold temperature, making the temperature of the plastic closer to that of the mold

In the mold control, the plastic can have good fluidity and flow forward smoothly without hindrance, thereby reducing air streaks.

3. In the first stage, inject at a relatively slow speed to reach the water outlet. After passing the air crease position, inject at a medium speed and switch to the second stage

"Hope. This way, the product neither lacks glue nor has air streaks.