Industry News

Solutions to the deformation at the sprue position of the mold, the flash at the round top pin position (excessive glue), and the baking mark at the glue inlet position

• 2025-09-02

Solutions to the deformation at the sprue position of the mold, the flash at the round top pin position (excessive glue), and the baking mark at the glue inlet position

Deformation of the sprue position of the mold

Phenomenon: During the production process of transparent lenses, unevenness often occurs near the water outlet.

Analysis: 1. Slow speed will cause the area near the sprue to cool down too quickly. 2. The gate continues to inject into the mold even when it has already cooled.

Characteristics of injection molding machines

Grade: DEMAG, clamping force: 50, plasticizing capacity: 64g

(2) Mold characteristics

Mold ejection number :1×2, glue injection method: point gate, ejection method: Ejection by ejector pin, mold temperature :70℃ (constant temperature machine)

(3) Product characteristics

Material :PMMA 8N, Color: Transparent, Product weight (single piece) :6.88g, spout weight: 5.57g

(4) Analysis of causes of defects

The main runner of the mold is quite large, and the injection port adopts a fan-shaped injection method. When the molten material flows to the vicinity of the injection port, due to the slow speed and the excessively long injection time, an uneven phenomenon occurs.

(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 medium speed and a very small position. In the third section, fill 90% of the mold cavity quickly to prevent the high-temperature molten glue from cooling. In the fourth section, fill the mold slowly to completely expel the air inside the mold cavity. Finally, switch to the pressure-holding switching position.

3. Appropriately increase the surface temperature of the mold to prevent the melt from cooling too early.

Car bumper mold Manufacturer in China (jfmoulds.com)

The circular top pin position of the mold has a flash (multi-glue)

Phenomenon: Due to the trapped air in the product, 0.025mm exhaust grooves are ground at the ejection points of each round ejector pin. This is prone to occur at the round ejector pin position during the glue injection process

"Feifeng (multi-glue)."

Analysis: There is a 0.025mm exhaust groove ground on the round ejector pin. If the injection molding speed is too fast, the plastic is prone to flash in the exhaust groove at the ejector pin position. 

Excessive injection pressure can cause the plastic to be squeezed into the exhaust slot of the ejector pin, resulting in burrs. Improper or too late position switching.

Characteristics of injection molding machines

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

(2) Mold characteristics

Mold ejection number :1x2, glue injection method: point gate, ejection method: push plate ejection, mold temperature: 83℃ (constant temperature machine)

(3) Product characteristics

Material: ABS, Color: Black + gold powder, Product weight (single piece) : 3g, spout weight :8g

(4) Analysis of causes of defects

Due to the 0.025mm exhaust groove ground on the round ejector pin, there is a 0.025mm gap space between the ejector pin and the ejector pin hole. If the injection speed and injection pressure are too high, combined with the fluidity of ABS material, it is very easy for flash (excessive glue) to occur in the exhaust groove of the ejector pin hole.

(5) Countermeasures

1. Utilize three-stage injection molding (medium pressure, slow speed) and position switching.

2. Fill the first section with glue to the area around the glue inlet of the product. Switch the filling position in the second section to about 80% of the product. Fill the third section with glue to ensure the appearance and size of the product.

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

The glue inlet position of the mold is baked and printed

Phenomenon: At the glue inlet, the thickness of the inner wall glue is uneven, and it is prone to being squeezed by pressure, causing the product to show baking marks (uneven surface gloss).

Characteristics of injection molding machines

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

(2) Mold characteristics

Mold ejection number :1×2, glue injection method: point gate, ejection method: push plate ejection, mold temperature: 90 ° C (constant temperature machine)

(3) Product characteristics

Material: ABS, Color: Black, Product weight (single piece) : 5g, nozzle weight: 8.6g

(4) Analysis of causes of defects

1. This area is at the glue inlet. The thickness of the inner wall glue is uneven. When the thin glue area is subjected to excessive injection pressure, a baking mark opening occurs.

2. After adjusting the tail wire of the product, baking marks appeared on the product surface.

3. The thickness of the glue position on the inner wall of the glue product is uneven

(5) Countermeasures

1. Utilize multi-level injection, pressure holding and position switching.

2. In the first section, fill the product's glue inlet at a slow and low speed until about 45% of the product is filled. In the second section, fill the product at medium speed and medium pressure, and ensure that there is no significant shrinkage in the product and the water inlet position. The third section of high voltage is slowly adjusted to a state where the wire connection is not obvious at the wire clamping position.

3. Use a higher first-stage holding pressure and a slower speed to fill the shrunk areas of the product, and use the second-stage holding pressure to control the size of the product's baking print to ensure quality, appearance and dimensions.