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Solution for mold fracture and air wrinkle treatment

2025-08-08

Solution for mold fracture and air wrinkle treatment

Fracture of the mold

Phenomenon: The scraper cover of the electrical product breaks in the middle during the production process.

Analysis: As the fracture site is the position of the weld line; The product is affected by stress.

（1）Characteristics of injection molding machines

Grade: HT80T, clamping force: 80t, plasticizing capacity: 130g.

（2） Mold characteristics

Mold ejection number: 1×2, glue injection method: point gate, ejection method: Ejection by ejector pin, mold temperature: 110°C (constant temperature machine)

（3）Product characteristics

Material: POM M270, Color: Grey, Product weight (single piece) :1.9g, nozzle weight: 3.6g.

（4） Analysis of causes of defects

The mold design adopts a one-point injection of glue. Due to the influence of the product structure, the exhaust is not smooth at the middle fusion point at the end of the material flow, and the welding mark is obvious. Excessive injection pressure and too fast injection speed can cause internal stress in the product, leading to product breakage.

（5） Countermeasures

1. Add venting to the mold.

2. Use multi-stage injection with low pressure, low speed and high mold temperature for filling injection.

3. Adjust to reduce the injection allowance.

Injection molding process table

Injection molding machine: HT80T, injection capacity 130g			Product Name: Scraper Cap
Raw material: POM M270	Colour: White	Drying temperature: 85°C	Drying method: Dehumidifying dryer	Drying time: 2 hours	Recycled material usage: 0
Finished product weight: 1.9g×2=3.8g		Nozzle weight: 3.6g	Mold output: 1×2	Gate injection method: Point gate

Barrel temperature					Mold temperature	Use machines	"Settings	"Actual
1	2	3	4	5	before	Oil temperature control machine	110°C	110°C
210°C	200°C	195°C	165°C	/	before	Oil temperature control machine	110°C	110°C
△	△	△	△	△	after	Oil temperature control machine	110°C	110°C
△	△	△	△	△	after	Oil temperature control machine	110°C	110°C

	/	35	Holding pressure	Pressure-holding position	50	75	65	Injection pressure
	/	0.5	Holding pressure time	7	9	14	18	Injection pressure position
Residual amount of injection glue		/		/	10	18	12	Injection velocity
4.2		/	/	/

Intermediate time	Injection time	Cooling time	The entire duration	Back 7 pressure	Rotational speed	Retraction speed	Material quantity position	Retraction position
5	1.6	6	20	5	10 15 10	10	22	2

Mold closing protection time	Supervise the feeding time	Clamping force	Ejection length	Ejection times	Rotation position	Blowing delay	Blowing time
1	10	65	32	1	11 22 25	/	/

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

The air streaks of the mold

Phenomenon: During the production process of transparent protective covers, thin layers of air streaks often appear near the water outlet.

Analysis: The raw material melt is prone to decomposition at high temperatures during shearing, generating gas. The high brightness of the mold surface is not conducive to the discharge of gas. The

gas is drawn in through the water inlet due to the pressure drop.

（1）Characteristics of injection molding machines

Grade: HT-DEMAG, clamping force: 100t, plasticizing capacity: 150g.

（2）Mold characteristics

Mold ejection number: 1×2, injection method: point gate, ejection method: Ejection by top block, mold temperature: 100°C (constant temperature machine)

（3）Product characteristics

Material: PC, Color: Transparent, Product weight (single piece) : 1.5g, nozzle weight: 13g.

（4）Analysis of causes of defects

The main channel of the mold is quite large. The method of injecting glue is submersible. The molten material flows near the glue inlet. Due to the excessive speed and the high gloss of the mold surface, the high shear causes the molten material to heat up rapidly in an instant, resulting in the decomposition of the raw material and the generation of gas and pressure drop. The gas is drawn in through the water inlet, forming gas streaks.

（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. In the third section, quickly fill 90% of the mold cavity to prevent the high-temperature molten rubber compound from cooling down. Finally, switch to the pressure-holding switch position and appropriately extend the pressure-holding time.

Injection molding process table

Injection molding machine: TMC 60T, Type B screw, injection capacity 133g			Product Name: Transparent Mirror
Raw material: PC LEXAN101	Color: Transparent	Drying temperature: 120°C	Drying method: Dehumidifying dryer	Drying time: 4 hours	Recycled material usage: 0
Finished product weight: 1.5g×8=12g		Nozzle weight: 13g	Mold output: 1×8	Gate injection method: Point gate

Barrel temperature					Mold temperature	Use machines	"Settings	"Actual
1	2	3	4	5	before	Oil temperature control machine	100°C	100°C
320°C	315°C	310°C	285°C	/	before	Oil temperature control machine	100°C	100°C
△	△	△	△	△	after	Oil temperature control machine	100°C	100°C
△	△	△	△	△	after	Oil temperature control machine	100°C	100°C

	/	45	50	Holding pressure	Pressure-holding position	110	110	110	Injection pressure
	/	1.5	1.8	Holding pressure time	12	16	23.6	25	Injection pressure position
Residual amount of injection glue			/		/	100	2	15	Injection velocity
8.2			/	/	/

Intermediate time	Injection time	Cooling time	The entire duration	Back 7 pressure	Rotational speed	Retraction speed	Material quantity position	Retraction position
5	1.3	15	30	5	10 15 10	10	25	3

Mold closing protection time	Supervise the feeding time	Clamping force	Ejection length	Ejection times	Rotation position	Blowing delay	Blowing time
1	10	550	45	1	15 25 28	/	/