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Methods for the easy breakage of the internal position of the mold and the easy damage of the screw column during the mold opening process

2025-08-07

Methods for the easy breakage of the internal position of the mold and the easy damage of the screw column during the mold opening process

The inner position of the mold is prone to breakage

Phenomenon: The battery cover is prone to breakage at the four inner positions during the molding process.

Analysis: The mold structure determines that these four rows are relatively thin. The material strength of the inner rows of the mold is relatively weak. During the molding process, due to the pressure effect of mold opening and injection molding, the inner rows have insufficient strength and are pulled apart.

（1）Characteristics of injection molding machines

Grade: HT120T, Clamping force: 120t, plasticizing capacity: 119g.

(2) Mold characteristics

Mold ejection number: 1×2, glue feeding method: dot glue feeding and plunger pin glue feeding, ejection method: plunger pin ejection, mold temperature: 105°C (constant temperature machine)

(3) Product characteristics

Material: ABS+PC HI-1001, color: grey, Product weight (single piece) : 16.21g, sprue weight: 5.62g.

(4) Analysis of causes of defects

1.The four inner positions of the battery cover are long and small in structure, resulting in insufficient strength. During the mold opening process, they cannot withstand the pressure of mold opening and are thus pulled apart.

2. The entry point of the glue is relatively small, but the pressure required during molding is relatively high. The internal position cannot withstand the pressure, resulting in fracture.

3. There is a false fit in the row position, and the mold breaks due to the shaking of the row position during the movement process.

(5) Countermeasures

1. Change the inner side of the battery cover to a slanted top.

2. The mold material is changed to DH31. The bottom of the row position is thickened by 3mm, and a 0.2mm gap is left at the intersection where the row position meets the pressure block.

3. Increase the sprue pin size to 0.3mm and the glue entry point to 0.8-1.0mm.

Injection molding process table

Injection molding machine: HT120T, Type B screw, injection volume 61g			Product Name: 1433 Main Unit Back Cover and Battery Cover
Raw materials: ABS+PC HI-1001IM	Colour: Grey	Drying temperature: 105°C	Drying method: Dehumidifying dryer	Drying time: 3 hours	Recycled material usage: 0
Finished product weight: 16.21g		Nozzle weight: 5.62g	Mold output: 1+1	The methods of pouring glue into the gate: glue injection by dot and glue injection by submersible needle

Barrel temperature					Mold temperature	Use machines	"Settings	"Actual
1	2	3	4	5	before	Oil temperature control machine	105°C	100°C
280°C	275°C	270°C	250°C	/	before	Oil temperature control machine	105°C	100°C
△	△	△	△	△	after	Oil temperature control machine	105°C	100°C
△	△	△	△	△	after	Oil temperature control machine	105°C	100°C

	/	115	Holding pressure	Pressure-holding position	115	120	125	Injection pressure
	/	3	Holding pressure time			15	23	Injection pressure position
Residual amount of injection glue		/	/	/	20	28	35	Injection velocity
3.0		/	/	/		15	23	Velocity of fire position

Intermediate time	Injection time	Cooling time	The entire duration	Back pressure	Rotational speed	Retraction speed	Material quantity position	Retraction position
1.0	0.8	10	23	5.6	20 45 55	10	30	1.0

Mold closing protection time	Supervise the feeding time	Clamping force	Ejection length	Ejection times	Rotation position	Blowing delay	Blowing time
0.7	10	115kN	45	1	18 20 26	/	/

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Cabinet mold Manufacturer in China (jfmoulds.com)

The screw columns are prone to damage during the mold opening process

Phenomenon: During the mold opening process of the front shell of 1433, the four screw columns are prone to being pulled and damaged.

Analysis: The mold structure design is unreasonable. When demolding, the screw column is not designed with a ejector pin, and it slides off the mold in the front mold position.

（1）Characteristics of injection molding machines

Grade: HT120T, Clamping force: 120t, plasticizing capacity: 119g.

(2) Mold characteristics

Mold ejection number: 1×2, glue injection method: Large water outlet (dot injection), ejection method: Ejection by ejector pin, mold temperature: 105°C.

(3) Product characteristics

Material: ABS+PC HI-1001, product weight (single piece) : 6.52g, nozzle weight: 4.76g.

(4) Analysis of causes of defects

The sequence of product ejection is that the front mold's row position slides down first, and then the product is ejected by the ejector pin. During the sliding down of the front mold's row position, since the product's screw column is relatively deep and does not completely detach from the row position, when the ejector pin pushes the product out, due to the force, the product may be pulled concave or damaged.

(5) Countermeasures

1.Increase the draft Angle of the four screw columns to ensure that the product can be completely removed from the front die position and then ejected.

2. Four springs are added at the position of the screw column in the front mold row. When the inner row slides down to the bottom, the elastic force of the springs is used to completely eject the product screw column from the row first, and then push the product out.

Injection molding process table

Injection molding machine: HT120T, Type B screw, injection volume 61g

Product Name: 1433 Front Shell

Raw materials: ABS+PC HI-1001 IM

Colour: Grey

Drying temperature: 120°C

Drying method: Dehumidifying dryer

Drying time: 3 hours

Recycled material usage: 0

Finished product weight: 6.52g

Nozzle weight: 4.76g

Mold output: 1×2

Gate injection method: Small gate to large gate

Barrel temperature l					Mold temperature	Use machines	"Settings	"Actua
1	2	3	4	5	before	Oil temperature control machine	105°C	100°C
280°C	275°C	270°C	250°C	/	before	Oil temperature control machine	105°C	100°C
△	△	△	△	△	after	Oil temperature control machine	105°C	100°C
△	△	△	△	△	after	Oil temperature control machine	105°C	100°C

	/	80	Holding pressure	Pressure-holding position	75	90	100	Injection pressure
	/		Holding pressure time		15	22	28	Injection pressure position
Residual amount of injection glu			/	/	10	52	75	Injection velocity
4.0		/	/	/	15	22	28	Velocity of fire position

Intermediate time	Injection time	Cooling time	The entire duration	Back pressure	Rotational speed	Retraction speed	Material quantity position	Retraction position
1.0	1.0	10	24	5.0	10 75 85	10	32	1.0

Mold closing protection time	Supervise the feeding time	Clamping force	Ejection length	Ejection times	Rotation position	Blowing delay	Blowing time
0.7	10	105kN	45	1	15 30 32	/	/