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The screw columns of the mold are prone to damage and weld marks/shrinkage

2025-08-07

The screw columns of the mold are prone to damage and weld marks/shrinkage

The screw columns of the mold are prone to being pulled out

Phenomenon: The screw columns on both sides of the back cover of the 1433 screen are prone to damage.

Analysis: The mold design is unreasonable, and the sequence of mold opening and closing actions is incorrect.

（1）Characteristics of injection molding machines

Grade: HT120T, clamping force: 12Ot, plasticizing capacity: 119g

(2) Mold characteristics

Mold ejection number: 1×2, glue feeding method: small water outlet to large water outlet, ejection method: Ejection with ejector pins, mold temperature: 105℃ (constant temperature machine)

(3) Product characteristics

Material: ABS+PC H-1001 IM, product weight (single piece) : 6.72g, sprue weight: 4.28g

(4) Analysis of causes of defects

The sequence of actions during mold closing; The A board is first closed to the front mold position and opens due to the base scraping effect. Then, the AB board is closed. During the process of closing the AB board

As the front die position has been opened, the hanging pins on the front die position are very likely to be broken by impact.

Mold opening sequence: The AB board is opened first. The front mold position is not closed, but the AB board is opened, causing the product screws and columns to break.

(5) Countermeasures

Two spring adhesives are added to the bottom of plate A, and two base switches, pull rods and four springs are added to plate AB to ensure that the mold opening action starts with Plate A

First, open the AB board. When closing the mold, ensure that the AB board is closed first, followed by the A board and the pulling plate.

Injection molding process table

Injection molding machine: HT120T, Type B screw, injection volume 61g			Product Name: 1433 Front Shell
Raw materials: ABS+PC HI-1001IM	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					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

	/	80	Holding pressure	Pressure-holding position	75	90	100	Injection pressure
	/		Holding pressure time		15	22	28	Injection pressure position
Residual amount of injection glue			/	/	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	/	/

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

Weld marks/shrinkage marks on the mold

Phenomenon: During the production process of the electrical knife dispensing table, obvious weld marks/shrinkage marks appeared at the middle bone position.

Analysis: Due to the two-point injection of the mold design, the exhaust at the end of the material flow fusion is not smooth, resulting in obvious weld marks and shrinkage.

Characteristics of injection molding machines

Grade: HT8OT, clamping force: 80t, plasticizing capacity: 130g

(2) Mold characteristics

Mold ejection number: 1x2, glue injection method: point gate, ejection method: Ejection by ejector pin, mold temperature: 85℃ (constant temperature machine)

(3) Product characteristics

Material: ABS PA757 Color: White Product Weight (single piece) : 7.5g Sprue Weight: 8.5g

(4) Analysis of causes of defects

The mold design adopts two-point injection of glue, using a fast material flow speed for glue filling. Due to the influence of the product structure, at the end of the material flow

The exhaust at the fusion point of the middle bone position is not smooth, and the trapped air causes obvious fusion marks and shrinkage marks.

(5) Countermeasures

1. Use multi-stage injection with slow speed and low mold temperature for filling injection.

2. In light of the glue flow condition of the product structure, three-stage injection should be adopted for adjustment. The mold temperature should not be too high, and a low injection speed should be used By allowing the material flow to move slowly and fill the glue, the position of the weld line is changed, thereby improving the obvious weld line and shrinkage mark defects of the product.

Injection molding process table

Injection molding machine: HT80T, injection capacity 130g			Product Name: Knife Dispenser
Raw material: ABS PA757	Colour: White	Drying temperature: 85°C	Drying method: Dehumidifying dryer	Drying time: 4 hours	Recycled material usage: 0
Finished product weight: 7.5g×2=15g		Nozzle weight: 8.5g	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	85°C	85°C
230°C	220°C	205°C	190°C	/	before	Oil temperature control machine	85°C	85°C
△	△	△	△	△	after	Oil temperature control machine	85°C	85°C
△	△	△	△	△	after	Oil temperature control machine	85°C	85°C

	/	45	50	Holding pressure	Pressure-holding position	85	110	95	Injection pressure
	/	0.5	1.3	Holding pressure time	11	14	19	28	Injection pressure position
Residual amount of injection glue			/		/	16	28	15	Injection velocity
7.5			/	/	/

Intermediate time	Injection time	Cooling time	The entire duration	Back pressure	Rotational speed	Retraction speed	Material quantity position	Retraction position
5	3.1	12	32	5	10 15 10	10	32	3

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	15 32 35	/	/