Treatment methods for mold weld marks/shrinkage marks and fractures
Treatment methods for mold weld marks/shrinkage marks and fractures
Mold weld marks/shrinkage marks
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 marks.
（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: 85°C (constant temperature machine)
(3) Product characteristics
Material: ABS PA757, Color: White, Product weight (single piece) :7.5g, Spout weight: 8.5g.
(4) Analysis of causes of defects
The mold design adopts two-point injection of glue and uses the material flow speed of blocks for glue filling. Due to the influence of the product structure, the exhaust at the middle bone position of the material flow end is not smooth, resulting in obvious weld 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 status of the product structure, the three-stage injection is adjusted. The mold temperature should not be too high. A low injection speed is used to allow the material to flow slowly for glue filling, thereby changing the position of the weld line and improving the obvious weld line and shrinkage 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 | / | ||||
| △ | △ | △ | △ | △ | 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 | / | / | / |
Middle position | 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 | Injection time | Clamping force | Ejection length | Ejection times | Rotation position | Blowing delay | Blowing time |
| 1 | 10 | 65 | 32 | 1 | 15 32 35 | / | / |
Auto Mould_Taizhou Jiefeng Mould Co.,Ltd. (jfmoulds.com)
Mold fracture
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 single-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 product stress and lead to product breakage.
(5) Countermeasures
1. Add venting to the mold
2. Use multi-stage injection with low pressure speed and high mold temperature for filling injection.
3. Adjust to reduce the residual amount of injection glue.
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 | / | ||||
| △ | △ | △ | △ | △ | 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 | / | / | / |
Middle position | Injection time | Cooling time | The entire duration | Back 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 | Injection time | Clamping force | Ejection length | Ejection times | Rotation position | Blowing delay | Blowing time |
| 1 | 10 | 65 | 32 | 1 | 11 22 25 | / | / |
Commodity Mould_Taizhou Jiefeng Mould Co.,Ltd. (jfmoulds.com)
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