Optimize Injection-Molding Process Parameters and Build an Adaptive Process Control System Based on Nozzle Pressure Profile and Clamping Force
Abstract
:1. Introduction
2. Methodology
2.1. P-V-T Relationship
2.2. Nozzle Pressure Profile
2.2.1. Single Nozzle Peak Pressure
- 1~2: When the screw goes forward to push the melt, the nozzle pressure will increase.
- 2~3: Because the cross-sectional area of the product changes, the melt pressure at the tip of the screw will decrease. In order to avoid the injection speed exceeding the set value, the hydraulic pressure will be restricted, and the nozzle pressure increment will become slow.
- 3~4: When the cavity is completely filled, the behavior of the melt changes from the flowing stage to the compressing stage, which causes a sudden rise in nozzle pressures.
- 4~5: The injection stage is converted to the packing stage.
- 5~6: Packing stage.
- 6: Cooling stage starts.
2.2.2. Double Nozzle Peak Pressure
- 1~2: When the screw goes forward to push the melt, the nozzle pressure will increase.
- 2~3: Because the cross-sectional area of the product changes, the melt pressure at the tip of the screw will decrease. In order to maintain the injection speed, the hydraulic pressure will decrease, and the nozzle pressure will decrease.
- 3~4: As the melt enters the cavity, the nozzle pressure will increase.
- 4~5: When the cavity is completely filled, the behavior of the melt changes from the flowing stage to the compressing stage, which causes a sudden rise in nozzle pressures.
- 5~6: The injection stage is converted to the packing stage.
- 6~7: Packing stage.
- 7: Cooling stage starts.
2.3. Nozzle Pressure Characteristics
- Nozzle peak pressure (Ppeak): When the cavity is completely filled, the behavior of the melt changes from the flowing stage to the compressing stage, which causes a sudden rise in nozzle pressures. Nozzle peak pressure is used to optimize V/P switchover point.
- Timing of peak pressure (tpeak): The time point corresponds to the nozzle peak pressure, and the timing of peak pressure is used to optimize injection speed.
- Pressure difference (∆P): The pressure difference mainly occurs when the injection stage is switched to the packing stage. If different packing pressures are set, the pressure difference response will be different. Pressure difference is used to optimize packing pressure.
- Viscosity index (VI): The integral time is from the start of injection to the end of cooling. Viscosity index is mainly used as the quality index of the adaptive process control system to judge the variation of product weight.
2.4. Clamping Force Difference Value
3. Experiment Setups
3.1. Materials
3.2. Equipment
4. Experiment Results and Discussion
4.1. V/P Switchover Point Optimization Experiments
4.2. Injection Speed Optimization Experiments
4.3. Packing Pressure Optimization Experiments
4.4. Clamping Force Optimization Experiments
5. Adaptive Process Control System
5.1. Control Strategy of Adaptive Process Control System
5.2. Experiment Results of the Adaptive Process Control System
6. Conclusions
- When the cavity is completely filled, the behavior of the melt changes from the flowing stage to the compressing stage, which causes a sudden rise in nozzle pressure. The nozzle peak pressure can be used to optimize the V/P switchover point.
- To avoid the melt’s over-compression and to make injection-molding cycle time as short as possible, the injection speed needs to be adjusted. The nozzle peak pressure and timing of peak pressure can be used to optimize the injection speed.
- Packing pressure setting should consider the product quality, for example, product weight. Product weight and pressure difference can be used to optimize the packing pressure.
- When the clamping force difference value is zero, it is the appropriate clamping force.
- Using three materials with different viscosities under the adaptive control system, the variation of product weight was reduced to 0.106%, 0.092%, and 0.079%. In addition, the standard deviation of the product weight was reduced to 0.0034 g, 0.0025 g, and 0.0025 g.
Author Contributions
Funding
Institutional Review Board Statement
Data Availability Statement
Conflicts of Interest
Appendix A
References
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Mold compression High clamping force setting Possible venting problem | Slight mold separation | Significant mold separation Too-low clamping force setting Possible flash defect |
Fixed Parameters | |||
---|---|---|---|
Injection pressure (bar) | Cooling time (s) | Packing time (s) | Mold temperature (°C) |
170 | 15 | 0.1 | 60 |
Melting temperature (°C) | Injection speed (%/(mm/s)) | Packing pressure (bar) | Clamping force (ton) |
210 | 50/81.35 | 10 | 40 |
Changed parameter | |||
V/P switchover point (mm) | 6331-8 | 6331 | PT231 |
7, 8, 9, 10, 11 | 8, 9, 10, 11, 12 | 9, 10, 11, 12, 13 |
Fixed Parameters | |||
---|---|---|---|
Injection pressure (bar) | Cooling time (s) | Packing time (s) | Mold temperature (°C) |
170 | 15 | 0.1 | 60 |
Melting temperature (°C) | Packing pressure (bar) | Clamping force (ton) | |
210 | 10 | 40 | |
V/P switchover point (mm) | 6331-8 | 6331 | PT231 |
10 | 11 | 12 | |
Changed parameter | |||
Injection speed (%/(mm/s)) | 30/48.81, 40/65.08, 50/81.35, 60/97.62 70/113.89, 80/130.16, 90/146.43 |
Fixed Parameters | |||
---|---|---|---|
Injection pressure (bar) | Cooling time (s) | Packing time (s) | Mold temperature (°C) |
170 | 15 | 3 | 60 |
Melting temperature (°C) | Injection speed (%/(mm/s)) | Clamping force (ton) | |
210 | 60/97.62 | 40 | |
V/P switchover point (mm) | 6331-8 | 6331 | PT231 |
10 | 11 | 12 | |
Changed parameter | |||
Packing pressure (bar) | 6331-8 | 6331 | PT231 |
4, 5, 6, …, 23, 24, 25 | 4, 5, 6, …, 18, 19, 20 | 4, 5, 6, …, 18, 19, 20 |
Fixed Parameters | |||
---|---|---|---|
Injection pressure (bar) | Cooling time (s) | Packing time (s) | Mold temperature (°C) |
170 | 15 | 3 | 60 |
Melting temperature (°C) | Injection speed (%/(mm/s)) | ||
210 | 60/97.62 | ||
V/P switchover point (mm) | 6331-8 | 6331 | PT231 |
10 | 11 | 12 | |
Packing pressure (bar) | 6331-8 | 6331 | PT231 |
15 | 14 | 13 | |
Changed parameter | |||
Clamping force (ton) | 10, 11, 12, …, 18, 19, 20 |
Fixed Parameters | |||
---|---|---|---|
Injection pressure (bar) | Cooling time (s) | Packing time (s) | Mold temperature (°C) |
170 | 15 | 3 | 60 |
Melting temperature (°C) | Injection speed (%/(mm/s)) | ||
210 | 60/97.62 | ||
V/P switchover point (mm) | 6331-8 | 6331 | PT231 |
10 | 11 | 12 | |
Packing pressure (bar) | 6331-8 | 6331 | PT231 |
15 | 14 | 13 | |
Clamping force (ton) | 19 |
Material | Without System (%) | With System (%) |
---|---|---|
6331-8 | 0.112 | 0.106 |
6331 | 0.152 | 0.092 |
PT231 | 0.132 | 0.079 |
Material | Without System (%) | With System (%) |
---|---|---|
6331-8 | 0.0037 | 0.0034 |
6331 | 0.0033 | 0.0025 |
PT231 | 0.0035 | 0.0025 |
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Liou, G.-Y.; Su, W.-J.; Cheng, F.-J.; Chang, C.-H.; Tseng, R.-H.; Hwang, S.-J.; Peng, H.-S.; Chu, H.-Y. Optimize Injection-Molding Process Parameters and Build an Adaptive Process Control System Based on Nozzle Pressure Profile and Clamping Force. Polymers 2023, 15, 610. https://doi.org/10.3390/polym15030610
Liou G-Y, Su W-J, Cheng F-J, Chang C-H, Tseng R-H, Hwang S-J, Peng H-S, Chu H-Y. Optimize Injection-Molding Process Parameters and Build an Adaptive Process Control System Based on Nozzle Pressure Profile and Clamping Force. Polymers. 2023; 15(3):610. https://doi.org/10.3390/polym15030610
Chicago/Turabian StyleLiou, Guan-Yan, Wei-Jie Su, Feng-Jung Cheng, Chen-Hsiang Chang, Ren-Ho Tseng, Sheng-Jye Hwang, Hsin-Shu Peng, and Hsiao-Yeh Chu. 2023. "Optimize Injection-Molding Process Parameters and Build an Adaptive Process Control System Based on Nozzle Pressure Profile and Clamping Force" Polymers 15, no. 3: 610. https://doi.org/10.3390/polym15030610