Dalian injection molding is a widely used plastic processing technology, and the adjustment of its process parameters has a significant impact on product quality, production efficiency, and production costs. The adjustment of injection molding process parameters requires comprehensive consideration of multiple factors such as material characteristics, mold design, equipment performance, and product requirements.

1. Injection pressure

Injection pressure is the main driving force that propels molten plastic into the mold cavity. The adjustment of injection pressure directly affects the filling effect and surface quality of the product.

Too low: may result in insufficient filling, product shortage, shrinkage, or uneven surface.

Excessive height: may cause product flash, excessive internal stress, or mold damage.

Adjustment method: Based on the material fluidity and product structure, gradually increase the injection pressure until the product is fully filled and has no obvious defects. For complex structures or thin-walled products, high injection pressure is usually required.

2. Injection speed

The injection speed determines the speed at which molten plastic enters the mold cavity, affecting the surface quality and internal structure of the product.

Too slow: It may cause the molten plastic to cool too quickly, resulting in insufficient filling or obvious weld marks.

Too fast: may cause flow marks, air streaks, or burning on the surface of the product.

Adjustment method: Select the appropriate injection speed based on the product structure and material characteristics. For thin-walled products, a faster injection speed is usually required; For thick walled products, the injection speed can be appropriately reduced.

3. Holding pressure and time

The pressure holding stage is to compensate for the volume loss caused by plastic cooling shrinkage and ensure product size stability.

Low holding pressure: may cause product shrinkage or unstable size.

Excessive holding pressure: may cause excessive internal stress or flash in the product.

Short holding time: may cause voids or shrinkage inside the product.

Long holding time: may prolong the production cycle and increase energy consumption.

Adjustment method: Set appropriate holding pressure and holding time based on product thickness and material shrinkage rate. Usually, the holding pressure is 50% -80% of the injection pressure, and the holding time is gradually adjusted according to the cooling condition of the product.

4. Mold temperature

The temperature of the mold affects the fluidity and cooling rate of the molten plastic, and has a significant impact on the surface quality and dimensional accuracy of the product.

Too low: may result in poor flowability of molten plastic, difficulty in filling, and the appearance of flow marks or weld marks on the surface of the product.

Excessive: It may lead to prolonged cooling time of the product, reduced production efficiency, and even deformation or burrs.

Adjustment method: Set the appropriate mold temperature based on material characteristics and product requirements. For crystalline plastics such as PP and PA, higher mold temperatures are usually required; For amorphous plastics such as PS and PC, the mold temperature can be appropriately reduced.

5. Melt temperature

Melt temperature refers to the temperature at which plastic is heated and melted in a barrel, which affects the flowability and formability of the plastic.

Too low: may result in poor plastic flowability, difficult filling, and rough product surface.

Excessive: may cause plastic to decompose, resulting in burnt, bubbly, or discolored products.

Adjustment method: Set the appropriate melt temperature based on the thermal stability of the material. Usually, the melt temperature should be slightly higher than the melting point of the plastic, but not exceed its decomposition temperature.

6. Cooling time

Cooling time refers to the time it takes for a product to cool and solidify in the mold, which affects the dimensional stability and production efficiency of the product.

Too short: may cause product deformation or dimensional instability.

Too long: may reduce production efficiency and increase energy consumption.

Adjustment method: Set an appropriate cooling time based on the product thickness and material cooling characteristics. Usually, the cooling time should ensure that the product is completely cooled and shaped, while avoiding excessively extending the production cycle.

7. Locking force

Locking force is the force that ensures the mold does not separate during the injection process, affecting the quality of product molding and the lifespan of the mold.

Too low: may cause burrs on the parting surface of the mold, and even damage to the mold.

Excessive: may increase equipment load and reduce mold life.

Adjustment method: Set the appropriate clamping force based on the product projection area and injection pressure. Usually, the locking force should be slightly greater than the product of the injection pressure and the projected area of the product.

8. Back pressure

Back pressure refers to the resistance experienced by the screw during the plasticization process, which affects the plasticization quality and melt uniformity of the plastic.

Too low: may cause uneven plasticization of the plastic, resulting in bubbles or uneven color of the product.

Excessive: It may cause plastic to overheat and decompose, and even increase equipment load.

Adjustment method: Set appropriate back pressure based on material characteristics and plasticization requirements. Usually, the back pressure is 5% -10% of the injection pressure.

9. Other parameters

Screw speed: affects the plasticizing speed and melt quality of plastics. Usually, the screw speed should be adjusted according to the plasticizing characteristics of the material.

Injection volume: affects the filling effect and weight of the product. The injection amount should be precisely controlled according to the product volume and material density.

Mold opening stroke and speed: affect production efficiency and mold life. The mold opening stroke and speed should be optimized according to the product structure and mold design.

10. Adjustment principle

Step by step adjustment: Adjust only one parameter at a time and observe its impact on product quality to avoid complicating the problem by adjusting multiple parameters simultaneously.

Record data: Record the parameters and results of each adjustment for subsequent optimization and problem troubleshooting.

Comprehensive consideration: When adjusting parameters, it is necessary to comprehensively consider material characteristics, mold design, equipment performance, and product requirements to ensure the rationality and stability of process parameters.

The adjustment of injection molding process parameters is a complex and meticulous process that requires operators to have rich experience and professional knowledge. By adjusting injection pressure, injection speed, holding pressure, mold temperature, melt temperature, cooling time and other parameters reasonably, product quality, production efficiency and economic benefits can be effectively improved. At the same time, in actual production, experience should be continuously summarized and process parameters optimized to meet the production needs of different materials and products.