In aluminium alloy die casting, precise control of process parameters is key to ensuring part strength, dimensional accuracy, and surface quality. Key parameters, such as injection speed, pressure, temperature, and time, must be optimized and coordinated with one another. Even slight deviations may lead to pores, deformation, or incomplete filling, which will affect product performance.
This article will focus on analyzing key process parameters such as injection speed, switching point, boost pressure, temperature control, cooling and holding time, and introduce equipment settings, simulation and monitoring methods, as well as parameter optimization solutions for typical die casting defects.
Injection Parameters
Injection Speed
The injection process is divided into two stages: slow and fast. Slow injection involves slowly introducing molten aluminum into the pressure chamber to minimize turbulence and air inclusions.
Fast injection requires rapid filling of the cavity before the metal solidifies, and must be precisely controlled to avoid turbulence, cold shut, and pores.
Switching Point Control
The switching point is the key node from slow injection to fast injection. Triggering too early will cause air inclusions, while triggering too late may cause the aluminum liquid to solidify midway.
Precise control through plunger position or pressure sensor helps to achieve complete cavity filling and avoid surface or internal defects.
Boost Pressure
The boost pressure applied after the cavity is filled can compact the molten aluminum, eliminate pores, improve mechanical strength, and reduce shrinkage.
This pressure needs to be synchronized with the solidification time of the aluminum alloy to work without disturbing the flow of molten aluminum.
Molten Aluminum Injection
Thermal Control Parameters
Pouring Temperature
Pouring temperature affects the fluidity of the aluminum liquid and gas absorption. Too high pouring temperature will cause pores and mold corrosion, while too low will easily cause poor filling and cold shut.
For aluminum die casting components, keeping them between 660–700°C can ensure fluidity and reduce casting defects.
Mold Temperature
The die casting mold temperature needs to be kept stable to ensure casting quality and dimensional accuracy.
Too low will result in insufficient filling or a rough surface, while too high will easily shrink and increase cooling time.
The recommended range is 180°C to 250°C, which should be flexibly adjusted based on alloy type and part structure.
Cooling Time
The cooling time determines whether the die casting parts are solidified enough for demolding.
Too short a cooling time can cause deformation or internal defects, while too long a cooling time reduces efficiency.
The cooling time should be optimized according to the wall thickness and alloy type of the casting to ensure quality while improving efficiency.
Press Holding Time
Pressing is to continue pressurizing after the cavity is filled to prevent pores and shrinkage during solidification.
Too short holding time can easily lead to internal pores, while too long holding time wastes equipment time.
It should be reasonably set according to the wall thickness, volume, and solidification speed of the casting.
Equipment Settings and Parameter Stability
Although parameters such as injection speed, temperature, and pressure determine the quality of aluminum die casting products, the stability of equipment settings directly affects whether these parameters can be accurately executed.
The following points are important foundations for ensuring effective implementation of parameter control:
Plunger and Shot Sleeve Settings
The plunger movement must be stable and controllable to avoid turbulence, air inclusion, and other problems during injection.
The lubrication state and wear of the shot sleeve affect the flow rate and consistency of the aluminum liquid.
The plunger position is also related to the accuracy of the switching point and is an important basis for injection parameter control.
Mold Lubrication Management
Reasonable lubrication can prevent mold sticking, ensure smooth demolding, and protect the mold surface.
Too little lubrication can easily damage the mold, while too much lubrication affects the filling quality and increases the risk of cold shut or pores.
Automated spraying systems help maintain lubrication consistency and stabilize production rhythm.
Auto Lubrication Spraying
Gate and Exhaust System Design
Gate and exhaust systems directly affect the flow state of aluminum liquid and gas discharge efficiency.
Good gate design can guide the flow path to avoid flow interruption and retention; effective exhaust helps eliminate pores and cold shuts.
These structural parameters play a basic supporting role in the stability of the entire process window.
Simulation and Monitoring in Parameter Control
In order to ensure that die casting process parameters can be accurately set and stably executed, modern high-pressure die casting processes are usually supplemented by simulation analysis and real-time monitoring systems.
Simulation Tools
Mold flow analysis and DFM software can predict the flow path, solidification behavior, and potential defect locations of molten aluminum before production, which helps to optimize injection speed, gate layout, and cooling channels.
Through simulation, the process window can be narrowed before mold trial, the first piece success rate can be improved, and the trial-and-error cost can be reduced.
Real-Time Monitoring and Sensors
During the production process, sensors can track key parameters such as plunger speed, cavity pressure, and mold temperature in real time.
Once deviated from the set range, the system can promptly warn or adjust to ensure the process consistency of each cycle.
Common Die Casting Defects and Parameter Optimization Solutions
Porosity
Causes
Porosity often occurs in the injection stage, often caused by too fast injection speed, poor exhaust, or excessive lubrication spraying, resulting in air being drawn into the aluminum liquid.
Optimization Solutions
The slow injection stage should be controlled at 0.1–0.3 m/s to ensure that the aluminum liquid is smoothly advanced without air entrainment.
The exhaust channel needs to be clean and unblocked, and the exhaust area design is recommended to be greater than 0.5% of the projected area of the casting.
Lubrication spraying should use a fine atomization nozzle, and the spray volume should be controlled in a slightly wet state on the surface to avoid the formation of a liquid film.
Cold Shut
Causes
Cold shut is caused by insufficient temperature at the front of the molten metal or too slow a flow rate, resulting in the inability of the two metals to merge smoothly.
Optimization Solutions
The pouring temperature is recommended to be maintained at 670–700°C, and the fast injection speed should reach 35–60 m/s to ensure that the metal has sufficient kinetic energy to fill quickly.
The gate and main runner should be kept smooth and without sharp corners to guide the aluminum liquid to flow along the set path and reduce front cooling.
Shrinkage
Causes
Shrinkage usually occurs when the shrinkage is insufficient during the solidification stage, mainly caused by too short holding time or insufficient boost pressure, which cannot fill the metal volume.
Optimization Solutions
The holding time should cover more than 80% of the solidification time of the main wall thickness area, and it is recommended to be set between 2–6 seconds.
The boost pressure should reach 40–70 MPa and be applied in time before the initial solidification of the aluminum liquid to ensure that the pressure can be effectively transmitted to the inside of the casting to achieve shrinkage compensation.
Flash
Causes
Flash is caused by excessive injection pressure or insufficient mold clamping force, which causes metal to overflow from the mold parting surface, affecting dimensional accuracy and post-processing efficiency.
Optimization Solutions
The maximum injection pressure should be reasonably set according to the casting size and mold strength, generally controlled within the range of 100-160 MPa.
The clamping force should be configured according to the standard ratio of 40-70 kN per square centimeter of the projected area of the casting to ensure that the parting surface is closed and seamless.
Surface Defects
Causes
Surface defects, such as flow marks and watermarks, are mostly caused by uneven mold temperature or inconsistent lubrication distribution, resulting in unstable metal flow.
Optimization Solutions
The mold temperature should be maintained in a stable range of 180-250°C, the cooling channel design should cover the thin-walled area, and the water channel should be evenly distributed.
Mold lubrication should be programmed and automatically sprayed, covering the entire cavity every 1-2 seconds, and the spraying angle should be maintained at 30-45 degrees with the mold surface to ensure uniform coverage.
CEX Casting’s Parameter Optimization Measures
Simulation-Based Parameter Setting
CEX Casting uses mold flow analysis and DFM reports in the early stage of the project to simulate the flow, solidification, and exhaust paths of molten aluminum.
By optimizing the gate, venting, and cooling layout, the injection speed, flow direction, and temperature distribution are balanced, and the accuracy of parameter setting and mold trial efficiency are improved.
Mold Accuracy Ensures Parameter Consistency
CEX Casting has in-house mold manufacturing capabilities to ensure that the key dimensions and runner design accuracy are consistent with the simulation results.
The higher the mold accuracy, the more repeatable the injection speed, switching point, and mold temperature control, which effectively ensures the stable execution of parameters in mass production.
Raw Material Stability Ensures Parameter Consistency
Through the central melting and purification system, CEX Casting can control the pouring temperature at 660–700°C and stabilize the alloy composition.
The aluminum liquid with stable composition and temperature provides stable input for subsequent parameter control, such as injection, solidification, and pressurization, ensuring the repeatability of the entire process window.
Conclusion
The success of aluminum alloy high-pressure die casting depends on the precise control of key parameters such as injection speed, pressure, temperature, and time.
These parameters work together to ensure casting quality, structural strength, and defect prevention.
As an experienced aluminum die casting manufacturer, CEX Casting provides full process parameter optimization to ensure you get high-performance aluminum alloy die castings.
Contact us today to see how we can make your next aluminum alloy die casting project a reality.