Low Pressure and Gravity Die Casting
Precise Cooling Improves Quality of Casting Processes
The quality of aluminum parts produced in die casting processes largely depends on the precise temperature control of the mold. However, cooling also has a decisive impact on the efficiency and speed of the casting process. Read in this article how you can reduce scrap rates and maximize product quality through optimized and customized cooling line control.
The automotive sector remains to be the most important sales market for die casting foundries. Suppliers in this sector need to produce die cast parts of consistently high quality in order to remain competitive. Two casting processes are primarily used in the manufacture of aluminum rims, transmission housings, pistons, chassis parts and cylinder blocks, both of which benefit from precise cooling: Low pressure casting and the gravity process. In both casting processes, cooling is an essential step. Their success depends largely on the implementation of accurate temperature control.
What Challenges Does the Cooling Process Involve?
Temperature control or cooling influences the material structure, i.e. the microstructure as well as the surface of the metal. Inaccuracies, failures or errors that occur during cooling, have a direct influence on the quality of the cast product. Inaccuracies in the temperature control can occur time again: For example, flow fluctuations must be expected - especially in the case of several cooling sections running in parallel or in systems with several die casting machines which are supplied simultaneously by a central control system. The cooling system must therefore be able to calculate the differences as quickly as possible and compensate them accordingly. This is because the dissipation of heat must be uniform at all points of the final product. Apart from a high reaction speed of the cooling section, an exact alignment and adjustment of the cooling section is required to ensure that the exact amount of cooling medium is applied to the area where it is needed: While less coolant is to be dispensed at narrower areas, more cooling is required at the wider areas of the product in order to reduce the internal thermal stress.
Cooling Strategies to Control the Process Temperature
Automated systems can help to ensure precise temperature control. This requires highly dynamic control systems that quickly and reliably control the heating and cooling rates of the temperature control process. These systems must be able to cool the process temperature through precisely controlled quantities of water, air or water-air mixtures ("Mist cooling"). An automated platform for process control, used to adjust temperatures, meets these requirements perfectly and thus facilitates the cooling processes during the production high-quality low-pressure cast parts considerably.
Bürkert Fluid Control Systems offers a complete solution that can be individually adapted to the specific needs of foundries. This is because the initial version of the system is modular and can be easily configured or flexibly adapted: Depending on the application, required pressures, temperatures and corresponding flow rates, a wide range of actuators and sensors is available. These sensors can also be easily installed and integrated into existing systems.
The more complex the cast product, the more cooling channels are required to cool the associated mold. The cooling strategy determines the sequence of the individual cooling channels. The time and quantity of the coolant can be determined individually for each cooling channel. The direction of the solidification front of the liquid aluminum can be controlled very precisely. This reduces internal material stresses, holes or cracks caused by uncontrolled shrinkage.
Digital Networking Makes Processes Reproducible and Documentable
A fieldbus interface with all common protocols (PROFINET, PROFIBUS, EtherNet/IP) ensures smooth communication with the controller. All process-relevant data, such as target value, actual value feedback and valve position, are available as digital data for the controller. This is where another advantage becomes apparent: Once the parameters have been determined, they are continuously documented and can be restored at any time. This means that the temperature control processes are reproducible. On the one hand, this increases the quality of the cast product and reduces expensive scrap, while on the other it increases efficiency in recurring processes or tool changes.
Bürkert Fluid Control Systems' automated temperature control platform offers a customized solution for precise cooling. The know-how of the Bürkert experts allows not only an individual adaptation to the respective casting situation, but also guarantees a service-friendly design in which the respective components can be easily exchanged. The pre-configured and tested systems also guarantee leak-free operation - even with high temperature fluctuations.