Die Design and Its Influence on Die Life of Die Casting
Die casting is one of the most commonly used manufacturing processes for creating precision parts and components. The process involves the injection of molten metal into a precision die or die casting die. The casting dies must be precisely machined to create a cavity that will produce a part with the desired geometry, surface finish and mechanical properties. Die casting dies are typically made from high strength alloys, such as steel or aluminum, and their design is critical for the quality of parts produced and the life of the die. This paper aims to provide an understanding of the effects of design parameters of die casting molds on die life.
Die design affects die life in a variety of ways. The flow of molten metal during die casting will be influenced by the geometry of the injection channels and the flow field created by the die walls. The geometry of the die cavity is a further important factor as incorrect floor angles, sharp edges, and cavities with excessive or insufficient draft can result in cavity breakouts that significantly reduce die life. Unevenly distributed pressure results in non-uniform wearing of die walls and variations in wall thickness diminish die strength and increase the risk of failure. Other factors that influence die life include the cooling system of the die, the operating parameters of the die-casting machine, the material selection of the casting die and the alloy used for the casting itself.
The cooling system of the die is a major factor in its life. As heat must be rapidly removed from the die during each injection cycle, proper cooling channels and a considerable surface area for heat transfer must be present within the die design. Unapproved cooling channels can cause uneven cooling which will reduce die life, as well as lead to thermal fatigue and cracking. In order to manage heat efficiently, the die must have compatible thermal properties with the molten metal injected. The design parameters that affect the cooling system must be adapted to ensure the cooling time and internal heat gradients remain within accepted limits.
The material selection of a die casting die is also very important. The die material must be able to withstand the operating temperatures, pressures and plastic abrasion that occurs during the casting process. The material must also have a low coefficient of thermal expansion in order to reduce the thermal stress in the die caused by the rapid cooling that occurs during the injection cycle. Commonly used material selections for die casting dies include tool steel and high strength alloys such as alloys that contain chromium and molybdenum.
The operator of a die-casting machine is also required to consider the operating parameters, such as the die temperature, injection pressure and injection speed, when setting up the machine for die casting. Improper setup of the die-casting machine may lead to an increase in operating temperature, an excessive injection pressure, inconsistency in the injection pressure, or incorrect injection speed. All of these inefficiencies may contribute to a shorter die life.
Finally, the alloys used for the die casting can also have a significant influence on die life. Improper alloys can lead to sticking of the molten metal to the walls of the die, causing non-uniform wear of the die walls and an overall reduction in die life. The alloy must be chosen based on the nature of the castings and must meet the requirements for both mechanical properties and surface finish.
In conclusion, the die design of a die casting die is critical for the quality of the parts that are produced and for the life of the die. Improper design of the die may lead to a reduction in die life, an increase in operating temperature, an excessive injection pressure, an inconsistent injection pressure and incorrect injection speed, as well as an increase in cost and a decrease in productivity. Proper design parameters must be taken into consideration when designing a die-casting die, such as the flow of the molten metal, the geometry of the die cavity, and the cooling system design. The material selection and the alloys used for the die casting must also be considered to ensure the proper operation of the die casting machine and a longer life of the die casting die.
