Temperature is one of core technological factors in the process of aluminium alloy die casting components. Quality of product and production efficiency are directly affected by temperature control of die casting mould. Choice of temperature control mode of die casting mould is particularly important. In this paper, according to actual situation of aluminium alloy die-casting, temperature control mode of aluminum die casting mold is analyzed in order to realize thermal balance of mould and solve hot spot problem.
1, Foreword
With vigorous development of automobile industry, more opportunities and new challenges have been brought to aluminium die casting suppliers. In aluminum parts manufacturing, die temperature has an important influence on casting quality, die life and production rhythm. Therefore, in modern die casting technology, control of die temperature is an indispensable technological means. This paper will have a brief analysis for importance, principles, control methods of die casting mould temperature, and a set of temperature control methods for die casting mould.
2, Importance and Control Principle of Die Casting Mould Temperature
(1) Importance of Temperature of Aluminium Die Casting Mold
Die-casting Mould is equipment of forming technology in process of casting production.Stability of temperature distribution in mould has an important impact on quality of castings, production efficiency and service life of mould. It is directly related to cost and economic benefits of casting production. Temperature field in mould should be within range of technological requirements so as to obtain qualified castings with good appearance and internal quality. On the contrary, excessive temperature will lead to defects such as strain and bubble, prolong cooling time and reduce production efficiency; too low temperature will lead to defects such as cold isolation, insufficient pouring and pore. Die-casting moulds are manufactured under high temperature and high pressure for a long time. If temperature field of moulds is unstable and moulds expand and shrink periodically for a long time, moulds are more likely to fail, which greatly shortens service life and reduces production efficiency.
(2) Temperature Control Principle of Aluminum Die Casting Mold
In the process of casting, heat exchange between mould and liquid metal achieves ideal heat balance, that is, heat absorbed and discharged by mould is equal, and dynamic heat balance is achieved. After process is selected, temperature of mould reaches range of working temperature of casting. Hot spot is cooled at a fixed point to promote formation of heat balance.
3, Hot Festival
(1) Generating position: Casting structure has the highest temperature in process of die casting, and it is easy to form shrinkage cavity, shrinkage and stress concentration in cooling process.
(2) Control mode – point cooler
In order to realize water saving, point cooler adopts water recycling mode. In order to ensure full pressure, a header is added.
(3) High pressure point cooling is added to the core of hot spot part of castings.
(4) Point cooling water treatment: Point cooling water in the cooling pipeline will encounter sudden cooling and sudden heat, small pipeline and other conditions. Old-style water treatment generally uses softening treatment, often fails to meet water quality requirements in production. Point cooling pipe blockage occurs frequently, resulting in huge human, material and financial losses. RO reverse osmosis water treatment device is generally used to treat the point cold water into pure water.
4, Heat balance
(1) Principle: In process of aluminum parts manufacturing, heat absorbed and discharged by mould should be kept same, so as to avoid die becoming cooler or hotter, and reduce casting defects such as shrinkage, porosity and porosity caused by uneven temperature of mould. Improve appearance and internal quality of castings, die life and production efficiency. Achieving thermal balance is process of cooling high temperature part of mould and heating up low temperature part.
(2) Control Mode-Temperature Machine for Aluminum Die Casting Mold
Temperature divider and oil type, control temperature is about 160 C and general choice of water type with higher environmental requirements, higher than 160 general choice of oil type. Main function of mould temperature machine is to use the cold die, which is not enough to regulate and control temperature in the process of die casting production.
(3) Control Mode-Die Cooling Unit
Cooling unit of mould is used with cooling circulating water of mould itself to cool parts with high temperature of mould so as to maintain thermal balance of cavity temperature of mould.
5, Temperature Monitoring Method of Die Casting Mould
(1) Handheld thermal imager
Thermal imaging test was carried out in each shift, and mould was adjusted according to temperature.
(2) Temperature monitoring system of thermocouple or thermal imager.
According to mold condition, thermocouple is embedded in mold (or thermal imager is placed on top and left sides of mold). Temperature distribution of mold is monitored in real time by control system. Through analysis of monitoring data, temperature of mold is adjusted to realize temperature monitoring of mold.
6, A Comprehensive Solution to Temperature of Aluminum Die Casting Mold-Temperature Control Island
Temperature control island is a comprehensive solution of die casting mould provided by Nanjing Euro Machinery for customers. Temperature control equipment such as mould temperature machine, high-pressure mould cooler, fine core point cooler, water supply constant temperature intelligent control and so on are used to provide temperature control scheme from point to line to surface for mould. Temperature control island can form a closed-loop system from water intake to mould backwater.
7, Concluding remarks
Mold temperature is one of the most important process parameters. It not only determines quality of castings, but also seriously affects service life and production efficiency of mould. Therefore, to ensure that parameters are controllable, automatic temperature control system should be adopted as far as possible. Temperature control of die casting die is a combination of many ways. It can not be considered that only one way of temperature control can control die temperature well. Different temperature control methods should be adopted according to different conditions of aluminum parts manufacturing process and die casting mould. With development of die-casting technology, new temperature control methods are constantly updated. The application of new methods can definitely further improve level of mould temperature control, and contribute to the production of faster and better die casting components.
