Nowadays, the most popular production method for manufacturing high quality casts of aluminium alloys is the hot and cold chamber die casting. Die casts made of hypereutectoid silumin Silafont 36 AlSi9Mg are used for construction elements in the automotive industry. The influence of the metal input and circulating scrap proportion on porosity and mechanical properties of the cast has been examined and the results have been shown in this article. A little porosity in samples has not influenced the details strength and the addition of the circulating scrap has contributed to the growth of the maximum tensile force. Introducing 80% of the circulating scrap has caused great porosity which led to reduce the strength of the detail. The proportion of 40% of the metal input and 60% of the circulating scrap is a configuration safe for the details quality in terms of porosity and mechanical strength.
A measuring system was developed for the measurement of ejector forces in the die casting process. When selecting the sensor technology, particular care was taken to ensure that measurements can be taken with a high sampling rate so that the fast-running ejection process can be recorded. For this reason, the system uses piezoelectric force sensors which measure the forces directly at the individual ejector pins. In this way, depending on the number of sensors, it is possible to determine both the individual ejector forces and the total ejector force. The system is expandable and adaptable with regard to the number and position of the sensors and can also be applied to real HPDC components. Automatic triggering of the measurements is also possible. In addition to the measuring system, a device and a method for in-situ calibration of the sensors have also been developed. To test the measuring system, casting experiments were carried out with a real aluminium HPDC aluminium component. The experiments showed that it is possible to measure the ejector forces with sufficient sampling rate and also to observe the process steps of filling, intensification and die opening by means of ejector forces. Experimental setup serves as a basis for future investigations regarding the influencing parameters on the ejection process.
For the die casting conditions of aluminium bronzes assumed based on the literature data, a thick-walled bush was cast, made of complex aluminium bronze (Cu-Al-Fe-Ni-Cr). After the cast was removed from the mould, cracks were observed inside it. In order to identify the stage in the technological production process at which, potentially, the formation of stresses damaging the continuity of the microstructure created in the cast was possible (hot cracking and/or cold cracking), a computer simulation was performed. The article presents the results of the computer simulation of the process of casting the material into the gravity die as well as solidifying and cooling of the cast in the shape of a thick-walled bush. The simulation was performed with the use of the MAGMA5 program and by application of the CuAl10Ni5,5Fe4,5 alloy from the MAGMA5 program database. The results were compared with the location of the defects identified in the actual cast. As a result of the simulation of the die-casting process of this bush, potential regions were identified where significant principal stresses accumulate, which can cause local hot and cold cracking. Until now, no research has been made of die-cast aluminium bronzes with a Cr addition. Correlating the results of the computer simulation validated by the analysis of the actual cast made it possible to clearly determine the critical regions in the cast exposed to cracking and point to the causes of its occurrence. Proposals of changes in the bush die casting process were elaborated, in order to avoid hot tearing and cold cracking. The article discusses the results of preliminary tests being a prologue to the optimization of the die-casting process parameters of complex aluminium bronze thick-walled bushs.
The paper deals with problem of optimal used automatic workplace for HPDC technology - mainly from aspects of operations sequence, efficiency of work cycle and planning of using and servicing of HPDC casting machine. Presented are possible ways to analyse automatic units for HPDC. The experimental part was focused on the rationalization of the current work cycle time for die casting of aluminium alloy. The working place was described in detail in the project. The measurements were carried out in detail with the help of charts and graphs mapped cycle of casting workplace. Other parameters and settings have been identified. The proposals for improvements were made after the first measurements and these improvements were subsequently verified. The main actions were mainly software modifications of casting center. It is for the reason that today's sophisticated workplaces have the option of a relatively wide range of modifications without any physical harm to machines themselves. It is possible to change settings or unlock some unsatisfactory parameters.