Mould filling is one of the most important stages of die casting and is done with utmost care due to the probability of several defects such as shrinkage porosity and air entrapment. The poured melt is used to compress the gas, which is discharged outside via a vent.
Avoiding many of the defects such as shrinkage porosity is possible using simulation software. The software can aid in predicting the occurrence of defects such as shrinkage porosity more quickly and with lesser costs than other methods.
Porosity is mainly the formation of cavities within the solidified casting material. The size, shape, location, and surface components of the cavities are some of the main factors that help to identify the defect and its cause. These defects can usually be resolved while the product is being manufactured or by altering the mold design.
In high-pressure die casting, the liquid melt flows with high velocity when it is injected into the die cavity. Upon filling the mold, the melted metal is maintained at the appropriate pressure by a stroke.
Causes of Shrinkage Porosity
The occurrence of this porosity defect is usually because the tendency of the melted material to take up much lesser space when it is solid than in liquid state. The occurrence of any hot spots in the casting will lead to the formation of these spaces.
Shrinkage porosity is mainly caused due to the differences in wall thickness, low metal pressure, thicker cross sections and thin gate. Usually, smaller shrinkage porosity does not cause any issues with the product. However, the occurrence of larger shrinkage porosity defects can cause the casting material to get weakened and also affect its aesthetic quality.
Using Simulation to Avoid Defects
Shrinkage porosity is mainly reduced in the casting by ensuring that the liquid metal maintains its flow into the voids. For this purpose, simulation is very useful as it can provide an accurate analysis of the casting. The simulation software can be utilized to further optimize the die casting process, castings, geometry design of the molds, gating, casting parameters, die layout etc. The obtained results can be highly useful to evaluate the problem and carry out the necessary corrections in the process.
A major benefit of using simulation in shrinkage porosity reduction is that it will reduce the number of products that are liable for rejection. This is especially useful for both the die casting companies and their customers as it will lead to a reduction in the delivery times, minimize costs, and improve the quality of the finished product. Moreover, it can also be used to determine the location and shape of the porosities as well as in predicting air entrapment.