Stress correlation between instrumentation and simulation analysis of the die for high pressure die casting

A strain gauge instrumentation trial on a high pressure die casting ‘HPDC’ die was compared to a corresponding simulation model using Magmasoft® casting simulation software at two strain gauge rosette locations. The strains were measured during the casting cycle, from which the von Mises stress was determined and then compared to the simulation model. The von Mises stress from the simulation model correlated well with the findings from the instrumentation trial, showing a difference of 5.5%, ~ 10 MPa for one strain gauge rosette located in an area of low stress gradient. The second rosette was in a region of steep stress gradient, which resulted in a difference of up to 40%, ~40 MPa between the simulation and instrumentation results. Factors such as additional loading from die closure force or metal injection pressure which are not modelled by Magmasoft® were seen to have very little influence on the stress in the die, less than 7%.

Modelling of porosity defects in high pressure die casting with a neural network

High Pressure Die Casting (HPDC) is a complex process that results in casting defects if configured improperly. However, finding out the optimal configuration is a non-trivial task as eliminating one of the casting defects (for example, porosity) can result in occurrence of other casting defects. The industry generally tries to eliminate the defects by trial and error which is an expensive and error -prone process. This paper aims to improve current modelling and understanding of defects formation in HPDC machines. We have conducted conventional die casting tests with a neural network model of HPDC machine and compared the obtained results with the current understanding of formation of porosity. While most of our findings correspond well to established knowledge in the field, some of our findings are in conflict with the previous studies of die casting.

Integrated optimization system for high pressure die casting processes

High pressure die casting (HPDC) is a versatile process for producing engineered metal parts by forcing molten metal under high pressure into reusable steel dies. However there are a large number of attributes involved which contribute to the complexity of the process. A novel integrated approach is developed to optimize the high pressure die casting processes. The die temperature profiles will be studied with infrared thermograph technology and the internal cooling system will be optimized to provide even cooling to the components and the die. The heat stored in the die and the components is studied with image processing. Based on the geometrical profile of the components, cooling channels can be redesigned to improve the cooling efficiency while the cooling time is reduced. This will not only significantly improve the quality of the castings but also improve the productivity of the process.

Thermal control of high pressure die casting using computational fluid dynamics

The quality of high pressure die castings is a function of many interdependent parameters. It has been observed that many defects detected in the HPDC castings can be tracked back to poor die temperature distribution in the critical areas. It has therefore been recommended that the development of a technique to directly control the critical features - making them less sensitive to thermal related parameters - be very beneficial to the HPDC industry. From the information obtained from thermal image (processing), computational fluid dynamics has been applied to design the layout of internal cooling system and assign the flow conditions such as flow rate and pressure of the cooling water. it is observed that CFD prediction provides an excellent insight into the thermal balance of the high pressure die casting.

Determination of the heat transfer coefficient at the metal–die interface for high pressure die cast AlSi9Cu3Fe

When simulating the High Pressure Die Casting ‘HPDC’ process, the heat transfer coefficient ‘HTC’ between the casting and the die is critical to accurately predict the quality of the casting. To determine the HTC at the metal–die interface a production die for an automotive engine bearing beam, Die 1, was instrumented with type K thermocouples. A Magmasoft® simulation model was generated with virtual thermocouple points placed in the same location as the production die. The temperature traces from the simulation model were compared to the instrumentation results. Using the default simulation HTC for the metal–die interface, a poor correlation was seen, with the temperature response being much less for the simulation model. Because of this, the HTC at the metal–die interface was modified in order to get a better fit. After many simulation iterations, a good fit was established using a peak HTC of 42,000 W/m2 K, this modified HTC was further validated by a second instrumented production die, proving that the modified HTC gives good correlation to the instrumentation trials. The updated HTC properties for the simulation model will improve the predictive capabilities of the casting simulation software and better predict casting defects.

Cracking and blowout in an aluminium high-pressure die casting die

Die cracking and metal blowout have been identified as problems in production of the structural sump, a high pressure die cast aluminium part, at Ford's Geelong manufacturing plant. Visual inspection, thermography and strain measurements have been performed and results are consistent with the view that cracking and blowout are caused by excessive stresses and deflections, respectively, generated by bending of the sliding cores. Models are being developed for finite element simulation of the stresses and deflections in the die during production, with a view to eliminating the aforementioned problems.

Squeeze pin implementation in a high pressure die casting

This paper discusses the implementation of hydraulically operated squeeze pins to reduce porosity formation in cast aluminium bearing caps. Two complete sets are cast in an eight-cavity die with a 2000t cold chamber high pressure die casting machine. The initial die configuration used a sliding core assembly with stationary pins to core a through hole in a thick section of the front cam caps. This configuration resulted in high post machining scrap rates, primarily due to porosity associated with solidification shrinkage. Replacement of the sliding core assembly with a squeeze pin unit substantially reduced shrinkage porosity in the critical region, with consequent reductions in the scrap rate. The squeeze pins are actuated 1.5s after the piston reaches the high shot changeover position, but can be successfully engaged between I and 3.5 seconds after high shot changeover. Density measurements and visual inspection confirmed the substantial improvement in porosity levels in the critical region of the castings.