Aluminum Casting Technologies

 by: Alexander Xiavier

Aluminum Casting Technologies and Cost effectiveness

Aluminum is the established metal of choice for the production of light weight components in the automotive, aerospace and transport industries. Casting liquid aluminum alloys into metal moulds using processes such as gravity, low pressure and high pressure die casting is a cost effective means of producing complex shapes that require minimal machining. Australia's automotive industry supports a strong local aluminum die casting industry, producing parts that include automotive transmission housings, cylinder heads, inlet manifolds and engine sumps.(Ref:www.reform.co.in)

Growth in world automotive markets for aluminium die cast components is creating

significant opportunities and challenges for the Australian industry, which is positioning itself as a global player. Through partnerships between our research organisations and key automotive participants such as Nissan and Ford, CAST has developed innovative and novel technologies that have benefited our partner's productivity. In turn, these technologies have created IP that is poised on the verge of commercialisation. An example featured is CASTcoat a project that began as postgraduate research at CSIRO and The University of Queensland. It was developed further under CAST project funding at CSIRO with industrial trials at Nissan, Ford, Merne Products, Castalloy and others. Now it is a provisionally patented technology. (Ref:www.reform.co.in)

Cycle Time Reduction
Automated Fault Detection in Aluminium Die Casting
Modelling of Fluid Flow Inside a Die Cavity Using Smoothed Particle Hydrodynamics
Tailoring of CAST's New Die Coat for LPDC and GDC
Integrated Gravity Die Design Methodology
Improved Quality Aluminium Automotive Castings
Reduction in Metal Pressure in the HPDC Process
Cycle Time Reduction

To increase productivity of high pressure die casting by reducing casting machine cycle time by 30%.

More than a 20% reduction in cycle time has been achieved and implemented on selected parts at two industry partner plants. The project has involved identification of opportunities to reduce the process cycle time, performing research to prove the concept and then carrying out the actual trial to prove the theoretical findings. This necessitated the involvement of shopfloor staff in order to implement changes to the process. Such trials are often in conflict with the day to day production of parts and only through true cooperation has it been possible to achieve the project objectives.

The third year of this project has shown the development of true cooperation between researchers and industrial partners where the latest research findings obtained through modelling and simulation have been implemented on the shopfloor with the help and support of staff from Ford and Nissan. The changes, once trialed during a production period, have been implemented as part of the process, hence providing ongoing cost benefits through a reduction in the time required to produce each component.

An example of implementation is a reduction in cycle time at Nissan on a gearbox side cover produced in a twin cavity die that has shown successful production results over many months from an original cycle time of 75 seconds down to 60 seconds. Whilst research at Ford on a converter housing casting has shown successful implementation of cycle time reduction from 90 seconds to 74 seconds.

In future work we will look for further opportunities with current stakeholders and the die casting industry in general, to implement the horizontal deployment of cycle time reduction across other machines and parts.

Automated Fault Detection in Aluminium Die Casting

To develop and implement an automatic fault detection system for surface and sub-surface defects.

A fully automated fault detection machine called CASTvision has been developed and a prototype system is ready for extended in-plant on-line trials. This project is in its third year and exciting results are now emerging. The results from the algorithm, which was designed and developed during the second year of the project, have been put to the test this year. Through prototyping, the CAST team have designed and developed a working system, CASTvision. For Ford's converter housing casting the off-line system can detect and discriminate between defective and good parts. The prototype system is capable of identifying blocked holes on any of the holes on this complex casting. Off-line systems have also been developed where hot tears and cold shuts can be detected on Ford's structural sump casting.

Work at Nissan on their pump cover casting has resulted in a CASTvision prototype system for in-line fault detection. The system is able to capture images and identify certain categories of defects on the surface of the part. This project has demonstrated that advances in machine vision applied to fault detection of aluminium castings can be taken from the concept stage through to a working prototype very successfully. The next step for this project is to take the concepts from single part to multi part systems able to handle more complex shapes and surfaces. This outcome will be a strong candidate for future commercialisation.

Modelling of Fluid Flow Inside a Die Cavity Using Smoothed Particle Hydrodynamics

To develop a simulation technique to assist industry in design and optimisation of dies and products.

This year has seen extensive developments in the Smoothed Particle Hydrodynamics (SPH) code along with testing undertaken to improve the robustness and speed of modelling. Enhancements were also made to the visualisation techniques used to display results from SPH's three dimensional (3D) simulation results. 3D SPH isothermal simulations and animations of parts from Nissan and Metaldyne showing complex filling patterns were completed. Observations by staff at Nissan Casting of the casting's filling pattern during production were consistent with the SPH modelling predictions.

Water analogue images from a clear perspex model of a servo piston die casting part and digitised short shots of an aluminium casting were completed for validation with flow predictions from SPH. The validation process and further computational speed improvements will be completed next year. Further developments of the SPH code particularly in the areas of heat transfer, solidification, surface oxide prediction, robustness and speed are planned in future work.

Tailoring of reform's New Die Coat for LPDC and GDC

To commercialise the die coat technology for low pressure and gravity die casting and further improve die coat properties.

Industrial trials were carried out successfully in several low pressure and gravity die casting plants. Its performance was enhanced in low draft angle areas of the die by application of a sealer. Two provisional patents covering inventions related to reform.com have been lodged.

Integrated Gravity Die Design Methodology

To develop an integrated die design methodology for gravity die casting that can achieve optimal die filling, optimal feeding and yield, and dimensional stability.

A new design of feeders to address the root cause of shrinkage porosity defects in an inlet manifold casting was implemented on a customer's die and resulted in excellent outcomes. A study was completed on the use of "squeeze pins" to reduce or eliminate shrinkage defects in a gravity test die. The squeeze pin technique demonstrated that surface shrinkage can be effectively eliminated and associated internal micro shrinkage can be significantly reduced in the locations tried. The squeeze pin concept was extended to include application as a mechanical squeeze/shear gate to reduce fettling requirement. The mechanism implemented on a test die allowed the shearing of the gate before full solidification, with adjustment to produce variable gate widths.

The final part of the methodology to be developed is optimal die filling through variable tilt pouring from a ladle. To ensure smooth flow, the variable tilting motion can be programmed to match the filling rate with changes in the instantaneous flow area. Flow evaluation is done by real time X-ray radiography on a test die. The effect of die geometry, especially wall thickness, on die distortion will be investigated using computer simulation that models thermal stresses in casting cycles.

Improved Quality Aluminium Automotive Castings

To improve the overall performance of low pressure die casting operations by implementing improved tools in design and process control to reduce casting defects.

Successful development of appropriate tooling design and process control has been achieved for the low pressure die casting (LPDC) process to cast small automotive components. A multi-cavity die design was selected and optimised by solidification simulation. Several dies of this design are being used to produce high-volume, high-integrity parts. Casting parameters were also investigated to improve the casting quality and reduce the cycle time. Die trials were conducted on an LPDC research die to investigate the effect of casting geometry and process parameters on shrinkage defects in castings having several fundamental features of cylinder heads. The die trial successfully produced castings with shrinkage defects in one particular area sandwiched in the sand core, as predicted. Analysis of castings made on the LPDC pseudo-cylinder head research die will be completed to establish relationships between porosity defects and process parameters.

Reduction in Metal Pressure in the HPDC Process

To investigate the role of metal pressure on the production of quality parts in high pressure die casting.

In the final six months of this project, effort was focused on innovative technologies. One such technology was designed to absorb impact pressure spikes that cause detrimental flashing and the other technology involved revamping the hydraulics of ageing die casting machines to improve product quality. A novel shock absorbing technology was developed that utilised existing casting overflows. Die casting trials at CSIRO confirmed the effectiveness of this technology in absorbing impact pressure shocks upon cavity filling. Through in-plant trials at Nissan Casting Plant the limits of hydraulic valve timing and circuit functioning were confirmed. A proposal for a revamp to improve intensification pressure response was put forward. The project concluded in December 2001. Ford Australia may adopt the reduced pressure operating parameters for the production of their new Barra model engine sumps later in 2002.

About The Author

Alexander Xiavier

We are promoting Technology to entire world community.

gurugantal2000@yahoo.com


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