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.
