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46 | DIECASTING www.mmcpublications.co.uk

Maximising the advantages of low

pressure diecasting

According to Rick Davies, Process Development Manager at Sarginsons Industries Ltd, low pressure diecasting is the

most controllable and repeatable diecasting process. Here, he explains its distinct advantages.

resulting in walls of 2mm-3mm and therefore
greatly reduced material costs.

Technical advantage
The quality and technical team at Sarginsons,
headed by Kevin Brierley, operates using the latest
Magma casting simulation V5.2 non-ferrous

programme. This enables the prediction of not only
porosity issues but also anticipated mechanical
properties within a casting design, meaning the
company is moving ever closer to design engineers’

FE analysis programmes.
By using LPM cells, Sarginsons can produce a
distinct casting number, date and operator code
that can be applied to each safety critical

diecasting. If required, the company can also
archive the data to customer requirements.
Sarginsons is also further extending its
technological advantage after being selected as low

pressure diecasting Industrial Partner for Brunel
University’s Advanced Material Casting Centre
(AMCC). This move will open up opportunities,
More complex aluminium solutions are being considered as Sarginsons endeavours to exceed customer expectations.
allowing the company to continue spearheading

innovation.
With up to 800kg of molten aluminium held loose cores to create hollow sections within
directly beneath the in-gate to the die, it is easy to components, although sand cores do require
Sarginsons future
see why low pressure diecasting is the optimum further process control of vacuum evacuation for
Sarginsons Managing Director, Anthony Evans process for perfect directional solidification and core resin gases from the die cavity during the die

(shown below) is confident of achieving the consequently, why it holds superior diecasting filling stages.
company’s ambition to create a low pressure properties.
Low pressure casting also allows components to
diecasting centre of excellence, built on the The low pressure process unlike other diecasting be fully heat treated, further enhancing their
cornerstones of research, leadership and best processes, is the only one that takes material from mechanical properties, doubling its tensile and

practice.
the very heart of the melt. None of the material 0.2% proof stress values. The homogenous grain
entering the die cavity has ever broken through structure and superior diecasting properties enable
surface oxides or been in contact with the external automotive chassis castings to be automatically
atmosphere. It is this that creates its special welded to aluminium extrusions, creating full

quiescent cavity fill characteristics.
vehicle sub-frames.
The casting process is usually completed in three
stages, using closed loop plc controls that supply Competitive advantage
negative dewpoint air into the furnace.
One of the main challenges facing the majority of

diecasting organisations is that of energy costs. The
Process stages
low pressure diecasting process constantly delivers
• Raise material to the top of the riser tube at a casting yields up to 96%, which means minimal
fixed velocity of 70mm/sec.
remelt and therefore melt losses. By operating fully
•
Fill the die cavity, maintaining a constant enclosed 36kw thyrister-controlled holding
velocity of a component dependent value.
furnaces, Sarginsons is able to ensure that energy
• Increase the pressure within five seconds of the consumption is minimised, resulting in a
solidification phase to 750 mbar.
sustainable carbon footprint profile, lower CO
2
Following the ejection of each casting, the volume emissions and lower operating costs.
“By establishing a strategic partnership with
of air injected into the furnace is increased to The exceptionally high yield also reduces the post LPM Group and teaming up with UK universities,
compensate for the reduction of mass in the casting finishing process, which lowers costs; and we are beginning to see low pressure casting using
furnace, therefore fully restoring each cavity fill thanks to superior dimensional accuracy, single aluminium silicon, aluminium copper,
hypereutectic and magnesium alloys emerging with
characteristic. The temperature of the die is CNC machining passes can be achieved with
maintained using oil, air or water mist cooling machining stock allowances of less than 1.5mm. potential manufacturing capabilities.
media and climatic conditions are frequently Low pressure diecasting also produces surface “These alloy innovations, coupled with the
analysed. Additional parameters are also monitored finishes of 3μm, meaning that paint applications continual development of aluminium matrix
using 4mA to 20mA data logging and interrogated can be added without additional preparation costs.
composites and alternative overcasting techniques,

using Minitab.
Low pressure diecasting is also exceptionally are allowing Sarginsons to consider more complex
Another distinct advantage of low pressure adept for casting thin wall sections. This is aluminium solutions as we endeavour to exceed
diecasting is the ability to use complex internal
particularly so when using a sand core application,
our customers’ expectations.”

Cast Metal & Diecasting Times January/February 2014