Component life extended at lower cost
Transmission life extended and waste reduced by conversion to Low Pressure Die Casting
An automotive transmission component often failed prematurely in service. The problem was solved by conversion to manufacture by low pressure die casting – and production costs were cut as well.
The challenge: Keeping your taxis on the road
An Australian-made transmission found in most taxis had a reputation for not going the distance. The problem was at the heart of the unit – an aluminium alloy casting known as the ‘clutch cylinder’. The unit would suffer a fatigue failure at about half its rated lifetime – the taxi would be off the road, and the transmission would need a rebuild. Many casting companies had unsuccessfully attempted to make a better version of the part without success – and the transmission was getting a bad reputation.
Our response: Working with industry as part of a new casting development team
The CSIRO worked with Nissan Casting Australia to redesign the part and tooling to make it suited to their Low Pressure Die Casting (LPDC) process. With this approach, the part could be made to solidify in the axially-symmetrical manner seen as the key to improving the part’s service fatigue life. CSIRO used its knowledge of the LPDC process to propose various designs that were then analysed with the MAGMAsoft flow and solidification simulation program. With the predictions looking good, the investment was made in the new tooling and ancillary equipment. CSIRO then worked as part of the in–plant team during the commissioning phase, collecting data and reconciling it with the simulation model – all with the aim of tuning the process to get the best result.
The results: A new casting process, a fundamental fix
The results for the LPDC version of the clutch cylinder casting were excellent. Not only did the finished components meet the required fatigue life for the first time, but the wastage due to production of reject parts was much reduced. Another benefit was the very high as-cast yield. This means that much less metal needs to be poured to produce the component, with the result that less energy is consumed. With an annual production in excess of 200,000 parts, the conversion to LPDC made a substantial positive benefit to the triple-bottom-line: for both the caster and the transmission maker.
Table: Comparison of clutch cylinder performance from two different casting processes
|Process||Reject rate(%)||Individual part weight (kg)||As-cast weight (kg)||As-cast yield (%)||Typical fatigue life (cycles)|
|Gravity Die Casting||20||2.025||4.132||49||< 600,000|
|Low Pressure Die Casting||3||1.803||1.898||95||> 1,000,000|
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