Several research institutions and companies have been involved with Thermally Assisted Machining, a solution aimed at making tough metals easier to work with. Brent Balinski spoke to the CSIRO’s Dr Nazmul Alam about TAM.
Titanium’s properties make it a highly useful metal, but manufacturers have long lamented how difficult it can be to work with.
For many of the reasons that it’s so useful – including in aerospace, chemicals, marine, medical and defence – making things out of titanium can be tricky.
For example, its low heat conductivity and its hardness at high temperatures mean it’s ideal for jet engine parts, but also mean that machining it will see the cutting zone get very hot and this heat slow to transfer.
An estimated 50 per cent of the cost of a part made of titanium – an expensive material to begin with – is from machining it. Try and go quicker and step up productivity and tools will get damaged.
At the same time, it’s indispensable for many high-value applications. An A380, for example, contains 77 tons of titanium, with 11 of this in its engine.
A collection of Australians have had a crack at making titanium easier to work with, and a method known as Thermally Assisted Machining is edging slowly towards commercial use.
TAM involves carefully and precisely heating a titanium part before cutting, with the part becoming more pliable (at 500 degrees Celsius, for example, the material’s strength decreases by 60 per cent) and material removal easier. TAM also has uses with other difficult materials such as Inconel and other alloys.
The CSIRO has been involved for several years with TAM, following work done by University of Swinburne through the CAST CRC.
“The CSIRO project is basically taking some of the information that CAST CRC initiated and produced more data and get it to the next stage of making a deployable, laser-assisted machine,” Dr Nazmul Alam, a research scientist/engineer who has been at the CSIRO since 1999, told Manufacturers’ Monthly.
Following its work for the F-35 Joint Strike Fighter through the New Air Combat Capability Program (and also involving Lockheed Martin, Ferra Engineering and RMIT), the research organisation is now on the task through internally-funded research, and is working towards developing a prototype TAM unit. This will include a fibre optic C02 line laser.
“It involves the laser beam in the form of a shape of a line has to move in the direction of the cutting,” explained Dr Alam.
“And it will stay always ahead of the cutting tools.”
This process has, accorded to the CSIRO, increased the speed of rough cuts by five times, and reduced costs by 80 per cent.
At present, what they have is “not a real prototype”, but are partnering with H&H Machine Tools Australia – a rarity as an Australian maker of CNC machining units – to deliver a prototype next year.
The company has exported to destinations including India, the USA and Malaysia. Its customers have included ACNI (of China) and Boeing Aerostructures Australia, for which it has provided a 5-axis gantry machine, capable of handling parts up to 13 metres long and made of composites.
The company’s specialty is gantry-style CNCs, and the prototype will involve a milling head, incorporating a laser and motion system, to function on one of these.
“This prototype that goes in the project can be used to retrofit an existing machine as well,” explained Dr Alam.
He explained that there were two major sets of challenges, which described as of an engineering and research or technical type.
In the first group he puts the motion control and incorporation of a line laser. (Previous attempts at the process had used circular lasers, though these left cold areas near the edges of where the beam would hit. This created extra work and wear issues for tools.)
The other major challenge involved a set of issues around the optimal dispersion of temperature, which can impact the fatigue properties of the finished part. To this he then added issues of the right shaped cutting inserts and engineering around the dry cut used (no coolants are used in the system, only chilled air).
If the Australian-made method of carefully heating titanium pre-cutting can be successfully brought to market, the benefits could be large. According to the CSIRO, the metal aerospace market is worth roughly $50 billion. Any solution that offers big savings and productivity gains in a market that size could be very sought after indeed.
The solution is unique in the world, said Dr Alam, and when it reaches the final stage of the technology readiness levels, it is hoped it will provide a valuable edge to H&H among aerospace and other customers requesting superior, high-speed titanium machining.
“H&H are a local manufacturer, a small company, and I think they have sold many milling machines,” said Dr Alam.
“So they can provide some help in the integration and also in the design of the milling head. They are interested. They see an advantage.”