Tough talking: machining titanium

Understanding the scientific properties of materials and their engineering performance is only one half of the equation in driving efficiency and innovation. The other half is in choosing the right machining platform.

A hugely complex task, getting the machining process right entails looking at the properties of the material and determining the correct way to cut it, while maintaining structural integrity and surface finish, at the same time as managing the removal of excess material in the most expedient manner possible.

One sector which has been transformed by the application of advanced materials is aerospace. Significantly lighter than steel or bronze, titanium is often the material of choice due to its strength/weight ratio and the accompanying benefit in fuel consumption. Strategically deployed in combination with carbon composite materials, titanium offers significant performance advantages over aluminium, providing the added safety protection required in areas subject to extreme stresses and higher temperatures.

However, titanium is very abrasive and difficult to cut and requires a robust machine platform that can deliver the necessary performance. The removal of large amounts of this tough material place a heavy demand on the structure of the machine, with an attendant risk of heat build-up and excessive energy transfer.

Specialists in large prismatic machines (LPM) Kingsbury, in collaboration with their principals Burkhardt & Weber and Waldrich Coburg, have engineered solutions specifically designed to cope with working with titanium.

Milling with a difference.
In the case of Waldrich Coburg machines, they incorporate two defining structural differences. First, gear-driven spindles, capable of delivering a high torque of up to 7,000 newton metres, provide the necessary speed and power to achieve the required performance levels.

Second, the machines are characterised by the exceptional use of uniquely designed hydrostatic guideways rather than a linear roller guide system, whereby the hydrostatic principle supports the high torque values and absorbs energy without transferring heat.

Designed for 4- and 5-axis machining, the hydrostatic design of these machines enables a high removal rate while reducing vibration. By eliminating the vibration, cutter wear is significantly reduced, with a cutter tip life expectancy of 200 minutes not unusual, compared to an industry average of 20-30 minutes.

The benefits of the new LPM machines are two-fold:
Increased machining stability prevents the stress which can otherwise lead to micro-cracks and surface compression during the milling process. Invisible to the naked eye, such weaknesses can over time lead to more severe cracks and even component failure, a serious concern within the aerospace sector where safety is paramount.

The new breed of stronger faster machines not only produces a higher quality component but it also offers huge lifecycle savings, with an added advantage of a 20-year guarantee on hydrostatic guideways. Cutter tools account for a high proportion of the ongoing cost of production. By reducing replacement costs and achieving greater milling speeds, the overall cost of production is dramatically lowered, giving manufacturers a competitive edge while minimising payback on the initial investment.

Share your experiences in machining titanium with us. Leave a comment or email us your story.

If you want to find out more about our LPM solutions for aerospace parts manufacturing, contact Simon Burrow and the LPM team.