The saying ‘good things come to those who wait’ no longer means extended delivery times for Walter GB’s aerospace customers who require special-purpose tool designs to tackle the upsurge in titanium machining, as well as the machining of aluminium workpieces.
Walter’s Xpress service now offers customer-specific solid carbide tooling within a maximum of three weeks.
The increasing use of titanium especially for structural components – such as doors, and door frame surrounds, landing gear supports, undercarriage struts and landing flap tracks – is placing further machining demands on the aerospace industry, says tooling expert Walter GB:
[] The material is more difficult to machine;
[] Its high chemical reactivity leads to chips/swarf being fused at the cutting edge during machining; and
[] Its poor thermal conductivity allows temperatures at the cutting edge to be significantly higher – which means the chips/swarf are often extremely tough and abrasive.
Together with material solidification in the machining zone, this all combines to reduce tool life, especially at low cutting speeds.
But Walter’s ongoing tool development work is providing answers to all these problems and in some cases extending tool life by more than 100 per cent.
For example, the Prototyp Ti38 Z6-10 solid carbide milling cutter with newly-developed substrate and PVD coating can operate at cutting speeds of up to 140 m/min. Multi-tooth solutions with up to ten teeth allow the feed to be increased by up to 50 per cent.
The result is an increase in metal removal rates of up to 50 per cent compared to conventional solutions.
In one case, tool life on a titanium window frame having a tensile strength of 1250 N/mm² has been raised by 154 per cent (from 175 minutes to 444 minutes) when semi-finishing and finishing using a Prototyp Ti40.
Using a Prototyp HDC Ti38 L for finishing the outer contour saw tool life extended by 116 per cent. In addition, cutting speed increased by 25 per cent and machining volume rose by 23 per cent.
Also, the use of Walter’s CVD coating technology for its WSM45X indexable insert cutting tool material – which, for instance, is used in the Walter Blaxx M3255 porcupine milling cutter – means cutting speeds can reach 65 m/min and tool life can be extended to up to 130 minutes in the machining of titanium structural components.
These are typically machined using a combination of full slotting and climb milling at a cutting speed of 45 m/min and a feed of 0.12 mm. A further option is to increase the cutting speed to 65 m/min with a constant tool life of around 60 minutes.
Finish milling can also be carried out with PCD (polycrystalline diamond) cutting edges, which are among the hardest materials known.
However, appropriate coolant strategies must accompany the use of such tools, to keep the machining temperature at the cutting edge under 600 °C, adds Walter GB. The cooling medium must be applied as directly as possible into the working zone, which is facilitated by special coolant-through holes in the tools. The application of coolant at 70 bar and cryogenic cooling are also especially relevant here.
Customers of the Xpress tool service can use the my.Walter software to design the tool online. This is followed by an email quote for the purpose-made tool along with a 2-D drawing and 3-D model within an hour!
