Cost-effective machining of aircraft materials

Aluminum

Despite the increased use of composites, aluminum continues to play an important role in modern aircraft. Development of new alloys with improved properties is ongoing, with the current trend toward aluminum-lithium (Al-Li) wrought alloys.

Al-Li alloys are lighter than other Al alloys and have a higher elasticity modulus. Pieces made from these materials are often similar to those made from titanium. Both have many pockets – and consequently high swarf volumes – the main difference is aluminum machining is a high-speed cutting (HSC) process. It’s not uncommon to see milling Vc values of >9,850sfm (3,000m/min), but cutting speeds too low form built-up edges and cause faster tool wear. Working with aluminum requires expertise and component knowledge to develop cost-effective, reliable processes – complete solutions matched to the application, with tool and machine optimized for aluminum.

With modern HSC machines equipped with 10hp to 200hp (120kW to 150kW) spindles, Walter M2131/M2331 roughing cutters can generate metal removal rates up to 610in3/min (10L/min). High-speed machining requires high-performance tools that match the machine for the most efficient process. Walter has M2131/M2331 and MB265 for roughing, MB266 for semi-finishing and finishing, and the new HPC Al 35 for one-shot finishing with base heights up to 5xD. Customers who require special versions receive custom-designed tools within 2-to-3 weeks via Walter’s Xpress service.

Titanium

More difficult to machine than aluminum, titanium has high chemical reactivity that fuses chips at the cutting edge during machining. Poor thermal conductivity raises cutting edge temperatures significantly, producing extremely tough and abrasive chips. The minimal modulus of elasticity leads to the workpiece bending easily, further reducing the tool edge life even at low cutting speeds. Using the right coolant influences tool life. Carbide substrates, new coating technologies, and macro- and micro-geometries of the cutting tools can reduce machining times, which can be further optimized with CAD/CAM specialists, making possible high-performance cutting (HPC) and high-dynamic cutting (HDC) for finishing and roughing titanium.

Dynamic milling with the Walter Prototyp HDC Ti38 Z6-10 and innovative new coating can achieve cutting speeds up to 420sfm (128m/min). Multi-tooth solutions with up to 10 teeth allow the feed to be increased up to 50% at low contact widths, increasing metal removal rate up to 50% compared with conventional solutions.

The M3255 solution

Heat management is difficult when working with titanium alloys, but an optimized coolant supply to each cutting edge alleviates this problem, guaranteeing safe chip removal even at high cutting speeds. Tangential and axial insert placement on the milling body ensures the indexable inserts are securely clamped for stability even in low diameter ranges. Each indexable insert has 2 or 4 cutting edges for maximum efficiency. With tangential arrangement, the M3255 tooling system can machine forged components.

A further innovation is CVD coating for the WSM45X indexable insert used for the Walter BLAXX M3255 helical milling cutter. The heat protection coating shield facilitates cutting speeds up to 215sfm (65m/min) and extends the tool edge life up to 130 minutes, making it possible to double the tool life during machining of titanium structural components.

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