By Simon Dutton
The machining of aerospace materials poses many challenges – not only to the machine, but also to the tooling and fixturing. Getting the right balance of an efficient process that consistently delivers quality with little or no manual intervention, is key in today’s climate.
The machining of aerospace materials poses many challenges – not only to the machine, but also to the tooling and fixturing. Getting the right balance of an efficient process that consistently delivers quality with little or no manual intervention, is key in today’s climate.
Components designed for use in aerospace applications contain very complex geometries. Each one is specifically developed to deliver the highest efficiency with the lowest weight impact, which in turn requires machines to be able to access features.
The machine selection is a critical building block to achieve a high performing machining process. The combination of design, thermal stability, stiffness, accuracy, dynamics and build quality offered by suppliers such as Hermle, are a fundamental enabler. The integration of both turning and milling onto a single platform enable vastly reduced numbers of operations and reduce the amount of datum and part transfers. This not only decreases the manufacturing time but also improves part quality.
The use of on-machine measurement through touch trigger probes and laser tool measurements allows the machining processes to be developed to remove the requirement for manual intervention. In doing so, a higher quality and efficient process is achieved.
Another important ingredient to ensuring a stable process is the choice of work-holding solution during the machining process. With the ever more complex geometries being designed, the given work-holding solution must also allow access to all features requiring machining in the operation. Accuracy and repeatability are key, with many solutions incorporating hydraulics for the activation of clamping rather than using manual means. As a minimum, all clamps should be applied using measured torque settings and set clamping procedures.
Choosing the correct cutting tools requires careful exploration. Size, grade, geometry, coating and cutting-edge preparation will need to be considered. Cycle time, quality and cost will be dramatically affected by the choice of the part’s material and geometry, coupled with the choice of machining strategy and tool selection.
Many components can only be manufactured using programs created using CAM (Computer Aided Manufacturing) software. There are many things to consider inside the program in order to achieve better results. These include point distribution, tolerance and tool axis control. Further systems are now available to optimise the load on the tool to both reduce cycle time and improve tool life. Due to geometry, these are proving very successful in machining titanium components which present varying stock levels throughout the process.
A post processor – often unique to the machine and controller type – is required to convert the code from the CAM system to the machine. With the right functionality, built-in the programs can utilise more machine functionality to optimise part production.
Data is a key part of any process development. Being able to capture and output information as a process runs, is key to understanding where issues may be occurring. This helps identify where processes can be optimised – not only for dimensional conformance, but also for improved production efficiency.
Process monitoring is a capability often specified by design engineers on critical aerospace parts to ensure the process has been run in accordance with what was validated and tested. This enables components to achieve higher in-service life cycles and ultimately extends the engine’s time on wing.
In summary, hard metal machining can be challenging with many options and parameters to consider and understand. Choosing the right partners is key; done correctly, it is possible to create stable and reliable processes which are truly world class and will give you a competitive advantage.
After 27 years working at Rolls-Royce PLC as an aerospace machining specialist, Simon Dutton moved to Kingsbury and brings a wealth of machining knowledge and experience. If you want to find out more about our solutions for aerospace parts manufacturing, please contact Simon.
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