The civil aerospace is currently experiencing unprecedented demand for new aircraft, with both Boeing and Airbus predicting a need for well over 30,000 new passenger and dedicated freighter aircraft in the next twenty years. Peter Dickin shares his thoughts.
The growth in the industry is driven mainly by increased demand from the growing middle classes in Asia but is also supported by the desire in North America and Europe to replace the existing fleet of aircraft with more fuel-efficient models.
At the same time, new methods for the design and manufacture of aircraft components are becoming available. New design techniques enable more efficient designs to be produced, so saving weight and, therefore, contributing to lower operating costs. Equally, new manufacturing methods allow faster, more automated production and so help suppliers to ramp up and meet the increased production rates that are being demanded.
The ‘Bionic Partition’
In an innovative developments, Airbus, a top aircraft manufacturer, has collaborated with 3D design and engineering software provider Autodesk to create the world’s largest 3D printed airplane cabin component.
Dubbed the ‘bionic partition,’ the component was created with custom algorithms that generated a design that mimics cellular structure and bone growth, and then produced using additive manufacturing techniques. This pioneering design and manufacture process renders the structure stronger and more light-weight than would be possible using traditional processes.
The partition is a dividing wall between the seating area and the galley of a plane and holds the jump-seat for the cabin attendants. As with many aircraft components, the partition has incredible design and structural requirements, including specific cut-outs and weight limits, making the generative design approach particularly appropriate.
In air travel, reducing weight means reducing fuel use. Designed in a structurally-strong, but lightweight micro-lattice shape, Airbus’ new ‘bionic partition’ is 45 percent (30 kg) lighter than current designs. When applied to the entire cabin and to the current backlog of A320 planes, Airbus estimates that the new design approach can save up to 465,000 metric tons of C02 emissions per year, the equivalent of taking about 96,000 passenger cars off the road for one year.
The new partition uses Scalmalloy, a second-generation aluminium-magnesium-scandium alloy created by APWorks, an Airbus subsidiary focused on additive manufacturing and advanced materials. Scalmalloy is specifically designed for use in 3D printing and offers outstanding mechanical properties, meaning that it will stretch more before breaking. This is the first time it has been used on a large scale inside an aircraft component.
The ability to harness infinite numbers of CPUs (central processing units) through cloud computing have made possible incredible advances in design and engineering. Generative design capitalises on the cloud to compute very large sets of design alternatives – hundreds to thousands – that meet specific goals and constraints. Generative design can explore new solutions that even experienced designers might not have considered, while improving design quality and performance. Because the designs created are nearly impossible to manufacture using traditional methods, additive manufacturing techniques like 3D printing are critical to generative design’s success.
“Generative design, additive manufacturing and the development of new materials are already transforming the shape of manufacturing and innovative companies like Airbus are showing what is possible,” said Jeff Kowalski, chief technology officer of Autodesk. “This is not just an interesting hypothetical experiment – this is a fully functioning component we can expect to see being deployed in aircraft in the very near future. We’re looking forward to further collaboration with Airbus on new components and designs for current and future aircraft.”
Peter Sander, vice president of emerging technologies and concepts at Airbus, expanded: “At Airbus we are always looking to push the boundaries of new technologies and explore how we can best innovate. The collaboration with Autodesk, APWorks and Concept Laser has proved very successful. Autodesk brings generative design technology and a real understanding of additive manufacturing, which is crucial to turning great concepts into real products. These technologies will ultimately revolutionise the way we design and build aircraft, enabling improvements in fuel efficiency, passenger comfort and a drastic reduction in the environmental footprint of air transport overall.”
The first phase of testing of the partition has been successfully completed. Further testing will be conducted in 2016, including a test flight.
The ‘bionic partition’ project is a joint collaboration between Autodesk, Airbus, APWorks and The Living, an Autodesk studio which specialises in applying generative design and new technologies across a wide range of fields and applications.
Robot Blade Polishing
The need for increased production, coupled with the health and safety problems of repetitive strain injuries, has prompted increased use of robots to replace manual operations in aerospace manufacturing. One example of these developments is a system for the polishing of aeroengine turbine blades by robot, which has been developed by Delcam Professional Services in association with Finland-based JOT Automation. The system uses an ABB robot driven by a combination of Delcam software including the PowerMill Robot programming system and the PowerInspect inspection software.
During the development of the process, simulations were undertaken in PowerMill robot to ensure that the robot could complete the progress of the blades around the cell without any collisions or any singularities resulting in erratic movements.
As well as showing how the use of a robot could replace manual operations, the cell provides an example of Delcam’s adaptive machining technology. As with other adaptive processes, the polishing operation is altered for each blade individually on the basis of inspection data collected at various stages in the process. This is essential to give accurate results as the shape of the individual blades will have been distorted by the heating and cooling cycles experienced in the engine during each flight.
Each blade is transferred into the cell on a conveyor and picked up by the robot. The robot completes an initial pattern of measurements on the blade surface by lifting the blade towards a fixed probe. These measurements are passed into PowerInspect to determine the amount of stock material remaining on the blade. The information is used to produce the polishing paths in PowerMill robot.
For the polishing operation, the blade is moved against a disk within the cell. Once the routine is complete, a further series of probing measurements are taken to check that the required amount of material has been removed and that the blade is within the specified tolerances. If it isn’t, further polishing can be undertaken until the blade conforms to the standard.
A similar sequence is followed to machine the tip of the blade. Probing measurements are made along the tip and any excess material machined away by moving the blade against a milling cutter.
Typically, one or two passes across the grinding wheel and the milling cutter are sufficient to bring the blade into tolerance, although the loop can continue through more cycles until compliance is reached. The polished blade is then returned to the conveyor for removal from the cell, ready to be fitted back into the engine.
Faster, Cheaper Blisk Machining
While generative design, additive manufacturing and robotics might gain more headlines, there are still many developments under way in the more traditional areas of programming strategies and cutting-tool design that can benefit aerospace manufacturers. In one such example, Delcam and tooling supplier Technicut partnered to produce a novel method for blisk machining that delivers remarkable savings in both time and cost.
Blisks machined from a single disc of material are used increasingly for aircraft engines in place of a series of individual blades fixed into a central hub. They offer advantages in weight, efficiency and through-life servicing but are challenging to manufacture because of their highly complex shapes and the hardness of the materials used, usually titanium or nickel alloys.
The new method covers the machining of the blisk from start to finish and combines new tooling concepts from Technicut with advanced machining strategies in Delcam’s PowerMill programming software for the rough, semi-finish and finish machining of integrally-bladed rotors. In one example, based on a typical aerospace design, the cycle time was reduced to 35 hours, less than half the time that would have been needed using conventional methods, while the costs for milling were reduced by 45 percent. The initial billet was 804 mm diameter Ti6-4 titanium, while the completed blisk had 31 blades, each 84mm in length with a root radius of 4mm and scallop height of 10µm.
With the process, the initial rough machining operation cuts between the blades with a series of slotting cuts using Technicut’s new Titan X-Treme Ripper endmill. As well as removing the bulk of the material between the blades, this operation relieves any stresses in the billet introduced during the forging process.
Both the semi-finishing and finishing operations on the individual blades are then undertaken in a series of vertical sections, working from the tip downwards. The lower sections are left in the rough state to maintain the stiffness of the blade in the area being machined and so to minimise push-off of the blade tip by the cutter.
In addition to the specific toolpaths for blisk machining in PowerMill, the key to the new method is the use of barrel cutters from Technicut for both semi-finishing and finishing. The tooling designs incorporate a much larger radius on the cutting surface than the ball-nose cutters that would normally be used and so can achieve the same cusp height with a stepdown up to three or four times as large. This larger stepdown means fewer cutting passes are needed to achieve the target smoothness in the surface, meaning that machining times can be reduced significantly.
Future Of The Supply Chain
While these new technologies might be developed by the major aerospace manufacturers, they will need to be adopted throughout the supply chain in order to meet the current demands for higher productivity and lower costs. The more complex shapes being specified to reduce weight will require the more widespread use of more sophisticated machine tools and of additive manufacturing. Companies wishing to continue to supply the aerospace industries will need to invest in these advanced technologies to preserve their place in the future of aerospace manufacturing.