Dan Stephenson, sales manager at Pryor Marking Technology, explains how robotic systems help to meet aerospace industry specifications for marking components.
Aerospace industry specifications insist that parts like engine components are permanently marked, to give each one a unique identification. Marking adds no value, however, the process is critical to the smooth running of the aerospace industry. Markings applied to parts during production allow it to be tracked, assembled, replaced, correctly maintained and positioned.
Historically parts have been marked manually and some short-run parts, which are not expensive, can be handled adequately using hand-held marking devices, however, for large, expensive parts – which may require multiple marks to be made, in precise locations – a more modern technique such as robotic control is required.
Aero engine components can be astronomically expensive, with some individual parts worth upwards of £100,000. The last thing needed is them to be rendered worthless by a poorly applied or positioned mark.
Aerospace industry specifications – such as the UID standards laid down by the US Department of Defence, or SAE International’s AS9132 marking standard – insist that parts are permanently marked to give them a unique identity. This is done by applying readable information and a data matrix code (similar to a barcode) onto the surface.
This unique ID is a ‘passport’ for the part that links it to all kinds of information on its manufacture – including details such as where the material came from, and which operator was running the machine when it was made. This allows precise traceability, in the case of part failure, for example.
On top of this, individual manufacturers have their own additional marking specifications, which include details of how the mark should be applied, formatted and positioned, as well as adding critical engineering details, and specific information on how parts are assembled in the engine.
Multi-axis marking
Pryor’s multi-axis robotic marking systems are generally used on round and cylindrical engine components, including disks, rings, blades and blisks. Although the robotic arm can incorporate any type of marking system, the aerospace industry typically uses dot peening to create permanent marks on metal components. Pryor’s system works with parts up to 1.2m in diameter, although larger parts can be handled if required.
When Pryor first introduced robotic control to aero components, it was dealing with relatively small parts. For this reason, it grasped the component, and moved it to a stationary marking head. Now, as it deals with much larger parts the robotic control has shifted to the marking head itself. This improves accuracy and allows multiple marks to be made to very tight tolerances across the surface.
In a typical scenario, a large part is moved into a ‘marking cell’, loaded onto a rotary table and clamped into place. An operator scans the part’s unique ID, which calls up a programme with marking instructions. These are carried out by the robot-mounted marking head. The whole process is controlled by Pryor’s software, which is linked to the supplier’s plant manufacturing system to ensure the correct data is applied.
A large part like a blisk may require 15 or more marks to be made at various points, with position tolerances of 0.1mm. On top of this, a typical aero engine will have hundreds of parts that need to be marked in this way.
A key element is Pryor’s vision system, which helps to validate and verify all marks. It checks that the marked information is correct and that it meets the relevant specification.
However, it can also help to ensure that the original positioning of the mark is correct. While this information will be loaded as part of the marking programme, a mark may have to be made relative to a certain feature of a component. The camera can find this feature and apply an offset to the marking program as a further check to ensure correct mark placement.
Pryor has found that customers often find a business case for purchasing a robotic system by using it to mark a wide range of parts – including smaller ones, that could be done manually. Overall, they have found they can mark parts more efficiently – and ensure better traceability – by using ‘idle time’ on these smaller components.
Aero engines are more complex than ever and as large parts like blisks become more commonplace and engine designs evolve to become more efficient, the need to track and assemble individual components will continue to grow in importance.
Whilst it technically has no value, robotic marking is an essential part of traceability in aerospace, in that it allows each individual component to be marked correctly at the first attempt, making the manufacturing process much more efficient. The cost of marking components incorrectly can be much greater than investing in a reliable system.
At the Paris Airshow, Pryor demonstrated a version of the company’s Aerospace Rotatives Marking Cell. The system used an ABB robot in combination with a rotary table, full marking head and vision system, to mark cylindrical parts.