Mobile Machining: A Revolution in Aerospace Production
Have you ever been to an aerospace factory? As a business developer in this industry, I know the numbers and a good deal about the technology behind building an aircraft. Still, seeing an aeroplane production hall for the first time left me dumbfounded. The sheer size of the parts, towering aircraft tail sections, large cantilevered wing surfaces, and huge fuselage parts, moved between gigantic manufacturing lines is awe-inspiring. At times, it even involves a crane picking up a 30 m fuselage part to bring it to the next machine.
How does this play into the ubiquitous effort to digitize industrial production and hook it up to the Industrial Internet of Things? It became very clear to me that aerospace production and the machining of large structures, in general, are facing major disruptions on the path to increased efficiency, higher flexibility, and digital readiness.
Classical aerospace production is rigid and inflexible. There are considerable production downtimes involved for transport and preparation of the various machines and fixtures. Many of these machines are developed for individual components and specific production processes only. Any shift in demand regarding individual aircraft models can result in expensive machinery not being used to capacity while bottlenecks occur for other machine tools.
The production of new aircraft models or increases in production capacity requires long lead times, as new machines have to be purchased and installed.
Why not bring the CNC machine to the workpiece?
Imagine a playground where children stay in one place and the parent’s team up to carry the jungle gym, the swing, and the slide to them. That’s what the state of affairs in aerospace production looks like. Siemens and Fraunhofer Institute for Manufacturing Technology and Advanced Materials (IFAM) in Stade, Germany, have teamed up to change that.
The idea is as simple as letting children explore a playground by themselves. Why not bring the CNC machine to the workpiece instead of laboriously moving around large structures? The idea of mobile machining was born.
Component 1: an AGV as a mobile platform
The greatest challenge for the project team was to achieve the degree of precision required in the aerospace industry. Together with various partners, the team developed an automated guided vehicle (AGV) as a base and stable mobile machining centre.
Because aviation components are often up to 20 meters in length, mobility was important when designing the new robot. The robot performing the machining procedures is mounted on the AGV and determines its precise position using a laser system. At six tons weight the mobile machine is rigid enough to achieve the precise machining results and yet is capable of moving around freely and even rotating around its axis. These machines can actually dance.
Component 2: a 6-axis robot
Robots have proven a high degree of performance when it comes to typical pick & place operations. However, compared to the precision of CNC machines their movements tend to be somewhat coarser. For the mobile machining project, the team, therefore, chose 6-axis robots with special precision drives consisting of servo converters and servo motors, special measuring systems on each axis for relative movements, a second encoder system on the robot joints and specially developed calibration routines.
Component 3: Direct Control
The breakthrough in terms of precision and flexibility, however, comes only with the third component of the solution. Robots usually require customized programming software, which has to be purchased from external suppliers. Personnel has to be specifically trained to program and operate the robots.
The Siemens and Fraunhofer team worked around this situation by looking at the robot like a machine tool. The idea is to directly program robots via a CNC (computerized numerical control), as is the case for machine tools on the shop floor. Now everything can run under one control user interface, which the technical staff knows well from classic CNC machining centres.
For the mobile machining project, a SINUMERIK system is used to control the robot path and a SIMATIC PLC is used to position the AGV. In this setup, the robot can achieve a much higher degree of precision via the path-controlled CNC and still has the capacity of moving around freely in the entire factory hall.
Siemens SINUMERIK RunMyRobot / Direct Control allows for seamless integration of the mobile machining system into the CNC machine tool operating system and the entire production landscape. An experienced CNC user can program the complete robot unit using the well-established G-code. CAM (computer-aided manufacturing) programs can be transferred directly to the robot. There is no need for extensive training and additional personnel.
Mobile machining is based on existing technologies and know-how
Siemens and Fraunhofer IFAM developed mobile machining based on technologies and know-how that already exist in production landscapes. This facilitates simple integration into CAD/CAM, PLM and planning systems or as a digital twin for simulation routines.
In a broader perspective, mobile machining lays the foundation for integrating the industrial production of large structures into the digitalization of the entire value and supply chain, unleashing great potentials for optimization, automation and scalability of operations.
An example: If a supplier of jet engines falls behind with the delivery schedule, a production line can easily come to a costly standstill. A fully integrated mobile machining production network would allow to flexibly fill in the gap, as mobile machines can easily be reequipped, repurposed, and deployed to another location.
Significantly faster machining operations
Visitors to the Hannover Messe in April 2018 could witness the successful operation of the first AGV prototype with a mounted robot. First tests have proven that the mobile machining prototypes developed by the Siemens and Fraunhofer team to date can perform machining operations typical for the aerospace industry with absolute and repeat accuracy.
But the real potential of mobile machining lies in having several robots work on one workpiece simultaneously. With two robots in simultaneous operation production, times are expected to be slashed by at least 30%. And this number can easily be topped when even more robots are deployed to work on one workpiece.
A glimpse into the future: swarms of autonomous robots
The follow-on projects for mobile machining have already been initiated. Where does it take us when several mobile robot units are flexibly deployed? Mobile machining transforms huge factory areas into flexible production networks easily interfaced with the Industrial Internet of Things (IoT) and the full potential of digital data management including the supply chain through IoT platforms like Siemens Mindsphere.
Till we see swarms of autonomous robots in large-scale industrial production like aerospace, there will be many obstacles to overcome. How can the safety of the workforce be ensured? How are collisions reliably avoided? That granted, mobile machining bears great potential for automated machining of large parts in a highly flexible manner. Aside from the aerospace production mobile machining can revolutionize the production of rotor blades, wind turbine systems, structures of rail vehicles, and large assemblies in the shipbuilding domain.
Mobile machining not only opens up new possibilities for optimization and scalability, but it also paves the way for the 4th industrial revolution in the aerospace industry. In the future, the remaining manual production procedures might be replaced by flexible mobile operations with much greater automation potential and full digital readiness unlocking access to a vast new playground for aerospace production including more flexible and rapid processes through the increased use e.g. of machine learning, robotics, and 3-D printing.
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