Last September, BAE Systems formally opened a titanium-machining facility at its Samlesbury site in Lancashire that will manufacture detail and assembly components of the aft fuselage, as well as the vertical and horizontal tails for the F-35 Lightning II combat aircraft.
The 9,000m2 machining facility took 10 months to complete and a further eight to become operational. But planning for the facility has been underway since 2006, during which time engineers at BAE considered a number of ways to ensure that it would be able to accommodate the high throughput of titanium military aircraft parts cost effectively.
According to Jon Warburton, BAE’s F-35 programme manager for machinery investment, after conducting a thorough examination of numerous potential manufacturing solutions, the BAE team finally decided to deploy a highly automated Computer Integrated Manufacturing (CIM) system.
The CIM system comprises key hardware and software elements that ensure that the titanium parts for the aircraft can be manufactured on a just-in-time basis. To do so, it co-ordinates the orders received into the plant, as well as the movement of raw materials and tooling, and optimises the use of the machine tools.
Cutters had to be continuously replaced due to the demanding nature of titanium manufacturing
A key element of the CIM strategy was the deployment of two Flexible Manufacturing Systems (FMS) that can accommodate the manufacture of different parts at different volumes. After an order for a part has been received, the data relating to it is passed to the FMS systems, which schedule the manufacture of a part in the most expedient way by examining the current workload across each of eight machine tools.
These eight Starrag Heckert STC1250 horizontal five-axis machine tools in each of the two FMS systems are complemented by two bespoke twin-spindle machine tools that BAE has developed with Starrag Heckert for the manufacture of the F35’s titanium longerons.
In the manufacturing process, the material to be machined for each of the parts is manually loaded onto a fixture located on a tombstone, which is delivered to the machine tool via a central stacker crane. If one of the eight machine tools is free to accept the material, the FMS robotically transfers it. If not, it is loaded into a stacking system to be delivered to the next available machine.
Each FMS also has the capability to store up to 1,000 cutting tools in a racking system ready to be loaded into the machine tools. A series of twin robot systems deliver the stored cutting tools into each machine, as well as replenishing any worn tools, which are transferred to a centralised cutter preset area for refurbishment or disposal.
Aside from the commissioning and installation of the machine tools themselves, the integration of the FMS with a dedicated Tool Management System (TMS) was key to the efficiency of the facility.
BAE’s head of machining operations F-35, Simon Bee explained that the decision to deploy a TMS was made because of the quantity of cutters that have to be continuously upgraded or replaced on the five-axis machine tools due to the demanding nature of the titanium manufacturing process. Hence, the BAE team decided to route all the requirements for building up the cutting tools through the TMS and to locate the assembly of the cutting tools into a centralised area.
’Traditional methods of making cutting-tool assemblies involve operators working at a number of assembly stations around a machine shop. We realised that performing all operations in one centralised area would reduce tool preload times while eliminating downtime,’ said Bee. At the centralised location, data from the FMS system is fed through the TMS to an operator, indicating which set of cutting tools is required by a specific order. With that information to hand, the operator collects the chucks, collets and cutting tools that are required before assembling them. Data specific to the functionality of the cutting tool is then written to a Baluff chip located on the finished assembly.
Under control of the FMS, a robot then takes the assembly to the racking system where the data is read from it before it is positioned in one of the thousand specific locations, ready to be collected when required by the FMS system.
Once a machine receives data regarding the next part to be machined, it performs a number of checks to ensure that the relevant cutting tools are available. If they are, the material is delivered to the machine. If not, the machine tool sends a message to the central tools store on the FMS, which determines if the relevant cutting tool has been assembled within its racking system. If it is, then the tool is robotically delivered to the machine tool before cutting can commence.
If the tool is not assembled, however, the system messages an operator to download the information from the TDM to assemble the tool before delivering it onto the FMS. Robots then convey the tooling to the relevant machine and the component is cut, after which an operator unloads the finished part.
The automated CNC machine tools are connected by a material-handling system. At the end of the operation, the parts are routed by the handling system to a secondary operation area where operations such as deburring take place. Once complete, the parts are transferred to a quality-control station where a Co-Ordinate Measurement Machine checks the parts’ tolerances.
“We realised that performing all operations in one area would reduce tool preload times and cut downtime”
SIMON BEE, BAE SYSTEMS
Warburton said the only capability missing from the entire manufacturing system is a means to further treat the titanium parts once manufactured. If such treatment is required, the parts must be transferred to another facility on the same site, where a number of secondary operations, such as adding additional bores, bushes or bearings, can be carried out.
’If the parts do not require additional secondary operations, they are transferred into an assembly facility where they can be delivered to the production line and operators can start the process of building the aft fuselage, and vertical and horizontal tail of the fighter,’ said Warburton.
Bee said the biggest challenge faced by the team in the development of the facility was to ensure that the FMS, the TDM and the five-axis machine tools communicated effectively with both one another and with BAE’s manufacturing system.
While Bee admitted that the use of application programming interfaces between each of the software systems had helped the system integrators, considerable work was required to ensure that the communications interfaces would be robust enough to account for all of the possible scenarios that might occur in the manufacturing environment.
Having ironed out the bugs, however, Bee and Warburton are confident that the capability of the plant will meet the demands of the F-35 Lightning II programme, which will potentially see aircraft produced at a rate of one per day.