When machining aluminium billets down to around 5% of the original mass, there is a significant amount of swarf. Apply the same scenario to Airbus wing spars then the amount of swarf is truly significant! One LCM (large component manufacture) machine that has a 4m x 44m long bed is designed to hold up to 18 of the ‘smaller’ work pieces but is also used to produce wing spars with a finished length of 10m. Some components start as 3.2t aluminium billets and come of the machine as 250kg components.
With this amount of reduction, this 3-spindle machine built by Henri Liné of Canada demands an effective means of removing the enormous volume of swarf produced.
Options considered included a vacuum process and a combination vacuum/blower technique. Both proved to be highly expensive whilst also presenting difficult engineering challenges with regard to making them operate efficiently, particularly relating to achieving an effective vacuum seal.
The solution, in engineering terms, turned out to be much simpler: banks of Airknives powered by a single blower supplied by Air Control Industries (ACI).
Mounted in the throat of the moving gantry that houses the 3 machining heads are 30 Airknives ranging in length from 150 to 1520mm. These ACI Airknives blow the machining debris towards the edges of the work bed into collecting gullies from where it is automatically transported into purpose-designed collection vehicles for transporting away for reprocessing.
Supplying air to these Airknives is single inverter-controlled 110kW radial blower which is housed in an acoustic cabinet, also supplied by ACI as part of the swarf removing package. Total capacity of the radial blower is 4000 CFM.
An inverter controlled blower is required to enable air delivery to be reduced to a minimum without total shut off to both provide a stable state appropriate for precision laser measuring of aluminium work pieces and to avoid stop/start loading of the blower and electrical system.
“To achieve efficient and accurate machining, a lot of fine adjustment was required during set up”, commented Peter Jarvis, Project Manger, Airbus UK. “ACI has been flexible and accommodating to help us accomplish our operating objectives with regard to finding the correct air delivery patterns, volumes and velocities – all to good effect,” he added.