High-speed milling of large aluminum structural aeronautical parts
Bulkheads, windshields, wing ribs and other aluminum structural aeronautical parts are made by milling large monolithic blocks, often greater than 1.5 by 3 meters, to obtain light and robust pieces.
The removal time required for these applications are today a critical issue for the production aircraft process, a sector where the two main players, Airbus and Boeing, record production back-logs of several years.
The request for new 5-axis machining centers has therefore been created, which can guarantee high speed combined with high precision, decrease the time and the difficulties required by the heavy pieces handling, facilitate the evacuation of large quantities of chips.
COMI has designed and produced Monnalisa, the innovative horizontal 5-axis high-speed machining center specifically developed to meet these needs.
A key requirement of a machining center for this application is to work with great strength and precision, so the Monnalisa structure is entirely in cast iron, all box-in-box, reinforced at strategic points to achieve maximum rigidity and dynamics with the minimum thermal drift.
Great attention was paid to the axes movement, which can be clearly appreciated by turning around the machine: the double-sided X-carriage has a Gantry configuration with two Twin Drive systems for the backlash recovery by means of electronic preload, the Y axis and the Z axis run on roller skids, while the position of all the axes is detected by pressurized and coded optical lines.
To speed up the removal and to respond to specific operating conditions, Monnalisa can be equipped with a spindle with a torque value of 29 Nm for all aluminum parts or with a torque of 83 Nm that allows milling operations even on titanium.
With the aim of ensuring the maximum efficiency of the heart of each milling machine, COMI has designed its own fork working head with continuous movement, equipped with refrigeration through the tool, air blow for the cone cleaning and rigid tapping.
Another big advantage is provided by the pallet change system that allows to always work in masked time by never stopping the machine: the preparation and replacement of a new piece takes place on the second table, during the milling of the one being machined inside the machine.
Loading, clamping, locking, positioning of the pieces to be machined are also not very heavy thanks to the system designed by COMI engineers: the piece is loaded easily and safely by the operator on one of the two steel tables, then clamped by vauum pumps or by an innovative “invertible” locking system or by traditional mechanical locking devices, positioned vertically thanks to the 90 ° rotation of the tilting table performed by two hydraulically operated mechanical arms.
The full milling of these blocks often involves cutting and removing 90% of the original weight: thanks to a large belt evacuator positioned under the working table, a volume of chips of about 1 m3/hour is continuously evacuated, while a tank under the walkable grill allows collecting the copious lubricant-coolant liquid.
A large capacity tool magazine (from 120 to 240 positions) and the high performance Siemens 840D SL control unit complete the configuration of this machine that does not accept any compromise on quality.
A test of excellence of Italian mechanics able to compete with its world competitors, that visitors to the COMI headquarters in Zingonia (Bergamo) where Monnalisa is installed can appreciate in person!