Trapezoidal screw 12m long in the rocket Ariane 5 assembly
Ariane 5 is a rocket capable of lifting a payload of 6,200 kg in a geo-stationary orbit (GTO). It is 59 m high, has a body diameter of 5.9 m and weighs 777,000 kg (777 Tons). The machining operations of the various rocket stages require the creation of 3 platforms that allow both the lifting and the machining of the stage within the platform itself. Each platform is capable of lifting 50,000 kg (50 Tons), inclusive of its own weight, at a linear speed of 0.5m/min and a stroke of 11 m.
For this application Servomech has supplied MA350 jack type A with 3:32 reduction ratio, acme screw lead pitch 100x16 (Tr 100x16) 12 m long. The screw jacks are fixed on the platforms using a trunnion-mount to allow a single degree of freedom. The screw used is connected to the top mounting structure through a clevis with the axis parallel to the trunnions. The system is suspended with the jacks connected to the moving platform and the screw stationary. A further redundancy is accomplished using a safety nut. Each jack has an actuator feedback to allow synchronous motion using the electric shaft principle. The platform configuration does not allow mechanical connections amongst the jacks thus each jack is individually motorized with a vector drive motor of 7.5 kW.
The 12 m long screws are machined from ground bar by metal removal using a whirling process. This process is performed at Servomech plant using 6-axis CNC equipment produced by a German company.