Text 4 A. Laser Revolutionizes Axle Design

The laser beam welding is used for joining components that need to be joined with high welding speeds, thin and small weld seams and low thermal distortion. The high welding speeds, excellent automatic operation and the possibility to control the quality online during the process make the laser welding an advanced joining method in welding complete car bodies in automobile construction.

1. A design and manufacturing revolution is taking place at an axle design and manufacturing facility in Italy. Just in production for Volvo and Iveco is a remarkable rear axle for heavy duty applications on which all but four of the normal 42 bolts have been replaced by laser welding or one-piece castings. The design is 13kg lighter than its equivalent predecessor, uses only two thirds of the amount of oil -a ?25 saving for OEMs in lubricant costs alone - and has reduced parasitic losses. And there's more to come including a 'smart lubrication' system that will cut splash losses even further.

Fig.4

2. The new axle - called the 17X - results from a ?20 million investment by Arvin Meritorin the Meritor HVS facility at Cameri between Milan and Turin. It has been designed for 44 ton-plus applications using engines delivering up to 560 hp and 2500 Nm of torque. Laser welding was the 'starting point' for the differential case design. Bolts eliminated include: ring gear to differential case (16); diff case to diff case (12); and pinion housing to carrier casting (10). The four remaining bolts are for the differential side gear bearing cover. The joining process is highly automated, at speeds of up to 1.5m/min, and involves autogenous welding where two components of the same metal are joined without the use of a sacrificial filler metal. This results in a very high quality joint with a smooth inside surface.

Fig.5

3. Laser welding has made the gear and differential case a single, exceptionally stiff, one-piece component. As a result, gears stay in mesh better, leading to longer life. It has even allowed designers to change the geometry, reducing the hypoid offset so that there is less sliding contact and, therefore, a higher efficiency. Interior axle surfaces are smooth, without ribbing, minimizing splash losses. This was made possible by the use of novel OptiStruct software that optimizes material distribution in accordance with the position of operational stress levels.

4. The axle also incorporates some interesting design features that bring its compatibility with current and future braking and chassis control strategies. An energy saving solenoid-driven electromechanical differential lock replaces the pneumatic system along with the associated valves and pipework. It can be automated from the ABS and ASR and should be available within one or two years. ( 2100 characters)

Exercise 5. Match the right and the left items. Use the key words in your answers.