We give voice to our TECH TEAM
by Lorenzo Calvi, Tecnical Director and Alessandro Albertazzi R&D
Which was the CHALLENGE: renew the test bench for running of larger geared machines
Which was the STARTING SITUATION: we had a bench for mechanical running in equipped with hydraulic brakes and large discs.
What about the PROBLEMS ENCOUNTERED: high temperature from frictional heat and energy dissipation during the running-in phases, high maintenance times and costs to restore wear on the calipers
Our PURPOSE: to reduce the friction heat and keep the rotation speed high; avoid energy expenditure and optimize running-in times. Extend this type of test to more machine types
Our SOLUTION: creation of a regenerative break-in bench with electric braking
ADVANTAGES OBTAINED: new bench capable of performing the running-in phases with low braking temperatures. Increase of the input speed; cycle times reduction; 75% energy recovery and energy optimization.
MISSION ACCOMPLISHED !!
Our intention is to move and consider a more sustainable future and therefore to consider actions that involve, even at an industrial level, an increasingly limited impact on CO2 emissions; therefore we have decided to completely change the running-in procedure of our larger gearboxes, starting with the most performing one in terms of loads and powers: gearbox type MB108. -
Until the recent past, the machine was run-in on a special bench equipped with hydraulic brakes with large discs in order to simulate the real resistant torques of the lift systems of destination.
This process, although mechanically valid and reliable in the final results of perfect adaptation of the contact surfaces between worm screw and worm-wheel, had the big limit of developing a strong frictional heat and dissipating a lot of electrical energy during operation. The need to maintain low rotation speeds on the braked axis in order not to further raise the temperatures of the system inevitably lengthened the running-in times, leading to a further waste of energy harmful to the environment.
The ten-year experience achieved on the new generation regenerative benches, already used in the other production lines on smaller gearboxes, has prompted the Alberto Sassi company to revisit also that of the MB108 which can install B3 motors up to size "315" from 110 kW.
In the regenerative bench, braking occurs electrically by means of a second motor-brake which acts as a generator and returns most of the energy used at the input of the first motor mounted on the fast axis to move the system. By optimizing the mechanical part located between the slow axis and the second motor-brake, it is possible to recover 75% of the energy that was lost in the old bench now disused. Thanks to this new construction philosophy, the final temperatures in the braking section are enormously lower than in the past, and thanks to this the speeds applicable at the input to the driving part can be up to 20 times higher: this means a reduction in cycle times and a further energy optimization of the system thanks to better lubrication of the gearbox parts subjected to running in.
The use of two separate inverters for the management of the driving and braking motor also avoids unnecessary current peaks at the start in motion reversals, further reducing the energy used at the input.
The excellent final results obtained in the worm/wormwheel contact confirmed the goodness of the project which will soon be extend