Insecta

Sirona T3 Racer: A Comprehensive Servicing

Model:     T3 Racer
Make:      Sirona
Owner:    Dr. C. S Basak

This is an interesting case of servicing of an old classic - Sirona T3 Racer Air-turbine handpiece. Originally manufactured by Sirona GmbH and belonging to one of our regular client from Keonjhar Dr. C S Basak, this particular Air-turbine handpiece had been under our servicing since 2013 whenever there was a requirement.

Nothing shall last till eternity. Dynamics of extreme parametric conditions for high speed motion lead to certain amount of natural wear and tear of air-turbine cartridge and its components. Spindles are made of high strength stainless steel that are chemically and heat treated further for better wear resistance and are less likely to wear out in comparison of the impeller which is made of aluminum alloys or the micro precision delicate ball bearings. Apart from the ball bearings, most wear and tear of cartridge is limited to the impeller.

This impeller was no different. It wore out with time. The impeller was thoroughly scrutinized. A tiny part of the impeller was torn giving it a mass unbalance that lead to undesirable vibration of higher amplitude and finally to the failure of mounted bearings. Any amount of service and maintenance would not ensure long life of the turbine as long as the unbalance mass remains.

To begin, the instrument was disassembled and the broken components like bearings were removed. All parts went through ultrasonic cleaning and scrubbing to remove the carbon deposits from the cartridge and the casing. The components were hot-air blow-dried.

Precise diagnosis of the unbalance mass determines the amount of unbalance and its angular position. Appropriate amount of mass to the tune of 760 micro-grams was removed to bring the unbalance amount down to the permissible limit. Such mass removal and impeller unbalance correction can be noticed from the tiny circular hole on the radial surface of the impeller as shown in the third Figure. Removal of unbalance mass reduced the rotational vibration to the large extent making the air-turbine stealthier.

Once the impeller/rotor is rectified over a repeated process of testing and fine-tuning and ensured that all kinematic parameters are within the prescribed limits, pair of pre-lubricated ceramic service radial ball bearings for Sirona of Myonic GmbH make has been gently mounted on the spindle. The reassembled cartridge got further inspected and lubricated before final assembling of the handpiece.