INVESTIGATION ON CORRECTING PROCESS OF SPHERICAL ROTOR IMBALANCE AT THIN FILM DEPOSITION STAGE

We propose a method of rotor imbalance correction for electrostatic gyroscope. The method is based on redistribution of the material on the beryllium rotor surface during deposition of the titanium nitride coating by cathodic arc physical vapor deposition (Arc-PVD) technique. The deposition process is carried out using one arc source made of BT-1-00 material, located in the horizontal plane of the vacuum chamber of "Bulat-6" installation at nitrogen pressure of 1.2ˑ10^-3 Pa. Size distortion of the rotor  caused by thermal expansion during heating to 300 °C, is not more than one hundredth of a micrometer because of the high dimensional stability of beryllium. The  titanium nitride coating with a thickness about 1 μm is formed during 30 min deposition on the spherical surface of the rotor with a diameter of 10 mm. The imbalance correction is achieved by deposition of the coating with the center of the coating sphere displaced relative to the geometrical center of the rotor in the direction opposite to the direction of the rotor imbalance vector. The required displacement is determined by the rotor kinematics during the deposition process and is provided by the developed device with three degrees of freedom: two rotational ones – constant and cyclic around two different axes of the rotor, and reciprocating displacement of the rotor relative to the source of the sputtered material along the flow axis of this material. The developed device provides fastening of the rotor in four- needle clamp. The calculation of rotor fixation scheme in this clamp is carried out, ensuring the positioning needles outside the area of the raster pattern formed in the rotor equatorial zone during the next laser marking operation. The experimental data showed that it is possible to produce real rotors with the imbalance correction accuracy within two decimal places of a micrometer.

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