The present invention relates to a system for automatic TIG welding of centrifugal compressor component and method for the same. More particularly, the invention relates to the development of a system and method for carrying out automatic TIG welding of impellers of varying sizes and varying vane profiles used in centrifugal compressor.
BACKGROUND OF THE INVENTION
The impeller is having two parts i.e., Disc and counter disc. A quality weld between these two parts is essential as the impeller is subjected to high rotational speeds. For this, the impeller is properly positioned, pre-heated and welded as per the Welding Procedure Specifications. This invention is giving a way to design and develop a work-cell for carrying out the welding process automatically for achieving uniform and higher material deposition at controlled heating condition.
The patent search has been carried out on this subject, but the complete information related to this invention is not directly available. The following patents (JP6198443, US4628180, US 4973813, US 20060124603, 7291807, EP1555080A1, 4801781, 4628182 etc….) related to the present invention were checked and found discrete information either related to TIG welding using robot or TIG welding process or

Hot wire TIG welding process. But there is no mention of a work cell, which uses a positioner designed to hold the impeller firmly with a provision for supply of purging gas, a dedicated heating system for pre-heating the work-piece, a seam tracking mechanism to correct the trajectory deviations automatically, a weld pool vision camera to monitor the welding process in-situ and automatic hot wire TIG welding for optimising the deposition efficiency of the welding process as per the welding procedure specification established for achieving higher and uniform deposition. Generally, a semi¬automatic kind of work cells are being used for doing the welding of these kind of jobs, which are dependent on the skill of the workforce and takes longer time. The quality and uniform weld metal deposition is dependent on the skill set and fatigue of the work force.
OBJECTS OF THE INVENTION
Therefore, it is an object of the invention to propose a system for automatic TIG welding of centrifugal compressor component and method for the same, which is capable of carrying out the welding process of impellers automatically and accurately.
Another object of the invention is to propose a system for automatic TIG welding of centrifugal compressor component and method for the same, which is able to improve productivity and quality with higher and uniform material deposition.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Figure 1: Shows schematic of the system consisting of a six axes articulated robot, a rotary table, work piece holder, heating system, hot wire power source, a wire feeding unit, a TIG torch, a seam tracking laser sensor and a weld pool monitoring camera.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
The developed system is consisting of a six axes articulated robot (1), a rotary table (2), work-piece holder (3), heating system (4) with a dedicated controller, TIG torch (5) attached to the flange of the robot and hot wire power source (6). A wire feeding unit (7) is mounted on the robot for continuous feeding of the filler wire into the weld pool. Seam tracking system and weld pool monitoring system are integrated for error free weld operation. A Seam tracking laser sensor (8) and a weld pool monitoring camera (9) are mounted to the robot flange with special fixtures. The compressor component is mounted on the work-piece holder, which is having a provision to send the purge gas during the welding process. The component is pre¬heated to the required temperature using the electrical heating system. The heating system is having temperature measuring sensors, which measure the temperature of the impeller and send the data to its controller. The controller effectively controls the set temperature and maintains the same during the welding process.

Programs are generated for robot path trajectories as per the component weld groove profile for doing the continuous as well as multi layer welding. The welding parameters are controlled directly from the robot program. Hence precise control of weld parameters is possible. Before welding of each weld groove, the robot path is checked using the seam tracking sensor (8). The program logics are generated in such a way that any deviation in the robot path due to improper fixing or machining inaccuracies of the component, the path is corrected automatically. This ensures high quality and defect free welding operation. After the first weld groove of the component is welded, the rotary table (2) indexes to the next groove as per the sequence established to minimise the distortion effect. A hot wire power source (6) is being used to pre-heat the filler wire just before it enters into the weld pool. Therefore the deposition efficiency of the filler wire is improved. The weld pool camera (9) mounted near the TIG torch (5) displays the live weld pool details to the welder on a colour screen, so that the welding process can be monitored in-situ. This will reduce the strain on welder due to hot working conditions and welding bright light.

WE CLAIM
1. A system for automatic TIG welding of centrifugal compressor component comprising;
a six-axes articulated robot (1);
a rotary table (2) for indexing the job to be welded;
a work-piece holder (3) for mounting of the job;
a heating system (4) equipped with temperature measuring sensors for measuring the temperature of the impeller;
a dedicated controller disposed in the heating system for receiving the data sent by temperature measuring sensor and for maintaining the same during the welding process;
a TIG torch (5) configured to the flange of the robot;
a hot wire power source (6) for pre-heating the filler wire;
a wire feeding unit (7) disposed on the robot (1) for continuous feeding of the filler wire into the weld pool;
a seam tracking laser sensor (8);
a weld pool monitoring camera (9);
characterized in that,
the seam tracking laser sensor (8) is disposed on the robot flange with special fixture for checking the robot-path before welding of each weld groove, wherein the

weld pool monitoring camera mounted to the robot flange is disposed near the TIG torch (5) for displaying the live weld pool details to the welder on a colour screen for monitoring the weld process for error free weld operation when the component/impeller is preheated to required temperature through the heating system (4) when the temperature data is sent to the controller by the sensor wherein the controller configured to maintain the temperature throughout the welding process, wherein programs are generated for robot path trajectories as per the component weld groove profile for doing the continuous as well as multi layer welding wherein the rotary index-able, after the first weld groove of the component/impeller is welded, configured to index to the next groove as per the sequence established to minimize the distortion effect.
2. A method of the system as claimed in claim 1 comprising the steps of;
generating a program for robot (1) path trajectories as per component/impeller weld groove profile to perform a continuous as well as multilayer welding;
mounting the component/impeller on the workpiece holder (3);
mounting the weld pool camera on the robot flange near the TIG torch (5) to display the live weld pool details for the welder to monitor the weld;
fixing a seam tracking laser sensor (8) on to a robot flange with special fixture;
mounting a Tig Torch (5) to the flange of the root;

disposing a wire feeding unit (7) on the robot to feed the filler wire continuously into the weld pool;
wherein,
a hot wire power source pre-heats the filler wire just before it enters into the weld pool improving the deposition efficiency of the filler wire, when the component/impeller is pre-heated to the required temperature by means of an electrical heating system (4) when the temperature measuring sensors send the data to the controller which controls and maintains the set temperature throughout the welding process, when robot path is checked by the seam tracking sensor (8) before welding of each weld groove wherein continuous as well as multilayer welding is performed controlling the welding parameter by the robot program.