Welding complex, consisting of 2 mirror positioned robotic cells, for welding the frame parts of excavator

"Kvadrat SG" LLC. together with STC "ROCAD“ CJSC and "Kaskad“ LLC. have implemented the project of welding robotic complex for the Customer - manufacturer of a heavy construction machinery. The system is designed for welding "motor support brackets“ ( frame element of a crawler-mounted excavator ).

As a result, the quality of welding is significantly higher than with manual welding, and fully meets the quality standards of the Customer. The system is convenient to operate and meets the requirements of ergonomics and safety (4 Safety Group). Thus, the „heavy welding“ technique was developed and higher performance was achieved, due to the use of - Fanuc Robot Arc Mate 120iB; two Fanuc double-axis positioning elements and a turntable.

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Brief description of the system:

Robotic welding system is designed for automatic arc welding of the products made of carbon steel with outline dimensions not exceeding 650 × 650 × 770 (length × width × height relative to working surface of a faceplate of the positioner) and weighing not more than 250 kg.

Pre-assembly of the product with „tack welds“ is carried out manually, on the assembly stand. Next, by means of the telpher, the product is moved over to the faceplate of the double-axis positioning element and is fixed on it with clamps.

The operator leaves the working area of the turntable and presses the light barrier release button (on the operator’s terminal) to activate the security system. In intersection of the rays of light barrier occurs, the turntable shall be stopped immediately.

Working with operator menu, by pressing the buttons on the control panel, the operator selects the desired part number. When standby mode is activated, the turntable swivels and the system is activated.

Before starting the welding cycle, the system runs check of the correctness of the part number input. Welding is carried out in horizontal position, by changing the orientation of the product in the space. To do this, changes in the positions of the robot and of the double-axis positioner are synchronized.

Welding is carried out in inert gas with automatic wire feeding. The arc welding source provides a continued welding at a current of 300 - 350 A.

Before starting the welding, the robot adjusts the program by tactile sensing of the surrounding surfaces.

Upon adjustment of the program, the arc is ignited and the welding process starts. During the welding, the weld seam tracking is carried out automatically in accordance with the TAST (Through Arc Seam Tracking) technology. The essence of this technique consists in adjusting the trajectory of welding by tracking changes in welding current, which, in turn, is a function of changing the distance between the nozzle of the welding gun and the surface of the metal.

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The oscillation setting function is built in the control system of the robot.

As a result of a continued period of welding, the welding torch heats up and deforms, due to the linear expansion of metal. The built-in TorchMateII function is used for correction of the tool coordinate system. The adjustment process takes less than five seconds.

A special device is used to clean and to blow-off the nozzle. This operation is performed at regular intervals, or upon completion of the run+through of the seam.

During the welding process, the operator removes the finished product from the faceplate of the dual-axis positioner, located in the zone of product loading and unloading, then puts a new piece, and activates the standby mode.

When the welding process is completed (and in case the standby mode is activated), the turntable swivels and the welding cycle for the next component starts.

Сomponents of each welding cell:

Welding robot
FANUC ArcMate-120iB
Dual-axis positioner FANUC
Turntable with protective screen
Protective guards
Light safety barrier
Welding unit
Lincoln Power Wave 655/R
Wire feeding unit
Lincoln Power Feed 10R
Nozzle cleaning system TBi BRG 2000

Technical characteristics of the integrated system

Production rate, units/hour
2 motors
Power input N, kW
Quantity of axes
Positioning accuracy, mm
Shutdown time (instantly), sec
Shutdown time (smoothly), sec
Decelerating torque of the turntable, [Nm]
Swing time of the table, sec
Compressed air pressure, атм
Qty of compressed air consumed, kg/cm3
Outline dimensions
Length, mm
Width, mm
Height, mm
Weight, kg

Products employed:

  • Robotized integrated processing systems