This robot is designed on a contract with Azarab Industries, Arak, Iran. One of main productions of Azarab Industries are power plant boilers, in which numerous pipes in different size and shapes must be welded with high precision. This robot automates welding of two perpendicularly intersecting pipes in a very limited maneuvering space.
Automatic Pipe Welding Robot is designed for automated welding of nozzles to headers used in power plant boilers. The radial welding of these pipes with different radii necessitates saddle curves tracking with adjustable dimensions. The mechanical subsystems controlled by individual micro-controllers being supervised by a central controller, provide a fully automated solution to this application, despite the geometrical limitations
A saddle curve is formed at the intersection of nozzle to the header. The welding torch needs three degrees of freedom to go through this curve :
· A revolute movement around the nozzle (φ movement).
· A prismatic movement along the nozzle axis ( Z movement).
· In addition, since the nozzles have variable diameters, a third degree of freedom is used to compensate this movement which moves the torch along the nozzle radius (r movement).
These three movements are supported by 3 gear groups. A general view of this mechanism is shown in the figure
Control system of automated welding machine which is equipped to a minimum system of MCS-51 microcontrollers, works as a multiprocessing system using serial communication protocol. In this system, a master controller by use of the other local (slave) controllers manages and controls actuators and welding process to accomplish a fine weld on the pipes. Also, This robot uses the MIG/MAG welding machine BDH550 to synergic control of the welding parameters. Block diagram of the control system of this robot is shown in figure.
