Method for manufacturing a door frame, welding arrangement and structure of a door frame

An automated door frame manufacturing method, according to which method an opening is made for a door in a tubular windmill tower shell made of metal sheet, and a door frame made of metal is placed in said opening and welded on the tubular windmill tower shell, comprising:

• measuring a shape of an outer circumference of the door frame for the tubular windmill tower shell and a shape of a surface of said tubular windmill tower shell at a location where the opening is to be made in the shell with a 3D measuring sensor connected to a robot to obtain measurement data,
• providing the measurement data to a computer system,
• determining (i) a cutting path in the shell for an opening (A) corresponding to the shape of the outer circumference of the door frame and (ii) a welding path between the door frame and the tubular windmill tower shell using the measurement data in the computer system,
• cutting the opening (A) in the tubular windmill tower shell with a cutting device controlled by the computer system,
• making a bevel in an edge of the opening (A) with the cutting device controlled by the computer system and,
• placing the door frame in the opening (A);
• welding the door frame on the tubular windmill tower shell with a double bevel weld, asymmetric double V butt weld, double J weld, or square butt weld from inside and outside of said shell using the computer system to adjust the welding process along an entire joint formed between the door frame and the tubular windmill tower shell so that the joint can be filled with a constant number of welding layers,
• wherein the welding of the door frame on the tubular windmill tower shell comprises the steps of:
• measuring actual groove geometry along an entire joint formed between the door frame and the opening (A) in the tubular windmill tower shell with the 3D measuring sensor connected to the robot to obtain measurement data,
• providing the measurement data to the computer system,
• calculating a welding path using the computer system,
• welding a sealing run using a welding device connected to the robot and the measuring 3D sensor,
• utilising the measurement data from the 3D measuring sensor for real-time monitoring and control of the welding process,
• recording welding device positions of an actual robot path during welding of the sealing run in a memory of a measuring system using the 3D measuring sensor, and
• welding fill runs using the welding device and welding parameters and recorded welding device positions.