Laser Cladding of Tubes Using Inversion and Equipotentiality
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Solution Overview
Problem
Existing laser welding devices for coating the inner surface of tubes face challenges such as non-uniform surfaces due to gravity, clogging of powder in vertical positions, and reflection of melted material onto optical components, which reduces efficiency and increases maintenance needs.
Innovation Solution
A laser cladding apparatus with an elongated arm, a focusing lens, a diffuser nozzle, and a reflective surface that allows for rotation and indexing of the tube, along with water cooling and a programmable robotic system to achieve uniform cladding and reduce back-spatter, using a carrier gas to manage powder velocity and a thermal switch for temperature control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a rotating laser head is used for welding in fixed pipes, then localized repairs can be made in heat exchanger tubes, but the surface becomes non-uniform and less smooth due to gravity's influence on the melt pool
Solution Approach 1:
Instead of rotating the laser head in fixed pipes as in conventional systems, this invention rotates the pipe itself while keeping the laser head stationary. The pipe rotation mechanism allows the laser to track along the inner circumference, creating uniform cladding surfaces by eliminating gravity's detrimental effect on melt pool geometry that occurs with stationary laser heads in vertical positions.
Solution Approach 2:
The invention replaces the mechanical rotation of the laser head with rotation of the workpiece (pipe). This substitution allows the laser to maintain a consistent position while the pipe rotates, enabling uniform material deposition around the entire circumference and eliminating the non-uniform surfaces caused by gravity in conventional rotating laser head systems.
2Productivity
If powder is introduced in vertical position without gravity assist, then cladding can proceed, but powder tends to clog and interrupt the cladding process
Solution Approach 1:
The pipe rotation mechanism creates a horizontal delivery path for powder throughout the cladding process. By rotating the pipe, the powder delivery system operates in an equipotential position where gravity does not cause powder to settle or clog, ensuring consistent powder flow and uninterrupted cladding operation throughout the entire circumference of the pipe.
3Duration of action of stationary object
If the laser head and reflecting mirrors are cooled using cooling fluid, then prolonged cladding can be performed, but auxiliary services must be introduced from the laser head end requiring additional complexity
Solution Approach 1:
The invention extracts the cooling function from the laser head assembly and implements it in the stationary base structure. The cooling system is integrated into the fixed mounting structure rather than being attached to the moving or inserted laser head, simplifying the overall system by eliminating the need for complex auxiliary cooling services that must be introduced through the laser head end.
4Productivity
If the tube is rotated at high speeds, then full-length cladding can be achieved, but the laser head and mirrors require extensive cooling and maintenance
Solution Approach 1:
Instead of rotating the laser head at high speeds as in conventional systems, this invention rotates the pipe while keeping the laser head stationary. This inversion allows for full-length cladding capability while the stationary laser head and its optical components require minimal cooling and maintenance, as they are not subjected to the mechanical stresses and heat loads of high-speed rotation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The apparatus ensures efficient and uniform laser cladding with reduced back-spatter and extended component life by maintaining a stable temperature and allowing for easy replacement of parts, achieving desired overlap and thickness of the cladding material on the inner surface of tubes.
Implementation Method 1
Lasers have been utilized as a coating process by melting the coating material with the desired surface to generate a 'melt pool' which subsequently hardens
Implementation Method 2
a reflective surface for reflecting the laser to exit through the outlet
Implementation Method 3
This can be done using a cooling fluid such as air or water
Implementation Method 4
a diffuser nozzle for delivering a cladding powder to an inner surface of the curved surface
Data Source
AI summary
The present invention relates to an apparatus for laser cladding of a curved surface comprising: (a) an elongated arm having first and second ends and defining a chamber through the arm from the first end to the second end; (b) a laser delivery source connected to a focusing lens mounted in a housing within an opening on the first end of the arm for delivering a laser beam through the chamber; (c) a delivery head mounted on the second end of the arm comprised of (i) an enclosure having an inlet for receiving the laser and an outlet for delivering the laser to the curved surface, (ii) a powder nozzle for delivering a cladding powder to an inner surface of the curved surface, and (iii) a reflective surface for reflecting the laser to exit through the outlet; (d) mounting means for rotating the curved surface for the cladding of the curved surface; and (e) indexing means for moving the arm substantially parallel to a longitudinal axis of the curved surface so as to clad the curved surface during the rotation of the curved surface. Typically, the curved surface is part of the inner surface of a tube used in industrial applications.