Laser Weld Bead Overlap to Prevent End-Point Indentation

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Solution Overview

Problem

The existing laser welding method prolongs irradiation time at the finishing end, leading to excessive heat input and potential indentation in the weld bead due to reversing the scanning direction, which can cause excessive melting of the base metal.

Innovation Solution

The method involves forming a second bead along a different path that overlaps with the finishing end region of the first bead, allowing molten metal to flow in a reverse direction and perpendicular to the scanning direction to fill any indentation, while restarting laser irradiation from a different position to minimize heat input and prevent indentation development.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the scanning direction is reversed at the finishing end to reduce indentation, then the weld bead shape is improved, but the irradiation time is prolonged causing excessive heat input and potential indentation

Engineering Contradiction:

Improveweld bead shapeVSAvoidirradiation time

Core Design Contradiction:

Manufacturing precisionVSDuration of action of moving object

Solution Approach 1:

The welding process is divided into two separate paths: a first path for primary welding and a second path for finishing. The laser beam performs welding along the first path, then moves to a different starting position for the second path, avoiding prolonged irradiation at the finishing end while still achieving indentation correction through overlapping bead formation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The second path is planned and executed with its starting position determined in advance, positioned to overlap with the finishing end region of the first bead. This preliminary positioning ensures that the laser beam can fill indentations without requiring reversal at the exact finishing point, thus preventing excessive heat accumulation.

Inventive Principle:

Principle #10Preliminary action

2Manufacturing precision

If the laser scanning is reversed at the finishing end, then the indentation is filled, but excessive heat input causes burn-through

Engineering Contradiction:

Improveindentation fillingVSAvoidexcessive heat input

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

Instead of reversing the scanning direction at the finishing end, the invention inverts the approach by starting a second path from a different position that overlaps with the finishing region. The laser beam moves in the opposite direction from conventional finishing, approaching the finishing end region from a new starting point rather than turning back at the same point.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The solution transitions from a one-dimensional reversal along the same path to a two-dimensional approach where the second path starts from a different position. By changing the spatial dimension of the approach (starting from a different location rather than reversing at the end), the laser can fill indentations without concentrating excessive heat at the finishing end.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Manufacturing precision

If the scanning direction is reversed to correct indentation, then the weld quality improves, but the process complexity increases

Engineering Contradiction:

Improveweld qualityVSAvoidprocess complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The welding process is segmented into two distinct paths with clearly defined purposes: the first path for primary welding and the second path for finishing and indentation correction. This segmentation simplifies the control logic compared to continuous reversal, as each path can be independently optimized and controlled without complex real-time direction changes.

Inventive Principle:

Principle #1Segmentation

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

This approach effectively prevents indentation at the finishing end region of the weld bead by controlling heat input and utilizing molten metal flow to fill any indentations, ensuring a smoother weld cross-section and preventing burn-through.

Implementation Method 1

a first irradiation process in which a laser is irradiated along a first path to form a first bead

Methodology Applied

Scientific EffectLaser heating: Laser

Implementation Method 2

Molten metal from laser irradiation has the property of flowing in a reverse direction to the scanning direction and perpendicular directions thereto

Methodology Applied

Scientific EffectMolten metal flow:

Data Source

PatentUS20230373029A1Laser welding joint and laser welding method

Publication Date: 2023.11.23 NHK SPRING CO LTD

AI summary

A laser welding joint S1 includes a first bead 10 formed along a first path R1 and a second bead 20 formed along a second path R2. The second bead 20 is formed such that a side portion 20S of the second bead 20 overlaps with a finishing end region 10A of the first bead 10. A starting point of the second path R2 is a position different to a finishing point of the first path R1.