Robot-Guided Seam Welding for Stable Electrode Tracking

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Solution Overview

Problem

Existing seam welding apparatuses face challenges in maintaining consistent electrode contact with complex-shaped workpieces, leading to detachment and meandering seams, while also requiring a large footprint and high costs.

Innovation Solution

A seam welding apparatus utilizing an articulated robot with a welding device and distance measuring means, allowing the robot to move independently and adjust its position to maintain consistent contact with the workpiece, regardless of shape, and incorporating a support frame and revolving means to reduce load and enable down-sizing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a complex rotation mechanism is used to prevent electrode detachment by rotating electrodes around a vertical line, then electrode contact stability is improved, but device complexity and footprint increase significantly

Engineering Contradiction:
Improveelectrode contact stabilityVSAvoidapparatus structure
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces the complex mechanical rotation mechanism with a robot system that uses sensors to detect workpiece geometry and dynamically adjusts electrode position. The robot's multi-axis movement capability substitutes for the dedicated rotation mechanism, achieving the same electrode contact stability without the bulky base and body structure.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The robot system performs multiple functions: it positions the electrodes, detects workpiece geometry through sensors, and adjusts to complex shapes. This multi-functional approach replaces the specialized rotation mechanism that only handled electrode orientation, reducing overall device complexity while maintaining reliability.

Inventive Principle:
Principle #6Universality (Multi-functionality)

2Reliability

If a complex rotation mechanism is used to maintain electrode contact on complex-shaped workpieces, then electrode detachment is prevented, but the apparatus footprint becomes large

Engineering Contradiction:
Improveelectrode contact stabilityVSAvoidapparatus footprint
Core Design Contradiction:
ReliabilityVSArea of stationary object

Solution Approach 1:

The patent replaces the bulky mechanical rotation mechanism with a compact robot system. The robot's base requires minimal footprint compared to the large base and body structure needed for the rotation mechanism, while still achieving reliable electrode contact through sensor-guided positioning and multi-axis movement.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If frequent rotation of electrodes around the vertical line is performed to adapt to complex workpiece shapes, then electrode contact is maintained, but the seam becomes meandered

Engineering Contradiction:
Improveelectrode contact stabilityVSAvoidseam straightness
Core Design Contradiction:
ReliabilityVSManufacturing precision

Solution Approach 1:

The patent uses dynamic sensor detection to identify the actual workpiece geometry and calculates the optimal electrode path in real-time. This dynamic adaptation allows the robot to maintain electrode contact without excessive rotation, producing straighter seams by following the detected geometry rather than forcing rotation around a fixed vertical line.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The sensor system provides feedback on workpiece geometry and electrode position, allowing the control system to adjust the electrode path dynamically. This feedback mechanism prevents over-rotation and meandering by continuously optimizing the seam path based on actual contact conditions and detected workpiece shape.

Inventive Principle:
Principle #23Feedback

4Reliability

If a large footprint apparatus with base and body is used to support the rotation mechanism, then electrode stability is improved, but the apparatus cost increases

Engineering Contradiction:
Improveelectrode stabilityVSAvoidapparatus cost
Core Design Contradiction:
ReliabilityVSEase of manufacture

Solution Approach 1:

The robot system serves multiple functions including positioning, sensing, and adaptation to complex geometries, replacing the dedicated rotation mechanism and its supporting infrastructure. This multi-functionality reduces the need for expensive, specialized components while maintaining electrode stability through intelligent control and sensor feedback.

Inventive Principle:
Principle #6Universality (Multi-functionality)

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 solution provides a seam welding apparatus that is unaffected by the shape of the workpiece, reduces the need for complex rotation mechanisms, and allows for a more compact design, ensuring consistent seam quality and reducing the load on the robot, enabling the use of less expensive robotic systems.

Implementation Method 1

a distance measuring means (50) to measure a distance to an edge (61a) of the steel plate (61)

Methodology Applied
Scientific EffectLight reflection: Reflection

Data Source

PatentEP2937167B1Seam welding apparatus, seam welding method, robot control device, and robot control method
Publication Date: 2021.04.14 YASKAWA DENKI KK
  • EP2937167B1 patent drawingFigure 1
  • EP2937167B1 patent drawingFigure 2(a)~2(b)
  • EP2937167B1 patent drawingFigure 3

AI summary

Providing a seam welding apparatus that is uninfluenced by the surface state and entire shape of a workpiece is a problem the present invention. To solve the problem, the seam welding apparatus (10) includes a pair of rotating electrodes (31, 32), an electrode supporting frame (37), a distance measuring means (50), and a controller (43). The electrode supporting frame supports the pair of rotating electrodes (31, 32). The distance measuring means is provided on the electrode supporting frame and measures a distance to an edge (61a) of the steel plate (61). The controller (43) controls the robot (20) to adjust a running direction of the rotating electrodes (31, 32) so that a deviation comes into zero when a distance actually measured by the distance measuring means (50) deviates from a predetermined distance. Thereby, it is accomplished that the seam welding apparatus is downsized as well as uninfluenced by the surface state and/or shape of workpiece (steel plate (61)).