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Article
Publication date: 1 August 2005

Eduardo J. Lima, Guilherme C. Fortunato Torres, Ivanilza Felizardo, Frederico A. Ramalho Filho and Alexandre Q. Bracarense

This work demonstrates the development of a robot, which was designed for the orbital welding of pipes.

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Abstract

Purpose

This work demonstrates the development of a robot, which was designed for the orbital welding of pipes.

Design/methodology/approach

The robot consists of a small car pressed against the pipe by means of chains, which are used by the robot to move around it. To provide all necessary torch movements, the robot must have four degrees of freedom: torch travel speed, stick‐out, torch angle and lateral motion. Thus, using a look‐up table‐which was specially designed to this application‐it is possible to follow the optimal parameters (voltage, current, welding speed, torch angle and stick‐out) for each welding position (flat, vertical and overhead).

Findings

The robotization of the orbital welding process brings enhancement in the final product quality, considerable increase of repeatability, reduction of rework and reduction of the weld execution time. At the very least, the robot is capable to reproduce the weld bead of the best human welder, through the use of the same paramenters contained in a table.

Practical implications

The use of this robot in welding with GMAW proved to be extremely viable. It was shown that the bead shape did not suffer great variations from one welding postion to another, thanks to the use of a gradual change of parameters.

Originality/value

Although, by RIA definition the devices for the orbital welding shown in literature up to now are not robots, the developed device can be called a robot due to its capability of being completely programmable and automatically carrying through all welding activities.

Details

Industrial Robot: An International Journal, vol. 32 no. 4
Type: Research Article
ISSN: 0143-991X

Keywords

Article
Publication date: 9 January 2009

Eduardo José Lima and Alexandre Queiroz Bracarense

Shielded metal arc welding (SMAW) is a typical manual process with many important but dangerous applications for the welder. The purpose of this paper is to present a methodology…

Abstract

Purpose

Shielded metal arc welding (SMAW) is a typical manual process with many important but dangerous applications for the welder. The purpose of this paper is to present a methodology developed for execution time trajectory generation for robotic SMAW which offers greater safety and improved weld quality and repeatability.

Design/methodology/approach

The study presents a methodology developed for execution time trajectory generation for the robotic SMAW. In this methodology, while the electrode is melted the robot makes the diving movement, keeping the electric arc length constant. The trajectory is generated during execution time as a function of melting rate and independent of the welding speed, given by the welding parameters. The proposed methodology uses a variable tool center point (TCP) model where the covered electrode is considered a prismatic joint, whose displacement is determined by the melting rate.

Findings

The proposed methodology was implemented in a KUKA robot. The electrode melting rate was determined by measuring the arc voltage and the electrode holder trajectory was determined during the weld, keeping the arc length and the welding speed constant. All the obtained weld beads have the same aspect, showing the process repeatability.

Research limitations/implications

Owing to its low productivity, robotic SMAW is only suitable to certain applications.

Practical implications

With this methodology, the TCP will always be located at the tip of the electrode (melting front), allowing one to program the welding speed independently of the electrode diving speed. The diving movement is automatically performed by the robot during the welding.

Originality/value

Robotic SMAW allows dangerous applications such as underwater welding and hot tapping of pipes without human intervention during the weld.

Details

Industrial Robot: An International Journal, vol. 36 no. 1
Type: Research Article
ISSN: 0143-991X

Keywords

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