Search results

This paper presents the design and validation of a universal 6D seam tracking system that reduces the need of accurate robot trajectory programming and geometrical databases in robotic laser scanning. The 6D seam tracking system was developed in the flexible unified simulation environment, integrating software prototyping with mechanical virtual prototyping, based on physical experiments. The validation experiments showed that this system was both robust and reliable and should be able to manage a radius of curvature less than 200 mm. In the pre‐scanning mode, a radius of curvature down to 2 mm was managed for pipe intersections at 3 scans/mm, using a laser scanner with an accuracy of 0.015 mm.

The development of robotized welding is truly impressive and is today one of the major application areas for industrial robots. The first industrial robots were introduced in the early 1960s for material transfer and machine tending. Not long after that, robots were used for spot welding and in the early 1970s for arc welding as well. During the years, significant developments have taken place both concerning the robot equipment and the welding equipment to meet the different challenges within the application area. This paper describes the development and progress of robotization in welding over the years and also some projections and trends for the near future.

Seeks to present a methodology for working with bottle‐neck reduction by using a combination of automatic data collection and discrete‐event simulation (DES) for a manufacturing system.

In the DES model, the bottle‐neck was identified by studying the simulation runs based on the collected automatic data from the different machines in the manufacturing system.

A case study showed an improvement of the availability in one machine from 58.5 to 60.2 percent. This single alteration with a minimum of investment resulted in a 3 percent increase of the overall output in the manufacturing system consisting of 11 numerically controlled machines and six other stations. A new simulation run was performed one year after the first study in order to see how the improvement work has progressed with the suggested method. The method resulted in an increase of 6 percent in overall output.

It could be assumed that machines in future manufacturing systems will provide automatic data. The data can then be used for DES models when identifying bottle‐necks in a manufacturing system.

Friction stir welding (FSW) is a novel method for joining materials without using consumables and without melting the materials. The purpose of this paper is to present the state of the art in robotic FSW and outline important steps for its implementation in industry and specifically the automotive industry.

This study focuses on the robot deflections during FSW, by relating process forces to the deviations from the programmed robot path and to the strength of the obtained joint. A robot adapted for the FSW process has been used in the experimental study. Two sensor‐based methods are implemented to determine path deviations during test runs and the resulting welds were examined with respect to tensile strength and path deviation.

It can be concluded that deflections must be compensated for in high strengths alloys. Several strategies can be applied including online sensing or compensation of the deflection in the robot program. The welding process was proven to be insensitive for small deviations and the presented path compensation methods are sufficient to obtain a strong and defect‐free welding joint.

This paper demonstrates the effect of FSW process forces on the robot, which is not found in literature. This is expected to contribute to the use of robots for FSW. The experiments were performed in a demonstrator facility which clearly showed the possibility of applying robotic FSW as a flexible industrial manufacturing process.

Aims to present general concepts and framework for increasing the flexibility in robotic arc welding with respect to use of sensors and small series production.

Presents a conceptual model with a framework that integrates existing tools and needed developments and research to increase the usefulness of sensors in robotic arc welding. The conceptual model is based on research within the field which covers supporting tools like robot simulation, sensor modelling and handling and optimization issues with respect to the robot task execution. A descriptive structure and concept is outlined to include welding procedure specifications (WPS) as a key module to provide an integrated and holistic control model of the robotic.

Finds that the outlined conceptual model and architecture supports an increased flexibility of sensor controlled robots for arc welding applications. The arguments are specifically made for small series and one‐off production.

The paper is limited to arc welding applications and the concept and arguments are made with small series and one‐off production in mind.

Increased use of sensors and robots in small series production.

Introduces a holistic approach for task level control of a robot which introduces a structured way for integrated and coordinated control of the arc welding task. The objective is to execute the welding task with maintained robustness with respect to predefined specifications (quality, productivity).

Presents an approach to improved performance and flexibility in industrial robotics by means of sensor integration and feedback control in task‐level programming and task execution. Also presents feasibility studies in support of the ideas. Discusses some solutions to the problem using six degrees of freedom force control together with the ABB S4CPlus system as an illustrative example. Consider various problems in the design of an open sensor interface for industrial robotics and discusses possible solutions. Finally, presents experimental results from industrial force controlled grinding.

This paper aims to present a deflection model to improve positional accuracy of industrial robots. Earlier studies have demonstrated the lack of accuracy of heavy-duty robots when exposed to high external forces. One application where the robot is pushed to its limits in terms of forces is friction stir welding (FSW). This process requires the robot to deliver forces of several kilonewtons causing deflections in the robot joints. Especially for robots with serial kinematics, these deflections will result in significant tool deviations, leading to inferior weld quality.

This paper presents a kinematic deflection model, assuming a rigid link and flexible joint serial kinematics robot. As robotic FSW is a process which involves high external loads and a constant welding speed of usually below 50 mm/s, many of the dynamic effects are negligible. The model uses force feedback from a force sensor, embedded on the robot, and predicts the tool deviation, based on the measured external forces. The deviation is fed back to the robot controller and used for online path compensation.

The model is verified by subjecting an FSW tool to an external load and moving it along a path, with and without deviation compensation. The measured tool deviation with compensation was within the allowable tolerance for FSW.

The model can be applied to other robots with a force sensor.

The presented deflection model is based on force feedback and can predict and compensate tool deviations online.

Focuses on the integrated use of simulation tools, particularly discrete‐event simulation, in the design and development of manufacturing systems in Japanese industry. The results are based on questionnaires and visits to seven large Japanese manufacturers and show that most of the visited companies do not use simulation to any large extent, particularly not discrete‐event simulation. Some of the reasons for this are general, while others are specific for Japan. However, the use of simulation is believed to increase in Japanese industry. Furthermore, argues that there is a large potential for increased use of advanced simulation techniques in Japanese manufacturing companies, mainly for two reasons. This would result in improved communication, reduced time‐to‐market and higher flexibility in volume and product‐mix.

Discrete‐event simulation (DES) and disturbance reduction techniques are a combination for improving efficiency in manufacturing systems. The DES modelling allows different tests to be carried out by step‐by‐step alteration. The use of manufacturing improvement techniques should be combined for best results. The changes in disturbances will show us different alternatives in output of the manufacturing system. Two case studies have been drawn up to study the possibilities for disturbance reduction in manufacturing systems by using DES with the proposed method for improved overall manufacturing efficiency. The case studies showed an improvement of output of 14 per cent and 18 per cent, respectively.