Original Date: 04/24/2007
Revision Date: / /
Best Practice : ShipWorks Robotics Laboratory
Although automation has been the norm in the automotive industry for many years, it is not adequate for the U.S. shipbuilding industry. Typical automation requires high volume and high precision, neither of which is characteristic of shipbuilding. The ShipWorks Robotics Laboratory was developed by the Gulf Coast Region Maritime Technology Center to demonstrate to shipbuilders how robotics and process simulation can be incorporated into shipbuilding processes.
The Gulf Coast Region Maritime Technology Center (GCRMTC) at the University of New Orleans, College of Engineering (UNO COE) undertook a research program that greatly assists the shipbuilding industry to incorporate robotics in its processes. The GCRMTC has developed the ShipWorks Robotics Laboratory (SWRL) with a goal to develop methodologies that provide rapid robotic programming, increase the tolerance of the robot to handle shipyard accuracy levels (which may require some type of vision system), provide a baseline for shipyards to estimate return on investment, seek other process applications beyond welding, and establish a training program to support shipyard applications. This research and demonstration project is a joint effort among GCRMTC, ManTech, the Naval Surface Warfare Center - Carderock, and the Navy Joining Center. Industrial collaborators include Northrop Grumman Ship Systems, Atlantic Marine, Bender Shipyards, Bollinger Shipyards, Electric Boat, Jeffboat, NASSCO, and the Northrop Grumman Newport News shipyard.
The GCRMTC-built SWRL (Figure 2-4) has two industrial welding robots with simulation software such as Delmia or vendor-proprietary tools incorporated. The facility provides the capability to model various robots, positioning devices such as gantries, and welding guns. During the planning phase, SWRL allows the designer to investigate various robots and positioners and to consider the range of parts to be welded. Part models can be loaded directly from computer-aided design models. After the welding system has been chosen, SWRL technologies can be used to simulate the specific welding process and prepare the off-line program (OLP) to actually weld a part. The OLP is loaded into the robot, and the welding is then carried out.
One industrial collaborator performed a complete study of the application of robotic welding to its processes and conducted a system study of alternative layouts and work flow. The simulation was provided to company executives, allowing them to see robotics in their facility. Following the simulation review, actual product testing was performed. The shipyard provided material cut with its standard processes, welding tack in the robotic cell; the robotic welding was then carried out by shipyard personnel. The results showed that one robot was adequate to meet the shipyard’s production needs.
Another study considered the application of robotics to the end cuts of structural members. The ends of a structural member must often be cut in a complex shape to fit up with other parts. The system study considered the workflow and throughput to determine the equipment needed to automate the process. Various cutting devices including oxy- gas, plasma, and laser were considered to attach to the robot arm. A simulation of the system allowed the shipbuilders to see how the new system would fit and to compare costs.
A key area where existing technology is not adequate to support robotic welding in shipyards is vision systems for welding. These systems allow the robot to locate the part and confirm its size. During welding the seam track for in- process changes can be modified and torch movement can be slowed to accommodate gaps. Unfortunately, few welding vision systems exist, while those that are available are bulky and designed for straight welds.
The GCRMTC engineers designed, built, and tested a welding vision system designed for shipbuilding with key detection and agility capabilities that include: Detection: Seam position, end of material, bead connection, root gap, molten pool, and bead appearance
Agility: Does not obstruct the torch, works around corners
The system consists of four small lenses mounted around the welding torch. Images are fed to a common screen via fiber optics. The image is captured by a high-performance camera that can accommodate a range of brightness from arc welding to natural light. Image processing is conducted real time to locate the seam and calculate the root gap. The system has been patented, and commercialization discussions are ongoing.
Another key area where current robotic welding technology is not adequate for shipbuilding is in the preparation of OLPs. In the automotive industry, the same weld is carried out thousands of times. As a result, workers will spend many hours developing the best OLP for welding. Shipbuilding, conversely, requires the welding of thousands of parts that are, for the most part, all different. Therefore, the time to program the part should be less than the time to weld the part.
GCRMTC engineers have developed technology based on Delmia UltraArc software, which substantially shortens the time to develop an OLP. The underlying concept is a “path macro” in which frequently recurring seam sequences (e.g., a water-tight clip) are saved and reused on various subassemblies. The macro contains not only the path motion but all the process parameters, which are then combined with air moves to build the complete welding program.
GCRMTC engineers are also working with Sandia National Laboratories to enhance an automated path planning called AutoGen. The tool, originally developed under the National Shipbuilding Research Program, automatically prepares the complete OLP using the three-dimensional product model and relevant weld procedures.
Figure 2-4. ShipWorks Robotics Laboratory
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