COROMA is a robotic system development and integration project to automate a variety of manufacturing tasks. Most of these tasks are secondary finishing operations, such as grinding, sanding and deburring, which are typically carried out manually on welded components such as nuclear fuel racks and tube structures.
Ozan Gurdal, research engineer at Nuclear AMRC, says: “Manual finishing can take tens of hours of cycle time, as well as being a health and safety issue. The idea of the COROMA project is to use robots to automate these processes with sensor and software assistance, and to demonstrate the work on full-scale demonstrators provided by the use-case owner companies.”
Nuclear AMRC’s involvement in the project was to develop a smart robotic grinding/deburring solution for welded components. The use-case owner was Equipos Nucleares SA, a nuclear fabricator from Spain.
“We developed an integrated end-effector for the robot with a Micro-Epsilon 2910-100 BL laser profile sensor on one end and a pneumatic spindle on the other – to eliminate the need to use a tool changing system, which is an expensive item,” says Gurdal. “It is not possible to use the part’s design CAD model when it comes to programming robots for weld grinding or conditioning as there is a significant difference [sufficient to affect robot paths] between the design and actual [as-welded] part because distortion and/or warpage is inevitable after welding and so exact weld sizes are unknown. Therefore, the 3D CAD model of the as-welded part is required to program paths accurately.”
The ScanControl 2910-100 BL laser sensor held by the end effector is used to scan the areas of interest on the part, which include welded joints and planar surfaces used for reference. The sensor provides the axial and lateral distance (2D) measurements between the scanned object and sensor frame, which is not sufficient for reconstruction. Therefore, the 2D data obtained from the laser sensor is combined with the position of the robot flange, which is read in real time from the robot controller using a LabVIEW-based central controller. Combining these two, the central controller generates the 3D reconstruction of the as-welded part as a point cloud and converts it into the desired CAD format.
“The 3D CAD model of the as-welded part is then used to generate grinding/deburring paths either offline [using CAM or robot path-programming software] or online using in-house developed path-generation algorithms,” he continues. “Once path generation has been completed, the grinding or deburring operation begins.”
The robot used for this work was a 6-axis Staubli TX200, as Staubli was one of the partners on the project.
ScanControl 2910-100 BL is a compact laser-profile sensor (laser-line scanner) with integrated electronics that makes it suited to robot mounting. The sensor operates using blue (violet) laser technology rather than red, which is especially useful for measuring against shiny metallic structures or difficult-to-measure surfaces. Micro-Epsilon’s sensor projects a wide laser line, from 58 to 143 mm, over the object, with a profile resolution of 1,280 measuring points. The measuring range in the Z axis is from 100 to 290 mm, which gives flexibility for robot positioning.
Featured on the sensor is a Gigabit Ethernet interface for transferring profile data, as well as a multi-purpose connector for RS422, encoder input triggering, Digital In (HTL/TTL), a power supply, and synchronisation. The sensors support Power-over-Ethernet (PoE), which means they can be operated with only one cable, simplifying installation even further. A simple and intuitive configuration interface is provided with all sensors to allow configuration. The sensors have a unique IP address (user changeable), which enables future remote configuration and diagnostics. A Modbus protocol, supported via Ethernet and the RS422 interface, also enables direct connection between the sensor and a PLC.
“There are a variety of APIs/software tools provided by Micro-Epsilon for integration with different software platforms and programming languages, such as LabVIEW and C++, so it was really a plug-and-play set up without much hassle, which saved precious time,” concludes Gurdal. “We’ve also been very happy with the technical support provided by Micro-Epsilon.”