Compact robot offers longer reach and faster cycles

Paul Boughton

Mitsubishi Electric is launching the compact Melfa RV-2SDB multi-axis articulated robot that has a maximum 3kg payload and offers cycle times as short as 0.6s. On show for the first time in Europe at Automatica 2010, the new robot is claimed to offer a significant productivity boost in assembly and production cells in a wide range of industries, with faster motion and innovative design features that improve cycle times, and a construction that gives greater freedom of movement over a larger motion space. Described as simple to program and easy to integrate, the Melfa RV-2SDB meets production needs and can be readily redeployed as requirements change.
Although the robot arm is more compact than previous generations, this is not at the detriment of reach. Indeed, the maximum reach has been extended to 504mm, and the length and shape of the arm have been optimised for maximum flexibility. An innovative flap arm construction reduces the minimum work area radius to just 139.5mm. In addition, a reduced protrusion of the elbow joint lessens interference in the rear space. All of this ensures that the maximum use can be made of the working space around the robot, and enables a more compact production area layout to be achieved.
The design of the robot enables further optimisation of the working space through a shoulder design that Mitsubishi claims is unique. The motion space of the shoulder is extended in the minus side so that it can be rotated into the space in the backward direction. This delivers a larger working area without the need to change the orientation of the robot, thereby eliminating wasted motion and further shortening cycle times. A further design feature is the wrist section, which has been made less bulky than traditional designs so that the arm can reach easily into narrow openings. This increases the flexibility of the robot for a wide range of applications.
In addition, the swing area extends to 240 degrees both left and right, enabling best use to be made of available space on the production line. With a total of 480 degrees of motion space available, the shortest motion path for any task can always be used, which helps to decrease overall cycle time.
Cycle times are also shortened by the increased speed of the robot. Maximum combined speed is 4400mm/s, but axes J4, J5 and J6 in particular have been given a significant speed boost – some 10 per cent faster than Mitsubishi Electric's generation RB-3SDB. This has been based on customer feedback and application analysis that highlighted the way many tasks require the robot to change its posture from one step to another. By enabling the robot to change its posture more quickly – with axes J4, J5 and J6 being key here – cycle times can be significantly reduced. Mitsubishi Electric has also focused on significantly raising the speed of the wrist section - again, reducing cycle times.
With the rigid design of the arm and advanced servo control, the RV-2SDB achieves a high accuracy in straight-ahead motion, with positioning repeatability to +/-0.02mm.
For more sophisticated set-up and control, Mitsubishi Electric provides a rich selection of software programs that guide users through their start-up phases. RT-Toolbox2 provides varied features essential for start-up, such as program editing, debugging and cycle time planning. The Melfa-Vision software makes it simple to employ a vision system on the robot, such as that supplied by the e-F@ctory Alliance Partner, Cognex. And Melfa-Works is a 3D robot and application simulator that provides powerful support for system design and preliminary study.
The wide variety of robot interfaces offered ensures a high degree of installation flexibility, as well as scalability for evolving applications. The robot comes as standard with an additional axis control interface, Ethernet communications interface and encoder interface for conveyor belt following, making it easy to build a complete manufacturing system around the robot. Data input/output to and from the robot can be controlled directly from a Mitsubishi Electric GOT series operator interface without any additional programming. Sample GOT graphics are provided as standard to highlight the robot's operational status in a clear, user-friendly manner, including current values, error indication and maintenance forecasts. A window containing the user manual is also included.
With the Melfa RV-2SDB being mountable in floorstanding, ceiling- or wall-mounted configurations, its versatility to suit different application requirements is assured.
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