During a press event at its Hatfield branch on 15 October, Mitsubishi Electric unveiled the Melfa Assista series of collaborative robots, or “cobots”.

The machines are designed to offer safety and durability combined with ease of use and programming, while maintaining high positional repeatability. Mitsubishi stressed, however, its cobots are not designed to replace its industrial robots, rather they are a “complementary” product aimed at companies looking to begin the transition to a more automated factory.

The RV-5AS-D-S99 Melfa Assista collaborative robot is aimed at production line automation applications: from machine loading, device assembly, kitting and un-kitting of parts to testing and inspection.

The challenge for a cobot is to remain helpful while allowing a high degree of autonomous interaction with a human operator.

Unlike an assistive arm used frequently for manipulation of heavy objects on car assembly lines for example, or an industrial robot that works at high speeds but merely slows down or stops in the presence of a human operative, a cobot has to be interactive.

Mitsubishi’s cobots can be programmed via a PC, touch screen HMI, or by hitting the ‘save’ button and guiding and teaching the arm through the required sequence of movements. EW saw a short demonstration of this process which appeared very simple, and Mitsubishi has claimed the cobot will be suitable for non-expert engineers, as an introductory step to using robots in a factory environment.

The firm says cobots are most suitable for complex or delicate assembly, work holding or pick and place tasks where the operator will have a preferred way of working and will benefit from the robot’s assistance to complete the task or sequence of operations.

Some examples include high-value manufacturing such as jewellery, electronics and life-science applications. Another benefit Mitsubishi suggested during its demonstration was the possibility for human visual inspection without completely halting the robot’s output.

As the cobot works not just alongside but directly with human operators, the design team that developed the RV Series Assista model prioritised safety. Payloads are consequentially relatively low as the arm is force limited for safety.

Mitsubishi noted in fact that some early access customers had ordered cobots for applications they later learned would be more appropriately served by co-operative, or more traditional industrial robots, and urged customers to be cognisant of their proposed use-case before making any commitments. The cobot also has to be very responsive in terms of touch sensitivity and this clearly limits overall speed. Positioning accuracy however is comparable with industrial robots.

The safety features and technical specifications are in accordance with ISO/TS 15066 guidelines on robots and robotic devices — collaborative robots. The six-axis articulated arm can be deployed as a desk-top unit or within the confines of an individual work cell.

Where the cobot stands out from other existing collaborative automation solutions, Mitsubishi claims, is in its positional repeatability. The firm’s cobot can offer positioning accuracies as low as ±0.02 mm. This is comparable with other industrial robots produced by the company.

The Melfa Assista uses some of the design principles of Mitsubishi’s industrial robots in order to maximise durability and reliability. The service life of this new cobot is claimed to be in line with standard Melfa industrial robots, some of which have been running for over 30 years.

One safety feature implemented on the cobot is a six-colour LED ring, mounted around the robot “forearm”, to provide quick visual recognition of the arm’s current status. Each colour identifies a different mode of operation, alarms or faults, which is coded in line with the aforementioned ISO/TS15066 standard.

This feature sits next to the keypad which provides an interface to teach the robot a task to perform, as well as to start and stop the robot or reset errors. In direct control mode the operator manipulates the robot into position by hand and with controlled force.

This position can then be stored and added to the existing motion sequence or attributed to an individual command without the need to open the programming tools. In the pre-production version EW saw however, the keypad was not yet implemented.

It is possible to programme motion sequences via a programming environment, called RT Visual which can run on conventional PC operating systems. As the name suggests, programming is designed to be graphical and intuitive. Operators can select drag-and-drop motion icons to define the intended movements, and simulate operations before having the robot perform them.

The RV-5AS-D-S99 MELFA Assista collaborative robot is due for commercial release in the UK during the first quarter of 2020.