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Pick-and-place robot cell is cost efficient for small batch sizes

09 July 2020

Sensor manufacturer Lenord + Bauer has used a MELFA RV Series robot from Mitsubishi Electric to optimise its manufacturing production cycle for frequent product changeovers. The robot cell has taken over monotonous manual pick and place tasks at its Gladbeck plant in North West Germany. Crucially the robot operates safely in close proximity to the rest of the workforce.

Simple set-up and operator controls allow the cell to be used cost effectively on a wide variety of batch sizes, releasing operators to perform more interesting and valuable work elsewhere in production. The solution is flexible, efficient and provides integration into the company’s higher-level enterprise systems. This constitutes an ideal platform for future developments such as the planned implementation of a Kanban warehouse.

Founded in 1965, Lenord + Bauer is a manufacturer of precision motion sensors, controllers and integrated drive technology. The company manufactures products such as compact encoders for logging speed and position in highly dynamic systems, including machine tool spindles. The products are modular, designed to be easily tailored for different individual requirements using customised cable assemblies and connectors, this results in a wide variety of batch sizes from single units to large-scale production runs.

The high levels of customisation and the varying sizes of production runs presented a challenge for more traditional forms of automation. Set-up had to be fast and flexible otherwise the automation wouldn’t be worth doing, so engineers from Lenord + Bauer approached Mitsubishi Electric to explore the options open to them.

“We didn’t have a fully prepared set of requirements at that time but Mitsubishi Electric gave us all the support and advice that we needed for our first foray into robotics,” says Ulrich Marl, Head of Business Production at Lenord + Bauer. “Besides a compact design, our main requirements included a high level of precision and flexibility – while complying with safety standards, as well as the ability to integrate with our in-house IT systems.”

Achieving fast programming is key to robot viability

The high variability of batch sizes the company manufactures makes frequent retooling necessary, as a result Lenord + Bauer required precision operation and for re-programming to be carried out as quickly as possible. 

A Mitsubishi Electric RV Series six-axis articulated arm robot with a load capacity of 4kg proved to be an ideal choice. The required pick-and-place tasks are now carried out to a positional accuracy of ± 20 µm. The cell – at 4m2 – is very compact and it can even be moved using a pallet truck if required. This was made possible by using a CR750-D controller – just like all Mitsubishi Electric robot controllers it is extremely compact and can be installed in a 19” rack. 

To provide the complete solution, the robot is equipped with the MELFA SafePlus safety system along with a controller and teach box. The teach box was ideal as it enables the complete system, comprising robot and controller to be intuitively programmed by the operator in a matter of minutes. 

Since bulky enclosures can hinder the feeding and removal of parts to and from the cell, the SafePlus function allows it to operate in close proximity to the workforce. Two laser scanners on opposite corners of the square-footprint frame each monitor an area 180° wide. As soon as a person, or object enters this safety zone, a signal is sent to the robot controller in real time to reduce the speed of the robot to a pre-defined setting.

If a person or object then further encroaches into the safety zone, entering the operating space or collision zone of the robot, a further signal stops the robot immediately. The frame of the robot cell is also fitted with a safety light curtain which sends an additional confirmation signal to the SafePlus safety system if an object is detected.

Connectivity for production systems

With future production requirements in mind, Lenord + Bauer was keen to integrate the solution into its higher-level enterprise systems such as ERP and quality assurance. As part of the continuous optimisation of production, a Kanban warehouse is to be implemented for the sub-assemblies required for the manual final installation process, so a futureproof solution was important. 

As soon as sub-assembly stocks drop below defined minimum levels, the warehouse will communicate autonomously with the robot and production will be increased accordingly. Thanks to an extensive coverage of protocols, interfaces and connectors, Mitsubishi Electric robots can be easily integrated into factory control and IT networks without any additional development work.

Future developments are planned to include applications such as the robot taking parts directly from stacking stations and use in other production processes such as soldering and laser marking applications.

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