In spite of advancing digitalization, manual workstations are still indispensable because automation is not always profitable with small batch quantities or complex processes. Such workstations are preferred at the Martinshof Werkstatt in Bremen, Germany, a sheltered workshop for a mixed workforce including people with handicaps, as the workstations are ideal for integrating people with physical or cognitive handicaps into the workforce.
“The Poka-Yoke principle has empowered our workers,” said Miriam Berger, in charge of production planning for Martinshof Werkstatt Bremen. “We use automation to avoid mistakes that previously occurred in the production process. Everyone must be able to work smoothly together.”
The Japanese Poka-Yoke principle, which targets the systematic elimination of human errors, coupled with “Guided Operator Solutions” from Mitsubishi Electric Automation Inc., ensures high quality for Martinshof’s customers, which include well-known automakers in the region.
With some 2,200 employees, Werkstatt Bremen is one of the city’s largest employers as well as Germany’s oldest and largest workshop for people with and without handicaps. The workshop is an in-house company of the City of Bremen. It is a recognized workshop that offers work and living opportunities for people with disabilities. The centerpiece is the Martinshof workshops, which manufacture various items in line with market requirements under a framework of professional support. Mitsubishi Electric Corp., headquartered in Tokyo, has operations around the world and offers a range of factory automation products, solutions, training and support services for the industrial and commercial sectors. Its U.S. unit, Mitsubishi Electric Automation Inc., is based in Vernon Hills, Illinois.
Apart from job order and contract production in the fields of metal and woodworking, electrical assembly, filling, and packaging, Werkstatt Bremen employs 500 workers alone in the automotive business sector, and has been supplying local automakers for more than 30 years.
Handke Industrie-Technik, a long-standing supplier of manual workstations to Werkstatt Bremen and a premium solution partner of Mitsubishi Electric, recognized the unique opportunity. Together with Mitsubishi Electric, Handke developed a Poka-Yoke solution for adapted working. The prototype of the error-free workstation convinced the customer, and was installed in the production line. Since May of 2018, a total of four identical zero-error workstations are in use for automotive parts production.
“The main challenge of this project involved the integration of existing technology into the new, error-free workstations,” said Nils Knepper, senior product manager, modular PLC/software at Mitsubishi Electric Germany. “However, thanks to the interfacing features of our Poka-Yoke controller, this was not a problem.”
The MELSEC iQ-F series PLC, installed onsite in a small control cabinet, is the intelligent, individually configurable and expandable heart of the solution that controls picking and assembly sequences. Apart from Mitsubishi Electric’s own components, the system can also handle third-party sensors and actuators. In this case, the solution included the digital torque wrench and a system for industrial image processing. The connection of a barcode printer is being implemented, and thanks to existing conventional interfaces, this can be done easily by the PLC.
“During the design of the user interface, Mitsubishi Electric was highly flexible and took all our requirements into account,” said Berger. “Because many of our employees cannot read very well, we make use of ‘smileys’ and other symbols. In addition to process reliability, the Poka-Yoke workstations have a great advantage: unlike past situations, today practically any employee can now do the job.” The supporting visualization in the solution uses a 10" (254-mm) touchscreen terminal connected in the background to the Poka-Yoke controller.
The hardware and software solution from Handke and Mitsubishi Electric delivers simple scalability, convenient configuration, programming and commissioning as well as comprehensive connection possibilities (including MES and ERP). And as soon as freedom from errors is achieved, and the technical potential is available, Werkstatt Bremen will investigate whether the buffer store can be dispensed with in the future, so that after assembly is completed the parts can be shipped directly to the automaker.
“The need to prevent errors exists everywhere during production and assembly,” said Andreas Kebbel, managing director of Handke Industrie-Technik. “What is most important is the quick and flexible adaptation to the needs of the people working there, and to the requirements of the process.”
That is why Mitsubishi Electric and Handke offer their solution in the form of a modular system with a wide range of components and interfaces for operator guidance. Among others, they include mechanisms to ensure the correct picking of parts, e.g. light barriers; pick-to-light push buttons or, alternatively, pick-to-voice buttons; barcode scanners; and proprietary pick-to-door devices with stroke switches. Moreover, there are monitoring devices such as electric screwdrivers with torque and angle detection, vision systems, and opportunities for robot integration. HMIs (human/machine interfaces) from Mitsubishi Electric’s GOT2000 series are used for displaying the individual process steps, offering direct connectivity to the Poka-Yoke controller and meeting every display requirement, from text through graphical symbols up to animations and augmented reality. Depending on requirements, the latest generation iQ-R or iQ-F PLCs can be used as controllers for the guided manufacturing solutions.
Mitsubishi Electric’s Guided Operator Solutions can be integrated into production systems so that workstations can be networked and resources controlled and monitored in real-time.
For information about Martinshof Werkstatt Bremen, visit www.werkstatt-bremen.de or phone + (04 21) 361-57 88. For information about Mitsubishi Electric Automation Inc., visit us.MitsubishiElectric.com/fa/en or phone 847-478-2100.
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