Transparency and connectivity in robot welding

Picture: The fixtures in the tacking and welding stations are complex; the process is clearly visualized at each station.

System: highly flexible and highly automated 

This system, designed and built by Yaskawa, handles the tacking and welding of central components of the new 1251 series of electric forklifts. Despite the variety of variants, it operates with a high degree of automation: there are seven very different frame variants (three- and four-wheel, lead-acid alternating battery and lithium-ion battery) and fourteen different safety guards.

The system, divided into two modules in which a total of 33 robots weld, tack and handle, is also extremely complex because Linde MH does not build “off-the-shelf” forklifts: manufacturing is generally order-specific. The multitude of possible product configurations combined with high production volumes requires a correspondingly flexible and powerful manufacturing solution.

YPS: “Backbone” of the system control

Those responsible at Linde MH and Yaskawa conceived and planned the Yaskawa Production System – YPS for short – right from the start of planning. The latter assumes the central control of the entire plant with connection to the IT infrastructure for forklift production. The term “control” is rather an understatement: the YPS receives production orders from the MES and ERP and implements them at system level. The system ultimately transmits all information to the higher-level control system, which then transmits the movements of all robot axes, setup and clamping processes, together with the parameters of each individual welding point, to the production automation system at robot and PLC level. Upon completion of the manufacturing process, data including quality and status information is automatically fed back to MES and ERP.

The concept of YPS includes comprehensive visualization that gives the operator a clear overview of the current status at all times. Monitors providing a digital display of the entire production line are installed around the system. This real-time visualization shows the status of each individual cell. Using intuitive colour coding, the operator can see at a glance whether the station is running smoothly in automatic mode, whether maintenance is necessary, or whether there is a fault that needs to be corrected. This means that system operators can react quickly, avoid downtimes and maintain process safety. Visualization is thus a central component of shop floor management, ensuring efficient and safe system operation.

Operator guidance: Poka-yoke principle prevents operating errors

At the manually operated welding stations, the Yaskawa Production System ensures protection according to the poka-yoke principle to prevent operating errors. Sensors monitor correct positioning of the components and pass this information on to the YPS visualization. Christopher Taupp, Project Manager Industrialization Projects at Linde MH: “Monitors are installed at each station to provide employees with comprehensive factory guidance. They display the insertion sequence, correct positioning and current production step. They also visualize feedback from the sensors, ensuring that all processes are transparent and error-free.”

The tasks of the YPS with regard to process quality and its visualization do not end when the workpieces are inserted into the fixtures. The system also specifies the target parameters of the robot-assisted welding process, and records the actual parameters – at each station, for each welding point and weld. Christopher Taupp explains why this is so: “We place extremely high demands on the quality of the welding process. The data is used both for documentation and for the targeted analysis and optimization of the systems when there is a change in relevant parameters. We also visualize this data at each individual welding station.”

Picture: Christopher Taupp, Project Manager Industrialization Projects at Linde MH, at the robot-assisted polishing station.

Inline test cell: each weld is tested and visualized with YPS

The inline test cell in the plant shows that the Yaskawa production system can also take on other tasks. Two fully automated measurement processes take place in the cell. First, the assemblies – as a combination of frame and associated driver protection roof – are comprehensively measured geometrically and all values compared with the target values.

The second method is a weld seam inspection according to DIN EN ISO 5817, including a check of length, location and suture geometry, in the course of which irregularities such as pores or end craters are detected. All collected data is clearly assigned to the respective component ID and documented. The data is simultaneously displayed on two monitors – one per measuring system. The component is shown as a photo with the NiO zones marked. These must be checked and assessed manually or visually.

However, the options offered by YPS go much further. In the event of a malfunction, service personnel can also “zoom in” to the cell via a tablet connected to the control system on-site, all the way down to the hydraulic block or valve. This has also proven to be practical and time-saving when starting up the system.

Pictue: View of the construction site with welding stations, showing visualization generated by the Yaskawa Production System (YPS).

“Digital twin” of the system enables offline programming 

All stations on the production line are additionally depicted as complete 3D cells in a digital YPS environment. This virtual representation makes it possible to program and optimize all robot programs offline, i.e. without interrupting ongoing operations. For example, adaptations to welding programs such as improving seam quality or optimizing robot movements can be tested and validated in a simulation before being transferred to the real system.

As Taupp explains: “This avoids downtime, increases process reliability and ensures that every change is implemented collision-free and within the cycle time. The 3D simulation is also used for accessibility testing and collision control of all components, so that even complex fixtures and movement sequences can be reliably planned. This concept is a key building block for our high system availability and flexibility.”

The experts from Linde MH and Yaskawa worked closely together throughout the intensive process that lasted almost four years from the initial concept to commissioning. This relates not only to the planning of the system, but also repeated adaptation of the Yaskawa Production System to the specific requirements and wishes of Linde MH. During the commissioning and ramp-up phase, members of the YPS team were permanently on site in Aschaffenburg.

Picture: Bird’s-eye view of welding stations: “visual twin” generated in YPS

Summary: Transparency and connectivity bring added value

After several months of operation, those responsible at Linde MH can confirm that the new welding system fully satisfies the requirements. In addition, the Yaskawa Production System offers significant added value on several levels. Taupp: “YPS enables end-to-end control, poka-yoke-secured processes and intuitive worker guidance. Furthermore, offline programming in 3D cells offers enormous advantages – optimizing measures can be carried out without system downtime.”

Data continuity is also a clear plus-point: from the adoption of manufacturing data from the ERP/MES to the data integration of all welding and handling processes, including data from inline quality control. All data is visualized and documented on a single platform – the YPS. Linde MH and Yaskawa have thus realized the concept of a large-scale digital factory.

Picture: Current performance and utilization data is also directly displayed on the welding system. 

YPS: The digital twin of automated production

With the Yaskawa Production System, YPS for short, Yaskawa has developed a control system that establishes a connection between the “shopfloor” level and higher-level IT infrastructure. It simultaneously controls all processes in a production line. In a nutshell: YPS represents the “digital twin” of manufacturing – not only as a real-time image, but also as the “brain” of the processes controlled, documented and visualized via YPS. This means that the operator is optimally involved in the processes – at manual workstations and automated production cells. Key data is always transparent, measurement data is recorded and stored, and the service can zoom into the respective system if necessary.

In practice, the user selects from various software modules (shift planning, process monitoring, reporting, etc.) that are generally adapted to individual requirements. This task is carried out by a YPS team which also accompanies the commissioning on site throughout Europe.

Module/package overview YPS:

•      Shift Planning

•      Process Monitoring

•      Traceability

•      MDA (Machine Data Acquisition)

•      ODA (Operational Data Acquisition)

•      Reporting

•      Dashboard Designer

•      Worker Guidance

•      SQL Database Viewer and Editor

•      MES-ERP Integration

•      Smart Maintenance

•      Quality Monitoring and Assurance

•      Energy Monitoring

Text: Ralf Högel (Industrie Kommunikation Högel)

Pictures: Yaskawa Europe GmbH