Gruner – Operational excellence in assembly

Digital transformation and machine learning

In order to raise process reliability and thus product safety to a new level in the face of increasing variant diversity, Gruner AG has introduced the SAP Manufacturing Execution (SAP ME) production system in electronics manufacturing. The integrated Assembly-by-Motion add-on from IGZ guides workers through the assembly process by gesture and controls the steps seamlessly.

Since its foundation in 1953, Gruner has succeeded in occupying a leading position in highly competitive markets with a finely tuned range of relays, solenoids and actuators. In Germany in particular, the manufacturer, which is based in Wehingen in Baden-Württemberg, pools its expertise in the areas of development and design, electronics manufacturing, toolmaking, stamping, injection moulding and actuators. As early as 1977, it began its internationalisation with the addition of an assembly site in Tunisia. Other factories can be found today in Serbia and India. Gruner AG has more than 1,400 employees worldwide. In 2019, sales amounted to around 100 million euros, with exports accounting for 60 per cent.

Flexible and precise

Gruner's core values find their expression in the 'Slinky', a coil spring invented by American mechanic Richard James that appears to move of its own accord. It shows the fascination with physics – and symbolises flexibility in its purest form. Alongside innovation, efficiency and quality, this ability distinguishes the medium-sized family business. "We have an extremely wide range of variants and work with a strong customer focus," says Martin Spreitzer, Chief Production Officer. "This also triggers us to map an extremely high level of quality in our processes." Due to the infrastructure that had grown over the years, the requirements for quality control and error prevention as well as other requirements for digitisation were increasingly difficult to meet. All this changed with the introduction of the standardised SAP ME production control system. The main reason for replacing the existing IT architecture was its complexity. It consisted of various purchased and self-developed sub-systems. These were partly outdated and required considerable effort and expense to maintain and synchronise. This was further complicated by PLC-bound test procedures, which had to be readjusted for each new product variant. The company was also no longer willing to tolerate the time delay between the start of the order and the final notification, which was created by a lack of transparency.

Pioneering pilot project

The goals of the SAP ME implementation as a central digital manufacturing solution were clearly defined: continuous transparency, also to ensure the ability to react more quickly to unplanned events on the basis of up-to-date information, as well as an improved and high level of documentation for the individual products. Another parallel goal was to ensure product quality by means of strict process interlocking. The project managers opted for SAP's Manufacturing Execution System (MES) because it was open and configurable, the user interface was convincing and all manufacturing processes could be digitally controlled and monitored – right down to batch size 1. In addition, this allowed Gruner to pursue the SAP strategy it had already adopted right through to production and familiarise itself with the Hana database used for ME before the planned switch to the SAP S/4 platform. Correspondingly high expectations were placed on the implementation partner. "The decisive factor in the selection process was a sound deployment analysis, during which IGZ's IT specialists demonstrated their proven expertise in the area of SAP Manufacturing," says Sebastian Kosicki, Project Manager and Coordinator for the digitisation of production at Gruner. Reference visits and the presentation of IGZ's new Best Practices Assembly-by-Motion (ASM), an ME-integrated, camera-based solution for assembly guidance and control, also helped to win the company over. Against this backdrop, IGZ received the order to implement SAP ME at the production site in Wehingen. At the same time, Gruner entered into a pilot partnership with the IT service provider to integrate ASM into its processes.

Lean production

The kick-off in mid-2018 was followed by a specification of the requirements for the new assembly line for actuators and a proof-of-concept for the Assembly-by-Motion add-on. During the review, it became apparent that the solutions would enable automated assembly control with object, position, colour and quality recognition without any compromises. In October 2019, the ASM-assisted production line went live in assembly. A few weeks later, the MES application went live in the punching and injection moulding areas. The punching and injection moulding machines as well as the new assembly line were connected using the OPC UA communication standard. The MES connects the ERP level with the machine level. The standard software takes over the operative online order management and control by recording and reporting operating data and communicating work instructions via worker dialogues. Label printing and a dedicated personnel time recording are also supported. The automatic order fine control is carried out according to ERP specifications via the IGZ Order Cockpit 4.0, which is also a preconfigured Best Practice provided by the SAP project centre from Falkenberg in the Upper Palatinate. The current workstation occupancy and order progress as well as any overloads are visualised. This graphically oriented control station allows assembly processes that have already been scheduled to be rescheduled as required via drag&drop.

Manual work reduced

The new system infrastructure is characterised by simplified processes and traceability for every installed component. Manual copying and posting activities are eliminated, as are printing and distribution of work instructions and drawings and manual completion of shift logs and checklists. The process lock helps to ensure a significantly increased quality level: an automated control mechanism ensures that a follow-up order can only be started if all the manufacturing and testing steps that must be carried out as part of the previous assembly order have been successfully completed.

Monitoring and data collection

With the ASM add-on, the manufacturer is even going one step further in terms of quality and process reliability. Along the new assembly line for actuators, the employees work using gesture control. This means that assembly processes are automatically recognised and booked; it is no longer necessary to make entries via keyboard or screen. Gesture control is used to monitor whether the correct components are removed and correctly installed. If there is a discrepancy, the system issues an error code. A camera system simultaneously ensures validation via quality gates. In addition to assembly control, the solution also automatically records demand-related serial numbers, barcodes and other characteristics and assigns them to the production process. The improved ergonomics of the work measurably increased the productivity of the workers.

Experience becomes knowledge

The add-on is controlled from SAP ME. Machine learning is used to generate knowledge from experience. This should make it easier to adapt to new products and variants in order to save reconfiguration costs. The previously considered alternative concept was discarded in favour of this solution at an early stage. At its core was the idea of integrating camera-based assembly controls into the PLCs. This would have left the problem of having to manually adjust the programming at the subordinate control level for each product change. Since this approach also offered poor integration into the ERP and MES level, ruling this option out was a no-brainer.

Project progress as planned

By integrating the MES application and the add-on in assembly, Gruner is fully committing itself to the digital manufacturing approach. "IGZ's overarching expertise in areas ranging from SAP ERP integration to machine connectivity helped us immensely when it came to implementing the project," says Sebastian Kosicki. "As a result, the project was successfully delivered on budget, on time and with the desired quality." In addition, the partner's innovative strength was convincing, especially with regard to assembly support and machine learning.

Template accelerates roll-out

Now that SAP ME has proven itself at the pilot site in Wehingen, the roll-out of the MES system to the Gruner plants in Serbia and Tunisia is next on the agenda. The template created by IGZ using the building-block principle will simplify and accelerate the introduction of the standard software at the local assembly sites specialising in relays and solenoids. Further cross-plant transparency for production processes can be unlocked by implementing SAP Digital Manufacturing Cloud for Insights. This allows companies to collect real-time data from several production sites across plants and compare this on the basis of standardised performance indicators. By doing so, responsiveness can be improved without having to accept local restrictions.

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