At the end of 2010, the Spezial-Transformatoren-Stockach GmbH, in brief: STS, found itself faced with a significant increase in demand on capacities. The solution: a comprehensive process and plant optimisation. Kurz Zinser … Plant Manager at STS.
Rainer Völker … consultant at Staufen AG. Since its establishment 39 years ago, medium-sized transformer manufacturer STS has developed from the extended workbench for various OEMs to the technology leader in its field. Correspondingly, there has been a steady rise in the demand for transformers and inductors. 2010 saw a further hike in demand as the result of the increased importance of renewable energies, in which context STS products are also used, . Capacities in Plant II, specifically leased for this purpose in 2010, very soon no longer sufficed. In addition, it became clear that the traditional workstation-based assembly would no longer be able to cope with the required production volume. At the end of 2010, STS therefore took on board experienced consultants from Staufen AG for the complete reorganisation of Plant II. Workshops and training seminars as the basis for mega-project The starting gun for the mega-project was fired in the initial workshop with the STS management team. In collaboration with the consultants, this workshop served to analyse the current situation and to uncover fundamental problems. This led to the development of initial quick steps for improving the plant in order to alleviate the most pressing bottlenecks. One of these items was restructuring the workstations into three production lines, accomplished in early 2011. The first and fundamental success had been to convince the management team of the optimisation plan and its implementation. They were fully committed to the project and put the new philosophy into practice in their daily work, thus transmitting their enthusiasm to their employees. The commitment and enthusiasm of the workforce was the essential basis for introduction of lean management principles. This enthusiasm was further intensified by Staufen and STS in a comprehensive training seminar, in which all team leaders and representatives took part. Over the course of three days, they learned to differentiate between value-creating processes and waste and gained first-hand experience in lean processes. Together with the consultants, they conducted their first own analyses. These results were used for designing the practical exercises to reflect actual requirements at STS, e.g. in the short workshop on workstation design using cardboard engineering. To this end, staff constructed their future workplaces from cardboard – in original size. The processes were then analysed and tested as to where a redesign would result in improvements and then tried out using the cardboard models. Optimisation of production processes and equipment Under consideration of current requirements, building conditions and results from the workshops, the Staufen AG consultants developed a layout for the assembly workstations. Equal importance in this was given to the smooth product flow through the production and to the segmentation of lines by products. Staff were closely involved in the implementation. In workshops, process chains were developed for each product, all process sequences analysed in detail and simulated using cardboard engineering. As a next step, the respective workstation was set up and brought on stream. Thanks to the modular work systems at STS which are not fixed to the floor, this could be speedily done. By now, workstations are built or remodelled in the plant itself, allowing STS to react very flexibly to changes – resulting from new staff suggestions or requirements based on the order situation. The restructuring made it possible to reduce to a large extent long distances and the multiple handling of components, and also waiting times resulting from frequent set-up changes from one product to another. Optimisation of the “factory” system as a whole These days, a production line focuses on the production of less customer-specific products with minimal set-up requirements such as inductors for inverters. These are produced in one-piece flow from the initial wire to the finished product. At the winding station at the start of the line, the material is coiled, then the output attached and the coil pairs connected and stripped. Then the ferrite cores are inserted and the entire assembly fitted into the housing. The required material is restocked from trolleys; the line operator thus has all the material at hand. Prior to optimisation, with workstation-based assembly using a lot of material which stood around the operators and often had to be looked for, the weekly production was 50 inductors. By now, output quantity is 700 pieces per week. In addition, the optimisation of the product makes production faster. Thanks to technical-economical product design such as the optimisation of the housing and a new joining technology in the production of the ferrite cores, it has been possible to save on processing steps, reduce production and cycle times and improve on quality. For example, STS and its employees constructed a pneumatic device to hold the litz wires, thus making their assembly easier and allowing the operator to set the measured values without having to move the part. An information board at each line provides at-a-glance information about the status quo: who is working here, what are they qualified to do, is the output quantity on target, is all equipment operating correctly , do operators heed the 5-S rules (sorting, set in order, systematic cleaning, standardizing, and sustaining), etc. The new factory layout and the optimised workstations gave rise to new requirements for up- and downstream functions as well as support functions such as internal logistics. In early 2011, optimisation began in these areas, too, for example by changes to the warehouse structure. A large proportion of materials is now delivered on order just-in-time, by now packaged in exactly the way as required for supplying the assembly. Small parts are provided on demand, i.e. following the kanban principle. Once a specified minimum level at the production lines has been reached, the logistics staff refill automatically. Space- and capital-intensive parts such as housing and upstream products are provided on demand as required for specific orders. Team leaders set out the order board in accordance with the orders for the coming week; logistics staff collect the orders and provide the correct material for each day which is then taken from the material station behind the board to the production line (see photo above). The lean principle has also been extended to the administrative areas at STS. Early this year, for example, the same 5-S principle of order and tidiness at the workplace was introduced as in assembly. In addition, a CIP (= continuous improvement process) annual ranking has been introduced across all areas – it goes without saying that audits are conducted unannounced; the reward for the best department is a bonus payment at the end of the year. Continuous improvement practised in its purest form Since the middle of 2011, Staufen AG consultants have only paid occasional visits. CIP coach Erik Graf, a regular member of the STS staff, has been in charge of all matters lean at STS – with great success and superb support by all staff. “There is a proper CIP culture in Plant II” boasts Graf. To that end, he works on the lines himself in order to understand the problems of operators. There is also a CIP mission statement – appropriately for STS in form of a coil (see previous page). Since the start of the optimisation process in early 2010, STS has been able to almost double its productivity in Plant II. Even during the solar crisis of 2011, it continued to rise steadily. The lead time was reduced from six weeks to one week, delivery reliability increased by 20 percentage points to more than 95 percent. Staff are fully behind their company and CIP, as shown by the results of an employee survey: “Our production has become faster, easier and better structured; all materials are on hand and within easy reach – and collaboration with management is very good”, one employee stated. Some points still need to be improved: The increased physical strain as the result of increased takting is a challenge. To that end, STS has already developed a concept for the ergonomically optimised workstation of the future in collaboration with staff as a cardboard and computer model. Processes are also being honed: There is the plan for a coiling centre to supply all lines, which will further increase productivity with multiple machine operation. To improve communication between production lines, a Shop Floor Management concept including a daily early morning meeting of all line supervisors is on the starting blocks. “Our example shows that an SME can achieve a lot with lean management – the important thing is to have a structure and to establish a vibrant CIP”, Graf concludes.
