RetroFit. ALTERNATE supplies its customers from its facility in Linden. High availability is mandatory. To ensure service, especially for online retail, the company modernized its stacker cranes (SRM) with intralogistics specialist TELOGS. Over several weekends, the maintenance and RetroFit expert converted the entire drive and control technology to PLC-S7 and upgraded the user comfort of the plant. The major challenges of the modernization project were due to the fact that the plant manufacturer and the installed spare parts were no longer available on the market, the technical documentation was incomplete and an interface description of the installed control technology was not available.
As one of the first hardware mail order companies, ALTERNATE taps into the enormous potential of the Internet in the 1990s. Today, the company is one of the best-known mail order companies for hardware, software, home and consumer electronics. The company now sells a range of more than 50,000 products to private and business customers throughout Germany and Europe via web stores and its own call centers. Like everywhere in the mail order business, ALTERNATE has to be very fast with the delivery of goods. True to the motto “Order today and delivery tomorrow”, reliable logistics is the be-all and end-all. The most important working tool for fulfilling this task is the logistics system. At ALTERNATE, this consists of a two-aisle automatic small parts warehouse supplied by two tote storage and retrieval systems. This complex is associated with a conveyor system with picking and storage zone. The high-bay warehouse has space for 5720 bins in which the electrical components of various packaging units are stored. Since no customer wants to wait longer than necessary for the ordered goods, reliable and fast delivery is required.
Tricky initial situation
The drive technology and especially the control technology of the logistics plant were getting on in years and could no longer withstand the growing demands of the operator. The load handling devices also caused problems. Equipment failures were occurring with increasing frequency. Maintenance of the plant became increasingly difficult. “The entire plant operation developed into a risk for us,” Markus Bau, Head of Logistics at ALTERNATE GmbH, describes the situation. “We never knew how long it would be until the next disruption and when it would be fixed.” In addition, the plant manufacturer Schön & Sandt is no longer represented on the market and many of the spare parts kept in stock have already been used up. This excluded the supply of spare parts through the manufacturer. It was also not possible to make inquiries about the incomplete, and in some cases missing, technical documentation. It was clear that the plant would be in operation from Monday to Saturday, which meant that there was hardly any time for modernization. Nevertheless, the availability of the plant had to be restored. ALTERNATE decided to modernize the plant with the aim of increasing availability and thus throughput by 15 percent.
Manufacturer-neutral modernization partner
ALTERNATE has been working with the intralogistics specialist TELOGS for over 10 years. “In TELOGS, we have not only found a good maintenance partner who also reacts excellently in the event of plant malfunctions, but above all a specialist who can convert existing technology into future-proof concepts,” reports Markus Bau. Before getting started, TELOGS presented various modernization options to the plant operator. In a subsequent workshop, the participants jointly decided on the appropriate modernization concept. In the process, the challenges became clear to the partners as the higher-level, undocumented S5 control system proved to be an unpredictable project risk. In addition, the work had to be carried out during ongoing operations. TELOGS was only able to retrofit and replace from Friday evening until 6:00 a.m. Monday morning. There was little time for much work. The implementation of the concept was only possible with a tight deployment plan and optimal project preparation.
Construction phase: From old to new
After the detailed inventory and requirements specification phase were completed, the TELOGS project team got started. Hardware was planned, specified and selected based on the inventory. The mechanical design department developed in-house production parts for adapting new hardware to the existing mechanics. Electrical Construction designed and fabricated new electrical schematics. In cooperation with the load handling attachment manufacturer AFB, the load handling attachments were planned and redesigned. In-house programming marked the beginning of another tricky project phase. The development of the new software for the RBG controllers, including the necessary driver development for peripheral devices and interfaces to third-party controllers, took place at the TELOGS site in Wettenberg. The new drive controllers were parameterized on the software side. At the same time, the control engineers worked their way into the existing conveyor S5 control system and programmed the adjustments for communication to the new RBG controls.
Lack of documentation complicates project
Due to the short implementation time, a detailed test scenario was run before the first changeover weekend. All components to be installed and newly supplied components were coupled together in-house and commissioned in advance as part of a test setup. To be on the safe side, the test setup took place not only at TELOGS in Wettenberg, but also at ALTERNATE in Linden. After all, successful pre-commissioning was a prerequisite for risk-free deployment at the customer’s site. Even before the conversion dates, several preparatory works were carried out in the logistics facility. To ensure safe access to the aisles and plant safety, TELOGS installed a stage in the apron. For this purpose, a platform and the machine protection fence were installed in the pre-zone conveyor area. At the same time, the stationary electrical installation work for the stacker cranes began.
Conversion took place over the weekend
After the successful test runs, TELOGS realized the conversion of the stacker cranes in one weekend each. The technicians replaced the complete drive units for the travel and hoist drives with new and energy-saving SEW bevel three-phase AC gearmotors with integrated safe encoders, installed newly designed drive shafts and flange bearings as well as specially manufactured torque supports to adapt the new drives to the existing structure. New and modern Siemens controls were used for the control technology. The stationary and traveling control cabinets of the storage and retrieval machines were completely replaced. Today, the condition of the stacker cranes is quite comparable to that of new stacker cranes. ALTERNATE can be sure that any spare parts needed will be easier to obtain in the future.
Throughput of goods increased by 15 percent
Even though the initial situation was clear to those involved in the project from the start, a real challenge arose in the middle of the project. “The entire project team rose to the task and really dug in,” says Jürgen Dönges, Managing Director of TELOGS GmbH, describing this difficult project phase. “Today we look back on a successful modernization project”. Logistics manager Markus Bau is also satisfied with the modernization. “As a side effect, TELOGS has made the system more productive and user-friendly for us. The modern drive technology leads to a higher performance of the stacker cranes. The clear masks on the operating panels enable our employees to operate the system easily and safely,” sums up Bau.