How a frequency inverter is built: A look behind the scenes in Aurich

Whether they are operated in Europe, China or the USA, every NORD frequency inverter - every control cabinet inverter or decentralised frequency inverter - was produced in the NORD production plant in Aurich, East Frisia. Since the early 1980s, NORD DRIVESYSTEMS, one of the world's leading full-range suppliers of electrical, mechanical and electronic drive technology, has had its own electronics production facility in the north-west of Lower Saxony. Over the years we have been continuously expanding both our portfolio and the site. Today, NORD Electronic DRIVESYSTEMS GmbH employs 180 people in this location (plus another 40 employees in development) and have produced 185,000 units in 2022, with an upward trend. The production area is 7,000 m2 and the office area is 1,300 m2. The range here includes electronic drive technology up to 160 kW (inverters, motor starters and electronics). For the series production of the NORDAC LINK frequency inverter a specific new assembly line started its operation as part of the site’s expansion.

Lean logistics – efficient processes

The decisive factor for the development of NORDAC LINK and our increased engagement for a state of the art production in drive electronic was the progressing digitalisation, flexibilisation and individualisation in the industry. The trend is pointing to custom orders, smaller lot sizes and decentralised devices. Modern drive technology must be flexible, customisable and easy to integrate into all plants and systems. With NORDAC LINK – and of course with all other new frequency inverters series – we will stay abreast of this trend.

The series was specially developed for applications in modern networked intralogistics systems and provides a convenient drive solution for flexible decentralised installation. Thanks to their integrated PLC the efficient frequency inverters can take over entire control sequences and control processes autonomously. All modules, components and connections are combined in NORDAC LINK by using simple plug connectors. In addition to the high plug-in capability, optional integrated maintenance switches and switches for manual operation ensure a high level of user-friendliness. The frequency inverter can be freely configured for any application and is compatible with all common bus systems. This allows it to offer the customer more possibilities for individualisation than previous products. Of course this also has an impact on production. The goal of planning the production processes for NORDAC LINK was to control all required assembly and test systems on basis of the individual configuration. This strategy was successfully implemented, from the generation of the assembly plan up to final testing and configuration.

From printed circuit board to frequency inverter

The automated and flexible production structure in Aurich is state-of-the-art and allows any size of order to be processed in the same manner. Even small batch sizes are possible thanks to flexible production. The NORDAC LINK is produced directly on order by the customer. It is configured in SAP at the final assembly level and then fitted and assembled to the customer's order. This enables the customer to configure considerably more features. There are also advantages for the production process: The entire production process is controlled via a central order. All data and information are combined online and can be accessed from anywhere at all times. Among other things, placement and test plans are automatically generated from the individual configuration, both in THT production and in the SMD (Surface Mounted Device) area. This is a novel approach to module assembly. Using a QR code on the module, the work plans can be displayed at the individual THT assembly stations. This not only ensures that the right component is placed in the right device, but also allows for greater flexibility. An automated guided vehicle (AGV) system also ensures greater efficiency. Among other things it is responsible for the transport from goods receipt to the automatic small parts warehouse and will gradually take over further routes.

The efficient process begins as early as at goods receipt. In order to bring as little packaging as possible into production, each package is freed from its outer packaging and transferred to standard crates. The downstream transport is handled by the AGV system. Each item is given a 2D code so that it can be fully tracked until it is used, or inversely from the serial number of the device back to the goods receipt.

The mainstay is the automated small parts warehouse. The automated small parts warehouse has more than 2,000 six-segmented standard crates and is centrally integrated into the production processes. It serves not only as a warehouse for components, but also for semi-finished products and for linking the production processes. After the SMD department, the assembled modules are returned to the small parts warehouse, from where they are removed for further THT processing. This implements an automatic FIFO procedure (First In, First Out) within the production process.

In SMD production, the two placement lines place as many as 60,000 components per hour at top speed. In order to ensure fault-free production, all modules are checked using an in-line AOI system (automatic optical inspection) after placement and soldering in a nitrogen atmosphere. In THT assembly, wired components are assembled and soldered with wave soldering systems in a nitrogen atmosphere. Depending on the complexity, a THT-AOI test and a subsequent 100% functional test are carried out. From THT production, the modules are conveyed to the final assembly Kanban warehouse. As all products are produced directly according to customers' orders, only a short production lead time and smaller storage spaces are required. At our headquarters in Bargteheide the individual devices – drives, motors and inverters – from different production facilities come together and are united into one complete drive solution. As a logistics hub, NORD DRIVESYSTEMS Bargteheide has a capacity of over 34,000 storage spaces, 17,000 in high-bay storage. With a new automated small parts warehouse, covering more than 70,000 spaces, the largest automated warehouse system in the NORD DRIVESYSTEMS Group was added in 2021. In addition to the automated small parts warehouse, a narrow-aisle warehouse is located in the new halls, providing 4,400 pallet spaces as well as a goods receipt and shipping area. Now, material packaging is also located here. This allows us to make deliveries of frequency inverters, gear units and motors even faster in the future for our customers and subsidiaries. Due to higher availability of many components, assembly times at the Bargteheide site will also shorten.

Eliminate sources of error, maintain quality standards

Before making their way to the drive technology centre in northern Germany, the frequency inverters have to pass the high bar in quality standards set by the market. To maintain this, appropriate quality controls are integrated in Aurich at all production stages. This starts with component checks in goods receipt and continues with the upgrading of the automatic placement machines. The AOI test in the in-line system is set up in such a way that even the slightest deviations are registered. After THT production, all modules are tested once again. Final testing of the complete devices includes the final inspection of all analogue and digital I/O interfaces as well as a final performance test under full load. All tests are based on the individual configuration. This ensures additional safety, as do the visualisation of the assembly instructions and the laser marking of the devices. This is the only way of guaranteeing the high quality and reliability of NORD products. Manufacturing the NORDAC LINK frequency inverter in Aurich demonstrates: We do not compromise at NORD DRIVESYSTEMS, even when it comes to our own manufacturing process. Digitalisation, automation and the highest possible flexibility when manufacturing frequency inverters have long since found their place on the factory floor.