Swissmill said it recognized decades ago the need for automated production processes that gave its operators permanent and unrestricted control over all the products and processes. To meet that goal, it installed its first Bühler automation system.
Swissmill is a division of Coop Group, and processes over 200,000 tonnes of grain annually into more than 100 different flour and semolina products plus flakes, blends, and specialties. The heart of the complex consists of two flour mills (2 x 300 tonnes per day), a specialty mill (40 tonnes per day), a durum mill (250 tonnes per day), an oat mill (60 tonnes per day), a corn (maize) mill (30 tonnes per day), and an extruder line. The complex also includes facilities for making finished products and processing byproducts such as batch and continuous blending and mixing installations plus transfer, bagging, and bulk out-loading systems. In all, the plant comprises over 70 sub-processes and more than 300 storage bins for holding raw materials and finished products.
Recently, Swissmill decided it was time for a new-generation automation system. The company said it needed a consistent system from intake to out-loading, with several rational control centers. This was implemented using a powerful, redundant ESX-i computer system supplemented with a G-Bit ring network using optical-fiber technology and equipped with 15 thin-client operator terminals.
The backbone of the underlying control level is formed by nine networked Simatic S7-400 PLCs. Some 160 control and motor cabinets with a total of 8500 PLC inputs and outputs are installed at the highly decentralized equipment control level. Here, too, efficient solutions were put to practice in the areas of new installation, maintenance, and operation.
The new concept supports the operators in many different ways. It ensures optimal utilization of the production systems while at the same time improving product safety and process uptime.
Production managers bear heavy responsibilities day in, day out. This means that the system is expected to offer a high level of flexibility and at the same time online guidance and support in order to ensure high efficiency and quality.
All processes are handled by WinCoS through customized dialogs. 24-hour production planning, at all times up-to-the-minute and modifiable, is managed by the automatic job queuing system. It is also possible to process express jobs in between. Supplier and customer management functions facilitate handling of the products coming into and going out of the plant.
The bulk out-loading systems can be operated by truck drivers themselves. Detailed graphic images showing all the important process data and supplemented with an efficient alarm system provide permanent information and support during ongoing production. This ensures optimal plant monitoring with automated remote access and remote messaging during unattended operation.
Product safety and production reliability start as early as during the planning stage. Clear requirements for this include consistent and reproducible products as well as specific online quality checks at the proper points. The functions implemented in this project include process-oriented formulations; automatic allocation of product formulas to finished products or vice-versa; strict classification and allocation of raw material plus semi-finished and finished product bins to the production jobs and their interlocking by WinCoS.
Products are continuously monitored at important points in the process. Examples of this include online NIR quality testing of incoming wheat and of processed wheat blends prior to grinding as well as in the main mixing systems for making the finished flours. Automatic samplers with job-related sample identification are part of this system. Deviations from the target values are recorded and if required will interrupt production.
The control system also contributes greatly to responsible utilization of energy. For example, all the air supplies for cleaning filter bags (sleeves), the major aspiration systems, and the important pneumatic conveying lines are automatically controlled as a function of their loading. Drives are strictly selected as required as a function of the process. Waiting times are if in any way possible eliminated, and idling motors are selectively cut off after a certain time has been exceeded. In addition, energy-efficient motors are systematically used.
All production data are recorded by the system and archived as raw data. Product movements in the 300-plus product storage bins are automatically tracked. Operators are offered a wide range of – if possible paperless – reporting and statistics options. In addition, WinCoS ensures complete online production traceability. On the one hand, this extends across all the production steps with detailed data from intake (reception) throughout loading (forward and backward), and on the other hand includes a sophisticated, up-to-the-minute layer model in the 300-plus product storage bins. These tools offer the operating personnel highly effective and realistic support at all times when faced with production challenges.