Renovating machines still in good mechanical condition
August 2012, System Integration & Control Systems Design
An electromechanical retrofit can improve functionality, ease of operation and diagnostics.
German based Goebel Schneid und Wickelsysteme has delivered approximately 9000 roll-cutting machines of various sizes to the international paper and foil producing industry since starting production. The manufacturer estimates that several hundred large plants utilise complex automation technology that can bring entire factories to a standstill if it fails. While the mechanical components of these machines are usually still in good condition, the increasingly shorter innovation cycles in microelectronics cause problems: modules and components are discontinued at shorter intervals and are no longer available or only deliverable at substantial cost. Components become more susceptible to faults after years in operation and service technicians have limited expertise in electronics used 20 to 30 years ago. This makes it increasingly difficult to ensure plant availability and productivity – countermeasures are inevitable sooner or later.
An efficient and economical option for improving availability and productivity in the long term, especially on larger machines, is upgrading the electronic components. Goebel perceives customer support as a service that extends beyond the lifecycle of the product and provides tailor-made modernisations for all delivered machines. The basis of this retrofit is the standardised automation technology that the company implements in practically all new plants. In most cases, the end customer chooses Siemens technology because the manufacturer is represented with offices worldwide and its products are widely distributed and accepted in the target industry. If all the automation components come from one supplier, the machine manufacturer can be certain of receiving well-adapted solutions from the start. This simplifies and speeds up commissioning and contributes significantly to the shortest possible conversion times and downtimes. The aim is to retain or reproduce the familiar processes for setup, operation, monitoring, maintenance and service as far as possible to avoid time-consuming re-training.
Modern machine control
The most important step is the replacement of the machine control with one of the current standard controllers used by the machine manufacturer. This is usually a Simatic S7-300 with a Profibus/Profinet-compatible S7-319 PN/DP CPU. A plant modernised in this way meets the highest standards of reliability and service life and is prepared for present and future standards of industrial communication. On the I/O level, the modular Simatic ET 200M I/O system allows the implementation of complex, application-specific automation solutions with little effort. Remote diagnostics and maintenance can be carried out via modem or LAN, benefitting both parties since downtime caused by faults is reduced. The measuring and control technology is another decisive factor for high cutting and winding quality in the machines; Simatic solutions also offer components and possibilities for implementing demanding tasks in this area. Ageing analog solutions or special solutions created in the Assembler programming language can be transferred on an internationally available, standardised, and therefore easy to handle and maintenance-friendly basis.
If the original DC motors and wiring are still in working condition, or the user still has sufficient numbers of large replacement motors in stock, it makes sense to replace only the analog current converters. Siemens recently added current converters of the Sinamics DC Master (DCM) series to its modular Sinamics drive family. This replaces the previous Simoreg DC Master generation and is started, like all Sinamics devices, with the Starter software tool. The functionality is identical.
If operation of the DC motors can no longer be reliably maintained, the retrofit specialist recommends changing over to modern, maintenance-free 3-phase current technology. The first choice here is asynchronous servomotors of the 1PH8 series, converters of the modular Sinamics S120 family, and comparatively very simple wiring via Profibus or the digital Drive-CLiQ system bus. The modular Sinamics drive system is made up of separate feed modules, feedback modules if necessary, power units and control units that can be combined with each other and replaced individually according to requirements.
All drive parameters are saved on a memory card in the control unit and are immediately available after replacing a module. The motors supply their data via an electronic rating plate, which also minimises time-consuming parameterisation. This reduces the commissioning time and minimises downtimes while keeping productivity high in the event of a replacement.
The age of a machine is shown very clearly on the HMI devices. High-performance Simatic industrial PCs are state of the art, with uninterruptible power supplies and convenient touch operation via robust industrial monitors. The machine manufacturer relies on the Simatic WinCC open scada system for data acquisition, visualisation, and archiving. The open standards in WinCC allow custom modules programmed in C++ to be integrated. standardised add-ons or option packages for WinCC can also be used for individual processing of operating and production data. This increases usability and functionality considerably and allows for safer and more efficient operation of the machine.
Goebel has develops most of its solutions in advance. The test and commissioning phase normally begins on the fourth day after shutdown and even the largest machines are back in full production after seven to ten days. Specialists from Siemens help develop the strategies that are individually tailored to the user’s production processes and that can be implemented in stages, during which consultants assess the state of the plant, advise the end user, define the modernisation steps and draw up the final implementation plan.
For more information contact Keshin Govender, Siemens Southern Africa, +27 (0)11 652 2412, email@example.com, www.siemens.co.za