Linking existing machine control with SAP system
25 September 2013
The aerosol generator of a nebulizer produced by PARI Pharma GmbH is used in the treatment of cystic fibrosis. The company made the decision to update its control systems to optimise automation of its production equipment.
The company began converting its systems to PC-based control in 2011. “Before the changeover our technical infrastructure was somewhat inefficient,” explained Ronald Schmidt, project manager at PARI Pharma. A heterogeneous and complex mix of control programs for the S7 PLC as well as PC programs in C++ and LabView made maintenance without specialised programming knowledge difficult. “In the event of a fault we had to call in external specialists on a regular basis,” continued Schmidt. “Moreover, the old system was error-prone since it was not possible to integrate the system control with a database. The PC data determined from the PLC had to be entered manually in the databases for further processing.”
The aerosol generator for the eFlow system needs to go through a total of 12 production and testing stations.
Unambiguous, traceable parts management is a prerequisite for such a complex production process, in which two separate machining operations are executed in one cell. After the first production step the part is removed, processed further and then returned to the machine for further machining. The parts need to be scanned and identified before each production step. “For years we had been looking for a machine control system able to communicate directly with the databases,” said Schmidt. “In the end we chose the TwinCAT Database Server in conjunction with the EL6731 Profibus master terminal for the EtherCAT Terminal system. However, we didn't want to replace the S7-PLC immediately during continuous operation. We were looking for an option to control it via the Beckhoff system without the need for proprietary hardware.”
The solution was provided by esqmate GmbH. The company was able to develop an MPI library for TwinCAT, which ensures that the Beckhoff controller can communicate directly with the old PLC via the PROFIBUS master terminal and the MPI protocol. No additional hardware is required. In this way it is possible to access S7 data blocks and flags directly from TwinCAT via an EtherCAT terminal. No modifications of the existing S7 controller were required. Data exchange takes place in TwinCAT via function blocks. “Based on the EL6731 Profibus master terminal we were able to successfully implement a Profibus/MPI stack for microcontrollers, which we had developed earlier in the TwinCAT library,” said Markus Kräutner, managing director at esqmate.
A CX5020 embedded PC is able to read data from the S7 controller via the EtherCAT terminal, link them with the new bar code system and sends them directly to an Oracle database or PARI Pharma's SAP system via the TwinCAT database server. In addition to reading and writing data, the database server also enables calling of ‘stored procedures’. In these PARI Pharma stores command and instruction sequences for processing in the database. The procedure results are sent to the database server and are then available in the PLC again. The PLC code is simplified through the option of executing procedures in the database.
A Beckhoff CP7902 control panel is used as the HMI. The interface was developed based on customer specifications and enables the operator to follow each process step exactly. Based on the scanned bar code the current production step is validated from the Oracle database, and the next required program is automatically started in the PLC via the EL6731. System operators can log in conveniently and securely via an integrated RFID token.
Central SAP evaluation
”Because direct communication is now possible between the existing S7-PLC, the new controller, the Oracle database and our SAP system, we are at last able to link the control world with business management solutions,” concludes Schmidt. Analyses no longer take place in the plant itself, but centrally in the SAP system, which receives test data from the Oracle databases connected to the Beckhoff systems and generates item lists, work schedules and approval reports or manages the inventory based on this data. This enables staff to focus on their core competence – production. Quality control has also become simpler and more reliable.
Staff members no longer have to acknowledge manually because approvals are automatic via bar codes. Thanks to the new control technology PARI Pharma is now also able to use parallel, rather than order-specific production. This comes in handy considering increasing production quantities. “We are now able to produce individual components in parallel and no longer have to move whole assemblies from line to line,” said Ronald Schmidt. “Since each part is furnished with a serial number, we have optimum control and can always deliver exactly what is required.”
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