When it comes to injection moulding technology, the

also demands maximum automation from all its tools, so as to liberate its staff from routine tasks and allow them to focus their talents on creative work. Once

Apart from the standard ECAD (electrical CAD) requirements, other key priorities at Arburg also include device lists, terminal diagrams and graphical connector pin assignment diagrams, designed to meet customer requirements as comprehensively as possible. It also stipulated a powerful programming interface to facilitate optimum integration of the ECAD solution into the existing in-house information and communications systems.
Test installations were requested for two out of the three ECAD systems. The final decision was based on a number of criteria, including compliance with the specified requirements, operation of the system, evaluation of the solution to the set task, and satisfaction with the support services provided during the test installation. The Arburg designers also considered any additional pros and cons of the systems which they had identified during the test phase. »Following an intensive selection period, we opted for the system from EPLAN Software & Service«, explains Fritz Mattheiß. »EPLAN 21 and the associated circuit diagram generator provided a practical solution which dovetailed very closely with our own ideas«.

In early 1999, the experts at Arburg, in collaboration with EPLAN specialists, drew up a pilot project, and work began on its implementation. However, after just a few weeks it became clear that Arburg's complex requirements could not be met with the existing circuit diagram generator, which lacked the relevant imaging standards in order to implement the wide range of injection moulding machine variants. For example, certain variables could not be controlled and loops could not be programmed. The EPLAN developers had designed the circuit diagram for sequential processing only, and it was not suitable for such complex tasks. »We sat down with the EPLAN developers to find a solution«, reports Fritz Mattheiß. »They were extremely co-operative and offered us the use of a future programming interface which was still in an early stage of development«. The existing circuit diagram generator was also integrated into the EPLAN 21 system via this interface, which conforms to the C++ programming language. Furthermore, EPLAN promised the Arburg designers that they would continue working on the programming interface until it met their requirements. Although the existing circuit diagram generator could not be used for these complex tasks, and the Arburg specialists programmed their own custom-designed generator, we were still able to meet all the deadlines. Even if they had used the standard circuit diagram generator, it would still have been necessary to implement a customised sequence control system. The generator is merely a tool which must be fleshed out and adapted to suit the relevant company-specific requirements. For example, at Arburg, an injection moulding machine or project is viewed from two different angles - from the point of view of sales, and from the point of view of production. A member of the sales force presents the machines and their various features to the customer, as specified in the sales catalogue. As such, the injection moulding machines are clearly defined in the form of so-called sales units. When an order is placed, the sales units required for that particular machine are entered into the manufacturing requirements planning (MRP) system. However, production requires additional information. To this end, the sales units must be supplemented with technical units, which are generated using clearly defined rules within the MRP system. Using this sales unit and technical unit information, which is based on a modular structure, a machine can then be released for production, since it is clearly defined right down to the very last screw and the tiniest wire. 
Circuit diagrams constitute an integral part of the technical units. In the past, only one circuit diagram representation was drawn for several machine variants. The viewer was required to locate the circuit diagram for his own particular machine variant using the notes and the dotted-line drawings. »In order words, the circuit diagram did not clearly reflect the machine variant«, explains Fritz Mattheiß. »Moreover, the circuit diagram pages, particularly the cross-references, were not aligned with one another. For example, contactor representations were not aligned with the corresponding cross-references. Such a highly complex task was beyond the capabilities of our old previous CAD system.«

It is easy to imagine the problems and time delays which customers or service engineers may face when locating the sources of errors. The new circuit diagram generator is expected to provide assistance in this respect. The Multilift from Arburg was selected as the pilot project. This is an optional extra for injection moulding machines which removes plastic parts from the machine and processes them further. The Multilift is capable of moving in three axes, either via servomotors or via a pneumatic drive. For automatic circuit diagram generation, the first step was to program an interface to the manufacturing requirements planning (MRP) system. This postprocessor for the DB2 database reads the necessary information from the host computer and transfers it via File Transfer Protocol to the Windows NT system on which the ECAD package is installed. The file thus generated contains customer data, machine data as well as function data, with the sales unit and technical unis information. In a second stage, each individual option of the Multilift, for example each drive, is described in the various variants, and stored in an Excel spreadsheet. The respective circuit diagram representations of the individual components were likewise stored in the EPLAN 21 system as symbols or macros. The sequential control system is defined in a subsequent stage. In this way, based on the sales unit/technical unit data from the manufacturing requirements planning system, the required information from the spreadsheet was read, linked to the relevant circuit diagram symbols or macros, and positioned in the circuit diagram. After passing through several iterative loops and processing all the sales unit and technical unit information, a circuit diagram is account. Upon delivery, therefore, the circuit diagram representations do not contain any additional options. The engineer no longer needs to find out which machine specifications are available in each individual case, but can instead concentrate on the task in hand, by consulting a clear circuit diagram containing all the cross-references. Around 170 circuit diagram macros were required for one Multilift. Overall, the circuit diagram components and generated which precisely matches the machine data of the injection moulding machine or, in the case of a pilot project, the selected Multilift variant. Within EPLAN, the devices are automatically connected to the wiring. The new system also eliminates the need for manual processing of the cross-references for contactors and interruption points.

The only instance where manual incorporation is required is if additional special customer requests need to be taken into implementation of the C++ program, which contains over 6,000 lines of programming code, took less than five man months. The full version of the Multilift comprises around 50 automatically generated circuit diagram sheets, whilst a complete injection moulding machine contains between 100 and 250 circuit diagram sheets, plus the corresponding lists and terminal diagrams. Arburg's circuit diagram generator was designed in such a way that it is not always necessary to start again from scratch with each new injection moulding machine or when upgrading existing models. Instead, the user simply needs to modify or supplement the existing routines slightly. »The effort involved really pays off, thanks to the high quality of the documentation produced«, stresses Fritz Mattheiß, »because it allows the customer service engineers to locate any faults and the affected components far more quickly, which in turn helps to boost overall customer satisfaction«.
Having started out initially with three EPLAN 21 workstations, Arburg now has eight systems in use. By the end of the year 2001, it hopes to have a total of 30 installations to replace the old system in full. In future, the circuit diagrams for all five series of Arburg injection moulding machines in at least five different sizes will be generated automatically, thanks to the EPLAN 21 system. The hydraulic and pneumatic diagrams can also be generated automatically with the circuit diagram generator developed by Arburg, in a direct transferral of the procedure from electrical engineering. There are also plans for automatic foreign language support, i.e. translation into the respective local language. The circuit diagram generator will subsequently produce trilingual documentation - in German, English and the local language. »Article alignment with the MRP system, which includes parts lists as well as the graphical circuit diagrams, is our next target«, explains Fritz Mattheiß. »To this end, the parts numbers and article numbers must be read from the MRP system, which requires allocation between the component in the circuit diagram and its definition in the MRP system. Initially, we only expect to be able to implement this as far as module level, because the different hierarchical levels will make implementation with the current tools too complicated.« The company is currently investigating the option of connection to automatic labelling systems for labels, stickers and cables. The individual projects are archived on the basis of EPLAN 21 data and additionally in the form of PDF files, which are generated automatically. The PDF files can be viewed from any PC equipped with standard programs such as Acrobat Reader, and can also be printed out. Finally, Fritz Mattheiß highlights the principal advantage of the EPLAN 21 system: »The greatest benefit for the company lies in the automatic generation of machine-specific circuit diagrams, including the relevant cross-references. We can depend on the fact that the documentationis 100 % accurate, and human error is excluded«.

Last edited: 2002-07-16 14:49