The requisite safety for programmable electronic controls developed in the 1980s for paper cutting guillotines was achieved by means of diversity or through conventional relay controls. Changes in technology and regulations mean that systems employing diversity are no longer absolutely essential for attainment of the same safety level. The leading manufacturers of paper cutting guillotines are currently planning new developments for the next generation of machines. This development work is to take the new European draft standards into account. The planned generation of machines will employ completely new technology, the use of which for safety-related applications is currently addressed only in draft standards. The objective of the project is to compare these new technologies (ASIC, safety-related control software written in C, the use of operating systems, and homogeneous redundancy with software comparators for safety) with familiar and proven technologies for safety circuits, and to demonstrate their equivalence. In order to attain this objective, the new control system concepts which are proposed are to be monitored through the course of their development. The experience gained during testing is to be passed on by the commissioning party, the "Printing and Paper Processing" BG expert committee, for inclusion in standardization work and in the exchange of information with other European testing bodies.
Tests were to be performed parallel to the development of the new systems referred to based upon the experience gained by the BG Institute for Occupational Safety (BIA) with redundant control systems in microprocessor technology. The fault detection mechanisms integrated into the familiar systems are to be implemented in the new systems in a comparable fashion. The project encompasses the following tasks: 1. Consultation with the companies with whom contact has been made, with reference to the new regulations; 2. Evaluation of the proposed concept solutions and their conformity with the regulations; 3. Testing of paper cutting guillotines with the following components: control system, two-hand control and electro-sensitive protective equipment; 4. Generation of a list of requirements for the use of high-level languages in safety-relevant systems; 5. Development of basic concepts for the use of ASICs in safety-related applications.
The development of a homogeneous redundant programmable electronic control system for paper cutting guillotines was monitored through to the final production stage by evaluations of the safety aspects. The study showed that the use of a macrolanguage, employed for example for the functionality of the protective equipment (light curtains, two-hand controls), is acceptable as regards the safety aspects. The homogeneous redundant processor channels are interconnected by a software interface for synchronization, and also by a hardware comparator. The comparator enables the power source for the manipulated variables for the drives, cutter and press bar, which present the principle hazards, only when the two processors have reached the same logic result from the input signals. The experience gained to date with production models of the new control systems has been positive.
printing industryType of hazard:
Maschinensicherheit, Sicherheitstechnik, UnfallgefahrDescription, key words:
paper cutting guillotines, programmable electronic controls, ASIC (application specific integrated circuit), C programming language, homogeneous redundancy