On conventional presses, few words were required to illustrate the need for reliable safety technology.
Presses have since become more sophisticated and versatile, and lately even smaller and more compact.
At the same time the demands on the safety systems have risen. Today they not only need to be flexible and powerful, but economical too.
Whether the press is large or small, the responsible safety system must relate as closely as possible to the respective press type and be simple to install and configure.
The responsible safety system must not obstruct the production process and must be deemed acceptable by the user.
Even today, most presses still operate with hydraulic or mechanical drive technology. Designed for a high pressing force, these machines are large, heavy and loud.
Quite often they require an increased load-bearing capacity or special foundations. As conventional presses are so cumbersome they are difficult to adapt to varying, frequently changing tasks or to integrate into production and logistics concepts.
Also, the safety technology is often based on traditional contactor control systems.
Sophisticated safety concepts with diagnostic functions, tailored exactly to the production process, cannot be implemented on this basis. Setup times and downtimes are long; the efficiency of many such machines is low.
The more varied the tasks on a press, the higher the demand on the safety concept. Whether in insertion mode or feeder mode: the safety of man and the environment is the top priority.
But these days even safety technology has to be justified in economic terms: it will only be endorsed if it does not obstruct the production process and users deem it acceptable.
Only an integrated, flexible, multifunctional safety system that is electronics-based can satisfy these different requirements.
The press manufacturer Hieger is based in Rietberg, East Westphalia. It has proved that presses do not have to be heavyweights, but can generate considerable pressure even without hydraulic oil.
Its synchropress product series is based on the continued technical development of electrical spindle drives, which can deploy up to 4,000 kN of pressing force.
Special feature: the machines are comparatively compact, light and quiet, and they do not require any foundation.
The special roller thread drives operate with precision and guarantee good parallelism between the press slide and table.
The wide range of application options, rapid availability and low maintenance requirement make this type of press particularly economical and attractive even to smaller companies.
It is often on smaller, more economical presses that costs are squeezed in terms of the safety concept.
Although presses always do the same in principle, the art is to tailor a safety control system as precisely as possible to the requirements of the respective machine type. Nobody likes to invest in performance features that are not needed. So the safety system should be flexible, modular, expandable and simple to install and configure.
The PNOZmulti safety system from Pilz has been specifically tailored for use with presses, regulating standard control functions and monitoring safety functions such as E-STOP, safety gate or two-hand controls.
The PNOZmulti safety system is ideal once you need to implement more than four functions. With the PNOZmulti safety system all the functions and safety devices on presses can be controlled and monitored safely and with flexibility. BG approved blocks for all common functions are available and ready to use (for example: camshaft and broken shearpin monitoring, cycle mode for electrosensitive protective equipment, setup mode, single-stroke mode). Configuration is carried out simply on the PC; no programming knowledge is required. The completed configuration is then stored on a chip card and inserted into the base unit on the machine.
The management at Hieger were also convinced by these performance features. The safety concept needed to be updated in order to satisfy international directives and standards (EC Machinery Directive 98/37/EC, Annex II; DIN EN 692) and therefore comply with Category 4 of EN 954-1.
On synchropress, the PNOZmulti safety system monitors all the safety-related functions:
E-STOP, safety gates, reduced spindle speed during setup in jog mode while the safety gate is open; all these count just as much as the monitoring of the drives’ direction of rotation. An E-STOP during the closing movement automatically reverses the direction of rotation and overrides the slide; an E-STOP during the opening movement causes an immediate stop. PNOZmulti also keeps an eye on the speed of the material infeed and evaluates the safety gates and light curtains.
“A flexible, modular, clear safety system which simply fits well into our press concept”, is how Dr. Holger Stritzke, the company’s Managing Director, sums up the decision to use the PNOZmulti safety system.
Previously the company had used conventional safety relays and mechanical limit switches; linking these was a difficult and expensive process.
The PNOZmulti safety system integrates all the functions within one system, which provides precise, reliable diagnostics for the connected components, such as E-STOP, Pilz PSENmag non-wearing magnetic safety switches for safety gates, foot switches and Pilz PSENopt light curtains.
Control data and diagnostic data are exchanged with the machine control system in both directions via a fieldbus module. This reduces downtimes, while increasing productivity.
“What convinced us was the simplicity of the installation and configuration and the way in which the safety system was adapted to our needs”, emphasises Bernd Neumann, Head of Electrical Engineering at Hieger.
With a comprehensive library of safety blocks, the PNOZmulti configuration tool is ready for all press-related cases. Because the PNOZmulti safety system is modular and flexible and its configuration can be adapted simply and directly to the individual case in hand, the PNOZmulti safety system provides an efficient, economical solution for equipping and upgrading smaller and larger presses.
Provided the machine does not undergo any substantial changes, its continued use is protected.
In both word and deed, Pilz can act as a specialist for control and safety functions during the planning process, when implementing retrofit measures and finally when having the press approved through BG. “Good service and excellent teamwork made a considerable contribution to the project’s success”, says Dr. Holger Stritzke, summing up how the project ran.