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Modern water hydraulics bring old presses up to the state of the art

Particularly in Eastern Europe, presses are in use in which no investments have been made for decades. For this reason, many of these machines are still at a technical level that is completely outdated.

Authors:

Dipl.-Ing. Ansgar Daniel Drees, Engineering of the 46MN Open-Die Forging Press Dipl.-Ing. Thomas Jockenhöfer, Engineering of the 100MN Closed-Die Forging Press

published in the German magazine SchmiedeJOURNAL (September 2014)

The following article outlines the necessary modernisation and retrofitting of two closed-die forging presses in Russia. In the past, the presses were maintained with only minimal expenditure, and the technology remains unchanged in most cases. As a result, there are in many cases profound technological differences between these and Western European presses. In Western Europe, increasing requirements in relation to system availability, reproducibility of manufacturing results, and safety, have meant that presses have continuously been modernised and adapted to the growing demands. Hauhinco specialises in the modernisation of water hydraulics press control systems, and makes old water hydraulics presses competitive again, thus presenting a real alternative to purchasing new equipment.

Advantages and objectives of a press modernisation

In the course of a modernisation, presses are equipped with new functions and modes of functioning. On the one hand, these include additional functions for the auxiliary movements and handling functions for workpieces and tools. On the other hand, new modes of functioning for press movements are added, which would not be possible in the same way with the existing system. In many cases, presses that were only designed for a single mode of operation are capable of performing various operating modes after the modernisation, thus expanding the production capabilities of the business. Closed-die forging presses, for example, should be capable after modernisation of additionally performing the work processes for punching and deburring, and where possible should also be capable of performing open-die forging processes. It is thus possible for a single press to perform various kinds of processing stages and to handle various workpieces.

In order to increase productivity, in many cases the travel speeds of the moving beam and the speeds of auxiliary movements are increased. Product quality is improved through the controlled activation of press movements using proportional valves. The operating concept for the modernised presses changes significantly. On very old systems, the valves of the hydraulic control systems are still operated directly by means of hand levers. The manufacturing results achieved on such presses are entirely dependent on the skill and dexterity of the press operator. In later models, the valves are actuated by hydraulic cylinders powered by oil hydraulics. The hydraulic cylinder either drives a control shaft, which actuates the individual valves, or each valve is actuated by its own hydraulic cylinder in a process known as "single-valve triggering".

Modern water hydraulics control systems by Hauhinco work with electrical hydraulic pilot valves, which are operated and actuated with joysticks via electrical control systems. Automatic and semi-automatic programs allow the pressing process to be automated, and result in reproducible manufacturing results, which can be documented in detail. With high-quality components and high quality requirements, particularly in the aerospace industry, this documentation of the manufacturing process is essential for a modern production facility. Speed regulators enable modes of operation that protect the equipment. In this manner, the deformation rates can be precisely adjusted to and coordinated for the requirements of the respective material. In modern water hydraulics control systems with proportional technology, the pressing force is in addition precisely coordinated for the requirements of the material and the pressing process.

Furthermore, the significantly increased safety requirements are implemented with the assistance of Hauhinco water hydraulics technologies, thus bringing the modernised systems up to the safety standards of a new system. Productivity is considerably increased, thanks to the high availability of the tailored hydraulic systems. Thanks to the generous dimensioning of the mechanical press components, the service lives of many presses are nowhere near over. In most cases, the existing pressure supply can continue to be used or can be expanded. Due to the existing system components and the space requirements, modernisation is therefore several times cheaper than the complete rehabilitation of the system, and thus often more economical than purchasing a new system. Furthermore, the downtime is several times shorter in direct comparison, and a modernisation project can be completed significantly faster.

Modernisation of the 46-MN and 100-MN water hydraulic presses at Stupino Metallurgical Company (SMK) in Russia

In terms of technology, the Stupino Metallurgical Company, or SMK for short, is the leading manufacturer for high-alloyed nickel alloys, special steel and aluminium for the Russian aerospace industry. The modernisation of the 46-MN and 100-MN closed-die forging presses was performed in cooperation with Siempelkamp Maschinen- und Anlagenbau GmbH & Co. KG. Siempelkamp did the entire electrical control systems and control stations of both presses were rehabilitated, and the assembly and piping installation work was performed. Furthermore, a tool heating system was adapted on the 100-MN closed-die forging press. The entire scope of supply for the water hydraulics was covered by Hauhinco, and included the drafting, design, manufacturing and testing.

Conversion of the 46-MN closed-die forging press into an open-die forging press

If we first consider the 46-MN closed-die forging press, the task was to convert a water hydraulics closed-die forging press, originally built by Fritz Müller Pressenfabrik, into an open-die forging press. Due to the complexity of the task and the tight schedule, this conversion could only be performed by a specialist with considerable experience in conducting such projects. The challenge for Hauhinco lay in achieving significantly higher dynamics for the open-die forging press, as compared to the closed-die forging press. The hydraulic and electrical control systems were specially designed and built for the new mode of functioning.

In order to achieve stroke rates of over 40 strokes in finishing operation, it is necessary both to tailor the hydraulic control systems to the new mode of operation and installation conditions, and to reinstall the entire pipework. When designing the piping, special attention was paid to ensuring that the piping plan and dimensioning facilitate easy flow of media, in order to achieve the substantially higher speeds and the high number of press strokes. A low-pressure shock absorber was therefore specially built by Hauhinco for the requirements of this press, in order to control the high flow speeds and the volumes of water being moved by the low-pressure supply during the rapid empty runs. Despite the high dynamics of the press, it was naturally also necessary to ensure high precision from the moving beam positioning system, and position reproducibility. In respect of safety, special load safety valves were used to prevent unintended dropping of the moving beam, even in the event of the high-pressure system and control pressure failing.

The 46-MN open-die forging press project also included the press cylinder control system developed by Hauhinco, the pullback cylinder control system, the hydraulic control system for table movement, the high-pressure locking system, the filling valve for the press cylinder, the 2/2-way valve for controlling the level in the low-pressure tank, and the filter stations of the control pressure supply system. In accordance with the company philosophy of "water hydraulics main valves with water hydraulics pilot valves", the control pressure supply system is likewise designed consistently using water hydraulics. All hydraulic control systems were equipped with a specially developed proportional valve technology, in order to ensure precise positioning and speed adjustments.

Modernisation of the 100-MN closed-die forging press

The 100-MN closed-die forging press to be modernised works with three equivalent vertical press cylinders, two compensating cylinders and two pullback cylinders and was originally built by the Schloemann AG. When designing the hydraulic control system, the focus was on improving positioning precision, both at very high and at very low speeds. This was achieved by means of multi-stage arrangements and different switching options for the proportional valves. This makes the manufacturing process both reproducible and documentable, meeting the manufacturing process requirements of the aerospace industry in their full scope.
Through the individual actuation of all three press cylinders, and through the use of the Hauhinco proportional technology in interaction with the control electronics, the press is capable of ensuring that the moving beam remains parallel, even during eccentric pressing processes.

Hauhinco paid particular attention to the safety devices when designing the 100-MN closed-die forging press. In order to avoid unwanted sinking movements, a safety control system was installed for each of the pullback and compensating cylinders. Alongside the hydraulic control systems for the main press movement, the scope of supply also included the actuation of one internal and one external ejector, and the table movement system. Just as with the 46-MN open-die forging press, the filling valves, the high-pressure locking system, the 2/2-way valve for controlling the level in the low-pressure tank, the filter stations of the control pressure supply system, and the engineering of the new piping plan were components of the project. One decisive price advantage during the modernisation of the two presses was the incorporation of the existing water pressure station. This supplies both presses with high pressure, and was retained in full.

Summary

The modernisation of water hydraulics presses is a practical option, even for very old systems, and represents an alternative to completely new investments, as both today's requirements for the manufacturing process and the high safety standards can be fulfilled in this way. During a modernisation process, existing high-cost system components can continue to be used. As a result, professional modernisation is usually an economically practical decision, for which the overall costs are several times cheaper than the investment costs of a new system. Hauhinco is able to implement even extensive modernisations with relatively short downtimes. Optimisations and necessary production process adaptations can often be achieved with a variety of modernisation options. Even new modes of functioning for the press movements can be realised. These approaches provide companies with new production capabilities, amongst other things by increasing the production speeds, precision, and ease of operation of the systems. Automated and reproducible manufacturing processes, and the documentation of the same, are indispensable for modern production facilities. When it comes to the bottom line, the aforementioned measures ensure higher product quality, greater reliability, and hence also increased competitiveness.

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