Hydraulic forge
High performing forging processes
For thousands of years forging processes have been a very effective way to produce high quality steel. Just think about the warriors' swords, which, from time out of mind, have been manufactured by skillful blacksmiths using coal forges, hammer and anvils. Such procedure, passing through the steam-hammers of the industrial revolution, has survived till nowadays by drawing new sap from the modern technologies. Instead of swords weighing only a few kilos, today the processes forge parts weighing tens of tons. The blacksmiths' expert hands do not clutch anymore hammers and red-hot pieces but they softly start accurate joysticks which, thanks to Bus communication systems, control closed loop systems capable to generate powers worth thousand of tons which are accurate to tenths of millimeters. The modern forging processes preserve of this ancient work only the charm of modeling metal using the intelligence of man, such charm being raised to the nth power thanks to the use of the modern technologies.
Nowadays forging processes are more and more used to manufacture high performing metal pieces with complex shapes. In comparison with processes based on metal fusion, the special fiber conformation obtained by forging makes forged pieces high quality elements and gives them a microstructure which is further more resistant to mechanical stresses. This is the reason why forged pieces are used in all industrial sectors: from aerospace to energy (in particular wind and nuclear), from naval to general mechanical engineering and many others.
Thanks to its proportional hydraulic controls and to the digital technology, Duplomatic Oleodinamica guarantees in all these sectors high level performances and reliability.
The basic features of a modern forging plant are reliability, speed, accuracy and energetic efficiency. A high forging speed allows to process the piece before it gets cold and therefore a fast press can create complex details with a single heating session, thus allowing to save considerable energy and time. The press of our application has a maximum working speed of 100mm/s, a maximum force of 2200 tons and an installed power of 1200kW.
The basic features of a modern forging plant are reliability, speed, accuracy and energetic efficiency. A high forging speed allows to process the piece before it gets cold and therefore a fast press can create complex details with a single heating session, thus allowing to save considerable energy and time. The press of our application has a maximum working speed of 100mm/s, a maximum force of 2200 tons and an installed power of 1200kW.
The press consists of a main single-acting cylinder starting the moving cross rail and of two cylinders performing the upward movement. The cross rail downward movement occurs by gravity during the manual functioning mode; in this case a big pre-filling valve, which allows flows up to 15,000 liters/min., guarantees the filling of the cylinder. When the cross rail touches the piece, the valve closes automatically and the oil flow sent into the cylinder by all the pumps lets the pressure increase up to a value capable to overcome the strength of the red-hot steel to be processed. The pumps are axial units with variable displacement which are started by electric motors and are supplied with power control: as a consequence the press can guarantee high speed processes with medium-low loads (finishing) and, at the same time, it allows to reach high pressures necessary during some specific phases of the process, when a high-level warp occurs. The distinctive feature of this plant is the lack of control valves between the pumps and the main cylinder: such a condition allows to reduce to the minimum the pressure drops and allows the system to deliver very high performances. The valve block has the task to pipe the flow of all pumps to the main cylinder, thus guaranteeing a safe system operation and allowing to disconnect each pump singularly.
The cylinder downward movement is controlled by contact-free magnetostrictive sensors. When the cylinder reaches the preset position, i.e. when the forger decides to stop the warp procedure, a high performing servo valve carries out the cylinder decompression and discharge. The decompression is a very important phase for these plants as it must be fast in order to ensure a good level of accuracy of the forged piece but, at the same time, it does not have to generate too high instant flows which might damage the circuit itself. The used valves allows to regulate flows of thousands of liters per minute with response times of about 10 ms. As a consequence, the plant repetition capacity is about 0,5 mm, thus delivering finished pieces featured by smoothness and accuracy. The upward movement is controlled by a DSPE8G closed loop proportional valve.
The cylinder downward movement is controlled by contact-free magnetostrictive sensors. When the cylinder reaches the preset position, i.e. when the forger decides to stop the warp procedure, a high performing servo valve carries out the cylinder decompression and discharge. The decompression is a very important phase for these plants as it must be fast in order to ensure a good level of accuracy of the forged piece but, at the same time, it does not have to generate too high instant flows which might damage the circuit itself. The used valves allows to regulate flows of thousands of liters per minute with response times of about 10 ms. As a consequence, the plant repetition capacity is about 0,5 mm, thus delivering finished pieces featured by smoothness and accuracy. The upward movement is controlled by a DSPE8G closed loop proportional valve.
The press can also perform automatic working cycles, where the only task of the operator is to control the right performance of the operation sequence. In particular conditions the press can even perform more than 80 cycles per minute with harmonious and smooth movements. In such a case the accuracy and the low response times of the Duplomatic valves play a fundamental role.
Apart from the main slide, the machine is supplied with a movable carriage used to move the lower hammer. The carriage is started by a closed loop controlled cylinder which is enabled by a DSPE8G proportional valve with integrated electronics and regenerative spool. Such a solution allows to obtain a symmetric behavior of strengths and speed even using a double acting cylinder with non-double-ended piston rod. Such a condition is particularly suitable to this specific application where the same control power is required in both directions.
The plant is completed by a system with two controlled axis for the automatic change of the equipment, which, also in this case, is managed with accuracy and reliability by the DSPE8G valves.
Particular care has been placed in the fluid conditioning, which is obtained via a specific recirculation pump which sends the oil first to a high performing filter and afterwards in the heat exchangers, whose activity is fortunately limited. The level, the oil temperature in the different strategic points of the circuit and the contamination degree (due to solid particles and water) are constantly monitored by a diagnostic system which guarantees stable fluid conditions and, as a consequence, a high reliability of the hydraulic circuit.
The forging manipulator is a very complex machine as it must be able to move cantilevered high loads of red-hot steel which require an extremely heavy structure capable to create a balance during the reversing process. The manipulator must also be fast and accurate, both during the transfer movements (back and forth) and during the movements of the pliers (vertical, oscillation angle, rotation, pliers control, horizontal transfer). The manipulator must also be compact in order to be able to move easily in every available space.
The forging manipulator is a very complex machine as it must be able to move cantilevered high loads of red-hot steel which require an extremely heavy structure capable to create a balance during the reversing process. The manipulator must also be fast and accurate, both during the transfer movements (back and forth) and during the movements of the pliers (vertical, oscillation angle, rotation, pliers control, horizontal transfer). The manipulator must also be compact in order to be able to move easily in every available space.
The manipulator core is an hydraulic circuit consisting of a closed-circuit hydrostatic system for the transfer movement, an open-circuit system for all movements of the pliers and a steering system. An offline filtering and cooling circuit is also present, which uses an effective hydraulic fan-drive capable to control the fan revolutions according to the oil temperature; as a consequence the system works producing a very low noise and with a low energy consumption when the machine working conditions do not require to dissipate a high thermal power.
The open circuit uses the "Load Sensing" technology which regulates the pump pressure and flow rate according to the circuit real needs. The absorbed power, therefore, is constantly slightly higher than the one really used: the offered advantages are energy saving and machine control. Such a technology usually foresees the use of specific valve banks, similar to those mounted on the earthmoving machines. Considering their application, such components have some limits as to the control dynamics and the possibility to be mounted in suitably built blocks, which are often necessary due to the small available spaces.
The problem has been solved by Duplomatic by developing a special valve supplied with a pressure compensator and some piloting circuits. Such valve, which is sandwich-mounted on a normal Cetop 8 plate, allows to operate the DSPE8G proportional valves with a fixed preset pressure drop, thus creating a proportion between the control and the movement speed independently of the load. This is an advantage for the control and the dynamics of the system. Inside the valve block there is a special logic for the piloting control which allows to pilot the pump simulating the functioning of a real Load Sensing system and to manage at best the maximum pressures of each load.
The problem has been solved by Duplomatic by developing a special valve supplied with a pressure compensator and some piloting circuits. Such valve, which is sandwich-mounted on a normal Cetop 8 plate, allows to operate the DSPE8G proportional valves with a fixed preset pressure drop, thus creating a proportion between the control and the movement speed independently of the load. This is an advantage for the control and the dynamics of the system. Inside the valve block there is a special logic for the piloting control which allows to pilot the pump simulating the functioning of a real Load Sensing system and to manage at best the maximum pressures of each load.
Immediately from the beginning this system has shown excellent stability and dynamics and is one of the best elements of this machine.
The use of Duplomatic valves allowed to concentrate into a single block all the functions of the open circuit, thus streamlining the hydraulic lines with consequent increasing reliability and decreasing overall dimensions and costs.
Furthermore, the presence of high performing proportional valves, such as the DSPE8G valves with integrated electronics, allows the use of control loops on some specific movements. Such a feature has turned out to be very useful to simplify the work of the operator during some repetitive phases.
The manipulators can be started via an electric motor, they can be mains powered via aerial cable or endothermic engine (diesel or gas) for the highest movement freedom. All manipulators are equipped with a conditioned operator's cab, which allows the operator to work in comfortable acoustic and thermal conditions, and with a touch-screen system for the setting of the working parameters and of the diagnostics. These and other features allow to obtain good results during the whole working shift.
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