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Hirschvogel has already opted on two occasions over the last two years for Fagor Arrasate’s transfer technology, for two identical systems. The two 2000-ton twin presses were awarded first in 2015 and the other in 2016. The first press commissioned successfully in January is already producing parts in China and the second is currently in the assembly process on site in the new plant of the Bavarian firm in Mexico.
Hirschvogel, with headquarters in Denklingen (Germany), is one of the major suppliers of steel and aluminum forged and machined parts as well as widely known for being in the forefront of the technique within its sector. Customers include all the world’s Tier1 and OEM automobile manufacturers. Besides the Denklingen headquarters, the company with a workforce of about 5.000 employees and a consolidated turnover of around 1,011 billion euros has subsidiaries in Germany, China, North America, Mexico, Poland and India.
The last project with Hirschvogel fits perfectly with the strategy of Fagor Arrasate, which is focused on remaining one of the world references in the supply of robust, complex transfer presses designed according to the customer’s requirements. The project we are currently referring to also meets the objective of the Forging product consisting of continuing to promote and develop mechanical, vertical transfer presses of a certain size and working in continuous operating mode. The eccentric kinematic chain presses (as in the case of this project), which are typically used in the warm forging, or the kinematic chain knucle-joint presses, which are usually used in the cold extrusion, are included among the forging presses for operating in continuous mode offered by Fagor Arrasate.
A key factor to the success of these developments is the close relationship of both technical teams and Fagor’s focus on recognizing and adhering to its customers technical demands. Fagor’s vast expertise in forming systems allows its technical team to adapt its designs to meet the requirements of Hirschvogel’s forging processes. This played a major role in their selection of the systems provider. The off-center working stations on the center of the die space, the adaptation of the servo-driven ejector of the bed and other critical solutions that have been implemented in the machine thru the course of the project, which are described below in this article, are some examples of the result of this joint effort.
Warm & Hot Forging Mechanical Presses
The entire system can be divided into four main subassemblies: press, bed ejector, slide ejector and transfer.
In order to counteract the effects of the previously mentioned high forces, several measures have been taken into consideration during the design phase. Among them: increasing the distance between the guides, increasing the structural integrity of the fabrications, adding stiffening elements and prioritizing the durability of the critical areas during the design.
In addition to the previously mentioned measures required to reduce the stress in the machine and increase its durability, another specific measure taken in this type of press was to overcome the eccentric loads. Focus has been redirected to shifting the stations so stations 4 and 5 are more towards the center of the die space.
This decision, which was made at the beginning of the design of the machine and involved the displacement of the ejection systems of the bed and slide, was the result of the study carried out by Hirschvogel, with which it was concluded that most of the critical parts intended to be processed in this machine would require higher stresses at the last stations.
The bed ejector is the section where Hirschvogel and Fagor Arrasate have most closely collaborated during the definition of the project. Although Fagor Arrasate has numerous ejector designs in its portfolio including the servo-driven ejector, Hirschvogel needed a servo-driven ejector with a different behaviour.
The servo-driven ejector the equipment was provided with, which is explained in this article, does not require each one of the pins of each station being capable of moving upwards separately or the automatic adjustment of the travel of each one of the pins, such as the original servo design of Fagor Arrasate. Notwithstanding, it requires that the force exerted by each pin be effective throughout its travel and that each one of the pins be operated separately at the time of moving downwards from the TDC.
The lifting of the pins of the bed ejector is carried out jointly for all the pins thru the motion produced by the two cams mounted on the same shaft, so that as it is a fully mechanical system, the lifting degrees are constant (80°). The starting point for the lifting is adjustable and can be selected by the user from the control panel, within a range from 145° to 210°.
On the other hand, each one of the ejection pins has been equipped with a separate servodrive, which allows both the start and end points of the pin movement in the downward motion to be adjusted. This system makes the downward motion of the bed pins fully programmable from the control panel.
Since each one of the pins downward motion is independantly servocontrolled, It is now possible to minimize the amount of ejection curves to be stored.
Each one of the ejection pins is secured by means of an electronically controlled mechanical fuse which fails in case there is an interference with the slide and the force on the pin exceeds the rated operating force. The status of each fuse is electronically controlled and, in the event of any of them failing, the press shall be stopped and a warning shall be displayed on the screen.
The slide ejector like the bed ejector are intended to eject the part once the forging operation has been carried out and, in some cases, hold the part as long as it is in the upwards position to be gripped by the transfer. Unlike the bed ejector, the torque and power necessary to eject the part comes from the press crown in the slide ejector.
The power and movement transmission from the crown to the ejector is carried out through a set of levers, which connect the kinematic chain to the ejection system and make the relative movement of the ejector in relation to the slide possible.
The experience and know-how of Fagor Arrasate allow the slide ejector to be designed, in the course of the definition phase of the project, for it to carry out the exact ejection curve required by the customer, in such a way that the customer shall be able to choose the time at which it is intended to eject the part as well as the point the maximum travel shall be performed.
Fagor Arrasate, with the introduction of the servomotors into the market, has designed servo-driven systems which have allowed quick changes to be carried out to the ejection curve, without having to make any mechanical adjustments. This improvement in the system has increased significantly the flexibility of the machine by means of the reduction of the reference changeover time.
However, in order to achieve this flexibility and dynamic capacity of the ejector, it is necessary to install large servomotors which demand excessive power at the time of the highest force of the ejector, making the necessary power at that time increase significantly.
The way of reducing the installed power in this case has been that of taking the necessary energy for the ejector from the inertia flywheel. Thus, when the motors of the ejector demand the power peak, the motor of the main drive turns into a generator mode absorbing the kinetic energy from the inertia flywheel and redirecting it to the servomotors of the ejector. To put it in other words, an electronic cardan has been developed for the ejector.
The ejection work, in relation to the forging work, requires very little energy. It is estimated that when the press operates at its maximum capacity, the energy required for the ejection might reach about 2% the maximum forging energy. This ejection energy, although it is very little, must be instantaneous, so that the required energy is significant.
With the electronic cardan, as well as keeping the flexibility the servo technology offers, the installed power is not higher than power installed in machines where the ejector is driven from the crown by means of a mechanical cardan.
Prior to implementing the electronic cardan in the project, the engineers from Fagor Arrasate worked with their R&D group to develop a prototype of electronic cardan. The result was it performed exactly as theoretically expected.
It should be noted that the machine supplied to Hirschvogel shall be the first press at the global level where the “electronic cardan” shall be used.
From an ecological point of view, as well as the fact that the servomotors controlling the lifting operation of the ejector reuse the energy accumulated in the inertia flywheel, the servomotors controlling the downward movement regenerate about 5kW per cycle.
INTEGRATION OF THE LINE
Within the forging line, the press of Fagor Arrasate is the machine governing the other sections of the line, that is, it is the master of the line or the “ID controller” of the whole process.
This integration of the “Controller device” is used in equipment based on programmable logic controllers, where the controller is capable of managing remote modules such as the transfer, the induction furnace, the conveyor belts or the loaders.
In the event that the press detects any anomaly or the operating conditions are changed, these set points are transferred to the other peripherals becoming themselves adapted to the new conditions that have arisen.
HIGH PROTECTION TO THE PROCESS LUBRICATION
The complex environmental conditions a warm forging press operates at, where the lubrication of the machine, the transfer and the process lubrication have to operate separately, involve taking certain specific measures providing the isolation of the different lubricants and ensure a proper operation of the machine and the forging process.
The first important measure implemented in this type of machine, in order to keep the oils of the process and machine separate from each other, is that of protecting most of the exposed areas of the machine so as to avoid a direct projection of the lubricant of the “forging process” onto these surfaces. For that, specific guarding and way covers have been incorporated protecting the most exposed areas of the crown and dies space. In addition, the machine has been equipped with a series of ducts which redirect the oil of the forging process falling on the bed and return it into the lubrication unit.
Other measures that should be taken based on Fagor’s experience is that of treating the air used in the press. The air filters used in the oil pans of the guides and the centralization of the exhaust of the pneumatic cylinders at the uprights, are an example.
Moreover, it should be noted that both the piping and the hydraulic joint elements exposed directly in the working area are manufactured with anti-corrosion materials and wiring is properly protected in accordance with all safety regulations.
Due to the fact that the mist of the process lubrication existing in the environment is mixed with the oil of the machine lubrication, a special decanting and filtering treatment of the press lubrication oil has been carried out. A special hydraulic unit has been used for this purpose, which is divided into two tanks: the first one has a double wall or partition with which an optimal decantation is carried out and all the ferromagnetic particles are removed. The oil, once it has passed through a series of special filters, processes to the second tank where it passes again through another filtering process.
The trust that Hirschvogel has placed in Fagor Arrasate thru these development years places Fagor Arrasate as one of the few global suppliers capable of offering a fast and reliable mechanical transfer press for forging, equipped with state-of-the-art technology and fully adapted to the customer’s requirements.
The dynamics of change and the current level of demand in the automotive market, which launches hundreds of new models a year and requires from its suppliers to deliver the parts just in time, forces to these suppliers to keep the highest levels of productivity, flexibility and efficiency in their production plants. This is the scenario where the transfer presses for forging take on special importance and provide a high added value to the production chain and response capacity from forging companies. That is the reason why, Fagor Arrasate has committed themselves to being at the forefront of the transfer presses for forging and developing different systems together with their customers, which provide their transfer presses with a higher flexibility.
Fagor Arrasate, with these two new projects, has proven that they are not only capable of manufacturing transfer presses for forging with excellent quality, but also are willing to listen to their customers and manufacture solutions to satisfy the demands from the highly skilled technical teams of its the customers (those of production, planning, process and maintenance).