Hydraulic plant philosophy
The traditional machines have always been characterized by an engineering foreseeing big tanks under pressure, the so called accumulators.
Such systems are subject to periodical revisions and controls from the part of the Bodies appointed by the Public Administration Authority. As a matter of fact as time passes by and also as a consequence of the corrosive action of the fluid, their trend is to deteriorate and therefore to get even dangerous. The checks foreseen are meant to control their compliance and endurance and eventually, if they proved to be not complying with their strict technical specifications, they are derated. When un accumulator get derated that means that its use in the circuit of the press has been accepted but it must work then absolutely under a lower pressure, which is established time by time by the Body in charge during its inspection. This entails that a lower force will be available to the press, thence by derating the accumulators, automatically also the press get derated. The components forged which before the periodical control of the accumulators proved to be perfect may then prove to get refused or even no more forgeable since the press has become too small. It is necessary to underline that such control activity can lead to some Machine-stop even of 3÷4 weeks. A system realized in such a way, foresees the use of a series of pumps having a fixed flow rate and which do pump continuously the fluid into the accumulators under the max pressure. In this way the energy wasting is maximum since the fluid which had been pumped under the maximum pressure is used also when only low forging forces are needed, and therefore by the maximum energy wasting.
In order to face this troublesome matter characterizing the 'old conception' machines the new TDS series definitely eliminated the use of the accumulators and of any tank under pressure. In this way the TDS series drastically reduces the Plant-stop and increases the average rate of machine availability to be working and always at its max nominal pressure.
It was possible to get these evident technical advantage by the use of a single tank small sized, under no pressure but always outdoors, equipped with its corresponding dust-proof protection devices. Even some pumps equipped with pistons, no valves, and having a variable flow rate are used. Such pumps are driven by electric three phase motors which are coupled directly to the pumps. The pumps are kept at zero flow rate at every pause or when the machine is not working and the corresponding motors are set at the minimum rotation (it is even possible to stop them by a suitable drive) and in this way the maximum energy yield is assured. In the forging phases the machine will be working in its maximum energy yield conditions since the pumps' flow rate percentage and the motors' rotation speed are adjusted.
The electrical Power yield is about 95% , its net cosφ being equal to 0,89÷0,90.
The benefits deriving from that are noted immediately during the production of the forged components: high speed forging is available, in an absolutely controlled manner, and a continuous thermic addition to the piece being forged is available so that the thermic losses of the material being worked are fed and therefore the forging time, before re-starting the heating in the oven is remarkably lengthened. In many instances the components which had to be set into the oven once again in order to end the forging, can now be obtained by a single heating. For this reason the machine has been equipped with remarkable installed electric power. Such power has been fractioned, therefore is possible to work even by two, three pumps at the same time and therefore once again some energy will be saved, thence the incidence of the electric energy on the piece will be always the smallest possible.
The new TDS series differentiates very clearly if compared to the traditional presses also due to the limited quantity of piping present in the press. Muraro applies the necessary cartridge valves directly onto the bottom of the various cylinders; such valves are needed for the working of each single cylinder, therefore the quantity of piping and joints is minimum and the answering time in each single movement will be the quickest one.
The tank has been carefully studied in order to be the very smallest possible. If compared to a traditional machine the capacity of the tank of TDS series has been reduced to one-tenth of what it was. A huge series of benefits outcomes thereof.. Tank's installation into the foundation is no needed any more. The tank in the new TDS series is placed on the top directly next to the cylinders groups and to the corresponding valves. This grants the pumps a slight over-feeding pressure which lenghtens their life and endurance considerably. First of all, at the first filling, 90% of oil is spared if compared to the traditional machine, the same is true as per the following periodic oil replacements. Thanks to this considerable oil saving oil replacement will be no more considered as an unbearable cost. Less of oil in the tank means that also the risk of a possible fire is prevented. In this respect the TDS series has been arranged in order to be able to work using non-flammable, synthetic and up to 400°C self-extinguishing, oil. Such characteristic is enough to avoid being obliged to arrange for the fire-fighting plant.
In traditional machines the huge quantity of oil permits the exploitation of its huge mass as a 'thermic lung”. The TDS series for such reason has been equipped with a series of efficient oil-water heat-exchangers for its thermic conditioning, working by tower water at the temperature of 30°C. It is also equipped with a continuous 10 micron filtration system. The system thus conceived permits the use of the oil for very long periods. The oil replacement is suggested every 45’000÷50'000 machine working hours.
The typical environment of a forge shop is particularly aggressive and the press get to be working at a temperature and in a general environment quality conditions which certainly are not likely to preserve it. The sealings or gaskets mounted in the traditional machines are made of plastic. By working in very difficult conditions and since they get weared out very easily due to their nature, such gaskets do not last very long. As a matter of fact, it is necessary to programm at least one Machine-stop per year in order to replace such sealings. When its sealings get weared out then the press is likely to be no more able to keep the position in which it was installed, get under pressure very hardly and the nominal force of the press is not attended any more. It may happen that a part of the oil leaked from the sealings get into the forging zone and then it is possible to contaminate such area and to make it dangerous since oil is easily flammable. The replacement of sealings in a medium-large sized press can be very onerous under an economical point of view and very complicated and also quite long as far as the Machine-stop duration is concerned. As a matter of fact replacing the wearings present in the pistons' heads requires suitable lifting means and however mounting and dismounting are very delicate operations even if they are carried out by a highly qualified personnel.
The new TDS serie solves radically this matter which is very well known to every forge man in the world. Sealings are made of a plastic material no more! Every sealing easily wearable has been replaced (the ones working under high pressure) with mechanic sealings. Mechanic sealings, the so-called “elastic bands or metallic segments” are granted by Muraro to be lasting at least 30 years in continuous service and without it being necessary to control and/or replace them. The mechanic sealings which are mounted work by the same principle as the ones which the cars' internal combustion motors do use, just imagine how many cycles can the motor perform in a single working year. The difference between the motors' and the presses' pistons is that the first ones work in a dry condition and at a high temperature while the second ones do work at very lower temperatures and get always lubricated by the oil itself. That is the reason why such metal sealings can be granted for so long a time.
As it can be easily understood, the mechanic sealing is not perfectly oil-proof, therefore if a small quantity of oil leaked from the piston, this problem is generally considered to be unaffordable. That is not the case, this is the reason why the TDS series uses a small gear-pump to compensate such leakage and then allows for its suspension at the pre-determined altitude. The consumption of such small pump is quite low on the contrary the benefits arising from such type of sealing are quite important. The bigger costs of such sealing are widely compensated during the normal service of the machine, they are refunded starting from immediately and all the plant's life long.
The frame of the new TDS series is monolitic type as far as this does not cause prejudice to its transportability, alternatively the frame is divided into various parts. In this case the frame is kept together by special tie rods which precharge it. In this way the max structural steadiness and an elevated working precision are granted at the same time and every annoying elastic movement of the machine during the pressing operation are drastically reduced, which would only cause an early ageing of the structure and some energy wasting all the machine's life long.
This max structural rigidity enormously easens the production speed and the high number of the strokes which can be carried out by the machine while finishing or hammering the products.
A further organ very easily wearable consists of the guides of the mobile table (traverse) of the press. As a matter of fact when charges are not completely centered to the principal forging axe of the machine, then guides do wear out in a non distributed and non uniform way. Often some operations which apparently seem to be harmless do wear out the guides too early and one is compelled to stop the machine since an extraordinary maintenance has become necessary. In the traditional presses it is not always easy to replace a guide, sometimes this operation proves to be very expensive both as far as either time or money are concerned. The worst mistake which can be done in such cases is to try to go further under such conditions. The machine will start then to work bad and some other damage much more serious than the only guides' replacement or restoration might be caused.
TDS series improves considerably in this regard. Every special guide mounted in the machine is made of anti-wear steel very hard (Hardox 400) and the counter-guides present in the mobile table are made of bronze aluminum-forged, this one also is very hard. On the bronze guides some special slots with no exits are realized. They are properly fed by a suitable fat under high pressure (standard is 400 bar) and the lubrication fat by intervals programmed is pumped into the control system. Intervals are managed in a dynamic and not static way.This means that the customer will get a remarkable fat saving since the electronic system can recognise the machine actual lubrication needs. Every indepedent lubrication group is properly monitored by a contemporary screen signaling the eventual anhomalies.
In order to easen the task of the technicians in charge of the maintenance every mechanic part concerned with the sliding guides of the machine can be adjusted externally and are easily replaceable by new unified spare parts, without it being necessary to dismount big parts of the machine. That was made modular and inter-changeable without using any big lifting means. The eventual spare parts to be stocked are quite few. The customer then can become completely self-standing and does not depend from the manufacturer of the machine any more, not even for the spare parts!
The benefits which can be enjoyed immediately after the first press ordinary maintenance are enormous. By this solution it will be no more necessary to dismount big parts of the machine or to arrange for heavy revamping by machine levelling workings in order to avoid its being partially dismounted, i.e. huge saving as far as costs and time are concerned.
Every new Muraro press is fed, controlled and protected by the last generation SIEMENS devices which properly interfaced with an industrial PC and a LCD Touch Screen of wide dimensions can be easily programmed and managed either for the manual, or the semiautomatic, or the completely automatic machine's cycles. The above results to be inter-faceable with the free of charge Muraro remote assistance service.
It is possible to work at a controlled speed in order to be able to work in the fields of speed and deformation imposed by the various materials with the contemporary possibility to register everything. Every registration can be saved in the form of a graphic or a table and it is possible to print them with reference to each component realized. A customizable certificate may be joint to each product stating its deformations, the forging speed and what else is required in order to be complying with current rules with ref. to the various components' final application fields.
TDS Series Fittings
The TDS series foresees a series of fittings especially useful for specific workings and when some extreme precision and repetitivity are required together with working times extremely low, thence the reheatings of the materials being worked are minimized.
- indexed of: 90°+90°+90°+90°
- controlled on 36'000 positions and then integrated in the general control of the machine
- upper rotating table qualified for the sensitive manual rotation, with rotation:
- Side centrators working between the uprights of the machine and able to center and to lift both the devices in the working stations of the principal lower sliding table and the ingots and/or the various pieces being worked. By these fittings it is possible to center, lift and deposit in the middle of the various working stations arranged in the principal sliding table and to obtain then n°3÷4 or even more working operations, without it being necessary an external aid and in a very short time.
- Upper dies bearing rotating arms. The upper mobile table can be equipped with 1 or 2 rotating arms able to hold the various equipment. These ones are very easy to be replaced outside the machine and when desidered each arm will care for the insertion of the desired equipment into the center of the machine under the upper rotating table and therefore the replacement of the upper die will be quick and sequential. In this way particular formings of shaped pieces can be obtained by progressive re-takes.
- Lower ejectors. Various models are available, their dimensional characteristics are various, they can work in the middle and/or outside the machine, however they always work in the middle of the various stations arranged for in the lower principal sliding table. Such ejectors, if properly dimensioned in order to exercise suitable working forces, can be used to carry out drillings by extrusion, working from the bottom upwards, to obtain cylindrical holes without it being necessary to use the charcoal for the extrusion of the extrusion plugs. In this way the working environment will be much more clean if compared to the traditional system.
- Drilling and bottom removing device. Various models of drilling and/or bottom removing devices are available, they can be mounted onto the upper principal vertical mobile table, in order to remove the bottoms left on the piece after the hole extrusion. Our drilling devices are, all of them, equipped with a suitable quick punch and ejection rings replacement system. The working procedure can be programmed in order to be working manually and/or automatically. Drilling and ejection of the punch are carried out without moving at all the piece being worked in order to make it easy the re- taking of the drilled piece even by an eventual automatic manipulation system.
- Dies blocking system. All these last generation machines can be equipped with modern hydromechanic device blocking and unblocking systems which are able to understand when a die is hooked and blocked in every possible machine working station.
- Automatic die replacement system. A suitable series of dies' stocks are available in which it is possible to precharge various dies, in order later on to carry out the automatic die replacement in any moment without any manual human intervention. It results then to be possible replacing a die on which a piece has just been forged and which then is extremely hot. The die replacement can be programmed electronically to be working by automatic cycle too and synchronized with the machine. The above once again to reduce drastically the products manufacturing times and to reduce thence the number of the following reheatings to complete the necessary forging operations.