Abrasive water-jet cutting machine

An abrasive water-jet cutting machine, comprising pumping means, fluidly connectable to a water source, a cutting head, comprising a mixing chamber, a dispensing system of powdered abrasive material, comprising a tank, a supply tube and an actuator interposed between the tank and the supply tube, which delivers the powdered abrasive material contained in the tank into the mixing chamber, through the supply tube; wherein the cutting head mixes, in the mixing chamber, the abrasive material with the water jet forming a water-abrasive material mixture jet, and said cutting head delivers the water-abrasive material mixture jet; wherein the powdered abrasive material delivered into the mixing chamber is homogeneously dispersed in suspension in a water-based gelatinous fluid; and wherein the actuator is a peristaltic pump.

CROSS REFERENCE TO RELATED APPLICATION

This application is related to and claims the benefit of Italian Patent Application Number 102020000006010 filed on Mar. 20, 2020, the contents of which are incorporated herein by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates to an abrasive water-jet cutting machine.

BACKGROUND ART

Abrasive water-jet cutting machines are machine tools which carry out the cutting and shaping of work pieces by means of a jet of a water-abrasive material mixture. Such technology is known as “abrasive water jet”.

Generally, abrasive water-jet cutting machines comprise:pumping means, fluidly connectable to a water source, for the generation of a pressurized water flow;a cutting head, comprising a primary nozzle, a mixing chamber and a focusing nozzle,where the pressurized water flow from the pumping means is conveyed into the primary nozzle of the cutting head where the pressure energy of the pressurized water flow is converted into kinetic energy so as to form a water jet, and in which said water jet is then conveyed into the mixing chamber;a gravity dispensing system of powdered abrasive material, comprisinga tank (e.g., a hopper) containing powdered abrasive material,a supply tube, which fluidly connects the tank to the mixing chamber of the cutting head, in which the powdered abrasive material gravity dispensing system delivers said powdered abrasive material into the mixing chamber of the cutting head through the supply tube;

in which the cutting head mixes, in the mixing chamber, the powdered abrasive material with the water jet, thus forming a water-abrasive material mixture jet, and said cutting head delivers the water-abrasive material mixture jet through the focusing nozzle.

The gravity dispensing systems of powdered abrasive material have several critical issues. In particular, such systems are excessively inconvenient when used to perform finer and more precise cutting processes, i.e., for so-called “micro Abrasive Water Jet” (μAWJ) processes.

Specifically, μAWJ processes require the use of low abrasive material mass flow rates (less than 20 g/min) and the use of powdered abrasive material with a finer grain size (mesh greater than #200) compared to the usual one for macro applications (which instead use meshes in the range of #80-#120).

The gravity dispensing systems cannot ensure a smooth and reliable delivery of abrasive material for μAWJ processes. In fact, the gravity dispensing systems have a variability in the delivery of the abrasive material mass flow rate which reaches values around 10%, which is not acceptable for μAWJ-type processes.

Furthermore, the abrasive water-jet cutting machines are often moved by means of handling systems such as, for example, beam, portal, anthropomorphic robotic arm, and such handling systems, when characterized by fast dynamics, generate further critical issues in the constant delivery of powdered abrasive material. Furthermore, the gravity dispensing systems of powdered abrasive material are incompatible with the use of the machine tool in an “overhead” configuration (implemented, for example, by anthropomorphic robots).

A further critical issue of these dispensing systems derives from the fact that the powdered abrasive material delivered by the dispensing system, which is particularly hygroscopic, is negatively exposed to the presence of environmental and process humidity present inside the ducts inside which the powdered abrasive material is conveyed.

In particular, at the interface between the supply tube and the mixing chamber of the cutting head, the hygroscopicity of the powdered abrasive material causes the agglomeration of a stationary layer of powdered abrasive material on the inner supply wall, which progressively reduces the useful section for delivering abrasive material into the mixing chamber, causing undesirable variations in the abrasive material mass flow rate.

In addition, the layer of powdered abrasive material agglomerated on the inner wall of the supply tube is subject to the risk of sudden detachments, which contribute to generating undesirable variations in the mass flow rate of the abrasive material, and which, in the most serious cases, can cause clogging of the cutting head focusing nozzle and damage to the machine tool.

An attempt was made to remedy these problems by using abrasive material dispensing systems according to the “Abrasive Suspension Jet” technology, in which the powdered abrasive material is previously dispersed in a dispersion liquid (for example water), so as to form a “hydro-abrasive” mixture stored in a tank. Such hydro-abrasive mixture is then delivered through a single nozzle for the formation of a pressurized jet of hydro-abrasive mixture.

However, such an abrasive material delivery system is usable only at low pressures (below 200 MPa), which are not high enough to perform cutting processes with the precision required in μAWJ applications.

Furthermore, in order to ensure an adequate dispersion of the powdered abrasive material in the dispersion substance, avoiding unwanted sedimentations, the mass ratio of the powdered abrasive material and the dispersion liquid of the aforesaid hydro-abrasive mixtures must be considerably low. This results in an exaggerated use of dispersion liquid in order to adequately disperse (and deliver) a low amount of powdered abrasive material.

A further problem of the known ASJ abrasive water-jet cutting machines lies in the abrasive material dispensing system. In fact, the known abrasive material tanks, of the hopper type, do not allow to deliver an amount of abrasive material which is constant over time. On the contrary, they provide an amount of abrasive material which decreases over time, due to the progressive emptying of the abrasive material tank placed upstream of the cutting head.

BRIEF SUMMARY

The present disclosure provides an abrasive water-jet cutting machine, and in particular for μAWJ-type processes, provided with a dispensing system for abrasive material having such features as to solve at least some of the drawbacks of the prior art.

It is a particular object of the present disclosure to provide such a powdered abrasive material dispensing system as to ensure a regular and reliable dispensing of powdered abrasive material, even at low dosages of powdered abrasive material (less than 20 g/min).

The disclosure further provides a powdered abrasive material dispensing system compatible with the use of the machine tool in an “overhead” configuration.

The disclosure further provides a powdered abrasive material dispensing system in which stationary agglomerations of powdered abrasive material and other critical issues deriving from the exposure of the powdered abrasive material to environmental and process humidity present inside the ducts in which the powdered abrasive material is conveyed are avoided.

The disclosure further provides an abrasive material dispensing system which also is usable at the pressures required to perform μAWJ-type processes (greater than 380 MPa).

The disclosure further provides a powdered abrasive material dispensing system which uses a smaller amount of dispersion substance to adequately deliver a larger amount of powdered abrasive material.

The disclosure further provides an abrasive material dispensing system capable of delivering a continuous amount of abrasive material, without however causing wear phenomena in the dispensing system.

The present disclosure relates to an abrasive water-jet cutting machine provided with an abrasive material dispensing system according to claim1. The dependent claims relate to advantageous and preferred embodiments.

In a further aspect, a composition is claimed herein comprising a powdered abrasive material dispersed in a gelatinous fluid, as well as the use of said material in abrasive water-jet cutting methods.

According to an aspect of the disclosure, an abrasive water-jet cutting machine comprises:pumping means, fluidly connectable to a water source, for the generation of a pressurized water flow;a cutting head, comprising a primary nozzle, a mixing chamber and a focusing nozzle,where the pressurized water flow from the pumping means is conveyed into the primary nozzle of the cutting head where the pressure energy of the pressurized water flow is converted into kinetic energy so as to form a water jet, and in which said water jet is then conveyed into the mixing chamber;a powdered abrasive material dispensing system, comprising:a tank containing powdered abrasive material,a supply tube, which fluidly connects the tank to the mixing chamber of the cutting head,an actuator, which delivers the powdered abrasive material contained in the tank into the mixing chamber, through the supply tube;in which the cutting head mixes, in the mixing chamber, the abrasive material with the water jet, thus forming a water-abrasive material mixture jet, and said cutting head delivers the water-abrasive material mixture jet through the focusing nozzle;in which the powdered abrasive material delivered in the mixing chamber is homogeneously dispersed in suspension in a water-based gelatinous fluid;and in which the actuator is a peristaltic pump.
Such a configuration of the dispensing system, and in particular of the abrasive material dispensed thereby, allows the control of the hygroscopic properties of the abrasive material. In fact, since the powdered abrasive material is homogeneously dispersed in the water-based gelatinous fluid, it is completely saturated with water, therefore it is immune to the critical issues deriving from the exposure thereof to environmental and process humidity.

Furthermore, since the powdered abrasive material is completely saturated with water and is homogeneously dispersed in the water-based gelatinous fluid, said dispensing system delivers the abrasive material regularly and reliably, even at low dosages of abrasive material (less than 20 g/min).

Furthermore, such a dispensing system is compatible with the use of the cutting machine in an “overhead” configuration.

Furthermore, such a dispensing system also is usable at the pressures required to perform μAWJ-type processes (greater than 380 MPa).

Furthermore, the implementation of a peristaltic pump ensures a continuous amount of abrasive mixture, without causing wear phenomena in the dispensing system.

DETAILED DESCRIPTION

With reference to the drawings, an abrasive water-jet cutting machine according to the disclosure is generally indicated by reference numeral1.

In accordance with an aspect of the disclosure, the abrasive water-jet cutting machine1comprises pumping means2, fluidly connectable to a water source3, for the generation of a pressurized water flow4.

The cutting machine1further comprises a cutting head5, comprising a primary nozzle27, a mixing chamber6and a focusing nozzle7.

According to an aspect of the disclosure, the pressurized water flow4from the pumping means2is conveyed to the primary nozzle27of the cutting head5where the pressure energy of the pressurized water flow4is converted into kinetic energy so as to form a water jet12, and, subsequently, the water jet12is conveyed into the mixing chamber6.

The cutting machine1further comprises a dispensing system8of powdered abrasive material comprising a tank9containing abrasive material, a supply tube10, which fluidly connects the tank9to the mixing chamber6of the cutting head5, and an actuator11which delivers the powdered abrasive material contained in the tank9into the mixing chamber6, through the supply tube10.

According to a further aspect of the disclosure, the cutting head5mixes, in the mixing chamber6, the abrasive material with the water jet12thus forming a water-abrasive material mixture jet13, which is delivered by the cutting head5through the focusing nozzle7.

The focusing nozzle7also has the task, upon mixing the abrasive material with the water jet12, of increasing the efficiency of the mixing and of the transfer of momentum from the water jet12to the abrasive material.

According to a further aspect of the disclosure, the powdered abrasive material contained in the tank9is homogeneously dispersed in suspension in a water-based gelatinous fluid60.

Therefore, the powdered abrasive material homogeneously dispersed in suspension in the water-based gelatinous fluid60forms an abrasive mixture160.

According to a further aspect of the disclosure, the actuator11is a peristaltic pump100.

Such a configuration of the dispensing system8, and in particular of the powdered abrasive material dispensed thereby, allows the control of the hygroscopic properties of the powdered abrasive material. In fact, since the powdered abrasive material is homogeneously dispersed in the water-based gelatinous fluid60, it is completely saturated with water, therefore it is immune to the critical issues deriving from the exposure thereof to environmental and process humidity.

Furthermore, since the powdered abrasive material is completely saturated with water and is homogeneously dispersed in the water-based gelatinous fluid60, said dispensing system8delivers the abrasive material regularly and reliably, even at low dosages of abrasive material (less than 20 g/min).

Furthermore, such a dispensing system8is compatible with the use of the cutting machine1in an “overhead” configuration.

Furthermore, such a dispensing system8also is usable at the pressures required to perform μAWJ-type processes (greater than 380 MPa).

Furthermore, the implementation of a peristaltic pump100ensures a continuous amount of abrasive mixture160, without causing wear phenomena in the dispensing system8.

According to an embodiment of the disclosure, the supply tube10is made of polymeric material.

Advantageously, the supply tube10made of polymeric material further reduces any wear phenomena in the dispensing system8, and further attenuates the pressure oscillations caused in the flow of abrasive mixture160by the peristaltic motion induced by the peristaltic pump100.

According to an embodiment, the cutting machine1comprises an air duct110which converges into the mixing chamber6.

Advantageously, the supply of air by means of the air duct110avoids the risk that the vacuum generated inside the mixing chamber6disturbs the amount of the abrasive mixture160introduced therein.

With a further advantage, the supply of air to the mixing chamber6through the air duct is self-stabilized, i.e., it does not require an external adjustment.

According to an embodiment of the disclosure, the cutting machine1comprises an electronic controller120.

The electronic controller120is configured to adjust the amount of abrasive mixture160delivered by the dispensing system8.

The electronic controller120can be, for example, a PC or a PLC.

Advantageously, the use of an electronic controller120further improves the precision of the dosage of abrasive mixture160.

According to an embodiment, the tank9contains the abrasive mixture160, in which the powdered abrasive material is homogeneously dispersed within the water-based gelatinous fluid60.

According to an embodiment, the electronic controller120is configured to adjust the amount of abrasive mixture160delivered by the actuator11, through an open-loop control180.

Advantageously, the electronic controller120adjusts the amount of abrasive mixture160by adjusting the speed of the peristaltic pump100. Following this adjustment, the dispensing system8self-stabilizes, so as to deliver a regulated and continuous amount of abrasive mixture160to the mixing chamber6.

In particular, the relationship between the speed of the peristaltic pump100and the amount of the abrasive mixture160is given by calibration curves obtained with experimental tests for each type of abrasive mixture.

According to a further embodiment of the disclosure, the tank9comprises at least a first tank130containing water-based gelatinous fluid60, and at least a second tank140containing powdered abrasive material.

Furthermore, the dispensing system8comprises a mixer150interposed between the tank9and the actuator11. That is, the mixer150is placed at least downstream of the at least first tank130and second tank140, and upstream of the actuator11, with reference to the flow direction of abrasive mixture160.

The mixer150is configured to mix the water-based gelatinous fluid60contained in the at least a first tank130with the powdered abrasive material contained in the at least a second tank140, so as to form an abrasive mixture160, and convey the abrasive mixture160into the actuator11.

Advantageously, a tank9thus configured avoids preparing the abrasive mixture in a separate step, and subsequently introducing it into the tank, with the risk of introducing and forming air bubbles which would cause drastic local reductions in the amount of abrasive.

This risk is considerably reduced through a direct “in-line” preparation of the abrasive mixture160carried out by means of at least two separate tanks and a mixer.

With further advantage, such a direct production of the abrasive mixture160allows a high control over various properties of the abrasive mixture160, such as composition, proportions, and rheology.

With further advantage, a tank9thus configured also allows mixing different powdered abrasives, which can be contained in several second tanks140, even continuously during the cutting performed by the cutting machine1.

According to an advantageous embodiment, the dispensing system8comprises a third tank200downstream of the at least first tank130, the at least second tank140and the mixer150. The third tank200is configured to contain the abrasive mixture160prepared by the mixer150, and to convey it towards the actuator11.

According to an embodiment of the disclosure, the cutting machine1comprises a pulsation damper170fluidly connected to the supply tube10.

Advantageously, the pulsation damper170further adjusts the amount of abrasive mixture160to be introduced into the mixing chamber6, further dampening the pressure oscillations of the abrasive mixture160conveyed by the supply tube10, and consequently increasing the precision of the cutting process performed by the cutting machine1.

According to an advantageous embodiment, the pulsation damper170is a gas, or diaphragm, or spring, or weight hydraulic accumulator.

According to an embodiment of the disclosure, the electronic controller120is configured to adjust the amount of abrasive mixture160delivered by the mixer150. Alternatively, or in addition, the electronic controller120is configured to adjust the amount of abrasive mixture160delivered by the actuator11. Alternatively, or in addition, the electronic controller120is configured to adjust the air amount introduced from the air duct110into the mixing chamber6. Alternatively, or in addition, the electronic controller120is configured to adjust the actuation of the pulsation damper170.

Advantageously, this ensures high adjustment and precision of the amount of abrasive mixture160introduced into the mixing chamber6.

According to an advantageous embodiment, the electronic controller120is configured to carry out the aforesaid adjustments by means of a closed-loop control190.

Advantageously, a closed-loop control of one or more of the aforesaid parameters ensures a further improvement in the adjustment and precision of the amount of abrasive mixture160conveyed into the mixing chamber6.

According to a preferred embodiment, in the abrasive mixture160, the mass ratio of the powdered abrasive material and the water-based gelatinous fluid60in which the powdered abrasive material is homogeneously dispersed in suspension is between 1.0 and 3.5.

According to a preferred and advantageous embodiment, in the abrasive mixture160, the ratio of the powdered abrasive material and the water-based gelatinous fluid60in which the powdered abrasive material is homogeneously dispersed in suspension is between 2.0 and 3.5.

According to a preferred and advantageous embodiment, in the abrasive mixture160, the ratio of the powdered abrasive material and the water-based gelatinous fluid60in which the powdered abrasive material is homogeneously dispersed in suspension is about 2.0.

Advantageously, by virtue of such a dosage of powdered abrasive material homogeneously dispersed in the water-based gelatinous fluid60, the dispensing system8uses a smaller amount of dispersion substance with respect to the dispensing systems of abrasive material according to the ASJ technology, to adequately deliver a greater amount of powdered abrasive material.

According to an embodiment, the supply tube10is connected to the cutting head5by means of an injector nozzle38, and the injector nozzle38protrudes inside the mixing chamber6.

Advantageously, this allows to convey the abrasive mixture160in the immediate vicinity of the water jet12, so that the conveyed abrasive mixture160does not accumulate on the walls of the mixing chamber6, nor is it suddenly released.

According to an embodiment, the particle size of the powdered abrasive material homogeneously dispersed in suspension in the water-based gelatinous fluid60is less than #200 mesh, preferably between #350 mesh and #600 mesh.

The average size of the granules of powdered abrasive material is less than 70 micrometers, preferably between 15 and 60 micrometers.

The nature and chemical composition of the abrasive used can be of different types, for example natural minerals such as Almandine Garnet or Olivine, synthetics, ceramics such as Silicon Carbide, metal compounds, biological material.

The water-based gelatinous fluid60is composed of distilled water and a gelling agent (e.g., a polymer) in sufficient amounts to keep the mixture in suspension without the granules of powdered abrasive material settling on the bottom of the tank9.

According to an embodiment of the disclosure, the cutting head5comprises a mixing chamber6of a substantially tubular shape, which forms a front surface14, a rear surface15parallel to the front surface14, and a peripheral surface29.

The terms “front” and “rear” refer to the flow direction of pressurized water4passing through the cutting head5.

The mixing chamber6forms a front seat16at the front surface14, and a rear seat17at the rear surface15, in which the front and rear seats16,17have a substantially cylindrical shape.

Furthermore, the mixing chamber6forms a water inlet opening18at the front seat16, and a mixture outlet opening19at the rear seat17.

The mixing chamber6forms a jet channel20, transverse to the front surface14and to the rear surface15, and in flow communication with the front seat16and the rear seat17by means of the water inlet opening18and the mixture outlet opening19.

The jet channel20and the front seat16form a front shoulder21at the water inlet opening18. Furthermore, the jet channel20and the rear seat17form a rear shoulder22at the mixture outlet opening19.

There is a primary nozzle housing23inside the front seat16, abutting the front shoulder21.

The primary nozzle housing23has a substantially cylindrical shape and defines a front base24and a rear base25, in which the rear base25abuts against the front shoulder21.

The primary nozzle housing23forms a primary nozzle seat26at the front base24.

There is a primary nozzle27in the primary nozzle seat26. The primary nozzle27transforms the flow of pressurized water4from the pumping means2into the water jet12.

The focusing nozzle7forms a focusing channel28adapted to concentrate the water jet12.

The focusing nozzle7is arranged in the rear seat17by interference locking. Advantageously, this interference locking ensures the correct centering and positioning of the focusing nozzle7with respect to the primary nozzle27.

The mixing chamber6forms an injection opening30at the peripheral surface29, and the injection opening30is transverse to the jet channel20and fluidly connected to the jet channel20.

The cutting head5further comprises a retaining flange31, forming a cavity32which receives and seals the mixing chamber6therein. Furthermore, the retaining flange31forms a second injection opening33, configured concentrically with respect to the injection opening30of the mixing chamber6.

The injection opening30and the second injection opening33allow, through connection with the supply tube10, the injection of the abrasive dispersed in the water-based gelatinous fluid60inside the mixing chamber6.

According to an embodiment of the disclosure, the supply tube10is connected at a first end34thereof to the tank9and is connected at a second end35thereof to an injector member36.

According to an embodiment of the disclosure, the injector member36comprises an injector housing37and an injector nozzle38.

The injector housing37forms a connection portion39adapted to connect the injector member36to the supply tube10.

Furthermore, the injector housing37forms a shaped channel40therein, adapted to receive the injector nozzle38.

The injector nozzle38forms an injection channel41therein, and an end portion45of the injector nozzle38is configured to protrude into the jet channel20of the mixing chamber6, so that the injection channel41places the supply tube10in fluid connection with the jet channel20.

According to an embodiment of the disclosure, the end portion45of the injector nozzle38extends by a fraction of a millimeter, preferably 0.5 mm, inside the jet channel20. Advantageously, this allows the abrasive, dispersed in the water-based gelatinous fluid60, to be conveyed in the immediate vicinity of the water jet12. Consequently, the conveyed abrasive does not accumulate on the walls of the jet channel20and is not suddenly released.

The positioning and connection of the injector nozzle38to the mixing chamber6is ensured through a threaded joint, bayonet connection or other attachment system which ensures strength and complete sealing.

According to an embodiment of the disclosure, the shaped channel40comprises an end portion42forming an air injection channel43concentric to the end portion42, and a coupling portion61adapted to obtain a shape coupling with the injector nozzle38.

Advantageously, the concentric configuration of the air injection channel43with respect to the end portion42reduces the dimensions of the injector member36.

With further advantage, the concentric configuration of the air injection channel43allows an optimal projection of the abrasive material dispersed in the water-based gelatinous fluid60towards the water jet12, keeping the air injection channel43clean and functioning.

The air injection channel43forms a gap44, between the air injection channel43and the end portion45of the injector nozzle38.

Furthermore, the injector housing37forms an air flow channel47flowing into the air injection channel43and forming a connection seat46.

The air flow channel47is connected to a pneumatic duct48at the connection seat46. Advantageously, the inner diameter of the pneumatic duct48is substantially identical to the diameter of the air flow channel47, so as to avoid steps which can negatively impact the air flow.

According to an embodiment, the air duct110comprises the air injection duct43, the air flow duct47and the pneumatic duct48.

There is a valve49on the pneumatic duct48for adjusting the air flow entering the air flow channel47. The air flow entering the air flow channel47is sucked in by the passage of the water jet12by Venturi effect.

Furthermore, a pressure gauge50and a flow meter51(analogue or digital) are arranged on the pneumatic duct48, adapted to monitor and allow the control of the air flow introduced into the pneumatic duct48.

Advantageously, by means of the adjustment valve49it is possible to reduce the air amount entering the pneumatic duct48, so as to reduce the air dosage of the water jet12. Thereby, the Venturi effect generated by the water jet12can be propagated to the abrasive dispersed in the water-based gelatinous fluid60, which can therefore be sucked into the mixing chamber6without the intervention of any upstream thrust.

Such a configuration of the pneumatic duct48also is usable for checking the assembly of the cutting head5, for monitoring the state of wear of the components (for example the injector nozzle38, the primary nozzle27, the mixing chamber6and the focusing nozzle7) and for the real-time verification of the correct execution of the cut.

To perform the assembly check, the access of air to the mixing chamber6must be completely blocked, so as to measure the level of pressure generated inside the mixing chamber6by the passage of the water jet12. Pressure values greater than, equal to or close to the atmospheric value indicate an incorrect alignment of the components, with probable contact between the water jet12and the channel and the inner walls of the jet channel20or of the focusing nozzle7. Values closer to vacuum (for example 0.2 or 0.1 absolute bar) indicate a valid alignment of the components, which generate a significant Venturi effect.

To check the state of wear of the components, the pressure variations in the mixing chamber6over a prolonged period must be recorded in order to determine the wear drift of the components of the cutting head5. In particular, a less accentuated Venturi effect in the jet channel20reveals the progressive wear of the primary nozzle, with a consequent decrease in the outflow speed of the water jet12.

In order to verify that the cut has been performed correctly in real time, the pressure variations in the mixing chamber must be recorded. Such events are attributable to malfunctions in the dispensing systems of the water jet12, of the abrasive dispersed in the water-based gelatinous fluid60, or of the air introduced through the air flow channel47. By evaluating these phenomena, the correct function of the water jet12is determined at all times, so as to predict the success of the cutting operation and, if otherwise, stop the cutting.

According to an embodiment of the disclosure, the tank9is a substantially cylindrically-shaped container.

According to a preferred embodiment, the tank9is configured in the shape of a syringe, and comprises a cylindrical portion52, inside which the abrasive material dispersed in the water-based gelatinous fluid60is loaded and stored, and a cannula portion53.

According to an embodiment, the actuator11is configured as a thrust member54which is slidably arranged inside the cylindrical portion52, and is configured to push the abrasive material dispersed in the water-based gelatinous fluid60contained in the cylindrical portion52of the tank9towards the cannula portion53.

The cannula portion53is connected to the first end34of the supply tube10so as to obtain a fluid connection between the tank9and the supply tube10.

According to a preferred embodiment, the thrust member54is configured to impart a thrust pressure of approximately 1 relative bar.

Advantageously, using such a pressure value causes the abrasive material dispersed in the water-based gelatinous fluid60to be substantially incompressible, therefore the advancement speed of the thrust member is easily and directly correlated to the delivered amount of abrasive material dispersed in the water-based gelatinous fluid60.

According to a further embodiment, the dispensing system8comprises an auxiliary refilling syringe, adapted to refill the tank9“in real time”, i.e., refilling the tank9with new abrasive material dispersed in the water-based gelatinous fluid60simultaneously with the execution of a cutting process by the same cutting machine1.

Preferably, such a “real-time” replenishment is performed in a lapse of time between the processing of two successive geometries belonging to the same component being made or to different components.

According to a further embodiment, the dispensing system8comprises an abrasive tank dedicated to the storage of abrasive material and a gel tank dedicated to the storage of water-based gelatinous fluid, in which the simultaneous mixing and pressurization of the abrasive material with the water-based gelatinous fluid occurs in the supply tube10, through a “turbulent” path.

Advantageously, the filling of the tank9occurs at the source through an auxiliary actuator to avoid the presence of air or other gas bubbles at the origin.

Furthermore, a rear discharge valve56is arranged on the thrust member54which expels air bubbles or other gases present in the water-based gelatinous fluid60inside which the abrasive material is dispersed, which could introduce compressibility or cause interruptions in the supply of the abrasive material dispersed in the water-based gelatinous fluid60to the cutting head5.

The thrust member54is connected to a motor58, preferably an electric motor, through a transmission57.

According to a preferred embodiment, a flow cut-off valve59is connected to the supply tube10. The flow cut-off valve59has the purpose of interrupting or diverting the flow of the abrasive material dispersed in the water-based gelatinous fluid60in an emergency.

Advantageously, it is thereby possible to stop the injection of abrasive material dispersed in the water-based gelatinous fluid60into the cutting head5, even if the dispensing system8continues the delivery of abrasive material dispersed in the water-based gelatinous fluid60from the tank9.

With further advantage, the flow cut-off valve59has the auxiliary function of interrupting any rising flows from the cutting head5, for example air or water if the focusing nozzle7is blocked, so as to protect the dispensing system8from overpressure damage.

In a further aspect, the present disclosure relates to a composition comprising a powdered abrasive material homogeneously dispersed in suspension in a water-based gelatinous fluid60, in which the mass ratio of dispersed powdered abrasive material and the water-based gelatinous fluid60is between 1.0 and 3.5, or between 2.0 and 3.5, or about 2.0 and in which the particle size of the powdered abrasive material homogeneously dispersed in suspension in the water-based gelatinous fluid60is between #350 mesh and #600 mesh.

Preferably, the average granule size of the abrasive material in said composition is between 15 and 60 micrometers.

A further aspect according to the present disclosure is an abrasive water-jet cutting method, where said method comprises the use of the abrasive composition according to the present disclosure.

According to an embodiment, the abrasive water-jet cutting method comprises the steps of:providing an abrasive water-jet cutting machine1as described above,adjusting the amount of abrasive mixture160delivered by the actuator11by means of an open-loop control180.

According to a further embodiment, the abrasive water-jet cutting method comprises the steps of:providing an abrasive water-jet cutting machine1as described above,performing at least one of the following adjustments by means of a closed-loop control190:adjustment of the amount of abrasive mixture160delivered by the mixer150;adjustment of the amount of abrasive mixture160delivered by the actuator11;adjustment of the air amount introduced from the air duct110into the mixing chamber6;adjustment of the actuation of the pulsation damper170.

Obviously, in order to meet contingent specific needs, those skilled in the art will be able to make further changes and variations all contained within the scope of protection as defined by the claims.

Some experimental tests carried out with the abrasive water-jet cutting machine and the composition comprising the abrasive claimed herein will be described below, aimed at highlighting the effectiveness and technical advantages thereof.

Cutting test on 2.0 mm thick austenitic stainless steel (AISI 301/EN 1.4310)

The cutting test is performed on 2.0 mm thick austenitic stainless steel (AISI 301/EN 1.4310), to verify the performance of the claimed cutting machine on a relatively thick material.

In fact, 2.0 mm is close to the maximum thickness which can be effectively cut with cutting machines in the μAWJ field of the state of the art known to the inventors.

The geometry of the cut groove and the roughness of the cut wall surface are measured at different depth levels:0.2 mm from the top (“top”)at half height (1.0 mm, “mid”)0.2 mm from the bottom (“bot”)

The following Tables 1.1 and 1.2 report the results obtained from the test:

TABLE 1.1cutting tests on 2 mm thick austenitic stainless steel(AISI 301/EN 1.4310). Macro-geometric check of the cuttingwall with varying advancement speeds.2.0 mm thick austenitic stainless steel (AISI 301/EN 1.4310)Cut groove width inspectionvfWtopWbotWaverageTaper[mm/min][mm][mm][mm][mm]30.1870.2210.204−0.01560.1720.1580.1650.00790.1710.1450.1580.013120.1650.1280.1460.018150.1640.1160.1400.024180.1570.1080.1330.024210.1530.0930.1230.030240.1520.0900.1210.031vf: head advancement speedWtop: upper groove widthWbot: lower groove widthWaverage: average groove widthTaper: inclination of the single wall

TABLE 1.2cutting tests on 2 mm thick austenitic stainless steel(AISI 301/EN 1.4310). Roughness check of thecutting wall with varying advancement speeds.2.0 mm thick austenitic stainless steel (AISI 301/EN 1.4310)Roughness inspectionRaRaRaRaRzRzRzRzvftopmidbotaveragetopmidbotaverage[mm/min][μm][μm][μm][μm][μm][μm][μm][μm]30.360.440.560.453.023.154.003.3860.380.490.640.513.283.955.014.0190.420.480.640.513.613.704.773.92120.440.590.810.673.774.345.905.05150.470.660.960.723.985.166.475.25180.490.831.270.903.906.698.156.57210.500.941.531.043.986.339.206.79240.641.292.321.525.059.2714.739.91vf: head advancement speedRatop: arithmetic average roughness near the upper surface of the pieceRamid: arithmetic average roughness at half thickness of the pieceRabot: arithmetic average roughness near the lower surface of the pieceRaaverage: average of the Ravalues detectedRztop: roughness on the 10 extreme points near the upper surface of the pieceRzmid: roughness on the 10 extreme points at half thickness of the pieceRzbot: roughness on the 10 extreme points near the lower surface of the pieceRzaverage: average of the Rzvalues detected

Two operating conditions are revealed by the test:a full but irregular cut is made at high vf=24 mm/min;a high-quality cut is made at lower vf, among which vf=6 mm/min is an ideal value as it minimizes the inclination of the wall, making both sides of the cut usable with a tolerance of 1 hundredth of a millimeter, without having to introduce head inclinations to compensate for the defect.

Complex Cutting Test

The new system proves effective in cutting thick metal plates (at least by abrasive micro-jet standards) at different levels of vfand also in drilling with different strategies.

A complex shape is chosen for a complete characterization of the new performance of the system. This is the letter “A” in a particular character, used as a reference piece, as it contains:straight lines, for measuring roughness and streaks due to irregularities in the formation of the jet;acute angles, both inner and outer, to show the precision of the jet in defining the edges with a low “jet lag” effect;small radius curves, to show the radius limit which can be reached according to the size of the jet;thin walls, to demonstrate the high stability and delicacy of the jet;long processing path, as a resistance test of system stability and robustness.

The smallest A obtainable with the focusing nozzle df=0.20 mm and the #230 mesh abrasive, the minimum jet size currently available in the micro AWJ commercial panorama, is 12 mm high and has a minimum radius of 0.12 mm. For the present study, the design is scaled down to 75%, thus achieving a final height of 9 mm and a minimum radius of 0.09 mm.

Table 2 summarizes the main processing parameters for the execution of this reference piece, cut with the claimed cutting machine, replicating the complete execution of the cutting program three times.

TABLE 2process configuration and parameters for making the sample in2 mm thick austenitic stainless steel (AISI 301/EN 1.4310).Parameter/OperationValue/StrategyPrimary nozzle diameter [mm]0.05Focusing nozzle diameter0.13Hydraulic pressure [MPa]350Abrasive [type and mesh]Garnet #600 meshAbrasive amount [g/min]3Mixing chamber pressure [bar]0.78-0.80Advancement speed [mm/min]6Drilling strategyCircularDrilling time [s]4Distance from the piece being drilled [mm]1.2Distance from the piece being cut [mm]0.2Cutting length [mm]90Cutting time [min]15

The sample is then detached from the base material to be observed and measured.FIG. 6shows the resulting sample in top view, where the precision and accuracy resulting from the cut can be observed. The sample is used to evaluate the width of the cut in different cutting directions, showing no significant variation in all the measurements.

Comparison with the State of the Art in the Execution of a Cut

The comparison between the abrasive water-jet cutting machine according to the disclosure and an abrasive water-jet cutting machine according to the state of the art is shown here, in the execution of a cut of a sample of 2 mm thick austenitic stainless steel (AISI 301/EN 1.4310).

The technical specifications of the abrasive water-jet cutting machine according to the disclosure and of the abrasive water-jet cutting machine according to the state of the art are listed in Table 3.1, while the results obtained following the test are reported in Table 3.2.

As evidenced by Tables 3.1 and 3.2, and as seen inFIG. 7, the abrasive water-jet cutting machine according to the disclosure boasts improvements with respect to the prior art, as regards the quality of the cutting groove, with cutting width reduced by 35%, and roughness quality, with Ra and Rz reduced by 57%.

Furthermore, the abrasive water-jet cutting machine according to the disclosure has obtained such results respecting the tolerance of 1 hundredth of a millimeter on the inclination of the wall (taper).

Obviously, in order to meet contingent specific needs, those skilled in the art will be able to make further changes and variations all contained within the scope of protection defined by the following claims.