IT202000006010A1 - Abrasive water jet cutting machine - Google Patents

Description

PATENT FOR INDUSTRIAL INVENTION

Abrasive water jet cutting machine

DESCRIPTION

[0001] The present invention relates to an abrasive water jet cutting machine.

[0002] State of the art

[0003] Abrasive water jet cutting machines are machine tools that perform the cutting and shaping of work pieces by means of a jet of a water-abrasive material mixture. Such technology? known as? abrasive water jet cutting? or? Abrasive Water Jet? (AWJ).

[0004] Generally, abrasive waterjet cutting machines include:

[0005] - pumping means, which can be fluidically connected to a water source, for generating a flow of pressurized water;

[0006] - a cutting head, comprising a primary nozzle, a mixing chamber and a focusing nozzle,

[0007] in which the flow of pressurized water from the pumping means? conveyed into the primary nozzle of the cutting head where the pressure energy of the pressurized water flow? converted into kinetic energy to form a jet of water, and in which said jet of water? subsequently conveyed into the mixing chamber;

[0008] - a gravity dispensing system of powdered abrasive material, comprising

- a tank (for example a hopper) containing abrasive powder material, - a feed tube, which fluidically connects the tank to the mixing chamber of the cutting head,

in which the gravity delivery system? of powdered abrasive material delivers said powdered abrasive material into the mixing chamber of the cutting head through the feed tube;

[0009] in which the cutting head mixes, in the mixing chamber, the abrasive powder material with the jet of water forming a jet of water-abrasive material mixture, and said cutting head delivers the jet of water-abrasive material mixture through the focusing nozzle.

[0010] Gravity dispensing systems of powdered abrasive material present different criticalities. In particular, such systems are excessively inconvenient when used to perform smaller cutting operations. fine and precise, that is for the so-called? micro-cutting with abrasive water jet? or? micro Abrasive Water Jet? (? AWJ).

[0011] Specifically, the AWJ processes require the use of reduced mass flow rates of abrasive (less than 20 g / min) and the use of abrasive material in powder with a particle size greater than 20 g / min. fine (mesh greater than # 200) than the usual one for macro applications (which instead use meshes in the range # 80 - # 120).

[0012] Gravity dispensing systems cannot guarantee a smooth and reliable supply of abrasive material for machining? AWJ. In fact, the gravity delivery systems? have a variability? in the delivery of the mass flow of abrasive material that reaches values around 10%, which is not? acceptable for machining of the type? AWJ.

[0013] Furthermore, 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 criticisms? in the constant supply of abrasive powder material. In addition, the gravity delivery systems? of powdered abrasive material are incompatible with the use of the machine tool in the? overhead? configuration. (implemented, for example, by anthropomorphic robots).

[0014] A further criticism? of these dispensing systems derives from the fact that the powder of abrasive material powder dispensed from the dispensing system, which? particularly hygroscopic,? negatively exposed to the presence of humidity, environmental and process, present inside the ducts inside which the abrasive material in powder? conveyed.

[0015] In particular, at the interface between the feed 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 wall of the feed tube, which progressively reduces the section useful for the delivery of abrasive material into the mixing chamber, causing undesirable variations in the mass flow of abrasive material.

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

[0017] Yes? attempted to overcome these problems by means of the use of abrasive material dispensing systems according to the technology? Abrasive Suspension Jet? (ASJ), in which the abrasive material in powder? previously dispersed in a dispersion liquid (e.g. water), to form a? hydro-abrasive? stored in a tank. Such a hydro-abrasive mixture? then delivered through a single nozzle for the formation of a pressurized jet of hydro-abrasive mixture.

[0018] However, such an abrasive material dispensing system? usable only at low pressures (less than 200 MPa), which are not high enough to perform cutting operations of the required precision in? AWJ applications.

[0019] Furthermore, in order to ensure an adequate dispersion of the powdered abrasive material in the dispersion substance, avoiding unwanted sedimentations,? the mass ratio between the powdered abrasive material and the dispersion liquid of the above hydro-abrasive mixtures must be remarkably low. There? determines an exaggerated use of dispersion liquid in order to adequately disperse (and dispense) a low quantity of abrasive powder material.

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

[0020] The purpose of the present invention? therefore that of providing an abrasive water jet cutting machine, and in particular for processing of the? AWJ type, equipped with a dispensing system for abrasive material having characteristics such as to solve at least some of the drawbacks of the known art.

[0021] A particular object of the present invention? that of providing a dispensing system of powdered abrasive material such as to guarantee a regular and reliable supply of powdered abrasive material, even at reduced dosages of powdered abrasive material (less than 20 g / min).

[0022] A further particular object of the present invention? to provide a system for dispensing abrasive powder material compatible with the use of the machine tool in the? overhead? configuration.

[0023] A further particular object of the present invention? that of providing a dispensing system of powdered abrasive material in which stationary agglomerations of powdered abrasive material are avoided, and other criticalities? deriving from the exposure of the abrasive material in powder form to humidity, environmental and process, present inside the ducts inside which the abrasive material in powder? conveyed.

[0024] A further particular object of the present invention? that of providing an abrasive material dispensing system that can also be used at the pressures required to perform? AWJ type machining (higher than 380 MPa).

[0025] A further particular object of the present invention? to provide a dispensing system of abrasive powder material that uses a smaller quantity? of dispersion substance to adequately dispense a greater quantity of powdered abrasive material.

[0026] A further particular object of the present invention? that of providing an abrasive material dispensing system capable of delivering a continuous flow rate of abrasive material, without however causing wear phenomena in the dispensing system.

[0027] Detailed description of the invention

[0028] The subject of the present invention is an abrasive water jet cutting machine equipped with an abrasive material dispensing system according to claim 1. The dependent claims refer to advantageous and preferred embodiments.

[0029] In a further aspect, a composition is claimed here which comprises an abrasive powder material dispersed in a gelatinous fluid, as well as the use of said material in abrasive water jet cutting methods.

In accordance with one aspect of the invention, an abrasive water jet cutting machine comprises:

[0031] - pumping means, which can be fluidically connected to a water source, for generating a flow of pressurized water;

[0032] - a cutting head, comprising a primary nozzle, a mixing chamber and a focusing nozzle,

[0033] in which the flow of pressurized water from the pumping means? conveyed into the primary nozzle of the cutting head where the pressure energy of the pressurized water flow? converted into kinetic energy to form a jet of water, and in which said jet of water? subsequently conveyed into the mixing chamber;

[0034] - a powder abrasive material dispensing system, comprising: - a tank containing powdered abrasive material,

- a feed tube, which fluidically connects the tank to the mixing chamber of the cutting head,

- an actuator, which delivers the abrasive material in powder contained in the tank into the mixing chamber, through the feeding tube;

[0035] in which the cutting head mixes, in the mixing chamber, the abrasive material with the jet of water forming a jet of water-abrasive material mixture, and said cutting head delivers the jet of water-abrasive material mixture, by means of the focusing nozzle;

[0036] wherein the powdered abrasive material dispensed into the mixing chamber? homogeneously dispersed in suspension in a water-based gelatinous fluid;

[0037] and in which the actuator? a peristaltic pump.

Such a configuration of the dispensing system, and in particular of the abrasive material dispensed by it, allows the control of the properties? of the abrasive material. In fact, since? the abrasive material in powder form? homogeneously dispersed in the water-based gelatinous fluid, it? completely saturated with water, therefore? immune to criticism? resulting from its exposure to humidity? environmental and process.

[0038] Furthermore, since? the abrasive material in powder form? completely saturated with water and? homogeneously dispersed in the water-based gelatinous fluid, said dispensing system dispenses the abrasive material in a regular and reliable way, even at reduced dosages of abrasive material (less than 20 g / min).

[0039] Furthermore, such a delivery system? compatible with the use of the cutting machine in the "overhead" configuration.

[0040] Furthermore, such a delivery system? it can also be used at the pressures required to perform? AWJ type machining (higher than 380 MPa).

[0041] Furthermore, the implementation of a peristaltic pump guarantees a continuous flow rate of abrasive mixture, without causing wear phenomena in the delivery system.

[0042] To better understand the invention and appreciate its advantages, will come? A description of some non-limiting exemplary embodiments is provided below, with reference to the figures, in which:

[0043] - Figure 1? schematic representation of the abrasive water jet cutting machine, according to an embodiment of the invention;

[0044] - Figure 2A? a front view of a cutting head, according to an embodiment of the invention;

[0045] - Figure 2B? an axial sectional view of the cutting head shown in Figure 2A;

[0046] - Figure 3A? a front view of an injector member, according to an embodiment of the invention;

[0047] - Figure 3B? an axial sectional view of the injector member shown in Figure 3A;

[0048] - Figure 4? a longitudinal section view of the assembled cutting head-injector unit;

[0049] - Figure 5A? a front view of a dispensing system according to an embodiment of the invention;

[0050] - Figure 5B? an axial sectional view of the dispensing system shown in Figure 5A;

[0051] - Figure 6 shows a sample of material cut by means of the abrasive water jet cutting machine, according to an embodiment of the invention.

[0052] - figure 7 shows two samples of the same material, cut by means of an abrasive water jet cutting machine according to the known art and according to the invention, [0053]? figure 8? a schematic view of an abrasive water jet cutting machine, according to a further embodiment of the invention,

[0054]? figure 9? a schematic view of an abrasive water jet cutting machine, according to a further embodiment of the invention,

[0055]? figure 10? a schematic view of an abrasive water jet cutting machine, according to a further embodiment of the invention.

[0056] With reference to the figures, an abrasive water jet cutting machine according to the invention? generally indicated with reference 1.

[0057] According to an aspect of the invention, the abrasive water jet cutting machine 1 comprises pumping means 2, which can be fluidically connected to a water source 3, for generating a pressurized water flow 4.

[0058] The cutting machine 1 further comprises a cutting head 5, which comprises a primary nozzle 27, a mixing chamber 6 and a focusing nozzle 7.

[0059] According to an aspect of the invention, the flow of pressurized water 4 coming from the pumping means 2? conveyed into the primary nozzle 27 of the cutting head 5 where the pressure energy of the pressurized water flow 4? converted into kinetic energy to form a jet of water 12, and, subsequently, the jet of water 12? conveyed into the mixing chamber 6.

[0060] The cutting machine 1 further comprises a dispensing system 8 of powdered abrasive material which comprises a tank 9 containing abrasive material, a feed tube 10, which fluidically connects the tank 9 to the mixing chamber 6 of the cutting head 5, and an actuator 11 which delivers the abrasive material in powder contained in the tank 9 into the mixing chamber 6, through the feed tube 10.

[0061] According to a further aspect of the invention, the cutting head 5 mixes, in the mixing chamber 6, the abrasive material with the jet of water 12 forming a jet of mixture 13 water-abrasive material, which is delivered by the head of cut 5 through the focus nozzle 7.

[0062] The focuser 7 also has the task, following the mixing of the abrasive material with the jet of water 12, of increasing the efficiency of the mixing and transfer of quantities. of motion from the jet of water 12 to the abrasive material.

[0063] According to a further aspect of the invention, the powdered abrasive material contained in the tank 9? homogeneously dispersed in suspension in a water-based gelatinous fluid 60.

The powdered abrasive material homogeneously dispersed in suspension in the water-based gelatinous fluid 60 therefore forms an abrasive mixture 160.

[0065] According to a further aspect of the invention, the actuator 11? a peristaltic pump 100.

[0066] Such a configuration of the dispensing system 8, and in particular of the powdered abrasive material dispensed by it, allows the control of the properties? hygroscopic of the powdered abrasive material. In fact, since? the abrasive material in powder form? homogeneously dispersed in the water-based gelatinous fluid 60, it? completely saturated with water, therefore? immune to criticism? deriving from its exposure to humidity? environmental and process.

[0067] Furthermore, since? the abrasive material in powder form? completely saturated with water and? homogeneously dispersed in the water-based gelatinous fluid 60, said delivery system 8 delivers the abrasive material in a regular and reliable manner, even at reduced dosages of abrasive material (less than 20 g / min).

[0068] Furthermore, this delivery system 8? compatible with use of the cutting machine 1 in the? overhead? configuration.

[0069] Furthermore, this delivery system 8? it can also be used at the pressures required to perform? AWJ type machining (higher than 380 MPa).

[0070] Furthermore, the implementation of a peristaltic pump 100 guarantees a continuous flow rate of abrasive mixture 160, without causing wear phenomena in the delivery system 8.

According to an embodiment of the invention, the feed tube 10? in polymeric material.

[0072] Advantageously, the feed tube 10 made of polymeric material further reduces any wear phenomena in the delivery system 8, and further attenuates the pressure oscillations caused in the flow of abrasive mixture 160 by the peristaltic motion induced by the peristaltic pump 100.

[0073] According to an embodiment, the cutting machine 1 comprises an air duct 110 which flows into the mixing chamber 6.

[0074] Advantageously, the supply of air by means of the air duct 110 avoids the risk that the depression generated inside the mixing chamber 6 disturbs the flow rate of the abrasive mixture 160 introduced therein.

[0075] With a further advantage, the supply of air to the mixing chamber 6 through the air duct is self-stabilized, ie it does not require external regulation.

[0076] According to an embodiment of the invention, the cutting machine 1 comprises an electronic controller 120.

[0077] The electronic controller 120? configured to regulate the flow rate of abrasive mixture 160 delivered by the dispensing system 8.

[0078] The electronic controller 120 can? be, for example, a PC or a PLC.

[0079] Advantageously, the use of an electronic controller 120 further improves the precision of the dosage of abrasive mixture 160.

[0080] According to one embodiment, the reservoir 9 contains the abrasive mixture 160, wherein the powdered abrasive material? homogeneously dispersed inside the water-based gelatinous fluid 60.

According to one embodiment, the electronic controller 120? configured to regulate the flow rate of abrasive mixture 160 delivered by the actuator 11, by means of an open-loop control 180.

[0082] Advantageously, the electronic controller 120 adjusts the flow rate of the abrasive mixture 160 by adjusting the speed? of the peristaltic pump 100. Following this adjustment, the delivery system 8 self-stabilizes, so as to deliver a regulated and continuous flow rate of abrasive mixture 160 to the mixing chamber 6.

[0083] In particular, the relationship between speed? of the peristaltic pump 100 and flow rate of abrasive mixture 160? achieved by calibration curves obtained with experimental tests for each type of abrasive mixture.

According to a further embodiment of the invention, the reservoir 9 comprises at least a first reservoir 130 containing water-based gelatinous fluid 60, and at least a second reservoir 140 containing powdered abrasive material.

[0085] Furthermore, the delivery system 8 comprises a mixer 150 interposed between the tank 9 and the actuator 11. That is, the mixer 150? placed at least downstream of the at least first tank 130 and second tank 140, and upstream of the actuator 11, with reference to the direction of the flow of abrasive mixture 160.

[0086] The mixer 150? configured to mix the water-based gelatinous fluid 60 contained in at least one first tank 130 with the powdered abrasive material contained in at least one second tank 140, so as to form an abrasive mixture 160, and convey the abrasive mixture 160 in the actuator 11.

[0087] Advantageously, a tank 9 so? configured avoids preparing the abrasive mixture in a separate phase, and subsequently introducing it into the tank, with the risk of introducing and forming air bubbles which would cause drastic local reductions in the abrasive flow rate.

[0088] This risk? considerably reduced by means of an in-line, direct preparation of the abrasive mixture 160 carried out by means of at least two distinct tanks and a mixer.

[0089] With further advantage, such a direct production of the abrasive mixture 160 allows a high control over several properties. of the abrasive mixture 160, such as composition, proportions and rheology.

[0090] With further advantage, a tank 9 so? configured also allows the mixing of different abrasive powders, which can be contained in several second tanks 140, even continuously during the cutting performed by the cutting machine 1.

[0091] According to an advantageous embodiment, the delivery system 8 comprises a third tank 200 downstream of the at least first tank 130, of the at least second tank 140 and of the mixer 150. The third tank 200? configured to contain the abrasive mixture 160 prepared by the mixer 150, and to convey it towards the actuator 11.

According to an embodiment of the invention, the cutting machine 1 comprises a pulsation damper 170 fluidically connected to the feed tube 10.

[0093] Advantageously, the pulsation damper 170 further regulates the flow rate of the abrasive mixture 160 to be introduced into the mixing chamber 6, further dampening the pressure oscillations of the abrasive mixture 160 conveyed by the feed tube 10, and consequently increasing the precision of the cutting processing performed by the cutting machine 1.

According to an advantageous embodiment, the pulsation damper 170? a hydraulic accumulator with gas, or with membrane, or with spring, or by weight.

According to an embodiment of the invention, the electronic controller 120? configured to regulate the flow rate of abrasive mixture 160 delivered by the mixer 150. Alternatively, or in addition, the electronic controller 120? configured to regulate the flow rate of abrasive mixture 160 delivered by the actuator 11. Alternatively, or in addition, the electronic controller 120? configured to regulate the flow of air introduced from the air duct 110 into the mixing chamber 6. Alternatively, or in addition, the electronic controller 120? configured to regulate the actuation of the pulsation damper 170.

[0096] Advantageously, there? guarantees high regulation and precision of the flow rate of the abrasive mixture 160 introduced into the mixing chamber 6.

[0097] According to an advantageous embodiment, the electronic controller 120? configured to perform the above adjustments by means of a closed loop control 190.

[0098] Advantageously, a closed-loop control of one or more? of the aforementioned parameters guarantees a further improvement in the regulation and precision of the flow rate of abrasive mixture 160 conveyed into the mixing chamber 6.

According to a preferred embodiment, in the abrasive mixture 160, the mass ratio between the powdered abrasive material and the water-based gelatinous fluid 60 in which? homogeneously dispersed in suspension the abrasive material in powder? between 1.0 and 3.5.

According to a preferred and advantageous embodiment, in the abrasive mixture 160, the ratio of the powdered abrasive material to the water-based gelatinous fluid 60 in which? homogeneously dispersed in suspension the abrasive material in powder? between 2.0 and 3.5.

According to a preferred and advantageous embodiment, in the abrasive mixture 160, the ratio of the powdered abrasive material to the water-based gelatinous fluid 60 in which? homogeneously dispersed in suspension the abrasive material in powder? about 2.0.

[00102] Advantageously, thanks to such a dosage of powdered abrasive material homogeneously dispersed in the water-based gelatinous fluid 60, the dispensing system 8 uses a smaller quantity? of dispersion substance compared to the dispensing systems of abrasive material according to the ASJ technology, to adequately dispense a greater quantity of powdered abrasive material.

[00103] According to one embodiment, the feed tube 10? connected to the cutting head 5 by means of an injector nozzle 38, and the injector nozzle 38 protrudes inside the mixing chamber 6.

[00104] Advantageously, there allows the abrasive mixture 160 to be conveyed in the immediate vicinity of the water jet 12, so that the conveyed abrasive mixture 160 does not accumulate on the walls of the mixing chamber 6, n? is released suddenly.

According to an embodiment, the particle size of the powdered abrasive material homogeneously dispersed in suspension in the water-based gelatinous fluid 60? less than # 200 mesh, preferably? between # 350 mesh and # 600 mesh.

[00106] The average size of the granules of powdered abrasive material? less than 70 micrometers, preferably? between 15 and 60 micrometers.

[00107] 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.

[00108] The water-based gelatinous fluid 60? composed of distilled water and a gelling agent (for example a polymer) in quantity? sufficient to keep the mixture in suspension without the granules of powdered abrasive material settling on the bottom of the tank 9.

[00109] According to an embodiment of the invention, the cutting head 5 comprises a mixing chamber 6 of substantially tubular shape, which forms a front surface 14, a rear surface 15 parallel to the front surface 14, and a peripheral surface 29 .

[00110] The terms? Anterior? and? rear? refer to the direction of flow of pressurized water 4 passing through the cutting head 5.

[00111] The mixing chamber 6 forms a front seat 16 at the front surface 14, and a rear seat 17 at the rear surface 15, in which the front and rear seats 16, 17 have a substantially cylindrical shape.

[00112] Furthermore, the mixing chamber 6 forms a water inlet opening 18 at the front seat 16, and a mixture outlet opening 19 at the rear seat 17.

[00113] The mixing chamber 6 forms a jet channel 20, transversal to the front surface 14 and to the rear surface 15, and in flow communication with the front seat 16 and the rear seat 17 by means of the water inlet opening 18 and the mixture outlet opening 19.

[00114] The jet channel 20 and the front seat 16 form a front shoulder 21 at the water inlet opening 18. Furthermore, the jet channel 20 and the rear seat 17 form a rear shoulder 22 at the opening mixture outlet 19.

[00115] A primary nozzle housing 23? received inside the front seat 16, in abutment with the front shoulder 21.

The primary nozzle housing 23 has a substantially cylindrical shape, and defines a front base 24 and a rear base 25, wherein the rear base 25 is. against the front shoulder 21.

The primary nozzle housing 23 forms a primary nozzle seat 26 at the front base 24.

[00118] A primary nozzle 27? received in the seat for the primary nozzle 26. The primary nozzle 27 transforms the flow of pressurized water 4 coming from the pumping means 2 into the water jet 12.

[00119] The focusing nozzle 7 forms a focusing channel 28 adapted to concentrate the jet of water 12.

[00120] The focusing nozzle 7? arranged in the rear seat 17 by means of locking by interference. Advantageously, this interference lock ensures correct centering and positioning of the focusing nozzle 7 with respect to the primary nozzle 27.

[00121] The mixing chamber 6 forms an injection opening 30 at the peripheral surface 29, and the injection opening 30? transversal to the jet channel 20 and fluidly connected to the jet channel 20.

[00122] The cutting head 5 further comprises a retaining flange 31, forming a cavity? 32 which houses and seals inside the mixing chamber 6. Furthermore, the retaining flange 31 forms a second injection opening 33, configured in a concentric manner with respect to the injection opening 30 of the mixing chamber 6.

[00123] The injection opening 30 and the second injection opening 33 allow, through connection with the feeding tube 10, the injection of the dispersed abrasive in the water-based gelatinous fluid 60 inside the mixing chamber 6 .

According to an embodiment of the invention, the feed tube 10? connected to one of its first extremities? 34 to tank 9, and? connected to a second end of it? 35 to an injector member 36.

According to an embodiment of the invention, the injector member 36 comprises an injector housing 37 and an injector nozzle 38.

[00126] The injector housing 37 forms a connection portion 39 adapted to connect the injector member 36 to the supply pipe 10.

[00127] Furthermore, the injector housing 37 forms inside it a shaped channel 40, adapted to receive the injector nozzle 38.

[00128] The injector nozzle 38 forms inside it an injection channel 41, and an end portion 45 of the injector nozzle 38? configured so as to protrude into the jet channel 20 of the mixing chamber 6, so that the injection channel 41 places the supply tube 10 in fluidic connection with the jet channel 20.

[00129] According to an embodiment of the invention, the end portion 45 of the injector nozzle 38 extends by a fraction of a millimeter, preferably 0.5 mm, inside the jet channel 20. Advantageously, this is the case. allows to convey the abrasive, dispersed in the water-based gelatinous fluid 60, in the immediate vicinity of the water jet 12. Therefore, the conveyed abrasive does not accumulate on the walls of the jet channel 20 and does not? released suddenly.

[00130] The positioning and connection of the injector nozzle 38 to the mixing chamber 6? secured by threaded joint, bayonet connection or other attachment system that guarantees robustness and complete sealing.

[00131] According to an embodiment of the invention, the shaped channel 40 comprises an end portion 42 which forms an air injection channel 43 concentric to the end portion 42, and a coupling portion 61 suitable for making a shape coupling with the ? injector nozzle 38.

[00132] Advantageously, the concentric configuration of the air injection channel 43 with respect to the terminal portion 42 reduces the overall dimensions of the injector member 36.

[00133] With a further advantage, the concentric configuration of the air injection channel 43 allows an optimal projection of the abrasive material dispersed in the water-based gelatinous fluid 60 towards the water jet 12, keeping the air injection channel 43 clean and functioning.

[00134] The air injection channel 43 forms an interspace 44, between the air injection channel 43 and the end portion 45 of the injector nozzle 38.

Furthermore, the injector housing 37 forms an air flow channel 47 which flows into the air injection channel 43, and which forms a connection seat 46.

[00136] The air flow channel 47? connected to a pneumatic duct 48 at the connection seat 46. Advantageously, the internal diameter of the pneumatic duct 48? substantially identical to the diameter of the air flow channel 47, so as to avoid steps which can negatively impact the air flow.

According to one embodiment, the air duct 110 comprises the air injection duct 43, the air flow duct 47 and the pneumatic duct 48.

[00138] On the pneumatic duct 48? a valve 49 is arranged to regulate the flow of air entering the air flow channel 47. The flow of air entering the air flow channel 47? sucked by the passage of the water jet 12 due to the Venturi effect.

[00139] Furthermore, a pressure meter 50 and a flow meter 51 (analogue or digital) are arranged on the pneumatic duct 48, suitable for monitoring and allowing the control of the air flow introduced into the pneumatic duct 48.

[00140] Advantageously, by means of the regulating valve 49? It is possible to reduce the flow of air entering the pneumatic duct 48, so as to reduce the air dosage of the water jet 12. In this way, the Venturi effect generated by the water jet 12? propagable to the abrasive dispersed in the water-based gelatinous fluid 60, which therefore? aspirable in the mixing chamber 6 without the intervention of a possible upstream thrust.

[00141] Such a configuration of the pneumatic conduit 48? it can also be used to check the assembly of the cutting head 5, to monitor the state of wear of the components (for example the injector nozzle 38, the primary nozzle 27, the mixing chamber 6 and the focusing nozzle 7) and for real-time verification of the correct execution of the cut.

[00142] To perform assembly verification? it is necessary to completely prevent the access of air to the mixing chamber 6, in order to measure the pressure level generated inside the mixing chamber 6 by the passage of the water jet 12. Pressure values higher than, equal to or close to the atmospheric value they indicate an incorrect alignment of the components, with probable contact between the jet of water 12 and the channel and the internal walls of the jet channel 20 or of the focusing nozzle 7. More values? close to vacuum (for example 0.2 or 0.1 absolute bar) signal a valid alignment of the components, which generate a significant Venturi effect.

[00143] To check the state of wear of the components? It is necessary to record the pressure variations in the mixing chamber 6 over a prolonged period to determine the wear drift of the components of the cutting head 5. In particular, a less accentuated Venturi effect in the jet channel 20 reveals the progressive wear of the cutting head. primary nozzle, with a consequent decrease in speed? outflow of the water jet 12.

[00144] To perform the real-time verification of the correct execution of the cut? It is necessary to record the pressure variations in the mixing chamber. These events are attributable to malfunctions in the delivery systems of the water jet 12, of the abrasive dispersed in the water-based gelatinous fluid 60, or of the air introduced through the air flow channel 47. By evaluating these phenomena the correct function of the water jet 12 is determined at all times, in order to predict the success of the cutting operation and, if not, to interrupt the cut.

[00145] According to an embodiment of the invention, the reservoir 9? a vessel with a substantially cylindrical shape.

[00146] According to a preferred embodiment, the tank 9? configured in the shape of a syringe, and includes a cylindrical portion 52, inside which? loaded and stored the abrasive material dispersed in the water-based gelatinous fluid 60, and a cannula portion 53.

[00147] According to an embodiment, the actuator 11? configured as a pusher member 54 which? slidably disposed inside the cylindrical portion 52, and configured in such a way as to push towards the cannula portion 53 the abrasive material dispersed in the water-based gelatinous fluid 60 contained in the cylindrical portion 52 of the tank 9.

The cannula portion 53? connected to the first end? 34 of the feed tube 10 so as to make a fluidic connection between the tank 9 and the feed tube 10.

[00149] According to a preferred embodiment, the pusher member 54? configured in such a way as to impart a thrust pressure of approximately 1 relative bar.

[00150] Advantageously, using such a pressure value does s? that the abrasive material dispersed in the water-based gelatinous fluid 60 is substantially incompressible, therefore the speed? advancement of the pusher organ? easily and directly correlated to the delivered flow rate of abrasive material dispersed in the water-based gelatinous fluid 60.

[00151] According to a further embodiment, the delivery system 8 comprises an auxiliary filling syringe, adapted to refill the tank 9? In real time?, That is, to supply the tank 9 with new abrasive material dispersed in the gelatinous fluid water-based 60 simultaneously with the execution of a cutting process by the same cutting machine 1.

[00152] Preferably, is this replenishment in real time? ? performed in a lapse of time between the machining of two successive geometries belonging to the same component under construction or to different components.

[00153] According to a further embodiment, the dispensing system 8 comprises 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 feed tube 10, through a "turbulent" path.

[00154] Advantageously, the filling of the tank 9 takes place at the source by means of an auxiliary actuator to originally avoid the presence of air or other gas bubbles.

[00155] Furthermore, on the pusher member 54? a rear discharge valve 56 is arranged which expels bubbles of air or other gases present in the water-based gelatinous fluid 60 inside which? dispersed the abrasive material, which could introduce compressibility? o cause interruptions in the feeding of the abrasive material dispersed in the water-based gelatinous fluid 60 to the cutting head 5.

[00156] The pusher member 54? connected to a motor 58, preferably electric, through a transmission 57.

[00157] According to a preferred embodiment, a flow cut-off valve 59? connected to the supply pipe 10. The flow cut-off valve 59 has the purpose of interrupting or diverting the flow of the abrasive material dispersed in the water-based gelatinous fluid 60 in the event of an emergency.

[00158] Advantageously, thus? It is possible to stop the injection of abrasive material dispersed in the water-based gelatinous fluid 60 into the cutting head 5, even if the delivery system 8 continues to dispense abrasive material dispersed in the water-based gelatinous fluid 60 from the tank 9.

[00159] With a further advantage, the flow cut-off valve 59 has the auxiliary function of interrupting any upward flows from the cutting head 5, for example air or water in the event of obstruction of the focusing nozzle 7, in order to protect the system delivery valve 8 from over pressure damage.

[00160] In a further aspect, the subject of the present invention is a composition comprising a powdered abrasive material homogeneously dispersed in suspension in a water-based gelatinous fluid 60, in which the mass ratio between the dispersed powdered abrasive material and the water-based gelatinous fluid 60? between 1.0 and 3.5, or between 2.0 and 3.5, or about 2.0 and wherein the particle size of the powdered abrasive material homogeneously dispersed in suspension in the water-based gelatinous fluid 60? between # 350 mesh and # 600 mesh.

[00161] Preferably, the average size of the abrasive material granules said composition? between 15 and 60 micrometers.

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

[00163] According to an embodiment, the abrasive water jet cutting method comprises the steps of:

[00164]? have an abrasive water jet cutting machine 1 as previously described,

[00165]? adjust the flow rate of abrasive mixture 160 delivered by the actuator 11 by means of an open-loop control 180.

[00166] According to a further embodiment, the abrasive water jet cutting method comprises the steps of:

[00167]? have an abrasive water jet cutting machine 1 as previously described,

[00168]? perform at least one of the following adjustments by means of a closed-loop control 190:

[00169]? regulation of the flow rate of abrasive mixture 160 delivered by the mixer 150;

[00170]? adjustment of the flow rate of abrasive mixture 160 delivered by the actuator 11;

[00171]? regulation of the flow rate of air introduced by the air duct 110 into the mixing chamber 6;

[00172]? adjusting the drive of the pulsation damper 170.

[00173] Of course, the person skilled in the art, in order to meet contingent and specific needs, will be able to do so. make further modifications and variations, all however contained in the scope of protection cos? as defined by the claims.

[00174] Some experimental tests carried out with the abrasive water jet cutting machine and the composition comprising the abrasive claimed here will be described below, aimed at highlighting its effectiveness and technical advantages.

[00175] Example 1: Shear test on austenitic stainless steel (AISI 301 / EN 1.4310) 2.0 mm thick

[00176] The cutting test? performed on austenitic stainless steel (AISI 301 / EN 1.4310) 2.0 mm thick, to verify the performance of the claimed cutting machine on a relatively thick material.

[00177] 2.0 mm?, In fact, close to the maximum thickness that can be cut effectively with cutting machines in the field of? AWJ of the state of the art known to the inventors.

[00178] The geometry of the cutting groove and the roughness? of the cut wall surface are measured at different depth levels:

[00179]? 0.2 mm from the top? (?top?)

[00180]? in the middle? height (1.0 mm,? mid?)

[00181]? 0.2 mm from the bottom (? Bot?)

[00182] The following Tables 1.1 and 1.2 report the results obtained from the test:

Table 1.1: Shear tests on austenitic stainless steel (AISI 301 / EN 1.4310) 2 mm thick. Macrogeometric verification of the shear wall as the speed varies? advancement.

vf: speed? head advancement

Wtop: upper width of the groove

Wbot: lower width of the groove

Waverage: average width of the sulcus

Taper: inclination of the single wall

Table 1.2: Shear tests on austenitic stainless steel (AISI 301 / EN 1.4310) 2 mm thick. Check of roughness? of the shear wall as the speed varies? advancement.

vf: speed? head advancement

Ra top: roughness? arithmetic mean in proximity? of the top surface of the workpiece

Ra mid: roughness? arithmetic mean in half? thickness of the piece

Ra bot: roughness? arithmetic mean in proximity? of the lower surface of the workpiece

Ra average: average of the Ra values detected

Rz top: roughness? on the 10 extreme points in the vicinity? of the top surface of the workpiece

Rz mid: roughness? on the 10 extreme points in the middle? thickness of the piece

Rz bot: roughness? on the 10 extreme points in the vicinity? of the lower surface of the workpiece

Rz average: average of the measured Rz values

[00183] Two operating conditions are revealed by the test:

[00184]? a full but irregular cut? performed at high vf = 24 mm / min;

[00185]? a high quality cut? ? performed 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 inclinations of the head to compensate for the defect.

[00186] Example 2: Complex cutting test

[00187] The new system proves effective in cutting thick metal plates (at least by abrasive microjet standards) at different vf levels and also in drilling with different strategies.

A complex shape is chosen for a complete characterization of the new system performance. This ? the letter "A" in a particular character, used as a reference piece, since? contains:

[00189] - straight lines, where to measure roughness? and streaks due to irregularities? in the formation of the jet;

[00190] - acute angles, both internal and external, to show the precision of the jet in defining the edges with reduced delay effect (? Jet lag?);

[00191] - small radius curves, to show the radius limit that can be reached according to the size of the jet;

[00192] - thin walls, to demonstrate the high stability? and delicacy of the jet;

[00193] - long working path, as a resistance test for stability? and system robustness.

[00194] The pi? small A obtainable with the focusing nozzle df = 0.20 mm and the abrasive # 230 mesh, the minimum size of the jet currently available in the commercial panorama of micro AWJ,? 12 mm high and? characterized by a minimum radius of 0.12 mm. For the present study, the design? downsized to 75%, reaching cos? a final height of 9 mm and a minimum radius of 0.09 mm.

[00195] Table 2 summarizes the main machining 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 2: configuration and process parameters for making the sample on 2 mm thick austenitic stainless steel (AISI 301 / EN 1.4310).

[00196] The champion? subsequently detached from the base material to be observed and measured. Figure 6 shows the resulting sample in top view, where? You can observe the precision and accuracy resulting from the cut. The sample is used to evaluate the width of the cut in different cutting directions, showing no significant variation in all measurements.

[00197] Example 3: Comparison with the state of the art in the execution of a cut

Here is illustrated the comparison between the abrasive waterjet cutting machine according to the invention and a state of the art abrasive waterjet cutting machine, in performing a cut of a sample of austenitic stainless steel (AISI 301 / EN 1.4310) 2 mm thick.

[00199] The technical specifications of the abrasive waterjet cutting machine according to the invention and the abrasive waterjet cutting machine according to the state of the art are listed in Table 3.1, while the results obtained following the tests are shown in Table 3.2.

[00200] As evidenced by Tables 3.1 and 3.2, and as can be seen from Figure 7, the abrasive water jet cutting machine according to the invention boasts improvements with respect to the prior art, in terms of quality. of the cutting furrow, with 35% reduced width of cut, and quality? of roughness, with Ra and Rz reduced by 57%.

[00201] Furthermore, the abrasive water jet cutting machine according to the invention has obtained these results respecting the tolerance of 1 hundredth of a millimeter on the inclination of the wall (taper).

Table 3.2: Test results

[00202] Naturally, the person skilled in the art, in order to satisfy contingent and specific needs, will be able? make further modifications and variations, all of which are contained within the scope of protection defined by the following claims.

Claims (14)

CLAIMS 1. Abrasive water jet cutting machine (1), comprising: - pumping means (2), which can be fluidically connected to a source of water (3), for generating a flow of pressurized water (4); - a cutting head (5), comprising a primary nozzle (27), a mixing chamber (6) and a focusing nozzle (7), wherein the flow of pressurized water (4) coming from the pumping means (2)? conveyed into the primary nozzle (27) of the cutting head (5) where the pressure energy of the pressurized water flow (4)? converted into kinetic energy to form a jet of water (12), and in which said jet of water (12)? subsequently conveyed into the mixing chamber (6); - a dispensing system (8) of powdered abrasive material, comprising: - a tank (9) containing abrasive powder material, - a feeding tube (10), which fluidically connects the tank (9) to the mixing chamber (6) of the cutting head (5), - an actuator (11) interposed between the tank (9) and the feeding tube (10), which delivers the abrasive material in powder contained in the tank (9) into the mixing chamber (6), through the feeding tube (10 ); in which the cutting head (5) mixes, in the mixing chamber (6), the abrasive material with the jet of water (12) forming a jet of water-abrasive material mixture (13), and said cutting head (5 ) delivers the jet of water-abrasive material mixture (13), through the focusing nozzle (7); in which the powdered abrasive material dispensed into the mixing chamber (6)? homogeneously dispersed in suspension in a water-based gelatinous fluid (60); and in which the actuator (11)? a peristaltic pump (100). Cutting machine (1) according to claim 1, wherein the feed tube (10)? in polymeric material. 3. Cutting machine (1) according to claim 1 or 2, comprising an air duct (110) which flows into the mixing chamber (6). Cutting machine (1) according to one of claims 1 to 3, comprising an electronic controller (120) configured to regulate the flow rate of abrasive mixture (160) delivered by the dispensing system (8). Cutting machine (1) according to one of claims 1 to 4, wherein the tank (9) contains an abrasive mixture (160). Cutting machine (1) according to claim 4 or 5, wherein the electronic controller (120)? configured to regulate the flow rate of abrasive mixture (160) delivered by the actuator (11), by means of an open loop control (180). Cutting machine (1) according to one of claims 1 to 4, wherein the reservoir (9) comprises at least a first reservoir (130) containing water-based gelatinous fluid (60), and at least a second reservoir ( 140) containing abrasive powder material, and in which the delivery system (8) comprises a mixer (150) interposed between the tank (9) and the actuator (11), and configured to mix the water-based gelatinous fluid (60) contained in the at least one first tank (130) with the powdered abrasive material contained in at least a second tank (140), so as to form an abrasive mixture (160), and convey the abrasive mixture (160) into the actuator (11). Cutting machine (1) according to any one of the preceding claims, comprising a pulsation damper (170) fluidically connected to the feed tube (10). Cutting machine (1) according to claim 4 and according to one of claims 3, 7 and 8, wherein the electronic controller (120)? configured to adjust: - the flow rate of abrasive mixture (160) delivered by the mixer (150) and / or - the flow rate of abrasive mixture (160) delivered by the actuator (11) and / or - the flow rate of air introduced by the air duct (110) into the mixing chamber (6) and / or - the actuation of the pulsation damper (170). Cutting machine (1) according to claim 9, wherein the electronic controller (120)? configured to adjust by closed loop control (190). Cutting machine (1) according to any one of the preceding claims, wherein, in the abrasive mixture (160), the mass ratio between the powdered abrasive material and the water-based gelatinous fluid (60)? between 1.0 and 3.5. Cutting machine (1) according to any one of the preceding claims, wherein the feed tube (10)? connected to the cutting head (5) by means of an injector nozzle (38), and in which the injector nozzle (38) protrudes inside the mixing chamber (6). 13. Abrasive water jet cutting method, comprising the steps of: - having an abrasive water jet cutting machine according to one of the preceding claims and according to claim 4; - adjust the flow rate of abrasive mixture (160) delivered by the actuator (11) by means of an open loop control (180). 14. Abrasive water jet cutting method, comprising the steps of: - having an abrasive water jet cutting machine according to one of the preceding claims and according to claims 4 and 9; - carry out at least one of the following adjustments by means of a closed loop control (190): - regulation of the flow rate of abrasive mixture (160) delivered by the mixer (150); - adjustment of the flow rate of abrasive mixture (160) delivered by the actuator (11); - regulation of the flow rate of air introduced by the air duct (110) into the mixing chamber (6); - adjustment of the pulsation damper actuation (170).