Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D17/00—Pressure die casting or injection die casting, i.e. casting in which the metal is forced into a mould under high pressure
  • B22D17/20—Accessories: Details
  • B22D17/32—Controlling equipment
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D46/00—Controlling, supervising, not restricted to casting covered by a single main group, e.g. for safety reasons

Definitions

• the present invention relates to a die-casting system for making metal objects by die-casting a liquid metal material in a foundry department.
• the present invention relates to a method for controlling a die-casting machine configured to make metal objects.
• each die-casting system comprises a die formed by a first fixed half and a second movable half; a cylinder, which is fluidically connected to the die and is configured to be fed with liquid metal material; a piston, which slides inside said cylinder so as to feed the liquid metal material into the die and keep the liquid metal material inside the die under pressure until the liquid metal material solidifies; and a control unit, which is configured to control the operating configuration of the die-casting system as a function of a plurality of preset die-casting parameters.
• the die-casting parameters are preset by skilled personnel based on their own experience. In other words, the management of the die-casting system is largely entrusted to the experience of the skilled personnel and, consequently, is based on empirical and poorly repeatable methods.
• One object of the present invention is to provide a die-casting system which mitigates the drawbacks of the prior art.
• a die-casting system for making metal objects comprising:
• a die-casting machine which is configured to make the metal objects by die-casting a liquid metal material
• a control unit which is configured to set a nominal value of each die-casting parameter of a plurality of die casting parameters, which control the operating configuration of the die-casting machine; to store a reference interval for each die-casting parameter as a function of the quality of the metal objects made by the die-casting machine; to acquire an operating value of each die-casting parameter of the die-casting machine during the die-casting of the liquid metal material; to compare the acquired operating value with the respective reference interval stored; and to vary the nominal value of each die casting parameter as a function of said comparison so that the operating value of each die-casting parameter is comprised within the respective reference interval.
• the present invention it is possible to apply a closed-loop control method in the management of the die-casting system, thereby increasing the quality of the metal objects produced and making the die-casting process reliable and repeatable.
• the operating configuration of the die-casting system can be automatically controlled by varying the nominal value of each die-casting parameter so as to guarantee an adequate quality of the metal objects produced.
• the control unit is configured to vary the nominal value of each die-casting parameter in the event that the operating value of said die-casting parameter is outside the respective reference interval stored.
• control unit is configured to correlate a change in the operating value of each die casting parameter with a change in the operating value of the further die-casting parameters; and to vary the nominal value of at least one die-casting parameter as a function of said correlation so that the operating value of each die-casting parameter is comprised within the respective reference interval.
• the changes in a die-casting parameter can be corrected by acting on the other die-casting parameters with which it is correlated by means of binary correlation techniques or multivariate statistical analysis.
• control unit is configured to linearly combine a plurality of die-casting parameters so as to define a respective die-casting factor; to store a reference interval for each die-casting factor; and to vary the nominal value of at least one linearly combined die casting parameter so that the respective die-casting factor is comprised within the respective reference interval.
• the nominal value of each die-casting parameter can be controlled through factor analysis of the operating values of the plurality of die-casting parameters.
• the operating value of a die-casting parameter can be varied without the need to directly control said die-casting parameter.
• control unit is configured to store a correlation matrix indicative of the change in the operating value of each die-casting parameter as a function of the change in the operating value of the further die casting parameters.
• the system comprises a plurality of sensors, each of which is connected to the control unit and is configured to acquire the operating value of a respective die-casting parameter so as to provide the control unit with said operating value.
• the die-casting machine comprises a die, which is provided with a fixed portion and a movable portion; a cylinder, preferably of the hydraulic type, which is connected in a fluidic manner to the die and is configured to be fed with liquid metal material; a piston, which slides inside the cylinder so as to feed the liquid metal material inside the die and keep the liquid metal material inside the die under pressure until the liquid metal material solidifies; the die-casting parameters comprising a sliding speed of the piston within the cylinder, and/or a stroke of the piston within the cylinder, and/or a pressure within the die, and/or a temperature of the liquid metal material, and/or a time for holding the liquid metal material under pressure within the die.
• a further object of the present invention is to provide a method for controlling a die-casting machine, which reduces at least one of the drawbacks of the prior art.
• a method for controlling a die-casting machine configured to make metal objects by die-casting a liquid metal material, the method comprising the steps of: setting a nominal value of each die-casting parameter of a plurality of die-casting parameters, which control the operating configuration of the die-casting machine; - providing a reference interval for each die-casting parameter as a function of the quality of the metal objects made by the die-casting machine; acquiring an operating value of each die-casting parameter during the die-casting of the liquid metal material; comparing the acquired operating value with the respective reference interval provided; and varying the nominal value of each die-casting parameter as a function of said comparison so that the operating value of each die-casting parameter is comprised within the respective reference interval.
• the present method increases the quality of the metal objects produced and guarantees the reliability and repeatability of the die-casting process.
• FIG. 1 is a schematic view of a die-casting system in a first operating configuration, made in accordance with the present invention
• Figure 2 is a schematic view of the die-casting system in Figure 2 in a second operating configuration
• Figure 3 is a flow chart of a first operating condition of the die-casting system in Figure 1;
• Figure 4 is a flow chart of a second operating condition of the die-casting system in Figure 1; and - Figure 5 is a graphical representation of a correlation matrix for correlating the die-casting parameters of the die-casting system in Figure 1.
• reference numeral 1 indicates, as a whole, a die-casting system for making metal objects.
• the present invention relates to a die casting system 1 for making metal objects by die-casting a liquid metal material 2 in a foundry department, without thereby limiting the wide range of possible applications of the present invention.
• the liquid metal material 2 can be an aluminium alloy, or a zinc alloy, or a magnesium alloy.
• the die casting system 1 comprises a die-casting machine 3, which is configured to make the metal objects by die-casting a liquid metal material 2.
• the machine 3 comprises a die 4, which is provided with a fixed portion 5 and a movable portion 6; a cylinder 7, preferably of the hydraulic type, which is connected in a fluidic manner to the die 4 and is configured to be fed with liquid metal material 2; a piston 8, which slides inside the cylinder 7 so as to feed the liquid metal material 2 into the die 4 and keep the liquid metal material 2 inside the die 4 under pressure until the liquid metal material 2 solidifies; and a control unit 9, which is configured to control the operating configuration of the machine 3.
• the fixed portion 5 and the movable portion 6 of the die 4 when coupled, delimit therebetween a cavity 10 having the shape of the metal object to be made.
• the movable portion 6 of the die 4 is provided with extraction pins 11, each of which is movable between a retracted position and an extended position, so as to allow the extraction of the metal object from the movable portion 6 of the die 4.
• the die-casting cycle comprises an injection step, in which the piston 8 pushes the liquid metal material 2 close to the cavity 10; a step of filling the cavity 10 with the liquid metal material 2; and a step of keeping the liquid metal material 2 under pressure inside the cavity 10 until the liquid metal material 2 solidifies.
• Figure 3 shows a first embodiment of the present invention, wherein the control unit 9 is configured to set a nominal value of each die-casting parameter of a plurality of die-casting parameters, which control the operating configuration of the machine 3; to store a reference interval for each die-casting parameter as a function of the quality of the metal objects made by the machine 3; to acquire an operating value of each die- casting parameter of the machine 3 during the die-casting of the liquid metal material 2; to compare the acquired operating value with the respective reference interval provided; and to vary the nominal value of each die-casting parameter as a function of said comparison so that the operating value of each die-casting parameter is comprised within the respective reference interval.
• control unit 9 is configured to vary the nominal value of each die-casting parameter in the event that the operating value of said die-casting parameter is outside the respective reference interval provided.
• the die-casting parameters are used to control the machine 3 during the die-casting of the liquid metal material 2.
• the die-casting parameters comprise the sliding speed of the piston 8, and/or the stroke of the piston 8 inside the cylinder 7, and/or the pressure within the cavity 10, and/or the temperature of the liquid metal material 2, and/or the time for holding the liquid metal material 2 under pressure within the cavity 10.
• the die-casting parameters comprise the stroke of the piston 8 inside the cylinder 7 during the injection step, and/or the stroke of the piston 8 inside the cylinder 7 during the filling step, and/or the sliding speed of the piston 8 during the injection step, and/or the sliding speed of the piston 8 during the filling step, and/or the maximum pressure in the cavity 10.
• control unit 9 is configured to convert the nominal value of a given die-casting parameter into an electrical signal and to provide a respective actuating device of the machine 3 with said electrical input signal.
• the nominal value of the sliding speed of the piston 8 is converted by the control unit 9 into a respective electrical signal and is transmitted by the control unit 9 to a device for actuating the piston 8, for example a pump, which makes the piston 8 slide inside the cylinder 7 at a sliding speed determined by said electrical signal.
• Figure 4 shows a second embodiment of the present invention, wherein the control unit 9 is configured to correlate a change in the operating value of each die casting parameter with a change in the operating value of the further die-casting parameters; and to vary the nominal value of at least one die-casting parameter as a function of said correlation so that the operating value of each die-casting parameter is comprised within the respective reference interval.
• the control unit 9 is configured to linearly combine a plurality of die-casting parameters so as to define a respective die-casting factor; to store a reference interval for each die-casting factor; and to vary the nominal value of at least one linearly combined die- casting parameter so that the respective die-casting factor is comprised within the respective reference interval.
• control unit 9 is configured to define a plurality of die-casting factors, each of which derives from a respective linear combination of the die casting parameters.
• control unit 9 is configured to store a correlation matrix 12 indicative of the change in the operating value of each die-casting parameter P1-P18 as a function of the change in the operating value of the further die-casting parameters Pl- P18.
• the colour shades of the elements of the correlation matrix 12 are indicative of the degree of influence that each die-casting parameter has on the other die-casting parameters.
• the die-casting system 1 comprises a plurality of sensors 13, 14, 15, and 16, each of which is connected to the control unit 9 and is configured to acquire the operating value of a respective die-casting parameter.
• the die-casting system 1 comprises a speed sensor 13, which is configured to acquire the sliding speed of the piston 8; a position sensor 14, which is configured to acquire the displacement of the piston 8 inside the cylinder 7; a pressure sensor 15, which is configured to acquire the pressure within the cavity 10; and a temperature sensor 16, which is configured to acquire the temperature of the liquid metal material 2 within the cavity 10.
• control unit 9 comprises a PLC controller 17, which is configured to store the nominal values of each die-casting parameter and the reference intervals of each die-casting parameter and each die casting factor.
• PLC Programmable Logic
• PLC Physical Process Controller
• a ladle 18 feeds the liquid metal material 2 into the cylinder 7.
• the amount of liquid metal material 2 fed into the cylinder 7 is sufficient to completely fill up the cavity 10 of the die 4.
• control unit 9 actuates the piston 8 so as to cause the sliding of the piston 8 inside the cylinder 7 and, consequently, the feeding of the liquid metal material 2 into the cavity 10 of the die 4.
• the piston 8 keeps the liquid metal material 2 inside the cavity 10 under pressure until the liquid metal material 2 solidifies.
• the fixed portion 5 and the movable portion 6 are cooled by respective cooling circuits, not shown in the accompanying drawings, thereby accelerating the solidification of the liquid metal material 2.
• control unit 9 commands the opening of the die 4, separating the movable portion 6 from the fixed portion 5. At this point, the extraction pins 11 are extended so as to extract the metal object from the movable portion 6 of the die 4.
• the control unit 9 stores a plurality of quality parameters (block 19), each of which is indicative of the quality of a respective metal object made by the machine 3.
• each quality parameter is indicative of a category and/or size of any defects found in the respective metal object made.
• the control unit 9 stores the operating values of the die-casting parameters of each metal object made (block 20) and associates each quality parameter with the respective operating values of the die-casting parameters stored (block 21).
• the control unit 9 correlates the stored quality parameters to the respective operating values of the stored die-casting parameters (block 22) and, by means of multivariate statistical analysis techniques, determines the influence of the operating values of the die-casting parameters on the respective quality parameters.
• the multivariate statistical analysis techniques used are known per se and include, for example, a Pareto analysis and/or a factor analysis of the operating values of the die-casting parameters.
• control unit 9 Based on the correlations between the operating values of the die-casting parameters and the respective quality parameters, the control unit 9 identifies a nominal value (block 23) and a reference interval (block 24) for each die-casting parameter so as to optimize the quality parameters of the metal objects made, and sets said nominal values (block 25) and said reference intervals (block 26) in the PLC controller 17.
• each sensor of the plurality of sensors 13, 14, 15, and 16 acquires a respective operating value of the die-casting parameters (block 27) and transmits said operating values to the control unit 9.
• the control unit 9 compares the acquired operating value with the respective stored reference interval (block 28) and, in the event that the acquired operating value is outside the respective stored reference interval, varies the setting of the nominal value of the respective die casting parameter (block 25) so that the operating value of said die-casting parameter is comprised within the respective reference interval during the subsequent die casting processes.
• control unit 9 stores a plurality of operating values of the die-casting parameters of each metal object made (block 20).
• control unit 9 Based on the plurality of operating values of the die casting parameters, the control unit 9, by using multivariate statistical analysis techniques, correlates a change in the operating value of each die-casting parameter with a change in the operating value of the further die casting parameters (block 29).
• control unit 9 through said correlation, provides a correlation matrix 12 ( Figure 5) indicative of the change in the operating value of each die-casting parameter as a function of the change in the operating value of the further die-casting parameters.
• control unit 9 linearly combines a plurality of die- casting parameters so as to define a respective die-casting factor (block 30) and, based on the reference intervals stored for each reference parameter, calculates a reference interval for each die-casting factor (block 31).
• each die-casting factor is determined by using a technique for factor analysis of the die-casting parameters .
• the control unit 9 sets said calculated reference intervals in the PLC controller 17 (block 32).
• the control unit 9 calculates each die-casting factor (block 33) based on the operating values of the acquired die-casting parameters and compares each calculated die-casting factor with the respective set reference interval (block 34). In the case where a calculated die-casting factor is outside the respective set reference interval, the control unit 9 varies the setting of the nominal value of at least one linearly combined die-casting parameter (block 25) so that the respective die-casting factor is comprised within the respective reference interval in a subsequent die casting process.

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• Molds, Cores, And Manufacturing Methods Thereof (AREA)

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• 2022
  • 2022-05-20 EP EP22726533.7A patent/EP4341020A1/de active Pending
  • 2022-05-20 WO PCT/IB2022/054719 patent/WO2022243950A1/en active Application Filing

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