CN113084202A - Melt flow control device and method for melt coating forming process - Google Patents

Melt flow control device and method for melt coating forming process Download PDF

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Publication number
CN113084202A
CN113084202A CN202110292839.7A CN202110292839A CN113084202A CN 113084202 A CN113084202 A CN 113084202A CN 202110292839 A CN202110292839 A CN 202110292839A CN 113084202 A CN113084202 A CN 113084202A
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pressure
melt
crucible
flow
plc
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CN113084202B (en
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魏正英
贺鹏飞
杜军
马琛
蒋敏博
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Xian Jiaotong University
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Xian Jiaotong University
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/115—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces by spraying molten metal, i.e. spray sintering, spray casting
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y30/00—Apparatus for additive manufacturing; Details thereof or accessories therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y50/00—Data acquisition or data processing for additive manufacturing
    • B33Y50/02—Data acquisition or data processing for additive manufacturing for controlling or regulating additive manufacturing processes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/25—Process efficiency

Abstract

The invention discloses a melt flow control device and method for a melt coating forming process. The water-cooled top cover is positioned above the smelting crucible, and the melting coating head is arranged below the smelting crucible; the crucible smelting unit is communicated with the pneumatic driving unit; the jet flow starting and stopping device drives the starting and stopping control rod to compress downwards or lift upwards so as to realize the starting and stopping of jet flow. The pressure control adopts three-level division: the computer sends injection pressure to the PLC according to the pressure-flow function relation, the PLC receives a melt liquid level signal from the laser ranging module and the injection pressure of the industrial computer at the same time, sends a pressure control instruction to the pressure controller, and the pressure controller realizes real-time control of gas pressure in the crucible, so that accurate control of jet flow in the forming process is realized, and high-precision and high-efficiency coating forming of the target part is completed.

Description

Melt flow control device and method for melt coating forming process
Technical Field
The invention belongs to the technical field of additive manufacturing (3D printing), and relates to a 3D printing head and a flow control method thereof, in particular to a 3D printing head for metal material coating forming and a flow control method thereof.
Background
The core idea of additive manufacturing technology (also known as "3D printing") is to perform two-dimensional discretization on three-dimensional parts to form slice data, gradually combine discrete forming materials together according to the layered data of the three-dimensional CAD model of the parts to form layered sections, and then build up layer by layer to form solid parts, without a mold, directly manufacture the parts, which can greatly reduce the cost and shorten the development cycle. The differences in the form of printed materials in the current methods for additive manufacturing of metallic materials are mainly classified into three categories, namely additive manufacturing techniques based on powdered materials, additive manufacturing techniques based on filamentary materials and additive manufacturing techniques based on molten metals.
The additive manufacturing technology based on the powder material is developed most mature, and mainly represents selective laser area forming (SLM), laser cladding (LD) and electron beam melting forming (EBM), wherein the SLM and EBM forming technology adopts a powder paving mode, and paved powder material is selectively melted by high-energy beams (laser or electron beams) and is formed layer by layer. The LD forming technology adopts an airflow powder loading mode to feed materials, a plurality of powder feeding pipes are externally arranged on a focused laser beam and are annularly arranged, and mixed airflow and powder are sprayed and converged near the focus of the laser beam through the plurality of powder feeding pipes, are melted under the action of the laser beam and are cladded layer by layer.
In the wire material additive manufacturing technology, high-energy beams such as electric arcs, lasers, electron beams and the like are mostly adopted to melt wire materials and matrixes in the feeding process, the melted wire materials are fed to a molten pool in a liquid drop or liquid bridge mode, and the matrixes refer to substrates or formed layers which are deposited layer by layer along with relative movement of the substrates and the high-energy beams.
Additive manufacturing technologies based on molten metal are mainly divided into two types, one is a micro-spray molten drop forming technology, and the other is a molten coating forming technology. Both adopt crucibles to melt the forming material, and adopt a pneumatic driving mode to spray the melted forming material from the bottom of the crucibles. The difference is that the micro-spray molten drop forming technology adopts a pulse air pressure or piezoelectric excitation mode to disperse the sprayed melt into uniform molten drops, and the uniform molten drops are selectively sprayed to specific positions by means of heat carried by the molten drops and are remelted and solidified to a certain degree with deposited parts around. The melting coating forming technology adopts continuous air pressure driving, and the molten metal in the crucible flows out at a certain flow and flow speed through a spray hole in the melting coating head at the bottom of the crucible under the driving of the air pressure. The lower end face of the coating head is at a small distance from the substrate or the upper shaping layer, the flowing metal forms molten metal filling or semi-molten metal filling between the end of the coating head and the upper shaping layer under the influence of gravity, surface tension and viscosity, and forms a thin-layer deposition layer during the relative movement of the coating head and the substrate. The heat carried by the melt sprayed by the coating head and the heat transferred downwards from the end face of the coating head act together to promote the sufficient metallurgical fusion of the current forming layer and the upper forming layer, so that the three-dimensional part is selectively deposited layer by layer to complete the manufacture of the three-dimensional part. If the thermal conductivity of the printing material is high, the heat carried by the sprayed melt and the heat transferred downwards by the coating head are not enough to form good metallurgical bonding, an auxiliary heat source is also required to be introduced to assist remelting, and the auxiliary heat source can adopt an electron beam, a laser beam, an electric arc or other high-energy beams with small impact.
The metal melting coating forming technology is a metal component rapid forming technology with wide prospect, has high forming efficiency and low manufacturing cost, and is particularly suitable for forming large metal thin-wall components. Its lower heat input results in less deformation and residual stress of the forming member. The contact type forming mode can effectively restrain the layer height of the forming layer, a forming surface with uniform layer height is formed, and a complex layer height control technology is not needed.
One of the core technologies for realizing the molten coating forming of the metal component is to form a melt jet with a stable and controllable flow rate, which is a precondition for the coating forming. Three key links are needed for realizing stable and controllable melt flow: the device comprises a reliable crucible smelting unit, an accurate air pressure driving unit and a jet flow starting and stopping unit with quick response.
The traditional method for stopping the jet flow by reducing air pressure or extracting negative pressure treats the jet flow stop as a special state with the jet flow rate of 0, which is widely applied to many occasions with low requirements on jet flow start-stop response, but for 3D printing, the response speed is far from the requirements of a process system.
The crucible smelting unit is responsible for melting original solid materials in the crucible to a specific temperature, a top cover which is communicated with water is arranged at the top of the crucible, a corresponding pipeline and sensing equipment are arranged above the top cover, and a coating head used for spraying and coating a melt is arranged at the bottom of the crucible. The control of the melt flow is accomplished by controlling the gas pressure above the melt, and for a particular coating head internal orifice, the flow is primarily dependent on the difference between the gas pressure inside the crucible and the external gas pressure, with greater pressure differences increasing the flow. The temperature of the melt can also interfere the flow to a certain extent, which is mainly shown in the influence on the viscosity of the melt, wherein the melt viscosity is small when the temperature is high, the outflow is easier, the melt viscosity is large when the temperature is low, and the outflow resistance is larger. In the practical process, the temperature of the melt is in a small range above the liquid phase line of the melting material, and the viscosity change of the melt is very small in the temperature range, so that the influence of the temperature of the melt on the flow is far lower than the influence of air pressure fluctuation on the flow of the melt, and the difficulty of temperature detection and control is far lower than the real-time detection and control of the pressure. Therefore, the key to flow stability control is to build an accurate pressure control unit.
A conventional pressure control unit includes an inert gas supply device for supplying an inert gas at a relatively high pressure, the inert gas at a high pressure is reduced to an appropriate value by a pressure reducing and regulating valve, the reduced gas is connected to a crucible pressure inlet through a high frequency solenoid valve, and a pressure sensor for detecting the crucible pressure is disposed on a bypass of the pressure inlet, and finally the control of the gas pressure in the crucible is controlled by opening and closing the high frequency solenoid valve. The pressure control system is simple in structure, economical and practical, is very suitable for occasions with low pressure control precision requirements, but has large pressure fluctuation, and the phenomenon of pressure overshoot is easy to occur, so that the phenomenon of unstable flow control is caused. The system adopting the pressure control scheme usually ignores the pressure generated by the weight of the melt, and the pressure control is inaccurate, and larger flow control errors are caused.
In order to realize the quick stop of the melt injection, a commonly adopted method is to add an air exhaust bypass on a crucible air inlet pipeline, the air exhaust bypass is connected with an exhaust fan with controllable rotating speed, after a system receives a jet flow stop command, an air inlet electromagnetic valve is quickly closed, the air exhaust bypass is opened, the pressure is quickly reduced, a certain degree of negative pressure is generated, and the jet flow is stopped along with the reduction of the pressure. When jet flow is needed, the air exhaust bypass is closed, the high-frequency electromagnetic valve works normally to inflate the crucible, and the melt flows out through the coating head under the action of gas pressure. The same method also has the great disadvantage that the flow start and stop can not respond quickly, and often needs several seconds. The reason for the large time lag is mainly because the pressure gas above the crucible has a certain volume, and the pressure increase or reduction is realized by inflation and air exhaust, and the process needs a certain time.
To ensure that the metal member melting coating forming process can realize the rapid forming of complex shapes, the flow of the melt must be accurately controlled, the flow can be dynamically adjusted within a certain range, and the melt jet flow generation and termination are in rapid response. Meanwhile, the temperature control mode of the melting crucible and the melting coating head needs to ensure the stability and controllability of the temperature of the outflow melt in the melting coating process.
Disclosure of Invention
The invention provides a melt flow control device and a flow control method for a melt coating forming process, which can realize stable low-speed melt jet flow capable of being adjusted on line and also provide a dynamic high-response jet flow starting and stopping method.
In order to achieve the purpose, the melt flow control device for the melt coating forming process comprises 1, a melt flow control device for the melt coating forming process, and is characterized by comprising a crucible smelting unit, a melt coating head assembly, a pneumatic driving unit, a jet flow starting and stopping device, a melt static pressure measuring device and a PLC (programmable logic controller);
the crucible smelting unit comprises a smelting crucible, a water-cooling top cover is arranged on the smelting crucible, a crucible air inlet/outlet is arranged on the water-cooling top cover, the crucible air inlet is connected with an air pressure driving unit, an air pressure detection port is arranged on the water-cooling top cover, and the air pressure detection port is connected with a pressure sensor for measuring real-time air pressure in the crucible;
the melt coating head assembly comprises a melt coating head, the melt coating head is arranged below the smelting crucible and is matched and sealed with the smelting crucible by a conical surface;
the air pressure driving unit comprises an argon tank, the argon tank is connected with an inlet of a pressure controller, and an outlet of the pressure controller is communicated with the crucible smelting unit through an exhaust protection temperature switch; the pressure controller comprises three gas interfaces and two signal interfaces, the two signal interfaces are respectively connected with the PLC and the pressure sensor, the three gas interfaces are respectively an air inlet, an air outlet and an air outlet, the air outlet and the air outlet are both connected in series with a high-frequency electromagnetic valve, and an operation controller for controlling the opening and closing states of the two high-frequency electromagnetic valves is arranged in the air outlet and the air outlet; the pressure sensor is connected with the input end of the signal distributor, and two output ends of the signal distributor are respectively connected with the PLC and the pressure controller;
the jet flow starting and stopping device comprises a starting and stopping control rod and an electromagnetic driving device for driving the starting and stopping control rod to compress downwards or lift upwards, and a sealing cone at the lower end of the starting and stopping control rod is matched with the upper end of the coating head through a conical surface to realize starting and stopping sealing;
the melt static pressure measuring device comprises a distance meter for measuring the height of the melt in the melting crucible, the distance meter is connected with a PLC, and the PLC is used for receiving an injection pressure control command and a jet state command sent by an industrial computer.
Further, the pressure control commandLet a value including the melt injection pressure Δ P, Δ P ═ Pj+ P, wherein PjStatic pressure of the melt is adopted, and P is the air pressure of a crucible above the melt; PLC according to injection pressure delta P and melt static pressure PjCalculating a required value P of the current crucible air pressure, and transmitting the required value P of the crucible air pressure to a pressure controller by an analog quantity signal;
the pressure controller is used for receiving a required air pressure P signal from the PLC in real time and a real-time air pressure P 'signal in the smelting crucible measured by the pressure sensor, comparing the required air pressure P with the real-time air pressure P' in real time, controlling the opening and closing of an air inlet electromagnetic valve and an air outlet electromagnetic valve in the pressure controller, and further controlling the air pressure in the crucible to a required value P;
the jet flow state command comprises the lifting or pressing of the start-stop control rod, the PLC sends an instruction to control the electromagnetic driving device to act, and then the lifting or pressing of the start-stop control rod is achieved, so that the starting and the quick stopping of jet flow are achieved.
Further, electromagnetic drive device includes electro-magnet and pressure spring, the electro-magnet inboard is provided with the iron core, and the iron core with open and stop the pole lock sleeve and pass through threaded connection, open and stop the pole lock sleeve design and have the toper locking head of petal form and be used for embracing tightly and start and stop the pole, pressure spring upper end and packing force adjusting nut fixed connection, lower extreme fixed connection open and stop control lever upper portion.
Furthermore, a thermocouple core for measuring the temperature of the melt in the smelting crucible is arranged in the start-stop control rod.
Further, the exhaust protection temperature switch comprises an electromagnetic valve, a first buffer gas cylinder and a second buffer gas cylinder which are sequentially connected, a pipeline temperature sensor is arranged on a pipeline between the first buffer gas cylinder and the second buffer gas cylinder and connected with a PLC, and the PLC is used for sending a control command to the electromagnetic valve 3-6.
Further, a crucible sealing ring is arranged between the water-cooling top cover and the smelting crucible.
Furthermore, the open end of the upper part of the smelting crucible is provided with a connecting thread, and the lower part of the connecting thread is provided with a throat part.
Further, the distance measuring instrument is a laser distance measuring instrument.
A melt flow control method of a melt coating forming process based on the device comprises the following steps:
step 1: assembling a melting crucible and a melt coating head assembly together; cleaning the blocky, filiform or powdery material to be melted, weighing and loading into a melting crucible, and then installing the melting crucible filled with the material to be melted on a water-cooled top cover;
step 2: replacing the atmosphere environment in the smelting crucible, filling inert gas into the smelting crucible, keeping a certain air pressure, lifting a start-stop control rod, and measuring the gas flow at the outlet of the coating head: if the gas flow is abnormal, checking and reassembling the melt coating head assembly; if the gas flow is normal, entering step 3;
and step 3: downwards pressing a start-stop control rod, opening an induction heater, and stabilizing the temperature in the smelting crucible to T1When the temperature is high, the nozzle heater is started; temperature of the nozzle stabilized to T2If so, entering the step 4;
and 4, step 4: obtaining the current crucible liquid level h0And calculating the current melt mass m'0(ii) a Mixing current melt mass m'0And the mass m of the raw material obtained in step 10Comparing and measuring the liquid level h0Correcting, and starting a crucible liquid level feedback mode in the air pressure driving unit;
and 5: generating a process control instruction, importing a model to be printed into model processing software in an industrial computer, setting the layering height and the flow, planning a printing path by the model processing software according to the model and basic settings, and forming an executable command document which can be identified by a process system;
step 6: importing a command document of a technological process into technological control software in an industrial computer; the jet flow state information is used for controlling the stopping and the generation of jet flow, and the flow information is used for controlling the pressure driving unit; the PLC receives the injection pressure delta P sent by the industrial computer; the distance meter transmits the real-time liquid level signal to the PLC, and the PLC converts the real-time liquid level signal into the static pressure value P of the current meltjThus according to the formula Δ P ═ Pj+ P obtains the air pressure requirement value P; the PLC converts the air pressure requirement value P into a corresponding analog quantity signal and transmits the analog quantity signal to the pressure controller, and the pressure controller receives and compares a real-time crucible air pressure signal P 'transmitted by the pressure sensor to control the opening and closing of two paths of high-frequency electromagnetic valves in the pressure controller, so that the pressure value P' in the crucible tends to the air pressure requirement value P; when a jet flow generation command is received, the start-stop control rod is lifted, the melt is sprayed under the action of the spraying pressure delta P, and when a jet flow stop command is received, the start-stop control rod is pressed downwards, so that the jet flow of the melt stops rapidly.
Further, before step 5, a melt flow verification is performed, wherein the melt flow verification comprises the following steps: adjusting the melt injection pressure delta P to be 20KPa, controlling the start-stop control rod to lift, enabling jet flow to occur, recording the flow of three groups of 1-2 min duration, taking an average value, and calculating as Qm-20(ii) a Comparison Qm-20And its theoretical value Q'm-20If the difference between the two is more than 10%, checking and reassembling the crucible melting unit; if Qm-20And Q'm-20If the difference is less than 10%, adjusting the melt injection pressure to be delta P of 40KPa, controlling the start-stop control rod to lift, enabling jet flow to occur, recording three groups of flow with the time length of 1-2 minutes, taking an average value, and calculating the average value as Qm-40(ii) a Using Qm-20And Qm-40Determines the pressure Δ P and the flow QmFunctional relationship between; calculating the flow Q 'when the pressure delta P is 30KPa by using the newly determined pressure-flow function relation'm-30(ii) a Adjusting the melt injection pressure delta P to be 30 KPa; controlling the start-stop control rod to lift, enabling jet flow to occur, recording the flow of three groups of 1-2 min duration, taking an average value, and calculating the average value as Qm-30(ii) a Comparative Q'm-30And Qm-30If the difference value between the two values is less than 2%, the flow verification is successful; if Q'm-30And Qm-30If the difference is greater than 2%, the pneumatic driving system needs to be checked to ensure that the flow is checked again after the pneumatic driving system works normally.
Compared with the prior art, the invention has at least the following beneficial technical effects:
the invention separates two key elements in flow control, namely the jet flow starting and stopping state and the jet flow, controls the jet flow starting and stopping state by controlling the lifting/pressing of the starting and stopping control rod, and controls the jet flow by controlling the air pressure of the crucible above the melt, thereby greatly improving the accuracy and the response capability of the flow control. The jet flow and the jet starting and stopping states are controlled by two independent subsystems which are matched with each other, so that the jet flow can be quickly stopped and generated on the premise of ensuring the stable control of the driving air pressure.
Furthermore, the jet flow start-stop control device adopts a spring to compress downwards, so that the pressing force is reliable and the adjustment is convenient; the lifting of the start-stop control rod is directly driven by an electromagnet, so that intermediate links are reduced, and the response speed is improved; the tail end of the start-stop control rod is provided with the replaceable sealing cone, so that the device can be ensured to have longer service life; the iron core and the start-stop control rod adopt petal-shaped tapered locking sleeves, so that the locking is reliable, and the dismounting is convenient.
Furthermore, the hollow part of the start-stop control rod is directly embedded into the thermocouple, and high-heat-conductivity magnesia powder is filled between the thermocouple wire and the tube wall of the start-stop control rod, so that the whole device is compact in spatial arrangement, and quick in temperature measurement response.
Furthermore, the invention provides a crucible connection mode which can be used in a high-temperature environment, the open end of the top of the melting crucible is in threaded connection with the water-cooling top cover, the sealing ring at the joint is made of rubber, and the throat part is arranged close to the threaded opening of the crucible and can effectively reduce the upward conduction of heat of the high-temperature part below the throat part, so that the temperature of the position where the sealing ring is located is not higher than the failure temperature of the rubber sealing ring. The crucible connecting scheme has a compact structure, does not have an outwardly protruding flange structure, can be conveniently disassembled and assembled under the condition that the heating coil is not disassembled, and is particularly suitable for being used in an atmosphere protection environment in which the heating coil is difficult to disassemble and assemble.
Furthermore, the influence of the static melt pressure on the jet flow injection pressure is considered, and the method has important significance for maintaining the stability of the melt injection pressure. For high-temperature metal melt, the liquid level detection is difficult, and the contact type measuring equipment is difficult to continuously work in a high-temperature environment. The invention adopts a laser ranging mode, so that the damage of high-temperature melt to detection equipment can be avoided. Any molten metal has more or less oxide layers on the upper surface of the melt, and the oxide layers can greatly reduce the specular reflection effect of the metal melt, so that the surface of the molten metal generates certain diffuse reflection, and the possibility of detecting the melt liquid level by adopting a laser ranging mode is provided. Therefore, the method for detecting the liquid level of the high-temperature metal melt by adopting the laser ranging method provides a reliable method for accurately controlling the melt injection pressure.
Furthermore, the device adopts a double-nut locking mode at the position for adjusting the electromagnet mounting seat and the pressing force adjusting nut, so that the device can be ensured to operate reliably in a vibration environment caused by the reciprocating motion of the start-stop control rod.
The method adopts an industrial computer-PLC-pressure controller multi-level control mode, wherein the industrial computer converts flow control into pressure control according to the corresponding relation between flow and pressure and sends a pressure control instruction to the PLC; the PLC receives a real-time liquid level signal transmitted by the laser range finder, converts the real-time liquid level signal into a melt static pressure signal and sends an air pressure control instruction to the pressure controller; the pressure controller receives a real-time pressure signal transmitted by the pressure sensor, compares the real-time pressure signal with a pressure control command transmitted by the PLC, and controls the opening and closing of the high-frequency electromagnetic valve inside in real time, so that the stable control of the crucible air pressure is realized. Obviously, the three levels of pressure control link respond differently, the fastest to respond is the pressure controller, followed by the PLC and finally the industrial computer. And the other process control tasks which are responsible for the industrial computer are the heaviest, and the PLC is the second one. The multi-stage air pressure control mode enables the task amount allocated by each control link to be equivalent, thereby avoiding mutual waiting among signals to a great extent and greatly improving the precision of pressure control.
Drawings
FIG. 1 is a schematic view of a melt flow control device for use in a metal melt coating process according to the present invention;
FIG. 2a is a schematic diagram of melt jet start-stop control in a lifting state;
FIG. 2b is a schematic diagram of start-stop control of melt jet flow in a compacted state;
FIG. 3 is a schematic diagram of a pneumatic drive unit of the present invention;
FIG. 4 is a start stop lever locking sleeve.
In the drawings: 1. a crucible smelting unit, 1-1 parts of a water-cooled top cover, 1-2 parts of a crucible sealing ring, 1-3 parts of a smelting crucible, 1-4 parts of an induction heating coil, 1-5 parts of a high-temperature melt, 1-6 parts of a cooling water inlet, 1-7 parts of a cooling water outlet, 1-8 parts of a throat part, 1-9 parts of a shallow hole, 1-10 parts of a crucible air inlet/outlet, 1-11 parts of an air pressure detection port, 1-12 parts of a laser distance sensor detection port, 1-13 parts of a start-stop control rod connection port, 2-1 parts of a coating head mounting screw, 2-2 parts of a melting coating head, 2-3 parts of a nozzle heater, 3 parts of an air pressure driving unit, 3-1 parts of an argon tank, 3-2 parts of a primary pressure reducing valve, 3-3 parts of a precise pressure regulating valve, 3-5 parts of discharge protector, 3-6 parts of electromagnetic valve, 3-7 parts of first buffer gas cylinder, 3-8 parts of pipeline temperature sensor, 3-9 parts of second buffer gas cylinder, 3-10 parts of high-temperature electromagnetic valve, 3-11 parts of signal distributor, 3-12 parts of PLC (programmable logic controller), 3-13 parts of solid-state relay, 3-14 parts of pressure sensor, 4-1 parts of corrugated pipe, 4-2 parts of sliding bearing seat, 4-3 parts of electromagnet locking nut, 4-4 parts of start-stop rod locking sleeve, 4-5 parts of iron core, 4-6 parts of electromagnet mounting seat, 4-7 parts of electromagnet, 4-8 parts of compression spring locking nut, 4-9 parts of compression force adjusting nut, 4-10 parts of compression spring, 4-11 parts of start-stop control rod, 4-12 parts of start-stop control rod, 4-13 parts of thermocouple core, 5-1 parts of sealing cone, 5-2 parts of range finder, 5-3 parts of quartz glass, 5-4 parts of quartz glass locking nut, 6 parts of sealing ring and an industrial computer.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.
In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on those shown in the drawings, and are used only for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.
Referring to fig. 1, a melt flow control device for a melt coating forming process includes a crucible melting unit 1, a melt coating head assembly, a pneumatic driving unit 3, a jet start-stop device, a melt static pressure measuring device, and an industrial computer 6.
The crucible smelting unit 1 is used for heating the melt to be molten and maintaining a proper temperature; the melt static pressure measuring device 5 is responsible for acquiring the real-time liquid level of the melt in the smelting crucibles 1-3 and transmitting the liquid level information to the air pressure driving unit 3 by analog quantity signals; the air pressure driving unit 3 receives real-time liquid level information from the melt static pressure measuring device 5 according to an air pressure control command of the industrial computer 6, adjusts the air pressure above the melt in the melting crucible 1-3, and the jet pressure at the front end of the melting coating head 2-2 meets the command requirement of the industrial computer 6; the jet flow starting and stopping device realizes the rapid stopping and generation of melt jet flow by the actions of downward pressing and upward lifting of the starting and stopping control rods 4-11; the melt coating head 2-2 realizes outward injection of melt in the melting crucible 1-3 under the action of pressure, and when the pressure control range of the air pressure driving unit 3 is determined, the melt coating head 2-2 determines the melt injection flow range and flow rate; the combination of the crucible smelting unit 1, the melt coating head assembly, the pneumatic driving unit 3, the jet flow starting and stopping device and the melt static pressure measuring device forms a melt flow control system taking a PLC3-12 as a core. The flow control system receives a melt injection pressure and jet state instruction from the industrial computer 6, when the jet state is 1, the jet is generated, and the melt injection pressure delta P determines the melt injection flow; when the jet flow state is 0, the jet flow is stopped, and at the moment, the melt jet flow is zero under any jet pressure delta P; the industrial computer 6 is used as an upper computer of the whole control system, integrates the whole forming process control software, can realize the layered processing and path planning of the three-dimensional model, forms a printing path instruction file, and sends instructions to each subsystem in the process system, including a melt flow control system, so as to ensure the automation of the part printing process. The industrial computer 6 is in serial communication connection with the PLC3-12, an analog quantity signal output end of the PLC3-12 is connected with a receiving end of the pressure controller 3-4, a signal output end of the pipeline temperature sensor 3-8 is connected with the PLC3-12, the pressure sensor 3-14 is connected with an input end of the signal distributor 3-11, and two output ends of the signal distributor 3-11 are respectively connected with the PLC3-12 and the pressure controller 3-4. The PLC sends control commands to the electromagnetic valves 3-6, the high-temperature electromagnetic valves 3-10 and the electromagnets 4-7 through the solid relays 3-13.
The crucible smelting unit 1 comprises a water-cooling top cover 1-1, a cooling water inlet 1-6, a cooling water outlet 1-7, a crucible air inlet/outlet 1-10, an air pressure detection port 1-11, a laser distance sensor detection port 1-12 and a start-stop control rod connection port 1-13 are formed in the water-cooling top cover 1-1, and threads are arranged at the bottom of the water-cooling top cover 1-1 and used for being connected with a smelting crucible 1-3. An industrial water cooler is connected between the cooling water inlet 1-6 and the cooling water outlet 1-7, so that the water cooling of the water cooling top cover 1-1 is realized, and all sensing devices on the upper part and the crucible sealing ring 1-2 on the lower part are ensured to be at proper working temperature; the crucible air inlet/outlet is connected with an air pressure driving unit 3, and the air pressure driving unit 3 receives a jet pressure instruction from an industrial computer 6 to realize the control of the air pressure in the crucible; the air pressure detection ports 1-11 are communicated with the pressure sensors 3-14, and the pressure sensors 3-14 are used for detecting the real-time air pressure in the crucible and feeding back the real-time air pressure to the air pressure driving unit 3 by analog quantity signals; a distance meter 5-1 is arranged above the detection port 1-12 of the laser distance sensor, the distance meter 5-1 is a laser distance meter, and the distance meter 5-1 is used for transmitting the real-time liquid level of the melt in the crucible to the air pressure driving unit 3 through an analog quantity signal; a set of mechanism for driving the start-stop control rods 4-11 to quickly compress and lift downwards is arranged on the start-stop control rod connecting ports 1-13 so as to realize the quick stop and generation of the melt injection process. The water-cooled top cover 1-1 is connected with the smelting crucible 1-3 through threads, and air sealing between the water-cooled top cover 1-1 and the smelting crucible 1-3 is realized through a crucible sealing ring 1-2. The heating coils 1-4 are arranged on the peripheries of the smelting crucibles 1-3, the open ends of the upper parts of the smelting crucibles 1-3 are provided with connecting threads, the lower parts of the connecting threads are provided with throats 1-8, and the throats can effectively reduce the heat of the high-temperature parts of the smelting crucibles 1-3 from being conducted upwards along the wall surface of the crucibles, so that the smelting temperature is not difficult to rise due to a top water cooling device; meanwhile, the connecting threads at the upper opening end of the melting crucibles 1 to 3 cannot be deformed and locked due to high temperature, even the connection fails; the sealing ring 1-2 can also be made of rubber materials with better air tightness without special high-temperature sealing elements. The bottom of the melting crucible 1-3 is provided with a shallow hole 1-9 for assisting screwing of a special spanner, so that the connecting thread between the melting crucible 1-3 and the water-cooling top cover 1-1 can be easily screwed, and the crucible sealing ring 1-2 between the melting crucible 1-3 and the water-cooling top cover can be effectively compressed, thereby ensuring reliable air sealing. The outer wall of the melting crucible 1-3 is not provided with a protruding part similar to a flange structure, so that the crucible can integrally pass through the peripheral induction heating coil 1-4 in the loading and unloading process without repeatedly dismounting and mounting the peripheral heating coil 1-4, and the service life of the induction heating coil 1-4 can be prolonged.
The melting coating head 2-2 and the melting crucible 1-3 are matched with each other through a conical surface to realize sealing of metal melt under low pressure, and the coating head is provided with a screw 2-1 to realize reliable locking of the matched conical surface. The periphery of the melt coating head 2-2 is coated with the nozzle heater 2-3 to heat the spray holes in the melt coating head 2-2, so that the spray holes are prevented from being blocked or the flow is prevented from being obviously reduced due to the temperature reduction of the spray holes in the coating and forming process.
Referring to FIG. 3, the pneumatic drive unit 3 includes a PLC3-12, PLC3-12 receiving pressure control commands and jet status commands from the industrial computer 6; the jet state is realized by lifting or pressing the start-stop control rod 4-11, the start-stop control rod 4-11 is lifted, namely jet flow is generated, the start-stop control rod 4-11 is pressed, namely jet flow is stopped, the lifting or pressing action is realized by an electromagnetic driving device, and the electromagnetic driving device is controlled by a PLC 3-12; the pressure control command comprises a melt sprayThe value of the injection pressure DeltaP, DeltaP being composed of two parts, respectively the static melt pressure PjAnd the pressure P of the crucible above the melt,. DELTA.P ═ Pj+ P. Static pressure of melt PjWill be measured by the melt static pressure measuring device and transmitted to the PLC3-12, the PLC3-12 will be based on the injection pressure delta P and the melt static pressure PjThe required value P of the current crucible gas pressure is calculated and transmitted to the pressure controller 3-4 in the form of an analog signal. The pressure controller 3-4 receives the required air pressure P signal from the PLC3-12 and the real-time air pressure P ' signal of the sensor 3-14 in real time, compares the required air pressure P with the real-time air pressure P ' in real time, controls the opening and closing actions of the air inlet electromagnetic valve and the air outlet electromagnetic valve inside the crucible, and further can control the air pressure in the crucible to the required value P in a short time, and when the difference value of P and P ' is smaller than the pressure control precision, the two can be considered to be equal. The pressure controller 3-4 comprises a three-way gas interface and two-way signal interfaces which are respectively an input signal receiving end and a feedback signal receiving end. The input signal receiving end is connected with the PLC3-12, and the feedback signal receiving end is connected with the pressure sensor 3-14 through the signal distributor 3-11. The three paths of gas interfaces are respectively an air inlet, an air outlet and an air outlet, the insides of the air outlet and the air outlet are connected with high-frequency electromagnetic valves in series, and a built-in operation controller controls the opening and closing actions of the two paths of high-frequency electromagnetic valves, so that the air inlet and the air outlet of the smelting crucible 3-1 are ensured to be rapid and stable, and obvious pressure overshoot is avoided. In order to ensure that the pressure of the air inlet of the pressure controller 3-4 is in a rated range, the air source is required to be subjected to pressure reduction operation, the air source comprises an argon tank 3-1, high-pressure air from the argon tank 3-1 is reduced to 0.4MPa through a primary pressure reducing valve 3-2, and the primarily reduced air is further reduced to the rated inlet pressure of the pressure controller 3-4 through a precision pressure regulator 3-3. The pressure controller 3-4 is provided with an air outlet which is communicated with the crucible smelting unit 1 sequentially through an electromagnetic valve 3-6, a first buffer air bottle 3-7, a pipeline temperature sensor 3-8, a second buffer air bottle 3-9 and a high-temperature electromagnetic valve 3-10. The electromagnetic valve 3-6, the first buffer gas cylinder 3-7, the pipeline temperature sensor 3-8 and the second buffer gas cylinder 3-9 form a temperature switch for high-temperature exhaust protection, and the temperature switch is used for protecting the pressure controller 3-4 from coming from the pressure controller in the pressure reduction operationHigh-temperature exhaust ablation inside the melting crucibles 1-3. The gas from the argon gas tank 3-1 is low-temperature gas, the gas exhausted from the smelting crucible 1-3 is high-temperature gas, when the real-time pressure P' inside the smelting crucible 1-3 is greater than the target pressure P, the high-temperature gas inside the crucible is exhausted to realize pressure reduction, and when the exhaust temperature detected by the pipeline temperature sensor 3-8 exceeds a rated value, the PLC3-12 closes the electromagnetic valve 3-6 to protect the pressure controller 3-4 from being at a safe working temperature. When the air pressure in the smelting crucible 1-3 needs to be reduced, the serial cavity formed by the smelting crucible 1-3, the first buffer air bottle 3-7 and the second buffer air bottle 3-9 needs to exhaust air to the external environment through the air outlet of the pressure controller 3-4, the air outlet is connected with the discharge protector 3-5, and the discharge protector 3-5 can prevent the air outlet from being polluted by the outside. When the pressure controller 3-4 performs the exhaust operation, the normal temperature gas in the first buffer gas cylinder 3-7 is firstly exhausted through the exhaust port, the gas in the second buffer gas cylinder 3-9 enters the first buffer gas cylinder 3-7, and the high temperature gas in the smelting crucible 1-3 enters the second buffer gas cylinder 3-9. If the pressure is reduced to a target value at the moment, the exhaust work is finished, and the temperature signals detected by the pipeline temperature sensors 3-8 do not exceed a safety value; if the exhaust work continues at this moment, the high-temperature gas in the second buffer gas bottle 3-9 is exhausted to the first buffer gas bottle 3-7, the temperature signal detected by the pipeline temperature sensor 3-8 is higher than a safety value, and the electromagnetic valve 3-6 is turned off to protect the safety of the system. The design capacities of the first buffer gas bottle 3-7 and the second buffer gas bottle 3-9 are slightly higher than the capacity of the smelting crucible 1-3, so that the exhaust protection temperature switch can not be triggered under the condition that the system works normally, and the part printing process is normally carried out. Real-time pressure signals inside the crucible, detected by the pressure sensors 3-14, are divided into two paths through the signal distributors 3-11, wherein one path is transmitted to the PLC3-12, and the PLC3-12 receives the pressure signals and the liquid level signals inside the crucible in real time and communicates with the industrial computer 6 through a serial port. In the whole pressure control process, the industrial computer 6, the PLC3-12 and the pressure controller 3-4 all participate in the operation control, but the tasks are relatively independent, and the industrial computer 6 is only responsible for issuing the task requirement, PLC3-12 is only responsible for calculating the current target pressure and transmitting the target command to pressure controller 3-4, while pressure controller 3-4 is responsible for achieving the current crucible pressure P' approaching the target crucible pressure P. By adopting the pressure control three-level division work mode, the air pressure control with good real-time performance can be realized in the 3D printing process, the mutual waiting in the signal processing process is avoided, and the response speed and the control precision of the pressure control are greatly improved.
The jet flow start-stop device comprises a start-stop control rod 4-11, the start-stop control rod 4-11 is inserted into the crucible smelting unit through a start-stop control rod connecting port 1-13 formed in a water-cooling top cover 1-1, the top of the water-cooling top cover 1-1 is provided with threads and connected with a sliding bearing seat 4-2, the upper part of the sliding bearing seat 4-2 is connected with the lower part of an electromagnet mounting seat 4-6 through threads, and an electromagnet locking nut 4-3 is positioned at the lower end of the electromagnet mounting seat 4-6; the upper part of the electromagnet mounting seat 4-6 is connected with a compression spring locking nut 4-8 through threads, and the compression spring locking nut 4-8 is arranged at the lower end of a compression force adjusting nut 4-9; a corrugated pipe 4-1 is arranged between the sliding bearing seat 4-2 and the water-cooling top cover 1-1, and the corrugated pipe 4-1 is sleeved on the periphery of the start-stop control rod 4-11; an electromagnet 4-7 is arranged in the electromagnet mounting seat 4-6, an iron core 4-5 is arranged on the inner side of the electromagnet 4-7, a start and stop rod locking sleeve 4-5 is arranged on the inner side of the iron core 4-5, the iron core 4-5 is in threaded connection with the start and stop rod locking sleeve 4-4, and the start and stop rod locking sleeve is sleeved outside a start and stop control rod 4-11; the upper part of the start-stop control rod 4-11 is provided with a bulge and is fixedly connected with the lower end of the compression spring 4-10, and the upper end of the compression spring 4-10 is fixedly connected with the compression force adjusting nut 4-9.
The bottom end of the start-stop control rod 4-11 is connected with a sealing cone 4-13, the outer conical surface of the sealing cone 4-13 is in conical surface fit with the inner conical surface at the upper end of the coating head 2-2, as shown in figure 2a, when the start-stop control rod is in a lifting state, the two conical surfaces are separated, and jet flow occurs; as shown in fig. 2b, when the start-stop control lever is in a downward pressing state, the two conical surfaces are closed, and the jet flow is stopped; the thermocouples 4-12 are arranged in the hollow parts of the start-stop control rods 4-11, magnesium oxide ceramic powder is filled around the thermocouples 4-12, good insulation and thermal conductivity are guaranteed in the using process, the thermocouples 4-12 can measure the temperature of the melt in the crucible and transmit temperature signals to corresponding temperature controllers, and therefore the current of the electromagnetic induction heating coils 1-4 is adjusted, and the high-temperature melt 1-5 in the melting crucible 1-3 is guaranteed to be at the proper temperature.
The upward lifting and downward pressing actions of the start-stop control rod 4-11 are completed through the cooperation of the electromagnet 4-7 and the pressing spring 4-10, when the start-stop control rod 4-11 needs to execute an upward lifting command, the PLC3-12 sends a command to electrify the electromagnet 4-7, the electrified electromagnet 4-7 attracts the iron core 4-5 to move upwards, the iron core 4-5 is connected with the start-stop rod locking sleeve 4-4 through the threads 4-42, and the hexagonal head 4-43 is arranged below the threads 4-42, as shown in FIG. 4. After the iron core 4-5 and the start-stop rod locking sleeve 4-4 are screwed, the petal-shaped conical sleeve 4-41 at the upper part of the start-stop rod locking sleeve 4-4 is slightly folded under the action of force to firmly lock the start-stop control rod 4-11, so that the start-stop control rod 4-11, the start-stop rod locking sleeve 4-4 and the iron core 4-5 move up and down integrally; when the start-stop control rod needs to execute a downward pressing command, the PLC3-12 sends a command to cut off the power of the electromagnets 4-7, so that the start-stop control rod 4-11 moves downward under the action of the pressing spring 4-10, and the coating head 2-2 and the corresponding conical surface of the sealing cone 4-13 are closed; downward pressing force of the pressing springs 4-10 can be adjusted through the pressing spring adjusting nuts 4-9, and after the positions of the pressing spring adjusting nuts 4-9 are adjusted, double-nut anti-loose locking can be achieved through the pressing spring locking nuts 4-8; the distance between the sealing cone 4-13 and the coating head 2-2 matched conical surface can be adjusted by adjusting the screwing depth of the threads between the electromagnet mounting seat 4-6 and the sliding guide rail mounting seat 4-2, the excessively small distance can interfere with the flow stability, and the excessively large distance can increase the response time of the starting and stopping process, so that the sealing cone needs to be adjusted to a proper position according to the actual condition, and after the position of the electromagnet mounting seat 4-6 is adjusted, double-nut loosening and locking can be realized through the electromagnet locking nut 4-3; the corrugated pipe 4-1 is applied, so that the starting and stopping control rod 4-11 can move smoothly in the vertical movement process, and compared with sliding sealing structures with other fixed positions, the starting and stopping control rod 4-11 can have smaller movement resistance, reliable sealing and quicker response by adopting the moving sealing structure with the corrugated pipe 4-1 as a key part.
The melt static pressure measuring device comprises a distance meter 5-1, the output end of the distance meter 5-1 is connected with the input end of a PLC3-12, the laser distance meter 5-1 can measure the height of melt in a melting crucible 1-5 through quartz glass 5-2, and the melt static pressure at the spray hole of the melting coating head 2-2 can be obtained through conversion. The detection port 1-12 of the laser distance sensor is provided with quartz glass 5-2, a sealing ring 5-4 is arranged between the quartz glass 5-2 and the water-cooling top cover 1-1, and the peripheries of the quartz glass 5-2 and the water-cooling top cover 1-1 are provided with quartz glass locking nuts 5-3. Because the oxide film on the surface of the melt can make the liquid level of the metal melt generate diffuse reflection, the laser range finder is adopted, the change of the liquid level can be accurately captured, and the influence of the height reflection rate of the melt can not be caused. The melt static pressure measuring device can transmit the liquid level information of the melt to the PLC3-12 in an analog quantity or serial port communication mode, and the PLC3-12 can calculate the current air pressure requirement in the crucible according to the liquid level information and the instruction of the industrial computer 6.
The invention also provides a melt flow control method for the melt coating forming process, which comprises the following steps:
step 1: preparation, inspection and cleaning of the crucible melting unit 1, ensuring good system operation. And closing the high-temperature electromagnetic valve 3-10, detaching the melting crucible 1-3, checking the crucible sealing ring 1-2, and timely replacing if the crucible sealing ring is damaged. Checking and cleaning a smelting crucible 1-3, a start-stop control rod 4-11, a sealing cone 4-15 and a coating head 2-2. If the surface is damaged after cleaning, a new part is repaired or replaced in time; and (3) starting the industrial computer 6, the air pressure driving unit 3 and the like, detecting whether the system runs well, and if the system runs well, entering the step (2).
Step 2: the raw materials are cleaned, weighed and loaded into a crucible melting unit. Taking a bar-shaped raw material as an example, firstly turning a bar to remove acid and wash the surface of the bar to expose the metallic luster; cleaning the material with the scale removed in an ultrasonic cleaning machine for 10 minutes; putting the material subjected to ultrasonic cleaning into industrial alcohol for further cleaning; the cleaned raw materials are weighed and then placed into a melting crucible 1-3, and the melting crucible 1-3 filled with the materials to be melted is arranged on a water-cooled top cover 1-1.
And step 3: replacing the atmosphere in the melting crucible. Opening the high-temperature electromagnetic valve 3-10, pressing the start-stop control rod 4-11 downwards, controlling the gas pressure output by the gas pressure driving unit 3 to be the maximum pressure of the system, filling inert gas into the smelting crucible 1-3 at the moment, and increasing the pressure of the smelting crucible 1-3; after the pressure is increased to the maximum pressure, performing exhaust operation; after the inflation-exhaust operation is repeated for 3 times, the pressure is adjusted to 8-12Kpa, the start-stop control rod 4-11 is controlled to lift, and at the moment, gas is sprayed out from the spray holes at the bottom of the coating head 2-2; placing an air inlet mask of a gas flowmeter on the conical surface of the coating head 2-2, detecting the gas flow, if the gas flow is abnormal, closing the high-temperature electromagnetic valve 3-10, detaching and rechecking and cleaning the coating head 2-2 to ensure that the coating head is installed again after sealing and cleaning are normal, and repeating the step 1 and the step 3; and if the gas flow is normal, entering the step 4.
And 4, step 4: heating the materials in the crucible to 30-50 ℃ above the melting point of the materials to fully melt the materials: the operation start-stop control rod 4-11 is pressed downwards, and the melting temperature T is set1And nozzle heating temperature T2Melting temperature T1Namely the temperature of the melt in the melting crucible 1-3; turning on an induction smelting device, electrifying an induction heating coil 1-4, and starting heating; when the temperature in the crucible is stabilized to T1When the temperature is high, the nozzle heater 2-3 is started; when the temperature of the nozzle reaches T2Then, the process proceeds to step 5.
And 5: and (6) checking the liquid level measurement. Ensuring that the laser distance sensor 5-1 is in a distance measurement mode to acquire the current crucible liquid level h0And calculating the current melt mass m'0(ii) a Measured Current melt Mass m'0And the mass m of the raw material obtained in step 20Comparing and measuring the liquid level h0Correcting to ensure that the liquid level measurement error is less than 2mm, wherein the true liquid level of the crucible is h'0(ii) a And starting a crucible liquid level feedback mode in the air pressure driving unit, and acquiring a liquid level signal in real time to adjust the gas pressure of the crucible so as to keep the injection pressure delta P constant.
Step 6: and checking the melt flow. Keeping the feedback opening of the liquid level of the crucible melt, adjusting the injection pressure delta P of the melt to be 20KPa, controlling the start-stop control rod (4-11) to lift, enabling the jet flow to occur, and recordingThree groups of flow rates with the time length of 1-2 minutes are averaged and are counted as Qm-20(ii) a Comparison Qm-20And its theoretical value Q'm-20If the difference is more than 10%, the crucible melting unit (1) needs to be checked and reassembled; if Qm-20And Q'm-20If the difference is less than 10%, adjusting the melt injection pressure delta P to 40KPa, controlling the start-stop control rods (4-11) to lift to enable jet flow to occur, recording three groups of flow with the time length of 1-2 minutes, taking an average value, and calculating the average value as Qm-40(ii) a Using Qm-20And Qm-40Determines the pressure Δ P and the flow QmFunctional relationship between; calculating the flow Q 'when the pressure delta P is 30KPa by using the newly determined pressure-flow function relation'm-30(ii) a Adjusting the melt injection pressure delta P to be 30 KPa; controlling the start-stop control rod (4-11) to lift to enable jet flow to occur, recording three groups of flow with the time length of 1-2 minutes, taking an average value, and calculating the average value as Qm-30(ii) a Comparative Q'm-30And Qm-30Difference therebetween, if Q'm-30And Qm-30If the difference is more than 2%, the pneumatic driving system (3) needs to be checked to ensure that the flow is checked again after the pneumatic driving system works normally; if the difference value between the two is less than 2%, the flow verification is successful, and the step 7 is entered.
And 7: and generating a technological process control instruction. The industrial computer 6 is provided with a coating and forming model processing software, a model to be printed is imported into the software, after basic parameters such as layering height, flow rate and the like are set, the software plans a printing path according to the model and the basic settings, and forms an executable command document which can be identified by a process system. The document includes location information, velocity information, fluidic state information, and flow information.
And 8: flow control of the forming process. The industrial computer 6 is provided with process control software for coating and forming, and command documents of the process are imported into the software, wherein the jet state information is used for controlling the stopping and the generation of jet, and the flow information is used for controlling the pressure driving unit; the industrial computer 6 is used for calculating the pressure delta P-flow Q according to the flow information and the verified pressure delta PmThe relation is converted into corresponding melt injection pressure delta P, and the melt injection pressure delta P is sent to the PLC 3-12; distance measuring instrument5-1 transmitting the real-time liquid level signal to a PLC3-12, and correcting the real-time signal and calculating the static pressure value P of the current melt by the PLC3-12jThus according to the relation Δ P ═ Pj+ P obtains the air pressure requirement value P; the PLC3-12 converts the pressure requirement value P into a corresponding analog quantity signal and transmits the analog quantity signal to the pressure controller 3-4, and the pressure controller receives and compares a real-time crucible air pressure signal P 'transmitted by the pressure sensor 3-14 to control the opening and closing actions of two high-frequency electromagnetic valves in the pressure controller so as to enable the pressure value P' in the crucible to approach the air pressure requirement value P; when a jet flow generation command is received, the start-stop control rod 4-11 is lifted, the melt is sprayed under the action of the spraying pressure delta P, and when a jet flow stop command is received, the start-stop control rod 4-11 is pressed downwards, so that the melt jet flow is stopped quickly. And finally, the formation of the target part is completed together under the coordination of other functional modules of the process system, including a three-dimensional motion unit, a temperature control unit and the like.
The melt flow control device and the melt flow control method for the melt coating forming process can be used for flow control in the forming process of different types of metals or low-viscosity non-metallic materials, the flow control is stable and accurate, and the possibility is provided for realizing coating forming of complex components.

Claims (10)

1. A melt flow control device for a melt coating forming process is characterized by comprising a crucible smelting unit (1), a melt coating head assembly, a pneumatic driving unit (3), a jet flow starting and stopping device, a melt static pressure measuring device and a PLC (3-12);
the crucible smelting unit (1) comprises a smelting crucible (1-3), a water-cooling top cover (1-1) is arranged on the smelting crucible (1-3), a crucible air inlet/outlet (1-10) is arranged on the water-cooling top cover (1-1), a crucible air inlet (1-10) is connected with an air pressure driving unit (3), an air pressure detection port (1-11) is arranged on the water-cooling top cover (1-1), and the air pressure detection port (1-11) is connected with a pressure sensor (3-14) for measuring real-time air pressure in the crucible;
the melt coating head assembly comprises a melt coating head (2-2), the melt coating head (2-2) is arranged below the melting crucible (1-3) and is sealed with the melting crucible (1-3) in a conical surface matching manner;
the air pressure driving unit (3) comprises an argon tank (3-1), the argon tank (3-1) is connected with an inlet of a pressure controller (3-4), and an outlet of the pressure controller (3-4) is communicated with the crucible smelting unit (1) through an exhaust protection temperature switch; the pressure controller (3-4) comprises three gas interfaces and two signal interfaces, the two signal interfaces are respectively connected with the PLC (3-12) and the pressure sensors (3-14), the three gas interfaces are respectively an air inlet, an air outlet and an air outlet, the air outlet and the air outlet are both connected with a high-frequency electromagnetic valve in series, and an operation controller for controlling the opening and closing states of the two high-frequency electromagnetic valves is arranged in the air outlet and the air outlet; the pressure sensors (3-14) are connected with the input ends of the signal distributors (3-11), and the two output ends of the signal distributors (3-11) are respectively connected with the PLC (3-12) and the pressure controllers (3-4);
the jet flow starting and stopping device comprises a starting and stopping control rod (4-11) and an electromagnetic driving device for driving the starting and stopping control rod (4-11) to be pressed downwards or lifted upwards, and a sealing cone (4-13) at the lower end of the starting and stopping control rod (4-11) is matched with the upper end of a coating head (2-2) through a conical surface to realize starting and stopping sealing;
the melt static pressure measuring device comprises a distance meter (5-1) for measuring the height of the melt in the melting crucible (1-3), wherein the distance meter (5-1) is connected with a PLC (3-12), and the PLC (3-12) is used for receiving an injection pressure control command and a jet state command sent by an industrial computer (6).
2. A melt flow control device for a melt coating forming process according to claim 1, wherein the pressure control command comprises a value of melt ejection pressure Δ P, Δ P ═ Pj+ P, wherein PjStatic pressure of the melt is adopted, and P is the air pressure of a crucible above the melt; PLC (3-12) according to injection pressure delta P and melt static pressure PjCalculating a required value P of the current crucible air pressure, and transmitting the required value P of the crucible air pressure to a pressure controller (3-4) by using an analog quantity signal;
the pressure controller (3-4) is used for receiving a required air pressure P signal from the PLC (3-12) and a real-time air pressure P 'signal in the smelting crucible (1-3) measured by the pressure sensor (3-14) in real time, comparing the required air pressure P with the real-time air pressure P' in real time, controlling the opening and closing of an air inlet electromagnetic valve and an air outlet electromagnetic valve in the pressure controller, and further controlling the air pressure in the crucible to be the required value P;
the jet flow state command comprises the lifting or pressing of the start-stop control rods (4-11), and the PLC (3-12) sends an instruction to control the electromagnetic driving device to act, so that the start-stop control rods (4-11) are lifted or pressed, and the jet flow is started and quickly stopped.
3. The melt flow control device for the melt coating forming process is characterized in that the electromagnetic driving device comprises an electromagnet (4-7) and a compression spring (4-10), an iron core (4-5) is arranged on the inner side of the electromagnet (4-7), the iron core (4-5) is in threaded connection with a start-stop rod locking sleeve (4-4), the start-stop rod locking sleeve (4-4) is designed with a petal-shaped conical locking head (4-41) for tightly holding a start-stop rod (4-11), the upper end of the compression spring (4-10) is fixedly connected with a compression force adjusting nut (4-9), and the lower end of the compression spring is fixedly connected to the upper part of the start-stop control rod (4-11).
4. A melt flow control device for a melt coating forming process according to claim 1, characterized in that a thermocouple core (4-12) for measuring the temperature of the melt inside the melting crucible (1-3) is arranged inside the start and stop control rod (4-11).
5. The melt flow control device for the melt coating forming process is characterized in that the exhaust protection temperature switch comprises a solenoid valve (3-6), a first buffer gas cylinder (3-7) and a second buffer gas cylinder (3-9) which are connected in sequence, a pipeline temperature sensor (3-8) is arranged on a pipeline between the first buffer gas cylinder (3-7) and the second buffer gas cylinder (3-9), the pipeline temperature sensor (3-8) is connected with a PLC (3-12), and the PLC (3-12) is used for sending a control command to the solenoid valve 3-6.
6. A melt flow control device for a melt coating forming process according to claim 1, characterized in that a crucible sealing ring (1-2) is arranged between the water-cooled top cover (1-1) and the melting crucible (1-3).
7. A melt flow control device for a fusion coating shaping process according to claim 1, characterized in that the upper open end of the melting crucible (1-3) is provided with a connecting screw thread, and the lower part of the connecting screw thread is provided with a throat.
8. A melt flow control device for a melt coating forming process according to claim 1, characterized in that the distance meter (5-1) is a laser distance meter.
9. A melt flow control method of a melt coating forming process based on the apparatus of claim 1, comprising the steps of:
step 1: assembling a melting crucible (1-3) and a melt coating head assembly together; cleaning and weighing blocky, filiform or powdery materials to be melted, loading the materials into a melting crucible (1-3), and then installing the melting crucible (1-3) filled with the materials to be melted onto a water-cooled top cover (1-1);
step 2: replacing the atmosphere in the smelting crucible (1-3), filling inert gas into the smelting crucible (1-3), keeping a certain air pressure, lifting a start-stop control rod (4-11), and measuring the gas flow at the outlet of the coating head (2-2): if the gas flow is abnormal, checking and reassembling the melt coating head assembly; if the gas flow is normal, entering step 3;
and step 3: downwards pressing a start-stop control rod (4-11), opening an induction heater, and when the temperature in the smelting crucible (1-3) is stabilized to T1When the nozzle is started, the nozzle heater (2-3) is started; temperature of the nozzle stabilized to T2If so, entering the step 4;
and 4, step 4: obtaining the current crucible liquid level h0And calculating the current melt mass m'0(ii) a Mixing current melt mass m'0And the mass m of the raw material obtained in step 10Comparing and measuring the liquid level h0Correcting, and starting a crucible liquid level feedback mode in the air pressure driving unit;
and 5: generating a process control instruction, importing the model to be printed into model processing software in an industrial computer (6), setting the layering height and the flow, planning a printing path by the model processing software according to the model and the basic setting, and forming an executable command document which can be identified by a process system;
step 6: importing a command document of a process into process control software in an industrial computer (6); the jet state information is used for controlling the stopping and the generation of the jet, and the flow information is used for controlling the pressure driving unit (3); the PLC (3-12) receives the injection pressure delta P sent by the industrial computer (6); the distance meter (5-1) transmits the real-time liquid level signal to the PLC (3-12), and the PLC (3-12) converts the real-time liquid level signal into the static pressure value P of the current meltjThus according to the formula Δ P ═ Pj+ P obtains the air pressure requirement value P; the PLC (3-12) converts the air pressure requirement value P into a corresponding analog quantity signal and transmits the analog quantity signal to the pressure controller (3-4), and the pressure controller (3-4) receives and compares a real-time crucible air pressure signal P 'transmitted by the pressure sensor (3-14) to control the opening and closing of two high-frequency electromagnetic valves in the pressure controller so as to enable the pressure value P' in the crucible to tend to the air pressure requirement value P; when a jet flow generation command is received, the start-stop control rod (4-11) is lifted, the melt is sprayed under the action of the spraying pressure delta P, and when a jet flow stop command is received, the start-stop control rod (4-11) is pressed downwards, so that the melt jet flow is stopped quickly.
10. The melt flow control method for the melt coating forming process according to claim 9, wherein a melt flow verification is performed before the step 5, and the process of the melt flow verification is as follows: adjusting the melt injection pressure delta P to be 20KPa, controlling the start-stop control rods (4-11) to lift, enabling jet flow to occur, recording the flow of three groups of 1-2 min-duration, taking an average value, and calculating the average value as Qm-20(ii) a Comparison Qm-20And its theoretical value Q'm-20If the difference is more than 10%, the crucible melting unit (1) needs to be checked and reassembled; if Qm-20And Q'm-20If the difference is less than 10%, the melt injection pressure is adjusted to be delta P of 40KPa, and the start-stop control rods (4-11) are controlled to liftEnabling jet flow to occur, recording three groups of flow with the time length of 1-2 minutes, taking an average value, and calculating the average value as Qm-40(ii) a Using Qm-20And Qm-40Determines the pressure Δ P and the flow QmFunctional relationship between; calculating the flow Q 'when the pressure delta P is 30KPa by using the newly determined pressure-flow function relation'm-30(ii) a Adjusting the melt injection pressure delta P to be 30 KPa; controlling the start-stop control rod (4-11) to lift to enable jet flow to occur, recording three groups of flow with the time length of 1-2 minutes, taking an average value, and calculating the average value as Qm-30(ii) a Comparative Q'm-30And Qm-30If the difference value between the two values is less than 2%, the flow verification is successful; if Q'm-30And Qm-30If the difference is larger than 2%, the pneumatic driving system (3) needs to be checked to ensure that the flow is checked again after the pneumatic driving system works normally.
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