Circulating ink supply system suitable for 3D inkjet printing and control method thereof

Abstract

The application discloses a circulating ink supply system suitable for 3D inkjet printing and a control method thereof, wherein the inkjet printing head has a plurality of nozzles for ejecting ink; the ink is high-temperature phase-change ink or high-viscosity ink; the circulating module is provided with a back-ink chamber and an ink inlet chamber, and the back-ink chamber and the ink inlet chamber are communicated; the back-ink chamber and the ink inlet chamber are connected with the inkjet printing head through back-ink pipes and ink inlet pipes respectively; a heating element is arranged for heating the circulating module; and a power module is arranged for providing kinetic energy for the circulating ink supply system, so that the ink circulates between the circulating module and the inkjet printing head. The heating element is arranged for heating the circulating module, so that the high-temperature phase-change ink or the high-viscosity ink has good fluidity; the power module provides circulating kinetic energy; the ink in the ink inlet chamber enters the inkjet printing head through the ink inlet pipe, and then flows to the back-ink chamber through the back-ink pipe; the ink in the back-ink chamber is transported to the connected ink inlet chamber, so that the circulation of the fluid is realized.

Description

Technical Field

[0001] This invention belongs to the field of 3D printing, specifically relating to a circulating ink supply system and method that supports high-flow, high-temperature, and high-viscosity phase change printing materials. Background Technology

[0002] 3D printers construct three-dimensional models using additive manufacturing methods. Wax-print 3D printers are a type of additive manufacturing equipment that uses purple wax as the printing material and white wax as the support material. The wax, heated to a liquid state, is sprayed onto the printing platform, where it then solidifies at room temperature. The model is built by stacking layers. Due to the high precision and smooth surface of wax-printed models, wax-print 3D printers are widely used in industries such as jewelry, aerospace, and engines. The printing materials used in wax-print 3D printers are white and purple wax. The wax is contained in a container, which is then inserted into an ink supply assembly. The wax flows into the ink supply assembly, is heated at high temperature, and flows into the inkjet printhead. The inkjet printhead prints the wax layer by layer onto the printing panel, constructing the three-dimensional model.

[0003] Typically, ink supply systems incorporate a circulation mechanism, usually consisting of an ink supply cartridge and a return cartridge. The printing material in the supply cartridge is pumped into the print head via a circulation pump, and then flows from the print head back to the return cartridge, thus achieving material circulation. However, for wax-based 3D printers, the printing material is wax. Wax has a high viscosity and is a high-viscosity, high-temperature phase change material with poor flowability. Uneven temperature can easily cause blockages in the circulation mechanism, slowing the flow rate. Since phase change materials solidify at their melting point and require reheating for a phase change process, current circulating ink supply systems cannot support wax printing. Summary of the Invention

[0004] The purpose of this invention is to provide a circulating ink supply system and its control method suitable for 3D inkjet printing, especially suitable for high-flow printing of high-temperature phase change or high-viscosity printing materials.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] Firstly, a circulating ink supply system suitable for 3D inkjet printing is provided, comprising:

[0007] Inkjet printheads have multiple nozzles for ejecting ink; the ink is either high-temperature phase-change ink or high-viscosity ink.

[0008] The circulation module includes an ink return chamber and an ink inlet chamber, which are connected to each other. The ink return chamber and the ink inlet chamber are connected to the inkjet printhead via ink return pipe and ink inlet pipe, respectively.

[0009] Heating element, used to heat the circulation module;

[0010] The power module provides kinetic energy to the circulating ink supply system, enabling the ink to circulate between the circulation module and the inkjet printhead.

[0011] Heating the circulation module with heating elements enables high-temperature phase change ink or high-viscosity ink to have good fluidity. The power module provides circulation kinetic energy. The ink in the ink inlet chamber enters the inkjet printhead through the ink inlet tube and flows to the ink return chamber through the ink return tube. The ink in the ink return chamber is then transported to the connected ink inlet chamber, thus realizing fluid circulation.

[0012] Furthermore, the power module is a circulation pump, which is located in the ink inlet pipe and is used to deliver ink from the ink inlet chamber to the inkjet printhead; or, the power module is a pneumatic control module, which is connected to the ink inlet chamber or the ink return chamber and is used to control the pressure difference between the ink inlet chamber and the ink return chamber, thereby converting it into the kinetic energy of the circulating ink supply system.

[0013] Furthermore, the circulation module also includes a buffer chamber, which is connected to the ink return chamber and the ink inlet chamber; the heating element heats the ink return chamber, the ink inlet chamber, the buffer chamber, and the pipes or channels connecting the buffer chamber to the ink return chamber and the ink inlet chamber.

[0014] Furthermore, the heating element enables the circulation module to be heated to 60-150°C.

[0015] The buffer chamber serves three purposes: first, it eliminates air bubbles mixed in the ink; second, it smooths the ink flow and eliminates flow pulsations; and third, it ensures a more uniform ink temperature. For low-flow conditions, a buffer chamber is unnecessary; however, for high-flow conditions, its presence makes the system more stable. The heating element heats the entire circulation module, keeping the ink in a flowable state and preventing it from cooling and solidifying or becoming immobile due to high viscosity. This is particularly suitable for high-temperature phase-change inks or high-viscosity inks (e.g., inks with viscosities ranging from 1-200 cP).

[0016] Furthermore, an ink inlet temperature sensor and an ink inlet level sensor are installed in the ink inlet chamber to monitor the ink temperature and level in the ink inlet chamber. An ink return level sensor is installed in the ink return chamber to monitor the ink level in the ink return chamber. An ink return temperature sensor is installed on the side wall of the ink return chamber to monitor the temperature of the side wall, that is, to detect the temperature of the entire chamber and prevent the initial heating from overheating.

[0017] Furthermore, the buffer chamber and the ink inlet chamber are connected through a connecting hole, and the ink return chamber and the buffer chamber are connected through a reflux device. The circulating ink supply system controls the pressure of the ink inlet chamber / ink return chamber through the air pressure control module, so that the ink enters the buffer chamber from the ink return chamber through the connecting hole, enters the ink inlet chamber through the reflux device, enters the inkjet printhead through the ink inlet pipe, and returns to the ink return chamber through the ink return pipe, forming a cycle.

[0018] Furthermore, the recirculation device includes a recirculation valve, a recirculation pump, and a filter connected in sequence. The inlet of the recirculation valve is connected to the ink return chamber, and the outlet of the filter is connected to the buffer chamber. The recirculation pump drives the ink circulation, and the flow rate of the recirculated ink is adjusted by adjusting the speed of the recirculation pump to ensure a stable fluid supply to the inkjet printhead.

[0019] Furthermore, the buffer chamber includes a return ink buffer chamber and an inlet ink buffer chamber. The return ink buffer chamber is connected to the return ink chamber through a connecting hole, and the inlet ink buffer chamber is connected to the inlet ink chamber through another connecting hole. The return ink buffer chamber and the inlet ink buffer chamber are connected by a reflux device.

[0020] Furthermore, the reflux device includes a reflux valve, a reflux pump, and a filter connected in sequence. The inlet of the reflux valve is connected to the ink return buffer chamber, and the outlet of the filter is connected to the ink inlet buffer chamber.

[0021] Furthermore, the power module is a pneumatic control module, which includes a first pressure control module and a second pressure control module. The first pressure control module is connected to the ink return chamber and is used to control the pressure of the ink return chamber, which is a negative pressure. The second pressure control module is connected to the ink inlet chamber and is used to control the pressure of the ink inlet chamber, which can be a positive or negative pressure. The circulating ink supply system uses the pneumatic control module to make ink enter the ink return buffer chamber from the ink return chamber through the connecting hole, and then enter the ink inlet buffer chamber through the reflux device. Then, it enters the ink inlet chamber through another connecting hole, and enters the inkjet printhead through the ink inlet pipe, and then returns to the ink return chamber through the ink return pipe, forming a cycle.

[0022] Furthermore, the air pressure control module includes a first air pressure chamber, a second air pressure chamber, a first buffer air pressure chamber, and a second buffer air pressure chamber. The ink return chamber is connected to the first air pressure chamber via a first positive / negative pressure switching valve, and the ink inlet chamber is connected to the second air pressure chamber via a second positive / negative pressure switching valve. The ink return buffer chamber is connected to the first buffer air pressure chamber via a third positive / negative pressure switching valve, and the ink inlet buffer chamber is connected to the second buffer air pressure chamber via a fourth positive / negative pressure switching valve. Each of the first and second air pressure chambers is connected to an air pressure sensor. The first, second, third, and fourth positive / negative pressure switching valves are all connected to the same positive pressure pump. The two buffer air pressure chambers eliminate air pressure fluctuations, making the air pressure control system more stable.

[0023] Furthermore, the first pressure chamber is connected to a first air source valve and a first pressure relief valve, the second pressure chamber is connected to a second air source valve and a second pressure relief valve, the first pressure chamber and the first buffer pressure chamber are connected through a first buffer connecting pipe, and the second pressure chamber and the second buffer pressure chamber are connected through a second buffer connecting pipe; each of the first and second pressure relief valves is connected to a filter, each of the first and second air source valves is connected to an air pump, and a balancing valve is connected between the first and second pressure chambers. The air source valves can pressurize the pressure chambers, and the pressure relief valves can depressurize them. The balancing valves ensure that the pressure difference between the first and second pressure chambers is zero, thus providing power-off protection.

[0024] Secondly, the present invention also provides a control method for a circulating ink supply system suitable for 3D inkjet printing, wherein the circulating ink supply system is as described above, and the control method includes the following steps:

[0025] (1) When the inkjet printhead is in the printing state, the power module provides kinetic energy for ink circulation;

[0026] (2) The ink in the ink inlet chamber enters the inkjet printhead through the ink inlet tube and then flows to the ink return chamber through the ink return tube;

[0027] (3) When the ink in the ink return chamber reaches a certain height, the ink enters the ink inlet chamber connected to the ink return chamber, so that the ink circulates in the inkjet printhead and the circulating ink supply structure.

[0028] Furthermore, the control method includes the following steps:

[0029] (1) When the inkjet printhead is in the printing state, the air pressure control module controls the pressure of the ink inlet chamber to make it greater than the pressure of the ink return chamber. The pressure of the ink inlet chamber is either positive or negative.

[0030] (2) The ink in the ink inlet chamber enters the inkjet printhead through the ink inlet tube and then flows to the ink return chamber through the ink return tube;

[0031] (3) When the reflux pump is turned on, the ink in the ink return chamber passes through the reflux valve, reflux pump and filter to the buffer chamber in sequence. When the ink in the buffer chamber reaches a certain height, the ink flows from the buffer chamber through the connecting hole to the ink inlet chamber, realizing the circulation of ink in the inkjet printhead and the circulation module.

[0032] Furthermore, the control method also includes step (4), monitoring the value of the pressure sensor, controlling and adjusting the speed of the return pump according to the comprehensive algorithm of the pressure sensor, the connected negative pressure and the speed of the return pump to match the corresponding material circulation speed, and adjusting the negative pressure to achieve a suitable meniscus pressure.

[0033] Furthermore, the control method includes the following steps:

[0034] (1) When the inkjet printhead is in the printing state, the air pressure control module controls the pressure between the ink inlet chamber and the ink return chamber, so that the pressure of the ink inlet chamber is greater than the pressure of the ink return chamber. The pressure of the ink inlet chamber is either positive or negative, and the pressure of the ink return chamber is controlled to be negative.

[0035] (2) The ink in the ink inlet chamber enters the printhead through the ink inlet tube and then flows to the ink return chamber through the ink return tube;

[0036] (3) When the ink in the ink return chamber reaches a certain height, the ink flows from the ink return chamber through the connecting hole to the ink return buffer chamber. When the ink return liquid level sensor in the ink return chamber detects ink when the liquid level in the ink return chamber reaches the set height, it is triggered and the reflux pump is turned on. The ink in the ink return buffer chamber flows to the ink inlet buffer chamber after being filtered by the reflux valve, reflux pump and filter in sequence. When the ink in the ink inlet buffer chamber reaches a certain height, the ink flows from the ink inlet buffer chamber to the ink inlet chamber, realizing the circulation of ink in the inkjet printhead and the circulation module.

[0037] Further, the specific operation of step (1) is as follows: the first air pressure chamber provides pressure to the ink return chamber through the first air pipe to maintain the printing pressure P1, the second air pressure chamber provides pressure to the ink inlet chamber through the second air pipe to maintain the printing pressure P2, the first buffer air pressure chamber provides printing pressure P1 to the ink return buffer chamber through the third air pipe, and the second buffer air pressure chamber provides printing pressure P2 to the ink inlet buffer chamber through the fourth air pipe, where P1 is a negative pressure and P2 > P1.

[0038] Furthermore, when the inkjet printhead is in the ink-pressing state, the circulating ink supply system performs the following control:

[0039] (1) The pressure sensor adjusts the working speed of the positive pressure pump to maintain a certain pressure.

[0040] (2) The first positive and negative pressure switching valve, the second positive and negative pressure switching valve, the third positive and negative pressure switching valve and the fourth positive and negative pressure switching valve are all switched to the positive pressure pump. The positive pressure pump applies positive pressure to the first air pipe, the second air pipe, the third air pipe and the fourth air pipe to press the inkjet printhead.

[0041] Furthermore, when the printhead is in sleep mode, the temperature inside the heating chamber is lowered, but remains above the freezing point of the high-temperature phase change material. The sleep pressure P1' of the first air pipe and the sleep pressure P2' of the second air pipe are adjusted to be the same, P1' = P2' = (P1 + P2) / 2 - P0, where P0 is the correction pressure from dynamic to static ink, P1 is the printing pressure of the ink return chamber during printing, and P2 is the printing pressure of the ink inlet chamber during printing. This pressure adjustment during sleep mode keeps the ink in a liquid state without circulation or allows it to circulate slowly, primarily to protect the lifespan of the components.

[0042] Furthermore, when the inkjet printhead is powered on, the ink temperature T1 in the ink cartridge and the inkjet printhead temperature T2 are detected. If T1 ≥ T0 and T2 ≥ T0, where T0 is the liquid ink temperature, the relevant protection is released, and the air pressure in the first and second air pipes is slowly adjusted to printing pressures P1 and P2, respectively, for ink circulation. If T1 or T2 ≤ T0, the reflux pump remains closed, and the air pressure in both the first and second air pipes is 0. The ink is first heated to a set temperature Ta by the heating element to keep it liquid. Once the ink is confirmed to be liquid, the air pressure in the first and second air pipes is adjusted to printing pressures P1 and P2, respectively. Upon power-on, if the ink temperature is greater than or equal to the liquid temperature, the reflux device is activated for ink circulation. If the ink temperature is below the liquid temperature, it needs to be heated to liquid status before the reflux device is activated for circulation. The heating time is determined based on material characteristics, heating logic, and heat transfer efficiency.

[0043] Furthermore, when the nozzle is powered off, the return pump is shut off, the balance valve is opened, and the pressure difference between the first air pressure chamber, the second air pressure chamber, the first buffer air pressure chamber, and the second buffer air pressure chamber is all 0.

[0044] Thirdly, the present invention also provides an integrated inkjet printing circulating ink supply device, comprising:

[0045] The heating chamber includes an ink return chamber, an ink return buffer chamber, an ink inlet buffer chamber, and an ink inlet chamber. The ink inlet chamber and the ink inlet buffer chamber are adjacent to each other and connected through a first channel within the heating chamber. The ink return chamber and the ink return buffer chamber are adjacent to each other and connected through a connecting hole.

[0046] A heating element is disposed on the outer periphery of the heating cavity to heat the heating cavity;

[0047] The reflow device is at least partially embedded in the heating chamber, and the reflow device connects the ink return buffer chamber and the ink inlet buffer chamber through an internal channel located in the heating chamber.

[0048] The ink inlet tube connects the ink inlet chamber to the inkjet printhead, and the ink return tube connects the ink return chamber to the inkjet printhead.

[0049] Furthermore, the heating chamber includes an ink cartridge and a cover plate, which are sealed and fixed. The ink return chamber, ink return buffer chamber, ink inlet buffer chamber, and ink inlet chamber are located inside the ink cartridge. The ink return chamber and ink inlet chamber are L-shaped, and the ink return buffer chamber and ink inlet buffer chamber are respectively located within the L-shaped semi-enclosed structure of the ink return chamber and ink inlet chamber, with their short sides adjacent to each other. The ink return buffer chamber and ink inlet buffer chamber do not need to occupy a large volume. The design of the ink return buffer chamber and ink inlet buffer chamber being located within the L-shaped semi-enclosed structure of the ink return chamber and ink inlet chamber respectively contributes to a compact space while ensuring the volume requirements of the ink inlet chamber and ink return chamber.

[0050] Furthermore, the cover plate is L-shaped and has a reflux pump mounting section. The reflux device includes a reflux pump, which is laterally fixed to the reflux pump mounting section. The reflux pump is arranged parallel to the length direction of the L-shaped cover plate. The reflux pump is relatively long, and the parallel arrangement of the reflux pump and the length direction of the L-shaped cover plate allows for a compact space.

[0051] Furthermore, the reflux device also includes a reflux valve, which is embedded in the cover plate and located at the upper end of the ink return buffer chamber. The cover plate has a third channel, which connects the inlet of the reflux pump and the outlet of the reflux valve. The cover plate, in conjunction with the ink cartridge, also has a fifth channel, partly located inside the ink cartridge and partly inside the cover plate. The fifth channel connects the reflux valve and the bottom of the ink return buffer chamber. Embedding the reflux valve in the cover plate and connecting the reflux pump and the ink return buffer chamber through an internal channel, and then heating the heating chamber through a heating element, can reduce the additional heating of external pipes and improve space utilization and energy efficiency.

[0052] Furthermore, the reflux device also includes a filter embedded below the ink inlet buffer chamber. A second channel is also provided inside the ink cartridge, connecting the filter to the ink inlet buffer chamber. A fourth channel is also provided in conjunction with the cover plate, connecting the reflux pump outlet to the filter inlet. Embedding the filter within the ink cartridge and connecting the reflux pump and ink inlet buffer chamber via internal channels, and then heating the heating chamber via a heating element, reduces the need for additional heating from external pipes, improving space and energy utilization.

[0053] Furthermore, the integrated inkjet printing circulating ink supply device also includes an air path interface, which is connected to the air pressure control module. The air path interface is located on the side wall of the cover plate and is connected to the ink inlet chamber or the ink return chamber through a channel inside the cover plate.

[0054] Furthermore, the cover plate is provided with a first air passage interface, a second air passage interface, a third air passage interface, and a fourth air passage interface. The cover plate has a sixth channel, a seventh channel, an eighth channel, and a ninth channel. The sixth channel connects the first air passage interface to the ink return chamber, and the seventh channel connects the third air passage interface to the ink return buffer chamber. The first and third air passage interfaces are located on the side near the ink return chamber and the ink return buffer chamber. The eighth channel connects the second air passage interface to the ink inlet chamber, and the ninth channel connects the fourth air passage interface to the ink inlet buffer chamber. The second and fourth air passage interfaces are located on the opposite side from the first and third air passage interfaces.

[0055] The first air circuit interface, the second air circuit interface, the third air circuit interface, and the fourth air circuit interface are respectively connected to the first air pipe, the second air pipe, the third air pipe, and the fourth air pipe of the air pressure control module.

[0056] Furthermore, a heat-conducting block is wrapped around the outside of both the ink inlet tube and the ink return tube, and the heat-conducting block contacts the ink cartridge for heat conduction. By using the heat-conducting block, heat is conducted from the ink cartridge to the heat-conducting block, and then to the ink inlet tube and ink return tube encased within it, reducing the need for additional heating components and improving heat utilization. The ink inlet chamber is equipped with an ink inlet temperature sensor and an ink inlet level sensor, while the ink return chamber is equipped with an ink return level sensor. An ink return temperature sensor is located on the outer wall of the ink return chamber to monitor the temperature of the ink cartridge.

[0057] Furthermore, an integrated inkjet printing circulating ink supply device includes:

[0058] The heating chamber is equipped with an ink return chamber, a buffer chamber and an ink inlet chamber. The buffer chamber is located between the ink return chamber and the ink inlet chamber. The ink inlet chamber and the buffer chamber are connected through a connecting hole in the heating chamber.

[0059] A heating element is disposed on the outer periphery of the heating cavity to heat the heating cavity;

[0060] A reflux device is at least partially embedded in the heating chamber, and the reflux device connects the ink return chamber and the buffer chamber through an internal channel located in the heating chamber.

[0061] The ink inlet tube connects the ink inlet chamber to the inkjet printhead, and the ink return tube connects the ink return chamber to the inkjet printhead.

[0062] Furthermore, the reflux device includes a reflux valve, a reflux pump, and a filter. The reflux valve is located above the ink return chamber and is connected to the bottom of the ink return chamber through an internal channel. The reflux pump is fixed to the upper part of the heating chamber, and the inlet of the reflux pump is connected to the outlet of the reflux valve through an internal channel. The filter is located near the buffer chamber, and the outlet of the reflux pump is connected to the filter through an internal channel. The outlet of the filter is connected to the buffer chamber through an internal channel.

[0063] By adopting the above technical solution, the present invention has the following beneficial effects:

[0064] 1. The heating component heats the entire circulation module, keeping the ink in a flowable state and preventing it from cooling and solidifying or becoming unable to flow due to high viscosity. This is particularly suitable for high-temperature phase change material inks or high-viscosity inks (e.g., inks with viscosities ranging from 1-200 cP are applicable). The power module circulates the ink within the inkjet printhead and circulation module, ensuring better temperature uniformity of the fluid, carrying away air bubbles and impurities in the printhead, and filtering them out.

[0065] 2. By incorporating a buffer chamber, the air pressure control module regulates the pressure difference between the ink inlet chamber and the ink return chamber. This allows ink in the ink return chamber to flow through the buffer chamber to the ink inlet chamber. Ink in the ink inlet chamber then enters the inkjet printhead through the ink inlet pipe and flows back to the ink return chamber through the ink return pipe, thus achieving fluid circulation. The buffer chamber serves three purposes: first, it eliminates air bubbles mixed in the ink; second, it smooths the ink flow and eliminates flow pulsations; and third, it ensures a more uniform ink temperature.

[0066] 3. Under different working conditions, the fluid flow rate in the circulating ink supply system is different. The speed of the reflux pump in the reflux device controls the fluid flow rate, so that the circulating ink supply system can supply ink stably.

[0067] 4. For different working states of the inkjet printhead, such as printing state, sleep state, ink pressing state, power-on state, etc., the ink supply system should have different methods to keep the ink supply system working stably.

[0068] 5. The integrated design of the circulation module, except for the air pressure control module, ink inlet tube, and ink outlet tube, places all other components and modules within a heating chamber with heating function. The fluid channel is realized through the internal flow channel of the heating chamber. The heating chamber uses a uniform heat-conducting material to ensure a uniform temperature throughout the circulation system through heat conduction, keeping the high-temperature phase change material in a molten state, thereby achieving high-flow printing. The integrated structural design makes the structure more compact, lower in cost, and easier to maintain, while the simpler and more centralized heating design ensures uniform fluid temperature.

[0069] 6. Temperature sensors are installed in both the ink inlet chamber and the side wall of the ink return chamber for two-stage control, ensuring uniform fluid temperature heating and preventing fluid deterioration due to overheating during initial heating. The temperature sensor in the ink inlet chamber directly measures the fluid temperature, providing direct feedback on the temperature of the fluid entering the printhead. Since the initial heating cycle has not yet started, especially for phase change fluids where the internal temperature is low, the temperature sensor installed on the side wall of the ink return chamber prevents the heating chamber from heating to excessively high temperatures, which could damage the fluid and affect printing.

[0070] 7. This circulating ink supply system supports high flow rate and high viscosity systems. High temperature phase change materials such as wax have high viscosity at certain temperatures. The power of the entire system circulation is determined by the pressure difference of the air pressure control module. Increasing the flow rate can be achieved simply by increasing the pressure difference. In addition, electronic components and pumps are all selected to support high viscosity fluids. Attached Figure Description

[0071] The invention will now be further described with reference to the accompanying drawings.

[0072] Figure 1 This is a schematic diagram of the circulating ink supply system in Example 1.

[0073] Figure 2A schematic diagram of an integrated inkjet printer's circulating ink supply system from one angle.

[0074] Figure 3 This is a structural schematic diagram of an integrated inkjet printer's circulating ink supply device from another angle.

[0075] Figure 4 This is a schematic diagram of the ink cartridge structure;

[0076] Figure 5 This is a structural diagram of the ink cartridge and cover plate; some internal flow channels in the cover plate are simply indicated by dashed lines.

[0077] Figure 6 Right view of an integrated inkjet printer with a circulating ink supply system;

[0078] Figure 7 For along Figure 6 The cross-sectional view obtained from the GG plane;

[0079] Figure 8 For along Figure 6 The sectional view obtained from the DD plane;

[0080] Figure 9 For along Figure 6 The sectional view obtained from the FF plane;

[0081] Figure 10 This is a schematic diagram of the inkjet printhead and circulation structure in the circulating ink supply system of Example 2;

[0082] Figure 11 This is a schematic diagram of the circulating ink supply system in Example 3. Detailed Implementation

[0083] Example 1

[0084] like Figure 1 The illustrated circulating ink supply system for 3D inkjet printing includes an inkjet printhead 1, a circulation module 2, and an air pressure control module 3. Figure 1The ink flow direction is shown by the arrow. The inkjet printhead 1 has multiple nozzles for ejecting ink, which can be fluids such as phase change waxes, binders, fluxes, finers, and photosensitive resins. It is particularly suitable for high-viscosity, high-flow-rate, high-temperature phase change wax systems. The melting point of waxes is typically 60-90℃. This inkjet printing circulating ink supply system can support heating temperatures of 60-150℃, supports materials with viscosities of 1-200 cP, and supports a single inkjet printhead flow rate greater than 100 ml / min. The circulation structure module 2 includes an ink return chamber 4, an ink inlet chamber 5, an ink return buffer chamber 6, and an ink inlet buffer chamber 7. The ink inlet chamber 5 is connected to the ink inlet (IN) of the printhead 1 via an ink inlet pipe 11, and the ink return chamber 4 is connected to the ink return (OUT) of the printhead 1 via an ink return pipe 10. The ink inlet chamber 5 is equipped with an ink inlet temperature sensor 8b and an ink inlet level sensor 9b, used to monitor the ink temperature and level in the ink inlet chamber 5, respectively. The ink inlet temperature sensor 8b extends deep into the ink inlet cavity 5 to directly measure the material temperature. An ink return temperature sensor 8a is installed on the outer wall of the ink return cavity 4 to monitor the temperature of the outer wall and prevent overheating during initial heating. For phase change fluids, the ink circulation does not start during the initial heating, and the core temperature of the fluid is low. A temperature sensor installed on the overall cavity is needed to prevent the cavity temperature from heating to a high enough level to damage the fluid adhering to the cavity surface, thus affecting printing. An ink return level sensor 9a is installed inside the ink return cavity 4 to monitor the ink level. The circulation module 2 connects to the heating assembly (…). Figure 1 Not shown in the image. Figure 2 Component number 52 heats the ink return chamber 4, ink inlet chamber 5, ink return buffer chamber 6, and ink inlet buffer chamber 7. A connecting hole 12a connects the ink return chamber 4 and the ink return buffer chamber 6. A connecting hole 12b connects the ink inlet chamber 5 and the ink inlet buffer chamber 7. The ink return buffer chamber 6 and the ink inlet buffer chamber 7 are connected by a reflux device. The reflux device includes a reflux valve 13, a reflux pump 14, and a filter 15a. The ink return buffer chamber 6 is connected to the reflux valve 13 via a pipe or channel, the reflux valve 13 is connected to the reflux pump 14 via a pipe or channel, the reflux pump 14 is connected to the filter 15a via a pipe or channel, and the filter 15a is connected to the ink inlet buffer chamber 7. The reflux valve 13 can be a one-way valve or a solenoid valve, etc., thereby allowing ink to flow in one direction. The filter 15a can be selected according to the ink material to filter the ink flowing back to the ink inlet buffer chamber 7.

[0085] like Figure 1As shown, the air pressure control module 3 is connected to the ink inlet chamber 5 and the ink return chamber 4, and is used to control the pressure difference between the ink inlet chamber 5 and the ink return chamber 4, thereby converting it into kinetic energy for the circulating ink supply system, allowing the ink to circulate between the circulation module 2 and the inkjet printhead 1. The air pressure control module 3 includes a first pressure control module and a second pressure control module. The first pressure control module controls the pressure of the ink return chamber 4, which has a negative pressure. The second pressure control module controls the pressure of the ink inlet chamber 5, which can have either a positive or negative pressure. The ink return buffer chamber 6 can also be connected to the first pressure control module, or it can be closed without a separate pressure control module, or it can be connected to a third pressure control module, which is connected to the first pressure control module. The ink inlet buffer chamber 7 can also be connected to the second pressure control module, or it can be closed without a separate pressure control module, or it can be connected to a fourth pressure control module, which is connected to the second pressure control module.

[0086] A feasible air pressure control module 3 principle is as follows Figure 1 As shown, the system includes a first pressure chamber 16, a second pressure chamber 17, a first buffer pressure chamber 18, and a second buffer pressure chamber 19. The first pressure chamber 16 is connected to the ink return chamber 4 via a first air pipe 20 and a first positive / negative pressure switching valve 21. The second pressure chamber 17 is connected to the ink inlet chamber 5 via a second air pipe 22 and a second positive / negative pressure switching valve 23. The first buffer pressure chamber 18 is connected to the ink return buffer chamber 6 via a third air pipe 24 and a third positive / negative pressure switching valve 25. The second buffer pressure chamber 19 is connected to the ink inlet buffer chamber 7 via a fourth air pipe 26 and a fourth positive / negative pressure switching valve 27. Pressure sensors 28a and 28b are connected to both the first and second pressure chambers 16 and 17, respectively. The first positive / negative pressure switching valve 21, the second positive / negative pressure switching valve 23, the third positive / negative pressure switching valve 25, and the fourth positive / negative pressure switching valve 27 are all connected to the same positive pressure pump 37. A filter 38 is connected to the inlet of the positive pressure pump 37.

[0087] The first pressure chamber 16 is connected to a first air source valve 30 and a first pressure relief valve 29. The second pressure chamber 17 is connected to a second air source valve 32 and a second pressure relief valve 31. The air source valves can pressurize the pressure chambers, and the pressure relief valves can depressurize them. The first pressure chamber 16 and the first buffer pressure chamber 18 are connected by a first buffer connecting pipe 33, and the second pressure chamber 17 and the second buffer pressure chamber 19 are connected by a second buffer connecting pipe 34. The first pressure relief valve 29 and the second pressure relief valve 31 are each connected to filters 15b and 15c. The first air source valve 30 and the second air source valve 32 are each connected to air pumps 35a and 35b. A balancing valve 36 is connected between the first pressure chamber 16 and the second pressure chamber 17. The balancing valve 36 is connected to a backup power supply 39, or the balancing valve 36 is a normally open solenoid valve connected to a pressure reduction module 39.

[0088] based on Figure 1The invention illustrates the principle of a circulating ink supply system suitable for 3D inkjet printing. It also designs an integrated 3D inkjet printing circulating ink supply device. (See attached image.) Figures 2-9 The integrated inkjet printer's circulating ink supply device includes a heating chamber, which contains an ink cartridge 40. The ink cartridge 40 is generally rectangular and includes an L-shaped ink return chamber 4, an L-shaped ink inlet chamber 5, an ink return buffer chamber 6, and an ink inlet buffer chamber 7. For a compact structure, such as... Figure 4 As shown, the ink return buffer chamber 6 is a slightly smaller cuboid structure located within the semi-enclosed structure of the L-shaped ink return chamber 4, and the ink inlet buffer chamber 7 is a slightly smaller cuboid structure located within the semi-enclosed structure of the L-shaped ink inlet chamber 5. The short sides of the L-shaped ink inlet chamber 5 and the L-shaped ink return chamber 4 are parallel to each other and located in the middle of the cuboid, while the long sides are located on both sides of the cuboid and extend in opposite directions. A connecting hole 12a is provided in the cavity wall separating the ink return chamber 4 and the ink return buffer chamber 6. A first channel 41 (equivalent to connecting hole 12b) is provided in the ink cartridge 40 at the bottom of the ink inlet buffer chamber 7, and the other end of the first channel 41 connects to the ink inlet chamber 5. Both the connecting hole 12a and the first channel 41 are achieved by setting channels inside the ink cartridge 40, rather than through external pipes, which saves space and reduces additional heating. The ink inlet chamber 5 is equipped with an ink inlet temperature sensor 8b and an ink inlet level sensor 9b, the ink return chamber 4 is equipped with an ink return level sensor 9a, and the outer wall of the ink return chamber 4 is equipped with an ink return temperature sensor 8a to monitor the outer wall temperature of the ink cartridge 40. Figure 9 As shown, the ink cartridge 40 below the ink inlet buffer chamber 7 has a mounting hole, and a filter 15a is provided in the mounting hole. The ink cartridge 40 also has a second channel 42, which connects the filter 15a and the ink inlet buffer chamber 7.

[0089] Combination Figure 2-9The heating chamber also includes a cover plate 43, and the ink cartridge 40 is sealed and fixedly connected to the cover plate 43. The cover plate 43 is generally L-shaped, and a reflux valve 13 is embedded at the end of the cover plate 43 away from the ink inlet buffer chamber 7. The cover plate 43 has a reflux pump mounting part 58, and a reflux pump 14 is horizontally fixed to the reflux pump mounting part 58. The reflux pump 14 is arranged parallel to the length direction of the L-shaped cover plate 43. The reflux valve 13 is embedded in the cover plate 43 and is located near the reflux pump mounting part 58. The reflux pump 14 has an inlet 141 and an outlet 142. The cover plate 43 is provided with a third channel 44, which connects the inlet 141 of the reflux pump 14 and the outlet of the reflux valve 13. The cover plate 43, in conjunction with the ink cartridge 40, also features a fourth channel 56. This fourth channel 56 connects the reflux pump outlet 142 and the inlet of the filter 15a. Part of the fourth channel 56 is located inside the ink cartridge 40, and part is located inside the cover plate 43. Since the reflux pump outlet 142 and the inlet of the filter 15a are located at opposite ends of the entire device, the fourth channel 56 spans across the cover plate 43. The reflux valve 13 is located at the upper end of the ink return buffer chamber 6. The cover plate 43, in conjunction with the ink cartridge 40, also features a fifth channel 45. This fifth channel 45 is partly located inside the ink cartridge 40 and partly inside the cover plate 43. The fifth channel 45 connects the reflux valve 13 and the bottom of the ink return buffer chamber 6. Positioning the reflux valve 13 at the upper end of the ink return buffer chamber 6 reduces the length of the fifth channel 45.

[0090] like Figure 2 , Figure 3 and Figure 5 As shown, heating elements 52 are provided on both side walls extending along the length of the ink cartridge 40 and the cover plate 43. The heating elements 52 heat the entire interior of the ink cartridge 40 and the cover plate 43. A heat insulation plate can be installed on the outside of the heating elements 52. The ink cartridge 40 also has an ink inlet 55, which is connected to the ink return chamber 4 and is used to inject ink into the entire circulating ink supply system. The ink inlet chamber 5 and the ink return chamber 4 are connected to the inkjet printhead 1 through the ink inlet pipe 11 and the ink return pipe 10. The ink inlet pipe 11 and the ink return pipe 10 are wrapped together with a heat-conducting block 51. The heat-conducting block 51 is in contact with the ink cartridge 40. Heat is conducted from the ink cartridge 40 to the heat-conducting block 51 and then to the ink inlet pipe 11 and the ink return pipe 10 inside it, reducing the need for additional heating components and improving heat utilization.

[0091] like Figure 2 , Figure 3 , Figure 5As shown, the cover plate 43 is also provided with a first air passage interface 46a, a second air passage interface 46b, a third air passage interface 46c, and a fourth air passage interface 46d. The cover plate 43 has a sixth channel 47, a seventh channel 48, an eighth channel 49, and a ninth channel 50 inside. The sixth channel 47 connects the first air passage interface 46a to the ink return chamber 4, and the seventh channel 48 connects the third air passage interface 46c to the ink return buffer chamber 6. The first air passage interface 46a and the third air passage interface 46c are located near the ink return chamber 4 and the ink return buffer chamber 6. The eighth channel 49 connects the second air passage interface 46b to the ink inlet chamber 5, and the ninth channel 50 connects the fourth air passage interface 46d to the ink inlet buffer chamber 7. The second air passage interface 46b and the fourth air passage interface 46d are located on the opposite side from the first air passage interface 46a and the third air passage interface 46c.

[0092] The first air path interface 46a, the second air path interface 46b, the third air path interface 46c, and the fourth air path interface 46d are respectively connected to the first air pipe 20, the second air pipe 22, the third air pipe 24, and the fourth air pipe 26 of the air pressure control module 3. The air pressure control module 3 is specifically composed as follows... Figure 1 As shown, it will not be described again from here on.

[0093] The integrated 3D inkjet printing circulating ink supply device, through a rational layout, houses all components and modules except for the air pressure control module 3, ink inlet pipe 11, and ink return pipe 10 within a heated ink cartridge 40 and cover plate 43. The fluid channel is achieved through the internal flow channels of the ink cartridge 40 and cover plate 43. The ink cartridge 40 and cover plate 43 utilize a uniform heat-conducting material, ensuring a uniform temperature throughout the circulation system through heat conduction, keeping the wax material in a molten state, thereby achieving high-flow printing. The integrated structural design makes efficient use of internal space, contributing to device miniaturization and space saving, and also improving heat utilization efficiency.

[0094] When inkjet printhead 1 is in printing mode, the circulating ink supply system performs the following control:

[0095] (1) The first air pressure chamber 16 provides pressure to the ink return chamber 4 through the first air pipe 20 to maintain the printing pressure P1. The second air pressure chamber 17 provides pressure to the ink inlet chamber 5 through the second air pipe 22 to maintain the printing pressure P2. The first buffer air pressure chamber 18 provides printing pressure P1 to the ink return buffer chamber 6 through the third air pipe 24. The second buffer air pressure chamber 19 provides printing pressure P2 to the ink inlet buffer chamber 7 through the fourth air pipe 26. P1 is a negative pressure, and there is a pressure difference between P1 and P2. The printing pressure P2 provided to the ink inlet buffer chamber 7 is greater than the printing pressure P1 provided to the ink return buffer chamber 6. P1 is a large negative pressure, and P2 is a small negative pressure or a positive pressure.

[0096] (2) The fluid (i.e. ink) in the ink inlet chamber 5 enters the inkjet printhead 1 through the ink inlet pipe 11 and then flows from the ink return pipe 10 to the ink return chamber 4.

[0097] (3) When the fluid in the ink return chamber 4 reaches a certain height, it flows from the ink return chamber 4 through the connecting hole 12 to the ink return buffer chamber 6. The ink return level sensor 9a in the ink return chamber 4 is triggered when the liquid level in the ink return chamber 4 reaches the set height, and the reflux pump 14 is turned on. The fluid in the ink return buffer chamber 6 flows to the ink inlet buffer chamber 7 after being filtered through the reflux valve 13, the reflux pump 14, and the filter 15a. When the fluid in the ink inlet buffer chamber 7 reaches a certain height, it flows from the ink inlet buffer chamber 7 to the ink inlet chamber 5, realizing the circulation of fluid in the inkjet printhead 1 and the circulation module 2. The operation of the reflux pump 14 is controlled by an algorithm based on the value of the liquid level sensor or the time parameter to match the corresponding material circulation speed. The circulation of fluid in the inkjet printhead 1 and the circulation module 2 can ensure better temperature uniformity of the fluid; it can support some printheads that do not have a heating module; the circulation can remove air bubbles and impurities in the printhead and filter them out; the circulation can support the printing of some special fluids (such as those that will precipitate or have high viscosity).

[0098] To maintain the nozzle condition of inkjet printhead 1 and ensure the nozzles are clean, ink pressing is required. When inkjet printhead 1 is in the ink pressing state, the circulating ink supply system performs the following control:

[0099] (1) The pressure sensor adjusts the working speed of the positive pressure pump 37 to maintain a certain pressure in the positive pressure pump 37.

[0100] (2) The first positive and negative pressure switching valve 21, the second positive and negative pressure switching valve 23, the third positive and negative pressure switching valve 25 and the fourth positive and negative pressure switching valve 27 are all switched to positive pressure pump 37 (originally, the positive and negative pressure switching valves were all connected to the corresponding air pressure chambers above). Positive pressure pump 37 applies positive pressure to the first air pipe 20, the second air pipe 22, the third air pipe 24 and the fourth air pipe 26 to press ink onto the inkjet print head 1.

[0101] When the inkjet printhead 1 is in sleep mode, the temperature inside the heating chamber is lowered, but remains above the solidification point of the wax to prevent it from solidifying. The circulating ink supply system operates as follows:

[0102] The dormant pressure P1' of the first trachea 20 and the dormant pressure P2' of the second trachea 22 are adjusted to be consistent.

[0103] P1' = P2' = (P1 + P2) / 2 - P0, where P0 is the corrected pressure from dynamic to static fluid; P1 is the printing pressure of the ink return chamber 4 during printing; and P2 is the printing pressure of the ink inlet chamber 5 during printing. Pressure adjustment during sleep mode prevents ink circulation or allows it to circulate slowly, thus protecting the lifespan of components.

[0104] When the inkjet printhead 1 is powered on, the ink supply system of the inkjet printhead 1 operates as follows: When the inkjet printhead 1 is powered on, the fluid temperature T1 in the ink cartridge 40 and the temperature T2 of the inkjet printhead 1 are detected. If T1 > T0 and T2 > T0, where T0 is the liquid temperature of the fluid, the relevant protections are released (e.g., the contact protection of the return pump 14 can be activated, and the negative pressure can function). The air pressure of the first air pipe 20 and the second air pipe 22 are slowly adjusted to the printing pressure P1 and the printing pressure P2, respectively, to circulate the fluid. If T1 or T2 ≤ T0, it indicates that some fluid has solidified. The return pump 14 is kept closed, and the air pressure of the first air pipe 20 and the second air pipe 22 are adjusted to circulate the fluid. The air pressure in the air pipe 22 is 0. First, the fluid is heated to the set temperature Ta by the heating component to keep the fluid in a liquid state. After confirming that the fluid is in a liquid state, the air pressure of the first air pipe 20 and the second air pipe 22 are adjusted to the printing pressure P1 and the printing pressure P2, respectively. The heating time can be obtained by first calculating the temperature difference ΔT1 = T1 - T0 between the fluid temperature T1 and T0 of the ink cartridge 40, and the temperature difference ΔT2 = T2 - T0 between the inkjet printhead 1 temperature T2 and T0, respectively. Based on the solid-liquid heating curve of the fluid and the heating and heat transfer design of the ink cartridge 40 and the inkjet printhead 1 and related empirical parameters, the required heating time of the ink cartridge 40 and the inkjet printhead 1 can be dynamically obtained.

[0105] When the inkjet printhead 1 is powered off, the circulating ink supply system operates as follows: the reflux pump 14 is turned off, the balance valve 36 is turned on, and the first pressure chamber 16 and the second pressure chamber 17 are connected through the balance valve 36, so that the pressure difference between the first pressure chamber 16 and the second pressure chamber 17 is 0. The first buffer pressure chamber 18 is connected to the first pressure chamber 16 through the first buffer tube 33, so the pressure of the first buffer pressure chamber 18 is equal to that of the first pressure chamber 16. Similarly, the pressure of the second buffer pressure chamber 19 is equal to that of the second pressure chamber 17, and the pressure difference between the first pressure chamber 16, the second pressure chamber 17, the first buffer pressure chamber 18, and the second buffer pressure chamber 19 is 0. In a conventional system, if the system suddenly loses power, the first air pressure chamber 16, the second air pressure chamber 17, the first buffer air pressure chamber 18, and the second buffer air pressure chamber 19 will maintain their current pressure. Therefore, the fluid in the ink cartridge 40 will still circulate. However, the return pump 14 will not work. After a certain period of time, the first air pipe 20 and the third air pipe 24 will draw in fluid. The pre-cooling and solidification of the fluid will damage the circulating ink supply system. Therefore, this circulating ink supply system stops the circulation when the pressure difference is 0 by setting a balance valve 36 to perform power failure protection. In addition, the inkjet printhead 1 also maintains an appropriate negative pressure to prevent leakage and waste of wax material.

[0106] Example 2

[0107] Similar to the circulating ink supply system in Embodiment 1, the circulating ink supply system in this embodiment also includes an inkjet printhead 1, a circulation module 2, and an air pressure control module 3. The difference is that the circulation module 2 in this embodiment only has one buffer chamber. The inkjet printhead 1 and circulation module 2 in Embodiment 2 are as follows... Figure 10 As shown.

[0108] The circulation module 2 includes an ink inlet chamber 5, an ink return chamber 4, and a buffer chamber 53. The ink inlet chamber 5 is connected to the first air pipe 20, which is used to regulate negative pressure. The first air pipe 20 is connected to the air pressure control module 3, which can... Figure 1 Modules that can achieve air pressure control and regulation, whether the functions are the same or different, are acceptable. The ink return chamber 4 and the buffer chamber 53 are connected via a reflux device. A connecting hole 12 is provided between the buffer chamber 53 and the ink inlet chamber 5. Pressure sensors 54a and 54b are respectively connected to the ink return chamber 4 and the ink return pipe 10. These two pressure sensors can measure the air pressure above the ink return chamber 4 and the fluid pressure inside the ink return pipe 10, respectively. The ink inlet chamber 5 is equipped with an ink inlet temperature sensor 8b and an ink inlet level sensor 9b. The fluid flow is as follows... Figure 10 As indicated by the arrow. The reflux device includes a reflux valve 13, a reflux pump 14, and a filter 15a connected in sequence via pipes or channels. The outlet of filter 15a is connected to the buffer chamber 53, and the inlet of reflux valve 13 is connected to the ink return chamber 4. Another filter 15d may be installed inside the ink inlet pipe 11 (or it may not be installed).

[0109] When inkjet printhead 1 is in printing mode, the circulating ink supply system performs the following control:

[0110] (1) The air pressure control module 3 controls the pressure of the ink inlet chamber 5 through the first air pipe 20, making it greater than the pressure of the ink return chamber 4. The pressure of the ink inlet chamber 5 is either positive or negative.

[0111] (2) The fluid in the ink inlet chamber 5 enters the inkjet printhead 1 through the ink inlet pipe 11 and then flows from the ink return pipe 10 to the ink return chamber 4.

[0112] (3) When the reflux pump 14 is turned on, the fluid in the ink return chamber 4 passes through the reflux valve 13, reflux pump 14, and filter 15a to the buffer chamber 53 in sequence. When the fluid in the buffer chamber 53 reaches a certain height, the fluid flows from the buffer chamber 53 through the connecting hole 12 to the ink inlet chamber 5, so that the fluid circulates in the inkjet printhead 1 and the circulation module 2.

[0113] (4) Monitor the values ​​of pressure sensors 54a and 54b. Based on the combined algorithm of pressure sensors 54a and 54b, the connected system negative pressure, and the rotation speed of the return pump 14, control and adjust the rotation speed of the return pump 14 to match the corresponding material circulation speed, and adjust the system negative pressure to achieve a suitable meniscus pressure. The meniscus pressure is the fluid pressure required by the inkjet printhead 1. The actual parameters are different for different printhead models. During printing, the pressure parameters are mainly adjusted according to whether the nozzle can hold the fluid without dripping and the printing effect. The system negative pressure here refers to the pressure difference of the entire system, that is, the difference between the pressure of the ink return chamber 4 and the pressure of the ink inlet chamber 5. This difference is negative.

[0114] According to Example 1 Figures 2-9 An integrated 3D inkjet printing circulating ink supply device is provided in this embodiment, and its structure is similar to... Figure 2-9 The structures shown are generally similar and include: a heating chamber, which has an ink return chamber 4, a buffer chamber 53 and an ink inlet chamber 5. The buffer chamber 53 is located between the ink return chamber 4 and the ink inlet chamber 5. The ink inlet chamber 5 and the buffer chamber 53 are connected through a connecting hole 12 inside the heating chamber; a heating element, which is disposed on the outer periphery of the heating chamber for heating the heating chamber; a reflux device, which is at least partially embedded in the heating chamber and is connected to the ink return chamber 4 and the buffer chamber 53 through an internal channel located inside the heating chamber; an ink inlet pipe 11 and an ink return pipe 10, whereby the ink inlet pipe 11 connects the ink inlet chamber 5 to the inkjet printhead 1, and the ink return pipe 10 connects the ink return chamber 4 to the inkjet printhead 1. The reflux valve 13 is located above the ink return chamber 4. The reflux valve 13 is connected to the bottom of the ink return chamber 4 through an internal channel. The reflux pump 14 is fixed to the upper part of the heating chamber. The inlet of the reflux pump 14 is connected to the outlet of the reflux valve 13 through an internal channel. The filter 15a is located near the buffer chamber 53. The outlet of the reflux pump 14 is connected to the filter 15a through an internal channel. The outlet of the filter 15a is connected to the buffer chamber 53 through an internal channel.

[0115] Example 3

[0116] like Figure 11As shown, the circulating ink supply system includes an inkjet printhead 1, a circulation module 2, and a circulation pump 57. The circulation module 2 includes an ink inlet chamber 5 and an ink return chamber 4, which are connected or integrated. The circulation pump 57 is located in the ink inlet pipe 11 and provides the power required for the circulating ink supply system. The inlet of the circulation pump 57 is connected to the ink inlet chamber 5 via the ink inlet pipe 11. The filter 15e is connected to the outlet of the circulation pump 57, and the outlet of the filter 15e is connected to the ink inlet IN of the inkjet printhead 1. The ink return OUT of the inkjet printhead 1 is connected to the ink return chamber 4 via the ink return pipe 10. The ink return pipe 10 is equipped with a return valve 13, which can be a one-way valve or a solenoid valve. The ink inlet chamber 5 is connected to a first air pipe 20, which regulates negative pressure. The first air pipe 20 is connected to a pneumatic control module. The ink inlet pipe 11 is equipped with a pressure sensor 54c.

[0117] When inkjet printhead 1 is in printing mode, the circulating ink supply system performs the following control:

[0118] (1) The first air tube 20 provides negative pressure to the inkjet printhead 1;

[0119] (2) When the circulation pump 57 is turned on, the fluid in the ink inlet chamber 5 enters the inkjet printhead 1 through the ink inlet pipe 11 and then flows from the ink return pipe 10 to the ink return chamber 4. The ink inlet chamber 5 and the ink return chamber 4 are connected, and the ink flows back to the ink inlet chamber 5, so that the fluid circulates in the inkjet printhead 1 and the circulation module 2.

[0120] (3) Monitor the value of pressure sensor 54c, and control and adjust the speed of circulation pump 57 according to the comprehensive algorithm of pressure sensor 54c, connected system negative pressure and rotation speed of circulation pump 57 to match the corresponding material circulation speed, and adjust the system negative pressure to achieve a suitable meniscus pressure. Here, system negative pressure refers to the negative pressure provided by the first air pipe 20 to inkjet printhead 1.

[0121] The above are merely specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications made based on the present invention to solve essentially the same technical problems and achieve essentially the same technical effects are all covered within the protection scope of the present invention.

Claims

1. A control method for a circulating ink supply system suitable for 3D inkjet printing, characterized in that... Includes the following steps: (1) When the inkjet printhead is in the printing state, the power module provides kinetic energy for ink circulation; (2) The ink in the ink inlet chamber enters the inkjet printhead through the ink inlet tube and then flows to the ink return chamber through the ink return tube; (3) When the ink in the ink return chamber reaches a certain height, the ink enters the ink inlet chamber connected to the ink return chamber, so that the ink circulates in the inkjet printhead and the circulating ink supply structure. The above control method is implemented using an integrated 3D inkjet printing circulating ink supply device, the circulating ink supply device comprising: The heating chamber includes an ink cartridge and a cover plate. The ink cartridge is provided with an ink return chamber, an ink inlet chamber, an ink return buffer chamber, and an ink inlet buffer chamber. The ink inlet chamber and the ink inlet buffer chamber are arranged adjacent to each other and are connected through a first channel in the heating chamber. The ink return chamber and the ink return buffer chamber are arranged adjacent to each other and are connected through a connecting hole. A heating element is disposed on the outer periphery of the heating cavity for heating the heating cavity; The ink inlet tube connects the ink inlet chamber to the inkjet printhead, and the ink return tube connects the ink return chamber to the inkjet printhead. A reflux device, wherein the reflux device connects the ink return buffer chamber and the ink inlet buffer chamber through an internal channel located within the heating chamber; An air path interface is provided, which is connected to the air pressure control module. The air path interface is connected to the ink return chamber, the ink return buffer chamber, the ink inlet chamber, and the ink inlet buffer chamber respectively. The cover plate has a channel that corresponds to each air path interface, so that each air path interface is connected to the corresponding cavity.

2. The control method for a circulating ink supply system suitable for 3D inkjet printing according to claim 1, characterized in that, The circulating ink supply system includes: An inkjet printhead having multiple nozzles for ejecting ink; the ink is a high-temperature phase-change ink or a high-viscosity ink. The circulation module includes an ink return chamber and an ink inlet chamber, which are connected to each other. The ink return chamber and the ink inlet chamber are respectively connected to the inkjet printhead via an ink return pipe and an ink inlet pipe. A heating element for heating the circulation module; A power module is provided to provide kinetic energy to the circulating ink supply system, enabling the ink to circulate between the circulation module and the inkjet printhead.

3. The control method for a circulating ink supply system suitable for 3D inkjet printing according to claim 2, characterized in that: The power module is a circulation pump, which is located in the ink inlet pipe and is used to transport the ink from the ink inlet chamber to the inkjet printhead; or, the power module is a pneumatic control module, which is connected to the ink inlet chamber or the ink return chamber and is used to control the pressure difference between the ink inlet chamber and the ink return chamber to convert it into the kinetic energy of the circulating ink supply system.

4. The control method for a circulating ink supply system suitable for 3D inkjet printing according to claim 3, characterized in that: The circulation module further includes a buffer chamber, which is connected to the ink return chamber and the ink inlet chamber; the heating element heats the ink return chamber, the ink inlet chamber, the buffer chamber, and the pipes or channels connecting the buffer chamber to the ink return chamber and the ink inlet chamber.

5. The control method for a circulating ink supply system suitable for 3D inkjet printing according to claim 2, characterized in that: The heating element can heat the circulation module to 60-150℃; the ink inlet chamber is equipped with an ink inlet temperature sensor and an ink inlet level sensor to monitor the ink temperature and level in the ink inlet chamber; the ink return chamber is equipped with an ink return level sensor to monitor the ink level in the ink return chamber; and the side wall of the ink return chamber is equipped with an ink return temperature sensor to monitor the temperature of the side wall.

6. The control method for a circulating ink supply system suitable for 3D inkjet printing according to claim 4, characterized in that: The buffer chamber is connected to the ink inlet chamber through a connecting hole, and the ink return chamber is connected to the buffer chamber through a reflux device. The circulating ink supply system controls the pressure of the ink inlet chamber / ink return chamber through the air pressure control module, so that the ink enters the buffer chamber from the ink return chamber through the connecting hole, enters the ink inlet chamber through the reflux device, enters the inkjet printhead through the ink inlet tube, and returns to the ink return chamber through the ink return tube, forming a cycle.

7. The control method for a circulating ink supply system suitable for 3D inkjet printing according to claim 6, characterized in that: The reflux device includes a reflux valve, a reflux pump, and a filter connected in sequence. The inlet of the reflux valve is connected to the ink return chamber, and the outlet of the filter is connected to the buffer chamber.

8. The control method for a circulating ink supply system suitable for 3D inkjet printing according to claim 4, characterized in that: The buffer chamber includes a return ink buffer chamber and an inlet ink buffer chamber. The return ink buffer chamber is connected to the return ink chamber through a connecting hole, and the inlet ink buffer chamber is connected to the inlet ink chamber through another connecting hole. The return ink buffer chamber and the inlet ink buffer chamber are connected by a reflux device. The reflux device includes a reflux valve, a reflux pump, and a filter connected in sequence. The inlet of the reflux valve is connected to the return ink buffer chamber, and the outlet of the filter is connected to the inlet ink buffer chamber.

9. The control method for a circulating ink supply system suitable for 3D inkjet printing according to claim 8, characterized in that: The power module is a pneumatic control module, which includes a first pressure control module and a second pressure control module. The first pressure control module is connected to the ink return chamber and is used to control the pressure of the ink return chamber, which is a negative pressure. The second pressure control module is connected to the ink inlet chamber and is used to control the pressure of the ink inlet chamber, which is a positive or negative pressure. The circulating ink supply system uses the pneumatic control module to allow ink to enter the ink return buffer chamber from the ink return chamber through the connecting hole, then enter the ink inlet buffer chamber through the reflux device, then enter the ink inlet chamber through the other connecting hole, and finally enter the inkjet printhead through the ink inlet pipe and return to the ink return chamber through the ink return pipe, forming a cycle.

10. The control method for a circulating ink supply system suitable for 3D inkjet printing according to claim 9, characterized in that: The air pressure control module includes a first air pressure chamber, a second air pressure chamber, a first buffer air pressure chamber, and a second buffer air pressure chamber. The ink return chamber is connected to the first air pressure chamber via a first positive / negative pressure switching valve. The ink inlet chamber is connected to the second air pressure chamber via a second positive / negative pressure switching valve. The ink return buffer chamber is connected to the first buffer air pressure chamber via a third positive / negative pressure switching valve. The ink inlet buffer chamber is connected to the second buffer air pressure chamber via a fourth positive / negative pressure switching valve. Each of the first and second air pressure chambers is connected to an air pressure sensor. The first, second, third, and fourth positive / negative pressure switching valves are all connected to the same positive pressure pump.

11. The control method for a circulating ink supply system suitable for 3D inkjet printing according to claim 10, characterized in that: The first pressure chamber is connected to a first air source valve and a first pressure relief valve; the second pressure chamber is connected to a second air source valve and a second pressure relief valve; the first pressure chamber and the first buffer pressure chamber are connected through a first buffer connecting pipe; the second pressure chamber and the second buffer pressure chamber are connected through a second buffer connecting pipe; each of the first pressure relief valve and the second pressure relief valve is connected to a filter; each of the first air source valve and the second air source valve is connected to an air pump; and a balancing valve is connected between the first pressure chamber and the second pressure chamber.

12. The control method for a circulating ink supply system suitable for 3D inkjet printing according to claim 1, characterized in that: (1) When the inkjet printhead is in the printing state, the air pressure control module controls the pressure of the ink inlet chamber to make it greater than the pressure of the ink return chamber. The pressure of the ink inlet chamber is either positive or negative. (2) The ink in the ink inlet chamber enters the inkjet printhead through the ink inlet tube and then flows to the ink return chamber through the ink return tube; (3) When the reflux pump is turned on, the ink in the ink return chamber passes through the reflux valve, reflux pump and filter to the buffer chamber in sequence. When the ink in the buffer chamber reaches a certain height, the ink flows from the buffer chamber through the connecting hole to the ink inlet chamber, realizing the circulation of ink in the inkjet printhead and the circulation module.

13. The control method for a circulating ink supply system suitable for 3D inkjet printing according to claim 12, characterized in that: The control method further includes step (4), monitoring the value of the pressure sensor, controlling and adjusting the speed of the return pump according to the comprehensive algorithm of the pressure sensor, the connected negative pressure and the speed of the return pump to match the corresponding material circulation speed, and adjusting the negative pressure to achieve a suitable meniscus pressure.

14. The control method for a circulating ink supply system suitable for 3D inkjet printing according to claim 1, characterized in that: (1) When the inkjet printhead is in the printing state, the air pressure control module controls the pressure between the ink inlet chamber and the ink return chamber, so that the pressure of the ink inlet chamber is greater than the pressure of the ink return chamber. The pressure of the ink inlet chamber is either positive or negative, and the pressure of the ink return chamber is controlled to be negative. (2) The ink in the ink inlet chamber enters the printhead through the ink inlet tube and then flows to the ink return chamber through the ink return tube; (3) When the ink in the ink return chamber reaches a certain height, the ink flows from the ink return chamber through the connecting hole to the ink return buffer chamber. When the ink return liquid level sensor in the ink return chamber detects ink when the liquid level in the ink return chamber reaches the set height, it is triggered and the reflux pump is turned on. The ink in the ink return buffer chamber flows to the ink inlet buffer chamber after being filtered by the reflux valve, reflux pump and filter in sequence. When the ink in the ink inlet buffer chamber reaches a certain height, the ink flows from the ink inlet buffer chamber to the ink inlet chamber, realizing the circulation of ink in the inkjet printhead and the circulation module.

15. The control method for a circulating ink supply system suitable for 3D inkjet printing according to claim 14, characterized in that: The specific operation of step (1) is as follows: the first air pressure chamber provides pressure to the ink return chamber through the first air pipe to maintain the printing pressure P1, the second air pressure chamber provides pressure to the ink inlet chamber through the second air pipe to maintain the printing pressure P2, the first buffer air pressure chamber provides printing pressure P1 to the ink return buffer chamber through the third air pipe, and the second buffer air pressure chamber provides printing pressure P2 to the ink inlet buffer chamber through the fourth air pipe, wherein P1 is a negative pressure and P2 is greater than P1.

16. The control method for a circulating ink supply system suitable for 3D inkjet printing according to claim 14, characterized in that: When the inkjet printhead is in the ink-pressing state, the circulating ink supply system performs the following control: (1) The pressure sensor adjusts the working speed of the positive pressure pump to maintain a certain pressure. (2) The first positive and negative pressure switching valve, the second positive and negative pressure switching valve, the third positive and negative pressure switching valve and the fourth positive and negative pressure switching valve are all switched to the positive pressure pump. The positive pressure pump applies positive pressure to the first air pipe, the second air pipe, the third air pipe and the fourth air pipe to press the inkjet printhead.

17. The control method for a circulating ink supply system suitable for 3D inkjet printing according to claim 15, characterized in that: When the nozzle is in dormant mode, the temperature inside the heating chamber is lowered, but still above the freezing point of the high-temperature phase change material. The dormant pressure P1 of the first gas pipe and the dormant pressure P2 of the second gas pipe are adjusted to be the same, i.e., dormant pressure P1 = dormant pressure P2 = -P0, where P0 is the correction pressure from dynamic to static ink pressure.

18. The control method for a circulating ink supply system suitable for 3D inkjet printing according to claim 14, characterized in that: When the inkjet printhead is powered on, the ink temperature T1 in the ink cartridge and the inkjet printhead temperature T2 are detected. If T1 ≥ T0 and T2 ≥ T0, where T0 is the liquid ink temperature, the relevant protection is released, and the air pressure of the first and second air pipes is slowly adjusted to the printing pressure P1 and printing pressure P2, respectively, to circulate the ink. If T1 or T2 ≤ T0, the reflux pump is kept off, and the air pressure of the first and second air pipes is 0. The ink is first heated to the set temperature Ta by the heating element to keep the ink in a liquid state. After confirming that the ink is in a liquid state, the air pressure of the first and second air pipes is adjusted to the printing pressure P1 and printing pressure P2, respectively.

19. The control method for a circulating ink supply system suitable for 3D inkjet printing according to claim 14, characterized in that: When the nozzle is powered off, the return pump is closed, the balance valve is open, and the pressure difference between the first air pressure chamber, the second air pressure chamber, the first buffer air pressure chamber, and the second buffer air pressure chamber is 0.

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