3D printing viscosity reduction mixing system, control method and 3D printer

Abstract

The present application relates to 3D printing viscosity reduction mixing system, control method and 3D printer, belong to 3D printing technical field, the 3D printing viscosity reduction mixing system includes viscosity detection mechanism, temperature detection mechanism, controller and the ultrasonic transducer for being arranged on the printing tank body side wall and with the printing tank body acoustic coupling, controller is connected with the communication of viscosity detection mechanism, temperature detection mechanism, the transducer drive circuit of ultrasonic transducer, the controller is also used for with the communication connection of the heating controller, platform lifting mechanism, exposure mechanism and printer control board of 3D printer.The present application monitors the real-time temperature of the prepared solidification resin layer to ensure that the exposure solidification and ultrasonic activation are carried out at a safe temperature;The present application also detects the real-time viscosity of the prepared solidification resin layer, and when the real-time viscosity is over-limit, the ultrasonic transducer and the platform lifting mechanism are used to reduce the viscosity, improve the feeding effect and the resin uniformity.

Description

Technical Field

[0001] This invention relates to a 3D printing viscosity-reducing mixing system, control method, and 3D printer, belonging to the field of 3D printing technology. Background Technology

[0002] Photopolymer 3D printing (such as DLP, LCD, SLA) has been widely used in the dental field to manufacture temporary crowns, models, guides, denture bases, clear aligners and related components.

[0003] Dental printing resins typically have high viscosity and commonly include single-component resins, filler resins containing inorganic fillers or functional particles, or composite resins that balance flowability, curing speed, optical and mechanical properties. During 3D printing, the high viscosity of dental printing resins can lead to the formation of a high-viscosity boundary layer on top of the release liner, resulting in insufficient material replenishment and ultimately poor printing quality.

[0004] Therefore, there is an urgent need for a 3D printer that can improve the curing and printing quality of dental printing resins. Summary of the Invention

[0005] The purpose of this invention is to provide a 3D printing viscosity reduction mixing system, control method, and 3D printer. The system monitors the real-time temperature of the pre-cured resin layer through a temperature detection mechanism to ensure that both exposure curing and ultrasonic activation are performed at safe temperatures. The invention also detects the real-time viscosity of the pre-cured resin layer through a viscosity detection mechanism. When the real-time viscosity exceeds the limit, the system uses an ultrasonic transducer and a platform lifting mechanism to reduce viscosity in tandem, improving the feeding effect and resin uniformity, thereby ensuring the curing and printing quality of the exposure printing.

[0006] In a first aspect, the present invention provides a 3D printing viscosity-reducing mixing system for use within the printing chamber of a 3D printer, the 3D printing viscosity-reducing mixing system comprising:

[0007] The viscosity detection mechanism and the temperature detection mechanism are used to detect the real-time viscosity and real-time temperature of the pre-cured resin layer, which is a printing resin layer of a preset thickness located above the release film of the printing tank.

[0008] An ultrasonic transducer is disposed on the side wall of the printing tank and acoustically coupled to the printing tank for ultrasonic activation of the pre-cured resin layer.

[0009] The controller is communicatively connected to the viscosity detection mechanism, the temperature detection mechanism, and the transducer drive circuit of the ultrasonic transducer. The controller is also used to communicate with the heating controller, platform lifting mechanism, exposure mechanism, and printer control board of the 3D printer.

[0010] The purpose of the viscosity detection mechanism in this invention is to address the issue that when the real-time viscosity of the pre-cured resin layer is greater than or equal to a preset viscosity threshold, a high-viscosity boundary layer is easily formed, leading to insufficient material replenishment and causing problems such as uneven layer thickness, material shortage, streaks, voids, under-curing, and interlayer instability. This invention, by incorporating the viscosity detection mechanism, can monitor the real-time viscosity of the pre-cured resin layer before exposure printing to ensure print quality. The purpose of the temperature detection mechanism in this invention is to address the issue that while the 3D printer's heating controller can maintain the printing resin in the printing tank within a set temperature range through continuous heating, prolonged heating and mixing may cause the temperature of the pre-cured resin layer to exceed its limit. Exceeding the temperature limit not only affects the print quality of the exposure mechanism but also the ultrasonic activation effect of the ultrasonic transducer. This invention requires obtaining the real-time temperature detected by the temperature detection mechanism before ultrasonic activation and before exposure printing to ensure that the real-time temperature of the pre-cured resin layer is below the preset temperature threshold.

[0011] The purpose of this invention is to incorporate an ultrasonic transducer so that the controller can output a PWM modulation signal to the transducer drive circuit, causing the ultrasonic transducer to output ultrasonic waves according to the target waveform. Under the action of the ultrasonic waves, the pre-cured resin layer undergoes instantaneous shear thinning, thereby reducing its real-time viscosity. This facilitates the smooth replenishment of the added printing resin to the pre-cured resin layer above the release film, thus improving the quality of the photopolymer-printed product. The purpose of the controller's communication connection with the platform lifting mechanism is to control the lifting movement of the 3D printer's printing platform, thereby stirring and turbulenting the pre-cured resin layer. This not only breaks up any potentially formed high-viscosity boundary layer but also promotes the flow and mixing of the printing resin, improving resin uniformity. Furthermore, by incorporating viscosity and temperature detection mechanisms to monitor the real-time viscosity and temperature of the pre-cured resin layer, this invention further controls the printing platform and ultrasonic transducer. This allows the stirring and turbulence of the printing platform, combined with the ultrasonic transducer, to create a multi-scale synergistic viscosity reduction, promoting resin replenishment flow and improving resin uniformity.

[0012] As an optional embodiment, the ultrasonic transducers are arranged in an array on the side wall of the printing tank relative to the center position of the printing tank.

[0013] The ultrasonic transducer array of the present invention is distributed on each side wall of the printing tank. During the initial viscosity reduction, in order to save ultrasonic resources as much as possible, the ultrasonic transducers arranged on the side walls of the printing tank can be controlled to work simultaneously to ultrasonically activate the pre-cured resin layer. After the stable waiting period ends, if the real-time viscosity is still greater than or equal to the viscosity threshold, multiple ultrasonic transducers arranged on the side walls of the printing tank relative to the center position of the printing tank are controlled to work in turn (time-division polling or phase staggered method can be used) to ultrasonically activate the pre-cured resin layer for secondary compensation viscosity reduction.

[0014] As an optional embodiment, it also includes:

[0015] An acoustic field optimization structure is provided within the printing tank; the acoustic field optimization structure is used to ensure that the ultrasonic activation range of the ultrasonic transducer covers the pre-cured resin layer.

[0016] This invention improves the ultrasonic propagation path of an ultrasonic transducer through an optimized acoustic field structure, enabling the ultrasonic activation range of the transducer to effectively cover the pre-cured resin layer. The optimized acoustic field structure can be implemented via CNC machining, molding, or additive manufacturing.

[0017] As an optional embodiment, the sound field optimization structure includes at least one of the following:

[0018] A zigzag reflective sidewall structure is provided on the sidewall and / or bottom non-transparent area of ​​the printing tank;

[0019] A sawtooth reflective structure is provided on the side wall and / or bottom non-transparent area of ​​the printing tank;

[0020] An arc-shaped transition structure is provided at the junction of the side wall and the bottom non-transparent area of ​​the printing tank.

[0021] The zigzag reflective sidewall structure of this invention comprises a zigzag-shaped inner wall formed by splicing multiple planar reflective surface segments, with zigzag angles formed between adjacent reflective surface segments; the tilt angle of each reflective surface segment relative to the vertical direction is 15° to 60°, the length of a single segment is 2mm to 30mm, and the number of zigzag segments is 3 to 50. The zigzag step height of the zigzag reflective structure is 0.2mm to 5mm, the pitch is 0.5mm to 20mm, and the zigzag apex angle is 30° to 120°. The arc-shaped transition structure is located at the junction of the cavity and the sidewall of the printing groove, with a radius of curvature of 1mm to 20mm, to reduce sound energy dissipation at sharp corners and improve sound field coverage in the edge area.

[0022] Secondly, the present invention provides a control method for a 3D printing viscosity-reducing mixing system, which is based on the aforementioned 3D printing viscosity-reducing mixing system, the control method comprising:

[0023] In response to receiving the layer timing printing signal sent by the printer control board, the real-time temperature detected by the temperature detection mechanism is obtained;

[0024] If the real-time temperature is greater than or equal to a preset temperature threshold, a stop heating signal is sent to the heating controller to stop heating the pre-cured resin layer.

[0025] In response to the real-time temperature detected by the temperature detection mechanism being lower than the temperature threshold, the real-time viscosity detected by the viscosity detection mechanism is obtained.

[0026] If the real-time viscosity is greater than or equal to a preset viscosity threshold, a working signal is sent to the transducer drive circuit to control the ultrasonic transducer to perform ultrasonic activation on the pre-cured resin layer for initial viscosity reduction. At the same time, a motion signal is sent to the platform lifting mechanism to control the printing platform of the 3D printer to perform lifting motion during the ultrasonic activation period and / or the stable waiting period after the ultrasonic activation ends, so as to mix and turbulent the pre-cured resin layer.

[0027] After the initial viscosity reduction and stabilization waiting period ends, the real-time viscosity and real-time temperature detected by the viscosity detection mechanism and temperature detection mechanism are obtained again. If the real-time temperature is less than the temperature threshold and the real-time viscosity is less than the viscosity threshold, a positioning signal is sent to the platform lifting mechanism to control the printing platform to move to the set printing position above the release film.

[0028] In response to receiving a platform positioning signal from the platform lifting mechanism when the printing platform reaches the printing position, an exposure access signal is sent to the exposure mechanism to control the exposure mechanism to perform exposure curing.

[0029] During the printing process, if the real-time temperature is greater than or equal to a preset temperature threshold, a stop heating signal needs to be sent to the heating controller to stop heating the pre-cured resin layer. Since the real-time temperature of the pre-cured resin layer directly affects the ultrasonic activation effect of the ultrasonic transducer, this invention uses real-time temperature detection as a pre-step for ultrasonic activation; if the real-time temperature exceeds the limit, heating needs to be stopped and the system needs to wait for cooling.

[0030] When the real-time temperature meets the requirements, the real-time viscosity is further obtained. If the real-time viscosity is greater than or equal to a preset viscosity threshold, direct exposure printing will result in poor print quality, and a compensation strategy needs to be implemented. This invention outputs a PWM modulation signal to the transducer drive circuit to cause the ultrasonic transducer to output ultrasonic waves according to the target waveform. Under the action of the ultrasonic waves, the pre-cured resin layer undergoes instantaneous shear thinning, thereby reducing the real-time viscosity. This ensures that the added printing resin can be smoothly added to the pre-cured resin layer above the release film before exposure printing, improving the product quality of the photocurable printed product. This invention also controls the lifting and lowering movement of the printing platform to stir and turbulent the pre-cured resin layer. This stirring and turbulence can, on the one hand, break up any high-viscosity boundary layers that may have already formed, and on the other hand, promote the flow and mixing of the printing resin, ensuring sufficient resin feeding and improving resin uniformity. In this embodiment, under the premise of setting up viscosity detection mechanism and temperature detection mechanism to monitor the real-time viscosity and real-time temperature of the pre-cured resin layer respectively, the printing platform and ultrasonic transducer are further controlled so that the stirring and turbulence of the printing platform and the ultrasonic transducer form a multi-scale synergistic viscosity reduction, which can achieve a stable and repeatable resin viscosity reduction optimization effect, with significant synergistic effect.

[0031] This invention incorporates a stabilization waiting period after ultrasonic activation to allow the physical state of the pre-cured resin layer to stabilize after ultrasonic activation, thereby ensuring the quality of subsequent exposure printing products. After the stabilization waiting period, the real-time viscosity and temperature detected by the viscosity and temperature detection mechanisms are acquired again. If the real-time temperature is lower than the temperature threshold and the real-time viscosity is lower than the viscosity threshold, a positioning signal is sent to the platform lifting mechanism to control the printing platform to move to the set printing position within the pre-cured resin layer. This invention re-measures the real-time viscosity and temperature after ultrasonic activation, and proceeds with the subsequent curing and printing steps only when both requirements are met simultaneously. Finally, in response to the platform positioning signal received from the platform lifting mechanism when the printing platform reaches the printing position, an exposure access signal is sent to the exposure mechanism to control the exposure mechanism to perform exposure curing. After exposure curing, the system waits for the next layer timing printing signal sent by the printer control board, thereby achieving sequential control of layer-by-layer printing.

[0032] As an optional embodiment, during the initial viscosity reduction, the ultrasonic transducers disposed on the side wall of the printing tank are controlled to work simultaneously to ultrasonically activate the pre-cured resin layer for the initial viscosity reduction.

[0033] After the initial viscosity reduction and stabilization waiting period ends, the real-time viscosity and temperature detected by the viscosity and temperature detection mechanisms are acquired again. If the real-time temperature is lower than the temperature threshold but the real-time viscosity is still greater than or equal to the viscosity threshold, a compensation signal is sent to the transducer drive circuit. All ultrasonic transducers arrayed on the side wall of the printing tank relative to the center position of the printing tank work in turn to ultrasonically activate the pre-cured resin layer for secondary viscosity reduction compensation. At the same time, a motion compensation signal is sent to the platform lifting mechanism to control the printing platform of the 3D printer to perform lifting and lowering movements during the ultrasonic activation period of secondary viscosity reduction compensation and / or the stabilization waiting period after ultrasonic activation, thereby mixing and turbulenting the pre-cured resin layer.

[0034] After the stabilization waiting period following the secondary viscosity reduction, the real-time viscosity and temperature detected by the viscosity and temperature detection mechanisms are acquired again. If the real-time temperature is lower than the temperature threshold and the real-time viscosity is lower than the viscosity threshold, a positioning signal is sent to the platform lifting mechanism to control the printing platform to move to the set printing position above the release film. If the real-time temperature is greater than or equal to the temperature threshold or the real-time viscosity is greater than or equal to the viscosity threshold after the secondary viscosity reduction, manual intervention is required.

[0035] As an optional embodiment, during the initial viscosity reduction, the ultrasonic operating frequency of the ultrasonic transducer is set to a fixed activation frequency;

[0036] During secondary compensation viscosity reduction, the ultrasonic operating frequency of the ultrasonic transducer continuously or alternately changes between the first lower limit frequency and the first upper limit frequency with a preset frequency sweep period.

[0037] As an optional embodiment, during secondary viscosity reduction, the duration of the ultrasonic activation period and the duration of the stabilization waiting period after ultrasonic activation are both longer than those during the initial viscosity reduction.

[0038] As an optional embodiment, when the printing platform performs lifting and lowering movements during the ultrasonic activation period and / or the stable waiting period after ultrasonic activation, the movement mode of the printing platform is a lifting and lowering reciprocating motion, and the upper limit of the lifting and lowering reciprocating motion needs to be higher than the pre-cured resin layer.

[0039] As an optional embodiment, during the secondary compensation viscosity reduction, the speed and number of reciprocating motions of the lifting and lowering motion are both greater than those of the initial viscosity reduction.

[0040] As an optional embodiment, during the initial viscosity reduction and secondary compensation viscosity reduction, when the printing platform performs lifting and lowering movements during the ultrasonic activation period and / or the stable waiting period after the ultrasonic activation ends, the movement mode of the printing platform is lifting and lowering reciprocating motion, and the upper limit position of the lifting and lowering reciprocating motion needs to be higher than the pre-cured resin layer.

[0041] This invention uses the lifting and lowering motion of the printing platform to stir and turbulent the pre-cured resin layer. The printing platform is set to a lifting and reciprocating motion, and the upper limit of the lifting and reciprocating motion needs to be higher than the pre-cured resin layer. Thus, through multiple lifting and reciprocating motions, the high-viscosity boundary layer that may have formed can be effectively destroyed, and the mixing and flow between the pre-cured resin layer and other printing resins above it can be promoted. While reducing the viscosity of the resin, the resin is replenished sufficiently and the resin uniformity is improved, resulting in a product with better quality.

[0042] Thirdly, the present invention provides a 3D printer comprising:

[0043] The printing tank has a cavity formed inside, and a release film is provided at the bottom of the cavity. The release film is fixed by a pressure frame to keep it flat. The 3D printing viscosity reduction and mixing system is also provided inside the printing tank.

[0044] The release film of the present invention requires the use of a light-transmitting release material for exposure printing. The light-transmitting release material is FEP (Fluorinated ethylene propylene copolymer), PFA (Polyfluoroalkoxy copolymer), or ETFE (ethylene-tetrafluoroethylene copolymer).

[0045] As an optional embodiment, the printing groove includes a first sidewall, a second sidewall, a third sidewall, and a fourth sidewall connected in sequence to enclose and form a cavity;

[0046] The ultrasonic transducer is disposed within the printing tank in the following manner:

[0047] The ultrasonic transducers are arranged in an array on the first sidewall, second sidewall, third sidewall, and fourth sidewall, relative to the center position of the printing tank.

[0048] The present invention enables the initial viscosity reduction and the secondary compensation viscosity reduction after the initial viscosity reduction fails by using ultrasonic transducers disposed on the first sidewall, the second sidewall, the third sidewall, and the fourth sidewall, thereby achieving effective viscosity reduction as much as possible.

[0049] As an optional embodiment, a resin feeding assembly is also included, which includes a resin tank and a feeding pipe. The feeding pipe is used to connect the resin tank and the printing tank. A one-way valve and a metering pump are provided at the feeding pipe. The one-way valve is used to enable unidirectional flow of the feeding pipe from the resin tank to the printing tank.

[0050] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0051] The controller of the 3D printing viscosity-reducing mixing system of the present invention is communicatively connected to the viscosity detection mechanism, the temperature detection mechanism, and the transducer drive circuit of the ultrasonic transducer. The controller is also used to communicate with the heating controller, platform lifting mechanism, exposure mechanism, and printer control board of the 3D printer. The controller, in response to receiving a layer timing printing signal from the printer control board, acquires the real-time temperature detected by the temperature detection mechanism. If the real-time temperature is greater than or equal to a preset temperature threshold, it sends a stop heating signal to the heating controller to stop heating the pre-cured resin layer, thereby ensuring that exposure curing and ultrasonic activation are performed at safe temperatures. In response to the real-time temperature detected by the temperature detection mechanism being less than the temperature threshold, it acquires the real-time viscosity detected by the viscosity detection mechanism. If the real-time viscosity is greater than or equal to a preset viscosity threshold, it sends a working signal to the transducer drive circuit to control the ultrasonic transducer to perform ultrasonic activation on the pre-cured resin layer for initial viscosity reduction. Simultaneously, it sends a motion signal to the platform lifting mechanism to control the 3D printer's printing platform to perform lifting motion during the ultrasonic activation period and / or the stable waiting period after ultrasonic activation to mix and turbulent the pre-cured resin layer. This invention achieves synergistic viscosity reduction through the ultrasonic transducer and platform lifting mechanism when the real-time viscosity exceeds the limit, effectively improving the feeding effect and resin uniformity, thus ensuring the curing printing quality of exposure printing.

[0052] After the initial viscosity reduction and stabilization waiting period, the real-time viscosity and temperature detected by the viscosity and temperature detection mechanisms are acquired again. If the real-time temperature is lower than the temperature threshold and the real-time viscosity is lower than the viscosity threshold, a positioning signal is sent to the platform lifting mechanism to control the printing platform to move to the set printing position within the pre-cured resin layer. This invention re-measures the real-time viscosity and temperature after ultrasonic activation, and only proceeds with subsequent curing and printing steps when both requirements are met simultaneously. Finally, in response to the platform positioning signal received from the platform lifting mechanism when the printing platform reaches the printing position, an exposure access signal is sent to the exposure mechanism to control exposure and curing. After exposure and curing, the system waits for the next layer printing sequence signal sent by the printer control board, thereby achieving sequential control of layer-by-layer printing. Attached Figure Description

[0053] Figure 1 The diagram shown is a structural schematic of a 3D printer according to an embodiment of the present invention.

[0054] Figure 2 The diagram shows a schematic of the structure of the 3D printing viscosity-reducing hybrid system arranged in the printing chamber of a 3D printer according to an embodiment of the present invention.

[0055] Figure 3The diagram shown is a schematic representation of the 3D printing viscosity-reducing hybrid system according to an embodiment of the present invention.

[0056] Figure 4 As shown Figure 2 Enlarged diagram of point A in the middle.

[0057] Numbering on the map:

[0058] 1. Printing tank; 11. Cavity; 12. Release film; 13. Press frame; 101. First sidewall; 102. Second sidewall; 103. Third sidewall; 104. Fourth sidewall; 2. Ultrasonic transducer; 21. Transducer drive circuit; 3. Sound field optimization structure; 31. Folded line reflection sidewall structure; 32. Sawtooth reflection structure; 33. Arc-shaped curved surface transition structure; 4. Heating coil; 41. Heating controller; 5. Temperature detection mechanism; 6. Viscosity detection mechanism; 7. Controller; 8. Printer control board; 9. Platform lifting mechanism; 10. Exposure mechanism; 14. Resin tank; 15. Feed pipe; 16. Metering pump; 17. One-way valve; 18. Printing platform. Detailed Implementation

[0059] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0060] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0061] With the widespread application of 3D printing in the dental field, the use of 3D printers to manufacture dental restorations (such as temporary crowns, models, guides, denture bases, clear aligners, and other related components) has achieved good results. However, most existing 3D printers are used in various fields, and most of these fields have relatively low requirements for the surface roughness of the product. During the printing process, the printing resin in the printing chamber is replenished directly after each exposure and curing to achieve layered printing. However, dental restorations, due to their small size and use in the human oral cavity, require a higher degree of surface roughness from 3D printed dental restorations to avoid affecting the user's experience. Furthermore, dental restorations require high mechanical strength and wear resistance, necessitating the use of high-viscosity printing resins. Commonly used resins include single-component resins (high-viscosity transparent light-curing resins), filler resins containing inorganic fillers or functional particles (light-curing resins containing microfillers with particle sizes of 100 nm to 5 µm, such as ZrO2 and SiO2), or composite resins that balance flow, curing speed, optical and mechanical properties (combinations of multiple monomers / oligomers, or multi-size fillers). If high-viscosity dental printing resins are used directly with conventional printing methods, insufficient replenishment can easily occur during the replenishment process after each printing cycle. Specifically, the printing resin consumed during each printing and curing cycle is the resin above the release liner. Due to the high viscosity of dental printing resins, a high-viscosity boundary layer easily forms above the release liner, directly hindering the smooth replenishment of additional printing resin above the release liner. This can directly lead to defective products (the surface roughness, mechanical strength, or wear resistance may not meet the standards for use). The reasons for defective products may include uneven layer thickness, insufficient material, streaks, voids, under-curing, unstable interlayer or residual air bubbles, which directly affect the production efficiency of dental restorations.

[0062] Combination Figure 1 and Figure 2This embodiment provides a 3D printing viscosity-reducing mixing system, which is installed in the printing tank 1 of a 3D printer. The cavity 11 in the printing tank 1 is used to store printing resin. A release film 12 is fixed to the bottom of the cavity 11 by a pressure frame 13. In this embodiment, a printing resin layer of a preset thickness above the release film 12 is used as a pre-cured resin layer for each print. The thickness of the pre-cured resin layer needs to be greater than the thickness of the actual cured resin layer in each print to ensure material redundancy. The release film 12 is made of a light-transmitting release material. As an example, the light-transmitting release material can be FEP (Fluorinated ethylene propylene), PFA (Polyfluoroalkoxy), or ETFE (ethylene-tetrafluoroethylene). The 3D printer also includes a resin feeding assembly, which includes a resin tank 14 and a feed pipe 15. The feed pipe 15 is used to connect the resin tank 14 and the printing tank 1. A one-way valve 17 and a metering pump 16 are provided at the feed pipe 15. The one-way valve 17 is used to realize one-way flow from the resin tank 14 to the printing tank 1 in the feed pipe 15.

[0063] Combination Figure 3 The 3D printing viscosity-reducing mixing system described in this embodiment includes a viscosity detection mechanism 6, a temperature detection mechanism 5, an ultrasonic transducer 2, and a controller 7.

[0064] The viscosity detection mechanism 6 and the temperature detection mechanism 5 are used to detect the real-time viscosity and real-time temperature of the pre-cured resin layer, respectively. In some specific embodiments, the viscosity detection mechanism 6 includes a microfluidic chip viscosity sensor, which can detect the real-time viscosity of the pre-cured resin layer through an array of microrheological vibrating needles. The temperature detection mechanism 5 includes a resistive temperature sensor, which detects the real-time temperature of the pre-cured resin layer through a thermistor array.

[0065] The ultrasonic transducer 2 is disposed on the side wall of the printing tank 1 and is acoustically coupled to the printing tank 1 for ultrasonic activation of the pre-cured resin layer. Under the action of the ultrasonic waves from the ultrasonic transducer 2, instantaneous shear thinning occurs inside the pre-cured resin layer, thereby reducing the real-time viscosity and facilitating photopolymerization printing.

[0066] In some specific embodiments, multiple ultrasonic transducers 2 are provided, and the multiple ultrasonic transducers 2 are arranged opposite each other on the side wall of the printing tank 1 or arranged in an array on the side wall of the printing tank 1 relative to the center position of the printing tank 1. In this embodiment, the printing tank 1 includes a first side wall 101, a second side wall 102, a third side wall 103, and a fourth side wall 104 connected in sequence to form a cavity 11; the ultrasonic transducers 2 are arranged in the printing tank 1 in an array on the first side wall 101, the second side wall 102, the third side wall 103, and the fourth side wall 104 relative to the center position of the printing tank 1.

[0067] Furthermore, to ensure that the ultrasonic activation range of the ultrasonic transducer 2 can cover the pre-cured resin layer, combined with Figure 4 In this embodiment, the printing tank 1 is further provided with a sound field optimization structure 3, which can be realized by CNC, molding, or additive manufacturing. In some specific embodiments, the sound field optimization structure 3 includes at least one of the following: a zigzag reflective sidewall structure 31, a sawtooth reflective structure 32, and a circular arc transition structure 33. As an example, the zigzag reflective sidewall structure 31 is provided on the sidewall and / or bottom non-transparent area of ​​the printing tank 1. The zigzag reflective sidewall structure 31 is formed by splicing multiple planar reflective surface segments to form a zigzag inner wall, and a zigzag angle is formed between adjacent reflective surface segments; the tilt angle of each reflective surface segment relative to the vertical direction is 15° to 60°, the length of a single segment is 2 mm to 30 mm, and the number of zigzag segments is 3 to 50. The sawtooth reflective structure 32 is disposed on the side wall and / or bottom non-transparent area of ​​the printing tank 1. The sawtooth step height of the sawtooth reflective structure 32 is 0.2 mm to 5 mm, the pitch is 0.5 mm to 20 mm, and the apex angle of the sawtooth is 30° to 120°. The arc-shaped transition structure 33 is disposed at the junction of the side wall and the bottom non-transparent area of ​​the printing tank 1, with a radius of curvature of 1 mm to 20 mm, to reduce sound energy dissipation at sharp corners and improve sound field coverage in the edge area.

[0068] The controller 7 is communicatively connected to the viscosity detection mechanism 6, the temperature detection mechanism 5, and the transducer drive circuit 21 of the ultrasonic transducer 2. The controller 7 is also communicatively connected to the heating controller 41, the platform lifting mechanism 9, the exposure mechanism 10, and the printer control board 8 of the 3D printer.

[0069] The purpose of the communication connection between the controller 7 and the viscosity detection mechanism 6 in this embodiment is that when the real-time viscosity of the pre-cured resin layer is greater than or equal to the preset viscosity threshold, a high viscosity boundary layer is easily formed, resulting in insufficient material replenishment and causing problems such as uneven layer thickness, material shortage, streaks, voids, under-curing and interlayer instability. Therefore, it is necessary to monitor the real-time viscosity of the pre-cured resin layer before exposure and printing to ensure printing quality.

[0070] The purpose of the communicative connection between the controller 7, the temperature detection mechanism 5, and the heating controller 41 of the 3D printer in this embodiment is to avoid affecting the 3D printing quality due to the temperature of the pre-cured resin layer exceeding the limit. The heating controller 41 is used to maintain the printing resin in the printing tank 1 within a set temperature range (for example, set to 35°C) through continuous heating. However, prolonged heating and prolonged mixing may cause the temperature of the pre-cured resin layer to exceed the limit. Exceeding the limit will not only affect the printing quality of the exposure mechanism 10 during exposure printing, but also affect the ultrasonic activation effect of the ultrasonic transducer 2. In this embodiment, the controller 7 needs to obtain the real-time temperature detected by the temperature detection mechanism 5 before ultrasonic activation and before exposure printing to ensure that the real-time temperature of the pre-cured resin layer is below the preset temperature threshold. In a specific embodiment, the heating controller 41 is electrically connected to the heating coil 4 arranged in the printing tank 1 to heat the printing resin in the printing tank 1.

[0071] The purpose of the communication connection between the controller 7 and the transducer drive circuit 21 of the ultrasonic transducer 2 in this embodiment is that the controller 7 can output a PWM (Pulse Width Modulation) signal to the transducer drive circuit 21 so that the ultrasonic transducer 2 outputs ultrasonic waves according to the target waveform.

[0072] The purpose of the communication connection between the controller 7 and the platform lifting mechanism 9 in this embodiment is to control the lifting movement of the printing platform 18, thereby stirring and turbulent the pre-cured resin layer. The stirring and turbulence of the printing platform 18 can work in conjunction with the ultrasonic transducer 2 to form multi-scale mixing enhancement, thereby reducing the resin viscosity while promoting the flow of feed material and improving resin uniformity, and avoiding the formation of a high-viscosity boundary layer. In a specific embodiment, the platform lifting mechanism 9 can be a lead screw module or other linear modules with the same function in the prior art.

[0073] The control method for a 3D printing viscosity-reducing mixing system according to this embodiment will be described in detail below. The control method includes:

[0074] Step S1: In response to receiving the layer timing printing signal sent by the printer control board 8, the real-time temperature detected by the temperature detection mechanism 5 is obtained; if the real-time temperature is greater than or equal to a preset temperature threshold (for example, set to 50℃), a stop heating signal is sent to the heating controller 41 to stop heating the pre-cured resin layer. Since the real-time temperature of the pre-cured resin layer directly affects the ultrasonic activation effect, this embodiment uses real-time temperature detection as a pre-step for ultrasonic activation. If the real-time temperature exceeds the limit, heating needs to be stopped and the temperature needs to be cooled down.

[0075] Step S2: In response to the real-time temperature detected by the temperature detection mechanism 5 being less than the temperature threshold, the real-time viscosity detected by the viscosity detection mechanism 6 is obtained; if the real-time viscosity is greater than or equal to the preset viscosity threshold, a working signal (in this embodiment, the working signal is a PWM modulation signal) is sent to the transducer drive circuit 21 to control the ultrasonic transducer 2 to perform ultrasonic activation on the pre-cured resin layer for initial viscosity reduction, and at the same time, a motion signal is sent to the platform lifting mechanism 9 to control the printing platform 18 of the 3D printer to perform lifting motion during the ultrasonic activation period and / or the stable waiting period after the ultrasonic activation ends, so as to mix and turbulent the pre-cured resin layer.

[0076] When the real-time viscosity is greater than or equal to a preset viscosity threshold, direct exposure printing will result in poor print quality. In this case, a compensation strategy is required. In this embodiment, a PWM modulation signal is output to the transducer drive circuit 21 to cause the ultrasonic transducer 2 to output ultrasonic waves according to the target waveform. Under the action of the ultrasonic waves, the pre-cured resin layer undergoes instantaneous shear thinning, thereby reducing the real-time viscosity. This allows the added printing resin to flow smoothly to the pre-cured resin layer above the release film 12 before exposure printing, thus improving the quality of the photocured printed product. In this embodiment, by controlling the lifting and lowering movement of the printing platform 18, the pre-cured resin layer can be stirred and turbulent. This stirring and turbulence can, on the one hand, break up any potentially formed high-viscosity boundary layer, and on the other hand, promote the flow and mixing of the printing resin, ensuring sufficient resin feeding and improving resin uniformity. In this embodiment, under the premise of setting a viscosity detection mechanism 6 and a temperature detection mechanism 5 to monitor the real-time viscosity and real-time temperature of the pre-cured resin layer respectively, the printing platform 18 and the ultrasonic transducer 2 are further controlled so that the stirring and turbulence of the printing platform 18, together with the ultrasonic transducer 2, form a multi-scale mixing enhancement to achieve a stable and repeatable viscosity reduction optimization effect, with obvious synergistic effect.

[0077] In this embodiment, a stabilization waiting period is set after ultrasonic activation to allow the physical state of the pre-cured resin layer to return to stability after ultrasonic activation, thereby ensuring the quality of the product after subsequent exposure and printing.

[0078] Step S3: After the initial viscosity reduction and stabilization waiting period ends, the real-time viscosity and real-time temperature detected by the viscosity detection mechanism 6 and the temperature detection mechanism 5 are obtained again. If the real-time temperature is lower than the temperature threshold and the real-time viscosity is lower than the viscosity threshold, a positioning signal is sent to the platform lifting mechanism 9 to control the printing platform 18 to move to the set printing position above the release film 12. After the stabilization waiting period ends, the physical state of the pre-cured resin layer returns to stability, and both the real-time temperature and real-time viscosity meet the requirements. At this point, all preparations before exposure printing can be considered complete, and exposure printing is permitted.

[0079] After the initial viscosity reduction stabilization waiting period ends, the real-time viscosity and real-time temperature detected by the viscosity detection mechanism 6 and the temperature detection mechanism 5 are obtained again. If the real-time temperature is lower than the temperature threshold but the real-time viscosity is still greater than or equal to the viscosity threshold (if the real-time temperature is greater than or equal to the temperature threshold, it is necessary to wait for the real-time temperature to drop below the temperature threshold before re-detecting the real-time viscosity), a compensation signal is sent to the transducer drive circuit 21. The compensation signal controls all the ultrasonic transducers 2 arrayed on the side wall of the printing tank 1 relative to the center position of the printing tank 1 to work in turn to perform ultrasonic activation on the pre-cured resin layer for secondary viscosity reduction compensation. At the same time, a motion compensation signal is sent to the platform lifting mechanism 9 to control the printing platform 18 of the 3D printer to perform lifting and lowering movements during the ultrasonic activation period of secondary viscosity reduction compensation and / or the stabilization waiting period after the ultrasonic activation ends, so as to mix and turbulent the pre-cured resin layer.

[0080] After the stabilization waiting period of the secondary compensation viscosity reduction ends, the real-time viscosity and real-time temperature detected by the viscosity detection mechanism 6 and the temperature detection mechanism 5 are obtained again. If the real-time temperature is less than the temperature threshold and the real-time viscosity is less than the viscosity threshold, the next step is initiated. If the real-time temperature detected after the secondary compensation viscosity reduction is greater than or equal to the temperature threshold or the real-time viscosity is greater than or equal to the viscosity threshold, manual intervention is required.

[0081] During the initial viscosity reduction, the ultrasonic transducer 2, which is disposed on the side wall of the printing tank 1, works simultaneously to ultrasonically activate the pre-cured resin layer. The ultrasonic working frequency is set to a fixed activation frequency (for example, 30 kHz), and the PWM duty cycle is set to the first interval (for example, 40% to 60%).

[0082] During secondary viscosity reduction, all ultrasonic transducers 2, arrayed relative to the center position of the printing tank 1 and distributed on the sidewall of the printing tank 1, work in turn (using time-division polling or phase staggering) to ultrasonically activate the pre-cured resin layer. The ultrasonic working frequency continuously or alternately changes between a first lower limit frequency (28kHz, for example) and a first upper limit frequency (35kHz, for example) with a preset sweep period (0.1–0.5 s for example). The PWM duty cycle is set to the second interval (50%–70% for example). During secondary viscosity reduction, the duration of the ultrasonic activation period and the duration of the stabilization waiting period after ultrasonic activation are both longer than those of the initial viscosity reduction. For example, the duration of the ultrasonic activation period during the initial viscosity reduction is set to 2.0–3.0 s (divided into two short activation segments); the duration of the stabilization waiting period is set to 0.4–0.8 s. The duration of the ultrasonic activation period corresponding to the secondary compensation viscosity reduction was set to 3.0–5.0 s (divided into 3–5 short activation segments), and the duration of the stabilization waiting period was set to 0.8–1.5 s.

[0083] Furthermore, during the initial viscosity reduction and secondary compensation viscosity reduction, when the printing platform 18 moves up and down during the ultrasonic activation period and / or the stable waiting period after ultrasonic activation, the movement mode of the printing platform 18 is a reciprocating motion. The upper limit of the reciprocating motion needs to be higher than the pre-cured resin layer to avoid the formation of a high-viscosity boundary layer. In this embodiment, the up and down motion of the printing platform 18 agitates and turbulents the pre-cured resin layer. By setting the movement mode of the printing platform 18 to a reciprocating motion and ensuring that the upper limit of the reciprocating motion is higher than the pre-cured resin layer, multiple reciprocating motions can effectively break up any potentially formed high-viscosity boundary layer and promote the mixing and flow between the pre-cured resin layer and other printing resins above it. This ensures sufficient resin feeding and improves the uniformity of the printing resin, resulting in better printed product quality. During the secondary compensation viscosity reduction, the movement speed and number of reciprocating motions are greater than during the initial viscosity reduction.

[0084] Step S4: In response to the platform positioning signal received from the platform lifting mechanism 9 when the printing platform 18 reaches the printing position, an exposure access signal is sent to the exposure mechanism 10 to control the exposure mechanism 10 to perform exposure curing. After exposure curing is completed, the system waits to receive the next layer timing printing signal sent by the printer control board 8, thereby realizing the timing control of layer-by-layer printing.

[0085] In another embodiment, a 3D printer is provided that includes the aforementioned 3D printing viscosity-reducing hybrid system.

[0086] It should be noted that the device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this application according to actual needs. Those skilled in the art can understand and implement this without any inventive effort.

[0087] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0088] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0089] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0090] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0091] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A control method for a 3D printing viscosity-reducing mixing system, characterized in that, The 3D printing viscosity-reducing hybridization system is used to be installed inside the printing chamber of the 3D printer, and the 3D printing viscosity-reducing hybridization system includes: The viscosity detection mechanism and the temperature detection mechanism are used to detect the real-time viscosity and real-time temperature of the pre-cured resin layer, which is a printing resin layer of a preset thickness located above the release film of the printing tank. An ultrasonic transducer is disposed on the side wall of the printing tank and acoustically coupled to the printing tank for ultrasonic activation of the pre-cured resin layer. The controller is communicatively connected to the viscosity detection mechanism, the temperature detection mechanism, and the transducer drive circuit of the ultrasonic transducer. The controller is also used to communicate with the heating controller, platform lifting mechanism, exposure mechanism, and printer control board of the 3D printer. The control method includes: In response to receiving the layer timing printing signal sent by the printer control board, the real-time temperature detected by the temperature detection mechanism is obtained; If the real-time temperature is greater than or equal to a preset temperature threshold, a stop heating signal is sent to the heating controller to stop heating the pre-cured resin layer. In response to the real-time temperature detected by the temperature detection mechanism being lower than the temperature threshold, the real-time viscosity detected by the viscosity detection mechanism is obtained. If the real-time viscosity is greater than or equal to a preset viscosity threshold, a working signal is sent to the transducer drive circuit to control the ultrasonic transducer to perform ultrasonic activation on the pre-cured resin layer for initial viscosity reduction. At the same time, a motion signal is sent to the platform lifting mechanism to control the printing platform of the 3D printer to perform lifting motion during the ultrasonic activation period of the initial viscosity reduction and / or the stable waiting period after the ultrasonic activation ends, so as to mix and turbulent the pre-cured resin layer. After the initial viscosity reduction and stabilization waiting period ends, the real-time viscosity and real-time temperature detected by the viscosity detection mechanism and temperature detection mechanism are obtained again. If the real-time temperature is less than the temperature threshold and the real-time viscosity is less than the viscosity threshold, a positioning signal is sent to the platform lifting mechanism to control the printing platform to move to the set printing position above the release film. In response to receiving a platform positioning signal from the platform lifting mechanism when the printing platform reaches the printing position, an exposure access signal is sent to the exposure mechanism to control the exposure mechanism to perform exposure curing.

2. The control method for the 3D printing viscosity-reducing mixing system according to claim 1, characterized in that, The ultrasonic transducers are arranged in an array on the side wall of the printing tank at a position relative to the center of the printing tank.

3. The control method for the 3D printing viscosity-reducing mixing system according to claim 1, characterized in that, Also includes: An acoustic field optimization structure is provided within the printing tank; the acoustic field optimization structure is used to ensure that the ultrasonic activation range of the ultrasonic transducer covers the pre-cured resin layer.

4. The control method for the 3D printing viscosity-reducing mixing system according to claim 3, characterized in that, The sound field optimization structure includes at least one of the following: A zigzag reflective sidewall structure is provided on the sidewall and / or bottom non-transparent area of ​​the printing tank; A sawtooth reflective structure is provided on the side wall and / or bottom non-transparent area of ​​the printing tank; An arc-shaped transition structure is provided at the junction of the side wall and the bottom non-transparent area of ​​the printing tank.

5. The control method for the 3D printing viscosity-reducing mixing system according to claim 1, characterized in that, During the initial viscosity reduction, the ultrasonic transducers positioned on the side wall of the printing tank are controlled to work simultaneously to ultrasonically activate the pre-cured resin layer for the initial viscosity reduction. After the initial viscosity reduction and stabilization waiting period ends, the real-time viscosity and temperature detected by the viscosity and temperature detection mechanisms are acquired again. If the real-time temperature is lower than the temperature threshold but the real-time viscosity is still greater than or equal to the viscosity threshold, a compensation signal is sent to the transducer drive circuit. All ultrasonic transducers arrayed on the side wall of the printing tank relative to the center position of the printing tank work in turn to ultrasonically activate the pre-cured resin layer for secondary viscosity reduction compensation. At the same time, a motion compensation signal is sent to the platform lifting mechanism to control the printing platform of the 3D printer to perform lifting and lowering movements during the ultrasonic activation period of secondary viscosity reduction compensation and / or the stabilization waiting period after ultrasonic activation, thereby mixing and turbulenting the pre-cured resin layer. After the stabilization waiting period of the secondary compensation viscosity reduction ends, the real-time viscosity and real-time temperature detected by the viscosity detection mechanism and the temperature detection mechanism are obtained again. If the real-time temperature is less than the temperature threshold and the real-time viscosity is less than the viscosity threshold, a positioning signal is sent to the platform lifting mechanism to control the printing platform to move to the set printing position above the release film.

6. The control method for the 3D printing viscosity-reducing mixing system according to claim 5, characterized in that, During the initial viscosity reduction, the ultrasonic operating frequency of the ultrasonic transducer is set to a fixed activation frequency. During secondary compensation viscosity reduction, the ultrasonic operating frequency of the ultrasonic transducer continuously or alternately changes between the first lower limit frequency and the first upper limit frequency with a preset frequency sweep period.

7. The control method for the 3D printing viscosity-reducing mixing system according to claim 5, characterized in that, During secondary viscosity reduction, the duration of the ultrasonic activation period and the duration of the stabilization waiting period after ultrasonic activation are both longer than those during the initial viscosity reduction.

8. The control method for the 3D printing viscosity-reducing mixing system according to claim 5, characterized in that, During the initial viscosity reduction and secondary compensation viscosity reduction, when the printing platform moves up and down during the ultrasonic activation period and / or the stable waiting period after the ultrasonic activation ends, the movement mode of the printing platform is a reciprocating motion, and the upper limit of the reciprocating motion needs to be higher than the pre-cured resin layer.

9. The control method for the 3D printing viscosity-reducing mixing system according to claim 8, characterized in that, During the secondary viscosity reduction, the speed and number of reciprocating motions of the lifting and lowering motion are both greater than those during the initial viscosity reduction.

10. 3D printer, characterized in that, A control method for executing the 3D printing viscosity-reducing hybrid system according to any one of claims 1-9, wherein the 3D printer comprises: The printing tank has a cavity formed inside, and a release film is provided at the bottom of the cavity. The release film is fixed by a pressure frame to keep it flat. The 3D printing viscosity reduction and mixing system is also provided inside the printing tank.

11. The 3D printer according to claim 10, characterized in that, The printing tank includes a first sidewall, a second sidewall, a third sidewall, and a fourth sidewall that are connected in sequence to enclose and form a cavity; The ultrasonic transducer is disposed within the printing tank in the following manner: The ultrasonic transducers are arranged in an array on the first sidewall, second sidewall, third sidewall, and fourth sidewall, relative to the center position of the printing tank.

12. The 3D printer according to claim 10, characterized in that, It also includes a resin feeding assembly, which includes a resin tank and a feeding pipe. The feeding pipe is used to connect the resin tank and the printing tank. A one-way valve and a metering pump are provided at the feeding pipe. The one-way valve is used to realize one-way flow of the feeding pipe from the resin tank to the printing tank.

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