Modular end effector and system for binder jet 3D printing using a gantry and computer implemented method

Abstract

A modular print head for binder jet three dimensional printing using a gantry, comprising: an elongated support module having a mounting portion attached to a vertical carrier arm of the gantry and having a longitudinal direction extending substantially horizontally in use; a first module for depositing a powder layer; a second module for levelling the height of the powder layer; and a third module for supplying binder fluid to the levelled powder layer to form a printed layer, wherein the first, second and third modules are respectively connected to different sides of the elongated support module, and during horizontal lateral movement the first, second and third modules pass through the same printing zone in the order first, second and third, and the third module is movably connected to the support module.

Description

[Technical field]

[0001] The present invention relates to binder jet three-dimensional (3D) printing, also known as inkjet 3D printing. In particular, the present invention relates to a modular additive manufacturing system capable of depositing jet droplets of powders and fluids using a gantry or robotic system with 2 up to 6 degrees of freedom. [Background technology]

[0002] In inkjet printing, small droplets of ink or fluid are jetted directly onto the receiver surface without any physical contact between the printing device and the ink receiver. The printing device stores the print data electronically and controls a mechanism that jets the droplets image-wise. Printing is done by moving the print head over the ink receiver and / or vice versa. Inkjet 3D printing jets a binder fluid instead of ink onto the powder layer, forming a hardened or coagulated pattern of powder particles within the powder layer. Both the powder and the binder fluid vary depending on the type of material being printed.

[0003] Early inkjet 3D printing used starch or gypsum plaster as powders, along with a binder fluid such as water, which may also contain dyes or additives to adjust the viscosity, surface tension, and rheological properties to suit the printhead's specifications. Plaster parts tend to lack strength and must be infiltrated with melted wax, cyanoacrylate glue, or epoxy resin before normal handling.

[0004] A variety of other powder and binder combinations are also used to form objects by chemical or mechanical means, and the resulting parts may undergo various post-processing steps, such as infiltration or bake-out, to remove the binder (e.g., by burning), to solidify the core material (e.g., by melting), or to form a composite material that combines the properties of the powder and binder.

[0005] As of 2014, there are systems on the market that form objects out of acrylic, cyanoacrylate, and ceramic powders using sand and calcium carbonate (to form artificial marble), liquid binders that may chemically react with the powders, or provide adhesion between the powder particles in a binder supply.

[0006] Three-dimensional inkjet printing is a relatively fast and flexible printing method for the production of prototype parts and tools, and for the rapid fabrication of three-dimensional complex structures directly from CAD files. Radiation curable compositions for use in three-dimensional printing methods of complex structures are disclosed in US Pat. No. 5,399,433, while US Pat. No. 5,499,463 and US Pat. No. 5,523,633 describe examples of methods for the layer-by-layer fabrication of ceramic materials.

[0007] Like many other additive manufacturing processes, a printed part is built up from many thin cross sections of a 3D model. An inkjet print head moves across a bed of powder, selectively depositing a liquid binder. It then spreads a thin layer of powder across the completed cross section. The bed is then lowered by submerging a support surface into a recess in the 3D printer, and the process is repeated, with each layer adhering to the previous one. Once the model is complete, the unadhered powder is removed in a process called depowdering, and may be reused to some extent.

[0008] Inkjet technology shows great potential for large-scale applications and high throughput. This is due to the high precision, scalability and reliability of the technology. The invention in US Pat. No. 5,399,633 concerns a sand mold for metal casting. Large printers can only deposit layers of sand, and therefore only very fluid materials can be used. The system is not scalable and cannot be resized.

[0009] Yet another prior art, the invention of US Pat. No. 5,399,633, relates to a method and apparatus for manufacturing composite structures. The apparatus is made for thick layers and very large droplet sizes. The resolution is very low and the apparatus is designed for manufacturing entire houses, whereas the subject system is designed for manufacturing modules, components or moulds. The machine design is aimed at low precision and low cost structures. Such techniques are in stark opposition to the purpose of the present invention, which is to improve the precision of larger structures. Such techniques are considered to be completely irrelevant to the purpose of the present invention. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] International Publication No. 2004 / 096514 [Patent Document 2] U.S. Patent No. 8,475,946 [Patent Document 3] US Patent Application Publication No. 2013 / 0157013 [Patent Document 4] U.S. Patent No. 9,333,709 [Patent Document 5] U.S. Patent No. 8,337,736 Summary of the Invention [Problem to be solved by the invention]

[0011] Inkjet 3D printing is popular for printing objects in high definition. Due to its material versatility, inkjet 3D printing can easily replicate 3D rendered digital models and other three-dimensional objects made of stone, ceramic, metal, polymer, composite, cementitious, etc. Such replication has proven to be extremely valuable in the field of historical preservation, proving to be a suitable technique to restore Notre Dame Cathedral to its former majesty after a fire devastated the famous cathedral in 2019. However, conventional inkjet 3D printers are usually limited to the production of palm-sized objects, whereas the present invention focuses on large printed objects, e.g. large printed objects the size of a person, a room, or a house. In particular, technical ceramics. It has been found that in the scale-up of 3D printers, the precision with which the layers are printed always decreases. This is due to the fact that lowerable support surfaces require more powerful hydraulics to facilitate their movement, and smaller adjustments become even more difficult to control.

[0012] It is therefore one object of the present invention to provide a print head that is scalable to a desired application and to provide a system that uses the print head that provides reliable print layer thickness, i.e., layer height, for objects that are greater than one meter in length, height, and / or width. [Means for solving the problem]

[0013] For this purpose, a modular printhead is provided according to claim 1. It is noted that the first module is also known as a powder recoating system, the second module is also known as a powder spreader and the third module is also known as an inkjet system. Each is discussed in the detailed description. The term elongated can be understood to mean a width to length ratio of 1:2 to 1:20, preferably 1:8 to 1:12, and the elongated support module is a hollow rectangular support beam of 0.5 to 6 m length and 8 to 20 mm thickness made of steel, stainless steel or aluminium, intended to protect against bending and to be used without adding excessive dynamic and static deflection to the gantry or robotic unit, e.g. the robotic arm. The elongated support module is preferably designed separately from the above to allow a dynamic deflection of up to 50 microns in use to ensure the accuracy of the 3D printing system. The dynamic deflection is the distance at which the end of the elongated support module is maximally deflected in response to movement in combination with a third module, e.g. a weight applied to the module. Static deflection is the distance that the end of an elongated support module will maximally deflect due to the maximum weight of the module.

[0014] It is optionally chosen to follow the features of claim 7. The term "substantially horizontal" is understood to mean within 1 degree of absolute horizontal. The local gravity direction is the reference frame for what is horizontal. In use refers to the situation where the end effector is connected to the gantry via a vertical arm or to the robot unit via an arm to perform printing. The vertical arm here corresponds to a movement in the Z axis direction, also called vertical movement. The direction of longitudinal extension of the elongated support module is preferably perpendicular to the direction of the printing movement in which the head moves horizontally. Optionally, it is optionally chosen that the first, second and third modules are arranged on the support module so that only the end effector is adapted to print in a single horizontal direction of movement. The direction of printing is understood to be the direction in which a new layer of powder is laid down. The direction of printing should not be misconstrued as the direction in which the inkjet system, i.e. the third module, supplies the binder fluid (this direction can be changed). The direction of printing is here perpendicular to the longitudinal direction of the support module. Optionally, apart from other options, the end effector can be selected to have a maximum weight of 1000 kg, including all parts of the end effector, including fluids and powders.

[0015] Optionally, the end effector comprises the features of claim 2. The features of claim 2 allow different modules to be slidably connected and disconnected relative to the end effector and replaced with modules of different sizes, so that the end effector can be adjusted to print objects of different scales without loss of precision.

[0016] To control the viscosity and meniscus of the binder fluid, and the recirculation pressure, the end effector may include an ink supply with a heater, such as an electric heater, designed to keep the binder fluid within a predetermined temperature range, for example 25 to 30±2°C. The ink supply may be a sub-tank connected to receive fluid from a tank external to the end effector. Each module includes an ink supply module that regulates pressure via a Venturi or membrane pump. The system may also regulate temperature. A temperature sensor may be placed in the tank to monitor temperature.

[0017] The support module may advantageously serve as a track for a stable movement of the inkjet system. To this end the features of claim 3 are provided. Preferably the third module is movably connected to a rear face of the support module, the first module is connected to a front face of the support module and the second module is connected to a lower face of the support module, where forward is determined by the direction in which the end effector moves to deposit the powder layer.

[0018] In order to provide improved structural support to the end effector and prevent vertical deflection at the end of the support module, the features of claim 4 are provided. Combining the features of claim 4 and claim 6 provides a synergistic effect that significantly reduces vibrations during operation. It is also possible to use the features of claim 6 without combining with claim 4 to obtain improved structural integrity.

[0019] To facilitate plug-and-play functionality of the module, the module may be provided with a local, reversible connection to a power source. For this purpose, the features of claim 5 are provided.

[0020] According to a second aspect of the invention there is provided a system as claimed in claim 8. Preferably the system is designed for a variable layer height between 80 and 500 microns and / or a minimum average speed of 200 mm / s at an ambient operating temperature of 15 to 25±2°C and an ambient air humidity of 55±5%, which provides the most detailed printing result.

[0021] A refiller, also known as an infiller or filling station, can be integrated into the gantry or simply be provided alongside it, so that the refiller re-supplies the end effector with powder in a consistent manner without the end effector needing complex vacuum or pneumatic transport systems, which are prone to failure and dust. For this purpose, a system is provided with the features of claim 9. The filling station may be connected to a storage tank for the powder and can therefore itself be re-fed using a pneumatic conveyor. To ensure that the powder is evenly distributed for printing, the system may comprise the features of claim 10.

[0022] It is not unexpected that the end effector, in particular the first and second modules, may become contaminated with particulate residues that may impair the accuracy of the function, in particular the accuracy of the inkjet system. To solve this problem, the system may comprise the features of claim 11.

[0023] Optionally, the system comprises the features according to claim 12. This design mitigates and prevents interruptions in the supply of binder fluid to the inkjet modules, allowing for printing high density images on the powder surface. Advantageously, this flow path structure not only makes it less prone to failures due to redundancy, but also improves the printing accuracy of 3D objects, i.e. the use of multiple inkjet modules. This further accelerates the printable speed of layers. The system can be further improved with the features of claim 13. 400 dpi in this particular embodiment corresponds to a minimum distinguishable step size of 63.5 microns.

[0024] In all embodiments of the system, the gantry may comprise a carriage running on a track forming part of the elevated part of the gantry located above the printing zone. The track allows reversible movement of the carriage exclusively in a single horizontal direction, preferably the printing direction. Here the movement of the printing third module is exclusively horizontal, perpendicular to the carriage movement direction, and is controlled locally on the end effector. The vertical carrier arm is a vertical metal beam, which provides a robust connection between the carriage and the end effector. The carriage is equipped with an actuator for reversibly raising the vertical arm during the printing stroke.

[0025] The vertical arm may be guided along a vertical track on the carriage. This allows the system to resist lateral forces on the end effector as a result of printing, or due to weight redistribution, or due to a shift in the center of gravity of the end effector during printing. Shifts in the center of gravity occur when the end effector is refilled and when powder is slowly expelled from the end effector during printing. The inverted T-shape of the end effector and the vertical arm has proven to be particularly stable.

[0026] According to a third aspect of the present invention there is provided a computer implemented method for binder jet 3D printing as claimed in claim 14. Optionally and advantageously the method includes the features of claim 15, in which the filling operation is automated. Similarly, the method may include a step f) of cleaning the end effector, in which case the system comprises a cleaning station and a capping station as claimed in claim 11.

[0027] Detailed Description In the present example, the following powder specifications are considered: - Particle size between 1 and 500 microns. - Bulk density is between 800 and 6000 kg / m3. - Angle of repose is 20 to a maximum of 46 degrees. · Liquidity: Carr index of 25 to 30, Hausner ratio of 0.9 to 1.6. Those skilled in the art will appreciate that other powder specifications may also be used. Further, the binder fluid may have the following properties: -Density: 900 to 1300kg / m3. Viscosity of 7 to 200 cps (ambient temperature may affect this value). Newtonian behavior of fluids

[0028] Those skilled in the art will appreciate that other binder fluid specifications can be used and that densities and viscosities may vary between binder fluids for cementitious, ceramic, metallic, and other printing applications. Newtonian behavior is desirable for improved printing control. [Brief description of the drawings]

[0029] The technical aspects of this invention are explained in further detail by the following figures: [Figure 1A] FIG. 2 is a diagram showing an end effector according to the present invention. [Figure 1B] FIG. 1 shows a cross section of the end effector, refiller, and cleaner. [Diagram 2] FIG. 1 shows the end effector and gantry system. [Diagram 3] FIG. 2 illustrates an elongated support module. [Figure 4] Diagram showing the first module, the powder recoating system. [Diagram 5] FIG. 2 shows the second module, the powder applicator. [Figure 6A] 1 illustrates an inkjet system including a third module, an ink supply module, a printhead, and electronic components. [Figure 6B] FIG. 2 shows a communication and electronics diagram for the inkjet system. [Figure 7] FIG. 2 shows a refiller and cleaner. [Figure 8] Diagram showing another system of 3D printing end effectors mounted on different gantry. [Figure 9] FIG. 1 shows a control diagram for printing and moving. [Figure 10] 13A-13C illustrate optional embodiments of the end effector. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Figure 1A shows a modular end effector 1 according to the present invention for binder jet 3D printing. The end effector 1 comprises an elongated support module 2 that acts as a core support structure to which all other modules are connected. The support module 2 comprises a mounting portion 3 centrally located on the top surface of the elongated support module in the longitudinal direction. The central beam allows for a deflection of up to 50 microns over a length of 3 meters.

[0031] The mounting 3 may be integral with the module or may be a separate metal structure that can be fixedly connected to the aforementioned upper surface. In the present example, only the latter is shown. At its upper end, the mounting comprises a receiving portion 3.1 for receiving the tip of the vertical carrier arm 101 of the gantry 100. Alternatively, the mounting may be integral with the vertical carrier arm 101. A system 1000 including such an arm 101 and a gantry 100 is shown in FIG. 2. In another alternative embodiment, not shown here, the connection portion may be a substantially flat surface of the upper surface with threads. FIG. 1B shows the end effector 1 in cross section. It is noted that, although not shown, the third module may, apart from this example, also include ultraviolet (UV) and / or infrared (IR) emitters. Such a feature advantageously allows the printing layer to be subjected to a localized direct heating treatment in the case of IR, or a curing treatment in the case of UV.

[0032] In FIG. 2, the end effector 2 is mounted so as to extend in a horizontal direction X. In use, i.e. when printing, the direction X corresponds to the width of the bed of powder (not shown, but in general). That is to say, the width of the printing area is equal to the length of the support module. Returning to FIG. 1A, three separate printing modules can be identified, namely the first, second and third modules 4, 5 and 6. The first module 4, also known as the powder recoating system, serves to deposit a powder layer as the end effector moves in the printing direction Y, in another horizontal direction perpendicular to the horizontal direction X in this example. The second module 5, also known as the powder spreader, comprises a roller 5.1 for levelling the height of the powder layer deposited by the first module 4. The third module 6, also known as the inkjet system, is arranged to supply binder fluid to the powder layer levelled by the second module to form the printing layer. Together, the first, second and third modules are essential for binder jet three-dimensional printing. The end effector 1 is designed for printing operations in a single moving direction Y perpendicular to the longitudinal direction X of the support module. Alternatively, in this example, the gantry comprises a carriage 102 movable along at least one track 103 provided on the upper part 104 of the gantry 100. In this example, a computer 200 with an associated human interface (201) controls the movement of the carriage along the track, the movement of the third module 6 along the elongated support module 2, and the movement of the vertical support arm 101 via actuators (not shown, but typical). Optionally, the computer and the interface are integral, for example a laptop with associated control software. In any case, the computer is arranged to control the first module 4, the second module 5, and the third module 6, as shown in FIG. 1A. The computer is arranged to be communicative, such as via a cable or wireless connection (not shown, but typical).

[0033] FIG. 3 shows an elongated support module 2. It is formed as a rectangular parallelepiped support beam with a first face in the printing direction Y, a second face in the downward direction G and a third face opposite the printing direction. The first module 4 is connected to the first face, the second module to the second face and the third module to the third face. This arrangement, and any arrangement according to claim 1, allows the first, second and third modules to pass through the same area in the first, second and third order, each of these modules working simultaneously in a single printing stroke. This allows each module to print at the same time and to process different parts of the powder layer to form the printed layer. A stroke in this case is a single horizontal movement of the print head to form the printed layer at the same vertical position.

[0034] The elongated module 2, also called the structural beam, houses all the modules, such as the aluminum profile, the spreader, the recoater, the X-axis actuation system, the junction box, the cable chain, the inkjet system, and the mechanical connection with the Z-axis (also called the vertical carrier arm 101), providing modularity to the system. This structural beam allows easy disassembly of the different components for maintenance, modifications, and improvements. The structural beam can also be fitted with tension cables 7 shown in Figure 2, which provide additional support and stiffness to the main structure and reduce bending. The structural beam is connected to the Z-axis through a connector that can be adapted according to the gantry connection used, this feature allows the end effector to be used with different types of gantries and robotic arms. In this particular case, a steel profile was chosen with a thickness of 8 to 13 mm and a size of 250 mm (*fixed size) x 300 mm (variable size). However, other dimensions are also possible. The steel profile and the connection plate can be customized in height and length to suit the gantry.

[0035] The first module 4 is shown in more detail in Figure 4A. The first module, also known as the recoater unit, is responsible for depositing powder on the print bed and is located in front of the second module 5, also known as the spreader roller. For this purpose, it comprises a storage container 4.3 and an adjustable powder outlet 4.2 for regulating the amount of powder deposited per layer, which is provided with a roller 4.1 located below the container.

[0036] The recoater deposits a very precise amount of powder onto the print bed through a surface covered with needles of 0.5 to 6 mm, the size of the needles depends on the type of material being spread, and the roller moves clockwise at a given speed along the print direction to deposit and regulate the amount of powder required to form a precise and uniform layer of particulate material according to the selected layer height. The particle size of the particulate material deposited on the powder bed is between 1 and 500 microns, and the material deposited with this technique can also have low flowability and cohesiveness due to the use of needles and moving brushes to transport the powder. The system is designed to deposit a variety of powder distributions, especially very fine powders such as cementitious powders, ceramics, and metals. The system also uses brushes to prevent the powder from adhering to the roller surface, especially for fine and highly cohesive powders that adhere to the needles. The brushes can be moved horizontally by using pneumatic motors and guides, which allows for complete removal of the powder during rotation and deposition on the print bed. A rotating brush can also be used for the purpose of removing the powder, but this option is less recommended due to the tendency of powder dusting. To prevent powder bridging in the container, the powder recoater can also include an internal infinite screw (similar to the screw used in the filling machine, represented in the new image) station, which produces a more homogeneous and distributed amount of powder along the X-direction. If powder bridging occurs, a vibration motor in the container wall can also be used to prevent this behavior. The features described in 4.1, 4.2, 4.3 above are compatible with all embodiments and may be separated individually as included in the claims. This configuration effectively replaces a conventional recoater module provided for a height-variable printing platform. At the side, a connection means is provided for a fixed connection to the first face of the support module 2. The module according to this embodiment further comprises a sensor (not shown, but typical) designed to quantify the current amount of powder in the storage container at different positions along the X-axis, in order to also monitor powder bridging. Such a sensor is communicatively connected, in use, to the computer of the system.That is, a sensor or a combination of sensors and computers is designed to detect when the amount of powder in the module is low, for example when there is only enough powder left to lay one or two layers. The system is then designed to move the end effector to a filling station 105, also known as a fixed filling station, shown in FIG. 2, to refill the storage vessel 4.3 with powder. The filling station 105 may comprise a pneumatic conveyor unit 105.1 designed to feed powder from an external nearby silo 105.3 to the filling station 105, as shown in FIG. 7. Such a refilling station may be assembled to the gantry. The system may also be designed to return the end effector to the filling station for refilling the first module between every 2 to 50 printed layers, depending on the size of the printer and the type of material to be deposited. An interval between every 5 to 15 layers is particularly beneficial in systems where both a refilling operation and cleaning of the end effector are performed, leading to a more optimal process cycle. Alternatively, the filling station is integrated with the end effector to operate in conjunction with the first module. This allows continuous refilling at the expense of making the system heavier, so that additional reinforcement to prevent sagging may be necessary. Figure 10 shows both an end effector 1 with a laterally arranged filling station and an alternative end effector 1' in which the filling station 105 is integrated with the first module. In the latter example, a pneumatic filling unit 105.1 is arranged to move along the length of the first module and fill the powder along the length of the unit. For this purpose, the filling unit is actuated by the computer of the system or the like. The discharge outlet 4.2 is adjustable by a manual or computer-controlled actuator, i) by moving or tilting a spreading wall 4.4 provided along the roller 4.1 relative to the roller, and / or ii) by adjusting the proximity of the roller to the container 4.3, so that the powder leaves the container between the roller 4.1 and the container.

[0037] The first module is designed to generate a so-called "bow wave" in front of the module by means of a roller. During printing, such a wave is generated and the module maintains a constant height of the bow wave over the length of the print bed. The powder outlet opening and the roller rotation speed are adjustable to achieve a constant and optimized deposition over the length of the print bed and thus obtain a uniform deposition of powder on the bed for high quality printing.

[0038] The recoater is fixed to the first face of the module to balance the weight distribution. In one example, the weight of the powder stored in the recoater unit is about 124 kg. The total weight of the unit, excluding the powder, is about 140 kg including the rollers, motors, side panels, reinforcements and their connectors. It should be noted that this is just an example and different weights may be selected. If necessary, a perimeter wall may be printed together with the 3D object to prevent the deposited powder from flowing out from the sides during printing. The three-dimensional area in which the printer operates is the boundary of a so-called bounding box, which can be automatically generated by software when the 3D model of the 3D object to be printed is sliced. Here the sliced ​​is divided into individual slices with the thickness of the layer to be printed.

[0039] The print size can also be adjusted in Y-direction by the software adjusting the maximum printable size so that no material is wasted over the entire length of the Y axis. The software can define the maximum print size for the system, as long as it is within the physical limits of the gantry or robot unit.

[0040] The second module 5 is shown in detail in FIG. 5. It has a roller 5.1 which is freely rotatable about an axis. At its tip, the roller has a connector part 5.2 which can be connected to the second side of the support module 2. Optionally, the roller may be replaced by a blade, such as a doctor blade, to reduce the number of moving parts and the total weight. This option is beneficial for applications where compaction of the powder is undesirable or unnecessary. The way in which the first and second modules cooperate is shown in FIG. 1B.

[0041] Desirably the rollers are designed to have a maximum deflection of less than 100 microns, ideally less than 20 microns over 4m. The precision runout of the rollers is a maximum of 0.110mm over 4m, ideally 0.2mm.

[0042] The roller spreader allows for very precise layer formation and powder compaction. This feature is very important to achieve a compact layer with tightly packed particles. This aspect is especially important for materials that require high packing density on the powder bed, such as cement-based materials, ceramics, and metals. The counterclockwise rotation of the rollers, in combination with the speed and size of the rollers, allows the degree of compaction of the material on the powder bed to be adjusted. It is the density distribution in the powder bed along the densified region in the rolling direction. It is shown how the layer thickness, the shape of the rollers, and the initial powder properties affect the relative density of the compacted powder, which directly affects the properties of the prototype part. It is noted that clockwise means rotating in the direction of movement, while counterclockwise means rotating against the direction of movement. Here, the direction of movement is the printing direction. Apart from this example, it is also noted that the first and second modules each have rollers, and that the rollers are designed to rotate in opposite directions to each other when in use. When in use, that is, during printing. This is also shown in Figure 1B.

[0043] The direction of the counter-rotating rollers is selected to avoid cracks on the surface of the layer after liquid injection. Compared with the counter-rotating rollers, the forward-rotating rollers achieve a much higher level of compaction, but the forward-rotating roller method is more likely to cause disturbances and cracks in the new powder layer after liquid injection. When the powder is compacted under the forward-rotating rollers, powder agglomerates will form, which will adhere to the rollers and leave craters in the new powder layer. Craters on the surface of the powder bed will have a negative impact on the printing result, so this must always be avoided. In addition, the diameter and speed of the rollers have a significant effect on the compaction of the powder, the degree of which directly affects the density and porosity of the powder layer, and more generally, the surface quality.

[0044] The third module 6 is shown in more detail in figure 6. The third module is also called the inkjet system and in this particular case comprises three independent sub-modules 6.1, 6.2, 6.3, each 500 mm wide, to cover a printing surface of 1500 mm wide. The inkjet modules are capable of recirculating the ink to prevent ink precipitation inside the printhead. They are also capable of degassing the ink through a degassing membrane inside the main module.

[0045] It is also possible to heat the ink up to 60 degrees to change its fluid dynamic properties. Inkjet nozzle distance can be varied from 30 microns to 500 microns, and drop size from 40 picoliters to 10 nanoliters. Different resolutions, material properties, chemistries, fluid properties and layer heights can be achieved by using different types of inkjet modules and printheads.

[0046] The inkjet module is capable of providing fluids with the following properties, which can be adjusted depending on the application and material system selected: Viscosity: 3 to 200 cps Surface tension: 20 to 60 dynes / cm Particle suspension up to 10 microns

[0047] Each module contains eight piezoelectric printheads PH, one ink supply system, eight head driver cards (HDCs) and one inkjet controller card (PCC). The HDCs and PCCs are not shown in Figure 6. The modules have removable covers that allow the user to access the printheads PH. Each of the modules is removably connected to the set of modules and can be replaced with other modules as required. The inkjet system is designed to move in the X direction along the X axis as shown in Figure 2. The inkjet modules can also be utilized to print along the X direction using only one 500mm module. The scanning mode of this configuration allows the system to be adapted to other types of applications and materials, and this configuration allows for the use of fewer printheads and electrical components at the expense of some loss of printing speed as more movement along the axis is required to achieve full coverage of the print bed. It should be noted that while it is possible, it is not necessary to feed the ink to the binder fluid. In fact, wherever ink is mentioned, the term binder fluid can be substituted. Figure 6B shows a communication and electronics diagram of the inkjet system. The diagram shows that the computer 200 controls the electronic switch 300, which controls the PCC, which controls the HDC, which controls the PH. The external encoder further communicates with the first PCC of the first sub-submodule, which communicates with the PCC of the second submodule, etc. There are four types of signals: S1 is the encoder pulse, which is transmitted to the various PCCs via a so-called "daisy chain" S2. Those skilled in the art will understand what is meant by that. S3 is the signal via Ethernet, and S4 is the signal via the dual HIB or so-called head interface board. Other architectures can be used depending on the inkjet module selected and the specific application.

[0048] The ink delivery system for the third module can be connected to a sub-tank (not shown, but typical) to provide a faster and more stable ink flow to the third module, depending on the distance from the main tank to the ink supply point. The sub-tank is provided on the print head 2 and is connected to the main tank (not shown, but typical) via a flexible tube that runs through the main energy chain of the gantry system. Overall, the third module uses multiple print heads capable of delivering a maximum droplet size of 10 nanoliters.

[0049] FIG. 7 shows a stationary filling station 105, also known as a refiller or infiller. The refiller is loaded with powder using a pneumatic vacuum conveyor and a rotary valve to regulate the amount of powder (illustrated but general). The pneumatic vacuum conveyor feeds the powder from the powder silo and sieves to remove impurities and particles over a certain size, which may clog the recoater. The infiller is the component of the 3D printing system that periodically replenishes the powder inside the recoater system. When the recoater powder container is close to empty, the printing system moves to the infiller unit. The aim is to fill the recoater powder container quickly so as not to delay the printing of the various layers. Preferably, the filling station is assembled on the gantry in a position close to the start of printing of a new layer. For this purpose, the filling station can be connected to the same surface on which the gantry rests at an elevated position from its surface, so that the print head 2 extends partially below the filling station 105, so that the first module 4 can be filled from the top by the filling station. It has been found that the stationary filling station is preferably filled at a rate of 0.15 liters per second to allow the powder to be properly spread along its length and to prevent overflow or uneven distribution of the powder. The filling station is provided with a screw conveyor (not shown, but typical) extending along the length of the filling station. The screw conveyor is arranged to deposit the powder evenly along the width of the infiller by rotating about its axis. After the printing cycle, every 2-50 layers, for example every 5-15 layers, the end effector moves to the infiller. The powder container of the recoater is filled from the top. This ensures a rapid filling of the container and minimizes printing delays. In figures 2 and 7, the infiller unit is installed on the floor using concrete anchors and a structural profile. This is an optional option.

[0050] The vacuum conveyor and rotary valve can also be mounted on top of the beam and move along the X-direction, which allows for even faster powder replenishment inside the recoater. This option is only recommended in some cases, such as when a long tube can be installed for powder replenishment.

[0051] The second module 5 is shown in more detail in figure 5. It comprises a roller 5.1 which is precisely rotatable about an axis. At its end the roller is provided with a connector part 5.2 which is connectable to the second side of the support module 2. Optionally the roller may be replaced by a blade, such as a doctor blade, to reduce the number of moving parts and the overall weight.

[0052] Roller spreaders allow for very precise powder layering and compaction.

[0053] FIG. 7 further shows a fixed washing station 106, also called a service station, designed for cleaning the print head 1. The service station includes a part 106.1 for purging and washing the print head. This is done before starting printing and during the printing process to ensure good quality of the print. The intervals between washing runs and the purge pressure are adjustable via a software interface, depending on the fluid used in the process. Purging may also be performed using a fluid to dry the head. Waste agent may be collected in the bottom part 106.2 of the washing station. The washing station may include a fluidically connected waste agent collection volume 106.3, which is arranged outside the printing area and not below the gantry, for draining waste liquid thereto. This advantageously prevents leakage and contamination of the print bed by stray droplets or dust. Furthermore, the part 106.1 may comprise a wiper for washing the print head to remove powder residues without leaving substantially any fluid residues. For this purpose, the washing station may comprise a pump unit (not shown, but generic). The service station unit is mounted on the floor using concrete anchors and a structural profile, but is also installed so that the print head can be lowered onto part 106.1, which may be designed as a longitudinal opening between two bars or upright wall parts to at least partially shield part of the print head from the environment during cleaning.

[0054] Figure 8 shows another example of a system 1000' according to the invention. The system 1000' differs from the system 1000 of figure 2 only in that at least one track 103 of the gantry comprises two parallel tracks 103.1, 103.2. Otherwise, the same features as described in relation to the system 1000 of figure 4A can be implemented in the system of figure 2. Here again, the gantry 100' comprises a vertical carrier arm 101 fixed to the aforementioned print head 1, where the gantry is arranged to reversibly move the carrier arm in one vertical direction Z and one horizontal direction Y. The elongated support module 2 preferably extends longitudinally in another horizontal direction X substantially perpendicular to the one horizontal direction Y, such that the length of the support module in the longitudinal direction is substantially equal to the width of the printed layer.

[0055] FIG. 9 shows the electromechanical system, junction box and cables. The 3D printing system may use a standalone controller (Programmable Machine Control) and CNC (Computerized Numerical Control). The system is designed to be modularly tuned, interfaced and integrated to be used with any existing CNC controller on the market. The system can also be integrated into a hybrid system that allows industrial operations for milling, automated de-powdering and other industrial CNC machining. In this figure, a computer 200 is equipped with a control program that establishes control authority over any of the aforementioned systems via the connections shown. The movement of the print head 2 in three-dimensional space is controlled by X, Y and Z axis actuators in the system. The X-axis actuator is actuator 6.1 shown in Figure 1A, which moves the third module 6 along the length of the support module 2, the Y-axis actuator is actuator 101.2, shown only in Figure 9, which moves the carriage 102 along at least one track 103, and the Z-axis actuator is actuator 101.1, which moves the vertical support arm 101 up and down, as shown in Figure 2. The inkjet system, i.e. third module 6, can use the encoder signal S1 to synchronize the X-direction movement with the ejection of droplets to achieve position-dependent actuation of each nozzle of the print head.

[0056] Optionally, the X-axis motor encoder can be connected to a pulse splitter S for incremental encoder signals for the inkjet system. In this example, C1 represents the fiber optic cable, C2 represents the I / O module cable, C3 represents the power cable, C4 represents the encoder cable, and C5 represents the servo power cable, although other communication connection configurations can be used. The electrical system includes a cabinet 400 with all the components of the electrical system such as drives, I / O modules, control units, junction boxes, etc. Such a cabinet 400 is only shown in FIG. 8, but is also present in the system of FIG. 2. The separate cabinet allows for easy integration of the 3D printing system into an existing gantry.

[0057] The junction boxes allow customers to plug cables directly into various systems and customize cable lengths depending on final requirements and the final location of the components.

[0058] Apart from all of the above, computer 200 may be preloaded with software that performs all steps of the printing operation, refilling, and cleaning.

Claims

1. A modular 3D printing end effector (1) for binder jet three dimensional printing using a gantry (100), comprising: - an elongated support module (2) having a mounting part (3) for mounting on a vertical carrier arm (101) of a gantry (100) and having a substantially horizontal longitudinal direction in use; - Mass median diameter (D ５０ a first module (4) for depositing a powder layer having a thickness of 1 to 500 microns; - a second module (5) for levelling the height of said powder layer; - a third module (6) for applying a binder fluid to the planarized powder layer to form a printed layer with a nozzle spacing of 30 to 500 microns and a droplet size of 40 picoliters to 10 nanoliters; Equipped with the first, second and third modules are connected to different sides of the elongated support module (2), An end effector, wherein in a horizontal printing operation, the first, second and third modules pass through the same area in the order of first, second and third, and the third module includes an actuator for moving the third module along the length of the support module.

2. 2. The end effector of claim 1, wherein the support module has a plurality of recesses extending longitudinally of the support module, and each of the first, second and third modules is connected to the support module via at least one of the plurality of recesses.

3. 3. A print head as claimed in claim 1 or claim 2, wherein the support module comprises an actuator for moving the third module along a longitudinally connected side of the support module.

4. 4. An end effector as described in any one of claims 1 to 3, wherein the mounting portion (3) is centrally located along the length of the support module and is positioned to receive the tip of the vertical carrier arm (101) so that the central support module forms an inverted T-shaped support structure with the vertical carrier arm (101).

5. The end effector of claim 4 , wherein the mounting portion comprises at least one electrical distribution junction box disposed on a side thereof.

6. 6. The end effector according to claim 4 or claim 5, wherein a (7) is attached to at least one of the upper surface of the support module (2) and the mounting portion (3) or the vertical arm (101).

7. 7. An end effector according to any preceding claim, wherein the elongated support modules form a rectangular parallelepiped support beam, preferably the beam enclosing a hollow interior volume extending substantially uninterrupted along its entire length.

8. a gantry (100) extending over a support surface for three-dimensional printing, said support surface being fixed in height or fixed to a robotic unit having from 2 to 6 degrees of freedom; - an end effector according to any one of claims 1 to 7; and - a communicatively connected computer (200) and a human interface and electrical system (201) for controlling the movement of said vertical carrier arm and the operation of said first, second and third modules; A system (1000) comprising: said gantry or robot unit comprising a carrier arm (101) fixed to said end effector (1), said gantry being arranged to reversibly move said carrier arm in one vertical direction (Z) and one horizontal direction (Y); The elongated support module (2) extends longitudinally in another horizontal direction (X), preferably substantially perpendicular to the one horizontal direction (Y), such that the length of the support module in the longitudinal direction is substantially equal to the width of the printing layer.

9. 9. The system of claim 8, further comprising an elevated, fixed filling station (105) designed to fill the first module with powder only when the end effector is in a filling position, the system being designed to move a print head to the filling position below the filling station when the system has deposited a predetermined number of printing layers.

10. 10. The system of claim 9, wherein the first module includes a top opening for receiving powder, the opening extending along substantially the entire length of the first module, the filling station includes a bottom opening of substantially equal length to the top opening of the first module, and the filling station includes a screw conveyor for depositing powder substantially uniformly along the length of the first module.

11. 10. The system of claim 8, further comprising a filling station integral with an end effector, such as the first module, and fluidly connected to a reservoir of powder external to the system, such as a silo, for pneumatic supply of powder from the reservoir to the first module.

12. 12. The system according to claim 8, further comprising a fixed cleaning station (106) designed to clean the end effector (1) only when the end effector is in a cleaning position on top or above the cleaning station, the system being designed to move the print head to said cleaning position before and during printing or between printing layers, said intervals being adjustable via the human interface.

13. 13. The system according to any one of claims 8 to 12, comprising a stationary main tank for containing a binder fluid, a secondary tank for containing a binder fluid provided on the print head (1) or on the vertical arm (101), said secondary tank being refilled from said main tank via a flexible fluid connection, and said third module being designed to receive or withdraw binder fluid from said secondary tank and comprising a number of inkjet modules for supplying said binder fluid to the levelled powder layer.

14. 14. The system of claim 13, wherein each inkjet module comprises eight printheads, each designed for a print density of at least 25 to 720 dots per inch, preferably 400 dots per inch, and arranged with eight head driver cards and one inkjet controller card for synchronous operation.

15. a) depositing a layer of powder using the end effector; b) leveling the powder bed using the end effector; c) applying a binder fluid to the leveled powder layer using an end effector to form a print layer; d) raising the end effector to a predetermined height; Including, Repeat steps a-d until the printed three-dimensional structure is completed.

15. A computer-implemented method for binder jet 3D printing using the system of any one of claims 8 to 14, wherein steps a-c occur simultaneously on different portions of the same layer during movement of the end effector in the one horizontal direction (Y).

16. e) filling said first module with powder at a filling position; Further comprising: A method as claimed in claim 15, using at least the system as claimed in claim 10, wherein step e occurs after a predetermined number of iterations of steps a-c, such as after 15 iterations.

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