Patent Application
20250033277
The present invention relates to binder jet three-dimensional (3D) printing, also known as inkjet 3D-printing. In particular, the invention relates to the modular additive manufacturing system able to deposit powder and jet droplets of fluids using a gantry or a robotic system with 2 to a maximum of 6 degrees of freedom.
In inkjet printing, small drops of ink or fluid are projected directly onto a receiver surface without physical contact between the printing device and the ink-receiver. The printing device stores the printing data electronically and controls a mechanism for ejecting the drops image-wise. Printing is accomplished by moving a printhead across the ink-receiver or vice versa or both. In inkjet 3D-printing instead of ink binder fluid is projected onto a powder layer in order to form a hardened or cohesive pattern of powder granules within the powder layer. Both the powder and binder fluid can vary depending on the type of materials printed.
In early versions of inkjet 3D-printing starch and gypsum plaster were used as powder together with a binder fluid, such as water. The binder fluid would in some cases include dyes and additives to adjust viscosity, surface tension, and rheological properties to match printhead specifications. The resulting plaster parts would tend to lack strength and require infiltration by melted wax, cyanoacrylate glue, epoxy, etc. before regular handling.
Various other powder-binder combinations are also deployed to form objects by chemical or mechanical means. The resulting parts may then be subjected to different post-processing regimes, such as infiltration or bakeout. This may be done, for example, to eliminate the binder (e.g., by burning) and consolidate the core material (e.g., by melting), or to form a composite material blending the properties of powder and binder.
As of 2014, systems came to market for forming objects from sand and calcium carbonate (forming a synthetic marble), acrylic powder and cyanoacrylate, ceramic powder and using liquid binder which may chemically react with the powder or provide adhesion between powder particles to which the binder has been provided.
Three-dimensional inkjet printing is a relatively speedy and flexible printing method to produce prototype parts, tooling, and rapid manufacturing of three-dimensional complex structures directly from a CAD file. Radiation curable compositions for use in three-dimensional printing methods of complex structures are disclosed by WO 2004/096514, whereas patent documents U.S. Pat. No. 8,475,946 B1 and US 2013/0157013 A1 describe examples of layer by layer ceramic material production methods.
As in many other additive manufacturing processes the part to be printed is built up from many thin cross sections of a 3D model. An inkjet printhead moves across a bed of powder, selectively depositing a liquid binding material. A thin layer of powder is then spread across the completed section. Subsequently, the bed is lowered by sinking the supporting surface into a recess of the 3D-printer and the process is then repeated with each layer adhering to the last. When the model is complete, unbound powder is removed in a process called de-powdering and may be reused to some extent.
The inkjet technologies are showing enormous potential for large scale applications and high throughput. This is due to the high precision, scalability, and reliability of the technology. U.S. Pat. No. 9,333,709 The invention is related to sand core for metal casting. The large printer is only able to deposit layers of sand and therefore very flowable material. The system is not scalable and cannot be adapted in size.
In yet another publication, U.S. Pat. No. 8,337,736 B2, the invention relates to a method for producing conglomerate structures and apparatus. This device is made for thick layers and very large drop size. Resolution is very low, and it is made to fabricate entire houses while our systems are made to make modules, components, or moulds. The mechanical design aim at low precision and low-cost structures. Such technology stands in strong opposition to the intention of the present invention which aims at improved precision for larger structures instead. Such technology is considered fully irrelevant to the purpose of the invention.
Any reference to prior publications in this application shall not be construed as an admission that such publication is prior art for purposes of determining patentability of the present invention. Such publications are referred to herein as a matter of giving a more complete background.
Inkjet 3D-printing is popular for printing objects in high detail. Inkjet 3D-printing through its material versatility allows 3D-rendered digital models and other stone, ceramic, metal, polymers, composites and cementitious three-dimensional bodies to be easily reproduced. Such reproduction has proven of immense value in the area of historical preservation and has proven to be a suitable technology to restore the Notre Dame to its former glory after a fire devastated the famous cathedral in 2019. However, conventional Inkjet 3D-printers are usually limited to producing hand-sized objects, whereas the present invention focusses on large printing objects, such as person, room, and house sized objects. In particular technical ceramics. In scale-up of the 3D-printers it was found that the precision with which layers were printed was consistently reduced. This is due to the fact that the lowerable support surface requires increasingly powerful hydraulics to facilitate its motion for which smaller adjustments are harder to control.
Accordingly, it is an object of the present invention to provide a printhead that is scalable to its desired use, as well as a system using such a printhead which provides a reliable printed layer thickness, that is to say layer height for objects larger than a meter in length, height and/or width.
To this end there is provided a modular printhead according to claim 1. It is noted that the first module is also known as a powder recoating system, the second module as a powder spreader, and the third module 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 between 1:2-1:20, and preferably 1:8-1:12 wherein the elongated support module is a hollow cuboid support beam between 0.5-6 m long made of steel, stainless steel or aluminum with a sheet thickness of 8-20 mm, to protect against bending, without adding undue dynamic and static deflection on a gantry or robotic unit, such as a robotic arm. The elongated support module is also separately from the above preferably designed to allow an, in use, maximum dynamic deflection of 50 microns to ensure the high precision of the 3D printing system. Dynamic deflection is the distance with which distal ends of the elongated support module maximally deflect in response to the moving of the third module, such as in combination with the added weight of the modules. Static deformation is the distance with which distal ends of the elongated support module maximally deflect by the maximum weight of the modules.
Optionally, in accordance with the features of claim 7. The term ‘substantially horizontal’ is understood to mean within 1 degree from absolute horizontal. The local gravitational direction provides the frame of reference for what is horizontal. In use, is given to mean the situation in which the end-effector is connected to the gantry, via the vertical arm, or to a robotic unit, via an arm, for printing. The vertical arm here corresponds to a Z-axis motion, otherwise known as vertical motion. The direction in which the elongated support module longitudinally extends is preferably the perpendicular the direction in which the head is moved in a horizontal printing motion. Optionally, the first, second and third modules are arranged on support module, so the end-effector is only suitable for printing in a single horizontal direction of movement. The direction of printing is here given to understand to be the direction in which a new layer of powder is laid down. The direction of printing is not to be misconstrued as the direction in which the inkjet system, that is to say third module, provides its binder fluid as this direction may be varied. The direction of printing is here perpendicular to the longitudinal direction of the support module. Optionally, also separately from any other option the end-effector can be chosen such that it has a maximum weight of 1000 kg which includes all parts of the end-effector including fluids and powder.
Optionally, the end-effector is provided with the features according to claim 2. The features of claim 2 allow the various modules to be slid into and out of connection with the end-effector, to allow them to be replaced with modules of different sizes. This allows the end-effector to be adjustable for printing objects at different scales without loss of precision.
To control the viscosity and meniscus and recirculation pressures of the binder fluid the end-effector may comprise an ink supply device with a heater, such as an electrical heater, which is designed to keep the binder fluid within a predetermined temperature range, such as 25 to 30+2° C. within said binder fluid tank. This ink supply can be a sub-tank which is connected to receive fluid from a tank external to the end-effector. Each module contains an ink supply module to regulate pressures through a venturi or a membrane pump. The system can also regulate the temperature. A temperature sensor may also be present in the tank to monitor the temperature.
The support module may beneficially act as track for the steady movement of the inkjet system. To this end the features according to claim 3 are provided. Preferably, the third module is movably connected to the face of the support module that faces rearward, whereas the first module is connected to the forward face of the support module and the second module is connected to the downward face of the support module, wherein forward is determined by the direction in which the end-effector moves in order to deposit a powder layer.
To provide increased structural support to the end-effector as well as prevent any vertical deviations at the distal ends of the support module, the features according to claim 4 are provided. The combination of features of claims 4 and 6 provide for a synergistic effect which substantially reduces operational vibrations. It is also possible to use the features of claim 6 without combination with claim 4 to obtain an increased structural integrity.
In order to facilitate plug and play functionality of the modules the modules can be provided to be locally reversibly connectable to electrical power. To this end there are provided the features according to claim 5.
According to a second aspect of the invention there is provided a system according to claim 8. Preferably the system is designed for a variable layer height between 80 and 500 micron and/or a minimum average speed of 200 mm/see in an environmental operating temperature of 15 to 25±2° C. and an environment air moisture of 55+5%. This will yield the most detailed printing results.
A refiller, also known as an infiller or filling station, can be assembled with the gantry, or simply provided alongside the gantry in order to provide a steady resupply of powder to the end-effector without the end-effector needing complex vacuum or pneumatic transport systems involving powder and flexible tubes, which may be prone to failure, and dust formation. To this end there is provided a system with the features according to claim 9. The filling station may be connected with a storage tank for powder and can therefore itself be resupplied using a pneumatic conveyor. To ensure that the powder is uniformly distributed for printing the system can be provided with features according to claim 10.
It is no surprise that the end-effector, in particular the first and second module may become contaminated with particulate residue which may interfere with the accuracy of function, especially with that of the inkjet system. To resolve this problem the system may be provided with the features of claim 11.
Optionally, the system is provided with the features according to claim 12. This design buffers and prevents binder fluid supply interruptions to the inkjet modules and enables high density images to be printed on the powder surface. Beneficially, this flow structure also increases the accuracy with which the 3D-objects are printed as well as being less prone to failure due to the provision of redundancies. That is to say, the use of a plurality of inkjet modules. This further accelerates the speed with which a layer can be printed. The system may further be improved by the features of claim 13. It is noted that 400 dpi for this specific embodiment corresponds to 63, 5 micron being the smallest distinguishable step size.
In embodiments of the system the gantry may comprise a carriage running across a track that forms part of a raised portion of the gantry which is overhead a printing area. The track exclusively enables reversible movement of the carriage in a single horizontal direction, preferably the printing direction. Movement of the third module for printing here being exclusively horizontally perpendicular to the direction of movement of the carriage and governed locally on the end-effector. The vertical carrier arm is a vertical metal beam, and thereby provides a sturdy connection between carriage and end-effector. The carriage is provided with an actuator for reversibly raising the vertical arm in between printing strokes.
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 because of the redistribution of weight, or shifting centre of mass of the end-effector during printing. A shifting centre of mass occurs when the end-effector is refilled and when the end-effector is slowly emptied of powder during printing. A reverse T-construction of end-effector and vertical arm have proven particularly steady.
According to a third aspect of the invention there is provided a computer implemented method for binder jet 3D printing according to claim 14. Optionally, and beneficially, the method includes the features of claim 15 in which the filling operation is automated. Similarly, the method may comprise a step f) of cleaning the end-effector, wherein the system comprises a cleaning and capping station according to claim 11.
Objects, advantages and novel features, and further scope of applicability of the present invention will be set forth in part in the detailed description to follow, taken in conjunction with the accompanying drawings, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
The accompanying drawings, which are incorporated into and form a part of the specification, illustrate one or more embodiments of the present invention and, together with the description, serve to explain the principles of the invention. The drawings are only for the purpose of illustrating one or more embodiments of the invention and are not to be construed as limiting the invention. In the drawings:
In an example of this invention the following powder specifications are considered:
Additionally, for the binder fluid the following characteristics may be considered:
The person skilled in the art will understand that other binder fluid specification may also be used and that density, viscosity may vary between binder fluids for cementitious, ceramic, metallic and other printing applications. Newtonian behaviour is preferable for an increased printing control.
The mounting portion 3 may be integral with the module or may be a separate metal structure that can be fixedly connected to said upper face. In this example only the latter is shown. The mounting portion has a receiving portion 3.1 at an upper end for receiving a distal end of a vertical carrier arm 101 of a gantry 100. Alternatively, the mounting portion can also be integral with the vertical carrier arm 101 of the A system 1000 comprising such an arm 101 and gantry 100 are shown in
In
The elongated module 2 is also called the structural beam and provides the modularity to the system, housing all modules, as aluminium profile, spreader, recoater, X-axis actuation system, Junction Box, cable chain, inkjet system and mechanical connection with Z-axis, also known as the vertical carrier arm 101. Using this structural beam, the different components can be easily taken apart for maintenance, changes or improvements. The structural beam can also host a tensioning cables 7, shown in
The first module 4 is shown in greater detail in
The recoater deposits very precise amounts of powder on the printing bed through the surface covered with needles between 0.5 and 6 mm, the size of the needles depends on the type of materials spreaded, the roller moves clockwise along the printing direction at a certain speed to deposit and regulate the powder amount necessary to create a precise and even layer of particulate material according to the layer height chosen. The particulate material deposited on the powder bed can have a granulometry between 1 and 500 micron, materials deposited with this technology can also have poor flowability and cohesive behaviours due to the use of needles and moving brush to transport powders. The system is designed to deposit different powder distributions and especially very fine powders like cementitious powders, ceramics and metals. The system can also use a brush to prevent powder to stick to the roller surface especially for fine and cohesive powders sticking to the needles. The brush can move horizontally through the use of pneumatic motors and a guide to allow a complete removal of the powder during rotation and deposition on the printing bed. A rotary brush can also be used for the purpose to remove powders, this option is less adviced because more prone to create powder dust clouds. To prevent powder bridging inside the container the powder recoater can also include an internal infinite screw (similar to the screw used in the infiller and represented in the new images) station to create a more homogeneous and distributed amount of powders along the X direction. In case of bridging of powders vibration motors on the walls of the container can also be used to prevent this behaviour. The features described herein above 4.1, 4.2 and 4.3 are compatible with all embodiments and may be separately isolated for inclusion in the claims. This setup beneficially replaces conventional recoater modules provided for height variable print platforms. A lateral side is provided with connection means for connecting to the first face of the support module 2 in a fixed manner. The module according to this example is further provided with sensors (not shown, but customary) that is designed to quantify the present amount of powder in the storage container in different positions along the X axis to also monitor powders bridging. Such as sensor would, in use, be communicatively connected to the computer of the system. That is to say, the sensor or combination of sensor and computer are designed to detect when the amount of powder in the module is low, such as when there is only enough powder left to lay down one or two layers. The system is then in turn designed to move end-effector to a refilling station, also known as a stationary filling station 105, shown in
The first module is designed to, by means of the roller produce a so called “bow wave” in front of the module. Such a wave is present during printing and the module maintains a bow wave with a constant height over the length of the printing bed. The opening of the powder outlet and the rotational speed of the roller are adjustable to achieve a constant and optimized deposition over the length of the printing bed and to obtain a uniform deposition of powder on the bed for a quality print.
The recoater is fixed to the module's first face to balance the weight distribution. In one example the weight of the powder that is stored in recoater unit is ˜124 Kg. The total weight of the unit without the powder is approximated to be ˜140 Kg including roller, motors, side panels, stiffeners, and their connectors. It should be noted that this is merely one example and other weights can be chosen. If necessary, a perimetral wall can be printed together with 3D objects to avoid that deposited powder flows out from the sides while printing. The three-dimensional area within which the printer operates is the so-called bounding box boundaries can be automatically generated by the software when 3D models of the 3D objects to be printed are sliced. Sliced here being separated into distinct slices with the thickness of the to be printed layers.
The printing size can also be adjusted in Y length through the software adjusting the max size printable to avoid to waste material over the entire length of the Y axis. The software allows to define the system's maximum printing size, as long as this is within the physical limits of the gantry or robotic unit.
The second module 5 is shown in greater detail in
The roller has connector portions 5.2 at its distal ends with which it can be connected to the second face of the support module 2. Optionally, the roller can be replaced with a blade, such as a doctor blade, to reduce the amount of moving components and decrease the total weight. This option is beneficial for applications in which compaction of the powder is undesirable or otherwise not required. The way the first and second module cooperate is shown in
Preferably, the roller is designed to have a maximum deflection of less the 100 micron and ideally less than 20 micron over 4 m. Roller precision runout should be maximum 0.110 mm over 4 m ideally 0.2 mm.
The roller spreader allows to create a very precise layer and compaction of the powder. This feature is very important to achieve compact layers with a tight particles packing. This aspect is very important especially for materials requiring high packing density on the powder bed like cementitious materials, ceramics and metals. The roller rotation counterclockwise in combination with the speed of rotation and size of the roller allows to adjust the compaction of the material on the powder bed. The density distribution in the powder bed along the densification zone, in the rolling direction. It was shown that how the layer thickness, roller geometry, and initial powder properties effect on the compacted powder relative density, which directly yields to the properties of the prototyped part. It is noted that clockwise means to rotate with the direction of motion, whereas counterclockwise means to rotate opposite the direction of motion. Herein the direction of motion being the printing direction. It should be noted that also separately from this example the first and second module each comprise a roller, wherein the rollers are designed for rotating counter to each other, in use. That is to say during printing. This is also visible in
Counter rotating roller direction was chosen to avoid the cracks on the surface of the layer after jetting the liquid. Compared to the counter-rotating roller on forward direction compaction level is much higher, but the forward-rotating roller method is prone to disturbance and cracking of the new powder layer after jet ting the fluid. As powder is compressed under a forward rotating roller, lumps of powder arise, that stick to the roller, leaving craters in the new layer of powder. As the presence of craters on the powder bed's surface is disastrous for the printing result, this should be always avoided. Also, the diameter and speed of the roller has a crucial influence on the powder compaction, this dimension directly affects powder layer density and porosity, we could say more in general its surface quality.
The third module 6 is shown in greater detail in
The ink can also be heated up to 60 degrees to change the rheological properties. The distance of inkjet nozzles can vary from 30 micron to 500 micron with a variation in drop size from 40 picoliters to 10 nanoliter. Different types of inkjet modules and printheads can be used to achieve different resolution, material properties chemistries, fluid properties or layer heights.
The inkjet modules can provide fluids with the following characteristics, the fluid characteristics can be adjusted according to the application and material system chosen:
Each module has 8 piezoelectric printheads PH, one ink delivery system, 8 HDC (head driver card) and 1 PCC (inkjet controller card). HDC and PCC aren't indicated in
The third module ink delivery system can be connected to a sub-tank (not shown, but customary) to provide a faster and constant ink flow to the third module, this aspect depends on the distance of the main tank to the ink supplies. The sub-tank is provided on the printhead 2 and is connected to the main tank (not shown, but customary) through a flexible tube passing through a main energy chain of the gantry system. In total, the third module uses several printheads able to provide a max drop size of 10 nanoliters.
The vacuum conveyor and rotary valve could also be mounted on top of the beam and move along the X direction allowing an even quicker refill of powder directly inside the recoater. This option is advisable only in some cases where for instance it is possible to install a long tube for powder refill.
The second module 5 is shown in greater detail in
The roller spreader allows to create a very precise layer and compaction of the powder.
Optionally it is possible to connect the motor encoder of the X-axis to a pulse splitter S for incremental encoder signals inkjet system. In this example, though other communicative connection arrangement may also be used C1 represents an optical fiber cable, C2 represents an I/O module cable, C3 represents a power cable, C4 an encoder cable and C5 a servo power cable. The electrical system includes a cabinet 400 with all the components of the electrical system like drives, I/O modules, control unit and junction boxes. Such a cabinet 400 is only shown in
The junction boxes allow the customer to directly plug the cables to the different systems and customize the length of the cables according to the final requirements and final position of the components. Separately, from all the above the computer 200 may be pre-loaded with a software that executes all steps of the printing operation, refilling, and cleaning.
Optionally, embodiments of the present invention can include a general or specific purpose computer or distributed system programmed with computer software implementing steps described above, which computer software may be in any appropriate computer language, including but not limited to C++, FORTRAN, BASIC, Java, Python, Linux, assembly language, microcode, distributed programming languages, etc. The apparatus may also include a plurality of such computers/distributed systems (e.g., connected over the Internet and/or one or more intranets) in a variety of hardware implementations. For example, data processing can be performed by an appropriately programmed microprocessor, computing cloud, Application Specific Integrated Circuit (ASIC), Field Programmable Gate Array (FPGA), or the like, in conjunction with appropriate memory, network, and bus elements. One or more processors and/or microcontrollers can operate via instructions of the computer code and the software is preferably stored on one or more tangible non-transitive memory-storage devices
Embodiments of the present invention can include every combination of features that are disclosed herein independently from each other. Although the invention has been described in detail with particular reference to the disclosed embodiments, other embodiments can achieve the same results. Variations and modifications of the present invention will be obvious to those skilled in the art and it is intended to cover in the appended claims all such modifications and equivalents. The entire disclosures of all references, applications, patents, and publications cited above are hereby incorporated by reference. Unless specifically stated as being “essential” above, none of the various components or the interrelationship thereof are essential to the operation of the invention. Rather, desirable results can be achieved by substituting various components and/or reconfiguration of their relationships with one another. The terms, “a”, “an”, “the”, and “said” mean “one or more” unless context explicitly dictates otherwise.
Note that in the specification and claims, “about” or “approximately” means within twenty percent (20%) of the numerical amount cited.
| Number | Date | Country | Kind |
|---|---|---|---|
| 22167911.1 | Apr 2022 | EP | regional |
This application is a continuation of International Patent Application No. PCT/NL2023/050193, filed Apr. 12, 2023, entitled “A MODULAR END-EFFECTOR AND SYSTEM FOR BINDER JET 3D-PRINTING USING A GANTRY, AND A COMPUTER-IMPLEMENTED METHOD”, which claims priority to and the benefit of European Patent Application No. 22167911.1, entitled “A MODULAR END-EFFECTOR AND SYSTEM FOR BINDER JET 3D-PRINTING USING A GANTRY, AND A COMPUTER-IMPLEMENTED METHOD”, filed Apr. 12, 2022, and the specifications and claims thereof are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/NL2023/050193 | Apr 2023 | WO |
| Child | 18912936 | US |
