Method for preventing deposits on nozzle plates

Abstract

To provide a method for preventing the formation of deposits at the lower face of a nozzle plate of a print head in a three-dimensional printer and the drying of printing raw material in a nozzle, and a three-dimensional printer.SOLUTION: A method for preventing the deposition of a printing liquid on a nozzle plate (101) of a print head in a three-dimensional printer comprises a step of increasing the saturation degree of a carrier liquid of the printing liquid in the air before the nozzle plate (101).SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for preventing the deposition of printing fluid on a nozzle plate of a printhead in a three-dimensional printer, as well as a three-dimensional printer having a printhead that includes a nozzle plate. [Background technology]

[0002] When printing with an aqueous slurry containing water and ceramic particles, the water evaporates above the nozzles, causing solids to clog the nozzles. To prevent nozzle clogging, cleaning can be performed in an ultrasonic bath or by manual cleaning. Current printers are equipped with a cleaning device that can move with the print head. In the cleaning device, the print head is usually moved through a wet cloth. However, cleaning can be performed in a variety of ways.

[0003] When jetting aqueous ceramic slurries or other aqueous or hydrophilic materials using an inkjet printhead, drying of the slurry on the underside of the nozzle plate occurs. If the humidity of the surrounding air is less than 90%, this can cause nozzle clogging. Even if there is slurry on the top surface of the nozzle plate, it is generally insufficient to convert the dried particles in the nozzles back into a flowable slurry that can flow through the nozzles. Summary of the Invention [Problem to be solved by the invention]

[0004] It is therefore an object of the present invention to prevent the formation of deposits on the underside of the nozzle plate and the drying of printing material within the nozzles. [Means for solving the problem]

[0005] The above-mentioned problem is solved by the subject matter of the independent claims. Technically preferred embodiments are the subject matter of the dependent claims, the description and the accompanying drawings.

[0006] According to a first aspect, the above technical problem is solved by a method for preventing deposition of printing liquid on a nozzle plate of a printhead in a three-dimensional printer, comprising increasing the saturation of the carrier liquid of the printing liquid in the air in front of the nozzle plate. The carrier liquid can be water or another suitable solvent. In the case of water, the saturation is the relative humidity, which can be directly detected by the degree to which the air is saturated with water vapor. Increasing the saturation of the carrier liquid in the air in front of the nozzle plate allows the carrier liquid to settle on the nozzle plate. Conversely, the carrier liquid on the nozzle plate also increases the saturation of the carrier liquid in the air in front of the nozzle plate. A film of carrier liquid on the nozzle plate additionally reduces deposition. This method eliminates the need for a separate cleaning station. In addition, the carrier liquid can be applied to the nozzle plate in a contactless manner, i.e., without mechanical contact with a separate implement such as a sponge. This method prevents, for example, a water-based slurry from drying on the underside of the nozzle plate or in the nozzles, thereby eliminating the possibility of nozzle clogging due to dried slurry.

[0007] According to a technically preferred embodiment of the method, the nozzle plate is wetted with the carrier liquid, whereby for example technical advantages are achieved in that the liquid film additionally prevents the formation of deposits on the nozzle plate.

[0008] According to another technically preferred embodiment of the method, the carrier liquid is deposited onto the nozzle plate, which achieves technical advantages, for example, in that the carrier liquid can be applied uniformly onto the nozzle plate and the liquid film additionally prevents deposition.

[0009] According to another technically preferred embodiment of the method, the carrier liquid is sprayed onto the nozzle plate, which achieves the technical advantage that, for example, the carrier liquid can be applied to the nozzle plate with less effort.

[0010] According to another technically preferred embodiment of the method, the carrier liquid is atomized in front of the nozzle plate, which achieves the technical advantage that, for example, the carrier liquid can be effectively saturated in front of the nozzle plate.

[0011] According to another technically preferred embodiment of this method, a highly saturated air is locally formed in front of the underside of the nozzle plate. The saturation is, for example, greater than 50%, more preferably greater than 90%, even more preferably greater than 95%, and most preferably greater than 99%. The locally highly saturated air is achieved, for example, by a directed airflow along the nozzle plate. This achieves the technical advantage of maintaining a high humidity in the air immediately before the underside of the nozzle plate. In this case, the water-based slurry cannot release moisture into the surrounding environment, thus preventing drying and maintaining nozzle flowability. This method can be performed "on the fly," eliminating the need to move the print head to a separate cleaning station.

[0012] According to another technically preferred embodiment of the method, the carrier liquid is ultrasonically atomized, which forms small droplets of the carrier liquid, thereby achieving technical advantages, for example, in that a mist of the carrier liquid can be formed with less effort.

[0013] According to another technically preferred embodiment of the method, the carrier liquid on the nozzle plate is aspirated by the nozzles, which achieves the technical advantage that, for example, the nozzles of the nozzle plate remain functional, i.e., capable of flowing.

[0014] According to another technically preferred embodiment of the method, the carrier liquid is applied to the nozzle plate before, during or after the printing operation, thereby achieving the technical advantage that, for example, the nozzle plate can be operational at any time.

[0015] According to another technically preferred embodiment of this method, the carrier liquid or air containing the carrier liquid is discharged through a discharge nozzle, or the carrier liquid is applied to the nozzle plate by a fabric or sponge. In this case, the fabric or sponge can be easily compressed. The fabric or sponge can be attached to the side of the nozzle plate. In this case, the fabric or sponge moves together with the nozzle plate. This achieves technical advantages, such as increased saturation immediately before the nozzle plate.

[0016] According to another technically preferred embodiment of the method, the carrier liquid or the air containing the carrier liquid is aspirated onto the nozzle plate by means of an aspirating nozzle, thereby achieving the technical advantage that, for example, used carrier liquid or desaturated air can be removed from the nozzle plate.

[0017] According to another technically preferred embodiment of the method, the carrier liquid has a temperature above 50° C. in order to increase the degree of saturation, thereby achieving the technical advantage that deposits on the nozzle plate can be effectively removed, for example.

[0018] According to another technically advantageous embodiment of the method, the carrier liquid deposited on the nozzle plate is sucked away by the nozzles, thereby achieving the technical advantage that, for example, the nozzle plate is automatically cleaned.

[0019] According to a second aspect, the technical problem is solved by a three-dimensional printer with a nozzle plate, which comprises a system for increasing the saturation of the carrier liquid of the printing liquid in the air in front of the nozzle plate, and which achieves the same technical advantages as the method according to the first aspect.

[0020] According to a technically preferred embodiment of the three-dimensional printer, the three-dimensional printer comprises a vaporizer for generating vapor of the carrier liquid in front of the nozzle plate, an ultrasonic device for forming atomized carrier liquid in front of the nozzle plate, and / or an injection device for injecting the carrier liquid onto the nozzle plate, thereby achieving technical advantages such as effectively increasing the saturation in front of the nozzle plate.

[0021] According to another technically preferred embodiment of the three-dimensional printer, the discharge nozzles for increasing the saturation are arranged on the nozzle plate, which achieves the technical advantage that, for example, humidity can be increased immediately before the nozzle plate.

[0022] According to another technically preferred embodiment of the three-dimensional printer, suction nozzles for sucking the carrier liquid or the air containing the carrier liquid are arranged on the nozzle plate, thereby achieving the technical advantage that, for example, used carrier liquid or desaturated air can be removed from the nozzle plate.

[0023] According to another technically preferred embodiment of the three-dimensional printer, the ejection nozzles are arranged on one side of the nozzle plate and the suction nozzles are arranged on the other side of the nozzle plate, thereby achieving technical advantages, for example, in that a high degree of saturation can be maintained in front of the nozzle plate by the air flow.

[0024] According to another technically preferred embodiment of the three-dimensional printer, the three-dimensional printer is provided with a heating device for heating the carrier liquid used for increasing the saturation level, thereby achieving the technical advantage that deposits on the nozzle plate can be effectively removed, for example.

[0025] According to another technically preferred embodiment, by applying negative pressure on the nozzles in the fluid system of the printer, the separated solids are re-sucked from the underside of the nozzle plate through the nozzles, thereby achieving the technical advantage, for example, of making the nozzles functional, i.e., flow-through, again.

[0026] Next, an embodiment of the present invention will be described in detail below with reference to the accompanying drawings. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is a schematic diagram illustrating the configuration of a three-dimensional printer. [Figure 2A] FIG. 1 is a schematic illustration of a nozzle plate without deposits. [Figure 2B] FIG. 1 is a schematic illustration of a nozzle plate with deposits. [Figure 3A] FIG. 1 is a schematic diagram of a nozzle plate with a water film. [Figure 3B] FIG. 1 is a schematic illustration of a nozzle plate with maximum deposits. [Figure 4] FIG. 1 is a schematic illustration of a printhead wetting system. [Figure 5] FIG. 10 is a schematic illustration of another wetting system for a printhead. [Figure 6] FIG. 2 is a schematic diagram of a socket for a print head. [Figure 7] FIG. 2 is a schematic diagram of a print head and a steam generator. DETAILED DESCRIPTION OF THE INVENTION

[0028] 1 shows a schematic diagram of a three-dimensional printer 100. The three-dimensional printer 100 performs free-flow material deposition in an additive manufacturing process, whereby feedstock in the form of small droplets is selectively contained in a printing fluid. In the case of polyjet or multijet modeling, the model is processed by a printhead 105 with multiple nozzles arranged linearly.

[0029] The three-dimensional printer 100 uses a printing fluid to, for example, build a dental prosthesis 127 layer by layer on a build platform 119. The printing fluid includes, for example, solid particles and a carrier liquid for the solid particles.

[0030] For printing, a material consisting of printing fluid is applied in dots using printing jets 123 from multiple nozzles. The print head 105 is movable in the X, Y, and Z directions, so that the printing jets 123 can reach any position on the build platform 119. The printing fluid is supplied to the print head 105 using a supply device 113.

[0031] However, this creates a problem in that deposits in the form of ink residue, foreign particles, or sediments can form inside the printhead 105. The deposits can adhere to the inner surfaces of the fluid system inside the printhead 105 and externally on the nozzle plate 101, which over time can cause clogging and affect the functionality of the nozzles 107 (printing nozzles) and the printhead 105.

[0032] 2A shows the appearance of a nozzle plate 101 without any deposits. The nozzle plate 101 has a number of nozzles 107 arranged in two parallel rows. Printing fluid is ejected from the nozzles 107.

[0033] 2B shows the nozzle plate 101 with deposits 109. Deposits 109 are caused by printing fluid that has dried during printing. For example, dried slurry residue forms around the nozzles 107 on the underside of the nozzle plate 101. If this deposit 109 cannot be removed, it can lead to poor print quality and clogged nozzles 107.

[0034] FIG. 3A shows a schematic representation of a nozzle plate 101 with a film of water deposited thereon as carrier liquid 103. The carrier liquid can generally be any suitable solvent. The water 103 is applied to the center of the nozzle plate 101, where it acts on the deposits 109. The water 103 dissolves the contamination. During operation of the three-dimensional printer, water vapor is applied to the nozzle plate 101, or fine water droplets are sprayed onto the nozzle plate 101, thereby wetting the nozzle plate 101. The carrier liquid of any printing liquid can also be used instead of water.

[0035] 3B shows a schematic of the nozzle plate 101 with the largest deposit 109. To prevent the printing fluid from dripping, the print head 105 is operated under a small negative pressure during printing. The negative pressure can be set to suck in a small amount of water or to fully wet the nozzle 107. The dissolved deposit 109 can then be sucked up by the nozzle 107.

[0036] This ensures that all nozzles 107 of the nozzle plate 101 are always functional, without the need to move them to a separate cleaning station, thereby saving costs and space and increasing printing speed. To enhance the cleaning effect, the negative pressure can also be temporarily increased. The nozzles 107 are opened and the nozzle plate 101 is cleaned on the fly during printing, eliminating the need for a separate cleaning station. Additionally, it is ensured that no printing nozzles become unusable. The jetting process can be controlled to prevent localized drying of the slurry on the underside of the nozzle plate 101.

[0037] The solution aspirated during the wash can then be collected in a tank and evaporated under reduced pressure, and removed again, while a small amount of particle-free liquid is continuously introduced into the system, without changing the solids content.

[0038] 4 shows a schematic of a wetting system 200 for a printhead 105. The wetting system 200 includes a water tank 115 in which water 103 is stored for wetting the nozzle plate 101. The water 103 is propelled to the printhead 101 through conduits using a pump 117.

[0039] There are discharge nozzles 131 on both sides of the nozzle plate 101. The discharge nozzles 131 discharge water 103 from the water tank 115 onto the nozzle plate 101, thereby not only wetting the nozzle plate 101 but also increasing the humidity in the space area in front of the nozzle plate 101. The re-dissolved solids then flow back into the fluid system through the nozzles 107 using negative pressure.

[0040] 5 shows a schematic of another saturation enhancing apparatus or system 200 for a printhead 105. The system 200 also includes a water tank 115 in which water 103 is stored for wetting the nozzle plate 101.

[0041] An ultrasonic piezoelectric element 121 is installed in the water tank 115 as an atomization device (vaporizer). The ultrasonic piezoelectric element 121 generates ultrasonic vibrations near the water surface in the water tank 115. The ultrasonic piezoelectric element 121 converts electrical vibrations into mechanical vibrations. The mechanical vibrations lead to the formation of capillary waves on the surface of the liquid film, which exponentially increase as the excitation frequency increases. When the excitation frequency reaches a certain value, droplets with a specific diameter are formed. Mist formation is performed using mechanical vibrations up to 3 MHz transmitted to the liquid. The diameter of the droplets decreases as the excitation frequency increases, or as the liquid's density and surface tension decrease. The ultrasonic piezoelectric element 121 can achieve droplet sizes of 2 to 4 μm. The ultrasonic piezoelectric element 121 makes it possible to atomize or vaporize the water in the water tank 115.

[0042] This forms a mist 125 made up of fine droplets above the water surface. The mist 125 thus formed is guided onto the nozzle plate 101 via a discharge nozzle (outlet) 131 and a suction nozzle (inlet) 129 by an air circulation system using a blower fan or pump 117. After being sucked by the suction nozzle 129, the mist 125 is returned to the water tank 115.

[0043] The discharge nozzles 131 and suction nozzles 129 can be located in the same plane as the nozzles 107 or integrated directly into the nozzle plate 101. The discharge nozzles 131 and suction nozzles 129 allow for the formation of a laminar flow of high humidity mist 125 along the underside of the nozzle plate 101, thereby preventing a humidity imbalance between the slurry and the air in the immediate vicinity of the nozzles 107.

[0044] The laminar flow along the underside of the nozzle plate 101 should have a flow velocity that is several times slower than the ejection velocity of the material droplets, so as not to have an excessively large effect on the flight direction of the material droplets. Additionally, the laminar flow should extend approximately perpendicular to the flight direction of the material droplets, ideally perpendicular to the row of nozzles 107. The laminar flow can be interrupted between printing of individual material droplets, so that the laminar flow does not affect the printing result.

[0045] The high humidity laminar flow adjacent to the underside of the nozzle plate 101 prevents the ambient air from absorbing water on the nozzles 107, thus preventing the slurry from drying out, thereby preventing deposits 109 on the nozzles 107 and nozzle plate 101.

[0046] This method reduces the technology costs and reduces the structural volume, since a separate cleaning station for the nozzle plate 101 is not required. Cleaning can be performed during printing, allowing printing jobs to be performed more quickly.

[0047] On the other hand, the air in the entire construction space of the three-dimensional printer can be maintained at a high humidity to the extent that the slurry on the underside of the nozzle plate 101 cannot release moisture into the surrounding environment and dry out.

[0048] 6 shows an outline of the socket 111 for the print head 105. The socket 111 is formed by a molding member, into which the print head 105 is inserted from above. The socket 111 has a supply pipe 137 and a discharge pipe 139, which are connected to the discharge nozzle 131 and the suction nozzle 129. Water vapor or water is supplied or discharged via the supply pipe 137 and the discharge pipe 139.

[0049] Everything needed to ensure reliable functioning of the printhead 105 can be contained within the socket 111 of the printhead 105, such as vacuum connectors, compressed air connectors, ultrasonic generators, vaporizers or atomizers, which move with the printhead 105. There is no need for a separate moving cleaning station, or for a separate cleaning station to move underneath the printhead even when the printhead is fixed and the build platform is moving.

[0050] Additionally, the socket 111 may include a vaporizer 133 for generating steam in front of the nozzle plate 101. A heating device is used in the vaporizer 133 to heat the water 103 around the nozzle plate 101, thereby generating steam. The vaporized water 103 condenses on the nozzle plate 101, thereby increasing the humidity around the nozzle plate 101 and also wetting the nozzle plate 101 with a liquid film, which prevents deposits 109.

[0051] The socket 111 may also be provided with an injector 135 for injecting water 103 onto the nozzle plate 101, for example by means of a nozzle. The injector 135 also makes it possible to wet the nozzle plate 101 with water 103, thus preventing deposits 109 by a liquid film.

[0052] 7 shows a schematic diagram of the print head 105 and the vapor generator 141. The vapor generator 141 can be formed, for example, as an ultrasonic piezoelectric element disposed in a water tank. The three-dimensional printer can include a vaporizer and / or a heat generating device as a system for increasing the saturation of the carrier liquid of the printing liquid in the air in front of the nozzle plate.

[0053] The generated mist 125 is directed to the nozzle plate 101 through the discharge nozzles (outlets) 131 using a blower fan or pump 117. The mist 125 can condense on the nozzle plate 101 where it falls as droplets. In the case of a non-horizontal build platform 119, the droplets can be collected in a collection basin and fed back to the water tank, thereby preventing re-absorption or re-suction of the carrier liquid into the nozzles.

[0054] The mist 125 for increasing saturation can have a temperature of 50°C or higher. A mist 125 having a temperature of at least 50°C can effectively soften printing fluid that has dried or accumulated on the nozzle plate 101. This achieves the technical advantage of being able to effectively, easily, and quickly remove deposits on the nozzle plate 101, for example. The use of a water mist 125 having a temperature of at least 50°C to 60°C eliminates the need for aggressive chemicals. This has another advantage of being able to effectively clean the nozzle plate 101 without the need for aggressive chemicals that may cause corrosion.

[0055] In this case, condensed carrier liquid is formed on the surface of the nozzle plate 101. Cleaning of the nozzle plate 101 is most efficient when the nozzle plate 101 has a temperature of 20°C to 25°C and the carrier liquid vapor for increasing saturation has a temperature of 50°C to 60°C. The atmospheric pressure can be 1013 hPa. The maximum possible carrier liquid saturation can be determined by a Mollier diagram, which is a graphical representation of the relationship between air temperature, moisture content, and air enthalpy at a given pressure.

[0056] All of the features described and illustrated in relation to individual embodiments of the invention can also be the subject of the invention in various combinations, whereby simultaneous advantageous results are achieved.

[0057] All method steps may be performed using apparatus suitable for performing each method step. All functions performed by the feature of interest may be method steps in this method.

[0058] The scope of protection of the present invention is defined by the appended claims and is not limited by the features described or shown in the description. [Explanation of symbols]

[0059] 100 3D printers 101 Nozzle plate 103 Carrier liquid / water 105 print head 107 Nozzle 109 Sediment 111 Socket 113 Feeding device 115 Water Tank 117 Pump 119 Building Platform 121 Ultrasonic Piezoelectric Element 123 Printing Jet 125 Fog 127 Dental Prostheses 129 Suction nozzle 131 Discharge nozzle 133 Vaporizer 135 Injection device 137 Supply pipeline 139 Discharge pipe 141 above generator 200 systems

Claims

1. 1. A method for preventing deposition of printing liquid on a nozzle plate (101) of a print head in a three dimensional printer (100), comprising increasing the saturation level of a carrier liquid (103) of the printing liquid in air in front of a nozzle plate (101), wherein the nozzle plate is wetted with the carrier liquid, the carrier liquid on the nozzle plate is aspirated through the nozzles, and the carrier liquid for increasing the saturation level has a temperature above 50°C, the 3D printer comprises a heater for heating the carrier liquid to increase the saturation level, and the 3D printer is adapted to apply a vacuum to the nozzles in the printer's liquid system, whereby dissolved solids are aspirated back out the bottom side of the nozzle plate through the nozzles, A method of atomizing the carrier liquid (103) by ultrasonic waves.

2. 2. The method of claim 1, further comprising spraying a carrier liquid (103) onto a nozzle plate (101).

3. 3. The method of claim 2, wherein the carrier liquid (103) is atomized in front of the nozzle plate (101).

4. 2. The method of claim 1, wherein the carrier liquid (103) is applied onto the nozzle plate (101) before, during or after the printing operation.

5. 2. The method of claim 1, wherein the carrier liquid (103) or the air containing the carrier liquid is aspirated onto the nozzle plate (101) by means of an aspirating nozzle (129).

6. A three-dimensional printer (100) having a nozzle plate (101) with a system (200) for increasing the saturation of a carrier liquid (103) of a printing liquid in the air in front of the nozzle plate (101), The three-dimensional printer comprises a vaporizer (133) for generating vapor of the carrier liquid in front of the nozzle plate (101), an ultrasonic device (121) for forming atomized carrier liquid (103) in front of the nozzle plate (101), and / or an injector (135) for injecting the carrier liquid (103) onto the nozzle plate (101), A discharge nozzle (131) for increasing saturation is arranged on the nozzle plate (101), A three-dimensional printer in which a suction nozzle (129) for sucking carrier liquid (103) or air containing carrier liquid is arranged on a nozzle plate (101).

7. 7. The three-dimensional printer of claim 6, wherein the ejection nozzles (131) are located on one side of the nozzle plate (101) and the suction nozzles (129) are located on the other side of the nozzle plate (101).

8. 7. The three-dimensional printer of claim 6, wherein the three-dimensional printer comprises a heating device for heating the carrier liquid (103) used for saturation.

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