Patent Grant
10596839
The invention is generally in the field of digital printing and relates to printing system and method, in particular for printing on a curved surface.
Digital printing is a printing technique commonly used in the printing industry, as it allows for on-demand printing, short turn-around, and even a modification of the image (variable data) with each impression. Some of the techniques developed for printing on a surface of a three-dimensional object are described hereinbelow.
U.S. Pat. No. 7,467,847 relates to a printing apparatus adapted for printing on a printing surface of a three-dimensional object. The apparatus comprises an inkjet printhead having a plurality of nozzles, and being operative to effect relative movement of the printhead and the object, during printing, with a rotational component about an axis of rotation and with a linear component, in which the linear component is at least partially in a direction substantially parallel with the axis of rotation and wherein the nozzle pitch of the printhead is greater than the grid pitch to be printed onto the printing surface in the nozzle row direction.
U.S. Pat. No. 6,769,357 relates to a digitally controlled can printing apparatus for printing on circular two-piece cans, the apparatus including digital print-heads for printing an image on the cans and drives for transporting and rotating the cans in front of the print-heads in registered alignment.
US Patent Application No. 2010/0295885 describes an ink jet printer for printing on a cylindrical object using printheads positioned above a line of travel and a carriage assembly configured to hold the object axially aligned along the line of travel and to position the object relative to the printheads, and rotate it relative to the printheads. A curing device located along the line of travel is used to emit energy suitable to cure the deposited fluid.
There is a need in the art for printing techniques that allow expediting the printing process while enabling maximal utilization (high efficiency) of the printing technology by allowing simultaneous printing on a plurality of objects. It is also required that such printing techniques retain a relatively high printing resolution, with very high system accuracies (microns), which makes inkjet printing technology very challenging for real production line use. Therefore, maintaining a high efficiency level by maximizing the printing engine utilization is necessary in such techniques to perform production runs.
In the above-mentioned patent publications (U.S. Pat. Nos. 7,467,847 and 6,769,357), printing takes place at discrete printing stations and is interrupted while the object is transported between printing stations. This interruption significantly slows the printing process. The inventor of the present invention has developed novel printing techniques enabling conducting a fast and efficient printing process on curved (and/or flat) surfaces of a plurality of objects streamed into the printing system from a production line.
The present invention is aimed at expediting the printing process, by providing a print head assembly which includes a plurality of print head units, where the print head units are arranged in a corresponding plurality of different (e.g., spaced-apart) locations along an axis of translation. In particular, in some embodiments a closed loop lane is used in the printing system to manage at least one stream of objects from a production line and move the stream of object over the lane through one or more stages of the printing process. A printing zone is defined along a section of the closed loop lane wherein a printing assembly is operatively installed for printing on external surfaces of the objects traversing the printing zone by at least one array of print head units of the print head assembly.
The at least one array of print head units is preferably configured to define at least one printing route along a printing axis for advancing the stream of objects therealong while printing over their external surfaces by the print head units of the assembly. The print head assembly may comprise several arrays of print head units, each configured to define at least one printing route along the printing axis and which may be used for passing additional streams of objects therealong for printing on the objects. For example, and without being limiting, each print head array may comprise one or more aligned columns of print head units, wherein the print head units in each column have a predefined slant defining a specific orientation of each column of print head units to thereby direct their printing elements (e.g., printing nozzles for ejecting a material composition, markers, engraving tools, laser markers, paint markers) towards a specific printing path covered by the array.
The lane may comprise a conveyor system configured to convey the stream of objects along the lane and pass the objects through one or more zones of the lane adapted for carrying out various functionalities of the system. One or more support platforms (also referred to herein as carriages) may be used in the conveyor system to translate the stream of objects over the lane. In some embodiments each support platform is configured to be loaded with at least one stream of objects from the production line and slide the objects over the lane through its one or more zones for processing and treatment. The support platform may be configured to maintain a stream of objects loaded thereto and aligned with respect to one or more printing routes defined by the print head assembly, and controllably rotate the objects carried by the platform whenever passing through certain zones of the lane (e.g., the printing zone).
The lane may include loading and unloading zones configured to receive one or more such streams of objects, and for removing the objects therefrom after completing the printing (typically requiring a single loop travel over the lane). A priming zone may be also defined on a section of the lane, typically upstream to the loading zone, wherein the surface areas of the loaded objects undergo a pre-treatment process designed to prepare the surface areas of the objects for the printing process. The lane may further comprise a curing zone, typically upstream to the printing zone, wherein the objects exiting the printing zone undergo a curing process (e.g., ultra violet-UV) to cure material compositions applied to their external surfaces.
In some embodiments, projections of the print head units on the axis of translations fall on different portions of the axis of translation. In this setup, the conveyor system effects a relative motion between the objects and the print head units. The relative motion provides both (i) a rotational motion around the axis of translation for bringing desired regions of the object's surface to the vicinity of the desired print head units and (ii) a translational motion along the axis of translation needed for bringing the object from one of print head units to a successive print head unit. This enables two or more print head units to print on the same object simultaneously. In the techniques of the present application the objects may be printed upon while being moved between groups of print head units. In this manner, the printing process is accelerated, and high printing throughput can be achieved. Additionally, the configuration of the printing system simultaneously prints on more than one object at the same time, by exposing consecutive objects to the arrays of print head units. It is further noted that the array of print head units is suitable for printing also on long objects at a variety of diameters.
The printing may be performed continuously (continuous printing) or in discrete steps (step printing). If the printing is continuous, the relative motion between object and print head units includes concurrent translation along the axis of translation and rotation around the axis of translation. In this manner printing of image data on the object's surface occurs along a substantially spiral path. If the printing occurs in discrete steps, a relative translation between the object and the print heads brings desired regions of the object in the vicinity of one or more groups. The translation is stopped, and a relative rotation is effected, in order to enable circumferential printing on the object's surface.
In some embodiments the print head assembly includes a plurality of groups of printing heads. Each group includes at least two print head units arranged in different locations along a curved path around said axis of translation and surrounding a respective region of the axis of translation.
Therefore, an aspect of some embodiments of the present application relates to a printing system configured for printing on an outer curved surface of a volumetric object. The system comprises a conveyor system and a print head assembly. The conveyor system is configured for effecting a relative translation between the object and the print head assembly along an axis of translation, and for effecting a relative rotation between the object and the print head assembly around the axis of translation. The print head assembly comprises a plurality of print head units, arranged such that projections of different print head units on the axis of translations fall on different portions of the axis of translation, each of the print head units having at least one nozzle and/or ejection aperture (also referred to herein as printing element) for ejecting a material composition onto the object's surface.
In a variant, the print head assembly further comprises additional print head units, such that the print head units are arranged in a plurality of groups, at least one group comprising at least two of the print head units arranged along a curved path around the axis of translation, and each group surrounding a respective region of the axis of translation.
In another variant, the printing system comprises a control unit configured to operate the conveyor system to carry out said translation and rotation and to operate at least some of the print head units according to a predetermined pattern.
The control unit may be configured to operate the conveyor system and at least some of the print head units, so as to effect simultaneous printing of image data on the object's surface by at least two print head units, each belonging to a respective one of the groups.
Optionally, the control unit is configured to operate the conveyor system and at least some of the print head units, so as to effect simultaneous printing of image data on the object's surface by different printing elements of a single one of the print head units.
The control unit may be configured to operate the conveyor system and at least some of the print head units, so as to effect simultaneous printing of image data on the object's surface by at least two print head units belonging to a single one of the groups.
In a variant, the conveyor system is configured for moving the object along the axis of translation. In another variant, the conveyor system is configured for moving the print head assembly along the axis of translation. In yet another variant, the conveyor system is configured for rotating the object around the axis of translation. In a further variant, the conveyor system is configured for rotating the print head assembly around the axis of translation.
In some embodiments the control unit is configured to operate the conveyor system to carry out the translation in a step-like fashion and to carry out the rotation at least during a time interval in which translation does not occur, and to operate at least some of the print head units to carry out the printing during the time interval in which translation does not occur and rotation occurs.
In some embodiments the control unit is configured for operating the conveyor system to carry out the translation and rotation simultaneously while operating at least some of the print head units to effect printing, such that continuous printing of image data is performed on the object's surface along at least one substantially spiral path.
In a variant, said conveyor system is further configured for effecting a relative motion between the object and the print head assembly along one or more radial axes substantially perpendicular to the axis of translation, in order to maintain a desired distance between at least one print head unit and the object's surface, while said at least one print head unit prints data on said surface.
In another variant, the conveyor system is configured for displacing at least one of the print head units to move towards and away from the translation axis.
In yet another variant, the conveyor system is configured and operable for displacing said at least one of said print head units with respect to the translation axis before operating the print head assembly to print the image data.
In a further variant, the conveyor system is configured and operable for displacing said at least one of the print head units with respect to the translation axis during the printing of the image data.
In yet a further variant, the conveyor system is configured and operable to operate said displacement to adjust a position of said at least one print head unit to conform to a shape of the surface of the object which is to undergo said printing.
In some embodiments of the present invention, the control unit is configured to operate said displacement of said at least one print head unit between an inoperative passive position and an operative active position of said at least one print head unit.
In a variant, the print head units of the same group are configured for ejecting a material composition of the same color. In another variant, each of the groups of print head units is configured for ejecting a material composition of a respective color.
In yet another variant, the printing system comprises at least one curing unit configured for curing a material composition ejected by any print head unit on the object's outer surface, the curing unit being located downstream along the translation axis of a last one of said print head units.
In a further variant, the printing system comprises at least one priming unit configured for priming at least one location of the object's surface to receive a composition to be ejected by at least one of the print head units, the priming unit being located upstream along the translation axis of a last one of said print head units. In yet a further variant, the printing system comprises at least a second curing unit located between print head units belonging to the same group. Optionally, the printing system comprises at least a second priming unit located between print head units belonging to the same group.
In a variant, projections along the translation axis of the print head units of at least one group fall on a single region of the translation axis. In another variant, the print head units of at least one of the groups are staggered, such that projections along the translation axis of at least two of the print head units of the at least one group fall on a different regions of the translation axis. In yet another variant, different print head units are configured for ejecting respective material composition on a region of the object's surface, such that a combination of the respective compositions on the object's surface forms a desired composition.
In a further variant, successive printing elements (e.g., nozzles and/or ejection apertures) of at least one of the print head units are configured for ejecting respective compositions on a region of the object's surface, such that a combination of the respective compositions on the object's surface forms a desired composition.
Optionally, the combination of the respective compositions comprises at least one of a mixing between the respective compositions and a chemical reaction between the respective compositions.
In yet another aspect there is provided a printing system for printing on outer surfaces of objects progressing on a production line. The system may comprise one or more print head assemblies comprising an array of print head units configured to define at least one printing route along a printing axis, the print head units being arranged in a spaced-apart relationship along the at least one printing route, each of the print head units having at least one printing element (e.g., comprising at least one of a nozzle for ejecting a material composition, a marker, an engraving tool, a laser marker, and a paint marker) for printing onto respective portions of the objects successively aligned with the at least one printing element while moving with respect to the print head assembly. A conveyor system is used for moving at least one stream of objects in a successive manner along a general conveying direction through said at least one printing route, the conveyor system comprising a closed loop lane, said at least one printing route being a substantially linear segment of said closed loop lane.
The system may comprise a support platform for supporting the at least one stream of objects respectively. The support platform is mountable on the conveyor system for moving the objects along the general conveying direction passing through the at least one printing route and configured to effect rotation of the objects about the printing axis while moving along the printing route.
In a possible embodiment the print head assembly comprises at least one additional array of the print head units, such that the printing units of the at least one additional print head array are arranged along at least one additional printing route along the printing axis, and at least two of the printing units in each one of the at least two arrays being spaced-apart along an axis traverse to the printing axis. Accordingly, the support platform may be configured to support at least one additional stream of objects and to move them on the conveyor system along the general conveying direction passing through the at least one additional printing route. For example, and without being limiting, the print head units of the at least two arrays may be arranged in a common plane such that each array of the print head units define a respective printing route, where the conveyor system and the support platform are configured for simultaneously moving the at least two streams of objects along the at least two printing routes covered by the respective at least two arrays of the printing head units.
In some embodiments a control unit is used to operate the conveyor system to carry out the translational movement along the general conveying direction, to operate the support platform to carry out the rotational movement, and to operate at least some of the print head units to concurrently print on the objects of the at least one stream of objects. The control unit may be configured to operate the support platform to carry out the rotational movement.
In some embodiments the control unit is configured to operate the conveyor system to carry out the translational movement along the general conveying direction in a step-like fashion, and to operate the support platform to carry out the rotation at least during a time interval in which translational movement does not occur, and to operate at least some of the print head units to carry out the printing during the time interval in which translation does not occur and rotation occurs.
Optionally, the control unit may be configured for operating the conveyor system and the support platform to carry out the translation and rotation simultaneously while operating at least some of the print head units to effect printing, such that substantially continuous printing of image data is performed on the surfaces of the objects in the stream of objects along a spiral path.
In a variant, the control unit is configured to operate the conveyor system and at least some of the print head units, so as to effect simultaneous printing of image data on surfaces of the objects by at least two print head units belonging to different arrays of print head units.
In some embodiments the control unit is configured and operable to effect a change in a distance between at least one print head unit and the object surface aligned with the at least one print head unit to thereby adjust a position of the at least one print head unit to conform to a shape of the surface of the object.
In a possible embodiment the print head units may be mounted for movement along radial axes or one or more axes substantially perpendicular to the printing axis.
Optionally, the control unit is configured to selectively shift one or more of the print head units between an inoperative passive state and an operative active state thereof, and between different operative states thereof.
In some possible embodiments the control unit is configured to generate a virtual signal for synchronizing operation of the printing elements according to angular and linear positions of the objects carried by the support platform along the printing route. More particularly, the virtual signal is used to synchronize the location of the carriages and the angular position of the objects carried by the carriages in the printing zone and operate the printing heads to apply a predetermined pattern to the surfaces of the objects after adjusting the location of the carriages and the angular orientation of the objects according to the virtual signal.
In yet another aspect there is provided a method of printing on outer surfaces of objects from a production line, the method comprising passing at least one stream of said objects through a printing route comprising at least one array of printing head units arranged along a printing axis, receiving data indicative of locations of the stream of objects passing through the printing route and of angular orientation of each object in the stream, determining, based on the received data, surface areas of the objects facing the print head units of the at least one array, and one or more printing patterns to be applied on the surface areas by the respective print head units, and operating the array of print head units to apply the one or more patterns on the surface area by the respective printing head units.
The method may comprise rotating the objects passing through the printing route during application of the one or more patterns. Optionally, the stream of objects are advanced along the at least one printing route during application of the one or more patterns. In some embodiments a pre-treatment process is applied to surface areas of the stream objects before passing them through the printing route. A curing process may be also applied to surface areas of the stream of objects before passing them through the printing route.
The method may further comprise generating a virtual signal for synchronizing operation of the printing head units according to angular and linear positions of the objects progressing through the printing route.
In order to better understand the subject matter that is disclosed herein and to exemplify how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:
The various embodiments of the present invention are described below with reference to
In some embodiments the loaded objects are attached to a plurality of carriages C1, C2, C3, . . . , Cn-1, Cn (also referred to herein as support platforms or as carriages Ci) configured for successive movement over the lane 10 and for communicating data with the control unit 300 regarding operational state of the carriages Ci (e.g., speed, position, errors etc.). As described hereinbelow in detail, the carriages Ci may be configured to simultaneously, or intermittently, or in an independently controlled manner, move the carriages Ci along the lane 10, and to simultaneously, or intermittently, or in an independently controlled manner, to move and rotate the object attached to them (e.g., using rotatable mandrels, not shown in
A size detection unit 13 may be used in the lane 10 to determine sizes (geometrical dimensions and shapes) of the objects received at the loading zone 306l and to communicate size data to the control unit 300. The size data received from the size detection unit 13 is processed and analyzed by the control unit 300 and used by it to adjust positions of print head units of the print head assembly 100 and alert on any possible collision scenarios.
A pre-treatment unit 204 may be also provided in the lane 10 to apply a pre-treatment process to the surfaces of the objects moved along the lane 10 (e.g., plasma, corona and/or flame treatment to improve adhesion of the ink to the container and create uniformity of the surface to the introduced printing/coating). Accordingly, control unit 300 may be configured to adjust operation of the pre-treatment unit 204 according to size data received from the size detection unit 13. As exemplified in
Objects exiting the printing zone 12z may be moved along a portion of the lane comprising a curing unit 202. The curing unit 202 may be operated by the control unit 300 and configured to finalize the printing process by curing the one or more layer of compositions applied to their surfaces (e.g., employing an ultra-violet/UV ink curing process or any other fixing or drying process such as IR, Electronic beam, chemical reaction, and suchlike). A vision inspection unit 16 may be further used to collect data (e.g., image data) indicative of the colors, patterns (e.g., print registration, diagnostics, missing nozzles, image completeness) applied to the objects exiting the printing zone 12z and/or the curing unit 202. After the printing, and optionally curing and/or inspection, process is completed the objects may be advanced over the lane 10 towards an unloading zone 306u for automatic removal thereof from the printing system 17. The unloading zone 306u may include an unloading unit employing an independent controller and one or more sensor units, motors, mechanics and pneumatics elements, and being configured to communicate sensor data with the control unit 300 of the printing system 17 for monitoring and managing the unloading process.
In the example of
In this non-limiting example the axis of translation 110 generally corresponds to an axis of the object 101, and is the axis along which a respective translation between the object 101 and the print head assembly 100 may occur. Moreover, a relative rotation between the object 101 and the print head assembly 100 may occur around the axis of translation 100. The details of the translational and rotational motions will be discussed later hereinbelow.
Referring now to
As exemplified in
Optionally, a print head unit used in the present invention can include a plurality of rows or columns of printing elements forming a two dimensional array defining a surface of the print head assembly facing the object. The print head assembly may be configured in any shape, such as, but not limited to, rectangular, parallelogram, or the like. Referring now to
In some embodiments, each print head unit includes one or more printing elements e.g., configured for jetting/applying a material composition (such as ink, powder, curing fluid, fixation fluid, pretreatment fluid, coating fluid, and/or a composition of one or more fluids to create a third fluid, and/or any solid/gas material that, while jetted, is a fluid) onto the outer surface of the object 101, as described above. The print head assembly 100 may be designed as the print head assemblies described in
In the example shown in
The conveyor system 302 is configured to move the object 101 and/or the print head assembly 100 such that a desired portion of the object 101 is brought to the vicinity of a desired print head unit at a desired time. In this manner, printing can be performed on the object's outer surface. The conveyor is configured for enabling at least two kinds of relative motion between the object 101 and the print head assembly: (i) a translational motion along or parallel to the axis of translation 110, and (ii) a rotation about the axis of translation 110. In this manner, any point on the outer surface of the object 101 can be brought to the vicinity of any print head unit. Optionally, a third kind of relative motion exists along one or more radial (or planar) axes substantially perpendicular to the axis of translation. This third motion may be necessary, in order to maintain a desired distance between at least one print head unit and the object's surface.
In some embodiments the control unit (300) is an electronic unit configured to transmit, or transfer from a motion encoder of the carriage, one or more signals to the print head units in the assembly 100 and to the conveyor system 302. Alternatively, the signals from the motion encoder are transferred directly to the print head assembly wherein they are translated by each print head unit into printing instructions based on signals received from the control unit 300. Accordingly, the positional control signal(s) transmitted from one of the carriage's encoders to the print head assembly 100, may be used by the control unit (300) to instruct individual print head units to eject their respective material compositions from one or more printing elements (e.g., nozzles/ejection apertures) at specific times. The control unit 300 further generated control signal(s) to the conveyor system 302, to instruct the conveyor system 302 to move (i.e., translate and/or rotate) the objects 101 and/or the print head assembly 100 according to a desired pattern. The control unit 300 therefore synchronizes the operation of the print head units with the relative motion between the object 101 and the print head assembly 100, in order to create a desired printing pattern on the object and therefore print a desired image on the object's outer surface.
The groups of print head units are set along the translation axis 110, such that during the relative motion between the object 101 and the print head assembly 100, the object 101 is successively brought in the vicinity of different print head units or groups of print head units. Moreover, during at least certain stages of this motion, different portions of the objects 101 may be located in the vicinity of print head units belonging to at least two consecutive groups or print head units located at successive positions along the axis of translation 110. In this manner, the object's outer surface may be printed upon simultaneously by print head units belonging to different groups or print head units located at successive positions along the axis of translation 110. Optionally, different printing elements of a single printing unit may print on two different objects at the same time. As explained above, this feature enables the system 200 to perform printing on one or more objects while optimizing the utilization of print heads, thereby achieving a high efficiency system capable of providing high objects throughput. As exemplified in
Besides enhancing the printing throughput on one or more objects, the structure of the system 200 also enables simultaneous printing on a plurality of objects 101. For this purpose, the objects 101 are fed into the system 200 one after the other, and the conveyor system 302 moves (i.e., translates and/or rotates) the objects 101 and/or the assembly 100 of print head units, so that each object 101 can be printed upon by certain portions of the print head units which are not printing on another object. For example, in
The printing system is considered fully utilized when under all the print heads units there are objects that are being printed on by the print heads units. To this end, any gap between the objects in the printing zone is considered as decreasing the efficiency, and therefore it is required that gaps between objects be minimized.
As can be seen in
In some embodiments of the present invention, the printing on the object's surface by different print head units or by different printing elements 130 of a print head unit may be performed for the purpose of creating a new path that was not printed beforehand. Optionally, some of the printing may be performed along or near an existing printed path. A path printed near or between two other paths may be used to achieve a predefined resolution. A path printed along an existing path may be used to complete the resolution of the existing path by adding more dots to create a denser spiral path. Moreover, printing a path along an existing path may be used to create redundancy between two different printing elements, i.e., if one printing element is not working then the second printing element prints a portion (e.g., 50%) of the desired data. Optionally, in case one of the printing element stops operating, the system can be controlled so as to enable the second printing element to print the data that was originally intended to be printed by the first printing element. This may be done, for example, by controlling (e.g., slowing) down the motion (translation and/or rotation) of the object 101 and/or print head array, or by controlling the second printing element to jet more ink. Optionally, the print head units belonging to the same group are configured for jetting ink of a single color to the object's surface, and the different groups of print head units are configured for jetting respective colors to the object's surface. Alternatively, different print head units belonging to the same group are configured for jetting ink of different colors.
It should be noted that although in the above-mentioned figures each group is shown to include three print head units, the groups may have any number of printing units, for example, one, two, four, etc. Moreover, though the above-mentioned FIGS. show the presence of four groups, any number of groups may be included in the system of the present invention. Additionally, the print head units in the above-mentioned figures are shown to be shorter than the length of the object 101. This may not be the case, as in some cases, the print head units may be as long as the object, or even longer.
The system 200 can be used to print on the object 101 according to two different printing sequences: continuous printing and step printing or any combination thereof. In continuous printing, the printing occurs during the relative motion between the object 101 and the print head arrangement 100, when such motion includes simultaneous translational motion along or parallel to the axis of translation 110 and a rotational motion around the axis of translation 110. In this kind of printing, image data is printed on the object's surface along a substantially spiral path.
In step printing, a relative translation between the object and the print heads brings desired regions of the object's surface to the vicinity of one or more print head groups or print head units located at successive positions along the axis of translation. The translation is stopped, while the relative rotation is effected. During the rotation, the print head units perform circumferential printing on the object's surface. After the printing is performed, the relative translation re-starts to bring one or more additional desired regions of the object's surface to the vicinity of one or more print head groups. The rotation may be maintained during the translation, or be discontinued at least during part of the translation.
The steps may be small steps, where translation occurs for moving a desired region of the object 101 from one printing element 130 to a consecutive printing element 130 of a single print head unit, or may be larger steps, where translation occurs for moving a desired region of the object from a first print head unit to a successive print head unit (e.g., belonging to a different group) along the axis of translation 110. In some embodiments, the steps may be large enough to translate a desired region of the object 101 from a first print head unit to a second print head unit while skipping one or more intermediate print head units.
In step printing, the circumferential printing may be activated by a trigger which confirms that the desired region of the object 101 has been translated by a desired distance. This trigger may be a positioning encoder signal and/or an index signal, which is active during translation and non-active when no translation occurs. Knowing the speed of translation and the position (along the axis of translation) of the desired print head units and its printing elements 130, the time point at which the desired region of the object 101 is exposed to the desired print head unit, and its printing element 130 can be calculated. Thus, when the trigger is activated by the positioning encoder and/or index signal, an instruction to effect printing is sent to the desired print head unit, and/or printing element 130 for example, according to the encoder position signals. Alternatively, the trigger may be activated by a light detector located on one side of the object 101 and corresponding light emitters located on a second side of the object 101. When the object 101 obscures the light detector, and the light from the light emitter does not reach the light detector, it is deemed that the desired region of the object's surface has been translated by the desired amount.
Optionally, a circumferential coordinate of a certain region of the object's surface is monitored (e.g., calculated via a known speed of rotation and the known radius of the object), and a second trigger is activated when the region reaches a desired circumferential coordinate which corresponds to the circumferential coordinate of desired print head unit, or printing element 130. In a variant, after translation is stopped, the relative rotation is performed to expose the desired region on the object's surface to the desired print head unit, or printing element 130, and only then printing (ejection of the material composition) is effected. In another variant, the second trigger is not used, and when translation ceases, the desired region of the object's surface is exposed to a different print head unit, or printing element 130. Because the circumferential coordinate of desired region is known, the control unit can instruct the different print head unit or printing element 130, to affect a desired printing onto the desired region. This last variant is useful for decreasing delays in the object's printing. A possible printing pattern may include both continuous printing and step printing, performed at different times.
It should be noted that the axis of translation 110 is shown in the figures as a straight line. This may not necessarily be the case. In fact, the axis of translation may be curvilinear, or may have straight sections and curvilinear sections.
Referring now to
In the non-limiting example shown in
The conveyor belt 152 may be a belt that is moved by a motion system, such as an electrical motor, linear motor system, multiple linear motor systems that combine to form a route, a magnetic linear system, or an air pressure flow system. In case a plurality of objects is handled, each of the objects may be handled separately by one or more object holders. It may be the case that at different places along the translation axis 110 each of the objects 101 is controlled to translate in a different manner (e.g., at a different speed) along the translation axis 110.
In the non-limiting example shown in
It should be added that, although not illustrated in the figures, other scenarios are also possible for giving rise to the relative translational and rotational motion between the object and the print head arrangement. In a first possible scenario, the conveyor system 302 is designed for moving the print head assembly 100 along the axis of translation 110 and includes an object holder for rotating the object around the axis of translation 110. In a second possible scenario, the conveyor system 302 is designed for moving the object 101 along the axis of translation 110 and for rotating the print head arrangement around the axis of translation 110.
In some embodiments both the object 101 and the print head arrangements 100 may be moved.
All the above-described manners of relative motion (fixed print head units and moving object, moving print head units and fixed object, translating the object and rotating the print head arrangement, rotating the object and translating the print head arrangement, moving print head units and moving object) are within the scope of the present invention and equivalent to each other. In order to simplify the description of the invention, in the remaining part of this document the description will relate to the case in which the print head units are fixed and the object 101 is moved (translated and rotated). However, references to the motion of the object 101 should be understood as references to the relative motion between the object 101 and the print head unit arrangements 100.
In both of the cases described above, individual print head units and/or individual groups may be movable along the translation axis 110 with respect to each other. This may be used for manual and/or automatic calibration prior and/or post printing. Optionally, individual print head units and/or groups may be movable around or perpendicularly to the translation axis 110. This may also be used for manual and/or automatic calibration prior and/or post printing.
Referring now to
In
The ability to move the print head units enables maintaining a desired distance between the print head units and the object 101. Also, the moving of the print head units enables moving the selected print head units between their active positions and their passive positions. This gives flexibility to the print head assembly, as it can be configured in different manners to print on surfaces of different diameters and lengths (e.g., for object of small diameters, the number of active print head units in a group is decreased, to enable the active print heads to be at a desired distance from the object's outer surface). In a variant, the print head units can be moved only prior to the printing, i.e., after the object starts to move the print head units maintain their position with respect to the axis of translation. This feature is advantageous, as it enables the system 200 to keep a desired distance between the print head units and objects having a plurality of diameters and lengths. In another variant, the print head units can be moved during the printing. The latter feature may be advantageous in the instance in which the cross-sectional size and/or shape of the object varies along the length of the object, or in the cases where the object is not circular (as exemplified in
Referring now to
In
It should be noted that in the previous figures, print head units of the same group have been shown to be located at the same coordinate along the axis of translation 110. However, this need not be the case. Referring now to
In
Referring now to
In
Techniques may also be used for priming/pretreating the object's surface prior to printing: exposing the printed surface of the object to a flame, and/or plasma, and/or corona, and/or surface cleaning equipment: and/or antistatic equipment; surface heating or drying equipment; applying a primer or coating material to the surface; exposing the surface printed or unprinted to a gas, such as nitrogen or an inert to enhance later curing. To this end, optionally, a priming station 204 is located upstream from the first print head group 102 (or the first print head unit 102a). In the priming station 204, the surface of the object 101 is treated so as to enhance the imminent printing upon it. The priming may be performed according to any of the above-mentioned manners used for priming/pretreating.
It should be noticed that the curing/drying station may include a single curing/drying unit or a group of curing/drying units set around the translation axis 110. Similarly, the priming station may include a single priming unit or a group of priming units set around the translation axis 110.
Referring now to
In some embodiments, it may be desirable to have a curing or priming station after (downstream from) one or some of the groups of print head units (or after some of the print head units located at successive positions along the axis of translation). For example, and without being limiting, if consecutive groups or print head units apply to the object compositions that may mix together and yield undesirable results a curing station is needed between these two consecutive groups or print head units. In another example, certain print head units or the print head units of a certain groups are configured for jetting a composition which needs a certain kind of priming prior to application on the object's surface. In this case, a priming station needs to be placed before the certain print head units or certain groups.
In the non-limiting example of
Referring now to
Referring now to
It is that in some embodiments shown in
Referring now to
In
This setup is advantageous in the instance in which the third composition 226 cannot be printed by the desired printing system. For example, and without being limiting, if the third composition is a solid, the third composition cannon be ejected in inkjet printing. The first and second liquid compositions are to be combined during the printing process according to the techniques of
A solid composition is an extreme example. In fact, even a desired liquid composition having fluid viscosity above a certain threshold cannot be delivered by certain print head units (many inkjet print head units, for example, can jet liquids having viscosity between 10-15 centipoises). However if the component compositions of the desired composition have a viscosity that is below the operating threshold of the print head units, the component compositions can be delivered by successive print head units and mix on the target area to form the more viscous desired composition.
The combination of compositions described in
Referring now to
In
It should be noted that though the examples of
Referring now to
As explained above, the print head units 102a, 102b, and 102c belong to a first group, the print head units 104a, 104b, and 104c belong to a second group, and the print head units 106a, 106b, and 106c belong to a third group. In the example of
In each column, the printing heads are joined to each other and form bars. The location of the print head units during printing is critical for achieving a successful printing. The print head units are to be aligned with each other along the translation axis at a high precision for high-resolution printing. Therefore, aligning the print head units with respect to each other is an important part of the printing process. The advantage of having the printing heads arranged in bars/columns lies in the fact that rather than adjusting a position of each printing head individually prior to printing, the positions of the bars/columns along the translation axis are adjusted. By adjusting the position of each bar/column, the position of a plurality of printing head units which constitute the bar/column is adjusted. Thus, once the position of the first bar/column is chosen, all the other bars/columns must simply be aligned with the first bar/column. This enables a precise and quick adjustment of the location of the printing heads prior to printing.
Though subsequent print head units of any bar of
Referring now to
The system 200 in this non-limiting example includes a control unit 300, a conveyor system 302, and a print head assembly 100, all of which have been described hereinabove. The print head assembly 100 may, or may not, include one or more priming (204) and/or curing (202) units or stations, as described hereinabove. Optionally, the system 200 includes a loader/unloader unit 306 configured for loading the object(s) onto the conveyor system 302 and unloading the object(s) from the conveyor system 302 once the printing (and optionally curing/drying and/or priming/pretreating) is completed. The control unit 300 operates the conveyor system 302, the print head assembly 100, and the loader/unloader device 306 (if present), to create a desired sequence of operations of these elements (printing pattern), in order to yield a printed image on the object (101).
Optionally, the sequence of operations is transmitted to the control unit 300 from an outer source as input data 308. The outer source may be a computer, which computes a suitable sequence of operations based on properties (e.g., colors, size, etc.) of an image which is to be printed on the object. In a variant, the control unit 300 includes a processor 302a configured for processing the image and determining the desired sequence of operations. In this case, the input data 308 is data indicative of the image to be printed, which the processor 302a uses to determine the sequence of operations.
In a variant, the system 200 includes a distance sensor 310 and an alignment sensor 312. The distance sensor 310 is configured for sensing the distance between at least one print head unit and the surface of the object. The alignment sensor 312 is configured for determining whether print head units (or bars/columns of such units, if present) are properly aligned with each other along the translation axis and/or around the translation axis.
The control unit 300 receives data from the distance sensor 310 and alignment sensor 312 in order to determine whether the print head units are in their proper positions, and determines whether or not to move them. In a variant, the control unit 300 instructs the print head units to move to their assigned positions before the printing starts (perpendicularly to the translation axis according to data from the distance sensor 310, and/or along and/or around the translation axis according to data from the alignment sensor 312). In another variant, the control unit 300 instructs the print head units to move to their assigned positions during the printing (for example, if the cross-sectional shape of the object varies along the object's length or the object's cross section is not circular, as explained above).
The distance sensor 310 and the alignment sensor 312 may operate by emitting radiation (e.g., electromagnetic, optical, acoustic) toward a target and receiving the radiation reflected/scattered by the target. A property of the received radiation (e.g., time period after emission, phase, intensity, etc.) is analyzed in order to determine the distance between the sensor and the target.
According to a first variant, a distance sensor element is mounted on at least one of the print head units and is configured for emitting radiation to and receiving radiation from the object. According to a second variant the distance sensor is an external element which determines the position of a print head unit and of the object's surface, and calculates the distance therebetween.
Similarly, in a variant, an element of the alignment sensor 312 is mounted on a print head unit and is configured for emitting radiation to and receiving radiation from another print head unit. In another variant, the alignment sensor 312 includes an external element configured for determining the position of two print head units (or bars/columns of such units) and calculating the distance therebetween.
In some embodiments of the present invention, the distance sensor and alignment sensor are not present, and a calibration process is required prior to printing. In the calibration process, the print head units of the assembly 100 are moved to their positions prior to printing, and a trial printing is performed. The image printed in the trial printing is analyzed either by a user or by a computer (e.g., an external computer or the control unit itself), and the positions of the print head units are adjusted accordingly, either manually or automatically. Once this calibration process is finished, the printing of one or more objects can take place.
With reference to
Implementing an elliptical lane 10 may be carried out using straight rails connected to curved rails to achieve the desired continuous seamless movement on the elliptical track. Accordingly, the sliding boards 22 may be configured to enable them smooth passage over curved sections of the lane 10. Printing zones 12z of the lane 10 are preferably located at substantially straight portions of the elliptical lane 10 in order devise printing zones permitting high accuracy, which is difficult to achieve over the curved portions of the lane 10. In some embodiments curved shape tracks have runners with a built in bearing system's tolerance to allow the rotation required by the nonlinear/curved parts of the track. Those tolerances typically exceed the total allowable error for the linear printing zone 12z. In the printing linear zone 12z, the tolerable errors allowed are in the range of few microns, due to high resolution requirements for resolution greater than 1000 dpi for high image qualities/resolutions. For such high resolutions require 25 micron between dots lines, which means that about ±5 micron dot accuracy is required in order for the sliding boards to pass the printing zone 12z in an accumulated printing budget error in X,Y,Z axis that will not pass the required ±5 micron tolerable dots placement position error.
The printing head assembly 100 comprises an array of printing head units 35 removably attached to a matrix board 30 and aligned thereon relative to the tracks 10r of the lane 10. The matrix board 30 is attached to the elevator system 27 which is configured to adjust the height of the printing elements of the printing heads units 35 according to the dimensions of the objects 101 held by the carriages C1, C2, C3, . . . , approaching the printing zone 12z.
Referring now to
Each carriage Ci being loaded onto the lane 10 at a loading zone (306l) with a plurality of objects 101 is advanced through the various stages of the printing system 17 (e.g., priming 204, printing 12z, curing 202 and inspection 16), and then removed from the lane 10 at an unload zone 306u, thereby forming a continuous stream of objects 101 entering the lane and leaving it after being printed on, without interfering the movement of the various carriages Ci. In this way, the closed loop lane 10 provides for a continuous feed of carriages C1, C2, C3, . . . , loaded with objects 101 into the printing zone 12z, and independent control over the position and speed of each carriage Ci (i=1, 2, 3, . . . ) maintains a minimum gap (e.g., of about 1 cm) between adjacent carriages Ci in the printing zone 12z.
In this non-limiting example the print head assembly 100 comprises ten sub-arrays Rj (j=1, 2, 3, . . . , 10) of printing head units 35, each sub-array Rj comprising two columns, Rja and Rjb (j=1, 2, 3, . . . , 10), of printing head units 35. The printing head units 35 in the columns Rja and Rjb of each sub-array Rj may be slanted relative to the matrix board 30, such that printing elements 130 of the printing head units of one column Rja are located adjacent the printing elements 130 of the printing head units of other column of the sub-array column Rjb. For example, and without being limiting, the angle α between two adjacent print head units Rja and Rjb in a sub-array Rj may generally be about 0° to 180°, depending on the number of print head units used. The elevator system 27 is configured to adjust the elevation of the print head units 35 according the geometrical dimensions of the objects 101 e.g., diameter. For example, in some possible embodiments the printing head assembly 100 is configured such that for cylindrical objects having a diameter of about 50 mm the printing heads 35 are substantially perpendicular to a tangent at the points on the surface of the object under the printing elements 130 of said printing heads 35. For cylindrical objects having a diameter of about 25 mm the angles between the printing heads remains in about 73 degrees and the tangent is not preserved, which in effect results in a small gap between the printing elements 130 of the print heads 35 and the surface of the objects located beneath them. The formation of this gap may be compensated by careful scheduling the time of each discharge of ink through the printing elements 130 according the angular and/or linear velocity of the object and the size of gap formed between the printing elements 130 and the surface of the objects 101.
Angular distribution of the print heads is advantageous since it shortens the printing route (e.g., by about 50%), by densing the number of nozzles per area, and as a result shortening the printing zone 12z (that is very accurate), thereby leading to a total track length that is substantially shortened.
In some embodiments the same belt 33q is used to simultaneously rotate all of the pulleys 33p of the rotatable mandrels arrangement, such that all the mandrels 33 can be controllably rotated simultaneously at the same speed, or same positions, and direction whenever the carriage Ci enters any of the priming, printing, and/or curing, stages of the printing system 17. A gap between pairs of adjacent mandrels 33a and 33b belonging to the different rows r1 and r2 of mandrels may be set to a minimal desirable value e.g., of about 30 mm Considerable efficiency may be gained by properly maintaining a small gap between carriages (e.g., about 1 cm) adjacently located on the lane 10, and setting the gap between pairs of mandrels 33a and 33b belonging to the different rows r1 and r2 (e.g., about 30 mm, resulting in efficiency that may be greater than 85%).
In order to handle the multiple mandrels 33 of each carriage Ci and obtain high printing throughput, in some embodiments all mandrels are rotated with a speed accuracy tolerance smaller than 0.5% employing a single driving unit (not shown). Accordingly, each carriage Ci may be equipped with a single rotation driver and motor (not shown), where the motor shaft drives all of the mandrels 33 using the same belt 33q. In some embodiments the speed of the rotation of the mandrel 33 is monitored using a single rotary encoder (not shown) configured to monitor the rotations of one of the pulleys 33p. In this non-limiting example, each row (r1 or r2) of mandrels 33 includes ten pulleys 33p, each pulley configured to rotate two adjacent mandrels 33a and 33b each belonging to a different row r1 and r2, such that the belt 33q concurrently rotates the ten pulleys, and correspondingly all twenty mandrels 33 of the carriage Ci are thus simultaneously rotated at the same speed and direction.
For example, and without being limiting, the magnetic track 10m used for the linear motors may be organized in straight lines over the straight portions of the lane 10, and with a small angular gap in the curved portion of the lane 10. In some embodiments this small angular gap is supported by special firmware algorithm provided in the motor driver to provide accurate carriage movements. The lane may further include an encoder channel 23 comprising a readable encoded scale 23t on a lateral side of the channel 23. The encoder scale 23t is preferably placed around the entire elliptical lane 10, and the encoder unit 23r attached to the bottom side of each carriage Ci is introduced into the encoder channel 23 to allow real time monitoring of the carriage movement along the lane 10.
High resolution encoding allows closing of position loops in accuracy of about 1 micron. For example, and without being limiting, the improved accuracy may be used to provide carriage location accuracy of about 5 microns, in-position time values smaller that 50 msec in the printing zone 12z, and speed accuracy smaller than 0.5%.
In some embodiments the lengths of the mandrels 33 may be also controllably adjusted according to the geometrical dimensions of the objects 101. For example, and without being limiting, each mandrel 33 may be configured to be inflated by preload pressure applied thereto, and stopped whenever reaching the length of the mandrel 33 i.e., when central shaft 41r elongation reaches the length of the inner space of the object 101. The mandrel elongation mechanism may be deflated by applying pressure higher than the preload for load/unload purpose. Accordingly, each carriage may be configured to controllably inflate/deflate 20 mandrels 33 using a single unit activated by pressure. However, mandrel length adjustment is not necessarily required because digital printing typically does not require full contact with the surface of the object 101 being printed accordingly, providing mechanical support by the mandrels 33 over a partial length of the objects 101 will be sufficient in most cases.
An alternative approach may be to establish direct connection, also called star connection (illustrated by broken arrowed lines) between the control unit 300 and power supply (not shown) units and the carriages Ci on the lane 10. Such direct connection with the carriages Ci may be established using an electrical slip ring and/or wirelessly (e.g., Bluetooth, IR, RF, and the like for the data communication and/or a wireless power supply scheme such as inductive charging).
A switching unit 56s may be use in the control unit 300 for carrying out the printing signals switching (index and encoder signals and other signals) of each carriage Ci to the respective print head units 35 above the carriages Ci traversing the printing zone 12z. The switching unit 56s may be configured to receive all printing signals from all the carriages Ci and switch each one of the received printing signals based on the position of carriages Ci with respect to the relevant print heads 35.
The control unit 300 may be configured to implement independent control of the carriage Ci typically requires monitoring and managing carriage movement and mandrel rotation speeds, and optionally also full stop thereof, at different stages of the printing process carried out over the elliptic lane 10 (e.g., plasma treatment, UV, inspection, printing, loading/unloading). For example, and without being limiting, the control unit 300 may be configured to perform loading/unloading of a plurality of objects 101 on mandrels 33 of one carriage, simultaneously advance another carriage in high speed through the printing zone 12z while printing desired patterns over outer surfaces of a plurality of objects 101 carried by the carriage, and concurrently advance and slowly rotate mandrels of yet another carriage under a UV curing process. The control unit 300 is further configured to guarantee high precision of the carriage movement and mandrel rotation of the carriages Ci traversing the printing zone 12z e.g., to maintain advance accuracy of about 5 microns for high print resolution of about 1200 dpi
In some possible embodiments each wagon is equipped with two driver units 51, two motors 52 (i.e., a linear carriage movement motor and a mandrel rotative motor), and one or more high resolution position encoders 53 (i.e., a linear encoder and a rotative encoder) which are configured to operate as an independent real time motion system. Each one of the drivers is configured to perform the linear or rotary axis movement, where the carriage linear advance and mandrels rotation per carriage (or per mandrel in other models) according to a general control scheme that is optimized to achieve high precision in real time. Accordingly, each carriage can effect both linear and rotatary motion of the objects,
In a possible embodiment the electrical slip ring mechanism 55 is installed at the middle of the elliptic lane 10, and the carriages Ci are electrically linked to the print head assembly via flexible cables (that are in between the carriages) electrically coupled to the electrical slip ring mechanism 55. The electrical slip ring mechanism 55 may be configured to transfer the signals from the carriages Ci to the switching unit 56s of the control unit 300, which generates control signals to operate the printing heads 35 for printing on the objects held by the respective carriages Ci traversing the printing zone 12z. In other possible scenarios the carriages Ci in the printing zone 12z are synchronized to one virtual pulse to create a synchronized fire pulse to the print head units 35 and thereby allow single print head printing on a plurality of different tubes carried by different carriages Ci at the same time.
With this design the printing system is capable of maintaining high efficiency of printing heads utilization in cases wherein the length of the objects 101 is greater than the length of a print head, and maintain high printing efficiency in cases wherein a single print head is printing simultaneously on two different objects 101. The print heads 35 may be organized to form a 3D printing tunnel shape.
Printing systems implementation based on the techniques described herein may be designed to reach high throughputs ranging, for example, and without being limiting, between 5,000 to 50,000 objects per hour. In some embodiments the ability to simultaneously print on a plurality of objects traversing the printing zone by the print head assembly may yield utilization of over 80% (efficiency) of the printing heads.
Functions of the printing system described hereinabove may be controlled through instructions executed by a computer-based control system. A control system suitable for use with embodiments described hereinabove may include, for example, one or more processors 302a connected to a communication bus, one or more volatile memories 56m (e.g., random access memory—RAM) or non-volatile memories (e.g., Flash memory). A secondary memory (e.g., a hard disk drive, a removable storage drive, and/or removable memory chip such as an EPROM, PROM or Flash memory) may be used for storing data, computer programs or other instructions, to be loaded into the computer system.
For example, computer programs (e.g., computer control logic) may be loaded from the secondary memory into a main memory for execution by one or more processors of the control system. Alternatively or additionally, computer programs may be received via a communication interface. Such computer programs, when executed, enable the computer system to perform certain features of the present invention as discussed herein. In particular, the computer programs, when executed, enable a control processor to perform and/or cause the performance of features of the present invention. Accordingly, such computer programs may implement controllers of the computer system.
As described hereinabove and shown in the associated Figs., the present invention provides a printing system for simultaneous printing on a plurality of objects successively streamed through a printing zone, and related methods. While particular embodiments of the invention have been described, it will be understood, however, that the invention is not limited thereto, since modifications may be made by those skilled in the art, particularly in light of the foregoing teachings. As will be appreciated by the skilled person, the invention can be carried out in a great variety of ways, employing more than one technique from those described above, all without exceeding the scope of the invention.
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