PREDICTIVE INK DELIVERY SYSTEM AND METHOD OF USE - Patent application

Abstract

A sub-controller, controller, fluid supply system, and apparatus for printing, as well as a method for printing, are provided. A processor-controlled sub-controller for controlling fluid pressure in one or more droplet ejection heads is provided, wherein the controller is configured to receive a droplet ejection head movement profile for each of the one or more droplet ejection heads, use the respective droplet ejection head movement profiles to determine a respective induced fluid pressure profile at one or more predetermined locations for each of the one or more droplet ejection heads, and generate respective pressure compensation data for each of the one or more droplet ejection heads based on the respective induced fluid pressure profiles and predetermined pressure windows to be maintained at the one or more droplet ejection heads. Also provided is a method for printing using one or more droplet ejection heads fluidically connected to a fluid supply system, the method including receiving a droplet ejection head movement profile, using the respective droplet ejection head movement profiles to determine a respective induced fluid pressure profile at one or more predetermined locations for each of the one or more droplet ejection heads, and generating respective pressure compensation data at the one or more predetermined locations based on the induced fluid pressure profile and the predetermined pressure window.

Description

[Technical field]

[0001] The present disclosure relates to sub-controllers, controllers, fluid supply systems and apparatus for printing, as well as methods for printing, which may be particularly suitable for applications where the droplet ejection head is accelerated / decelerated during printing, or perhaps even subjected to position and orientation changes, multiple directions and degrees of freedom. Such applications may include printing on large or complex shapes, such as walls and inclined surfaces, or 3D objects. [Background technology]

[0002] Droplet ejection heads are now widely used, whether in more traditional applications such as inkjet printing, or in 3D printing or other rapid prototyping techniques. Thus, fluids, e.g., inks, can have novel chemical properties that adhere to new substrates and increase the functionality of the deposited material. Droplet ejection heads have been developed that can be used for industrial applications, e.g., for printing directly onto substrates such as ceramic tiles or textiles, or to form elements such as color filters in LCD or OLED displays for flat screen televisions. Such industrial printing techniques using droplet ejection heads allow for short production runs, customization of products, and even printing of bespoke designs. Thus, it should be appreciated that droplet ejection heads continue to evolve and specialize to be suitable for new and / or increasingly challenging ejection applications. However, despite the numerous developments in the field of droplet ejection heads, there is still room for improvement.

[0003] In most applications, some form of fluid supply system is required to deliver fluid to the droplet ejection head. The purpose of the fluid supply system may be limited to replenishing the fluid ejected by the droplet ejection head, or more complex systems may control the temperature at one or more points within the droplet ejection head, fluid flow rate, pressure, e.g., pressure within the nozzle so that the meniscus position is controlled, etc.

[0004] To ensure reliable performance of the droplet ejection head, it is desirable to maintain a fluid meniscus within the nozzle of the droplet ejection head to prevent fluid from weeping onto the nozzle plate, and to do this, the pressure within the nozzle(s) of the droplet ejection head is kept below atmospheric pressure. This negative pressure is commonly referred to as back pressure or meniscus pressure. It is also desirable to prevent air from being entrapped within the droplet ejection head, which occurs when the back pressure is too low so that the meniscus is pulled back into the droplet ejection head. Therefore, the back pressure must be kept within a window that is generally determined by 1) the pressure at which fluid begins to weep onto the nozzle plate, and / or 2) the pressure at which air is entrapped through the nozzle. Furthermore, variations in back pressure within this window can be sufficient to result in undesirable droplet volumes and velocity variations that can lead to observable defects in the image printed on the substrate. Therefore, for reliable, high-quality droplet ejection, it is often necessary to control the back pressure and keep its variations to a minimum (e.g., for the Xaar 1003 print head, a range of ±2 mbar is specified). Fluctuations in backpressure can come from a variety of sources, such as variations in print duty, and in scanning applications where the droplet ejection head is moved over the substrate, acceleration and deceleration of the droplet ejection head can also lead to fluctuations in backpressure. Therefore, fluid supply systems for droplet ejection heads often include some form of control device or process to respond to and compensate for changes in backpressure. Control can be active (such as a feedback loop) or passive (such as a pressure attenuator / damper).

[0005] In recent years, there has been an increased interest in printing on more complex and / or large shapes, such as three-dimensional objects, or surfaces, such as walls, or objects, such as vehicles, either to cover the entire surface or to decorate and / or customize the surface with images and / or text and / or textiles. Traditionally, many of these are coated using techniques such as spray painting, which may be undesirable due to the release of large amounts of small particles of fluid into the atmosphere, which may be difficult or expensive to deal with to prevent environmental damage or harm to operators. Therefore, printing on complex and / or large shapes and surfaces using droplet ejection heads is of interest due to the ability to print on surfaces in a targeted and controlled manner without the release of large amounts of small particles into the atmosphere. Such techniques may also reduce the ink / fluid volume requirements and, therefore, costs. Furthermore, printing techniques may enable the use of multiple colors or fluid types at once, and the printing of complex print jobs in a limited number of passes.

[0006] Printing on large / complex shapes and surfaces may require the use of, for example, multi-axis machines or industrial robots such as gantry systems or robotic arms. Movement of the droplet ejection head in such applications may lead to large and rapid pressure changes that existing control methods may not be able to compensate for, making it difficult to prevent droplet ejection head weeping or air entrapment or causing observable defects in the printed image. It is an object of the present invention to prevent such disadvantages.

[0007] FIG. 10a illustrates printing onto a substrate 81 using a moving droplet ejection head 60 in a scanning application. In a scanning application, the droplet ejection head 60 is moved back and forth in only one direction, while the substrate 81 is moved underneath the droplet ejection head 60 in a substrate movement direction 83 that is perpendicular to the droplet ejection head movement direction 84. In operation, the idle droplet ejection head 60 is accelerated to reach a certain printing speed before moving over the substrate (FIG. 10a(i)) to print a first swath 82(i). After completion of the first print swath, the droplet ejection head 60 is decelerated and then accelerated in the opposite direction to print the next swath 82(ii), as shown in FIG. 10a(ii). Acceleration and deceleration of the droplet ejection head 60 will induce pressure changes due to inertial forces acting on the fluid, but the effect is typically limited by implementing the acceleration / deceleration in areas outside the print area, for example to either side of the substrate 81.

[0008] FIG. 10b illustrates printing on a three-dimensional (3D) object 80 using a moving droplet ejection head 60. For the scanning application illustrated in FIG. 10a, the droplet ejection head 60 is accelerated and decelerated to obtain the correct location and velocity at various parts of the object 80. In addition, the orientation of the droplet ejection head 60 will have to change to keep the droplets oriented toward the surface of the object 80. However, unlike scanning applications, such velocity and orientation changes cannot be restricted to non-printed areas, and the induced pressure changes need to be compensated for in order to keep the meniscus within a desired position within the nozzle. To do this, the back pressure needs to be controlled, as discussed above.

[0009] 11a-c illustrate the droplet ejection head 60 in three different positions and illustrate how a change in the orientation of the droplet ejection head 60 changes the height of the fluid column acting on the fluid at the nozzle plate 61 of the droplet ejection head 60 (Δh), and therefore the induced pressure 170 (ΔP). In FIGS. 11a and 11b, the droplet ejection head 60 is rigidly fixed to the sensor / controller 50 / 10, whereas in FIG. 11c, the droplet ejection head 60 is allowed to rotate relative to the sensor / controller 50 / 10 and move along a curved path 160. The height difference Δh3 in FIG. 11c is shown for a given time instance as the droplet ejection head 60 moves along the curved path 160.

[0010] ΔP=ρgΔh, where ρ is the density of the fluid (typically around 1000 kg / m 3 ), and Δh is the height of the fluid column between the nozzle plate 61 and a given location 51 on the sensor / controller 50 / 10. 2 If we assume that [Table 1]

[0011] It can therefore be seen from the above that a printing strategy that involves moving one or more droplet ejection heads 60 to address three-dimensional objects, or surfaces that are not horizontal, can lead to induced pressure changes as the fluid column height Δh varies, which can cause changes in backpressure and potentially lead to the meniscus moving outside of its desired range of positions within the nozzle. In, for example, gravity-fed systems that are known to actively control backpressure, the level of fluid in the reservoir can be adjusted to control the height Δh of the fluid column, as measured between the fluid level in the reservoir and the nozzle plate 61. In other systems, such as those shown in Figures 11a-c, the critical fluid column height Δh is the height between the nozzle plate 61 and a predetermined location 51 where the control device 10 is located (shown in Figures 11a-c). The pressure is measured at the predetermined location 51 and can be adjusted using the control device 10 to maintain the backpressure within a desired range. However, if the droplet ejection head 60 is rapidly accelerated / decelerated or has a change in orientation or direction, adjusting the backpressure in response to the measured pressure change may be too slow, leading to undesirable variations in droplet ejection performance that may lead to observable defects in the printed image on the object / substrate at best, or to weeping or air entrapment at worst, which may lead to nozzle failure if the air cannot be removed from the droplet ejection head. The present invention aims to provide more effective pressure prediction to prevent the above defects, and to provide more effective pressure control by using the pressure prediction, as well as fluid supply systems, controllers, and apparatus for implementing the pressure prediction in a correction method. Summary of the Invention

[0012] Aspects of the invention are set out in the accompanying independent claims, and details of particular embodiments of the invention are set out in the accompanying dependent claims.

[0013] According to a first aspect of the present disclosure, there is provided a processor-controlled sub-controller for controlling fluid pressure in one or more droplet ejection heads, the sub-controller comprising: receiving a droplet ejection head movement profile for each of the one or more droplet ejection heads; determining a respective induced fluid pressure profile at one or more predetermined locations for each of the one or more droplet ejection heads using the respective droplet ejection head movement profiles; generating respective pressure compensation data for each of the one or more droplet ejection heads based on the respective induced fluid pressure profile and a predetermined pressure window to be maintained in the one or more droplet ejection heads.

[0014] According to a second aspect of the present disclosure, there is provided a processor-controlled controller configured to control a printing process including controlling a fluid pressure in one or more droplet ejection heads, the controller comprising: receiving a printing policy; calculating a respective drop ejection head movement profile for each of the one or more drop ejection heads using the print strategy.

[0015] According to a particular embodiment there is provided a controller according to the second aspect further configured to send one or more droplet ejection head movement files to a sub-controller according to the first aspect.

[0016] According to certain other embodiments there is provided a controller according to the second aspect further configured to incorporate functionality of a sub-controller according to the first aspect.

[0017] According to a third aspect of the present disclosure, there is provided a fluid supply system comprising a fluid supply unit and a sub-controller according to the first aspect or a controller according to the second aspect, the fluid supply unit comprising a fluid reservoir and one or more fluid supply paths, the one or more fluid supply paths being configured to connect to the fluid supply unit at a first end and to connect to one or more droplet ejection heads at a second end.

[0018] According to a particular embodiment there is provided a fluid supply system according to the third aspect, the fluid supply system further comprising one or more control devices located at one or more predetermined locations, the one or more control devices being in communication with a sub-controller according to the first aspect and / or a controller according to the second aspect.

[0019] According to certain embodiments there is provided a fluid supply system according to a third aspect, further comprising one or more pressure sensors located to measure pressure at one or more predetermined locations and in communication with the sub-controller according to the first aspect and / or the controller according to the second aspect to provide pressure measurements thereto.

[0020] According to a fourth aspect of the present disclosure, there is provided an apparatus comprising a fluid supply system according to the third aspect, the apparatus further comprising one or more droplet ejection heads fluidly connected to the fluid supply system at a second end of the one or more fluid supply paths, and one or more moving devices configured to mount one or more of the one or more droplet ejection heads thereon.

[0021] According to a fifth aspect of the present disclosure there is provided a method of printing using one or more droplet ejection heads fluidly connected to a fluid supply system according to the third aspect, or an apparatus according to the fourth aspect, the method comprising: receiving a droplet ejection head movement profile; determining a respective induced fluid pressure profile at one or more predetermined locations for each of the one or more droplet ejection heads using the respective droplet ejection head movement profiles; generating pressure correction data at one or more predefined locations based on the induced fluid pressure profile and predefined pressure windows; generating a respective pressure compensation file(s) for the one or more predetermined locations based on the pressure compensation data.

[0022] According to one embodiment, generating the pressure compensation file(s) may further include adjusting for more predictable pressure variations in the fluid delivery system.

[0023] Alternatively, or in addition, the method may further include adjusting the pressure in the fluid supply system if a difference exists between the sensed pressure and the predetermined pressure window. [Brief description of the drawings]

[0024] [Figure 1] A processor, a fluid supply system, a movement device, and a droplet ejection head are illustrated, the fluid supply system comprising a fluid supply, a sub-controller controlled by the processor, and a control device. [Figure 2a] 1 illustrates a droplet ejection head and a sensor / controller moving together in a semicircular path. [Figure 2b] FIG. 2b is a representative diagram of an induced pressure profile and a pressure regulation profile for the droplet ejection head and sensor / controller of FIG. 2a. [Diagram 3] 2 illustrates process steps for the sub-controller of FIG. 1; [Figure 4] A processor, fluid supply system, movement device, and droplet ejection head similar to those in FIG. 1 are shown, further including a control device and a pressure sensor in the fluid reservoir. [Diagram 5] 5 illustrates process steps for the sub-controller of FIG. 4. [Figure 6] 1 illustrates a through-flowable fluid supply system including a control device, a sensor, a sub-controller, and a master controller, the through-flowable fluid supply system being connected to a droplet ejection head. [Figure 7] 7 illustrates process steps for the controller of FIG. 6. [Figure 8]1 illustrates an apparatus for addressing a 3D object, the apparatus comprising a fluid supply system, a movement device, and a droplet ejection head connected to the fluid supply system and mounted on the movement device. [Figure 9] 1 illustrates a fluid delivery system comprising a control device, a master controller, and a fluid delivery system connected to a droplet ejection head. [Figure 10a] 1 illustrates printing onto a moving substrate using a moving droplet ejection head. [Figure 10b] 1 illustrates printing onto a 3D object using a moving droplet ejection head. [Figure 11a] 1 illustrates a vertically oriented droplet ejection head and sensor / controller. [Figure 11b] 1 illustrates a horizontally oriented droplet ejection head and sensor / controller. [Figure 11c] 1 illustrates a droplet ejection head that rotates independently of the sensor / controller.

[0025] It should be noted that the drawings are not to scale and that certain features may be shown in an exaggerated size so that they can be more clearly seen. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] DETAILED DESCRIPTION OF THE DRAWINGS The embodiments and various implementations thereof will now be described with reference to the drawings, in which like reference numerals are used for like elements throughout the following description, where appropriate.

[0027] 1 illustrates a processor 35, a fluid supply system 40, a moving device 70, and a droplet ejection head 60 mounted on the moving device 70, where the fluid supply system 40 comprises a fluid supply 46, a sub-controller 20 controlled by the processor 35, and a control device 10. The fluid supply 46 comprises a fluid reservoir 41 and a fluid supply path 42, where a first end of the fluid supply path 42 is connected to the fluid reservoir 41 and a second end of the fluid supply path 42 is configured to connect to the droplet ejection head 60 such that, during operation, the fluid supply 46 delivers fluid (such as ink) from the fluid reservoir 41 through the fluid supply path 42 to the droplet ejection head 60, as indicated by arrow 44. It can be appreciated that in other configurations, the fluid supply may include further components required for operation of the fluid supply, such as pumps, dampers, flow meters, flow regulators, additional intermediate reservoirs, valves, heaters / coolers, temperature sensors, degassers, etc. Processor 35 is configured to control sub-controller 20, droplet ejection heads 60, movement devices 70, and any of its components such as fluid reservoirs 41, if present, pumps, flow regulators, etc. Processor 35 may also include means for an operator to interface with it and regulate the printing process, for example, processor 35 may be a personal computer, or any other suitable device.

[0028] The control device 10 is part of a fluid supply system located within or adjacent to the fluid supply path 42 such that the control device 10 is fluidly connected to the fluid supply path 42 such that the pressure of the fluid supply 46 can be controlled. In this embodiment, the control device 10 is located proximate to the droplet ejection head 60. The sub-controller 20 is configured to control the control device 10. The sub-controller may be a system-on-chip module. The sub-controller may include software elements and / or FPGA logic.

[0029] Reference is now made to Figure 2a, which illustrates a droplet ejection head 60 and control device 10 moving together such that a movement profile can be derived from (e.g., calculated based on) a semicircular path 160 traced by the droplet ejection head 60. Figure 2b is a schematic diagram of how a predicted induced fluid pressure profile 170 may vary when the height Δh of the fluid column between the nozzle plate 61 and the predetermined location 51 varies with time as the droplet ejection head 60 of Figure 2a moves along the semicircular path 160. Figure 2b also illustrates a representation of a corrected pressure profile 200, where the induced pressure profile 170 has been corrected to remain within a predetermined pressure window 150.

[0030] As already explained, methods exist for adjusting the fluid supply in response to measurements of induced pressure changes, but in applications where the induced pressure is changing rapidly (due to changes in orientation and / or position and / or velocity), such methods may be too slow to respond and therefore unable to control the pressure at the nozzle plate 61 within a predefined pressure window 150 to prevent weeping / air entrapment or undesirable variations in droplet size and velocity and therefore print quality / appearance. The present application compensates for some / all of the induced pressure changes by determining (predicting) them before executing the print strategy, and then using the predicted induced pressure changes and the predefined pressure window 150 to calculate the desired pressure compensation scheme. An apparatus such as that illustrated in FIG. 1 is then used during printing, where the control device 10 adjusts the pressure of the fluid supply 46 over time to compensate for the predicted pressure changes as the print strategy is executed and as the print progresses. 3, which illustrates a series of process steps 140 that may be implemented within sub-controller 20 when provided with a movement profile 111 from processor 35. Thus, when droplet ejection head movement profile 111 is provided to sub-controller 20 by processor 35, sub-controller 20 may: determining 115 an induced fluid pressure profile 170 at a given location 51 for the droplet ejection head 60 using the droplet ejection head movement profile 111; determining (step 120) pressure correction data for the droplet ejection head 60 based on the induced fluid pressure profile 170 and a predetermined pressure window 150 to be maintained at the droplet ejection head 60.

[0031] The sub-controller 20 is then configured to generate a pressure compensation file 180 for the droplet ejection head 60 (step 125) and then provide the pressure compensation file 180 to an external device, or use the pressure compensation file 180 to directly control the control device 10 (step 126), or supply the pressure compensation file to the control device 10, which may have an internal controller, to adjust and control the pressure over time in the fluid supply 46. Locating the sub-controller 20 in close proximity to the control device 10 may be desirable to ensure that communications sent to / from the control device are transmitted and received on short timescales.

[0032] The predetermined pressure window 150 may be a meniscus pressure window, whereby the upper limit is the pressure at which the nozzle plate 61 begins to wet (Pm=0 mbar) and the lower limit is the pressure at which air is entrapped through the nozzle. These limits depend on various factors, such as the type of droplet ejection head used, the nozzle size and shape (nozzle layout), and the properties of the fluid used. It may also be appreciated that a predetermined pressure window 150 narrower than the meniscus pressure window may be used, for example, if pressure variations within the meniscus pressure window are significant enough to lead to undesirable variations in droplet size and velocity, and therefore print appearance.

[0033] It may further be appreciated that the predetermined location 51 is a location where control will be applied to adjust the fluid pressure to maintain a predetermined pressure window 150 at the droplet ejection head 60. It may further be appreciated that depending on where and how such control is applied, the predetermined location 51 may be a fixed location or a moving location. For example, the control device 10 may be located on the moving device 70 and move with the droplet ejection head 60, or the two may move independently of one another, or only the droplet ejection head may move, but the location of the control device is fixed. However, as already explained, with reference to Figures 11a-11c, it is the height Δh of the fluid column between the predetermined location 51 and the nozzle plate 61 that is important when determining the relative movement, and therefore the induced pressure 170.

[0034] It may be understood that there are several ways in which the pressure compensation data may be determined, for example, the sub-controller 20 may perform calculations to generate the pressure compensation data. This may be calculated using physical laws, or the sub-controller 20 may use a look-up table or have a comparator to generate the respective pressure compensation data. The comparator may compare the determined induced fluid pressure with a predetermined or pre-stored induced pressure and output the pressure compensation data based on the comparison. Furthermore, if the sub-controller uses a look-up table, this may be pre-determined and coded into the sub-controller 20 or provided to the sub-controller along with the movement profile 111. Alternatively, the sub-controller 20 may use a pre-calibration process to generate the induced pressure profile 170 and / or pressure compensation data, for example, the device may be used to perform a calibration sweep to generate a look-up table, or the device may be used to follow the droplet ejection head path using the movement profile 111, so that the induced pressure profile 170 is measured and recorded, and compared to a predetermined induced pressure profile, from which the pressure compensation data may be calculated or determined. As an example, one or more pressure sensors 50 may be moved along the path that the droplet ejection head will be traversed, and pressure variations may be measured. When performing such a calibration sweep using one or more pressure sensors 50 in this manner, it may be understood that the sensors must be integrated such that the measured pressures represent the pressures in the nozzle. Alternatively, any other suitable method may be used to determine the pressure compensation data. The pressure compensation data may then be used to generate a pressure compensation file 180, and the sub-controller 20 may be further configured to control the control device 10 located at the predetermined location 51 using the pressure compensation file 180 to dynamically adjust the fluid pressure of some or all of the fluid supply system 40 to maintain a predetermined pressure window 150 in the droplet ejection head 60 when the droplet ejection head 60 and the control device 10 are fluidly connected to the fluid supply 46.

[0035] It can be appreciated that in many embodiments it may be convenient to locate the control device 10 near the droplet ejection head 60. However, in other embodiments it may be preferable to locate the control device 10b within the fluid reservoir 41, as illustrated by the dotted lines in Fig. 4, and further, more than one control device 10 may be desirable in some embodiments, as illustrated in Fig. 4. For example, in Fig. 4 at least one of the control devices is either located adjacent to and fluidly connected to the fluid reservoir 41 or located within the fluid reservoir 41, and at least one of the control devices 10 is fluidly connected to the fluid supply path 42. Additionally, at least one of the control devices 10 is located adjacent to and fluidly connected to a second end of the fluid supply path 42. For example, more than one control device 10 may be desirable when pressure compensation data may be split into global and local data, so that slower changes in droplet ejection head height may be compensated for globally by adjusting the pressure of fluid in the fluid supply 46 by controlling the fluid in the fluid reservoir 41, while more rapid changes (e.g., in the orientation of the print head at a given height) are controlled locally using a control device 10 located proximate to the droplet deposition head 60. In such a situation, the pressure compensation file 180 may be two pressure compensation files 180, one for each control device 10. Additionally, it should be understood that there may be other sources of pressure fluctuations in the fluid supply system 40, some of which may also be predictable / calculatable / measurable / calibrated in advance, such as changes in fluid demand as print load or duty varies, or variations due to depletion of the fluid reservoir 41 causing hydrostatic pressure fluctuations or known performance of the pump(s) in the fluid supply system 40, pressure fluctuations due to pipe lengths, or viscous damping, etc.The process steps in such a case may be similar to those illustrated in FIG. 5, which is similar to those of FIG. 3, except that additional information, such as pump performance, fluid demand data, reservoir depletion information, etc., is provided to the sub-controller 20 to determine more induced pressure changes 170 and generate pressure compensation file(s) 180 that compensate for more factors.

[0036] FIG. 4 also illustrates the fluid supply system 40 further comprising a pressure sensor 50 located proximate the droplet ejection head 60 to measure pressure at or adjacent a predetermined location adjacent the droplet ejection head 60. Additionally, the sensor 50 is in communication with the sub-controller 20 to provide it with a pressure measurement. Additionally, it can be understood that if the sensor 50 measures pressure at a location adjacent to but not at the predetermined location, the sensor providing the pressure measurement or the sub-controller 20 / controller 30 can adjust the pressure measurement to account for the difference in location. It can be understood that there can be more than one sensor 50 in the fluid supply system 40, for example, one adjacent to each control device 10 present in the system, or one adjacent to each droplet ejection head 60 (if applicable). In other words, the pressure sensor 50 is connected to and controlled by the sub-controller 20, such that the sub-controller 20 is configured to receive one or more pressure measurements of pressure in the fluid supply path 42 measured at or adjacent to the predetermined location 51. Such a sensor 50 may provide a check that the control device 10 is performing as expected and regulating the fluid pressure as desired. Alternatively, the sensor 50 may also detect unpredictable pressure fluctuations in the fluid supply system 40. These may be due to noise or vibration from the environment in which the system is operating, or the like from a moving device, or any other unpredictable pressure fluctuation source. In some implementations, it may be desirable to have a system that can adjust for both predictable induced pressure fluctuations and unpredictable pressure fluctuations, and accordingly, the sub-controller 20 may be further configured to determine one or more responsive pressure compensations based on at least one or more pressure fluctuation measurements, the predefined pressure window 150, and / or the respective pressure compensation data. The sub-controller 20 may then be further configured to control one or more of the control devices 10 using the responsive pressure compensations to dynamically adjust the fluid pressure in some or all of the fluid supply system 40 to maintain the predefined pressure window 150 at the droplet ejection head 60.The use of a sub-controller 20 located within the fluid supply system 40 may be desirable in such a scenario to ensure a rapid response to any measured pressure fluctuations.

[0037] Reference is now made to Figure 6, which illustrates a processor 35 and an apparatus for printing 90 comprising a fluid supply system 40 similar to that already described, a droplet ejection head 60 connected to the fluid supply system 40 at a second end of a fluid supply path 42, and a movement device 70 to which the droplet ejection head 60 is mounted. The main difference from the already described configurations is that Figure 6 illustrates a flow-through system, which is a fluid supply system 40 comprising one or more fluid supply paths 42 and one or more fluid return paths 43, such that a fluid return path 43 is connected at its first end to a fluid reservoir 41 and at its second end to the droplet ejection head 60. By flow-through, it is meant that fluid circulates around the fluid supply system 40 and through the droplet ejection head 60, as indicated by the return flow arrows 45, with a proportion of the fluid being drawn out and ejected from the nozzles in the droplet ejection head 60, and the remaining proportion being returned to the fluid reservoir 41. Further, it can be seen that the control device 10a located adjacent the droplet ejection head 60 is configured to control fluid pressure in either the fluid supply path 42 and / or the fluid return path 43, such that at least one of the control devices is located adjacent a second end of one of the one or more fluid return paths, such that a first end of the fluid return path is located at the fluid reservoir 41 and a second end is adjacent the droplet ejection head 60.

[0038] 6 further differs from the previously described configurations in that the fluid supply system 40 includes a controller 30 and a sub-controller 20. It can be seen that the controller 30 of FIG. 6 performs some of the steps performed by the processor 35 in the previously described configurations. Thus, for example, in FIG. 6 the controller 30 is a processor-controlled controller 30 configured to control the printing process, including controlling the fluid pressure in the droplet ejection heads 60; receiving a print policy from the processor 35; · Calculating a droplet ejection head movement profile 111 for the droplet ejection head 60 using the print strategy.

[0039] The controller 30 is then configured to send a droplet ejection head movement profile 111, which may be substantially as described herein, to the sub-controller 20. Figure 7 illustrates the main steps in the process: Step 100 - receiving print job data; Step 105 - Using the print job data, determine a print direction 106; Step 110 - determining a movement profile 111; Performing step 140 (as previously described with reference to FIG. 3) to determine the pressure compensation file 126; Step 130 - Execute the print job.

[0040] In the apparatus 90 of FIG. 6, the controller 30 sends the movement profile to the sub-controller 20 to perform step 140. Once the pressure compensation file 126 is determined by the sub-controller 20, the controller 30 then executes the print job. This means that the controller 30 may be further configured to control the movement device 70 to move the droplet ejection head 60 according to the droplet ejection head movement profile 111, and the print strategy may include print commands, and the controller 30 may be further configured to control the droplet ejection head 60 to execute the print commands. Still further, the print strategy may include fluid requirements, and the controller 30 may be further configured to control the fluid supply system 40 and / or the fluid reservoir 41 to meet the fluid requirements. It can be understood that the above process is one particular portion of the necessary tasks or steps, and that in other embodiments, the balance of tasks may be distributed differently between the processor 35, the controller 30, and the sub-controller 20.

[0041] Considering now FIG. 8, this illustrates the processor 35 and the apparatus 90. The apparatus 90 is similar to that described in FIG. 6. For simplicity, the fluid supply system is illustrated in simplified form with arrows indicating the fluid supply path. In this configuration, the movement device 70 is shown generally as a robotic arm 72, and the droplet deposition head 60 is shown disposed on a mount 71 on the robotic arm 72 and addressing the 3D object 80. It can be seen that the use of the robotic arm 72 allows the droplet ejection head to address bumps and contours on the surface or non-flat surface of the 3D object 80. Thus, the apparatus 90 comprises a movement device 70 configured to be movable in more than two directions and / or orientations, and further, the movement device 70 is a robotic arm 72 having multiple degrees of freedom. It can be understood that the movement device 70 can be any suitable device or mechanism having multiple degrees of freedom. The main difference with the configuration illustrated in FIG. 6 is that in the configuration of FIG. 8, the sub-controller 20 is omitted and the controller 30 is configured to incorporate the functionality of the sub-controller 20. It can be understood that depending on the requirements of a particular implementation, the fluid supply system 40 may include one or more control devices 10 located at one or more predetermined locations 51, and the control device 10 may communicate with the sub-controller 20 and / or the controller 30.

[0042] Referring now to FIG. 9, this illustrates a similar configuration to the previous figures, including an apparatus 90 and a processor 35. The apparatus 90 includes similar features to the above embodiment, but instead of one droplet ejection head 60, there are two, both mounted on the same moving device 70. In other embodiments, there may be multiple droplet ejection heads 60, all mounted on the same moving device 70, or there may be one droplet ejection head 60 per moving device 70 or robotic arm 72, or there may be any other configuration of a row or array of droplet ejection heads 60 mounted on one or more moving devices 70, including multiple droplet ejection heads 60 and multiple moving devices 70, where there is more than one droplet ejection head 60 per moving device 70. Like FIG. 8, FIG. 9 includes a controller 30, but not a sub-controller 20, so that the controller 30 includes the functionality of the sub-controller 20. The controller may also include additional functionality. 9 is in communication with and controls the droplet ejection heads 60, the movement device 70, and the fluid supply 41 incorporating the control device 10b. There are also three further control devices, one (10a) located adjacent the point where the fluid supply path 42 splits into two sub-paths 42-1 and 42-2, and one (10-1, 10-2) located adjacent each droplet ejection head 60, with each of the two sub-paths 42-1, 42-2 connected to the droplet ejection head 60 at their respective second ends. It may be appreciated that the fluid supply path 42 may split into more sub-paths if more than two droplet ejection heads 60 are present, or a separate fluid supply path 42 a, b, c...n may be provided for each droplet ejection head 60 or for each group of droplet ejection heads 60, with similar fluid supply path division points in the latter such that each droplet ejection head 60 is connected to and supplied with fluid by the fluid supply system 40. Thus, the fluid supply system 40 may comprise multiple fluid supply paths 42 and multiple control devices 10.9 illustrates a control device (10-1 and 10-2) for each droplet ejection head 60, it can be understood that a 1:1 relationship may not be required and a single control device 10 may, for example, control several droplet ejection heads 60, for example if they are closely grouped and / or in a fixed positional relationship between the droplet ejection heads 60. One or more control devices 10 may be configured to be controllable to dynamically adjust fluid pressure within some or all of the fluid supply system 40 during operation, and the control devices 10 may be controlled by a controller 30, as in FIG. 9, or by a sub-controller as illustrated in other implementations.

[0043] The configurations and embodiments described herein may be used in conjunction with methods for printing on vertical or non-flat or three-dimensional surfaces, or on complex shapes, such as three-dimensional shapes or objects. Such methods may use one or more droplet ejection heads 60 fluidly connected to a fluid delivery system 40 as described herein, and the methods may include: receiving one or more droplet ejection head movement profiles 111; determining a respective induced fluid pressure profile at one or more predetermined locations for each of the one or more droplet ejection heads using the respective droplet ejection head movement profile 111; generating pressure compensation data at the one or more predefined locations based on the induced fluid pressure profile and the predefined pressure window.

[0044] The predetermined pressure window may depend on the droplet ejection head used, the fluid used, the distance and / or angle between the fluid supply system 40 and the droplet ejection head 60, the fluid supply pipe diameter, and any other components that the fluid supply system 40 may comprise, and further, the predetermined pressure window may be a meniscus pressure window or a (possibly narrower) pressure range to optimize printing performance. The method of printing may further include controlling the fluid pressure in the fluid supply system 40 during operation, thereby maintaining the predetermined pressure window 150 in the one or more droplet ejection heads 60, while receiving print commands and executing the print commands, whereby the droplet ejection head(s) 60 print the image on the substrate, while moving the one or more droplet ejection heads 60 according to a movement profile 111 of the droplet ejection heads 60.

[0045] If other predictable pressure variations are present within the fluid supply system 40, it may be appreciated that generating the pressure compensation data may further include adjusting for the further predictable pressure variations within the fluid supply system 40. Depending on the embodiment, one or more ways of calculating the pressure compensation data may be implemented, for example, a method of printing may include one or more of the following: generating the pressure compensation data includes performing calculations, e.g., using formulas and / or laws of physics; generating the pressure compensation data includes using a lookup table; generating the pressure compensation data includes using a comparator; Generating the pressure correction data includes performing a pre-print calibration process.

[0046] Once the pressure compensation data has been determined, the method of printing may include controlling the fluid pressure in the fluid supply system 40 during operation by dynamically adjusting the pressure in the fluid supply system 40 using one or more control devices 10 and the pressure compensation data, which may be provided as a pressure compensation file.

[0047] The method of printing may further include sensing the pressure in the fluid supply system 40 at one or more locations, for example using one or more sensors 50 at one or more predefined locations 51. This may be performed as a check that the control device is correctly compensating for induced pressures in the fluid supply system, or the sensors may additionally / alternatively be used to measure unpredictable pressure fluctuations in the fluid supply system 40 due to, for example, environmentally induced vibrations or vibrations from components of the apparatus 90. Hence, the method may further include adjusting the pressure in the fluid supply system 40 if there is a difference between the sensed pressure and a predefined pressure window.

[0048] It can be understood that to determine the movement profile 111, a print strategy may need to be determined, which may be calculated / defined within the processor 35. For example, the method of printing may involve determining or receiving print job data and using the print job data, such that determining the print strategy includes using one or more of a print grid, a print resolution, a swath profile, a number of layers, and stitching. Once it is determined what is to be printed, the method of printing further includes determining a print strategy, where determining the print strategy includes calculating a droplet ejection head movement profile 111 for one or more droplet ejection heads 60. It can be understood that such calculations may include calculating a droplet ejection head path, a droplet ejection head velocity, a droplet ejection head acceleration or deceleration, and / or a droplet ejection head orientation. Determining the print strategy may also include determining print commands and fluid requirements.

[0049] The controller may be a computing device, a microprocessor, an application specific integrated circuit (ASIC), a system-on-chip module including processor elements and FPGA logic, or any other suitable device for controlling the functions of various components of the fluid delivery system and / or droplet ejection head. The processor may be, for example, a microprocessor or a computer.

Claims

1. A processor-controlled sub-controller (20) for controlling fluid pressure within one or more droplet ejection heads (60), comprising: Prior to executing the print policy (106), the sub-controller (20) receiving a droplet ejection head movement profile (111) for each of the one or more droplet ejection heads (60), the droplet ejection head movement profile (111) being determined using the print strategy (106); determining a respective induced fluid pressure profile (170) at one or more predetermined locations (51) for each of the one or more droplet ejection heads (60) using the respective droplet ejection head movement profile (111); generating respective pressure compensation data for each of the one or more droplet ejection heads based on the respective induced fluid pressure profile and a range of predetermined pressure values ​​to be maintained at the one or more droplet ejection heads; generating a respective pressure compensation file (180) using the respective pressure compensation data for each of the one or more droplet ejection heads (60), the one or more predetermined locations (51) being positions that will be controlled to adjust fluid pressure to maintain the predetermined pressure value range (150) for the one or more droplet ejection heads (60); A sub-controller (20) configured to:

2. the sub-controller (20) is configured to perform calculations to generate the respective pressure compensation data, and / or the sub-controller (20) is configured to generate the respective pressure compensation data using a look-up table, and / or the sub-controller (20) is configured to generate the respective pressure compensation data using a comparator. The sub-controller (20) of claim 1.

3. the sub-controller (20) is configured to generate the induced fluid pressure profile and / or the respective pressure correction data using a pre-calibration process; A sub-controller (20) according to claim 1 or 2.

4. and further configured to use the pressure compensation file (180) to control the one or more control devices (10) located at the one or more predetermined locations (51) to dynamically adjust the fluid pressure in some or all of the fluid supply system (40) to maintain the predetermined pressure value range (150) at the one or more droplet ejection heads (60) when the one or more droplet ejection heads (60) and one or more control devices (10) are fluidly connected to a fluid supply system (40). A sub-controller (20) according to any one of claims 1 to 3.

5. further configured to receive one or more pressure measurements measured at the one or more predetermined locations (51); the sub-controller (20) is optionally further configured to determine one or more respective pressure compensations based on at least one of the pressure measurements and the predetermined pressure value range (150) and / or the respective pressure compensation data, and the sub-controller (20) is further configured to control the one or more control devices (10) located at the one or more predetermined locations (51) using the respective pressure compensations to dynamically adjust the fluid pressure in some or all of a fluid supply system to maintain the predetermined pressure value range (150) at the one or more droplet ejection heads (60) when the one or more droplet ejection heads (60) and one or more control devices (10) are fluidly connected to the fluid supply system (40). A sub-controller (20) according to claim 4.

6. A processor-controlled controller (30) configured to control a printing process including controlling fluid pressure within one or more droplet ejection heads (60), The controller (30) receives a printing policy; calculating a respective droplet ejection head movement profile (111) for each of the one or more droplet ejection heads (60) using the print strategy; further configured to transmit the droplet ejection head movement profile (111) to a sub-controller (10) according to any one of claims 1 to 5, or incorporating the functionality of a sub-controller (10) according to any one of claims 1 to 5; The controller (30) is configured to:

7. further configured to control one or more movement devices (70) to move the one or more droplet ejection heads (60) according to the droplet ejection head movement profile (111), the one or more droplet ejection heads (60) being mounted on the one or more movement devices (70); The controller (30) of claim 6.

8. the print policy includes a print command; the controller (30) is further configured to control the one or more droplet ejection heads (60) to execute the print commands; the printing strategy includes fluid requirements; the controller (30) is further configured to control a fluid supply (41) to meet the fluid requirements. A controller (30) according to claim 6 or 7.

9. A fluid supply system (40) comprising a fluid supply unit (41) and a sub-controller (20) according to any one of claims 1 to 5 and / or a controller (30) according to any one of claims 6 to 8, the fluid supply (41) comprises a fluid reservoir (41) and one or more fluid supply paths (42); the one or more fluid supply paths (42) are configured to connect at a first end to the fluid reservoir (41) and to connect at a second end to one or more droplet ejection heads; The fluid supply system (40) is optionally configured as a once-through system comprising the one or more fluid supply paths (42) and one or more fluid return paths (43). A fluid supply system (40).

10. the fluid supply system (40) further comprising one or more control devices (10) located at the one or more predetermined locations (51); one or more of said control devices (10) in communication with said sub-controller (20) and / or said controller (30); one or more of the control devices (10) are configured to be controllable to dynamically adjust the fluid pressure within some or all of the fluid supply system (40) during operation; The control device (10) is controlled by the sub-controller (20) and / or the controller (30); The fluid delivery system (40) of claim 9.

11. the one or more predetermined locations (51) include one or more of: a location adjacent to and fluidly connected to the fluid reservoir (41); and / or a location located within the fluid reservoir (41); and / or a location located within or fluidly connected to one of the one or more fluid supply paths (42); and / or a location located adjacent to or fluidly connected to the second end of the one or more fluid supply paths; and / or a location located adjacent to or fluidly connected to the second end of the one or more fluid return paths (43); A fluid supply system (40) according to claim 9 or 10.

12. one or more pressure sensors (50) positioned to measure pressure at the one or more predetermined locations (51) within the fluid supply system (40); the one or more sensors (50) in communication with the sub-controller (20) and / or the controller (30) to provide pressure measurements thereto; A fluid supply system according to any one of claims 9 to 11.

13. A method of printing using one or more droplet ejection heads (60) fluidly connected to a fluid delivery system (40) according to any one of claims 9 to 12, and one or more movement devices (70), comprising the steps of: the one or more movement devices (70) are configured to mount one or more of the one or more droplet ejection heads (60); Prior to executing the print policy (106), the method further comprises: receiving a droplet ejection head movement profile (111); determining a respective induced fluid pressure profile (170) at one or more predetermined locations (51) for each of the one or more droplet ejection heads (60) using the respective droplet ejection head movement profile (111); generating respective pressure correction data based on the respective induced fluid pressure profiles and predetermined pressure value ranges (150) to be maintained at the one or more droplet ejection heads (60); generating a respective pressure compensation file (180) for the one or more predetermined locations (51) based on the respective pressure compensation data; controlling the fluid pressure in the fluid supply system (40) during operation when printing, thereby maintaining the predetermined pressure value range (150); Including, a method for printing.

14. generating the respective pressure compensation data includes performing a calculation, and / or generating the respective pressure compensation data includes using a look-up table, and / or generating the respective pressure compensation data includes using a comparator, and / or generating the induced fluid pressure profile and / or the respective pressure compensation data includes performing a pre-print calibration process. The method of claim 13.

15. the method including sensing the pressure in the fluid delivery system (40) at the one or more predetermined locations; The method further includes adjusting the pressure in the fluid supply system (40) if there is a difference between the sensed pressure and the predetermined pressure value width (150). The method according to claim 13 or 14, which refers to claim 12.

Images