WO2014000801A1

WO2014000801A1 - Drop tail reduction waveforms

Info

Publication number: WO2014000801A1
Application number: PCT/EP2012/062594
Authority: WO
Inventors: Gregory Katz; Yaron Grinwald; Tzahi MASWARI; Inbar ADI
Original assignee: Hewlett-Packard Indigo B.V.
Priority date: 2012-06-28
Filing date: 2012-06-28
Publication date: 2014-01-03

Abstract

In one embodiment, target velocity data, indicative of a target velocity for fluid ejection from a printhead channel, is received. A waveform capabilities database is accessed, the database including descriptions of pulse waveforms available to be applied to an actuator to cause fluid drop ejection from the channel at the target velocity. Each description includes a pulse width. A tail reduction waveform having a lowest pulse width is identified from the descriptions. The tail reduction waveform is provided to the actuator.

Description

DROP TAIL REDUCTION WAVEFORMS

BACKGROUND

[0001 ] Image printing may be accomplished by providing relative movement between a printhead and a print substrate while both the printhead and the substrate are travelling in one or two orthogonal directions. The printhead ejects droplets of ink or other fluid onto the print substrate to form an image.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] The accompanying drawings illustrate various embodiments and are a part of the specification. The illustrated embodiments are examples and do not limit the scope of the claims. Throughout the drawings, identical reference numbers designate similar, but not necessarily identical elements.

[0003] FIG. 1A provides an example of a fluid drop ejected from a printhead, the fluid drop having a tail.

[0004] FIG. 1 B provides an example of lengthening of the fluid drop tail, such that at a certain point the tail will break off to form a satellite fluid droplet.

[0005] FIG. 1 C provides an example of satellite droplets deposited upon a substrate as a result a tail breaking off from a fluid drop.

[0006] FIG. 2 is a block diagram illustrating a system, according to various embodiments.

[0007] FIG. 3A provides examples of pulse waveform descriptions that may be included within a database, according to various embodiments.

[0008] FIG. 3B provides an example of a fluid drop ejected from a printhead, the fluid drop having a reduced tail, according to various embodiments.

[0009] FIG. 3C provides an example of improved image quality resulting from fluid drop tail reduction, according to various embodiments.

[00010] FIG. 4 is a block diagram illustrating a system according to various embodiments.

[0001 1 ] FIG. 5 is a block diagram illustrating a system according to various embodiments.

[00012] FIG. 6 is a block diagram illustrating a system according to various embodiments. [00013] FIG. 7 is a flow diagram depicting steps taken to implement various embodiments.

[00014] The same part numbers designate the same or similar parts throughout the figures.

DETAILED DESCRIPTION OF EMBODIMENTS

[00015] In certain printing systems, piezoelectric printheads are utilized to eject inks or other fluids. In an example, a piezoelectric printhead may include a plurality of printhead channels, with each channel having an adjacent piezoelectric actuator. When a voltage waveform is applied, the piezoelectric actuator generates a pressure pulse that causes the channel to change shape, forcing a droplet of the fluid from the channel. Piezoelectric printheads have an advantage of working with a wide variety of fluids, as since the ejection is via pressure rather than an explosion there is no requirement that the fluid include a volatile component. Further, the piezoelectric printhead can eject the fluid at a variety of ejection velocities, according to what will most advantageous for a particular print job or printer.

[00016] One difficulty in utilizing piezoelectric printheads has been controlling the shape of the fluid drop that is ejected from the channel. Without a proper combination of applied voltage, pulse width, and ejection velocity, the ejected fluid drop may include a long "tail" portion that follows the main body of the drop. The tail portion frequently separates from the main body of the fluid drop prior to impact the substrate, such the tail portion forms one or more an unintended satellite droplets that also strike the substrate to cause errors in an to be formed with deposited fluid drops. Such tail portions are particularly prevalent when utilizing oil-based inks or other fluids that have a low viscosity and/or low surface tension.

[00017] Accordingly, various embodiments described herein were developed to provide a tail reduction waveform, that when supplied to a printhead actuator, causes ejection of a fluid drop with a short tail to minimize creation of fluid satellites on a substrate. In an example of the disclosure, a tail reduction waveform service executing at a computing device receives data indicative of a target velocity for fluid ejection from a printhead channel. The tail reduction waveform service accesses a database that includes descriptions of pulse waveforms available to be applied to an actuator to cause fluid drop ejection from the channel at the target velocity. Each of the pulse waveform descriptions includes a pulse width. The tail reduction waveform service identifies from the descriptions a tail reduction waveform having a lowest pulse width, and provides the tail reduction waveform to the actuator.

[00018] Advantages of the disclosure include that the disclosure makes it possible to improve fluid jetting and print quality, without any new hardware or changes in hardware, by effecting a low pulse width waveform customized according to a target ejection velocity. The customized low pulse width waveform controls the shape of a fluid drop that is ejected from the channel of a piezoelectric printhead. By incorporating the proper combination of applied voltage and pulse width, the fluid drop is ejected at the needed ejection velocity and without a long tail portion that frequently follows the main body of the drop. The result is the reduction or elimination of unintended satellite droplets that appear on a substrate when a long tail of a drop separates from the main body of the fluid drop prior to impact the substrate, and thus the reduction of errors in the printed image. Another advantage of the disclosure is that it provides for considerable flexibility when utilizing a plurality of piezoelectric printheads with different ejection velocity requirements, or when printing print jobs with different ejection velocity requirements, by enabling a customized waveform according to the ejection velocity requirement. Yet another advantage of the disclosure is that it improves printing performance when utilizing oil-based inks or other fluids that have a low viscosity and/or low surface tension with piezoelectric printheads.

[00019] As used herein, a "printer" or "printing device" refers to any electronic device that prints and includes multifunctional electronic devices that perform additional functions such as scanning and/or copying. A "printhead" refers to a mechanism having a plurality of nozzles through which ink or other fluid is ejected. Examples of printheads are drop on demand inkjet printheads, such as piezoelectric printheads and thermo resistive printheads. Some printheads may be part of a cartridge which also stores the fluid to be dispensed. Other printheads are standalone and are supplied with fluid by an off-axis fluid supply. "Ink" refers to any fluid that includes a pigment, dye, or other marking agent and is used for printing. "Ink" includes, but not limited to, aqueous inks, solvent inks, UV-curable inks, dye sublimation inks and latex inks. "Actuator" refers to a device that converts input electrical energy or current into output energy of in the form of an acoustic wave that activates (e.g., by vibrating, shaking or deforming) a printhead structure. A "piezoelectric actuator" refers to an actuator that includes piezoelectric material that mechanically deforms when an external electric field or current is applied to the material. "Pulse" refers to a change in voltage or in current intensity. "Pulse waveform" or "waveform" refers to a pattern of voltage fluctuation. "Pulse width" refers to an interval between (a) the time, during a first transition, that a pulse amplitude reaches a specified fraction (level) of its final amplitude, and (b) the time a pulse amplitude drops, on a last transition, to the same level. A "channel" refers to a gap, groove, passage, or duct included within a printhead to hold and guide flow of a liquid. It should be noted that a same channel may hold a liquid during a first time period, and guide flow or expression of the liquid during a second time period. A "satellite" or "satellite droplet" refers to a droplet that occurs when a tail portion of a fluid drop breaks off from the fluid drop. A "database" refers to any organized collection of data in digital form such that it can be stored in computer memory or a data storage device.

[00020] FIG. 1A provides an illustration of a single fluid drop 102 ejected from a nozzle 1 14 of a printhead 106 towards a substrate 1 12, the fluid drop 102 having a tail 108. In FIG. 1 B, it can be seen that as the tail 108 lengthens, the tail at a certain point will break off to form a satellite fluid droplet 1 10. FIG. 1 C provides an illustration of satellite droplets 1 10 that have impacted a substrate 1 12 as a result of tails breaking off of fluid drops 102. In this example a printhead has ejected three fluid drops 102 towards a substrate 1 12 to form a printed image. However, three satellite droplets 1 10 were created and have landed upon the substrate 1 12 as a result of three fluid drop tails 108 breaking off as described above. The deposited satellite droplets 1 10, particularly when viewed in combination with other satellite droplets deposited across the entire image, can cause image artifacts, blurring of image attributes, and other undesirable image degradation.

[00021 ] FIG. 2 is a block diagram illustrating a system according to various embodiments. FIG. 2 includes particular components, modules, etc. according to various embodiments. However, in different embodiments, more, fewer, and/or other components, modules, arrangements of components/modules, etc. may be used according to the teachings described herein. In addition, various components, modules, etc. described herein may be implemented as one or more software modules, hardware modules, special purpose hardware (e.g., application specific hardware, application specific integrated circuits (ASICs), embedded controllers, hardwired circuitry, etc.), or some combination of these.

[00022] FIG. 2 shows a computing device 202 electronically connected to printhead structure 204. Computing device 202 represents generally any computing device or group of computing devices configured to execute a tail reduction waveform service ("TRW service") 206. In an embodiment, computing device 202 is a controller or other computer or group of computers included within a printing device, e.g., an inkjet printer that includes printhead structure 204. In another embodiment, computing device 202 is a computer or computer system that is electronically connected to a printhead. In embodiments, computing device 202 may be or include a server, desktop computer, notebook computer, mobile device, tablet computer, and/or any other computing device electronically connected to a printhead.

[00023] Printhead structure 204 represents generally any printhead. As previously noted, printhead 204 may be a piezoelectric printhead, thermo resistive printhead, or other printhead configured to eject an ink upon a substrate during printing operations. In other embodiments, printhead 204 may be a piezoelectric printhead, thermo resistive printhead, or other printhead configured to eject ink or inks for printing. In other embodiments, printhead 204 may be a piezoelectric printhead, thermo resistive printhead, or other printhead configured to eject fluids other than inks for purposes unrelated to printing, e.g., to medicines, fuels, juices and other fluids. [00024] Printhead structure 204 includes a channel 208, to hold ink 210 to be expelled from the channel 208 during a printing event. Printhead structure 204 also includes an actuator 212 to cause the printhead structure 204 to vibrate or shake. During a printing event, vibration or shaking is induced at a level that causes expulsion of the ink 210 from channel 208 through a nozzle 214 that is connected to, or a part of, channel 208.

[00025] Computing device 202 is shown to include a tail reduction tail reduction waveform initiator service 206, a processor 216, and a memory 218. Tail reduction waveform service 206 represents generally any combination of hardware and programming configured to provide a waveform, 220 that when supplied to the printhead actuator 212, causes ejection of an ink drop 222 with a short tail to minimize creation of ink satellites on a substrate.

[00026] In an example, the TRW service 206 receives target velocity data 224 indicative of a target velocity for ejection of the ink 210, in the form of the ink drop 222, from the printhead channel 208. In an example, the target velocity data 224 may be received from another service executing at computing device 202. In another example, the target velocity data 224 may be retrieved from a database at computing device 202 and received at TRW service 206. In other examples, the target velocity data 224 may be received from an application executing at a computing device that is external to computing device 202, or retrieved from a database external to computing device 202.

[00027] Continuing with the example of FIG. 2, the TRW service 206 next accesses a database 226 that includes descriptions 228 of pulse waveforms available to be applied to the actuator 212 to cause ink drop ejection from the channel 208 at the target velocity. FIG. 3A provides examples of descriptions 228 of pulse waveforms that may be included a database 226. In this example, the database 226 holds descriptions 228 of eight pulse waveforms that will cause ink ejection from the channel 208 at the 6 m/s target velocity 308 indicated by the target velocity data 224. Each of the pulse waveform descriptions includes a pulse width 302 and a voltage 304.

[00028] The TRW service 206 identifies from the waveform descriptions 228 a tail reduction waveform 220 having a lowest pulse width 306 amongst the waveforms that will cause ejection of ink drops at the target velocity 308. In the example of FIG 3A, the tail reduction waveform 220 has a pulse width of 4.5 sec and a voltage of 60.00 v. The TWR service 206 then provides the tail reduction waveform 220 to the actuator 212. When the actuator 212 receives the tail reduction waveform 220, the actuator 212 is caused to vibrate or shake the printhead structure 204 to force the ink drop 222 out of the channel 208 through the nozzle 214 at the target velocity 308 of 6 m/s.

[00029] FIG. 3B illustrates that as a result of the TRW service 206 providing the tail reduction waveform 220 to the actuator, ink drop 222 that is expelled from the nozzle 314 of the printhead 316 towards the substrate 312 has a reduced tail 310 that does not break off to form a satellite ink droplet. FIG. 3C provides an illustration of a substrate 312 printed upon utilizing the TRW service 206. In this example, the actuator 212 has shaken or vibrated the printhead structure 204 to cause ejection of three ink drops 222 towards the substrate 312 to form a printed image. No satellite droplets were created or landed upon the substrate 312 as a result of an ink drop tail breaking off. Accordingly, the resulting image is improved in comparison with the example of FIG. 1 C, as image artifacts and blurring of image attributes that might occur as a result of the deposit of satellite droplets have been avoided.

[00030] The functions and operations described with respect to the TRW service 206 and the computing device 202 may be implemented as a computer- readable storage medium containing instructions executed by a processor (e.g., processor 216) and stored in a memory (e.g., memory 218). In a given implementation, processor 216 may represent multiple processors, and memory 218 may represent multiple memories. Processor 216 represents generally any instruction execution system, such as a computer/processor based system or an ASIC (Application Specific Integrated Circuit), a computer, or other system that can fetch or obtain instructions or logic stored in memory 218 and execute the instructions or logic contained therein. Memory 218 represents generally any memory configured to store program instructions and other data.

[00031 ] It should be noted that while the disclosure is discussed frequently with reference to ink, inkjet printers, and printing, the teachings of the present disclosure are not so limited. The teachings of the present disclosure may also be applied to ejection of fluids other than inks, including ejection of fluids for purposes unrelated to printing. Examples of ejection of fluids for purposes other than printing include the dispensing of certain medicines, fuels, juices and other fluids.

[00032] FIG. 4 is a diagram illustrating a system according to various embodiments. FIG. 4 includes particular components, modules, etc. according to various embodiments. However, in different embodiments, more, fewer, and/or other components, modules, arrangements of components/modules, etc. may be used according to the teachings described herein. In addition, various components, modules, etc. described herein may be implemented as one or more software modules, hardware modules, special purpose hardware (e.g., application specific hardware, application specific integrated circuits (ASICs), embedded controllers, hardwired circuitry, etc.), or some combination of these.

[00033] FIG. 4 shows a printer 402, representing generally any computing device that is operable to produce printed content. In some embodiments, printer 402 is a multifunctional electronic device that performs additional functions such as scanning and/or copying. Printer 402 includes a piezoelectric printhead 430, drive circuit 434, and controller 438.

[00034] In this example, piezoelectric printhead 430 represents generally a drop on demand printhead for expelling a fluid (e.g., but not limited to, an ink) upon a substrate. In this example, printhead 430 includes a micro-machined silicon chip structure 404 that is adjacent to, and forms the walls of, fluid channels 408. Fluid channels 408 extend from fluid supply reservoir 432 and terminated by fluid-ejecting nozzles 414. In other embodiments, the channels 408 may be adjacent to the printhead structure but not formed by the printhead structure. The width of the channels 408 is such that ample and stable fluid flow can be provided through channel 408 to nozzle 414 during printing operations. In certain examples, the width of the channel 408 may vary from 300 microns to 600 microns. In the example of FIG. 4, a printhead structure includes a diaphragm or glass plate 468 that is bonded to the silicon chip portion 404 of the structure and overlays the channels 408. Associated with each channel 408 is a piezoelectric actuator 412, which when selectively actuated, vibrates, shakes bends, and/or deforms a respective section of the glass plate 468 portion of the printhead structure to pressurize fluid in the channel 408.

[00035] Drive circuit 434 represents generally a circuit arrangement for activating actuators 412. Voltage is applied to the drive circuit 434 via a voltage source 436. Drive circuit 434 is electronically connected to actuators 412. In an embodiment, the electronic connection between drive circuit 434 and actuators 412 includes electrodes embedded in actuators 412. In this example, the voltage is a direct current ("DC") voltage from a battery or other DC voltage source. In other examples, the voltage may be alternating current ("AC") voltage from an AC voltage source.

[00036] Controller 438 represents generally any computing device or group of computing devices internal to printer 402 that controls printing and other operations performed by printer 402. Controller 438 includes a TRW service 406, a processor 416 and a memory 418, and is electronically connected to drive circuit 434.

[00037] TRW service 406 represents generally any combination of hardware and programming configured to provide a DC waveform 420 with specifications such that when the waveform 420 is supplied to the printhead actuator 412, the waveform 420 causes ejection of an ink drop 422 with a short tail to minimize creation of ink satellites. The short tail of the ink drop 422 is less likely to separate from the main body of the ink drop than is the case with a long tailed ink drop. This reduces the creation of ink droplet satellites and undesirable artifacts in printed images that result from such satellites. In this example, TRW service 406 includes a target velocity module 440, a database accessing module 442, a waveform selection module 444, and an actuation module 446.

[00038] In the example of FIG. 4, the target velocity module 440 receives from a computing device 448 separate from printer 438 target velocity data 424. The target velocity data 424 is data indicative of a target velocity for ejection of fluid 410, in the form of a fluid drop 422, from a printhead channel 408. In another example, the target velocity data 424 may be received from another service executing at computing device 402.

[00039] Continuing with the example of FIG. 4, the database accessing module 442 accesses a database 426 that includes descriptions 428 of DC pulse waveforms available to be applied to the actuator 412 to cause fluid drop ejection from the channel 408 at the target velocity indicated by the target velocity data 424. Each of such DC pulse waveform descriptions 428 includes a pulse width and a voltage.

[00040] The waveform selection module 444 identifies from the DC waveform descriptions 428 a tail reduction waveform 420 having a lowest pulse width 306. The actuation module 446 then provides the identified tail reduction waveform 420 to the actuator 412. When the actuator 412 receives the tail reduction waveform 420, the actuator 412 is caused to vibrate or shake the printhead structure 404 to force the fluid drop 422 out of the channel 408 through the nozzle 414 at the target velocity that was indicated by the target velocity data 424.

[00041 ] As a result of the actuation module 446 providing the tail reduction waveform 420 to the actuator 412, the fluid drop 422 that is expelled from the channel 408 has a reduced tail that is less likely to break off to form a satellite fluid droplet than would be the case for a fluid drop with a long tail. The TRW service 406 thus causes user satisfaction with printed images and printing to increase as image artifacts and blurring of image attributes that might otherwise occur as a result of the deposit of satellite droplets are decreased.

[00042] The functions and operations described with respect to TRW service 406, controller 438, and printer 402 may be implemented as a computer-readable storage medium containing instructions executed by a processor (e.g., processor 416) and stored in a memory (e.g., memory 418). In a given implementation, processor 416 may represent multiple processors, and memory 418 may represent multiple memories. Processor 416 represents generally any instruction execution system, such as a computer/processor based system or an ASIC (Application Specific Integrated Circuit), a computer, or other system that can fetch or obtain instructions or logic stored in memory 418 and execute the instructions or logic contained therein. Memory 418 represents generally any memory configured to store program instructions and other data.

[00043] FIG. 5 is a diagram illustrating a system according to various embodiments. FIG. 5 includes particular components, modules, etc. according to various embodiments. However, in different embodiments, more, fewer, and/or other components, modules, arrangements of components/modules, etc. may be used according to the teachings described herein. In addition, various components, modules, etc. described herein may be implemented as one or more software modules, hardware modules, special purpose hardware (e.g., application specific hardware, application specific integrated circuits (ASICs), embedded controllers, hardwired circuitry, etc.), or some combination of these.

[00044] FIG. 5 shows a printer 502, includes a piezoelectric printhead 530, drive circuit 534, and controller 538.

[00045] In this example, piezoelectric printhead 530 represents generally a drop on demand printhead for expelling a fluid (e.g., but not limited to, an ink) upon a substrate 550. In this example, printhead 530 includes a micro-machined silicon chip structure 504 that is adjacent to, and forms the walls of, fluid channels 508. Fluid channels 508 extend from fluid supply reservoir 532 and terminated by fluid-ejecting nozzles 514. In the example of FIG. 5, a printhead structure includes a diaphragm or glass plate 568 that is bonded to the silicon chip portion 504 of the structure and overlays the channels 508. Associated with each channel 508 is a piezoelectric actuator 512, which when selectively actuated, vibrates, shakes bends, and/or deforms a respective section of the glass plate 568 portion of the printhead structure to pressurize fluid in the channel 508.

[00046] Drive circuit 534 represents generally a circuit arrangement for activating actuators 512. Voltage is applied to the drive circuit 534 via a voltage source 536. Drive circuit 534 is electronically connected to actuators 512.

[00047] Controller 538 represents generally any computing device or group of computing devices internal to printer 502 that controls printing and other operations performed by printer 502. Controller 538 includes a TRW service 506, a print job analysis service 562 to provide target velocity data to the TRW service 206 based attributes of a received print job, a processor 516 and a memory 518, and is electronically connected to drive circuit 534.

[00048] TRW service 506 represents generally any combination of hardware and programming configured to provide a waveform 520 with specifications such that when the waveform 520 is supplied to the printhead actuator 512, the waveform 520 causes ejection of an ink drop 522 with a short tail to minimize creation of ink satellites. In this example, TRW service 506 includes a target velocity module 540, an acceptable voltage module 552, a waveform set module 554, a database accessing module 542, a waveform selection module 544, and an actuation module 546.

[00049] In the example of FIG. 5, the target velocity module 540 receives a print job 554 from a computing device 548 that is a device separate from the printer 502. The print job analysis service 562 analyzes the received print job 556, and based upon the analysis creates target velocity data 524 and send the data 524 to the TRW service 506. The target velocity data 524 is data indicative of a target velocity for ejection of fluid 510, in the form of a fluid drop 522, from a printhead channel 508. In another example, the print job analysis service 562 may execute at computing device 548, or another computing device separate distinct from the printer 502.

[00050] In the example of FIG. 5, the database accessing module 542 accesses a database that includes descriptions of pulse waveforms available to be applied to the actuator 512 to cause fluid drop ejection from the channel 508 at the target velocity indicated by the target velocity data 524. Each of the pulse waveform descriptions includes a pulse width and a voltage.

[00051 ] In the example of FIG. 5, the acceptable voltage module 552 receives data 558 indicative of a highest acceptable voltage for the printhead actuator 512 associated with the channel that will expel the fluid drop 522. In an example, the highest acceptable voltage data 558 may be data that stored at the printer 502, e.g., data that is provided by a manufacturer at the time of manufacturing of the printer 502. In another example, the highest acceptable voltage data 558 may be data that stored at a memory or computing device separate from, but electronically accessible to, printer 502.

[00052] Continuing with the example of FIG. 5, the waveform set module 554, utilizing the highest acceptable voltage data 558, identifies from the pulse waveform descriptions an acceptable voltage waveform set 560. The waveform selection module 544 identifies from the acceptable voltage waveform set 560 a tail reduction waveform 520 having a lowest pulse width 306. The actuation module 546 then provides the identified tail reduction waveform 520 to the actuator 512. When the actuator 512 receives the tail reduction waveform 520, the actuator 512 is caused to vibrate or shake the printhead structure 504 to force the fluid drop 522 out of the channel 508 through the nozzle 514 at the target velocity that was indicated by the target velocity data 524.

[00053] As a result of the actuation module 546 providing the tail reduction waveform 520 to the actuator 512, a fluid drop 522 that is expelled from the channel 508 toward the substrate 550. The fluid drop 522 has reduced tail that is less likely to break off to form a satellite fluid droplet that would be the case for a fluid drop with a long tail. The TRW service thus causes user satisfaction with printed images and printing to increase as image artifacts and blurring of image attributes that might occur as a result of the deposit of satellite droplets are decreased.

[00054] The functions and operations described with respect to TRW service 506, controller 538, and printer 502 may be implemented as a computer-readable storage medium containing instructions executed by a processor (e.g., processor 516) and stored in a memory (e.g., memory 518). In a given implementation, processor 516 may represent multiple processors, and memory 518 may represent multiple memories. Processor 516 represents generally any instruction execution system, such as a computer/processor based system or an ASIC (Application Specific Integrated Circuit), a computer, or other system that can fetch or obtain instructions or logic stored in memory 518 and execute the instructions or logic contained therein. Memory 518 represents generally any memory configured to store program instructions and other data.

[00055] FIG. 6 is a diagram illustrating a system according to various embodiments. FIG. 6 includes particular components, modules, etc. according to various embodiments. However, in different embodiments, more, fewer, and/or other components, modules, arrangements of components/modules, etc. may be used according to the teachings described herein. In addition, various components, modules, etc. described herein may be implemented as one or more software modules, hardware modules, special purpose hardware (e.g., application specific hardware, application specific integrated circuits (ASICs), embedded controllers, hardwired circuitry, etc.), or some combination of these.

[00056] FIG. 6 shows a printer 602, which includes a piezoelectric printhead 630, drive circuit 634, a controller 638, and sensor 664. In an example, piezoelectric printhead 630 represents generally a drop on demand printhead for expelling an ink having an oil based carrier portion having with a viscosity of less than 5 cps. In another example, piezoelectric printhead 630 represents generally a drop on demand printhead for expelling an ink with an oil based carrier portion having a surface tension of less than 30 dyne/cm upon a substrate 650. In this example, printhead 630 includes a micro-machined silicon chip structure 604 that is adjacent to, and forms the walls of, ink channels 608. Ink channels 608 extend from ink supply reservoir 632 and terminated by ink-ejecting nozzles 614. Associated with each channel 608 is a piezoelectric actuator 612, which when selectively actuated, vibrates, shakes bends, and/or deforms a respective section of the printhead structure 604 to pressurize ink in the channel 608.

[00057] Drive circuit 634 represents generally a circuit arrangement for activating actuators 612. Voltage is applied to the drive circuit 634 via a voltage source 636. Drive circuit 634 is electronically connected to actuators 612.

[00058] Controller 638 represents generally any computing device or group of computing devices internal to printer 602 that controls printing and other operations performed by printer 602. Controller 638 includes a TRW service 606, an ink drop satellite detection service 662 to analyze ink drops expelled or ejected from the channel 608 and provide tail detection data to the TRW service based upon the analysis, a processor 616, and a memory 618. Controller 638, is electronically connected to drive circuit 634.

[00059] Sensor 664 represents any sensor configured to detect and/or measure tails of ink drops ejected from printhead channel 608. In the example of FIG. 6, sensor 664 detects the ink drop tails as the ink drops are airborne and en route to the substrate. In other examples, the sensor may detect ink drop tails by analyzing the drops and satellites droplets that are part of the printed image, i.e. detecting the drops and/or satellite droplets after they have impacted the substrate. In examples, the sensor may be an optical sensor, a piezoelectric sensor, an acoustic sensor, or any other sensing device that detects tails of ejected ink drops.

[00060] TRW service 606 represents generally any combination of hardware and programming configured to provide a waveform 620 with specifications such that when the waveform 620 is supplied to the printhead actuator 612, the waveform 620 causes ejection of an ink drop 622 with a short tail to minimize creation of ink satellites. The tail of the short tailed ink drop 622 is less likely to separate from the main body of the ink drop than is the case with a long tailed ink drop. This reduces the creation of ink droplet satellites and undesirable artifacts in printed images that result from such satellites. In this example, TRW service 606 includes a target velocity module 640, a database accessing module 642, a waveform selection module 644, and an actuation module 646.

[00061 ] In the example of FIG. 6, the printer 602 expels ink drops upon a substrate 650 to print a print job. In this example sensor 664 is an optical sensor that detects tail size of ink drops as ink drops are ejected towards the substrate 650. The ink drop satellite detection service 662 receives ink drop satellite data 666 from the sensor 664 and analyzes the data 666 with respect to ink drops ejected from the channel 608 after activation by the actuator 612. Based upon the analysis, the ink drop satellite detection service 662 creates target velocity data 624 indicative of a target velocity for ejection of ink 610, in the form of an ink drop 622, from a printhead channel 608. In another example, the ink drop satellite detection service 662 may execute at another computing device distinct from the printer 602.

[00062] Continuing with the example of FIG. 6, the database accessing module 642 accesses a database 626 that includes descriptions 628 of pulse waveforms available to be applied to the actuator 612 to cause ink drop ejection from the channel 608 at the target velocity indicated by the target velocity data 624. Each of the pulse waveform descriptions 628 includes a pulse width and a voltage. The waveform selection module 644 identifies, from the descriptions of waveforms that that cause ejection of ink drops at the target velocity, a tail reduction waveform 620 having a lowest pulse width 306.

[00063] The actuation module 646 then provides the identified tail reduction waveform 620 to the actuator 612. When the actuator 612 receives the tail reduction waveform 620, the actuator 612 is caused to vibrate or shake the printhead structure 604 to force the ink drop 622 out of the channel 608 through the nozzle 614 at the target velocity that was indicated by the target velocity data 624. As a result of the actuation module 646 providing the tail reduction waveform 620 to the actuator 612, the ejected ink drop 622 has a reduced tail that is less likely to break off to form a satellite ink droplet that would be the case for an ink drop with a long tail.

[00064] The functions and operations described with respect to TRW service 606, controller 638, and printer 602 may be implemented as a computer-readable storage medium containing instructions executed by a processor (e.g., processor 616) and stored in a memory (e.g., memory 618). In a given implementation, processor 616 may represent multiple processors, and memory 618 may represent multiple memories. Processor 616 represents generally any instruction execution system, such as a computer/processor based system or an ASIC (Application Specific Integrated Circuit), a computer, or other system that can fetch or obtain instructions or logic stored in memory 618 and execute the instructions or logic contained therein. Memory 618 represents generally any memory configured to store program instructions and other data.

[00065] FIG. 7 is a flow diagram of operation in a system according to various embodiments. In discussing FIG. 7, reference may be made to the diagrams of FIGS. 4, 5, and 6 to provide contextual examples. Implementation, however, is not limited to those examples. Starting with FIG. 7, target velocity data is received. The target velocity data is indicative of a target velocity for fluid ejection from a printhead channel (block 702). Referring back to FIGS. 4, 5, and 6, target velocity module 440, 540, 640 may be responsible for implementing block 702.

[00066] Continuing with FIG. 7, a waveform capabilities database is accessed. The database includes descriptions of pulse waveforms available to be applied to an actuator to cause fluid drop ejection from the channel at the target velocity. Each description includes a pulse width (block 704). Referring back to FIGS. 4, 5, and 6, database accessing module 442, 542, or 642 may be responsible for implementing block 704.

[00067] Continuing with FIG. 7, a tail reduction waveform having a lowest pulse width is identified from the descriptions (block 706). Referring back to FIGS. 4, 5, and 6, waveform selection module 444, 544, or 644 may be responsible for implementing block 706. [00068] Continuing with FIG. 7, the tail reduction waveform is provided to the actuator (block 708). Referring back to FIGS. 4, 5, and 6, actuation module 446, 546, or 646 may be responsible for implementing block 708.

[00069] Various modifications may be made to the disclosed embodiments and implementations without departing from their scope. Therefore, the illustrations and examples herein should be construed in an illustrative, and not a restrictive, sense.

Claims

CLAIMS What is claimed is:

1 . A non-transitory computer-readable storage medium containing instructions to provide a drop tail reduction waveform, the instructions when executed by a processor causing the processor to:

receive target velocity data indicative of a target velocity for fluid ejection from a printhead channel;

access a waveform capabilities database, the database including descriptions of pulse waveforms available to be applied to an actuator to cause fluid drop ejection from the channel at the target velocity, wherein each description includes a pulse width;

identify from the descriptions a tail reduction waveform having a lowest pulse width; and

provide the tail reduction waveform to the actuator.

2. The medium of claim 1 , wherein the pulse waveforms described in the database are direct current pulse waveforms.

3. The medium of claim 1 ,

wherein the instructions cause the processor to receive data indicative of a highest acceptable voltage for a printhead actuator associated with the channel;

wherein each description includes a voltage;

wherein the instructions cause the processor to identify from the descriptions an acceptable voltage waveform set; and

wherein the tail reduction waveform is identified from the set.

4. The medium of claim 1 , wherein the instructions cause the processor to determine the target velocity data responsive to receipt of data resulting from analysis of satellite droplets ejected from the channel after such droplets have impacted a substrate.

5. The medium of claim 1 , wherein the instructions cause the processor to receive a print job, and to determine the target velocity data responsive to analysis of the print job.

6. The medium of claim 1 , wherein the actuator is piezoelectric.

7. The medium of claim 1 , wherein the applied waveform causes vibration of printhead structure to cause ejection of the fluid drop from the channel.

8. The medium of claim 1 , wherein the fluid includes an ink.

9. A system to provide a drop tail reduction waveform, comprising a memory and a processor to execute instructions stored in the memory to implement modules, the modules comprising:

a target velocity module, to receive target velocity data indicative of a target velocity for fluid ejection from a printhead channel;

a database accessing module, to access a waveform capabilities database, the database including descriptions of pulse waveforms available to be applied to an actuator to cause fluid drop ejection from the channel at the target velocity, wherein each description includes a pulse width;

a waveform selection module, to identify from the descriptions a tail reduction waveform having a lowest pulse width; and

an actuation module, to provide the tail reduction waveform to the actuator.

10. The system of claim 9, wherein the pulse waveforms described in the database are direct current waveforms.

1 1 .The system of claim 9,

further comprising

an acceptable voltage module, to receive data indicative of a highest acceptable voltage for a printhead actuator associated with the channel; and a waveform set module, to identify from the descriptions an acceptable voltage waveform set;

wherein

each description includes a voltage; and

the waveform selection module identifies the tail reduction waveform from the set.

12. The system of claim 9, wherein the actuator is piezoelectric.

13. The system of claim 9, wherein the applied waveform causes vibration of printhead structure to cause ejection of the fluid drop from the channel.

14. The system of claim 9, wherein the fluid includes an ink with an oil based carrier portion having a viscosity of less than 5 cps or a surface tension of less than 30 dyne/cm.

15. A method to provide a drop tail reduction waveform, comprising: receiving target velocity data indicative of a target velocity for ejection of an ink from a printhead channel;

receiving data indicative of a highest acceptable voltage for a piezoelectric printhead actuator associated with the channel;

accessing a waveform capabilities database, the database including descriptions of single pulse waveforms available to be applied to the actuator to cause vibration of printhead structure to cause ejection of a drop of the ink from the channel at the target velocity,

wherein each description includes a pulse width and a voltage;

identifying from the descriptions an acceptable voltage waveform set;

identifying from the set a tail reduction waveform having a lowest pulse width; and

providing the tail reduction waveform to the actuator.