Patent Publication Number: US-2021178759-A1

Title: Nozzle geometry for printheads

Description:
RELATED APPLICATIONS 
     This non-provisional patent application is a continuation-in-part of U.S. patent application Ser. No. 16/999,301 filed on Aug. 21, 2020, which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The following disclosure relates to the field of printheads, and more particularly, to fabrication of printheads. 
     BACKGROUND 
     Image formation is a procedure whereby a digital image is recreated on a medium by propelling droplets of ink or another type of print fluid onto a medium, such as paper, plastic, a substrate for 3D printing, etc. Image formation is commonly employed in apparatuses, such as printers (e.g., inkjet printer), facsimile machines, copying machines, plotting machines, multifunction peripherals, etc. The core of a typical jetting apparatus or image forming apparatus is one or more liquid-droplet ejection heads (referred to generally herein as “printheads”) having nozzles that discharge liquid droplets, a mechanism for moving the printhead and/or the medium in relation to one another, and a controller that controls how liquid is discharged from the individual nozzles of the printhead onto the medium in the form of pixels. 
     A typical printhead includes a plurality of nozzles aligned in one or more rows along a discharge surface of the printhead. Each nozzle is part of a “jetting channel”, which includes the nozzle, a pressure chamber, and a mechanism for ejecting the print fluid from the pressure chamber and through the nozzle, which is typically a diaphragm that is driven by an actuator (e.g., a piezoelectric actuator). A printhead also includes a drive circuit that controls when each individual jetting channel fires based on image data. To jet from a jetting channel, the drive circuit provides a jetting pulse to the actuator, which causes the actuator to deform a wall of the pressure chamber via the diaphragm. The deformation of the pressure chamber creates pressure waves within the pressure chamber that eject a droplet of print fluid (e.g., ink) out of the nozzle. A drop emerging from the nozzle will extrude as a jet which necks down and breaks off from the print fluid remaining in the nozzle. In an ideal case, the jet will move towards the medium with surface tension forces pulling the liquid into a spherical droplet. The surface tension will also cause the print fluid still attached to the nozzle to be drawn back into the nozzle. After the initial break-off, the jet has a head containing most of the print fluid, and a ligament or tail that extends from the head. When detached, the ligament will start to merge into the head of the jet. Depending on the viscosity of the print fluid, jetting velocity, and other jetting characteristics, the ligament may not merge into the head before it reached the medium, which results in satellites that are undesirable. 
     SUMMARY 
     Embodiments described herein comprise a tool and methods for forming improved nozzle geometries for printheads. The nozzle shape creates an instability in the print fluid as it passes through the nozzle, which reduces the length of a ligament for a jet. In one embodiment, nozzles as described herein may have a shape that converges for a portion of the length of the nozzle, stays uniform for the next portion of the length, and then converges again. This shape causes the velocity of the print fluid to increase initially in the nozzle, to remain constant along a partial length of the nozzle, and then to increase again before being ejected out of the nozzle. In another embodiment, the nozzles may have a shape that converges for a portion of the length of the nozzle, and then converges again for the remaining portion of the length. These nozzle shapes act to create instability in the jet that is discharged from the nozzle. It is one effective means for interacting with the print fluid closest to its exit point from the printhead. As such, the nozzle acts as a way to affect the shape of the jet in a manner that is closest to the desired output. In the case of high viscosity print fluids, droplet formation is hampered by the viscosity and the surface tension of the print fluid being jetted. In jetting these types of print fluids, the jet becomes exceedingly long as the viscous forces dominate over inertial forces. A break-off of the jet from the rest of the print fluid in the nozzle occurs late and at a long distance from the orifice. Thus, the ligament of the jet may become exceedingly long, and does not merge into the head of the jet. The shape of the nozzles described herein creates a difference in speed of the print fluid, and causes an artificial instability within the jet. This instability accelerates the break-off time, and reduces the length of the ligament to form a more desirable droplet. 
     One embodiment comprises a method of fabricating a printhead. The method comprises punching first nozzle holes in a first nozzle plate with a first punch, where each of the first nozzle holes includes a first converging section. The method further comprises punching second nozzle holes in a second nozzle plate with a second punch, where each of the second nozzle holes includes a second converging section. The method further comprises bonding the first nozzle plate and the second nozzle plate to form a nozzle plate stack, where the first nozzle holes and the second nozzle holes define nozzles of the printhead. 
     In another embodiment, the first nozzle holes are punched from a first side through a second side of the first nozzle plate, and the method further comprises polishing the second side of the first nozzle plate to form a planar surface on the second side of the first nozzle plate prior to the bonding. 
     In another embodiment, the second nozzle holes are punched from a first side through a second side of the second nozzle plate forming extrusions around the second nozzle holes on the second side of the second nozzle plate, and the method further comprises polishing the second side of the second nozzle plate to remove a portion of the extrusions and leave surface features around the second nozzle holes that define orifices of the nozzles where a print fluid exits the nozzles. 
     In another embodiment, a first convergence angle of the first converging section is greater than a second convergence angle of the second converging section. 
     In another embodiment, a first convergence angle of the first converging section is less than a second convergence angle of the second converging section. 
     In another embodiment, each of the first nozzle holes in the first nozzle plate includes the first converging section, and a neck adjoining the first converging section having a diameter that is uniform. 
     In another embodiment, the second converging section converges from a first side to a second side of the second nozzle plate, and a diameter of the second converging section at the first side of the second nozzle plate is equivalent to the diameter of the neck. 
     In another embodiment, the second converging section converges from a first side to a second side of the second nozzle plate, and a diameter of the second converging section at the first side of the second nozzle plate is greater than the diameter of the neck. 
     Another embodiment comprises a fabrication system for a printhead. The fabrication system comprises at least one punch press configured to punch first nozzle holes in a first nozzle plate with a first punch, where each of the first nozzle holes includes a first converging section. The at least one punch press is further configured to punch second nozzle holes in a second nozzle plate with a second punch, wherein each of the second nozzle holes includes a second converging section. The fabrication system further comprises a bonding tool configured to bond the first nozzle plate and the second nozzle plate to form a nozzle plate stack, where the first nozzle holes and the second nozzle holes define nozzles of the printhead. 
     In another embodiment, the at least one punch press is configured to punch the first nozzle holes from a first side through a second side of the first nozzle plate, and the fabrication system further comprises a polishing tool configured to polish the second side of the first nozzle plate to form a planar surface on the second side of the first nozzle plate prior to bonding by the bonding tool. 
     In another embodiment, the at least one punch press is configured to punch the second nozzle holes from a first side through a second side of the second nozzle plate forming extrusions around the second nozzle holes on the second side of the second nozzle plate, and the fabrication system further comprises a polishing tool configured to polish the second side of the second nozzle plate to remove a portion of the extrusions and leave surface features around the second nozzle holes that define orifices of the nozzles where a print fluid exits the nozzles. 
     In another embodiment, a first convergence angle of the first converging section is greater than a second convergence angle of the second converging section. 
     In another embodiment, a first convergence angle of the first converging section is less than a second convergence angle of the second converging section. 
     In another embodiment, each of the first nozzle holes in the first nozzle plate includes the first converging section, and a neck adjoining the first converging section having a diameter that is uniform. 
     In another embodiment, the second converging section converges from a first side to a second side of the second nozzle plate, and a diameter of the second converging section at the first side of the second nozzle plate is equivalent to the diameter of the neck. 
     In another embodiment, the second converging section converges from a first side to a second side of the second nozzle plate; and a diameter of the second converging section at the first side of the second nozzle plate is greater than the diameter of the neck. 
     Another embodiment comprises a non-transitory computer readable medium embodying programmed instructions executed by a processor. The instructions direct the processor to implement a method of fabricating a printhead. The method comprises controlling at least one punch press to punch first nozzle holes in a first nozzle plate with a first punch, where each of the first nozzle holes includes a first converging section. The method further comprises controlling the at least one punch press to punch second nozzle holes in a second nozzle plate with a second punch, where each of the second nozzle holes includes a second converging section. The method further comprises controlling a bonding tool to bond the first nozzle plate and the second nozzle plate to form a nozzle plate stack, where the first nozzle holes and the second nozzle holes define nozzles of the printhead. 
     In another embodiment, the first nozzle holes are punched from a first side through a second side of the first nozzle plate, and the method further comprises controlling a polishing tool to polish the second side of the first nozzle plate to form a planar surface on the second side of the first nozzle plate prior to the bonding. 
     In another embodiment, the second nozzle holes are punched from a first side through a second side of the second nozzle plate forming extrusions around the second nozzle holes on the second side of the second nozzle plate, and the method further comprises controlling a polishing tool to polish the second side of the second nozzle plate to remove a portion of the extrusions and leave surface features around the second nozzle holes that define orifices of the nozzles where a print fluid exits the nozzles. 
     In another embodiment, each of the first nozzle holes in the first nozzle plate includes the first converging section, and a neck adjoining the first converging section having a diameter that is uniform. 
     The above summary provides a basic understanding of some aspects of the specification. This summary is not an extensive overview of the specification. It is intended to neither identify key or critical elements of the specification nor delineate any scope particular embodiments of the specification, or any scope of the claims. Its sole purpose is to present some concepts of the specification in a simplified form as a prelude to the more detailed description that is presented later. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       Some embodiments of the present disclosure are now described, by way of example only, and with reference to the accompanying drawings. The same reference number represents the same element or the same type of element on all drawings. 
         FIG. 1  is a schematic diagram of a jetting apparatus in an illustrative embodiment. 
         FIG. 2  is a perspective view of a printhead in an illustrative embodiment. 
         FIG. 3  is an exploded, perspective view of a printhead in an illustrative embodiment. 
         FIG. 4  is a cross-sectional view of jetting channels in a printhead in an illustrative embodiment. 
         FIGS. 5-6  are cross-sectional views of a traditional nozzle of a printhead. 
         FIG. 7  is a cross-sectional view of a nozzle of a printhead in an illustrative embodiment.  FIG. 8  is a cross-sectional view of a nozzle formed by two nozzle plates in an illustrative embodiment. 
         FIG. 9  is a cross-sectional view of a nozzle formed by three nozzle plates in an illustrative embodiment. 
         FIG. 10  is a cross-sectional view of a nozzle of a printhead in another illustrative embodiment. 
         FIG. 11  is a cross-sectional view of a nozzle formed by two nozzle plates in an illustrative embodiment. 
         FIG. 12  is a cross-sectional view of a nozzle formed by three nozzle plates in an illustrative embodiment. 
         FIG. 13  is a cross-sectional view of a nozzle of a printhead in another illustrative embodiment. 
         FIG. 14  is a cross-sectional view of a nozzle formed by two nozzle plates in an illustrative embodiment. 
         FIG. 15  is a cross-sectional view of a nozzle of a printhead in another illustrative embodiment. 
         FIG. 16  is a cross-sectional view of a nozzle formed by two nozzle plates in an illustrative embodiment. 
         FIG. 17  is a block diagram of a fabrication system in an illustrative embodiment. 
         FIG. 18  is a block diagram of a punch press in an illustrative embodiment. 
         FIG. 19  is a flow chart illustrating a method of fabricating a nozzle plate stack in an illustrative embodiment. 
         FIG. 20  is a perspective view of a blank nozzle plate in an illustrative embodiment. 
         FIG. 21  is a block diagram of a fabrication system in another illustrative embodiment. 
         FIG. 22  is a flow chart illustrating an additional step of the method in  FIG. 19  in an illustrative embodiment. 
         FIG. 23  illustrates a nozzle punch and a nozzle plate in an illustrative embodiment. 
         FIG. 24  illustrates a nozzle punch pressed into a nozzle plate in an illustrative embodiment. 
         FIG. 25  illustrates a nozzle punch withdrawn from a nozzle plate in an illustrative embodiment. 
         FIG. 26  illustrates polishing of a nozzle plate in an illustrative embodiment. 
         FIG. 27  illustrates a nozzle plate after polishing in an illustrative embodiment. 
         FIG. 28  illustrates a nozzle punch and a nozzle plate in an illustrative embodiment. 
         FIG. 29  illustrates a nozzle punch pressed into a nozzle plate in an illustrative embodiment. 
         FIG. 30  illustrates a nozzle punch withdrawn from a nozzle plate in an illustrative embodiment. 
         FIG. 31  illustrates polishing of a nozzle plate in an illustrative embodiment. 
         FIG. 32  illustrates a nozzle plate after polishing in an illustrative embodiment. 
         FIG. 33  illustrates a nozzle plate stack in an illustrative embodiment. 
         FIG. 34  illustrates a nozzle punch and a nozzle plate in an illustrative embodiment. 
         FIG. 35  illustrates a nozzle punch pressed into a nozzle plate in an illustrative embodiment. 
         FIG. 36  illustrates a nozzle punch withdrawn from a nozzle plate in an illustrative embodiment. 
         FIG. 37  illustrates polishing of a nozzle plate in an illustrative embodiment. 
         FIG. 38  illustrates a nozzle plate after polishing in an illustrative embodiment. 
         FIG. 39  illustrates a nozzle punch and a nozzle plate in an illustrative embodiment. 
         FIG. 40  illustrates a nozzle punch pressed into a nozzle plate in an illustrative embodiment. 
         FIG. 41  illustrates a nozzle punch withdrawn from a nozzle plate in an illustrative embodiment. 
         FIG. 42  illustrates polishing of a nozzle plate in an illustrative embodiment. 
         FIG. 43  illustrates a nozzle plate after polishing in an illustrative embodiment. 
         FIG. 44  illustrates a nozzle plate stack in an illustrative embodiment. 
         FIG. 45  illustrates a nozzle punch and a nozzle plate in an illustrative embodiment. 
         FIG. 46  illustrates a nozzle punch pressed into a nozzle plate in an illustrative embodiment. 
         FIG. 47  illustrates a nozzle punch withdrawn from a nozzle plate in an illustrative embodiment. 
         FIG. 48  illustrates polishing of a nozzle plate in an illustrative embodiment. 
         FIG. 49  illustrates a nozzle plate after polishing in an illustrative embodiment. 
         FIG. 50  illustrates a nozzle punch and a nozzle plate in an illustrative embodiment. 
         FIG. 51  illustrates a nozzle punch pressed into a nozzle plate in an illustrative embodiment. 
         FIG. 52  illustrates a nozzle punch withdrawn from a nozzle plate in an illustrative embodiment. 
         FIG. 53  illustrates polishing of a nozzle plate in an illustrative embodiment. 
         FIG. 54  illustrates a nozzle plate after polishing in an illustrative embodiment. 
         FIG. 55  illustrates a nozzle plate stack in an illustrative embodiment. 
         FIG. 56  illustrates a nozzle punch and a nozzle plate in an illustrative embodiment. 
         FIG. 57  illustrates a nozzle punch pressed into a nozzle plate in an illustrative embodiment. 
         FIG. 58  illustrates a nozzle punch withdrawn from a nozzle plate in an illustrative embodiment. 
         FIG. 59  illustrates polishing of a nozzle plate in an illustrative embodiment. 
         FIG. 60  illustrates a nozzle plate after polishing in an illustrative embodiment. 
         FIG. 61  illustrates a nozzle punch and a nozzle plate in an illustrative embodiment. 
         FIG. 62  illustrates a nozzle punch pressed into a nozzle plate in an illustrative embodiment. 
         FIG. 63  illustrates a nozzle punch withdrawn from a nozzle plate in an illustrative embodiment. 
         FIG. 64  illustrates polishing of a nozzle plate in an illustrative embodiment. 
         FIG. 65  illustrates a nozzle plate after polishing in an illustrative embodiment. 
         FIG. 66  illustrates a nozzle plate stack in an illustrative embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The figures and the following description illustrate specific exemplary embodiments. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the embodiments and are included within the scope of the embodiments. Furthermore, any examples described herein are intended to aid in understanding the principles of the embodiments, and are to be construed as being without limitation to such specifically recited examples and conditions. As a result, the inventive concept(s) is not limited to the specific embodiments or examples described below, but by the claims and their equivalents. 
       FIG. 1  is a schematic diagram of a jetting apparatus  100  in an illustrative embodiment. One example of jetting apparatus  100  is an inkjet printer that performs single-pass or multi-pass printing. Jetting apparatus  100  includes a mounting bracket  102  that supports one or more printheads  104  above a medium  112 . Mounting bracket  102  may be disposed on a carriage assembly that reciprocates back and forth along a scan line or sub-scan direction for multi-pass printing. Alternatively, mounting bracket  102  may be fixed within jetting apparatus  100  for single-pass printing. Printheads  104  are a device, apparatus, or component configured to eject droplets  106  of a print fluid, such as ink (e.g., water, solvent, oil, or UV-curable), through a plurality of orifices or nozzles (not visible in  FIG. 1 ). The droplets  106  ejected from the nozzles of printheads  104  are directed toward medium  112 . Medium  112  comprises any type of material upon which ink or another print fluid is applied by a printhead, such as paper, plastic, card stock, transparent sheets, a substrate for  3 D printing, cloth, etc. Typically, nozzles of printheads  104  are arranged in one or more rows so that ejection of print fluid from the nozzles causes formation of characters, symbols, images, layers of an object, etc., on medium  112  as printhead  104  and/or medium  112  are moved relative to one another. Media transport mechanism  114  is configured to move medium  112  relative to printheads  104 . Jetting apparatus  100  also includes a jetting apparatus controller  122  that controls the overall operation of jetting apparatus  100 . Jetting apparatus controller  122  may connect to a data source to receive image data, and control each printhead  104  to discharge the print fluid on a desired pixel grid on medium  112 . Jetting apparatus  100  also includes one or more reservoirs  124  for a print fluid. Although not shown in  FIG. 1 , reservoirs  124  may be connected to printheads  104  via hoses or the like. 
       FIG. 2  is a perspective view of a printhead  104  in an illustrative embodiment. Printhead  104  includes a head member  202  and electronics  204 . Head member  202  is an elongated component that forms the jetting channels of printhead  104 . A typical jetting channel includes a nozzle, a pressure chamber, and a mechanism for ejecting the print fluid from the pressure chamber and through the nozzle, which is typically a diaphragm that is driven by an actuator (e.g., a piezoelectric actuator). Electronics  204  control how the nozzles of printhead  104  jet droplets in response to control signals. Although not visible in  FIG. 2 , electronics  204  may include a plurality of actuators (e.g., piezoelectric actuators) that contact the diaphragms of the jetting channels. Electronics  204  also include cabling  206 , such as a ribbon cable, that connects to a controller (e.g., jetting apparatus controller  122 ) to receive the control signals. Printhead  104  also includes attachment members  208 , which are configured to secure printhead  104  to a jetting apparatus, such as to mounting bracket  102  as illustrated in  FIG. 1 . Attachment members  208  may include one or more holes  209  so that printhead  104  may be mounted within a jetting apparatus by screws, bolts, pins, etc. 
     The bottom surface  220  of head member  202  includes the nozzles of the jetting channels, and represents the discharge surface of printhead  104 . The top surface  222  of head member  202  represents the Input/Output (I/O) portion for receiving print fluids into printhead  104  and/or conveying print fluids (e.g., fluids that are not jetted) out of printhead  104 , such as with the case of a flow-through printhead. Top surface  222 , which is also referred to as the I/O surface, includes a plurality of I/O ports  211 - 214 . Top surface  222  has two ends  226 - 227  that are separated by electronics  204 . I/O ports  211 / 213  are disposed toward end  226 , and I/O ports  212 / 214  are disposed toward end  227 . I/O ports  211 - 214  may include a hose coupling, hose barb, etc., for coupling with a supply hose of a reservoir  124 , a cartridge, or the like. 
     Head member  202  includes a housing  230  and a plate stack  232 . Housing  230  is a rigid member made from stainless steel or another type of material. Housing  230  includes an access hole  234  that provides a passageway for electronics  204  to pass through housing  230  so that actuators may interface with diaphragms of the jetting channels. Plate stack  232  attaches to an interface surface (not visible) of housing  230 . Plate stack  232  (also referred to as a laminate plate stack) is a series of plates that are fixed or bonded to one another to form a laminated stack. 
       FIG. 3  is an exploded, perspective view of printhead  104  in an illustrative embodiment. Printhead  104  is a flow-through type of printhead in this embodiment, but non-flow-through types of printheads are considered herein. In this embodiment, printhead  104  includes piezoelectric device  302 , housing  230 , and plate stack  232 . Piezoelectric device  302  includes a plurality of piezoelectric actuators  304  or piezoelectric elements; one for each of the jetting channels. The ends of piezoelectric actuators  304  contact diaphragms at positions opposite the pressure chambers. 
     Housing  230  includes a groove  310  on interface surface  312  facing plate stack  232  that encompasses or substantially surrounds access hole  234 . Groove  310  forms a supply manifold for printhead  104  that is configured to supply a print fluid to the jetting channels. I/O ports  211  and  214  are fluidly coupled to groove  310 . Housing  230  further includes one or more grooves  314  on interface surface  312  that are separate or isolated from groove  310 . Grooves  314  form a return manifold for printhead  104  that is configured to receive print fluid that flows through the jetting channels and is not ejected from the nozzles. I/O ports  212  and  213  are fluidly coupled to grooves  314 . 
     Plate stack  232  includes plates  320 - 325  that are fixed or bonded to one another to form a laminated plate structure. Plate stack  232  illustrated in  FIG. 3  is intended to be an example of a basic structure of a printhead. There may be additional plates that are used in the plate stack  232  that are not shown in  FIG. 3 , and the configuration of the various plates may vary as desired. Also,  FIG. 3  is not drawn to scale. 
     In this embodiment, plate stack  232  includes the following plates: a diaphragm plate  320 , an upper restrictor plate  321 , chamber plates  322 - 323 , a lower restrictor plate  324 , and an orifice or nozzle plate  325 . Diaphragm plate  320  is a thin sheet of material (e.g., metal, plastic, etc.) that is generally rectangular in shape and is substantially flat or planar. Diaphragm plate  320  includes diaphragm sections  330  comprising a sheet of a semi-flexible material that forms diaphragms for the jetting channels. Diaphragm sections  330  are disposed longitudinally to correspond with the pressure chambers. Diaphragm plate  320  further includes filter sections  332  that are disposed longitudinally on opposing sides of diaphragm sections  330  to coincide with the supply manifold. Filter sections  332  are configured to remove foreign matter from print fluid flowing in the jetting channels from the supply manifold. Although diaphragm plate  320  is shown as including both diaphragm sections  330  and filter sections  332  in this embodiment, diaphragm sections  330  and filter sections  332  may be implemented in separate plates in other embodiments. Diaphragm plate  320  also includes return openings  334  that are part of the return manifold for printhead  104 . The return openings  334  are positioned to coincide with at least a portion of groove  314  of housing  230 . 
     Upper restrictor plate  321  is a thin sheet of material that is generally rectangular in shape and is substantially flat or planar. Upper restrictor plate  321  includes restrictor openings  340 . Restrictor openings  340  comprise elongated apertures or holes through upper restrictor plate  321  transversely disposed or oriented. Restrictor openings  340  are configured to fluidly couple pressure chambers of the jetting channels with the supply manifold. Upper restrictor plate  321  also includes return openings  344  disposed toward ends of upper restrictor plate  321  to coincide with return openings  334  of diaphragm plate  320 . 
     Chamber plate  322  is a thin sheet of material that is generally rectangular in shape and is substantially flat or planar. Chamber plate  322  includes chamber openings  350  disposed toward a middle region of chamber plate  322 . Chamber openings  350  comprise apertures or holes through chamber plate  322  that form pressure chambers for the jetting channels. Chamber plate  322  also includes return openings  354  disposed toward ends of chamber plate  322  to coincide with return openings  344  of upper restrictor plate  321 . 
     Chamber plate  323  is a thin sheet of material that is generally rectangular in shape and is substantially flat or planar. Chamber plate  323  includes chamber openings  360  disposed toward a middle region of chamber plate  323 . Chamber openings  360  coincide with chamber openings  350  of chamber plate  322  to form the pressure chambers for the jetting channels. Chamber plate  323  also includes return openings  364 , which comprise elongated apertures or holes through chamber plate  323  disposed longitudinally along a length of chamber plate  323 . Return openings  364  are disposed toward the long sides of chamber plate  323  on opposing sides of chamber openings  360  to form the return manifold. At least a portion of return openings  364  coincide with return openings  354  of chamber plate  322 . 
     Lower restrictor plate  324  is a thin sheet of material that is generally rectangular in shape and is substantially flat or planar. Lower restrictor plate  324  includes restrictor openings  370 , which comprise elongated apertures or holes through lower restrictor plate  324  transversely disposed or oriented. Restrictor openings  370  are configured to fluidly couple pressure chambers of the jetting channels with the return manifold. 
     Nozzle plate  325  is a thin sheet of material that is generally rectangular in shape and is substantially flat or planar. Nozzle plate  325  includes orifices that form nozzles  380  of the jetting channels. Each nozzle  380  represents an individual jetting channel in printhead  104  for ejecting a print fluid. In this embodiment, nozzles  380  are arranged in two nozzle rows. However, nozzles  380  may be arranged in a single row or in more than two rows in other embodiments. 
       FIG. 4  is a cross-sectional view of jetting channels in printhead  104  in an illustrative embodiment. The view in  FIG. 4  is as if a slice were taken transversely through printhead  104 . From top to bottom in  FIG. 4 , printhead  104  includes housing  230 , diaphragm plate  320 , upper restrictor plate  321 , chamber plates  322 - 323 , lower restrictor plate  324 , and nozzle plate  325 . A jetting channel includes diaphragm  410 , pressure chamber  412 , and nozzle  380 . Pressure chamber  412  is fluidly coupled to a supply manifold  420  via an upper restrictor  414 . Upper restrictor  414  controls the flow of print fluid from the supply manifold  420  to pressure chamber  412 . Pressure chamber  412  is also fluidly coupled to a return manifold  422  via a lower restrictor  416 . Lower restrictor  416  controls the flow of print fluid from pressure chamber  412  to return manifold  422 . Actuation by a piezoelectric actuator  304  will cause the print fluid to be ejected out of the jetting channel through nozzle  380 . 
     Although a piezoelectric printhead  104  is illustrated in  FIGS. 3-4 , other types of printheads  104  may be used in jetting apparatus  100 , such as a thermal printhead. 
       FIGS. 5-6  are cross-sectional views of a traditional nozzle of a printhead. Nozzle  500  in  FIG. 5  is a cone-shaped nozzle, and nozzle  600  in  FIG. 6  is a bell-shaped nozzle. Nozzles  500 - 600  are both convergent nozzles where the cross-sectional area decreases. As a print fluid enters the smaller cross-section, it increases in velocity due to the conservation of mass. Although these nozzle shapes may be effective for their intended purpose, other nozzle shapes may provide different or better jetting characteristics. 
       FIG. 7  is a cross-sectional view of a nozzle  700  of a printhead in an illustrative embodiment. Nozzle  700  may be an example of a nozzle  380  described above for printhead  104 . Nozzle  700  comprises an aperture or opening through one or more nozzle plates  702 . Nozzle plate(s)  702  in  FIG. 7  may be an example of nozzle plate  325  shown in  FIG. 3 . Nozzle plate  702  includes an interface surface  704  and a discharge surface  706 . Interface surface  704  represents a surface that abuts another plate in a plate stack, such as a lower restrictor plate  324  in  FIG. 3 . Discharge surface  706  represents the surface from which a droplet of print fluid is ejected or jetted from a printhead. One end of nozzle  700  is toward a higher-pressure region within a printhead (e.g., a pressure chamber), and is the entrance  710  for a print fluid into nozzle  700 . The other end of nozzle  700  is toward a lower-pressure region outside of the printhead (e.g., ambient air), and is the exit  711  for the print fluid out of nozzle  700 . Exit  711  may also be referred to as the orifice. Entrance  710  has a diameter  720  that is larger than a diameter  721  of exit  711 . 
     From entrance  710  to exit  711  along its length, nozzle  700  is comprised of a first converging section  732 , a neck  733  that abuts or adjoins first converging section  732 , and a second converging section  734  that abuts or adjoins neck  733 . First converging section  732  has a cross-sectional area (taken transverse or width-wise, which is into the page in  FIG. 7 ) that decreases in the flow direction of print fluid through nozzle  700 , which is indicated by arrow  750 . First converging section  732  has a cone shape that tapers or angles from end  740  to end  741  so that the diameter of first converging section  732  decreases from end  740  to end  741 . Neck  733  has a cross-sectional area that is generally constant, uniform, or otherwise continuous in the flow direction of print fluid through nozzle  700 . The diameter of neck  733  may correspond with the diameter of first converging section  732  at end  741 , and remains uniform along a length of neck  733  in the flow direction (e.g., arrow  750 ). Second converging section  734  has a cross-sectional area that decreases in the flow direction of print fluid through nozzle  700 . Second converging section  734  has a cone shape that tapers or angles from end  744  to end  745  so that the diameter of second converging section  734  decreases from end  744  to end  745  (i.e., exit  711 ). In this embodiment, the diameter (or cross-sectional area) of second converging section  734  at end  744  is generally the same as or equivalent to the diameter (or cross-sectional area) of neck  733 . The diameter  721  of second converging section  734  at end  745  is less than the diameter of neck  733  and first converging section  732  at end  741 . 
     A head designer may adjust the convergence angle  742  of first converging section  732 , the convergence angle  746  of second converging section  734 , and/or the diameter of neck  733  based on the desired jetting characteristics. In one embodiment, the convergence angles  742 / 746  may be the same or equivalent. In another embodiment, the convergence angle  742  of first converging section  732  may be greater than the convergence angle  746  of second converging section  734 . In another embodiment, the convergence angle  746  of second converging section  734  may be greater than the convergence angle  742  of first converging section  732 . 
     As a print fluid travels through first converging section  732 , the velocity of the print fluid increases due to the converging shape of first converging section  732  (i.e., conservation of mass). As the print fluid travels through neck  733 , the velocity of the print fluid stays constant due to the uniform diameter of neck  733 . As a print fluid travels through second converging section  734 , the velocity of the print fluid again increases due to the converging shape of second converging section  734 . The difference in velocity of the print fluid in the different sections of nozzle  700  affects the viscous forces of the print fluid in nozzle  700 , and creates an instability in the jet discharged from nozzle  700 . This instability accelerates the break-off time of the jet from nozzle  700 , and reduces the length of the ligament of the jet. This may be beneficial with high viscosity print fluids (e.g., 100 cP or more) or ultra-high viscosity print fluids (e.g., 1,000-10,000 cP or more). The difference in velocity may be exploited further for different objectives by using different firing modes to create the desired droplet shape. Larger or smaller droplet sizes may be created by means of adjusting the firing order of the wave-form. For example, a fill-before-fire favors a large inertial force over viscous forces, which in turn leads to an accelerated break-off of the jet. This is often characterized by the shortest ligament and fastest break-off time. It has the added benefit of creating fewer or no satellites. This leads to higher frequency jetting combined with less ill effects of the satellites or the creation of mist. The fire-before-fill is to be contrasted with fill-before-fire, which leads to smaller droplets and longer ligaments but within an acceptable range for jetting at these viscosities. 
     Nozzle  700  may be formed in a single nozzle plate  702  as shown in  FIG. 7 . Alternatively, a plurality of nozzle plates may be stacked together to form nozzle  700 .  FIG. 8  is a cross-sectional view of nozzle  700  formed by two nozzle plates in an illustrative embodiment. In this embodiment, nozzle  700  is formed with nozzle plates  801 - 802 . Nozzle plate  801  defines or forms first converging section  732  and neck  733 , while nozzle plate  802  defines or forms second converging section  734 .  FIG. 9  is a cross-sectional view of nozzle  700  formed by three nozzle plates in an illustrative embodiment. In this embodiment, nozzle  700  is formed with nozzle plates  901 - 903 . Nozzle plate  901  defines or forms first converging section  732 , nozzle plate  902  defines or forms neck  733 , and nozzle plate  903  defines or forms second converging section  734 . Nozzle  700  may be formed by more nozzle plates in other embodiments. 
       FIG. 10  is a cross-sectional view of a nozzle  1000  of a printhead in another illustrative embodiment. Nozzle  1000  may be another example of a nozzle  380  described above for printhead  104 . Nozzle  1000  comprises an aperture or opening through one or more nozzle plates  1002 . Nozzle plate(s)  1002  in  FIG. 10  may be an example of nozzle plate  325  shown in  FIG. 3 . Nozzle plate  1002  includes an interface surface  1004  and a discharge surface  1006 . Interface surface  1004  represents a surface that abuts another plate in a plate stack, such as a lower restrictor plate  324  in  FIG. 3 . Discharge surface  1006  represents the surface from which a droplet of print fluid is ejected or jetted from a printhead. One end of nozzle  1000  is toward a higher-pressure region within a printhead (e.g., a pressure chamber), and is the entrance  1010  for a print fluid into nozzle  1000 . The other end of nozzle  1000  is toward a lower-pressure region outside of the printhead (e.g., ambient air), and is the exit  1011  for the print fluid out of nozzle  1000 . Entrance  1010  has a diameter  1020  that is larger than a diameter  1021  of exit  1011 . 
     From entrance  1010  to exit  1011 , nozzle  1000  includes a first converging section  1032 , a neck  1033  that abuts or adjoins first converging section  1032 , and a second converging section  1034  that abuts or adjoins neck  1033 . First converging section  1032  has a cross-sectional area that decreases in the flow direction of print fluid through nozzle  1000 , which is indicated by arrow  1050 . First converging section  1032  has a cone shape that tapers or angles from end  1040  to end  1041  so that the diameter of first converging section  1032  decreases from end  1040  to end  1041 . Neck  1033  has a cross-sectional area that is generally constant, uniform, or otherwise continuous in the flow direction of print fluid through nozzle  1000 . The diameter of neck  1033  may correspond with the diameter of first converging section  1032  at end  1041 , and remains uniform along a length of neck  1033  in the flow direction (e.g., arrow  1050 ). Second converging section  1034  has a cross-sectional area that decreases in the flow direction of print fluid through nozzle  1000 . Second converging section  1034  has a cone shape that tapers or angles from end  1044  to end  1045  (i.e., exit  1011 ) so that the diameter of second converging section  1034  decreases from end  1044  to end  1045 . In this embodiment, the diameter (or cross-sectional area) of second converging section  1034  at end  1044  is larger than the diameter (or cross-sectional area) of neck  1033 . Thus, nozzle  1000  diverges in the region where neck  1033  transitions into second converging section  1034 . The diameter  1021  of second converging section  1034  at end  1045  is less than the diameter of neck  1033  and first converging section  1032  at end  1041 . 
     A head designer may adjust the convergence angle  1042  of first converging section  1032 , the convergence angle  1046  of second converging section  1034 , and/or the diameter of neck  1033  based on the desired jetting characteristics. In one embodiment, the convergence angles  1042 / 1046  may be the same or equivalent. In another embodiment, the convergence angle  1042  of first converging section  1032  may be greater than the convergence angle  1046  of second converging section  1034 . In another embodiment, the convergence angle  1046  of second converging section  1034  may be greater than the convergence angle  1042  of first converging section  1032 . 
     As a print fluid travels through first converging section  1032 , the velocity of the print fluid increases due to the converging shape of first converging section  1032  (i.e., conservation of mass). As the print fluid travels through neck  1033 , the velocity of the print fluid stays constant due to the uniform diameter of neck  1033 . As a print fluid travels out of neck  1033  and into second converging section  1034 , the velocity of the print fluid decreases due to the larger diameter of second converging section  1034 . As the print fluid travels through second converging section  1034 , the velocity of the print fluid again increases due to the converging shape of second converging section  1034 . The difference in velocity of the print fluid in the different sections of nozzle  1000  affects the viscous forces of the print fluid in nozzle  1000 , especially where the shape of nozzle  1000  sharply deviates from the uniform diameter of neck  1033  to the larger diameter of second converging section  1034 . This creates an instability in the jet discharged from nozzle  1000 , which accelerates the break-off time of the jet from nozzle  1000 , and reduces the length of the ligament of the jet. The difference in velocity is helped in this case by the presence of a geometry that increases the inertial force by increasing the fluid mass available at the base of second converging section  1034 . This design makes available an inertial mass that is faster to deploy into the jet from the layer closest to nozzle  1000 . 
     Nozzle  1000  may be formed in a single nozzle plate  1002  as shown in  FIG. 10 . Alternatively, a plurality of nozzle plates may be stacked together to form nozzle  1000 .  FIG. 11  is a cross-sectional view of nozzle  1000  formed by two nozzle plates in an illustrative embodiment. In this embodiment, nozzle  1000  is formed with nozzle plates  1101 - 1102 . Nozzle plate  1101  defines or forms first converging section  1032  and neck  1033 , while nozzle plate  1102  defines or forms second converging section  1034 .  FIG. 12  is a cross-sectional view of nozzle  1000  formed by three nozzle plates in an illustrative embodiment. In this embodiment, nozzle  1000  is formed with nozzle plates  1201 - 1203 . Nozzle plate  1201  defines or forms first converging section  1032 , nozzle plate  1202  defines or forms neck  1033 , and nozzle plate  1203  defines or forms second converging section  1034 . Nozzle  1000  may be formed by more nozzle plates in other embodiments. 
       FIG. 13  is a cross-sectional view of a nozzle  1300  of a printhead in an illustrative embodiment. Nozzle  1300  may be an example of a nozzle  380  described above for printhead  104 . Nozzle  1300  comprises an aperture or opening through one or more nozzle plates  1302 . Nozzle plate(s)  1302  in  FIG. 13  may be an example of nozzle plate  325  shown in  FIG. 3 . Nozzle plate  1302  includes an interface surface  1304  and a discharge surface  1306 . Interface surface  1304  represents a surface that abuts another plate in a plate stack, such as a lower restrictor plate  324  in  FIG. 3 . Discharge surface  1306  represents the surface from which a droplet of print fluid is ejected or jetted from a printhead. One end of nozzle  1300  is toward a higher-pressure region within a printhead (e.g., a pressure chamber), and is the entrance  1310  for a print fluid into nozzle  1300 . The other end of nozzle  1300  is toward a lower-pressure region outside of the printhead (e.g., ambient air), and is the exit  1311  for the print fluid out of nozzle  1300 . Exit  1311  may also be referred to as the orifice. Entrance  1310  has a diameter  1320  that is larger than a diameter  1321  of exit  1311 . 
     From entrance  1310  to exit  1311  along its length, nozzle  1300  is comprised of a first converging section  1332 , and a second converging section  1334  that abuts or adjoins first converging section  1332 . First converging section  1332  has a cross-sectional area that decreases in the flow direction of print fluid through nozzle  1300 , which is indicated by arrow  1350 . First converging section  1332  has a cone shape that tapers or angles from end  1340  to end  1341  so that the diameter of first converging section  1332  decreases from end  1340  to end  1341 . Second converging section  1334  has a cross-sectional area that decreases in the flow direction of print fluid through nozzle  1300 . Second converging section  1334  has a cone shape that tapers or angles from end  1344  to end  1345  so that the diameter of second converging section  1334  decreases from end  1344  to end  1345  (i.e., exit  1311 ). In this embodiment, the diameter (or cross-sectional area) of second converging section  1334  at end  1344  is generally the same as or equivalent to the diameter (or cross-sectional area) of first converging section  1332  at end  1341 . The diameter  1321  of second converging section  1334  at end  1345  is less than the diameter of first converging section  1332  at end  1341 . 
     A head designer may adjust the convergence angle  1342  of first converging section  1332 , and/or the convergence angle  1346  of second converging section  1334  based on the desired jetting characteristics. The convergence angles  1342 / 1346  are different to create velocity changes of the print fluid through nozzle  1300 . In this embodiment, the convergence angle  1342  of first converging section  1332  is less than the convergence angle  1346  of second converging section  1334 . 
     As a print fluid travels through first converging section  1332 , the velocity of the print fluid increases due to the converging shape of first converging section  1332 . As a print fluid travels through second converging section  1334 , the velocity of the print fluid again increases due to the converging shape of second converging section  1334 . The difference in velocity of the print fluid in the different sections of nozzle  1300  affects the viscous forces of the print fluid in nozzle  1300 , and creates an instability in the jet discharged from nozzle  1300 . This instability accelerates the break-off time of the jet from nozzle  1300 , and reduces the length of the ligament of the jet. 
     Nozzle  1300  may be formed in a single nozzle plate  1302  as shown in  FIG. 13 . Alternatively, a plurality of nozzle plates may be stacked together to form nozzle  1300 .  FIG. 14  is a cross-sectional view of nozzle  1300  formed by two nozzle plates in an illustrative embodiment. In this embodiment, nozzle  1300  is formed with nozzle plates  1401 - 1402 . Nozzle plate  1401  defines or forms first converging section  1332 , while nozzle plate  1402  defines or forms second converging section  1334 . Nozzle  1300  may be formed by more nozzle plates in other embodiments. 
       FIG. 15  is a cross-sectional view of a nozzle  1500  of a printhead in an illustrative embodiment. Nozzle  1500  may be an example of a nozzle  380  described above for printhead  104 . Nozzle  1500  comprises an aperture or opening through one or more nozzle plates  1502 . Nozzle plate(s)  1502  in  FIG. 15  may be an example of nozzle plate  325  shown in  FIG. 3 . Nozzle plate  1502  includes an interface surface  1504  and a discharge surface  1506 . Interface surface  1504  represents a surface that abuts another plate in a plate stack, such as a lower restrictor plate  324  in  FIG. 3 . Discharge surface  1506  represents the surface from which a droplet of print fluid is ejected or jetted from a printhead. One end of nozzle  1500  is toward a higher-pressure region within a printhead (e.g., a pressure chamber), and is the entrance  1510  for a print fluid into nozzle  1500 . The other end of nozzle  1500  is toward a lower-pressure region outside of the printhead (e.g., ambient air), and is the exit  1511  for the print fluid out of nozzle  1500 . Exit  1511  may also be referred to as the orifice. Entrance  1510  has a diameter  1520  that is larger than a diameter  1521  of exit  1511 . 
     From entrance  1510  to exit  1511  along its length, nozzle  1500  is comprised of a first converging section  1532 , and a second converging section  1534  that abuts or adjoins first converging section  1532 . First converging section  1532  has a cross-sectional area that decreases in the flow direction of print fluid through nozzle  1500 , which is indicated by arrow  1550 . First converging section  1532  has a cone shape that tapers or angles from end  1540  to end  1541  so that the diameter of first converging section  1532  decreases from end  1540  to end  1541 . Second converging section  1534  has a cross-sectional area that decreases in the flow direction of print fluid through nozzle  1500 . Second converging section  1534  has a cone shape that tapers or angles from end  1544  to end  1545  so that the diameter of second converging section  1534  decreases from end  1544  to end  1545  (i.e., exit  1511 ). In this embodiment, the diameter (or cross-sectional area) of second converging section  1534  at end  1544  is generally the same as or equivalent to the diameter (or cross-sectional area) of first converging section  1532  at end  1541 . The diameter  1521  of second converging section  1534  at end  1545  is less than the diameter of first converging section  1532  at end  1541 . 
     A head designer may adjust the convergence angle  1542  of first converging section  1532 , and/or the convergence angle  1546  of second converging section  1534  based on the desired jetting characteristics. The convergence angles  1542 / 1546  are different to create velocity changes of the print fluid through nozzle  1500 . In this embodiment, the convergence angle  1542  of first converging section  1532  is greater than the convergence angle  1546  of second converging section  1534 . 
     As a print fluid travels through first converging section  1532 , the velocity of the print fluid increases due to the converging shape of first converging section  1532 . As a print fluid travels through second converging section  1534 , the velocity of the print fluid again increases due to the converging shape of second converging section  1534 . The difference in velocity of the print fluid in the different sections of nozzle  1500  affects the viscous forces of the print fluid in nozzle  1500 , and creates an instability in the jet discharged from nozzle  1500 . This instability accelerates the break-off time of the jet from nozzle  1500 , and reduces the length of the ligament of the jet. 
     Nozzle  1500  may be formed in a single nozzle plate  1502  as shown in  FIG. 15 . Alternatively, a plurality of nozzle plates may be stacked together to form nozzle  1500 .  FIG. 16  is a cross-sectional view of nozzle  1500  formed by two nozzle plates in an illustrative embodiment. In this embodiment, nozzle  1500  is formed with nozzle plates  1601 - 1602 . Nozzle plate  1601  defines or forms first converging section  1532 , while nozzle plate  1602  defines or forms second converging section  1534 . Nozzle  1500  may be formed by more nozzle plates in other embodiments. 
     The following describes fabrication systems and methods that may be used to form nozzles having the nozzle geometries discussed above, along with other geometries/shapes.  FIG. 17  is a block diagram of a fabrication system  1700  in an illustrative embodiment. Fabrication system  1700  is configured to form a nozzle plate (e.g., nozzle plate  325 ) or a plate stack (e.g., plate stack  232 ) for a printhead (e.g., printhead  104 ). Fabrication system  1700  includes a plurality of fabrication devices that represents various stages of fabrication. Tasks performed at the fabrication devices may be automated, may be manual, or may be a combination of automated tasks and manual tasks. In this embodiment, fabrication system  1700  includes a punch press  1702  (or multiple punch presses), which is type of machine or equipment configured to form a hole in a workpiece, such as a nozzle plate. Punch press  1702  includes a plurality of nozzle punches  1710 - 1711 . A nozzle punch  1710 - 1711  is a tool that is forced through a workpiece to create a hole in the workpiece via shearing to form at least part of a nozzle of a printhead. Nozzle punches  1710 - 1711  may have a variety of shapes to create different holes in a workpiece for a nozzle. Although one punch press  1702  is shown in  FIG. 17 , fabrication system  1700  may include multiple punch presses each having a nozzle punch  1710 - 1711 . 
     Fabrication system  1700  further includes a bonding tool  1704 . Bonding tool  1704  is a type of device that bonds or laminates two or more plates together to form a plate stack or laminated plate stack. For example, bonding tool  1704  may be configured to bond multiple plates for a printhead together in a stack, such as multiple nozzle plates  325 , restrictor plates  321 / 324 , chamber plates  322 - 323 , a diaphragm plate  320 , etc. Bonding tool  1704  may include alignment pins or other alignment features configured to align the plates in parallel. Bonding tool  1704  may use an adhesive, heat, pressure, etc., to form bonds between the major surfaces of the plates. 
     Fabrication system  1700  may further include a controller  1706  that is configured to manage the (automated) operations for one or more of the fabrication devices. Controller  1706  may be implemented on a hardware platform comprised of a processor  1720  that executes instructions stored in memory  1722  as shown in  FIG. 17 . A processor  1720  comprises an integrated hardware circuit configured to execute instructions, and memory  1722  is a non-transitory computer readable storage medium for data, instructions, applications, etc., and is accessible by processor  1720 . Although not shown in  FIG. 17 , controller  1706  may be implemented on a hardware platform comprised of analog circuitry, digital circuitry, or a combination of the two. 
     Fabrication system  1700  may further include a transport device  1708  that is configured to transport nozzle plates between punch press  1702  and bonding tool  1704 . Transport device  1708  may comprise a conveyor, robotic arm, etc. 
     Fabrication system  1700  may include other fabrication devices that are not shown for the sake of brevity. 
     As a high-level overview of the operation of fabrication system  1700 , nozzle plates  1730 - 1731  are loaded or otherwise registered in punch press  1702 . For nozzle plate  1730 , punch press  1702  performs a punching process that forces nozzle punch  1710  through nozzle plate  1730  to create a plurality of nozzle holes  1740  that form part of the nozzles for a printhead. For nozzle plate  1731 , punch press  1702  performs a punching process that forces nozzle punch  1711  through nozzle plate  1731  to create a plurality of nozzle holes  1741  that form another part of the nozzles for a printhead. Punch press  1702  may perform a punching process on a number of other nozzle plates as desired. With nozzle holes  1740 - 1741  punched in nozzle plates  1730 - 1731 , the nozzle plates  1730 - 1731  may be transferred to bonding tool  1704 . Bonding tool  1704  bonds the nozzle plates  1730 - 1731  together to form a nozzle plate stack  1736 . Within nozzle plate stack  1736 , the nozzle holes  1740  of nozzle plate  1730  are aligned with the nozzle holes  1741  of nozzle plate  1731  to define the nozzles of a printhead. Bonding tool  1704  may also receive additional plates for the printhead, such as restrictor plates  321 / 324 , chamber plates  322 - 323 , a diaphragm plate  320 , etc., and bond these plates along with the nozzle plates  1730 - 1731  to form the plate stack  232  for the printhead. 
     Although the above described two nozzle plates  1730 - 1731  as forming the nozzle plate stack  1736 , it is noted that more than two nozzle plates may be fabricated with punch press  1702  and bonded together to form nozzle plate stack  1736  in other embodiments. 
       FIG. 18  is a block diagram of punch press  1702  in an illustrative embodiment. Punch press  1702  includes a nozzle punch  1710 , and a die  1802  located on the opposite side of a workpiece (i.e., a nozzle plate  1730 ). Die  1802  is held in place by a die support  1804 . Die  1802  includes a die hole  1803 , and acts to support the material around the perimeter of the hole formed in the workpiece and localize the shearing forces for a cleaner edge. Nozzle punch  1710  and die  1802  are made from a harder material than a nozzle plate  1730 , such as a hardened steel, tungsten carbide, etc. Nozzle punch  1710  attaches to a punch coupler  1810 , which in turn is attached to a ram  1812 . Although not shown, punch press  1702  may also include a mechanism of delivering power to ram  1812  (e.g., mechanical, electro-mechanical, or hydraulic). Ram  1812  is configured to move punch coupler  1810  and nozzle punch  1710  up and down in a vertically linear motion in  FIG. 18 . Thus, with a nozzle plate  1730  loaded between nozzle punch  1710  and die  1802 , ram  1812  is able to move nozzle punch  1710  toward die  1802  and force nozzle punch  1710  through nozzle plate  1730  and into the die hole  1803  of die  1802 . When pressed together, nozzle punch  1710  and die  1802  form a hole in nozzle plate  1730 . The length of the stroke in which ram  1812  moves nozzle punch  1710  downward toward die  1802  is adjustable and controllable. 
       FIG. 19  is a flow chart illustrating a method  1900  of fabricating a nozzle plate stack  1736  in an illustrative embodiment. The steps of method  1900  will be described with respect to fabrication system  1700  of  FIG. 17 , although one skilled in the art will understand that the methods described herein may be performed by other types of systems. The steps of the methods described herein are not all inclusive and may include other steps not shown. The steps for the flow charts shown herein may also be performed in an alternative order. 
     To begin, a nozzle plate  1730  is obtained and loaded/registered on punch press  1702 . At this point, nozzle plate  1730  may be considered “blank” as it has not yet been punched with holes for nozzles.  FIG. 20  is a perspective view of a blank nozzle plate  1730  in an illustrative embodiment. Nozzle plate  1730  is a thin sheet of material that is generally rectangular in shape and is substantially flat. Nozzle plate  1730  may be made from a metal material (e.g., stainless steel, copper, alloys, etc.), a synthetic material (e.g., plastic), or another type of material. Nozzle plate  1730  has a first side  2001  and a second side  2002  opposite the first side  2001  that define the major surfaces of nozzle plate  1730 . Nozzle plate  1730  has a dimension indicated by a width (W 1 ), a length (L 1 ), and a thickness (T 1 ). The thickness of nozzle plate  1730  may be in the range of about 50 μm to 150 μm. Other nozzle plates  1731  described herein may be similar to nozzle plate  1730  shown in  FIG. 20 . However, the thicknesses of the individual nozzle plates may vary as desired. 
     In  FIG. 19 , punch press  1702  punches a plurality of nozzle holes  1740  in nozzle plate  1730  with nozzle punch  1710  (step  1902 ). A nozzle hole comprises a hole in a nozzle plate that forms a portion of a nozzle of a printhead. In one embodiment, nozzle punch  1710  may be configured to punch nozzle holes  1740  one at a time. Thus, punch press  1702  may sequentially punch the nozzle holes  1740  in nozzle plate  1730  in one or more rows to correspond with one or more rows of nozzles desired for the printhead. In another embodiment, nozzle punch  1710  may be configured to punch multiple nozzle holes  1740  simultaneously (i.e., at the same time). As will be described in more detail below, each of the nozzle holes  1740  punched in nozzle plate  1730  includes a converging section. After punching is completed, the nozzle plate  1730  may be unloaded from punch press  1702 , and transferred to another tool, such as bonding tool  1704 . 
     Another nozzle plate  1731  is obtained and loaded/registered on punch press  1702 . At this point, nozzle plate  1731  may also be considered “blank” as it has not yet been punched with holes for nozzles. Punch press  1702  punches a plurality of nozzle holes  1741  in nozzle plate  1731  with nozzle punch  1711  (step  1904 ). In one embodiment, nozzle punch  1711  may be configured to punch nozzle holes  1741  one at a time. Thus, punch press  1702  may sequentially punch the nozzle holes  1741  in nozzle plate  1731  in one or more rows to correspond with one or more rows of nozzles desired for the printhead. In another embodiment, nozzle punch  1711  may be configured to punch multiple nozzle holes  1741  simultaneously (i.e., at the same time). As will be described in more detail below, each of the nozzle holes  1741  punched in nozzle plate  1731  includes a converging section. After punching is completed, the nozzle plate  1731  may be unloaded from punch press  1702 , and transferred to another tool, such as bonding tool  1704 . 
     Nozzle plates  1730 - 1731  are loaded or registered on bonding tool  1704 . When loaded on bonding tool  1704 , the nozzle holes  1740  in nozzle plate  1730  are aligned with the nozzle holes  1741  in nozzle plate  1731 , with the first side  2001  of nozzle plate  1731  facing the second side  2002  of nozzle plate  1730 . Bonding tool  1704  bonds nozzle plate  1730  and nozzle plate  1731  to form nozzle plate stack  1736  (step  1906 ). For example, bonding tool  1704  may use an adhesive or the like, along with heat, pressure, etc., to bond nozzle plates  1730 - 1731  together into a laminated stack. Thus, the first side  2001  of nozzle plate  1731  is bonded to the second side  2002  of nozzle plate  1730 . When bonded, nozzle holes  1740  in nozzle plate  1730  and nozzle holes  1741  in nozzle plate  1731  define nozzles of the printhead. 
     In the above embodiment, two nozzle plates  1730 - 1731  were punched and bonded to form nozzle plate stack  1736 . However, more than two nozzle plates  1730 - 1731  may be punched and bonded to form nozzle plate stack  1736  in other embodiments. Also, bonding tool  1704  may bond nozzle plates  1730 - 1731  along with other plates, such as restrictor plates  321 / 324 , chamber plates  322 - 323 , a diaphragm plate  320 , etc., to form a plate stack  232  for a printhead. 
     Depending on the set up of nozzle punches  1710 - 1711  and/or die  1802  (see  FIG. 18 ), the punching process performed by punch press  1702  may result in material projecting from one side of nozzle plates  1730 - 1731  around the holes that are formed in the nozzle plates  1730 - 1731 , which may be referred to herein as extrusions, burrs, etc. Thus, nozzle plates  1730 - 1731  may be polished after being punched and before bonding.  FIG. 21  is a block diagram of a fabrication system  1700  in another illustrative embodiment. In this embodiment, fabrication system  1700  further includes a polishing tool  2110 . Polishing tool  2110  is a type of device that smoothes and/or removes material from a surface of a workpiece to increase the flatness of the surface or of features projecting from the surface. Polishing tool  2110  may use mechanical forces from a polishing pad, an abrasive pad, or the like for smoothing or planarization of the surface. Polishing tool  2110  may also use mechanical forces in combination with chemical forces for smoothing or planarization of the surface, such as with Chemical-Mechanical Polishing (CMP). Polishing tool  2110  may use other types of material-removal processes as desired. 
       FIG. 22  is a flow chart illustrating an additional step of method  1900  in an illustrative embodiment. In this embodiment, when nozzle holes  1740  are punched from a first side  2001  through a second side  2002  of nozzle plate  1730 , extrusions may result on the second side  2002  of nozzle plate  1730  around the nozzle holes  1740 . Thus after punching, nozzle plate  1730  may be loaded or registered on polishing tool  2110 . Polishing tool  2110  polishes the second side  2002  of nozzle plate  1730  (step  2208 ) to form a planar surface on the second side  2002  of nozzle plate  1730  prior to bonding. The second side  2002  of nozzle plate  1730  is a bonding surface that will be bonded to nozzle plate  1731  by bonding tool  1704 , and it is beneficial to planarize the second side  2002  of nozzle plate  1730  to improve bonding. In another embodiment, polishing tool  2110  may also polish the first side  2001  of nozzle plate  1730  (step  2208 ) to form a planar surface on the first side  2001  of nozzle plate  1730  prior to the bonding. 
     Similarly, when nozzle holes  1741  are punched from a first side  2001  through a second side  2002  of nozzle plate  1731 , extrusions may result on the second side  2002  of nozzle plate  1731  around the nozzle holes  1741 . The second side  2002  of nozzle plate  1731  will represent the bottom surface or discharge surface of the printhead (i.e., the surface facing the medium from which print fluid is jetted). After punching, nozzle plate  1731  may be loaded or registered on polishing tool  2110 . Polishing tool  2110  polishes the second side  2002  of nozzle plate  1731  (step  2208 ) prior to bonding. In one embodiment, polishing tool  2110  may polish the second side  2002  of nozzle plate  1731  to form a planar surface on the second side  2002  of nozzle plate  1731 . In another embodiment, polishing tool  2110  may polish the second side  2002  of nozzle plate  1731  to remove a portion of the extrusions and leave surface features around nozzle holes  1741  that define orifices of the nozzles where a print fluid exits the nozzles. Any of the above steps of method  1900  may be performed by controller  1706  controlling operations of fabrication system  1700  according to instructions stored in memory  1722 . 
     The following examples further illustrate fabrication of a nozzle plate stack  1736 . In one embodiment,  FIGS. 23-33  illustrate fabrication of a nozzle plate stack  1736  where the geometry of the nozzles resembles  FIG. 13  described above. A blank nozzle plate  1730  is loaded onto punch press  1702  where nozzle holes  1740  are formed in nozzle plate  1730  with nozzle punch  1710 .  FIG. 23  illustrates a nozzle punch  1710  and a nozzle plate  1730  in an illustrative embodiment. Nozzle punch  1710  includes a body  2302  that couples to punch holder  1810  of punch press  1702 , and a head  2304  that projects from body  2302 . Head  2304  is the member of nozzle punch  1710  that forms a nozzle hole  1740  in a nozzle plate  1730 . The shape or dimensions of head  2304  therefore defines the shape or dimensions of nozzle hole  1740 . Along a length of head  2304  from body  2302  to tip  2306 , head  2304  includes a converging portion  2308  that is generally cone-shaped, and converges or tapers toward tip  2306 . Thus, the diameter of converging portion  2308  decreases or gets progressively smaller at a convergence angle  2310 . Although not shown, tip  2306  may include a point, a cutting edge, etc., to facilitate punching a hole in a nozzle plate. 
     Punch press  1702  forces nozzle punch  1710  through nozzle plate  1730  from side  2001  to create a nozzle hole  1740 .  FIG. 24  illustrates nozzle punch  1710  pressed into nozzle plate  1730  in an illustrative embodiment. Punch press  1702  forces the head  2304  of nozzle punch  1710  through nozzle plate  1730  based on a controllable stroke length  2402 , with the tip  2306  of nozzle punch  1710  at least partially extending through side  2002  of nozzle plate  1730 . Punch press  1702  then withdraws nozzle punch  1710  from nozzle plate  1730 .  FIG. 25  illustrates nozzle punch  1710  withdrawn from nozzle plate  1730  in an illustrative embodiment. The punching process forms a nozzle hole  1740  through the thickness (T 1 ) of nozzle plate  1730  from side  2001  to side  2002 . Nozzle hole  1740  has a convergence angle  1342  matching the convergence angle  2310  of head  2304 . Punch press  1702  may repeat this process to form a plurality of nozzle holes  1740  in nozzle plate  1730 . 
     Punching may result in an extrusion  2510  surrounding nozzle hole  1740  on side  2002 . Side  2002  of nozzle plate  1730  will subsequently be bonded to another nozzle plate, so it may be desirable to form a planar surface on side  2002  with polishing tool  2110 .  FIG. 26  illustrates polishing of nozzle plate  1730  in an illustrative embodiment. Polishing tool  2110  is represented in  FIG. 26  generally by a polishing pad  2604  that polishes side  2002  of nozzle plate  1730 . It is noted that polishing tool  2110  may also polish side  2001  of nozzle plate  1730  if desired.  FIG. 27  illustrates nozzle plate  1730  after polishing in an illustrative embodiment. Polishing removes extrusion  2510  and forms a planar surface on side  2002  of nozzle plate  1730 , and the dimensions of nozzle hole  1740  are defined. As in  FIG. 13 , nozzle hole  1740  includes a first converging section  1332  having a cone shape that tapers or angles from end  1340  to end  1341  so that the diameter of first converging section  1332  decreases from end  1340  to end  1341 . 
     A blank nozzle plate  1731  is loaded onto punch press  1702  where nozzle holes  1741  are formed in nozzle plate  1731  with nozzle punch  1711 .  FIG. 28  illustrates a nozzle punch  1711  and a nozzle plate  1731  in an illustrative embodiment. Nozzle punch  1711  includes a body  2802  that couples to punch holder  1810  of punch press  1702 , and a head  2804  that projects from body  2802 . Along a length of head  2804  from body  2802  to tip  2806 , head  2804  includes a converging portion  2808  that is generally cone-shaped, and converges or tapers toward tip  2806 . Thus, the diameter of converging portion  2808  decreases or gets progressively smaller at a convergence angle  2810 . In this embodiment, the convergence angle  2810  of the head  2804  of nozzle punch  1711  is different (i.e., greater) than the convergence angle  2310  of the head  2304  of nozzle punch  1710  as shown in  FIG. 23 . Although not shown, tip  2806  may include a point, a cutting edge, etc., to facilitate punching a hole in a nozzle plate. 
     Punch press  1702  forces nozzle punch  1711  through nozzle plate  1731  from side  2001  to create a nozzle hole  1741 .  FIG. 29  illustrates nozzle punch  1711  pressed into nozzle plate  1731  in an illustrative embodiment. Punch press  1702  forces the head  2804  of nozzle punch  1711  through nozzle plate  1731  based on a controllable stroke length  2902 , with the tip  2806  of nozzle punch  1711  at least partially extending through side  2002  of nozzle plate  1731 . Punch press  1702  then withdraws nozzle punch  1711  from nozzle plate  1731 .  FIG. 30  illustrates nozzle punch  1711  withdrawn from nozzle plate  1731  in an illustrative embodiment. The punching process forms a nozzle hole  1741  through the thickness (T 1 ) of nozzle plate  1731  from side  2001  to side  2002 . Nozzle hole  1741  has a convergence angle  1346  matching the convergence angle  2810  of head  2804 . Punch press  1702  may repeat this process to form a plurality of nozzle holes  1741  in nozzle plate  1731 . 
     Punching may result in an extrusion  3010  surrounding nozzle hole  1741  on side  2002 . Side  2002  of nozzle plate  1731  represents the discharge surface of a printhead where a print fluid is jetted out of the printhead. Thus, side  2002  of nozzle plate  1731  may be polished to define the orifice of a nozzle.  FIG. 31  illustrates polishing of nozzle plate  1731  in an illustrative embodiment. Polishing tool  2110  is represented in  FIG. 31  generally by a polishing pad  2604  that polishes side  2002  of nozzle plate  1731 . It is noted that polishing tool  2110  may also polish side  2001  of nozzle plate  1731  if desired.  FIG. 32  illustrates nozzle plate  1731  after polishing in an illustrative embodiment. After polishing in this embodiment, a portion of extrusion  3010  is removed, leaving a surface feature  3210  that projects from side  2002  around nozzle hole  1741 . Polishing defines the orifice of the nozzle where a print fluid exits the nozzle at an end of nozzle hole  1741 . Nozzle hole  1741  includes a second converging section  1334  having a cone shape that tapers or angles from end  1344  to end  1345  so that the diameter of second converging section  1334  decreases from end  1344  to end  1345 . The diameter of second converging section  1334  at end  1344  is generally the same as or equivalent to the diameter of first converging section  1332  at end  1341  (see  FIG. 27 ). The diameter of second converging section  1334  at end  1345  defines the orifice of a nozzle, which is circular. 
     With nozzle plates  1730 - 1731  punched and polished as desired, nozzle plates  1730 - 1731  may be loaded onto bonding tool  1704 , which bonds the nozzle plates  1730 - 1731  to form a nozzle plate stack  1736 .  FIG. 33  illustrates a nozzle plate stack  1736  in an illustrative embodiment. When bonded, nozzle hole  1740  of nozzle plate  1730  and nozzle hole  1741  of nozzle plate  1731  define a nozzle  1300  of a printhead as shown in  FIG. 13 . End  1340  of first converging section  1332  is the entrance of nozzle  1300 , and end  1345  of second converging section  1334  is the exit or orifice  1310  of nozzle  1300 . From the entrance to orifice  1310  along its length, nozzle  1300  is comprised of first converging section  1332  and second converging section  1334  that abuts or adjoins first converging section  1332 . First converging section  1332  has a diameter that decreases in the flow direction of print fluid through nozzle  1300 , and second converging section  1334  has a diameter that decreases in the flow direction at a different angle than the first converging section  1332 . 
     In another embodiment,  FIGS. 34-44  illustrate fabrication of a nozzle plate stack  1736  where the geometry of the nozzles resembles  FIG. 15  described above. A blank nozzle plate  1730  is loaded onto punch press  1702  where nozzle holes  1740  are formed in nozzle plate  1730  with nozzle punch  1710 .  FIG. 34  illustrates a nozzle punch  1710  and a nozzle plate  1730  in an illustrative embodiment. Nozzle punch  1710  includes a body  3402  that couples to punch holder  1810  of punch press  1702 , and a head  3404  that projects from body  3402 . Along a length of head  3404  from body  3402  to tip  3406 , head  3404  includes a converging portion  3408  that is generally cone-shaped, and converges or tapers toward tip  3406 . Thus, the diameter of converging portion  3408  decreases or gets progressively smaller at a convergence angle  3410 . Although not shown, tip  3406  may include a point, a cutting edge, etc., to facilitate punching a hole in a nozzle plate. 
     Punch press  1702  forces nozzle punch  1710  through nozzle plate  1730  from side  2001  to create a nozzle hole  1740 .  FIG. 35  illustrates nozzle punch  1710  pressed into nozzle plate  1730  in an illustrative embodiment. Punch press  1702  forces the head  3404  of nozzle punch  1710  through nozzle plate  1730  based on a controllable stroke length  3502 , with the tip  3406  of nozzle punch  1710  at least partially extending through side  2002  of nozzle plate  1730 . Punch press  1702  then withdraws nozzle punch  1710  from nozzle plate  1730 .  FIG. 36  illustrates nozzle punch  1710  withdrawn from nozzle plate  1730  in an illustrative embodiment. The punching process forms a nozzle hole  1740  through the thickness (T 1 ) of nozzle plate  1730  from side  2001  to side  2002 . Nozzle hole  1740  has a convergence angle  1542  matching the convergence angle  3410  of head  3404 . Punch press  1702  may repeat this process to form a plurality of nozzle holes  1740  in nozzle plate  1730 . 
     Punching may result in an extrusion  3610  surrounding nozzle hole  1740  on side  2002 . Side  2002  of nozzle plate  1730  will subsequently be bonded to another nozzle plate, so it may be desirable to form a planar surface on side  2002  with polishing tool  2110 .  FIG. 37  illustrates polishing of nozzle plate  1730  in an illustrative embodiment. Polishing tool  2110  is represented in  FIG. 37  generally by a polishing pad  2604  that polishes side  2002  of nozzle plate  1730 . It is noted that polishing tool  2110  may also polish side  2001  of nozzle plate  1730  if desired.  FIG. 38  illustrates nozzle plate  1730  after polishing in an illustrative embodiment. Polishing removes extrusion  3610  and forms a planar surface on side  2002  of nozzle plate  1730 , and the dimensions of nozzle hole  1740  are defined. As in  FIG. 15 , nozzle hole  1740  includes a first converging section  1532  having a cone shape that tapers or angles from end  1540  to end  1541  so that the diameter of first converging section  1532  decreases from end  1540  to end  1541 . 
     A blank nozzle plate  1731  is loaded onto punch press  1702  where nozzle holes  1741  are formed in nozzle plate  1731  with nozzle punch  1711 .  FIG. 39  illustrates a nozzle punch  1711  and a nozzle plate  1731  in an illustrative embodiment. Nozzle punch  1711  includes a body  3902  that couples to punch holder  1810  of punch press  1702 , and a head  3904  that projects from body  3902 . Along a length of head  3904  from body  3902  to tip  3906 , head  3904  includes a converging portion  3908  that is generally cone-shaped, and converges or tapers toward tip  3906 . Thus, the diameter of converging portion  3908  decreases or gets progressively smaller at a convergence angle  3910 . In this embodiment, the convergence angle  3910  of the head  3904  of nozzle punch  1711  is different (i.e., less) than the convergence angle  3410  of the head  3404  of nozzle punch  1710  as shown in  FIG. 34 . Although not shown, tip  3906  may include a point, a cutting edge, etc., to facilitate punching a hole in a nozzle plate. 
     Punch press  1702  forces nozzle punch  1711  through nozzle plate  1731  from side  2001  to create a nozzle hole  1741 .  FIG. 40  illustrates nozzle punch  1711  pressed into nozzle plate  1731  in an illustrative embodiment. Punch press  1702  forces the head  3904  of nozzle punch  1711  through nozzle plate  1731  based on a controllable stroke length  4002 , with the tip  3906  of nozzle punch  1711  at least partially extending through side  2002  of nozzle plate  1731 . Punch press  1702  then withdraws nozzle punch  1711  from nozzle plate  1731 .  FIG. 41  illustrates nozzle punch  1711  withdrawn from nozzle plate  1731  in an illustrative embodiment. The punching process forms a nozzle hole  1741  through the thickness (T 1 ) of nozzle plate  1731  from side  2001  to side  2002 . Nozzle hole  1741  has a convergence angle  1546  matching the convergence angle  3910  of head  3904 . Punch press  1702  may repeat this process to form a plurality of nozzle holes  1741  in nozzle plate  1731 . 
     Punching may result in an extrusion  4110  surrounding nozzle hole  1741  on side  2002 . Side  2002  of nozzle plate  1731  represents the discharge surface of a printhead where a print fluid is jetted out of the printhead. Thus, side  2002  of nozzle plate  1731  may be polished to define the orifice of a nozzle.  FIG. 42  illustrates polishing of nozzle plate  1731  in an illustrative embodiment. Polishing tool  2110  is represented in  FIG. 42  generally by a polishing pad  2604  that polishes side  2002  of nozzle plate  1731 . It is noted that polishing tool  2110  may also polish side  2001  of nozzle plate  1731  if desired.  FIG. 43  illustrates nozzle plate  1731  after polishing in an illustrative embodiment. After polishing in this embodiment, a portion of extrusion  4110  is removed, leaving a surface feature  4310  that projects from side  2002  around nozzle hole  1741 . Polishing defines the orifice of the nozzle where a print fluid exits the nozzle at an end of nozzle hole  1741 . Nozzle hole  1741  includes a second converging section  1534  having a cone shape that tapers or angles from end  1544  to end  1545  so that the diameter of second converging section  1534  decreases from end  1544  to end  1545 . The diameter of second converging section  1534  at end  1544  is generally the same as or equivalent to the diameter of first converging section  1532  at end  1541  (see  FIG. 38 ). The diameter of second converging section  1534  at end  1545  defines the orifice of a nozzle, which is circular. 
     With nozzle plates  1730 - 1731  punched and polished as desired, nozzle plates  1730 - 1731  may be loaded onto bonding tool  1704 , which bonds the nozzle plates  1730 - 1731  to form a nozzle plate stack  1736 .  FIG. 44  illustrates a nozzle plate stack  1736  in an illustrative embodiment. When bonded, nozzle hole  1740  of nozzle plate  1730  and nozzle hole  1741  of nozzle plate  1731  define a nozzle  1500  of a printhead as shown in  FIG. 15 . End  1540  of first converging section  1532  is the entrance of nozzle  1500 , and end  1545  of second converging section  1534  is the exit or orifice  1510  of nozzle  1500 . From the entrance to orifice  1510  along its length, nozzle  1500  is comprised of first converging section  1532  and second converging section  1534  that abuts or adjoins first converging section  1532 . First converging section  1532  has a diameter that decreases in the flow direction of print fluid through nozzle  1500 , and second converging section  1534  has a diameter that decreases in the flow direction at a different angle than the first converging section  1532 . 
     In another embodiment,  FIGS. 45-55  illustrate fabrication of a nozzle plate stack  1736  where the geometry of the nozzles resembles  FIG. 7  described above. A blank nozzle plate  1730  is loaded onto punch press  1702  where nozzle holes  1740  are formed in nozzle plate  1730  with nozzle punch  1710 .  FIG. 45  illustrates a nozzle punch  1710  and a nozzle plate  1730  in an illustrative embodiment. Nozzle punch  1710  includes a body  4502  that couples to punch holder  1810  of punch press  1702 , and a head  4504  that projects from body  4502 . Along a length of head  4504  from body  4502  to tip  4506 , head  4504  includes a converging portion  4508  and a neck portion  4509 . Converging portion  4508  is generally cone-shaped, and converges or tapers toward tip  4506 . Thus, the diameter of converging portion  4508  decreases or gets progressively smaller at a convergence angle  4510 . Neck portion  4509  is generally cylindrical in shape, and has a constant or uniform diameter. The diameter of neck portion  4509  may correspond with the diameter at an end of converging portion  4508 . Although not shown, tip  4506  may include a point, a cutting edge, etc., to facilitate punching a hole in a nozzle plate. 
     Punch press  1702  forces nozzle punch  1710  through nozzle plate  1730  from side  2001  to create a nozzle hole  1740 .  FIG. 46  illustrates nozzle punch  1710  pressed into nozzle plate  1730  in an illustrative embodiment. Punch press  1702  forces the head  4504  of nozzle punch  1710  through nozzle plate  1730  based on a controllable stroke length  4602 , with the tip  4506  of nozzle punch  1710  at least partially extending through side  2002  of nozzle plate  1730 . Punch press  1702  then withdraws nozzle punch  1710  from nozzle plate  1730 .  FIG. 47  illustrates nozzle punch  1710  withdrawn from nozzle plate  1730  in an illustrative embodiment. The punching process forms a nozzle hole  1740  through the thickness (T 1 ) of nozzle plate  1730  from side  2001  to side  2002 . Punch press  1702  may repeat this process to form a plurality of nozzle holes  1740  in nozzle plate  1730 . 
     Punching may result in an extrusion  4710  surrounding a nozzle hole  1740  on side  2002 . Side  2002  of nozzle plate  1730  will subsequently be bonded to another nozzle plate, so it may be desirable to form a planar surface on side  2002  with polishing tool  2110 .  FIG. 48  illustrates polishing of nozzle plate  1730  in an illustrative embodiment. Polishing tool  2110  is represented in  FIG. 48  generally by a polishing pad  2604  that polishes side  2002  of nozzle plate  1730 . It is noted that polishing tool  2110  may also polish side  2001  of nozzle plate  1730  if desired.  FIG. 49  illustrates nozzle plate  1730  after polishing in an illustrative embodiment. Polishing removes extrusion  4710  and forms a planar surface on side  2002  of nozzle plate  1730 , and the dimensions of nozzle hole  1740  are defined. As in  FIG. 7 , nozzle hole  1740  includes a first converging section  732  having a cone shape that tapers or angles from end  740  to end  741  at a convergence angle  742  so that the diameter of first converging section  732  decreases from end  740  to end  741 . Nozzle hole  1740  further includes a neck  733  having a constant or uniform diameter. The diameter of neck  733  may correspond with the diameter of first converging section  732  at end  741 , and remains uniform along a length of neck  733  to end  4902 . 
     A blank nozzle plate  1731  is loaded onto punch press  1702  where nozzle holes  1741  are formed in nozzle plate  1731  with nozzle punch  1711 .  FIG. 50  illustrates a nozzle punch  1711  and a nozzle plate  1731  in an illustrative embodiment. Nozzle punch  1711  includes a body  5002  that couples to punch holder  1810  of punch press  1702 , and a head  5004  that projects from body  5002 . Along a length of head  5004  from body  5002  to tip  5006 , head  5004  includes a converging portion  5008  that is generally cone-shaped, and converges or tapers toward tip  5006 . Thus, the diameter of converging portion  5008  decreases or gets progressively smaller at a convergence angle  5010 . In this embodiment, the convergence angle  5010  of the head  5004  of nozzle punch  1711  may be the same, larger, or smaller than the convergence angle  4510  of the head  4504  of nozzle punch  1710  as shown in  FIG. 45 . Although not shown, tip  5006  may include a point, a cutting edge, etc., to facilitate punching a hole in a nozzle plate. 
     Punch press  1702  forces nozzle punch  1711  through nozzle plate  1731  from side  2001  to create a nozzle hole  1741 .  FIG. 51  illustrates nozzle punch  1711  pressed into nozzle plate  1731  in an illustrative embodiment. Punch press  1702  forces the head  5004  of nozzle punch  1711  through nozzle plate  1731  based on a controllable stroke length  5102 , with the tip  5006  of nozzle punch  1711  at least partially extending through side  2002  of nozzle plate  1731 . Punch press  1702  then withdraws nozzle punch  1711  from nozzle plate  1731 .  FIG. 52  illustrates nozzle punch  1711  withdrawn from nozzle plate  1731  in an illustrative embodiment. The punching process forms a nozzle hole  1741  through the thickness (T 1 ) of nozzle plate  1731  from side  2001  to side  2002 . Nozzle hole  1741  has a convergence angle  746  matching the convergence angle  5010  of head  5004 . Punch press  1702  may repeat this process to form a plurality of nozzle holes  1741  in nozzle plate  1731 . 
     Punching may result in an extrusion  5210  surrounding nozzle hole  1741  on side  2002 . Side  2002  of nozzle plate  1731  represents the discharge surface of a printhead where a print fluid is jetted out of the printhead. Thus, side  2002  of nozzle plate  1731  may be polished to define the orifice of a nozzle.  FIG. 53  illustrates polishing of nozzle plate  1731  in an illustrative embodiment. Polishing tool  2110  is represented in  FIG. 53  generally by a polishing pad  2604  that polishes side  2002  of nozzle plate  1731 . It is noted that polishing tool  2110  may also polish side  2001  of nozzle plate  1731  if desired.  FIG. 54  illustrates nozzle plate  1731  after polishing in an illustrative embodiment. After polishing in this embodiment, a portion of extrusion  5210  is removed, leaving a surface feature  5410  that projects from side  2002  around nozzle hole  1741 . Polishing defines the orifice of the nozzle where a print fluid exits the nozzle at an end of nozzle hole  1741 . Nozzle hole  1741  includes a second converging section  734  having a cone shape that tapers or angles from end  744  to end  745  so that the diameter of second converging section  734  decreases from end  744  to end  745 . The diameter of second converging section  734  at end  744  is generally the same as or equivalent to the diameter of neck  733  (see  FIG. 49 ). The diameter of second converging section  734  at end  745  defines the orifice of a nozzle, which is circular. 
     With nozzle plates  1730 - 1731  punched and polished as desired, nozzle plates  1730 - 1731  may be loaded onto bonding tool  1704 , which bonds the nozzle plates  1730 - 1731  to form a nozzle plate stack  1736 .  FIG. 55  illustrates a nozzle plate stack  1736  in an illustrative embodiment. When bonded, nozzle hole  1740  of nozzle plate  1730  and nozzle hole  1741  of nozzle plate  1731  define a nozzle  700  of a printhead as shown in  FIG. 7 . End  740  of first converging section  732  is the entrance of nozzle  700 , and end  745  of second converging section  734  is the exit or orifice  710  of nozzle  700 . From the entrance to orifice  710  along its length, nozzle  700  is comprised of first converging section  732 , a neck  733  that abuts or adjoins first converging section  732 , and second converging section  734  that abuts or adjoins neck  733 . First converging section  732  has a diameter that decreases in the flow direction of print fluid through nozzle  700 , neck  733  has a uniform diameter in the flow direction of print fluid through nozzle  700 , and second converging section  734  has a diameter that decreases in the flow direction of print fluid through nozzle  700 . 
     The above embodiment described forming the first converging section  732 , neck  733 , and the second converging section  734  for nozzle  700  by punching two nozzle plates  730 - 731 . In other embodiments, more nozzle plates may be punched to form nozzle  700 . For example, first converging section  732  may be formed by punching a first nozzle plate with a first nozzle punch, neck  733  may be formed by punching a second nozzle plate with a second nozzle punch (i.e., a nozzle punch with a cylindrical head), and second converging section  734  may be formed by punching a third nozzle plate with a third nozzle punch. 
     In another embodiment,  FIGS. 56-66  illustrate fabrication of a nozzle plate stack  1736  where the geometry of the nozzles resembles  FIG. 10  described above. A blank nozzle plate  1730  is loaded onto punch press  1702  where nozzle holes  1740  are formed in nozzle plate  1730  with nozzle punch  1710 .  FIG. 56  illustrates a nozzle punch  1710  and a nozzle plate  1730  in an illustrative embodiment. Nozzle punch  1710  includes a body  5602  that couples to punch holder  1810  of punch press  1702 , and a head  5604  that projects from body  5602 . Along a length of head  5604  from body  5602  to tip  5606 , head  5604  includes a converging portion  5608  and a neck portion  5609 . Converging portion  5608  is generally cone-shaped, and converges or tapers toward tip  5606 . Thus, the diameter of converging portion  5608  decreases or gets progressively smaller at a convergence angle  5610 . Neck portion  5609  is generally cylindrical in shape, and has a constant or uniform diameter. The diameter of neck portion  5609  may correspond with the diameter at an end of converging portion  5608 . Although not shown, tip  5606  may include a point, a cutting edge, etc., to facilitate punching a hole in a nozzle plate. 
     Punch press  1702  forces nozzle punch  1710  through nozzle plate  1730  from side  2001  to create a nozzle hole  1740 .  FIG. 57  illustrates nozzle punch  1710  pressed into nozzle plate  1730  in an illustrative embodiment. Punch press  1702  forces the head  5604  of nozzle punch  1710  through nozzle plate  1730  based on a controllable stroke length  5702 , with the tip  5606  of nozzle punch  1710  at least partially extending through side  2002  of nozzle plate  1730 . Punch press  1702  then withdraws nozzle punch  1710  from nozzle plate  1730 .  FIG. 58  illustrates nozzle punch  1710  withdrawn from nozzle plate  1730  in an illustrative embodiment. The punching process forms a nozzle hole  1740  through the thickness (T 1 ) of nozzle plate  1730  from side  2001  to side  2002 . Punch press  1702  may repeat this process to form a plurality of nozzle holes  1740  in nozzle plate  1730 . 
     Punching may result in an extrusion  5810  surrounding a nozzle hole  1740  on side  2002 . Side  2002  of nozzle plate  1730  will subsequently be bonded to another nozzle plate, so it may be desirable to form a planar surface on side  2002  with polishing tool  2110 .  FIG. 59  illustrates polishing of nozzle plate  1730  in an illustrative embodiment. Polishing tool  2110  is represented in  FIG. 59  generally by a polishing pad  2604  that polishes side  2002  of nozzle plate  1730 . It is noted that polishing tool  2110  may also polish side  2001  of nozzle plate  1730  if desired.  FIG. 60  illustrates nozzle plate  1730  after polishing in an illustrative embodiment. Polishing removes extrusion  5810  and forms a planar surface on side  2002  of nozzle plate  1730 , and the dimensions of nozzle hole  1740  are defined. As in  FIG. 10 , nozzle hole  1740  includes a first converging section  1032  having a cone shape that tapers or angles from end  1040  to end  1041  at a convergence angle  1042  so that the diameter of first converging section  1032  decreases from end  1040  to end  1041 . Nozzle hole  1740  further includes a neck  1033  having a constant or uniform diameter. The diameter of neck  1033  may correspond with the diameter of first converging section  1032  at end  1041 , and remains uniform along a length of neck  1033  to end  6002 . 
     A blank nozzle plate  1731  is loaded onto punch press  1702  where nozzle holes  1741  are formed in nozzle plate  1731  with nozzle punch  1711 .  FIG. 61  illustrates a nozzle punch  1711  and a nozzle plate  1731  in an illustrative embodiment. Nozzle punch  1711  includes a body  6102  that couples to punch holder  1810  of punch press  1702 , and a head  6104  that projects from body  6102 . Along a length of head  6104  from body  6102  to tip  6106 , head  6104  includes a converging portion  6108  that is generally cone-shaped, and converges or tapers toward tip  6106 . Thus, the diameter of converging portion  6108  decreases or gets progressively smaller at a convergence angle  6110 . In this embodiment, the convergence angle  6110  of the head  6104  of nozzle punch  1711  may be the same, larger, or smaller than the convergence angle  5610  of the head  5604  of nozzle punch  1710  as shown in  FIG. 56 . Although not shown, tip  6106  may include a point, a cutting edge, etc., to facilitate punching a hole in a nozzle plate. 
     Punch press  1702  forces nozzle punch  1711  through nozzle plate  1731  from side  2001  to create a nozzle hole  1741 .  FIG. 62  illustrates nozzle punch  1711  pressed into nozzle plate  1731  in an illustrative embodiment. Punch press  1702  forces the head  6104  of nozzle punch  1711  through nozzle plate  1731  based on a controllable stroke length  6202 , with the tip  6106  of nozzle punch  1711  at least partially extending through side  2002  of nozzle plate  1731 . Punch press  1702  then withdraws nozzle punch  1711  from nozzle plate  1731 .  FIG. 63  illustrates nozzle punch  1711  withdrawn from nozzle plate  1731  in an illustrative embodiment. The punching process forms a nozzle hole  1741  through the thickness (T 1 ) of nozzle plate  1731  from side  2001  to side  2002 . Nozzle hole  1741  has a convergence angle  1046  matching the convergence angle  6110  of head  6104 . Punch press  1702  may repeat this process to form a plurality of nozzle holes  1741  in nozzle plate  1731 . 
     Punching may result in an extrusion  6310  surrounding nozzle hole  1741  on side  2002 . Side  2002  of nozzle plate  1731  represents the discharge surface of a printhead where a print fluid is jetted out of the printhead. Thus, side  2002  of nozzle plate  1731  may be polished to define the orifice of a nozzle.  FIG. 64  illustrates polishing of nozzle plate  1731  in an illustrative embodiment. Polishing tool  2110  is represented in  FIG. 64  generally by a polishing pad  2604  that polishes side  2002  of nozzle plate  1731 . It is noted that polishing tool  2110  may also polish side  2001  of nozzle plate  1731  if desired.  FIG. 65  illustrates nozzle plate  1731  after polishing in an illustrative embodiment. After polishing in this embodiment, a portion of extrusion  6310  is removed, leaving a surface feature  6510  that projects from side  2002  around the nozzle hole  1741 . Polishing defines the orifice of the nozzle where a print fluid exits the nozzle at an end of nozzle hole  1741 . Nozzle hole  1741  includes a second converging section  1034  having a cone shape that tapers or angles from end  1044  to end  1045  so that the diameter of second converging section  1034  decreases from end  1044  to end  1045 . The diameter of second converging section  1034  at end  1044  is larger than the diameter of neck  1033  (see  FIG. 60 ). The diameter of second converging section  1034  at end  1045  defines the orifice of a nozzle, which is circular. 
     With nozzle plates  1730 - 1731  punched and polished as desired, nozzle plates  1730 - 1731  may be loaded onto bonding tool  1704 , which bonds the nozzle plates  1730 - 1731  to form a nozzle plate stack  1736 .  FIG. 66  illustrates a nozzle plate stack  1736  in an illustrative embodiment. When bonded, nozzle hole  1740  of nozzle plate  1730  and nozzle hole  1741  of nozzle plate  1731  define a nozzle  1000  of a printhead as shown in  FIG. 10 . End  1040  of first converging section  1032  is the entrance of nozzle  1000 , and end  1045  of second converging section  1034  is the exit or orifice  1010  of nozzle  1000 . From the entrance to orifice  1010  along its length, nozzle  1000  is comprised of first converging section  1032 , a neck  1033  that abuts or adjoins first converging section  1032 , and second converging section  1034  that abuts or adjoins neck  1033 . First converging section  1032  has a diameter that decreases in the flow direction of print fluid through nozzle  1000 , neck  1033  has a uniform diameter in the flow direction of print fluid through nozzle  1000 , and second converging section  1034  has a diameter that decreases in the flow direction of print fluid through nozzle  1000 . 
     The above embodiment described forming the first converging section  1032 , neck  1033 , and the second converging section  1034  for nozzle  1000  by punching two nozzle plates  730 - 731 . In other embodiments, more nozzle plates may be punched to form nozzle  1000 . For example, first converging section  1032  may be formed by punching a first nozzle plate with a first nozzle punch, neck  1033  may be formed by punching a second nozzle plate with a second nozzle punch (i.e., a nozzle punch with a cylindrical head), and second converging section  1034  may be formed by punching a third nozzle plate with a third nozzle punch. 
     Although specific embodiments were described herein, the scope of the invention is not limited to those specific embodiments. The scope of the invention is defined by the following claims and any equivalents thereof.