Abstract:
Among other things, in one aspect, an apparatus comprises features to enable mounting first and second jetting assemblies on a frame. The features comprise first and second alignment datums pre-fixed with respect to the frame for establishing respective positions of the first and second jetting assemblies, when mounted, so that at least some of the nozzles along a length of one of the jetting assemblies have predetermined offsets relative to at least some of the nozzles along a length of the other of the jetting assemblies, and an opening exposing all of the nozzles along the lengths of the first and second jetting assemblies are exposed to permit jetting of a fluid onto a substrate.

Description:
TECHNICAL FIELD 
       [0001]    This description relates to positioning jetting assemblies. 
       BACKGROUND 
       [0002]    An ink jet printer can include one or more jetting assemblies, each capable of jetting ink from nozzles that are connected to corresponding pumping chambers. Jetting of ink from a chamber can be triggered by a piezoelectric actuator adjacent to the pumping chamber. To precisely print an image having a high resolution, the jetting assemblies need to be positioned in the printer with a high precision relative to each other and relative to the ink jet printer. 
       SUMMARY 
       [0003]    In one aspect, an apparatus comprises features to enable mounting first and second jetting assemblies on a frame. The features comprise first and second alignment datums pre-fixed with respect to the frame for establishing respective positions of the first and second jetting assemblies, when mounted, so that at least some of the nozzles along a length of one of the jetting assemblies have predetermined offsets relative to at least some of the nozzles along a length of the other of the jetting assemblies, and an opening exposing all of the nozzles along the lengths of the first and second jetting assemblies are exposed to permit jetting of a fluid onto a substrate. 
         [0004]    Implementations may include one or more of the following features. The features also include at least one fastener for the jetting assemblies. The fastener includes a piece to fix the fastener to the apparatus and a resilient piece to exert forces on the jetting assemblies. The fastener comprises a screw. The resilient piece comprises a spring. The fastener imposes no torque on the jetting assemblies. The frame is coated with a Teflon-nickel coating. The coating includes a homogeneous mixture of Teflon and nickel. The coating has a thickness of about 2 microns to about 8 microns. The features also include at least one flexure corresponding to the first or second alignment datum. The features also include additional alignment datums for establishing respective positions of the jetting assemblies along a direction perpendicular to the length of the jetting assemblies. 
         [0005]    In another aspect, an apparatus comprises a support for mounting a jetting assembly to permit jetting of a fluid from the nozzles onto a substrate in a jetting direction, and a fastener that applies a force on the jetting assembly in the jetting direction to hold the jetting assembly firmly against a precision surface of the support in at least one point, the fastener permitting torque-free motion of at least a portion of the jetting assembly, relative to the support, around an axis that lies in the direction of jetting. 
         [0006]    Implementations may include one or more of the following features. The fastener includes a resilient element located between an end of the fastener and the jetting assembly. The resilient element is the only portion of the fastener that contacts the jetting assembly. The fastener comprises helical threads for fastening to the support. The resilient element exerts a force of about 2 pounds to about 10 pounds on the jetting assembly. The resilient element exerts a force of about 5 pounds on the jetting assembly. 
         [0007]    In another aspect, an apparatus comprises a support for mounting a jetting assembly to permit jetting of a fluid from the nozzles, the support comprising an alignment datum at one end of the jetting assembly; and a resilient sheet metal flexure between the support and a second end of the jetting assembly, the flexure having a fastened end connected to a free end at a bend to exert a force along a length of the jetting assembly toward the alignment datum. 
         [0008]    Implementations may include one or more of the following features. The flexure has a spring constant of about 200 pounds per inch to about 600 pounds per inch. The flexure exerts a force of about 5 pounds to about 20 pounds on the jetting assembly. The free end includes an additional bend that contacts the jetting assembly. The free end includes a distal end beyond the additional bend, the distal end extending in a direction opposite to the location of the jetting assembly. The distal end can be stopped by a stop surface on the support. The distal end of the free end is about 600 microns to about 1000 microns from a stop surface on the support. The additional bend is about 3.0 mm to about 3.3 mm from a surface of the fastened end. 
         [0009]    In another aspect, an apparatus comprises a metallic support body for mounting a jetting assembly that jets a fluid, and a coating that is on the metallic support body and is thermally and electrically conductive and chemically resistant to the fluid. 
         [0010]    Implementations may include one or more of the following features. The coating includes Teflon, nickel, chromium nickel nitride, or the combination of two or more of them. The coating includes a homogeneous mixture of nickel and Teflon. The coating has a thickness of about 2 microns to 10 microns. A surface of the coating has a friction coefficient of less than 0.35. 
         [0011]    In another aspect, an apparatus comprises a support for a jetting assembly, the support comprising an alignment datum, and a jetting assembly. The jetting assembly comprises an array of nozzles that jet a fluid, and a bezel having at least one precision surface in contact with the alignment datum, the precision surface including a coating that is chemically resistant to the fluid. 
         [0012]    Implementations may include one or more of the following features. The coating includes a mold releasing agent. The precision surface is a surface of a graphite layer. The bezel includes a hole through which a fastener can be applied to fasten the jetting assembly onto the support. The hole is free of threads and is free from contacting the fastener. 
         [0013]    In another aspect, a method comprises forcing one end of a first jetting assembly against a first pre-fixed alignment datum of a support along a length of the first jetting assembly; and forcing one end of a second jetting assembly against a second pre-fixed alignment datum of a support along a length of the second jetting assembly so that at least some jetting nozzles of the first jetting assembly are offset relative to corresponding jetting nozzles of the second jetting assembly in a predetermined configuration, the first jetting assembly being in direct contact with the second jetting assembly. 
         [0014]    Implementations may include one or more of the following features. Offset between the corresponding jetting nozzles of the first and second jetting assemblies is obtained without adjusting the first and second alignment datums. Another end of the first jetting assembly along the length of the first jetting assembly presses against a first flexure and another end of the second jetting assembly along the length of the second jetting assembly presses against a second flexure. The method also includes fastening the first and second jetting assemblies relative to the first and second alignment datums. 
         [0015]    In another aspect, a method comprises forming a metallic support for mounting a jetting assembly so that jetting nozzles of the jetting assembly are exposed to permit jetting of a fluid from the nozzles onto a substrate in a jetting direction, and applying to a support a coating that is thermally and electrically conductive and chemically resistant to the ink. The coating can include a homogeneous mixture of Teflon and nickel. 
         [0016]    In another aspect, an apparatus comprises an opening defined in a support for mounting a frame capable of carrying one or more jetting assemblies, and a first resilient element and a second resilient element arranged diagonally with respect to the opening to exert a first force and a second force on different surfaces of the frame, the first spring force being in an opposite direction to a direction of the second spring force to enable a rotation of the frame to be mounted on the support. 
         [0017]    Implementations may include one or more of the following features. The apparatus also includes a first alignment datum corresponding to the first resilient element and a second, adjustable alignment datum corresponding to the second resilient element. The second alignment datum is movable along the direction of the first force. The second alignment datum comprises a contact point on a surface of a tapered cone. The apparatus also comprises alignment features located at opposite ends of the opening for linear adjustment of the frame. The alignment features comprise a spring plunger. The apparatus also includes fastening features for fastening the frame to the support. The fastening features comprise a spring plunger or a spring. The fastening is done without inducing a torque on the frame. The apparatus also comprises a first adjustment mechanism and a second adjustment mechanism located on the same end of the support, the first adjustment mechanism capable of adjusting a position of the frame linearly and the second adjustment mechanism capable of rotating the frame. The support further defines additional openings for mounting additional frames. 
         [0018]    In another aspect, an apparatus comprises an opening defined in a support for mounting a frame capable of carrying one or more jetting assemblies, and a mechanism that is accessible from one side of the support for adjusting both a linear position of the frame and an angle of the frame relative to a direction of jetting. 
         [0019]    Implementations may include one or more of the following features. The mechanism comprises an adjustment screw. The mechanism comprises a screw for adjusting a contact point on a surface of a tapered cone. The apparatus also includes one or more openings and one or more corresponding mechanisms, all mechanisms being accessible from one common end to all openings. 
         [0020]    In another aspect, a method comprises seating a frame capable of carrying one or more jetting assemblies onto a support, the frame being in contact with alignment features of an adjustment mechanism, at least one of the alignment features relating to a direction parallel to an array of nozzles of the jetting assemblies, and at least another one of the alignment features relating to a direction perpendicular to the parallel direction, and accessing the adjustment mechanism from an edge of the support to linearly adjust a position of the frame along the parallel direction, and to adjust an angular orientation of the frame relative to the parallel and perpendicular directions. 
         [0021]    The at least another one of the alignment features can include resilient elements arranged diagonally relative to the frame. 
         [0022]    In another aspect, an apparatus comprises an opening defined in a support for mounting a frame capable of carrying one or more jetting assemblies onto the support, and a tapered cone having a surface to be in contact with an edge of the frame, the tapered cone movable linearly along a first direction and capable of moving the edge of the frame along a second direction perpendicular to the first direction. 
         [0023]    Implementations may include one or more of the following features. The surface of the tapered cone and the edge of the frame are in point contact. The movement of the edge of the frame along the second direction induces a rotation of the frame. 
         [0024]    In another aspect, a method comprises inserting a frame capable of carrying one or more jetting assemblies onto a support, the frame having an edge in contact with a surface of a tapered cone attached to the frame; and moving the edge of the frame along a first direction by adjusting the linear position of the tapered cone along a second direction perpendicular to the first direction. The he edge of the frame and the surface can be in point contact. 
         [0025]    These and other aspects and features, and combinations of them, can be expressed as methods, apparatus, systems, means for performing a function, and in other ways. 
         [0026]    Other features and advantages will be apparent from the following detailed description, and from the claims. 
     
    
     
       DESCRIPTION 
         [0027]      FIG. 1  is a perspective view of a jetting module. 
           [0028]      FIG. 2  is a bottom view of a jetting module (nozzle arrays are not to scale). 
           [0029]      FIG. 3  is a top view of a portion of a module frame. 
           [0030]      FIGS. 4 and 5  are two perspective views of portions of a module frame. 
           [0031]      FIG. 6  is a perspective view of a flexure. 
           [0032]      FIGS. 7 ,  8 , and  9  are respectively perspective and top views of portions of a jetting assembly. 
           [0033]      FIG. 10  is a side view of a fastener. 
           [0034]      FIG. 11  is a top view of the frame. 
           [0035]      FIGS. 12 ,  13 , and  14  are schematic side views of arrays of pumping chambers and nozzles (not to scale). 
           [0036]      FIG. 15  is a schematic bottom view of a jetting module (not to scale). 
           [0037]      FIGS. 16 ,  17  and  19  are schematic top views of printbars. 
           [0038]      FIG. 18  is a schematic perspective view of a printbar. 
       
    
    
       [0039]    One or more jetting modules  10  shown in  FIG. 1  (only one module is shown in  FIG. 1 ) can be positioned onto a printbar  12  of a printer (not shown) to print an image  14  on a substrate  16  that lies adjacent (e.g., vertically beneath) the jetting module  10  along a z direction. The jetting module  10  includes two jetting assemblies  18 ,  20  precisely positioned adjacent, parallel to, and slightly offset along a y direction relative to one another on a frame  22 . The jetting module  10  can print with a high precision at a resolution higher than a resolution at which each jetting assembly  18 ,  20  prints alone. Each jetting assembly  18 ,  20  includes one or more arrays of (e.g., rows of parallel) pumping chambers  24  that are actuated by piezoelectric elements that cover the pumping chambers (not shown). The piezoelectric elements can be activated by signals from integrated circuits  26  to cause the corresponding pumping chamber  24  to jet ink that has been received at ink inlets  28 ,  30  from ink supplies (not shown) through one or more corresponding nozzles ( FIG. 2 ) onto the substrate  16  to form the image  14 . 
         [0040]    In the example shown in  FIG. 2 , coplanar bottom surfaces  32 ,  34  of the jetting assemblies  18 ,  20  each includes an array (e.g., a row) of evenly-spaced nozzles  36 ,  38  along the y direction (the spaces between nozzles are not to scale). Each nozzle is connected to one end of a corresponding pumping chamber  24  ( FIG. 1 ) to receive ink that is pumped from that pumping chamber and deliver it to the substrate  16 . Each array  36 ,  38  is capable of printing at a predetermined resolution (dots per inch or dpi) along the array direction (y direction) based on a distance d by which each nozzle in the array is separated from its neighboring nozzle(s). For example, d can range from about 0.0025 inches to about 0.02 inches and the jetting assembly  18 ,  20  can print at about 50 dpi to about 400 dpi. Each jetting assembly  18 ,  20  can include about 128 to about 512 nozzles. In the implementation shown in  FIG. 2 , the jetting assemblies  18 ,  20  are positioned such that a nozzle  36   a  in the nozzle array  36  is offset by an offset distance  40  of d/2 relative to a corresponding nozzle  38   a  in the nozzle array  38 . Because of this offset, the jetting module  10  can effectively print at a resolution along they direction that is twice as high as a resolution at which each jetting assembly  18 ,  20  prints alone. For example, the jetting module  10  can print at about 100 dpi to about 800 dpi and cover a printing range R of about 64.5 mm to about 129 mm. 
         [0041]    Referring again to  FIG. 1 , the frame  22  of the module carries alignment datums  42 ,  44 ,  66 ,  70  and flexures  46 ,  48 ,  68 ,  72  with pre-determined precisions. The alignment datums cooperate with alignment surfaces (not labeled in  FIG. 1 , see for example, surfaces  148 ,  150 ,  152  of  FIG. 8 ) on bezels  58 ,  60 ,  61  (another bezel of the jetting assembly  18  not shown in  FIG. 1 ) of the two jetting assemblies  18 ,  20 , so that when the jetting assemblies  18 ,  20  are mounted onto the frame  22  and the flexures apply alignment forces  91 ,  93 ,  95 ,  97  (only schematically showing the directions of the forces) against the force-bearing surfaces of the bezels of the two jetting assemblies. The jetting assemblies become very precisely aligned and positioned and the jetting module  10  automatically is configured to print with a high precision at the desired resolution described with respect to  FIG. 2 . Because of the configurations of the module frame  22  and the jetting assembly bezels, and the precision with which the alignment datums and alignment surfaces are formed and located, no further positioning adjustment or testing is required for each of the jetting assemblies  18 ,  20  to achieve the desired precision and resolution associated with the jetting module  10 . As a result, the arrays of nozzles can be positioned with a precision of ±15 microns or less in the x direction, ±15 microns or less in they direction, and ±65 microns or less, or ±35 microns or less in the z direction. 
         [0042]    The module frame  22  is precisely designed and manufactured based on the intended values of parameters, such as types, dimensions, dpi, alignment precision, of the jetting assemblies. In particular, the jetting assemblies are precisely positioned relative to each other and relative to the frame along all three directions x, y, z. Along an x direction and perpendicular to they direction, the flexures  68 ,  72  push (through one or more of the force-bearing surfaces  148 ,  150 ,  152  of  FIG. 8 ) the jetting assemblies  18 ,  20  against each other and against the corresponding alignment datums  66 ,  70  using the forces  95 ,  97 . When assembled in the module, the jetting assemblies  18 ,  20  are in contact with each other only at surfaces  150 ,  152  of their respective bezels, e.g., bezels  58 ,  61  ( FIG. 1 ), so that only the bezel surfaces affect the relative positioning of the two jetting assemblies along the x direction. 
         [0043]    Along they direction, the flexures  46 ,  48  apply forces  91 ,  93  on the jetting assemblies  18 ,  20  against the alignment datums  42 ,  44 . The offset distance  40  shown in  FIG. 2  is provided by the design of alignment datums  42 ,  44  and the flexures  46 ,  48  (explained below). Along the z direction, the bottom surfaces  32 ,  34  ( FIG. 2 ) of the jetting assemblies  18 ,  20  are substantially within the same plane. In some embodiments, the bottom surfaces  32 ,  34  are less than 120 microns, 100 microns, 80 microns, 60 microns, 40 microns, 20 microns, or even less apart from each other along the jetting direction z. 
         [0044]    The jetting module  10  of  FIG. 1  can be readily assembled. First, the jetting assembly  20  is pressed, e.g., spring loaded, along the z direction into a space between the alignment datum  44  and the flexure  46  to expose the nozzle array through an opening  62  ( FIG. 2 ) of the frame  22 . The jetting assembly  20  is inserted and pushed down until bottom surfaces (see e.g., surface  153  of  FIG. 7 ) of bezels  58 ,  60  of the jetting assembly  20  are stopped by an upper surface  64  of the frame  22 , and the jetting assembly  20  is positioned tightly between the alignment datum  44  and the flexure  46  along the y direction. Fasteners  54 ,  56  can be used to fasten the jetting assembly  20  onto the frame  22 , for example, to prevent the jetting assembly  20  from popping up along the z direction. 
         [0045]    The jetting assembly  18  can be mounted in a similar way between an alignment datum  44  and a flexure  46  and can be fastened using fasteners  50 ,  52  onto the frame  22 . Along the x direction, the two jetting assemblies  18 ,  20  are pressed tightly against each other toward alignment datums  66 ,  70  by the flexures  68 ,  72 . 
         [0046]    The jetting module  10  is also easy to disassemble and maintain. For example, when one of the jetting assemblies  18 ,  20  is found to be malfunctioning or is worn or needs to be maintained or replaced, it can be removed by reversing the installation steps and replaced by a jetting assembly of the same type conveniently without use of additional tools or specialized services to reach the original precision and resolution. The function of the remaining jetting assembly and the performance the jetting module  10  are not affected by such a replacement and the cost for maintenance can be kept low. 
         [0047]    Referring to  FIGS. 3 ,  4 , and  5 , the frame  22  can be a continuous metallic (e.g., aluminum) piece  74  that is machined to include alignment datums  42 ,  44 ,  66 ,  70 . Two flexure supports  78 ,  80  can be attached to and extend in the z direction from an upper surface  64  of the frame. The flexure support  78  is mounted to the base by a screw (not shown) that passes through a hole  84  and into internal threads (not shown) and a corresponding hole  82  in the frame. Similarly, the flexure support  80  is mounted to the frame  22  by a screw that passes through a hole  86  and into internal threads (not shown) of a hole  76  in the frame. The positions of the flexure supports  78 ,  80  along the x, y, and z directions relative to the metallic piece  74  are precisely pre-determined based on, for example, the dimensions of the flexure supports  78 ,  80 , the flexures to be attached to the flexure supports, the configurations of the jetting assemblies  18 ,  20  to be mounted, the positions of the alignment datums  42 ,  44 ,  66 ,  70  and the configuration of the upper surface  64  of the frame, among other things. Generally, the positions of the alignment datums and the flexure supports can be freely selected as long as the positioning of the jetting assemblies  18 ,  20  described above can be realized. 
         [0048]    The alignment datums  42 ,  44 ,  66 ,  70  can be high precision surfaces of mechanical units  92 ,  94 ,  96  that extend away from the top surface  64  (see also,  FIG. 1 ). The high precision surfaces can be smooth and have low friction coefficients. For example, each of the surfaces can be machined and polished, and can have a friction coefficient, for example, of less than about 0.5, 0.4, 0.3, 0.25, 0.2, or 0.15, relative to the same material the surface contains or to other materials, such as carbon, aluminum, or anodized aluminum. The smoothness of the high precision surfaces not only makes the alignment of the jetting assemblies on the frame highly precise, but also provides a low drag force on the jetting assembly at interfaces between each alignment surface on the jetting assembly and the corresponding alignment datum on the frame  22  when there are relative movements at the interfaces. Such movements can be caused by, for example, expansion or shrinking of the frame and the jetting assembly upon temperature variations. The alignment datums  66 ,  70  are precisely aligned along they direction so that when a jetting assembly is pressed against the alignment datums  66 ,  70  along the x direction, the array of nozzles of the jetting assembly is precisely parallel to they direction. 
         [0049]    The alignment datums  42 ,  44  provide a desired offset distance (for example, d/2 in  FIG. 2 ) along the x direction between corresponding nozzles (e.g., nozzles  36   a ,  38   a ) when the jetting assemblies are mounted on the frame. In the example shown in the figure, the alignment datum  44  extends toward the opening  62  along they direction by an extension distance (not shown) that is substantially equal to the desired offset distance (e.g., d/2) further than the alignment datum  42 . The desired offset distance can be, for example, about 20 microns to about 200 microns or about 50 microns to about 150 microns, e.g., 127 microns. The alignment datums  42 ,  44  are precisely machined such that the difference between the extension distance and the desired offset distance is within ±1 micron, ±2 microns, or ±5 microns. The top surface  64  is substantially smooth and can have a friction coefficient of less than about 0.35, 0.3, 0.25, 0.2, or 0.15, relative to the same material contained in the top surface  64  or other materials such as anodized aluminum contained in the bezel contacting the top surface  64  (e.g., the bezels  58 ,  60  of  FIG. 1 ). The top surface  64  is also substantially flat within the x-y plane and perpendicular to the jetting direction. The tilting of the surface  64  relative to the x-y plane is less than 0.02 degrees or less in they direction and less than 0.05 degrees in the x direction. The top surface  64  is also a high precision surface for aligning the jetting assemblies along the z direction. 
         [0050]    The metallic piece  74  also includes two pairs of holes  85 ,  86  and  88 ,  90 , each including helical threads (not shown) and having an opening on the surface  64 . The two holes in each pair are located on two sides of the opening  62  of the frame and the centers of the two holes align precisely along they direction. The locations of the holes  85 ,  86 ,  88 ,  90  on the metallic piece  74  are precisely pre-determined and manufactured, such that when the jetting assemblies  18 ,  20  ( FIG. 1 ) are mounted onto the frame  22 , a hole in each bezel (e.g., bezel  58 ,  60 ) of the jetting assemblies aligns precisely with one of the holes  85 ,  86 ,  88 ,  90  along the z direction. To provide the offset distance discussed previously, like the alignment datums  44 ,  42 , along the y direction, the hole  88  adjacent to the extended alignment datum  44  has its center extended by substantially the desired offset distance further toward the opening  62  than the center of the other hole  85 . 
         [0051]    The distance between the two holes within each pair along the y direction and the distance between the holes from different pairs along the x direction are precisely pre-determined based on the distance between the holes of the bezels of an individual jetting assembly and its neighboring jetting assembly. The precision can facilitate reducing tensions or other forces within each jetting assembly and/or between the jetting assemblies when the jetting assemblies are fastened to the frame  22 . In particular, a distance D y  between the centers of the two holes  85 ,  86 , or  88 ,  90  along they direction can be substantially equal to a distance D b  between the centers of the two bezels  58 ,  60  ( FIG. 1 ) of the jetting assembly to be mounted on the frame. For example, D y  can be about 100 mm to 225 mm, depending on the type of the jetting assemblies used. The difference between D y  and D b  can be, for example, within ±30 micron, ±40 microns, or 80 microns, or ±125 microns. A distance D x  between the centers of the two holes  85 ,  88 , or  86 ,  90  along the x direction is substantially equal to a distance D a  between the centers of the two bezels of the adjacent jetting assemblies. For example, D x  can be about 6 mm, about 8 mm, about 10 mm, or about 12 mm, and the difference between D x  and D a  can be within ±30 micron, ±40 microns, or ±80 microns, or ±125 microns. In some embodiments, the difference between D y  and D b  or D x  and D a  is non-critical (details discussed below). 
         [0052]    Referring to  FIG. 6 , each flexure  102  to be fastened to the flexure supports  78 ,  80  ( FIGS. 4 and 5 ) can include a machined metal sheet  104  having a first bending point  106  and a second bending point  108 . The metal sheet  104  includes a hole  110  and can be fastened to the flexure supports  78 ,  80  by, for example, applying a screw into the hole  110  when it is aligned with one of the holes  112 ,  114 ,  116 ,  118  of the supports. When the flexure  102  is fastened to the flexure supports  78 ,  80  and the metallic piece  74  of the module frame ( FIG. 3 ), a surface  132  of a non-bent portion that contains the hole  110  substantially fully contacts a corresponding setting surface  134 ,  136 ,  138 ,  140  of the flexure supports  78 ,  80 . A bent portion  120  of the metal sheet  104  beyond the first bending point  106  bends by an angle α relative to the surface  132  towards the corresponding alignment datum  42 ,  44 ,  66 ,  70 , and a bent portion  122  beyond the second bending point  106  bends by an angle β relative to the bent portion  120  towards a corresponding stopping surface  124 ,  126 ,  128 ,  130  of the flexure supports  78 ,  80 . The ramp shape of the flexure enables the jetting assembly to be conveniently pressed or pulled along the z direction against the second bending point  108  to be positioned onto or removed from the frame  22 . The positioned jetting assemblies  18 ,  20  of  FIG. 1  each contacts the second bending point  108  of the flexure  102  with a small contact surface. The contact surface can be smooth and can have a low friction coefficient to provide a small drag force on the jetting assemblies when there are relative movements within the contact surface. The contact surface can have a surface area of about 0.125 to 1.25 square millimeters and the surface area can be polished, e.g., electro-polished. The small drag force between the flexure and the jetting assemblies can allow the jetting assemblies to expand or shrink, for example, when the temperature varies, without disturbing the pumping chambers or nozzles and maintain the precision of the printing done by the jetting module  10  (discussed in detail below). 
         [0053]    The first bending point  106  exerts a spring force against the jetting assembly to push the jetting assembly tightly against the alignment datum  42 ,  44 . The spring force is also selected so that when the jetting assembly experiences expansion or shrinking, for example, when the temperature varies, the flexure  102  follows the changes of the jetting assembly while keeping the jetting assembly tightly matched against the corresponding alignment datum. For example, when the jetting assembly is positioned, the spring force against the jetting assembly can be about 5 pounds to about 20 pounds, or about 8 pounds to about 12 pounds. The magnitude of the spring force can be controlled by a spring constant k of the flexure  102 , which can be pre-selected by choosing a material, shape, or related parameters, for example, a thickness t, the angles α, and a width w, of the machined metal sheet  104 . The spring constant k can be about 200 pounds per inch to about 600 pounds per inch, or about 300 pounds per inch to about 600 pounds per inch, or about 400 pounds per inch to about 500 pounds per inch, for example, 450 pounds per inch. In some examples, the material can be stainless steel, or other suitable metal or plastic materials. The material can also be coated with one or more coatings to provide desired smoothness or other electrical, thermal, and/or mechanical properties. The various parameters such as α are chosen such that a distance q between the surface  132  and the second bending point  108  along the second bending point  108  along the y direction is about 2.0 mm, 2.5 mm, 3.0 mm, 3.043 mm, 3.1 mm, 3.2 mm, 3.293 mm, 3.3 mm, and/or up to about 3.5 mm, 3.45 mm, or 3.40 mm. The angle α can be, for example, about 5 degrees, 8 degrees, 10 degrees, 13 degrees, 13.7 degrees, 15 degrees, and/or up to about 25 degrees, 22 degrees, 20 degrees or other degrees. The width w can be, for example, about 3 mm to about 10 mm, e.g., 6 mm., or other width The thickness t can be, for example, about 0.4 mm to about 1.0 mm or about 0.5 mm to about 0.8 mm, e.g., 0.64 mm, or other thickness. 
         [0054]    The flexure  102  includes an inherent working condition so that the flexure does not wear out and lose its spring feature. For example, under the working condition, the angle α is compressed so that the second bending point  108  and/or a front edge  142  of the bent portion  122  each travels toward the flexure supports  78 ,  80  by less than about 600 microns, 550 microns, 500 microns, 475 microns, or 450 microns along the y direction. Compression of the angle α beyond the compression range is prevented using the design of the bent portion  122  and the stop surfaces  124 ,  126 ,  128 ,  130  of the flexure supports  78 ,  80  ( FIGS. 4 and 5 ). In particular, the length l of the bent portion  122 , the angle β, and other related parameters are selected so that when needed, the front edge  142  of the bent portion  122  is stopped by the stop surface  124 ,  126 ,  128 ,  130  to prevent the further compression of the angle α. The angle β can be about 60 degrees, 70 degrees, 80 degrees, 90 degrees, 100 degrees, and/or up to about 175 degrees, 165 degrees, 155 degrees, 145 degrees, 145.7 degrees, or 130 degrees. In some embodiments, prior to the loading of the jetting assemblies  18 ,  20  ( FIG. 1 ), in an assembled frame  22 , a distance between the front edge  142  of the bent portion  122  and the stop surface  124 ,  126 ,  128 ,  130  is, for example, about 600 microns, 650 microns, 700 microns, 750 microns, 762 microns, 800 microns, and/or up to about 1000 microns, 950 microns, or 900 microns. The metal piece  74  of the frame  22  can also include additional alignment datums  98 ,  100  for precisely positioning the jetting module  10  onto the printbar  10 . 
         [0055]    The precise positioning of the jetting assemblies  18 ,  20  on the frame  22  ( FIG. 1 ) is also facilitated by the high precision alignment datums on the jetting assemblies that match or engage with the alignment datums carried by the frame  22 .  FIG. 7  shows a portion  146  of a jetting assembly that includes a base  144  that includes the ink inlet  28  and a bezel  58  (see also,  FIG. 1 ). The portion  146  of  FIG. 7  is attached, e.g., screwed or glued, to a body (not labeled) that includes the pumping chambers  24  of the jetting assembly on each side of the body. The bezel  58  and the base  144  can be machined as an integrated piece having a desired configuration for attaching to jetting assemblies of different types. In some implementations, the bezel  58  can be designed or manufactured uniformly and can be fastened to bases, like the base  144 , having different configurations and sizes for different types of jetting assemblies. With the assistance of the portion  146 , different jetting assemblies known in the art can be readily used in the jetting module  10  ( FIG. 1 ) without modification of the body. 
         [0056]    Referring to  FIG. 8 , in the jetting module  10  of  FIG. 1 , two identical portions  146   a ,  146   b  each being the same as the portion  146  of  FIG. 7  and attached to one of the adjacently positioned jetting assemblies  18 ,  20  are in contact with each other through the surfaces of the bezels. Each bezel  58   a ,  58   b  can include three alignment datums  148 ,  150 ,  152  in the form, for example, of high precision surfaces. The alignment datum  148  along they direction can contact the alignment datum  42 ,  44  ( FIG. 1 ), or the second bending point  108  of the flexure  102  ( FIG. 6 ). Along the x direction, each bezel  146   a ,  146   b  has a width D that is larger than a width of any other portion of the jetting assembly such that the two jetting assemblies contact with each other only at the high precision surfaces of the bezels  58   a ,  58   b . In the example shown in the figure, the high precision surface  152  of the bezel  58   a  engages with the high precision surface  150  of the bezel  58   b . The two high precision surfaces  152 ,  150  of the two bezels  146   a ,  146   b  are pressed tightly against each other between the alignment datum  58  and the flexure  72  or the alignment datum  66  and the flexure  68  ( FIG. 1 ). The high precision surfaces  150 ,  148 ,  152  can have the same features, for example, dimensions or low friction coefficients, as the high precision surfaces  42 ,  44 ,  66 ,  70  of  FIG. 3  and function similarly. For example, the surface area of each high precision surface  150 ,  148 ,  152  is about 4 mm 2  to about 10 mm 2 , e.g., about 5 mm 2  and the surface area of each precision surface  42 ,  44 ,  66 ,  70  is about 4 mm 2  to about 10 mm 2 , e.g., about 5 mm 2 . The surface areas of these high precision surfaces are sufficiently large for the engagement of the surface and at the same time sufficiently small for reducing drag forces on the engaged surfaces when relative movements between the engaged surfaces occur. The bottom surface  153  (not fully visible) of the bezel  58   a  or  58   b  can also be a high precision surface with low friction coefficient so that when it is in contact with the top surface  64  of the frame  22 , the nozzle arrays of the jetting assemblies are substantially within the same, horizontal x-y plane. 
         [0057]    Referring to  FIG. 10 , the fasteners  50 ,  52 ,  54 ,  56  of  FIG. 1  can each include a spring  156  and a ring  158  assembled on a shoulder screw  154 . The spring  156  winds around the middle body  166  of the screw  154  between the ring  158  and the head  164 , and is held captive between the head  164  and the ring  158 . In use, a distal end  160  of the shoulder screw  154  can be screwed into the holes  85 ,  86 ,  88 ,  90  of the metal piece  74  ( FIG. 3 ) and the spring  156  can compress through the ring  158  the bezel  58  tightly against the surface  64  of the metal piece  74  ( FIG. 3 ). The distal end  160  carries helical threads  160  that corresponds to the helical threads in the holes  85 ,  86 ,  88 ,  90  of the metal piece  74  ( FIG. 3 ). The distal end  160  can have a length h which is less than the depth of the holes  85 ,  86 ,  88 ,  90 . When the distal end  160  is fully inserted in the holes of the frame  22 , the shoulder  167  of the shoulder screw  154  contacts the top surface  64  of the frame  22 . Such a contact acts as a stop so that the spring  156  is compressed by a predetermined amount. Because of the stop, the amount of torque used to seat the shoulder screw does not affect the amount of compression on the spring. In some embodiments, the torque used to seat the screw can be from about 0.5 inch pounds to about 20 inch pounds. 
         [0058]    The middle body  166  of the screw  154  can have a diameter d m  smaller than the diameter d b  of the hole  168  and can pass through a hole  168  of the bezel ( FIG. 8 ) without contacting the bezel so that the screw body is thermally insulated from the bezel. For example, the diameter d m  can be about 3 mm to about 8 mm or about 4 mm to about 6 mm and the diameter d b  can be about 3.5 mm to about 8.5 mm or about 4 mm to about 6.5 mm. In addition, the room between the screw body the bezel allows the bezel to expand or shrink, e.g., when the temperature changes, within the x-y plane without the screw&#39;s interference. The difference between the diameter d m  and the diameter d b  can be large, for example, up to about 1000 microns, 750 microns, or 500 microns and such a difference also allows the difference between D y  and D b  or D x  and D a  ( FIG. 3 ) to be relatively large so that machining of the these relative distances D y , D b , D x , and D a  does not have to be done with a super-high precision. 
         [0059]    The spring  156  exerts a force of about 2 pounds to about 10 pounds or about 4 pounds to about 8 pounds, e.g., 5 pounds, through the ring  158  onto the bezel  58 . The bezel  58  is clamped between the spring and the frame. The use of the fastener  154  creates no torque between the bezel  58  and the surface  64  within the x-y plane and generates no influence on the previously precisely positioned jetting assemblies within the x-y plane. The spring  156  also allows the bezel to expand or shrink along the z direction when the temperature changes. The ring  60  can be made of a thermally and electrically non-conductive material so that the bezel (and therefore, the jetting assembly) is thermally and electrically insulated from the shoulder screw  154  and the spring  156 . The shoulder screw  154  and the spring  156  can be made of a metallic material, for example, stainless steel or others. The ring  60  can be made of, for example, a plastic, a rubber, or a homopolymer acetal (e.g., Delrin available from Professional Plastics, Inc. at CA, USA) One or more coatings can be applied to these elements, for example, to change the mechanical, chemical, or electrical properties of the elements. 
         [0060]    The frame  22  ( FIG. 1 ), which includes the metallic piece  74  and the flexure supports  78 ,  80  ( FIGS. 3-5 ), and the portion  146  ( FIG. 7 ) of each jetting assembly can include a same structural material to provide a uniform thermal and electrical conductivity throughout the frame  22  and the portion  146 . The uniform thermal or electrical conductivity can allow the jetting assembly and the frame to be capable of reacting to thermal or electrical variations in the module or in the environment in a substantially similar way. For example, the jetting assemblies  18 ,  20  and the frame  22  can expand or shrink by a similar amount (e.g., the difference being less than about 200 microns or less than about 100 microns, e.g., about 65 microns to about 75 microns) in different directions when the temperature of the jetting module  10  varies (e.g., by about 20° C. to about 80° C.). The uniform conductivity can allow charges, for example, static charges, accumulated during printing on different parts of the jetting module  10  to be eliminated through the grounded frame  22 . Suitable structural materials can include, for example, aluminum, in particular, cast aluminum tooling plate (e.g., MIC-6 available from Radwell International at Lumberton, N.J.). The cast aluminum tooling plate can be resistant to twisting or warping during machining or thermal cycling. 
         [0061]    In some implementations, one or more additional thermally and electrically conductive, and chemically and mechanically resistant coatings can be formed on the entire surface of the frame  22 , including surfaces of the flexure supports  78 ,  80 , or selected surfaces, for example, the high precision surfaces, of the frame  22 . The coating is thermally and electrically conductive so that the desired thermal and electrical properties of the structural materials of the frame and the portion  146  are maintained. The chemical resistance of the coating can prevent the frame  22  and the portion  146  from chemically reacting with each other or with ink that is spilled or leaked onto the external surfaces of the jetting module  10  and facilitate maintaining the precision of the alignment datums on the frame. The high mechanical resistance of the coating prevents wearing of the alignment datums and other surfaces. For example, the surfaces of the alignment datums or the flexures can be prevented from being mechanically removed or changed by the friction caused by the contact and movements (e.g., during assembling) of the surfaces of the jetting assemblies. 
         [0062]    Suitable coating materials can include, for example, aluminum nitride, chromium, nickel, Teflon-nickel, or their combinations. In some embodiments, the coating material includes a homogeneous Teflon-nickel mixture that contains, for example, about 20 wt % to about 30 wt % or about 22 wt % to about 24 wt % of polytetrafluoroethylene (PTFE). The coating can have a thickness of about 2 μm, 4 μm, 5 μm, 8 μm, 10 μm, and/or up to about 20 μm, 18 μm, 15 μm, 13 μm, 12 μm. One commercially known Teflon-nickel coating material is NICKLON available from Bales Mold Service at Downers Grove, Ill. Similar coating materials such as TEFNI-2000 available from Westfield Electroplating at Westfield, Mass. In some embodiments, the coating material includes a nodular, thin, and dense chromium, which can be electroplated onto desired surfaces and can have a thickness of about 1 micron to about 10 microns, for example, about 2.5 microns, 5 microns, 5.5 microns, 7 microns, or 7.5 microns. A commercially known technique of such a chromium coating is available from the Armoloy® Corporation, Dekalb, Ill. In some embodiments, multiple coating materials and processes can be used. For example, a duplex nickel/Armoloy plating process can be used. 
         [0063]    In some embodiments, the surfaces of the alignment datums on the jetting assembly are coated with one or more chemical-resistant, e.g., ink-resistant, coatings to chemically protect the surfaces and maintain the high precisions of these surfaces. For example, the surfaces  148 ,  150 ,  152  of  FIG. 8  are coated with a release agent, for example, a mold release agent SK22 (available at Stoner Inc., Quarryville, Pa.). In some implementations, the surface of the alignment datums on the jetting assembly can be anodized (for example, anodize per MIL-A-8625F Type A, Class 2, Black). The chemical-resistant coatings can be optionally applied onto the anodized surfaces. 
         [0064]    In the example shown in  FIG. 9 , the alignment datums on the portion  146  of a jetting assembly can include a chemical-resistant protrusion unit  154  attached, e.g., glued, onto each surface  148 ,  150 ,  152  (see also,  FIG. 8 ). The protrusion  154  can partially or entirely cover the surface onto which it is attached and can have a precision surface that contacts the corresponding alignment datums or flexures on the frame  22  in replacement of the surfaces  148 ,  150 ,  152 . These protrusion units  154  separate the originally contacting surfaces of the alignment datums to prevent the contacting surfaces from chemical reactions in presence of ink. The protrusion unit  154  can be made of a material with good thermal conductivity, for example, graphite, e.g., DFP carbon (available from Poco Graphite, Inc., at Decatur, Tex.), or ACF-10Q (available from Poco Graphite, Inc., at Decatur, Tex.), so that the thermal conductivity of the entire jetting module  10  ( FIG. 1 ) is not affected. The jetting assemblies are kept in electrical contact with the frame  22  through the contact of the bezels and the top surface  64  of the frame ( FIGS. 1 and 3 ). 
         [0065]    Referring back to  FIG. 1 , a heating element  156  is attached to a surface of the frame  22  to heat the ink within the pumping chambers of the jetting assembly  20  to reduce the ink viscosity and facilitate ink jetting. Another heating element (not shown) can be similarly placed and used for the jetting assembly  18 . The heating element  156  extends along they direction to cover the row of pumping chambers  24  and can heat the frame to about 30° C. to about 65° C. Examples of the heating element  156  can include a 60 watt strip heater. 
         [0066]    The heating of the frame  22  can cause the frame  22  and the jetting assemblies  18 , to expand along all three directions. For example, heating the frame  22  from a room temperature (about 7° C. to about 32° C.) to about 80° C. or 60° C., the frame  22  and each jetting assembly expand naturally by about 30-40 microns along they direction. The term “naturally” as used herein, means that the amount of expansion or shrinking is measured as if the frame  22  or the jetting assemblies  18 ,  20  were free-standing and were not positioned or confined (e.g., by the printbar  12  or the frame  22 , respectively). In some embodiments, the jetting assembly and the frame  22  may naturally expand by a different distance along one or more of the directions. For example, the difference can be about ±50 microns to about ±200 microns or about ±65 microns to about ±100 microns. It is desirable for the jetting assemblies to expand or shrink freely by the distance they naturally would have under the environmental conditions without the confinement of the frame  22 . The natural shapes of the pumping chambers, nozzle arrays, and other parts of the jetting assemblies as machined or made can be preserved during the natural expansion of the jetting assemblies so that, for example, the nozzles in the nozzle arrays are kept equally distanced and the high precisions of the relative alignments of the jetting assemblies are maintained. 
         [0067]    The free-expansion or shrinking of the jetting assemblies by their natural amount independent of the frame is realized by the design of the jetting module  10  discussed previously and the jetting module  10  is capable of printing at a desired resolution with a high precision throughout the printing process. The jetting module  10  can absorb the difference between the expansion of the frame and the jetting assembly up to about 300 microns, 275 microns, or 250 microns while keeping the precisions of the alignments and positioning of the jetting assemblies.  FIG. 11  schematically shows the top view of the frame  22  (some parts are not shown) described in FIGS.  1  and  3 - 6 . In each of the x and y directions, one alignment datum that includes a hard stop pairs with a corresponding flexure structure (e.g., the alignment datum  42  and the flexure  48 , the alignment datum  44  and the flexure  46 , the alignment datum  70  and the flexure  72 , and the alignment datum  66  and the flexure  68 ). The jetting assemblies  18 ,  20  can be loaded between the alignment datum-flexure pair such that each has one end engaged with the hard stop of an alignment datum and the other corresponding end loaded by the corresponding flexure. Along the direction, the jetting assemblies  18 ,  20  each is positioned between the high precision surface  64  serving as a hard stop when the fastener (e.g., the fastener  54 ) is screwed into the frame  22  and the spring  156  ( FIG. 10 ). Accordingly, in each direction, the jetting assemblies  18 ,  20  are capable of expanding or shrinking relative to the frame  22  at the ends that are in contact with the flexures or the spring. The difference between the natural expansion or shrinking of the jetting assemblies and the frame is small because of the material used and uniform thermal conductivity within the jetting module  10  and can be tolerated by the flexures and the spring. In addition, drag forces within all surfaces with which the jetting assemblies contact with each other or with the frame are small so that the jetting assemblies can be substantially free to expand or shrink without substantial drags. For example, when expanding or shrinking along the x or y direction, the total drag forces on each jetting assembly is less than 20 pounds, less than 18 pounds, less than 15 pounds, less than 12 pounds, less than 10 pounds, less than 8 pounds, or less than 6 pounds. 
         [0068]    In the example shown in  FIGS. 12 ,  13 , and  14 , along they direction, a pumping chamber array  158  including pumping chambers  24  is precisely positioned on a frame  22  ( FIG. 1 ) between a hard stop and a flexure. Each neighboring pair of pumping chambers  24  is equally apart by a distance d c . When the environmental temperature changes, for example, by heating the frame  22  as explained above, the pumping chamber array  158  expands and pushes the flexure back by a distance de that is substantially equal to a difference between the natural expansion distances of the pumping chamber array  158  and the frame  22 . The pumping chambers  24  remain equally-spaced with a neighboring distance larger than d c . A second pumping chamber array of the other jetting assembly on the frame  22  can undergo the same expansion and the precise offsets of the pumping chambers from the two jetting assemblies along the x direction as described in  FIG. 2  are maintained. In contrast, if the pumping chamber array  156  had been fixed between two hard stops or the fasteners  50 ,  52 ,  54 ,  56  had prevented the array from expanding, upon heating, the array  160  would form an arc shape (if the frame expands less than the array), causing the neighboring distances d 1 , d 2 , d 3  to be different from each other. The pumping chamber array  160  would then print printlines that are not equally-spaced and the precisions of the pre-determined offsets of the pumping chambers  161  relative to those of the other jetting assembly on the same frame along the x direction are lost. 
         [0069]    Although in the example shown in  FIG. 1 , only two jetting assemblies are positioned within the frame  22 , three or more jetting assemblies can be positioned in a similar manner to that of the jetting assemblies  18 ,  20  onto a frame that is designed similar to the frame  22  to provide the capability of printing at an even higher resolution than the module  10 . For example, such a frame can include an opening larger than the opening  62  ( FIG. 3 ) and suitable for exposing three rows of nozzles from three or more jetting assemblies stacked along the x direction. One or more additional sets of flexure and alignment datum can be arranged next to the flexure  46  and alignment datum  44  to receive the additional jetting assembly. The alignment datums  42 ,  44 , and the additional alignment datum can provide an offset of about d/n for each nozzle relative to a corresponding nozzle of a neighboring jetting assembly, where n is an integer that represents the total number of jetting assemblies. 
         [0070]    In some embodiments, a frame  162  ( FIG. 15 , details not shown) can allow precise positioning of four identical jetting assemblies  164 ,  166 ,  168 ,  170  to provide a capability of printing at a resolution twice as high as the resolution at which each jetting assembly is capable of printing, and an print width S of about 1.5 to 2 times as large as a the printing range (e.g., R of  FIG. 2 ) of a single jetting assembly (the jetting assemblies can be in contact with each other and/or with the frame  162 , which is not shown in the figure). For example, the width S can be about 60 mm to about 130 mm, e.g., 64.5 mm, or about 130 mm to about 260 mm. The frame  162  has a zigzag shape including a first half portion  172  and a second half portion  174 , each for positioning of two jetting assemblies. Each half portion  172 ,  174  can be similar (e.g., including alignment datums and flexures) to the frame  22  of  FIG. 1  to allow a easy positioning of the two jetting assemblies  164 ,  166  or  168 ,  170  to provide the capability of printing at a resolution twice as large as a resolution at which each jetting assembly is capable of printing. The jetting assemblies in the first half portion  172  each has its nozzles aligned along the x direction with the nozzles of a corresponding jetting assembly in the second half portion  174 . In the example shown in  FIG. 15 , nozzles  176   a ,  176   b  of the jetting assembly  164  align with nozzles  178   a ,  178   b  of the jetting assembly  168 , and nozzles  180   a ,  180   b  of the jetting assembly  166  align with nozzles  182   a ,  182   b  of the jetting assembly  170 . The overlapping distance p, and therefore, the number of the aligned nozzles along the x direction can be selected as desired and can be controlled by the shape and alignment datums of the frame  162 . For example, the overlapping distance p can be, for example, about 0 mm to about 5 mm. Additional alignment datums, flexures, springs, and/or fasteners similar to those discussed previously can be used to facilitate the positioning and the alignment of the jetting assemblies in different portions of the frame  162 . In some embodiments, each half portion  172 ,  174  of the frame  162  is designed for positioning of three or more jetting assemblies. The two half portions  172 ,  174  can receive the same or a different number of assemblies. In addition, the frame can be extended to have a stair shape and include three or more portions, each being similar to the half portions  172 ,  174 . The stair-shaped frame can provide a larger printing width. Other shaped, for example, pyramid-shaped ( FIG. 17  below), frame can also be used. 
         [0071]    Referring back to  FIG. 1 , similar to the positioning of the jetting assemblies in the jetting module  10 , the jetting module  10  can be positioned on the printbar  12  with one of the two alignment datums  98 ,  100  engaged with a hard stop on the print bar  12  and the other one of the two alignment datums  98 ,  200  spring loaded, for example, with a flexure or a spring. The frame  22  of the jetting module  10  can expand or shrink naturally on the printbar  12  when needed. For example, the alignment datum  100  can be spring loaded with a loading force of about 10 pounds to about 50 pounds, for example, 12 pounds, along they direction. The alignment datum  98  can engage with a hard stop that provides a force of about 50 N to about 100, for example 80N. The positioning of the jetting module  10  along the other directions can be done similarly or differently. For example, along the x and z directions, the jetting module  10  can be spring loaded with a loading force of about 2-10 pounds, e.g., 5 pounds, and about 20 pounds, 15 pounds, 10 pounds, or 5 pounds, respectively. The loading of the jetting module can also allow the jetting module to expand or shrink up to an amount of about 300 microns, 275 microns, or 250 microns. 
         [0072]    In some embodiments, the printbar  12  can be designed such that the precise positioning of multiple jetting modules  10  of  FIG. 1  on the printbar  12  enables the printer to print at an even higher resolution, or a larger print width along they direction, than each jetting module  10  is capable of printing. For example, two or more jetting modules  10  can be positioned on the printbar in a manner similar to the way in which the two jetting assemblies  18 ,  20  are positioned on the frame  22 . The corresponding nozzles of different jetting modules can offset relative to each other to provide a high nozzle density along the rows of the nozzles. The two jetting assemblies in each jetting module  10  can print with the same color or with two different colors. In some embodiments, the multiple jetting modules  10  positioned on the printbar  12  can print with more than two colors. 
         [0073]    The printbar  12  can include pre-determined alignment datums and their corresponding springs or flexures similar to alignment datums  42 ,  44  to enable each jetting module  10  to be precisely positioned onto the printbar  12 . The printbar  12  can also include adjustable alignment datums, for example, screw adjustable, and can be used to receive jetting modules of different sizes and types. High precision can be reached by test printing and fine tuning of the adjustable alignment datums. The printbar  12  can contain the same material as the base material of the frame  22 , for example, aluminum, stainless steel, or plated steel. Other materials can also be used. 
         [0074]    In the example shown in  FIG. 16 , the printbar  12  can have a set of openings  190 ,  192 ,  194  arranged in a pyramid arrangement. Each opening in the set includes a predetermined alignment datum  196  and a corresponding flexure or spring  198  to load a jetting module  10 . Each alignment datum and flexure can be similar to or the same as those discussed above. Other arrangement of the datums and the flexures in the set of openings are possible. More alignment datums and flexures or springs can be used and each loaded jetting module  10  can expand or shrink relative to the printbar  12  in a manner similar to the way each jetting assembly  18 ,  20  expands or shrinks relative the frame  22 . The opening  194  at the top of the pyramid had each of its two ends overlap with each opening  190 ,  192  along the x direction. The jetting modules  10  positioned in these openings can overlap in overlapping ranges  200 ,  202  so that the nozzles from the jetting modules  10  loaded in the bottom openings  190 ,  192  are aligned with nozzles from the jetting module  10  loaded in the top opening  194  along the x direction within the overlapping ranges  200 ,  202 . A printing width  204  of the three loaded jetting modules  10  can be about three times as large as a printing width of an individual jetting module and within the printing width  204 , the nozzles from all three jetting modules  10  can be equally spaced along the row of the nozzles (y direction). The overlapping ranges  200 ,  202  can be selected based on the dimensions of the jetting modules  10 , the number of nozzles to be overlapped along the x direction, and other parameters or conditions. The printbar  12  can include two or more sets of openings like the set of openings  190 ,  192 ,  194  along the x direction to increase the overall nozzle density along the y direction, or along they direction to obtain an even larger printing width  204 . 
         [0075]    In the example shown in  FIG. 17 , the printbar  12  can include one or more openings  206  each being capable of receiving three jetting modules  10 . Each opening  206  corresponds to the set of openings  190 ,  192 ,  194  of  FIG. 16 . In particular, the opening  206  includes three portions  190   a ,  192   a ,  194   a  arranged in a pyramid arrangement. The top portion  194   a  is connected to the bottom portions  190   a ,  192   a  in the opening areas  200   a ,  202   a . Each portion of the opening  206  can include features, e.g., alignment datums and flexures or springs (not shown), similar to those of each opening of  FIG. 16 . The jetting modules  10  can be loaded into the opening  206  in a manner similar to the way they are loaded into the set of openings of  FIG. 15  and can have features, for example, an expanded printing width, similar to those of the jetting modules  10  of  FIG. 16 . Each jetting module  10  can include one or more additional alignment datums such that each jetting module  10  loaded in the bottom portion  190   a ,  192   a  registers with the jetting module  10  loaded in the top portion  194   a  directly through the alignment datums in the open areas  200   a ,  202   a . The printbar  12  can also include other shaped openings. In some embodiments, each opening or opening portion of  FIGS. 16 and 17  can load two or more jetting modules. 
         [0076]    In a particular example shown in  FIGS. 18 and 19 , a print bar  220  includes four parallel openings  222   a - 222   d  defined in a base plate  223  and separated from each other by separation bars  244 . Each opening is sized for positioning one jetting module, for example, the jetting module  10  of  FIG. 1 , and exposing the nozzles of the jetting module  10  for printing. For illustration purposes, one frame  22   a  (like the frame  22  of  FIG. 1 ) is shown in the opening  222   d  (without the jetting assemblies, e.g., jetting assemblies  18 ,  20 , being shown). Along they direction (parallel to the direction along which each separation bar  244  extends), the frame  22   a  is tightly fitted between a spring plunger  228  at the opposite side  226  of the printbar  220  and an adjustment screw  230  at the operating side  224  of the printbar  220 . In particular, the frame  22   a  has one end  260  carrying the alignment datum  100  spring loaded against the spring plunger  228 . The spring plunger  228  can have a curved, e.g., ball-shaped, contact head  232  extending from a main body  229  and in point contact with the alignment datum  100 . The contact head  232  can exert on the alignment datum a spring force determined by a spring constant of the spring plunger  228  and a predetermined linear displacement of the contact head  232  when the frame is inserted. Each spring plunger  228  can have a spring constant of about 10 N/m to about 50 N/m and can exert a force of about 25 N to about 100 N on the frame  22   a.    
         [0077]    In the same direction, the frame  22   a  has another end  262  carrying the alignment datum  98  in contact with a hard stop provided by a head  234  of the adjustment screw  230 . The head  234  can also have a curved surface to provide only a point contact between the adjustment screw  230  and the alignment datum  98 . The adjustment screw  230  can move back and forth along the y direction by turning the screw. The spring loaded alignment datum  100  can move against the spring force exerted by the contact head  232  of the spring plunger  228  and the location of the frame  22   a  along they direction relative to the printbar  220  can be adjusted. In some embodiments, the adjustment screw  230  can move by a distance of about 0 microns to about 1000 microns along the y direction, and the movement can be as precise as about 1 micron to about 15 microns. 
         [0078]    Along the x direction, the frame  22   a  is positioned between a first pair of a flexure  236   a  and a corresponding hard stop  238   a  and a second pair of a flexure  236   b  and a corresponding surface  239  of a tapered cone  252 . In some examples, the two flexures  236   a ,  236   b  can be identical and diagonally arranged relative to each opening  222   a - 222   d . Each flexure  236   a ,  236   b  can include a fastened end and a free end extending from the fastening end. Each free end carries an alignment datum  240   a ,  240   b  exerting a force on a side surface  241   a ,  241   b  ( FIG. 19 ) of the frame  22   a . Each force is in an opposite direction to a force exerted by the corresponding hard stop  238   a  and the surface  239  of the tapered cone  252 . When the flexures are diagonally arranged, a straight line connecting the alignment datums  240   a ,  240   b  is not parallel to the x direction and the extensions of the directions of the forces exerted by the hard stops  238   a  and the surface  239  on the frame  22   a  do not overlap. At the fastened end, the flexures  236   a ,  236   b  can be attached to edges  246 ,  248  of the printbar  220  and the separation bars  244  using, for example, one or more del pins  242  (not all shown) and screws  250 . The hard stops  238   a  can be a continuous portion of the ends  246 ,  248  and the separation bars  244 , and can have a flat or curved high precision surface to contact an external surface on each side of the frame  22   a  in the x direction. 
         [0079]    An edge point  245  of the frame  22   a  contacts a contact point  243  on the cone surface  239 . The edge point  245  can be pressed up and down along the x direction when the contact point  243  moves on the cone surface  239 . In the example shown in the figure, the cone  252  tapers in from the end of the opening  222   d  toward the center of the opening  222   d  continuously. The large-diameter end  253  is connected to an adjustable screw  254  and the small-diameter end  255  rests on a guide  238   b  so that when the screw  254  turns, the small-diameter end  255  (and the entire cone  252 ) moves linearly back and forth along they direction on the guide  238   b . In particular, when the cone  252  is adjusted to move in towards the guide  238   b , the contact point  243  moves to a spot on the surface  239  that corresponds to a large diameter and presses the edge point  245  towards the flexure  236   b . On the other hand, when the cone  252  is adjusted to move out towards the operation side  224 , the contact point  243  moves to a spot on the surface  239  that corresponds to a small diameter and releases the edge point  245  back towards the cone  252 . The edge point  245  of the frame  22   a  can move along the x direction by a distance value of about 0 microns to about 500 microns, and the movement can be as precise as about 1 micron to about 10 microns. The surface  239  of the cone  252  is smooth and is made with a high precision to facilitate the high precision adjustment of the edge point  245  of the frame. The tapering angle  257  of the tapered cone  252 , the density of the threads  259  of the screw  254 , the total tunable distance (not shown) of the screw  254 , and other parameters can be selected to obtain a desired precision and total distance the edge point  245  is capable of moving. 
         [0080]    The movement of the edge point  234  of the frame  22   a  adjusts the orientation of the frame  22   a  within the x-y plane. The orientation can be characterized by an orientation angle θ (exaggerated for demonstration) between a long axis  256  of the frame  22   a  and the y direction in the x-y plane. For example, when the edge point  245  is pushed to move towards the flexure  236   b  along the −x direction, the frame  22   a  pushes against the alignment datum  240   b  of the flexure  236   b  so that the alignment datum  240   b  retreats back towards the end  246  of the printbar  220  along the −x direction. At the same time, the hard stop  238   a  pushes the frame  22   a  against the alignment datum  240   a  of the flexure  236   a  so that the frame  22   a  rotates clockwise and the angle θ increases. By reversing the direction of the movement of the edge point  245 , the frame  22   a  can rotate anti-clockwise and angle θ can decrease. The diagonal arrangement of the flexures  236   a ,  236   b  and the point contacts between the frame  22   a  and the surface  239 , the adjustment screws  252 ,  254  and other components of the printbar  220  facilitate the movement of the frame  22   a  and the adjustment of the angle θ. In some implementations, each flexure  236   a ,  236   b  has a spring constant of about 20 N/m to about 60 N/m and exerts a force of about 10 N to about 100 N on the frame  22   a . The angle θ can be adjusted by a value up to about ±0.4 degrees and the precision of the adjustment can be about 0.01 degrees to about 0.05 degrees. In some embodiments, the cone  252  can taper in in a direction opposite to the direction (−y) shown in the figure. Other suitable devices with a tapered surface can also be used. 
         [0081]    Each jetting module  10  or frame  22   a  positioned in one of the four openings  222   a - 222   d  can be adjusted for precise alignment with other jetting modules or frames positioned in the other openings without affecting the positions and orientations θ of the other jetting modules or frames. The adjustment of the position can be independent of the adjustment of the orientation of each jetting module  10  or frame  22   a . For example, after the position and the orientation of the first frame  22  in the opening  222   d  are adjusted and set, the tapered cone  252  corresponding to the opening  222   c  can be adjusted to align a long axis of a second frame in the opening  222   c  to the long axis  256  of the first frame  22   a . The relative positions of the nozzles of the first and second frames along the x direction can then be adjusted by turning the adjustment screws  230  of the opening  222   c  (y-direction pixel adjustment) without affecting the previously aligned orientations of the frames. The additional two frames in the openings  222   b ,  222   a  can be similarly aligned. The amount to be adjusted for θ and for the y-direction pixel can be determined by test printing or by optical measurements. The y-direction pixel adjustment can make the nozzles of each jetting module  10  align or offset with respect to each other along the x direction, depending on different printing needs. The alignment adjustment can be operated and completed by accessing only the operating side  224  of the frame and can be conveniently done by users without special tools. 
         [0082]    After the adjustments for all four jetting modules  10  are done, the adjustment screws  230  and the tapered cones  252  with the screws  254  can be fixed relative to the base plate  223  and the separation bars  244 . 
         [0083]    Once the jetting modules are set, if one or more jetting modules  10  needs to be replaced or removed and reinstalled, this can be done quickly and easily by pulling out the one or more jetting modules  10  and inserting new (or reinstalled) jetting modules  10  between the flexures, spring plungers, hard stops, and the fixed adjustment screws  230  and tapered cones  252 , without repeating the procedures of aligning the new jetting modules  10 . The replacement of one or more jetting assemblies in the jetting modules  10  can be done directly in the jetting module  10  without affecting the positioning of the jetting modules  10  in the printbar  220 . 
         [0084]    As shown in  FIG. 18 , the frame  22   a  can be fastened to the printbar  220  by pressing the two ends  260 ,  262  of the frame  22   a  along the z direction against surfaces  264 ,  266  of the printbar  220  using a spring plunger  268  and a shoulder screw  270 , respectively. The surfaces  264 ,  266  are substantially leveled in the same plane parallel to the x-y plane so that the arrays of nozzles of the jetting module  10  are horizontally parallel to they direction. The spring plunger  268  can have features, such as a spring constant, similar to the spring plunger  228 . In some embodiments, the spring plunger  268  also has a curved contact head (not labeled) being in point contact with an upper surface  271  or extending into an alignment hole  272  of the end  260  ( FIG. 11 ). A force exerted by the spring plunger  268  on the frame  22   a  along the z direction is about 10 N to about 40 N. The spring plungers  228 ,  268  can have their fixed to a standing element  225  that is screwed to the base plate  223  using screws  227 . The shoulder screw  270  can have a body  274 , a spring  276 , and an insulating ring  278  arranged similarly to those of the shoulder screw  154  of  FIG. 10 . The body  274  is screwed into the printbar  220  without contacting the frame  22   a  and the spring  276  exerts a force of about 20 N to about 100 N on the frame  22  along the z direction. Both the spring plunger  268  and the shoulder screw  270  fastens the frame  22   a  to the printbar  220  without inducing a torque on the frame  22   a  so that the aligned angle θ is not affected. In some embodiments, the y-direction pixel adjustment and the orientation adjustment of the angle θ of the frame  22   a  can also be done in the manner described previously after the spring plunger  268  and the shoulder screw  270  are applied to the frame  22   a.    
         [0085]    In some embodiments, an insulating, e.g., thermally-insulating and/or electrically-insulating, sheet  282  can be applied on each top surface  264 ,  266  of the printbar  220  so that the ends  260 ,  262  of the frame  22   a  are thermally and/or electrically insulated from the printbar  220 . Overall, among the portions or elements of/on the printbar  220 , the frame  22   a  only directly contacts the contact heads  232 ,  234  of the spring plunger  228  and the adjustment screw  230  (y direction), the alignment datums  240   a ,  240   b  of the flexures  236   a ,  236   b , the hard stops  238   a  and surfaces  239  (x direction), and the insulating sheets  282  (z direction). The contacts between the printbar  220  and the frame  22   a  in the x and y directions are minimal and the frame  22   a  is substantially thermally and electrically insulated from the printbar  220 . The spring loading of the frame  22   a  in three directions x, y, and z allows the frame  22  to expand or shrink freely when experiencing thermal or other changes. 
         [0086]    The base plate  223  of the printbar  220  can be made of a metal, for example, aluminum, e.g., cast aluminum (MIC-6 available from Alcoa at Pittsburgh, Pa.), stainless steel, e.g., 304 or 316 stainless steel, A2 tool steel, or stainless steel with coatings. The screws  227 ,  254 , the body  270 , and the tapered cones  252  can be made of stainless steel or other suitable materials. The spring plungers  228 ,  268  can have different shapes be commercially obtained, for example, from Monroe Engineering at Auburn Hills, Mich. The flexures  236   a ,  236   b  can be made of a plastic, for example, Acetal, which is commercially available as Delrin from Professional Plastics at Brooklyn Heights, Ohio, stainless steel, mild steel, or elastomeric materials. The insulating sheets  282  can also include a plastic, for example, phemolic, available from Electrical Insulating Material at Chambersburg, Pa., or Nomex Aramide paper available from Lucite International at Southampton, UK. Other suitable materials having similar properties can also be used for different components of the printbar  220 . 
         [0087]    In some embodiments, the four openings  222   a - 222   d  can be arranged in different configurations. The printbar  220  can include more than four openings, for example, five, six, or even more. The base plate  223  and the standing element  225  can be a continuously machined piece. Flexures or elastomeric profiles can be used in replacement of the spring plungers  228 ,  268  and vertically orientated expanding mandrels can be used in replacement of the tapered cones  252 . The flexures  236   a ,  236   b  can have other shapes, for example, ramp-shaped, and can be arranged in a configuration different from the configuration shown in  FIG. 18 . 
         [0088]    The printbar  220  also includes mechanisms, such as dowell pins  280 , for aligning with other printbars  220  or mounting onto another printbar. The printbar  12 ,  220  can be a printbar of a step-and-repeat printer, in which the jetting module  10  scans back and forth across the substrate  16  along the x direction when the substrate  16  is stationary and the substrate  16  proceeds with a predetermined distance along the y direction between the scans. The printbar  12  can also be a printbar of a single-pass printer, in which the jetting module  10  stays stationary and prints on the substrate  16  that is moving along the x direction. 
         [0089]    The resolution of the image  14  printed by the step-and-repeat printer or the single-pass printer is associated with the resolution at which the jetting module  10  is capable of printing but can also be increased by positioning multiple jetting modules  10  along the x direction to provide a desired high nozzle density along the y direction. Similar to the way the jetting assemblies  18 ,  20  are assembled on the frame  22 , the nozzle arrays in one jetting module can include an offset along the x direction with respect to one or more nozzle arrays of other jetting modules mounted on the printbar  12  to increase the number of nozzles per inch along the y direction. In some embodiments, the multiple jetting modules can also be arranged in a similar way to that of the jetting assemblies  164 ,  166 ,  168 ,  170  to further increase the expansion of the nozzle arrays along they direction. A large expansion along they direction is desired in a single-pass printer when the image  14  has a large width. 
         [0090]    The two jetting assemblies of the jetting module  10  can jet ink having the same color or each can jet ink having a color different from the color of the ink that the other one jets. Multiple, e.g., three, jetting modules  10  can also be used in the printer to print images with colors. 
         [0091]    Jetting assemblies of different types can be used in the jetting module  10 . Discussions of different types of jetting assemblies are provided in U.S. Pat. No. 5,265,315 and U.S. Ser. No. 12/125,648, filed May 22, 2008, the entire contents of each are incorporated herein by reference. Each portion of the frame  22  can be in a different shape or form and can be positioned at a different location, as long as the goal and/or manner of the positioning of the jetting assemblies on the frame  22  is not substantially affected. The alignment datums can be in forms other than high precision surfaces, for example, engageable protrusions and indents or others. The metal piece  74  and the flexure supports  78 ,  80  of  FIGS. 3-5  can be a machined, continuous piece. The flexure supports  78 ,  80  can have various shapes, e.g., cylindrical, and thickness and can be located at positions different from those shown in  FIGS. 1 and 3 . The metal piece  74 , including the alignment datums, can also have configurations different from those shown in the figures. The flexures  46 ,  48  can also be in the form other than metal sheets, for example, springs. The different parts of metal sheet  104  of the flexure  102  ( FIG. 4 ) can have different shapes other than rectangular, for example, oval, circular, or others. Positioning of the jetting assemblies is also described in U.S. Ser. No. 11/118,704, filed Apr. 29, 2005, U.S. Ser. No. 11/118,293, filed Apr. 29, 2005, U.S. Ser. No. 11/117,146, filed Apr. 27, 2005, and U.S. Ser. No. 12/058,139, filed Mar. 28, 2008, the entire contents of each are incorporated herein by reference. The ink jetted by the jetting assemblies can include conductive inks, magnetic inks, or materials used in the fabrication of light emitting diode (LED) displays. The jetting assemblies can be also used to dispense or deposit fluids other than ink onto a substrate. The fluids can include non-image forming fluids. For example, three-dimensional model pastes can be selectively deposited to build models. Biological samples can be deposited on an analysis array. 
         [0092]    Other embodiments are also within the scope of the following claims.