Patent Publication Number: US-7708483-B2

Title: Unbacked fabric transport and condition system

Description:
This is a division of application Ser. No. 10/388,060, filed Mar. 12, 2003 now U.S. Pat. No. 6,988,797. 

   FIELD OF THE INVENTION 
   The present invention generally relates to textile printing systems. 
   BACKGROUND OF THE INVENTION 
   In the fabric printing industry, fabrics are typically colored with coloring agents, such as dyes or pigments, using a screen printing technology. Most large-scale fabric printing operations employ rotary screen printing technologies that utilize patterns incorporated into fine metal screens that are shaped into cylindrical forms. The coloring agents, are often in a fluid paste form, are pumped through dedicated tubing into the interior of fine cylindrical metal screens and are subsequently transferred to the fabric through the patterned pathways in the fine metal screens by a squeegee that presses the paste through the screens and onto the fabric. After each screen print run, with each color way (i.e., a color variant of the same pattern that uses different color combination), the rotary screen printer must be shut down to clean the various color pastes from the tubing and screens. This cleanup process is time intensive and environmentally unfriendly because it produces a large amount of effluent stream during the cleanup process. In addition to cleaning the rotary screen printer, a different screen must be inserted, aligned and adjusted into the printer to print a different pattern on the fabric. 
   To ensure that the pattern printed on the fabric is not distorted, industrial fabric printing machines stretch the fabric, and subsequently glue the stretched fabric to a belt that is run through the printing machine. The moving belt is indexed through the printing machine and the various screen stages. By attaching the fabric to the belt, the fabric is prohibited from moving with respect to the belt, which ensures fabric motion control that helps guarantee adequate registration of the fabric through the various stages in such a way that the fabric moves in a path corresponding to the movement path of the belt. However, gluing the fabric to the belt is an extremely dirty process that creates a significant environmentally unfriendly waste stream resulting from the gluing process and the subsequent washing and stripping processes. These inherent problems make industrial fabric printing processes prohibitive for use by smaller-scale users in the short run or sample printing situations. Furthermore the need for short and sample quantity runs generally exists in an office or a store setting, which generally is not designed to handle, treat and dispose of industrial waste streams. 
   To remedy the need for printing processes available on a smaller than industrial scale, digital ink-jet printing processes on fabrics have been developed. As known to those of ordinary skill in the art, digital printers utilize minute droplets of ink colorant that are ejected from nozzles of the ink-jet printer onto a target surface, such as, paper or fabric. In order to produce an image or pattern with the desired print quality on the fabric, special pre and post-treatment processes are employed. Pre &amp; Post printing processes are used to deposit an ink receptive layer, and then to condition the fabric and the ink receptive layer for optimal print quality condition. Finally, the colorants require a fixing process (post processing) that either physically or chemically fix the colorants to the fabric fibers. The pre-printing conditioning steps are used to initially control the humidity and temperature of the fabric to provide an optional ink reception state for the fabric, and the post-processing steps are used to “fix” the ink colorant to the fabric, after the ink colorant has been received by the fibers in the fabric. In addition, pre-treating the fabric with organic materials increases ink receptivity and reduces the amount of ink spread, which arises from bleeding of the printed ink along the fibers in the fabric. The ink colorant is generally prevented from “blowing through” in digital printing systems by laminating the fabric with a paper-backing layer. This produces a barrier to the ink “blow through.” The paper layer also stabilizes the fabric for feeding through a traditional ink-jet printer media path. 
   Backed fabrics may be passed through some modified ink-jet printers for the printing of a pattern on the backed fabric. However, the use of off-line paper backings may be costly, time consuming, and may limit the range of fabrics that may be fed through the ink-jet printer. Furthermore, the fabric may be damaged when the fabric is removed from the paper backing. Thus, printing on unbacked fabrics is often desirable. 
   As known to those of ordinary skill in the art, the problems of printing on unbacked fabrics using an ink-jet printer are not trivial. The fundamental nature of woven fabrics makes feeding the unbacked fabric and printing a pattern on the unbacked fabric more complex than traditional ink-jet printing on paper. For instance, fabrics have an almost infinite variation in fabric characteristics due to various factors including, but not limited to, the type of fiber used in the fabric, the fiber weight, the fabric weight, the different blends of materials used in the fiber, the weave pattern used to create the fabric, the environmental conditions existing at the time of printing, the pre-treatments used on the fabric, the surface finish of the fabric, the varying moisture contents of the fiber in the fabric, the non-linear behavior of woven materials, and the difference in fabric behavior between wet and dry fabrics. These factors prohibit the unbacked fabrics from moving accurately and uniformly through the printing processes using standard media-moving machines used in the traditional ink-jet printers. 
   The challenge is to make a clean, versatile and user-friendly, unbacked printing system for non-mill applications for producing printed fabrics in the short run and sampling quantities. An inkjet textile printing system that addresses the issues of tension control, closed-loop displacement control, fabric conditioning, and fabric motion control using an unbacked fabric transfer system would be desirable. A digital ink-jet textile printing system that produces printed patterns consistently, with a low level of distortion, and yet is practical for use in the short-run and sampling industries, would likewise be desirable. Of course, improvements to a printing system that allow the ink-jet printer to print a pattern with a low level of distortion on the unbacked fabric would also have utility in industrial screen printing processes, especially for proofing, color matching, and precise pattern replication needs. 
   BRIEF SUMMARY OF THE INVENTION 
   In accordance with one embodiment of the invention, an unbacked fabric transport and conditioning system for printing a pattern on a fabric is disclosed. A winding subsystem is included in the unbacked fabric transport and conditioning system that rotates a roll of the fabric. The unbacked fabric transport and conditioning system also includes a fabric characterization and tension control subsystem, for obtaining real time information on variations in the mechanical behavior of the fabric, throughout the whole length or the fabric roll. The unbacked fabric transport and conditioning system may further include an ink-jet printer configured for depositing ink in a pattern on the fabric. 
   A method for printing a pattern on a fabric is also disclosed. In a particular embodiment of the invention, the method includes unwinding a fabric from a fabric roll, and draping the fabric between rollers. The apex of the draped fabric can be then be sensed by a level sensor. The unwinding speed of the fabric is controlled by observing the apex of the draped fabric, with a set of sensors. Subsequently, the characteristics of the fabric are ascertained by observing the weave pattern variations as a function of the predetermined strain condition in the fabric. A pattern is then printed on the fabric, the printed image is dried and post processed. The printed fabric is then rewound on a roll. 
   A digital printing system that transports, conditions, and prints a pattern on an unbacked fabric is also described. In another embodiment of the invention, the printing system includes an unwind system for unrolling the fabric from a roll. The unwind system comprises a first advance motor configured to unroll the fabric from the roll and a first fabric level sensor for detecting an amount of the fabric draped from the roll of fabric. A fabric characterization subsystem gathers information on variations in the fabric, and is included in the printing system. The fabric characterization subsystem contains a pair of skewed &amp; driven rollers for the specific purpose of inducing a variety of strain patterns in the fabric, and cameras for observing the mechanical response of the fabric. The printing system further includes an irregularity detection subsystem for discovering irregularities in the fabric. The irregularity detection subsystem comprises of a pair of rollers for stretching the fabric, and the aforementioned camera for observing the irregularities in the fabric. A fabric control subsystem including a plurality of motion synchronized belts for advancing the fabric through a print zone that is also included within the printing system. A printing subsystem configured to deposit ink on the fabric may also be included in the printing system. The printing system may also include a closed-loop color control subsystem for detecting color variations in the ink deposited on the fabric. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     While the specification concludes with claims particularly pointing out and distinctly claiming that which is regarded as the present invention, the present invention can be more readily ascertained from the following description of the invention when read in conjunction with the accompanying drawings in which: 
       FIG. 1  is a schematic diagram of an unbacked fabric transport and conditioning system according to one embodiment of the present invention; 
       FIG. 2  is an expanded, perspective view of a portion of one embodiment of an unwind subsystem of the present invention; 
       FIG. 3  is a partial, perspective view the unwind subsystem of  FIG. 2  and a rewind subsystem substantially similar to the unwind subsystem of an embodiment of the present invention; 
       FIG. 4  is a perspective view of skewed rolls and drive motors of the skewed rollers of a first embodiment of a fabric characterization and tension control subsystem of the present invention; 
       FIG. 5  is a perspective view the fabric characterization and tension control subsystem of  FIG. 4  in relation to a steam table and ironing roller of an embodiment of the present invention; 
       FIG. 6  is a perspective view of a second embodiment of a fabric characterization and tension control subsystem in relation to a steam table and ironing roller of the present invention; 
       FIG. 7A  is a schematic representation of one embodiment a low angle lighting system used in one embodiment of a crease &amp; irregularity detection subsystem embodying teachings of the present invention; 
       FIG. 7B  is a diagram depicting an illumination sequencing scheme used in one embodiment of the present invention in the crease &amp; irregularity detection and removal subsystem of  FIG. 7A ; 
       FIG. 8  is cross-sectional view of one possible configuration of a steam table and ironing roller of one embodiment of a crease removal subsystem of one embodiment of the present invention; 
       FIG. 9  is a perspective view of the steam table in one embodiment of the present invention shown in  FIG. 8 ; 
       FIG. 10  is a flowchart of one embodiment, and an algorithm used to detect irregularities, and based upon the detection data, adjust the pen-to-fabric spacing so that damage to the print heads can be avoided, embodying teachings of one embodiment of the present invention; 
       FIG. 11  is a schematic representation of one possible configuration of print head carriage, used in one embodiment of a print subsystem of the present invention that protects the inkjet element from intimate contact with knots and other fabric defects; 
       FIG. 12  is schematic representation of one embodiment of a layout of the fabric characterization and tension control subsystem in relation to a fabric pre-conditioning subsystem embodying teachings of the present invention; 
       FIG. 13  is schematic representation of a possible orthogonal fabric strain behavior as a function of the induced tension within the fabric. These determinations are made in the fabric characterization and tension control subsystem of on one embodiment of the present invention shown in  FIG. 5 ; 
       FIG. 14  is a schematic representation of the placement of a CCD array in the fabric characterization and tension control subsystem of  FIG. 5 ; 
       FIG. 15  is a flowchart depicting an algorithm used to maintain web tension in a fabric passing through the fabric characterization and tension control subsystem of one embodiment of the present invention shown in  FIG. 5 ; 
       FIG. 16  is an expanded view of one embodiment of a fabric tension control subsystem used in the unbacked fabric transport and conditioning system of  FIG. 1 ; 
       FIG. 17  is a schematic representation of the fabric motion control subsystem of  FIG. 16  in relation to a print subsystem of one embodiment of the present invention; 
       FIG. 18  is a schematic representation of a second embodiment of a fabric motion control subsystem in relation to an adjustable print head to fabric distance-control system in a print subsystem embodying teachings of one embodiment of the present invention; 
       FIG. 19  is a diagram of one embodiment of a print pattern that could be used to monitor the color and the actual density of an ink that is being deposited, using a color consistency densitometry subsystem of  FIG. 1  embodying teachings of one embodiment of the present invention; 
       FIG. 20A  is a diagram of a field of view of a current carriage sensor in one embodiment of the present invention used to measure color in a closed-loop color control subsystem of  FIG. 1 ; and 
       FIG. 20B  is a diagram of an embodiment of a widened field of view of a carriage sensor used in the closed-loop color control subsystem of  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The invention described herein is directed to an unbacked fabric transport and conditioning system for use with fabric printing processes that use digital ink-jet printers or other printing devices that deposit ink colorants on a fabric. More specifically, a system that characterizes the unbacked fabric before the fabric is presented to the print zone is disclosed. The present system enables a user to print a pattern on an unbacked fabric, or other textiles, with an ink-jet printer, and actively controls the distortion of the printed image on the fabric. As used herein, the term “pattern” will be used to refer to any type of design, mark, figure, identification code, graphic, work, image, or the like which may be printed. It will be apparent from the following description that the drawings described herein used to represent various features of the present invention are not drawn to scale, but are rather for illustrative and exemplary purposes only. 
   Referring now to drawing  FIG. 1 , there is shown a schematic diagram of an un-backed fabric transport and conditioning system (hereinafter “UFTCS”) employing teachings of the present invention generally at  10 . The UFTCS  10  broadly includes three zones. For ease of explanation, dashed lines  12  have been added to the diagram to separate the UFTCS  10  into the three zones. The first zone is a material delivery, characterization, and conditioning zone indicated generally at  100 . The second zone is a print and printer control zone indicated generally at  200 , and the third zone is a post print processing, drying, and rewind zone indicated generally at  300 . 
   Each of the three zones  100 ,  200  and  300  includes various subsystems, wherein each subsystem performs a function that will be described in the following detailed description. It will be apparent that the various subsystems and components of each zone  100 ,  200  and  300  of the UFTCS  10  described herein may have utility in other broader fields of textile printing and weaving systems, other than digital printing systems employing an ink-jet printer, such as industrial screen printing systems. 
   As shown in  FIG. 1 , the material delivery, characterization, and conditioning zone  100  includes components within an unwind subsystem indicated by bracket  110 , components within two fabric characterization and tension control subsystems illustrated with brackets  130   a  and  130   b , components within a crease, and irregularity detection and crease removal subsystem  150 , and components within a fabric drying and conditioning subsystem  170 . Although various components described herein will be referred to as being within a subsystem or zone, the subsystems and zones described herein are not meant to be so limited. It will be apparent that various components may be added or removed from particular subsystems or zones and not depart from the scope of the present invention. Also, some components described herein may be located in and have use in more than one subsystem. Further, some of the subsystems described herein may be located in more than one zone. The UFTCS  10  may be controlled by a single central processing unit (CPU), such as a computer (not illustrated), which receives, processes, and advances information received from various sensors and subsystems described herein. In an alternative embodiment, each sensor or subsystem may also have a separate, dedicated CPU that controls and processes data received from the individual sensor or subsystem and transfers the data to the CPU for further processing and the derivation of control signals for the subsystems of the UFTCS  10 . 
   The unwind subsystem  110  is used to unwind a fabric roll  112 , and relax and dissipate winding stresses that were induced in a fabric  114  when the fabric  114  is rolled and stored on the fabric roll  112 . The unwind subsystem  110  includes an optical fabric level sensor  116  operably connected to a standard surface- or center-wound unwind station that receives control feed signals from the optical fabric level sensor  116 . Advance signals from the optical fabric level sensor  116  are issued to rollers  118   a  and  118   b  in the case of a surface wound system, or the roller  118   c  in a center wound system in a synchronous manner to speed up, slow down, or stop the unwinding of the fabric roll  112 . As illustrated, the fabric  114  drapes from roller  118   a  towards the optical fabric level sensor  116 . The fabric  114  is subsequently taken up by skewed rollers  132 . A relaxation zone  113  is also present in the unwind subsystem  110 , wherein stresses introduced into the fabric  114  during winding, and storage of the fabric  114  in the roll  112  are relieved. 
   Referring now to  FIG. 2 , there is shown an expanded perspective view of a section of the unwind subsystem  110 . As illustrated, the fabric  114  is draped, where an apex  115  of the fabric  114  hangs between two fabric level sensors  116   a  and  116   b . As illustrated, the fabric level sensor  116  includes three zones, a feed zone  120 , a no action zone  122 , and a stop feed zone  124 . As the fabric  114  unwinds from the fabric roll  112 , the apex  115  of the draped fabric  114  may travel vertically from one zone of the fabric level sensor  116  to another zone. For instance, if the speed of the unwinding of the fabric  114  exceeds the uptake of the fabric  114  by the UFTCS  10 , the apex  115  of the fabric  114  will move to a lower zone. 
   As illustrated in  FIG. 2 , if the uptake of the fabric  114  by the UFTCS  10  slows, the apex  115  of the fabric  114  will move downward from the feed zone  120  to the no action zone  122 , and maybe even into the stop feed zone  124 . If the apex  115  reaches the stop feed zone  124 , the optical fabric sensor  116  stops sending feed fabric signals, indicated by arrow  126  to a fabric advance motor  128 . In turn, the fabric advance motor  128  quits unwinding the fabric roll  112 . As illustrated, since the apex  115  of the fabric  118  is in the feed zone  120 , the optical fabric sensor  116  instructs the fabric advance motor  128  to unwind the fabric roll  112 . 
   As illustrated, the optical fabric level sensor  116  is an infrared sensor, but it is understood that any type of sensor that performs functions the same as the optical fabric level sensor  116  described herein is encompassed by the present invention. The unwind system  110  may also be configured to detect differential side-to-side imbalances of the fabric  114 , such that if one side of the fabric  114  advances faster than the other side of the fabric  114 , the unwind system  110  corrects for the effect by differentially advancing the fabric roll  112 . 
   The illustrated unwind system  110  does not create a significant variation in a back tension force applied to the draped fabric  114 . Rather, variable back tension force on the draped fabric  114  in the illustrated embodiment is due to the weight of a few inches of draped fabric  114  between the optical fabric level sensors  116   a  and  116   b  which can be considered as negligible. In contrast, when standard dancer bars are used to sense the unwinding of the fabric roll  112 , changes in weight vector forces applied to the fabric  114  can cause substantial back tension variations in the fabric  114 . These back tension variable forces create scaling artifacts in a finished printed fabric when the printed fabric reverts to a relaxed state. By using the optical fabric level sensors  116   a  and  116   b  to provide the control signals for the unwinding of the fabric  114  from the fabric roll  112 , the resultant draping of the fabric  114  relaxes the fabric  114  and allows the draped fabric  114  to dissipate the winding and storage stresses induced in the fabric  114  as the fabric  114  is rolled on the fabric roll  112 , as previously described herein with reference to the relaxation zone  113 . 
   Referring now to  FIG. 3 , there is shown a perspective view of the unwind subsystem  110  of  FIG. 2  and a rewind subsystem  370  of the UFTCS  10 . As illustrated, the unwind subsystem  110  is substantially the same as the rewind subsystem  370 , except the unwind subsystem  110  operates in a direction opposite to that of the rewind subsystem  370 . A finished printed roll  372  of the rewind subsystem  370  is substantially the same as the fabric roll  112  of the unwind system  110 . The rewind subsystem  370  and unwind subsystem  110  also include substantially identical rollers  118   a ,  118   b  or  118   c , and fabric level sensors  116 . 
   As previously discussed herein with reference to the relaxation zone  113  of the unwind subsystem  110 , the fabric  114  relaxes and dissipates winding stresses induced in the fabric  114  during the rolling and storing of the fabric roll  112 . Furthermore, the condition of the fabric  114 , such as its moisture content and temperature, equilibrate to the ambient conditions surrounding the system in the relaxation zone such that the fabric  114  is in the same ambient environment as a printing subsystem  250  when a pattern is printed on the fabric  114 . By allowing the fabric  114  to equilibrate to the ambient environment where the printing system is located, the characteristics of the fabric  114  will vary less during the printing process. 
   The UFTCS  10  of  FIG. 1  is able to feed about 20 linear meters of fabric  114  per hour using a 0.85″ inch thermal ink-jet (TIJ) scanning writing system in the print subsystem  250 . It is understood that other ink-jet systems can also be used interchangeably in the place of a scanning head thermal Ink-Jet system. It will be appreciated by those of ordinary skill in the art that the printing of patterns on fabrics is substantially slower than the printing of patterns on paper because the ink flux required for printing fabrics is significantly higher than the ink flux used on paper, i.e., by factors of two to ten times depending on the type of fabric and the specific pattern being printed. Therefore, the time required for the fabric  114  to pass through the relaxation zone  113  of the UFTCS  10  provides ample opportunity for the fabric  114  to relax, and equilibrate to the ambient environment of the UFTCS  10  after the fabric  114  exits the unwind zone  110 . 
   Although not illustrated, the unwind subsystem  110  may also include a small diameter rod of various weights which may be used to add additional back tension to the draped fabric  114 , if necessary. The small diameter rod may be placed in the cradle created by the apex  115  of the draped fabric  114 . It will be further appreciated that the angle of the fabric drape in the material delivered to the conditioning zone  100  should be as acute as possible, such that variations in the back tension force applied to the fabric  114  due to rod weight would not vary by more than about 2 to 3 percent. 
   As known in the art, fabrics have an almost infinite variability in their characteristics due to factors including, but not limited to, the type of fiber used in the fabric, the weight of the fiber, the different blend of material used in the fiber, the weave pattern used to create the fabric, the environmental conditions existing at the time of printing, the pre-treatments used on the fabric, the surface finish of the fabric, the varying moisture contents of the fiber in the fabric, the non-linear behavior of woven materials, and the differences in fabric behavior when wet or dry. Therefore, since these fabric variations are usually present in the entire length of the fabric  114  of the fabric roll  112 , the continually changing fabric variations can be a major cause of defects and pattern variation in all fabric printing systems. Accordingly, it is important in any fabric printing system, especially digital printing systems, to acquire as much information as possible about various multi-dimensional force displacement characteristics inherently present in the fabrics in order to accurately advance the fabric through the printing system. Once information about these characteristics is gathered, the information may then be used to adjust operating parameters of a fabric advance subsystem in order to accommodate for the aforementioned fabric variations. 
   One type of device that may be used in the characterization of the fabric  114  is a skewed driven roller. Skewed driven rollers are well known to those of ordinary skill in the art of textile printing and may be used to guide and stretch the fabric  114 . As known in the art, skewed rollers are set at an angle with respect to a web of the fabric and are capable of inducing various degrees of stretch, and translation in a fabric in both X and Y directions. 
   Referring again to  FIG. 1 , the UFTCS  10  of the present invention characterizes the fabric  114  with a fabric characterization  130   a  and tension control subsystem  130   b . As illustrated in this particular embodiment, a first fabric characterization and tension control subsystem  130   a  is illustrated just above the optical fabric level sensor  116  in the path of the fabric  114  and is used to modify multi-dimensional force displacement characteristics of the fabric  114 . The fabric characterization and tension control subsystem  130   a  includes a set of two skewed driven rollers  132  and a charge couple device (hereinafter “CCD”) array  134 . 
   The skewed rollers  132  are used to stretch the fabric  114  in a controlled manner and induce a wide range of multi-directional distortion conditions in the fabric  114 . Although skewed driven rollers  132  are used in the illustrated embodiment, it will be appreciated by those of ordinary skill in the art that other devices that perform functions the same as, or equivalent to, the skewed driven rollers  132  described herein are meant to be encompassed by the present invention. For instance, a segmented individually driven belt system (not shown) may also be used. 
   Referring now to  FIG. 4 , there is shown an expanded, perspective view of the skewed driven rollers  132  of the fabric characterization  130   a  and tension control subsystem  130   b  of  FIG. 1 . As illustrated, the skewed drive rollers  132 , or guiding tensioning active rollers, are used to stretch the fabric  114  in both X and Y directions in a predetermined and preset displacement, range, and amplitude. Drive motors  136  that control the skewed rollers  132  are also illustrated wherein the drive motors  136  are configured to move in X, Y and Z directions such that the skewed rollers  132  may be used to stretch the fabric  114  in both the X and Y directions, as determined by the set angle of the rollers with respect to the fabric web. As the fabric  114  is stretched, a weave pattern frequency of the fibers within the fabric  114  changes and is observed with the CCD array  134  ( FIG. 1 ). The weave pattern frequency of the fibers in the fabric  114  is monitored as a change in a function of the induced deformation patterns induced into the fabric  114  by the skewed rollers  132 . In the illustrated embodiment, three or five area CCD arrays  134  may be positioned across the web of the fabric  114  and used to monitor the weave pattern frequency change as a function of the induced tension in both the X and Y directions. 
   Using the fabric weave information gathered by the CCD array  134 , and low angle lighting, a fundamental frequency content of the fabric weave may be derived as a function of the deformations induced in the fabric  114 . The signals from the CCD array  134  may then be assigned appropriate numerical values that would be proportional to the frequency content of the fabric weave. Using these numerical values, a Fast Fourier Transform algorithm may be used to derive the fundamental frequency content of the fabric weave as a function of the X and Y deformations introduced in the fabric  114 . Since the frequency content of threads in the fabric  114  is inversely proportional to the tension in the fabric  114 , the characteristic tension may be derived for any given fabric  114  present in the UFTCS system  10  during the set-up steps of the print job. Also, since a fabric characterization and tension control subsystem  130  may be introduced at various locations within the UFTCS system  10 , the characteristics of the fabrics  114  may be determined and compensated for in real time throughout the print job. In this manner, since another fabric characterization and tension control subsystem  130   b  is implemented in the UFTCS system  10  before a fabric control subsystem  210 , the predetermined and preset displacement range and amplitude functions that were previously characterized for the fabric  114  may be accurately induced into the fabric  114  before the fabric  114  is introduced into the fabric control subsystem  210 . 
   The use of the characterization and tension control subsystems  130   a  and  130   b  allows the machine operator of the UFTCS  10  to set optimal tension derived in the setup of a print job, and to further allow the machine operator to continuously monitor and control the parameters for the given print job, with respect to changing environmental conditions and fabric types. The machine operator is also able to control tension induced artifacts i.e., image scaling and distortion, that may be introduced into the printed fabric  114  during the set-up steps. 
   It will be appreciated that the characterization and tension control subsystems  130   a  and  130   b  described herein may be useful in traditional textile printing systems because the traditional printing systems, and also address other fabric non-linearity issues. In traditional printing systems, a significant savings in an amount of fabric that is wasted due to these variations is minimized by reducing the amount of “scrap yardage” produced by distorted images printed due to the aforementioned non-linear behaviors of fabrics. 
   As previously described herein, the mechanical behavior of any given fabric is directly coupled to and is a fundamental function of the weave, thread type, moisture content, temperature, tension strain in both the X and Y directions, pretreatments used, and coating weight used on the fabric. Therefore, it is desirable to have a characterization and tension control subsystem  130   b  before the fabric  114  enters a fabric motion control zone  210  and the printing subsystem  250  because these subsystems are highly sensitive to the real time mechanical variations of the fabric. 
   In addition to ascertaining characteristics of the fabric  114  after the fabric  114  is unwound from the fabric roll  112 , the fabric  114  may also need to have creases removed, the location of tread knots and irregularities ascertained in order to avoid printing on those areas, the pen-to-media distance adjusted in order to miss the knots. Accordingly, the UFTCS  10  of  FIG. 1  also includes a tread knot, irregularity, and crease detection subsystem  150  and a fabric drying and conditioning subsystem  170 . These subsystems include components used to de-crease and iron the fabric  114  before a pattern is printed thereon. After the fabric  114  is de-creased and ironed, and before printing begins, the fabric  114  should be at an optimal moisture content and temperature range. It will become apparent from the following description that since the fabric  114  is deformed in many directions to ascertain a minimum crease condition of the fabric  114 , the de-creasing and ironing of the fabric  114  may also occur within, or in close proximity, to the fabric characterization and tension control subsystem  130  such that these processes are most efficiently accomplished at the same time. 
   As previously discussed herein, traditional processes used to manufacture fabric in the textile industry results in the fabric  114  on the fabric roll  112  to include many creases and surface irregularities. These irregularities may cause head crashes of the ink-jet printer used in the print and printer control zone  200  or may cause other technical/practical problems in the UFTCS  10 . Additionally, fabric characteristics for the same type of fabric may vary from fabric roll to fabric roll. Accordingly, these creases and irregularities need to be constantly monitored and removed along the flow of the fabric  114  by steaming and ironing the fabric  114  before the fabric  114  passes to subsystems downstream in the UFTCS  10 . Furthermore, since fabric that is wound close to the core of the fabric roll  112  is not exposed to the same environmental conditions as the outer layers of fabric  114  of the fabric roll  112 , variations in fabric  114  will change as the fabric  114  in a single fabric roll  112  passes through the UFTCS  10 . 
   Referring now to  FIG. 5 , there is shown an expanded perspective view of a first embodiment of the fabric characterization and tension control subsystem  130  located just ahead of components used in the irregularity detection and removal subsystem  150 . As illustrated, the irregularity detection and removal system  150  includes a steam table  152  and an ironing roller  154 . Once the fabric  114  is characterized by the fabric characterization and tension control subsystem  130 , the fabric  114  is moved in a direction illustrated by arrow  14 . The fabric  114  crosses the steam table  152  and is ironed with the ironing roller  154  to remove wrinkles and creases. It will be apparent that steam tables  152  and ironing rollers  154  are well known in the art. Accordingly, any steam table  152  and ironing roller  154  that performs functions the same as, or equivalent to, the steam table  152  and ironing roller  154  described herein are meant to be encompassed by the present invention. 
   Referring to  FIG. 6 , there is shown an expanded perspective view of a second embodiment of the fabric characterization and tension control subsystem  130  in relation to the irregularity detection and crease removal subsystem  150 . As illustrated, the fabric characterization and tension control subsystem  130  includes skewed rollers  132  and drive motors  136  to drive the skewed rollers  132 . Also included are a bowed roller  138  and a bowed roller drive motor  139 . The bowed roller  138  is used to remove soft creases and provide a light cross-web tension to the fabric  114 . Once the soft creases are removed, the fabric  114  may be stretched in multiple directions by the skewed rollers  132  and bowed roller  138  before the fabric  114  is transported to the steam table  152 . 
   Additionally, the skewed rollers  132  may provide web guidance of the fabric  114  when used in conjunction with the CCD array  134 , as illustrated in  FIG. 5 . It will be appreciated that depending on the type of fabric  114  in the UFTCS  10 , the fabric characterization and tension control subsystem  130  may utilize only skewed rollers  132 , only a bowed roller  138 , or a combination of skewed rollers  132  and the bowed roller  138 , as illustrated in  FIG. 6 . Although  FIG. 6  illustrates the use of one bowed roller  138 , it will be apparent that more than one bowed roller  138  may be used in the UFTCS system  10  without departing from the spirit of the present invention. Also, the bowed roller  138  may be located before or after the skewed rollers  132  and still be encompassed by the present invention. 
   Referring again to  FIG. 1 , the irregularity detection and removal system  150  may also include a CCD camera  156  that may used to observe irregularities, such as crease patterns, in the fabric  114 . Once the fabric  114  is stretched in multiple directions with the skewed rollers  132 , the CCD camera  156  may be used in conjunction with a multiple time phased low angle lighting system (hereinafter “low angle lighting system”) (shown in  FIG. 7A ). The low angle lighting system is used to illuminate the fabric  114  such that shadows are cast by raised creases, or other irregularities, on the surface of the fabric  114 . The CCD camera  156  may also be used to gather crease vector information from the fabric  114 . Once the crease vector information is known, antivector forces can be introduced into the fabric  114  with skewed rollers  132  to remove the creases resulting from the crease vectors and flatten the fabric  114 . As known in the art, the skewed rollers  132  may be used to introduce force vectors perpendicular to the creases in the fabric  114  to remove the creases. In an alternative embodiment, differential sectioned drive belts (not illustrated) may be incorporated into the UFTCS  10  to remove creases from the fabric  114 . 
   When the surface of the fabric  114  is illuminated with the low angle lighting system, one or more shadow(s) are cast by any given crease or surface irregularity on the surface of the fabric  114 . By observing a contrast in light and dark areas on the surface of the fabric  114 , the crease condition of the fabric  114  may be ascertained. For instance, a minimum crease condition of the fabric  114  is observed as a low amount of contrast on the surface of the fabric  114  because a shallow crease will not cast a large shadow area. Alternatively, if many creases are present on the surface of the fabric  114 , then a plurality of shadows are cast which can be observed as having a higher contrast ratio. The contrast may be measured using the CCD camera  156 . As known in the art, CCD cameras  156  observe pixels of information in a field of view. An average contrast on the surface of the fabric  114  may be determined by averaging the output value of each of the CCD pixels over the field of view of the fabric surface. A determination of the lowest crease condition of the fabric  114  in the UFTCS  10  is achieved by averaging the output value of each CCD pixel in each of the camera frames, while the fabric is stretched in a predetermined stretch pattern. A highest average pixel value for the vectors of force introduced into the fabric  114  may be ascertained such that an optimal stretch condition is determined for each fabric  114 . The highest average pixel output condition corresponds to the lowest contrast condition and represents a smooth state of the fabric  114  with the minimum crease condition. Larger shadows are created when the light source is oriented in a low angle in relation to the fabric  114 , thus amplifying the shadow of a crease. 
   Referring now to  FIG. 7A , there is shown a schematic representation of the CCD camera  156  of  FIG. 6  positioned to observe a fabric  114 . A plurality of light sources  158  making up the low angle lighting system is illustrated as illuminating the surface of the fabric  114 . The light sources  158   a  through  158   f  are arranged such that light is cast upon the surface of the fabric  114  from various angles such that the CCD camera  156  observes multiple shadow patterns caused by the crease patterns, or other surface irregularities present on the surface of the fabric  114 . 
     FIG. 7B  illustrates the timing diagram for strobing of the light sources  158   a  through  158   f . For instance, timing diagram  157   a  represents the on time of the light source  158   a , line  157   b  represents the on time of the light source  158   b , etc. Rectangular waveforms  159   a  through  159   f  represent pulses of light generated from each light source  158   a  through  158   f . Thus, the light sources  158  are switched sequentially onto the surface of the fabric  114  in a time-dependent manner wherein  158   a  pulses first, then  158   b , etc. It will be apparent that although there are six light sources  158  illustrated, there may be any number of light sources. Line  157   h  shows each light source  158  in the plurality pulsing simultaneously to calibrate the CCD camera  156 . The timing of the CCD camera  156  image-capture cycles will be synchronized with the strobing of the light sources  158 . Calibration may be accomplished at any time, such as when a different type of fabric  114  is introduced into the UFTCS  10 , to achieve the best print quality. 
   If a crease is present on the surface of the fabric  114 , the low angle light source  158  casts a shadow on one side of the crease, while the other side of the crease is illuminated. Thus, a pixel of the CCD camera  156  in the field of view of the shadow is sensed as a dark output, while another pixel of the CCD camera  156  in the field of view on the other side of the crease is sensed as a light output. Using the light and dark output information gathered by the CCD camera  156 , the CPU of the UFTCS  10  may be used to ascertain the position of the crease on the surface of the fabric  114 . In order to obtain the average contrast, the CCD camera  156  is periodically calibrated for both full white and full dark output values for each pixel of a CCD chip within the CCD camera  156 . The calibration enhances a dynamic range of the CCD camera, accounts for the degradation of the light source, and enhances the fidelity of the pixels of information. Analysis of the shadow pattern created by the light and dark outputs observed by the CCD camera  156  may be accomplished in any manner known in the art. 
   Referring again to  FIG. 1 , by observing and recreating the minimal crease condition, the skewed rollers  132  may be used to remove creases sensed by the CCD camera  156  to make the fabric  114  as flat as possible before being presented to the steam table  152  and ironing roller  154 . Once the fabric  114  is presented to the ironing roller  154 , the fabric  114  is ironed substantially flat prior to the fabric  114  entering the fabric drying and conditioning subsystem  170 . In order to iron the fabric  114  to a substantially flat condition, steam from the steam table  152  is delivered to the fabric  114 . As known by those of ordinary skill in the art, the severity of a crease in the fabric  114  dictates an amount of steam required to iron out the crease because there is a fundamental relationship between the severity of creases and the amount of steam required to remove the crease. Thus, a moisture content of the fabric  114  may vary depending on the severity of the crease, and thus the amount of steam delivered to the fabric  114  to remove the crease. 
   Referring now to  FIG. 8 , there is shown a cross sectional view of the steam table  152  and ironing roller  154  of the present invention. A source of water used to generate the steam in the steam table  152  should be distilled/de-ionized water such that mineral build up does not occur on the steam table  152 . As illustrated, a container  160  of distilled/de-ionized water can be utilized such that a water line hookup is not required for use of the UFTCS  10 . The steam table  152  also includes a mesh  162  for transferring the steam from the steam table  152  to the fabric (not illustrated), a steam channel  164 , a heat capacitor  166 , and heating elements  169  for the steam generation. 
   Referring now to  FIG. 9 , there is shown a perspective view of the steam table  152  of  FIG. 8  (ironing roller not illustrated). Also illustrated in  FIG. 9  is a water valve  161  for controlling the flow of the water from the water container  160 , a heat control element  168 , and water channels  164 . It will be appreciated that since many standard components are known in the art for the production of steam tables, that many possible embodiments of the steam table  152  exist and the invention is not meant to be limited by the steam table  152  configuration depicted. In an alternative embodiment, a steam re-circulation system (not illustrated) may be added to the UFTCS  10  to enhance the energy/water usage efficiency of the UFTCS  10 , thus making the UFTCS more energy efficient and less costly to operate. 
   To accommodate for the widest range of surface irregularities and creases that may be present in the fabric  114 , an operator of the UFTCS  10  may adjust various set up parameters for each fabric  114  including, but not limited to, the steam temperature used to remove creases, the amount of steam transferred to the fabric  114 , an amount of pressure applied to the fabric  114  by the ironing roller  154 , and the amount of tension introduced in the fabric  114  by the fabric characterization and tension control subsystem  130 . For ease of use, the set up parameters may be stored in a UTFCS  10  controller module (not shown) such that the various set up parameters are available for easy reload for repeating particular print jobs using similar fabrics and fabric conditions. 
   In addition to detecting creases in the fabric  114 , components of the irregularity detection and removal subsystem  150  may be used to detect other types of defects, such as knots. As known in the art, during the process of weaving fabric, loom operators tie knots at the end of one of the thread bobbins to start a new bobbin of thread. As the fabric  114  is woven, the knots go through a loom and are woven into the finished fabric. Some of the knots and other irregularities present in the fabric may protrude higher than a distance between the fabric  114  and a pen used to print a pattern in the print subsystem  250 . When a knot or irregularity is too large to pass between the fabric  114  and the pen, the pen of a print head in the print subsystem  250  may be damaged. To protect the print heads, the knots or irregularities may be detected before the print zone and indexed over, such that the print heads will be protected from impact with them and damage to the print head can be avoided. 
   In the illustrated UFTCS  10  of the present invention, knots and other irregularities may be detected in the irregularity detection and removal subsystem  150  in a manner similar to the detection of creases as previously described herein. The CCD camera  156  and low angle lighting system may be used to scan for knots and other irregularities that are larger than, for example, 1 mm in height, width and length. Generally, the CCD pixel values are compared as previously described herein with reference to the detection of creases. When a knot or other irregularity is detected, the localized CCD pixel value corresponding to the reflection of the low angle light off of the fabric  114  will decrease. When the irregularity detection and removal subsystem  150  detects the knot or other irregularity, the data corresponding to the irregularity may be fed to the printer subsystem  250  such that the printer subsystem  250  may be directed to skip printing a swath of fabric  114  before and after the knot, thus avoiding costly replacement of the print heads. 
   Referring now to  FIG. 10 , there is illustrated an algorithm flow chart. The algorithm is used to process values obtained from the CCD camera  156  and may be performed by the CPU of the UFTCS  10 . Data generated using the illustrated algorithm is used to notify the print subsystem  250  when to skip printing in order to miss the knot or irregularity. Although the algorithm indicates that the fabric path is moved such that the defect is avoided by the print heads, in an alternative embodiment, the print heads are raised to avoid the defect contacting the print head. 
   In addition to protecting print heads from damage by locating and subsequently avoiding knots and irregularities in the fabric, the print subsystem  250  of the present invention may also be configured with a pen head construction that helps minimize potential damage to the pen heads. Referring now to  FIG. 11 , there is shown a schematic representation of a configuration of pens within a print head carriage employing teachings of the present invention. As illustrated, pens  254  inserted in a print head carriage  252  have rigid fins  253  located between the pens  254 . Therefore, if a tread knot or other irregularity is missed by the detection system and works its way into the print zone, the rigid fins will prohibit them from striking the print head and, hence, damaging the sensitive assembly. Referring again to  FIG. 1 , the illustrated design of the print subsystem  250  also helps prevent damage to the print heads  252  because no hard backing is present underlying the print subsystem  250 . Rather, as illustrated, the region directly underlying the print subsystem  250  that the pens  254  pass over, allows the fabric  114  to float freely and stretch. Therefore, if a knot passes under the print head  252  and contacts one of the pens  254 , the unbacked fabric  114  under the print head  252  may bow downwards and not injure the pen  254 . 
   Although the irregularity detection and removal subsystem  150  and specific configuration of the pens  254  in the print subsystem  250  may help prevent damage to the print heads  252 , the described subsystems do not solve print defect issues due to imperfections in the fabric  114 . As known to those of ordinary skill in the art, print defects of one kind or another occur when a pattern is printed onto the fabric defect area in the fabric  114 . Therefore, components within the fabric characterization and tension control subsystem  130 , the irregularity detection and removal subsystem  150 , the fabric drying and conditioning subsystem  170 , the fabric control subsystem  210 , and the color consistency densitometry subsystem  270  may individually, or collectively, be used to ensure that the number and types of print defects are minimized. 
   For instance and referring to  FIG. 1 , once the fabric  114  exits the irregularity detection and removal subsystem  150 , the fabric  114  has a high moisture content from the steam transferred to the fabric from the steam table  152 . The excess water in the fabric  114  needs to be removed from the fabric  114  such that the fabric  114 , or an ink receptive layer of the fabric  114  (not shown), are at an optimal moisture content before the pattern is printed on the fabric  114  in the print subsystem  250 . Accordingly, the fabric drying and conditioning subsystem  170  is used to precondition the fabric  114  prior to printing. 
   The fabric drying and conditioning subsystem  170  includes an air flow means  172 , such as a blower in combination with a heater. In the illustrated embodiment, the blower and the heater are on different controls, such that the blower and heater can be adjusted independent from each other, thus providing operators of the UFTCS  10  a large degree of freedom to accommodate various moisture and environmental conditions in the fabric  114 . In an alternative embodiment, the CPU operatively connected with the UFTCS  10  may be used to monitor and adjust the moisture and environmental conditions in the fabric  114 . 
   As previously discussed herein, placement of the fabric drying and conditioning subsystem  170  before the print subsystem  250  allows the fabric  114  to be at an optimal moisture content and temperature range for printing of the pattern on the fabric  114 . However, since the fabric  114  is de-creased before being ironed, the fabric  114  is deformed in many directions in an effort to ascertain the minimum crease condition. This deformation of the fabric  114  induces strain conditions in the fabric  114  which may need to be removed before the pattern is printed on the fabric  114 . 
   Deformations are induced into the fabric  114  in various subsystems of the UFTCS  10  For instance, the deformations are induced by a feed mechanism used to deliver the fabric  114  to the print subsystem  250 , the fabric drying and conditioning subsystem  170 , the fabric control subsystem  210 , and some of the other subsystems. To continually account for the various deformations, the fabric  114  is characterized just before the fabric  114  enters the fabric control subsystem  210 . Accordingly, the fabric  114  may be characterized before the fabric drying and conditioning subsystem  170 , after the fabric drying and conditioning subsystem  170 , or in both locations as illustrated in  FIG. 12 .  FIG. 12  shows the fabric characterization  130   a  and tension control subsystem  130   b  located before and after the fabric drying and conditioning subsystem  170 . 
   To ensure maximum print quality, the pattern should ideally be printed on the fabric  114  in a flat, relaxed, and crease-free state. However, since the fabric  114  is unwound from the fabric roll  112  and subjected to various deformation stresses throughout the machine, presenting the fabric  114  to the print zone in a zero stress condition is not practical. Therefore, a key parameter becomes the minimization of the local distortion and recovery characteristics of the fabrics under the multi-directional strain induced by the various unwinding, de-creasing, ironing, conditioning and feeding stresses. Other stresses induced into the fabric  114  stem from conditioning of the fabric  114  which may include treating the fabric  114  in such a way that various coloring agents adhere more efficiently to the fabric  114 . Accordingly, the fabric characterization and tension control subsystems  130   a  and  130   b  are utilized to solve the problems of variable fabric distortions resulting from the various tension forces introduced in the fabric  114 . These fabric characterization and tension control subsystems  130  result in decreased variable directional scaling distortions introduced into the fabric  114  throughout the print job. 
   As further known in the art, stress induced displacements in a fabric  114  greatly affect image distortion, banding, and variations in color plain from color plain alignment in digital and conventional fabric printing systems. Therefore, it is useful to control post-printing distortion of the fabric  114 , in addition to the deformations induced from pre-printing load characteristics in the fabric  114 . In both post-printing and pre-printing conditioning steps performed on the fabric  114 , a stress-free state of the fabric  114  before and after a pattern has been printed thereon should be maintained to minimize the objectionable distortions in the fabric  114 . 
   An additional consideration in post processing is maintaining the same pre-printing fabric characteristics after the pattern is printed on the fabric  114 . Therefore, running the fabric  114  through the post-printing process and ascertaining the post-printing characteristics before a pattern is printed thereon helps minimize final variations. Accordingly, measuring the X and Y directional distortions in the post-printing processing and adjusting the pre-printing conditions to accommodate for the post-processing variations helps decrease the specific distortion/scaling within the fabric  114 . 
   As previously discussed herein, since fabric behavior is variable throughout the roll of fabric  114 , it is desirable to ascertain the stress/strain behavior in the fabric  114  and set the tensions in the fabric  114  to an optimal and uniform state to better control distortions in the fabric before printing begins. Accordingly, the fabric characterization and tension control subsystem  130  described herein is one possible way to achieve close-loop control needed. Once characterization information is obtained by the fabric characterization and tension control subsystem  130 , the information is used to control the pre-printing forces in the fabric and stretch the fabric before it is introduced into the fabric control subsystem  210 , thus effectively closing the feedback loop in the UFTCS  10 . 
   In an alternative embodiment, the fabric characterization and tension control subsystem  130  is used as a standalone subsystem in conventional large-scale fabric printing systems. However, the fabric characterization and tension control subsystem  130  works effectively when it is operatively linked to a printing system, such that the fabric characterization and tension control subsystem  130  may be used to dynamically monitor the fabric characteristics throughout the entire printing process. 
   Referring again to  FIG. 1 , the fabric characterization and tension control subsystem  130   b  located before the fabric control subsystem  210  is substantially similar to the fabric characterization and tension control subsystem  130   a  located before the irregularity detection and removal subsystem  150 . However, the function of the fabric characterization and tension control subsystem  130   b  located before the fabric control subsystem  210  is to control the multi-directional web tension of the fabric  114  before the fabric  114  is laid down on a fabric transfer belt  212   a  of the fabric control subsystem  210  by comparing fast fourier transfer algorithm values, as previously described herein with reference to  FIG. 10 . The first fabric characterization and tension control subsystem  130   a  is operably connected to the second fabric characterization and tension control subsystem  130   b , such that data gathered by the first fabric characterization and tension control subsystem  130   a  about fabric characteristics may be utilized by the second fabric characterization and tension control subsystem  130   b.    
   Referring now to  FIG. 13 , typical frequency content as a function of displacements is shown in X direction as  214 , and in Y direction as  216  in the fabric  114 . As shown in  FIG. 14 , a position of a two dimensional CCD array  134  in relation to the web of the fabric  114  is illustrated. As displayed, the CCD array  134  is across the web of the fabric  114 . 
   The amount of web tension in the fabric  114  could be preset as a constant value that is maintained and controlled by the UFTCS  10  or the web tension may be monitored and controlled in real time. If the web tension is maintained and controlled in real time, a control system of the UFTCS  10  may continually adjust the optimal tension for a given fabric type and variation using a flowchart algorithm illustrated in  FIG. 15 . 
   Once the web tension in the fabric  114  is characterized, the fabric  114  enters the fabric control subsystem  210  in as flat and controlled manner as possible. As illustrated in the embodiment of  FIG. 1 , the fabric control subsystem  210  comprises a pair of substantially identical fabric transfer belts  212   a  and  212   b  supported by two fabric transfer belt idler rollers  219 , a fabric advance sensor  220 , the print subsystem  250 , and a dryer  222 . The fabric control subsystem  210  functions to hold and advance the fabric  114  received from the tension control subsystem  130   b  and present the fabric  114  to the print subsystem  250  in a flat and controlled manner. After a pattern is printed on the fabric  114 , the fabric control subsystem  210  transports the fabric  114  to the drying and post processing subsystem  310 . 
   The fabric transfer belts  212   a  and  212   b  are individually driven by fabric transfer belt rollers  218   a  and  218   b  and are configured to move synchronously with respect to each other. Referring to  FIG. 16 , there is shown an expanded view of one of the fabric transfer belts  212   a  located between the print subsystem  250  and the bowed roller  138  driven by the bowed roller drive motor  139 , and the skewed roller  132 . The fabric transfer belts  212  are metallic or fiber reinforced polymer belts that span the driven roller  218  and an idler roller  219 . A curved plate  224  is placed under each fabric transfer belt  212 , wherein the curved plate  224  is configured to induce a large radius in the surface of the fabric transfer belt  212 , which helps to hold the fabric down on the belt. The radius of the curved plate  224  provides a perpendicular component from the tension force, as illustrated by arrows  226  to the fabric  114 , wherein the tension force  226  induces a normal force due to the curved plate  224  onto the fabric  114  on the fabric transfer belt  212  and prohibits the fabric  114  from moving in relation to the fabric transfer belt  212 . 
   A surface  213  of the fabric transfer belts  212  may be roughened by plasma treatment of the surface of the fabric transfer belts  212 , if the belts are metallic, or by gluing a layer of abrasive particles to a surface of the fabric transfer belts  212 , if the belts are polymeric. The roughened surface  213  provides randomly positioned high points that dig into the weave of the fabric  114 , and functions in concert with the normal force  226  to prevent the fabric  114  from moving with respect to the fabric transfer belt  212 , thus negating the need for adhesives. Various types, grades and levels of roughness on the surface of the fabric transfer belts  212  may be provided to accommodate the different weaves or types of fabric  114  of the UFTCS  10 . Accordingly, the fabric control subsystem  210  is configured to allow for easy removal and replacement of the fabric transfer belts  212 . 
   The fabric transfer belts  212  also have encoders (not illustrated) on an underside or edge thereof that allow control feedback signals to be accurately monitored by a fabric advance subsystem of the UFTCS  10 . The encoders may comprise carriage axis encoder strips known to those of ordinary skill in the art and conform to the actual shape of the fabric transfer belts  212 . The driven rollers  218  are powered with matched encoded servo drives such that each driven roller  218   a  and  218   b  moves synchronously in relation to each other. The separate drive systems that power the fabric transfer belts  212  may be controlled and synchronized using a closed-loop control scheme. The closed-loop control scheme may include high precision encoders on the matched servo drives powering each driven roller  218  that function in concert with the encoders of the fabric transfer belts  212 , thus functioning to control the displacement of the fabric transfer belts  212   a  and  212   b  and minimizing changes in characteristics in the fabric  114  during printing. Further, it will be apparent that a width of the fabric transfer belts  212  is wider than the widest width of the fabric  114  that will be used in the UFTCS  10 , such that the entire width of the fabric  114  is supported by the fabric transfer belts  212 . To provide for better accommodation and tension control of various fabrics, the fabric control subsystem  210  is configured such that the fabric transfer belts  212  may travel in a direction indicated by arrow  215 . 
   As further illustrated in  FIG. 1 , the fabric advance sensor  220  includes a navigation sensor system (such as that described in U.S. Pat. No. 6,195,475, “Navigation System for Handheld Scanner,” Beausoleil and Allen, assigned to Hewlett-Packard Company). The fabric advance sensor  220  uses low angle lighting to create high contrast shadow patterns on a surface of the fabric  114 , such that a CCD array of the fabric advance sensor  220  captures images of the surface of the fabric  114 . Using electronics and software of the navigation sensor system, the axis motion of the fabric  114  may be controlled in order to minimize banding and other motion variables of the fabric  114  in order to minimize distortion and irregular printing patterns of the fabric  114  during the printing process. The fabric advance sensor  220  is operably connected to both fabric characterization and tension control subsystems  130   a  and  130   b , such that the fabric characteristics may be accounted for in the printing process. 
   Referring to  FIG. 17 , the print subsystem  250  is located between fabric control belt  212   a  and fabric control belt  212   b . As illustrated, as the fabric  114  passes from fabric control belt  212   a  to fabric control belt  212   b  under the print subsystem  250 , the fabric  114  is unsupported for a distance  232 . As known in the art, ink-jet droplets may pass through, or blow through, the fabric  114  as the ink droplets are transferred through the air during the printing process and would contaminate a continuous belt supporting the fabric  114 . Contamination of the belt requires use of a solvent or water to clean the belt. By designing the system to print on the unsupported fabric  114  in the illustrated print subsystem  250 , the ink may blow through the unsupported distance  232  and will not contaminate the fabric control belts  212   a  and  212   b . In this manner, the UFTCS  10  does not require water hook ups or other solvent cleaning systems, which are dirty and environmentally unfriendly. As illustrated, the ink that inevitably blows through the fabric  114 , may then be collected by a collection device  234 . Such as a trough, pad, or a vacuum system located under the printing subsystem  250 . 
   In addition to preventing ink contamination on the fabric control belts  212 , the two fabric control belts  212   a  and  212   b  are configured to provide back resistance to tensioning rollers of the UFTCS  10 . The fabric control belts  212  are configured to move in a direction indicated by arrow  215  such that tension applied to the fabric by the UFTCS  10  may be accurately controlled. The design of the illustrated fabric control subsystem  210  also dictates that the unsupported distance  232  between fabric control belts  212   a  and  212   b  is minimized, such that the distance  232  of the unsupported fabric  114  floating freely is minimized. Accordingly, the distance  232  between fabric control belts  212  should be slightly larger than a swath height of an ink jet head used in order to avoid ink droplets contaminating the same. 
   Referring now to  FIG. 18 , there is shown a cross sectional view of a mechanism generally at  236  designed to allow the fabric transfer belts  212  travel in the direction indicated by arrows  216   a  and  216   b . An adjustable print head  252  to fabric  114  gap  238 , thus allowing for an optimal print quality of patterns to be printed on a wide variety of fabric weights and thicknesses. The mechanism  236  communicates with the irregularity detection and removal subsystem  150  such that the fabric  114  may be lowered away from the print subsystem  150  to prevent a knot from contacting and potentially damaging the print heads  252 . A T-bracket  240  on each end of idler shafts  242 , which support the idler rollers  219 , include slide guides by which the idler rollers  219  may be raised and lowered to control the distance between the fabric  114  and the print heads  252  of the print subsystem  250 . The T-brackets  240  may be moved up and down, thereby moving the fabric surface up and down. The T-brackets  240  may be moved with a screw drive  241  that is powered by a servo drive  243 . The pivot points of the idler rollers  219  will be upwardly spring loaded onto the guide grooves of the T-brackets  240  in order to provide controlled vertical movement of the idler rollers  219  and the spring-loaded tension will force the idler shaft  242  to pivot, such that the surface of the fabric  114  runs in a controlled manner. The above spring force also provides a backlash control force to the rack and pinion arrangement on the bracket. 
   Since the actual printed colors on the fabric  114  do not develop their final color appearance until the fabric  114  is post-processed, the real color value of the printed fabric  114  cannot be ascertained until the post-processing of the fabric  114  is complete. An actual ink flux and lay down pattern of the ink printed on the fabric  114  varies throughout the print job due to thermal head assembly (THA) variations, thermal drift, the varying fabric white point and the lack of weave uniformity in the fabric  114 . Accordingly, these variations affect the final color of the fabric, and hence the outcome of the print job after post-processing. These variations may be sensed and adjusted in real time throughout the print job to accommodate these dynamic variations and minimize varying color appearances on the printed fabric. 
   In the illustrated embodiment, these variations are sensed in the color consistency densitometry subsystem  330  of  FIG. 1 . As known in the art, these variations are amplified in digital printing processes by a natural color of the fabric, because unlike traditional printing systems, the fabric  114  printing process using ink jet printers do not saturate the fabric with the coloring agents. Rather, a minimal amount of ink is placed upon the fabric in digital printing systems that are only 10 to 20 percent of the amount of coloring agents applied to the fabric in conventional printing systems. Since a white point of the fabric  114  varies throughout the fabric roll  112 , a carriage sensor  270  may be used as a white point calibration system for the color consistency densitometry subsystem  330 . The carriage sensor is used to sense the white point of the fabric and may be operatively configured to direct the components of the print subsystem  250  to adjust the amount of ink laid down on the fabric  114  and ensure color consistency. 
   Color consistency needs are further ensured in real time by printing specific fill patterns on a fabric salvage area and scanning an optical densitometer over these fill patterns in real time. As known in the art, the fabric salvage area is usually a ¼- to ½-inch strip along both edges of the fabric  114 . A choice of fill patterns may be made automatically and dynamically, or manually, for each individual print job in accordance with the print patterns and respective patterns printed on the fabric  114 . By observing a drift of the reflectance values of the fill patterns, the thermal ink jet drive data may be corrected for some of the thermal head drift effects. 
   It will be apparent to those of ordinary skill that actual image coverage patterns are printed on the fabric  114  and, when combined, form the desired colors in any given print job. The actual image coverage patterns are loaded into their respective registers at the appropriate time, i.e., after tension and color calibrations are determined when fabric dependent calibrations are initially performed, before printing. Signals required to produce the actual image coverage patterns are sent to a carriage board, and printed on the salvage area of the fabric for monitoring. The carriage sensor  270  of the color consistency densitometry subsystem  330  is used to read an average value of the optical density of the printed patterns on the fabric salvage area during the print job. The average values are compared to pre-print job calibration values and the timing and operating parameters of the thermal head assembly may be varied to compensate for the variations. To enhance the ability of the carriage sensor to sense the color variations, several additional multicolor LED light sources may be added such that the carriage sensor is able to recognize additional wavelengths of the textile inks. 
   Referring now to  FIG. 19 , there is illustrated one possible embodiment of an edge print pattern that may be printed in the fabric salvage area  256  of the fabric  114 . The edge print pattern may be printed at all times throughout the print job or performed as needed by the UFTCS  10 . As illustrated, each edge of the fabric  114  includes the fabric salvage area  256 . Boxes  258  are test areas printed in the fabric salvage area  256  for each printed color. For instance, box  258   b  can be printed with black ink, box  258   m  can be printed with magenta ink, box  258   y  can be printed with yellow ink, and box  258   c  can be printed with cyan ink. After the pattern is printed on the fabric  114  in the print zone  262 , the boxes  258  are scanned by the carriage sensor, or densitometer, in a scan zone  260 . Circular area  264  is expanded in area  266  which includes a plurality of boxes, wherein each box  269  represents a swath of ink printed by each print head  252 . Circular area  266  is further expanded in area  268  and includes each box  269 , or swath of printed ink. 
   The edge print pattern, illustrated in  FIG. 19 , is performed substantially continuously throughout a printing process, such that densitometry of the predetermined ink lay-down patterns represented by boxes  269  is determined. As known in the art, the drop volume, directionality, and velocities of the ink released from each print head  252 , as well as the average and local adsorption of the test swaths of ink, will drift and vary. Therefore, continuous monitoring of the test swaths serves as a control parameter that may be fed into the energy management and the drop generation systems of the UFTCS  10 . Proper adjustment of the energy, timing and the ink lay-down patterns of the print heads  252  minimize the drop volume and directionality drifts of the ink released from the print heads  252 , and therefore minimize variation of a final color outcome printed on the fabric  114  in the print job. 
   After a pattern is printed on the fabric  114 , post-processing of the fabric  114  is required. Since fabrics do not dry as rapidly as paper after printing, drying equipment is often a standard feature of fabric ink-jet printing systems. Also, since ink-jet printing on fabric requires two to six times the amount of ink that is traditionally printed on paper, drying of the printed fabric is important. To aid the drying process, a dryer  222 , such as a heater blower, is a rapid drying device that can be incorporated in the drying and post processing subsystem  310  of  FIG. 1 . As illustrated, the dryer  222  is located directly after the print subsystem  250  and produces enough heat energy output capacity to also cure two-part pigmented ink systems. 
   After drying, the fabric  114  is subjected to further post-processing steps in order to fix and develop a final color of the dye or pigment on the fabric  114 . As known in the art, post-processing may be accomplished either mechanically or chemically. Depending on the type of ink printed on the fabric, various fixing, or post-processing, steps used on the fabric  114  may include the following: dry heat for use with pigment/binder inks and dispersed dyes; saturated steam for use with acid dyes, dispersed dyes, and reactive dyes; or saturated steam combined with a chemical for use with some reactive dyes. In the illustrated UFTCS  10  of  FIG. 1 , there is shown a dry heat device  312  and a steamer  314  within the drying and post processing subsystem  310 . It will be apparent that the illustrated UFTCS  10  may include a different type of post-processing device, or no post-processing device, depending on the type of ink used. For instance, if the fabric  114  is stored and post-processed off-line with another piece of equipment, a post-processing device may not be part of the UFTCS system  10 . Of course, since inks may not be in a stable state, the rolls of printed fabric may need to be dried and carefully handled in order to ensure that the printed patterns are not degraded or distorted by factors such as touch, pressure, tension, etc. 
   Incorporation of the post-processing subsystem  310  within the print system allows a color fidelity check to be performed on-line with the printing process. Thus, it is efficient to incorporate the post-processing subsystem  310  within the print system as illustrated in  FIG. 1 . For instance, since certain color chemistries dramatically shift after post processing, i.e. blue to brown in a reactive system, incorporation of the drying and post-processing subsystem  310  into the print system allows a closed-loop color control subsystem to be incorporated within the printing system. Without post-processing, initial calibration and instrument readings of a pseudo closed-loop system would need to be the indicator of the true color, and any color variation or shift could not be corrected in the same roll of fabric that is being printed. 
   In implementing the drying and post-processing subsystem  310 , factors to be considered in the design of the dry heat device  312  and steamer  314  include: time required for the post-processing stage of the type of ink chemistry employed, control of steam temperature, amount of steam required, consistency of steam flux, need for a hard water line, and segregation of the unfixed printed fabric face from the steam before the unfixed printed fabric is post-processed. These factors affect the quality, durability and the handling characteristics of the finished printed fabrics. The construction and configuration of the drying and post-processing subsystem  310  is similar to the configuration of the fabric drying and conditioning subsystem  170 ,  150  (illustrated in  FIG. 1 ) and the components thereof, as described with reference to  FIG. 8  and  FIG. 9 . 
   Once the fabric  114  is post-processed, the fabric  114  passes through the closed-loop color control subsystem  330 , as illustrated in  FIG. 1 . It will be apparent to those of ordinary skill in the art that if the closed-loop color control subsystem  330  is part of the UFTCS  10 , that the UFTCS  10  will also include the drying and post-processing subsystem  310  because the quality of the color printed on the fabric  114  cannot be ascertained unless the ink is post-processed. As known in the art, fabrics have a larger variation with printed colors than paper because variations in fabric weaves and interactions between the ink and the fabric. Accordingly, values of actual achieved colors are loaded into the UFTCS  10  on a job-to-job basis depending on the type of fabrics and inks used. These values may be loaded once the color map of the final proof is calibrated and linearization is performed, such that the desired adjustments are included. Also, since there is a time delay between the moment the ink is laid down and the time that the final colors are measured, adjustments made to the UFTCS  10  to accommodate for color variation is limited by the time delay. 
   The closed-loop color control subsystem  330  may use a variety of different sensors to measure the color variation of the printed fabric. For instance, a sensor  332  of the closed-loop color control subsystem  330  may be similar to the carriage sensor of the color-consistency densitometry subsystem  270 . However, to achieve a higher resolution due to a small field of view of the carriage sensors, the carriage sensors can be widened. For instance, as illustrated in  FIG. 20A , there is shown a field of view  333  within a weave of a fabric  114 , while a wider field of view  334  that may be achieved by widening the field of view of the carriage sensor, which is illustrated in  FIG. 20B , as encompassing a larger weave area in the fabric  114 . Furthermore, various light sources of differing color wavelengths can be used to further enhance the color information being gathered. Widening the carriage sensors provides a more integrated average signal and avoids localized ink-to-fabric interactions that may produce an abnormal color measurement. For ease of color measurement, the colors printed on the fabric salvage area in the color consistency densitometry subsystem  270  may be used for color measurement in the closed-loop color control subsystem  330 . If the colors of the fabric salvage area are measured, a well balanced and natural light source should be used for color measurement in both the color consistency densitometry subsystem  270  and the closed-loop color control subsystem  330 . It will be appreciated that an algorithm may be used to process the measured color of the fabric  114 . 
   Once the fabric  114  has been post-processed, the fabric  114  passes through a relaxation subsystem  350 , as illustrated in  FIG. 1 . The relaxation subsystem  350  includes an optical dancer bar  116 , similar to the optical dancer bar  116  of the unwind subsystem  110 , and a relaxation subsystem  350 , which performs functions essentially the same as those described herein with reference to the relaxation zone  113  related to the unwind subsystem  110 . 
   As further illustrated in  FIG. 1 , the UFTCS  10  also includes the rewind zone  370 . It will be apparent to those of ordinary skill in the art that the rewind zone  370  is substantially identical to the unwind subsystem  110  of  FIG. 1 , except that the rewind zone  370  winds the fabric  114  onto a finished printer roll  372  instead of unwinding the fabric from the roll  112  of unprinted fabric. 
   Although various components of the subsystems have been described herein as being in-line with the UFTCS  10 , it will be apparent that various components, subsystems, and zones of the UFTCS  10  may be implemented off-line or separate from the UFTCS  10  and still be encompassed by the present invention. Thus, the various components, subsystems, and zones of the described UFTSC  10  may be used with other digital printing systems or utilized in conjunction with other conventional printing systems. 
   Although the present invention has been shown and described with respect to various illustrated embodiments, various additions, deletions and modifications that are obvious to a person of ordinary skill in the art to which the invention pertains, even if not shown or specifically described herein, they are deemed to lie within the scope of the invention as encompassed by the following claims.