Abstract:
A metering roller, for a fuser release oil applicator, which enables precise and consistent application of a predetermined target amount of release oil to the fuser roller. Starting with tubing stock that has been machined and course ground to a final outside diameter, the metering roller is produced by initial pre-finish polishing, electroplating with Nickel, heat treatment to achieve a hardened surface, and final post-finish polishing. Both pre-finish and post-finish polishing steps are performed on a lathe with continuously fed polishing paper according to a parameter recipe that includes lathe spindle rpm and lead screw speed, and polishing paper grit, feed rate, pressure, and oscillatory rate.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates generally to electrostatographic reproduction apparatus, and more particularly, to metering rollers in fuser release oil applicators.  
       BACKGROUND OF THE INVENTION  
       [0002]     In typical electrostatographic reproduction apparatus, a latent image charge pattern is formed on a uniformly charged charge-retentive member or photoconductor having dielectric characteristics. Charged thermoplastic, pigmented marking particles are attracted to the latent image charge pattern to render the latent image visible. A receiver member, such as a sheet of paper, transparency, or other medium, is then brought into contact with the photoconductive member, and an electric field applied to transfer the marking particle developed image to the receiver member from the photoconductive member. The electric field to transfer the marking particle developed image to the receiver member from the photoconductive member is typically applied by spraying the backside of the receiver member with electrically charged ions from a corona charging device, or, alternatively, by contacting the backside of the receiver member with an electrically biased roller. The receiver member could, alternatively, be carried on a transport member such as a flexible belt, in which case the electrically biased transfer roller contacts the backside of the transport member that is interposed between the electrically biased transfer roller and the receiver member. Another alternative is to first transfer the marking particle developed image directly to an electrically biased intermediate transfer member in the form of a roller or belt and then from the intermediate transfer member to the receiver member.  
         [0003]     After transfer to the receiver member, by any of the above alternatives, the receiver member bearing the transferred marking particle image is transported to a fusing station where the marking particle image is fused to the receiver member, typically by heat and pressure, to form a permanent reproduction on the receiver member. To print an image on both sides of the receiver member, hereafter referred to as duplex printing, a fused marking particle image is formed on side one of the receiver member by the above process, whereafter the receiver member is returned to the process via a duplex return path wherein the receiver member is turned over so as to have a second marking particle developed image transferred and fused to side two of the receiver member.  
         [0004]     The fusing station includes a fuser member, which can be a roller, belt, or any surface having a suitable shape for fixing thermoplastic marking particles to the receiver member. The fusing step using a roller fuser member commonly includes passing the receiver member, with the marking particle image thereon, between a pair of engaged rollers that produce an area of pressure contact known as a fusing nip. In order to form the fusing nip, at least one of the rollers typically includes a compliant or conformable layer. Heat is transferred from at least one of the rollers to the marking particles in the fusing nip, causing the marking particles to partially melt and attach to the receiver member. In the case where the fuser member is a deformable heated roller, a resilient elastomeric layer is typically bonded to the core of the roller, with the roller having a smooth outer surface. Where the fuser member is in the form of a belt, e.g., a flexible endless belt that passes around the heated roller, it typically has a smooth outer surface, which may also be hardened.  
         [0005]     Simplex fusing stations fuse marking particles to only one side of the receiver member at a time. In this type of station, the engaged roller that contacts the unfused marking particles is commonly known as the fuser roller and is a heated roller. The roller that contacts the other side of the receiver member is known as the pressure roller and is usually unheated. Either or both rollers can have a compliant layer on or near the surface. It is common for one of these rollers to be rotated by an external source while the other roller is rotated frictionally by the nip engagement.  
         [0006]     The most common type of fuser roller is internally heated, i.e., a source of heat is provided within the roller for fusing. Such a fuser roller generally has a hollow core, inside of which is located a source of heat, usually a lamp. Surrounding the core can be an elastomeric layer through which heat is conducted from the core to the surface, and the elastomeric layer typically contains fillers for enhanced thermal conductivity. In order to prevent the receiver member bearing the fused marking particle image from sticking to the fuser roller, release oil is typically applied to the fuser roller. The release oil is typically applied to the surface of the fuser roller by an oiling mechanism including a wick in contact with release oil in a reservoir, a metering roller which receives release oil from the wick, a blade which controls the amount of release oil on the metering roller, and a donor roller which transfers the release oil from the metering roller to the fuser roller.  
         [0007]     In electrostatographic reproduction apparatus for printing high quality color images, besides fusing the pigmented marking particle image to render it permanent on the receiver member, an additional function of the fusing step is to impart a desired level of gloss to the fused image. The level of gloss imparted to the image by the fuser station is typically dependent upon such parameters as the surface finish on the fuser roller, the amount of release oil on the fuser roller, and the pressure between the fuser roller and the pressure roller. In high quality color electrostatographic reproduction apparatus it is critical that the predetermined target amount of release oil is applied to the fuser roller with consistent high precision and uniformity. If the amount of release oil applied to the fuser roller deviates too much from the predetermined target amount or if it becomes too non-uniform, image quality defects will occur in the output prints.  
         [0008]     A primary problem associated with too much release oil on the fuser roller occurs during duplex printing runs. As described above, in duplex printing, a fused marking particle image is formed on side one of the receiver member, whereafter the receiver member is returned to the process via a duplex return path wherein the receiver member is turned over so as to have a second marking particle developed image transferred and fused to side two of the receiver member. When the marking particle image on side one of the receiver member is fused in the first pass through the fuser nip, the release oil film on the fuser roller splits, and some of the release oil transfers to side one of the receiver member. During subsequent transfer of a marking particle developed image to side two of the receiver member, if the electric field for transfer is applied by an electrically biased roller as described above, some of the fuser release oil from side one of the receiver member, which is now in contact with the biased roller, transfers to the surface of the biased roller. During a long duplex printing run a relatively large amount of fuser release oil can thereby accumulate on the biased roller. During times such as cycle-down, non-imaging skip frames, or recovery from receiver jams, the biased roller is in direct contact with the photoconductive member. During these times some of the fuser release oil accumulated on the biased roller during duplex printing transfers to the photoconductive member. Release oil on the photoconductive member causes several types of image quality defects including background and streaks due to non-uniform transfer from the photoconductive member to the receiver member. These release oil related problems during duplex printing occur much sooner if oil in excess of the predetermined target amount is being applied to the fuser roller.  
         [0009]     As mentioned above, the amount of release oil on the fuser roller affects the gloss level imparted to the high quality color image during the fusing step. Therefore, if the amount of release oil being applied to the fuser roller deviates from the predetermined target amount, the gloss level of the image will also vary from the target level. This problem will occur during simplex and duplex printing.  
       SUMMARY OF THE INVENTION  
       [0010]     In view of the above, this invention is directed to an improved metering roller for a fuser release oil applicator. The release oil metering roller of this invention enables precise and consistent application of a predetermined target amount of release oil to the fuser roller of an electrostatographic reproduction apparatus fuser, thus avoiding image quality defects that result when the amount of release oil being applied to the fuser roller deviates from the predetermined target amount. Applicant has discovered a novel method of providing a surface finish on the release oil metering roller of this invention, the parameters of which can be varied to achieve a predetermined target release oil metering rate from within a range of rates, and which, additionally, precisely maintains the target metering rate under varying operating conditions.  
         [0011]     Starting with tubing stock that has been machined and course ground to a final outside diameter, the method of this invention includes the steps of pre-finish polishing of the machined and course ground tubing stock, electroplating of the tubing stock with Nickel, heat treatment of the plated tubing stock to achieve a hardened surface, and a final post-finish polishing of the hardened Nickel surface. Both pre-finish and post-finish polishing steps are performed on a lathe with continuously fed polishing paper according to a parameter recipe that includes the lathe spindle rpm and lead screw speed, and the polishing paper grit, feed rate, pressure, and oscillatory rate.  
         [0012]     The invention, and its objects and advantages, will become more apparent in the detailed description of the preferred embodiment presented below. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  shows a side elevational view of an exemplary prior art fusing station including an oiling roller mechanism with a metering roller; and  
         [0014]      FIG. 2  shows a schematic diagram of a polishing apparatus for practicing the method of preparing the metering roller surface, according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0015]     Fusing stations and fuser rollers for use therein, including metering roll surfaces prepared according to this invention are readily includable in typical electrostatographic reproduction machines of many types, such as for example electrophotographic color printers. Since such color printers are well known in the prior art, they will not be described at length herein, but only to the extent necessary for a full understanding of the instant invention.  
         [0016]     The invention relates to an electrostatographic reproduction or printing machine for forming a toner image on a receiver member and utilizing a fusing station employing a deformable fuser member for thermally fusing or fixing the toner image to a receiver member, e.g., of paper. The deformable fuser member can be a roller, belt, or any surface having a suitable deformable shape for fixing thermoplastic toner powder to the receiver member. The fusing station preferably includes two rollers which are engaged to form a fusing nip in which an elastically deformable fuser roller comes into direct contact with an unfused toner image as the receiver member is being frictionally moved through the nip. The fuser roller may be heated by an external source of heat, such as by direct contact with one or more heating rollers. Alternatively, the fuser roller may be heated via absorbed radiation, e.g., as provided by one or more lamps, or by any other suitable external source of heat. The toner image in an unfused state may include a single-color toner or it may include a composite image of at least two single-color toner images, e.g., a full color composite image made for example from superimposed black, cyan, magenta, and yellow single-color toner images. The unfused toner image is previously transferred, e.g., electrostatically, to the receiver member from one or more toner image bearing members such as primary image-forming members or intermediate transfer members. It is well established that for high quality electrostatographic color imaging with dry toners, small toner particles are necessary.  
         [0017]     The fusing station and fuser roller of the invention are suitable for the fusing of dry toner particles having a mean volume weighted diameter in a range of approximately between 2 mm-9 mm, and more typically, about 7 mm-9 mm, but the invention is not restricted to these size ranges. The fusing temperature to fuse such particles included in a toner image on a receiver member is typically in a range 100° C. -200° C., and more usually, 140°-180° C., but the invention is not restricted to these temperature ranges.  
         [0018]     The electrostatographic reproduction or printing apparatus may utilize a photoconductive electrophotographic primary image-forming member or a non-photoconductive electrographic primary image-forming member. Particulate dry or liquid toners may be used.  
         [0019]     Turning now to the figures,  FIG. 1  illustrates an exemplary simplex fusing station well known in the prior art, indicated generally by the numeral  100 . The fusing station includes an externally heated, elastically deformable fuser roller  10 , engaged under pressure with a relatively harder, i.e., relatively nondeformable, pressure roller  20  so as to form a fusing nip  25 . The fuser roller, described in detail below, is a multilayer roller incorporating a heat storage layer. Fuser roller  10  is externally heated by direct contact with one or more heating rollers, e.g., rollers  30  and  35 . (Pressure roller  20 , though not heated by any dedicated internal or external source of heat, is generally indirectly heated to a certain extent via contact in the nip  25 ). A receiver member  15  carrying an unfused toner image  16  is shown moving in direction of arrow A, towards the fusing nip  25  for passage therethrough. Receiver member  15  is made of any suitable material, e.g., of paper or plastic, and the receiver member can be in cut sheet form (as depicted) or be a continuous web.  
         [0020]     Fuser roller  10  generally includes a rigid, cylindrical, core member  11 , around which is a deformable annular structure  12  including at least one elastomeric layer. The core member  11  is preferably made of a thermally conductive material such as a metal, preferably aluminum, and the core member is typically (but not necessarily) hollow as shown. Preferably an outer diameter of the core member is in a range between about 5 inches and 7 inches, and the outer diameter is more preferably about 6.0 inches. The deformable annular structure  12  includes an elastomeric base cushion layer closest to core member  11 , a flexible heat storage layer around the base cushion layer, and, a thin flexible outer gloss control layer (release layer) around the heat storage layer (individual layers of structure  12  not separately shown). Preferably, the individual layers of structure  12  are successively coated on the core member  11  by using suitable coating techniques and post-coating curing and grindings of each successive layer as may be necessary. The outer release layer (gloss control layer) is preferably made of a low surface energy material such as for example a polyfluorocarbon, and preferably has a very smooth surface suitable for glossing the fused toner image. Preferably, the total thickness of the deformable annular structure  12  is in a range of approximately 0.180 inch −0.240 inch, although a total thickness outside of this range is not excluded.  
         [0021]     It is important to have a contact width in nip  25  which is large so as to effect efficient transfer of heat from fuser roller  10  to the toner image  16 . The contact width in nip  25  is preferably in a range of approximately between 15 mm-25 mm, and more preferably, 17 mm-19 mm.  
         [0022]     Pressure roller  20  includes a rigid, cylindrical, core member  21  around which is an annular structure  22  including one or more layers, with the core member  21  usually made of a metal, preferably aluminum, and typically (but not necessarily) hollow as shown. Preferably an outer diameter of the core member  21  is in a range between about 3 inches and 4 inches, and the outer diameter is more preferably about 3.5 inches. A preferred annular structure  22  includes a resilient base cushion layer and an outer layer around the base cushion layer (individual layers of structure  22  not separately shown). The base cushion layer of annular structure  22  preferably has a thickness in a range of approximately between 0.18 inch and 0.22 inch, and the thickness is more preferably about 0.20 inch. The base cushion layer of structure  22  can for example be made of a commercially available condensation-crosslinked PDMS elastomer which contains about 32-37 volume percent aluminum oxide filler and about 2-6 volume percent iron oxide filler, sold by Emerson and Cuming (Lexington, Mass.) under the trade name EC 4952. Preferably the base cushion layer of structure  22  is coated on the core member  21  and the outer layer of structure  22  is formed as a topcoat layer on the underlying base cushion layer, with the topcoat layer preferably made of a fluorocarbon thermoplastic random copolymer (FLC) material such as for example the copolymer of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene disclosed in Chen, et al. U.S. Pat. No. 6,429,249, issued Aug. 6, 2002. The topcoat layer thickness is preferably in a range of approximately between 0.001 inch-0.004 inches, and more preferably 0.0015 inch-0.0025 inch. A suitable pressure roller  20  is preferably similar to the pressure roller disclosed in Chen, et al. U.S. Pat. No. 6,660,351, issued Dec. 9, 2003. Due to the incorporated fillers, the EC 4952 material usable for the base cushion layer of structure  22  has a relatively high nominal thermal conductivity of about 0.35 BTU/hr/ft/° F. However, the thermal conductivity of the base cushion layer of structure  22  is not critical to the operation of fusing station  100 . In certain circumstances, a considerably lower thermal conductivity of the base cushion layer of structure  22  may be preferable so as not to drain too much heat from the contact zone of nip  25 . A preferred base cushion layer of pressure roller  20  is made of an elastomeric material having any suitable thermal conductivity, which elastomeric material has a Shore A hardness greater than about 50, preferably greater than about 60. The base cushion layer may include a particulate filler.  
         [0023]     The external heating roller  30  is preferably a hard, thermally conductive, roller. It is preferred that roller  30  be made of an annular aluminum member  31  with the outer surface (in contact with fuser roller  10 ) being preferably anodized. Within the interior hollow of member  31  is a source of heat, which source of heat is preferably a tubular heating lamp  32  coaxially located along the central longitudinal axis of member  31 . Ohmic heating of filament  34  included in lamp  32  is controlled by a programmable power supply (not shown) so as to provide variable heating power, either continuously or intermittently. Any suitable outer diameter of roller  30  may be used, with a preferred outer diameter being about 1.0 inch. Heating roller  35  includes member  36  and lamp  37  which are respectively entirely similar to member  31  and lamp  32  of roller  30 , with a filament  39  of lamp  37  similarly controlled by a programmable power supply (not shown). Both rollers  30  and  35  are frictionally driven by the fuser roller  10  and are engaged under pressure to form respective heating nips  33  and  38 . The contact zone of each of nips  33  and  38  has a width, which is preferably in a range of approximately between 10 mm-12 mm, and more preferably about 11 mm. Preferably, the operating temperature of heating rollers  30  and  35  is in a range of approximately 230° C.-270° C., resulting in a surface temperature of the fuser roller  10  which is preferably in a range of approximately between 140° C.-170° C., with the required surface temperature in this range being dependent on the thickness of the receiver members passing through nip  25 . These surface temperatures are suitable for well-known polyester toners, yet may require small adjustments for different types of toners or unusual receiver member materials.  
         [0024]     The surface temperatures of the heating rollers  30  and  35  and the fuser roller  10  are preferably measured by any suitable temperature sensing devices external to the rollers (not shown), such as for example contacting sensors, in contact with each of the fuser roller and heating rollers. Alternatively, non-contacting temperature sensors, e.g., infrared sensors, can be used with any of these rollers. Preferably, each temperature-sensing device can be connected to a controller (not shown) for controlling the surface temperature of the respective roller.  
         [0025]     A heating roller cleaning station  50  includes a cleaning web  55  for cleaning the surface of the fuser roller  10 , a take-out spool  53  from which web  55  is unwindable, and a take-up spool  54  upon which web  55  is windable. The heating roller cleaning station  50  further includes pressure backup rollers  51  and  52  for tensing the cleaning web  55  against the respective heating rollers  30  and  35 . Alternatively, a single backup roller may be used (not illustrated) which presses against both the heating rollers  30  and  35 . Web  50  is typically a single-use web such that the entire cleaning web is discarded when the take-out spool  53  is exhausted. The web  50  may be made of any suitable material, such as for example a polyethyleneterephthalate (PET) woven fiber sold under the tradename Nomex from DuPont.  
         [0026]     Within the interior hollow of core member  11  is an auxiliary optionally activated source of heat, which internal source of heat is preferably a tubular heating lamp  13  coaxially located along the central longitudinal axis of core member  11 , the lamp  13  including a filament  14 . Intermittent or variable ohmic heating (as may be required) of filament  14  is controllable by a programmable power supply (not shown). The auxiliary optionally activated source of heat or lamp  13  can be used intermittently so as to augment or supplant the heating provided by the external heating rollers  30  and  35 . For example, the lamp  13  can be turned on when an electrostatographic printer is in standby mode in order to keep the fuser roller  10  suitably warn, so that when the printer is restarted the heating rollers  30  and  35  can rapidly restore steady state thermal conditions for fusing. Conversely, when steady state has been achieved after a start-up, any auxiliary heating may be reduced or shut off as may be necessary. The lamp  13  can also be suitably activated so as to avoid a fusing defect known as “droop”, which is the result of inadequate fusing caused by a thermal transient when cold receiver members first enter the fusing nip  25  after start-up of the printer after a stand-by or a shutdown.  
         [0027]     Operating in conjunction with fusing roller  10  is an oiling roller mechanism  40  including a wick  46  in contact with a liquid release agent (e.g., fuser oil)  43  contained in reservoir  44 . Wick  46  absorbs the release agent  43  and transfers the release agent to a metering roller  48 , with the amount of release agent on the surface of roller  48  controlled by blade  49 . Metering roller  48  is in contact with a release-agent-donor roller  47 , which release-agent-donor roller contacts fuser roller  10  and thereby delivers to the surface of the fuser roller a continuous flow of release agent  43 . A preferred donor roller is similar to that of Chen, et al. U.S. Pat. No. 6,721,529, issued Apr. 13, 2004. Approximately 1-20 milligrams of release agent  43  is needed for each receiver member (e.g., receiver member sheet  15 ) passing through nip  25 . As is well known, a suitable release agent is typically a silicone oil. A preferred polymeric release agent  43  for use in fusing station  100  is an amine-functionalized polydimethylsiloxane having a preferred viscosity of about  300  centipoise as disclosed in Chen, et al. U.S. Pat. No. 6,190,771, issued Feb. 20, 2001. A suitable release-agent-donor roller  47  for use in fusing station  10  includes for example a hollow aluminum core of outer diameter about 0.875 inch, the core coated by a cushion layer about 0.230 inch thick made of a compliant material having a low thermal conductivity such as for example obtainable commercially as S5100 from Emerson and Cuming (Lexington, Mass.), with a release layer about 0.0025 inch thick coated on the cushion layer (individual layers not illustrated in  FIG. 1 ). The release layer can be made from an interpenetrating network composed of a crosslinked fluoroelastomer and two different silicone elastomers such as disclosed in Davis, et al. U.S. Pat. No. 6,225,409, issued May 1, 2001. More preferably, the release layer is made of a copolymer of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene as disclosed in Chen, et al. U.S. Pat. No. 6,429,249, issued Aug. 6, 2002. Any suitable dimensions of the core, cushion layer, and release layer may be used.  
         [0028]     A release aid mechanism such as for example air knives  61  and  62  can be provided to aid release of a fused receiver member after passage of the receiver member through the fusing nip  25 , with pressured air from air knife  61  generally directed towards the surface of fuser roller  10  and pressured air from air knife  62  generally directed towards the surface of pressure roller  20 . Alternatively, any suitable release aid mechanism for preventing the fused receiver member from wrapping on one or other of rollers  10  and  20  may be used, including skives, blades, and so forth.  
         [0029]     As mentioned above, typically approximately 1-20 milligrams of release agent  43  is needed to be delivered to the fuser roller  10  for each receiver member  15  passing through nip  25 . The precise amount of release agent  43  required depends upon several factors including the material and thickness of receiver member  15 , the velocity at which receiver member moves through nip  25 , the temperature of the fuser roller  10 , the specific rheological properties of the toner in unfused toner image  16 , and the desired gloss level of toner image  16  after fusing. Typically the target amount of release agent  43  applied to fuser roller  10  must be held to a tolerance of ±1.25 milligram per receiver member  15  in order to maintain reliable performance of fusing station  100  and consistent image quality of the fused toner image on receiver member  15 . One of the factors that critically affects the amount of release agent  43  applied to fuser roller  10  by oiling roller mechanism  40  is the surface finish on metering roller  48 . Applicant has discovered a method of providing a surface finish to metering roller  48 , the parameters of which can be varied to achieve, from within a range, a predetermined target amount of release agent  43  per receiver member  15 , and which, additionally, precisely maintains the target amount under varying operating conditions.  
         [0030]     Starting with the raw cylindrical stock, which is to become a metering roller by the method of this invention, the first step is to grind the raw stock, for example in a lathe, to a predetermined outside diameter. In the preferred embodiment of this invention described herein the starting raw stock is stainless steel, but it should be understood that any other metal could be used as the starting raw stock. The remaining steps in the method of the present invention include a pre-finish polishing step performed on the stock that was ground to the final diameter in step one, plating the pre-finish polished stock with a harder material such as, for example, chrome or nickel, and a final post-finish polishing of the plated stock to create the finished metering roller.  
         [0031]     Attention is now drawn to  FIG. 2 , which shows a schematic of an example of an apparatus in which both the pre-finish and post-finish polishing steps of the method of this invention may be performed. In  FIG. 2 , numeral  200  designates the work piece in one of either the pre-finish or post-finish polishing steps. The work piece is rotated, for example in a lathe, in the direction indicated by arrow A, at a speed in the range 500-1000 rpm. Polishing apparatus, designated collectively by numeral  205 , engages rotating work piece  200 . The abrasive in the polishing steps comprises Aluminum Oxide bonded to outer surface  215  of flexible belt  210 . Flexible belt  210  is fed from supply roll  220  to take-up roll  225 , in the direction indicated by arrows B and C, in a path defined by rollers  230 ,  235 ,  240 , and  245 . The feed rate of flexible belt  210  from supply roll  220  to take-up roll  225  is in the range 2-4 inches per minute. The grit grade of the Aluminum Oxide abrasive on surface  215  is in the range 9-30 microns. Exemplary of a commercially available abrasive that may be used in the method of this invention is 3M™ Microfinishing Film-373L. The Aluminum Oxide abrasive on surface  215  of flexible belt  210  is engaged with rotating work piece  200  by roller  235 , with a pressure in the range 10-15 psi. The complete polishing apparatus  205  comprising Aluminum Oxide abrasive on surface  215  of flexible belt  210 , feed roll  220 , rollers  230 ,  235 ,  240 ,  245 , and take-up roll  225 , axially traverses rotating work piece  200 , at a steady speed in the range 25-35 inches per minute, while simultaneously oscillating axially at an oscillation rate in the range 70-90 cycles per second.  
         [0032]     Following a pre-finish polishing step in the apparatus described above, work piece  200  is electroplated with Nickel to a minimum thickness 25.4 microns. The work piece  200  is then heat treated by steadily increasing the temperature of the work piece from ambient temperature to 750° F. in one hour, maintaining the temperature at 750° F. for three hours, and steadily cooling the temperature from 750° F. to ambient temperature in one hour, thereby resulting in a surface hardness of the work piece in the range 69÷4 Rockwell C. The plated and heat treated work piece  200  is then subjected to a post-finish polishing step in the apparatus described above and depicted in  FIG. 2 .  
         [0033]     When a roller prepared by the method of the present invention, described above, is used as the metering roller  48  in oiling roller mechanism  40  in  FIG. 1 , an oiling application rate to fuser roller  10  in the range 1.5-6.0 milligrams per receiver member can be achieved by appropriate selection of the parameters of the method of this invention. Moreover, the target oiling rate selected will be held to a tolerance less than ±1.25 milligrams per receiver member. The parameters of the method of this invention that control the target oiling rate include the grit grade of the Aluminum Oxide abrasive on surface  215  of flexible belt  210 , the feed rate of flexible belt  210  from supply roll  220  to take-up roll  225 , the pressure with which roller  235  is applied to work piece  200 , the steady rate at which the polishing apparatus  205  axially traverses work piece  200 , and the rated at which the polishing apparatus  205  axially oscillates.  
       EXAMPLE  
       [0034]     An exemplary metering roller according to the method of this invention was prepared as follows:  
         [0035]     1. 316 L Stainless Steel tubing stock was ground to an outside diameter of 30.1 mm.  
         [0036]     2. The ground tubing stock was pre-finish polished by the method described above and depicted in  FIG. 2  with the following set of parameters: 
        Tubing stock rotational speed—570 rpm,     Aluminum Oxide abrasive grit—30 microns,     Flexible belt feed rate—4.0 inches/minute,     Pressure applies to tubing stock by roller  235 —13 psi,     Steady axial speed of polishing apparatus—35 inches/minute,     Axial oscillating speed of polishing—8.3 cycles/second.        
 
         [0043]     3. The pre-finished tubing stock was electroplated with Nickel to a thickness of 8 microns.  
         [0044]     4. The plated tubing stock was heat treated by steadily increasing the temperature of the stock from ambient temperature to 750° F. in one hour, maintaining the temperature at 750° F. for three hours, and steadily cooling the temperature from 750° F. to ambient temperature in one hour, thereby resulting in a surface hardness of the stock of 69 Rockwell C.  
         [0045]     5. The heat-treated tubing stock was post-finish polished by the method described above and depicted in  FIG. 2  with the following set of parameters: 
        Tubing stock rotational speed—1000 rpm,     Aluminum Oxide abrasive grit—30 microns,     Flexible belt feed rate—2.2 inches/minute,     Pressure applies to tubing stock by roller  235 —10 psi,     Steady axial speed of polishing apparatus—25 inches/minute,     Axial oscillating speed of polishing—8.3 cycles/second.        
 
         [0052]     The metering roller made as described above was tested in an apparatus similar to fusing station  100  in  FIG. 1 , as the metering roller  48  in oiling roller mechanism  40 . The fusing station  100  was substantially that used in a NexPress 2100 digital printing press. In printing runs as long as 100,000 prints, the rate of release oil application to fuser roller  10  was 5.1 milligrams per receiver sheet, and held to a tolerance of ±1.25 milligrams per receiver sheet.  
         [0053]     The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.