Patent Publication Number: US-2002007898-A1

Title: Engineered wood and methods therefor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
     [0001] The present application claim the benefit of U.S. Provisional Application Ser. No. 06/192,561 filed Mar. 28, 2000, the disclosure of which is hereby incorporated herein. 
    
    
     
       BACKGROUND OF THE INVENTION  
       [0002] The present invention is directed to printing patterns on substrates and is particularly directed to using a hydrographic process to produce wood fiber substrates having a wood-grain pattern printed thereon.  
       [0003] The interior passenger compartments of today&#39;s high-end vehicles typically have wooden trim and panels. Conventional techniques used to make wooden trim and panels are generally time-consuming and expensive. One technique involves molding a wood veneer layer over a plastic molded part or metal substrate. This technique is very time consuming and expensive because of the slow and labor intensive process of molding, bonding and finishing sheet wood veneer onto complex shaped substrates. Moreover, the rejection rate of parts having a wood veneer is unusually high, which also increases the cost of parts.  
       [0004]FIG. 1 shows a conventional wooden trim part  20  including a metal substrate  21 , mounting stud  21 B, first and second wood filler layers  22 ,  24  and face wood veneer  26 . The adhesive sheets  21 A,  22 A and  24 A are all formed atop the metal substrate. The wood veneer  26  typically has a thickness of about 0.30-0.50 millimeters. In FIG. 1 the thickness of wood veneers has been greatly exaggerated and only layers of wood are shown for purposes of clarity. The number of layers or plies and the use of aluminum layers can vary as required for a specific application. As mentioned above, the process used to mold wood veneer  22 ,  24  and  26  and the shape of an underlying substrate is extremely labor intensive and expensive. Moreover, the wood veneer  26 , and particularly outer peripheral edges  28 , may crack as the veneer layer is molded to the shape of the underlying substrate. As a result, installers must typically repair the defects using wood filler compounds, then sand smooth and touch up the veneer with paint to hide the cracks formed during the installation process and to improve the overall appearance of the wooden trim part  20 . In spite of these efforts, the rejection rate of parts using wood veneer is unusually high, adding further costs to the production of vehicles. After the wood veneer  26  is molded in place, a transparent protective top coat  30  is applied over the veneer. The protective top coat  30  gives the wooden trim part  20  a glossy appearance and protects the wood veneer  26  from nicks and cuts and is required to meet automotive durability standards. Although wood veneer  26  is expensive and difficult to use, it has one major benefit: it enables car dealers and salesmen to properly state that the part is made with “real wood.” 
       [0005]FIG. 2 shows another conventional auto part  120  including a plastic or metal substrate  122  having a top surface  124  and securing prong  126  extending from a bottom surface  125 . A wood veneer  126  is molded and affixed to the top surface  124  of plastic or metal substrate  122 . As described above, the wood veneer  126 , and particularly the outer peripheral edges  128  of wood veneer  126 , must be molded to conform to the shape of plastic or metal substrate  122 . This may result in the formation of cracks in the wood veneer  126  that must be repaired and painted at selected locations to remove imperfections from the veneer. A protective top coat  130  is applied over wood veneer  126  to provide the part  120  with a glossy appearance and to protect the wood veneer  126  from moisture and wear and to meet the automotive standards for durability.  
       [0006]FIGS. 3A and 3B show yet another conventional design for providing a wood-grain pattern on a substrate that does not require the use of wood veneer. The part  220  includes the substrate  222  made of metal or plastic having a first surface  224  and a mounting projection  226  extending from a second surface  228 . A foil layer  230  having a wood-grain pattern printed on a first surface  232  is formed in a tool (not shown) and the formed foil is affixed to closely conform to the shape of the underlying substrate  222 . In other conventional methods, the foil is held by a tool and a material forming the substrate is injection molded onto the back of the foil for interconnecting the foil and the supporting substrate. Unlike auto parts that use wood veneer, auto dealers and car salesmen cannot ethically refer to the part  220  as being made of “real wood” because no portion of the part is actually made from wood.  
       [0007] In order to avoid the problems and costs associated with wood veneer, U.S. Pat. No. 4,010,057 discloses a hydrographic printing apparatus wherein a liquid soluble film having a pattern (e.g. wood-grain) printed thereon is floated on the surface of a liquid. The pattern is transferred from the liquid soluble film to the surface of a part by pressing the part onto the film and submerging the part into the liquid.  
       [0008] One advantage of the hydrographic printing apparatus disclosed in the &#39;057 patent is that a pattern may be printed directly onto curved and irregular surfaces. However, a part manufactured using the above-described hydrographic process cannot be referred to as a “real wood” part. This fact may discourage potential customers that want their cars to have “real wood” trim and panels.  
       [0009] Thus, there is a need for methods for making real wood parts for automobiles.  
       SUMMARY OF THE INVENTION  
       [0010] In certain preferred embodiments of the present invention a method of making molded wood parts having a wood-grain pattern thereon includes providing a wood fiber mat made of wood fiber and a heat-activated resin, and molding the wood fiber mat using pressure and heat to form a wood fiber substrate having an outer surface. The molded wood fiber substrate may have any shape, dimension and contour, may have a face wood veneer on the outer surface and may be used for a wide variety of purposes including interior panels, trim, control knobs, shift knobs and steering wheels for passenger vehicles. After the wood fiber mat has been shaped into a molded wood fiber substrate, a water-impermeable sealant is preferably applied over the outer surface of the substrate. In one particular embodiment, the step of applying a water-impermeable sealant includes dipping the molded part into a tank holding the water-impermeable sealant. The water-impermeable sealant may also be applied in many other ways, including spraying and brushing the sealant onto the outer surface of the molded wood fiber substrate.  
       [0011] Providing a water-impermeable sealant over the outer surface of the wood fiber substrate is highly preferred. If water-impermeable sealant is not used to coat the outer surface of the wood fiber substrate during the hydrographic printing process, moisture may seep into the wood fibers present at the outer surface thereof. The seepage of moisture into the wooden fibers of the wood fiber substrate is highly undesirable, as moisture will have an adverse effect on the condition of the finished outer surface. In particular, the individual wood fibers at the surface will swell upon absorbing moisture. This swelling of the wood fibers will alter the smooth outer surface of the wood fiber substrate, changing the smooth outer surface into a bumpy and/or grainy surface. As is known to those skilled in the art, a smooth surface is highly preferable over a bumpy and/or grainy surface when printing a hydrographic pattern onto an article. The presence of moisture in the wood fibers of the molded part may also reduce the level of adhesion between a transparent protective top coat and the molded wood fiber substrate.  
       [0012] In other preferred embodiments, the wood fiber mat may have the water-impermeable sealant provided therein before the mat is pressed and heated to form the molded wood fiber substrate. During the molding step, the water-impermeable composition, mixed with the wood fibers and the heat-activated resin, travels to the outer surface of the part, whereupon the outer surface is coated with the water-impermeable sealant.  
       [0013] A hydrographic printing process is preferably used to print a wood-grain pattern onto the outer surface of the molded part. In one particular preferred embodiment, a liquid soluble film having a pattern printed thereon is provided adjacent a tank having a liquid, such as water. The liquid soluble film is preferably floated over a top surface of the liquid toward a transfer point. As used herein, the term “transfer point” means the location in the tank at which the design is transferable to the molded wood fiber substrate. Once the pattern on the film has reached the transfer point, the molded wood fiber substrate is abutted against the liquid soluble film floating atop the liquid. The substrate may be immersed into the liquid for more completely transferring the pattern to the outer surface of the molded wood fiber substrate. Preferred hydrographic processes are disclosed in U.S. Pat. No. 4,436,571.  
       [0014] During the floating step, the liquid soluble film is fed toward the transfer point atop the liquid. As the film floats on the liquid, the film tends to expand in size and to dissolve. The liquid in the tank preferably moves from an upstream to a downstream end of the tank so as to urge the film toward the transfer point of the tank. The rate at which the liquid soluble film moves toward the transfer point is preferably controlled so that the print on the liquid soluble film is transferable upon reaching the transfer point. In some embodiments, the film is substantially dissolved upon reaching the transfer point. The molded wood fiber substrate is abutted against the liquid soluble film at the transfer point for transferring the pattern on the film to the molded wood fiber substrate. The forward movement of the film toward the transfer point is preferably interrupted at the moment the substrate engages the film so that the pattern on the film is stable at the moment of transfer.  
       [0015] The liquid soluble film is desirably decorated with a range of natural and abstract patterns to decorate complex shaped parts, such as the molded wood fiber substrate disclosed herein. In preferred embodiments, the pattern is a wood-grain pattern, however, the pattern may be of any image or design. As a result, decoration of complex three dimensional parts is possible. In highly preferred embodiments, the pattern printed on the liquid soluble film is a wood-grain pattern made using one or more inks. The liquid for floating the liquid soluble film is desirably water and the liquid soluble film is desirably water soluble.  
       [0016] After the pattern from the liquid soluble film has been transferred to the molded wood fiber substrate, any film residue remaining on the outer surface of the molded wood fiber substrate is removed, such as by washing the substrate with water. A protective top coat, such as a polyester or polyurethane material, is desirably applied over the pattern printed on the outer surface of the part. The protective top coat is preferably transparent, and may have a glossy finish for enhancing the appearance of the pattern printed on the wood fiber substrate.  
       [0017] In another preferred embodiment of the present invention, a method of making molded wood having a wood-grain pattern printed thereon includes providing a mat comprising wood fiber and a heat-activated resin, and molding the mat using compression and heat to form a molded wood fiber substrate having a substantially smooth outer surface. A water-impermeable sealant is desirably applied over the outer surface of the molded wood fiber substrate. The water-impermeable sealant is preferably selected from the group consisting of latex-based and chemical-based sealants. In certain preferred embodiments, the entire outer surface of the molded wood fiber substrate is covered with the water-impermeable sealant. In other preferred embodiments, the water-impermeable material may be embedded in the wood fiber mat before the molding step. During the molding step, the water-impermeable sealant passes through the individual wood fibers of the mat and toward the outer surface of the mat for providing a water-impermeable layer over the outer surface. A liquid soluble film, preferably having a wood-grain pattern printed thereon, is utilized in a hydrographic process to transfer the pattern from the liquid soluble film to the outer surface of the molded wood fiber substrate. In some embodiments, the molded wood fiber substrate is washed with a liquid before undergoing the hydrographic process, which removes contaminants from the outer surface of the molded wood fiber substrate, thereby enhancing adhesion of the ink from the film to the wood fiber substrate. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0018]FIG. 1 shows a cross-sectional view of a prior art mounting including a filler wood layer, a wood face veneer layer, adhesive layers, aluminum layer and a clear top coat.  
     [0019]FIG. 2 shows a cross-sectional view of another prior art mounting including a plastic substrate, a wood veneer layer and a clear top coat.  
     [0020] FIGS.  3 A- 3 B show a method of making still another prior art mounting including a foil having a wood-grain pattern and a mounting part.  
     [0021]FIG. 4 shows a moldable mat including wood fiber and a heat-activated resin, in accordance with certain preferred embodiments of the present invention.  
     [0022]FIG. 5A shows a cross-sectional view of a die for molding the mat of FIG. 4, in accordance with certain preferred embodiments of the present invention.  
     [0023]FIG. 5B shows the die of FIG. 5A in a closed position for molding the wood fiber mat of FIG. 4.  
     [0024]FIG. 6 shows a molded wood fiber substrate made by compressing the mat of FIG. 4 using the die of FIGS.  5 A- 5 B.  
     [0025]FIG. 7 shows an enlarged view of the dashed-circle portion of the molded wood fiber substrate of FIG. 6.  
     [0026]FIG. 8 shows a cross-sectional side view of a hydrographic printing system, in accordance with certain preferred embodiments of the present invention.  
     [0027]FIG. 9 shows a simplified top view of the hydrographic printing system of FIG. 8.  
     [0028]FIG. 10 shows a simplified perspective view of a hydrographic printing process whereby a wood-grain pattern is printed on a molded wood fiber substrate.  
     [0029]FIG. 11 shows a fragmentary cross-sectional view of the molded wood fiber substrate of FIG. 10.  
     [0030]FIG. 12 shows the part of FIG. 11 being washed to remove film residue therefrom.  
     [0031]FIG. 13 shows a drying step that follows the washing step of FIG. 12.  
     [0032]FIG. 14 shows the application of a transparent protective top coat that follows the drying step of FIG. 13.  
     [0033]FIG. 15 shows a cross-sectional view of a molded wood fiber substrate having a pattern printed thereon, in accordance with another preferred embodiment of the present invention.  
     [0034]FIG. 16 shows a cross-sectional view of a molded wood fiber substrate including a veneer layer and a pattern printed thereon, in accordance with another preferred embodiment of the present invention.  
     [0035]FIG. 17 shows a cross-sectional view of a molded wood fiber substrate having a pattern printed on an outer surface thereof, in accordance with still further preferred embodiments of the present invention.  
     [0036]FIG. 18 shows a cross-sectional view of a molded wood fiber substrate having a pattern printed on an outer surface thereof, in accordance with yet further preferred embodiments of the present invention.  
     [0037]FIGS. 19A and 19B show respective exploded and cross-sectional views of a wood steering wheel, in accordance with still further preferred embodiments of the present invention.  
     [0038]FIGS. 20A and 20B show respective cross-sectional and perspective views of a wood control knob, in accordance with other preferred embodiments of the present invention.  
     [0039]FIGS. 21A and 21B show respective cross-sectional and perspective views of a wood stick shift knob, in accordance with still other preferred embodiments of the present invention. 
    
    
     DETAILED DESCRIPTION  
     [0040]FIG. 4 shows a mat  340  made of wood fiber  342  and a heat-activated resin  344 . The heat-activated resin  344  is preferably transformable by pressure and heat during a molding process from a solid state to a liquid state, and then back to a cured solid state. During the molding process, the mat is shaped into a molded wood fiber substrate having an outer surface. After the mat is molded, the cured resin preferably maintains the shape of the molded wood fiber substrate. The outer surface of the molded wood fiber substrate is substantially smooth. The molded wood fiber substrate may be molded into any shape including a substrate having the shape of a control knob, steering wheel, knob attachable to an upper end of a stick shift, curved surface, etc.  
     [0041] FIGS.  5 A- 5 B show a press  346  for shaping the molded parts movable between open and closed positions. Press  346  includes an upper die  348  having a concave face  350  and a lower die  352  having a convex face  354 . The specific shape of the faces of the opposing die  348 ,  352  may be readily modified depending upon the shape desired for the molded wood fiber substrate. The respective concave and convex faces  350 ,  354  of the opposing die desirably mirror one another so that the press  346  may be utilized to mold a wood fiber substrate when the press is in its closed position. The upper and lower die members  348 ,  352  may be heatable to a temperature at or above the melting point of the heat-activated resin  344 .  
     [0042] Referring to FIG. 5A, in one preferred embodiment, the wood fiber mat  340  is placed atop the convex face  354  of lower die member  352 . Before the molding step, the mat  340  may at least partially flex so as to conform to the contour of the convex face  354 . As shown in FIG. 5A, wood fiber mat  340  conforms to the shape of the convex face  354  of lower die member  352 .  
     [0043] Referring to FIG. 5B, press  346  is closed by moving upper and lower die members  348 ,  352  toward one another for compressing and heating wood fiber mat  340  therebetween. Pressure and heat are applied until the heat-activated resin in mat  340  is cured for holding the molded shape of the part. The thickness of the mat  340  is preferably reduced during the compressing step. In some embodiments, the wood fiber mat  340  includes a water-impermeable sealant. During the pressing and heating of the mat, the sealant gravitates toward the outer surface of the molded wood fiber substrate for preventing the wood fibers at the outer surface from absorbing moisture and swelling, which has been observed to change the outer surface of a molded wood fiber substrate from a smooth surface to a bumpy or grainy surface.  
     [0044] Referring to FIG. 6, after the molded wood fiber substrate  340  is removed from press  346  (FIG. 5B), the substrate preferably retains its molded shape. This is due, in part, to the curing of the resin during the molding step. As mentioned above, the molded wood fiber substrate  340  desirably has an outer surface  354  that is substantially smooth. Referring to FIG. 7, in order to prevent water or other liquids from being absorbed by the wood fibers  342  at the outer surface  354 , a water-impermeable sealant  356  is applied over the outer surface  354 . In highly preferred embodiments, the entire outer surface  354  is covered with the water-impermeable sealant  356 . Sealant layer  356  may be applied in a number of different ways including brushing or spraying the sealant over the outer surface  354  or dipping all or a portion of the molded wood fiber substrate  340  into a reservoir of sealant material.  
     [0045]FIG. 8 shows a hydrographics printing system for applying a pattern, such as a wood-grain pattern, to the outer surface  354  of molded wood fiber substrate  340 . The hydrographic system includes a tank  360  for holding a liquid  362 , such as water, and a heater  364  for maintaining liquid  362  at a desired temperature. The tank  360  may also include a circulation piping system  366  interconnected with a pump  368  for urging the liquid  362  in the tank  360  to flow in a fixed direction. In preferred embodiments, piping system  366  urges liquid  362  to flow from the right side  376  (upstream) to the left side  378  (downstream) of tank  360 .  
     [0046] A film supplying assembly  370 , such as that disclosed in U.S. Pat. No. 6,103,342, is arranged at the right side  376  of tank  360 . Film supplying assembly  370  includes a roll  372  having liquid soluble film  374  wound thereon. Liquid soluble film  374  is preferably an elongated strip made of a material that gradually dissolves after the film contacts the liquid in the tank  360 . A design or pattern (not shown) is preferably printed on one side of the liquid soluble film  374 .  
     [0047] In operation, the liquid soluble film  374  is fed into tank  360  by film supplying assembly  370 , with the printed side of film  372  facing toward the wood fiber substrates  340 . The liquid soluble film  374  is floated atop liquid  362 , the liquid urging film  374  to move from the right side  376  toward the left side  378  of tank  360 . Upon contacting the liquid  362 , the liquid soluble film  374  generally expands and dissolves, allowing the ink pattern to float on the liquid. In some embodiments, in order to prevent the edges of the film  374  from becoming wrinkled or curled during expansion of the film, an air blower (not shown) may be provided above the tank  360 . The air blower is preferably adapted to apply pressure onto a top surface of film  374 . The force of the air blower may be directed toward the left side  378  or downstream side of tank  360 .  
     [0048] A wood fiber substrate supplying assembly  380  is provided above tank  360  for moving the molded wood fiber substrates  340  toward tank  360  and immersing the substrates  340  or parts into the liquid  362 . The molded wood fiber substrate supplying assembly  380  is adapted to move the substrates along a conveyor path for immersing the substrates  340  in the liquid  362 . The substrates  340  are preferably immersed in the liquid  362  as the substrate is moving toward the left side of tank  360 . The molded part supplying assembly  380  preferably abuts the molded wood fiber substrate  340  against the pattern printed on the film  374 , and immerses all or a portion of the substrate  340  into the liquid  362 , while keeping the substrate  340  in contact with the ink pattern. In certain preferred embodiments, the molded wood fiber substrate supplying assembly  380  includes a series of securing elements  384  for securing the substrates  340  on conveyor belt  386 . The securing elements  384  are preferably positioned at spaced intervals along the conveyor belt  386 . The molded wood fiber substrate supplying assembly may also include one or more pulleys  388  for moving the conveyor belt  386  along its circular path.  
     [0049] By constructing the molded wood fiber substrate supplying assembly  380  as shown in FIG. 8, the substrates  340  are forced to contact the film  374  at a first angle, pivoted into the liquid  362  in the tank  360  and lifted up at a second angle so as to prevent the formation of bubbles or imperfections between the liquid soluble film  374  and the outer surface  354  of the substrate  340 . The particular angle at which the wood fiber substrates  340  are passed through the film  374  and liquid  362  may be varied depending upon the specific shape and size of the substrates  340 .  
     [0050]FIGS. 9 and 10 show simplified top and perspective views, respectively, of the hydrographic printing system shown in FIG. 8. Referring to FIGS. 9 and 10, roll  372  includes liquid soluble film  374  having a wood-grain pattern  375  printed on a surface thereof. The liquid soluble film  374  is paid out from roll  372  and floated over the top surface of liquid  362  in tank  360 . The molded substrate  340  is preferably abutted against the liquid soluble film at transfer point  381 . The timing of the substrate supplying assembly  380 , including the rate at which the liquid soluble film  374  is paid out, is coordinated so that the condition of film  374  is optimized for transferring the ink pattern from the film to the substrate  340 . In particular preferred embodiments, the liquid soluble film  374  is substantially dissolved at the transfer point  381  so that the pattern on the film may be effectively printed on the molded wood fiber substrate, with preferably only a slight residue of the film remaining on the substrate  340 .  
     [0051]FIG. 11 shows molded wood fiber substrate  340  after the wood-grain pattern  375  has been printed thereon. Substrate  340  includes outer surface  354  covered by water-impermeable layer  356 , with pattern  375  printed atop water-impermeable layer  356 . The pattern is preferably a wood-grain pattern.  
     [0052] Referring to FIG. 12, the molded wood fiber substrate having the wood-grain pattern printed thereon is subjected to a washing step whereby residue of the film remaining on the substrate  340  is removed or washed away. In the particular embodiment shown in FIG. 12, a showerhead  390  discharges water  392  from removing residue of the film remaining on substrate  340 . During the residue removal step, the substrate may be moved along the conveyor  396  in a direction indicated by arrow B. In certain preferred embodiments, an underside  394  of part  340  faces toward conveyor belt  396  and the printed side  398  including wood-grain pattern  375  faces away from conveyor belt  396 . Referring to FIG. 13, the substrate  340  may be passed by a dryer  397  adapted to direct a stream of air  398  toward the substrate for drying substrate  340  and the pattern  375  printed thereon.  
     [0053] Referring to FIG. 14, a protective top coat  400  is desirably provided over the wood-grain pattern  375 . The protective top coat  400 , preferably selected from the group of polymer based materials consisting of polyurethanes and polyesters, protects the pattern  375  from nicks or cuts that may mar the aesthetic appearance of the part  340 . The protective top coat  400  preferably provides a glossy finish to the substrate  340  and wood-grain pattern. The protective top coat may be applied in many ways, including using a brush or sprayer. The protective top coat is desirably cured, such as by allowing the protective coat to air dry. Protective top coat  400  is preferably transparent so that the pattern  375  transferred to substrate  340  may be seen therethrough. The above-described hydrographic printing process may be applied to a molded wood fiber part having any shape, size or contour. The process is particularly preferred for molded parts having irregular or curved surfaces that are not compatible with wood veneer. As known to those skilled in the art, the use of wood veneer is typically limited to its application over substantially flat surfaces.  
     [0054] As shown in FIG. 15, in one preferred embodiment, a part  440  includes molded wood fiber substrate  442  having a top surface  454  with a hydrographic wood-grain pattern  475  printed thereon. A transparent protective top coat  477  is applied over the wood-grain pattern  475 . The protective top coat  477  preferably provides a glossy appearance to the part  440  and protects the wood-grain pattern  475  from nicks, cuts or other aesthetic imperfections. The part  440  may be mounted atop a support plate  479 , with a mounting stud  481  secured to support plate  497 . The support plate  497  and mounting stud  481  enable part  440  to be secured to a structure, such as inside the passenger compartment of an automobile. Part  440  may have a wood-grain pattern printed thereon so that the part may be used as wood trim or a wood panel within the passenger compartment of a vehicle. The particular pattern  475  printed atop the wood fiber substrate  442  may be modified to have a different appearance. For example, the pattern may being any type of design including stone, marble, brick, etc. Thus, a wide variety of patterns may be printed upon the part  440 .  
     [0055]FIG. 16 shows a part  540  in accordance with yet further preferred embodiments of the present invention. Part  540  includes molded wood fiber substrate  542  having a top surface  554  and wood veneer  555  molded over top surface  554 . A hydrographic printing process is used to print a pattern  575 , such as a wood-grain pattern, atop wood veneer  555 . A substantially transparent protective top coat  577  is desirably applied over the wood-grain pattern  575 . In order to mount the part, the part  540  preferably includes a support  583  comprising plate  579  and mounting stud  581 . The support  583  and/or plate  579  may be first molded and then adhered to an underside  554  of molded wood fiber substrate  542 . In other embodiments, support  583  may be molded directly onto the underside  554  of molded wood fiber substrate  542 .  
     [0056] In other preferred embodiments, the above-described methods may be used to form an object having a circular cross section, such as a steering wheel  640  shown in FIG. 17. The steering wheel  640  desirably includes a core  679  having a molded wood fiber substrate  642  formed about the core  679 . The core  679  may be made of wood. In one particular preferred embodiment, a mat including wood fiber and a heat-activated adhesive is wrapped around core  679 . Compression and heat are applied to the mat to cure the adhesive and form a molded wood fiber substrate  642  having a circular shape. The molded wood fiber substrate  642  is preferably covered with a water-impermeable sealant for preventing the wood fibers at the outer surface of the molded part from swelling or changing shape during the hydrographic printing steps. After water-proofing, substrate  642  is subjected to a hydrographic printing process whereby a pattern  675 , such as a wood-grain pattern, is printed onto the outer surface  654  of molded wood fiber substrate  642 . A transparent protective top coat  677  is applied over the printed wood-grain pattern  675  for protecting the pattern  675  from nicks and cuts that may mar the aesthetic appearance of the part. In certain preferred embodiments, the part  640  may be used to provide a steering wheel having a wood-grain appearance. The use of molded wood fiber with a wood-grain pattern printed thereon enables auto dealers to claim that the part  640  (e.g., steering wheel) is made of “real wood” because a relatively high percentage of the part is actually made of wood (i.e. wood fiber). Moreover, the method disclosed herein is simpler than prior art methods that mold wood veneer around a central core of a steering wheel. Thus, printing a wood-grain pattern on the steering wheel shaped wood fiber substrate is simpler and more cost efficient than using a wood veneer to provide the wood-grain pattern.  
     [0057]FIG. 18 shows yet another preferred embodiment of the present invention whereby the molded wood fiber substrate  742  is formed of two parts  742 A and  742 B. The molded substrates  742 A and  742 B are preferably formed separate from one another and are later joined together at an interface  745  extending therebetween. In one preferred assembly method, a metal core  779  has first and second molded wood fiber substrates  742 A and  742 B secured about the core  779 . A hydrographic process is used to print a wood-grain pattern  775  over the outer surface  754  of the substrates  742 A,  742 B. A transparent protective top coat  777  is preferably applied over the wood-grain pattern  775 . In alternative embodiments, the wood-grain pattern  775  may be applied over the outer surfaces  754  of the respective first and second molded wood fiber substrates  742 A,  742 B before the two substrates  742 A,  742 B are assembled together around metal core  779 . A gap  781  may be present between one or more of the molded substrates  742 A,  742 B and a portion of the metal core  779  to provide a tolerance for the parts of a steering wheel or other component.  
     [0058]FIGS. 19A and 19B show a wood steering wheel  840  in accordance with yet another preferred embodiment of the present invention whereby the molded wood fiber substrate is formed as two separate parts  842 A,  842 B that are assembled together around a metal core  879 . The two separate parts  842 A,  842 B are preferably formed and finished separate from one another and are later joined mechanically together along opposing interfaces  845 A,  845 B. In one preferred embodiment, metal core  879  has holes (not shown) provided to affix the first and second molded wood fiber substrates  842 A and  842 B thereto. A hydrographic process is used to print wood-grain patterns  875 A,  875 B over the outer surfaces  854 A,  854 B of the respective substrates  842 A,  842 B. Transparent protective top coats  877 A,  877 B are preferably applied over the wood-grain patterns  875 A,  875 B. After the wood-grain patterns  875 A,  875 B are applied over the outer surfaces  854 A,  854 B of the respective first and second molded wood fiber substrates  842 A,  842 B before the two substrates  842 A,  842 B are assembled together around metal core  879 .  
     [0059]FIGS. 20A and 20B show a wood control knob  940 , such as a control knob for a radio or a push button for a dashboard, made using one or more of the preferred methods described above. Control knob  940  includes plastic or metal core  979  having a wood fiber substrate  942  affixed thereto. A wood-grain pattern  975  is printed over the wood fiber substrate  942  and a transparent protective top coat  977  in applied over the printed wood-grain pattern  975 .  
     [0060]FIGS. 21A and 21B show a wood knob  1040  attachable to an upper end of a stick shift (not shown) made using one or more of the preferred methods described above. Wood stick shift knob  1040  includes plastic or metal core  1079  having a wood fiber substrate  1042  affixed thereto. A wood-grain pattern  1075  is printed over the wood fiber substrate  1042  and a transparent protective top coat  1077  in applied over the printed wood-grain pattern  1075 .  
     [0061] It will be appreciated that the present invention is not restricted to the particular embodiments that have been described and illustrated herein, and that variations may be made to the described and illustrated embodiments without departing from the scope of the invention as claimed herein.