GB1570821A - Back-up rollers for cylindrical embossing dies and method for preparation - Google Patents

Description

(54) BACK-UP ROLLERS FOR CYLINDRICAL EMBOSSING DIES AND METHOD OF PREPARATION (71) We, HALLMARK CARDS, INCORPORATED, a corporation organised and existing under the laws of the State of Missouri, United States of America, of 25th & McGee Trafficway, County of Jackson, State of Missouri 64141, United States of America do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to back-up rollers adapted for use against cylindrical embossing dies having modeled surfaces presenting a design therein, and especially to improved manufacturing processes, equipment and products which have inherent advantages over the production methods and counters disclosed in U.S. Patent No. 3,560,289 entitled "Rotary Embossing Die Counter" and owned by the assignee hereof.

As explained in the '289 patent, a number of different techniques have heretofore been employed in the graphic arts field to prepare back-up rollers which are run against embossing or foil stamping dies having either raised or depressed areas in the surface thereof to present artistic designs. Typical products which have been embossed or foil stamped with a rotary die and roller set include greeting cards, calendars, party accessories, napkins, wrapping paper, appliques for various paper and metal items, and decorative sheet articles. Rotary systems for impressing paper, metal and plastic sheet materials have the advantage of being operable on a continuous basis and are especially effective for long runs with a repeating design.

By virtue of the modeled, normally intaglio relief in the surface of the rotary die defining the design therein, a roller rotatable against the die having a modeled face which conforms to and is a reverse of the irregular surface of the die is required to assure uniform embossing or foil stamping of the sheet material passed between the rolls. The process of U.S. Patent No.

3,560,289 represents one procedure for preparing a roller in a more economical manner than theretofore available. In the production procedure of the patent, several layers of an ultraviolet sensitive, thermosetting, partially cured synthetic resin blanket reinforced with glass cloth (known as "pre-preg") is applied to a counter roll. After further curing of the resin to reduce the tackiness thereof, the die is rotated against the resin blanket on the counter roll to cause the outer face of the blanket to conform to the die surface as a reverse thereof.

Final cure of the resin on the counter roll is effected by application of ultraviolet energy to the resin during rotation of the counter roll. This procedure was offered as a replacement for the conventional practice of running the die against a pressure deformable counter roll made up of cloth, paper or similar material until the surface of the counter substantially assumed a relatively permanent set conforming to a reverse of the die. Not only was considerable operator skill required with such prior methods to determine exactly when the counter had been shaped sufficiently for effective use thereof, but operation of the process was inherently expensive because of the time consumed in preparing a useful counter coupled with the need to replace the cotton or felt pads at relatively frequent intervals to maintain proper quality of the impressed design of the sheet material being processed.

Although the roller preparation procedures of the '289 patent represented a distinct improvement over previously available counter preparation methods, competitive cost fac tors and spiraling labor costs dictated a search for even more economical counter manufacturing methods and procedures which would result in a roller having a significantly longer useful life than that of the previously patented process.

An object of the present invention to obviate or mitigate the aforementioned disadvantages.

An advantage of a back-up roller as hereinbefore described is that it is resurfaceable for use against a cylindrical embossing die and has greater inherent strength than previous synthetic resin prepared in place rollers without destruction of the required inherent resiliency thereof necessary to preclude cracking and crazing of the roller surface caused by excessive brittleness.

An advantage of the method of preparing a back-up roller as hereinbefore described for a cylindrical embossing die is that it provides a roller which is recyclable in that the back-up surface of the roller may be readily removed and replaced thus producing considerable cost savings by virtue of the fact that the roller core may be used over and over when wear dictates preparation of a new surface, or the need to run a new design.

An advantage of the process for preparing rotary die back-up roller is the provision of a steel core having a relatively shallow, circumferentially extending relieved area therein adapted to be filled with a synthetic resin material containing pretensioned, spiral wound glass fiber roving with the resin system being curable in place so that after application of the resin to the roll and partial curing thereof, the resin may be run in against the die and then finally hardened in operative position on the press to the end that a minimum of downtime is experienced while at the same time allowing repair of the roller on the press as may be necessary during the production run.

Another advantage is that a prepared-in-place back-up roller wherein the end cylindrical segments of the counter roll on opposite extremities of the resin receiving relieved area in the face thereof serve as bearer surfaces engagable with complementary surfaces of the die to provide extremely close tolerances for the resin part of the counter to assure impressed designs of required clarity, precision and uniformity.

A still further advantage in the process for preparing rotary die back-up rollers is that a more economical manner of preparation than heretofore is possible by virtue of the fact that the resin applied to the relieved area of the counter core has not been partially pre-cured but has sufficient viscosity to substantially retain its shape without significant defcrmation until curing of the resin can be effected with means such as an ultraviolet light source. This allows the fabricator to quickly and readily apply resin to the core and effect cure thereof in a very short period of time while mounted m operative position on the press. These production steps especially lend themselves to preparation of a counter surface made up of a number of successively applied layers which bond one to another and which are effectively strengthened by pretensioned reinforcement comprising wound glass fiber roving incorporated into an inner layer of resin during fabrication of the counter. By virtue of the restraint placed on the continuous glass fiber strands during winding of the same about an inner resin layer on the cylinder, the roving is placed under a certain degree of tension so that the next coating of the resin material applied to the cylinder and at least partially cured incorporates the reinforcing glass into the cylindrical interior of the resin counter to ultimately produce a much stronger than anticipated counter surface without attendant cracking or deterioration problems.

Also advantageous is the use of initially uncured viscous resin systems for the roller which may be applied in layers and only partially cured with a UV source during buildup of the back-up roller surface so that final cure to bond all layers into a hardened, essentially monolithic mass may be accomplished after impression of the image layer thus allowing selective partial and then final cure as well as glass fiber reinforcement of the resin in place on the counter core.

Back-up rollers prepared in accordance with present invention are especially adapted for use against an embossing die usable to impress an overall embossing pattern in a sheet of web-fed material. The die itself is normally of metal and prepared in accordance with standard techniques such as electro-deposition methods, formation of thermosetting, initially planar blanks which are pierced and blanked at opposite ends thereof so that the mats may be attached to a suitable supporting cylinder therefore, or machined to present an intaglio model design in any type of suitable material including steel, brass, thermosetting synthetic resin, nickel or copper. For purposes of describing the present rotary counters and the procedures of constructing the same, it is assumed that the embossing die cylinder is of the type described and prepared in accordance with the conventional methods outlined.

According to one aspect of the present invention there is provided a back-up roller for use with a rotary embossing die comprising a cylindrical core; a wrap of reinforcing roving material spirally wound about said core under tension and bonded to the core; and at least one layer of hardened synthetic resin material over said pre-tensioned roving, the outer surface of said resin material having a configuration conforming to a die as the reverse thereof.

According to another aspect of the present invention there is provided a method of producing a back-up roller for use against a cylindrical die surface presenting a design said method comprising the steps of providing a roller cylinder; wrapping under tension a continuous roving of reinforcing material around said cylinder in a spiral manner, and bonding the roving to said cylinder; applying at least one layer of synthetic resin material over said roving for defining the outer periphery of said counter, said material being characterised by the property of being hardenable to an extent to substantially permanently retain a deformed shape; simultaneously rotating the die and said cylinder with the modelled surface of the die engaging said layer of resin material for causing the outer surface of the layer to be deformed to an extent to substantially conform to the modelled surface of the die as a reverse thereof; and hardening the layer of deformed resin material to produce said roller.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is an essentially schematic front elevational view of one type of press on which the rotary die counters of this invention may be prepared and used illustrating the normal operative disposition of the back-up roller with respect to the embossing die, along with a removable source of ultraviolet light for curing the resin in place on the roller core; Fig. 2 is a cross-sectional view taken substantially on line 2-2 of Fig. 1 and looking in the direction of the arrow; Figure 3 is a schematic showing of the roller core having a layer of resin thereon being leveled with a doctor blade during rotation of the counter and illustrating the normal position of the roller core with respect to the die; Figure 4 is a schematic showing similar to Figure 3 and illustrating the way in which the resin may be cured in place upon activation of the ultraviolet light source; Figure 5 illustrates schematically the way in which tensioned glass roving made up of continuous glass fibers is spirally wound around the resin coated roller core to reinforce the roller material; Figure 6 illustrates schematically another step in the process wherein a layer of resin is applied to the roller and doctored to desired height by the shiftable doctor blade; Figure 7 is a schematic representation of the following step in the process wherein the layer of resin over the roving is cured in place through use of the ultra-violet source located above the roller; Figures 8, 9, 10 and 11 show in schematic form how successive layers of resin are applied to the roller core and cured in place; Figures 12 and 13 schematically illustrate the way in which the die is run against the partially cured outer resin layer on the roller core to produce a modelled surface in the resin which is a reverse duplicate of the die face whereupon the roller is subjected to a final ultraviolet cure; and Figure 14 is an enlarged fragmentary schematic cross-sectional view of the roller and die showing the way in which the resin fills a relieved area in the roller core and has in the instance illustrated, raised areas which complementally extend into the intaglio design of the die.

The embossing press 20 shown schematically in Figures 1 and 2 is preferably of the type which allows at least one of the cylinders thereof to be shifted relative to the other without loss of registration therebetween with the cylinders being operably interconnected by gearing to avoid slippage therebetween during rotation. Useful press structure in this respect is shown for example in U.S. Patent No. 3,302,558 and particularly Figure 6 thereof. In the schematic showing, base 22 supports a pair of spaced, parallel, upright structures 24 and 26 which in turn rotatably carry horizontal, vertically spaced shafts 28 and 30 of counter roll 32 and embossing die 34 respectively. Gear sections 36 and 38 of back-up roller 32 and die 34 respectively are adapted to intermesh and preclude rotation of the die and counter at different relative surface speeds. However, the gear sections do not interfere with relative parting movement of the back up roller and die yet assure proper registration thereof upon return of the embossing components to operative relationship as illustrated in Figures 1 and 2.

As is evident from Figure 2, the press chosen for illustration purposes only has a shiftable embossing die 34 rotatably carried by vertically movable end blocks 40 on structures 24 and 26 respectively, with suitable hydraulically actuated mechanism 42 of conventional nature for vertically reciprocating the die 34 while maintaining the shaft 30 thereof essentially parallel to the shaft 28 of roller 32. The core 44 of roller 32 (see Figure 1) is preferably fabricated of suitable metallic material such as steel carried by opposed shafts 28 which may either be bolted to or integral with the core.

The outer cylindrical surface of core 44 is relieved to present a cylindrical area 46 extending around the circumference of the roller and spaced inwardly from the opposed end bearing surfaces 48 at opposite ends of the cylinder. Area 46 is preferably machined to a depth of about 0.020 in. below the level of co-cylindrical surfaces 48 and as will be explained, the relieved area 46 is filled with specially reinforced synthetic resin material and then run against the modeled surface of die 34 to produce a reverse of the modeled design. Mechanism 42 serves to force the outer face of die 34 into operative engagement with the resin coated surface of core 44 and thus the paper stock or other sheet material to be processed is passed between die 34 and roller 32 with the design bearing or printed face toward the outer surface of die 34. The various adjustments on the press allow side to side registration of the die cylinder for gear alignment, front to back registration of the die cylinder relative to the counter, and vertical adjustment between the two cylinders.

In a typical application, the die cylinder may have an overall length of 50 to 60 inches (e.g., 57 inches) with a design bearing surface of 40 inches leaving opposed bearing sections 50 adapted to complementally engage the surfaces 48 of roller 32, and a finished diameter of 7.639 in., giving a 24 inch design repeat blank. The basic die cylinder may for example be constructed from 2 inch thick tubular steel with welded end plates and shafts 30 on each end, along with internally welded steel support plates as required. Following machining to provide the design-defining area, electroformed copper is deposited onto the face of the cylinder. This provides the medium into which the die design is photoengraved and then suitably etched for completion of the die cylinder. This electrodeposited surface can also be machined, redeposited with copper and finished to a 7.639 in. diameter for recycle and preparation of new designs. Following the completion of each design photo-engraving on the die cylinder, chrome plating is then deposited on the copper over at least the full 40 inch length of the design portion of the cylinder.

The core cylinder of roller 32 is constructed in a manner very similar to that of die 34 in that the wall thickness is also 2 inches and the overall length of this cylinder is approximately that of the die. The relieved area 46 machined in roller 32 is preferably sandblasted to provide a somewhat roughened face for bonding the resin material to the counter thus insuring against slippage of the resin relative to the roller core during extended use. This is particularly important during long runs of the same design. Referring to Figure 3 of the drawings, it is to be seen that the hydraulic mechanism 42 is actuated to shift die cylinder 34 away from roller 32 whereupon a layer of synthetic resin material of a thickness of about 0.002 in. is applied to the cylindrical surface area 46 of core 44. The horizontal doctor blade 52 carried by support 54 on angle 56 extending across the front of the press 20 is adjusted to assure that the resin material is of uniform thickness throughout the circumference of the roller.

A number of different resins may be used for preparing the roller surface. Exemplary compositions are those generically known as radiation curable (usually UV) urethanes, acrylates, thiophenes, polyesters, and other similar type materials having an olefinic type bond. These resins may all be partially cured with a radiation source such as UV and then fully cured to a fused mass state where the individually applied layers are no longer readily discernible as separate entities. The preferred resins are either a polythene-polythiol acrylate and acrylate monomer combination along with an initiator, or an acrylate prepolymer combined with, for example, an acetophenone or benzophenone initiator. A suitable acrylate resin system is a product of Polychrome Corporation, Yonkers, New York sold under the trade designation of Uvimer Resin 1713-H. A typical formulation is Uvimer 1713-H (98No) and 2,2 diethoxy-acetephenone (2S o), having a viscosity range of 50,000 - 100,000 centipoises. Other useful formulas include: 1. Polyene/polythiol photopolymer 3811A sold by W. R. Grace and Co. (90So hydroxypropyl acrylate (lONo) 2. Polyene/polythiol photo polymer 3811A sold by W. R.

Grace and Co. (87So) 1,6 hexanediol diacrylate (13So) 3. Acrylate prepolymer Uvimer DV-53 sold by Polychrome Corporation (76No) hydroxypropyl acrylate (200/0) Trigonal 14 (a photoinitiator sold by Noury Chemical Company, Burt, N.Y.) (4 s) 4. Polyene/polythiol photo polymer 6011-G sold by W.R. Grace and Co. and containing a radiation response initiator or curing agent (uncured viscosity - 8000 11,000 cps.) (lOOSo) The principal characteristics necessary for the resin material comprise (1) ability to effect hardening of the resin formulation on the press in a relatively short period of time (e.g., no more than about 20 total minutes for all of the resin layers , (2) sufficient viscosity in an uncured state that the resin material does not undergo significant flow when applied to the roller prior to curing thereof with the source of radiation or other curing medium and (3) capable of being selectively partially and then finally fully cured with a UV source or the like whereby successively applied layers of the resin may be hardened into an essentially monolithic coating reinforced with glass fiber. In all instances, cure characteristics and the physical properties of the final resin roller are governed by the speed of rotation of the roll, the thickness of the overall coating, the amount of glass roving applied, the total cure time, and the intensity of the radiation.

It has been determined in this respect that the resin composition should have a viscosity when applied to the roller surface of at least about 6000 cps. and preferably at least about 25,000 centipoises. Best results obtain in the 50,000 - 250,000 centipoises range. The upper limit of viscosity is that at which the material is so thick that it is impractical to apply the same to the counter surface or preceding resin layers. Certain formulations are useful in viscosity ranges up to about 1,000,000 centipoises. In the most preferred embodiment of this invention, as evidenced by the specific formulations referenced above, the polymeric material is curable by application of ultraviolet radiation thereto by virtue of the fact that this materially lessens the make-ready time and lends itself to simple processing techniques since it is only necessary to appropriately place an ultraviolet lamp on the press in disposition spanning uprights 24 and 26 as indicated in Figures 1, 2, 4, 7, 9, 11 and 13. In the instance shown, inverted reflector and support 58 for UV lamp 60 make up a source 62 of ultraviolet radiation which is directed against the top part of roller 32 as the latter is rotated about the axes of shafts 28.

Curing unit 62 preferably has a power supply, high voltage wiring from the power supply to the assembly, an irradiator such as UV lamp, and a blower and duct mounted at one end of the reflector assembly to exhaust hot air therefrom. The bulb 60 may for example be a medium pressure, high intensity mercury lamp capable of emitting 200 watts of power per lineal inch and designed for a three inch focal length or distance from the adjacent surface of counter 32.

Although the amperage and voltage parameters of UV sources may vary, an exemplary unit as described hereinafter for illustrative purposes only has been found to be especially suitable.

After application of the initial resin layer 64 to roller 32 as depicted in Figure 3, and following doctoring of the resin to product a layer on the order of 0.002 in., the resin is subjected to a cure for approximately one second by operation of the UV source unit 62 at 1/2 power (11.7 amps. at 220 v.) while roller 32 is rotating at 70 rpm (see Figure 4).

The next step of the operation is illustrated in Figure 5 wherein it can be seen that fiber glass roving 66 made up of substantially continuous strands of glass fibers is spirally wound around counter 32 in overlying relationship to partially cured resin layer 64 throughout the length of area 46. Owens Corning Fiberglass roving type 30 (6-8 mils thick) has been found to be satisfactory with the spiral wind being effected while tension is maintained on the roving during rotation of roller 32 and with the individual lays of the glass roving being spaced a slight distance apart which for example may be of the order of 1/4 to 3/4 of the width of the roving as pressed flat against layer 64. It is important that the roving be applied under sufficient pre-tensioning conditions to cause the same to lay flat and true on the underlying partially cured resin. It is to be understood that the distance between the roving lays may be varied as desired but it is preferred that some space therebetween be provided to permit resin to firmly bond to the underlying layer 64 in surrounding relationship to the glass fibers.

Greater spacing than preferred may be used but somewhat at a sacrifice in the overall strength of the roller surface. The applied tension should not be so excessive as to cause the roving to completely penetrate the resin layer therebeneath and lay flat against the metal cylindrical supporting surface.

After completion of the roving application, another resin layer 68 (see Figure 6) is applied to roller 32 over the roving and initial resin coating 64 and doctor blade 52 is adjusted to provide a second resin layer covering the fiberglass by approximately 0.003 in. thickness.

This layer is cured for three to seven seconds (preferably three to five) at 1/2 power (11.7 amps. at 220 v.) while the roller continues to rotate at 70 rpm. (See Figure 7) A 0.004 in. layer 70 of resin is applied to roller 32 as shown in Figure 8 by appropriate adjustment of doctor blade 52 and layer 70 is then cured by operation of UV source 62 as shown in Figure 9 for three to seven seconds (preferably three to five) at 1/2 power (11.7 amps. at 220 v.) while rotating the roller cylinder at 70 rpm.

Another resin layer (not illustrated schematically in the drawings) of about 0.004 in. thick may be applied over layer 70 if desired and again cured within the time and power parameters specified with respect to Figures 6 to 9 inclusive.

The final layer 72 is then applied to roller 32 with the thickness thereof being sufficient to bring the same into substantially conforming relationship to the outer faces of bearer surfaces 48. Doctor blade 52 controls the thickness of the layer as illustrated in Figure 10. Layer 72 is partially cured as depicted in Figure 11 by subjection of the resin to ultraviolet radiation for a time period of about 30 seconds while operating lamp 60 at 1/2 power (11.7 amps. at 220 v.) during rotation of roller 32 at about 9 rpm. The level of radiation and the time of partial cure may be varied as necessary to harden the material without making the same completely nondeformable.

Next, the die 34 is shifted by hydraulically actuated mechanisms 42 into pressure engagement with counter 32 (approximately three hundred pounds pressure) and wet resin applied to the face of roller 32 to provide an image layer 78 sufficient to fill the intaglio design 74 in the outer metal layer 76 of embossing or foil stamping die 34. The UV source 62 is again energized and the resin cured at full power for a time of approximately one and 1/2 minutes while rotating cylinders 32 and 34 in contacting engagement at 9 rpm as shown in Figure 13.

The resulting back-up roller 32 nas been found to have an exceptional life under continuous use and can be produced at a small fraction of the cost of prior back-up rollers, particularly those of the conventional paper or cotton pad type while at the same time being fully recyclable in that the resin coating may be readily removed and replaced in a relatively short period of time as required.

One particularly important feature of the invention is the fact that the completed roller has sufficient rigidity to withstand long continuous use but is not so brittle as to be subject to crazing or cracking. It is to be recognized in this respect that as paper or other sheet stock is passed between roller 32 and die 34, the resin is displaced slightly adjacent the nip in a direction opposite rotation of the rolls producing, on an exaggerated basis, a welling up or deflected standing wave the full length of the roller which would rapidly crack the material if it did not retain a certain degree of inherent resiliency. However, the glass roving spirally wound about the roller core imparts sufficient strength to the resin body to prevent the continuously moving raised area of the resin at the nip from cracking the material and causing rapid deterioration thereof. It is believed to be especially significant to long operable life that the roving be spirally wound about the cylinder under tension and in a continuous noninterrupted fashion for relatively uniform stress distribution throughout the circumference of the resin part of the counter thus giving unexpected roller longevity. Tests have shown that rollers made in accordance with the preferred concepts of this invention have up to a tenfold life expectancy over those produced under U. S. Patent No. 3,560,289.

Claims (20)

WHAT WE CLAIM IS:

1. A back-up roller for use with a rotary embossing die comprising: a cylindrical core; a wrap of reinforcing roving material spirally wound about said core under tension and bonded to the core; and at least one layer of hardened synthetic resin material over said pre-tensioned roving, the outer surface of said resin material having a configuration conforming to a die as the reverse thereof.

2. A roller as claimed in Claim 1, including a primary layer of synthetic resin material applied directly to said core, with said roving material wrapped around and bonded to the primary layer.

3. A roller as claimed in Claim 1 or 2, wherein the convolutions of said spiral wrap are spaced to provide a gap between roving lays.

4. A roller as claimed in Claim 1, 2 or 3, including a plurality of superposed, secondary layers of synthetic resin material over said roving, the innermost of said secondary layers being directly bonded to said primary layer through the gaps between said roving convolutions.

5. A roller as claimed in any one of Claims 1 to 4, wherein said roving comprises substantially continuous strands of glass fibres.

6. A roller as claimed in Claim 6, wherein said resin is a radiation curable urethane, acrylate or thiophene.

7. A roller as claimed in any one of the preceding claims, wherein said cylinder core is provided with cylindrical bearer surfaces at opposite ends thereof and a relieved area therebetween, said resin and roving material filled only the said relieved area of said core.

8. A method of producing a back-up roller for use against a cylindrical die surface presenting a design, said method comprising the steps of providing a roller cylinder; wrapping under tension a continuous roving of reinforcing material around said cylinder in a spiral manner, and bonding the roving to said cylinder; applying at least one layer of synthetic resin material over said roving for defining the outer periphery of said counter, said material being characterised by the property of being hardenable to an extent to substantially permanently retain a deformed shape; simultaneously rotating the die and said cylinder with the modelled surface of the die engaging said layer of resin material for causing the outer surface of the layer to be deformed to an extent to substantially conform to the modelled surface of the die as a reverse thereof; and hardening the layer of deformed resin material to produce said roller.

9. A method as claimed in Claim 8, including the steps of applying a primary layer of hardenable resin material directly to said cylinder, wrapping said roving around said primary layer, and at least partially hardening the primary layer for bonding said roving thereto.

10. A method as claimed in Claim 8 or 9, wherein is included the steps of providing a relieved area between the ends of the cylinder to define cylindrical bearer surfaces at opposite ends thereof, and filling only said relieved area with said material.

11. A method as claimed in any one of Claims 8 to 10, including the step of locating the convolutions of said roving in relative dispositions permitting passage of a bonding agent therebetween to bond the roving to said cylinder.

12. A method as claimed in any one of Claims 8 to 11, including the steps of applying a plurality of superposed, secondary, hardenable layers of resin material over said roving, at least partially hardening each of said secondary layers, and bonding at least the innermost of said secondary layer to said primary layer through the spaces between said roving convolutions.

13. A method as claimed in any of Claims 8 to 12, including the steps of applying a coating of said resin material on the cylinder in an initially flowable state, and effecting partial hardening of the latter prior to significant deformation of said material on the cylinder.

14. A method as claimed in any one of Claims 8 to 13, wherein is included the step of subjecting the viscous resin coating to a source of ultraviolet energy for a time period to effect said hardening thereof.

15. A method as claimed in any one of Claims 8 to 14, wherein said resin is a radiation curable urethane, acrylate or thiophene.

16. A method as claimed in any one of Claims 8 to 15, wherein said resin has an initial viscosity of at least 6000 cps.

17. A method as claimed in any one of Claims 8 to 16, wherein said resin has a minimum viscosity of about 25,000 centipoises.

18. A method as claimed in any one of Claims 8 to 17, wherein said roving comprises strands of glass fibres of substantially continuous length.

19. A method as claimed in any one of Claims 8 to 18, including the step of causing at least one end of said die, and the adjacent end of said roller cylinder, to bear directly against each other during said simultaneous rotation for maintaining a predetermined forming contact between the modelled surface of said die and the other surface of said layer of material.

20. A method of producing a back-up roller for use against a cylindrical die surface presenting a design, substantially as hereinbefore described.

20. A back-up roller substantially as hereinbefore described, with reference to the accompanying drawings.