Patent Publication Number: US-2020290915-A1

Title: Methods of manufacturing glass ribbon

Description:
This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application Ser. No. 62/579,556 filed on Oct. 31, 2017, the content of which is relied upon and incorporated herein by reference in its entirety. 
    
    
     FIELD 
     The present disclosure relates generally to methods of manufacturing glass ribbon and, more particularly, to methods of manufacturing glass ribbon with a first pair of rollers and a second pair of rollers. 
     BACKGROUND 
     It is known produce glass ribbon with a precision glass roll forming apparatus. It is known to provide a pair of forming rolls vertically below a glass feed to thin the supplied stream of molten glass to produce a formed glass ribbon. It is further known to place another pair of sizing rolls vertically below the forming rolls. 
     SUMMARY 
     The following presents a simplified summary of the disclosure to provide a basic understanding of some embodiments described in the detailed description. 
     In some embodiments, a method of manufacturing glass ribbon can comprise feeding molten material through a minimum width of a first gap defined between a first roller and a second roller of a first pair of rollers. A first pool of molten material can be formed upstream from the minimum width of the first gap. The viscosity of the molten material within the first pool of molten material can be from about 5 Poises to about 5,000 Poises. A ribbon of molten material can exit the first gap. The methods can further include passing the ribbon of molten material through a minimum width of a second gap defined between a first roller and a second roller of a second pair of rollers. The minimum width of the first gap can be greater than the minimum width of the second gap. A second pool of molten material can be formed upstream from the minimum width of the second gap and the viscosity of the molten material within the second pool of molten material can be from about 10,000 Poises to about 100,000 Poises. 
     In some embodiments, a method of manufacturing glass ribbon can comprise feeding molten material through a minimum width of a first gap defined between a first roller and a second roller of a first pair of rollers while adjusting the minimum width of the first gap. A first pool of molten material may be formed upstream from the minimum width of the first gap. A ribbon of molten material can exit the first gap. The method can include passing the ribbon of molten material through a minimum width of a second gap defined between a first roller and a second roller of a second pair of rollers. The minimum width of the first gap can be greater than the minimum width of the second gap. A second pool of molten material can be formed upstream from the minimum width of the second gap. 
     In some embodiments, a method of manufacturing glass ribbon can comprise feeding molten material through a minimum width of a first gap defined between a first roller and a second roller of a first pair of rollers without contacting at least the first roller of the first pair of rollers. A first pool of molten material can be formed upstream from the minimum width of the first gap. A ribbon of molten material can exit the first gap. The methods can further include passing the ribbon of molten material through a minimum width of a second gap defined between a second pair of rollers. The minimum width of the first gap can be greater than the minimum width of the second gap. A second pool of molten material may formed upstream from the minimum width of the second gap. 
     In some embodiments, the second pair of rollers can impart at least one major surface of the ribbon of molten material passing through the second gap with a surface roughness of from 0.5 microns to 100 microns. 
     In some embodiments, the minimum width of the first gap can be from 1 mm to 5 mm. 
     In some embodiments, the minimum width of the second gap can be from 0.5 mm to 2.5 mm. 
     In some embodiments, the ribbon of molten material may not contact at least the first roller of the first pair of rollers when passing through the first gap. 
     In some embodiments, a first fluid cushion can be positioned between the first roller of the first pair of rollers and a first major surface of the ribbon of molten material passing through the first gap. 
     In some embodiments, the ribbon of molten material may not contact the second roller of the first pair of rollers when passing through the first gap. 
     In some embodiments, a second fluid cushion can be positioned between the second roller of the first pair of rollers and a second major surface of the ribbon of molten material passing through the first gap. 
     In some embodiments, the methods may further comprise adjusting the minimum width of the first gap while passing the ribbon of molten material through the minimum width of the first gap. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects and advantages are better understood when the following detailed description is read with reference to the accompanying drawings, in which: 
         FIG. 1  illustrates a perspective view of a glass manufacturing apparatus producing glass ribbon from molten material; 
         FIG. 2  illustrates a perspective view of another glass manufacturing apparatus producing glass ribbon from molten material; 
         FIG. 3  illustrates a sectional view of a first embodiment of the glass manufacturing apparatus of  FIG. 1  along line  3 - 3  of  FIG. 1  and a first embodiment of the glass manufacturing apparatus of  FIG. 2  along line  3 - 3  of  FIG. 2 ; and 
         FIG. 4  illustrates a sectional view of a second embodiment of the glass manufacturing apparatus of  FIG. 1  along line  3 - 3  of  FIG. 1  and a second embodiment of the glass manufacturing apparatus of  FIG. 2  along line  3 - 3  of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments will now be described more fully hereinafter with reference to the accompanying drawings in which example embodiments are shown. Whenever possible, the same reference numerals are used throughout the drawings to refer to the same or like parts. However, this disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. 
       FIGS. 1 and 2  each illustrate alternative embodiments of a glass manufacturing apparatus  101 ,  201  for manufacturing a glass ribbon  103 . The glass manufacturing apparatus  101 ,  201  can include a molten material delivery conduit  117  that can include an outlet port  119  to dispense molten material  105 ,  205  to a first pair of rollers  107 ,  207 . In some embodiments, as shown in  FIG. 1 , the outlet port  119  can include a flared end portion  121  to cause the stream of molten material  105  flow downwardly in an elongated stream of molten material. Alternatively, as shown in  FIG. 2 , the outlet port  119  may deliver a circular cylindrical stream of molten material  205  although an elliptical cylindrical or other shaped stream of molten material may also be provided. 
     Unless otherwise noted, the first pair of rollers  107  can be identical structurally and/or functionally to the second pair of rollers  207 . As such, unless otherwise noted, discussion of features and/or functionality of one of the pairs of rollers  107 ,  207  can apply to the other of the pairs of rollers  107 ,  207 . As shown in  FIG. 1 , the first pair of rollers  107  can include a first roller  109   a  and a second roller  109   b.  In some embodiments, each roller  109   a,    109   b  can comprise a circular cylindrical roller and can include identical outer diameters. Furthermore, as shown, in some embodiments, each roller  109   a,    109   b  can be identical to one another. 
     In some embodiments, one or more motors (not shown) may rotate the rollers  109   a,    109   b  in opposite rotation directions  117   a,    117   b  about corresponding rotation axes  119   a,    119   b.  For instance, as shown in  FIG. 3 , in one embodiment, the first roller  109   a  of the first pair of rollers  107  can be a rear side roller that rotates in a clockwise rotation direction  117   a  about a first rotation axis  119   a.  As further shown in  FIG. 3 , the second roller  109   b  of the first pair of rollers  107  can be a front side roller that rotates in a counterclockwise rotation direction  117   b  about a second rotation axis  119   b.    
     As shown in  FIG. 3 , a first gap G 1  can be defined between the first roller  109   a  and the second roller  109   b  of the first pair of rollers  107 . A minimum width “W 1 ” of the first gap “G 1 ” can be defined between the points of each roller  109   a,    109   b  that are closest to one another. As shown in  FIG. 3 , in some embodiments, the planes  303   a,    303   b  of tangency at the closest points may be parallel to one another such that the minimum width “W 1 ” is the same across the entire length “L” (see  FIG. 1 ) of the pair of rollers  109   a,    109   b.  In such embodiments, the resulting ribbon  301  of molten material may have a substantially constant thickness across the width of the resulting ribbon  301 . Although not shown, in some embodiments, the minimum width may not occur across the entire length “L”. For instance, the minimum width may be located at outer end portions of the rollers such that the resulting ribbon  301  of molten material may have a relatively thick central portion that tapers to each end edge of the ribbon  301  in the direction of the width of the ribbon  301  of molten material. 
     Furthermore, the planes  303   a,    303   b  of tangency may extend in the draw direction  305  of the ribbon  301  of molten material that, in some embodiments, may be the direction of gravity. Furthermore, as shown, the velocity of points of tangency of each roller  109   a,    109   b,  due to rotation of the rollers in rotational directions  117   a,    117   b,  may be identical to one another and extend in the draw direction  305  (e.g., the direction of gravity). 
     In some embodiments, the minimum width “W 1 ” of the first gap “G 1 ” is from about 1 millimeter (mm) to about 5 mm. In further embodiments, the minimum width “W 1 ” of the first gap “G 1 ” is from about 2 mm to about 4 mm. In still further embodiments, the minimum width “W 1 ” of the first gap “G 1 ” is from about 2 mm to about 3 mm although other minimum widths may be provided in further embodiments. Moreover, one or both of the rollers  109   a,    109   b  of the first pair of rollers  107  may be adjustable to adjust the minimum width “W 1 ”. For instance,  FIG. 3  illustrates that each roller  109   a,    109   b  may be adjusted along an adjustment direction arrows indicated at reference number  306 . In some embodiments, the adjustment direction may be in the direction of the minimum width “W 1 ” and/or in a direction perpendicular to the draw direction  305  (e.g., perpendicular to gravity). In some embodiments, adjustment of the first gap “G 1 ” can provide an adjusted minimum width “W 1 ” of from 1 mm to 5 mm, from 2 mm to 4 mm, or from 2 mm to 3 mm although other adjusted minimum widths may be provided in further embodiments. 
     As shown in  FIG. 3 , any of the rollers of the disclosure can include an optional cooling coil  307  to allow adjustment of cooling of the molten material passing through the gaps of the pairs of rollers. As such, the temperature of the molten material can be adjusted to provide desirable attributes to the glass ribbon  103 . 
     As shown in  FIGS. 1 and 3 , in some embodiments, each roller  109   a,    109   b  of the first pair of rollers  107  may include a smooth outer surface  123  and/or comprise an outer surface  123  that is impermeable to fluid. In alternative embodiments, the outer surface may comprise a patterned or other non-smooth surface. Furthermore, some embodiments may provide an outer surface that is permeable to fluid. For instance, as shown in  FIG. 4 , each roller  209   a,    209   b  can include passages  405  to allow passage of fluid such as gas (e.g., air, nitrogen, inert gas) as indicted by exiting fluid streams  407 . As shown, the passages  405  can comprise apertures through an outer wall  409  of the rollers  209   a,    209   b.  In further embodiments, the passages may comprise paths between a porous wall (e.g., resulting from sintering to produce the roller). 
     The glass manufacturing apparatus can also include a second pair of rollers  111 . Unless otherwise noted, the first pair of rollers  107 ,  207  can be identical structurally and/or functionally to the second pair of rollers  111 . As such, unless otherwise noted, discussion of features and/or functionality of one of the pairs of first rollers  107 ,  207  and the second pair of rollers  111  can apply to the other of the pairs of rollers  107 ,  207  and the second pair of rollers  111 . As shown in  FIG. 1 , the second pair of rollers  111  can include a first roller  113   a  and a second roller  113   b.  In some embodiments, each roller  113   a,    113   b  can comprise a circular cylindrical roller and can include identical outer diameters. Furthermore, as shown, in some embodiments, each roller  113   a,    113   b  can be identical to one another. 
     As shown in  FIG. 1 , in some embodiments, each roller  113   a,    113   b  of the second pair of rollers  111  may include a textured outer surface  124  although only one of the rollers  113   a,    113   b  may be provided with the textured outer surface  124  in further embodiments. Still further, although not shown, the outer surface may optionally comprise a smooth surface. Providing a textured outer surface  124  can allow the second pair of rollers  111  to imprint at least one major surface  403   a,    403   b  of the ribbon  301  of molten material passing through a second gap “G 2 ” with a surface roughness of from 0.5 microns to 100 microns. 
     In some embodiments, as shown in  FIG. 3 , one or more motors (not shown) may rotate the rollers  113   a,    113   b  in opposite rotation directions  117   a,    117   b  about corresponding rotation axes  120   a,    120   b.  For instance, as shown in  FIG. 3 , in one embodiment, the first roller  113   a  of the second pair of rollers  111  can be a rear side roller that rotates in a clockwise rotation direction  117   a  about a first rotation axis  120   a.  As further shown in  FIG. 3 , the second roller  113   b  of the second pair of rollers  111  can be a front side roller that rotates in a counterclockwise rotation direction  117   b  about a second rotation axis  120   b.    
     As shown in  FIG. 3 , a second gap G 2  can be defined between the first roller  113   a  and the second roller  113   b  of the second pair of rollers  111 . A minimum width “W 2 ” of the second gap “G 2 ” can be defined between the points of each roller  113   a,    113   b  that are closest to one another. As shown in  FIG. 3 , in some embodiments, the planes  304   a,    304   b  of tangency at the closest points may be parallel to one another such that the minimum width “W 2 ” is the same across the entire length “L” (see  FIG. 1 ) of the rollers  113   a,    113   b.  In such embodiments, the resulting ribbon  301  of molten material may have a substantially constant thickness across the width of the resulting glass ribbon  103 . Although not shown, in some embodiments, the minimum width may not occur across the entire length “L”. For instance, the minimum width may be located at outer end portions of the rollers such that the resulting glass ribbon  103  may have a relatively thick central portion that tapers to each end edge of the glass ribbon  103  in the direction of the width of the glass ribbon  103 . 
     Furthermore, the planes  304   a,    304   b  of tangency may extend in the draw direction  305  of the ribbon  301  of molten material that, in some embodiments, may be the direction of gravity. Furthermore, as shown, the velocity of points of tangency of each roller  113   a,    113   b,  due to rotation of the rollers in rotational directions  117   a,    117   b,  may be identical to one another and extend in the draw direction  305  (e.g., the direction of gravity). 
     In some embodiments, the minimum width “W 1 ” of the first gap “G 1 ” can be greater than the minimum width “W 2 ” of the second gap “G 2 ”. In some embodiments, minimum width “W 2 ” of the second gap “G 2 ” can be from 0.5 mm to 2.5 mm, or from 0.5 mm to 2 mm, or from 0.5 mm to 1 mm although other minimum widths may be provided in further embodiments. Moreover, one or both of the rollers  113   a,    113   b  of the second pair of rollers  111  may be adjustable to adjust the minimum width “W 2 ”. For instance,  FIG. 3  illustrates that each roller  113   a,    113   b  may be adjusted along an adjustment direction arrows indicated at reference number  306 . In some embodiments, the adjustment direction may be in the direction of the minimum width “W 2 ” and/or in a direction perpendicular to the draw direction  305  (e.g., perpendicular to gravity). In some embodiments, adjustment of the second gap “G 2 ” can provide an adjusted minimum width “W 2 ” of from 0.5 mm to 2.5 mm. In further embodiments, adjustment of the second gap “G 2 ” can provide an adjusted minimum width “W 2 ” of from 0.5 mm to 2 mm. In still further embodiments, adjustment of the second gap “G 2 ” can provide an adjusted minimum width “W 2 ” of from 0.5 mm to 1 mm. 
     Example methods of manufacturing glass ribbon  103  can feed molten material molten material  105 ,  205  through a minimum width “W 1 ” of a first gap “G 1 ” defined between the first roller  109   a,    209   a  and the second roller  109   b,    209   b  of the first pair of rollers  107 ,  207 . As shown in  FIG. 1 , some embodiments may flare the molten material outwardly (e.g., with flared end portion  121 ) such that the molten material  105  is elongated in the direction of the length of the first gap “G 1 ”. Flaring the molten material outwardly can facilitate initial placement and subsequent flow of the molten material along the upper portion of the first gap “G 1 ” before reaching the minimum width “W 1 ” of the first gap “G 1 ”. Alternatively, as shown in  FIG. 2 , some embodiments may allow a flow of molten material to be introduced into the upper portion of the first gap “G 1 ” with a nonflared flow of molten material  205 . For instance, the molten material may simply flow from the outlet port  119  (e.g., circular outlet port) to be introduced into the upper portion of the first gap “G 1 ”. In such embodiments, the molten material may still have time to quickly flow along a length of the first gap “G 1 ” before reaching the minimum width “W 1 ” of the first gap “G 1 ” due to the relatively low viscosity of the molten material  205 . 
     In some embodiments, the methods may include adjusting the minimum “W 1 ” width of the first gap “G 1 ” while passing a ribbon  301  of molten material through the minimum width “W 1 ” of the first gap “G 1 ”. For example, actuators (not shown) may increase or decrease the minimum width “W 1 ” of the first gap “G 1 ” by moving one or both of the first roller  109   a  and second roller  109   b  of the first pair of rollers  107  in alternative directions as shown by reference number  306 . Adjustment of the minimum width “W 1 ” of the first gap “G 1 ” can control the flow of material through the first gap “G 1 ” to be received by the second gap “G 2 ” of the second pair of rollers  111 . 
     The flow of material  105 ,  205  flows at a rate fast enough that a first pool  115   a  of molten material is formed upstream from the minimum width “W 1 ” of the first gap “G 1 ”. In some embodiments the first pool  115   a  of molten material can quickly spread along a length of the first gap “G 1 ” due to the relatively low viscosity of the molten material within the first pool  115   a.  In some embodiments, the viscosity of the molten material within the first pool  115   a  can be from about 5 Poises to about 5,000 Poises. In another embodiment, the first pool  115   a  can have a viscosity of from about 500 Poises to about 2,000 Poises to allow quick spreading of the molten material along a length of the first gap “G 1 ”. 
     For purposes of this application, “pool of molten material” is considered a reservoir of accumulated molten material positioned upstream from the minimum width of the corresponding gap between the pair of rollers that can exist at a steady state where the mass flow rate of the molten material entering the first gap equals the mass flow rate of the molten material of the ribbon exiting the gap. The reservoir of accumulated molten material permits consistent continuous feeding of molten material to the minimum width of the gap even during an interruption or other inconsistency in the mass flow rate of the material being fed to the gap. For example, a momentary abrupt reduction in the mass flow rate of the material being fed to the gap may be compensated by the pool of molten material as accumulated molten material within the pool of molten material may be used to counter the short abrupt reduction in the mass flow rate of molten material being fed to the gap; thereby maintaining thickness uniformity in the ribbon exiting the gap. During such an event, the mass of molten material within the pool of molten material may be reduced. Nonetheless, the depleted molten material within the pool of molten material may be replenished once the flow rate returns to normal and steady state is again achieved. 
     As such, the first pool of material  115   a  can comprise a reservoir of accumulated molten material positioned upstream from the minimum width “W 1 ” of the first gap “G 1 ” between the first pair of rollers  107 ,  207  that can exist at a steady state where the mass flow rate of the molten material  105 ,  205  entering the first gap “G 1 ” equals the mass flow rate of molten material of the ribbon  301  exiting the first gap “G 1 ”. 
     As shown in  FIG. 4 , in some embodiments, the first pool of material  115   a  and/or the ribbon  301  of molten material does not contact at least the first roller  209   a  of the first pair of rollers  207  when passing through the first gap “G 1 ”. For instance, as shown, a first fluid cushion  401   a  may be positioned between the first roller  209   a  of the first pair of rollers  207  and a first major surface  403   a  of the ribbon  301  of molten material passing through the first gap “G 1 ”. Furthermore, as shown the first fluid cushion  401   a  may also be positioned between the first roller  209   a  of the first pair of rollers  207  and the first pool of material  115   a.    
     As further shown in  FIG. 4 , in some embodiments, the first pool of material  115   a  and/or the ribbon  301  of molten material does not contact the second roller  209   b  of the first pair of rollers  207  when passing through the first gap “G 1 ”. For instance, as shown, a second fluid cushion  401   b  may be positioned between the second roller  209   b  of the first pair of rollers  207  and a second major surface  403   b  of the ribbon  301  of molten material passing through the first gap “G 1 ”. Furthermore, as shown the second fluid cushion  401   b  may also be positioned between the second roller  209   b  of the first pair of rollers  207  and the first pool of material  115   a.    
     The fluid cushions  401   a,    401   b  can be produced in some embodiments with pressurized fluid within the hollow interior being emitted through the outer wall  409  such that the molten material is pushed away from contacting the first pair of rollers  207 . Preventing contact between the molten material and the rollers  207  can help reduce loss of heat to the rollers as the molten material passes through the first gap “G 1 ” since the fluid cushion does not transfer heat as quickly as direct contact with the rollers  207 . In addition to the fluid cushions  401   a,    401   b,  the first roller  209   a  and second roller  209   b  of the first pair of rollers  207  may continuously rotate along rotation directions  117   a,    117   b  to provide a uniform temperature distribution and the capability to maintain the first and second rollers  209   a,    209   b  at a desired operating temperature. 
     The ribbon  301  of molten material may then pass through the minimum width “W 1 ” of the first gap “G 1 ” of the first pair of rollers  107 ,  207  and fall to the second pair of rollers  111  underlying the first pair of rollers  107 ,  207 . As shown, in some embodiments, the first gap “G 1 ” and second gap “G 2 ” may be aligned along a vertical plane in the draw direction  305  (e.g., direction of gravity). Thus, as shown, the ribbon  301  of molten material may travel in the draw direction  305  to the second gap “G 2 ” of the second pair of rollers  111 . The ribbon  301  of molten material may then pass through the minimum width “W 2 ” of the second gap “G 2 ” defined between the first roller  113   a  and the second roller  113   b  of the second pair of rollers  111 . In some embodiments, the second gap “G 2 ” have a minimum width “W 2 ” (e.g., from 0.5 mm to 2.5 mm) that is less than the minimum width “W 1 ” (e.g., from 1 mm to 5 mm) of the first gap “G 1 ”. Consequently, the thickness of the ribbon  301  of molten material may be reduced to the glass ribbon  103  with a thickness (e.g., from 0.5 mm to 2.5 mm) that may match the minimum width “W 2 ” of the second gap “G 2 ”. 
     A second pool  115   b  of molten material may be formed upstream from the minimum width “W 2 ” of the second gap “G 2 ”. The second pool  115   a  of molten material can comprise a reservoir of accumulated molten material positioned upstream from the minimum width “W 2 ” of the second gap “G 2 ” between the second pair of rollers  111  that can exist at a steady state where the mass flow rate of the ribbon  301  of molten material entering the second gap “G 2 ” equals the mass flow rate of glass ribbon  103  exiting the second gap “G 2 ”. 
     The viscosity of the molten material within the second pool  115   b  of molten material can be from about 10,000 Poises to about 100,000 Poises. In another embodiment, the viscosity of the molten material within the second pool  115   b  of molten material can be from about 10,000 Poises to about 50,000 Poises. These viscosity ranges still permit pooling of molten material to allow consistent feeding of molten material through the minimum width “W 2 ” of the second gap “G 2 ”. 
     As mentioned previously, the first roller  113   a  and/or the second roller  113   b  can include a textured outer surface  124 . In such embodiments, the second pair of rollers  111  can impart at least one or both major surfaces of the glass ribbon  103  passing through the gap “G 2 ” with a surface roughness. Furthermore, providing the second pool  115   b  of molten material ensures continuous stamping of the major surface(s) of the ribbon  301  of molten material to provide a consistent corresponding surface roughness corresponding to the textured outer surface  124 . In some embodiments the surface roughness can be from 0.5 microns to 100 microns. Providing one or both major surfaces with a surface roughness (e.g., from 0.5 microns to 100 microns) can allow stacking of sheets separated from the glass ribbon  103  without undesired bonding between the sheets that might otherwise occur with smooth-surfaced glass sheets that are stacked together. 
     The manufacturing apparatus  101  and methods of manufacturing glass ribbon  103  discussed throughout the disclosure can allow for production of thin sheets of glass ribbon  103  produced from a glass composition that may be delivered at low viscosities and/or a glass composition that sets relatively slowly. For instance, some glass ceramic precursors used to make strengthened glass can exhibit low liquidus viscosities that benefit from the present apparatus and methods that accommodate molten material with relatively low viscosities. In some embodiments, each pair of rollers  107 ,  111  can catch molten material falling from above and form respective first and second pools  115   a,    115   b  of molten material; thereby controlling the drawing process to generate a thin glass ribbon with a thickness from 0.5 mm to 2.5 mm, or from 0.5 mm to 2 mm, or from 0.5 mm to 1 mm although other thicknesses may be provided in further embodiments. In some embodiments, the first pair of rollers  107 ,  207  can pre-shape the flow of molten material and modify its average viscosity. 
     Furthermore, in some embodiments, the minimum width “W 1 ” of the first gap “G 1 ” of the first pair of rollers  107 ,  207  may be adjusted to change the thickness and/or temperature distribution of the ribbon  103  of molten material exiting the first gap “G 1 ”. Furthermore, adjustment of the minimum width “W 1 ” of the first gap “G 1 ” can be used to quickly compensate for some temperature of flow variation for the delivery system that can have a longer response time to correct. Still further, adjustment of the minimum width “W 1 ” of the first gap “G 1 ” and the rotational speed differential between the first pair of rollers  107  and second pair of rollers  207 , it may be possible to adjust the width of the ribbon  301  and average viscosity of the molten material being introduced to the second pair of rollers  207 . These adjustments can be useful to address a variety of conditions such as increased flow density, decreased viscosity at the delivery, and cases where glass viscosity increases slowly. 
     It should be understood that while various embodiments have been described in detail with respect to certain illustrative and specific examples thereof, the present disclosure should not be considered limited to such, as numerous modifications and combinations of the disclosed features are possible without departing from the scope of the following claims.