Patent Publication Number: US-2015068266-A1

Title: Positive stop systems and methods for extrusion press

Description:
BACKGROUND 
     Deformation is the process of forcing a piece of material to permanently change its thickness or shape, and some deformation techniques include forging, rolling, extruding, and drawing. Deformation of a material typically generates heat. In the context of extrusion processes, excess heat at the interface between two components can contribute to wear and result in the production of flash, where flash is the undesirable passage of the extrusion material through clearance spaces between the two components. Present systems thus have limited operational run times because of the generation of excess heat and associated problems. 
     SUMMARY 
     Disclosed herein are systems, devices, and methods for extruding a material. In certain embodiments, the systems, devices, and methods include a positive stop between the extrusion die and a component positioned against the extrusion die. In certain embodiments, the extrusion die is a rotating extrusion die. The positive stops may reduce and/or eliminate the occurrence of flash at an interface between the extrusion die and the component. For example, the positive stops may reduce the amount of heat at the interface. In some embodiments the component is a centering insert that guides a material to be extruded into the rotating extrusion die. 
     In one aspect, the systems, devices, and methods include an extrusion press system comprising an extrusion die supported by a first support structure, a centering insert supported by a second support structure, wherein the centering insert guides a material to be extruded into the extrusion die, and a positive stop coupled to the first support structure and extending towards the second support structure, wherein the positive stop defines a travel distance between the first support structure and the second support structure. In certain implementations, the extrusion die rotates within the first support structure, and the centering insert is positioned against the extrusion die and does not rotate. The centering insert may include gripping features that frictionally engage the material to be extruded and thereby prevent the material from rotating while engaged and as the material enters the rotating extrusion die. In certain implementations, the extrusion press system further comprises a second positive stop. 
     In certain implementations, the first support structure is stationary, the second support structure is configured to move relative to the first support structure, and movement of the second support structure towards the first support structure is limited by the positive stop to the travel distance. In certain implementations, the centering insert is a consumable part that is partially consumed when the second support structure moves towards the first support structure a distance of the travel distance. In certain implementations, the travel distance is between about zero inches and about 100/1000 inch. In certain implementations, the travel distance is between about 10/1000 inch and about 50/1000 inch. In certain implementations, the travel distance is between about 10/1000 inch and about 30/1000 inch. In certain implementations, the travel distance is about 20/1000 inch. 
     In certain implementations, the positive stop is configured to adjust the travel distance. For example, the positive stop may include an adjustable portion that rotates about a threaded shaft for increasing or decreasing the travel distance. In certain implementations, the positive stop comprises an adjustable portion that slides along a shaft for increasing or decreasing the travel distance. In certain implementations, the positive stop comprises a recess configured to mate with a plurality of end portions, each respective end portion having a respective thickness for increasing or decreasing the travel distance. In certain implementations, the positive stop further comprises a through-hole into which a locking pin is positioned. 
     In one aspect, a method for extruding a material is provided that includes positioning a centering insert in a first position against an extrusion die, exerting a force on the centering insert to maintain a desired pressure of the centering insert against the extrusion die, wherein the force moves the centering insert from the first position to a second position, and preventing further movement of the centering insert at the second position. In certain implementations, upon preventing further movement, a pressure of the centering insert against the extrusion die decreases relative to the desired pressure. In certain implementations, the force continues to be exerted while movement of the centering insert is prevented at the second position. In certain implementations, a distance between the first position and the second position defines a travel distance. In certain implementations, the method further includes adjusting the travel distance. In certain implementations, the extrusion die rotates, and the centering insert does not rotate. 
     In one aspect, an extrusion press system is provided that comprises extrusion means supported by a first support structure, guiding means for guiding a material to be extruded into the extrusion means, the guiding means supported by a second support structure, and means for limiting movement of the second support structure with respect to the first support structure. In certain implementations, the extrusion means rotates within the first support structure, and the guiding means is positioned against the extrusion means and does not rotate. The guiding means may include gripping features that frictionally engage the material to be extruded and thereby prevent the material from rotating while engaged and as the material enters the rotating extrusion means. In certain implementations, the extrusion press system further comprises a second means for limiting movement of the second support structure with respect to the first support structure. 
     In certain implementations, the first support structure is stationary, the second support structure is configured to move relative to the first support structure, and movement of the second support structure towards the first support structure is limited by the limiting means to a travel distance. In certain implementations, the guiding means comprises a consumable part that is partially consumed when the second support structure moves towards the first support structure a distance of the travel distance. In certain implementations, the travel distance is between about zero inches and about 100/1000 inch. In certain implementations, the travel distance is between about 10/1000 inch and about 50/1000 inch. In certain implementations, the travel distance is between about 10/1000 inch and about 30/1000 inch. In certain implementations, the travel distance is about 20/1000 inch. 
     In certain implementations, the limiting means is configured to adjust a travel distance. For example, the limiting means may include an adjustable portion that rotates about a threaded shaft for increasing or decreasing the travel distance. In certain implementations, the limiting means comprises an adjustable portion that slides along a shaft for increasing or decreasing the travel distance. In certain implementations, the limiting means comprises a recess configured to mate with a plurality of end portions, each respective end portion having a respective thickness for increasing or decreasing the travel distance. In certain implementations, the limiting means further comprises a through-hole into which a locking pin is positioned. 
     Variations and modifications of these embodiments will occur to those of skill in the art after reviewing this disclosure. The foregoing features and aspects may be implemented, in any combination and subcombination (including multiple dependent combinations and subcombinations), with one or more other features described herein. The various features described or illustrated herein, including any components thereof, may be combined or integrated in other systems. Moreover, certain features may be omitted or not implemented. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other objects and advantages will be apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout, and in which: 
         FIG. 1  shows a schematic side elevation view of illustrative positive stops in an extrusion press system according to certain embodiments; 
         FIGS. 2-4  show various side elevation views of illustrative adjustable positive stops for the extrusion press system of  FIG. 1  according to certain embodiments; and 
         FIG. 5  shows a side elevation view of an illustrative extrusion press system that includes positive stops according to certain embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     To provide an overall understanding of the systems, devices, and methods described herein, certain illustrative embodiments will be described. Although the embodiments and features described herein are specifically described for use in connection with extrusion press systems, it will be understood that all the components, connection mechanisms, manufacturing methods, and other features outlined below may be combined with one another in any suitable manner and may be adapted and applied to systems to be used in other manufacturing processes, including, but not limited to cast-and-roll, up-casting, other extrusion, and other manufacturing procedures. Furthermore, although certain embodiments described herein relate to extruding metal tubing from hollow billets, it will be understood that the systems, devices, and methods herein may be adapted and applied to systems for extruding any suitable type of product. 
     The extrusion press system operates using frictional heat generated from a non-rotating hollow billet contacting a rotating die to facilitate deformation and extrusion of the billet. There is thus no requirement of pre-heating the billets or the rotating die before the extrusion. The amount of heat generated is generally determined by the rate at which the billets are fed into the rotating die (e.g., controlled by the press-ram speed of the press-ram elements  130 ,  140  of  FIG. 5 ) and the rotation speed of the die (e.g., controlled by the rotation speed of the spindle  172  of  FIG. 5 ), as well as the interior profile of the rotating die. Higher press-ram speeds and spindle rotation speeds generate relatively greater amounts of heat. 
     The rotating die forms the outer diameter of an extruded tube produced by the extrusion press system, and a mandrel bar tip positioned within the rotating die forms the inner diameter of the extruded tube. In certain embodiments, chilled process water, or any other suitable cooling fluid, is used to cool the process elements including the rotating die, the centering insert, the billets, and the gear box oil, as well as the extruded tubing product. Unlike conventional extrusion techniques, the extrusion press system of the present disclosure does not require any container within which to hold the billet for extrusion. Therefore the billets to be extruded preferably have sufficient column strength to withstand the pressure applied by the press-ram elements during the extrusion process. A programmable logic controller, or PLC, controls all or a subset of movements of the extrusion press system while the system is set in automatic mode. 
       FIG. 1  shows a schematic side elevation view of positive stops  30 ,  40  in an extrusion press system  5  according to certain embodiments. The extrusion press system  5  includes an extrusion die  10  supported by a die-backer plate or support structure  12 . In some embodiments, the extrusion die  10  rotates within the support structure  12 . For example, the extrusion die  10  may be coupled to a spindle (e.g., spindle  172  of  FIG. 5 ) operated by a motor. A centering insert  20  is positioned against the extrusion die  10  and supported by a platen or support structure  22 . The centering insert  20  guides a material to be extruded into the extrusion die  10 . For example, the centering insert  20  is hollow along its length so that the material to be extruded passes through the centering insert  20  before entering the extrusion die  10 . The centering insert  20  preferably does not rotate. In some embodiments, the centering insert  20  has one or more gripping features (e.g., teeth, grooves, or other detents) that frictionally engage the material to be extruded and thereby prevent the material from rotating while engaged. 
     As shown in  FIG. 1 , a positive stop  30  is coupled to the first support structure  12  and extends towards the second support structure  22 , with a gap  34  of distance d 1  between a contact surface  30   a  of the positive stop  30  and a contact surface  22   a  of the second support structure  22 . During operation, the first support structure  12  is stationary and the second support structure  22  moves relative to the first support structure  12 . For example, one or more piston/cylinder drive units may be coupled to the support structure  22  to advance and optionally retract the structure. In certain embodiments, the second support structure  22  moves in a direction towards the first support structure  12  (along arrow A) and a direction away from the first support structure (opposite arrow A). The positive stop  30  therefore defines a travel distance d 1  between the respective support structures  12 ,  22 . Although the positive stop  30  is shown as coupled to and extending from the first support structure  12  towards the second support structure  22 , other configurations may be used. For example, in some embodiments, a positive stop may be coupled to the second support structure  22  and extend towards the first support structure  12 , with a gap between respective contact surfaces of the positive stop and first support structure  12 . Any suitable arrangement for preventing motion of one (or more) of the support structures may be used. 
     The movement of the second support structure  22  towards the first support structure  12  is limited by the positive stop  30  to the travel distance d 1 . That is, the positive stop  30  acts as a physical stop or barrier to the movement of the support structure  22 . During operation, for example, the centering insert  20  is positioned against the extrusion die  10  as shown in  FIG. 1 . From that position, the second support structure  22  can move (together with the centering insert  20 ) towards the first support structure  12  by a distance up to the travel distance d 1 . For example, in some embodiments, the centering insert  20  is a consumable part that is partially consumed when the second support structure  22  moves towards the first support structure  12  by a distance up to the travel distance. In some embodiments, whether or not any components are consumable, compression of the respective components (e.g., the adjacent die  10 /insert  20 ) allows for movement of the support structure  22  by a distance up to the travel distance. 
     As discussed above, the extrusion die  10  may be a rotating extrusion die, and the centering insert does not rotate, but serves to guide a material to be extruded into the rotating extrusion die. The centering insert  20  is positioned against the extrusion die  10  to minimize any clearance between the two components. A force is exerted on the centering insert  20  (e.g., by way of the support structure  22 ) to maintain a desired pressure of the centering insert  20  against the extrusion die  10  during operation. This applied pressure maintains a seal between the two components. It is desirable to spread the work done by the extrusion die across the length of the die to avoid the generation of excess heat at the entrance of the extrusion die. In some embodiments, however, the amount of pressure applied can cause undesirable heat generation at the interface of the centering insert  20  and the extrusion die  10  (e.g., because the extrusion die  10  rotates and the centering insert  20  does not rotate). Such heat can prematurely heat the material being extruded as it enters the die, causing a “flash” of the material, where flash is the undesirable passage of the extrusion material through clearance spaces between the extrusion die and the centering insert. 
     The positive stop  30  reduces flash and/or other undesirable heat generated at the entrance of the die by preventing movement of the centering insert relative to the rotating extrusion die after a given amount of travel. For example, the force exerted on the centering insert  20  can move the centering insert  20  along the direction of arrow A from a first position (e.g., shown in  FIG. 1 ) to a second position (e.g., displacement of travel distance d 1 ). At the second position, the positive stop  30  prevents further movement of the centering insert  20  (notwithstanding, in some embodiments, the continuous application of force at that position). Any suitable travel distance may be used in the extrusion press systems of the present disclosure, including, for example, a travel distance of zero when the positive stop is positioned against the centering insert. In some embodiments, the travel distance is between zero inches and 100/1000 inch. In some embodiments, the travel distance is between 10/1000 inch and 50/1000 inch. In some embodiments, the travel distance is between 10/1000 inch and 30/1000 inch. For example, a travel distance of 20/1000 inch has been used in extrusion press systems for the continuous and uninterrupted extrusion of materials. 
     When the centering insert  20  reaches the second position and further movement is prevented, the pressure of the centering insert  20  against the extrusion die  10  decreases relative to the pressure exerted while the centering insert  20  was moving. This decreased pressure is enough to allow for continuous extrusion of a material (e.g., there is a sufficient seal between the centering insert and the extrusion die), yet reduced enough to prevent the generation of excess heat that can lead to unwanted flash. Moreover, this decreased pressure can increase the life of various components of the extrusion press system  5 . For example, the centering insert  20  is typically a consumable part, and during operation, portions of the extrusion die  10  may also be consumed. Absent a positive stop, the force exerted on the centering insert  20  to maintain pressure on the extrusion die  10  may cause a substantial portion of the centering insert  20  and/or extrusion die  10  to be consumed as a result of frictional contact, in some cases leading to a halt in the extrusion process to replace the part(s). Limiting the travel distance of the centering insert, however, allows for minimal, if any, consumption of the part(s). In certain embodiments, some consumption of the centering insert and/or extrusion die  10  is desirable because controlled heat deformation of the centering insert and/or extrusion die  10  at the interface with the die may contribute to the seal between the rotating extrusion die and the non-rotating centering insert. 
     In some embodiments, a single positive stop may be used to limit the movement of a support structure. In some embodiments, more than one positive stop may be used to limit the movement of a support structure. For example, as shown in  FIG. 1 , a second positive stop  40  in the extrusion press system  5  is coupled to the first support structure  12  and extends towards the second support structure  22 , with a gap  36  of distance d 2  between a contact surface  40   a  of the positive stop  40  and a contact surface  22   b  of the second support structure  22 . The contact surfaces  22   a / 22   b  of the second support structure  22  are shown as being part of the same planar surface  22   c  of the support structure, although any surfaces could be used, so long as the gap distances d 1  and d 2  (e.g., the amount of travel) are preferably the same. This prevents the positive stops  30 ,  40  from causing different portions of the structure to move different amounts. For example, in some embodiments, the two positive stops  30 ,  40  may have different respective lengths, yet the allowed travel distances d 1  and d 2  are the same. Although two positive stops  30 ,  40  are depicted, it will be understood that any suitable number of positive stops may be provided to limit the travel distance of a support structure. Furthermore, the positive stops may be provided in any suitable arrangement. For example, in a system having three positive stops, each of the positive stops may be spaced about the extrusion die  10  in a generally triangular pattern. 
     In some embodiments, the travel distance (e.g., travel distance d 1  and d 2 ) may be adjusted prior to or during operation of the extrusion press system  5 . For example, prior to operation, the positive stops  30 ,  40  may be removed and replaced with positive stops allowing a different respective travel distance. In some embodiments, prior to or during operation, the positive stops are configured to adjust the travel distance. As shown in  FIG. 2 , a positive stop  300  includes a first portion  302  and a second portion  304 . The second portion  304  is an adjustable portion that, when adjusted, changes the respective travel distance allowed by the positive stop  300 . For example, the adjustable portion  304  can rotate about a threaded shaft  306  to increase or decrease the travel distance allowed by the contact surface  304   a  of the positive stop  300 . There are many variations of positive stops having an adjustable portion. For example, as shown in  FIG. 3 , a positive stop  310  includes a first portion  312  and a second portion  314 . The second portion  314  is an adjustable portion that, when adjusted, changes the respective travel distance allowed by the positive stop  310 . The adjustable portion  314  can slide along a shaft  316  to any position along the shaft. In some embodiments, the shaft  316  has a plurality of holes  317  that align with a respective through-hole  319  in the adjustable portion  314 . When aligned, a locking pin  318  may be placed within the through-hole  319  to secure the adjustable portion  314  in place with the hole  317 . In some embodiments, a similar locking mechanism may be used with the positive stop  300  discussed above for preventing rotation of the adjustable portion  304 , when locked, about the threaded shaft  306 . 
     In some embodiments, a positive stop is configured to adjust a given travel distance without an adjustable portion. For example, as shown in  FIG. 4 , a positive stop  320  comprises a first portion  322  that optionally receives removable end portions. The first portion  322  has a recess  324  formed in a distal end  322   a  thereof that is configured to mate with a plurality of end portions  326 ,  328 , each respective end portion having a respective thickness for increasing or decreasing the travel distance allowed by the positive stop  320 . End portion  326  has a contact surface  326   a  and a connector  327  that is received within the recess  324 . End portion  328  similarly has a contact surface  328   a  and a connector  329  that is received within the recess  324 . The end portions  326 ,  328  have different respective thicknesses t 1 , t 2  that changes the respective travel distance allowed by the positive stop  320 . When no end portion is used, the positive stop  320  has yet another travel distance allowed by the contact surface  322   a  of the first portion  322 . In some embodiments, a similar locking mechanism to that discussed above in connection with  FIG. 3  may be used with the positive stop  320  for preventing removal, when locked, of the end pieces. 
     As discussed above, the positive stops may be configured to adjust the travel distance during operation of the extrusion press system. In some embodiments, the adjustable portion of the positive stop (e.g., adjustable portions  304 ,  314 ) can be adjusted manually or using the PLC system to change the travel distance without interruption of the extrusion process. Manual adjustment may be done by hand or by using tools to prevent the risk of injury. Adjustment using the PLC system is automatic or in response to an operator request, and may cause the adjustment of adjustable portions that are electro-mechanically controlled (e.g., a piston-cylinder arrangement). Thus adjustment of the travel distance may be done at any time during operation of the extrusion press system. In some embodiments, the travel distance can be increased stepwise during operation. A first travel distance is set and a support structure moves by the first travel distance until it contacts the positive stop. After a suitable amount of time, the travel distance may be increased to a second travel distance, and the support structure again moves until contacting the positive stop. Further stepwise (or continuous) adjustments to the travel distance can be made at any time. This allows an operator to control, throughout the extrusion process, the heat generated at the interface between components of the extrusion press system (e.g., the extrusion die  10  and the centering insert  20 ). 
     The positive stops of the present disclosure (e.g., positive stops  30 ,  40 ,  300 ,  310 ,  320 ) may be used for forming an extruded material in any suitable system including, for example, the extrusion press systems described in U.S. patent application Ser. No. 13/650,977, filed Oct. 12, 2012, the disclosure of which is hereby incorporated by reference herein in its entirety. For example, positive stops  154 ,  156  may be incorporated into the extrusion press system of  FIG. 5 , which shows an extrusion press system  200  according to certain embodiments. The extrusion press system  200  includes a mandrel carriage section  280  and a platen structure section  290 . The mandrel carriage section  280  includes a mandrel bar  100 , fluid clamps or cooling elements  102  and  104 , mandrel grips or gripping elements  106  and  108 , and a billet delivery system. The mandrel carriage section  280  is supported by a physical carriage structure, which is not shown in  FIG. 5  to avoid overcomplicating the drawing, but which carriage structure serves as a mount for the components of the mandrel carriage  280 . The platen structure section  290  includes an entry platen  120  and a rear die platen  122 , press-ram platens  130  and  140 , a centering platen  152 , and a rotating die  160  that presses against the rear die platen  122 . The platen structure section  290  is supported by a frame  190  that may also serve as a mount for the motor  170  and related gearbox components (not shown). The direction along which billet loading, transport, and extrusion occurs according to the extrusion press system  10  is denoted by arrow B. The extrusion press system  200  may be operated, at least in part, by a PLC system that controls aspects of the billet delivery subsystem  220 , extrusion subsystem  240 , and quenching or cooling subsystem  260  of the extrusion press system  200 . 
     The mandrel grips  106 ,  108  comprise a mandrel bar gripping system  105  designed to hold the mandrel bar in place while allowing a plurality of billets to be continuously fed along and about the mandrel bar  100  to provide for continuous extrusion. The billets may be formed from any suitable material for use in extrusion press systems including, but not limited to, various metals including copper and copper alloys, or any other suitable non-ferrous metals such as aluminum, nickel, titanium, and alloys thereof, ferrous metals including steel and other iron alloys, polymers such as plastics, or any other suitable material or combinations thereof. The mandrel grips  106 ,  108  may be controlled by the PLC system to securely hold in place and prevent the mandrel bar  100  from rotating such that at any given time during the extrusion process, at least one of the mandrel grips  106 ,  108  is gripping the mandrel bar  100 . The mandrel grips  106 ,  108  set the position of the mandrel bar  100  and prevent the mandrel bar  100  from rotating. When the mandrel grips  106 ,  108  are in a gripping or engaged position, thereby gripping the mandrel bar  100 , the mandrel grips  106 ,  108  prevent billets from being transported along the mandrel bar  100  through the grips. 
     The mandrel grips  106 ,  108  operate by alternately gripping or engaging the mandrel bar  100  to allow one or more billets to pass through a respective mandrel grip at a given time. For example, the upstream mandrel grip  106  may release or disengage the mandrel bar  100  while the downstream mandrel grip  108  is gripping the mandrel bar  100 . At any given time, at least one of the mandrel grips  106 ,  108  is preferably gripping or otherwise engaged with the mandrel bar  100 . One or more billets queued or indexed near the upstream mandrel grip  106 , or being transported along the mandrel bar  100 , may pass through the open upstream mandrel grip  106 . After a specified number of billets has passed through the open upstream mandrel grip  106 , the gripper  106  may close and thereby return to gripping the mandrel bar  100 , and the billets may be advanced to the downstream gripping element  108 . The downstream gripping element  108  may remain closed, thereby gripping the mandrel bar  100 , or the downstream mandrel grip  108  may open after the upstream mandrel grip  106  re-grips the mandrel bar  100 . Although two mandrel grips  106 ,  108  are shown in the extrusion press system  10 , it will be understood that any suitable number of mandrel grips may be provided. 
     The fluid clamps  102 ,  104  comprise a mandrel bar fluid delivery system  101  designed to supply cooling fluid along the interior of the mandrel bar  100  to the mandrel bar tip during the extrusion process. The fluid clamps  102 ,  104  also receive cooling fluid from the mandrel bar  100  that has returned from the mandrel bar tip. Any suitable cooling fluid may be used, including water, various mineral oils, brines, synthetic oils, any other suitable cooling fluid, including gaseous fluids, or any combination thereof. The fluid clamps  102 ,  104  may be controlled by the PLC system to continuously supply process cooling fluid to the mandrel bar during the extrusion process while allowing a plurality of billets to be continuously feed along and about the mandrel bar  100 . The fluid clamps  102 ,  104  operate such that there is no or substantially no interruption to the supply of process cooling fluid to the mandrel bar tip during the extrusion process. Similar to the operation of the mandrel grips  106 ,  108  discussed above, when the fluid clamps  102 ,  104  are clamped to or engaged with the mandrel bar  100 , the fluid clamps  102 ,  104  prevent billets from being transported along the mandrel bar  100  through the fluid clamps. 
     The fluid clamps  102 ,  104  operate such that at any given time during the extrusion at least one of the fluid clamps is clamped to or engaged with the mandrel bar  100  and thereby delivers cooling fluid into the mandrel bar  100  for delivery to the mandrel bar tip. When a billet passes through one of the fluid clamps  102 ,  104 , the respective fluid clamp discontinues delivering (and receiving) cooling fluid and releases or disengages the mandrel bar  100  to allow the billet to pass therethrough before re-clamping the mandrel bar  100  and continuing to deliver (and receive) cooling fluid. While one of the fluid clamps  102 ,  104  is unclamped or disengaged from the mandrel bar  100 , the other fluid clamp continues to deliver cooling fluid to the mandrel bar. 
     For example, the upstream fluid clamp  102  may release the mandrel bar  100  while the downstream fluid clamp  104  is clamped to the mandrel bar  100 . At any given time, at least one of the fluid clamps  102 ,  104  is preferably clamped to the mandrel bar  100  to continuously deliver cooling fluid. One or more billets queued or indexed near the upstream fluid clamp  102 , or being transported along the mandrel bar  100 , may pass through the open upstream fluid clamp  102 . After a specified number of billets has passed through the open upstream fluid clamp  102 , the fluid clamp  102  may close and thereby return to clamping the mandrel bar  100  and delivering cooling fluid, and the billets may be advanced to the downstream fluid clamp  104 . The downstream fluid clamp  104  may remain closed, thereby clamping the mandrel bar  100 , or the downstream fluid clamp  104  may open after the upstream fluid clamp  102  re-clamps to the mandrel bar  100 . Although two fluid clamps  102 ,  104  are shown in the extrusion press system  10 , it will be understood that any suitable number of fluid clamps may be provided. 
     The billet delivery system ensures that a continuous supply of billets is present for the extrusion process. When additional billets are needed, the PLC system will cycle the proper mandrel bar grips  106 ,  108 , fluid clamps  102 ,  104 , and billet delivery rollers to ensure that the billet supply is continuous. The section of the mandrel carriage  280  located between the mandrel grip  106  and the entry platen  120  may continuously index to minimize the gap between billets fed into the ram platen sections  141  of the platen structure  290 . For example, at this location of the mandrel carriage  280 , the track assembly may continuously cycle the track to feed billets into the platen structure  290 . 
     The mandrel bar  100  extends along substantially the length of the extrusion press system  200  and is positioned to place the mandrel bar tip within the rotating die  160 . The adjustment to properly position the mandrel bar tip within the rotating die  160  is accomplished by moving the mandrel carriage section  280 , thus moving the mandrel bar  100 . The adjustments to the mandrel bar  100  and the mandrel carriage section  280  may be towards or away from the die  160 . The mandrel bar  100  and the mandrel carriage section  280  preferably cannot be adjusted while the extrusion press system  200  is in operation, although it will be understood that in certain embodiments the mandrel bar  100  and/or mandrel carriage section  280  may be adjusted during operation. 
     As discussed above, the extrusion press system  200  includes a platen structure section  290  having an entry platen  120  and a rear die platen  122 , press-ram platens  130  and  140 , a centering platen  152 , and a rotating die  160  pressed against the rear die platen  122 . Near the entry platen  120  is the press-ram assembly  141  that includes a first press-ram platen  130  and a second press-ram platen  140 . The first and second press-ram platens  130 ,  140  feed billets into the centering platen  152 , which grips the billets and prevents the billets from rotating prior to entering the rotating die  160 , which presses against the rear die platen  122 . The entry platen  120  and the rear die platen  122  are coupled by a series of tie rods  124  that act as guides for the press-ram platens  130 ,  140  and the centering platen  152 , each of which includes bearings  126   a,    126   b,    126   c  that move along the tie rods  124 . The rear die platen  122  and the entry platen  120  have mounting locations  127  through which the tie rods  124  are fixed. The entry platen  120 , rear die platen  122 , and tie rod structure  124  are supported by the frame  190 . The frame  190  also holds the spindle  172  and motor  170 . At the exit of the rotating die  160  is a quench tube  180  for rapidly cooling the extruded tubing. 
     The press-ram platens  130 ,  140  operate by gripping the billets and providing a substantially constant pushing force in the direction of the extrusion die stack  160 . At any given time at least one of the press-ram platens  130 ,  140  grips a billet and advances the billet along the mandrel bar  100  to provide the constant pushing force. The press-ram platens  130 ,  140  form the final part of the billet delivery subsystem  220  before the billet enters the centering insert  150  of centering platen  152  and the rotating die  160  of the extrusion subsystem  240 . Similar to the billet feed track section before the entry platen  120 , the section prior to the press-ram platens  130 ,  140  preferably continuously indexes the billets to minimize any gaps between a billet that is gripped the press-ram platens  130 ,  140  and the next billet. 
     As discussed above, the press-rams  130 ,  140  continuously push billets into the rotating die  160 . The press-rams  130 ,  140  alternate gripping and advancing billets towards and into the rotating die  160  and then ungripping the advanced billets and retracting for the next gripping/advancing cycle. There is preferably an overlap between the time when one press-ram stops pushing and the other press-ram is about to start pushing so that there is always uniform pressure on the rotating die  160 . The press-rams  130 ,  140  advance and retract via press-ram cylinders coupled to the respective press-ram. As shown there are two press-ram cylinders  132 ,  142  per press-ram. A first set of press-ram cylinders  132  is located to the left and right of the entry platen  120  (although the right-side press-ram cylinder is hidden from view by the left-side press-ram cylinder). The first set of press-ram cylinders  132  couples with the first press-ram platen  130  and is configured to move the first press-ram  130  along the tie rods  124  as the first press-ram  130  advances billets and then retracts for subsequent billets. A second set of press-ram cylinders  142  is located on the top and bottom of the entry platen  120 . The second set of press-ram cylinders  142  couples with the second press-ram platen  140  and is configured to move the second press-ram  140  along the tie rods  124  as the second press-ram  140  advances billets and then retracts for subsequent billets. Although two press-ram cylinders are shown for each of the first and second press-ram platens  130 ,  140 , it will be understood that any suitable number of press-ram cylinders may be provided. In certain embodiments, press-ram cylinders may be coupled to both press-rams  130 ,  140 . 
     The centering platen  152  receives billets advanced by the press-rams  130 ,  140  and functions to hold the billets during the extrusion process prior to entry of the billets into the rotating die  160 . When the centering platen  152  is positioned in place for the extrusion process, the centering platen  152  substantially becomes part of the extrusion die  160 . That is, a centering insert  150  of the centering platen  152  substantially abuts the rotating die  160 . The centering platen  152  itself, however, and the components therein including the centering insert  150 , do not rotate with the rotating die  160 . The centering platen  152  prevents billets that are no longer held by the second press-ram  140  from rotating while the die  160  rotates by gripping the billets and thereby preventing the billets from rotating prior to entry of the billets into the rotating die  160 . 
     As discussed above, the extrusion press system  200  includes positive stops  154 ,  156 . The positive stops  154 ,  156  are coupled to a first support structure  162  and extend towards a second support structure, the centering platen  152 , with a gap between contact surfaces of the respective components that amounts to a travel distance. During operation, the first support structure  162  is stationary and the second support structure  152  moves relative to the first support structure  162 . For example, one or more piston/cylinder drive units (similar to the press-ram cylinders discussed above with respect to the press-ram operation) may be coupled to the support structure  152  to advance and optionally retract the structure along the tie rods  124 . In certain embodiments, the second support structure  152  moves in a direction towards the first support structure  162  (along arrow B) and a direction away from the first support structure (opposite arrow B). The positive stops  154 ,  156  therefore define a travel distance between the respective support structures  162 ,  152 . Although the positive stops  154 ,  156  are shown as coupled to and extending from the first support structure  162  towards the second support structure  152 , other configurations may be used. For example, in some embodiments, a positive stop may be coupled to the second support structure  152  and extend towards the first support structure  162 , with a gap between respective contact surfaces of the positive stop and first support structure  162 . Any suitable arrangement for preventing motion of one (or more) of the support structures may be used. 
     The rotating die  160  may have a unibody design, or may include a plurality of die plates stacked together. In certain embodiments, the die includes a base plate, a final plate, a second intermediate plate, a first intermediate plate, an entry plate, and a steel end holder, and the die plates are bolted together or otherwise coupled to form the die  160 . In some embodiments, additional plates may be added to form the rotating die. The rotating die  160  is bolted to or otherwise coupled with the spindle  172 , which is operated by the motor  170 . A gear box is bolted to the rear die platen  122  and contains the spindle  172  as well as the drive chain, motor drive gear, gear oil reservoir, and gear oil heat exchanger, which are not shown in  FIG. 5  to avoid overcomplicating the figure. In certain embodiments, the spindle motor  170  and the spindle/die gear tooth ratio is 2.5:1, although it will be understood that any suitable gear ratio may be used for the rotation of the rotating die  160 . 
     At the extrusion end of the extrusion press system  200  is a quench box  185  bolted or otherwise coupled to the exit side of the gear box on the rear die platen  122 . In certain embodiments, within the quench box  185  is a quench tube  180  for rapidly quenching or cooling the extruded material as it exits the rotating die  160 . Water may be used as the quenching or cooling fluid, and the water may contact the extruded material sometime after the exit of the extruded material from the rotating die  160 . For example, in certain embodiments, the extruded material is quenched with cooling fluid within approximately 1 inch, or less, of exiting the rotating die  160 . Any suitable cooling fluid may be used for quenching an extruded material, including water, various mineral oils, brines, synthetic oils, any other suitable cooling fluid, including gaseous fluids, or any combination thereof. The quench tube  180  may be formed of one or more tubes having a channel therein for delivering the cooling fluid to the extruded material. In certain embodiments, the quench tube  180  further includes an end cap or other structure through which the cooling fluid is delivered to the extruded material. Any suitable quench tube may be used the extrusion press system of this disclosure. 
     In certain embodiments, nitrogen gas, or another suitable inert gas, is delivered to the interior of an extruded material as the material exits the rotating die. For example, nitrogen gas may be delivered to the interior of extruded tubing using a cap placed on the leading end of the extruded tubing as it exits the rotating die. Injecting gaseous or liquid nitrogen into the rotating die assembly, or the interior of the extruded material itself, can minimize oxide formation by displacing the oxygen-laden air. 
     The foregoing is merely illustrative of the principles of the disclosure, and the systems, devices, and methods can be practiced by other than the described embodiments, which are presented for purposes of illustration and not of limitation. It is to be understood that the systems, devices, and methods disclosed herein, while shown for use in extrusion press systems, may be applied to systems, devices, and methods to be used in other manufacturing procedures including, but not limited to, cast-and-roll, up-casting, other extrusion, and other manufacturing procedures. 
     Variations and modifications will occur to those of skill in the art after reviewing this disclosure. The disclosed features may be implemented, in any combination and subcombination (including multiple dependent combinations and subcombinations), with one or more other features described herein. The various features described or illustrated above, including any components thereof, may be combined or integrated in other systems. Moreover, certain features may be omitted or not implemented. 
     Examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and could be made without departing from the scope of the information disclosed herein. As used herein, the term “about” refers to a number that varies by up to 5%, or in other embodiments up to 10%, and in other embodiments up to 25%, from the number being referred to. The allowable variation encompassed by the term “about” will depend upon the particular system, and can be readily appreciated by one of ordinary skill in the art. Whenever a range is recited within this disclosure, every whole number integer within the range is also contemplated as an embodiment of the disclosure. All references cited herein are incorporated by reference in their entirety and made part of this application.