Patent Publication Number: US-2018029094-A1

Title: Methods and apparatus to determine a plunge depth position of material conditioning machines

Description:
RELATED APPLICATIONS 
     This patent arises from a continuation of U.S. patent Ser. No. 14/729,821, which was filed on Jun. 3, 2015, and is hereby incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE DISCLOSURE 
     The present disclosure relates generally to material conditioning machines and, more particularly, to apparatus and methods to determine a plunge depth position of material conditioning machines. 
     BACKGROUND 
     Material conditioners have long been used in processing strip material used in connection with mass production or manufacturing systems. In a manufacturing system, a strip material (e.g., a metal) is typically removed from a coiled quantity of the strip material. However, uncoiled rolled metal or strip material may have certain undesirable characteristics such as, for example, coil set, crossbow, edgewave and centerbuckle, etc. due to shape defects and internal residual stresses resulting from the manufacturing process of the strip material and/or storing the strip material in a coiled configuration. 
     To achieve a desired material condition, a strip material removed from a coil often requires conditioning (e.g., flattening and/or leveling) prior to subsequent processing in a roll forming machine or laser cutter. For optimum part production, a strip material should have uniform flatness along its cross-section and longitudinal length and be free from any shape defects and any internal residual stresses. Flatteners and/or levelers can substantially flatten a strip material to eliminate shape defects and/or release the internal residual stresses as the strip material is uncoiled from the coil roll. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an example strip material in a coil condition. 
         FIG. 2  illustrates an example stress-strain graph of a material. 
         FIG. 3A  illustrates example areas of compression and tension on a section of a strip material engaged by a work roll. 
         FIG. 3B  illustrates the effect of plastic deformation of a strip material resulting from a plunge force applied by a work roll against the strip material. 
         FIG. 4  is a side view of an example production system having an example leveler configured to process a moving strip material in accordance with the teachings disclosed herein. 
         FIG. 5  illustrates an example configuration of work rolls of the example leveler of  FIG. 4 . 
         FIG. 6  is a side view illustration of the example leveler of  FIGS. 4-5 . 
         FIG. 7  is a plan view of a portion of the example leveler of  FIGS. 4-6 . 
         FIG. 8  is a side view of the example strip material positioned between two work rolls of the example leveler of  FIGS. 4-7 . 
         FIG. 9  is a front view of the example leveler of  FIGS. 4-8 . 
         FIG. 10  illustrates an example controller that may be used to operate the example leveler of  FIGS. 4-9 . 
         FIG. 11  is a flow diagram of an example method to implement an example plunge depth determiner of the example controller of  FIG. 10 . 
         FIG. 12  illustrates an example display illustrating results of a strip material processed using the example plunge depth determiner of the example controller of  FIG. 10  and the example method of  FIG. 11 . 
         FIG. 13  is a flow diagram of an example method that may be used to calibrate one or more sensors of the example leveler of  FIGS. 4-10 . 
         FIG. 14  is a block diagram of an example processor system that may be used to implement the example methods and apparatus described herein. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a strip material  100  in a coiled state or condition  102 . Coiled strip material frequently manifests undesirable material conditions that are the result of longitudinal stretching of the strip material  100  during coiling and as a result of remaining in the coiled condition  102  for a period of time. In particular, the coil winding process is usually performed under high tension, which may cause a condition commonly referred to as coil set. If significant, coil set may also manifest itself as a condition commonly referred to as crossbow. Both of these undesirable conditions are manifest in an uncoiled condition or state  104  when the strip material  100  is unwound from a roll or coil  10 . Due to being in the coiled condition  102 , an upper surface  106  of the strip material  100  is longer (e.g., bent along a longitudinal axis of the strip material  100 ) relative to an inner surface  108  of the strip material  100 . As a result, the upper surface  106  of the strip material  100  tends to curl toward the inner surface  108  of the strip material  100 . As the uncoiled portion  104  is pulled straight, a varying coil set effect in the strip material  100  between a leading edge  110  and a trailing edge  112  causes the longer upper surface  106  to curl or bend (e.g., inward) relative to the shorter inner surface  108 . 
     Undesirable material conditions such as coil set and crossbow can be substantially eliminated using leveling or flattening techniques. Leveling and/or flattening techniques are implemented based on the manners in which strip materials react to stresses imparted thereon (e.g., the amount of load or force applied to a strip material). For example, the extent to which the structure and characteristics of the strip material  100  change is, in part, dependent on the amount of load, force, or stress applied to the strip material  100 . 
     For example,  FIG. 2  illustrates an example stress-strain graph  200  of a material such as, for example, aluminum or other type of metal. Based on Hooke&#39;s law, material remains elastic and returns to its original shape until the material passes Young&#39;s modulus of elasticity at which time a yield point  202  of the material is exceeded, and the material enters into a state of plasticity. The amount of stress causing a metal or a material to change from an elastic condition to a plastic condition is commonly known as the yield strength. A hook  204  shown on the stress-strain graph  200  is typically representative of an indication that the yield point  202  of a material is met. In some instances, applying a stress to the material greater than the yield point  202  of the strip material  100  (e.g., an Ultimate Strength  206 ) may cause the material to be over stressed. As a result, the strip material  100  may harden and/or form dislocations in the strip material  100 . For example, a stress applied to the strip material  100  that is representative of an ultimate stress value of a material may cause the strip material to harden. In other words, applying a stress on the material at approximately the yield point  202  of the strip material causes internal stresses in the strip material to release, but applying a stress to the strip material  100  significantly greater than the yield point  202  of the strip material  100  adds internal stresses to the strip material  100  and/or causes the strip material  100  to harden. A strip material  100  that is hardened may provide undesired shape characteristics for downstream processing equipment such as, for example, laser cutters, forming equipment, shearing equipment, etc. Additionally or alternatively, applying a stress to the strip material  100  that is greater than the yield point  202  may decrease an efficiency of a leveler and/or may cause damage to the leveler. A stress applied to the strip material  100  that is greater than a fracture stress  208  causes the strip material  100  to crack, break or become damaged. 
     Levelers typically bend a strip material back and forth through a series of work rolls to reduce internal stresses (and reduce undesired characteristics) by permanently changing the memory of the strip material  100 . More specifically, the work rolls are positioned or nested to a plunge depth position required to plastically deform the strip material. In particular, a plunge depth positioned to apply a stress to the strip material approximate the yield point  202  of the strip material  100  results in a maximum reduction of internal stresses. 
       FIG. 3A  illustrates example areas of compression and tension on a section of the strip material  100  passing over a work roll  108  of a leveler. The magnitude of the forces used to condition the strip material  100  depends on the type or amount of reaction the strip material  100  has to being wrapped or bent about a surface of the work roll  108 . For purposes of discussion, the strip material  100  is described herein as if the strip material  100  were formed using planar layers. As shown in  FIG. 3A , the work roll  108  is typically used to apply a load (i.e., a plunge force F) to the strip material  100 . The plunge force F applied by the work roll  108  to the strip material  100  is created by increasing a plunge of the work roll  108  toward the strip material  100 . The plunge force F causes a bottom surface  302  of the strip material  100  to be in compression and a top surface  304  of the strip material  100  to be in tension. A neutral axis  308  shown along the center of the strip material  100  is neither in compression nor tension. Deforming the strip material  100  in this manner causes the strip material  100  to bend or stretch. 
       FIG. 3B  illustrates an elastic region  306  and a plastic region  310  in the strip material  100 . Bending the strip material  100  using a relatively low plunge force F maintains the material in an elastic phase represented by the elastic region  306  about the neutral axis  308 . In an elastic phase, residual stresses of a strip material  100  remain unchanged. To substantially reduce or eliminate residual stresses, the strip material  100  must be stretched beyond the elastic phase to a plastic phase represented by the plastic region  310 . That is, the strip material  100  must be stretched so that the plastic region  310  extends substantially the entire thickness of the strip material  100 . Otherwise, when the plunge force F applied to a portion of the strip material  100  is removed without having stretched portions (e.g., between 70% and 80%) of the strip material  100  to the plastic phase, the residual stresses remain in those portions of the strip material  100  causing the strip material  100  to return to its shape prior to the force being applied. In such an instance, the strip material  100  has been flexed, but has not been bent. 
     The plunge force F applied to the strip material  100  can be increased to transition the material from the elastic phase to the plastic phase to substantially reduce or eliminate the residual stresses of the strip material  100  that cause undesired characteristics or deformations. Specifically, small increases in the force or load applied to the strip material  100  cause relatively large amounts of stretching (i.e., deformation) to occur in the plastic region  310 . 
     In known leveling systems, the amount of plunge force F needed to exceed the yield strength of a material is determined based on the diameters of the work rolls, the horizontal separation between neighboring work rolls, Young&#39;s modulus of elasticity, a yield strength of the material, and a thickness of the material. Leveler manufacturers may provide a chart of start-up settings that help an operator achieve a proper plunge amount based on input values including a material thickness and material yield strength given that all other parameters such as work roll diameter and/or work roll horizontal separation are fixed values. However, it is often difficult to precisely determine the yield strength and/or the yield point. Although material thickness is easily measurable, the yield of the material is rarely displayed on the coil, causing most operators to guess the yield strength value of the material. Consequently, an incorrect yield strength value is often employed leading to an improper and/or less effective plunge depth. Additionally, some materials, such as steel, are often rated by grade. For example, grade A36 steel is a softer material that has a yield strength range between approximately 30,000 and 45,000 pounds/int 2  (psi). Grade G50 steel typically has a yield strength range between approximately 50,000 psi and 65,000 psi. Grade G65 steel typically has a yield strength range between approximately 65,000 psi and 80,000 psi. Thus, the yield strength of a rated material varies significantly. For example, an operator can determine that the yield strength for G50 rated steel is 50,000 psi, but the actual yield strength of that particular roll of material is 65,000 psi. As a result, the plunge depth of the leveler apparatus may not be set to a sufficient depth needed to plastically deform the strip material. Thus, although some operators estimate yield strength of a rated material that is within a range provided for that given rated material, the estimated yield strength may still be insufficient to plastically deform the strip material. In some instances, the accuracy of the estimated yield strength significantly deviates from the actual yield stress by approximately between 5% and 15%. Such deviation often results in less effective leveling and/or provides a processed strip material that does not comply with a specified percent of cross-section area yield in the plastic region. For example, some compliance restrictions require 80% of a cross-section area of the strip material (e.g., outer surfaces extending toward the center axis) to be processed in the plastic region and 20% of the cross-section area (e.g., extending from the center axis) to be processed in the elastic region. Alternatively, for example, an operator can determine that the yield strength for a G50 rated steel is 65,000 psi, but the actual yield strength of that particular roll of material is 50,000 psi. As a result, the plunge depth may be set to impart a stress that is significantly greater than the yield strength, which results in material hardening by imparting too much stress to the strip material. 
     The example methods and apparatus described herein detect or estimate a plunge depth without requiring yield strength input from an operator. In particular, the example method and apparatus disclosed herein determine a plunge depth position required to impart a stress within a threshold (e.g., deviating by less than about 3%) of an actual yield strength of a given strip material to be processed by the example leveler apparatus disclosed herein. For example, the example methods and apparatus determine a plunge depth that provides a stress or force to the strip material that is between approximately 0.1% and 5% of the actual yield strength of the strip material. As a result, adjusting a plunge depth representative of a stress corresponding to an approximate yield point of the strip material to be processed by the example levelers disclosed herein provides optimal material conditioning because processessing the strip material at or substantially close (e.g., within about 0.1 and 10%) to the yield point provides the greatest effective internal stress reduction. For example, the greatest release of internal stresses occurs when the strip material is processed at its yield point. As a result, stresses in the strip material are significantly reduced to provide significantly improved flatness properties and/or flat laser burning properties in the strip material after leveling. 
     To detect or determine a plunge depth associated with and/or corresponding to the yield strength of a strip material, the example methods and apparatus disclosed herein measure, monitor or detect a pressure associated with a cylinder of the leveler. For example, a pressure of a control fluid (e.g., pressurized hydraulic oil) used to adjust a plunge depth of a work roll in a particular zone may be monitored or measured as a plunge depth is adjusted incrementally (e.g., a preset or predetermined incremental value) during a set-up condition. For example, the pressurized control fluid may be provided to a piston or cylinder of an actuator (e.g., a hydraulic actuator) to adjust a plunge depth of a work roll. 
     To detect, monitor or sense a pressure of the control fluid in the actuator (and, thus, a vertical force imparted to the strip material via the work roll) when the work roll is nested or in a plunge position, the example methods and apparatus disclosed herein detect or sense forces imparted to the strip material by the work rolls based on changes in pressure of a control fluid in a cylinder of an actuator when the plunge depth is adjusted (e.g., increased or decreased incrementally) during, for example, a set-up operation. In this manner, the detected or sensed force provides an indication of whether a force applied to the strip material based on a current plunge depth position of the work rolls is sufficient to deform the strip material at approximately its yield strength. Specifically, during a set-up operation, a plunge depth is adjusted incrementally between an initial value and a final value. At each incremental plunge depth position, a pressure reading of the control fluid of a cylinder is measured. For example, pressure readings of only a central cylinder (e.g., aligned with a longitudinal axis of the strip material) are measured at each of the incremental plunge depths. Once all the pressure readings have been measured at each of the incremental plunge depths between the initial and final plunge depth positions, the pressure readings are compared. The smallest or lowest pressure reading is detected. The smallest or lowest pressure corresponds approximately to the yield point of the strip material. The plunge depth corresponding to the detected smallest pressure reading is identified. During operation, the strip material is processed at the identified plunge depth. The material is processed based on the plunge depth corresponding to the smallest or lowest detected pressure, which provides a stress to the strip material that is approximately the yield point of the strip material. 
     In some examples, the pressure readings of a control fluid in two or more cylinders representative of different zones across the width of the strip material are measured. An average of the smallest pressure readings is determined and the plunge depth is provided at a plunge depth associated with the average pressure value. In some examples, the smallest pressure reading for each of the zones is determined and a plunge depth of each zone is adjusted to a position corresponding to the smallest pressure reading in that particular zone. Thus, in some such examples, the plunge depth adjustment of each zone is independent of the other plunge depth adjustments of the other zones. 
       FIG. 4  illustrates an example production system  40  configured to process a moving strip material  400  using an example leveler  402  disclosed herein. In some example implementations, the example production system  40  may be part of a continuously moving strip material manufacturing system, which may include a plurality of subsystems that modify, condition or alter the strip material  400  using processes that, for example, level, flatten, punch, shear, and/or fold the strip material  400 . In alternative example implementations, the leveler  402  may be implemented as a standalone system. 
     In the illustrated example, the example leveler  402  may be placed between an uncoiler  404  and a subsequent operating unit  406 . The strip material  400  may be a metallic substance such as, for example, steel or aluminum, or may be any other suitable material. In a coiled state, the strip material  400  may be subject to variable and asymmetrical distribution of residual stresses along its width and length that cause shape defects in the strip material  400 . As the strip material  400  is uncoiled or removed from a coiled roll  408 , it may assume one or more uncoiled conditions or shape defects such as, for example, coil set and crossbow. 
     To condition the strip material  400  and remove internal stresses that may cause the uncoiled conditions such as coil set, the strip material  400  travels from the uncoiler  404 , through the leveler  402 , and to the subsequent operating unit  406  in a direction generally indicated by arrow  410 . The subsequent operating unit  406  may be a continuous material delivery system that transports the strip material  400  from the leveler  402  to a subsequent operating process such as, for example, a punch press, a shear press, a roll former, a laser cutter, etc. For example, during the leveling operation, subsequent operations may be performed as the strip material  400  moves continuously through the leveler  402  (e.g., a cutting operation performed by a laser cutter). In other example implementations, sheets precut from, for example, the strip material  400  can be sheet-fed through the leveler  402 . 
     The leveler  402  of the illustrated example employs a plurality of work rolls  412  to reshape or work the strip material  400  to reduce coil set and/or the internal stresses in the strip material  400  and to impart a flat shape on the strip material  400  as the strip material  400  leaves the leveler  402 . In particular, a force is imparted to the strip material by the work rolls  412  to condition the strip material  400 . 
       FIG. 5  illustrates an example configuration of the work rolls  412  of the example leveler  402  of  FIG. 4 . As shown in the illustrated example of  FIG. 5 , the plurality of work rolls  412  of the leveler  402  arranged as a plurality of upper work rolls  502  and lower work rolls  504 . To reshape or work the strip material  400 , the upper work rolls  502  and the lower work rolls  504  are arranged in an offset relationship (e.g., a nested or alternating relationship) relative to one another on opposing sides of the strip material  400  being processed to create a material path that wraps above and below opposing surfaces of the alternating upper work rolls  502  and lower work rolls  504 . Engaging opposing surfaces of the strip material  400  using the upper work rolls  502  and lower work rolls  504  in such an alternating fashion facilitates releasing the residual stresses in the strip material  400  to condition (e.g., flatten, level, etc.) the strip material  400 . 
     In the illustrated example, the work rolls  502  and lower work rolls  504  are partitioned into a plurality of entry work rolls  506  and a plurality of exit work rolls  508 . The entry work rolls  506  may be driven independent of the exit work rolls  508 , and the entry work rolls  506  can be controlled independent of the exit work rolls  508 . The entry work rolls  506  reshape the strip material  400  by reducing the internal stresses of the strip material  400 . The exit work rolls  508  adjust any remaining internal stresses of the strip material  400  to impart a flat shape on the strip material  400  as the strip material  400  leaves the leveler  402 . The leveler  402  of the illustrated example may also employ a plurality of idle work rolls  510  positioned between and in line with the entry work rolls  506  and the exit work rolls  508 . For example, the entry work rolls  506  and the exit work rolls  508  may be driven via, for example, a motor, and the idle work rolls  510  may non-driven (but can be driven in some implementations). 
     The magnitudes of the forces used to condition the strip material  400  depend on the type or amount of reaction the strip material  400  has to being wrapped or bent about a surface of the work roll  412 . As shown in  FIG. 5 , the work roll  412  is used to apply a load (i.e., a plunge force F) to the strip material  400 . The plunge force F applied by the work roll  412  to the strip material  400  is created by increasing a plunge of the work roll  412  toward the strip material  400 . More specifically, to vary the plunge force, a work roll plunge can be varied by changing a center distance (d 1 ) or plunge depth position  512  between center axes  514  and  516  of the respective work rolls  502  and lower work rolls  504 . In general, for any given work roll plunge depth or plunge, a decreased center distance increases the tensile stress imparted to the strip material  400  and, thus, the potential for plastic deformation, which conditions the strip material  400 . In the illustrated example, the plunge of the entry work rolls  506  is set to deform the strip material  400  at or beyond its yield strength and, thus, the plunge of the entry work rolls  506  is relatively greater than a plunge  518  (d 2 ) of the exit work rolls  508 . In some example implementations, the plunge  518  of the exit work rolls  508  can be set so that they do not deform the strip material  400  by any substantial amount but, instead, adjust the shape of the strip material  400  to a flat shape (e.g., the plunge  518  of the exit work rolls  508  is set so that a separation gap between opposing surfaces of the upper and lower work rolls  502  and  504  is substantially equal to a thickness Ti of the strip material  400 ). Applying a relatively greater plunge (i.e., a smaller distance between the work roll center axes  502   a  and  502   b ) at the entry work rolls  502  requires a relatively stronger plunge force to reduce a substantial amount of internal stresses (e.g., 70%, 80%, etc.) that are trapped in the strip material  100  by stretching and/or elongating the strip material  100 . As disclosed below, a controller  520  determines a plunge depth (e.g., the plunge depth position  512 ) of the entry work rolls  506  that imparts a stress to the strip material  400  that is approximately the actual yield strength of the strip material  400 . In particular, the controller  520  determines the plunge depth position  512  without requiring an operator to estimate or guess the yield strength of the strip material  400  during a set-up operation. 
       FIG. 6  illustrates a side view of the example leveler  402  of  FIG. 4 . Referring to  FIG. 6 , the leveler  402  has an upper frame  602  and a bottom frame  604 . The upper frame  602  includes an upper backup  606  mounted thereon and the bottom frame  604  includes an adjustable backup  608  mounted thereon. In the illustrated example of  FIG. 6 , the upper backup  606  is non-adjustable and fixed to the frame  602  and the adjustable backup  608  is adjustable relative to the upper backup  606 . However, in other example implementations, the upper backup  606  may also be adjustable. 
     The upper backup  606  includes a row of backup bearings  610  supported by a non-adjustable flight  612  and the plurality of upper work rolls  502  that are supported by the upper backup bearings  610 . Thus, the upper backup bearings  610  fix the upper work rolls  502  in place. The adjustable backup  608  includes a row of lower backup bearings  616  supported by an adjustable flight  618 . The lower backup bearings  616  support the plurality of lower work rolls  504 . In some examples, intermediate rolls (not shown) may be positioned between the backup bearings  610  and the upper work rolls  502  and/or between the lower backup bearings  616  and the lower work rolls  504  to substantially reduce or eliminate work roll slippage that might otherwise damage the strip material  400  or mark relatively soft or polished surfaces of the strip material  400 . Generally, journals (not shown) rotatably couple the upper work rolls  502  and the lower work rolls  504  to the frame  602  to allow rotation of the upper work rolls  502  and the lower work rolls  504 . The work rolls  412  are small in diameter and are backed up by the respective backup bearings  610  and  616  to prevent unwanted deflection along the length of the work rolls  412 . 
     In the illustrated example, the leveler  402  uses the adjustable backup  608  (i.e., adjustable flights) to adjust the plunge or a position of the lower work rolls  504  relative to the fixed upper work rolls  502 . More specifically, actuators or hydraulic cylinders  622  and  624  move the lower backup bearings  616  via the adjustable flight  618  to increase or decrease a plunge depth between the upper work rolls  502  and the lower work rolls  504  (e.g., to increase or decrease the plunge depth position  512  and/or the plunge depth position  516  between the upper work rolls  502  and the lower work rolls  504  of the entry work rolls  506  or the exit work rolls  508 ). In particular, the leveler  402  can change the length of the strip material  400  by adjusting the position of the lower work rolls  504  relative to the upper work rolls  502  via the hydraulic cylinders  622  and  624  to create a longer path. Creating a longer path by increasing a plunge of the upper work rolls  502  and the lower work rolls  504  causes the strip material  400  to stretch and elongate further than a shorter path created by decreasing a plunge of the upper work rolls  502  and the lower work rolls  504 . Adjustment of the lower work rolls  504  relative to the fixed upper work rolls  502  may enable substantially continuous or stepwise variation of the plunge of the work rolls  412 , thereby enabling a substantially continuous or stepwise variation of the stress imparted to the strip material  400 . 
     In the illustrated example of  FIG. 6 , the hydraulic cylinder  622  moves a first end  626  of the adjustable flight  618  relative to a second end  628  of the adjustable flight  618  to adjust a position of the lower work rolls  504  relative to the upper work rolls  502  at an entry  630  of the leveler  402  (e.g., the plunge depth position  512  of the entry work rolls  506  of  FIG. 5 ). The hydraulic cylinder  624  moves the second end  628  of the adjustable flight  618  relative to the first end  626  to adjust the position of the lower work rolls  504  relative to the upper work rolls  502  at an exit  632  of the leveler  402  (e.g., the plunge depth position  516  of the exit work rolls  508  of  FIG. 5 ). In this manner, the lower backup bearings  616  supported adjacent the first end  626  of the adjustable flight  618  can be positioned at a first distance or height relative to the fixed upper work rolls  502  adjacent the entry  630 , and the lower backup bearings  616  supported adjacent the second end  628  of the adjustable flight  618  can be positioned at a second distance or height (e.g., different from the first height) relative to the fixed upper work rolls  502  adjacent the exit  632 . In other example implementations, the position or plunge of the work rolls  412  can be adjusted by moving the upper backup  606  with respect to the adjustable backup  608  using, for example, motor and screw (e.g., ball screw, jack screw, etc.) configurations. 
       FIG. 7  illustrates a plan view of the adjustable backup  608  of the leveler  402  of  FIG. 6 . Referring to  FIG. 7 , the adjustable backup  608  of the leveler  402  includes a plurality of backup bearings  616  and  702   a - f  supported by a respective plurality of adjustable flights  618  and  704   a - f  extending across a width  706  (e.g., a cross-width) of the strip material  400 . More specifically, the movable or adjustable backup bearings  616  and  702   a - f  are arranged on independently movable or adjustable flights  618  and  704   a - f . For example, the adjustable flights  618  and  704   a - f  slide relative to the frame  602  to move the respective backup bearings  616  and  702   a - f  relative to respective upper backup bearings (e.g., backup bearings  610  of  FIG. 6 ). For example, each respective first ends  626 ,  708   a - f  of the adjustable flights  618  and  704   a - f  slide or move independently relative to the entry  630  of the frame  602 , and the second ends  628  and  710   a - f  of the adjustable flights  618  and  704   a - f  slide or move independently relative to the exit  632  of the frame  602  and/or the respective first ends  626  and  708   a - f . In this manner, a plunge depth can be varied across the width  706  (e.g., a cross-width) of the strip material  400  as shown in  FIG. 8  to provide or cause the workrolls  412  to impart a stress or force across the width W of the strip material  400 . 
     As shown in  FIG. 7 , a plurality of actuators  620 ,  622 ,  712   a - f  and  714   a - f  are associated with respective ones of the adjustable flights  618  and  704   a - f . For example, the entry  630  of the leveler  402  includes actuators  620  and  712   a - f , and the exit  632  of the leveler  402  includes actuators  622  and  714   a - f . Each of the actuators  620 ,  622 ,  712   a - f  and  714   a - f  moves independent of the other actuators. In particular, the actuators  620 ,  622 ,  712   a - f  and  714   a - f  (e.g., hydraulic actuators) may be controlled to adjust the positions of the respective ones of the adjustable flights  618  and  704   a - f  independently from other ones of the adjustable flights  618  and  704   a - f . More specifically, respective ones of the actuators  620  and  712   a - f  adjust the respective first sides  626  and  708   a - f  of the adjustable flights  618  and  704   a - f , and respective ones of the actuators  622  and  714   a - f  adjust the respective second sides  628  and  710   a - f  of the adjustable flights  618  and  704   a - f . In this manner, the work rolls  412  at the entry  630  of the leveler  402  (e.g., the entry work rolls  506  of  FIG. 5 ) may be positioned to a plunge depth (e.g., the plunge depth position  512  (d 1 ) of  FIG. 5 ) that is greater than a plunge depth (e.g., the plunge depth position  516  (d 2 ) of  FIG. 5 ) of the work rolls  412  at the exit  632  of the leveler  402  (e.g., the exit work rolls  508  of  FIG. 5 ). Additionally or alternatively, a plunge depth of the work rolls  412  supported by one of the adjustable flights  618  and  704   a - f  at the entry  630  (and/or the exit  632 ) of the leveler  402  may vary across the width  706  of the strip material  400  relative to another adjacent work roll  412  supported by another one of the adjustable flights  618  and  704   a - f  at the entry  630  (and/or the exit  632 ). 
       FIG. 8  is a diagrammatic view showing an example adjustment of the lower work rolls  504  relative to the upper work rolls  502  at the entry  630  of the leveler  402 . For purposes of clarity, only two work rolls  412  are shown of each of the flights  618  and  704   a - f . In the illustrated example, the work rolls  502  and  504  have lengths that traverse the width W of the strip material  400 . 
     As the strip material  400  passes through the work rolls, the strip material  400  imparts a force to the work rolls  412 . In the illustrated example, the strip material  400  may impart respective forces F 1 -F 7  to the work rolls  412  that may be sensed or detected by a control fluid in the respective actuators  620  and  712   a - f  associated with respective zones  802 - 814 . In some examples, the work roll  412 ,  504  defines a plurality of zones  802 - 814  across the width W of the strip material  400 . In particular, the force imparted to the work roll  412  may be caused by a varying coil set effect in the strip material  400  between a leading edge (e.g., the leading edge  110 ) and a trailing edge (e.g., the trailing edge  112 ) of the strip material  400 . Therefore, the respective forces F 1 -F 7  may vary depending on, for example, the hardness of the strip material  400  across its width  706  and/or its length. Thus, the forces F 1 -F 7  may be substantially similar and/or may vary as the strip material  400  moves through the leveler  402 . 
     The adjustable flights  618  and  704   a - f  can be positioned independently relative to each other. As shown in  FIG. 8 , the adjustable flights  618  and  704   a - f  of the illustrated example enable the bottom backup bearings  616  and/or  702   a - f  to be adjusted independently (e.g., at different or the same heights or plunge depths) across the width  706  of the strip material  400 . As shown, each of the adjustable flights  618  and  704   a - f  may represent one of the zones  802 - 814  across the width  706  of the strip material  400 . In some examples, each of the zones  802 - 814  can be positioned to a plunge depth independently from a plunge depth of another one of the adjacent zones  802 - 814 . For example, the regions or zones  802 - 814  may correspond to, for example, peripheral or outer edges (e.g., zones  802  and  814 ), mid-edges (e.g., zones  804 ,  806 ,  810  and  812 ) and a center portion (e.g., zone  808 ) of the strip material  400 . The adjustable flights  618  and  712   a - f  of the illustrated example may be configured to correspond to respective ones of the zones  802 - 814 . For example, the first backup bearing  616  is configured to engage the work roll  504  at the first zone  802  (e.g., via the first adjustable flight  618 ), and the second backup bearing  702   a  is configured to engage the work roll  504  at the second zone  804  (e.g., via the second adjustable flight  712   a ). 
       FIG. 9  is a front view illustrating the entry  630  of the example leveler  402  of  FIGS. 1-8 . As shown in  FIG. 9 , each of the actuators  620  and  712   a - f  includes a pump  902   a - g  (e.g., hydraulic pumps such as gear pumps, rotary vane pumps, etc.) to operate (e.g., move) the respective ones of the actuators  620  and  712   a - f . To move each of the actuators  620  and  712   a - f , each pump  902  a-g provides a control fluid (e.g., a pressurized fluid such as a hydraulic fluid or oil) from a respective reservoir  904   a - g  to the respective actuators  620  and  712   a - f . Each pump  902   a - g  includes a respective first fluid line  906  (e.g., a hydraulic hose, pipe, or other conduit) to fluidly couple the control fluid to respective first chambers  908   a - g  of the actuators  620  and  712   a - f  and a respective second fluid line  910   a - g  (e.g., a hose) to fluidly couple the control fluid to respective second chambers  912   a - g  of the actuators  620  and  712   a - f . The leveler  402  of the illustrated example employs positioning valves  914   a - g  (e.g., shut-off valves) that move between an open position to allow the control fluid to flow between the respective reservoirs  904   a - g  and the respective actuators  620  and  712   a - f  and a closed position to prevent fluid flow between the respective reservoirs  904   a - g  and the respective actuators  620  and  712   a - f . For example, to move the first end  626  of the adjustable flight  618  toward the upper backup bearings  610  (e.g., increase a plunge force), a control fluid is supplied to the first chamber  908   a  of the actuator  620  via the first fluid line  906   a . To move the first end  626  of the adjustable flight  618  away from the upper backup bearings  610  (e.g., to decrease a plunge force), the control fluid is provided to the second chamber  912   a  of the actuator  620  via the second fluid line  910   a.    
     The position or location (e.g., the plunge) of each of the respective backup bearings  616  and  702   a - f  relative to the upper work rolls  502  may be sensed or detected by a respective position sensor  916   a - g  (e.g., a transducer). The position sensors  916   a - g  may include linear voltage displacement transformers (LVDTs) or any other suitable position sensing device or combination of devices. In the illustrated example, each of the actuators  620  and  712   a - f  employs a respective one of the position sensors  916   a - g  to detect a position of a respective arm or bracket  918   a - g  movably attached to the actuators  620  and  712   f . For example, each bracket  918   a - g  moves with a piston (not shown) of a respective one of the actuators  620  and  712   a - f  as the actuators  620  and  712   a - f  move between a first position (e.g., a zero stroke position) and a second position (e.g., a 100% stroke position). By detecting the position of the actuators  620  and  712   a - f , the position sensors  916   a - g  can provide an indication or correlation of a plunge depth between the upper work rolls  502  and the lower work ro 11 s  504  (or the work rolls  412 ) for a corresponding zone (e.g., zones  802 - 814 ) associated with the respective ones of the actuators  620  and  702   a - f . In other examples, position transducers, strain gauges, and/or any other suitable position sensors may be employed to detect the plunge depth position of the work rolls  412 . 
     Further, a plurality of respective pressure sensors  920   a - g  are coupled to respective ones of the actuators  620 ,  622 ,  712   a - f  and  714   a - f  to detect or sense pressure changes in the actuators  620 ,  622 ,  712   a - f  and  714   a - f  caused by forces imparted to the work rolls  412  by the strip material  400  as the strip material  400  is processed by the work rolls  412 . For example, a change in pressure in the actuators  620 ,  622 ,  712   a - f  or  714   a - f  may be caused by a deviation in a plunge depth position of the work rolls  412  due to the strip material  400  imparting forces to the work rolls  412 . To sense a pressure in the actuators  620  and  712   a - f  (and/or the actuators  622 ,  714   a - f ), pressure sensors  920   a - g  may be fluidly coupled between the respective pumps  902   a - g  and the actuators  620  and  702   a - f . As shown, the pressure sensors  920   a - g  are fluidly coupled to the first fluid lines  904   a - g  of each of the actuators  620  and  712   a - f . For example, when a particular plunge depth is provided to the work rolls  412 , the pressure sensors  920   a - g  detect the pressure (e.g., the pressure of the control fluid) in the respective actuators  620  and  714   a - f . Further, when a plunge depth of the work rolls  412  is positioned, the positioning valve  914   a - g  associated with a particular actuator  620  and  712   a - f  in which the plunge depth is set is moved to a closed position. As a result, any deviation (e.g., a slight deviation or movement) in the position of the work roll  412  will affect (e.g., increase) the pressure of the control fluid in the respective actuator  620  and  712   a - f . In addition, because an area of a piston in each of the actuators  620  and  712   a - f  is known, and the volume capacity of a cylinder of each of the actuators  620  and  712   a - f  is known, a force imparted to the work rolls  412  by the strip material  400  can be determined by sensing the pressure of the control fluid in the respective actuators  620  and  712   a - f . In other examples, load cells may be used instead of the pressure sensors  920   a - g . For example, a load cell may be positioned under each of the actuators  620  and  712   a - f  to detect a force (e.g., a vertical or reactive force) imparted to the work rolls  412  associated with the respective actuators  620  and  712   a - f . In other examples, other pressure sensors, transducers, etc. may be employed that provide an electrical signal related to a magnitude of an applied pressure or force in the actuators  620  and  712   a - f.    
     In some examples, only one pump  902   a , one fluid reservoir  904   a , one valve  914   a , and/or one pressure sensor  920   a  may be employed to provide fluid to the first changes  908   a - g  and the second chambers  912   a - g  of the actuators  620 ,  712   a - f  and/or  622 ,  714   a - f . For example, in some such examples, the plurality of lines  906   a - g  and  910   a - g  may fluidly communicate the pump  902   a  and the respective first chambers  908   a - g  and second chambers  912   a - g . In some such examples, only one actuator  620  may be provided to adjust the upper work rolls  502  and the lower work rolls  504 . In some examples, each of the respective first changes  908   a - g  may be coupled to a respective or dedicated pump (e.g., pumps  902   a - g ), and each of the respective second changes  912   a - g  may be coupled to a dedicated pump. 
       FIG. 10  is a block diagram of the example controller  520  of  FIG. 5  for automatically determining a plunge depth required to impart a stress to the strip material  400  associated with or approximate a yield strength or yield point (e.g., an actual yield point) of the strip material  400 . In particular, the example controller  520  may be used in connection with and/or may be used to implement the example leveler  402  of  FIG. 1-9  or portions thereof to adjust a plunge depth of the work rolls  412  based on a sensed pressure in any one of the actuators  620  and  712   a - f  and/or the actuators  622  and  714   a - f  (e.g., the entry work rolls  506  associated with a corresponding zone  802 - 814 , the exit work rolls  508 ). In some examples, the example controller  520  may also be used to implement a feedback process to adjust a plunge depth (e.g., the plunge depth position  512  and/or  518  of  FIG. 5 ) of the entry and/or exit work rolls  506  and  508  ( FIG. 5 ) to condition the strip material  400  based on the pressures sensed by the respective pressure sensors  920   a - g , for example, in each of the zones  802 - 814 . 
     As shown in  FIG. 10 , the example controller  520  includes a user input interface  1002 , a plunge position determiner  1004 , a plunge position adjustor  1006 , a plunge position detector  1008 , a pressure sensor interface  1010 , a comparator  1012 , a storage interface  1014 , a calibrator  1016 , and a positioning valve controller  1018 , all of which may be communicatively coupled as shown or in any other suitable manner. 
     The user input interface  1002  may be configured to determine strip material characteristics. For example, the user input interface  1002  may be implemented using a mechanical and/or graphical user interface via which an operator can input the strip material characteristics. The material characteristics can include, for example, a thickness of the strip material  400  (e.g., thickness T 1  of  FIG. 5 ), a width of the strip material  400 , the type of material (e.g., aluminum, steel, etc.), Young&#39;s modulus of elasticity, etc. In some examples, the storage interface  1014  can retrieve information (e.g., Young&#39;s modulus of elasticity) from a reference table or data structure for different material type(s) based on material information received by the input interface  1002 . The user input interface  1002  may be configured to communicate the strip material characteristics to the plunge position determiner  1004 . 
     The plunge position determiner  1004  of the illustrated example determines a plunge depth based on the material characteristics received by the input interface  1002 . In particular, the example plunge position determiner  1004  determines or calculates a plunge depth that provides a plunge force or stress to the strip material  400  that is within a threshold (e.g., three percent) of an actual yield point of the strip material  400 . In particular, the plunge position determiner  1004  determines or identifies a plunge depth position during a set-up operation prior to processing the strip material  400 . 
     To determine a plunge depth associated with an actual yield strength of the strip material  400 , the plunge position determiner  1004  causes the plunge position adjustor  1006  to incrementally adjust a plunge depth of the work rolls  412  (e.g., the entry work rolls  506 ) between an initial position and a final position. Incrementally increasing the plunge depth results in a distance (e.g., the distance d 1  of  FIG. 5 ) between the upper work rolls  502  and the lower work rolls  504  that decreases. The plunge position determiner  1004  may increase the plunge depth by a preset or predetermined incremental value (e.g., a value of approximately 0.002 inches). Using a smaller incremental value (e.g., 0.001 or 0.0005 inches) increases the accuracy of identifying a plunge depth that imparts a stress to the strip material  400  at the actual yield strength or point of the strip material  400 . 
     In some examples, to determine the initial value, the plunge position determiner  1004  may retrieve an initial plunge depth value and/or a final plunge depth value from the user interface  1002  (e.g., provided by an operator). Thus, the initial and/or final plunge depth value can be provided by an operator during, for example, a set-up operation. 
     In some examples, the plunge position determiner  1004  may determine the initial plunge position and/or the final plunge depth position from a reference table stored in the storage interface  1014 . For example, the plunge position determiner  1004  may determine the initial plunge position and/or the final plunge depth position from a reference table based on the material characteristics received via the user input interface  1002  (e.g., Young&#39;s modulus of elasticity, material type, the grade of material, etc.). Thus, the initial plunge depth and/or the final plunge depth can be determined from a reference table based on, for example, empirical data and/or estimates based on the type(s) of material being plunged. For example, in some such examples, the plunge position determiner  1004  determines the initial plunge value and/or the final plunge value based on a range of yield strengths provided by a particular grade of the strip material (e.g., Grade A particular grade of steel). The plunge position determiner  1004  sets the initial plunge position based on a lowest yield strength of the range and sets the final plunge position based on a highest yield strength of the range. For example, grade A 36  steel has a yield strength range between approximately 30,000 and 45,000 pounds/in 2  (psi). Thus, the plunge position determiner  1004  may determine the initial plunge position based on the yield strength of 30,000 psi (e.g., or a value or buffer less than 30,000 psi (e.g., 25,000 psi)) and may determine the final plunge position based on the yield strength of 45,000 psi (e.g., or a value or buffer greater than 45,000 psi (e.g., 50,000 psi)). 
     In some examples, the plunge position determiner  1004  determines the final plunge position based on the output of pressure readings provided by the pressure sensor interface  1010 . For example, the plunge position determiner  1004  may determine an increase in consecutive pressure readings and then detects a drop in pressure readings. After detection of the drop, a final plunge position value may be determined when the pressure readings provided by the pressure sensor interface  1010  provide a pattern such as three consecutive increases in pressure after detection of a drop in pressure. The plunge position determiner  1004  may determine the final plunge position value corresponding to the third consecutive pressure increase reading. 
     In some examples, the plunge position determiner  1004  may employ one or more of, and/or any combination of, user input information, reference table information and/or pressure reading information to determine the initial plunge depth value or position and/or the final plunge depth value or position. 
     To adjust the plunge depth of the work rolls  412  incrementally (e.g., the entry work rolls  506  in each of the different zones  802 - 814 ), the plunge position adjustor  1006  causes the pumps  902   a - g  to supply the control fluid to the respective actuators  620 ,  622 ,  712   a - f  and  714   a - f . For example, to adjust the plunge depth positions of the entry work rolls  506 , the plunge depth determiner  1004  may command the plunge position adjustor  1006  to initiate one or more of the pumps  902   a - g  to supply pressurized control fluid from one or more of the reservoirs  904   a - g  to one or more of the respective chambers  908   a - g  and/or  912   a - g  of the actuators  620  and  712   a - f . The plunge position adjustor  1006  may command one or more of the pumps  902   a - g  to deliver pressurized control fluid sufficient to position the respective adjustable flights  618  and  704   a - f  and, thus, the backup bearings  616  and  702   a - f  relative to the upper work rolls  502  to provide desired plunge depths (e.g., incremental plunge depths) determined or calculated by the plunge position determiner  1004 . For example, the plunge position adjustor  1006  may adjust the position (e.g., the stroke position) of the actuators  620  and  712   a - f  until the plunge position detector  1008  determines that the respective actuators  620  and  712   a - f  are at the desired position (e.g., a stroke position) corresponding to a desired plunge depth of the work rolls  412 . 
     The plunge position detector  1008  may be configured to sense or detect the incremental plunge depth position values of the work rolls  412 . For example, the plunge position detector  1008  can detect the vertical position or distance between the work rolls  412  (i.e., the upper work rolls  502  and the lower work rolls  504 ) to achieve a particular plunge depth position  512  (e.g., the distance (d 1 ) between the upper work rolls  502  and the lower work rolls  054  of  FIG. 5 ). To detect the position of the plunge depth, the plunge position detector  1008  receives a position signal value from the position sensors  916   a - g  of  FIG. 9 . For example, the positions sensors  916   a - g  provide a signal to the plunge position detector  1008  based on the position of the respective brackets  918   a - g , which correlate to the stroke position of the respective actuators  620  or  712   a - f . The plunge position detector  1008  can then communicate the plunge depth position value to the plunge position determiner  1004 , the plunge position adjustor  1006  and/or the comparator  1012 . 
     The positioning valve controller  1018  is configured to prevent or restrict control fluid from flowing between the reservoirs  904   a - g  and the respective actuators  620  and  712   a - f . For example, after the plunge depth positions of the work roll  412  in of the zones  802 - 814  are positioned, the positioning valve controller  1018  may cause each of the positioning valves  914   a - g  to move to a closed position. With the positioning valve  914   a - g  in the closed position, a volume of control fluid in each of the respective actuators  620  and  712   a - f  is known and/or controlled. 
     The pressure sensor interface  1010  can be configured to obtain the pressure value, for example, of the control fluid in the actuators  620 ,  622 ,  712   a - f  and  714   a - f . For example, the pressure sensor interface  1010  may be configured to obtain pressure values at each of the incrementally adjusted plunge depth positions for each of the actuators  620 ,  622 ,  712   a - f  and  714   a - f . In some examples, the pressure sensor interface  1010  obtains the pressure values at each incrementally adjusted plunge positions after a predetermined time delay (e.g., between approximately 1 second and 10 seconds). The pressure sensor interface  1010  may be communicatively coupled to one or more pressure sensors or pressure measurement devices such as, for example, the pressure sensors  920   a - g  of  FIG. 9 . For example, the pressure sensors  920   a - g  may provide signals (e.g., electric signals) to the pressure sensor interface  1010 , which correlate to pressures of the control fluid in the respective actuators  620  and  712   a - f.    
     In some examples, the pressure sensor interface  1010  may receive pressure measurement values from the pressure sensor  920   d  associated with the actuator  712   c  (e.g., a central actuator) at the entry of the leveler  402  (e.g., only from the actuator  712   c ). 
     The comparator  1012  may be configured to receive the pressure measurement values from the pressure sensor interface  1010  for each of the incremental plunge depths of each of the actuators  620 ,  622 ,  712   a - f  and  714   a - f . For example, the comparator  1012  may receive the pressure measurement values for each of the respective incremental plunge depths associated with the actuator  712   c . The comparator  1012  may be configured to perform comparisons of the pressure measurement values provided by the pressure sensor  920   d  associated with the actuator  712   c . The comparator  1012  may be configured can determine a lowest or smallest pressure reading and identify the incremental plunge depth value of the entry work rolls corresponding to the detected smallest pressure reading. More specifically, the lowest or smallest pressure reading detected is associated with or corresponds to the hook  202  of the graph  200  of  FIG. 2 . In particular, the lowest or smallest detected pressure measurement value approximates the yield point of the strip material  400  within a threshold (e.g., about 3 percent). In this manner, the detected smallest pressure measurement value associated with the incremental plunge depth position is approximately equal to the yield point of the strip material  400 . The smaller the incremental values, the measured pressure measurement values approximate the actual yield point (e.g., the yield point  202 ) associated with the strip material  400 . Thus, the plunge position determiner  1004  detects a plunge depth (e.g., the incremental plunge depth position associated with the smallest pressure reading) that imparts a stress to the strip material  400  that is approximate to an actual yield point (e.g., the yield point  202  of the graph  200  of  FIG. 2 ). 
     In turn, the plunge position determiner  1004  causes the plunge position adjustor  1006  to adjust or set a plunge depth or vertical positions of the entry work rolls  506  to the calculated or identified work roll plunge depth (e.g., the plunge depth d 1  of  FIG. 5 ). In some examples, the plunge depth determiner  1004  causes the plunge position adjustor  1006  to adjust a plunge depth (e.g., the plunge depth d 2  of  FIG. 5 ) of the exit work rolls  508  based on the particular strip material data (e.g., the thickness T 1  of the strip material  400 ) provided by the user via the user input interface  1002 . For example, the plunge of the exit work rolls  308  may be set so that a separation gap between opposing surfaces of the upper and lower work rolls is substantially equal to the thickness of the strip material  400 ). Thus, the entry work rolls  506  may be adjusted to provide a plunge depth that is deeper (e.g., greater) than the plunge depth of the exit work rolls  508  (e.g., d 1  of  FIG. 5  is less than d 2  of  FIG. 5 ). 
     Additionally or alternatively, in some examples, the pressure measured values may be provided from each of the actuators  620 ,  622 ,  712   a - f  and  714   a - f  and/or the zones  802 - 814 . In some such examples, the pressure sensor interface  1010  may receive pressure measurement values from each pressure sensor  920   a - g  associated with the respective actuators  620 ,  622 ,  712   a - f  and  714   a - f . The pressure sensor interface  1010  may be configured to then send the pressure measurement values to the plunge position determiner  1004  and/or the comparator  1012 . The comparator  1012  may be configured to detect the smallest pressure reading and the associated incremental plunge depth position for each of the actuators  620  and  712   a - f . In some examples, the plunge position determiner  1004  causes the plunge position adjustor  1006  to adjust each of the actuators  620  and  712   a - f  to their respective identified incremental plunge depth position associated with the detected smallest pressure reading of the respective actuator  620  and  712   a - f . In some such examples, the plunge position determiner  1004  causes the plunge position adjustor  1006  to adjust the plunge depths (e.g., the plunge depth distance d 1  of  FIG. 5 ) of each of the actuators  620  and  712   a - f  to their respective incremental plunge depth values corresponding to the smallest pressure measure measurement value of the particular actuator  620  and  712   a - f . In some examples, the comparator may determine an average value of the incremental plunge depth value associated with the smallest pressure measurement values in each of the actuators  620  and  712   a - f . In some such examples, the plunge position determiner  1004  causes the plunge position adjustor  1006  to adjust the plunge depths (e.g., the plunge depth distance d 1  of  FIG. 5 ) of each of the actuators  620  and  712   a - f  to the determined average incremental plunge depth position to process the strip material  400 . 
     The storage interface  1014  may be configured to store data values (e.g., the incremental plunge depth value, the initial plunge depth value, the final plunge depth value, the pressure measurement values, the smallest detected pressure measurement value, etc.) in a memory such as, for example, the system memory  1413  and/or the mass storage memory  1428  of  FIG. 14 . Additionally, the storage interface  1014  may be configured to retrieve data values from the memory (e.g., the incremental plunge depth values, the pressure measurement values, etc.). For example, the storage interface  1014  may be configured to store data values associated with a particular type of strip material and/or material characteristics received by the user input interface  1002 . For example, the storage interface  1014  may store an initial plunge value and a maximum plunge value for a particular grade of steel of a strip material. For example, grade A36 steel may have a yield strength range between approximately 30,000 and 45,000 pounds/in 2  (psi). In such example, a first or initial plunge depth may be associated with the 30,000 psi yield strength and a second or maximum plunge depth may be associated with the 45,000 psi yield strength. 
     The calibrator  1016  may be configured to calibrate the position sensors  916   a - g  and/or the pressure sensors  920   a - g  of the example leveler  402 . For example, the calibrator  1016  may initiate a calibration of the sensors  916   a - g  and/or  920   a - g  prior to processing the strip material  400  through the leveler  402 . The calibrator  1016  may be configured to initiate when a user input command is selected via the user input interface  1002 . Additionally or alternatively, the calibrator  1016  may be configured to automatically initiate calibration of the positioning sensors  916   a - g  and/or the pressure sensors  920   a - g  prior to beginning a production run to condition the strip material  400 . 
     The calibrator  1016  may be configured to command and/or communicate with the plunge position detector  1008  and/or the pressure sensor interface  1010 . To calibrate the position sensors  916   a - g  and/or the pressure sensors  920   a - g , the calibrator  1016  may be configured to command the plunge position adjustor  1006  to move the work rolls  412  to a closed position. For example, the work rolls  412  may be in a closed position when the lower work rolls  504  engage the upper work rolls  502  prior to the strip material  400  passing through the leveler  402 . Alternatively, calibration plates having a known thickness may be positioned between the upper work rolls  502  and the lower work rolls  504  and the calibrator  1016  may instruct the plunge position adjustor  1006  to move the lower work rolls  504  toward the upper work rolls  502  until the upper work rolls  502  and the lower work rolls  504  engage or close against opposing surfaces of the calibration plates. For example, an operator may position the calibration plates between the upper work rolls  502  and the lower work rolls  504 . 
     Once the upper work rolls  502  and the lower work rolls  504  are in a closed position, the calibrator  1016  may be configured to determine and/or record the measured position values provided by the position sensors  916   a - g  for each of the actuators  620 ,  622 ,  712   a - f  and  714   a - f  and/or zones  802 - 814  and/or the plunge position pressure values provided by the pressure sensors  920   a - g  for each of the actuators  620 ,  622 ,  712   a - f  and  714   a - f  and/or zones  802 - 814 . For example, because the thickness of the calibration plates is known, position signals provided by the position sensors  916   a - g  can correlate to respective plunge depth position values that correspond to respective stroke positions of the actuators  620 ,  622 ,  712   a - f  and  714   a - f  and/or zones  802 - 814 . Additionally, the pressure values sensed by the pressure sensors  920   a - g  may correlate to a force (e.g., a vertical force) imparted to the strip material  400  by the work rolls  412  associated with the respective actuators  620 ,  622 ,  712   a - f  and  714   a - f  and/or zones  802 - 814  when the respective actuators  620 ,  622 ,  712   a - f  and  714   a - f  and/or zones  802 - 814  are positioned to the plunge depth positions. After the sensors  916   a - g  and/or  920   a - g  are calibrated, the calibrator  1016  may communicate to the plunge depth determiner  1004  that the calibration is complete. 
     While an example manner of implementing the controller  520  is illustrated in  FIG. 10 , one or more of the elements, processes and/or devices illustrated in  FIG. 10  may be combined, divided, re-arranged, omitted, eliminated and/or implemented in any other way. Further, the example user input interface  1002 , the example plunge depth determiner  1004 , the plunge position adjustor  1006 , the example plunge position detector  1008 , the example pressure sensor interface  1010 , the example comparator  1012 , the example storage interface  1014 , the example calibrator  1016  and/or the example positioning valve controller  1018  and/or, more generally, the example controller  520  of  FIG. 10  may be implemented by hardware, software, firmware and/or any combination of hardware, software and/or firmware. Thus, for example, any of the example user input interface  1002 , the example plunge depth determiner  1004 , the plunge position adjustor  1006 , the example plunge position detector  1008 , the example pressure sensor interface  1010 , the example comparator  1012 , the example storage interface  1014 , the example calibrator  1016  and/or the example positioning valve controller  1018  and/or, more generally, the example controller  520  of  FIG. 10  could be implemented by one or more analog or digital circuit(s), logic circuits, programmable processor(s), application specific integrated circuit(s) (ASIC(s)), programmable logic device(s) (PLD(s)) and/or field programmable logic device(s) (FPLD(s)). When reading any of the apparatus or system claims of this patent to cover a purely software and/or firmware implementation, at least one of the example, the example user input interface  1002 , the example plunge depth determiner  1004 , the plunge position adjustor  1006 , the example plunge position detector  1008 , the example pressure sensor interface  1010 , the example comparator  1012 , the example storage interface  1014 , the example calibrator  1016  and/or the example positioning valve controller  1018  and/or, more generally, the example controller  520  of  FIG. 10  is/are hereby expressly defined to include a tangible computer readable storage device or storage disk such as a memory, a digital versatile disk (DVD), a compact disk (CD), a Blu-ray disk, etc. storing the software and/or firmware. Further still, the example controller  520  of  FIG. 10  may include one or more elements, processes and/or devices in addition to, or instead of, those illustrated in  FIG. 10 , and/or may include more than one of any or all of the illustrated elements, processes and devices. 
       FIG. 11  illustrates a flowchart representative of example machine readable instructions for implementing the controller  520  of  FIGS. 5 and 10  and/or the plunge depth determiner  1104  of  FIG. 10 .  FIG. 13  illustrates a flowchart representative of example machine readable instructions for implementing the controller  520  of  FIGS. 5 and 10  and/or the calibrator  1016  of  FIG. 10 . In this example, the machine readable instructions comprise a program for execution by a processor such as the processor  1412  shown in the example processor platform  1400  discussed below in connection with  FIG. 14 . The program may be embodied in software stored on a tangible computer readable storage medium such as a CD-ROM, a floppy disk, a hard drive, a digital versatile disk (DVD), a Blu-ray disk, or a memory associated with the processor  1412 , but the entire program and/or parts thereof could alternatively be executed by a device other than the processor  1412  and/or embodied in firmware or dedicated hardware. Further, although the example programs are described with reference to the flowcharts illustrated in  FIGS. 11 and 13 , many other methods of implementing the example controller  520 , the example plunge depth determiner  1004  and/or the calibrator  1016  may alternatively be used. For example, the order of execution of the blocks may be changed, and/or some of the blocks described may be changed, eliminated, or combined. 
     As mentioned above, the example processes of  FIGS. 11 and 13  may be implemented using coded instructions (e.g., computer and/or machine readable instructions) stored on a tangible computer readable storage medium such as a hard disk drive, a flash memory, a read-only memory (ROM), a compact disk (CD), a digital versatile disk (DVD), a cache, a random-access memory (RAM) and/or any other storage device or storage disk in which information is stored for any duration (e.g., for extended time periods, permanently, for brief instances, for temporarily buffering, and/or for caching of the information). As used herein, the term tangible computer readable storage medium is expressly defined to include any type of computer readable storage device and/or storage disk and to exclude propagating signals and to exclude transmission media. As used herein, “tangible computer readable storage medium” and “tangible machine readable storage medium” are used interchangeably. Additionally or alternatively, the example processes of  FIGS. 11 and 13  may be implemented using coded instructions (e.g., computer and/or machine readable instructions) stored on a non-transitory computer and/or machine readable medium such as a hard disk drive, a flash memory, a read-only memory, a compact disk, a digital versatile disk, a cache, a random-access memory and/or any other storage device or storage disk in which information is stored for any duration (e.g., for extended time periods, permanently, for brief instances, for temporarily buffering, and/or for caching of the information). As used herein, the term non-transitory computer readable medium is expressly defined to include any type of computer readable storage device and/or storage disk and to exclude propagating signals and to exclude transmission media. As used herein, when the phrase “at least” is used as the transition term in a preamble of a claim, it is open-ended in the same manner as the term “comprising” is open ended. 
     Turning in detail to  FIG. 11 , the plunge position determiner  1004  receives or obtains strip material characteristics information (block  1102 ). For example, a user can input the material characteristics via a controller user interface such as, for example, the user input interface  1002  of  FIG. 10 . 
     The plunge depth determiner  1004  instructs or causes the plunge depth adjustor to move the work rolls  412  to an initial plunge depth (block  1104 ). For example, the plunge position adjustor  1006  commands one or more of the pumps  902   a - g  to deliver pressurized control fluid to one or more of the respective actuators  620 ,  622 ,  712   a - f  and  714   a - f . More specifically, as noted above, the plunge position adjustor  1006  adjusts the plunge position of the work rolls  412  at the entry  630  of the leveler  402  (e.g., the plunge depth distance d 1  at the entry work rolls  506 ) and the plunge position of the work rolls  412  at the exit  632  of the leveler  402  (e.g., the exit work rolls  508 ). The work rolls  412  at the exit  632  may be set to a plunge depth that is equal to a thickness (e.g., the thickness T 1 ) of the strip material  100  received via the user input interface  1002 . In some examples, the plunge position determiner  1004  retrieves the initial plunge depth value via the user input interface  1002 . In some examples, the initial plunge depth value is determined using a reference table retrieved from the storage interface  1014 . For example, based on the material characteristics received from the input interface  1002 , the plunge position determiner  1004  determines a plunge depth value associated with a minimum yield strength of the strip material. 
     After the initial plunge depth is set and prior to processing the strip material, a pressure value is measured (block  1106 ). For example, the pressure value may be a pressure provided by the pressure sensor  920   d  of the cylinder  712   c  when the work rolls  412  at the entry  630  are positioned at the initial plunge depth. For example, the pressure sensor interface  1010  may detect, via the pressure sensor  920   d , a pressure value in the actuator  712   c  when the actuator  712   c  is positioned at a stroke position that correlates to the initial plunge depth position of the respective work rolls  412  associated with the actuator  712   c . In some examples, the pressure sensor interface  1010  may measure the pressure in the actuator  712   c  after a predetermined time period has lapsed (e.g., three seconds, five seconds, etc.) from the time that the plunge position adjustor  1006  positions the work rolls  412  to the initial plunge depth position. In some examples, a pressure in each of the zones  804 - 814  associated with the cylinders  620  and  712   a - f  is recorded. For example, the pressure sensor interface  1010  may detect, via one or more of the pressure sensors  920   a - g , a pressure value in each of the actuators  620 ,  712   a - f  and/or zones  802 - 814  when the actuators  620 ,  712   a - f  are at respective initial stroke positions that correlate to the initial plunge depth positions of the respective work rolls  412  associated with the actuators  620 ,  712   a - f.    
     The plunge position determiner  1004  associates the measured pressure with the current plunge depth (block  1108 ). For example, at the initial plunge depth, the pressure sensor interface  1010  determiners the pressure in the cylinder  712   c  and associates the pressure value with the initial plunge depth position. 
     The plunge position determiner  1004  then determines if a maximum plunge depth has been reached (block  1110 ). For example, based on the material characteristics received from the input interface  1002 , the plunge position determiner  1004  determines a maximum plunge depth value associated with a maximum yield strength of the strip material based on the material characteristics. For example, the plunge position determiner  1004  may retrieve a reference table from the storage interface  1014  providing a plunge depth associated with a maximum yield strength of the strip material. In some examples, a user or operator may input the maximum plunge depth value via the user input interface  1002 . In some examples, the maximum plunge depth value is determined based on a comparison and/or a pattern of the output pressure sensor readings provided by the pressure sensor interface  1010 . For example, the comparator  1012  compares a first pressure output and a second pressure output to detect consecutive increases in pressure. For example, if a pressure increase is detected between two consecutive values, the comparator  1012  compares a third pressure output with the second pressure output. The plunge position determiner  1004  causes the plunge depth adjustor  1006  to adjust the plunge by another incremental plunge depth. If the pressure decreases after the incremental plunge adjustment, the comparator  1012  compares the next subsequent pressure reading with the preceding pressure reading until a number (e.g., three) of consecutive pressure increases is detected. At the last pressure increase detected after the consecutive pressure increase threshold is met, the plunge position determiner  1004  stops sampling and the maximum plunge depth is determined. In some examples, the comparator  1012  compares the pressure outputs and after a second drop in pressure compared to a preceding pressure reading is detected, the comparator  1012  continues to monitor until a number of consecutive pressure increases is achieved. Once the number of consecutive pressure readings is detected, the maximum plunge depth is reached. 
     If a maximum plunge depth has not been reached at block  1110 , the plunge position determiner  1004  proceeds to the next incremental plunge depth (block  1112 ). Specifically, the plunge position determiner  1004  causes the plunge position adjustor  1006  to increase a plunge depth by an incremental value. For example, the incremental value may be a five-thousandths of an inch (e.g., 0.0005 inches), ten-thousandths of an inch (0.001 inches), twenty-thousandths of an inch (0.0020) and/or any other incremental value. A smaller incremental value enables the plunge depth determiner  1004  to more accurately determine a plunge depth associated with an actual yield point of a strip material. For each incremental value, the pressure is measured (block  1106 ) and the measured pressure is associated with the current plunge depth (block  1108 ). As noted above, the pressure at each incremental plunge depth position may be measured after a predetermined period of time has lapsed (e.g., after three seconds). 
     When the maximum plunge depth is met at block  1110 , the plunge depth determiner  1004  compares the measured pressure readings (block  1114 ). For example, each of the measured pressure readings associated with the various incremental plunge depths are compared via the comparator  1012 . 
     The comparator  1012  and/or the plunge depth determiner  1004  detect or determine the smallest pressure reading and identifies the plunge depth corresponding to the smallest pressure reading (block  1116 ). The smallest pressure reading is associated with a plunge depth that imparts a stress to the strip material  400  that is closest (e.g., within three percent) of a yield point (e.g., of an actual yield point) of the strip material  400 . For example, the stress or pressure determined by the plunge depth determiner  1004  is associated with the yield point  202  of the strip material  400  provided by the stress-strength curve of  FIG. 2 . In some examples, the plunge depth determiner  1004  measures the pressure of each of the cylinders  620  and  712   a - f  at each of the incremental plunge depths. The plunge depth determiner  1004  and/or the comparator  1012  determine the smallest pressure reading for each of the cylinders  620  and  712   a - f  and the associated plunge depths corresponding to the respective smallest pressure readings. The plunge depths of each of the cylinders  620  and  712   a - f  corresponding to the smallest pressure readings are identified and the controller  518  determines an average plunge depth value. The plunge adjustor  1006  adjusts the plunge depth of the entry work rolls  506  via the cylinders  620  and  712   a - f  to the determined average plunge depth value. In yet other examples, the plunge depth determiner  1004  determines the plunge depth of each of the different cylinders  620  and  712   a - f  and adjusts each of the cylinders  620  and  712   a - f  to the respective plunge depth corresponding to a smallest pressure reading. In this manner, each of the cylinders  620  and  712   a - f  are adjusted independently of each other to a plunge depth associated with their respective smallest pressure reading. In other words, in some such examples, the method  1100  of  FIG. 11  is conducted for each cylinder  620  and  712   a - f  and independently of each other. 
     The plunge depth determiner  1004  and/or the plunge position adjustor  1006  adjusts the plunge depth of the work rolls  412  (e.g., at the entry work rolls) based on the identified plunge depth associated with the smallest pressure reading (block  1118 ). For example, the plunge depth determiner  1004  and/or the plunge position adjustor  1006  adjusts the plunge depth of the entry work rolls  506  via the cylinders  620  and  712   a - f  to the identified plunge depth corresponding to the smallest pressure reading. The plunge depth determiner  1004  and/or the plunge position adjustor  1006  positions the exit work rolls  508  corresponding to the thickness of the strip material (e.g., obtained via the user input interface  1002 ). For example, the plunge depth determiner  1004  and/or the plunge position adjustor  1006  adjusts the plunge depth of the exit work rolls  508  via the cylinders  622  and  714   a - f  to the identified plunge depth corresponding to the thickness of the strip material (e.g., a gap or vertical distance between a lowermost point of the upper work rolls and the uppermost point of the lower work rolls is substantially equal to the thickness of the strip material). 
     After the cylinders  620  and  712   a - f  are set at the identified plunge depth position and/or the cylinders  622  and  714   a - f  are set at the plunge depth corresponding to the thickness of the strip material, the strip material (e.g., the strip material  400 ) is processed. In operation, the strip material may be continuously fed to the leveler  402  from an uncoiler (e.g., the uncoiler  408  of  FIG. 4 ). 
       FIG. 12  illustrates an example display or output  1200  provided by the plunge depth determiner  1004  when executing the example method  1100  of  FIG. 11  to process an example strip material composed of steel. In particular, prior to processing the strip material, the plunge depth determiner  1004  determines a plunge depth approximate to a yield point (e.g., the yield point  202  of the stress-strain graph  200  of  FIG. 2 ) of the strip material. 
     In the illustrated example, the strip material processed in the example of  FIG. 12  is composed of carbon steel and has characteristics including a thickness of 0.1720 inches, a width of sixty inches (60 in), Young&#39;s Modulus of Elasticity of 30 Mpsi, and a minimum yield strength of approximately 50,000 psi. The material characteristics may be received via the user input interface  1002 . The display  1200  includes a number  1202  of incremental plunge depth positions, entry gap values  1204  corresponding to the respective incremental plunge depth positions, and measured pressures  1206  associated with the incremental plunge depth positions. The display  1200  of the illustrated example also provides a total number of samples  1208  to be measured (e.g., 40 samples), a time delay  1210  for measuring the pressure values after an incremental plunge depth position is adjusted or positioned (e.g., a three second delay), an incremental plunge depth distance or value  1212  (e.g., 0.002 inches) between the incremental plunge depth positions, a thickness  1214  of the strip material (e.g., 0.1720 inches), a width of the strip material  1216  (e.g., 60 inches), a percent of cross section area to plastically yield  1218  (e.g., 80 percent), and a calculated gap setting window  1220  illustrating an entry gap of the entry work rolls (e.g., 0.087 inches), an exit gap of the exit work rolls (e.g., 0.172 inches), a minimum gap of the entry work rolls (e.g., 0.087 inches), and the maximum percent of cross section area of the strip material to be yielded (e.g., 80 percent). 
     The sequence illustrated by the display  1200  starts at gap positions 01 through 10. This example took ten readings to detect the plunge position associated with a lowest pressure reading  1222 . The example plunge position determiner  1004  detected the increase in pressure in the readings 8-10 and determined based on these readings that no additional readings were needed (e.g., based on a difference or comparison with the pressure output at reading 1-7). The lowest or smallest pressure reading  1222  is at reading 7 in the column representing the number  1202  of incremental plunge depth positions. At reading 7, the plunge depth position is 0.0960 inches and the pressure reading associated with or corresponding to the plunge depth position of 0.096 inches at reading 7 is 730 pounds-per-square inch (e.g., 730 lbs/in 2 ). The calculated yield point given the material thickness, the material type and the pressure (730 lbs/in 2 ) provided at the plunge depth position of 0.096 inches is 48,583 lbs/in 2 . Lab testing determined the actual yield for the sample strip material represented by FIG. 12  is 49,850 lbs/in 2 . The calculated yield provided by the smallest pressure value at reading 7 and the actual test yield provided via lab testing is a difference of approximately 2.54%. Thus, the example plunge depth determiner  1004  of the illustrated example determined a plunge depth position that provides a stress to the strip material within three percent of the actual yield point of the strip material. 
       FIG. 13  illustrates an example method  1300  that may be used to implement the controller  520  and/or the calibrator  1016  of  FIG. 10 . More specifically, the method  1300  may be performed prior to receiving the strip material characteristic(s) at block  1102  of  FIG. 11 . In other words, the example method  1300  may be performed prior to a production run of the strip material  400 . 
     To calibrate the position sensors and the pressure sensors, the calibrator initiates calibration (block  1302 ). To initiate the calibration, a calibration control may be selected via the user input interface  1002  and/or may be initiated prior to a production run. 
     To calibrate the position sensors  916   a - g  and the pressure sensors  920   a - g , the work rolls  412  in each zone are adjusted to a closed position (block  1304 ). For example, the calibrator  1016  instructs or commands the plunge position adjustor  1006  to control the pumps  902   a - g  and provide a control fluid to the respective actuators  620 ,  712   a - f  until the lower work rolls  504  engage the upper work rolls  502 . In some examples, a plurality of ground plates each having a known or substantially similar thickness may be positioned between the upper works rolls  502  and the lower work rolls  504  in each of the zones (e.g., the zones  802 - 814 ). In examples in which the calibration plates are employed, the lower work rolls  504  are adjusted until the lower work rolls  504  and the upper work rolls  502  engage respective opposing surfaces of the calibration plates positioned between the upper work rolls  502  and the lower work rolls  504  (e.g., spaced apart by a vertical distance defined by a thickness of the calibration plate(s)). 
     The controller  520  and/or the plunge position detector  1008  detects if the work rolls  412  in each zone are in the closed position (block  1306 ). If the work rolls  412  are not in the closed position, then the system returns to block  1304 . If the work rolls  412  are in the closed position, the positioning valve controller  1018  causes the positioning valves  914   a - g  to move to a closed position for each zone associated with the work rolls  412  positioned in the closed position. In the closed position, the positioning valves  914   a - g  prevent or restrict the flow of the control fluid between the reservoir  904   a - g  and the respective chambers  808   a - f.    
     If the work rolls  412  in each zone is in a closed position, the calibrator  1016  records the position value for each zone (block  1308 ) and the pressure values for each zone and/or actuators (block  1310 ). For example, after the positioning valves (e.g., the positioning valves  914   a - g ) are moved to the closed positions, the position value provided by the position sensors  916   a - g  corresponding to the plunge depth position and, thus, the stroke position of each of the respective actuators associated with the respective zones is recorded. Additionally, the pressure value provided by the pressure sensor  920   a - g  associated with the actuator or particular zone is recorded. 
     If all the recorded pressure values are equal or substantially equal (within ten percent) in each zone (block  1314 ), then the system records the plunge position value in each zone (block  1316 ) and correlates the pressure value in each zone to the respective recorded plunge position value (block  1318 ). 
       FIG. 14  is a block diagram of an example processor platform  1400  capable of executing the instructions of  FIGS. 11 and 13  to implement the controller  520  of  FIGS. 5 and 10 . The processor platform  1400  can be, for example, a server, a personal computer, a mobile device (e.g., a cell phone, a smart phone, a tablet such as an iPad™), a personal digital assistant (PDA), an Internet appliance, a DVD player, a CD player, or any other type of computing device. 
     The processor platform  1400  of the illustrated example includes a processor  1412 . The processor  1412  of the illustrated example is hardware. For example, the processor  1412  can be implemented by one or more integrated circuits, logic circuits, microprocessors or controllers from any desired family or manufacturer. 
     The processor  1412  of the illustrated example includes a local memory  1413  (e.g., a cache). The processor  1412  of the illustrated example is in communication with a main memory including a volatile memory  1414  and a non-volatile memory  1416  via a bus  1418 . The volatile memory  1414  may be implemented by Synchronous Dynamic Random Access Memory (SDRAM), Dynamic Random Access Memory (DRAM), RAMBUS Dynamic Random Access Memory (RDRAM) and/or any other type of random access memory device. The non-volatile memory  1416  may be implemented by flash memory and/or any other desired type of memory device. Access to the main memory  1414 ,  1416  is controlled by a memory controller. 
     The processor platform  1400  of the illustrated example also includes an interface circuit  1420 . The interface circuit  1420  may be implemented by any type of interface standard, such as an Ethernet interface, a universal serial bus (USB), and/or a PCI express interface. 
     In the illustrated example, one or more input devices  1422  are connected to the interface circuit  1420 . The input device(s)  1422  permit(s) a user to enter data and commands into the processor  1412 . The input device(s) can be implemented by, for example, an audio sensor, a microphone, a camera (still or video), a keyboard, a button, a mouse, a touchscreen, a track-pad, a trackball, isopoint and/or a voice recognition system. 
     One or more output devices  1424  are also connected to the interface circuit  1420  of the illustrated example. The output devices  1424  can be implemented, for example, by display devices (e.g., a light emitting diode (LED), an organic light emitting diode (OLED), a liquid crystal display, a cathode ray tube display (CRT), a touchscreen, a tactile output device, a printer and/or speakers). The interface circuit  1420  of the illustrated example, thus, typically includes a graphics driver card, a graphics driver chip or a graphics driver processor 
     The interface circuit  1420  of the illustrated example also includes a communication device such as a transmitter, a receiver, a transceiver, a modem and/or network interface card to facilitate exchange of data with external machines (e.g., computing devices of any kind) via a network  1426  (e.g., an Ethernet connection, a digital subscriber line (DSL), a telephone line, coaxial cable, a cellular telephone system, etc.). 
     The processor platform  1400  of the illustrated example also includes one or more mass storage devices  1428  for storing software and/or data. Examples of such mass storage devices  1428  include floppy disk drives, hard drive disks, compact disk drives, Blu-ray disk drives, RAID systems, and digital versatile disk (DVD) drives. 
     The coded instructions  1100  and  1300  of  FIGS. 11 and 13  may be stored in the mass storage device  1428 , in the volatile memory  1414 , in the non-volatile memory  1416 , and/or on a removable tangible computer readable storage medium such as a CD or DVD. 
     From the foregoing, it will be appreciated that the above disclosed methods, apparatus and articles of manufacture use a pressure measured value to determine if a sufficient force is applied to plastically deform or yield the strip material (e.g., the strip material  400 ) passing through the nested work rolls (e.g., the work rolls  412 ). In this manner, the pressure measured value correlates to a force imparted to the strip material via the work rolls  412 . The measured force can be used to determine if the force is sufficient to plunge (e.g., stretch or bend) the strip material  400  beyond its yield strength to release internal stresses (e.g., remove coil set) in the strip material  400 . 
     At least some of the aforementioned examples include one or more features and/or benefits including, but not limited to: 
     In some examples, a method for setting a plunge depth of a leveler includes: incrementally adjusting, via an actuator, a first work roll relative to a second work roll between a plurality of incremental plunge depth positions; measuring a pressure value in the actuator at the respective incremental plunge depth positions; associating the measured pressure values with the corresponding incremental plunge depth positions; detecting a smallest one of the measured pressure values; and identifying a first one of the incremental plunge depth positions corresponding to the smallest one of the measured pressure values. 
     In some examples, the method includes processing a strip material at the identified first one of the incremental plunge depth positions. 
     In some examples, the method includes receiving material characteristics of the strip material prior to incrementally adjusting the first and second work rolls between the incremental plunge depth positions. 
     In some examples, the method includes receiving material characteristics by receiving a width value and a thickness value of the strip material. 
     In some examples, the method includes incrementally adjusting the first and second work rolls by incrementally adjusting a plunge depth between the first and second work rolls by a preset incremental value. 
     In some examples, the method includes incrementally adjusting the first and second work rolls by adjusting the first and second work rolls at an initial plunge depth position and adjusting the initial plunge depth by a preset incremental value. 
     In some examples, the method includes positioning a strip material in the leveler between the first work roll and the second work roll prior to incrementally adjusting the plunge depth positions. 
     In some examples, the method includes displaying, via a user interface, the incremental plunge depth positions and the measured pressure values corresponding to the respective incremental plunge depth positions. 
     In some examples, a tangible computer-readable medium comprising instructions that, when executed, cause a machine to: incrementally adjust, via an actuator, a first work roll relative to a second work roll between a plurality of incremental plunge depth positions; measure a pressure value in the actuator at the respective incremental plunge depth positions; associate the measured pressure values with the corresponding incremental plunge depth positions; detect a smallest one of the measured pressure values; and identify a first one of the incremental plunge depth positions corresponding to the smallest one of the measured pressure values. 
     In some examples, the instructions cause the machine to set a plunge depth between the first and second work rolls at the identified first one of the incremental plunge depth positions and process a strip material at the identified first one of the incremental plunge depth positions. 
     In some examples, the instructions cause the machine to receive material characteristics of the strip material prior to incrementally adjusting the first and second work rolls between the incremental plunge depth positions. 
     In some examples, the instructions cause the machine to receive material characteristics comprises receiving a width value and a thickness value of the strip material. 
     In some examples, the instructions cause the machine to incrementally adjust the first and second work rolls by incrementally adjusting a plunge depth between the first and second work rolls by a preset incremental value. 
     In some examples, the instructions cause the machine to incrementally adjust the first and second work rolls by adjusting the first and second work rolls at an initial plunge depth position and adjusting the initial plunge depth by a preset incremental value. 
     In some examples, the instructions cause the machine to display the incremental plunge depth positions and the measured pressure values corresponding to the respective incremental plunge depth positions. 
     In some examples, a leveler to condition a strip material includes a first plurality of entry work rolls, a second plurality of entry work rolls supported by an adjustable flight, and an actuator associated with the adjustable flight. The actuator incrementally adjusts a position of the adjustable flight to move the second plurality of entry work rolls relative to the first plurality of entry work rolls between a plurality of incremental plunge depth positions. A pressure sensor is coupled to the actuator to measure a pressure value in a control fluid of the actuator when the first and second work rolls are positioned at the respective incremental plunge depth positions. A controller is configured to determine a smallest one of the pressure values and identify a first one of the incremental plunge depth positions corresponding to the smallest one of the pressure values. 
     In some examples, the controller adjusts the first and second work rolls to the identified first one of the plunge depth positions. 
     In some examples, the adjustable flight includes a plurality of adjustable flights to define respective zones across a width of the strip material. 
     In some examples, the actuator includes a plurality of actuators associated with respective ones of the adjustable flights, the actuators to adjust positions of the respective ones of the adjustable flights to enable each of the zones to be positioned between the incremental plunge depth positions. 
     In some examples, the pressure sensor comprises a plurality of pressure sensors coupled to a respective one of the actuators, each pressure sensor to detect pressure changes in a control fluid of its respective actuator. 
     In some examples, the controller adjusts the plunge depth position of each of the zones to the first one of the plunge depth positions corresponding to the smallest pressure value. 
     Although certain example methods and apparatus have been described herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all methods, apparatus, and articles of manufacture fairly falling within the scope of the appended claims either literally or under the doctrine of equivalents.