High Precision Thickness Control on a Rolling Mill for Flat Rolled Metal

Abstract

The high precision rolling design utilizes a high speed hydraulic roll position control along with a high accuracy roll gap measurement. The lower work roll position is fixed and the upper work roll is positioned by a hydraulic roll force cylinder using an inner and outer control loop. The inner loop is a cylinder position control that moves the upper work roll. The outer loop uses a measurement of the work roll gap to trim the inner cylinder positioning control. Both control loops coordinate together to provide a high precision and even strip thickness tolerance to +/−0.15 mils or less. Both sides of the upper work roll are controlled separately to achieve the overall tolerance goal.

We claim: 
     
         1 . A single stand rolling mill with a thickness control system designed to roll a flat metal product comprising:
 A) a pair of work rolls, wherein one work roll is designed to be separately movable on each side of said rolling mill for metal thickness control purposes,   B) wherein said thickness control system is designed to position said movable work roll on both sides of said rolling mill,   C) wherein said thickness control system comprises the following features on each side of said movable work roll:
 a) a roll force cylinder designed to position said movable work roll, 
 b) a roll gap sensor, wherein said roll gap sensor has an accuracy of +/−0.08 mils or less, 
 c) an outer roll gap position control loop, wherein said outer roll gap position control loop is connected to said roll gap sensor, 
 d) wherein said outer roll gap position control loop is additionally connected to an inner roll force cylinder position control loop, 
 e) wherein said an inner roll force cylinder position control loop is connected to a hydraulic control valve, 
 f) wherein said hydraulic control valve is connected to said roll force cylinder, and 
 g) said hydraulic control valve and associated hydraulic system is designed to move said movable work roll 0.001 inches in 50 milliseconds or less, 
   D) whereby said thickness control system is designed to roll said flat metal product within +/−0.15 mil of a desired thickness.   
     
     
         2 . The single stand rolling mill according to  claim 1  wherein said pair of work rolls are designed to roll said flat metal product in dry conditions. 
     
     
         3 . The single stand rolling mill according to  claim 2  wherein said thickness control system design requires multiple rolling passes. 
     
     
         4 . The single stand rolling mill according to  claim 2  wherein said thickness control system is designed to roll said flat metal product used for coins. 
     
     
         5 . The single stand rolling mill according to  claim 4 , wherein said flat metal product comprises gold, silver, and platinum products useful for said coins. 
     
     
         6 . The single stand rolling mill according to  claim 1  wherein said movable work roll is an upper work roll. 
     
     
         7 . The single stand rolling mill according to  claim 1  wherein said roll gap sensor uses to measure a gap between said pair of work rolls. 
     
     
         8 . A single stand rolling mill with a thickness control system designed to roll a flat metal product comprising:
 A) a pair of work rolls, wherein one work roll is designed to be separately movable on each side of said rolling mill for metal thickness control purposes,   B) wherein said thickness control system is designed to position said movable work roll on both sides of said rolling mill,   C) a roll gap sensor, wherein said roll gap sensor has an accuracy of +/−0.08 mils or less,   D) wherein said thickness control system comprises the following features on each side of said movable work roll:
 a) a roll force cylinder designed to position said movable work roll, 
 b) an outer roll gap position control loop, wherein said outer roll gap position control loop is connected to said roll gap sensor, 
 c) wherein said outer roll gap position control loop is additionally connected to an inner roll force cylinder position control loop, 
 d) wherein said an inner roll force cylinder position control loop is connected to a hydraulic control valve, 
 e) wherein said hydraulic control valve is connected to said roll force cylinder, and 
 f) said hydraulic control valve and associated hydraulic system is designed to move said movable work roll 0.001 inches in 50 milliseconds or less, 
   E) whereby said thickness control system is designed to roll said flat metal product within +/−0.15 mil of a desired thickness.   
     
     
         9 . The single stand rolling mill according to  claim 8  wherein said pair of work rolls are designed to roll a flat metal product in dry conditions. 
     
     
         10 . The single stand rolling mill according to  claim 9  wherein said rolling mill thickness reduction design requires multiple passes. 
     
     
         11 . The single stand rolling mill according to  claim 9  wherein said thickness control system is designed to roll said flat metal product used for coins. 
     
     
         12 . The single stand rolling mill according to  claim 11 , wherein said flat metal product comprises metals that are gold, silver, and platinum. 
     
     
         13 . The single stand rolling mill according to  claim 8  wherein said movable work roll is an upper work roll. 
     
     
         14 . A single stand rolling mill with a thickness control system comprising:
 A) a pair of work rolls, wherein one work roll is designed to be separately movable on each side of said rolling mill for metal thickness control purposes,   B) wherein said thickness control system comprises the following features on each side of said movable work roll:
 a) a roll force cylinder designed to position said movable work roll, 
 b) a roll gap sensor, wherein said roll gap sensor has an accuracy of +/−0.08 mils or less, 
 c) an inner roll force cylinder position control loop, 
 d) an outer roll gap position control loop, and 
 e) a hydraulic servovalve designed to move said movable work roll 0.001 inches in 50 milliseconds or less, 
   C) wherein said thickness control system is designed to roll a flat metal product used for coins, and   D) whereby said thickness control system is designed to roll said flat metal product within +/−0.15 mil of a desired thickness.   
     
     
         15 . A single stand rolling mill with a thickness control system comprising:
 A) a pair of work rolls, wherein one work roll is designed to be separately movable on each side of said rolling mill for metal thickness control purposes,   B) wherein said thickness control system comprises the following features on each side of said movable work roll:
 a) a roll force cylinder designed to position said movable work roll, 
 b) a roll gap sensor, wherein said roll gap sensor has an accuracy of +/−0.08 mils or less, 
 c) a roll gap position control loop, and 
 d) a hydraulic servovalve designed to move said movable work roll 0.001 inches in 50 milliseconds or less, 
   C) wherein said thickness control system is designed to roll a flat metal product used for coins, and   D) whereby said thickness control system is designed to roll said flat metal product to within +/−0.15 mil of a desired thickness.