Method for the optimization of the configuration of multiroll mill housings, particularly for cluster-type mills

Abstract: A method for the optimization of the configuration of multi-roll mill housings, particularly for mills of the cluster type constituted by two half-housings, said housings comprising eccentric rolls, first intermediate rolls, second intermediate rolls, and work rolls, characterized in that it comprises the steps that consist in: calculating the coordinates of the center of rotation of first intermediate rolls, second intermediate rolls and work rolls on the basis of data related to the position of eccentric rolls and to the diameter of said eccentric rolls; calculating a position value for said eccentric rolls which satisfies mechanical constraints set by the configuration of said mill; calculating the current minimum distance between a line which is tangent to each work roll and a reference axis which represents the edge of the corresponding housing section; and calculating the minimum and maximum values of the diameters of part of the rolls of the housing as a function of the diameter of the remaining rolls provided in the housing.

Description: The present invention relates to a method for the optimization of the configuration of multi-roll mill housings, particularly for cluster-type mills. In multiple-roll mills of the mono-block or cluster type and with reference to figure 1, which illustrates the configuration of the rolls of the housing, the presetting of the gap of the work rolls for correct gauge rolling of the strip entails positioning the top lateral eccentric rolls A, D, E, H and of the top and bottom hydraulic rolls (which act respectively on the rolls B/C and F/G) so as to provide a correct arrangement on the pass-line (otherwise defined as the imaginary straight line that lies tangent to the top surfaces of the bending rolls or strip flatness measurement rolls) of the bottom work roll, in the case of a mono-block mill, or top work roll, in the case of cluster or split-housing type mills. This automatic positioning with calculated position preset assumes the availability of a geometric model of the housing which, once the diameters of the rolls installed in the housing are known, calculates the correct position of the top and bottom lateral eccentric rolls A, D, E, H in order to be able to perform the cycles for the automatic positioning of said eccentric rolls and of the hydraulic screwdown systems without causing mechanical interference among said rolls and particularly between the top second intermediate rolls, between the bottom second intermediate rolls, between the top first intermediate rolls, and between the bottom first intermediate rolls, at the same time reaching the pass-line position with the work roll being considered. This geometric model is known and applied in plants currently in operation. The limitations of this geometric model lie in the fact that it performs its calculations on a configuration of rolls chosen beforehand by the operator, which might be unsuitable to achieve the correct pass-line position. The results of a non-optimized selection of the diameters of the rolls, particularly of the first intermediate rolls and of the work rolls, entails one or more of the following drawbacks, which are reported by means of alarm messages by a geometric model for calculating pass-line positioning: mechanical interference during positioning (because the movements of the roll axes arc not monotonic functions); mechanical interference in the final positioning of said rolls; failure to reach the ideal pass-line position, that is to say, failure to achieve the tolerance between the point of tangency of the top and bottom work rolls and the supporting structure of the corresponding housing section (in the case of cluster-type mills); failure to achieve the required closure positions of the top work roll for the final reduction of the gauge of the strip (in the case of mono-block mills). These drawbacks sometimes entail replacing the work rolls (more rarely the first and intermediate rolls), that is to say, the need to perform a new pass-line positioning during the multiple-pass rolling of the strip, with a considerable expenditure of time. The aim of the present invention is therefore to provide a system with multiple algorithms which provides optimized selection of the diameters of the top and bottom work rolls, of the top and bottom first intermediate rolls, and of the top and bottom second intermediate rolls, as a function of the given diameters of the remaining rolls and of the geometric configuration of the housing. Within the scope of this aim, an object of the present invention is to provide a method for the optimization of the configuration of multi-roll mill housings, which allows to calculate the combinations of the rolls to be used as a function of the intended rolling cycle. Another object of the present invention is to provide a method for the optimization of the configuration of multi-roll mill housings, in which the output result is constituted by the minimum and maximum diameters of the rolls to be selected, as a function of the initial and final gauges of the strip to be rolled. Another object of the present invention is to provide a method for the optimization of the configuration of multi-roll mill housings, which allows an operator to prepare in advance the rolls required for the next process, accordingly eliminating downtimes and ensuring high continuity of operation of the mill. Another object of the present invention is to provide a method for the optimization of the configuration of multi-roll mill housings, which is highly reliable, relatively easy to provide and at competitive costs. This aim, these objects and others which will become apparent hereinafter are achieved by a method for the optimization of the configuration of multi-roll mill housings, particularly for mills of the cluster type constituted by two housing sections or half-housings, said housings comprising eccentric rolls, first intermediate rolls, second intermediate rolls, and work rolls, characterized in that it comprises the steps that consist in: calculating the coordinates of the center of rotation of first intermediate rolls, second intermediate rolls and work rolls on the basis of data related to the position of eccentric rolls and to the diameter of said eccentric rolls; calculating a position value for said eccentric rolls which satisfies mechanical constraints set by the configuration of said mill; calculating the current minimum distance between a line which is tangent to each work roll and a reference axis which represents the edge of the corresponding housing section; and calculating the minimum and maximum values of the diameters of part of the rolls of the housing as a function of the diameter of the remaining rolls provided in the housing. Further characteristics and advantages of the invention will become apparent from the description of a preferred but not exclusive embodiment of the method according to the invention, illustrated only by way of non-limitative example in the accompanying drawings, wherein: figure 1A is a schematic view of a housing for mono-block mills; figure 1B is a schematic view of the arrangement of the rolls for a housing of the cluster type: figure 2 is a schematic view of the minimum distance between the line that is tangent to the top and bottom work rolls and a reference axis which constitutes the edge of the housing section associated with each roll; figure 3 is a schematic view of the calculation of the coordinates of the backing rolls; figures 4 and 5 are diagrams useful for explaining the method according to the invention; figure 6 is a block diagram of the method for calculating the preset for the eccentric rolls of the housing; figure 7 is a schematic diagram of the calculation of the minimum diameter of the work rolls with a set of predefined rolls; and figure 8 is a schematic view of the set of rolls of the housing, with the corresponding coordinates defined by means of the method according to the present invention. With reference now to the above figures, and particularly to figure 1B, said figures illustrate in detail a housing of a mill of the cluster type which is divided into two sections, a top one 100 and a bottom one 200; each section contains a set of ten rolls which constitute the top and bottom housing sections, which are mutually independent. The rolls designated by the reference numerals 1 and 4 in figure 1B are the eccentric backing rolls; the rolls 2-3 are the fixed hacking rolls; the rolls 5 and 7 are motorized second intermediate rolls; the rolls designated by the reference numeral 6 are free second intermediate rolls; the numerals 8-9 designate first intermediate rolls, and the numeral 10 designates the work rolls. The backing rolls 1 and 4 have a maximum rotation of 180° and are driven by means of eccentric elements. By virtue of the rotation of these rolls on the eccentric axis, the work rolls 10 undergo a movement which is a function of the rotation angle reached by the backing rolls 1-4 and by the combination of the diameters of the rolls 5, 6, 7, 8, 9 and 10. In figure 1B, the reference numeral 300 designates the so-called pass-line mentioned above and the reference numerals 110 and 120 respectively designate bending rolls or flatness measurement rolls, on which the strip to be rolled is conveyed and is unwound and wound, respectively and alternatively, from and on takeup/feeder reels 130 and 140. With reference now to figure 2, the minimum top tolerance, designated by the reference numeral 150, is defined as the minimum distance between the line that lies tangent to the top work roll 10 and the reference axis X (line CS). Likewise, the bottom minimum tolerance is defined in the same figure, is designated by the reference numeral 160 and is represented by the minimum distance between the line that is tangent to the bottom work roll 10 and the reference axis X (line CI). The margin between the pairs of rolls 5-6 and 6-7 and 8-9 is also defined as the minimum distance between a pair of rolls, which must never be lower than a certain value (margin) in order to avoid possible sliding friction which might cause fire in the mill or spoil the surfaces of the rolls. With reference now to figure 3, a method for calculating coordinates of backing rolls 1-4 of the top and bottom housing sections is described. For each backing roll 1, 2, 3 and 4, the relation that links the position (from 0 to 100%) to the coordinates of the respective center of rotation is given by: X = X exc + exc*cos(alpha) Y = Y exc + exc*sin(alpha) where alpha = alpha + POS/100*(alpha 10- alpha 0 ) expressed in degrees POS is the current position, from 0 to 100, expressed as a percentage alpha 0 is the angle that corresponds to the zero position, expressed in degrees alpha 10 is the angle that corresponds to the 100 position, expressed in degrees X exc , Y exc are the coordinates of the roll, expressed in millimeters exc is the eccentricity of the roll, expressed in millimeters. In this manner it is possible to calculate the coordinates of the backing rolls 1-4 of the top and bottom housing sections. By means of these coordinates, and if the diameter of the rolls 1-4 is known, it is possible to calculate the values of the coordinates of the center of all the other rolls 5, 6, 7, 8, 9 and 10. The method is based on calculating the distance between the centers of rotation of the rolls that do not bear on each other, which is given by: DIST a,b = (X a - X b ) 2 + (Y a - Y b ) 2 and on calculating the distance between the centers of rotation of the rolls that make mutual contact, which is given by: DIST a,n = D a + D n 2 DIST b,n = D b + D n 2 where D(a) = diameter of the roll a; D(b) = diameter of the roll b; D(n) = diameter of the roll n. The above relations are evident from figure 4 of the accompanying drawings, in which the terms X(a), X(b), X(n) and Y(a), Y(n), Y(b) are the coordinates of the respective rolls a b and n, taken as example rolls to illustrate the method for calculating the coordinates of the rolls of a mill according to the invention. After calculating the sides of the triangle formed by the three centers of rotation, as shown in figure 4, it is possible to calculate the coordinates X(n) and Y(n) of the roll n as follows: Beta = arctg[ Y a - Y b X a - X b ] Gamma = arcos[ (DIST a,n ) 2 - (DIST b,n ) 2 + (DIST a,b ) 2 2*DIST a,n *DIST a,b ] from which X n = X a + DIST a,n *cos(Beta-Gamma); Y n = Y a + DIST a,n *sen(Beta-Gamma). By applying this method repetitively to the various sets of three rolls, it is possible to calculate the coordinates of all the centers of rotation. During calculation it is necessary to check that the rotation of the eccentric rolls 1-4 does not lead to contact or, worse still, interference between the pairs of rolls 5-6, 6-7 and 8-9, and therefore the following relation must apply: DIST a;b > D a + D b 2 + margin The margin is designated by the reference numeral 190 in figure 5 and is defined as the distance between the two rolls a and b. By calculating the coordinates of the center of rotation of the rolls it is possible to calculate the value of the minimum tolerance as follows: MINIMUM TOLERANCE = D 10 2 - Y 10 where D 10 is the diameter of the work roll 10 and Y10 is its coordinate on the Y axis. The offline calculation of the preset for positioning the eccentric rolls 1-4 is achieved by simulating the position of the eccentric rolls and by checking that the value of the tolerance between the work rolls and the lines CS and CI, respectively, is greater than a minimum value. Noninterference between the pairs of rolls 5-6, 6-7 and 8-9 is also checked during this step. It is therefore necessary to define a search strategy whose result meets the set conditions. The method followed consists in considering the eccentric rolls 1-4 in the maximum closure position. The result of this condition is a maximum tolerance value (figure 2). If the tolerance value exceeds the minimum value and no interference between pairs of rolls has occurred, the search for the preset value is considered over. Otherwise, if interference has occurred, the maximum closure position assumed for the eccentric rolls 1-4 is decreased (that is to say, the eccentric rolls 1-4 are opened) until the required conditions are met or until the maximum opening value, which corresponds to the zero position, has been reached. To summarize, the conditions that can occur during the search for the preset value are as follows: Condition I: simulated preset position for eccentric rolls 1-4 at 100% (initial condition) Calculation: work roll - cluster line tolerance Result: tolerance higher than minimum value and no interference Preset value: 100% Condition 2: simulated preset position for eccentric rolls 1-4 at 100% (initial condition) Calculation: work roll - cluster line tolerance Result: interference between roll pairs Action: reduction of the simulated preset position Calculation: work roll - cluster line tolerance Result: tolerance higher than minimum value and no interference Preset value = ≤ 100% Condition 3: simulated preset position for eccentric rolls 1-4 at 100% (initial condition) Calculation: work roll - cluster line tolerance Result: interference between roll pairs Action: reduction of the simulated preset position Preset value= < 100% Calculation: work roll - cluster line tolerance Result: interference between roll pairs Preset value = 0% Calculation failed. Condition 4: simulated preset position for eccentric rolls 1-4 at 100% (initial condition) Calculation: work roll - cluster line tolerance Result: interference between roll pairs Action: reduction of the simulated preset position Preset value = < 100% Calculation: work roll - cluster line tolerance Result: interference between roll pairs Preset value = 0% Result: no interference between roll pairs Tolerance smaller than minimum value Calculation failed. The block diagram of figure 6 illustrates the method for calculating the preset for eccentric rolls 1-4. In particular, a step 300 defines the simulated preset at 100% and is followed by a step 310 for calculating a geometric model from which, if there is no interference among the various rolls of the mill, the tolerance of the work rolls with respect to the cluster line is calculated in step 320, which then also determines whether said tolerance is higher than a minimum value, in which case the method moves on to a step 330 in which the preset value is defined as 100%. Otherwise the method moves on to a step 340, during which a preset error is reported. In case of interference between the rolls of the mill, the method moves on from step 310 to a step 350 with a simulated preset of less than 100%, from which the method returns to step 310 and also moves on to step 340 to determine a preset error. In the method according to the invention it is necessary, at this point, to calculate the minimum diameter of the work roll 10 with a set of adjacent predefined rolls which are assumed to be installed in the housing. The method consists in searching first of all for the preset of the eccentric rolls 1-4 that does not determine interference conditions. Then, by using the calculation of the LY(10) coordinate of the work roll 10 (that is to say, the Y-axis coordinate of the center of the work roll 10) and by using the required minimum tolerance value with respect to the cluster line, designated by the reference numeral 150, as a fixed value, it consists in simulating a reduction in the diameter of the work roll 10 until its minimum value that meets the minimum required tolerance conditions 150 is found. Therefore: TOL = D 10 2 - Y 10 D 10 2 = (Y 10 + TOL) with TOL = constant = minimum tolerance value from which D 10 =(Y 10 + TOL)*2 TOL = minimum tolerance required between the tangent of each work roll and the respective housing section edge (lines CS and CI, respectively) D 10 / 2 = radius of the work roll D 10 = diameter of the work roll Y 10 = Y-axis coordinate of the work roll where the minimum required tolerance, designated by the reference numeral 150 (or 160 for the bottom housing section) in figure 7 and in the preceding figures, is now designated by TOL for the sake of simplicity. With this method for searching for the diameter of the work roll 10 it is necessary to repeat the calculation of the Y 10 coordinate n times. Table 1 lists the input data used by the method according to the invention to calculate the coordinates of the first and second intermediate rolls and of the work rolls, respectively for the top cluster section (or housing section) 100 and for the bottom cluster section 200. In particular, Tables 1 and 2 respectively list the diameters of the rolls accommodated in the top and bottom cluster section and the geometric data of the top and bottom cluster section. Table 3 instead lists the result data, that is to say, the coordinates of the diameters of the upper cluster section 100 and of the lower cluster section 200, obtained by means of the method according to the invention. Finally, figure 8 is a schematic view of the rolls of the upper cluster section 100 and of the lower cluster section 200 with the corresponding coordinates obtained by means of the method according to the invention. In practice, the method described above allows to check data with different housing configurations in the cluster-type mill. The method essentially consists of four main subroutines, which respectively calculate: the coordinates of the center of rotation of the rolls; the preset for the eccentric rolls; the current tolerance of the work rolls with respect to the footings of the housing sections; and the minimum diameter of the work rolls. Coordinates for top cluster section 100 Rolls Roll number Value Unit Name X coordinate of second intermediate roll 5 mm UX (5) Y coordinate of second intermediate roll 5 mm UY (5) X coordinate of second intermediate roll 6 mm UX (6) Y coordinate of second intermediate roll 6 mm UY (6) X coordinate of second intermediate roll 7 mm UX (7) Y coordinate of second intermediate roll 7 mm UY (7) X coordinate of first intermediate roll 8 mm UX (8) Y coordinate of first intermediate roll 8 mm UY (8) X coordinate of first intermediate roll 9 mm UX (9) Y coordinate of first intermediate roll 9 mm UX (9) X coordinate of work roll 10 mm UX (10) Y coordinate of work roll 10 mm UY (10) Calculated tolerance mm TOL top cluster Coordinates for bottom cluster section 200 Rolls Roll number Value Unit Name X coordinate of second intermediate roll 5 mm LX (5) Y coordinate of second intermediate roll 5 mm LY (5) X coordinate of second intermediate roll 6 mm LX (6) Y coordinate of second intermediate roll 6 mm LY (6) X coordinate of second intermediate roll 7 mm LX (7) Y coordinate of second intermediate roll 7 mm LY (7) X coordinate of first intermediate roll 8 mm LX (8) Y coordinate of first intermediate roll 8 mm LY (8) X coordinate of first intermediate roll 9 mm LX (9) Y coordinate of first intermediate roll 9 mm LX (9) X coordinate of work roll 10 mm LX (10) Y coordinate of work roll 10 mm LY (10) Calculated tolerance mm TOL (bottom cluster) Tables 1 and 2 show that the required input data relate to the diameters of the eccentric backing rolls, to the backing rolls, to the second intermediate rolls, to the first intermediate rolls, and to the work rolls, and to the geometric data related to the bottom cluster section, that is to say, the respective coordinates of the eccentric backing rolls, of the hacking rolls, the eccentricity of the eccentric backing rolls, the angles of the eccentric backing rolls, and the minimum tolerance of the work rolls with respect to the base of the corresponding housing section. In practice it has been found that the method according to the invention allows to determine the coordinates of some rolls of the mill, starting from data related to other rolls installed in the housing of the mill, so as to allow an operator to set in advance the rolls for the rolling to be performed, accordingly reducing the downtimes between one setup of the mill and its subsequent setup. The method thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the invention as defined in the claims. Thus, for example, the above described algorithm can also be used to calculate the minimum and maximum diameters of the pairs of top and bottom first intermediate rolls 8 and 9 if the diameters of the remaining rolls available in the housing are defined. The above also applies to the calculation of the diameters of the top and bottom second intermediate rolls 5-7. Finally, all the details may be replaced with other technically equivalent elements.

Claims: A method for the optimization of the configuration of multi-roll mill housings, particularly for mills of the cluster type constituted by two housing sections or half-housings (100,200), said housings comprising eccentric rolls (1,4), first intermediate rolls (8,9), second intermediate rolls (6), and work rolls (10), characterized in that it comprises the steps that consist in: calculating the coordinates of the center of rotation of first intermediate rolls (8,9), second intermediate rolls (6) and work rolls (10) on the basis of data related to the position of eccentric rolls (1,4) and to the diameter of said eccentric rolls; calculating a position value for said eccentric rolls (1,4) which satisfies mechanical constraints set by the configuration of said mill; calculating the current minimum distance (150,160) between a line which is tangent to each work roll and a reference axis (x) which represents the edge of the corresponding housing section; and calculating the minimum and maximum values of the diameters of part of the rolls of the housing as a function of the diameter of the remaining rolls provided in the housing. A method according to claim 1, characterized in that the step that consists in calculating the minimum and maximum values of the diameters of part of the rolls of the housing consists in calculating the diameters of the work rolls (10). A method according to claim 1, characterized in that the step that consists in calculating the minimum and maximum values of the diameters of part of the rolls of the housing consists in calculating the diameter of the first intermediate rolls (8,9). A method according to claim 1, characterized in that the step that consists in calculating the minimum and maximum values of the diameters of part of the rolls of the housing consists in calculating the diameters of the second intermediate rolls (6). A method according to claim 1, characterized in that the step that consists in calculating the coordinates of the rotation centers of the first intermediate rolls (8,9), of the second intermediate rolls (6) and of the work rolls (10) consists in: calculating the coordinates of backing rolls by knowing their respective centers of rotation; calculating the value of the coordinates of the centers of rotation of the first intermediate rolls (8,9), of the second intermediate rolls (6) and of the work rolls (10). A method according to claim 1, characterized in that it comprises the step that consists in calculating the distance between the centers of rotation of rolls that do not make mutual contact and in calculating the distance between the centers of rotation of the rolls that are in mutual contact. A method according to one of the preceding claims, characterized in that it comprises a step for checking whether the rotation of the eccentric rolls (1,4) causes contact between pairs of the first intermediate rolls (8,9) and of the second intermediate rolls (6). A method according to one of the preceding claims, characterized in that the step that consists in calculating the position value for the eccentric rolls (1,4) that meets the mechanical constraints of said mill consists in: simulating the position of the eccentric rolls (1,4) and checking whether the tolerance value of the work rolls (10) with respect to the reference axis is higher than a minimum value; checking that there is no interfere between a pair of the first intermediate rolls (8,9) and the second intermediate rolls (6). A method according to one of the preceding claims, characterized in that the step for calculating the position of the eccentric rolls (1,4) furthermore comprises the steps that consist in: determining a maximum tolerance value of the work rolls (10) with respect to the reference axis (x), checking whether said maximum tolerance exceeds said minimum value and there is no interference between roll pairs; and if there is interference, reducing the angular position of said eccentric rolls, opening said eccentric rolls, until noninterference conditions are achieved or until a maximum value of the opening of said eccentric rolls is reached. A method according to one of the preceding claims, characterized in that the step that consists in calculating the minimum diameter of said work rolls comprises the steps that consist in: seeking a preset for said eccentric rolls (1,4) so as to have no interference; calculating the coordinates of the work rolls along an axis which is perpendicular to the rotation axis of said work rolls; using a minimum required value of said tolerance with respect to the reference axis; decreasing the diameter of said work rolls by a value which represents a difference with respect to said minimum tolerance; finding a minimum diameter value which is suitable to meet the minimum tolerance conditions with respect to the reference axis. A method according to one of the preceding claims, characterized in that said mill of the cluster type comprises a top cluster section (100) and a bottom cluster section (200). said method being applied to each one of said top and bottom cluster sections. A method according to one of the preceding claims, characterized in that the step that consists in checking that the rotation of said eccentric rolls does not produce the mutual contact of rolls that constitute pairs of first intermediate rolls (8,9) and second intermediate rolls (6) consists in calculating whether a distance between each roll of said pairs is greater than half the sum of the diameters of said rolls plus a value which represents a margin. A method according to one of the preceding claims, characterized in that the calculation of the coordinates of the rolls is performed on sets of three rolls, said calculation being performed a number n of times where n is equal to the number of said sets of three rolls present in said mill.

Inventors: ANDREOLLI MARCO, FREGNAN ALDO, ANDREOLLI, MARCO, FREGNAN, ALDO
Applicants: ABB PROCESS SOLUTIONS & SERVIC, ABB PROCESS SOLUTIONS & SERVICES S.P.A.
Application year: 1998
Main classification: B21B38
IPC codes: B21B13, B21B31, B21B38