Abnormal-Vibration-Predicting Method for Roll Grinder, Rolling-Roll-Grinding Method, Metal-Strip-Rolling Method, Abnormal-Vibration-Predicting Device for Roll Grinder, and Roll-Grinding Apparatus

This application is a National Stage of International Application No. PCT/JP2023/004277 filed Feb. 9, 2023, which is based upon and claims the benefit of priority from Japanese Patent Application No. 2022-086592 filed May 27, 2022, the entire contents of the prior applications being incorporated herein by reference.

This application relates to an abnormal-vibration-predicting method for a roll grinder, a rolling-roll-grinding method, a metal-strip-rolling method, an abnormal-vibration-predicting device for a roll grinder, and a roll-grinding apparatus.

Chatter marks are examples of surface defects that occur in a cold rolling process. The chatter marks are surface defects including linear patterns that extend in a width direction of a metal strip caused by variations in the thickness of the metal strip and that appear periodically in a longitudinal direction of the metal strip. The chatter marks are known to occur due to rolling mill vibration (hereinafter referred to as chattering). The chatter marks formed on the metal strip by chattering lead to product defects due to poor appearance. If severe chattering occurs, the metal strip may break, for example, due to a sudden change in tension, and the productivity may be significantly reduced.

Chattering is often caused by, for example, flaws in rotating components, such as bearings, that constitute a rolling mill, poor lubrication between a rolling roll and the metal strip, or an abnormal profile of the rolling roll. In particular, when chattering occurs due to an abnormal profile of an outer peripheral surface of the rolling roll caused in a process of grinding the rolling roll, the vibration of the rolling mill continues until the rolling roll with the abnormal profile is replaced, and a large amount of product defects occur.

The abnormal profile of the rolling roll is caused by abnormal vibration of a grinder in the process of grinding the rolling roll as a workpiece. The vibration of the grinder generated in the process of grinding the rolling roll increases due to resonance when the natural frequency of a grinding wheel, the natural frequency of a workpiece support system, or the natural frequency of the entire mechanical system including the grinding wheel and the workpiece coincides with the excitation frequency. As a result, abnormal vibration of the roll grinder occurs.

As a technique for preventing the above-described abnormal vibration of the roll grinder, Patent Literature 1 discloses a method for preventing chatter vibration of a roll grinder. According to Patent Literature 1, the chatter vibration can be predicted based on the correlation between a chatter waveform detected by a chatter detector using an optical sensor and a vibration waveform measured by a vibration meter provided on a wheel spindle stock and a tail stock.

PTL 1: Japanese Unexamined Patent Application Publication No. 52-56468

The method disclosed in Patent Literature 1 prevents the chatter vibration of the roll grinder. Since the chatter vibration occurs at a grinding point, which is the point of contact between the grinding wheel and the rolling roll serving as the workpiece, the method disclosed in Patent Literature 1 focuses on the vibration generated at the grinding point and transmitted to the roll grinder. However, the abnormal vibration generated in the roll grinder is caused not only by the vibration generated at the grinding point; the abnormal vibration may also occur due to the natural frequency of the entire mechanical system including the grinding wheel and the workpiece. Therefore, the method disclosed in Patent Literature 1 has a problem in that it cannot predict the occurrence of the abnormal vibration corresponding to the natural frequency of the entire mechanical system including the grinding wheel and the workpiece.

The present disclosure has been made to solve the above-described problem of the related art, and an object of the present disclosure is to provide an abnormal-vibration-predicting method for a roll grinder, an abnormal-vibration-predicting device for a roll grinder, and a roll-grinding apparatus capable of predicting the occurrence of the abnormal vibration of the roll grinder corresponding to the natural frequency of the entire mechanical system including the grinding wheel and the workpiece. Another object of the present disclosure is to provide a rolling-roll-grinding method in which the occurrence of the abnormal vibration of the roll grinder is suppressed in a grinding process using the grinding wheel and a metal-strip-rolling method using the rolling roll ground by the rolling-roll-grinding method.

Means for solving the above-described problem are as follows.

roll grinder according to [11], wherein the input data acquired by the data acquisition unit includes the rigidity parameter, the wheel rotation parameter, and a load parameter related to a load applied to the grinding wheel.

roll grinder according to [11] or [12], further including: a guidance-information-acquisition unit that determines the input data for which the abnormal vibration does not occur by using the abnormal-vibration-prediction model.

According to the present disclosure, the abnormal vibration of the roll grinder is predicted using the rigidity parameter and the wheel rotation parameter. Therefore, the occurrence of the abnormal vibration of the roll grinder corresponding to the natural frequency of the entire mechanical system including the grinding wheel and the workpiece can be predicted.

A first embodiment will now be described with reference to the drawings.is a schematic diagram illustrating the structure of a roll-grinding apparatuscapable of carrying out an abnormal-vibration-predicting method for a roll grinder according to the first embodiment.is a top view of the roll-grinding apparatus.is a front view of a roll grinder. The roll grinderillustrated inis a roll grinder that uses a cylindrical grinding wheel to grind an outer peripheral surface of a rolling roll. The rolling rollto be ground is carried to a roll shop by a crane or the like after being used in a rolling mill. After that, the rolling rollis removed from a bearing box, allowed to be naturally cooled to normal temperature, and set to the roll grinderindividually.

The roll grinderincludes a grinding headthat supports a grinding wheel, a support tablethat supports the grinding head, guidesand, a roll support base, and a vibration meter. The grinding headsupports the grinding wheeland a wheel rotation motorthat drives the grinding wheel. A pulley and a belt for transmitting power are disposed between the grinding wheeland the wheel rotation motor. The grinding wheelmay be rotationally driven directly by the wheel rotation motor.

The support tableis guided by the guideand moves parallel to an axial direction of the rolling roll. The movement of the support tablealong the guideis performed under position control using a servo motor, so that the relative position between the grinding wheeland the rolling rollin the axial direction is controlled. The grinding headis guided by the guideand moves in a direction perpendicular to an axis of the rolling roll. The movement of the grinding headalong the guideis also performed under position control using a servo motor, so that the cutting depth of the grinding wheelis controlled. Alternatively, the support tablemay be composed of a two-axis table that moves along the guideand the guide. When the two-axis table is used, the support tablemoves along the guidedisposed parallel to the axial direction of the rolling roll, and also moves the grinding wheelalong the guidein a direction perpendicular to the axis of the rolling roll. In the following description, the structure composed of the grinding head, the support table, the guide, and the wheel rotation motorthat directly or indirectly support the grinding wheelis referred to as a grinding-wheel support unit.

The roll support baseincludes a roll chuckthat supports the rolling rollat one end of the rolling rollin the axial direction, a roll rotation motorthat rotationally drives the rolling rollat a predetermined number of revolutions, and a tail stockthat supports the rolling rollat the other end of the rolling rollin the axial direction. The tail stockserves to align the axis of the rolling rollwith an axis of a rotating shaft of the roll rotation motor. The tail stockincludes a cone-shaped portion that comes into contact with the rolling roll, and an end of the cone-shaped portion is inserted into a counterbore formed at the center of an axial end portion of the rolling rolland a counterbore in a fixing jig. Thus, the rolling rollis fixed with the axis thereof coinciding with the axis of the rotating shaft of the roll rotation motor. The number of revolutions of rolling rollduring grinding is controlled by a controllerof the roll grinder.

The rolling rollis ground from one end to the other end in the axial direction of the rolling roll, and then continuously ground from the other end to the one end. The one-round trip of the grinding wheelis defined as a traverse. A typical grinding process includes a rough grinding process in which the grinding amount is set to a large value, and a finish grinding process performed to finish the surface of the rolling roll. In general, the number of traverses for rough grinding is aboutto, and the number of traverses for finish grinding is aboutto. The rough grinding process is a grinding process performed to cut the surface of the rolling rollto remove a fatigue layer and a portion having microscopic cracks. The finish grinding process is a weak grinding process performed to adjust the surface roughness of the rolling roll within a predetermined range.

The roll-grinding apparatusillustrated infurther includes a control computerand a controller. The control computersets grinding conditions for the rolling rollto be ground based on information including the dimension information of the rolling roll, the grinding amount, and the target surface finish roughness.

The grinding conditions include at least three setting conditions: the number of revolutions of the roll, the number of revolutions of the grinding wheel, and the cutting depth of the grinding wheelduring grinding. The grinding conditions are set for each traverse from rough grinding to finish grinding. A current value set for the wheel rotation motormay be used instead of the wheel cutting depth. An operator may check the state of grinding of the rolling rolland adjust the grinding conditions of the roll grinderas appropriate. In this case, the adjusted grinding conditions of the roll grinderare output to the control computer.

The grinding conditions of the roll grindermay be set by using a setting table that takes into account factors such as the diameter, surface hardness, and surface roughness before grinding of the rolling rollto be ground. The grinding conditions are also set by taking into account the conditions of the grinding wheel, such as the grit number of the grinding wheel, the initial wheel diameter, the current wheel diameter, the cumulative grinding time of the grinding wheel, and the total grinding amount after dressing by a dressing device.

The initial wheel diameter is the wheel diameter before the first use of the grinding wheelin roll grinding after production. The current wheel diameter is the wheel diameter measured before starting the grinding of the rolling rollto be ground. Multiple locations are selected on the outer periphery of the grinding wheel, and the wheel diameter is measured using a micrometer at the selected locations. Alternatively, marks may be formed on a side surface of the grinding wheelwith a pitch of 1 to 5 mm in the radial direction in advance, and the wheel diameter may be determined by reading the marks. The grinding wheelhas an initial wheel diameter of 850 to 950 mm. The grinding wheelis discarded when the wheel diameter is reduced to about 450 to 600 mm.

The control computersets control target values for operation conditions of the roll grinder. The controllercontrols each device so that the number of revolutions of the roll, the number of revolutions of the grinding wheel, and the cutting depth of the grinding wheelduring grinding are equal to the control target values thereof in each traverse from the start to the end of the grinding operation. The controlleracquires an actual value of the wheel rotation motorthat drives the grinding wheelduring grinding. When actual values of the number of revolutions of the roll, the number of revolutions of the grinding wheel, and the cutting depth of the grinding wheelduring grinding can be measured, the controlleracquires these actual values. The thus-acquired actual values are output to the control computeras data for analyzing the operational state of roll grinding. The control computerand the controllerare workstations or general-purpose computers, such as personal computers. The control computerand the controllermay be composed of a single computer.

In the above-described roll-grinding apparatus, the rolling rollthat has undergone finish grinding is transferred to a ground-roll storage area, and is returned to a roll replacing device and assembled into the rolling mill in its turn. The roll grinderincludes the vibration meter. The vibration meteracquires actual data regarding abnormal vibration in the process of grinding the rolling roll. The vibration meteris preferably installed on the grinding heador the roll support base, and more preferably at a position close to the grinding wheel. When the vibration meteris provided at such a position, vibration generated in at a contact portion between the grinding wheeland the rolling rollcan be detected. Although the measurement direction of the vibration is not limited, the vibration in the same direction as the direction in which the grinding wheelcuts into the rolling rollis preferably measured.

In the abnormal-vibration-predicting method for a roll grinder according to the first embodiment, the abnormal vibration of the roll grinderis predicted using a rigidity parameter related to the rigidity of the roll grinderand a wheel rotation parameter related to the rotational speed of the grinding wheel. The rigidity parameter of the roll grinderwill now be described.

The rigidity parameter related to the rigidity of the roll grindermeans the parameter that influences the rigidity of the roll grinderwhen the rolling rollserving as the workpiece is supported by the roll support base. The rigidity of the roll grinderrepresents the degree of influence of the external force applied to the roll grinderon the displacement of a portion of the grinding wheelin contact with the rolling roll.

Specifically, the rigidity of the grinding-wheel support unitthat directly or indirectly supports the grinding wheel(hereinafter referred to as grinder rigidity) is defined as the rigidity parameter related to the rigidity of the roll grinder. The mass and the rigidity of the rolling rollserving as the workpiece and the roll support baseare greater than the mass and the rigidity of the grinding-wheel support unit. Therefore, the contribution of the rolling rolland the roll support baseon the overall vibration of the roll grinderis small relative to that of the grinder rigidity. Therefore, it is not necessary that the rigidity parameter of the grinderinclude the parameters of the rolling rollserving as the workpiece and the roll support base.

The distance between the rotation center of the rolling rolland the rotation center of the grinding wheelis preferably used as the rigidity parameter. This is because the position of the grinding headrelative to the support tablein the grinding process changes depending on the distance between the rotation center of the rolling rolland the rotation center of the grinding wheel, and the ease of vibration of the grinding headchanges accordingly. The sum of the diameter of the rolling rolland the diameter of the grinding wheelmay be used instead of the distance between the rotation center of the rolling rolland the rotation center of the grinding wheel. In an example described below, the sum of the diameter of the rolling rolland the diameter of the grinding wheelis used as the rigidity parameter.

shows front views of roll grinders including grinding wheels having different diameters.illustrates a roll grinderhaving a large-diameter grinding wheel.illustrates a roll grinderhaving a small-diameter grinding wheel. When the diameter of the grinding wheel is small and the distance between the rotation center of the rolling rolland the rotation center of the grinding wheel is short, the grinding headneeds to be moved forward toward the rolling rollalong the guideto bring the grinding wheelinto contact with the rolling roll. Therefore, the distance between the rotation center of the grinding wheeland the center of gravity of the grinding-wheel support unit(hereinafter referred to as an arm length) is longer in the roll grinderthan in the roll grinder.

As the arm length increases, the rotational moment about the center of gravity of the grinding-wheel support unitincreases even when the grinding force applied between the rolling rolland the grinding wheel(tangential force in the direction of rotation of the grinding wheel) is constant. Therefore, the rigidity of the grinding-wheel support unitchanges, and the vibration of the roll grinder changes accordingly. In other words, when the distance between the rotation center of the rolling roll and the rotation center of the grinding wheelis short and the above-described arm length is long, the rigidity of the roll grinder is reduced.

is a graph showing the relationship between the sum of the diameter of the rolling rolland the diameter of the grinding wheeland the grinder rigidity. In, the horizontal axis represents the sum of the diameter of the rolling rolland the diameter of the grinding wheel(mm), and the vertical axis represents the grinder rigidity (N/mm). The grinder rigidity is determined by approximating the grinding-wheel support unitwith a vibration model of a mass-spring-damper system and determining the parameters of the vibration model to match the relationship between the vibration frequency and the vibration intensity measured by the vibration meter. Alternatively, a hammering test may be performed on the grinding-wheel support unitto measure the natural frequency, and the grinder rigidity may be calculated from the mass of the grinding-wheel support unit.

As illustrated in, the grinder rigidity increases as the sum of the diameter of the rolling rolland the diameter of the grinding wheelincreases, that is, as the distance between the rotation center of the rolling rolland the rotation center of the grinding wheelincreases. This result shows that when the distance between the rotation center of the rolling rolland the rotation center of the grinding wheelincreases, the ease of vibration of the grinding-wheel support unitchanges, and the grinder rigidity tends to increase accordingly. This is because when the sum of the diameter of the rolling rolland the diameter of the grinding wheelincreases, the arm length decreases and the rotational moment around the center of gravity of the grinding-wheel support unitdecreases accordingly. It is clear from this result that the sum of the diameter of the rolling rolland the diameter of the grinding wheelis preferably used as the rigidity parameter.

The wheel rotation parameter related to the rotational speed of the grinding wheelwill now be described. The wheel rotation parameter is the parameter related to the rotational speed of the grinding wheelamong the parameters representing the grinding conditions under which the rolling rollis ground. Specifically, one of the number of revolutions, the rotation frequency, and the rotational angular speed of the grinding wheelmay be used as the wheel rotation parameter, and the number of revolutions, the rotation frequency, and the rotational angular speed of the wheel rotation motorthat drives the grinding wheelmay be used as these values. The wheel rotation parameter affects the vibration of the grinding-wheel support unitas the frequency of the vibration source that externally acts on the grinding-wheel support unit. In other words, the vibration of the roll grinderis determined by the rigidity of the grinding-wheel support unitthat supports the grinding wheeland the frequency of the vibration source.

is a graph showing the relationship between the vibration frequency and the vibration intensity.shows the frequency spectrum for a specific number of revolutions of the wheel. In, the horizontal axis represents the vibration frequency (Hz) and the vertical axis represents the vibration intensity (m/sec). The graph ofshows the vibration intensity measured when the sum of the diameter of the rolling rolland the diameter of the grinding wheeland the wheel load current value, which is a load parameter, are constant and when the number of revolutions of the wheel is 8.5 rps (frequency corresponding to the wheel rotation is 8.5 Hz).

As illustrated in, the vibration intensity of the roll grindermeasured by the vibration meterhas peaks at vibration frequencies corresponding to integer multiples of the number of revolutions of the wheel. However, the vibration at the wheel rotation frequency of 60 Hz is a disturbance caused by the frequency of the power supply system and not the vibration intensity of the roll grinder. Thus, it is clear that the vibration intensity has peaks at integer multiples of a specific number of revolutions of the wheel. In the first embodiment, the peak values at the frequencies equal to the integer multiples of a specific number of revolutions N of the wheel is defined as PNi. Here, i is the multiple for the number of revolutions of the wheel, and i is any integer of 1 or more. The multiple i for the number of revolutions of the wheel may be determined in the range of 6 to 12 at a maximum. This is because the occurrence of the abnormal vibration may not be predictable when the maximum value of the multiple i for the number of revolutions of the wheel is less than 6, and the peak values of the vibration tend to be smaller when the maximum value of the multiple i for the number of revolutions of the wheel is greater than 12.

is a graph showing the relationship between the wheel rotation frequency and the vibration intensity. In, the horizontal axis represents the wheel rotation frequency (Hz) and the vertical axis represents the vibration intensity (m/sec). The graph shown inis obtained by changing the number of revolutions N of the wheel while the rigidity parameter is maintained constant, determining the peak values PNi (i=1 to 6) corresponding to the frequencies of integer multiples of the number of revolutions of the wheel, and plotting the determined values for each multiple i. The graph shown inplots the peak intensities for each multiple i for the number of revolutions of the wheel. This graph is referred to as a peak intensity map.

As illustrated in, when the number of revolutions N of the wheel is changed while the rigidity parameter is constant, the vibration intensity has peaks corresponding to the frequencies of integer multiples of the number of revolutions N of the wheel. In other words, if the relationship illustrated inis known, it becomes clear how the peak value of the vibration intensity changes for each of the integer multiples i of the number of revolutions N of the wheel when the number of revolutions N of the wheel, which is the wheel rotation parameter, is changed. Thus, when the relationship between the wheel rotation frequency and the vibration intensity is determined, the range of the number of revolutions N of the wheel in which the abnormal vibration of the roll grinderoccurs and the multiple i corresponding thereto can be determined by setting the threshold for the abnormal vibration (for example, 10m/s).

When the relationship illustrated inis obtained while changing the rigidity parameter, an abnormal vibration map for the roll grindercan be created.is an abnormal vibration map related to the rigidity parameter. In, the horizontal axis represents the sum (mm) of the wheel diameter and the rolling roll diameter, and the vertical axis represents the number of revolutions of the wheel (rps).

In the abnormal vibration map illustrated in, the sums (points) of the diameter of the rolling roll and the diameter of the grinding wheel are set on the horizontal axis as the rigidity parameter, and bars representing the ranges of the number of revolutions N of the wheel in which the vibration intensity exceeds the threshold are shown for each multiple i. The abnormal vibration map shown for discrete values of the parameter represented by the horizontal axis as inis referred to as a discrete abnormal vibration map. The discrete abnormal vibration map is preferably created by changing the condition of the rigidity parameter to 3 or more and 15 or less values. When the discrete abnormal vibration map is created by changing the condition of the rigidity parameter to less than 3 values, the abnormal vibration that occurs under the condition of a different value of the rigidity parameter cannot be easily predicted. When the discrete abnormal vibration map is created by changing the condition of the rigidity parameter to more than 15 values, the workload of creating the map increases with no significant improvement in the prediction accuracy of the abnormal vibration.

It is clear fromthat the ranges in which the abnormal vibration of the roll grinderoccurs are determined by the number of revolutions of the wheel, which is the wheel rotation parameter related to the rotational speed of the grinding wheel. It is also clear that the ranges of the number of revolutions of the wheel in which the abnormal vibration occurs vary depending on the sum of the diameter of the rolling roll and the diameter of the grinding wheel, which is the rigidity parameter.

Referring to, when the sum of the diameter of the rolling roll and the diameter of the grinding wheel is constant, the vibration intensity of the roll grinderexceeds the threshold in the ranges of the number of revolutions of the wheel shown by the bars in. Therefore, it can be predicted that, in these ranges, the abnormal vibration of the roll grinderwill occur in the process of grinding the rolling roll.is an example in which the threshold of the abnormal vibration is set to 10m/s. The threshold of the vibration intensity may be determined based on actual values of the vibration data obtained during roll grinding of the rolling roll in which chattering has occurred.

is another example of an abnormal vibration map related to the rigidity parameter. The vibration map illustrated inis obtained by connecting, with continuous curves, the upper limits and the lower limits of the ranges of the number of revolutions of the wheel in which the abnormal vibration occurs for the same multiple in the abnormal vibration map illustrated in. By creating this abnormal vibration map, the range in which the abnormal vibration of the roll grinderoccurs can be determined for each multiple i for the number of revolutions of the wheel for any sum of the diameter of the rolling roll and the diameter of the grinding wheel. Thus, the abnormal vibration of the rolling roll can be predicted. An abnormal vibration map shown for continuous changes in the parameter represented by the horizontal axis as inis referred to as a continuous abnormal vibration map.

When the continuous abnormal vibration map illustrated inis prepared in advance, the occurrence of the abnormal vibration in the process of grinding the rolling rollusing the roll grindercan be predicted by acquiring the sum of the diameter of the rolling roll and the diameter of the grinding wheel as the rigidity parameter and the number of revolutions of the grinding wheelas the wheel rotation parameter.

In the abnormal-vibration-predicting method for a roll grinder according to the first embodiment, an acquisition step is executed to acquire the rigidity parameter and the wheel rotation parameter. After that, a prediction step is executed to predict the abnormal vibration in the process of grinding the rolling roll by using the parameters and the abnormal vibration map (continuous abnormal vibration map) illustrated inprepared in advance. Thus, the abnormal vibration of the roll grindercorresponding to the natural frequency of the entire mechanical system including the grinding wheeland the workpiece can be predicted.

The load parameter related to the load applied to the grinding wheelwill now be described. In the abnormal-vibration-predicting method for a roll grinder according to the first embodiment, the load parameter may be additionally used, and the abnormal vibration of the roll grindermay be predicted using the rigidity parameter, the wheel rotation parameter, and the load parameter.

The load parameter related to the load applied to the grinding wheelis the parameter related to the load (load, tangential force) applied to the contact portion between the grinding wheeland the rolling rollin the grinding process. The load parameter may be a load current value of the wheel rotation motor, which is an electric motor that rotates the grinding wheel(hereinafter referred to as a wheel load current value) or the wheel cutting depth in the grinding process.

The load parameter related to the load applied to the grinding wheelaffects the elastic deformation of the contact portion between the grinding wheeland the rolling roll. The load parameter also affects the mechanical rattling of the grinding-wheel support unit, and therefore indirectly affects the grinder rigidity. When the load parameter, which is the wheel cutting depth or the wheel load current value, is large, the reaction force that the grinding wheelreceives from the rolling rollincreases, and the force received by the grinding-wheel support unitalso increases. As a result, the mechanical rattling of the grinding-wheel support unitis suppressed, and the apparent rigidity of the grinding-wheel support unitincreases.

is a graph showing the relationship between the wheel load current value and the grinder rigidity. In, the horizontal axis represents the wheel load current value (A), and the vertical axis represents the grinder rigidity (N/mm). The graph shown inis the result obtained by studying the relationship between the wheel load current value and the grinder rigidity when the sum of the diameter of the rolling roll and the diameter of the grinding wheel is constant in the rough grinding process performed by the roll grinder. It is clear fromthat when the wheel load current value increases, the apparent rigidity of the grinding-wheel support unitvaries, and the rigidity of the roll grindertends to increase.

shows the abnormal vibration map (continuous abnormal vibration map) related to the load parameter. In, the horizontal axis represents the wheel load current value (A), and the vertical axis represents the number of revolutions of the wheel (rps). The abnormal vibration map illustrated incan be created by the same method as that for creating the abnormal vibration map for the rigidity parameter described in. Specifically, the frequency spectrum for a specific number of revolutions of the wheel is measured, and a peak intensity map is created by plotting the peak intensities for each multiple i for the number of revolutions of the wheel. Then, multiple peak intensity maps are created by changing the load parameter, and the continuous abnormal vibration map related to the load parameter is created from a discrete abnormal vibration map related to the load parameter.

As illustrated in, the load parameter affects the rigidity of the roll grinder, and therefore affects the occurrence of the abnormal vibration of the roll grinder. Accordingly, it is clear that the load parameter is preferably additionally used, and that the abnormal vibration of the roll grinderis preferably predicted using the rigidity parameter, the wheel rotation parameter, and the load parameter. In particular, the abnormal vibration of the roll grinderis preferably predicted by using the distance between the rotation center of the rolling rolland the rotation center of the grinding wheelor the sum of the diameter of the rolling rolland the diameter of the grinding wheelas the rigidity parameter, the wheel load current value as the load parameter, and the wheel rotation parameter in addition to the above-described parameters. This is because the prediction accuracy of the abnormal vibration of the roll grinderincreases by using the structural rigidity and the apparent rigidity of the grinding-wheel support unit. Specifically, the abnormal vibration map (continuous abnormal vibration map) related to the rigidity parameter illustrated inmay be prepared for each load parameter, and the abnormal vibration of the roll grindermay be predicted using the abnormal vibration map related to the rigidity parameter corresponding to the acquired load parameter. Thus, the prediction accuracy of the occurrence of the abnormal vibration of the roll grindercan be increased.