Method of and machine for grinding a roll

Abstract

A method and machine for grinding a rolling mill roll in which the grinding wheel is rotated against the working surface of the rotating mill roll and is displaced back and forth longitudinally along this surface and simultaneously or subsequently the surface is examined for defects by sensors capable of evaluating the geometry of the roll surface. The measured results are compared with stored images or data representing defects in the surface and measured surface defects are compared with the stored data and if they exceed a certain threshold or defect tolerance, an appropriate output is provided by the grinding machine.

Description

FIELD OF THE INVENTION

My present invention relates to a method of grinding a roll on a roll-grinding machine in which the working surface of the roll, i.e. the surface which is intended to bear upon the rolled workpiece, is ground by a grinding wheel or disk. The invention also relates to the roll-grinding machine for use with that machine.

BACKGROUND OF THE INVENTION

In the production of strip and metal foil, it is a current practice to roll the workpiece until a certain strip thickness and certain surface quality is obtained. In order to ensure the quality of the rolled metal strip, the metal strip is scanned in the last production stage as a sensor system and surface defects on the strip are detected. The scanned images can be compared with previously stored defect images and the quality of a particular length of the strip can be established, e.g. as a function of a number defects or the nature of the defect.

That portion of the strip which may be classified as defective, can then be cut out and discarded.

For the scanning of the strip, commercially available sensors are used. Equally known are evaluating systems which can include image recognition software and analytical software for determining defect frequency or which can weigh particular defects relative to others. It is known, in this connection that a considerable part of the surface defects found in metal strip have their origins in defects in the working surface of the roll. It is important to distinguish between those defects in the surface of the roll which arise in the course of the rolling process and thus which are already present at the time of manufacture of the roll.

In the machining of the roll it is known to provide a largely automated approach in which the high precision of the surface geometry of the roll is ensured by a grinding process, usually the last grinding step in the case of a new roll or even in the case of a remachined used roll before it is mounted for use anew in the rolling mill. The roll grinding is usually subjected to a form of quality control by for example a visual inspection of the roll surface by trained personnel seeking to detect the presence of any defects arising from the machining operation.

This kind of quality control is a strain on personnel since there are many possible defects which can be present and the result of the quality testing is basically very subjective and may depend on the state of the quality control personnel and their experience.

A nondetected defect arising during the grinding process in the roll may be only found out too late during the rolling of strip or foil. Although usually that detection occurs very early on in the initial use of the roll, generally in the first few hundred meters of rolled strip or after, say 3 to 4 minutes of production time.

As a rule, therefore, overlooked or erroneously classified defects in the grinding of the roll clan have very negative effects on the efficiency of the manufacturing processes for rolled strip or foil.

OBJECTS OF THE INVENTION

It is, therefore, the principal object of the invention to provide a roll-grinding process or method and roll-grinding machine for practicing that method which can avoid the foregoing drawbacks.

More particularly, it is the object of the invention to provide an improved method of grinding a roll for producing strip for foil which is free from the subjectivity of inspection and process-control previously carried out and thus which can allow greater efficiency and less waste in the rolling process for the production of strip and foil.

Still another object of the invention is to provide a roll-grinding method and machine, especially for rolls used in the production of rolled strip and foil, whereby higher quality surface-ground rolls can be obtained.

SUMMARY OF THE INVENTION

These objects are attained, in accordance with the invention, in a method of grinding a roll which comprises the steps of:

• • (a) mounting a roll for the rolling of workpieces in a roll-grinding machine having a grinding wheel engageable with said roll and grinding a working surface of said roll therewith;
  • (b) subsequent to or simultaneously with the grinding of the working surface of the roll, scanning the working surface of the roll for defects with at least one sensor on the machine capable of recognizing the geometry of the working surface;
  • (c) then automatically evaluating results of the scanning in step (b) by automatically comparing the results with stored data as to qualities of said surface; and
  • (d) automatically outputting information as to the evaluation in step (c).

The roll grinding machine for that purpose can then comprise:

• • a machine structure for receiving and rotating a roll for the rolling of workpieces;
  • a grinding wheel engageable with the roll for grinding a working surface of the roll;
  • at least one sensor capable of recognizing the geometry of the working surface for scanning the working surface of the roll for defects subsequent to or simultaneously with the grinding of the working surface of the roll;
  • circuitry connected to the sensor for automatically evaluating results of the scanning by automatically comparing the results with stored data as to qualities of the surface; and
  • a device connected to the circuitry for automatically outputting information as to the evaluation.

With the method of the invention, initially the roll surface, referred to herein as the working surface of the roll and the surface which engages the workpiece when the roll is mounted in a mill stand, is ground with at least one grinding wheel or disk in a roll-grinding machine in which the grinding wheel or tool is moved along the roll or the roll is moved relative to a grinding head so that the grinding action, with rotation of the roll, will cover the entire working surface.

Simultaneously therewith or subsequently, the ground surface of the roll is scanned with at least one sensor capable of recognizing the geometry of the roll surface and detecting defects thereon.

Then the results of that scan or test of the roll surface is automatically evaluated at least in part by an automatic comparison of the result of that scan with stored data as to the quality and characteristics of the desirable roll surface.

Finally information as to the result of that comparison is outputted, also automatically.

Thus with the invention in the roll-grinding machine itself, there is an examination of the ground roll surface with respect to its geometry, namely the surface characteristics and microgeometry which may be significant for the rolling properties of the roll and quality of the metal strip to be produced therewith.

The defects can be optically detected since they will represent deviations from the ideal geometry represented by the data stored in memory and with which the comparison is made. The invention enables, from the multiplicity of known possible and different surface defects, specific defects to automatically be recognized and classified so that for any further processing steps, automatically determined grinding parameters can be altered and such that in the subsequent grinding operations those defects can be removed.

So that the examination can be effected as rapidly and as economically as possible and will also be free from subjective input, the evaluation is carried out based on comparison with a data base and stored information in a type of expert system in which the evaluation is made without input from the operating personnel.

According to a feature of the invention, the stored data can be quality setpoint data as to the rolled surface and/or typical defect data. The preferably typical defect data can be stored and compared with the results of the scan to see if any defect represented by the stored data is present. Similarly it is possible to register properties of the surface in the data base which represents the desirable or setpoint property, against which a comparison is made to determine if a defect is present.

Usually the sensor carrying out the inspection of the roll will be an optical sensor.

The information outputted in accordance with the invention can include a warning signal which can indicate an evaluation result showing a deviation of the inspected roll surface from stored data representing a satisfactory surface which exceeds a predetermined and stored tolerance. That permits certain tolerances within which the geometrical data from the roll surface can vary. When these tolerances are exceeded there is a corresponding warning which makes it possible for personnel to react even prior to the development of significant machining defects in the roll surface or at a time when any such defect can be ameliorated at relatively low cost.

The outputting of information can be effected graphically on a machine cabinet. Alternatively or in addition the information can be made available in a printed form which has the advantage that it can provide a written documentation of the roll quality.

It has been found to be advantageous to provide a sensor which is or includes a laser and/or a camera, especially a digital camera.

BRIEF DESCRIPTION OF THE DRAWING

The above and other objects, features, and advantages will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

FIG. 1 is a perspective view of a roll grinding machine;

FIG. 2 is a perspective view of an alternative roll grinding machine for carrying out the method of the invention;

FIG. 3 is an elevational view of a roll grinding machine showing the roll in place and a flow diagram of the inspection, evaluation and output of the roll grinding process;

FIG. 4 is another elevational view of the roll grinding machine drawn to a larger scale;

FIGS. 5a and 5b are elevational views of a portion of a roll and a radial section of that roll, respectively, showing a defect pattern in the form of staggered crests;

FIGS. 6a and 6b are views similar to FIGS. 5a and 5b, respectively, showing a defect pattern produced by machine chatter and in the form of a faceting of the roll surface;

FIG. 7 is a schematic illustration of a third defect pattern in the form of facets constituted by interruptions and discontinuities in the surface of the roll in an elevational view of the working surface thereof;

FIG. 8 is a diagrammatic illustration of a fourth defect image with faceting as seen in a front elevational view of the roll;

FIG. 9 shows diagrammatically a fifth defect image having the appearance of wake-like facets as also seen in a front elevational view of he roll;

FIG. 10a and 10b are views similar to FIGS. 5a and 5b diagrammatically showing a sixth defect image in the form of a checkerboard pattern;

FIGS. 11a, 11b AND 11c are respectively a front elevational view of a pattern of the working surface of the roll, an axial section in one configuration and an axial section in a second configuration, schematically illustrating a seventh defect pattern in the form of a twist;

FIG. 12 schematically shows an eighth defect pattern having a trapezoidal configuration as seen in a front elevational view of the roll;

FIG. 13 is a diagram of a ninth image pattern having the appearance of a shift mark impressed on the roll and seen in a diagrammatic front elevational view thereof;

FIGS. 14a and 14b are diagrammatically a front elevational view of a roll and an axial section therethrough diagrammatically illustrating a tenth defect pattern in the form of scratches in the roll surface;

FIG. 15 is a schematic illustration in a front elevation of the roll illustrating an eleventh defect pattern in the form of overlapping scales;

FIGS. 16a and 16b are views similar to FIGS. 12a and 12b schematically showing a twelfth defect pattern in the form of closely-spaced grooves;

FIG. 17 shows a thirteenth defect pattern with a cloudlike appearance in a front elevational view of the working surface of the roll; and

FIG. 18 is a diagram of a fourteenth defect pattern in the form of large-area islands with closely delimited regions in a front elevational view of the working surface of the roll.

SPECIFIC DESCRIPTION

FIGS. 1 and 2 show roll grinding machines 2 upon which a mill roll for the rolling of strip and foil of metal can be ground. In both of these machines, the grinding wheel or disk has been shown at 4.

In the machine of FIG. 1, the ends of the roll can be clamped between a head stock 10 and a tail stock 11 supporting the roll for rotation on a bed 12. The working surface of the roll can be supported on a traveling carriage 13 and the grinding head 14 can be displaced radially against the roll transversely of the axis thereof. The head stock and tail stock can be positioned with respective servomotors and a drive motor 15 can rotate the roll during the grinding operation. The cross slide or head 14 can have an outrigger 16 carrying the sensor which will be described in greater detail hereinafter and can include an electronic memory for detecting the defect pattern on the roll.

In the embodiment of FIG. 1, the cross slide or head 14 is mounted on a bed 17 which is displaceable along the roll and in the embodiment of FIG. 2 the grinding head 14 is stationary and the roll is displaceable as represented diagrammatically at 18.

The roll grinding machines themselves insofar as they have been described and without the sensor or automatic inspection facility are conventional in the art and thus need not be described in greater detail. In the past, after grinding, e.g. say in one of the machines of FIGS. 1 and 2, there has been a visual inspection of the surface of the rotation roll by an operator of the machine whose conclusions as to whether or not defects might be present was subjective.

With the system of the invention (FIG. 3), as an alternative to the visual inspection of the surface by the machine operator, the sensor 5 is provided to scan the working surface 3 of the roll 1 automatically and during the grinding operation or subsequently thereto. The sensor 5 in a preferred form is a laser sensor or a camera and, advantageously can be a commercially available video or column or row camera responsive to dark/light differentiations and utilizing appropriate software. The sensor 5 scans the surface as the roll rotates over the entire length of the working surface and can be perpendicular to the surface for that purpose. It also may be vertically oriented as shown or otherwise oriented along the radius to the roll.

The sensor 5 optically scans the working surface 3 of the roll as it is ground or following grinding (block 20 of FIG. 3). The measured signal can optionally be converted to digital signals. In FIG. 4 a holder 8 has been shown by which the sensor is held in the requisite position for scanning the roll surface.

The sensor 5 can be mounted on a measuring unit especially provided for this purpose on the grinding machine or can be mounted on a part of the machine which normally is provided for measurement purposes. In either case the measuring device is provided on a support which can move along the roll relative to the roll should the roll be movable along its axis. The scanning of the roll surface may be in helical or spiral patterns as the roll 1 is rotated. The scanning signals can be stored and in a subsequent step represented by block 21, the signal is evaluated and compared with a defect library 7 provided to the comparitor included in the block 21 and as part of the CNC (computer numerical control) unit. The defect library 7 can be a memory for the CNC. Based upon the comparison, the CNC can control further grinding operations automatically.

In addition, since the data in the defect library 7 represents typical defect images as for example have been shown in FIGS. 5-18, the comparison of the scanning signals with the defect library can indicate the nature of the defect and test the measured defect status to determine if it exceeds a stored threshold represented by allowed tolerances or known error for example.

The detected defects are likewise classified to determine whether they fall within the wide range of possible defects and whether, depending upon the application, they render the roll unsuitable for use. The defects which can be determined are not only those which result from grinding operations but any which arise from other causes and, of course, may have an effect in the subsequent rolling operation. The comparison can result in a graphic display of the defect signal at 22 at the machine cabinet, a printout of the results and a display of any signal exceeding the threshold or tolerance limits, including the emission of a warning signal acoustically or visually.

At the machine control cabinet, if a printer is provided, a quality certificate can issue (block 23) as may be desirable.

If the determination at 24 shows that the defects on the roll surface lie within predetermined tolerances, i.e. below a given threshold, there is an automatic release of the ground workpiece at 25. Should that not be the case, a locking of the workpiece takes place at 26 so that the surface of the roll can be reground.

As a consequence, there is an automatic quality test of the ground roll while it is on the machine and as a result of the test the roll is either released or held back for regrinding. The proportion of defective rolls is thereby significantly reduced.

The described inspection is a component of the grinding process in the roll grinding machine itself and can detect possible defects in the finished ground roll surface independently from any subjective input from the machine operator. It is also independent of the material of the roll, i.e. whether it is of forged steel or a casting and the results can follow a protocol and be documented to serve as a quality warning as to the roll for the production of metal strip and foil.

The analysis of the surface scan for the defect on the surface can use image recognition software and a computer in the form of a neural network as is known in the art.

The memory 7 can be used to store images or measured signals representing images of typical defects found on a surface 3 of the roll. FIGS. 5-18 show only by way of example a number of possible defect images which have been described in greater detail below and which may require further machining or grinding to eliminate the defect. The defects and the Figures themselves should be understood to be purely diagrammatic and have been intended to show defects only in a stylized form. In most of these Figures, the pattern of the defect is seen as it might appear on the surface 3 of the roll 1.

1. Chatter Marks

In FIGS. 5a and 5b a front elevational view of the roll 1 and its working surface 3 is shown together with a radial section and on which the chatter marks 30 can be seen in a helical pattern. The marks can also be considered to be mouse-tooth or similar patterns. The chatter marks are macrogeometric deviations from a perfect cylindrical shape of the roller which close together with a spacing of say 3 to 5 mm and of a length which corresponds to the width of the grinding wheel. Depending upon the speed with which the wheel sweeps along the length of the roll, the chatter marks can overlap in successive passes as shown in FIG. 5a. The chatter marks result from vibrations in oscillations which develop by themselves between the grinding wheel and workpiece and may originate in nonuniformities in hardness of the grinding wheel and the roll or problems with the concentricity of the grinding wheel. The energy of the oscillations or vibrations is drawn from the grinding operation itself. Such marks are most pronounced when the grinding wheel is less than perfectly circular across its entire width. The frequency is in the range of the characteristic frequency of the machine, here meaning the system of the grinding spindle, the grinding wheel, the head and/or the roll. The chatter marks can be eliminated by alignment and truing of the grinding wheel and with fine and superfinish grinding.

2. Faceting

Faceting can also be in the form of strips, lines or transverse patterns. The facets also deviate from the macrogeometric perfection of the circular cylinder which is desired and can appear over the entire length of the working surface, only a part thereof, and usually in a pattern which is independent from the width of the grinding wheel. They lie parallel to the axis of the roll or at a slight inclination thereto and consist usually of fairly machinable rises and depressions in the workpiece surface.

The facets can be made more visible by bringing the surface in contact with an inked steel strip or with copper wire, especially after the surface of the roll has been treated with oil and chalk. The following types of faceting can be distinguished:

2.1 Facets Because of Machine Defects.

In FIGS. 6a and 6b an elevational view and a radial section have been shown of the working surface of a roll having facets because of machine defects. These facets are the result of oscillations having their origins in the drives or drive elements, i.e. motors, gearing, chains and the like or in friction in which the workpiece may engage in the head stock or tail stock with a high degree of friction and the pattern derives from the characteristic vibration frequency of the workpiece. The more developed they are, the more likely it is that their origins are at the workpiece.

When the excitation force acts only on a part of the workpiece periphery or part of the workpiece length, facts are generated there and can be propagated over the entire workpiece (see 2.4 below).

Mainly the source of the disturbance which causes the faceting can be seen in terms of measurements of the dimensions or spacing which agrees how the defects and when the defects can be alleviated. For example, when the excitation of the defects is seen in terms of an excitation rotation (for example in RPM—revolutions per minute), the relationship can be n_e=(d_w/a)×n_w. In this relationship, n_e is the excitation speed in RPM, d_w is the diameter of the workpiece or roll in mm, n_w is the workpiece or roll speed n_w in RPM and the facet spacing is given by a in RPM. The excitation speed can also be a multiple of the speed of the roll.

2.2 Faceting as a Consequence of Discontinuities in the Workiece Surface.

In FIG. 7 facets are shown which are a consequence of discontinuities in the workpiece or roll surface. Their origin is in the grinding of the interrupted workpiece surface, for example, by wedge-shaped grooves and differ as a consequence of differing grinding pressures. In the case of longitudinal grinding, they form dislocations in the surface. These defects can be avoided or removed by operating at higher workpiece or roll speeds, sharper abrasives in the grinding wheel and reduced material removal in the finished machining.

2.3 Notch Faceting.

In FIG. 8 notch faceting has been shown schematically. This faceting has its origin in beveling of the grinding wheel and the action of a beveled grinding wheel against a hard smooth workiece surface. It occurs when the grinding pressure is greater than the centering hydrodynamic pressure in the grinding spindle of the grinding wheel bearing system or the stiffness of the workpiece or roll. The result is a short duration self-excited vibration.

The problem can be dealt with by making the grinding wheel so hard that a deformation of the grinding wheel cannot occur. Generally the defect can be removed by further grinding at a different workpiece or roll speed.

2.4 Drag Faceting.

FIG. 9 shows schematically the defect structure formed by drag faceting. The origin can be the faceting problems arising in 2.1 through 2.3 and can extend longitudinally over the roll as a result of vibrations produced in the grinding wheel from these other sources as the grinding wheel continues to move across the surface. The appearance of such faceting is similar to the others and this type of drag faceting arises primarily in the case of slender workpieces. The problem can be alleviated by truing the grinding wheel and regrinding with the altered removal state and above all at a different rotary speed of the roll and workpiece and reduced removal rates.

3. Checkerboard Pattern.

FIGS. 10a and 10b show a checkerboard pattern on the roll which represents a deviation from the macrogeometric form of the surface formed by imparting thereto chatter marks and facts parallel to the workpiece or roll axis and are interrupted as the grinding wheel moves along the length of the roll. The origin of these chatter marks is self-excited vibration which has a forced vibration superimposed thereto. It may derive from some imbalance in the grinding wheel or some electrical defect in the energization of the motor or in the operation of the motor. It can be alleviated or reduced by balance of the grinding wheel and improving the motor operation.

4. Twist.

In FIGS. 11a to 11c a defect pattern in the form of a twist has been shown. The twist can also be formed by spiral or inclined lines impressed in the surface of the roll. The twist-type of deformation is a microgeometric deviation from the normal surface configuration. It is usually formed by a pattern of uniformly distributed irregularities or discontinuities which may be seen as dark and light regions. The eye detects the irregularities as parallel lines with a pitch which can assume any value and is dependent on the.

The ratio of the grinding wheel speed to the workpiece or roll speed.

In the spacing of the imaginary twist lines the following relationship applies.

The spacing of the twist lines a_dw in the circumferential direction of the workpiece and in mm is given by the formula a_du=d_w×(n_w/n_s) whre d_w is the workpiece or roll diameter in mm, n_w is the workpiece or roll speed in RPM and n_s is the grinding wheel speed in RPM.

The spacing of the twist line in the axial direction in the mm is given by a_da=V_v/n_w where a_da is the spacing of the twist line in the axial direction, V_v is the axial speed of advance of the grinding wheel over the working surface of the roll in mm/min and n_w is the workpiece or roll speed in RPM.

Frequently twist lines of difference sources can be superimposed on one another so that one must sort out the twist lines and their dimensions to determine the causes. Where the nonuniformities run precisely axially in the surface, it is difficult to distinguish between such twist lines and the faceting described. The twist line, by contrast with the facets do not affect the surface of the roll as significantly and are not macrogeometric defects causisng significant depressions or projections in the surface. The problem with them can be ameliorated by changing the way in which the workpiece twist is rotated, e.g. by providing a range of roll speeds. It should be noted that a range of speeds of the grinding wheel does not produce a uniform roughness on the roll surface.

The following types of twist can be distinguished.

4.1 Twist as a Result of Grinding Wheel Defects.

These twists arise with longitudinal grinding as a result of the development of a uniform grinding wheel surface or edge and the action thereof on the workpiece. Possible grinding wheel defects which contribute to such twists include nonuniform hardness of the periphery of the grinding wheel, a damage to the grinding surface or edge, an impact against the cutting edge and the inclination of the workpiece and the grinding wheel.

The problem can be ameliorated by substituting a grinding wheel of uniform hardness or eliminating damage to the grinding surface or the cutting edge or truing the wheel. If the problem arises, it can result in a limited operating period between truing of the wheel.

4.2 Twist from Forced Vibration of the Grinding Wheel Spindle.

As the grinding wheel rotates defects in the grinding wheel spindle-grinding wheel spindle bearings can result in forced vibrations at a frequency corresponding to the rotating speed of the wheel or a multiple thereof. The system because of nonuniform loading has intervals of high maximum load followed by intervals of reduced load-producing marks on the workpiece surface. Such twist defects frequently cannot be distinguished from twist defects resulting from defects in the grinding wheel surface. The problem can frequently be avoided by frequent checks of the grinding wheel spindle and the spindle bearings.

4.3 Rhombic Patterns.

FIG. 2 shows a defect pattern having a trapezoidal shape. The trapezoidal pattern is the special case of a twist which arises in longitudinal grinding without resetting of the grinding wheel when, for example, the grinding wheel is moved back and forth along the workpiece and produces a twist in one direction which is superimposed upon the twist in the other.

The origins and amelioration of this type of defect formation are discussed in points 4.1 and 4.2 above.

5. Shift Markings

FIG. 13 shows the defect pattern which can arise which shift markings of the roll during the grinding operation. In appearance the shift marking extends in spiral lines around the working surface of the roll with a fairly steep pitch, which depends upon the workpiece or roll speed and the axial shift. Its origin during longitudinal grinding comes from an increased grinding pressure at the cutting edge of the grinding wheel relative to the following more cylindrical zones thereof. The problem can be ameliorated by reducing the grinding pressure and changing the ratio of the workpiece speed to the axial shift. It can also be helped by rounding the edge of the grinding wheel.

6. Scratch Patterns

FIGS. 14a and 14b show the defect pattern arising in the ground roll in the form of scratch or broken lines or decimal points. The scratches or points are small depressions in the surface of the roll with a microgeometric appearance.

The origins of the scratches or broken line defects or points lies in the penetration of grains from the grinding wheel which breaks loose at the surface and are pressed into the surface or which derive from impurities in the cooling which are pressed into the surface between the grinding wheel and the workpiece. They may also arise if the grinding wheel is too soft. The solution can be better pressurized flushing of the grinding wheel, using a grinding wheel of greater porosity, improvements in cooling, cleaning, changing the cooler, grinding with the wheel and the workpiece in counterrotation, and/or the use of a grinding wheel with a ceramic pointer.

7. Scale Patterns

FIG. 15 shows a defect state in the form of a scale pattern or, as it may be known, as an orange pattern. The scale pattern is a macrogeometric deviation of the surface from the truly cylindrical form with the configuration of scale-like depressions. The depressions originate from vibrations of the truing diamonds during the truing operations on the grinding wheel resulting from a defective retention or application of the diamond to the wheel. Frustoconical diamonds create the scale pattern. The solution can be better control and mounting of the truing operating.

8. Grooving

FIGS. 16 and 16b show a defect pattern in the form of grooves formed in the roll surface during the grinding operation. The grooves are macrogeometric defects in the surface of the roll extending circumferentially with a spacing corresponding to the truing spacing. They originate from a truing operation which tends to cut a screw thread profile into the grinding wheel utilizing a pointed diamond, a high penetration of the truing tool and a high degree of shift of the truing tool per revolution of the grinding wheel which can be greater than the wear surface of the diamond.

The problem can be reduced by limiting the shift of the truing tool and the penetration thereof.

9. Cloud-Like Surface Patterns.

FIG. 17 shows this type of defect, which can also be referred to as a streaking or schlieren defect pattern. The cloud-shape covers large areas in general which are nonuniform deviations in the microgeometry of the workpiece or roll surface which only arise in the case of fine grinding and superfinishing of the surface and appear as differences in the reflectivity of the surface. The origin is aperiodic stiffness variations between the grinding wheel and the workpiece which takes place during the relative movement and appears predominantly with older machines or with nonuniform pressure of the grinding wheel or with pressure reduction which may result from use of a next coarser grinding wheel.

The cloud patterns which are produced by aperiodic stiffness differences cannot be easily avoided or removed. They can be minimized by polishing with very low grinding pressures. The cloud patterns which derive from inefficient grinding pressure reduction must be ground away with coarser grinding wheels.

10. Large-Area Clearly Delimited Surface Markings.

Such surface markings have been shown diagrammatically with the defect pattern in FIG. 18. Such markings are in the form of deviations from the microgeometry of the workpiece surface and are visible on finely ground surfaces as reflection variations with a form which is determined by their origin. They can be the result of external effects, for example impacts which slowly diminish the workpiece characteristics like limited surface zones with different hardnesses, of machine characteristics like, for example, gearing interactions, or coolant effects like, for example. sludge trappings between the grinding wheel and the workpiece. They can be ameliorated by attention to the causes.

The storage of the defect pattern and other typical conditions which can give rise to defects, as data in memory and the comparison to the measured signals or images with these defect images enables automatic evaluation as to the cause and can trigger not only the warning but an output of data to enable the system to be adjusted to eliminate the defect. The defect can be automatically eliminated, where appropriate, for example, by a suitable automatic input to the CNC controller.

Claims

1. A method of grinding a roll comprising the steps of:

(a) mounting a roll for the rolling of workpieces in a roll-grinding machine having a grinding wheel engageable with said roll and grinding a working surface of said roll therewith;

(b) subsequent to or simultaneously with the grinding of said working surface of said roll, scanning said working surface of said roll for defects with at least one sensor on said machine capable of recognizing the geometry of said working surface;

(c) then automatically evaluating results of the scanning in step (b) by automatically comparing the results with stored data as to qualities of said surface; and

(d) automatically outputting information as to the evaluation in step (c).

2. The method defined in claim 1 wherein the stored data includes at least one data set selected from a data set of data describing set-point qualities of said working surface and a data set of data describing typical defects of said working surface.

3. The method defined in claim 2 wherein the scanning is carried out in step (b) with an optical sensor.

4. The method defined in claim 3 wherein the information outputted in step (d) is a warning signal produced when the result of the evaluation in step (c) indicates a deviation of a measurement of said surface from the stored data exceeding a predetermined and stored tolerance.

5. The method defined in claim 4 wherein the information outputted in step (d) is displayed graphically on a cabinet of the machine.

6. The method defined in claim 4 wherein the information outputted in step (d) is displayed in printed form.

7. The method defined in claim 1 wherein the scanning is carried out in step (b) with an optical sensor.

8. The method defined in claim 1 wherein the information outputted in step (d) is a warning signal produced when the result of the evaluation in step (c) indicates a deviation of a measurement of said surface from the stored data exceeding a predetermined and stored tolerance.

9. The method defined in claim 1 wherein the information outputted in step (d) is displayed graphically on a cabinet of the machine.

10. The method defined in claim 1 wherein the information outputted in step (d) is displayed in printed form.

11. A roll-grinding machine comprising:

a machine structure for receiving and rotating a roll for the rolling of workpieces;

a grinding wheel engageable with said roll for grinding a working surface of said roll;

at least one sensor capable of recognizing the geometry of said working surface for scanning said working surface of said roll for defects subsequent to or simultaneously with the grinding of said working surface of said roll;

circuitry connected to said sensor for automatically evaluating results of the scanning by automatically comparing the results with stored data as to qualities of said surface; and

a device connected to said circuitry for automatically outputting information as to the evaluation.

12. The roll-grinding machine defined in claim 11 wherein said sensor capable of recognizing the geometry of said working surface includes a laser.

13. The roll-grinding machine defined in claim 12 wherein said sensor capable of recognizing the geometry of said working surface includes a camera.

14. The roll-grinding machine defined in claim 13 wherein said camera is a digital camera.

15. The roll-grinding machine defined in claim 11 wherein said sensor capable of recognizing the geometry of said working surface includes a camera.

16. The roll-grinding machine defined in claim 15 wherein said camera is a digital camera.

17. The roll-grinding machine defined in claim 11, further comprising a digital memory connected to said circuit for stored data including at least one data set selected from a data set of data describing set-point qualities of said working surface and a data set of data describing typical defects of said working surface.