HONING METHOD AND MACHINE TOOL FOR CONTOUR HONING

Abstract

In the case of a honing method for machining the internal face (214) of a bore (210) in a workpiece (200) with the aid of at least one honing operation, during a honing operation a flaring-capable honing tool (150) that is coupled to a spindle is moved back and forth within the bore for generating a reciprocating movement in the axial direction of the bore, and are simultaneously rotated for generating a rotating movement that superimposes the reciprocating movement. A bore shape having an axial contour profile which is rotationally symmetrical in terms of a bore axis (212) and deviates from the circular cylindrical shape is generated herein. For generating an axially variable material removal in at least one stroke modification phase a stroke length and/or a stroke orientation of the reciprocating movement is modified. A honing tool (150) which has an annular cutting group (155) having a plurality of radially actuatable cutting material members (156) that are distributed about the circumference of the tool body (152) is used herein. The honing method is distinguished in that during the stroke modification phase a measurement of the actual diameter of the bore (210) is carried out for determining a diameter measurement signal which represents the actual diameter of the bore in a measurement plane, and the stroke length and/or the stroke orientation of the reciprocating movement is controlled as a function of the diameter measurement signal. Also described is a machine tool that is suitable for carrying out the honing method. The honing method is particularly suitable for honing cylinder running faces in the production of cylinder blocks or cylinder liners for reciprocating piston engines.

Claims

1. A honing method for machining the internal face of a bore in a workpiece with the aid of at least one honing operation, in particular for honing cylinder running faces in the production of cylinder blocks or cylinder liners for reciprocating piston engines, wherein during a honing operation a flaring-capable honing tool that is coupled to a spindle is moved back and forth within the bore for generating a reciprocating movement in the axial direction of the bore, and is simultaneously rotated for generating a rotating movement that superimposes the reciprocating movement; a bore shape having an axial contour profile, which is rotationally symmetrical in terms of a bore axis and deviates from the circular cylindrical shape, is generated; and for generating an axially variable material removal in at least one stroke modification phase a stroke length and/or a stroke orientation of the reciprocating movement is modified; wherein a honing tool which has an annular cutting group having a plurality of radially actuatable cutting material members that are distributed about the circumference of a tool body is used, wherein during the stroke modification phase a measurement of the actual diameter of the bore is carried out for determining a diameter measurement signal which represents the actual diameter of the bore in a measurement plane; and the stroke length and/or the stroke orientation of the reciprocating movement is controlled as a function of the diameter measurement signal.

2. The honing method as claimed in claim 1, wherein the reciprocating movement comprises a multiplicity of successive strokes which run in each case between a lower reversal point and an upper reversal point, and in that the axial position of at least one of the reversal points of a stroke is dynamically modified as a function of a diameter measurement signal that is determined in a preceding stroke; wherein the axial position of one of the reversal points is preferably fixed and only the axial position of the other reversal point is dynamically varied as a function of the diameter measurement signal; wherein the axial contour profile has in particular a portion in which the nominal diameter continuously increases between a first axial position having a smallest diameter within the portion, and a second axial position having a largest diameter within the portion, wherein the reversal point associated with the second axial position is fixed and the axial position of the other reversal point is dynamically varied as a function of the diameter measurement signal.

3. The honing method as claimed in claim 1, wherein prior to the honing operation an axial nominal contour profile which represents a nominal diameter as a function of the axial stroke position is predefined, in that in a stroke the actual diameter measured at a stroke position is compared with the nominal diameter associated with the stroke position, and a diameter deviation for the stroke position is determined from the comparison, and in that the stroke length and/or the stroke orientation of a subsequent stroke in relation to a nominal stroke length and/or a nominal stroke orientation is modified as a function of the diameter deviation; wherein the stroke length and/or the stroke orientation of the reciprocating movement is preferably modified as a function of the determined diameter deviation in such a manner that the diameter deviation at the axial position is at least in part compensated for by modifying the number of overlapping honing actions at the axial position.

4. The honing method as claimed in claim 3, wherein a reduction in the number of overlapping honing actions at an axial position is generated by modifying the stroke length and/or the stroke orientation of the reciprocating movement when the diameter deviation results in an actual diameter that is too large in comparison to the nominal diameter, and in that an increase in the number of overlapping honing actions at an axial position is generated by modifying the stroke length and/or the stroke orientation of the reciprocating movement when the diameter deviation results in an actual diameter that is too small in comparison to the nominal diameter.

5. The honing method as claimed in claim 1, wherein in the diameter measurement for determining a diameter measurement signal a measured value detection takes place by way of a floating mean value, in particular by way of an adjustable quantity of measuring points, wherein the floating mean value is determined in a portion of the bore or across the entire currently machined portion of the bore.

6. The honing method as claimed in claim 1, wherein the measurement of the actual diameter is carried out when the honing tool is situated in the region of a reversal point of the reciprocating movement; wherein the diameter measurement is preferably carried out such that the honing tool during the diameter measurement rotates in an axially narrow measurement zone in the region of a reversal point, wherein a plurality of diameter measurement values are within the narrow measurement zone detected, and averaging across the plurality of diameter measurement values detected in short succession takes place in order for the diameter measurement value to be determined.

7. The honing method as claimed in claim 3, wherein the diameter measurement signals utilized for the nominal/actual comparison and/or for forming the mean value are detected in an intermediate region between the reversal points, in particular in a central region between the reversal points.

8. The honing method as claimed in claim 1, characterized by a continuous actuation of cutting material members of the honing tool during the stroke modification phase, in particular at a constant or pulsed actuation rate.

9. The honing method as claimed in claim 1, characterized by controlling the contact pressure force of cutting material members of the honing tool that is transmitted to the honing tool in a manner that the contact pressure force remains substantially constant during the stroke modification phase.

10. The honing method as claimed in claim 1, wherein the honing tool has at least one of the following properties: (i) the axial length of the cutting material members is less than 50% of the effective external diameter of the cutting group, in particular between 10% and 30% of said external diameter; (ii) the axial length of the cutting material members is in the range from 5 mm to 90 mm; (iii) the axial length of the cutting material members is less than 35% of the bore length of the bore; (iv) the cutting material members are configured as cutting material strips that are narrow in the circumferential direction, the width of said cutting material members measured in the circumferential direction being small in relation to the axial length of the cutting material strips, wherein an aspect ratio between the length and the width is preferably in the range from 4:1 to 20:1; (v) measuring sensors of a diameter measurement system, in particular measuring nozzles of a pneumatic diameter measurement system, are attached in the axial region of the cutting material members, in particular at half the height of the axial length of the cutting material members.

11. The honing method as claimed in claim 1, wherein a honing tool with double flaring is used, wherein the cutting group has two sub-groups of cutting material members which are actuatable in a mutually separate manner, wherein the cutting material members of the sub-groups preferably have grit sizes of dissimilar fineness or coarseness.

12. The honing method as claimed in claim 1, wherein a honing tool in which the cutting group has a plurality of radially actuatable cutting material member supports which cover in each case one circumferential angle range is used, said circumferential angle range being greater than the axial length of the cutting material members, wherein each of the cutting material member supports preferably supports two, three, four, or more, individual cutting material members in the form of narrow honing strips.

13. The honing method as claimed in claim 1, wherein a honing tool is used which for guiding the honing tool in the bore has non-cutting guide strips, wherein the guide strips are fixedly assembled on the tool body, or are actuatable separately from the cutting material members.

14. A machine tool for the precision machining of an internal face of a bore in a workpiece with the aid of at least one honing operation, in particular for honing cylinder running faces in the production of cylinder blocks or cylinder liners for reciprocating piston engines, having at least one spindle for moving a honing tool coupled to the spindle in such a manner within the bore that machining of the internal face takes place by at least one of the cutting material members attached to the honing tool, wherein the machine tool is configured for carrying out on the workpiece a honing method as claimed in claim 1.

15. The machine tool as claimed in claim 15, wherein a control installation of the machine tool is specified for processing diameter measurement signals of a diameter measurement system and for controlling a reciprocating drive of the spindle as a function of the diameter measurement signals.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Further advantages and aspects of the invention are derived from the claims and from the description hereunder of preferred exemplary embodiments of the invention, which are explained hereunder by means of the figures in which:

[0045] FIG. 1 schematically shows some components of a honing machine when machining the internal face of a bore having an axial contour profile;

[0046] FIG. 2 shows the decomposition of a conical bore portion into virtual circular cylinders;

[0047] FIG. 3 shows the decomposition of a bore portion having a free-form contour profile into virtual circular cylinders;

[0048] FIG. 4 shows a diagram having the profile of various process parameters while carrying out a honing method according to one exemplary embodiment; and

[0049] FIGS. 5 and 6 show fragments of the diagram from FIG. 4 in a modified illustration.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0050] Some components of a honing machine 100 which in the context of various embodiments of methods according to the invention can be used as a machine tool for machining internal faces of bores in workpieces is schematically shown in FIG. 1. The honing machine can be operated such that one or a plurality of conventional honing operations can thus be carried out on the workpiece, on the one hand. On the other hand, the honing machine is also specified for carrying out honing methods according to embodiments of the invention on the same workpiece.

[0051] A workpiece holding device 104 which supports a workpiece 200 clamped thereon is assembled on a workpiece support (not illustrated in more detail) of the honing machine. The workpiece in the exemplary case is an engine block (cylinder crankcase) of a multi-cylinder internal combustion engine. A plurality of bores 210 having a generally vertical alignment of the bore axes thereof are formed in the engine block. The bores are also referred to as cylinder bores, even when the bore shape thereof significantly deviates from the shape of an ideal circular cylinder. In the case of the honing method described here, a bore shape which is rotationally symmetrical in terms of a bore axis 212 and deviates from the circular cylindrical shape and has an axial contour profile is generated by means of honing. The term axial contour profile here means in particular that the bore has dissimilar diameters at different axial positions. The cylinder running faces formed by the internal faces 214 of the cylinder bores are subjected to quality-determining final machining with the aid of the honing machine, wherein the macro shape of the cylinder running faces (thus the macroscopic design of the bore) as well as the surface topography thereof are generated by way of suitable honing operations.

[0052] The nominal shape of the bore is rotationally symmetrical in terms of the bore axis 212 thereof, and from a bore entry 214 that in the installed state faces the cylinder head extends across a bore length L to the bore exit 216 at the opposite end. The bore in the completely honed state should have a substantially conical, or truncated conical, respectively, design. FIG. 1 shows the bore in an intermediate phase of the machining by honing, in which an upper portion OA has already been conically honed, while the lower portion UA however still has the circular cylindrical initial shape which was present at the beginning of the stroke modification phase.

[0053] The nominal contour profile 215 of the bore can be seen by way of a dashed line in the lower portion of the bore 210, said portion not yet having been machined. The nominal diameter continuously increases in the linear manner from the bore entry to the bore end. The cone angle (angle between the bore axis and a shell line of the bore running in an axial plane) can be, for example, in the range of less than 5, even less than 1, possibly even be 0.2 or less.

[0054] The diameter difference between the first diameter D1 at the bore entry and the second diameter D2 at the end remote from the entry is significantly outside the tolerances that are typical for the conventional cylindrical machining by honing, said tolerances for a cylindrical shape being in the magnitude of at most 10 m (in terms of the diameter). In the case of an absolute value of the internal diameter in the magnitude between 50 mm and 500 mm (the latter in the case of marine engines, for example) the maximum diameter difference can be between 20 m and 500 m, for example.

[0055] The dimensions can be optimized such that a low blow-by, a low oil consumption, and low wear on the piston rings result in typical operating states of the engine.

[0056] The honing machine 100 has a plurality of honing units. A few components of a honing unit 110 are schematically illustrated in FIG. 1. The honing unit comprises a spindle box 120 which is fastened to a support construction of the honing machine and in which the honing spindle 140 serving as the tool spindle of the machine tool is rotatably mounted. The honing spindle by means of a spindle drive fastened to the spindle box can be rotated about the longitudinal axis (spindle axis) 142 of said honing spindle. The spindle drive has a servomotor which is controllable inter alia in terms of the rotating speed thereof and the torque generated.

[0057] A toggle link is attached at the lower end of the honing spindle, the honing tool 150 serving as the machining tool being mechanically coupled to the lower free end of said toggle link so as to be movable in a limited manner, said coupling being performed by way of a bayonet connection, for example. The honing tool can have an integrated joint so as to enable a limited mobility in relation to the toggle link.

[0058] The honing tool is particularly suitable for machining rotationally symmetrical bores which have bore portions of dissimilar diameters and/or dissimilar designs, for example bottle-shaped bores, barrel-shaped bores, and/or bores which have at least one conical bore portion having a diameter which is continuously variable in axial terms. The honing tool can however also be utilized for machining circular-cylindrical bores, thus rotationally symmetrical bores without an axial contour profile.

[0059] The honing tool has a tool body 152 which is made from a steel material and defines a tool axis which simultaneously is the rotation axis of the honing tool during the machining by honing. A coupling structure for coupling the honing tool to a drive rod or an operating spindle of a honing machine is situated at the spindle-side end of the honing tool.

[0060] A single flaring-capable annular cutting group 155 is situated at the end portion of the tool body that faces away from the spindle, said cutting group 155 having a multiplicity of cutting material members 156 which are distributed about the circumference of the tool body, the axial length of said cutting material members 156 measured in the axial direction being smaller by a multiple than the effective external diameter of the cutting group 155 in the case of cutting material members that are fully retracted in the radial direction. The cutting material members are configured as cutting material strips that are narrow in the circumferential direction, the width of said cutting material members measured in the circumferential direction being small in relation to the axial length of the cutting material strips. An aspect ratio between the length and the width can be in the range from 4:1 to 20:1, for example.

[0061] The honing tool has only a single annular cutting group 135. Said cutting group 135 is disposed so as to be more or less flush with the end of the tool body that is remote from the spindle such that pocket hole bores can optionally also be machined down to the bore base.

[0062] The cutting group, or the cutting material members of the cutting group, respectively, is/are actuatable in a radial manner in relation to the tool axis by means of an actuator system assigned to the cutting group. Since the functionality typical of honing tools is known per se, the components provided to this end (for example actuator rod(s), flaring cone, etc.) are not described in more detail here.

[0063] The honing tool can be equipped with single flaring or double flaring. In the case of single flaring, all cutting material members of the cutting group are collectively actuated in a radial manner. In the case of double flaring, the cutting group has two sub-groups of cutting material members which can be actuated in a mutually separate manner. The cutting material members of the sub-groups can have grit sizes of dissimilar fineness or coarseness, for example, such that, for example, after a pre-honing operation by means of a first sub-group having comparatively coarse cutting material members a final honing stage can be carried out using the cutting material members of the second sub-group without a tool change.

[0064] The flaring-capable annular cutting group 130 comprises a plurality of radially actuatable cutting material member supports 158 which cover in each case one circumferential angle range which is greater than the axial length of the cutting material members, or of the cutting group, respectively. In the exemplary case of FIG. 1 six cutting material member supports which cover in each case a circumferential angle range of between 45 and 60 and are disposed uniformly across the circumference of the honing tool are provided. Each of the cutting material member supports two, three, four, or more, individual cutting material members 156 in the form of relatively narrow honing strips.

[0065] A reciprocating drive 160 of the honing machine is provided for causing vertical movements of the honing spindle in a manner parallel with the spindle axis 142. The reciprocating drive causes, for example, the vertical movement of the honing spindle when introducing the honing tool into the workpiece, or when retracting said honing tool from the workpiece, respectively. The reciprocating drive during the machining by honing is actuated such that the honing tool within the bore 210 of the workpiece carries out an oscillating reciprocating movement, thus a back-and-forth movement in a manner substantially parallel with the spindle axis.

[0066] The reciprocating movement can be characterized by various parameters. The stroke length herein corresponds to the axial spacing between an upper reversal point UO and a lower reversal point UU of the reciprocating movement (cf. FIG. 4). The upper reversal point herein is that reversal point which is closer to the bore entry; the lower reversal point is the reversal point which is remote from the entry. The reciprocating movement can also be characterized by the term stroke orientation. The term stroke orientation herein refers to the region between the upper reversal point of a reciprocating movement (close to the bore entry) and the lower reversal point of the reciprocating movement (closer to the end of the bore that is remote from the entry) in terms of a fixed machine coordinate system. Each axial relocation of at least one of the reversal points thus modifies the stroke orientation. The stroke length is typically also modified, for example when the axial position of one of the reversal points remains unmodified, and only the axial position of the other reversal point is modified.

[0067] The honing machine is equipped with an actuating system which permits the effective diameter of the honing tool (plus the external diameter of the cutting group) to be modified by actuating in the radial direction cutting material members 156 attached to the honing tool. This flaring can be implemented in a force-controlled or path-controlled manner, for example, by means of a servomotor. An hydraulic actuation is also possible. An actuating system having a single actuation or a double actuation can be provided. Since such actuating systems are known per se, a detailed description is dispensed with here.

[0068] The honing machine 100 is furthermore equipped with a diameter measurement system 170 for measuring the actual diameter of the bore in predefinable measurement planes or measurement zones during the machining by honing (in-process measurement). To this end, measuring sensors of the diameter measurement system are attached to the honing tool 150. The diameter measurement system in the exemplary case is conceived as a pneumatic diameter measurement system (air measurement system). Accordingly, the honing tool at two diametrically opposite positions between neighboring cutting material members has in each case one measuring nozzle 172-1, 172-2 of the diameter measurement system. A very exact diameter measurement of the currently machined bore portion is possible by virtue of the arrangement of the measuring nozzles in the axial region of the cutting material members, for example at mid-height, so as to be centric in the narrow zone of the ring occupied by the cutting material members.

[0069] The diameter measurement system can operate according to the nozzle/impact plate principle. Compressed air from the measuring nozzles for the measurement herein is blown in the direction of the bore wall, or the internal face 2014, respectively. The backpressure resulting in the region of the measuring nozzles can serve as a measure for the spacing of the measuring nozzle from the bore wall. A measurement transducer connected to the measuring nozzle by way of a pressurized line ensures the conversion of the (pneumatic) pressure signal to a voltage signal which can be electrically further processed and here is referred to as the diameter measurement signal. Instead of the backpressure, the volumetric flow of the compressed air can also be used for the evaluation. Diameter measurement systems which operate according to other principles, for example capacitive measurement systems or inductive measurement systems, or measurement systems using radar sensors (cf. DE 10 2010 011 470 A1, for example) can also be used in principle.

[0070] The spindle drive, the reciprocating drive, the at least one drive of the actuating system, as well as the converter of the diameter measurement system are connected to a control installation 180 which is a functional component part of the machine controller and can be operated by way of an operator installation 190. Numerous process parameters required for defining the honing process can be set by a machine operator by way of the operator installation.

[0071] An axial nominal contour profile which represents the nominal diameter as a function of the axial stroke position in the bore to be machined can inter-alia be predefined prior to the beginning of the honing operation. The predefining of the nominal contour profile, thus the predefining of the contour honing, can take place, for example, by defining the contour as an analytic formula (for example a linear equation or a non-linear equation) or as a point grid (for generating free-form curves).

[0072] The holding machine for generating a specific axial contour profile on the bore can be programmed such that an axially variable material removal can be generated in a targeted manner in at least one stroke modification phase by way of a targeted modification of the stroke length and/or the stroke orientation of the honing tool, so as to achieve in this way with high accuracy parameters in terms of the axial contour profile.

[0073] To this end, a measurement of the actual diameter of the bore is carried out during a stroke modification phase according to the stipulation of a pre-definable measuring condition, so as to determine a diameter measurement signal which corresponds to the actual diameter of the bore in that measurement plane or narrow measurement zone in which the measurement has been carried out. The stroke length and/or the stroke orientation of the reciprocating movement are then variably controlled as a function of the diameter measurement signal. A controlled contour honing process can be implemented in this way. Some basic considerations and technical measures for implementing this principle will be explained hereunder in an exemplary manner by means of instructive exemplary embodiments.

[0074] A problem of many in-process measurement systems available today lies in that said in-process measurement systems are not sufficiently dynamic so as to be able to measure with sufficiently high accuracy non-cylindrical bores, in particular such bores having an axial contour profile. The problem of the in-process measurement of a non-cylindrical bore can be solved in that a desired axial contour, that is to say the axial nominal contour profile, is divided into many nested virtual cylinders. FIG. 2 schematically shows this concept. FIG. 2 shows a conical portion AB of a bore, thus an axial bore portion, in which the diameter changes in the axial direction AX, according to a linear function. Further bore portions can join at the top and/or at the bottom. It is also possible for the portion AB to comprise the entire bore length such that the bore overall is purely conical.

[0075] It is shown how this rotationally symmetrical but non-circular cylindrical bore shape can be virtually divided into a multiplicity of circular cylinders Z1, Z2, . . . , Z.sub.n of dissimilar heights and dissimilar diameters. A non-cylindrical bore is thus never to be measured despite such a non-cylindrical bore nevertheless being generated at the end of the honing process. The contour honing by means of the modification of the stroke can thus be imagined as a series of classic cylindrical interlinked machining actions by honing.

[0076] In the case of one embodiment such machining is implemented in that the axial position of the lower reversal point UU of the reciprocating movement of successive double strokes remains fixed, or unchanged, respectively, while the upper reversal point UO is dynamically relocated in a step-by-step manner (incrementally) in the direction of the lower reversal point. In the exemplary case of a contour opening in a downward manner illustrated, the lower reversal point can remain fix and the upper reversal point is dynamically shortened.

[0077] However, the nested cylinders resulting on account thereof in the case of the honing method are not fixedly predetermined in terms of the diameter and the axial position of the upper end of said cylinders, but, by way of calculations within the control installation 190, are dynamically determined anew after each stroke in a manner corresponding to the current measured result of the diameter measurement, and are set in a corresponding manner with the aid of the reciprocating drive.

[0078] This takes place by determining the best adapted shortening of the upper reversal point UO to be dynamically modified according to the contour predefined by the machine operator.

[0079] Prior to beginning the honing operation in which an axial contour profile is to be generated, an axial nominal contour profile which represents the nominal diameter of the bore as a function of the axial stroke position is predefined. In the case of a pure conical shape of a bore of a predetermined bore length, it can be sufficient to enter only the diameter difference between the diameter at the upper end (relatively small nominal diameter) and the diameter at the lower end (relatively larger nominal diameter). The controller can therefrom calculate a linear equation which represents the nominal contour profile.

[0080] The predefining of the nominal contour profile, thus the predefining of the contour honing, can generally take place, for example, by defining the contour as an analytical formula (for example a linear equation or a non-linear equation) or as a point grid which describes the correlation between the stroke position and the desired contour dimension. In the simple case of a purely conical portion of the bore, the nominal contour profile can be indicated by a straight line. More complex cases can be indicated by correspondingly more complicated analytic formulae such as, for example, non-linear equations or by a points grid, wherein interpolation optionally takes place between the points. FIG. 3 shows an example of such a portion AB in which the diameter from the smallest diameter lying above to the largest diameter lying below does not change in a linear manner but according to a curved curve, wherein the increase of the diameter per axial increment continuously decreases from the smallest diameter to the largest diameter such that a radially outward curved contour results.

[0081] The actual diameter measured at a predefined stroke position in a stroke is then compared with the nominal diameter of the nominal contour profile associated with the stroke position in a comparison operation. A diameter deviation for the stroke position is determined from the result of the comparison operation. The stroke length and/or the stroke orientation of a subsequent stroke is then modified relative to a nominal stroke length and/or a nominal stroke orientation according to the nominal contour profile as a function of the diameter deviation.

[0082] A control intervention in the sense of a modification of the stroke parameters typically takes place only when the diameter deviation exceeds a predefinable limit value so as to generate control interventions only when significant diameter deviations are to be determined.

[0083] The controlling is particularly simple when a portion to be honed is chosen such that the diameter within the portion continuously changes, thus continuously decreases or increases, in one direction. In each of these cases the stroke modification for the portion can be programmed such that one of the reversal points, specifically the reversal point associated with the larger diameter, remains fixed, while the other reversal point (closer to the tight end) by way of a variable step size moves step-by-step toward the fixed reversal point.

[0084] To the extent that the axial contour profile in a bore to be honed cannot be described as a portion across the complete length of said axial contour profile in which the diameter continuously changes always in the same direction (decrease or increase) between an extreme value and another extreme value, the bore for the purpose of controlling can be divided into a plurality of portions to which said preconditions then apply again. Said plurality of portions can then be sequentially worked according to the method described. A special case is present, for example, when there are two such portions and one of the portions in terms of the diameter grows in a downward manner, and the lower portion in terms of the diameter grows in an upward manner. In this case, both reversal points at the top and at the bottom can be simultaneously shortened in a manner corresponding to the current measured results and the predefined profile curve (axial nominal contour profile).

[0085] A honing operation by way of which a bore having a purely conical contour profile has been generated in the context of an experiment will now be explained by means of FIG. 4 and by means of a specific example. In the case of the honing operation documented here, the desired axial contour profile was generated so as to proceed from a circular-cylindrical bore shape which previously was generated by long-stroke honing using relatively long honing strips, for example.

[0086] In the case of the experiments, various process parameters that are relevant here were detected with the aid of a system for diagnosing machine parameters and the results evaluated. FIG. 4 in an exemplary manner shows a diagram resulting therefrom, in which the honing time t.sub.H (in seconds) of the honing operation is illustrated on the x-axis, and various parameters as a function thereof are illustrated so as to be plotted conjointly on the y-axis. [0087] Curve HP represents the stroke position of the honing tool, thus the position in the axial direction. The strokes run in each case between a lower reversal point UU and an upper reversal point UO; [0088] Curve AP represents the flare position AP being modified by the radial actuation of the cutting material members; [0089] Curve DM-I represents the diameter measurement values of the in-process diameter measurement; [0090] Curve DM-S represents the nominal diameters, thus those diameter values which in the nominal contour profile are present at the corresponding stroke position, or at the corresponding honing time, respectively; [0091] Curve OFF represents the correction of the stroke increment resulting from the diameter comparison, thus a value which is added to a stroke increment predefined so as to be based on the nominal contour profile, or is subtracted from said stroke increment. The control interventions are particularly readily seen by way of the irregular profile of this curve.

[0092] In the honing operation shown, the rotating speed of the honing spindle in an initial phase was increased to a nominal value and then remained substantially constant during the entire honing operation. The reciprocating controller was set such that the stroke length (axial spacing between the upper and the lower reversal point) in an initial first honing phase PH1 was so large that the honing tool with the aid of the annular cutting group machines the entire bore length between the bore entry and the bore exit by means of a few complete double strokes. The axial positions of the upper reversal point UO and of the lower reversal point UU herein remained constant across a plurality of double strokes.

[0093] The subsequent second honing phase PH1 here is referred to as the stroke modification phase since the stroke orientation of the honing tool and/or the stroke length are modified, or can be modified, respectively, from one stroke to another stroke in said second honing phase. The term stroke orientation herein refers to the region between the upper reversal point UO of a reciprocating movement (close to the bore entry) and the lower reversal point UU of the reciprocating movement closer to the end of the bore that is remote from the entry, in each case in relation to a fixed machine coordinate system. Each axial relocation of the position of a reversal point thus also changes the stroke orientation. In the exemplary case of FIG. 4 the axial position of the lower reversal point UU was kept constant across the complete second honing phase PH2, while the axial position of the upper reversal point UO was variably controlled by the control installation 190 as a function of the diameter measurement signal (DM-I).

[0094] The general trend in terms of the temporal profile of the upper reversal point herein is such that the axial position thereof across the honing time in a step-by-step manner approximates the lower reversal points such that the stroke length was reduced in a step-by-step manner from one stroke to another stroke. In this way, the portion of the bore that is more remote from the entry is machined by way of more strokes than the portion closer to the entry such that a plurality of overlapping honing actions take place in the portion that is more remote from the entry and thus more material is subtracted there than in the region closer to the entry.

[0095] A particularity of the method now lies in that the extent of the stroke shortening between successive strokes, or in more general terms: the absolute size of the stroke increment, respectively, is not fixedly predefined but can vary as a function of the results of the in-process diameter measurement.

[0096] Those diameter measurement values in the course of a stroke which were detected when the honing tool was situated at the upper reversal point UO or close thereto were in each case selected for the diameter measurement. Under these conditions, the diameter measurement value utilized for controlling is detected in a phase of a very low axial velocity of the honing tool such that the measuring sensors (air measuring sensors) are situated substantially in the same axial portion, or in an axially narrow measurement zone of the bore, respectively, over a comparatively long period, and the diameter present therein can thus be determined with high accuracy (possibly by way of forming a mean value). The axial extent of the measurement zone can be, for example, 10 mm or less, and in particular be in the range from 3 mm to 8 mm.

[0097] From the profile of the flaring position AP it can be seen that constant flaring, that is to say a constant actuation rate, was used in this exemplary embodiment such that of all of the process variables illustrated only the axial position of the upper reversal point varied as a function of the diameter measurement.

[0098] The honing operation is terminated when the diameter measurement indicates that the targeted contour profile has been reached within the tolerances. The switching-off thus takes place as a function of the in-process measurement.

[0099] In order for the control procedures to be better visualized, fragments of the diagram of FIG. 4 across a few double strokes are shown in a somewhat different illustration in FIGS. 5 and 6.

[0100] It can be particularly readily seen in the diagram of FIG. 5 that the correction value resulting from the diameter comparison for the stroke increment (curve OFF) from one upper reversal point UO to the next (directly following) upper reversal point can assume significantly different values. The first correction value I1 on the double stroke shown at the left is of approximately double the size of the correction value I2 of the directly following, central, double stroke, while the following third correction value I3 has an absolute value which lies between the absolute values of the two preceding correction values. On account thereof it becomes obvious that the actually implemented stroke increments which in the exemplary case lead to a stroke shortening (relocation of the upper reversal point in the direction of the lower reversal point) can vary from one double stroke to another double stroke as a function of the diameter measurement. The stepped curve which connects the upper reversal points of successive double strokes visualizes the resulting stroke relocation, thus the shortening of the stroke length from one stroke to another stroke. The absolute value of this relocation is derived by forming the sum of the absolute value of the stroke relocation which is derived from the calculation based on the nominal contour profile, and the correction value, thus the value of the curve OFF (offset value) shown thereabove.

[0101] In addition to the two curves mentioned above in another region of the stroke modification phase, the nominal value of the diameter measurement (DM-S) as well as the diameter actual value (DM-I), thus the result of the current diameter measurement, are illustrated in the region of the respective upper reversal point of the reciprocating movement in FIG. 6. The comparison of the two upper curves DM-S and DM-I clearly visualizes that the nominal value DM-S should increase from one stroke to another stroke by the same amount so as to correspond to the linear profile of the oblique contour of the cone. This corresponds to the linear profile of the contour of a cone which in terms of parameters can be expressed, for example, by a linear equation. By contrast, the curve of the actual diameter values DM-I illustrated therebelow has steps of dissimilar heights. This proves that there are differences between the nominal contour and the measured actual contour that are locally dissimilar in size. The curve OFF represents the correction values resulting from a comparison operation of the diameter values, said correction values leading to a corrective intervention in the honing process in the course of controlling taking place in a manner that the desired contour profile results in an ideally precise manner. It can also be seen herein by way of the curve OFF that the correction values which are added to a nominal value of the stroke relocation can assume positive as well as negative values such that the absolute variables of the stroke increments between successive strokes can be both smaller as well as larger than the stroke increments to be expected in the case of an ideal contour profile.

[0102] This finely tuned controlling of the stroke lengths during the stroke modification phase leads to an axial contour profile which corresponded to the nominal contour profile with high accuracy (within a range of a few micrometers) across the entire bore length.

[0103] There are a plurality of possibilities in terms of the implementation of the concept of controlling. The variant described in more detail here provides a fixed predefining of nominal stroke shortenings (corresponding to the nominal contour profile) and a correction for determining the stroke shortenings actually implemented or set, respectively, in the process by way of the offset or the correction value, respectively, according to the current measured results. A calculation of the stroke shortening according to the removal, and predefining the contour without a nominal stroke shortening, is also possible, for example.