WO2012065949A1

WO2012065949A1 - Method and device for finish machining curved workpiece surfaces on workpieces by means of a finish belt

Info

Publication number: WO2012065949A1
Application number: PCT/EP2011/070056
Authority: WO
Inventors: Phillip Utsch
Original assignee: Nagel Maschinen- Und Werkzeugfabrik Gmbh
Priority date: 2010-11-17
Filing date: 2011-11-14
Publication date: 2012-05-24
Also published as: CN103402703A; HUP1300374A2; DE102010052311A1; HU229618B1

Abstract

The invention relates to a method for finish machining curved workpiece surface on workpieces, wherein an endless finish belt provided with a cutting means is used, wherein said belt runs between a first belt roller and a second belt roller. One end of the finish belt is attached to one belt roller, and the other end to the other belt roller. The finish belt is pressed against the workpiece surface of the workpiece at an engagement area and the workpiece is rotated about a workpiece axis. The finish belt is first displaced by a first feed length in the direction of the first belt roller during a first motion phase at a first feed rate suitable for removing material, and after reversing the direction of motion is displaced by a second feed length in the direction of the second belt roller during a second motion phase at a second feed rate suitable for removing material. Material removal can take place in both feed directions at a high cutting speed.

Description

description

Method and device for finishing curved workpiece surfaces on workpieces by means of finishing tape

TECHNICAL AREA

The invention relates to a method for finishing curved workpiece surfaces on workpieces according to the preamble of claim 1 and to a device for finishing curved workpiece surfaces on workpieces according to the preamble of claim 11. Furthermore, the invention relates to a finishing unit according to the preamble of claim 15.

STATE OF THE ART

Finishing, which is also referred to as superfinishing, is a machining process with indefinite cutting edges. By finishing work surfaces of rotationally symmetric or non-rotationally symmetrical workpiece sections on workpieces such as crankshafts, camshafts, transmission shafts or other components for power and working machines can be edited to produce a desired surface fine structure. When finishing, a machining tool (finishing stone or finishing tape) set with granular cutting material is pressed against the peripheral surface to be machined. To produce the cutting speed required for the material removal, the workpiece is rotated about its workpiece axis. In some process variants of finishing, a relative movement between the workpiece and the machining tool resting against the peripheral surface is simultaneously generated parallel to the workpiece axis. Due to the combination of rotation - Movement of the workpiece and the superimposed oscillatory motion, a so-called cross-cut pattern can be generated, whereby the machined workpiece surfaces, for example, as running surfaces for plain bearings or bearings or the like are particularly suitable. The workpiece section to be machined may be, for example, a main bearing or a crank bearing of a crankshaft or a camshaft bearing. Even rotationally asymmetric workpiece surfaces, such as the outer surfaces of cams, can be machined by means of finishing. Finishing procedures without oscillating relative movement are also possible.

In contrast to grinding, finishing is a thermally neutral processing method in which no soft skin interspersed with microcracks or surface tensions arises. Finishing is often used after a grinding process as the last machining process of a processing chain to remove the soft skin, to expose the original microstructure again, to increase the carrying portion of the roughened surface structure and to improve the component geometry. In contrast to lapping, bonded grain processing tools are used so that washing operations and facilities for the disposal of lapping slurry can be eliminated.

During strip finishing, a finishing belt is used as a processing tool. A finishing belt has a band-shaped flexible carrier in which cutting grains are applied on the front side facing the workpiece with the aid of a binder. One class of tape finishing method involves the use of a finite (non-continuous) finishing tape, the tape ends of which are each secured to a tape roll. The fresh, still unused finishing belt is held on a supply roll and guided by means of tape guide devices over the engagement area on the workpiece to a driven tape roll, which receives the used finishing tape. The tape feed is over - Achieved a drive of this tape roll, which pulls the tape through the entrance area. The reel with the fresh finishing belt acts as a band brake and maintains the belt tension. In some variants of this class of belt finishing process, the finishing belt rests during processing, so that the cutting speed is generated exclusively by the rotational movement of the workpiece and possibly also by the superimposed axial oscillating relative movement between the workpiece and finishing belt. At regular or irregular time intervals, a used finishing belt section is replaced with a fresh finishing belt section by advancing the finishing belt by a predetermined belt advance distance in a processing break with unloaded finishing belt. There are also process variants with a slow tape feed during the machining operation, in order to achieve that as uniform as possible engagement conditions prevail with each fresh cutting grain. In any case, by the continuous or discontinuous supply of fresh, unused finishing tape sections, even with large series of workpieces, well reproducible machining results can be achieved. Devices and methods for carrying out these variants of strip finishing are disclosed, for example, in WO 2009/049868 A1 or DE 199 25 077 A1.

For certain component geometries, these conventional banding methods are limited in their performance. If, for example, cylindrical components with relatively small diameters are machined or components with circumferentially varying radius (eg cams of a camshaft), the contribution of workpiece rotation to the cutting speed is limited, because in the first case, even at high speeds, only relatively low circumferential speeds can be achieved and second case, the workpiece speed must be kept relatively low in order to ensure sufficiently constant engagement conditions. - - Afford. These limitations can only be partially compensated by a superposed oscillation or by increasing the oscillation speed and / or longer finishing times, so that a compromise between sufficient surface quality and effectiveness of the processing process must be found.

In another class of methods for finishing workpiece surfaces on workpieces, the workpiece is also rotated about its axis of rotation. Similar to a belt sander, a continuously driven, endless finishing belt is used which partially wraps around a workpiece surface (peripheral surface) of the workpiece to be machined during machining and rests flat against the workpiece in a region predetermined by the wrap angle. Examples of such methods are given in EP 1 514 640 B1 or EP 1 514 643 B1. This process is known in the art as "CAB process", where the abbreviation CAB stands for "Continuous Abrasive Belt". The finishing belt running over pulleys should be able to adapt flexibly to the geometry of the rotating workpiece and ensure high surface quality. As a rule, circumferential machining marks are generated.

By using a continuous endless finishing belt, a high belt advance speed can be achieved so that a reduced peripheral speed of the machined workpiece surface, which may be due to the workpiece geometry, can be compensated. At the same time can be achieved by the surface contact a high removal rate. However, with the use of endless circumferential finishing tapes, the conditions of engagement are not constant in principle, since the rotating finishing belt can wear out with increasing processing time and / or become clogged with abrasion. The varying engagement conditions can lead to a steadily increasing - - Reducing material removal and, depending on the pre-processing, possibly lead to a deterioration of the process result.

TASK AND SOLUTION

The invention has for its object to provide a method for finishing curved workpiece surfaces on workpieces, a suitable for performing the method finishing equipment and a Finisheinheit thereby used, with which nen finishing machining in a variety of workpieces of different geometry with high productivity and simultaneously largely constant high processing quality is possible. To achieve this object, the invention provides a method with the features of claim 1 and a device with the features of claim 1 1 ready. Furthermore, a finisher unit with the features of claim 15 is provided. Advantageous developments are specified in the dependent claims. The content of all claims is incorporated herein by reference.

In the method, the tape feed of the finishing belt contributes significantly to the decisive for the chip removal cutting speed on the machined workpiece surface. As a result, if necessary, high removal rates are possible even if the workpiece, for example, can only be rotated relatively slowly due to its geometry and / or if only relatively low peripheral speeds can be realized even with relatively large workpiece speeds due to a relatively small diameter of a workpiece section to be machined. At the same time, the use of finite finishing tapes with large overall length can ensure that too - When finishing large workpiece series always finishing belt with relatively uniform Schneidfreudigkeit or uniform cutting behavior is available, so that a largely constant quality machining is possible. A wear-related replacement of finishing tapes is therefore much less necessary than when using endless finishing tapes, which machine downtime can be reduced and the productivity of finish machining can be improved. Furthermore, a finishing tape can be used in two opposite directions for material removal. As a result, wear-related quality losses can be reduced.

In a further development, the finishing belt is moved during the processing of a single workpiece surface at least once in the direction of the first roll of tape and after a reversal of the direction of movement in the direction of the second roll of tape. The finite finishing tape is thus used here once or several times in opposite directions for the removal of material when machining a single workpiece surface. As a result, the tape consumption per machined workpiece surface can be reduced. Under certain circumstances, this reversing operation can lead to better machining results, even with special workpiece geometries. For example, in the case of cam surfaces which are finished only in one machining direction, so-called shadow effects may occur if the local radius decreases during a circumferential section during the workpiece rotation and, as a result, the pressing force of the finishing belt becomes uneven. If such peripheral portions are also processed with opposite tape feed, the uniformity of the processing result can be improved over the circumference. In principle, however, it is also possible that a complete workpiece surface or several successively machined workpiece surfaces only with a direction of movement of the finishing belt - - be machined and that then after a reversal of direction one or more then machined other workpiece surfaces are processed with the opposite direction of movement. In general, the direction of rotation of the workpiece is reversed in the reversal of the direction of movement of the finishing belt, so that a machined workpiece surface can always move in opposite directions to the feed direction of the finishing belt. As a result, particularly high cutting speeds can be achieved, whereby the cycle times can be shortened.

A variant of the method is characterized in that the finishing belt cyclically first moves during the first movement phase by a first feed length in the direction of the first tape roll during processing of a workpiece surface and after reversing the direction of movement during a second movement phase by a second feed length in the direction of second tape roll is moved, wherein the second feed length is greater than the first feed length by a defined feed length difference. This special process kinematics is also referred to below as the "pilgrim step method".

The term "cyclic" in this context means that the machining of the workpiece surface is carried out in one or more movement cycles, wherein a movement cycle contains movement phases in both possible directions of advance, in that the second feed length is greater than the defined feed length difference First feed length, it can be achieved that at the beginning of a subsequent cycle of motion is always a schneidfreudiger tape section is available .Thus largely continuous engagement conditions for the finish machining can be ensured, so that even at very high quantities - - Without tape exchange over long processing times a very high quality processing can be ensured.

During the second movement phase, the finishing belt is preferably brought out of engagement with the workpiece after reaching the initial belt position before the first movement phase in such a way that the finishing belt does not undergo material-removing engagement with the workpiece during the feed by the feed length difference. At the beginning of the immediately following movement phase is then each a fresh, previously unused finishing tape section available.

It is possible that during the processing of a single workpiece surface several motion cycles with opposite directions of movement and intermediate movement direction reversal are passed through. In some variants of the method, the feed lengths and the feed speeds in the two opposite directions of movement are matched to a desired removal on the workpiece surface such that the workpiece surface is processed during the duration of a single movement cycle. The complete processing stage for the workpiece surface then has only one movement cycle. As a result, the movement phase of the fresh-tape feed can be synchronized with the workpiece change at the end of the second movement phase of a movement cycle, whereby the cycle times per processed workpiece surface can be kept short.

In some variants of the method, for example, in the first movement phase and the second movement phase, the finishing belt is moved with a feed rate that is substantially uniform (outside of unavoidable acceleration phases) in order to arrive at - - uniform component rotation to achieve a uniform cutting speed.

It is possible to perform a pure control (open loop control) of the feed rate according to a predetermined control program. Preferably, a regulation of the feed rate (feedback control) during finish machining is carried out by means of a control device. As a result, the feed rates or their possibly desired changes during the phases of movement and times for a reversal of the direction of movement under changing process conditions must be set and maintained particularly accurately. It is possible to specify any motion profiles which, if necessary, can have phases with a constant feed rate and / or phases with a defined varying feed rate.

As part of the scheme, various measured variables can be detected individually or in combination and fed back to the control device for the purpose of controlling the motion profiles. By way of example, a measurement of the drive torque of a first roller drive and / or a second roller drive can be carried out with the aid of suitable sensors. With the help of sensors for winding diameter determination, a measurement of the tape winding diameter at the first tape roll and / or on the second tape roll can be performed. With the aid of a rotational speed measuring system, a measurement of the angular velocity of a rotation of the first belt roll and / or the second belt roll can be carried out. It is also possible to provide a direct measurement of the tape feed speed, eg with a mechanical measuring device (eg with a measuring wheel which rolls on the finishing belt) or with an optical measuring device, which may have a laser, for example. - -

The required for the process variants movements of the finishing belt can be constructively produced in different ways. A variant of the method is characterized in that in the first movement phase, the first tape roll is driven by a first roller drive and pulls finishing tape from the second tape roll and the second tape roll by means of a second roller drive generates a braking torque to produce a belt tension. In the opposite movement in the second phase of movement then the roles of the tape rolls are reversed. The tape feed is thus achieved by driving the tape rolls. As a result, it is possible to dispense with separate drives or brakes from the roller drives. It is also possible to provide a tape feeding device separate from the tape rolls, which has for example in front of and behind the engaging region counter-rotating pairs of driving rollers each defining a gap through which the finishing belt to be conveyed is passed.

Within the scope of the method, it is possible to work without an oscillating relative movement between the workpiece and the finishing strip that is parallel to the workpiece axis. In this case, rotating machining tracks can be generated on the machined workpiece surface. This may be desirable, for example, when a machined workpiece surface is intended to be used as a sealing surface in intended use in cooperation with a mating surface. In other variants of the method, a relative movement oscillating parallel to the workpiece axis is generated between the workpiece and the finishing belt. As a result, textures can be broken on the machined workpiece surface, if necessary, which can be improved for certain applications, the surface structure in terms of the desired function when used as intended. For example, on a workpiece surface, a surface structure with crossed machining - - Traces (cross-grinding) are generated, which can be particularly advantageous in tribologically stressed storage areas.

The invention also relates to a device for finish machining of curved workpiece surfaces on workpieces by means of a finite finishing belt coated with cutting means. The device has a rotating device for generating a rotational movement of the workpiece about a workpiece axis and at least one finishing unit, a first tape roll for receiving a first end portion of a finishing tape, a second tape roll for receiving a first end portion opposite the second end portion of the finishing tape and a pressure device for pressing the finishing tape to a workpiece surface to be machined. The device has a first roller drive coupled to the first belt reel for reversibly rotating the first belt reel, a second reel drive coupled to the second belt reel for reversibly rotating the second reel and a control device for coordinated activation of the first and second reel drives. With the aid of this device, it is possible to carry out all of the method variants of strip finishing described above and below. For this purpose, the device for carrying out these variants can be configured by means of suitable settings or programming of the control device. If necessary, however, conventional belt finishing methods can also be carried out with the aid of the device. For example, the device may be programmed so that the roller drives during the processing of a workpiece surface do not drive the tape rolls, so that the finishing tape rests during processing. By activating the roller drives, the finishing belt can then be advanced during processing breaks for the supply of fresh belt. It is also possible to create a long - - To produce seed tape feed, which makes virtually no contribution to the effective cutting speed on the workpiece.

The invention also relates to a finishing unit which can be used in this device or in other devices. The finishing unit has a first tape roll for receiving a first end portion of a finishing tape, a second tape roll for receiving a second end portion of the finishing tape opposite the first end portion, and a pressing means for pressing the finishing tape against a workpiece surface to be processed. Furthermore, the finisher unit has a first roller drive coupled to the first belt reel for reversibly rotating the first belt reel and a second reel drive coupled to the second belt reel that can be controlled separately from the first roller drive for reversibly rotating the second belt reel. The roller drives can be connected or connected to a control device for coordinated activation of the first and the second roller drive. This control device can be integrated into the finisher unit. It is also possible that the finisher unit does not have its own control device, but is set up, for example, by means of suitable interfaces (eg connection sockets, plugs, etc.) for interacting with an external control unit, for example the control unit of a processing machine. The first and the second roll of tape as well as elements of the first and the second roller drive and the pressure device can be arranged on a common carrier element, so that they can be exchanged and replaced in the manner of a belt module. Such a finisher unit can have a fastening device for fastening the finisher unit to a processing machine, which in turn has a workpiece holding device and a rotary drive for workpiece rotation. For example, the finishing unit may be constructed so that it can be mounted on a lathe. In this way, the lathe can be converted to a belt finishing machine. - -

These and other features are apparent from the claims and from the description and the drawings, the individual features each alone or more in the form of sub-combinations in an embodiment of the invention and in other fields be realized and advantageous and for can represent protectable designs. Embodiments of the invention are illustrated in the drawings and are explained in more detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows an embodiment of a belt finishing machine with a plurality of finishing units;

Fig. 2 shows a plan view of an embodiment of a Finisheinheit with two separately and each driven in two directions of rotation tape rolls; Fig. 3 shows a side view of the finisher unit of Fig. 2;

Fig. 4 shows a schematic representation of a Finisheinheit with means for controlling the movements of the tape rolls; 5 shows a schematic diagram for explaining the time course of the tape feed in a variant of a pilgrim step method;

6 shows a schematic diagram for illustrating the cutting ability of the finishing strip, which varies stepwise along a finishing belt; - -

Fig. 7 shows an embodiment of a pressure device with a pressure roller; and

Fig. 8 shows an embodiment of a pressure device with two band deflection rollers.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS The diagrammatic oblique perspective view in FIG. 1 shows an embodiment of a device 100 hereinafter referred to as a strip finishing machine 100 for finishing curved workpiece surfaces of workpiece sections on workpieces by means of abrasive, flexible finishing tapes. The band finishing machine is set up in the example for a simultaneous finish machining of a plurality of axially adjacent cylindrical and non-cylindrical peripheral surfaces of a workpiece 110 in the form of a camshaft. Workpiece surfaces on other wave-shaped workpieces, for example on crankshafts, can also be machined with such a belt finishing machine.

The workpiece 1 10 is clamped with a horizontal workpiece axis 1 12 in a workpiece holding device, whose elements are arranged on the top of the machine inenbetts 102 of the belt finishing machine. The workpiece holding device comprises a rotating device 122 with a horizontally oriented workpiece spindle, which has at its end a clamping device for clamping one end of the workpiece. The opposite end of the workpiece is held by the tip of a tail stock 124. The rotating device is designed for a reversing operation, so that the workpiece can be rotated in two opposite directions of rotation with infinitely adjustable speed. - -

Furthermore, an optionally switchable oscillation device is provided, with which the workpiece can be displaced as needed in an axially short-stroke oscillating movement with strokes in the order of a few millimeters. For this purpose, the oscillator has a drive independent of the workpiece rotation, which, e.g. may contain a pneumatic or electromechanical vibrator.

Alternatively or additionally, an optionally switchable oscillation device can be provided, which can set a finisher unit or a part of a finishing unit in an oscillation running parallel to the workpiece axis, so that a relative oscillation contributing to the cutting speed results between the finishing belt and the workpiece surface.

The belt finishing device has a plurality (seven in the example in the example) juxtaposed finishing units 150, which are arranged in series above the workpiece holding device and the workpiece clamped therein. FIGS. 2 to 6 show schematically details of the finishing units. The finishing units are secured to two vertically spaced, horizontal support rods 104A, 104B, the ends of which are attached to vertical uprights 106A, 106B mounted on the machine bed 102. The axial positions of the interchangeable finishing units on the handrails are infinitely adjustable to adapt to different workpiece geometries.

As can be seen particularly well in the side view of FIG. 3, the finishing units 150 are each very narrow, so that it is possible to machine all the peripheral surfaces of the camshaft to be machined at the same time by the finishing units threaded onto the support rods 104A, 104B, both the Rotationsunsymmetrischen cams, and the rotationally symmetric cam bearing surfaces. - -

Each of the finishing units is arranged to use a finite (i.e., non-continuous) finishing tape 15. The finite length of the finishing belt is normally several meters, for example more than 10 meters or more than 50 meters. The length can be 100 m to 150 m or more, for many applications belt lengths up to 300 m are sufficient. The bandwidth can be on the order of one or a few centimeters, possibly even less. In general, the bandwidth is in the range of 2 mm to 150 mm, in particular in the range of 4 mm to 100 mm.

A finisher unit 150 has a flat, substantially plate-shaped and vertically mounted support element 152 made of steel, which has in the reinforced center section two overlying through-holes 154A, 154B for passing through the support bars 104A, 104B. As a result, a simple assembly at any axial positions and a simple replacement of the finishing units on the belt finishing machine is possible. At the visible in Fig. 2 front of the support member two tape rollers 155- 1, 155-2 are rotatably mounted with parallel axes of rotation. A first tape roll 155-1 serves to receive a first end portion of the finishing tape. The first end portion may be attached to the roll core or fixed non-slip by firm winding. The second end portion opposite to the tape direction is wound on the roll core of a second tape roll 155-2 so that the finishing tape passes between the first tape roll and the second tape roll.

Elements of a pressure device 160 are mounted on the carrier element 152 in the middle between the belt rollers and underneath the through-holes 154A, 154B. The pressure device is used for pressing the finishing tape to a peripheral surface of the workpiece to be machined such that the occupied with bonded cutting grains front - -

1 16 of the finishing belt can finish the peripheral surface under a defined contact pressure or with a defined surface pressure. In the example of FIG. 2, the pressure device 160 has a single pressure roller 162, which is rotatably mounted on the carrier element 152 and can be displaced vertically to a limited extent against the force of a spring device. During the processing, the finishing belt runs between the pressure roller and the peripheral surface of the workpiece to be machined, with a more or less narrow, substantially linear engagement region for the material removal between the abrasive front side of the finishing belt and the workpiece outer surface.

The tape rolls 155-1, 155-2 can be driven separately in each case in two directions of rotation. For this purpose, a first roller drive 158-1 is provided for reversibly rotating the first belt roller 155-1 and a second roller drive 158-2 for reversibly rotating the second belt roller 155-2. The mutually movable parts of the electric drives (stator and rotor) are each housed within the roll core of the respective roll of tape. In some embodiments, servomotors with particularly high torque (torque motors) are used as roller drives.

The roller drives are connected via electrical lines to the control device 180 of the band finishing machine (FIG. 4). As a result, a coordinated control of the first and the second roller drive is possible. Each of the belt rollers 155-1, 155-2 is assigned its own measuring device M1 or M2 for determining the current torque of the roller drive. In the exemplary embodiment, in addition to the roller drive to each of the tape rolls also includes a Drehzahlmesssys- system with sensors W1 and W2 to determine the current angular velocity or speed of the respective roll of tape and a sensor D1 or D2 for measuring the diameter of each on the core - - The tape roll wound tape roll. These measuring devices and the control device 180 belong to a control device, which allows control of the feed rate during finish machining.

Since the first and the second roll of tape and, with the exception of the electrical leads, all elements of the first and second roller drives, including the sensors and also the mechanical elements of the pressure device are attached to the common carrier element 152, the finisher unit forms a relatively easily replaceable belt module. By exchanging differently configured band modules and / or by combining similar and / or different band modules, the band finishing machine can be adapted very flexibly to different workpiece types and workpiece geometries.

A possible mode of operation of such a finisher unit will be explained with reference to FIG. 4. For processing, one of the tape rolls can specify a desired speed for the machining, so that the finishing tape is moved in the direction of this tape roll with a feed rate suitable for substantial material removal, where it is rolled up or wound up there. This tape roll may also be referred to as a pull roll or drive roll. The other reel simultaneously tensions the finishing belt by producing a defined braking torque. This tape roll can also be referred to as a brake roller.

In the movement phase represented by the arrows running in the direction of rotation of the tape rolls, the first tape roll 155-1 serves as a pull roll, by the roller drive 158-1 of which a continuous tape feed in the direction of the first tape roll is produced. The second strip roll 158-2 or its roller drive generates the counter-moment or braking torque. - Ment in such a way that the desired finish band tension is maintained. The dashed line represents the finishing belt before the start of the winding on the first roll of tape, the solid line the course of the finishing belt after complete winding on the first roll of tape. In this movement phase, the tape feed takes place from right to left, ie from the second tape roll in the direction of the first tape roll.

Both roller drives are designed for a Reversierbetrieb, so that a corresponding belt movement in the opposite direction is possible. In this reversing operation, the second belt roller 155-2 shown on the right then serves as a tension roller which predefines a defined speed and thus a defined feed speed in the reverse direction, while the first belt roller 155-1 shown on the left serves as a brake roller for generating the belt tension. Since the tape rolls and the associated sensors and control can be constructed essentially identical, tape feeds with high feed speeds are equally possible in both directions. For typical finish processes that can be performed with this finishing unit, the maximum feed rates may be on the order of at least 0.5 m / s, for example in the range of 0.5 m / s to 4 m / s. Frequently, maximum feed rates in the range of 1 m / s to 2 m / s are advantageous. The higher the feed speed, the greater the proportion of the cutting speed resulting from the tape feed. In the embodiment, the feed rates are infinitely adjustable, which can be used if necessary, with higher feed rates up to, for example, 3 m / s or even 4 m / s.

With the help of the sensors for the winding diameter determination and a simultaneous active speed measurement, a belt speed - - possible. For example, the tape speed (feeding speed) can be kept substantially constant throughout a winding operation by gradually reducing the number of revolutions of the tape roll used as a drawing roll as the diameter of the tape roll on the drawing roll gradually increases. The measurement of the drive torque, that is, the torque on the tape roll serving as a tension roller, can be used, for example, to detect the end of the tape, ie the moment from which no further tape should or can be unwound from the trailing brake roller. When reaching the end of the tape, for example, a reversal of the direction of pull roller and brake roller can be automatically effected. The detection of the output torque, ie the torque applied to the brake roller, can be used, for example, to maintain a belt tension in order to prevent the finishing belt from becoming loose. The driven-side tape roll diameter (tape roll diameter at the serving as a brake roller tape roll) can be used for tape consumption level control. The drive-side angular velocity or rotational speed, that is to say the angular velocity or rotational speed of the tension roller, can be processed for the belt feed control. The output side angular velocity or speed can also be used in the context of tape feed control and possibly also for tape breakage control.

5 and 6, a process control for finishing processing in which a finishing belt feed is produced in what is referred to as the "pilgrim step." This process variant is therefore also referred to in this application as "pilgrim step process". In the schematic diagram of Fig. 5, the abscissa represents the processing time t and the ordinate the finishing tape feed VS. The finish belt advance is represented by the zigzag line where the top-to-bottom sections have a tape feed in the forward direction (arrow "V") and in time In the case of the upward-pointing line segments, a tape feed in the opposite reverse direction (arrow "R"), ie reversing operation, is represented by the slope triangle shown in dashed lines, the tape feed speed VB, the absolute value of which in the forward direction and in the example The oblique arrow VSM represents the time-averaged tape feed.

In the schematic diagram of Fig. 6, the abscissa represents the parameter FBZ describing the finishing tape within one cycle of motion. The ordinate corresponds to the parameter KTZ, which describes the contact time over which a corresponding finishing band section has already been in a machining contact with a workpiece surface. Tape wear is also sometimes quantified with the parameter "Coverage Level", which represents the number of already existing cutting overflows of a strip section The pictorial symbols make it clear that at relatively low contact times there is still a relatively fresh cutting-ready finishing belt, while with increasing contact time the finishing belt tends to become more clogged and eventually wears out, so that the ease of cutting decreases The abrasive machining of a circumferential surface, for example a bearing point of a crankshaft or on the circumferential surface of a cam, begins at the time t1 and ends at the time t3 a high feed rate in the opposite direction to the component rotation in the forward direction V moves. This forward direction runs in the example in the direction of the first roll of tape, which serves as a pull roll, but also the umgege- - - reversed variant (second tape roll as a pull roll) is possible. After about half of the processing time, in the example at time t2, the component rotation and the tape feed are reversed (reversal of direction of rotation). Thereafter, therefore, in the example, the second tape roll serves as a tension roller and the first tape roll maintains the tape tension. Both in the first movement phase in forward operation between the times t1 and t2 and in the second movement phase during the reversed operation between the times t2 and t3, the feed rate of the finishing belt is in each case so large that the tape feed makes a substantial contribution to the material removal. The feed rate may be, for example, in the order of 0.5 m / s to 2 m / s. As a result, if necessary, a significant proportion of the cutting speed is achieved by the tape feed in comparison to the component rotation.

The tape feed ratio of feed to return, ie the ratio of the first feed length in the direction of the first tape roll and the second feed length in the direction of the second tape roll, is preferably adjusted so that at the beginning of processing, ie at the beginning of processing a new peripheral surface, always fresh grain or A previously unused section of tape is available. This is realized in that the finishing strip is disengaged from the workpiece immediately after processing (at time t3) and that the finishing strip is then advanced by a defined band length amount until time t4. It is therefore nachgefördert before the start of processing on the next workpiece WS2, which is at time t4, a defined piece of fresh tape. This strip length corresponds to the strip consumption of the strip finishing device per cycle and results from the fact that the feed length conveyed during the second movement phase is greater by a defined feed length difference than that in the first movement phase (between - - t1 and t2) used first feed length. The feed length difference AVS in this case corresponds to the tape consumption per cycle.

In the example case, the total time between the start of the processing of a peripheral surface at the time t1 to the end of the second movement phase (feed in the reversing direction) of the processing of this peripheral surface at the time t4 is referred to as a "movement cycle." The first movement cycle Z1 is the processing of the associated with the first workpiece section WS1.

Subsequently machined peripheral sections are machined in corresponding motion cycles. For example, a subsequently machined second workpiece section WS2 is processed in a second processing cycle Z2, which immediately follows the first movement cycle. At the beginning of the second cycle of movement (at time t4), the processing begins again with a fresh, unused section of tape, since in the previous first cycle Z1 in the final phase (between times t3 and t4) a fresh piece of tape was nachgefördert. When viewed in the band direction, this band section is adjoined by an adjacent band section, which was already used during the processing of the preceding workpiece section. This is followed by a band section which has already been used in the machining of two preceding workpiece sections and so on. The machining time already provided by a finishing belt section, which is represented in FIG. 6 by the contact time KTZ and which can alternatively also be described by the parameter covering degree, starts from the beginning of a movement cycle until the belt reversal point, ie until the feed direction is reversed the time too. As shown in Fig. 6, this increase in jumps, wherein the plateau length of the respective stages (with step height ΔΚΤΖ) the predefined amount of freshly tracked finishing tape per processing, ie the tape consumption of - -

Bandfinishvorrichtung per cycle or the feed length difference AVS corresponds. In reversing mode (opposite feed direction), the contact time is reduced again step by step. Within a cycle of movement, the finishing belt engaging the workpiece thus successively passes discrete levels of consumption, wherein in the first phase of motion, the finishing belt from the beginning to the tape reversal in its Schneidfreudigkeit increasingly decreases because of increasing contact time, while it increases successively after cutting reversal movement direction in the second movement phase on Schneidfreudigkeit , The discrete consumption levels can be adjusted with the help of suitable programming of the control with regard to step height and plateau length such that in sum the statistically comparable contact time can be mapped compared to a conventional processing without tape feed. Thus, during each cycle of motion, substantially identical engagement conditions prevail. Thus, substantially the same machining quality can be realized on all machined peripheral surfaces. The pilgrim step kinematics can thus on the one hand provide high removal rates and, on the other hand, at the same time substantially constant removal conditions. Even for problematic components, such as components with very small diameters and / or components with non-circular peripheral sections, high cutting speeds can be realized. At the same time, the finished finishing belt has the same belt state for each processing cycle in view of the overflows already made (contact time), whereby a constant quality of processing can be ensured. The high consistency of the quality of the machined peripheral surfaces, even for very large series of workpieces, represents a major technological advantage of this special process kinematics over conventional belt finishing methods. - -

The feed length difference AVS is usually only a small fraction of the total length of the finite finishing tape, for example less than 1 percent or even less than 5 parts per thousand. In this way, many movement cycles can be performed with a single finishing belt of finite length before an exchange must be made.

The strip feed progression shown schematically in FIG. 5 corresponds to the retracted operation of the strip finishing device. For retracting fresh tape, adjustment possibilities are provided on the control device in order, if necessary, to apply contact factors and / or tape feed speeds with correction factors. As a result, largely equivalent machining results can also be achieved in the run-in mode.

Thanks to the integrated sensors, numerous parameters can be regulated or detected. Thus, for example, the belt speed can be controlled by means of the return of the angular diameter in favor of a continuous tape feed speed. By monitoring the speed of the brake roller (output speed) and the torque of the tension roller (drive torque) can also be detected a band break or the band end. The pressure device can be designed differently depending on the type and geometry of a workpiece section to be machined. In the embodiment of FIG. 2, the pressure device 160 has a single pressure roller 162, by means of which the finishing belt is pressed against the peripheral surface of the workpiece section. The engaging surface which is decisive for the material removal is narrow in a linear manner. Pressure device with a pressure roller can both in the processing of rotationally symmetrical peripheral surfaces (see FIG .. 2) and - - be used when machining non-rotationally symmetric peripheral surfaces. In FIG. 7, for example, the processing of the peripheral surface of a cam 11 is shown. The non-circular peripheral surface of the cam is curved convexly everywhere in the illustrated example. With pressure rollers and rotationally asymmetric peripheral surfaces can be edited, which are curved in sections concave, in which case the radius of the pressure roller should be smaller than the smallest radius of curvature of a concave peripheral portion. In some embodiments with a pressure roller, a cam or other device is provided in the region of the pressure roller, which converts the rotational movement of the (otherwise non-driving) pressure roller caused by the movement of the finishing belt into a movement that oscillates parallel to the axis of rotation of the pressure roller. As a result, cross-cut structures can be produced on the machined circumferential surfaces without the workpiece and / or the finishing unit as a whole having to be moved in an oscillating manner. Due to the low mass of the pressure roller and the correspondingly low inertia high oscillation frequencies can be achieved if necessary.

The embodiment of a pressure device 660 shown schematically in FIG. 8 has two guide rollers 664, 666 mounted on the carrier element 652 and rotating the finishing belt between the two belt rollers in such a way that a freely stretched belt section remains between the deflection rollers, as long as the finishing belt is not is engaged with a workpiece peripheral surface. In the illustrated engagement position, the finishing belt lies flat against the workpiece outer surface over a certain circumferential angular range, so that surface contact with increased removal rate can be achieved. The pressure force can be specified via the belt tension. If necessary, an additional, mechanically acting on the band back pressure device provided in the wrap - - be. Numerous configurations of pressure devices are possible, for example, pressure devices according to International Patent Application Publication No. WO 2009/049868 A1, the relevant disclosure content of which is incorporated by reference into the content of this description.

The exemplary embodiments explained in conjunction with the figures are designed for machining curved workpiece surfaces (peripheral surfaces) on the outside. The finish band width may correspond approximately to the axial width of the peripheral surfaces to be machined (e.g., bearing surfaces, cam outer surfaces). With appropriate dimensioning and rotationally symmetric or non-rotationally symmetrical inner surfaces, ie concave workpiece surfaces can be edited. In this case, the finishing tape is then pressed against the inner surface by means of a separate pressure device, e.g. by means of a pressure roller.

Since, in the case of the finishing unit, a significant proportion of the cutting speed acting on the workpiece surface in the engagement area results from the tape feed speed, it is also possible, if necessary, to machine a workpiece resting during machining by finishing. It is also possible in principle to machine a plane surface, ie a flat workpiece surface, by means of a finishing unit with two actively reversibly drivable tape rolls. For this purpose, the Finisheinheit example, stand firmly while the workpiece by means of a cross table or the like. is linearly advanced in one or more directions and a pinch roller presses the moving at high speed finite finishing tape on the plane to be machined plane. The plan finish machining can be performed with or without relative oscillation between finishing belt and workpiece surface. - -

Regardless of whether the workpiece surfaces to be machined are convex or concave or flat, a belt finishing machine may have a single finishing unit or multiple finishing units as needed and machining task.

Claims

claims

A method of finishing curved workpiece surfaces on workpieces using a finite finish belt covered with a cutting means extending between a first tape roll and a second tape roll, the finishing tape being pressed against a workpiece surface of the workpiece in an engagement region and the workpiece being wrapped around a workpiece Workpiece axis is rotated, characterized

that the finishing belt first moves during a first movement phase with a suitable for a material removal first feed speed in the direction of the first tape roll and after a reversal of the direction of movement during a second movement phase with a suitable material removal for a second feed speed by a second feed length in the direction the second tape roll is moved.

2. The method of claim 1, wherein the finishing belt is moved during the processing of a workpiece surface at least once in the direction of the first roll of tape and is moved after a reversal of the direction of movement in the direction of the second roll of tape.

3. The method of claim 1 or 2, wherein in the reversal of the direction of movement of the finishing belt and the direction of rotation of the workpiece is reversed.

4. The method according to any one of the preceding claims, wherein the finishing belt cyclically during the processing of a workpiece surface initially moves during the first movement phase by a first feed length in the direction of the first roll of tape and after reversing the direction of movement during the second movement phase by a second feed length in Direction of the second tape roll moves is, wherein the second feed length is greater than the first feed length by a defined feed length difference.

5. The method of claim 4, wherein the finishing belt is brought out of engagement with the workpiece during the second movement phase after reaching the present before the first movement phase output tape position such that the finishing belt at a feed to the feed length difference not in a material-removing engagement with the workpiece is.

6. The method according to any one of the preceding claims, wherein the feed lengths and feed rates in the first and second movement phase are tuned to a desired removal on the workpiece surface such that the workpiece surface is processed with a single processing cycle.

7. The method according to any one of the preceding claims, wherein an oscillating relative to the workpiece axis relative movement between the workpiece and finishing belt is generated.

8. The method according to any one of the preceding claims, wherein in the first movement phase, the first tape roll is driven by a first roller drive and finishing belt pulls from the second tape roll and the second tape roll by means of a second roller drive generates a braking torque for generating a belt tension and in the second phase of movement the second tape roll is driven by the second reel drive and pulls finishing tape from the first reel and the first reel produces a braking torque to produce a tape tension by means of the first reel drive.

A method according to any one of the preceding claims, wherein a feed rate control during finish machining is carried out, wherein preferably for the control at least one of the following measurements is carried out:

a measurement of the drive torque of a first roller drive and / or a second roller drive;

a measurement of a tape winding diameter at the first tape roll and / or at the second tape roll;

a measurement of the angular velocity of rotation of the first roll of tape and / or the second roll of tape.

A method according to any one of the preceding claims, wherein the finishing belt is moved in the first movement phase and the second movement phase at a substantially uniform feed speed.

1 1. Device (100) for finishing curved workpiece surfaces on workpieces (1 10) by means of a coated with cutting medium finite finishing belt (1 15), in particular according to the method according to one of the preceding claims, with

a rotating device (122) for generating a rotational movement of the workpiece about a workpiece axis (1 12); and

at least one finishing unit (150), the

a first tape roll (155-1) for receiving a first end portion of a finishing tape,

a second tape roll (155-2) for receiving a second end portion of the finishing tape opposite to the first end portion; and

a pressure device (160) for pressing the finishing belt against a workpiece surface to be machined,

marked by

a first reel drive (158-1) coupled to the first reel for reversibly rotating the first reel, a second roller drive (158-2) coupled to the second belt reel for reversibly rotating the second belt pulley, and

a control device (180) for coordinated activation of the first and the second roller drive.

12. The apparatus of claim 1 1, characterized by an oscillation device for generating a parallel to the workpiece axis (1 12) aligned oscillating relative movement between the workpiece (1 10) and the finishing belt (1 15).

13. The apparatus of claim 1 1 or 12, wherein the first tape roll (155-1) and the second tape roll (155-2) and elements of the first roller drive (158-1) and the second roller drive (158-2) and the pressure device (160) are arranged on a common carrier element (152).

14. Device according to one of claims 1 1 to 13, characterized by a control device for controlling the feed rate of the finishing belt during finish machining, wherein the control device preferably comprises at least one of the following devices:

a measuring device (M1, M2) for measuring the drive torque of a first roller drive and / or a second roller drive;

a measuring device (D1, D2) for measuring a ribbon winding diameter at the first strip roll and / or at the second strip roll; a measuring device (W1, W2) for measuring the angular velocity of a rotation of the first roll of tape and / or the second roll of tape.

15. finisher unit (150) for finishing of Werkstückoberflä- surfaces on workpieces, in particular for carrying out the method according to one of claims 1 to 10 by means of a device according to one of claims 1 1 to 14, with a first tape roll (155-1) for receiving a first end portion of a finite finishing tape (15),

a second tape roll (155-2) for receiving a first end portion opposite the second end portion of the finishing strip (1 15) and

marked by:

a coupled to the first tape roll first roller drive (158-1) for reversibly rotating the first roll of tape and

a second roller drive (158-2) coupled to the second tape reel for reversibly rotating the second tape reel.