EP2750829B1 - Finishing machine for finish machining of curved workpiece surfaces on workpieces - Google Patents

Description

TECHNICAL AREA

The invention relates to a finishing machine for finishing curved workpiece surfaces on workpieces according to the preamble of claim 1.

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 abutting the peripheral surface is simultaneously generated parallel to the workpiece axis. By combining the rotational movement of the workpiece and the superimposed oscillation movement, a so-called cross-cut pattern can be generated, whereby the machined workpiece surfaces, for example, as running surfaces for plain bearings or rolling 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 re-release the original structure, to increase the support of the roughened surface structure and to improve the component geometry. Unlike lapping, bonded grain tools are used, eliminating the need for washing operations and lapping sludge disposal facilities.

For the workpiece to rotate, it must be picked up and driven by a suitable device. For this purpose, a finishing machine of the type considered in this application has at least one workpiece spindle, which is rotatable about a spindle axis by means of a spindle drive and has a workpiece holder for receiving a workpiece. The workpiece holder is designed such that the workpiece received by the workpiece holder is rotatable about its workpiece axis by rotation of the workpiece spindle. Furthermore, at least one Finisheinheit is provided, which has a pressing device for pressing a machining tool occupied with cutting means to a machined curved peripheral surface of the workpiece, wherein the drive means a directed radially to the workpiece axis pressing force is exerted on the machining tool.

In general, a finishing machine also has an optionally optionally switchable or switchable oscillation device, which can generate a parallel to the workpiece axis oscillating relative movement between the workpiece and the machining tool.

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 achieved via 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. Devices and methods for carrying out these variants of belt finishing are described, for example, in US Pat WO 2009/049868 A1 or the DE 199 25 077 A1 disclosed.

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 grinder, a continuously driven, endless finishing belt is used, which partially wraps around a workpiece surface (peripheral surface) of the workpiece to be machined during processing and in a predetermined by the wrap angle range flat against the workpiece. Examples of such methods are in EP 1 514 640 B1 or the EP 1 514 643 B1 specified. The finishing belt running over pulleys should adapt flexibly to the geometry of the rotating workpiece and ensure high surface quality. As a rule, circumferential machining marks are generated.

In the DE 100 16 897 A1 An apparatus for multiple processing of a workpiece in a clamping with a plurality of processing stations will be described. The device comprises a rotary table which is rotatable about a horizontal rotary table axis and has a plurality of workpiece spindles. The workpieces are clamped with three-jaw chucks. In one embodiment, a grinding device is provided at one of the processing stations. After grinding, the workpieces are moved to a downstream processing station for superfinishing. The associated finish unit has a honing stone, which can be offset in an oscillatory movement axially parallel to the axis of the machined workpieces. In superfinishing, the cutting motion results from the superposition of the axial oscillatory motion of the finish stone and the rotational movement of the workpiece about its axis.

The EP 1 518 643 A1 describes a finishing device for a microfinishing machine. In one embodiment, the finishing device is attached to one of two processing arms of a processing tongs. At the free end of the other processing arm, a holding bracket is attached, on which a bezel is integrally formed. The bezel serves to receive an insert, in which two pieces of equipment are arranged, which bear against the workpiece. Due to the centrifugal forces, the steady rest is only needed when machining crankpins of a crankshaft.

Alternatively, a finish stone may also be provided as a processing tool in a finisher unit.

There is a need for finish machines that can process large numbers of similar workpieces with high quality machining and high productivity and can be used for different workpiece geometries.

TASK AND SOLUTION

The invention has for its object to provide a finishing machine for finishing curved workpiece surfaces on workpieces, can be subjected to the finishing of large numbers of workpieces at short cycle times with high quality machining. The finishing machine should be usable for different workpiece geometries without sacrificing quality.

To achieve this object, the invention provides a device with the features of claim 1.

Advantageous developments are specified in the dependent claims. The content of all claims is incorporated herein by reference.

In the finishing machine according to the claimed invention, a rotary table is provided, which is cyclically rotatable about a rotary table axis is. On the rotary table several workpiece spindles are arranged in a predetermined angular pitch. A workpiece picked up by a workpiece holder can be moved by turning the rotary table into a processing position on the finishing unit and can be transported out of this processing position to a subsequent workstation after finishing machining.

Preferably, the rotary table carries at least three workpiece spindles, for example three or four workpiece spindles, but possibly also more. As a result, high productivity can be achieved. It is also possible to equip the rotary table with only two workpiece spindles.

In such a finishing machine, it is thus possible that a workpiece, which is received by the workpiece holder of a workpiece spindle, moved by rotation of the rotary table in its processing position on a Finisheinheit and transported after completion of finish machining from this processing position out to a subsequent workstation. During this rotation, at the same time the next workpiece to be machined can be transported to the finishing machine. As a result, the non-productive time for the workpiece change compared to conventional finishing machines can be significantly reduced.

In addition, it is easily possible to integrate the finish machining in a process chain with further upstream and / or downstream machining operation, wherein the associated processing units can also be operated via the rotary table.

Preferably, the rotary table is indexable by means of an indexing device in each angular position or angle position belonging to a processing position. As a result, an exact workpiece positioning is possible, which also under the influence of machining forces does not change. This ensures a high quality of processing. Alternatively or additionally, a clamping device may be provided for clamping the rotary table in the respective angular position.

In order to achieve sufficient surface finishes and to maintain the intended shape parameters during finishing, it is important that the workpiece is rotated exactly around its workpiece-specific rotation axis (workpiece axis) during machining. At the same time, however, the machining forces, especially during finish machining, act in the radial direction with respect to the workpiece axis. These transverse forces could lead to inclination and / or bending of the workpiece to be machined and corresponding loss of quality. A coaxial to the spindle axis and against transverse forces stable workpiece clamping is therefore desirable.

A one-sided workpiece holder (support exclusively on the workpiece holder of the workpiece spindle) is possible. This can be realized by appropriately robust dimensioned active clamping systems on the workpiece spindles, e.g. by a collet or a chuck. A one-sided workpiece clamping may possibly be sufficient for axially relatively short and relatively thick compared to the length of workpieces. For longer and / or thinner and / or structurally more unstable workpieces, however, the transverse forces can lead to quality losses.

In the claimed invention, an active support of the workpiece against transverse forces on at least one axially spaced from the workpiece holder workpiece section or a corresponding device is provided. There are different possibilities for this.

Some embodiments have an abutment device engaging the workpiece at an axial distance from the workpiece holder for fixing the workpiece in a machining position aligned coaxially with the spindle axis of the workpiece spindle when the workpiece spindle is in a processing position associated with a processing station.

The workpiece can be used e.g. be recorded with its axial ends between centering acting tips. In some embodiments, for this purpose, a tailstock device is provided with at least one tailstock unit, which has a tailstock spindle rotatable about a tailstock spindle axis and preferably also movable parallel to the tailstock spindle axis. Two, three or more tailstock spindles can be provided. In particular, a separate tailstock spindle can be provided for each processing station provided for workpiece machining.

The tailstock spindles can be permanently installed. They are then first withdrawn before further indexing of the rotary table and then advanced again before the start of the subsequent machining operation to clamp the workpieces axially.

It is also possible to provide one or more tailstock spindles on a further rotary table, which can be rotated axially parallel or coaxially with the rotary table carrying the workpiece spindles.

An embodiment is characterized in that in addition to the rotary table (first rotary table) carrying the workpiece spindles, a further rotary table (second rotary table) is provided, which is rotatable coaxially with the rotary table carrying the workpiece spindles and carries at least one counter bearing device, eg in the form of a tailstock spindle , Preferably, at the further rotary table for each workpiece spindle the first rotary table provided its own tailstock spindle.

Preferably, each of the two rotary tables is assigned a separate rotary drive, wherein the rotary actuators (first and second rotary drive) are independently controllable via the machine control. A synchronous rotation of the rotary tables is possible by means of synchronization of the rotary actuators via the machine control. This concept is also referred to in this application as a "twin drive", the advantages of which will be explained in connection with an embodiment.

The further (second) rotary table is in some embodiments parallel to its axis of rotation in the direction of the workpiece spindles bearing (first) rotary table or in the opposite direction movable. As a result, an adaptation to workpieces of different lengths is easily possible. In addition, the workpiece change is facilitated.

Alternatively or additionally, as an abutment device, a steady rest or another support element may be provided, which engages at a distance from the workpiece holder between this and the free end of the workpiece to a workpiece section suitable for supporting.

In one embodiment, the active support of the workpiece against transverse forces on at least one axially spaced from the workpiece holder workpiece section is achieved in that at a processing station for finishing a first Finisheinheit and at least one second Finisheinheit is provided which simultaneously attack the workpiece during machining , Wherein the pressure forces of the first and the second finishing units acting radially to the workpiece axis are aligned substantially symmetrically to the workpiece axis. This compensates for the through the finishing units applied pressing forces each other, so that a stabilized against transverse forces machining is possible. In one embodiment, two diametrically opposite, substantially identical finishing units are provided at a processing station for finish machining. A star-shaped arrangement of three or more finishing units is also possible.

In some embodiments, a plurality of machining units associated with the rotary table are provided for performing a machining operation on a workpiece received by a workpiece holder, wherein at least one of the machining units is a finishing unit.

In addition to one or more processing units that can perform one or more work operations that alter the workpiece, a loading unit may be provided at a work station (loading station) to populate the rotary table or to remove the finished workpieces.

The finishing machine may have a single finisher unit. In some embodiments, several finishing units are provided, for example two, three or four finishing units served by the same rotary table. As a result, a plurality of different finishing operations (different machining parameters on the same workpiece section and / or identical or different finishing operations on different workpiece sections) on the same workpiece in one clamping can be performed.

In some embodiments, there are a plurality of processing stations, each having a finishing unit and operated sequentially by the rotary table, eg two three or four finishing units. It is also possible for one processing station to have two or more finishing units having. If necessary, they can at the same time machine the same workpiece located in its machining position, ie perform parallel machining on the same workpiece.

The term "finishing machine" in this application refers to a finishing machine which is set up for finish machining on the workpiece and for this purpose has at least one finishing unit. The finishing machine may be configured as a pure finishing machine having two or more finishing units but no processing units set up for other processing methods. In addition, e.g. still be provided a measuring unit. It is also possible to combine several different processing methods on the finishing machine. Therefore, a finishing machine may have further processing units provided for other machining operations, e.g. a deburring unit and / or a plan finisher unit for performing other machining operations on a workpiece in addition to one or more finishing operations.

There are different possibilities for the design of the spindle-side workpiece holder. For example, a centering chuck or a collet can be provided for the spindle-side workpiece holder, which are actuated by means of a clamping drive. Depending on the workpiece type, e.g. a receptacle on the outer diameter may be provided by jaw chuck or a receptacle on the inner diameter of the workpiece by a mandrel.

In preferred embodiments, the workpiece holder is designed as a passive plug-in receptacle, so that the workpiece holder has no actuatable via a clamping drive clamping means, because they are not needed. The workpiece is merely plugged or plugged in and possibly against twisting and / or falling off secured, but not clamped for centering. As a result, a particularly fast workpiece change is possible.

At the workpiece holder at least one retaining spring and / or at least one spring-loaded retaining element may be provided to hold the plugged onto the workpiece holder or inserted into the workpiece holder workpiece frictionally and secure against falling.

Preferably, the plug-in receptacle is designed for a rotationally fixed reception of a workpiece, so that the spindle rotation can be transmitted to the workpiece without slippage.

In some embodiments, the workpiece holder has a spring-loaded driver element, which engages positively in the circumferential direction when receiving a workpiece in a recess of the workpiece. As a result, on the one hand a passive anti-rotation to secure the recorded workpiece against rotation is created and on the other hand, the workpiece can also be secured against falling down by pressing the spring-loaded driving element. However, an axial insertion or attachment of the workpiece or a removal of the workpiece held thereby overcoming the frictional engagement for the workpiece change is readily possible.

The workpiece spindles need not be oriented for receiving a workpiece or fixed in a specific rotational position.

In some embodiments, the workpiece spindles are attached to the rotary table in such a way that the spindle axes run parallel to the rotary table axis. As a result, a particularly favorable, compact design can be realized. It is also possible, the workpiece spindles so on Rotary table to install, that the spindle axes transverse, in particular run radially to the rotary table axis.

The orientation of the rotary table or the rotary table axis can be adapted to the intended application. In some embodiments, the rotary table axis is horizontal, so that the rotary table is. Then the workpieces can be clamped horizontally or horizontally. There are also embodiments with horizontal rotary table in which the rotary table axis is vertical.

It is possible in some finishing operations without working parallel to the workpiece axis oscillating relative movement between the workpiece and the machining tool. 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 between the workpiece and the machining tool, e.g. a finishing tape produced. 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, a surface structure with crossed machining marks (cross-section) can be produced on a workpiece surface, which may be advantageous in tribologically stressed bearing surfaces in particular.

In embodiments which are set up for the workpiece rotation at the same time also a relative to the workpiece axis oscillating relative movement between the workpiece and on the peripheral surface To produce adjacent machining tool, a corresponding oscillation device is provided. Preferably, the oscillation device is integrated into the finishing unit, so that no means for generating an axial workpiece oscillation must be realized on the side of the workpiece holder or the workpiece spindles. However, this is basically possible.

These and other features will become apparent from the claims and from the description and drawings, wherein the individual features each alone or more in the form of sub-combinations in one embodiment of the invention and in other fields be realized and advantageous and protectable Can represent versions. Embodiments of the invention are illustrated in the drawings and are explained in more detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

• Fig. 1 shows a side view of a finishing machine designed as a belt finishing machine according to a first embodiment of the invention;
• Fig. 2 shows a plan view of the finishing machine of Fig. 1 from above;
• Fig. 3 shows an oblique perspective view of some components of the belt finishing machine Fig. 1 and 2 ;
• Fig. 4 Figures 4A and 4B show details of workpiece clamping means;
• Fig. 5 shows a side view of a finishing machine designed as a belt finishing machine according to a second embodiment of the invention; and
• Fig. 6 shows a side view of an embodiment with two coaxial rotatable rotary tables, wherein the first rotary table carries the workpiece spindles and the opposite second rotary table has means for abutment of the workpieces.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The schematic Fig. 1 FIG. 12 shows a side view of a finishing machine 100 designed as a belt finishing machine according to a first embodiment of the invention in a direction parallel to the z-direction of the machine-fixed machine coordinate system MKS. In Fig. 2 is a plan view of the same finishing machine from above in the direction of the direction perpendicular to the z-direction y direction shown. Fig. 3 shows an oblique perspective view of some essential components of the same belt finishing machine.

The belt finishing machine is adapted for machining fixed and variable cam pieces for a camshaft valvetrain. Only the peripheral surfaces of the cams are finished, not the adjacent cylindrical bearing surfaces. The finish machining is the last material-removing finishing, so a finishing. The finishing machine is located in the material flow behind an upstream grinding machine and in front of a downstream washing system.

The workpieces 200 to be processed are the finishing machine in the representation shown from the right via a horizontal transport device 205 fed automatically loaded into the finishing machine by means of a handling system and unloaded after completion of a multi-stage processing (brush deburring and subsequent Bandfinishen) and discharged via the transport device 205.

The band finishing machine is designed as a rotary indexing machine and allows short non-productive times for the workpiece change and thus a high workpiece throughput and short cycle times, so that an economic processing with high quality machining is possible.

The finishing machine has a rotary table 110, which by means of a rotary drive, not shown, cyclically about a parallel to the z-direction horizontal rotary table axis 112 is rotatable. The standing rotary table is rotatably mounted by means of suitable bearings in a vertical support member of the machine frame and can be driven by means of an electromechanical rotary drive or an NC-controlled direct drive.

Four workpiece spindles are arranged radially outside the rotary table axis 112 on the rotary table, namely a first workpiece spindle 120, a second workpiece spindle 130, a third workpiece spindle 140 and a fourth workpiece spindle 150. Each of the workpiece spindles is rotatable about a spindle axis 122, 132, 142 and 152 wherein the spindle axes parallel to each other and parallel to the rotary table axis 112 extend in the horizontal direction and have the same radial distance from the rotary table axis. For each workpiece spindle, a separate spindle drive is provided, so that the rotation of each workpiece spindle can be controlled independently of the rotations of other workpiece spindles.

Each of the workpiece spindles has a workpiece holder with which a single workpiece can be accommodated so that a through the Workpiece receiving recorded workpiece by rotation of the workpiece spindle can be rotated about its workpiece axis. The workpiece spindles and the workpiece holders attached to them are identical in each case. Special features of the workpiece holders provided here will be discussed later, especially in connection with Fig. 4 the example of the workpiece holder 160 of the second workpiece spindle 130 explained in detail.

The rotary table "operates" four work stations arranged in the circumference of the rotary table. At the first workstation, a loading unit 210 is provided for loading and unloading the workpiece holders. In the in Fig. 1 The first workpiece spindle 120 is in the loading and unloading position in the working area of the loading unit 210. This grasps a finished workpiece via a gripper system and transports it to the discharge belt of the transport device 205. Thereafter, a premachined workpiece is gripped by the feed belt of the transport device and transported to the workpiece holder of the first workpiece spindle and attached there.

A 90 ° clockwise rotation of the rotary table then transports the workpiece to be machined into the second work station, which has a brush deburring unit 220. By means of a deburring brush 222, which is rotatably mounted at the end of a pivoting arm, the outside of the rotating workpiece can be processed by brush deburring, to remove any burrs still existing after grinding. The second workstation is thus a processing station at which a workpiece machining takes place.

An indexing of the rotary table by 90 ° then brings the deburred workpiece to a further processing station, namely the third workstation in the working area of a first finishing unit 230. This is constructed as a belt finishing unit and has two parallel belt conveyors, so that on the workpiece two axially staggered workpiece sections (cams) can be processed simultaneously by means of band finishing. The first Finisheinheit is set up in the process exemplified here for processing rotationally symmetric peripheral surfaces of the so-called Nullhubnocken.

When this processing is completed, the rotary table is indexed by 90 °, so that the workpiece is finally transported to the fourth workstation in the working area of a second Finisheinheit 240, with which the non-rotationally symmetrical peripheral surfaces of the adjusting cams of the workpiece are processed. The second finishing unit is also designed as a twin-tape machine, so that at the same time two adjusting cams offset axially relative to one another can be machined on their circumference by finishing.

A further rotation of the rotary table by 90 ° brings the in three consecutive machining operations by means of three successively approached processing stations finely machined workpiece again to the first workstation, where it is removed by means of the loading unit 210 from the workpiece holder and transported to the removal.

In order to accurately position the workpiece spindles or the workpieces in a workstation, the rotary table is indexed in the respective rotational positions or angular positions by means of an automatic indexing device and clamped by means of an automatic clamping device. Before the handover, it is released again. These devices are controlled by the machine control.

For belt finishing, a finite (non-continuous) finishing belt is used, the belt ends of which are each attached to a belt reel. The fresh, still unused finishing tape is kept on a supply roll and guided over the engagement region on the workpiece (area of the pressure roller) with the aid of belt guiding devices to a driven belt roller which picks up the used finishing belt. The tape feed is achieved via 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 the top view of Fig. 2 It can be clearly seen that the first finishing unit 230 has two finishing tapes 232, 234 running parallel to one another, which at the same time in each case process the peripheral surface of an adjusting cam of the workpiece 200. During machining, the workpiece 200 is rotated around its workpiece axis 202 by means of the spindle drive of the third workpiece spindle 140. The finishing tapes are pressed by means of a pressure roller 236 with a pressure force acting radially to the workpiece axis to the rotating peripheral surface of the workpiece. The pressure roller is on its outer periphery of a hard elastic material with a low compliance, so that Andrückkraftspitzen can be avoided. At the same time, the pressure roller is offset by means of an integrated oscillation device into a short-stroke oscillation movement parallel to the workpiece axis 202 (see double arrow). Through the combination of the rotational movement of the workpiece and the superimposed oscillatory movement of the machining tool (finishing belt), a cross-cut pattern is produced on the machined circumferential surface, which is advantageous for the function of the cam surfaces.

Preferably, these workpieces are operated with discontinuous tape feed, so that the finishing belt rests during processing and the cutting speed exclusively by the rotational movement of the workpiece in combination with the superimposed axially oscillating relative movement between the workpiece and finishing belt is produced. 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. It is also possible to work 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 in large series of workpieces can be achieved well reproducible machining results.

The second finishing unit 240 is constructed substantially identically.

In order to achieve sufficient surface qualities and to maintain the intended shape parameters, it is important that the workpiece is rotated exactly around its workpiece-specific rotation axis (workpiece axis) during machining. At the same time, however, the machining forces in the finish machining with respect to the workpiece axis in the radial direction. These transverse forces could lead to tilting of the workpiece to be machined and corresponding loss of quality. A coaxial to the spindle axis and against transverse forces stable workpiece clamping is therefore desirable.

For cost-effective production, the cycle times during machining should be kept as low as possible, so that a workpiece change should be as fast as possible. In the embodiment, a solution is realized for the workpiece clamping, on the one hand allows a quick workpiece change and on the other hand, a stable against transverse forces coaxial tension of the workpieces.

On the part of the workpiece spindle is provided for this purpose that the workpiece holder is designed as a passive plug-in receptacle for rotationally fixed receiving a workpiece. Such passive workpiece holders do not require a tensioning drive operable clamping means for clamping the workpiece. The workpiece is not clamped radially, but only more or less plugged in the axial direction, non-positively held against falling and secured against rotation. As a result, a quick picking up and removing the workpieces is realized.

Furthermore, an abutment device for fixing a recorded in a workpiece holder workpiece is provided in a coaxial with the spindle axis of the workpiece spindle machining position, wherein the abutment means engages the workpiece at an axial distance from the workpiece holder when the workpiece spindle is in a processing station belonging to the processing position.

These devices allow a workpiece holder between tips.

Based on Fig. 2 to 4 These elements will now be explained in more detail using the example of the workpiece holder 160 attached to the second workpiece spindle 130 and an associated tailstock unit 300. The tailstock unit 300 is part of a tailstock device 350, which is mounted at an axial distance in the z direction in front of the rotary table and mounted on the front workpiece holders on the machine bed. In the embodiment, the tailstock device 350 has three identically constructed tailstock units 300, 360, 370, namely one tailstock unit for each of the processing stations 220, 230 and 240. As above all Fig. 3 can be seen, the tailstock unit 300 is assigned to the brushing, while the tailstock unit 360 of the first finishing unit and tailstock unit 370 is associated with the second finishing unit.

The tailstock unit 300 has a tailstock spindle 310 that is passive, i. without its own drive, about a tailstock spindle axis 312 is rotatable and by means of a feed drive parallel to the tailstock axis in the direction of the opposite workpiece holder and movable away from it. The tailstock spindle axis is arranged to coincide with the workpiece spindle axis of that workpiece spindle which is in the machining position at the brushing direction, in the example case with the spindle axis 132 of the second workpiece spindle 130.

The spindle-side workpiece holder 160 is formed as a passive plug-in receptacle for rotationally fixed receiving the workpiece. A front end portion of the workpiece holder for this purpose forms a mandrel portion 162 having a cylindrical outer surface which has an outer diameter which is adapted to the inner diameter of the workpiece to be clamped (indicated by dashed lines), that the mandrel portion can be introduced axially into the workpiece to form a clearance fit. The workpiece is thus already aligned largely coaxially with the spindle axis. At the mandrel section 162, a conical centering section 164 adjoins the spindle side with a diameter which increases in size toward the rotary table. A workpiece plugged onto the mandrel section is thereby centered with respect to the spindle axis 132.

Fig. 4B shows a perpendicular to the spindle axis 132 extending section through the mandrel portion 162 and the elements contained therein of a passive anti-rotation device for securing a recorded workpiece against rotation. A driver element 166 is pivotably mounted about an axis of rotation extending parallel to the spindle axis and has a radially outwardly projecting latching lug 165, in the swung-out state of the driver element protrudes through a slot 167 on the circumference of the mandrel portion to the outside. In the interior of the mandrel portion, a compression spring 168 is arranged, which biases the driver element in this disengaged position. Against the force of the compression spring, the driver element can be pressed inwards.

If a workpiece is then pushed onto the mandrel section substantially axially from the front, then it is centered when it comes into contact with the conical centering section 164 with respect to the spindle axis 182. The here provided as a workpiece cam pieces have on their inner side an internal toothing for the rotationally fixed coupling to axially adjacent components of the camshaft. The locking lug 166 of the driver engages in one of the tooth gaps, so that in the circumferential direction a positive connection between the driver element and the workpiece is formed, whereby this is secured against rotation relative to the mandrel portion. In addition, the compression spring presses the driver against the inside of the workpiece, wherein the spring force is dimensioned so that the workpiece is secured by this frictional connection against falling from the mandrel portion. The axial connector between the workpiece holder and the workpiece can be solved by axial removal of the workpiece during workpiece change in a simple manner.

For centering the workpiece on the workpiece holder, the opposite tailstock spindle at its workpiece receiving end facing a conical centering portion 364 which engages the axial feed of the tailstock spindle in the workpiece, whereby the workpiece is centered with respect to the spindle axis 132. The workpiece is thus in this embodiment in principle axially between points or between the conical centering sections 164 and 364th tense and is thereby stabilized against the radial machining forces acting on the machining at both ends.

This type of workpiece clamping between tips in conjunction with a rotary table can of course be provided not only in the workpieces described here by way of example, but is also useful for other workpiece geometries, especially for those workpieces that have a relatively long compared to their diameter, ie protrude relatively far beyond a spindle-side workpiece holder. This workpiece clamping between peaks is also possible for massive workpieces, for example by the tailstock has a tip which engages in a front-side central recess of the workpiece. Instead of an outer cone on the workpiece spindle side, an inner cone could also be provided for clamping solid workpieces with cylindrical end sections.

The schematic Fig. 5 shows a side view of a designed as a band finishing machine finishing machine 500 according to a second embodiment in a direction parallel to the z-direction of the machine-fixed machine coordinate system MKS. The finishing machine is designed in the example for the same workpieces (cam pieces) and arranged in the material flow in line behind an upstream grinding machine and before a downstream washer.

The workpieces 200 to be processed are fed to the finishing machine in the illustration shown from the right via a horizontal transport device 605, automatically loaded into the finishing machine with the aid of a handling system (loading device 610) and unloaded again after completion of a strip finishing operation and conveyed off to the left. In addition to the charging station, there is only one processing station for belt finishing. For belt finishing, two finishing units 620, 630 acting simultaneously on the workpiece are provided.

The finishing machine has a rotary table 510, which by means of a rotary drive, not shown, cyclically about a parallel to the z-direction horizontal rotary table axis 112 is rotatable.

On the rotary table, two diametrically opposed workpiece spindles are arranged radially outside the rotary table axis 512, namely a first workpiece spindle 520 rotatable about a first spindle axis 522 and a second workpiece spindle 530 rotatable about a second spindle axis 532. The spindle axes lie parallel to one another and parallel to the rotary table axis 512 in horizontal Direction. For each workpiece spindle, a separate spindle drive is provided so that the rotation of each workpiece spindle can be controlled independently of the rotations of the other workpiece spindle.

The workpiece spindles and the workpiece holders attached to them are identical in each case. The workpiece holders are designed as collets, which are actuated by their own clamping drives and hold the clamped workpiece by clamping torque-proof and center.

The rotary table "operates" two work stations arranged on the circumference of the rotary table. At the overhead first workstation, the loading unit 610 is provided for loading and unloading the workpiece holders. In the in Fig. 5 the situation shown is the first workpiece spindle 520 in the loading and unloading in the working area of the loading unit 610. The loading is done from the right, the removal to the left.

Turning the rotary table clockwise by 180 ° will then feed the workpiece to be machined into the second work station, which is the only processing station of the finishing machine. The processing station has two substantially identical finishing units 620, 630 which engage diametrically opposite sides of the workpiece. The finishing units can each be moved horizontally parallel to the x-axis. Furthermore, a linear axis is provided in the z-direction for the axial positioning of the finishing units on the workpiece.

Both the first finisher unit 620 and the second finisher unit 630 are constructed as a belt finisher and have two parallel belt conveyors, so that two axially staggered workpiece sections (cams) can be simultaneously machined on the workpiece by belt finishing. The first Finisheinheit is set for processing axially offset from each other first cam, while the second Finiseinheit machined axially to the first cam offset second cam. For belt finishing, a finite (non-continuous) finishing belt is used, the belt ends of which are each fastened to a belt reel. It is worked with slow continuous or discontinuous tape feed. In that regard, reference is made to the above description.

When finish machining is complete, the rotary table is indexed 180 °. This rotation brings the finished workpiece back to the first workstation, where it is removed by means of the loading unit 610 from the workpiece holder and transported for removal.

In contrast to the embodiment of Fig. 1 to 4 the workpieces are here only one-sided (in the workpiece holder) and not stretched between peaks and there are no corresponding tailstock facilities. Nevertheless, even with large radial pressure forces during finishing a stabilized against transverse forces, the workpiece spindle coaxial workpiece rotation is ensured. The arrangement of the finishing units is chosen such that the pressure forces acting radially to the workpiece axis the first and second Finisheinheit are aligned substantially symmetrically to the workpiece axis. As a result, the pressure forces applied by the finishing units during machining compensate each other, so that processing stabilized against transverse forces is possible. Each Finisheinheit acts as a support or counter-bearing for receiving the respective lateral forces introduced by the other Finisheinheit.

Based on Fig. 6 For example, special devices for workpiece clamping are shown in a finishing machine 800, which in example is adapted for machining relatively long workpieces 805 in the form of crankshafts. The processing means include several finishing units which can simultaneously handle both main bearings and crank bearings of the crankshaft by means of band finishing on a crankshaft held in a machining position. The workpiece clamping devices can simultaneously clamp four crankshafts each between points and move them in cycles to different workstations.

For workpiece clamping two coaxial rotatable rotary tables are provided, one of which belongs to a headstock unit and four separately driven workpiece spindles and the other belongs to a tailstock unit which serves as an abutment means for fixing the workpieces in a coaxial with the spindle axis of the workpiece spindles aligned machining position.

The headstock unit includes a first rotary table 810, which can be cyclically rotated about its horizontal rotary table axis 812 by means of an electric first rotary drive 814. The first rotary table is mounted in a vertical support element which is mounted fixed in the axial direction on the machine bed 802 of the finishing machine. At the first rotary table 810, four workpiece spindles are radially outside of Round table arranged, of which only two workpiece spindles 820, 830 can be seen in the side view. To each of the workpiece spindles belongs an independently controllable from the other rotary actuators rotary drive, which can rotate the workpiece spindle to the associated spindle axis 822, 832. The four integrated in the headstock rotary axis workpiece spindles are each equipped with an axially sprung tip 824, 834 and drivers, which ensure that the clamped workpieces are taken in rotation in the circumferential direction of the respective workpiece spindle and taken along. The first rotary table 810 is rotated about its horizontal rotary table axis 812 and indexed to a four discrete positions associated with four workstations of the finishing machine. In the situation shown, the upper workpiece spindle 820 is in the loading and unloading position in the working area of a loading unit, not shown. In this working position, a fixedly mounted pneumatic actuator 860 acts as an actuator to retract the tip of the workpiece tip located in the loading and unloading position.

Viewed in the axial direction relative to the first rotary table 810, a second rotary table 910 is arranged, which is part of the tailstock unit. The second rotary table can be rotated by means of an electric second rotary drive 914 about its horizontal rotary table axis 912, which is coaxial with the axis of rotation or rotary table axis 812 of the first rotary table. The first and the second rotary drive can be controlled independently of one another via the machine control. This can ensure a synchronous rotation of the rotary tables with control technology. This concept is also referred to here as a "twin drive".

The common axis of rotation forms the symmetry axis of the arrangement. The second rotary table 910 is axially movable for the conversion operation, ie, parallel to the symmetry axis of the arrangement. The rotary table is mounted for this purpose in a vertical support member which on a carriage 970 is mounted, which is axially displaceably guided on axial guide rails and can be reciprocated horizontally by means of a NC-axis 975 with ball screw.

The second rotary table 910 carries four identical tailstock spindles in 90 ° angle division, of which only two tailstock spindles 920 and 930 are shown. Each of the tailstock spindles has a passively rotatable, roller bearing, spring loaded tip 924, 934 so that each one long workpiece can be clamped spring loaded between the tips of the opposing workpiece spindle and the associated tailstock spindle. The rotary table is indexed at four discrete positions corresponding to the workstations of the finishing machine. At the position belonging to the loading and unloading station, a stationary pneumatic drive 960 is provided for retracting the tailstock-side tip.

During operation of the finishing machine 800, a workpiece to be machined is clamped in the region of the loading and unloading position by first moving a free workpiece spindle and an associated free tailstock spindle into the working position belonging to the loading and unloading station. The workpiece is then gripped by means of a gripper unit and held between the tips, which are retracted by the pneumatic drives against the force of the respective associated return springs. To clamp the workpiece, the drives are deactivated, so that the workpiece is clamped axially between the tips under the force of the springs belonging to the tips. The workpiece can then be moved by synchronous rotation of the two rotary tables 810, 910 by means of synchronized control of the first and second rotary drive in a first processing station and then optionally up to two other processing stations before it is conveyed back to the loading and unloading. Different directions of rotation are possible. In the processing stations, different machining operations on the workpiece be performed. The workpieces each remain clamped between clamps from the clamping to the subsequent clamping and can be rotated at the respective workstations by means of the workpiece spindle about its longitudinal axis.

In principle, it would be possible to provide only a single, common rotary drive for both rotary tables and the rotary tables, for. mechanically coupled together so that the driven rotary table takes the other, passive rotary table. It could also lead starting from a common rotary drive two separate drive trains to the rotary tables. The concept with "twin drive" of the two rotary tables is considered to be advantageous, in particular if more than two workpieces are clamped and / or if the workpieces are relatively large and heavy.

The counter-bearing second rotary table 910 includes the passive workpiece abutments (eg tip, bezel) driven by the workpiece rotation induced on the opposite main drive side and the workpieces (in the case of an inter-tip solution) by a constant clamping force (eg Spring force) in the other five degrees of freedom between the tips fixed. This clamping force can be released by an external workpiece removal operation (e.g., stationarily located at the loading / unloading station).

Since the rotary table alone by the eccentric distance of the workpieces and their recordings to the rotary table axis of rotation has a high rotational moment of inertia (Steiner proportion of moment of inertia) is provided in the twin drive that the second rotary table is not passively taken over the first round table 810, but has its own rotary drive (second rotary drive 914), which is advantageously a servo-controlled rotary drive (NC axis). This embodiment provides advantages in terms of geometric Accuracy and the drive dynamics achieved: Firstly, angular offsets between two rotary tables can be virtually eliminated by interrogation and comparison of the two-sided angle encoder systems of the rotary actuators, so that always (regardless of the dimensions of the arrangement) a synchronous rotation of the round tables is ensured. The rotary tables are on the machine side only via the machine control, but not mechanically coupled. Inevitable compliances that might occur with mechanical coupling of the rotary tables are eliminated. On the other hand, the execution of the twin drive due to the inertia issue described the dynamics and energy consumption compared to a passive entrainment of the second rotary table significantly improve.

The arrangement allows maximum productivity even when machining axially long workpieces. The transverse forces acting radially on the workpieces during machining are reliably absorbed by the workpiece clamping between coaxial tips.

Some aspects of the invention have been illustrated by the example of belt finishing machines having two finishing units arranged as belt finishing units, in one case in addition to a deburring unit. It is also possible that one or more finishing units are equipped with a finishing stone as a processing tool. Like the example of Fig. 5 shows the finishing machine can also be designed as a pure finishing machine, in which all processing units Finisheinheiten.

In some, not illustrated embodiments, only a single Finisheinheit is provided in addition to a loading and unloading unit. It is also possible to provide more than two finishing units, for example three or four finishing units. These can be set up for similar or different finishing operations. In the embodiments shown, all machining operations are performed on the rotating workpiece, wherein it is not important for the machining to fix the workpiece in a certain rotational position. The workpiece spindles can therefore have a relatively simple structure without means for setting and fixing a specific rotational position.

The equipped with workpiece spindles rotary table is rotatable in the embodiments about a horizontal rotary table axis. There are also embodiments with a horizontal, lying rotary table, which is rotatable about a vertical rotary table axis. Accordingly, the axes of Finisheinheiten and optionally other processing units are orientable differently. In the example, the workpiece spindles mounted on the rotary table rotate axially parallel to the rotary table. The spindle axes in workpiece spindles can also be aligned transversely, in particular perpendicularly to the rotary table axis, for example radially to the rotary table axis, so that a uniform or non-uniform star-shaped arrangement of the workpiece spindles results.

This application discloses, inter alia, a workpiece holding device with two coaxially rotatable rotary tables, wherein the first rotary table carries the (via a spindle drive rotatable about a spindle axis) workpiece spindles and the opposite second rotary table has means for abutment of the workpieces. These devices for abutment can be designed for example as tailstock spindles, but possibly also have other design. Such a workpiece holding device can be used independently of the other features of the claimed invention also in processing machines without finishing units to support workpieces, in particular relatively long workpieces, during machining against transverse forces, which are exerted by a machining tool on the possibly rotating workpiece.

Claims (15)

1. A finishing machine (100) for the finish machining of curved workpiece surfaces on workpieces (200), having:

   at least one workpiece spindle, which is rotatable about a spindle axis by means of a spindle drive and has a workpiece mounting for mounting a workpiece, such that the workpiece mounted by the workpiece mounting is rotatable about a workpiece axis by rotation of the workpiece spindle;

   at least one finishing unit, which has a pressing device for pressing a machining tool provided with cutting means against a curved circumferential surface of the workpiece with a pressing force directed radially with respect to the workpiece axis; and

   a rotary table (110), which is rotatable cyclically about a rotary table axis (112),

   wherein a plurality of workpiece spindles (120, 130, 140, 150) are arranged on the rotary table at a predetermined angular pitch and a workpiece mounted by a workpiece mounting is movable into a machining position on the finishing unit by rotation of the rotary table and, after completion of the finish machining operation, is transportable out of this machining position to a subsequent workstation,

   characterized by

   a device for actively supporting the workpiece against transverse forces on at least one workpiece section located at an axial distance from the workpiece mounting.
2. The finishing machine according to claim 1, characterized in that the rotary table is indexable in any angular position pertaining to a machining position by means of an indexing device and/or is clampable by means of a clamping device.
3. The finishing machine according to claim 1 or 2, characterized by a counter-bearing device, acting on the workpiece at an axial distance from the workpiece mounting, for fixing the workpiece in a machining position oriented coaxially with the spindle axis of the workpiece spindle, when the workpiece spindle is located in a machining position pertaining to a machining station.
4. The finishing machine according to any of the preceding claims, wherein the finishing machine is set up such that a workpiece is mountable at at least one machining station with its axial ends between tips which have a centering effect.
5. The finishing machine according to any of the preceding claims, characterized by a tailstock device (350) having at least one tailstock unit (300, 360, 370), which has a tailstock spindle that is rotatable about a tailstock spindle axis and is movable preferably parallel to the tailstock spindle axis, wherein preferably a separate tailstock spindle is provided for each machining station provided for workpiece machining.
6. The finishing machine according to any of the preceding claims, characterized in that, in addition to the rotary table (810) carrying the workpiece spindles (820, 830), a further rotary table (910) is provided, which is rotatable coaxially with the rotary table carrying the workpiece spindles and carries at least one counter-bearing device, in particular a tailstock spindle (920, 930), wherein preferably a separate tailstock spindle is provided for each workpiece spindle.
7. The finishing machine according to claim 6, characterized in that each of the two rotary tables (810, 910) is assigned a separate rotary drive (814, 914), wherein synchronous rotation of the rotary tables (810, 910) is achievable by means of synchronization of the rotary drives via a machine control system of the finishing machine, and/or characterized in that the further rotary table (910) is movable parallel to its rotation axis (912) in the direction of the rotary table (810) carrying the workpiece spindles or in the opposite direction.
8. The finishing machine according to any of the preceding claims, characterized by a plurality of machining units (220, 230, 240), assigned to the rotary table, for carrying out machining operations on a workpiece mounted by a workpiece mounting, wherein at least one of the machining units is a finishing unit (230, 240), wherein preferably at least one machining unit is configured for a different machining operation, in particular for deburring.
9. The finishing machine according to any of the preceding claims, wherein the finishing machine has a plurality of finishing units (230, 240, 620, 630) which are served by the same rotary table (110), in particular precisely two finishing units (230, 240, 620, 630), which are preferably arranged such that they are served successively by the rotary table.
10. The finishing machine according to any of the preceding claims, wherein a machining station of the finishing machine has two finishing units (620, 630), which are set up to simultaneously machine the same workpiece positioned in a machining position pertaining to the machining station, and/or wherein a first finishing unit (620) and at least one second finishing unit (630) are provided on a machining station for finish machining, said finishing units acting simultaneously on the workpiece during the machining operation such that pressing forces, acting radially to the workpiece axis, of the first and of the second finishing unit are oriented substantially symmetrically with respect to the workpiece axis, wherein preferably two diametrically opposite, substantially identical finishing units (620, 630) are provided on a machining station for finish machining.
11. The finishing machine according to any of the preceding claims, wherein the workpiece mounting (160) is configured as a passive plug-type mounting, wherein preferably the workpiece mounting (160) has at least one retaining spring and/or at least one spring-loaded retaining element (166) in order to hold the workpiece plugged onto the workpiece mounting or plugged into the workpiece mounting in a frictional manner and to secure it against falling out.
12. The finishing machine according to any of the preceding claims, wherein the workpiece mounting is configured to mount a workpiece for conjoint rotation, wherein the workpiece mounting preferably has a passive twist prevention device for securing a mounted workpiece against twisting, wherein preferably the workpiece mounting has a spring-loaded driver element (166) which, when a workpiece is mounted, engages in a recess in the workpiece in a form-fitting manner in the circumferential direction, and/or wherein the workpiece mounting (160) has a conical centering section (164) for centering the workpiece with respect to the spindle axis (132).
13. The finishing machine according to any of the preceding claims, wherein the workpiece spindles (120, 130, 140, 150) are fitted on the rotary table (110) such that the spindle axes (122, 132, 142, 152) extend parallel to the rotary table axis (112).
14. The finishing machine according to any of the preceding claims, wherein the finishing unit (230, 240) has an oscillation device for producing an oscillating movement of the machining tool parallel to the workpiece axis.
15. The finishing machine according to any of the preceding claims, wherein at least one finishing unit (230, 240) is a belt finishing unit.

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