Turning equipment

Abstract

The invention relates to a turning device for cutting a workpiece, comprising: a workpiece holder configured to receive the workpiece and driven in rotation about a virtual axis of rotation; the turning tool is provided with a cutter; a main feed drive which causes a main feed movement in the feed direction, the turning tool and the workpiece holder being movable close to or away from each other by means of the feed movement; the turning tool and the axis of rotation can be moved closer to or away from each other by means of the main transverse movement, and a secondary transverse drive for driving the turning tool and the axis of rotation to move closer to or away from each other by means of the main transverse movement. The secondary transverse movement of the secondary transverse drive is oriented in the same direction as the transverse movement of the primary transverse drive, wherein the turning tool and the axis of rotation can be moved close to and away from each other by superposition of the primary and secondary transverse movements.

Description

[0001] This application is a divisional application of the Chinese patent application with application number 202011079566.X, application date October 10, 2020, and name “Tool drive unit, turning equipment, turning method and application thereof”. Technical Field

[0002] The invention relates to a tool drive unit according to the preamble of claim 1, a turning device according to claim 7, a method for cutting the end face of a workpiece driven around a virtual rotation axis by means of a turning tool according to claim 10, and a turning device for carrying out the method according to claim 21. Background Art

[0003] The tool drive unit is used to automatically position the tool at a defined position of the machine in order to be able to precisely machine the workpiece. In addition, such a tool drive unit is present in a turning device in order to be able to position a turning tool with a cutter relative to a rotating workpiece. Then, according to the method, the turning tool is brought into engagement with the workpiece and chips are removed from the workpiece by the main movement of the rotation of the workpiece. By moving the turning tool relative to the workpiece, the workpiece is machined into a desired shape by cutting away material.

[0004] Thus, for example, a turning device is known from EP 2 998 067 A2, which has two turning stations, each of which has a rotatable workpiece spindle for accommodating a lens blank and a turning tool for cutting the accommodated lens blank. The lens blank is rotated around a virtual axis of rotation by means of the workpiece spindle. For machining, the turning tool is engaged with the end face further outward and then moved in the direction of the axis of rotation. This produces a spiral working path. Here, during lens machining and in particular during the manufacture of eyeglass lenses, surfaces with height curves are produced. These machined surfaces are not rotationally symmetrical. Therefore, it is necessary to adapt the feed of the turning tool according to the height curve every time the lens blank rotates. For this purpose, a very fast-working linear motor with a small adjustment path is used. This has a piezoelectric actuator or an oscillating coil and is also called a fast tool or a fast tool servo (motor).

[0005] In the prior art, it is problematic to comply with manufacturing tolerances in the area directly around the axis of rotation. If the tool is lifted from the end face too early, the bolt remains in the middle around the axis of rotation. If the turning tool is completely moved to the axis of rotation, the cutter of the turning tool has partially extended beyond the axis of rotation. As a result, contact is caused between the blunt back side of the cutter and the surface that has been processed, thereby damaging the surface. The workpiece passes through the cutter in this area, especially in the wrong or opposite direction. The more concave or inclined the end face in the area of ​​the axis of rotation, the more serious the problem. In addition, this problem is very critical in optical lenses and glasses because optical errors are generated in the center of the lens. Therefore, for example, by using the smallest possible tool radius, reducing the rotation speed, reducing the extrusion force and by reprocessing, such as polishing, to remedy. Even in the case of a known small tool radius, prism processing still has problems, because it is difficult to keep the surface quality of spheres and cylinders within tolerance in a machining center, especially for optical lenses and glasses. Therefore, the production time is long, and it is expensive to produce high-quality surfaces in a machining center. Summary of the invention

[0006] The object of the present invention is therefore to provide a device and a method for turning a workpiece, which allows rapid and precise machining of surfaces up to the axis of rotation of the workpiece. In this context, a solution which is retrofitted into existing turning devices is desirable.

[0007] The essential features of the invention are described in the characterizing parts of claims 1 and 7, 10 and 21. Alternative embodiments are the subject matter of the dependent claims and the description.

[0008] In a tool drive unit of a turning device for cutting a workpiece, wherein the tool drive unit has a tool holder for accommodating a turned workpiece with a cutting tool, wherein the tool holder can be driven slidably, in particular linearly, along a feed direction by means of a first linear motor having a first oscillating coil or a first piezoelectric element, the present invention proposes that the tool holder is driven in a swinging or slidable manner along a lateral direction transverse to the feed direction by means of a second linear motor having a second oscillating coil or a second piezoelectric element.

[0009] The advantage is that completely new kinematics can be achieved when machining the working surface. Although previously only rapid, oscillating position changes were possible in the feed direction, now the cutter can also move in an extremely fast oscillating manner in the transverse direction. This also makes it possible to use turning tools with a larger radius of curvature, because from now on, working paths on the workpiece surface are possible, in which the cutter can be better manipulated around multiple positions so that material is not stripped at undesired locations. As a result, when machining the end face of a rotating workpiece, it is possible to deviate from the original machining path to the left or right depending on the rotation angle position. In addition, if the cutter is turned 90 degrees, there is the option of the cutter moving unsteadily along the machining path. The linear motor has a piezoelectric actuator or an oscillating coil and can also be called a fast tool or a fast tool servo (motor). In principle, the present invention can also be implemented with the aid of a fast tool or a fast tool servo (motor) of a technically different design.

[0010] If two motion profiles in the transverse direction are to be realized simultaneously, there is a design option according to the invention: the tool holder is driven in a swinging or slidable manner in a second transverse direction transverse to the feed direction and transverse to the first transverse direction by means of a third linear motor having a third oscillating coil or a third piezoelectric element. This enables movement in all three machine axis directions, i.e., in a three-dimensional and four-dimensional oscillating manner, in particular in terms of feed depth (in / out relative to the workpiece) by means of the first linear motor, transverse to the cutting direction (left / right relative to the cutting direction) by means of the second linear motor, and along the cutting direction (forward / backward relative to the cutting direction) by means of the third linear motor.

[0011] Optionally, the first and second linear motors (and optionally the third linear motor) can be arranged in a common housing. Due to the short adjustment paths in the transverse and feed directions, such a housing can be designed to be relatively small. In this way, a finished assembly is provided which can be replaced and retrofitted in existing machines. The tool holder should protrude from the housing.

[0012] In a first variant, the first linear motor is driven together with the tool holder in a swiveling or slidable manner in a transverse direction by means of a second linear motor (optionally also in a second transverse direction by means of a possible third linear motor). This makes it possible to produce the first linear motor and the tool holder in a stable manner together. Preferably, the first linear motor and the tool holder are arranged on a slide, on which they are slidably supported by means of the second linear motor. The slide can also be arranged in an optional common housing. Optionally, the tool holder can be rigidly connected to the first linear motor. This enables a high-precision adjustment path. The tool holder can also optionally be rigidly connected to the second linear motor. This makes it possible to implement the adjustment commands of the second linear motor with high precision.

[0013] In a second variant, the first linear motor and the second linear motor (optionally also the optional third linear motor) are fixed firmly relative to each other. They cannot therefore move relative to each other. As a result, the mass to be moved can be reduced and adjustments can be performed more quickly than if one of the linear motors were driven by the other linear motor. It is possible here that the tool holder can be connected to the first linear motor in a floating or swinging manner or via a bending element. This allows a defined movement between the tool holder and the first linear motor, which movement is performed by the tool holder via the second linear motor. In addition or as an alternative, the tool holder can be connected to the second linear motor in a floating or swinging manner or via a bending element. This allows a defined movement between the tool holder and the second linear motor, which movement is performed by the first linear motor.

[0014] In one embodiment of the tool drive unit, it is proposed that the tool holder, the first linear motor and the second linear motor (optionally also the optional third linear motor) form an assembly or part of the assembly, wherein the assembly is arranged on a cross slide. The cross slide enables additional movements for positioning the tool holder, which is particularly helpful due to the limited adjustment path of the oscillating coil or the piezoelectric element. In addition, cross slides are already present in a large number of machine tools, so that the assembly can be easily retrofitted by being mounted on such a cross slide. In particular, the common housing of the first and second linear drives (optionally also the third linear motor) can belong to the assembly.

[0015] Optionally, the cross slide has a cross slide drive, by means of which the component can be driven linearly slidably in the feed direction and linearly slidably in the transverse direction. This allows movements that cannot be performed by the oscillating coil or the piezoelectric element alone due to the limited adjustment path.

[0016] The first and second linear drives (optionally also the optional third linear motor) and the cross slide drive preferably have a common control or regulating unit. This allows the movement for positioning the tool holder to be superimposed in a targeted manner. For the same reason, the regulating unit should control or regulate the rotation of the workpiece.

[0017] In a more detailed design, the free adjustment path of the cross slide is at least ten times larger than the free adjustment path of the first and second linear motors (optionally also the optional third linear motor). This allows large adjustment paths to be achieved, for example for workpiece or tool switching.

[0018] Furthermore, in a specific embodiment, it is proposed that the free adjustment path of the first linear motor in the feed direction is at least five times, preferably at least eight times, and particularly preferably at least ten times larger than the free adjustment path of the second linear motor in the transverse direction. This has the advantage that during turning, considerable height differences can be generated on the surface by the oscillating movement of the first linear motor, whereas in the transverse direction only relatively small corrections of the tool cutter are almost always required. Running along a small adjustment path in the transverse direction almost always requires very small transverse corrections of the tool cutter. Running along a small adjustment path in the transverse direction stably supports and focuses the second linear motor on fast, short movements. The optional third linear motor preferably has a free adjustment path in the transverse direction, which is at most one-fifth, preferably at most one-eighth, and particularly preferably at most one-tenth of the free adjustment path of the first linear motor in the feed direction.

[0019] In practice, it is proposed to configure the tool drive unit so that the free adjustment path of the first linear motor in the feed direction is between 5 mm and 60 mm, preferably between 10 mm and 50 mm, more preferably between 15 mm and 40 mm, even more preferably between 18 mm and 35 mm, and particularly preferably between 20 mm and 30 mm. In practice, this adjustment path meets most height curves that require rapid rotation.

[0020] Furthermore, it is recommended in practice to design the tool drive unit such that the free adjustment path of the second linear motor and / or the optional third linear motor in the transverse direction is between 0.5 mm and 10.0 mm, preferably between 1.0 mm and 7 mm. 0.0 mm, more preferably 1.2 mm to 5.0 mm, even more preferably 1.4 mm to 3.5 mm, and particularly preferably 1.5 mm to 2.5 mm. In practice, this adjustment path satisfies most corrections of the workpiece support in the transverse direction relative to the workpiece.

[0021] Optionally, a turning tool with a cutter can be arranged on the tool holder. This can be, for example, a cutting blade or an indexing blade. The cutter should be designed in a defined manner in particular. The cutter can have a curvature and a cutting radius, preferably in the cutting plane. The curvature ensures that only a portion of the cutting length is sunk into the workpiece and that a groove is cut into the workpiece to a certain extent. The cutting radius should define the sharpness of the cutter.

[0022] In a preferred embodiment, the curvature of the cutting blade of the turning tool has a radius between 3.0 mm and 12.0 mm, preferably between 3.5 mm and 10.0 mm, more preferably between 4.0 mm and 9.0 mm, and particularly preferably between 5.0 mm and 8.0 mm. The advantage of such a large tool radius is that the spiral length required for producing the flat surface is short. Thus, for example, when producing a flat surface with a diameter of 70 mm, the spiral length is halved, which is close to the processing surface of the lens blank for producing eyeglass lenses, from about 72 mm with a 2 mm tool radius to about 38 mm with an 8 mm tool radius. Accordingly, the processing time is significantly shortened, and there is no need to increase the workpiece speed for this purpose. Therefore, with such a large radius, the workpiece can be processed quickly and efficiently. Here, the problem of generating a height curve on the processing surface, which typically results in a large tool radius, can be compensated by the second linear drive.

[0023] Preferably, the cutting radius of the cutting blade of the turning tool is preferably between 0.5 μm and 8.0 μm, preferably between 1.0 μm and 7.0 μm, more preferably between 1.5 μm and 5.0 μm, and particularly preferably between 2.0 μm and 3.0 μm. The cutting radius is particularly suitable for processing materials for optical lenses, such as glass and plastic.

[0024] Furthermore, the cutting blade of the turning tool should consist of natural diamond, synthetic diamond or ceramic, or have a CVD diamond layer (CVD=Chemical Vapor Deposition) on a carrier substrate. As a result, the cutting blade is long-lived and its geometry hardly changes during its life.

[0025] Typically, the cutter has a main cutting direction in which the cutter and the workpiece move relative to each other for cutting. Preferably, the transverse direction is oriented transversely to the main cutting direction. However, alternatively or additionally to the superposition, the transverse direction can also be oriented identically to the main cutting direction.

[0026] The invention also relates to a turning device for machining a workpiece, comprising: a workpiece support, which is configured to accommodate the workpiece and is driven to rotate about a virtual rotation axis; and a turning tool, which has a cutter. In addition, the turning device has a main feed drive, which causes a main feed movement in a feed direction, wherein the turning tool and the workpiece support can move closer to each other or farther from each other by the feed movement, which is preferably oriented substantially or exactly in the same direction as the rotation axis. In addition, the turning device has a main transverse drive, which causes a main transverse movement in a transverse direction transverse to the feed direction, wherein the turning tool and the rotation axis can move closer to each other or farther from each other by the main transverse movement, which is preferably oriented substantially or exactly in the transverse direction relative to the rotation axis. Here, according to the invention, it is proposed that the turning device has a secondary transverse drive, the secondary transverse movement of which is oriented in the same direction as the transverse movement of the main transverse drive, wherein the turning tool and the rotation axis can move closer to each other and farther from each other by superposition of the main and secondary transverse movements.

[0027] The advantages are new possibilities for kinematics when machining the working surface. From now on, the cutter can be moved in a transverse direction in an extremely fast oscillating manner. This also makes it possible to use turning tools with a larger radius of curvature, since now a working path on the workpiece surface is possible, in which the cutter can be better manipulated around multiple positions so that material is not stripped off at undesired locations. As a result, when machining the end faces of rotating workpieces, it is possible to deviate from the original machining path to the left or right, depending on the rotation angle position. In addition, if the cutter is turned 90 degrees, there is the option of the cutter moving unsteadily along the machining path. This makes it possible, for example, to temporarily reduce the absolute cutting speed in order to implement a position change of the cutter in the feed direction.

[0028] As a result, a steeper rise in the height curve can be achieved and, for example, an otherwise too slow feed change can be compensated.

[0029] The workpiece support is designed to be rotatably drivable about a virtual axis of rotation by means of a workpiece spindle drive.

[0030] The workpiece can be an optical lens or an optical lens blank, and the workpiece holder can be designed to accommodate the optical lens or the optical lens blank.

[0031] The relative movement according to the invention can alternatively or additionally be generated on the side of the workpiece support in the turning device according to the invention. Due to the lower mass inertia, the secondary traverse movement and the secondary feed movement of the turning tool should preferably be carried out. The main traverse movement and the main feed movement can mainly be carried out optionally by the movement of the tool support or the turning tool. In a specific embodiment, it is proposed that the tool drive unit carries out at least the secondary traverse movement and the secondary feed movement as described above and below.

[0032] In a specific embodiment, it is proposed that the turning device has a tool drive unit as described above and below, wherein a turning tool with a cutting blade is accommodated in a tool holder, wherein a first linear motor causes a secondary feed movement in a feed direction that is (at least substantially or exactly) the same as the feed direction of the main feed drive, wherein the turning tool and the workpiece holder can be moved toward each other and away from each other by superimposing the main and secondary feed movements, and wherein the second linear motor forms a secondary transverse drive. These advantages correspond to the advantages described for the possible design possibilities of the tool drive unit.

[0033] Optionally, the turning device can have a tool drive unit, wherein the tool holder, the first linear motor and the second linear motor constitute a component or are part of the component, wherein the component (G) is arranged on a cross slide, and wherein the cross slide belongs to the main feed drive and the main transverse drive and serves as a movement axis to realize the main feed movement and the main transverse movement.

[0034] In principle, optional design variants of the turning device also consist in optional design variants of the tool drive unit. This means that the turning device can optionally be equipped with one or more of the following features, with reference to the advantages described above in each case:

[0035] The first linear motor and the tool support are driven in a lateral direction so as to be swingable or slidable by means of a second linear motor;

[0036] The first linear motor and the tool holder are arranged on the slide, and they are slidably supported on the slide by means of the second linear motor;

[0037] The tool support is rigidly connected to the first linear motor;

[0038] The tool support is rigidly connected to the second linear motor;

[0039] The first linear motor and the second linear motor are fixedly secured relative to each other;

[0040] The tool support is connected to the first linear motor in a floating or swinging manner;

[0041] The tool support is connected to the second linear motor in a floating or swinging manner;

[0042] The tool support, the first linear motor and the second linear motor form or are part of an assembly, wherein the assembly is arranged on a cross slide;

[0043] The tool holder is driven in a pivotable or slidable manner in a second transverse direction transverse to the feed direction and transverse to the first transverse direction by means of a third linear motor having a third oscillating coil or a third piezoelectric element;

[0044] The cross slide has a cross slide drive, by means of which the component can be driven linearly movably in the feed direction and can be driven linearly movably in the transverse direction;

[0045] The free adjustment path of the cross slide, in particular the main feed movement and the main lateral movement, is at least ten times greater than the free adjustment path of the first and second linear motors or the secondary feed movement and the secondary lateral movement;

[0046] The free adjustment path of the first linear motor in the feed direction is at least five times, preferably at least eight times, and particularly preferably at least ten times greater than the free adjustment path of the second linear motor in the transverse direction;

[0047] The free adjustment path of the first linear motor in the feed direction is between 5 mm and 60 mm, preferably between 10 mm and 50 mm, more preferably between 15 mm and 40 mm, still more preferably between 18 mm and 35 mm, and particularly preferably between 20 mm and 30 mm;

[0048] The free adjustment path of the second linear motor in the transverse direction is between 0.5 mm and 10.0 mm, preferably between 1.0 mm and 7.0 mm, more preferably between 1.2 mm and 5.0 mm, still more preferably between 1.4 mm and 3.5 mm, and particularly preferably between 1.5 mm and 2.5 mm;

[0049] Definitely constitute a cutter;

[0050] The cutter has a curvature preferably in a cutting plane and has a cutting radius;

[0051] The curvature of the cutting blade of the turning tool has a radius of 3.0 mm to 12.0 mm, preferably 3.5 mm to 10.0 mm, more preferably 4.0 mm to 9.0 mm, particularly preferably 5 mm. 0 mm and 8.0 mm;

[0052] The seven radii of the cutter of the turning tool are between 0.5 μm and 8.0 μm, preferably between 1.0 μm and 7.0 μm, more preferably between 1.5 μm and 5.0 μm, and particularly preferably between 2.0 μm and 3.0 μm;

[0053] The cutting blades of the turning tools consist of natural diamond, synthetic diamond or ceramic or have a CVD diamond layer (CVD = chemical vapor deposition) on a carrier substrate;

[0054] The cutter has a main cutting direction in which the cutter and the workpiece are moved relative to each other for cutting, and

[0055] Furthermore, there are the above-mentioned optional embodiments of the tool drive unit.

[0056] The present invention also relates to a method for cutting an end face of a workpiece driven around a virtual rotation axis by means of a turning tool having a cutter, the method comprising the following steps:

[0057] Rotating the workpiece about a virtual rotation axis;

[0058] Bringing the cutting blade into engagement with an end face of the workpiece spaced apart from the axis of rotation; this is particularly carried out during a rotation of the workpiece about a virtual axis of rotation;

[0059] performing a main transverse movement of the cutter towards the axis of rotation, while the cutter also engages in the end face of the rotating workpiece, so that the cutter is guided along a helical working path over the end face by the superposition of the rotation of the workpiece and the transverse movement of the cutter,

[0060] The main transverse movement of the cutting knife is superimposed with a secondary transverse movement of (at least substantially or exactly) the same orientation, which takes place towards and away from the axis of rotation, wherein the secondary transverse movement is carried out as a function of the rotational angle position of the workpiece.

[0061] The advantage is that the main transverse movement can be performed by a first drive, which is designed for slow and long adjustment paths, while the secondary transverse movement can be implemented by means of a drive, which is designed for short, fast and direction-changing adjustment paths. In this way, the position of the cutter along the processing path is changed in a targeted manner with the secondary transverse movement according to the main transverse movement. This allows, for example, cutting with a large radius in order to manipulate around a locally generated bulge on the processing surface. This prevents unintentional straightening of such a bulge. This is achieved in the area around the axis of rotation, because it can be determined at what angle the cutter moves close to the axis of rotation and at what angle it does not approach the axis of rotation. In this case, the main transverse movement and the secondary transverse movement should be generated by different drives.

[0062] In particular, the method can be carried out using the tool drive unit or the turning device described above and below and corresponding optional design options.

[0063] This method is particularly suitable when the workpiece is an optical lens or an optical lens blank with a curved end face. With this method, it is possible to produce a machined surface which has a tangent in the region of the axis of rotation which is not orthogonal to the axis of rotation. This is particularly important when producing ophthalmic lenses, since in this case the surface must be curved. As a good approximation, the surfaces around the axis of rotation can usually be considered as prismatic surfaces, ie planes that are inclined relative to the axis of rotation.

[0064] In one method variant, it is proposed that the secondary transverse movement of the cutter consists of a forward and backward movement for each revolution of the tool. The contact can be formed to a certain extent in the main movement path at each revolution, and / or the spiral path can be offset laterally relative to the axis of rotation, and / or the spiral shape can be elliptically tightened.

[0065] According to a specific method embodiment, it is proposed that the secondary transverse movement comprises a stroke per revolution of the tool, that is, in particular, it has exactly one secondary transverse movement directed forward and exactly one secondary transverse movement directed backward, so that in certain rotational angle positions of the workpiece, a deviation from the spiral working path of the main transverse movement occurs. In this way, in particular, a heart-shaped working path can be generated from the spiral working path to a certain extent. In this case, the tip of the heart-shaped working path can be used to briefly move the cutter to the axis of rotation.

[0066] In this case, there is a method option in which the spiral working path has a height curve with at least one vertex and a valley, wherein the stroke approaches the axis of rotation to the greatest extent at a rotation angle at which the axis of rotation is located between the cutter and the valley. This makes use of the fact that the cutter does not come into contact with the surface on the rear side of the axis of rotation when approaching the axis of rotation, since the valley is located there at the time of the stroke. The cutter can therefore be moved to such an extent that it protrudes into the valley without damaging the end face of the workpiece there. This makes it possible to achieve kinematics by means of which prismatic machining can be carried out with a larger tool radius, so that the measured values ​​of the sphere and cylinder in the region of the machining center, i.e. the axis of rotation, are within the required tolerances.

[0067] For the same reasons, in a specific method variant, it is provided that the cutter moves, with a stroke as close to the axis of rotation as possible, until it passes over the axis of rotation and into the valley. In particular, it should be provided that the cutter floats above the end face in the region of the valley with a stroke as close to the axis of rotation as possible and engages with the end face on the opposite side of the valley. The end face is held in the region of the valley without damage by the suspension.

[0068] Alternatively, for machining a prismatic end face that is U-shaped in the center about the axis of rotation, it can also be provided that two strokes of the secondary transverse movement are also performed corresponding to two valleys and two vertices per revolution. This is also applicable in even more complex designs with more vertices and valleys per revolution, where this is more theoretical. In most cases, the tangent in the region of the axis of rotation can be regarded as a prismatic surface.

[0069] According to a specific embodiment of the method, at least one depression or heart-shaped indentation of the working path is produced in the direction of the rotation axis by superimposing a primary transverse movement by a secondary transverse movement along the spiral working path, so that the cutter is moved closer to the rotation axis at a defined rotation angle than at other rotation angles.

[0070] Preferably, the main transverse movement is only a forward movement. Accordingly, a relatively cheap drive can be used for this purpose, which drive can also implement a large adjustment path.

[0071] One method configuration provides that the main transverse movement has a continuous speed profile, for example a constant speed. Such a continuous speed profile can also be realized with the aid of a relatively inexpensive drive, which is suitable for large adjustment paths.

[0072] A special method variant is that no secondary lateral movement is performed outside the limit distance of the cutter from the rotation axis and only from the limit distance. This allows machining to be performed in a classical manner further out, while the peculiarities of the cutter approaching the rotation axis can be taken into account in the center.

[0073] In particular, experiments have shown that the limit distance is less than 2.00 mm, preferably less than 1.20 mm, more preferably less than 0.70 mm, even more preferably less than 0.50 mm, and particularly preferably less than 0.35 mm. In this region, the phenomenon occurs that the cutter contacts the end face with its rear side and is damaged as soon as it protrudes slightly beyond the axis of rotation. The greater the curvature of the channel, the greater the limit distance should be selected.

[0074] Depending on how machining looks, especially in the outer regions of the end face, the spiral working path can result from an Archimedean spiral, a logarithmic spiral or a hyperbolic spiral. Most likely, an Archimedean spiral is used in order to turn the entire end face. A hyperbolic spiral is particularly suitable for remachining regions of the end face around the axis of rotation. This allows the axis of rotation to be approached relatively quickly. In the case of a logarithmic spiral, the approach to the axis of rotation is particularly slow. Therefore, it is optionally proposed to use an Archimedean spiral or a hyperbolic spiral in the outer regions and to transition to a logarithmic spiral when the limit distance from the axis of rotation is reached.

[0075] The workpiece can be, for example, an optical lens or an optical lens blank. In this method compensation concept, it is provided that the workpiece is a blank for producing an ophthalmic lens and that free-form surfaces are produced from the end faces by turning, depending on the prescription, by means of which the vision defects of the prescription holder can be corrected.

[0076] In addition, it can be provided that after the end face machining is completed, the workpiece is circumferentially adapted to the spectacle frame, thereby enabling the workpiece to be installed in the frame of the desired spectacle frame.

[0077] The invention further relates to the use of a tool drive unit as described above and below or a turning device as described above and below for carrying out a method as described above and below, which enables fast and efficient turning of the end face, which itself is very precise in the area of ​​the axis of rotation. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] Further features, details and advantages of the invention are apparent from the wording of the claims and from the following description of an exemplary embodiment with reference to the accompanying drawings. It is shown:

[0079] Figure 1 A perspective view showing a tool drive unit;

[0080] Figure 2 Show according to Figure 1 Different perspective views of a tool drive unit;

[0081] Figure 3 Shows that the Figure 1 A horizontal cross-section of a tool drive unit;

[0082] Figure 4 Shown according to Figure 1 A perspective view of a turning device with a tool drive unit of the type;

[0083] Figure 5 Shows that the Figure 4 Horizontal section of the turning equipment;

[0084] Figure 6 a schematic sketch showing a turning tool engaging a prismatic end face of a workpiece;

[0085] Figure 7 a second schematic sketch showing a turning tool engaging a prismatic end face of a workpiece;

[0086] Figure 8 a third schematic sketch showing a turning tool engaging a prismatic end face of a workpiece; and

[0087] Fig. 9 A phase diagram with feed motion and lateral motion is shown.

[0088] Description of Reference Numerals

[0089] 1 Turning equipment

[0090] 2 Tool drive unit

[0091] 3 Housing

[0092] 4 Coolant supply line

[0093] 5 Coolant drain line

[0094] 10 Workpiece support

[0095] 11 Bed

[0096] 12 Workpiece spindle drive

[0097] 20 Turning tools

[0098] 20b Second turning tool

[0099] 21 Cutter

[0100] 40 Main feed drive

[0101] 50 Main transverse drive

[0102] 55 Transverse drive

[0103] 80 Tool holder

[0104] 81 First Linear Motor

[0105] 82 First oscillation coil

[0106] 83 Slider

[0107] 84 Slider lubricant line

[0108] 85 Second linear motor

[0109] 86 Second oscillation coil

[0110] 87 Lubricant lines

[0111] 88 Compressed air connection

[0112] 90 Cross Slider

[0113] 91 Cross slide drive

[0114] 92 Milling Stations

[0115] 93 Milling head

[0116] 100 workpieces

[0117] A Rotation axis

[0118] B Vertex

[0119] F End face

[0120] G Structural unit

[0121] H Main cutting direction

[0122] K Curvature

[0123] QPS primary and secondary lateral motion

[0124] QR horizontal direction

[0125] T Valley

[0126] SR cutting radius

[0127] X limit spacing

[0128] ZPS main and auxiliary feed motion

[0129] ZR Feed direction DETAILED DESCRIPTION

[0130] Figure 1 A perspective view showing a tool drive unit 2 of a turning device for turning a workpiece (see FIG. Figure 5 ), the tool drive unit is configured as a component G. Figure 2 The component G is shown from different perspectives in FIG. The same reference numerals therefore relate to the same components, since Figure 1 and 2 are described together. Component G has a common housing 3. A tool holder 80 protrudes on one side of the housing 3, in which a turning tool 20 with a defined cutter 21 is accommodated and a second turning tool 20b is additionally accommodated adjacently. The cutter 21 can, for example, consist of natural diamond, synthetic diamond or ceramic, or have a CVD diamond layer (CVD=chemical vapor deposition) on a carrier substrate. The cutter 21 has a main cutting direction H, in which the cutter 21 and the workpiece 100 move relative to each other for cutting. When using the tool drive unit 2 to process a lens blank during the manufacture of an eyeglass lens, a cutter 21 having a curvature in the cutting plane and a cutting radius having the following dimensions is used. The curvature of the cutter should be between 3.0 mm and 12.0 mm. The cutting radius of the cutter 21 should be between 0.5 μm and 8.0 μm.

[0131] The tool support 80 is driven by means of a first linear motor 81 so as to be slidable along the feed direction ZR. Figure 3 It can be seen from the sectional view of that the first linear motor 81 has a first oscillating coil 82. In addition, a first piezoelectric element can also be provided. In addition, the tool holder 80 is driven in a swinging or sliding manner in a transverse direction QR transverse to the feed direction ZR by means of a second linear motor 85. In particular, the transverse direction QR is also oriented transversely to the main cutting direction H. As shown in Figure 3 As can be seen in the sectional view of , the second linear motor 85 has a second oscillating coil 86. Alternatively, a second piezoelectric element can be used here. The second linear motor 85 thus forms a secondary transverse drive 55 for the turning process.

[0132] If also from Figure 3It can be seen that the first linear motor 81 together with the tool holder 80 can be driven in the transverse direction QR by means of the second linear motor 85. For this purpose, the first linear motor 81 and the tool holder 80 are placed on a slide 83, on which they are slidably supported by means of the second linear motor 85. The tool holder 80 is rigidly connected to the first linear motor 81 and indirectly via the slide 83 is also rigidly connected to the second linear motor 85.

[0133] In addition, Figure 3 8 and 9 show the various connections for the fluid lines. Thus, a coolant supply line 4 and a coolant discharge line 5 are provided for the cooling assembly G. The slide 83 is lubricated by means of a slide lubricant line 84. The lubricant line 87 serves to lubricate the bearing of the secondary feed movement in the feed direction ZR. Finally, a compressed air connection 88 is provided, by means of which the housing 3 is pressurized so that no dirt can enter the interior of the housing 3 through any seals.

[0134] like Figure 1 , 2 Such a component G shown in FIG. 3 can be arranged, for example, on a cross slide of a turning device. Such a cross slide then has a cross slide drive, by means of which the component G is driven in a linearly slidable manner in the feed direction ZR and in a linearly slidable manner in the transverse direction QR.

[0135] Of course, unlike this optional application, according to Figure 4 and Figure 5 The cross slide 90 of the turning device 1 is arranged on the workpiece side, and the assembly G is connected to the frame or machine base 11 in a fixed position. The cross slide 90 also places the assembly G on the machine base 11 and carries the workpiece support 10, which is configured to accommodate the workpiece 100 and is driven in a rotational manner around the virtual rotation axis A. For this purpose, the workpiece support 10 is driven in rotation by means of a workpiece spindle drive 12. The workpiece 100 is an optical lens blank having a curved and prismatic end face F for manufacturing eyeglass lenses.

[0136] On the one hand, the cross slide 90 forms a main feed drive 40 which brings about a main feed movement in a feed direction ZR, wherein the turning tool 20 and the workpiece support 10 or the cutter 21 and the end face F of the workpiece 100 can be moved toward or away from each other by the feed movement, which is currently oriented in the same direction as the rotation axis A.

[0137] On the other hand, the cross slide 90 constitutes a main transverse drive 50, which causes a main transverse movement along a transverse direction QR transverse to the feed direction ZR, wherein the turning tool 20 or its cutter 21 and the rotation axis A can be moved towards or away from each other by the main transverse movement, and this transverse movement can move relative to or away from each other, which in the present case is currently oriented in the same direction as the rotation axis A.

[0138] By means of the tool drive unit 2 arranged opposite, in particular the first linear motor 81, an auxiliary feed movement is generated in the feed direction ZR oriented in the same direction as the main feed drive 40. Thus, by superposition of the main and auxiliary feed movements, the turning tool 20 and the workpiece support 10 are driven in a movement that allows them to move toward and away from each other.

[0139] The second linear motor 85 of the tool drive unit 2 forms a secondary transverse drive 55, whose secondary transverse movement is oriented in the same direction as the secondary transverse movement of the main transverse drive 50. As a result, the turning tool 20 or its cutting tool 21 and the axis of rotation A are driven in a movement that can move toward and away from each other by superimposing the main and secondary transverse movements.

[0140] The free adjustment path of the cross slide 90 is at least ten times greater than the free adjustment path of the first and second linear motors 81, 85. Furthermore, the free adjustment path of the first linear motor 81 in the feed direction ZR is at least five times greater than the free adjustment path of the second linear motor 85 in the transverse direction QR. When manufacturing an ophthalmic lens from a lens blank, the free adjustment path of the first linear motor 81 in the feed direction ZR is preferably between 5 mm and 60 mm. In contrast, the free adjustment path of the second linear motor 85 in the transverse direction QR should only be between 0.5 mm and 10.0 mm.

[0141] exist Figure 4 and Figure 5 In the figure, adjacent to the tool drive unit 2, a milling head 93 of an optional milling station 92 can also be identified in the work space. The workpiece 100 can also be positioned in the milling station 92 for milling processing by means of the workpiece support 10 and the cross slide 90.

[0142] With the aid of such a turning device 1, it is now possible to carry out a method for machining an end face F of a workpiece 100 driven about a virtual axis of rotation A by means of a turning tool 20 or its cutter 21. In this method, during the rotation of the workpiece 100 about the virtual axis of rotation A, the cutter 21 engages with the end face F of the workpiece 100 in a manner spaced apart from the axis of rotation A. Prior to or since the engagement, a main transverse movement of the cutter 21 towards the axis of rotation A has already been carried out, while the cutter 21 also engages in the end face F of the rotating workpiece 100, so that the cutter 21 is guided along a spiral working path over the end face F by the superposition of the rotation of the workpiece 100 and the transverse movement of the cutter 21. This engagement is Figure 6 , in which it can be seen that the end face F of the workpiece 100 to be machined is inclined relative to the virtual rotation axis A, i.e. prismatic. For example, the workpiece 100 can already be pre-machined in this way at an inclined position in the milling station 92. The spiral working path thus has a height curve with apex B and valley T, wherein the travel to the rotation axis A of the secondary transverse movement takes place at a rotation angle in which the rotation axis A is located between the cutter 21 and the valley T.

[0143] The inclined end face F makes it particularly necessary that the position of the cutter 21 moves back in the feed direction ZR during each revolution of the workpiece 100, as is done in accordance with Fig. 9 Each peak of the variation curve ZPS obtained by summing the main feed motion and the secondary feed motion here represents a 360-degree rotation of the workpiece. The closer the cutter 21 is to the axis of rotation A, the smaller the feed motion ZPS becomes, because the height positions of the apex B and the valley T of the end face F are no longer so far apart from each other. Figure 6 In particular, the distance of the cutting blade 21 from the axis of rotation A is shown, wherein there is absolutely no risk of the cutting rear side coming into contact with the end face F. Fig. 9 The phase diagram of corresponds to segment I. In this case, the cutter 21 is moved towards the axis of rotation A solely by a main transverse movement, wherein the main transverse movement is only a forward movement with a continuous, in particular linear, speed profile.

[0144] In addition, according to the method, a superposition of a main transverse movement of the cutting knife 21 with a phase-oriented secondary transverse movement can be performed, which takes place towards the rotation axis A and away from the rotation axis A, wherein the secondary transverse movement is performed as a function of the rotational angle position of the workpiece 100. Fig. 9 The main lateral movement, which is also linear and axial in phase I, is then significantly superimposed by the secondary lateral movement in phases II and III. Therefore, no secondary lateral movement is performed outside the limit distance X of the cutter 21 from the axis of rotation A, and the secondary lateral movement is only performed from the limit distance X. In the production of ophthalmic lenses with a cutting curvature K of a radius of 8 mm, it is proposed that the limit distance X is determined to be approximately 0.35 mm.

[0145] The secondary transverse movement starts slowly in phase II and then develops in phase III. A cumulative transverse movement curve QPS is then generated therefrom, which is composed of the primary and secondary transverse movements. The peak of the cumulative transverse movement curve QPS can be identified because the secondary transverse movement is in phase with the peak of the cumulative feed movement. This is confirmed in the case of a prismatic end face F by the fact that for each revolution of the workpiece 100, the cutter must approach the axis of rotation A to the maximum extent just once and then move away from the axis of rotation A so that the area on the side of the end face F opposite the axis of rotation A is not damaged by the cutter 21.

[0146] To this end, according to Figure 7 It is obvious from the schematic diagram of FIG: the approach of the cutter 21 to the axis of rotation A in the illustrated embodiment does not appear to be critical, since the cutter is significantly suspended above the valley side T. However, if the workpiece 100 is rotated 180 degrees about the axis of rotation and the penetration depth of the cutter in the end face F is to be maintained by means of a change in position in the feed direction ZR, this inevitably leads to contact between the cutter and the peak side B. Therefore, as in FIG Figure 8 It can be clearly seen that the cutter 21 is again pulled a certain distance away from the rotation axis A in the transverse direction QR. In order to also be able to turn off the remaining last area around the rotation axis A, it is necessary to reduce the penetration depth of the cutter 21 into the end face F for the sake of finishing, wherein the pullback of the cutter 21 according to the invention in the transverse direction is finally maintained at each penetration depth in order to cause damage to the end face F on the side of the peak side B and nevertheless be able to approach the rotation axis A to the greatest extent possible. In this regard, from Fig. 9 It is evident from the curve ZPS in FIG. 1 that the accumulated feed movement not only becomes smaller and smaller, but also decreases once to a zero value at the end of phase III per revolution. Thus, material removal only takes place adjacent to this rotational angle position of the workpiece 100, with the maximum material removal taking place on the side of the peak side B. Finally, the zero value is reached at the intersection of the horizontally marked zero point line and the axis of rotation A.

[0147] If the influence of the secondary transverse movement is taken into account in terms of the change of the Archimedean spiral as a function of the primary transverse movement, it is recognized that the axis of rotation A is always approached on the peak side B and is always moved away from the axis of rotation A on the opposite valley side T. This results in a deformation of the actual Archimedean spiral or an eccentric positioning, for example a depression or a heart-shaped recess in the working path in the direction of the axis of rotation A, or also a displacement of the center point of the working path relative to the axis of rotation A. This also depends in particular on how quickly the secondary transverse movement is carried out. The invention is not limited to one of the above-described embodiments, but can be modified in many ways.

[0148] All features and advantages resulting from the claims, the description and the drawings, including structural details, spatial arrangements and method steps, are essential to the invention, both individually and in multiple combinations.

Claims

1. A turning device (1) for cutting a workpiece (100), comprising: A workpiece support (10), which is configured to accommodate the workpiece (100) and is driven to rotate about a virtual rotation axis (A), A turning tool (20) having a cutting tool (21), a main feed drive (40) which brings about a main feed movement in a feed direction (ZR), wherein the turning tool (20) and the workpiece support (10) can be moved toward one another or away from one another by means of the feed movement, and a main transverse drive (50) which brings about a main transverse movement in a transverse direction (QR) transverse to the feed direction (ZR), wherein the turning tool (20) and the axis of rotation (A) can be moved towards one another or away from one another by means of the main transverse movement, It is characterized in that The turning device (1) has a secondary transverse drive (55), the secondary transverse movement of which is oriented in the same direction as the transverse movement of the main transverse drive (50), wherein the turning tool (20) and the axis of rotation (A) can be moved towards and away from each other by superimposing the main and secondary transverse movements.

2. The turning device (1) according to claim 1, characterized in that The turning device (1) has a tool drive unit (2) for cutting a workpiece (100) to be processed, wherein the workpiece (100) is an optical lens or an optical lens blank having a curved end face (F), and the tool drive unit (2) has a tool holder (80) for accommodating a turning tool (20) having a cutter (21). The tool support (80) can be driven in a sliding manner in a feed direction (ZR) by means of a first linear motor (81), wherein the first linear motor (81) has a first oscillating coil (82) or a first piezoelectric element. The tool support (80) is driven in a pivotable or slidable manner in a transverse direction (QR) transverse to the feed direction (ZR) by means of a second linear motor (85), wherein the second linear motor (85) has a second oscillating coil (86) or a second piezoelectric element, wherein the turning tool (20) having the cutting blade (21) is accommodated in the tool holder (80), wherein the first linear motor (81) causes a secondary feed movement in the same feed direction (ZR) as the feed direction of the main feed drive (40), wherein the turning tool (20) and the workpiece support (10) can be moved towards each other and away from each other by superposition of the main and secondary feed movements, and The second linear motor (85) constitutes a secondary transverse drive (55).

3. The turning device (1) according to claim 2, characterized in that The first linear motor (81) is driven together with the tool holder (80) by means of the second linear motor (85) in a pivotable or slidable manner in the transverse direction (QR).

4. The turning device (1) according to claim 2 or 3, characterized in that The tool support (80), the first linear motor (81) and the second linear motor (85) form a component (G) or are part of the component (G), wherein the component (G) is arranged on a cross slide (90).

5. The turning device (1) according to claim 4, characterized in that The cross slide (90) belongs to the main feed drive (40) and the main transverse drive (50) and serves as a movement axis to realize the main feed movement and the main transverse movement.

6. The turning device (1) according to claim 4, characterized in that The free adjustment path of the cross slide (90) is at least ten times the free adjustment path of the first linear motor (81) and the second linear motor (85).

7. The turning device (1) according to claim 6, characterized in that The free adjustment path of the first linear motor (81) in the feed direction (ZR) is at least five times greater than the free adjustment path of the second linear motor (85) in the transverse direction (QR).

8. The turning device (1) according to claim 1, characterized in that The cutter (21) has a curvature (K) and a cutting radius (SR), wherein the curvature (K) of the cutter (21) of the turning tool (20) has a radius between 3.0 mm and 12.0 mm.

9. The turning device (1) according to claim 1, characterized in that The workpiece support (10) is designed to have a workpiece spindle drive, and the workpiece support (10) can be driven by the workpiece spindle drive to rotate around a virtual rotation axis.

10. The turning device (1) according to claim 1, characterized in that The tool drive unit (2) performs a secondary traverse movement and a secondary feed movement.

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