DE102010048638A1 - Machine tool, workpiece machining process - Google Patents

Abstract

A machine tool (10) has a cutting tool (7) for workpiece machining with a cutting movement (76) of the tool (7) relative to the workpiece (6) and a vibration unit (11) for generating a vibratory movement (75) between the tool (7) and the workpiece (6). In a workpiece machining method, a cutting movement (76) is caused relatively between a cutting tool (7) and a workpiece (6) and, simultaneously or alternately thereto, a vibratory movement (75) is produced.

Description

The invention relates to a machine tool and a workpiece machining method according to the preambles of the independent claims.

It is known to machine workpieces with tools with a defined cutting edge. The best known methods here are drilling, turning, milling and planing. The associated tools have one or several clearly defined, clearly writable cutting edges. By a relative movement between the tool, in particular the cutting edge thereof, and the workpiece (cutting movement), the machining is effected. It is done with a certain removal rate under a certain tool wear and leaves surfaces with predictable properties within certain limits. When drilling, the tool is usually moved, while turning the workpiece. When milling usually rotates the milling tool, while it or the workpiece itself is moved. When planing the tool or the workpiece can be moved.

It is also known to process workpieces by means of vibrating tools without a defined cutting edge. The vibrating tools are rough, work abrasive and vibrate relatively high frequency (vibrational motion), for example at frequencies above 5 kHz or above 10 kHz or above 20 kHz. Because of the high vibration frequencies, which can be beyond the human ear, the processing is often referred to as ultrasonic processing and the machine as an ultrasonic machine. The vibration of the tool may be a translational or a rotational vibration. The tool can move parallel to the surface of the workpiece and then quasi filing material ablate. But it can also act impacting on the workpiece.

A disadvantage of the known machining methods with tools with a defined cutting edge is that in certain machining situations, in particular for certain workpiece materials, the removal rate is relatively low or the tool wear is relatively high or the surface quality of the machined workpiece is relatively poor. It has been shown that the chip breakage during machining with conventional tools with a defined cutting edge leaves comparatively rough and torn surfaces which are not mechanically resistant and are prone to environmental influences (corrosion, rust).

The object of the invention is to specify a machine tool and a workpiece machining method, which result in improved machining performance in an improved removal rate and / or lower tool wear and / or improved surface qualities, especially smoother and more compact surfaces or surfaces with relatively high compressive residual stress on the workpiece.

This object is achieved with the features of the independent claims. Dependent claims are directed to preferred embodiments of the invention.

A machine tool has a cutting tool for workpiece machining with a cutting movement of the tool relative to the workpiece and a vibration unit for generating a vibrating movement between the tool and the workpiece. In a workpiece machining method, a cutting motion is caused relatively between a cutting tool and a workpiece, and at the same time or alternately, causes a vibratory motion.

The combination of cutting and vibrating machining has the advantage that the removal of the chips from the workpiece with the defined cutting edge of the tool with variable relative movements between the workpiece and the cutting edge. The dissolution of the chips happens thereby less tearing, but increasingly cutting. This results in less rough surfaces, and the workpiece surface has a relatively high compressive residual stress after machining and is less torn and ripped after machining, which is desirable in terms of hardness and surface resistance to environmental and mechanical stress.

The vibration unit is preferably located close to the tool. It can have one or more piezo actuators or electromagnetic actuators. The vibration frequency can be over 5 kHz, over 10 kHz, over 20 kHz or over 40 kHz. The machine tool may be a drill, a milling machine, a lathe, a planer, or the like. The direction of the vibratory motion may be parallel and / or perpendicular to the cutting motion of the tool or have an angle therebetween. It can be parallel to the local instantaneous workpiece surface or have a certain angle greater than 0 ° relative thereto. It can be perpendicular to the workpiece surface.

The tool may be adapted to the possible vibratory motion, such as by roughening, serrating, or otherwise overcoming certain surfaces or edges thereof Tools are modified. The modification may be such that the tool has or avoids certain resonant frequencies.

The vibration unit can be part of a quick-change (automatically changeable) tool and then receive energy through suitable means. For example, a wireless (inductive) energy transmission can be provided.

A controller may control the cutting motion and the vibratory motion.

It can be provided for the determination of process parameters sensor, the process parameters can be returned to the controller. The controls of cutting motion and vibratory motion may follow each other independently or interleaved with each other. The one can be controlled or regulated in accordance with driving or measuring parameters of the other.

Cutting movement and vibration movement can be controlled simultaneously with each other or alternatively independently of each other.

Hereinafter, with reference to the drawings, individual embodiments of the invention will be described. Show it:

1 schematically the view of a machine tool,

2 schematically a control of the machine tool,

3 schematically a tool,

4 schematically directional information

1 schematically shows a machine tool 10 , It has a machine frame 1 on. In operation are on various intermediate links on the machine frame 1 on the one hand, the workpiece 6 and on the other hand, the tool 7 attached. There can be several adjustment axes 2a . 2 B be provided for static adjustment of the translational and / or rotational positions of the tool and / or the workpiece. It can axles 2a between machine frames 1 and tool table 4 be provided and / or adjusting axles 2 B between machine frames 1 and tool 7 ,

Furthermore, at least one drive 3a . 3b provided for the cutting tool or the workpiece table or Werkstückeinspannung. Generally, the drive may be electrical and have a mechanical translation or reduction. The tool may be a milling cutter, in particular an end mill, which is set in rotary motion during workpiece machining in an electrically driven manner. In the case of a drill, the drive can 3b For example, be an electric motor with gearbox, the drill 7 or the drill chuck is rotated. In the case of a lathe, the drive 3a an electric motor with gear, which sets the lathe in rotation. Generally, a drive 3a between machine frames 1 and workpiece 6 lie, and / or it may be a drive 3b between machine frames 1 and tool 7 lie.

The tool 7 can via a quick release 5 . 5a and / or via a tool interface 5b be exchangeable, so that it can be changed quickly and, if necessary, automatically. The quick coupling 5 . 5a can be a conventional cone clutch with a tool-side cone 5a and a corresponding machine-side recording or the like. The tool interface 5b can lie directly on the actual tool and have a receptacle for a tool shank and can have a collet or the like. The workpiece 6 can work on a workpiece table 4 lie and can be tightened there.

It is a vibration unit 11 provided in addition to the conventional cutting motion between tool 7 and workpiece 6 causes a vibratory motion relatively between them. In 1 schematically shows an embodiment in which the vibration unit 11 at the machine frame side end of a quick coupling 5a located. But there are also other positions of the vibration unit 11 possible in the power flow. The vibration unit can also be located closer to the tool, for example on the tool side of the quick coupling 5 , where then between vibration unit 11 and tool still called the other tool interface 5b can be located. The vibration unit 11 can also be near the workpiece table 4 located between the workpiece table 4 and drive 3a or with the actuators 2a or on the machine frame 1 ,

In the embodiment shown, the vibration unit 11 designed the tool 7 to vibrate. The vibration may be a linear vibration or a rotational vibration.

A linear vibration may have directional components parallel and / or perpendicular to the local workpiece plane. In the case of a drill, the vibration can take place along the drill axis. In the case of a drill, the vibration can take place along the drill axis. In a lathe, the lathe tool may be vibrated become. With a milling cutter, the milling tool or the workpiece can be vibrated.

A rotational vibration can take place around an axis of rotation which is already present in the machine and can be introduced by means of a suitably mounted and actuated vibration unit. It can generally be introduced into the component of the machine which has already been subjected to the rotational movement (eg drill chuck or drill). But it can also - around the same axis - generally introduced into the respective opposite of the component acted upon by the rotational movement (in the case of a drill so in the workpiece table or in the workpiece). In a lathe, the lathe chuck may be subjected to a rotational vibration about the axis of rotation. In a milling machine, the milling tool can be acted upon by a rotary vibration around its axis of rotation.

Multiple vibrations, and in particular rotational vibration and linear vibration, can be introduced simultaneously and superimposed over a plurality of vibration units. If several vibration units are provided, they can partly attack on the workpiece or on the workpiece table and partly on the tool or on the tool holder.

A vibration unit may include one or more vibrators, e.g. B. piezo elements having. You can receive the same or different signals. The difference can be a phase offset or an inversion.

The vibration frequency may be above 5 kHz or above 10 kHz or above 20 kHz or above 40 kHz. vibration unit 11 and drive 3a . 3b can be actuated simultaneously or individually alternately operable. The controller can be designed for both operating modes (common, alternating)

The machine tool 10 can be general sensor technology 14 to capture process parameters. The sensor system can have one or more sensors distributed over the machine tool. Via cables 16 the signals are used for control 12 returned and logged there and / or output and / or in turn taken into account for controlling the various machine components. The control 12 has control cables 15 to the individual components of the machine, so in particular to the drives 3a . 3b , Axles 2a . 2 B and to the vibration unit 11 ,

In addition, an output unit, not shown, can be present for operating personnel. 13 symbolizes a data memory (eg semiconductor and / or disk), which on the one hand contains, for example, a machining program for the workpiece, but on the other hand also characteristic values for the cutting movement, for the vibration movements or for the dependencies of control parameters, in particular for the cutting movement and for the Vibration movement of input parameters or determined / measured parameters (tabular, formulaic). The controller can have access to the memory and access there, for example, to two- or multi-dimensional tables for determining manipulated variables from input variables.

At the vibration unit 11 the individual parameters can be adjustable / controllable, in particular vibration frequency, vibration amplitude, waveform of the driving signals, vibration direction, and the like. Individual or several parameters may be controllable, that is to be corrected in accordance with recorded, returned values.

2 schematically shows the control engineering part of a controller. 12 symbolizes the controller of the 1 , Not shown is the program engineering part, which may also be present. It can have stored a machining program that controls the individual machine components and specifies control parameters and setpoints for controls and controls. The control 12 may be digital and may include analog-to-digital converters not shown at the interface to the process. Depending on the respective operating state, the controller 12 or regulation 12 each receive default values, for example, a memory 13 or determined by the said control program.

In 2 is the controller 12 shown schematically as consisting of two parts, namely on the one hand a controller 21 for the conventional drive 3b of the cutting tool 7 , So for example, an electric motor for a drill. The real process is by box to that extent 3b symbolizes. 14a symbolizes sensor technology concerning the conventional cutting motion, which is transmitted via cable 16a is returned.

It is another regulator 22 provided that controls or regulates the vibration movement according to the invention. He gives over lead 15b Signals to the real process from, in particular to the vibration unit 11 , 14b symbolizes sensors for vibration-specific values that are transmitted via line 16b can be traced back.

Basically, vibration movement and cutting motion can be controlled simultaneously or alternately controlled. The controls of each movement can be up Control level independently of each other in accordance with respective individual specifications, or it can be done entangled, for example, by output signals 15a for conventional cutting motion drive also in the controller 22 be introduced for the vibration drive (line 23 ) and / or vice versa, by output signals 15b for the vibration drive 11 into the regulator 21 be entered for the cutting drive (line 24 ). Also, the feedback of signals 16a . 16b if it is provided, also done "crosswise", ie by the controller 22 for the vibration drive process signals relating to the cutting movement receives (line 16a ) and / or vice versa by the controller 21 for the cutting movement receives process signals relating to the vibration movement (line 16b ). The linking and interleaving of the individual parameters can be done formulaically or on the basis of tables which are suitably deposited and kept in reserve.

However, it may also be provided a comparatively simple control, which controls the cutting movement and the vibrational movement simply in accordance with default values without any feedback, but of course the default values with respect to each other may have been determined.

There may be one or more vibration units 11 be provided. It may for example be a first vibration unit 11 close to the tool 7 be provided and a second vibration unit 11 close to the workpiece 6 or workpiece table 4 , They may be individually controllable or controllable with respect to each other, similar to cutting motion control 21 and vibration motion control 22 Referring to 2 was explained. It can be a single vibration unit 11 be designed for vibration along several axes, the individual axes can be controlled independently.

It should be noted that 2 only parts of the overall control shows. Not shown are the control of conventional components (eg adjusting axes, tool changer), which may also be present. The control 12 can be part of a process computer equipped according to the requirements.

The sensors in the machine tool 10 may comprise one or more of the following sensors, in which respect the term "sensor" may also include more complex evaluation mechanisms: sensor for vibration amplitude or vibration amplitude change in the range of the frequency of the vibration unit 11 Sensor for voltage and / or current at one of the drives, in particular at the vibration drive 11 , where appropriate, also for the phase relationship between voltage to current at the respective drive, and possibly the changes of the respective values (current, voltage, phase), sensor for the feed rate of cutting processing. Further sensors can be provided.

3 schematically shows an embodiment of a quick-change tool unit 30 , It shows the actual tool 7 on, for example, an end mill. In addition, it has the vibration unit 11 on. It also has an energy supply 31 on and a coupling part 5a to the tool unit 30 to connect with the machine tool. The coupling part 5a may be a conventional cone clutch or the like. Between vibration unit 11 and tool 7 can be the tool interface 5b be provided, the replacement of the tool 7 erlaubbt.

The vibration unit 11 may be an electromechanically actuated vibration unit or a piezoelectrically actuated vibration unit. In both cases, electrical energy is needed. It can be supplied via a conventional electrical connection, which in the case of rotating tools then, however, would have to be designed to be abrasive and thus relatively complicated. The energy supply can also be wireless, for example, inductively, for example, by an induction coil in the tool unit 32 is provided, relative to an external magnetic field, indicated by arrow 33 , changes. For example. can the coil 32 lie in a plane perpendicular to the axis of rotation of a rotating tool and be traversed by a changing with a certain frequency external magnetic field. However, it can also be oriented in such a way that, in a static external magnetic field, it already experiences a changing magnetic field through the coil surface due to the rotational movement of the tool. The result is an induced AC voltage that can be applied directly to the actuators. But there may also be other (not shown) electrical or electronic elements for stress forming.

The advantage of the embodiment of 3 is it that such a trained tool unit 30 relatively easy in a conventional machine tool 10 can be used. In particular, no electrical contacts must be provided. To ensure the sufficient effectiveness of the inductive coupling, however, it may be necessary to generate a suitable magnetic field locally.

4a schematically shows a representation for explaining directions in a router as a tool 7 , Shown is schematically a working from left to right on a workpiece surface end mill (arrow 74 ). He turns according to arrow 42 counterclockwise about axis 43 , 71 are the cutting edges of the end mill. The relative cutting movement between cutters 7 and workpiece 6 also runs in the direction of the arrow 74 (X-direction). The vibration movement may be perpendicular to it, approximately perpendicular to the plane of the drawing (y-direction). The direction of vibration may also be different than shown, for example along the x-direction or along the z-direction or may be oblique to these directions.

4b schematically shows a representation for explaining directions in a drill as a tool 7 , Shown is schematically a in a workpiece 6 stuck drill 7 , 71 symbolizes a cutting edge of the drill. In conventional operation, the drill rotates 7 around his axis 73 as by arrow 74 indicated. Every point on the cutting edge 71 then performs a circular cutting motion as indicated by arrow 74 indicated from. The cutting motion, symbolized by arrow 74 , According to the invention, a vibratory motion 75 be superimposed, or the movements 75 . 74 are done alternately. 4b shows an embodiment in which the vibration movement along arrow 75 takes place, ie in the direction of the drill axis 73 (Z-direction). The drill axis 73 (Z-direction). The vibration movement 75 is not parallel to the cutting motion direction 74 , It can be approximately at right angles to it or in particular in the direction of the drill axis. It is not parallel to the local workpiece surface below the drill bit edge in the embodiment shown. Rather, it bumps into the surface.

The tool can be designed to vibrate as compared to conventional tools. For example, certain surfaces or edges of the tool may be roughened or modified in certain ways as compared to conventional tools. In particular, for example, the rake face of a tool or the cutting edge of a tool or the flank of a tool can be roughened or toothed, at least in some areas, in order to be able to set the effectiveness of the vibratory motion in the desired manner. The tool can also be designed so that in view of the desired vibration excitation certain resonance frequencies of the tool are given or avoided in certain frequency ranges. There may be a predetermined detuning (difference) between the resonant frequency of the tool and the excitation frequency of the vibration, which can be controlled and, if necessary, can also be controlled. The tool design can be done by targeted material additions or material removal on the tool.

Features that are shown in this description of the prior art or the invention, should also be combined with each other, if not expressly stated, as far as the combination is technically possible. Descriptions of method steps will also be understood as describing devices implementing these steps, and descriptions of particular devices and components shall also be understood as describing method steps implemented by those devices and components.

Claims (15)

Machine tool ( 10 ) with a tool ( 7 ) with a defined cutting edge ( 71 ) for workpiece machining with a cutting movement ( 74 ) of the tool ( 7 ) relative to the workpiece ( 6 ), characterized by a vibration unit ( 11 ) for generating a vibratory movement ( 75 ) between tools ( 7 ) and workpiece ( 6 ). Machine tool according to claim 1, characterized in that the vibration unit ( 11 ) is adapted to the tool ( 7 ) or the workpiece table ( 6 ) in vibrating motion ( 75 ) to move. Machine tool according to claim 1 or 2, characterized in that the vibration unit ( 11 ) for generating a vibration reversing along one direction ( 75 ), wherein the direction is parallel or perpendicular to the direction of the cutting movement ( 74 ) or at a certain angle to it. Machine tool according to one or more of the preceding claims, characterized in that the tool ( 7 ) is a drill, a milling cutter, in particular a end mill, a planer or a turning tool. Machine tool according to one or more of the preceding claims, characterized in that the tool ( 7 ) is an end mill or a drill and the vibration unit ( 11 ) for vibrating the end mill or the drill ( 7 ) in one direction ( 75 ) parallel or perpendicular to its axis of rotation ( 73 ) or at a certain angle is designed. Machine tool according to one or more of the preceding claims, characterized by a plurality of dependent or independently controllable vibration units ( 11 ). Machine tool according to one or more of the preceding claims, characterized that the vibration unit ( 11 ) has an electromagnetic or a piezoelectric drive and preferably operates with a vibration frequency greater than 5 kHz or greater than 10 kHz or greater than 20 kHz. Machine tool according to one or more of the preceding claims, characterized by a controller ( 12 ) for controlling the separation movement ( 74 ) and for controlling the vibration movement ( 75 ). Machine tool according to claim 8, with a device ( 21 ) for controlling one or more adjustable parameters of the cutting movement ( 74 ) in accordance with one or more adjustable or determined parameters of the vibration movement ( 75 ), and / or with a device ( 22 ) for controlling one or more adjustable parameters of the vibratory movement ( 75 ) in accordance with one or more adjustable or determined parameters of the cutting movement (14). Machine tool according to claim 8 or 9, characterized by one or more sensors ( 14 ) for detecting one or more parameters relating to the cutting movement ( 74 ) and / or concerning the vibration movement ( 75 ), in particular vibration amplitude and / or voltage and / or current at one or more of the actuators and / or phase angle between two of mechanical vibration, voltage and current of the vibration unit ( 11 ), and / or feed rate ( 77 ) of cutting. Machine tool according to one or more of claims 8 to 10, characterized in that the controller ( 12 ) the cutting movement ( 74 ) and the vibration movement ( 75 ) can cause each individually or simultaneously with the same tool. Machine tool according to one or more of the preceding claims, characterized in that the tool ( 7 ) has an at least partially roughened rake surface or free surface or cutting edge. Machine tool according to one or more of the preceding claims, characterized in that the tool ( 7 ) is replaceable and the vibration unit ( 11 ) is provided in the interchangeable tool, wherein the vibration unit ( 11 ) preferably a device ( 31 - 35 ) for receiving wireless energy. Workpiece machining method in which a cutting movement and a vibrating motion are caused relatively between a tool having a defined cutting edge and a workpiece, wherein the cutting motion and the vibrating motion can be used both simultaneously and individually. A method according to claim 14, characterized in that the vibration takes place along a translatory and / or about a rotational axis.

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