JP3564585B2 - Machine Tools - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a machine tool, and more particularly, to a machine tool capable of automatically exchanging a tool mounted on a spindle supported in a non-contact manner by magnetic bearings with another type, such as a machining center.
[0002]
2. Description of the Related Art
2. Description of the Related Art In recent years, magnetic bearing spindle devices that support a main shaft in a non-contact manner with magnetic bearings have been widely used in machine tools such as machining centers for the purpose of speeding up the main shaft. Such a magnetic bearing spindle device generally includes a main shaft, a plurality of sets of magnetic bearings using electromagnets that support the main shaft in a non-contact manner, and a magnetic bearing control device that controls the magnetic bearings. The machine tool is provided with a machining control device and an automatic tool changing device. The machining control device controls the rotation speed, the depth of cut and the feed speed of the spindle, that is, the tool, and the automatic tool changing device issues a command from the machining control device. The tool mounted on the spindle is automatically replaced with another type based on the above. The so-called processing conditions such as the rotation speed, the depth of cut and the feed rate of the tool are externally given, and the processing control device keeps these processing conditions constant during the processing.
[0003]
By the way, even if the processing conditions are constant, when the type of tool changes, the processing force acting on the tool changes, and the optimum processing condition changes depending on the type of tool. The processing conditions given from the outside are not always optimal for the tool, and may be lower than or exceed the capabilities of the tool or the magnetic bearing. If the machining conditions are lower than the capabilities of the tool or the magnetic bearing, there is a problem that the machining efficiency is poor. Conversely, if it exceeds this, the position control of the spindle by the magnetic bearing becomes unstable, and the finished state of the workpiece And adversely affect tool life.
[0004]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems, always optimize the machining conditions regardless of the type of tool, to improve machining efficiency, stability of spindle position control by a magnetic bearing, a finished state of a workpiece, and a tool. An object of the present invention is to provide a machine tool that can improve the life.
[0005]
Means and effects for solving the problem
In a machine tool according to the present invention, a spindle on which a tool is mounted is supported in a non-contact manner by a plurality of sets of magnetic bearings using electromagnets, and the tool mounted on the spindle can be automatically changed to another type of tool. In the machine, a machining force calculation pattern representing a relationship between an exciting current of the electromagnet and a machining force acting on the tool is stored for each type of tool mounted on the spindle, and a machining force calculation pattern for the tool mounted on the spindle is stored. A machining force is obtained from an excitation current of the electromagnet using a machining force calculation pattern, and the rotation speed, the cutting depth, and the feed speed of the tool are controlled based on the machining force. Things.
[0006]
For example, a machine tool includes a spindle on which a tool is mounted, a plurality of sets of magnetic bearings using electromagnets that support the spindle in a non-contact manner, magnetic bearing control means for controlling the magnetic bearing, and rotationally driving the spindle. Rotation drive means, processing control means for controlling the rotation speed, depth of cut and feed rate of the tool, and automatically setting the tool mounted on the spindle to another type based on a command from the processing control means. Automatic tool changing means for changing the machining force, the magnetic bearing control means for each type of tool mounted on the spindle, a machining force representing the relationship between the exciting current of the electromagnet and the machining force acting on the tool the operation pattern stores, by selecting the working force calculation pattern with respect to the tool mounted on the spindle than the command related to a tool from the machining control means, processing the excitation current of the electromagnet Look, the machining control means, the rotational speed of the tool based on the machining force, is adapted to control the depth of cut and feed rate.
[0007]
A machining force calculation pattern representing the relationship between the excitation current of the electromagnet and the machining force acting on the tool is stored for each type of tool mounted on the spindle, and the machining force calculation pattern for the tool mounted on the spindle is used. The machining force is obtained from the excitation current of the electromagnet, and the rotational speed, cutting depth and feed rate of the tool are controlled based on the machining force.Thus, even if the type of tool changes, these machining conditions are always optimized. can do. Therefore, the machining efficiency can be maximized with respect to the capabilities of the tool and the magnetic bearing, and furthermore, the position control of the main shaft by the magnetic bearing is stabilized, and the finished state of the workpiece and the tool life are improved.
[0008]
Preferably, the magnetic bearing control means comprises a digital signal processor.
[0009]
In this specification, a digital signal processor (Digital Signal Processor) refers to dedicated hardware that inputs a digital signal, outputs a digital signal, is software-programmable, and is capable of high-speed real-time processing. Hereinafter, this is abbreviated as DSP.
[0010]
When the magnetic bearing control means comprises a DSP, high-speed real-time processing of signals can be performed.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0012]
FIG. 1 shows a spindle device (1) of a machine tool such as a machining center, a numerical control device (hereinafter abbreviated as an NC device) (2) as processing control means, and an automatic tool changing device (18) as automatic tool changing means. ) Are shown schematically.
[0013]
The spindle device (1) has a main shaft (4) vertically arranged in a casing (3). In the casing (3), one set of axial magnetic bearings (5) for supporting the main shaft (4) in a non-contact manner, and two sets of upper and lower radial magnetic bearings (6) (7), and a main shaft (4) are provided. One axial position sensor (8) for detecting the position in the axial direction, two sets of upper and lower radial position sensors (10) and (11) for detecting the position of the main shaft (4) in the radial direction, and the main shaft ( 4) A high-frequency motor (12) is provided as a rotation driving unit for rotating the at a high speed. Usually, the axial magnetic bearing (5) is composed of a pair of electromagnets (5a), and each radial magnetic bearing (6) (7) is composed of four sets of electromagnets (6a) (7a). Since the magnetic bearings (5), (6), (7), the position sensors (8), (10), (11) and the motor (12) are known, their detailed description is omitted.
[0014]
The axial position sensor (8) and the radial position sensors (10) and (11) are driven by a sensor drive circuit (13), and the sensor drive circuit (13) outputs the output of each position sensor (8) (10) (11). Based on this, the axial position of the main shaft (4) and the radial position at two locations above and below are detected. An analog position detection signal from the sensor drive circuit (13) is converted into a digital position detection signal by an A / D converter (14) and input to a magnetic bearing control device (15) as magnetic bearing control means. The magnetic bearing control device (15) controls the exciting current of the electromagnets (5a) (6a) (7a) of each magnetic bearing (5) (6) (7) based on the digital position detection signal. And is composed of a DSP. The digital control signal from the magnetic bearing control device (15) is converted into an analog control signal by the D / A converter (19), and based on the analog control signal, the power amplifier (16) sends each of the electromagnets (5a) (6a). The exciting current is supplied to (7a), and as a result, the main shaft (4) is supported in a predetermined position in the axial direction and the radial direction in a non-contact manner.
[0015]
A tool (17) is attached to the lower end of the spindle (4), and the automatic tool changer (18) automatically changes the tool (17) to another type based on a tool number command from the NC device (2). Is to be exchanged. Since the automatic tool changing device (18) is a known device, illustration and description of its specific configuration will be omitted. The tool number command from the NC device (2) is also input to the magnetic bearing control device (15).
[0016]
The NC device (2) controls the rotational speed of the main shaft (4), and also controls the position, the moving direction, and the moving speed of the casing (3), that is, the main shaft (4). The speed, depth of cut and feed rate are controlled. The processing conditions of the rotation speed, the cutting depth, and the feed speed of the tool (17) usually vary depending on the type of the tool (17). These processing conditions are automatically controlled by the NC device (2) during the processing, as described later. However, the initial processing conditions may be externally provided, or the internal of the NC device (2). May be set automatically.
[0017]
When processing is performed by the above-described machine tool, the processing is first performed under processing conditions given from the outside or processing conditions automatically set inside the NC device (2). Then, during machining, the magnetic bearing control device (15) uses the tool (17) based on the tool number command from the automatic tool changer (18) and the excitation current of each electromagnet (5a) (6a) (7a). And outputs information on the processing force to the NC device (2). There is a certain relationship between the exciting current of each of the electromagnets (5a), (6a), (7a) and the working force acting on the tool (17), and the working force can be obtained by calculation from the exciting current. However, since the relationship between the exciting current and the machining force varies depending on the type of tool, for example, the magnetic bearing control device (15) determines the machining force representing the relationship between the exciting current and the machining force for each type of tool (17). The calculation pattern is stored, and the calculation pattern for the tool (17) at that time is selected by the tool number command from the NC device (2), and the processing force is calculated using this. The NC device (2) is based on information on the machining force from the magnetic bearing control device (15), and is designed to be optimal for the magnetic bearings (5), (6), (7) and the tool (17) at that time. (17) The rotation speed, the cutting depth and the feed speed are automatically controlled.
[0018]
For this reason, even if the type of the tool (17) changes, the machining conditions can always be optimized, so that the machining efficiency can be reduced between the magnetic bearings (5), (6), (7) and the tool (17) at that time. The capacity can be maximized, and the support of the main shaft (4) by the magnetic bearings (5), (6), (7) is stabilized, and the finished state of the workpiece and the tool life are improved.
[0019]
In the NC device (2), the information on the processing force from the magnetic bearing control device (15) can be used not only for controlling the processing conditions but also for other purposes. Further, based on the tool number command from the NC device (2), the magnetic bearing control device (15) controls each of the magnetic bearings (5) (6) so that the tool (17) at that time and the processing conditions are optimal. The control condition of (7) can be automatically changed.
[0020]
The configuration of each part of the machine tool is not limited to that of the above embodiment, but can be changed as appropriate.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a main part of a machine tool showing an embodiment of the present invention.
[Explanation of symbols]
(2) Numerical control device (processing control means)
(4) Main shaft (5) Axial magnetic bearing (5a) Electromagnet (6) (7) Radial magnetic bearing (6a) (7a) Electromagnet (8) High-frequency motor (rotation drive means)
(15) Magnetic bearing control device (magnetic bearing control means)
(17) Tool (18) Automatic tool changer (automatic tool changer)

Claims (3)

In a machine tool in which a main shaft on which a tool is mounted is non-contact supported by a plurality of sets of magnetic bearings using electromagnets, and a tool mounted on the main shaft can be automatically replaced with another type.
A machining force calculation pattern representing a relationship between an exciting current of the electromagnet and a machining force acting on the tool is stored for each type of tool mounted on the spindle, and a machining force calculation for the tool mounted on the spindle is stored. A machine tool wherein a machining force is obtained from an exciting current of the electromagnet using a pattern, and the rotational speed, the cutting depth, and the feed speed of the tool are controlled based on the machining force . A spindle on which a tool is mounted, a plurality of sets of magnetic bearings using electromagnets that support the spindle in a non-contact manner, magnetic bearing control means for controlling the magnetic bearing, rotation driving means for rotating and driving the spindle, Machining control means for controlling the rotation speed, depth of cut and feed rate of the tool, and automatic tool exchange for automatically exchanging a tool mounted on the spindle with another type based on a command from the machining control means Machine tool comprising:
The magnetic bearing control means stores a machining force calculation pattern representing a relationship between an exciting current of the electromagnet and a machining force acting on the tool for each type of tool mounted on the spindle. A machining force calculation pattern for the tool mounted on the spindle is selected from a command related to the tool, and a machining force is obtained from an excitation current of the electromagnet; and the machining control unit rotates the tool based on the machining force. A machine tool characterized by controlling a speed, a cutting depth and a feed rate. 3. The machine tool according to claim 2, wherein said magnetic bearing control means comprises a digital signal processor.

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