JP5631467B1 - Drilling method and numerical control device - Google Patents

Abstract

Provided is a hole machining method capable of finely dividing chips, which can be applied to an existing machine tool without increasing the processing time, making the apparatus complicated and large. In a hole drilling method in which a rotary tool (T) and a workpiece (W) are moved relative to each other and a hole is formed in the workpiece (W), the feed speed in the central axis direction of the rotary tool (T) is changed to a feed rate. Periodically increased or decreased within a range where the direction of the angle does not change. [Selection] Figure 2

Description

  The present invention relates to a drilling method using a machine tool and a numerical control device for carrying out the drilling method.

  A chip processing device that damages the tool due to continuous chips generated during drilling and boring operations such as boring, damages the work surface due to chips, and discharges chips from the processing machine. Conventionally, problems such as clogging of chips have been a problem.

  In order to solve this problem, conventionally, during drilling, the drill is retracted in the axial direction, chips are discharged from the hole being processed, and then the drill is advanced again in the axial direction. There is a step feed machining method that drills holes to the depth. For example, Patent Document 1 discloses a drilling device that uses a cam to reciprocate a drill unit in a sinusoidal shape in the axial direction.

  Patent Document 2 discloses a deep hole drill cycle in which the Z-axis is retracted when the actual load acting on the spindle during deep hole processing exceeds a value obtained by multiplying the initial load of the spindle by a predetermined value. A control method is disclosed. The invention of Patent Document 2 describes that the drill cycle itself is based on standards such as JIS B6314, international standard ISO 1056, US standard EIA RS-274.

  Further, in Patent Document 3, a linear motor is arranged on a base table, a spindle table arranged on the linear motor, and a spindle arranged on the spindle table, and the spindle table is moved in the feed direction by the linear motor. A hole drilling machine that is reciprocally moved is disclosed. In the invention of Patent Document 3, since the spindle is reciprocated together with the spindle base by the linear motor, the reciprocating speed and the reciprocating distance can be easily changed.

JP-A-2-36009 JP-A-62-246408 Japanese Patent Application Laid-Open No. 2004-261928

  In the invention of Patent Document 1, since the drill unit is reciprocated in the axial direction using a cam, the moving speed and the reciprocating distance (amplitude) are always fixed values, and optimally adapted to various machining conditions. There is a difficult problem. Further, since the drill unit is retracted until the tip of the tool is exposed from the hole being processed during the reciprocating operation of the drill unit, the reciprocating operation takes time, and the processing time becomes long. Furthermore, when the drill unit reciprocates, the tip of the drill separates from the workpiece, so that when the tip of the drill strikes the workpiece again, there is a problem that the cutting edge is chipped or noise is generated due to the collision. . The impact is a contact with impact.

  In the invention of Patent Document 2, since the Z-axis is retracted when the load acting on the spindle becomes high, the chips do not break until the load acting on the spindle becomes high. There is a problem in that scraps are easily generated, and scratches are likely to occur on the processed surface due to the chips. Furthermore, in the invention of Patent Document 2, when the Z-axis is retracted, the drill tip is separated from the work, and therefore there is a problem of generation of noise due to the chipping of the cutting edge as in Patent Document 1 and collision. . Furthermore, in the invention of Patent Document 2, the conventional drill cycle determined by international standards and the like gives a problem that the machining time becomes long, and copes with reducing the number of times the Z-axis is retracted. There is still room for improvement because there is still an action to move the Z-axis backward.

  In the invention of Patent Document 3, it is difficult to apply to a general-purpose machine such as a machining center because the spindle is microvibrated in the axial direction together with the spindle base by a linear motor, and is particularly applicable to existing machine tools. Can not do it.

  The present invention has a technical problem to solve such problems of the prior art, and does not lengthen the machining time, and does not increase the complexity and size of the apparatus, and can be applied to existing machine tools. An object of the present invention is to provide a hole drilling method capable of finely dividing generated chips and a numerical control device for carrying out the hole drilling method.

  Another object of the present invention is to provide a drilling method in which tool damage such as breakage of a tool or chipping of a cutting edge is prevented during drilling, and a numerical control device for carrying out the drilling method.

In order to achieve the above-described object, according to the present invention, in a drilling method for machining a hole in a workpiece by relatively moving a rotary tool of a drill, a boring cutter or a counterbore cutter and the workpiece, There is provided a drilling method in which a hole is formed in the workpiece by changing the feed speed in the central axis direction so as to repeat increase and decrease within a range in which the rotary tool does not retract in the central axis direction .

According to another aspect of the present invention, a machining program is read in a numerical control device for a machine tool that relatively moves a rotary tool of a drill, a boring cutter or a counterbore cutter and a workpiece to machine a hole in the workpiece. A reading interpretation unit that outputs a feed operation command at a constant speed in the central axis direction of the rotary tool, and interprets the feed speed in the central axis direction of the rotary tool according to machining conditions. A storage unit including a database for selecting a reciprocating operation command to be changed so as to repeatedly increase and decrease within a range not retreating in the axial direction, a constant speed feed operation command output by the reading interpretation unit, and an output from the storage unit and superimposed a reciprocating operation command, superimposing unit and the position finger operation command interpolation operation to output from the superimposing unit for generating operation commands to the central axis direction of the rotary tool An interpolation section for generating a numerical control apparatus having a servo control unit for generating a current value for driving the feed shaft sending the rotary tool to the center axis direction based on the position instruction is provided.

  As described above, according to the present embodiment, the hole is formed in the workpiece by feeding the rotary tool relative to the workpiece in the central axis direction while periodically changing the feed rate. The thickness of the material changes periodically, and chips are easily divided. This makes it easier for chips to be discharged from the machined hole, prevents the chips from getting tangled in the rotary tool, reduces heat generation in the machining area (hole), and further reduces the surface of the workpiece and machining the workpiece. The inner surface of the hole is prevented from being damaged. As a result, it is not necessary to supply high-pressure coolant to the processing region, and power consumption for driving the pump for high-pressure coolant can be reduced as compared with the conventional case.

  According to the present invention, the relative axial feed speed of the rotary tool is controlled so as to periodically increase and decrease within a range in which the feed direction does not change. That is, the rotary tool does not retreat in the axial direction, and the tip of the rotary tool always contacts the workpiece and does not separate from the workpiece W. Therefore, it is possible to prevent the chipping of the cutting edge and the generation of noise, which are caused by the impact and separation of the tool against the workpiece as in the prior art.

  Furthermore, according to the present invention, during drilling, the rotary tool is fed relative to the center axis so that the feed direction does not change with respect to the workpiece, so that the feed axis, usually the Z axis, is configured. The ball screw does not reverse. Therefore, since the Z-axis does not stop or retract, the phenomenon that the machining time, which is a problem of the conventional drill cycle, becomes long does not occur.

It is a side view showing an example of a machine tool to which the present invention is applied. It is a block diagram which shows an example of the numerical control apparatus for enforcing the hole drilling method of this invention. It is a graph which shows Z-axis operation command (feed amount). It is a graph which shows Z-axis operation command (feed speed). 4 is a graph similar to FIG. 3 according to another example. 4 is a graph similar to FIG. 3 according to another example.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.
Referring to FIG. 1, an example of a machine tool to which the present invention is applied is shown. 1, a machine tool 100 according to a preferred embodiment of the present invention constitutes a vertical machining center, and includes a bed 102 as a base fixed to the floor of a factory, a front portion of the bed 102 (in FIG. 1). A table 106 on which the workpiece W is fixed and is movable in the front-rear direction or the Y-axis direction (left-right direction in FIG. 1) on the upper surface of the left side) and the rear end side (right side in FIG. 1) of the bed 102 A column 104 which is erected and fixed on the upper surface, an X-axis slider 108 which is movably provided in the left-right direction or the X-axis direction (the direction perpendicular to the paper surface in FIG. 1) on the front surface of the column 104, A spindle head 110 is mounted on the front face so as to be movable in the vertical direction or the Z-axis direction and rotatably supports the spindle 112.

  The table 106 is provided on a top surface of the bed 102 so as to reciprocate along a pair of Y-axis guide rails (not shown) extending in the horizontal Y-axis direction (left-right direction in FIG. 1). Reference numeral 102 denotes a Y-axis feeding device that reciprocates the table 106 along the Y-axis guide rail, and a ball screw (not shown) extending in the Y-axis direction, and a Y screw connected to one end of the ball screw. A shaft servomotor 116 is provided, and a nut (not shown) that engages with the ball screw is attached to the table 106. A Y-axis scale (not shown) for measuring the coordinate position in the Y-axis direction of the table 106 in the Y-axis direction is also attached to the table 106.

  The spindle head 110 supports the spindle 112 so as to be rotatable around a central axis O extending in the vertical direction parallel to the Z axis. The spindle 112 has a tool mounting hole (not shown) for mounting the rotary tool T at the tip portion facing the table 106. The spindle head 110 has a servo motor (not shown) that rotationally drives the spindle 112. The servo motor can be attached to the outside of the housing of the spindle head 110, but a stator coil (not shown) is provided on the inner surface of the housing of the spindle head 110, and a rotor coil (not shown) is provided on the spindle 112. And it is good also as what is called a built-in motor.

  The X-axis slider 108 is provided so as to reciprocate along a pair of X-axis guide rails (not shown) extending in the X-axis direction on the front surface of the upper portion of the column 104. The column 104 is connected to a ball screw (not shown) extending in the X-axis direction and one end of the ball screw as an X-axis feeding device that reciprocates the X-axis slider 108 along the X-axis guide rail. An X-axis servo motor 114 is provided, and a nut (not shown) that engages with the ball screw is attached to the X-axis slider 108. An X-axis scale (not shown) for measuring the coordinate position of the X-axis slider 108 in the X-axis direction is also attached to the column 104.

  The spindle head 110 is provided so as to reciprocate along a pair of Z-axis guide rails extending in the Z-axis direction (vertical direction in FIG. 1) on the front surface of the X-axis slider 108. The X-axis slider 108 includes a ball screw (not shown) extending in the Z-axis direction as one Z-axis feeding device that reciprocates the spindle head 110 along the Z-axis guide rail, and one end of the ball screw. A coupled Z-axis servomotor 118 is provided, and a nut (not shown) that engages with the ball screw is attached to the spindle head 110. A Z-axis scale (not shown) for measuring the coordinate position of the spindle head 110 in the Z-axis direction is also attached to the X-axis slider 108. The rotary tool T is fed along its central axis by a Z-axis feeder.

  The X-axis servo motor 114, the Y-axis servo motor 116, the Z-axis servo motor 118, and the X-axis scale, the Y-axis scale, and the Z-axis scale are connected to the numerical controller 10 that controls the machine tool 100. The numerical control device 10 controls the power (current value) supplied to the X-axis servo motor 114, the Y-axis servo motor 116, and the Z-axis servo motor 118.

  Referring to FIG. 2, which is a block diagram illustrating an example of a numerical control device for carrying out the hole drilling method of the present invention, the numerical control device 10 includes a reading interpretation unit 12, a superposition unit 14, an interpolation unit 16, and a servo control unit. 18 and a storage unit 20 are provided. The reading / interpreting unit 12 reads and interprets the machining program from the CAM system 30 and outputs an operation command. This operation command includes the feed amount and feed speed in the X-axis, Y-axis, and Z-axis directions. The operation command output by the reading / interpreting unit 12 is sent to the superimposing unit 14. The CAM (Computer Aided Manufacturing) system 30 is a device that automatically inputs a machining model and machining conditions and generates a machining program.

  The storage unit 20 has a database that stores reciprocating operations for various types of drilling, that is, a feed amount that periodically varies in the Z-axis direction with a constant amplitude. The storage unit 20 refers to a database on the basis of conditions (reciprocating operation conditions) related to drilling that are input from an input unit 32 such as a touch panel that is normally provided in the numerical control device 10, and superimposes the reciprocating operation command 14. Output to. The reciprocating operation conditions include the material of the workpiece, the diameter and depth of the hole to be machined, the feed rate of the tool, the rotational speed of the tool (main spindle), the number of blades, the type of tool such as a drill or counterbore tool, and the like. The storage unit 20 may cumulatively store past reciprocating operation conditions in a database.

  The superimposing unit 14 superimposes the reciprocating operation command output from the storage unit 20 on the Z-axis operation command output from the reading interpretation unit 12. The Z-axis operation command on which the reciprocating operation command is superimposed is output to the interpolation unit 16 together with the X-axis and Y-axis feed operation commands generated by the reading interpretation unit 12.

  The interpolation unit 16 performs an interpolation operation on the received X-axis, Y-axis, and Z-axis operation commands, and outputs a position command (pulse position command) that matches the interpolation function and feed speed to the servo control unit 18. The servo control unit 18 outputs current values for driving the X-axis, Y-axis, and Z-axis feed axes of the machine tool 100 from the received X-axis, Y-axis, and Z-axis position commands. It is sent to servo motors 114, 116, and 118 for the axis, Y axis, and Z axis.

  Referring to FIG. 3, which is a graph showing the Z-axis operation command (feed amount), an example of the Z-axis operation command (feed amount) output from the reading interpretation unit 12 to the superposition unit 14 is indicated by a broken line. In FIG. 3, the vertical axis represents the feed amount, that is, the Z coordinate, and the horizontal axis represents time. In the example of FIG. 3, it will be understood that the operation command output from the reading interpretation unit 12 to the superposition unit 14 is an operation command for sending the rotary tool T at a constant speed in the Z-axis direction. In FIG. 3, an example of a reciprocating operation command output from the storage unit 20 to the superimposing unit 14 is indicated by a one-dot chain line. In the example of FIG. 3, the reciprocating motion command is a feed motion command in which the feed amount (Z coordinate) in the Z-axis direction changes with time at a constant period and constant amplitude. Further, the superimposing unit 14 superimposes or combines the Z-axis operation command output from the reading interpretation unit 12 to the superimposing unit 14 and the reciprocating operation command output from the storage unit 20 to the superimposing unit 14. The Z-axis direction feed operation command output from the superimposing unit 14 to the interpolating unit 16 is indicated by a solid line.

  An example of the Z-axis operation command (feed speed) is shown in FIG. In FIG. 4, the vertical axis represents the feed rate, the horizontal axis represents time, the broken line represents the Z-axis operation command output from the reading interpretation unit 12 to the superimposition unit 14, and the alternate long and short dash line is output from the storage unit 20 to the superposition unit 14. The solid line indicates the operation command after superposition or combination output from the superimposition unit 14 to the interpolation unit 16. The Z-axis operation command output from the reading / interpreting unit 12 to the superimposing unit 14 has a constant feed rate. The feed operation command (feed speed) in the Z-axis direction output from the storage unit 20 to the interpolation unit 16 is a rectangular wave in which the sign (±) is switched at a constant period with a constant amplitude (the absolute value is equal). . Note that the reciprocating operation command output from the storage unit 20 to the superimposing unit 14 is not a rectangular wave but may be another curve, for example, a sine wave.

  In the present embodiment, the Z-axis operation command output from the reading interpretation unit 12 to the superimposition unit 14 and the feed operation command (feed speed) in the Z-axis direction output from the superposition unit 14 to the interpolation unit 16 are combined or superimposed. Then, it becomes a rectangular wave centered on a constant feed rate output from the reading interpretation unit 12 to the superimposition unit 14. This rectangular wave changes with a constant period and amplitude within a positive range, and the feed speed in the Z-axis direction of the rotary tool T does not become a negative value.

  As described above, according to this embodiment, during drilling, the rotary tool T is fed in the Z-axis direction so that the feed direction does not change. In the example of FIG. 3, the rotary tool T is always sent in the Z-axis direction with a feed amount larger than the Z-axis feed amount output from the reading interpretation unit 12 to the superposition unit 14, that is, the solid line in FIG. It is sent to be on the upper side. However, as shown in FIG. 5, it is possible to feed in the Z-axis direction with a feed amount smaller than the Z-axis feed amount output from the reading interpretation unit 12 to the superposition unit 14, or as shown in FIG. The feed amount may be increased and decreased in the Z-axis direction around the Z-axis feed amount output from 12 to the superimposing unit 14. In short, it is sufficient that the gradient of the feed amount is always zero or a positive value. In other words, it is sufficient if the time derivative of the feed amount does not become negative.

The inventors changed the material of the workpiece W to stainless steel (SUS403), ductile cast iron (FCD450), and aluminum (A5052), and drilled a 5mm diameter hole (drilling) while periodically changing the feed rate or feed rate. ) Was actually performed and compared with the case of machining without changing the feed rate or feed amount. Furthermore, in addition to the above drilling, drilling of 30 mm in diameter and counterbore of 6 mm in diameter are performed on aluminum (A5052) workpieces while periodically changing the feed rate or feed rate. Comparison was made with the case of processing without change. Table 1 shows the change (amplitude) and frequency of the feed amount in the Z-axis direction. In any case, by changing the feed rate periodically, the chips are divided, and even if high-pressure coolant is not supplied, holes can be machined better than when machining without changing the feed rate. It was confirmed that

  As described above, according to the present embodiment, since the hole is machined by feeding the rotary tool T in the Z-axis direction while periodically changing the feed rate, the thickness of the chip generated during machining is periodic. Changes and the chips are easily divided. This makes it easier for chips to be discharged from the machined holes, prevents the chips from getting tangled with the rotary tool T, reduces heat generation in the machining area (holes), and further reduces the surface of the workpiece W by the chips. And the inner surface of the processed hole is prevented from being damaged. This further eliminates the need to supply high-pressure coolant to the processing region, and can reduce power consumption for driving a conventional pump for high-pressure coolant.

  Further, since the feed speed in the Z-axis direction of the rotary tool T does not become a negative value, the feed of the rotary tool T in the Z-axis direction does not change or retract, and the tip of the rotary tool T is The workpiece W is always kept in contact with the workpiece W and never leaves the workpiece W. Therefore, since the Z-axis does not stop or retract, the phenomenon that the machining time, which is a problem of the conventional drill cycle, becomes long does not occur.

  As described above, according to the present embodiment, during drilling, the rotary tool T is fed in the Z-axis direction so that the feed direction does not change, and the Z-axis ball screw is not reversed. Therefore, since the Z-axis does not stop or retract, the phenomenon that the machining time, which is a problem of the conventional drill cycle, becomes long does not occur.

  In the embodiment described above, a periodically changing reciprocating operation command output from the storage unit 20 to the superimposing unit 14 is added to the constant-speed Z-axis operation command output from the reading interpretation unit 12 to the superimposing unit 14. The present invention is not limited to this, but the coordinates are directly described in the NC program so that the Z-axis feed speed is periodically increased or decreased within a range in which the feed direction does not change. It may be. However, as described above, it is easier and more reliable to superimpose a reciprocating motion command that periodically changes on a constant speed Z-axis motion command.

DESCRIPTION OF SYMBOLS 10 Numerical control apparatus 12 Reading interpretation part 14 Superimposition part 16 Interpolation part 18 Servo control part 20 Storage part 30 CAM system 32 Input part 100 Machine tool 102 Bed 104 Column 106 Table 108 X-axis slider 110 Spindle head 112 Spindle 114 X-axis servo motor 116 Y-axis servo motor 118 Z-axis servo motor

Claims (3)

In the hole drilling method that drills, boring cutter or counterbore cutter rotary tool and the workpiece relative to each other to drill a hole in the workpiece,
A hole drilling method characterized in that a hole is machined in the workpiece by changing the feed speed of the rotary tool in the central axis direction so as to repeat increase and decrease within a range in which the rotary tool does not retract in the central axis direction .   By generating a feed command at a constant speed in the central axis direction of the rotary tool and superimposing a periodically changing feed speed command on the feed command at the constant speed, the feed speed in the central axis direction of the rotary tool The hole drilling method according to claim 1, wherein the number of holes is periodically increased or decreased. In a numerical control device for a machine tool for machining a hole in a workpiece by relatively moving a rotary tool of a drill, boring cutter or counterbore cutter and the workpiece,
A reading and interpreting unit that reads and interprets a machining program and outputs a feed operation command at a constant speed in the direction of the central axis of the rotary tool;
A storage unit having a database for selecting a reciprocating operation command for changing the feed speed in the central axis direction of the rotary tool in accordance with the machining conditions so as to repeat increase and decrease within a range in which the rotary tool does not retract in the central axis direction When,
A feed operation command constant speed which the reading interpreting unit is output, a superimposing unit that superimposes a reciprocal operation command which the storage unit is output, to generate the operation command to the central axis direction of the rotary tool,
An interpolation unit that interpolates the operation command output from the superimposition unit to generate a position command;
A servo control unit that generates a current value for driving a feed shaft that sends the rotary tool in a central axis direction based on the position command;
A numerical control device comprising:

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