Machine tool control device

Abstract

A control device for a machine tool is provided, which can reliably reduce noise when gears are meshed and achieve desired processing quality. The control device (10) for a machine tool that processes a workpiece (W) having at least one tooth surface comprises: a processing condition input unit (15) capable of inputting processing conditions including at least one of the specifications of the workpiece (W), the specifications of the tool (T), the feed rate, the spindle speed, and the number of teeth; a surface pattern calculation unit (16) that calculates a surface pattern specified based on the intervals of scratches generated on the processed surface based on the processing conditions; a swing command generation unit (17) that generates a swing command for a surface pattern having a portion with uneven intervals of scratches based on the surface pattern; and a position and speed control unit (14) that swings the workpiece (W) and the tool (T) relative to each other based on the swing command generated by the swing command generation unit (17) to perform processing.

Description

Technical Field

[0001] The present invention relates to a control device for a machine tool. Background Art

[0002] During machining, a collection of microscopic flaws is formed, resulting in a machined surface. For example, in gear machining, the microscopic flaws are typically spaced evenly apart. However, when gears with evenly spaced flaws are meshed, a periodic sound is generated, causing noise during operation.

[0003] Therefore, a technique for dynamically changing the feed speed so that the intervals between scratches become irregular is disclosed (for example, see Patent Document 1). This technique can reduce noise when the gears are meshed.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent No. 4824947 Summary of the Invention

[0007] Problems to be solved by the invention

[0008] However, Patent Document 1 does not disclose a specific method for making the intervals between scratches irregular. Therefore, there is a possibility that the noise reduction effect cannot be obtained due to difficulty in reproducibility, and there is a possibility that the processing quality will be unstable.

[0009] Therefore, a control device for a machine tool is desired that can reliably reduce noise generated when gears are meshed and achieve desired machining quality.

[0010] Means for solving problems

[0011] One embodiment of the present disclosure is a control device for a machine tool that processes a workpiece having at least one tooth surface, comprising: a processing condition input unit that can input processing conditions including at least one of the specifications of the workpiece, the specifications of the tool, the feed rate, the spindle speed, and the number of teeth; a surface pattern calculation unit that calculates a surface pattern specified based on the intervals of scars generated on the processed surface based on the processing conditions input by the processing condition input unit; a swing instruction generation unit that generates a swing instruction for a surface pattern having portions in which the intervals of the scars are unequally spaced based on the surface pattern calculated by the surface pattern calculation unit; and a control unit that causes the workpiece and the tool to swing relative to each other for processing based on the swing instruction generated by the swing instruction generation unit.

[0012] Effects of the Invention

[0013] According to the present disclosure, it is possible to provide a control device for a machine tool that can reliably reduce noise generated when gears are meshed and achieve desired machining quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a diagram showing the axis structure of a machine tool according to one embodiment of the present disclosure.

[0015] Figure 2 This is a functional block diagram of a control device for a machine tool according to one embodiment of the present disclosure.

[0016] Figure 3 This is a diagram illustrating the principle of gear machining performed using a control device for a machine tool according to an embodiment of the present disclosure.

[0017] Figure 4 This figure shows an example of processing a spur gear.

[0018] Figure 5 This is a diagram showing an example of processing a helical gear.

[0019] Figure 6 This is a flowchart showing the processing steps of the control device 10 of the machine tool according to one embodiment of the present disclosure. DETAILED DESCRIPTION

[0020] Hereinafter, one embodiment of the present disclosure will be described in detail with reference to the accompanying drawings.

[0021] Figure 1 The figure shows the shaft structure of a machine tool according to one embodiment of the present disclosure. The machine tool according to this embodiment processes a workpiece having at least one tooth surface, such as Figure 1 The gear processing machine 1 shown. As the gear processing machine 1, a gear grinding machine capable of grinding a gear or a grinding machine (hob?) capable of cutting a gear can be cited.

[0022] like Figure 1 As shown, the axis structure of the machine tool of this embodiment is composed of an X-axis feed axis in the radial direction (radial direction of the workpiece) relative to the cylindrical workpiece W, a Y-axis feed axis in the tangential direction (tangential direction of the workpiece), a Z-axis feed axis in the axial direction (axial direction of the workpiece), an A-axis (tool tilting axis) rotation axis about the X-axis, a B-axis (tool rotation axis) rotation axis about the Y-axis, and a C-axis (workpiece rotation axis) rotation axis about the Z-axis. In order to move in the direction of each axis and rotate about each axis, a movement and rotation mechanism (not shown) including an electric motor is provided on each axis. In this gear processing machine 1, the workpiece W is rotated about the C-axis by the workpiece axis 2, and the tool T is rotated about the B-axis by the tool axis 3, so that the workpiece W and the tool T are relatively moved in the directions of each axis to perform grinding or cutting.

[0023] Figure 2 This is a functional block diagram of a machine tool control device 10 according to one embodiment of the present disclosure. The machine tool control device 10 according to this embodiment controls the spindle motor that rotates the tool T and workpiece W relative to each other, and controls the feed axis motor 30 that moves the tool T and workpiece W while swinging relative to each other, thereby performing grinding or cutting. The machine tool control device 10 according to this embodiment is comprised of, for example, a computer having a CPU, memory, and other components.

[0024] like Figure 2 As shown, the machine tool control device 10 of this embodiment includes an adder 11 , an accumulator 12 , an adder 13 , a position and speed control unit 14 , a machining condition input unit 15 , a surface pattern calculation unit 16 , a swing command generation unit 17 , and a display unit 18 .

[0025] The adder 11 calculates the position deviation. Specifically, the adder 11 calculates the position deviation, which is the difference between the position feedback based on the position detection of the encoder of the feed axis motor 30 and the position command of the feed axis from a numerical controller (not shown).

[0026] The accumulator 12 calculates an accumulated value of the position deviation. Specifically, the accumulator 12 calculates an accumulated value of the position deviation by accumulating the position deviation calculated by the adder 11.

[0027] The adder 13 generates an overlap command. Specifically, the adder 13 adds (overlaps) the swing command generated by the swing command generator 17 (described later) to the accumulated value of the position deviation calculated by the accumulator 12, thereby generating the overlap command. Alternatively, the adder 13 may add the swing command generated by the swing command generator 17 to the movement command (position command).

[0028] More specifically, the adder 13 superimposes the swing command generated by the swing command generator 17 (described later) with the position command or position deviation (accumulated value) for at least one axis. The axis on which the swing command is superimposed is at least one of the axes of the machine tool involved in machining. Specifically, it is at least one selected from a total of five axes: the three feed axes (X, Y, and Z), the tool rotation axis (B), and the workpiece rotation axis (C). If the swing command is superimposed on the tool tilt axis (A), the meshing of the grooves between the workpiece W and the tool T may change. Therefore, it is preferable to superimpose the swing command on the other five axes excluding the A axis.

[0029] Furthermore, this embodiment may also include a learning control unit (not shown) that calculates a correction amount for the overlap command based on the position deviation and adds the calculated correction amount to the overlap command to correct the overlap command. The learning control unit includes a memory that stores the deviation between the ideal position and the actual position of the motor 30, which can define a certain cycle. The stored deviation is read from the memory for each cycle to calculate a correction amount to bring the deviation close to zero. The calculated correction amount is then superimposed on the overlap command to correct the overlap command. Although the overlap command of this embodiment is susceptible to position deviation due to the inclusion of an oscillation command, the correction by the learning control unit improves the ability to follow the periodic oscillation command.

[0030] The position and speed control unit 14 generates a torque command for the motor 30 driving the feed axis based on the superposition command generated by the adder 13, and controls the motor 30 according to the generated torque command. In this way, gear machining is performed while the workpiece W and the tool T are relatively swung.

[0031] Furthermore, the position and speed control unit 14 may synchronously control a plurality of axes so that the relative swing direction of the workpiece W and the tool T is along the tooth marks (tooth surfaces). This will be described in detail later.

[0032] The machining condition input unit 15 can input machining conditions including at least one of the specifications of the workpiece W, the specifications of the tool T, the feed rate, the spindle speed, and the number of teeth. Examples of workpiece W specifications include the diameter and material of the workpiece W. Tool T specifications include the number of blades in the case of a grinding wheel and the number of cutting edges in the case of a cutting edge. The number of teeth refers to the number of teeth on the gear.

[0033] The surface pattern calculation unit 16 calculates a surface pattern defined by the spacing of flaws produced on the machined surface, based on the machining conditions input by the machining condition input unit 15. The flaws produced on the machined surface are scratches formed when the tool T contacts the workpiece W, and the surface pattern is defined by the spacing of these flaws. The spacing of these flaws is determined by the machining conditions input by the machining condition input unit 15 and is constant. In other words, flaws are formed at equal intervals on the machined surface of the workpiece W machined according to the input machining conditions. The method for calculating the surface pattern will be described in detail later.

[0034] The swing command generating unit 17 generates a swing command for a surface pattern having a portion with unevenly spaced intervals of scratches based on the surface pattern calculated by the surface pattern calculating unit 16. Specifically, a swing command is generated with a swing frequency or a swing frequency multiplier such as that of the surface pattern having a portion with unevenly spaced intervals of scratches. More specifically, a swing command is generated with a swing frequency or a swing frequency multiplier that is different from the frequency that is the main cause of the evenly spaced scratches. There are no particular restrictions on the swing amplitude or the swing amplitude multiplier, and they are generated based on the swing frequency or the swing frequency multiplier. In addition, the surface pattern having a portion with unevenly spaced intervals of scratches does not require that all the scratches have unevenly spaced intervals; it is sufficient as long as there is a portion with unevenly spaced intervals of scratches.

[0035] Here, Figure 3 1 is a diagram showing the principle of gear machining by the control device 10 of the machine tool according to this embodiment. Figure 3 In the following Figure 4 Similarly, an example of machining a spur gear is shown. The workpiece W1 rotates along the C-axis through the workpiece axis 2, and the tool T rotates along the B-axis through the tool axis 3. The workpiece W1 and the tool T rotate along the Z-axis ( Figure 3 Grinding or cutting is performed by moving relatively in the up and down directions.

[0036] exist Figure 3 In FIG, enlarged views of the area along the tooth marks are shown for the gear processing of the prior art and the present embodiment. Figure 3 As shown, in gear machining using conventional position commands, the intervals between the contact points CT between the workpiece W1 and the tool T, in other words, the intervals between the flaws, are constant and uniform across all paths. In contrast, in gear machining using overlap commands according to this embodiment, the intervals between the contact points CT between the workpiece W1 and the tool T, in other words, the intervals between the flaws, are unequal across all paths.

[0037] By setting the spacing of the scratches to unequal intervals, the peak of the spectrum of the noise generated when the gears mesh is reduced and dispersed, resulting in reduced noise. In addition, by overlapping the swing commands, the spacing of the scratches is staggered to unequal intervals, so that the spacing of the scratches can be set to the desired regular unequal intervals.

[0038] Furthermore, the swing command generating unit 17 can also generate a swing command for a surface pattern having unevenly spaced flaws based on a target surface pattern having unevenly spaced flaws input by the user. This makes it possible to more reliably obtain the unevenly spaced surface pattern desired by the user.

[0039] return Figure 2The display unit 18 can display at least one of the processing conditions input by the processing condition input unit 15, the image of the target surface pattern input by the user, the parameters of the target surface pattern, the image of the surface pattern calculated by the surface pattern calculation unit 16, and the image of the surface pattern when processed based on the overlap instruction. Thus, the user can visually confirm the processing conditions, the image of the target surface pattern with unequal intervals, the parameters, the image of the surface pattern with equal intervals calculated, and the image of the surface pattern with unequal intervals when processed based on the overlap instruction through the display on the display unit 18.

[0040] Next, refer to Figure 4 The method for calculating the surface pattern (interval between scratches) by the surface pattern calculation unit 16 and the method for setting the interval between scratches to unequal intervals will be described in detail. Figure 4 This figure shows an example of machining a spur gear. Figure 4 In the figure, F represents the machining direction, and the workpiece W1 and the tool T are in the workpiece axis direction of the workpiece W1, that is, the Z axis direction ( Figure 4 Move relatively in the up and down directions).

[0041] exist Figure 4 The figure shows the tool contact point CT during the current pass, focusing on a tooth mark on workpiece W1. Assuming the grinding / cutting speed V [mm / min] and the workpiece rotation speed S [rpm], the distance d [mm] between the tool contact point CT during the current pass and the tool contact point CT during the next pass is expressed by the following equation (1). That is, the distance d between adjacent tool contact points CT, or in other words, the distance d between the scratches, is determined by the grinding / cutting speed V and the workpiece rotation speed S and is constant.

[0042] [Mathematical formula 1]

[0043]

[0044] Therefore, in the present embodiment, in order to make the intervals d between the flaws unequal, the swing commands Vo are superimposed as shown in the following equation (2).

[0045] [Mathematical formula 2]

[0046]

[0047] Here, for example, if it is assumed that the swing command Vo is a sine wave V(t) = Asin(ωt), and the time required for the workpiece W from the start of processing to the nth rotation is set to t(n), then the change Δd in the interval d of the scar is expressed by the following formula (3).

[0048] [Mathematical formula 3]

[0049]

[0050] It can be seen that the time t(n) required for the workpiece W from the start of machining to the nth rotation is calculated based on the workpiece rotation speed. Therefore, according to the above formula (3), Δd can be controlled by A and ω. This means that the interval d between the scars can be controlled by the swing instruction Vo. The ω used to make the interval d between the scars unequal is selected from a frequency group that is not synchronized with the workpiece rotation speed. This is because, in the frequency group synchronized with the workpiece rotation speed (including integer multiples of the workpiece rotation speed), as can be seen from the above formula (3), the cos component becomes 0, Δd becomes 0, and therefore the interval d between the scars cannot be made unequal.

[0051] In the above description, the swing in the Z-axis direction is described as an example, but the swing in other axial directions can also be described in the same manner.

[0052] Next, refer to Figure 5 The structure of synchronously controlling multiple axes by the position and speed control unit 14 so that the relative swing direction of the workpiece W and the tool T becomes along the direction of the tooth mark (tooth surface) (Z-axis direction) will be described in detail. Figure 5 This is a diagram showing an example of processing a helical gear.

[0053] exist Figure 5 In FIG, the tool contact point CT in this path is shown when focusing on a certain tooth mark of the workpiece W2. Figure 5 As shown, the tooth marks on workpiece W2 are tilted relative to the workpiece's rotation axis (Z-axis direction). To machine this type of helical gear, tool T must be moved not only in the Z-axis direction but also in the Y-axis direction. In other words, if only the Z-axis direction is oscillated, the machined shape will be distorted. To prevent this, multiple axes must be oscillated. Therefore, when machining this type of helical gear, it is preferable to synchronize and oscillate multiple axes using the position and speed control unit 14.

[0054] Next, refer to Figure 6 The processing sequence of the control device 10 of the machine tool of this embodiment will be described. Figure 6 This is a flowchart showing the processing procedure of the control device 10 of the machine tool according to the present embodiment.

[0055] First, in step S1, the user inputs processing conditions via the processing condition input unit 15. After the input, the process proceeds to step S2.

[0056] In step S2, based on the processing conditions input in step S1, the surface pattern calculation unit 16 calculates a surface pattern defined by the intervals between the scratches generated on the processed surface. Specifically, the intervals between the scratches are calculated using the aforementioned equation (1). After the calculation, the process proceeds to step S3.

[0057] In step S3, an oscillation command is generated based on the surface pattern calculated in step S2. Specifically, an oscillation command Vo is generated to achieve the desired surface pattern (scar spacing) using equations (2) and (3). After generation, the process proceeds to step S4.

[0058] In step S4, the swing command generated in step S3 is superimposed on the position command or position deviation to generate a superimposition command. After the superimposition command is generated, the process proceeds to step S5.

[0059] In step S5 , the position and speed of the motor 30 are controlled based on the overlap command generated in step S4 , and the present process ends.

[0060] According to this embodiment, the following effects are achieved.

[0061] In this embodiment, there are provided: a processing condition input unit 15, which is capable of inputting processing conditions including at least one of the specifications of the workpiece W, the specifications of the tool T, the feed speed, the spindle speed, and the number of teeth; a surface pattern calculation unit 16, which calculates a surface pattern specified based on the intervals of scars generated on the processed surface based on the processing conditions input by the processing condition input unit 15; a swing instruction generation unit 17, which generates a swing instruction for a surface pattern having a portion with scars at unequal intervals based on the surface pattern calculated by the surface pattern calculation unit 16; and a position and speed control unit 14, which causes the workpiece W and the tool T to swing relative to each other for processing based on the swing instruction generated by the swing instruction generation unit 17.

[0062] This allows the spacing of the scratches on the machined surface to be unequal, reducing and dispersing the peaks in the spectrum of noise generated when the gears mesh. This results in suppressing the generation of periodic sounds and reducing noise. Furthermore, by overlapping the swing commands, the spacing of the scratches can be staggered to unequal intervals, allowing the scratches to be spaced at the desired regular unequal intervals, and achieving the desired machining quality with high reproducibility.

[0063] Furthermore, in the present embodiment, an adder 13 is provided for superimposing a swing command on a movement command for relatively moving the workpiece W and the tool T or on a position deviation.

[0064] Thereby, the above-mentioned effect can be obtained more reliably.

[0065] Furthermore, in this embodiment, a swing instruction is generated to create a surface pattern having a portion with uneven intervals of flaws based on a target surface pattern having a portion with uneven intervals of flaws input by a user.

[0066] This makes it possible to reliably reduce noise generated when the gears are meshed, and to obtain processing quality desired by the user.

[0067] In addition, in the present embodiment, the axis on which the swing command is superimposed is configured to be at least one of the feed axis, the tool rotation axis, and the workpiece rotation axis.

[0068] Therefore, by overlapping the swing instruction on at least one axis selected from a total of five axes, namely the feed axis, namely the X-axis, Y-axis, and Z-axis, the tool rotation axis, namely the B-axis, and the workpiece rotation axis, namely the C-axis, it is possible to avoid changes in the engagement of the grooves of the workpiece W and the tool T with each other, as in the case of overlapping the swing instruction on the tool tilt axis, namely the A-axis.

[0069] In addition, in the present embodiment, a configuration is made so that the plurality of axes are synchronously controlled so that the relative swinging direction of the workpiece W and the tool T becomes a direction along the tooth marks.

[0070] Therefore, for example, when machining a helical gear in which the tooth marks are inclined relative to the workpiece rotation axis (Z-axis direction), the machine is swung not only in the Z-axis direction but also in the Y-axis direction, thereby preventing deformation of the machined shape when only the Z-axis direction is swung.

[0071] In addition, in the present embodiment, a learning control unit is further provided. The learning control unit calculates a correction amount for the superimposition command based on the positional deviation and corrects the superimposition command by adding the calculated correction amount to the superimposition command.

[0072] This improves the ability to follow periodic swing commands, resulting in more reliable production of the aforementioned effects and further improved machining quality.

[0073] In addition, in this embodiment, a display unit 18 is further provided, which is capable of displaying at least one of the processing conditions input by the processing condition input unit 15, the image of the target surface pattern input by the user, the parameters of the target surface pattern, the image of the surface pattern calculated by the surface pattern calculation unit 16, and the image of the surface pattern when processing is performed based on overlapping instructions.

[0074] Thus, the user can visually confirm the machining conditions, the unequally spaced target surface pattern images and parameters, the calculated unequally spaced surface pattern images, and the unequally spaced surface pattern images during machining based on the overlap command through the display on the display unit 18 .

[0075] The present invention is not limited to the above-described embodiments, and modifications and improvements within the scope that can achieve the object of the present invention are also included in the present invention.

[0076] Description of Reference Signs

[0077] 1 Gear processing machine (machine tool)

[0078] 2 Workpiece axis

[0079] 3 Tool axis

[0080] 10 Machine tool control device

[0081] 11 Adder

[0082] 12 Accumulator

[0083] 13 Adder

[0084] 14 Position and speed control unit (control unit)

[0085] 15 Machining condition input unit 16 Surface pattern calculation unit 17 Swing command generation unit 18 Display unit 30 Motor CT Tool contact point T Tool W Workpiece

Claims

1. A control device for a machine tool for machining a workpiece having at least one tooth surface, characterized in that: The machine tool's control device has: a machining condition input unit capable of inputting machining conditions including at least one of the specifications of the workpiece, the specifications of the tool, the feed rate, the spindle speed, and the number of teeth; a surface pattern calculation unit that calculates a surface pattern specified by intervals between flaws generated on the processed surface based on the processing conditions input by the processing condition input unit; an oscillation command generating unit for generating an oscillation command having an oscillation frequency or an oscillation frequency multiplication factor different from a frequency that is a main cause of the flaws, so as to form a surface pattern having portions with unequal intervals between the flaws, based on the surface pattern calculated by the surface pattern calculating unit; and A control unit performs machining by relatively swinging the workpiece and the tool based on the swing command generated by the swing command generating unit.

2. The machine tool control device according to claim 1, wherein: The control device of the machine tool further includes an adder that generates a superimposition command by superimposing the swing command with a movement command or a position deviation for relatively moving the workpiece and the tool.

3. The control device for a machine tool according to claim 2, wherein: The control device of the machine tool further includes a learning control unit that calculates a correction amount for the overlap command based on the position deviation and adds the calculated correction amount to the overlap command to correct the overlap command.

4. The control device for a machine tool according to claim 2, wherein: The axis on which the swing command is superimposed is at least one of a feed axis, a tool rotation axis, and a workpiece rotation axis.

5. The control device for a machine tool according to claim 3, wherein: The axis on which the swing command is superimposed is at least one of a feed axis, a tool rotation axis, and a workpiece rotation axis.

6. The control device for a machine tool according to any one of claims 2 to 5, characterized in that: The control device of the machine tool also has a display unit, which is capable of displaying at least one of the processing conditions input by the processing condition input unit, the image of the target surface pattern input by the user, the parameters of the target surface pattern, the image of the surface pattern calculated by the surface pattern calculation unit, and the image of the surface pattern when processing is performed based on the overlapping instruction.

7. The control device for a machine tool according to claim 1, wherein: The swing command generation unit further generates a swing command for a surface pattern having a portion where the intervals between the flaws are unequally spaced, based on a target surface pattern input by a user and having a portion where the intervals between the flaws are unequally spaced.

8. The control device for a machine tool according to claim 2, wherein: The swing command generation unit further generates a swing command for a surface pattern having a portion where the intervals between the flaws are unequally spaced, based on a target surface pattern input by a user and having a portion where the intervals between the flaws are unequally spaced.

9. The control device for a machine tool according to claim 6, wherein: The swing command generation unit further generates a swing command for a surface pattern having a portion where the intervals between the flaws are unequally spaced, based on a target surface pattern input by a user and having a portion where the intervals between the flaws are unequally spaced.

10. The control device for a machine tool according to claim 1, wherein: The control unit synchronously controls the plurality of axes so that the direction of relative swing of the workpiece and the tool is along the tooth mark.

11. The control device for a machine tool according to any one of claims 2 to 5, characterized in that: The control unit synchronously controls the plurality of axes so that the direction of relative swing of the workpiece and the tool is along the tooth mark.

12. The control device for a machine tool according to claim 6, wherein: The control unit synchronously controls the plurality of axes so that the direction of relative swing of the workpiece and the tool is along the tooth mark.

13. The control device for a machine tool according to claim 7, wherein: The control unit synchronously controls the plurality of axes so that the direction of relative swing of the workpiece and the tool is along the tooth mark.

14. The control device for a machine tool according to claim 8, wherein: The control unit synchronously controls the plurality of axes so that the direction of relative swing of the workpiece and the tool is along the tooth mark.

15. The control device for a machine tool according to claim 9, wherein: The control unit synchronously controls the plurality of axes so that the direction of relative swing of the workpiece and the tool is along the tooth mark.

Images